Research Outputs

A list of known research outputs coming from work carried on Viper can be found below, sorted by publication date with a further list of preprints.

The HPC Steering Group has agreed that where appropriate, the use of Viper on a research project should be acknowledged in publications with the following statement:

“We acknowledge the Viper High Performance Computing facility of the University of Hull and its support team”

We are always interested to know of any output that features work carried out on Viper, please contact viper@hull.ac.uk

Publications (202 outputs)

2024 (6 outputs)

E Roediger, I Vaezzadeh, P Nulsen, 2024-02-28, A toy model for gas sloshing in galaxy clusters, Monthly Notices of the Royal Astronomical Society, doi: 10.1093/mnras/stae493

Abstract

We apply a toy model based on ‘pendulum waves’ to gas sloshing in galaxy clusters. Starting with a galaxy cluster potential filled with a hydrostatic intra-cluster medium (ICM), we perturb all ICM by an initial small, unidirectional velocity, i.e., an instantaneous kick. Consequently, each parcel of ICM will oscillate due to buoyancy with its local Brunt-Vaisala (BV) period, which we show to be approximately proportional to the cluster radius. The oscillation of gas parcels at different radii with different periods leads to a characteristic, outwards-moving coherent pattern of local compressions and rarefactions; the former form the sloshing cold fronts (SCFs). Our model predicts that SCFs (i) appear in the cluster centre first, (ii) move outwards on several Gyr timescales, (iii) form a staggered pattern on opposite sides of a given cluster, (iv) each move outwards with approximately constant speed; and that (v) inner SCFs form discontinuities more easily than outer ones. These features are well known from idealised (magneto)-hydrodynamic simulations of cluster sloshing. We perform comparison hydrodynamic+N-body simulations where sloshing is triggered either by an instantaneous kick or a minor merger. Sloshing in these simulations qualitatively behaves as predicted by the toy model. However, the toy model somewhat over-predicts the speed of sloshing fronts, and does not predict that inner SCFs emerge with a delay compared to outer ones. In light of this, we identify the outermost cold front, which may be a ‘failed’ SCF, as the best tracer of the age of the merger that set a cluster sloshing.


Michele Scandola, Emmanuele Tidoni, 2024-02-09, Reliability and feasibility of Linear Mixed Models in fully crossed experimental designs, Advances in Methods and Practices in Psychological Science, doi: 10.1177/25152459231214454

Abstract

The use of linear mixed models (LMMs) is increasing in psychology and neuroscience research In this article, we focus on the implementation of LMMs in fully crossed experimental designs. A key aspect of LMMs is choosing a random-effects structure according to the experimental needs. To date, opposite suggestions are present in the literature, spanning from keeping all random effects (maximal models), which produces several singularity and convergence issues, to removing random effects until the best fit is found, with the risk of inflating Type I error (reduced models). However, defining the random structure to fit a nonsingular and convergent model is not straightforward. Moreover, the lack of a standard approach may lead the researcher to make decisions that potentially inflate Type I errors. After reviewing LMMs, we introduce a step-by-step approach to avoid convergence and singularity issues and control for Type I error inflation during model reduction of fully crossed experimental designs. Specifically, we propose the use of complex random intercepts (CRIs) when maximal models are overparametrized. CRIs are multiple random intercepts that represent the residual variance of categorical fixed effects within a given grouping factor. We validated CRIs and the proposed procedure by extensive simulations and a real-case application. We demonstrate that CRIs can produce reliable results and require less computational resources. Moreover, we outline a few criteria and recommendations on how and when scholars should reduce overparametrized models. Overall, the proposed procedure provides clear solutions to avoid overinflated results using LMMs in psychology and neuroscience.


Holly N. Wilkinson, Amber R. Stafford, Michelle Rudden, Nina D.C. Rocha, Alexandria S. Kidd, Sammi Iveson, Andrea L. Bell, Jeffrey Hart, Ana Duarte, Johan Frieling, Ferd Janssen, Christian Rohrig, Bob de Rooij, Peter F. Ekhart, Matthew J. Hardman, 2024-02-01, Selective depletion of S. aureus restores the skin microbiome and accelerates tissue repair following injury., Journal of Investigative Dermatology, doi: 10.1016/j.jid.2024.01.018

Abstract

Our skin is home to a diverse community of commensal microorganisms integral to cutaneous function. However, microbial dysbiosis and barrier perturbation increase the risk of local and systemic infection. Staphylococcus aureus is a particularly problematic bacterial pathogen, with high levels of antimicrobial resistance and direct association with poor healing outcome. Innovative approaches are needed to selectively kill skin pathogens, such as S. aureus, without harming the resident microbiota. Here we provide important data on the selectivity and efficacy of an S. aureus-targeted endolysin (XZ.700) within the complex living skin/wound microbiome. Initial cross-species comparison using Nanopore long-read sequencing identified the translational potential of porcine, rather than murine, skin for human-relevant microbiome studies. We therefore performed an interventional study in pigs to assess the impact of endolysin administration on the microbiome. XZ.700 selectively inhibited endogenous porcine S. aureus in vivo, restoring microbial diversity and promoting multiple aspects of wound repair. Subsequent mechanistic studies confirmed the importance of this microbiome modulation for effective healing in human skin. Taken together, these findings strongly support further development of S. aureus-targeted endolysins for future clinical management of skin and wound infections.


Lydia Bryan-Smith and Nina Dethlefs, 2024-02, Towards AI for approximating hydrodynamic simulations as a 2D segmentation task, Proceedings of the 5th Northern Lights Deep Learning Conference (NLDL), link: https://proceedings.mlr.press/v233/bryan-smith24a/bryan-smith24a.pdf

Abstract

Traditional predictive simulations and remote sensing techniques for forecasting floods are based on fixed and spatially restricted physics-based models. These models are computationally expensive and can take many hours to run, resulting in predictions made based on outdated data. They are also spatially fixed, and unable to scale to unknown areas. By modelling the task as an image segmentation problem, an alternative approach using artificial intelligence to approximate the parameters of a physics-based model in 2D is demonstrated, enabling rapid predictions to be made in real-time.


Alexander P. Ji, Sanjana Curtis, Nicholas Storm, Vedant Chandra, Kevin C. Schlaufman, Keivan G. Stassun, Alexander Heger, Marco Pignatari, Adrian M. Price-Whelan, Maria Bergemann, Guy S. Stringfellow, Carla Frohlich, Henrique Reggiani, Erika M. Holmbeck, Jamie Tayar, Shivani P. Shah, Emily J. Griffith, Chervin F. P. Laporte, Andrew R. Casey, Keith Hawkins, Danny Horta, William Cerny, Pierre Thibodeaux, Sam A. Usman, Joao A. S. Amarante, Rachael L. Beaton, Phillip A. Cargile, Cristina Chiappini, Charlie Conroy, Jennifer A. Johnson, Juna A. Kollmeier, Haining Li, Sarah Loebman, Georges Meynet, Dmitry Bizyaev, Joel R. Brownstein, Pramod Gupta, Sean Morrison, Kaike Pan, Solange V. Ramirez, Hans-Walter Rix, Jose Sanchez-Gallego, 2024-01-31, Spectacular nucleosynthesis from early massive stars, The Astrophysical Journal Letters, doi: 10.3847/2041-8213/ad19c4

Abstract

Stars that formed with an initial mass of over 50 Mʘ are very rare today, but they are thought to be more common in the early Universe. The fates of those early, metal-poor, massive stars are highly uncertain. Most are expected to directly collapse to black holes, while some may explode as a result of rotationally powered engines or the pair-creation instability. We present the chemical abundances of J0931+0038, a nearby low-mass star identified in early follow-up of the SDSS-V Milky Way Mapper, which preserves the signature of unusual nucleosynthesis from a massive star in the early Universe. J0931+0038 has a relatively high metallicity ([Fe/H] = -1.76 ± 0.13) but an extreme odd-even abundance pattern, with some of the lowest known abundance ratios of [N/Fe], [Na/Fe], [K/Fe], [Sc/Fe], and [Ba/Fe]. The implication is that a majority of its metals originated in a single extremely metal-poor nucleosynthetic source. An extensive search through nucleosynthesis predictions finds a clear preference for progenitors with initial mass >50 Mʘ, making J0931+0038 one of the first observational constraints on nucleosynthesis in this mass range. However, the full abundance pattern is not matched by any models in the literature. J0931+0038 thus presents a challenge for the next generation of nucleosynthesis models and motivates the study of high-mass progenitor stars impacted by convection, rotation, jets, and/or binary companions. Though rare, more examples of unusual early nucleosynthesis in metal-poor stars should be found in upcoming large spectroscopic surveys.


Jaehyun Lee, Changbom Park, Juhan Kim, Christophe Pichon, Brad K. Gibson, Jihye Shin, Yonghwi Kim, Owain N. Snaith, Yohan Dubois, C. Gareth Few, 2024-01-09, Identification of Galaxy Protoclusters Based on the Spherical Top-hat Collapse Theory, The Astrophysical Journal, doi: 10.3847/1538-4357/ad0555

Abstract

We propose a new method for finding galaxy protoclusters that is motivated by structure formation theory and also directly applicable to observations. We adopt the conventional definition that a protocluster is a galaxy group whose virial mass Mvir < Mcl at its epoch, where Mcl = 1014Mʘ, but would exceed that limit when it evolves to z = 0. We use the critical overdensity for complete collapse at z = 0 predicted by the spherical top-hat collapse model to find the radius and total mass of the regions that would collapse at z = 0. If the mass of a region centered at a massive galaxy exceeds Mcl, the galaxy is at the center of a protocluster. We define the outer boundary of a protocluster as the zero-velocity surface at the turnaround radius so that the member galaxies are those sharing the same protocluster environment and showing some conformity in physical properties. We use the cosmological hydrodynamical simulation Horizon Run 5 (HR5) to calibrate this prescription and demonstrate its performance. We find that the protocluster identification method suggested in this study is quite successful. Its application to the high-redshift HR5 galaxies shows a tight correlation between the mass within the protocluster regions identified according to the spherical collapse model and the final mass to be found within the clusters at z = 0, meaning that the regions can be regarded as the bona fide protoclusters with high reliability. We also confirm that the redshift-space distortion does not significantly affect the performance of the protocluster identification scheme.



2023 (25 outputs)

Ling Qin, Wenjia Du, Silvia Cipiccia, Andrew J. Bodey, Christoph Rau, Jiawei Mi, 2023-12-14, Synchrotron X-ray operando study and multiphysics modelling of the solidification dynamics of intermetallic phases under electromagnetic pulses, Acta Materialia, doi: 10.1016/j.actamat.2023.119593

Abstract

In this paper, we used synchrotron X-ray radiography and tomography to study in operando conditions the growth dynamics of the primary Al3Ni intermetallic phases in an Al-15wt%Ni alloy in the solidification process with magnetic pulses of up to 1.5 T. The real-time observations clearly revealed the growth dynamics of the intermetallics in time scale from millisecond to minutes, including phase growth instability, side branching, fragmentation and orientation alignment under different magnetic fluxes. A multiphysics numerical model was also developed to calculate time-evolved Lorentz forces and stresses acting on the Al3Ni phases and the nearby melt. The differential forces between the growing Al3Ni phases and the nearby melt can create slip dislocations at the growing crystal front which can be further developed into nm and μm crystal steps for initiating phase branching. Furthermore, the magnitudes of the shear stresses are strongly related to the size, morphological and geometric features of the growing Al3Ni phases. Dependent on the magnitude of the shear stresses, phase fragmentation could occur in a single pulse period or in multiple pulse periods via fatigue mechanism. The combined real-time experimental observation and modelling work allowed us to elucidate some of the long-time debated hypotheses concerning intermetallic phases growth instability and phase fragmentation in pulse magnetic fields.


Sema Ebrahimi, Alina Muravitskaya, Ali M. Adawi, Anne-Laure Baudrion, Pierre-Michel Adam, and Jean-Sebastien G. Bouillard, 2023-08-25, Magnetic Mode Coupling in Hyperbolic Bowtie Meta-Antennas, The Journal of Physical Chemistry Letters, doi: 10.1021/acs.jpclett.3c01620

Abstract

Hyperbolic metaparticles have emerged as the next step in metamaterial applications, providing tunable electromagnetic properties on demand. However, coupling of optical modes in hyperbolic meta-antennas has not been explored. Here, we present in detail the magnetic and electric dipolar modes supported by a hyperbolic bowtie meta-antenna and clearly demonstrate the existence of two magnetic coupling regimes in such hyperbolic systems. The coupling nature is shown to depend on the interplay of the magnetic dipole moments, controlled by the meta-antenna effective permittivity and nanogap size. In parallel, the meta-antenna effective permittivity offers fine control over the electrical field spatial distribution. Our work highlights new coupling mechanisms between hyperbolic systems that have not been reported before, with a detailed study of the magnetic coupling nature, as a function of the structural parameters of the hyperbolic meta-antenna, which opens the route toward a range of applications from magnetic nanolight sources to chiral quantum optics and quantum interfaces.


James D Keegans, Marco Pignatari, Richard J Stancliffe, Claudia Travaglio, Samuel Jones, Brad K Gibson, Dean M Townsley, Broxton J Miles, Ken J Shen, Gareth Few, 2023-08-22, Type Ia Supernova Nucleosynthesis: Metallicity-Dependent Yields, The Astrophysical Journal Supplement Series, doi: 10.3847/1538-4365/ace102

Abstract

Type Ia supernova explosions (SN Ia) are fundamental sources of elements for the chemical evolution of galaxies. They efficiently produce intermediate-mass (with Z between 11 and 20) and iron group elements – for example, about 70% of the solar iron is expected to be made by SN Ia. In this work, we calculate complete abundance yields for 39 models of SN Ia explosions, based on three progenitors – a 1.4 M deflagration detonation model, a 1.0 M double detonation model, and a 0.8 M double detonation model-and 13 metallicities, with 22Ne mass fractions of 0, 1 x 10-7, 1 x 10-6, 1 x 10-5, 1 x 10-4, 1 x 10-3, 2 x 10-3, 5 x 10-3, 1 x 10-2, 1.4 x 10-2, 5 x 10-2, and 0.1, respectively. Nucleosynthesis calculations are done using the NuGrid suite of codes, using a consistent nuclear reaction network between the models. Complete tables with yields and production factors are provided online at Zenodo:Yields (https://doi.org/10.5281/zenodo.8060323). We discuss the main properties of our yields in light of the present understanding of SN Ia nucleosynthesis, depending on different progenitor mass and composition. Finally, we compare our results with a number of relevant models from the literature.


Ankit Singh, Changbom Park, Ena Choi, Juhan Kim, Hyunsung Jun, Brad K. Gibson, Yonghwi Kim, Jaehyun Lee, and Owain Snaith, 2023-08-02, On the Effects of Local Environment on Active Galactic Nucleus (AGN) in the Horizon Run 5 Simulation, The Astrophysical Journal, doi: 10.3847/1538-4357/acdd6b

Abstract

We use the Horizon Run 5 cosmological simulation to study the effect of galaxy intrinsic properties and the local environment on active galactic nuclei (AGNs) characterized by their threshold of the accretion rate. We select galaxies in the stellar mass range 109.5≤ M/M≤ 1010.5 in the snapshot at redshift z = 0.625. Among various intrinsic properties, we find that the star formation rate of the host galaxy is most correlated to the AGN activity. To quantify the environment, we use background galaxy number density (large-scale environment) and distance and morphological type of the nearest neighbors (small-scale environment), and study their relative effects on the AGN properties. We find that, compared to the background density, the nearest neighbor environment is the dominant quantity determining the bolometric luminosity, star formation rate, and kinematic properties of AGNs and better dictates the gas mass of the host galaxy. We show that the cold gas content in the host galaxies is crucial in triggering AGN activity. However, when the nearest neighbor environment effects start to act at the neighbor distance of less than about half the virial radius of the neighbor, the neighbor environmental effects are the most dominant factor for quasar activity.


Marco Pignatari, Thomas C L Trueman, Kate A Womack, Brad K Gibson, Benoit Cote, Diego Turrini, Christopher Sneden, Stephen J Mojzsis, Richard J Stancliffe, Paul Fong, Thomas V Lawson, James D Keegans, Kate Pilkington, Jean-Claude Passy, Timothy C Beers, Maria Lugaro, 2023-07-21, The chemical evolution of the solar neighbourhood for planet-hosting stars, Monthly Notices of the Royal Astronomical Society, doi: 10.1093/mnras/stad2167

Abstract

Theoretical physical-chemical models for the formation of planetary systems depend on data quality for the Sun’s composition, that of stars in the solar neighbourhood, and of the estimated “pristine” compositions for stellar systems. The effective scatter and the observational uncertainties of elements within a few hundred parsecs from the Sun, even for the most abundant metals like carbon, oxygen and silicon, are still controversial. Here we analyse the stellar production and the chemical evolution of key elements that underpin the formation of rocky (C, O, Mg, Si) and gas/ice giant planets (C, N, O, S). We calculate 198 galactic chemical evolution (GCE) models of the solar neighbourhood to analyse the impact of different sets of stellar yields, of the upper mass limit for massive stars contributing to GCE (Mup) and of supernovae from massive-star progenitors which do not eject the bulk of the iron-peak elements (faint supernovae). Even considering the GCE variation produced via different sets of stellar yields, the observed dispersion of elements reported for stars in the Milky Way disk is not reproduced. Among others, the observed range of super-solar [Mg/Si] ratios, sub-solar [S/N], and the dispersion of up to 0.5 dex for [S/Si] challenge our models. The impact of varying Mup depends on the adopted supernova yields. Thus, observations do not provide a constraint on the Mup parametrization. When including the impact of faint supernova models in GCE calculations, elemental ratios vary by up to 0.1-0.2 dex in the Milky Way disk; this modification better reproduces observations.


S.Q. Hou, C. Iliadis, M. Pignatari, J.B. Liu, T. C. L. Trueman, J.G. Li, X.X. Xu, 2023-07-10, Improved thermonuclear rate of 42Ti(p,gamma)43V and its astrophysical implication in the rp process, Astronomy & Astrophysics, doi: 10.1051/0004-6361/202347054

Abstract

Context. Accurate 42Ti (p, γ) 43V reaction rates are crucial for understanding the nucleosynthesis path of the rapid capture process (rp process) that occurs in X-ray bursts.
Aims. We aim to improve the thermonuclear rates of 42Ti (p, γ) 43V based on more complete resonance information and a more accurate direct component, together with the recently released nuclear masses data. We also explore the impact of the newly obtained rates on the rp process.
Methods. We reevaluated the reaction rate of 42Ti (p, γ) 43V by the sum of the isolated resonance contribution instead of the Hauser-Feshbach statistical model. We used a Monte Carlo method to derive the associated uncertainties of new rates. The nucleosynthesis simulations were performed via the NuGrid post-processing code ppn. Results. The new rates differ from previous estimations due to the use of a series of updated resonance parameters and a direct S factor. Compared with the previous results from the Hauser-Feshbach statistical model, which assumes compound nucleus 43V with a sufficiently high-level density in the energy region of astrophysical interest, large differences exist over the entire temperature region of rp-process interest, up to two orders of magnitude. We consistently calculated the photodisintegration rate using our new nuclear masses via the detailed balance principle, and found the discrepancies among the different reverse rates are much larger than those for the forward rate, up to ten orders of magnitude at the temperature of 108 K. Using a trajectory with a peak temperature of 1.95 X109 K, we performed the rp-process nucleosynthesis simulations to investigate the impact of the new rates. Our calculations show that the adoption of the new forward and reverse rates result in abundance variations for Sc and Ca of 128% and 49%, respectively, compared to the variations for the statistical model rates. On the other hand, the overall abundance pattern is not significantly affected. The results of using new rates also confirm that the rp-process path does not bypass the isotope 43V. Conclusions. Our study found that the Hauser-Feshbach statistical model is inappropriate to the reaction rate evaluation for 42Ti (p, γ) 43V. The adoption of the new rates confirms that the reaction path of 42Ti (p, γ) 43V (p, γ) 44Cr (β+) 44V is a key branch of the rp process in X-ray bursts.


Juhan Kim, Jaehyun Lee, Clotilde Laigle, Yohan Dubois, Yonghwi Kim, Changbom Park, Christophe Pichon, Brad Gibson, C. Gareth Few, Jihye Shin, Owain Snaith, 2023-07, Low-Surface-Brightness Galaxies are missing in the observed Stellar Mass Function, The Astrophysical Journal, doi: 10.3847/1538-4357/acd251

Abstract

We investigate the impact of the surface-brightness (SB) limit on the galaxy stellar mass functions (GSMFs) using galaxy catalogs generated from the Horizon Run 5 (HR5) simulation. We compare the stellar-to-halo-mass relation, GSMF, and size-stellar mass relation of the HR5 galaxies with observational data and other cosmological simulations. The mean SB of simulated galaxies are computed using their effective radii, luminosities, and colors. To examine the cosmic SB dimming effect, we compute k-corrections from the spectral energy distributions of individual simulated galaxy at each redshift, apply the k-corrections to the galaxies, and conduct mock surveys based on the various SB limits. We find that the GSMFs are significantly affected by the SB limits at the low-mass end. This approach can ease the discrepancy between the GSMFs obtained from simulations and observations at 0.6 ∼≤ z ≤ 2. We also find that a redshift survey with an SB selection limit of (Ur)e 25 mag arcsec-2 will miss 20% of galaxies with M*g = 109 Mʘ at z = 0.625. The missing fraction of low-surface-brightness galaxies increases to 35%, 55%, and 80% at z = 0.9, 1.1, and 1.9, respectively, at the same SB limit.


Lydia Bryan-Smith, Jake Godsall, Franky George, Kelly Egode, Nina Dethlefs, Dan Parsons, 2023-06-28, Real-time social media sentiment analysis for rapid impact assessment of floods, Computer & Geosciences, doi: 10.1016/j.cageo.2023.105405

Abstract

Traditional approaches to flood modelling mostly rely on hydrodynamic physical simulations. While these simulations can be accurate, they are computationally expensive and prohibitively so when thinking about real-time prediction based on dynamic environmental conditions.

Alternatively, social media platforms such as Twitter are often used by people to communicate during a flooding event, but discovering which tweets hold useful information is the key challenge in extracting information from posts in real time.

In this article, we present a novel model for flood forecasting and monitoring that makes use of a transformer network that assesses the severity of a flooding situation based on sentiment analysis of the multimodal inputs (text and images). We also present an experimental comparison of a range of state-of-the-art deep learning methods for image processing and natural language processing. Finally, we demonstrate that information induced from tweets can be used effectively to visualise fine-grained geographical flood-related information dynamically and in real-time.


S.Q. Hou, J.B. Liu, T. C. L. Trueman, J.G. Li, M. Pignatari, C. Bertulani, X.X. Xu, 2023-06, New 26P(p,γ)27S thermonuclear reaction rate and its astrophysical implication in rp-process, The Astrophysical Journal, doi: 10.3847/1538-4357/accf9c

Abstract

Accurate nuclear reaction rates for 26P(p,γ)27S are pivotal for a comprehensive understanding of the rp-process nucleosynthesis path in the region of proton-rich sulfur and phosphorus isotopes. However, large uncertainties still exist in the current rate of 26P(p,γ)27S because of the lack of nuclear mass and energy level structure information for 27S. We reevaluate this reaction rate using the experimentally constrained 27S mass, together with the shell model predicted level structure. It is found that the 26P(p,γ)27S reaction rate is dominated by a direct capture reaction mechanism despite the presence of three resonances at E = 1.104, 1.597, and 1.777 MeV above the proton threshold in 27S. The new rate is overall smaller than the other previous rates from the Hauser-Feshbach statistical model by at least 1 order of magnitude in the temperature range of X-ray burst interest. In addition, we consistently update the photodisintegration rate using the new 27S mass. The influence of new rates of forward and reverse reaction in the abundances of isotopes produced in the rp-process is explored by postprocessing nucleosynthesis calculations. The final abundance ratio of 27S/26P obtained using the new rates is only 10% of that from the old rate. The abundance flow calculations show that the reaction path 26P(p,γ)27S(β+,v)27P is not as important as previously thought for producing 27P. The adoption of the new reaction rates for 26P(p,γ)27S only reduces the final production of aluminum by 7.1% and has no discernible impact on the yield of other elements.


Lauric Feugere, Adam Bates, Timothy Emagbetere, Emma Chapman, Linsey Malcolm, Kathleen Bulmer, Jorg Hardege, Pedro Beltran-Alvarez, Katharina C. Wollenberg Valero, 2023-05-23, Heat induces multi-omic and phenotypic stress propagation in zebrafish embryos, PNAS Nexus, doi: 10.1093/pnasnexus/pgad137

Abstract

Heat alters biology from molecular to ecological levels, but may also have unknown indirect effects. This includes the concept that animals exposed to abiotic stress can induce stress in naive receivers. Here, we provide a comprehensive picture of the molecular signatures of this process, by integrating multiomic and phenotypic data. In individual zebrafish embryos, repeated heat peaks elicited both a molecular response and a burst of accelerated growth followed by a growth slowdown in concert with reduced responses to novel stimuli. Metabolomes of the media of heat treated vs. untreated embryos revealed candidate stress metabolites including sulfur-containing compounds and lipids. These stress metabolites elicited transcriptomic changes in naive receivers related to immune response, extracellular signaling, glycosaminoglycan/keratan sulfate, and lipid metabolism. Consequently, non-heat-exposed receivers (exposed to stress metabolites only) experienced accelerated catch-up growth in concert with reduced swimming performance. The combination of heat and stress metabolites accelerated development the most, mediated by apelin signaling. Our results prove the concept of indirect heat-induced stress propagation toward naive receivers, inducing phenotypes comparable with those resulting from direct heat exposure, but utilizing distinct molecular pathways. Group-exposing a nonlaboratory zebrafish line, we independently confirm that the glycosaminoglycan biosynthesis-related gene chs1 and the mucus glycoprotein gene prg4a, functionally connected to the candidate stress metabolite classes sugars and phosphocholine, are differentially expressed in receivers. This hints at the production of Schreckstoff-like cues in receivers, leading to further stress propagation within groups, which may have ecological and animal welfare implications for aquatic populations in a changing climate.


Maren Brauner, Thomas Masseron, D. A. Garcia-Hernandez, Marco Pignatari, Kate A. Womack, Maria Lugaro, Christian R. Hayes, 2023-05-17, Unveiling the chemical fingerprint of phosphorus-rich stars I. In the infrared region of APOGEE-2, Astronomy & Astrophysics, doi: 10.1051/0004-6361/202346048

Abstract

Context. The origin of phosphorus, one of the essential elements for life on Earth, is currently unknown. Prevalent models of Galactic chemical evolution (GCE) systematically underestimate the amount of P compared to observations, especially at low metallicities. The recently discovered P-rich ([P/Fe] ~ ≥ 1.2 dex) and metal-poor ([Fe/H] ≅ -1.0 dex) giants further challenge the GCE models, calling current theories on stellar nucleosynthesis into question. Aims. Since the observed low-mass giants are not expected to produce their high P contents themselves, our primary goal is to find clues on their progenitor or polluter. By increasing the number of known P-rich stars, we aim to narrow down a statistically reliable chemical abundance pattern that defines these peculiar stars. In this way, we place more robust constraints on the nucleosynthetic mechanism that causes the unusually high P abundances. In the long term, identifying the progenitor of the P-rich stars may contribute to the search for the source of P in our Galaxy. Methods. We performed a detailed chemical abundance analysis based on the high-resolution near-infrared (H band) spectra from the latest data release (DR17) of the APOGEE-2 survey. Employing the BACCHUS code, we measured the abundances of 13 elements in the inspected sample, which is mainly composed of a recent collection of Si-enhanced giants. We also analyzed the orbital motions and compared the abundance results to possible nucleosynthetic formation scenarios, and also to detailed GCE models. These models were produced with the OMEGA+ chemical evolution code, using four different massive star yield sets to investigate different scenarios for massive star evolution. Results. We enlarged the sample of confirmed P-rich stars from 16 to a group of 78 giants, which represents the largest sample of P-rich stars to date. The sample includes the first detection of a P-rich star in a Galactic globular cluster. Significant enhancements in O, Al, Si, and Ce, as well as systematic correlations among the studied elements, unveil the unique chemical fingerprint of the P-rich stars. In contrast, the high [Mg/Fe] and [(C+N)/Fe] found in some of the P-rich stars with respect to P-normal stars is not confirmed over the full sample because of the current uncertainties. Strikingly, the strong overabundance in the α-element Si is accompanied by normal Ca and S abundances. This is at odds with current stellar nucleosynthesis models of massive stars. Our analysis of the orbital motion showed that the P-rich stars do not belong to a locally specific population in the Galaxy. In addition, we confirm that the majority of the sample stars are not part of binary systems.


Ryan K. Alexander, Fiorenzo Vincenzo, Alexander P. Ji, Hannah Richstein, Chris J. Jordan, Brad K. Gibson, 2023-05-03, Inhomogeneous Galactic Chemical Evolution: Modelling Ultra-Faint Dwarf Galaxies of the Large Magellanic Cloud, Monthly Notices of the Royal Astronomical Society, doi: 10.1093/mnras/stad1312

Abstract

Ultra-faint dwarf galaxies (UFDs) are among the oldest and most metal-poor galaxies in the cosmos, observed to contain no gas and a high dark matter mass fraction. Understanding the chemical abundance dispersion in such extreme environments could shed light on the very first generations of stars. We present a novel inhomogeneous chemical evolution model, I-GETOOL, that we apply to two UFDs, Carina II and Reticulum II, both satellites of the Large Magellanic Cloud. Our model is based on the Monte Carlo sampling of the initial mass function as star formation proceeds in different gas cells of the galaxy volume. We account for the chemical enrichment of supernova (SN) bubbles as they spread in the interstellar medium, causing dispersion in the elemental abundances. We recreate the abundance patterns of α- and odd-Z elements, predicting two sequences in [C/Fe] and [N/Fe] at all metallicities. Our models underestimate [C/Fe] and [Ti/Fe] because of the large uncertainty in the adopted stellar nucleosynthesis yields. We discuss that the observed C and N abundances had likely been affected by internal mixing processes, which changed the initial surface abundances in the red giants. Our SN feedback scheme is responsible for driving galactic outflows, which quench the star formation activity at early times. We predict an average outflow mass-loading factor ≈ 10³, which extrapolates towards very low galaxy stellar masses the trend observed at high masses. Finally, by combining our model with the MIST isochrone database, we compare our synthetic colour-magnitude diagrams to observations.


Jack L. Eatson, Jacob R. Gordon, Piotr Cegielski, Anna L. Giesecke, Stephan Suckow, Anish Rao, Oscar F. Silvestre, Luis M. Liz-Marzan, Tommy S. Horozov, and D. Martin A. Buzza, 2023-04-18, Capillary Assembly of Anisotropic Particles at Cylindrical Fluid-Fluid Interfaces, Langmuir, doi: 10.1021/acs.langmuir.3c00016

Abstract

The unique behavior of colloids at liquid interfaces provides exciting opportunities for engineering the assembly of colloidal particles into functional materials. The deformable nature of fluid-fluid interfaces means that we can use the interfacial curvature, in addition to particle properties, to direct self-assembly. To this end, we use a finite element method (Surface Evolver) to study the self-assembly of rod-shaped particles adsorbed at a simple curved fluid-fluid interface formed by a sessile liquid drop with cylindrical geometry. Specifically, we study the self-assembly of single and multiple rods as a function of drop curvature and particle properties such as shape (ellipsoid, cylinder, and spherocylinder), contact angle, aspect ratio, and chemical heterogeneity (homogeneous and triblock patchy). We find that the curved interface allows us to effectively control the orientation of the rods, allowing us to achieve parallel, perpendicular, or novel obliquely orientations with respect to the cylindrical drop. In addition, by tuning particle properties to achieve parallel alignment of the rods, we show that the cylindrical drop geometry favors tip-to-tip assembly of the rods, not just for cylinders, but also for ellipsoids and triblock patchy rods. Finally, for triblock patchy rods with larger contact line undulations, we can achieve strong spatial confinement of the rods transverse to the cylindrical drop due to the capillary repulsion between the contact line undulations of the particle and the pinned contact lines of the sessile drop. Our capillary assembly method allows us to manipulate the configuration of single and multiple rod-like particles and therefore offers a facile strategy for organizing such particles into useful functional materials.


J. W. den Hartogh, A. Yague Lopez, B. Cseh, M. Pignatari, B. Vilagos, M. P. Roriz, C. B. Pereira, N. A. Drake, S. Junqueira and M. Lugaro, 2023-04-17, Barium stars as tracers of s-process nucleosynthesis in AGB stars: II. Using machine learning techniques on 169 stars, Astronomy & Astrophysics, doi: 10.1051/0004-6361/202244189

Abstract

Context. Barium (Ba) stars are characterised by an abundance of heavy elements made by the slow neutron capture process (s-process). This peculiar observed signature is due to the mass transfer from a stellar companion, bound in a binary stellar system, to the Ba star observed today. The signature is created when the stellar companion is an asymptotic giant branch (AGB) star.
Aims. We aim to analyse the abundance pattern of 169 Ba stars using machine learning techniques and the AGB final surface abundances predicted by the FRUITY and Monash stellar models.
Methods. We developed machine learning algorithms that use the abundance pattern of Ba stars as input to classify the initial mass and metallicity of each Ba star’s companion star using stellar model predictions. We used two algorithms. The first exploits neural networks to recognise patterns, and the second is a nearest-neighbour algorithm that focuses on finding the AGB model that predicts the final surface abundances closest to the observed Ba star values. In the second algorithm, we included the error bars and observational uncertainties in order to find the best-fit model. The classification process was based on the abundances of Fe, Rb, Sr, Zr, Ru, Nd, Ce, Sm, and Eu. We selected these elements by systematically removing s-process elements from our AGB model abundance distributions and identifying the elements whose removal had the biggest positive effect on the classification. We excluded Nb, Y, Mo, and La. Our final classification combined the output of both algorithms to identify an initial mass and metallicity range for each Ba star companion.
Results. With our analysis tools, we identified the main properties for 166 of the 169 Ba stars in the stellar sample. The classifications based on both stellar sets of AGB final abundances show similar distributions, with an average initial mass of M = 2.23 Mʘ and 2.34 Mʘ and an average [Fe/H] = -0.21 and -0.11, respectively. We investigated why the removal of Nb, Y, Mo, and La improves our classification and identified 43 stars for which the exclusion had the biggest effect. We found that these stars have statistically significant and different abundances for these elements compared to the other Ba stars in our sample. We discuss the possible reasons for these differences in the abundance patterns.


Harshal Deshmukh, Kazeem A. Adeleke, Emmanuel Ssemmondo, Emma G. Wilmot, Najeeb Shah, Beatrice Pieri, Robert Gregory, Anne Kilvert, Alistair Lumb, Peter Christian, Dennis Barnes, Jane Patmore, Chris Walton, Robert E. J. Ryder, Thozhukat Sathyapalan, 2023-03-30, Ethnic disparities in people accessing FreeStyle Libre in the United Kingdom: Insights from the Association of British Clinical Diabetologists audit, Diabetic Medicine, doi: 10.1111/dme.15095

Abstract


Laird, A. M.; Lugaro, M.; Kankainen, A.; Adsley, P.; Bardayan, D. W.; Brinkman, H. E.; Cote, B.; Deibel, C. M.; Diehl, R.; Hammache, F.; den Hartogh, J. W.; Jose, J.; Kurtulgil, D.; Lederer-Woods, C.; Lotay, G.; Meynet, G.; Palmerini, S.; Pignatari, M.; Reifarth, R.; de Sereville, N.; Sieverding, A.; Stancliffe, R. J.; Trueman, T. C. L.; Lawson, T.; Vink, J. S.; Massimi, C.; Mengoni, A., 2023-02-28, Progress on nuclear reaction rates affecting the stellar production of 26Al, Journal of Physics G: Nuclear and Particle Physics, doi: 10.1088/1361-6471/ac9cf8

Abstract

The radioisotope 26Al is a key observable for nucleosynthesis in the Galaxy and the environment of the early Solar System. To properly interpret the large variety of astronomical and meteoritic data, it is crucial to understand both the nuclear reactions involved in the production of 26Al in the relevant stellar sites and the physics of such sites. These range from the winds of low- and intermediate-mass asymptotic giant branch stars; to massive and very massive stars, both their Wolf-Rayet winds and their final core-collapse supernovae (CCSN); and the ejecta from novae, the explosions that occur on the surface of a white dwarf accreting material from a stellar companion. Several reactions affect the production of 26Al in these astrophysical objects, including (but not limited to) 25Mg(p, γ)26Al, 26Al(p, γ)27Si, and 26Al(n, p/α). Extensive experimental effort has been spent during recent years to improve our understanding of such key reactions. Here we present a summary of the astrophysical motivation for the study of 26Al, a review of its production in the different stellar sites, and a timely evaluation of the currently available nuclear data. We also provide recommendations for the nuclear input into stellar models and suggest relevant, future experimental work.


Najeeb Shah, Harshal Deshmukh, Emma G. Wilmot, Jane Patmore, Peter Christian, Dennis J. Barnes, Chris Walton, Robert E. J. Ryder, Thozhukat Sathyapalan, 2023-02-16, The long-term impact of glucose monitoring with the FreeStyle Libre on glycaemic control and hypoglycaemia awareness in people with type 1 diabetes: Insights from the Association of British Clinical Diabetologists national audit, Diabetic Medicine, doi: 10.1111/dme.15070

Abstract

Aims
To investigate the change in glycated haemoglobin (HbA1c), hypoglycaemia awareness and diabetes-related distress in people with type 1 diabetes (T1D) using FreeStyle Libre (FSL) over a 2-year follow-up period.

Methods
FSL user data from U.K wide hospitals collected during routine clinical care were analysed. People living with T1D were categorised into four groups based on the duration of follow-up. Group I (< 1 year, n = 6940), group II (1 to 1.5 years, n = 662), group III (1.5 to 2 years, n = 385), and group IV (> 2 years, n = 642). The t-test was used to compare the baseline and follow-up HbA1c, GOLD score (a measure of hypoglycaemia awareness) and diabetes-related distress scale (DDS score) (quality of life measure).

Results
The study consisted of 16,834 people, with follow-up data available for 8,629 participants. The change in HbA1c, GOLD and DDS score from baseline within the follow-up sub-groups (group I vs group II vs group III vs group IV) was HbA1c (-6 vs -6 vs -4 vs -4 mmol/mol; p < 0.001) (-0.55 vs -0.55 vs -0.37 vs -0.37 %), GOLD score (-0.31 vs -0.45 vs -0.26 vs -0.42; p < 0.0001 group I, II, IV and p 0.07 group III), and DDS score(-0.59 vs -0.58 vs -0.63 vs -0.50; p < 0.001), respectively.

Conclusions
In people with T1D, FSL use resulted in a sustained improvement in HbA1c, hypoglycaemia awareness and diabetes-related distress for over two years.


Ling Qin, Zhiguo Zhang, Baisong Guo, Wei Li & Jiawei Mi, 2023-02-11, Determining the Critical Fracture Stress of Al Dendrites near the Melting Point via Synchrotron X-ray Imaging, Acta Metallurgica Sinica, doi: 10.1007/s40195-023-01531-w

Abstract

Dendrites are the most common microstructural features in the cast metals, significantly affecting the structure integrity and mechanical properties of the castings. In this study, the in situ synchrotron X-ray radiographic and tomographic imaging techniques were combined to evaluate the critical fracture stress of the growing dendrite tip during the solidification of an Al-15 wt% Cu alloy under an external electromagnetic force. Two dendritic 3D models have been proposed to simulate the dendrite 3D morphologic characteristics and thus revealed that the critical fracture stresses of the Al dendrites at temperatures close to its melting point were in the range of 0.5 kPa-0.05 MPa. The present results demonstrate the feasibility of measuring the high-temperature mechanical properties of the metallic dendrites.


Peter Hoppe, Jan Leitner, Marco Pignatari, and Sachiko Amari, 2023-02-01, New Constraints for Supernova Models from Presolar Silicon Carbide X Grains with Very High 26Al/27Al Ratios, The Astrophysical Journal Letters, doi: 10.3847/2041-8213/acb157

Abstract

We report C, N, Mg-Al, Si, and S isotope data of six 1-3 μm-sized SiC grains of Type X from the Murchison CM2 chondrite, believed to have formed in the ejecta of core-collapse supernova (CCSN) explosions. Their C, N, and Si isotopic compositions are fully compatible with previously studied X grains. Magnesium is essentially monoisotopic 26Mg which gives clear evidence for the decay of radioactive 26Al. Inferred initial 26Al/27Al ratios are between 0.6 and 0.78 which is at the upper end of previously observed ratios of X grains. Contamination with terrestrial or solar system Al apparently is low or absent, which makes the X grains from this study particularly interesting and useful for a quantitative comparison of Al isotope data with predictions from supernova models. The consistently high 26Al/27Al ratios observed here may suggest that the lower 26Al/27Al ratios of many X grains from the literature are the result of significant Al contamination and in part also of an improper quantification of 26Al. The real dispersion of 26Al/27Al ratios in X grains needs to be explored by future studies. The high observed 26Al/27Al ratios in this work provide a crucial constraint for the production of 26Al in CCSN models. We explored different CCSN models, including both “classical” and H ingestion CCSN models. It is found that the classical models cannot account for the high 26Al/27Al ratios observed here; in contrast, H ingestion models are able to reproduce the 26Al/27Al ratios along with C, N, and Si isotopic ratios reasonably well.


C. J. Lloyd, K. Mittal, S. Dutta, R. M. Dorrell, J. Peakall, G. M. Keevil and A. D. Burnsa, 2023-02-01, Multi-fidelity modelling of shark skin denticle flows: insights into drag generation mechanisms, Royal Society Open Science, doi: 10.1098/rsos.220684

Abstract

We investigate the flow over smooth (non-ribletted) shark skin denticles in an open-channel flow using direct numerical simulation (DNS) and two Reynolds averaged Navier-Stokes (RANS) closures. Large peaks in pressure and viscous drag are observed at the denticle crown edges, where they are exposed to high-speed fluid which penetrates between individual denticles, increasing shear and turbulence. Strong lift forces lead to a positive spanwise torque acting on individual denticles, potentially encouraging bristling if the denticles were not fixed. However, DNS predicts that denticles ultimately increase drag by 58% compared to a flat plate. Good predictions of drag distributions are obtained by RANS models, although an underestimation of turbulent kinetic energy production leads to an underprediction of drag. Nevertheless, RANS methods correctly predict trends in the drag data and the regions contributing most to viscous and pressure drag. Subsequently, RANS models are used to investigate the dependence of drag on the flow blockage ratio (boundary layer to roughness height ratio), finding that the drag increase due to denticles is halved when the blockage ratio δ/h is increased from 14 to 45. Our results provide an integrated understanding of the drag over non-ribletted denticles, enabling existing diverse drag data to be explained.


Michele Scandola, Emily S. Cross, Nathan Caruana & Emmanuele Tidoni, 2023-01-24, Body Form Modulates the Prediction of Human and Artificial Behaviour from Gaze Observation, International Journal of Social Robotics, doi: 10.1007/s12369-022-00962-2

Abstract

The future of human-robot collaboration relies on people’s ability to understand and predict robots’ actions. The machine-like appearance of robots, as well as contextual information, may influence people’s ability to anticipate the behaviour of robots. We conducted six separate experiments to investigate how spatial cues and task instructions modulate people’s ability to understand what a robot is doing. Participants observed goal-directed and non-goal directed gaze shifts made by human and robot agents, as well as directional cues displayed by a triangle. We report that biasing an observer’s attention, by showing just one object an agent can interact with, can improve people’s ability to understand what humanoid robots will do. Crucially, this cue had no impact on people’s ability to predict the upcoming behaviour of the triangle. Moreover, task instructions that focus on the visual and motor consequences of the observed gaze were found to influence mentalising abilities. We suggest that the human-like shape of an agent and its physical capabilities facilitate the prediction of an upcoming action. The reported findings expand current models of gaze perception and may have important implications for human-human and human-robot collaboration.


Umberto Battino, Claudia Lederer-Woods, Marco Pignatari, Benjamin Soos, Maria Lugaro, Diego Vescovi, Sergio Cristallo, Philip J Woods, Amanda Karakas, 2023-01-12, Impact of newly measured 26Al(n, p)26Mg and 26Al(n, α)23Na reaction rates on the nucleosynthesis of 26Al in stars, Monthly Notices of the Royal Astronomical Society, doi: 10.1093/mnras/stad106

Abstract

The cosmic production of the short-lived radioactive nuclide 26Al is crucial for our understanding of the evolution of stars and galaxies. However, simulations of the stellar sites producing 26Al are still weakened by significant nuclear uncertainties. We re-evaluate the 26Al(n, p)26Mg and 26Al(n, α)23Na ground state reactivities from 0.01 GK to 10 GK, based on the recent n_TOF measurement combined with theoretical predictions and a previous measurement at higher energies, and test their impact on stellar nucleosynthesis. We computed the nucleosynthesis of low- and high-mass stars using the Monash nucleosynthesis code, the NuGrid mppnp code, and the FUNS stellar evolutionary code. Our low-mass stellar models cover the 2-3 M⊙ mass range with metallicities between Z=0.01 and 0.02, their predicted 26Al/27Al ratios are compared to 62 meteoritic SiC grains. For high-mass stars, we test our reactivities on two 15 M⊙ models with Z=0.006 and 0.02. The new reactivities allow low-mass AGB stars to reproduce the full range of 26Al/27Al ratios measured in SiC grains. The final 26Al abundance in high-mass stars, at the point of highest production, varies by a factor of 2.4 when adopting the upper, or lower, limit of our rates. However, stellar uncertainties still play an important role in both mass regimes. The new reactivities visibly impact both low- and high-mass stars nucleosynthesis and allow a general improvement in the comparison between stardust SiC grains and low-mass star models. Concerning explosive nucleosynthesis, an improvement of the current uncertainties between T9∼0.3 and 2.5 is needed for future studies.


Alana C. Sharp, Hugo Dutel, Peter J. Watson, Flora Groning, Nick Crumpton, Michael J. Fagan, Susan E. Evans, 2023-01-11, Assessment of the mechanical role of cranial sutures in the mammalian skull: Computational biomechanical modelling of the rat skull, Journal of Morphology, doi: 10.1002/jmor.21555

Abstract

Cranial sutures are fibrocellular joints between the skull bones that are progressively replaced with bone throughout ontogeny, facilitating growth and cranial shape change. This transition from soft tissue to bone is reflected in the biomechanical properties of the craniofacial complex. However, the mechanical significance of cranial sutures has only been explored at a few localised areas within the mammalian skull, and as such our understanding of suture function in overall skull biomechanics is still limited. Here, we sought to determine how the overall strain environment is affected by the complex network of cranial sutures in the mammal skull. We combined two computational biomechanical methods, multibody dynamics analysis and finite element analysis, to simulate biting in a rat skull and compared models with and without cranial sutures. Our results show that including complex sutures in the rat model does not substantially change overall strain gradients across the cranium, particularly strain magnitudes in the bones overlying the brain. However, local variations in strain magnitudes and patterns can be observed in areas close to the sutures. These results show that, during feeding, sutures may be more important in some regions than others. Sutures should therefore be included in models that require accurate local strain magnitudes and patterns of cranial strain, particularly if models are developed for analysis of specific regions, such as the temporomandibular joint or zygomatic arch. Our results suggest that, for mammalian skulls, cranial sutures might be more important for allowing brain expansion during growth than redistributing biting loads across the cranium in adults.


Kate A Womack, Fiorenzo Vincenzo, Brad K Gibson, Benoit Cote, Marco Pignatari, Hannah E Brinkman, Paolo Ventura, Amanda Karakas, 2023-01, Chemical evolution of fluorine in the Milky Way, Monthly Notices of the Royal Astronomical Society, doi: 10.1093/mnras/stac3180

Abstract

Fluorine has many different potential sites and channels of production, making narrowing down a dominant site of fluorine production particularly challenging. In this work, we investigate which sources are the dominant contributors to the galactic fluorine by comparing chemical evolution models to observations of fluorine abundances in Milky Way stars covering a metallicity range of −2<[Fe/H]<0.4 and upper limits in the range of −3.4<[Fe/H]<−2.3. In our models, we use a variety of stellar yield sets in order to explore the impact of varying both asymptotic giant branch (AGB) and massive star yields on the chemical evolution of fluorine. In particular, we investigate different prescriptions for initial rotational velocity in massive stars as well as a metallicity-dependent mix of rotational velocities. We find that the observed [F/O] and [F/Fe] abundance ratios at low metallicity and the increasing trend of [F/Ba] at [Fe/H]~>−1 can only be reproduced by chemical evolution models assuming, at all metallicities, a contribution from rapidly rotating massive stars with initial rotational velocities as high as 300km s−1. A mix of rotational velocities may provide a more physical solution than the sole use of massive stars with vrot = 300kms−1, which are predicted to overestimate the fluorine and average s-process elemental abundances at [Fe/H]~>−1. The contribution from AGB stars is predicted to start at [Fe/H]&asymp−1 and becomes increasingly important at high metallicity, being strictly coupled to the evolution of the nitrogen abundance. Finally, by using modern yield sets, we investigate the fluorine abundances of Wolf-Rayet winds, ruling them out as dominant contributors to the galactic fluorine.


S Huang, L Qin, J Zhao, K Xiang, S Luo, S Michalik and J Mi, 2023-01, Revealing atomic structure evolution of an Al-1.5Fe alloy in the liquid state using X-ray total scattering and empirical potential structure refinement, IOP Conference Series: Materials Science and Engineering, doi: 10.1088/1757-899X/1274/1/012007

Abstract

We used in-situ real-time synchrotron X-ray total scattering and empirical potential structure refinement method to study the evolution of atomic structure of an Al-1.5Fe alloy melt from 750oC to 630oC. Detailed data normalization and analyses for the total scattering data were presented in order to achieve sensible atomic structure simulation using the empirical potential structure refinement (EPSR) method with constraints of R-factor is < 10-3. Reliable construction of 3D atomic structure of Al-Fe melt in the temperature range reveals that more Al atoms coordinate Fe atoms and the Fe-centered clusters get more compact with the temperature decreases. More systematic work linking the liquid structure to the nucleation structure is under way.



2022 (33 outputs)

Donatello Pagnotto, Alina Muravitskaya, David M. Benoit, Jean-Sebastien G. Bouillard, and Ali M. Adawi, 2022-12-20, Stark Effect Control of the Scattering Properties of Plasmonic Nanogaps Containing an Organic Semiconductor, ACS Applied Optical Materials, doi: 10.1021/acsaom.2c00135

Abstract

The development of actively tunable plasmonic nanostructures enables real-time reconfigurable and on-demand enhancement of optical signals. This is an essential requirement for a wide range of applications such as sensing and nanophotonic devices, for which electrically driven tunability is required. By modifying the transition energies of a material via the application of an electric field, the Stark effect offers a reliable and practical approach to achieve such tunability. In this work, we report on the use of the Stark effect to control the scattering response of a plasmonic nanogap formed between a silver nanoparticle and an extended silver film separated by a thin layer of the organic semiconductor PQT-12. The plasmonic response of such nanoscattering sources follows the quadratic Stark shift. In addition, our approach allows one to experimentally determine the polarizability of the semiconductor material embedded in the nanogap region, offering a new approach to probe the excitonic properties of extremely thin semiconducting materials such as 2D materials under applied external electric field with nanoscale resolution.


Bastianon, E. and Hope, J. A. and Dorrell, R. M. and Parsons, D. R., 2022-11, Effect of hydro-climate variation on biofilm dynamics and its impact in intertidal environments, Earth Surface Dynamics, doi: 10.5194/esurf-10-1115-2022

Abstract

Shallow tidal environments are very productive ecosystems but are sensitive to environmental changes and sea level rise. Bio-morphodynamic control of these environments is therefore a crucial consideration; however, the effect of small-scale biological activity on large-scale cohesive sediment dynamics like tidal basins and estuaries is still largely unquantified. This study advances our understanding by assessing the influence of biotic and abiotic factors on biologically cohesive sediment transport and morphology. An idealised benthic biofilm model is incorporated in a 1D morphodynamic model of tide-dominated channels. This study investigates the effect of a range of environmental and biological conditions on biofilm growth and their feedback on the morphological evolution of the entire intertidal channel. By carrying out a sensitivity analysis of the bio-morphodynamic model, parameters like (i) hydrodynamic disturbances, (ii) seasonality, (iii) biofilm growth rate, (iv) temperature variation and (v) bio-cohesivity of the sediment are systematically changed. Results reveal that key parameters such as growth rate and temperature strongly influence the development of biofilm and are key determinants of equilibrium biofilm configuration and development under a range of disturbance periodicities and intensities. Long-term simulations of intertidal channel development demonstrate that the hydrodynamic disturbances induced by tides play a key role in shaping the morphology of the bed and that the presence of surface biofilm increases the time to reach morphological equilibrium. In locations characterised by low hydrodynamic forces, the biofilm grows and stabilises the bed, inhibiting the transport of coarse sediment (medium and fine sand). These findings suggest biofilm presence in channel beds results in intertidal channels that have significantly different characteristics in terms of morphology and stratigraphy compared abiotic sediments. It is concluded that inclusion of bio-cohesion in morphodynamic models is essential to predict estuary development and mitigate coastal erosion.


Thomas W. Price, Isaline Renard, Timothy J. Prior, Vojtech Kubicek, David M. Benoit, Stephen J. Archibald, Anne-Marie Seymour, Petr Hermann, and Graeme J. Stasiuk, 2022-10-17, Bn2DT3A, a Chelator for 68Ga Positron Emission Tomography: Hydroxide Coordination Increases Biological Stability of [68Ga][Ga(Bn2DT3A)(OH)], Inorganic Chemistry, doi: 10.1021/acs.inorgchem.2c01992

Abstract

The chelator Bn2DT3A was used to produce a novel 68Ga complex for positron emission tomography (PET). Unusually, this system is stabilized by a coordinated hydroxide in aqueous solutions above pH 5, which confers sufficient stability for it to be used for PET. Bn2DT3A complexes Ga3+ in a hexadentate manner, forming a mer-mer complex with log K([Ga(Bn2DT3A)]) = 18.25. Above pH 5, the hydroxide ion coordinates the Ga3+ ion following dissociation of a coordinated amine. Bn2DT3A radiolabeling displayed a pH-dependent speciation, with [68Ga][Ga(Bn2DT3A)(OH)] being formed above pH 5 and efficiently radiolabeled at pH 7.4. Surprisingly, [68Ga][Ga(Bn2DT3A)(OH)] was found to show an increased stability in vitro (for over 2 h in fetal bovine serum) compared to [68Ga][Ga(Bn2DT3A)]. The biodistribution of [68Ga][Ga(Bn2DT3A)(OH)] in healthy rats showed rapid clearance and excretion via the kidneys, with no uptake seen in the lungs or bones.


Anne W. Baar, Lisanne Braat, Daniel R. Parsons, 2022-10-17, Control of river discharge on large-scale estuary morphology, Earth Surface Processes and Landforms, doi: 10.1002/esp.5498

Abstract

Estuaries are dynamic landscapes with complex bar and channel patterns formed by interactions between tidal and fluvial currents. River discharge dampens the tidal wave, enhances the ebb flow, and supplies sediment to the estuary. However, it is largely unknown how river discharge influences overall estuary morphology. The objective of the current study is to quantify the control of river discharge on bar and channel dimensions and sediment transport throughout the estuary. To this end, a long-term and large-scale Delft3D-2DH estuary model was designed with a suite of model runs undertaken where discharge systematically varied. Results show that tide-dominated estuaries with significant river discharge can develop towards a dynamic equilibrium with a constant tidal prism through adjustment of channel dimensions to accommodate the supplied river discharge. It is essential to account for this morphodynamic adjustment when considering the transition from tide-dominated estuaries to aggrading river-dominated estuaries. After this transition, the estuary evolution depends on the discharge-to-width ratio. Tidal prism either decreases with higher river discharge as the tidal flow is dampened and the estuary aggrades, or increases when the estuary widens as it adjusts to the increase in total discharge. Additionally, results show that a higher river discharge increases the difference between the limit of flood-dominant sediment transport and the limit of flow reversal, which has important implications for the preservation of the tidal signal in the stratigraphy. Estuary dimensions and channel patterns can be described as a function of river and tidal discharge. These findings indicate that the dynamic spatial component in numerical models is crucial in predicting trends in long-term estuary morphology as well as in inverse predictions from stratigraphy.


Andrew I. Furness, Isabella Capellini, 2022-10-01, The reproductive ecology drivers of egg attendance in amphibians, Ecology Letters, doi: 10.1111/ele.14109

Abstract

Parental care is extremely diverse but, despite much research, why parental care evolves is poorly understood. Here we address this outstanding question using egg attendance, the simplest and most common care form in many taxa. We demonstrate that, in amphibians, terrestrial egg deposition, laying eggs in hidden locations and direct development promote the evolution of female egg attendance. Male egg attendance follows the evolution of hidden eggs and is associated with terrestrial egg deposition but not with direct development. We conclude that egg attendance, particularly by females, evolves following changes in reproductive ecology that are likely to increase egg survival, select for small clutches of large eggs and/or expose eggs to new environmental challenges. While our results resolve a long-standing question on whether reproductive ecology traits are drivers, consequences or alternative solutions to caring, they also unravel important, yet previously unappreciated, differences between the sexes.


Gao, B. and Jiao, T. Y. and Li, Y. T. and Chen, H. and Lin, W. P. and An, Z. and Ru, L. H. … and Pignatari, M., 2022-09-23, Deep Underground Laboratory Measurement of ¹³C(α,n)¹⁶O in the Gamow Windows of the 𝑠 and 𝑖 Processes, Physical Review Letters, doi: 10.1103/PhysRevLett.129.132701

Abstract

The ¹³C(α(α,n)¹⁶O reaction is the main neutron source for the slow-neutron-capture process in asymptotic giant branch stars and for the intermediate process. Direct measurements at astrophysical energies in above-ground laboratories are hindered by the extremely small cross sections and vast cosmic-ray-induced background. We performed the first consistent direct measurement in the range of 𝐸c.m.=0.24 to 1.9 MeV using the accelerators at the China Jinping Underground Laboratory and Sichuan University. Our measurement covers almost the entire intermediate process Gamow window in which the large uncertainty of the previous experiments has been reduced from 60% down to 15%, eliminates the large systematic uncertainty in the extrapolation arising from the inconsistency of existing datasets, and provides a more reliable reaction rate for the studies of the slow-neutron-capture and intermediate processes along with the first direct determination of the alpha strength for the near-threshold state.


Jordan Schofield, Marco Pignatari, Richard J Stancliffe, Peter Hoppe, 2022-09-08, Isotopic ratios for C, N, Si, Al, and Ti in C-rich presolar grains from massive stars, Monthly Notices of the Royal Astronomical Society, doi: 10.1093/mnras/stac2498

Abstract

Certain types of silicon carbide (SiC) grains, e.g. SiC-X grains, and low density (LD) graphites are C-rich presolar grains that are thought to have condensed in the ejecta of core-collapse supernovae (CCSNe). In this work, we compare C, N, Al, Si, and Ti isotopic abundances measured in presolar grains with the predictions of 21 CCSN models. The impact of a range of SN explosion energies is considered, with the high energy models favouring the formation of a C/Si zone enriched in 12C, 28Si, and 44Ti. Eighteen of the 21 models have H ingested into the He-shell and different abundances of H remaining from such H-ingestion. CCSN models with intermediate to low energy (that do not develop a C/Si zone) cannot reproduce the 28Si and 44Ti isotopic abundances in grains without assuming mixing with O-rich CCSN ejecta. The most 28Si-rich grains are reproduced by energetic models when material from the C/Si zone is mixed with surrounding C-rich material, and the observed trends of the 44Ti/48Ti and 49Ti/48Ti ratios are consistent with the C-rich C/Si zone. For the models with H-ingestion, high and intermediate explosion energies allow the production of enough 26Al to reproduce the 26Al/27Al measurements of most SiC-X and LD graphites. In both cases, the highest 26Al/27Al ratio is obtained with H still present at XH ≈ 0.0024 in He-shell material when the SN shock is passing. The existence of H in the former convective He-shell points to late H-ingestion events in the last days before massive stars explode as a supernova.


Ling Qin, Kyriakos Porfyrakis, Iakovos Tzanakis, Nicole Grobert, Dmitry G. Eskine, Kamel Fezzaa, Jiawei Mi, 2022-09-06, Multiscale interactions of liquid, bubbles and solid phases in ultrasonic fields revealed by multiphysics modelling and ultrafast X-ray imaging, Ultrasonics Sonochemistry, doi: 10.1016/j.ultsonch.2022.106158

Abstract

The volume of fluid (VOF) and continuous surface force (CSF) methods were used to develop the bubble dynamic models for the simulation of bubble oscillation and implosion dynamics under ultrasound. The model was calibrated and validated by the X-ray image data acquired by ultrafast synchrotron X-ray. Coupled bubble interactions with bulk graphite and freely moving particles were also simulated based on the validated models. Simulation and experiments revealed the surface instability developed along the bubble surface under the influence of ultrasound fields. Once the surface instability exceeds a certain amplitude, bubble implosion occurs, creating shock waves and highly deformed, irregular bubble boundaries and smaller bubble fragments. Bubble implosion can produce cyclic impulsive stresses sufficient enough to cause µs fatigue exfoliation of graphite layers. Bubble-particle interaction simulations reveal the underlying mechanisms for efficient particle dispersion or particle wrapping which are all strongly related to the oscillation dynamics of the bubbles and the particle surface properties.


Ian U. Roederer, John J. Cowan, Marco Pignatari, Timothy C. Beers, Elizabeth A. Den Hartog, Rana Ezzeddine, Anna Frebel, Terese T. Hansen, Erika M. Holmbeck, Matthew R. Mumpower, Vinicius M. Placco, Charli M. Sakari, Rebecca Surman and Nicole Vassh, 2022-09-01, The R-Process Alliance: Abundance Universality among Some Elements at and between the First and Second R-Process Peaks, The Astrophysical Journal, doi: 10.3847/1538-4357/ac85bc

Abstract

We present new observational benchmarks of rapid neutron-capture process (r-process) nucleosynthesis for elements at and between the first (A ~ 80) and second (A ∼ 130) peaks. Our analysis is based on archival ultraviolet and optical spectroscopy of eight metal-poor stars with Se (Z = 34) or Te (Z = 52) detections, whose r-process enhancement varies by more than a factor of 30 (−0.22 ≤ [Eu/Fe] ≤ +1.32). We calculate ratios among the abundances of Se, Sr through Mo (38 ≤ Z ≤ 42), and Te. These benchmarks may offer a new empirical alternative to the predicted solar system r-process residual pattern. The Te abundances in these stars correlate more closely with the lighter r-process elements than the heavier ones, contradicting and superseding previous findings. The small star-to-star dispersion among the abundances of Se, Sr, Y, Zr, Nb, Mo, and Te (≤0.13 dex, or 26%) matches that observed among the abundances of the lanthanides and third r-process-peak elements. The concept of r-process universality that is recognized among the lanthanide and third-peak elements in r-process-enhanced stars may also apply to Se, Sr, Y, Zr, Nb, Mo, and Te, provided the overall abundances of the lighter r-process elements are scaled independently of the heavier ones. The abundance behavior of the elements Ru through Sn (44 ≤ Z ≤ 50) requires further study. Our results suggest that at least one relatively common source in the early Universe produced a consistent abundance pattern among some elements spanning the first and second r-process peaks.


Changbom Park and Jaehyun Lee and Juhan Kim and Donghui Jeong and Christophe Pichon and Brad K. Gibson and Owain N. Snaith and Jihye Shin and Yonghwi Kim and Yohan Dubois and C. Gareth Few, 2022-09, Formation and Morphology of the First Galaxies in the Cosmic Morning, The Astrophysical Journal, doi: 10.3847/1538-4357/ac85b5

Abstract

We investigate the formation and morphological evolution of the first galaxies in the cosmic morning (10 ≳ z ≳ 4) using the Horizon Run 5 (HR5) simulation. For galaxies above the stellar mass ${M}_{\star ,\min }=2\times {10}^{9}\,{M}_{\odot }$, we classify them into disk, spheroid, and irregular types according to their asymmetry and stellar-mass morphology. We find that about two-thirds of the galaxies have a Sérsic index <1.5, reflecting the dominance of disk-type morphology in the cosmic morning. The rest are evenly distributed as incidental and transient irregulars or spheroids. These fractions are roughly independent of redshift and stellar mass up to ∼1010 M⊙. Almost all the first galaxies with ${M}_{\star }\gt {M}_{\star ,\min }$ at z > 4 form at initial peaks of the matter-density field. Large-scale structures in the universe emerge and grow like cosmic rhizomes as the underlying matter-density fluctuations grow and form associations of galaxies in rare overdense regions and the realm of the galactic world is stretched into relatively lower-density regions along evolving filaments. The cosmic web of galaxies forms at lower redshifts when most rhizomes globally percolate. The primordial angular momentum produced by the induced tidal torques on protogalactic regions is correlated with the internal kinematics of galaxies and tightly aligned with the angular momentum of the total galaxy mass. The large-scale tidal field imprinted in the initial conditions seems responsible for the dominance of disk morphology and for the tendency of galaxies to reacquire a disk postdistortion.


Harshal Deshmukh, Emma Wilmot, Beatrice Pieri, Pratik Choudhary, Najeeb Shah, Robert Gregory, Anne Kilvert, Alistair Lumb, Peter Christian, Dennis Barnes, Jane Patmore, Chris Walton, Robert E. J. Ryder, Thozhukat Sathyapalan, 2022-08-26, Time in range following flash glucose monitoring: Relationship with glycaemic control, diabetes-related distress and resource utilisation in the Association of British Clinical Diabetologists national audit, Diabetic Medicine, doi: 10.1111/dme.14942

Abstract

Aims
The aim of this study was to understand the relationship between time in range (TIR) achieved using the isCGM with changes in glycaemic control, diabetes-related distress (DRD) and resource utilisation in people living with diabetes.

Methods
Clinicians from 106 National Health System (NHS) UK hospitals submitted isCGM user baseline and follow-up data in a web-based tool held within the UK NHS network. Linear regression analysis was used to identify the relationship between follow-up glucose TIR (3.9–10 mmol/L) categories (TIR% 50–70 and TIR% >70) with change in haemoglobin A1c (HbA1c), DRD and Gold score (measure of hypoglycaemia unawareness, where a score ≥4 suggests impaired awareness of hypoglycaemia).

Results
Of 16,427 participants, 1241 had TIR follow-up data available. In this cohort, the mean TIR was 44.8% (±22.5). With the use of isCGM, at 7.9 months mean follow-up, improvements were observed in HbA1c (−6.9 [13.5] mmol/mol, p < 0.001), Gold score (−0.35 [1.5], p < 0.001) and Diabetes Distress Screening (−0.73 [1.23], p < 0.001). In the regression analysis restricted to people living with type 1 diabetes, TIR% 50–70 was associated with a −8.9 mmol/mol (±0.6, p < 0.001) reduction in HbA1c; TIR% >70 with a −14 mmol/mol (±0.8, p < 0.001) reduction in HbA1c. Incremental improvement in TIR% was also associated with significant improvements in Gold score and DRD. TIR% >70 was associated with no hospital admissions due to hypoglycaemia, hyperglycaemia/diabetic ketoacidosis, and a 60% reduction in the paramedic callouts and 77% reduction in the incidence of severe hypoglycaemia.

Conclusion
In a large cohort of UK isCGM users, we demonstrate a significant association of higher TIR% with improvement in HbA1c, hypoglycaemia awareness, DRD and resource utilisation.


Mishenina, T., Pignatari, M., Gorbaneva, T., Cote, B., Yague Lopez, A., Thielemann, F. K., Soubiran, C, 2022-08-25, Enrichment of the Galactic disc with neutron-capture elements: Gd, Dy, and Th, Monthly Notices of the Royal Astronomical Society, doi: 10.1093/mnras/stac2361

Abstract

The study of the origin of heavy elements is one of the main goals of nuclear astrophysics. In this paper, we present new observational data for the heavy r-process elements gadolinium (Gd, Z= 64), dysprosium (Dy, Z= 66), and thorium (Th, Z= 90) in a sample of 276 Galactic disc stars (-1.0 < [Fe/H] < + 0.3). The stellar spectra have a high resolution of 42 000 and 75 000, and the signal-to-noise ratio higher than 100. The LTE abundances of Gd, Dy, and Th have been determined by comparing the observed and synthetic spectra for three Gd lines (149 stars), four Dy lines (152 stars), and the Th line at 4019.13 Ã… (170 stars). For about 70 per cent of the stars in our sample, Gd and Dy are measured for the first time, and Th for 95 per cent of the stars. Typical errors vary from 0.07 to 0.16 dex. This paper provides the first extended set of Th observations in the Milky Way disc. Together with europium (Eu, Z= 63) data from our previous studies, we have compared these new observations with nucleosynthesis predictions and Galactic Chemical Evolution simulations. We confirm that [Gd/Fe] and [Dy/Fe] show the same behaviour of Eu. We study with GCE simulations the evolution of [Th/Fe] in comparison with [Eu/Fe], showing that unlike Eu, either the Th production is metallicity dependent in case of a unique source of the r-process in the Galaxy, or the frequency of the Th-rich r-process source is decreasing with the increase in [Fe/H].


Beatrice Pieri MBBS, Harshal Deshmukh PhD, Emma G. Wilmot PhD, Pratik Choudhary MD, Najeeb Shah MRCP, Robert Gregory DM, Dennis Barnes FRCP, Simon Saunders MD, Jane Patmore FRCP, Chris Walton FRCP, Robert E. J. Ryder MD, Thozhukat Sathyapalan MD, 2022-08-18, Impaired awareness of hypoglycaemia: Prevalence and associated factors before and after FreeStyle Libre use in the Association of British Clinical Diabetologists audit, Diabetes, Obesity and Metabolism: A Journal of Pharmacology and Therapeutics, doi: 10.1111/dom.14841

Abstract


Lugaro, Maria and Yague Lopez, Andres and Soos, Benjamin and Cote, Benoit and Peto, Maria and Vassh, Nicole and Wehmeyer, Benjamin and Pignatari, Marco, 2022-06-22, Origin of Plutonium-244 in the Early Solar System, Universe, doi: 10.3390/universe8070343

Abstract

We investigate the origin in the early Solar System of the short-lived radionuclide 244Pu (with a half life of 80 Myr) produced by the rapid (r) neutron-capture process. We consider two large sets of r-process nucleosynthesis models and analyse if the origin of 244Pu in the ESS is consistent with that of the other r and slow (s) neutron-capture process radioactive nuclei. Uncertainties on the r-process models come from both the nuclear physics input and the astrophysical site. The former strongly affects the ratios of isotopes of close mass (129I/127I, 244Pu/238U, and 247Pu/235U). The 129I/247Cm ratio, instead, which involves isotopes of a very different mass, is much more variable than those listed above and is more affected by the physics of the astrophysical site. We consider possible scenarios for the evolution of the abundances of these radioactive nuclei in the galactic interstellar medium and verify under which scenarios and conditions solutions can be found for the origin of 244Pu that are consistent with the origin of the other isotopes. Solutions are generally found for all the possible different regimes controlled by the interval (δ) between additions from the source to the parcel of interstellar medium gas that ended up in the Solar System, relative to decay timescales. If r-process ejecta in interstellar medium are mixed within a relatively small area (leading to a long δ), we derive that the last event that explains the 129I and 247Cm abundances in the early Solar System can also account for the abundance of 244Pu. Due to its longer half life, however, 244Pu may have originated from a few events instead of one only. If r-process ejecta in interstellar medium are mixed within a relatively large area (leading to a short δ), we derive that the time elapsed from the formation of the molecular cloud to the formation of the Sun was 9-16 Myr


Emmanuele Tidoni, Henning Holle, Michele Scandola, Igor Schindler, Loron Hill, Emily S. Cross, 2022-06-17, Human but not robotic gaze facilitates action prediction, iScience, doi: 10.1016/j.isci.2022.104462

Abstract

Do people ascribe intentions to humanoid robots as they would to humans or non-human-like animated objects? In six experiments, we compared people’s ability to extract non-mentalistic (i.e., where an agent is looking) and mentalistic (i.e., what an agent is looking at; what an agent is going to do) information from gaze and directional cues performed by humans, human-like robots, and a non-human-like object. People were faster to infer the mental content of human agents compared to robotic agents. Furthermore, although the absence of differences in control conditions rules out the use of non-mentalizing strategies, the human-like appearance of non-human agents may engage mentalizing processes to solve the task. Overall, results suggest that human-like robotic actions may be processed differently from humans’ and object’s behavior. These findings inform our understanding of the relevance of an object’s physical features in triggering mentalizing abilities and its relevance for human-robot interaction.


Quan Le Quan, Grigorios Vasilopoulos, Christopher Hackney, Daniel Parsons, Hung Nguyen Nghia, Stephen Darby, Robert Houseago, 2022-05, Sediment routing though the apex of a mega-delta under future anthropogenic impacts and climate change, EGU General Assembly 2022, doi: 10.5194/egusphere-egu22-9871

Abstract

Deltas are home to 4.5% of the global population and support a range of ecosystem services that are vital to lives and livelihoods. As low-lying regions, deltas are also amongst the most vulnerable areas to the threat climate change and relative sea-level rise, which are being exacerbated by ongoing local resource exploitation. Anthropogenic activities such as riverine sand mining, construction of flood embankments, deforestation and changes of land use and hydropower dams are disrupting the natural evolution of deltaic systems, with many of the world’s large deltas now being sediment starved. This is important because changes of the sediment flux into large deltas can have implications for the evolution of the morphology of delta bifurcations and their function at routing water and sediment seaward. This can amplify flood hazard and risk for riparian communities and intensify processes such as bank erosion, presenting hazards to human lives and exacerbating land loss. The present study focuses on the Chaktomuk junction at the apex of the Mekong delta, connecting the Mekong with the Tonle Sap Lake and the downstream delta. The junction is important as it provides the connection between the Mekong and the largest freshwater lake in Southeast Asia and because of the proximity of the junction to the rapidly expanding urban centre of Phnom Penh. We present a combined 2D hydrodynamic and sediment transport model for the Chaktomuk junction, constructed and based on high-resolution bathymetric data obtained with multibeam echosounders. A series of established sediment transport equations are adopted and tested through a sensitivity analysis to identify the most appropriate sediment transport solver for the model, which is then validated against field observations. The model was forced with a series of scenario combinations including changes of water and sediment flux and rates of sand mining. Simulation runs are presented that project the future evolution of the apex of the Mekong delta, including changes in bifurcation morphology, water and sediment routing seaward through delta distributary channels and changes in water and sediment exchanges between the Mekong and the Tonle Sap. The implications of these future trajectories will be discussed in terms of the sustainability of the delta to future change.


S. O. Morgan, A. Muravitskaya, C. Lowe, A. M. Adawi, J.-S. G. Bouillard, T. S. Horozov, G. J. Stasiuk and D. M. A. Buzza, 2022-04-25, Using adsorption kinetics to assemble vertically aligned nanorods at liquid interfaces for metamaterial applications, Physical Chemistry Chemical Physics, doi: 10.1039/D1CP05484H

Abstract

Vertically aligned monolayers of metallic nanorods have a wide range of applications as metamaterials or in surface enhanced Raman spectroscopy. However the fabrication of such structures using current top-down methods or through assembly on solid substrates is either difficult to scale up or have limited possibilities for further modification after assembly. The aim of this paper is to use the adsorption kinetics of cylindrical nanorods at a liquid interface as a novel route for assembling vertically aligned nanorod arrays that overcomes these problems. Specifically, we model the adsorption kinetics of the particle using Langevin dynamics coupled to a finite element model, accurately capturing the deformation of the liquid meniscus and particle friction coefficients during adsorption. We find that the final orientation of the cylindrical nanorod is determined by their initial attack angle when they contact the liquid interface, and that the range of attack angles leading to the end-on state is maximised when nanorods approach the liquid interface from the bulk phase that is more energetically favorable. In the absence of an external field, only a fraction of adsorbing nanorods end up in the end-on state (≲40% even for nanorods approaching from the energetically favourable phase). However, by pre-aligning the metallic nanorods with experimentally achievable electric fields, this fraction can be effectively increased to 100%. Using nanophotonic calculations, we also demonstrate that the resultant vertically aligned structures can be used as epsilon-near-zero and hyperbolic metamaterials. Our kinetic assembly method is applicable to nanorods with a range of diameters, aspect ratios and materials and therefore represents a versatile, low-cost and powerful platform for fabricating vertically aligned nanorods for metamaterial applications.


Shi Huang, Shifeng Luo, Ling Qin, Da Shu, Baode Sun, Alexander J G Lunt, Alexander M Korsunsky and Jiawei Mi, 2022-04-01, 3D local atomic structure evolution in a solidifying Al-0.4Sc dilute alloy melt revealed in operando by synchrotron X-ray total scattering and modelling, Scripta Materialia, doi: 10.1016/j.scriptamat.2021.114484

Abstract

Using synchrotron X-ray total scattering and empirical potential structure refinement modelling, we studied systematically in operando condition the disorder-to-order local atomic structure transition in a pure Al and a dilute Al-0.4Sc alloy melt in the temperature range from 690℃ to 657℃. In the liquid state, icosahedral short-range ordered Sc-centred Al polyhedrons form and most of them with Al coordination number of 10-12. As the melt is cooled to the semisolid state, the most Sc-centred polyhedrons become more connected atom clusters via vertex, edge and face-sharing. These polyhedrons exhibit partially icosahedral and partially face-centred-cubic symmetry. The medium-range ordered Sc-centred clusters with face-sharing are proved to be the “precursors” of the L12 Al3Sc primary phases in the liquid-solid coexisting state.


Iraj Vaezzadeh, Elke Roediger, Claire Cashmore, Matthew Hunt, John ZuHone, William Forman, Christine Jones, Ralph Kraft, Paul Nulsen, Yuanyuan Su, Eugene Churazov, 2022-03-30, Resilience of Sloshing Cold Fronts against subsequent minor mergers, Monthly Notices of the Royal Astronomical Society, doi: 10.1093/mnras/stac784

Abstract

Minor mergers are common in galaxy clusters. They have the potential to create sloshing cold fronts (SCFs) in the intracluster medium (ICM) of the cluster. However, the resilience of SCFs to subsequent minor mergers is unknown. Here we investigate the extent to which SCFs established by an off-axis minor merger are disrupted by a subsequent minor merger. We perform a suite of 13 hydrodynamic + N-body simulations of idealised triple cluster mergers in which we vary the approach direction and impact parameter of the tertiary cluster. Except for ~1 Gyr after the first core passage of the tertiary cluster, clear SCFs are present in all merger configurations. Subsequent head-on minor mergers reduce the number of SCFs significantly, while subsequent off-axis minor mergers only moderately reduce the number of SCFs. In particular, outer (⪆500kpc) SCFs are resilient. The results of this work indicate that SCFs are easily formed in the course of a minor merger and are long-lived even if a further minor merger takes place. SCFs thus should be ubiquitous, but deriving the merger history of a given cluster based on its observed SCFs might be more complex than previously thought.


Blissett R, Blissett D, Levrat-Guillen F, Deshmukh H, Wilmot EG, Ryder REJ, Walton C, Sathyapalan T., 2022-03-28, FreeStyle Libre Flash Glucose Monitoring system for people with type 1 diabetes in the UK: a budget impact analysis, BMJ Open Diabetes Research & Care, doi: 10.1136/bmjdrc-2021-002580

Abstract

Introduction This study aims to estimate the budget impact of increased uptake of the FreeStyle Libre Flash Glucose Monitoring system in people with type 1 diabetes mellitus (T1DM) in the UK.

Research design and methods A budget impact model was developed, applying real-world data collected in the Association of British Clinical Diabetologists (ABCD) FreeStyle Libre Nationwide Audit. Costs of diabetes glucose monitoring in a T1DM population (n=1790) using self-monitoring of blood glucose (SMBG) or the FreeStyle Libre system were compared with a scenario with increased use of the FreeStyle Libre system.

Results The ABCD audit demonstrates FreeStyle Libre system use reduces diabetes-related resource utilization. The cost analysis found that higher acquisition costs are offset by healthcare costs avoided (difference £168 per patient per year (PPPY)). Total costs were £1116 PPPY with FreeStyle Libre system compared with £948 PPPY with SMBG. In an average-sized UK local health economy, increasing FreeStyle Libre system uptake from 30% to 50% increased costs by 3.4% (£1 787 345–£1 847 618) and when increased to 70% increased by a further 3.3%.

Conclusion Increased uptake of the FreeStyle Libre system in the T1DM population marginally increases the cost to UK health economies and offers many system benefits.


Onatkut Dagtekin and Nina Dethlefs, 2022-03-28, Modelling Phytoplankton Behaviour in the North and Irish Sea with Transformer Networks, Proceedings of the Northern Lights Deep Learning Workshop 2022, doi: 10.7557/18.6229

Abstract

Climate change will affect how water sources are managed and monitored. Continuous monitoring of water quality is crucial to detect pollution, to ensure that various natural cycles are not disrupted by anthropogenic activities and to assess the effectiveness of beneficial management measures taken under defined protocols. One such disruption is algal blooms in which population of phytoplankton increase rapidly affecting biodiversity in marine environments. The frequency of algal blooms will increase with climate change as it presents favourable conditions for reproduction of phytoplankton. Machine learning has been used for early detection of algal blooms previously, with the focus mostly on single closed bodies of water in Far East Asia with short time ranges. In this work, we study four locations around the North Sea and the Irish Sea with different characteristics predicting activity with longer time-spans and explaining the importance of the input with regard to the output of the prediction model. This work aids domain experts to monitor potential changes to the ecosystem over longer time ranges and to take action when necessary.


Jacqueline den Hartogh, Maria K. Peto, Thomas Lawson, Andre Sieverding, Hannah Brinkman, Marco Pignatari, and Maria Lugaro, 2022-03-17, Comparison between Core-collapse Supernova Nucleosynthesis and Meteoric Stardust Grains: Investigating Magnesium, Aluminium, and Chromium, The Astrophysical Journal, doi: 10.3847/1538-4357/ac4965

Abstract

Isotope variations of nucleosynthetic origin among solar system solid samples are well documented, yet the origin of these variations is still uncertain. The observed variability of 54Cr among materials formed in different regions of the protoplanetary disk has been attributed to variable amounts of presolar, chromium-rich oxide (chromite) grains, which exist within the meteoritic stardust inventory and most likely originated from some type of supernova explosion. To investigate if core-collapse supernovae (CCSNe) could be the site of origin of these grains, we analyze yields of CCSN models of stars with initial masses 15, 20, and 25 Mo, and solar metallicity. We present an extensive abundance data set of the Cr, Mg, and Al isotopes as a function of enclosed mass. We find cases in which the explosive C ashes produce a composition in good agreement with the observed 54Cr/52Cr and 53Cr/52Cr ratios as well as the 50Cr/52Cr ratios. Taking into account that the signal at atomic mass 50 could also originate from 50Ti, the ashes of explosive He burning also match the observed ratios. Addition of material from the He ashes (enriched in Al and Cr relative to Mg to simulate the make-up of chromite grains) to the solar system’s composition may reproduce the observed correlation between Mg and Cr anomalies, while material from the C ashes does not present significant Mg anomalies together with Cr isotopic variations. In all cases, nonradiogenic, stable Mg isotope variations dominate over the variations expected from 26Al.


Battino, Umberto and Pignatari, Marco and Tattersall, Ashley and Denissenkov, Pavel and Herwig, Falk, 2022-03-09, The NuGrid AGB Evolution and Nucleosynthesis Data Set, Universe, doi: 10.3390/universe8030170

Abstract

Asymptotic Giant Branch (AGB) stars play a key role in the chemical evolution of galaxies. These stars are the fundamental stellar site for the production of light elements such as C, N and F, and half of the elements heavier than Fe via the slow neutron capture process (s-process). Hence, detailed computational models of AGB stars’ evolution and nucleosynthesis are essential for galactic chemical evolution. In this work, we discuss the progress in updating the NuGrid data set of AGB stellar models and abundance yields. All stellar models have been computed using the MESA stellar evolution code, coupled with the post-processing mppnp code to calculate the full nucleosynthesis. The final data set will include the initial masses Mini/M⊙ = 1, 1.65, 2, 3, 4, 5, 6 and 7 for initial metallicities Z = 0.0001, 0.001, 0.006, 0.01, 0.02 and 0.03. Observed s-process abundances on the surfaces of evolved stars as well as the typical light elements in the composition of H-deficient post-AGB stars are reproduced. A key short-term goal is to complete and expand the AGB stars data set for the full metallicity range. Chemical yield tables are provided for the available models.


David Rapagnani, Chemseddine Ananna, Antonino Di Leva, Gianluca Imbriani, Matthias Junker, Marco Pignatari and Andreas Best, 2022-02-24, Shades – ²²Ne(α, n)²⁵Mg reaction rate in the Gamow window, EPJ Web of Conferences, doi: 10.1051/epjconf/202226011031

Abstract

Neutron capture reactions are the main contributors to the synthesis of the heavy elements through the s-process. Together with 13C(α, n)16O, which has recently been measured by the LUNA collaboration in an energy region inside the Gamow peak, 22Ne(α, n)25Mg is the other main neutron source in stars. Its cross section is mostly unknown in the relevant stellar energy (450 keV < Ecm < 750 keV), where only upper limits from direct experiments and highly uncertain estimates from indirect sources exist. The ERC project SHADES (UniNa/INFN) aims to provide for the first time direct cross section data in this region and to reduce the uncertainties of higher energy resonance parameters. High sensitivity measurements will be performed with the new LUNA-MV accelerator at the INFN-LNGS laboratory in Italy: the energy sensitivity of the SHADES hybrid neutron detector, together with the low background environment of the LNGS and the high beam current of the new accelerator promises to improve the sensitivity by over 2 orders of magnitude over the state of the art, allowing to finally probe the unexplored low-energy cross section. Here we present an overview of the project and first results on the setup characterization.


Shifeng Luo, Jia Chuan Khong, Dominik Daisenberger, Shi Huang, Paul F. McMillan, and Jiawei Mi, 2022-02-10, Synchrotron x-ray total scattering and modeling study of high-pressure-induced inhomogeneous atom reconfiguration in an equiatomic Zr50 Cu50 metallic glassy alloy, Physical Review B, doi: 10.1103/PhysRevB.105.064203

Abstract

We studied in situ the local atomic structure evolution of an equiatomic Zr50 Cu50 metallic glassy alloy under high pressure compression inside a diamond anvil cell using synchrotron x-ray total scattering. The empirical potential structure refinement method was used to reconstruct the three-dimensional atomic models at each pressure step, and to analyze the spatially averaged local atomic structure configurations. The interatomic distances of different atomic pairs are reduced at different rates with increasing pressure and the Cu-Cu pairs exhibit the highest percentage reduction. Between ambient pressure and 36.85 GPa, the atomic separation of the Cu-Cu pairs is reduced by ~12% compared to ~5% for Zr-Zr and Zr-Cu pairs. Such disproportional decrease in interatomic distance results in inhomogeneous atom reconfiguration in the short atomic range. With the increase of pressure, the Zr atoms move preferentially towards the Zr-Zr pairs, while the Cu atoms move preferentially towards the Cu-Cu pairs, creating inhomogeneous atom reconfiguration with positive short-range order coefficients of 0.0309 and 0.0464 for Zr-Zr and Cu-Cu respectively, but a negative value of −0.0464 for Zr-Cu pairs. Voronoi tessellation method was also used to study the evolution of the short-range atom packing versus pressure, elucidating the cause for the bimodal distribution of the bond angle distributions. The research sheds light on understanding of the atomic reconfiguration of equiatomic alloys under high pressure.


D’Orazi, Valentina and Baratella, Martina and Lugaro, Maria and Magrini, Laura and Pignatari, Marco, 2022-02-09, The Complex Behaviour of s-Process Element Abundances at Young Ages, Universe, doi: 10.3390/universe8020110

Abstract

Open clusters appear as simple objects in many respects, with a high degree of homogeneity in their (initial) chemical composition, and the typical solar-scaled abundance pattern that they exhibit for the majority of the chemical species. The striking singularity is represented by heavy elements produced from the slow process of the neutron-capture reactions. In particular, young open clusters (ages less than a few hundred Myr) give rise to the so-called barium puzzle: that is an extreme enhancement in their [Be/Fe] ratios, up to a factor of four of the solar value, which is not followed by other nearby s-process elements (e.g., lanthanum and cerium). The definite explanation for such a peculiar trend is still wanting, as many different solutions have been envisaged. We review the status of this field and present our new results on young open clusters and the pre-main sequence star RZ Piscium.


Hamza, Abdullah O. and Bouillard, Jean-Sebastien G. and Adawi, Ali M., 2022-02-02, Förster Resonance Energy Transfer Rate and Efficiency in Plasmonic Nanopatch Antennas, ChemPhotoChem, doi: 10.1002/cptc.202100285

Abstract

Abstract Successful control of Förster resonance energy transfer (FRET) through the engineering of the local density of optical states (LDOS) will allow us to develop novel strategies to fully exploit this phenomenon in key enabling technologies. Here we present an experimental and theoretical study on the effect of the LDOS on the FRET rate and efficiency in plasmonic nanopatch antennas formed between a gold nanoparticle and an extended silver film. Our results reveal that plasmonic nanopatch antennas of similar levels of LDOS exhibit comparable levels of FRET rate and FRET efficiency, demonstrating that LDOS plays an important part in controlling both FRET rate and efficiency. Our findings contribute to the ongoing debate about the relation between the FRET process and the LDOS, as well as directly impacting the development of novel FRET based light harvesting and sensing devices.


Harshal Deshmukh, Najeeb Shah, Maria Papageorgiou, Mohammed Altigani Abdalla, Fadel Lhaf, Mo Aye, Thozhukat Sathyapalan, 2022-02, Genetic risk for the polycystic ovary syndrome, bone mineral density and fractures in women and men: A UK Biobank Mendelian randomisation study, Bone, doi: 10.1016/j.bone.2021.116285

Abstract

There is conflicting data on the effect of polycystic ovary syndrome (PCOS) on bone mineral density (BMD) and fracture risk. Recent genetic data suggest that men may also carry genetic risk factors for PCOS; the associations of these factors with parameters of bone health remains unknown. We aimed to investigate if the genetic risk of PCOS is associated with BMD and fracture risk in women and men in the UK Biobank dataset.


Thomas M. Cross, David M. Benoit, Marco Pignatari, and Brad K. Gibson, 2022-01-25, A Large-scale Approach to Modeling Molecular Biosignatures: The Diatomics, The Astrophysical Journal, doi: 10.3847/1538-4357/ac3976

Abstract

This work presents the first steps to modeling synthetic rovibrational spectra for all molecules of astrophysical interest using a new approach implemented in the Prometheus code. The goal is to create a new comprehensive source of first-principles molecular spectra, thus bridging the gap for missing data to help drive future high-resolution studies. Our primary application domain is for molecules identified as signatures of life in planetary atmospheres (biosignatures), but our approach is general and can be applied to other systems. In this work we evaluate the accuracy of our method by studying four diatomic molecules, H2, O2, N2, and CO, all of which have well-known spectra. Prometheus uses the transition-optimised shifted Hermite (TOSH) theory to account for anharmonicity for the fundamental v = 0 -> v = 1 band, along with thermal-profile modeling for the rotational transitions. To this end, we expand TOSH theory to enable the modeling of rotational constants. We show that our simple model achieves results that are a better approximation of the real spectra than those produced through an harmonic approach. We compare our results with high-resolution HITRAN and ExoMol spectral data. We find that modeling accuracy tends to diminish for rovibrational transition away from the band origin, thus highlighting the need for the theory to be further adapted.


C.J. Lloyd, R.M. Dorrell and C.P. Caulfield, 2022-01-14, The coupled dynamics of internal waves and hairpin vortices in stratified plane Poiseuille flow, Journal of Fluid Mechanics, doi: 10.1017/jfm.2021.1007

Abstract

A simulation of stably stratified plane Poiseuille flow at a moderate Reynolds number (Re.=550) and Richardson number (Ri.=480) is presented. For the first time, the dynamics in the channel core are shown to be described as a series of internal waves that approximately obey a linear wave dispersion relationship. For a given streamwise wavenumber kx there are two internal wave solutions, a dominant low frequency mode and a weaker-amplitude high-frequency mode, respectively corresponding to ‘backward’ and ‘forward’ propagating internal waves relative to the mean flow. Analysis of linearised equations shows that the dominant low-frequency mode appears to arise due to a particularly sensitive response of the mean flow profiles to incoherent forcing. Instantaneous visualisations reveal that hairpin vortices dominate the outer region of the channel flow, neighbouring the buoyancy dominated channel core. These hairpins are fundamentally different from those observed in canonical unstratified boundary layer flows, as they arise via quasi-linear local processes far from the wall, governed by background shear. Outer region ejection events are common and can be induced by high amplitude waves. Ejected hairpins are transported into the channel core, in turn ‘ringing’ the prevailing strong buoyancy gradient and thus generating high-amplitude internal waves, high dissipation and wave breaking, induced by spanwise vortex stretching and baroclinic vorticity generation. Such spontaneous and sustained generation of quasi-linear internal waves by wall-bounded sheared turbulence may provide novel idealised solutions for, and insight into, large-scale turbulent mixing in a wide range of environmental and industrial flows.


Thomas C. L. Trueman, Benoit Cote, Andres Yague Lopez, Jacqueline den Hartogh, Marco Pignatari, Benjamin Soos, Amanda I. Karakas, and Maria Lugaro, 2022-01-05, Galactic Chemical Evolution of Radioactive Isotopes with an s-process Contribution, The Astrophysical Journal, doi: 10.3847/1538-4357/ac31b0

Abstract

Analysis of inclusions in primitive meteorites reveals that several short-lived radionuclides (SLRs) with half-lives of 0.1-100 Myr existed in the early solar system (ESS). We investigate the ESS origin of 107Pd, 135Cs, and 182Hf, which are produced by slow neutron captures (the s-process) in asymptotic giant branch (AGB) stars. We modeled the Galactic abundances of these SLRs using the OMEGA+ galactic chemical evolution (GCE) code and two sets of mass- and metallicity-dependent AGB nucleosynthesis yields (Monash and FRUITY). Depending on the ratio of the mean-life τ of the SLR to the average length of time between the formations of AGB progenitors γ, we calculate timescales relevant for the birth of the Sun. If τ/γ ≳ 2, we predict self-consistent isolation times between 9 and 26 Myr by decaying the GCE predicted 107Pd/108Pd, 135Cs/133Cs, and 182Hf/180Hf ratios to their respective ESS ratios. The predicted 107Pd/182Hf ratio indicates that our GCE models are missing 9%–73% of 107Pd and 108Pd in the ESS. This missing component may have come from AGB stars of higher metallicity than those that contributed to the ESS in our GCE code. If τ/γ ≲ 0.3, we calculate instead the time (TLE) from the last nucleosynthesis event that added the SLRs into the presolar matter to the formation of the oldest solids in the ESS. For the 2 Mo, Z = 0.01 Monash model we find a self-consistent solution of TLE = 25.5 Myr.


Andrew I. Furness, Chris Venditti, Isabella Capellini, 2022-01-04, Terrestrial reproduction and parental care drive rapid evolution in the trade-off between offspring size and number across amphibians, PLOS Biology, doi: 10.1371/journal.pbio.3001495

Abstract

The trade-off between offspring size and number is central to life history strategies. Both the evolutionary gain of parental care or more favorable habitats for offspring development are predicted to result in fewer, larger offspring. However, despite much research, it remains unclear whether and how different forms of care and habitats drive the evolution of the trade-off. Using data for over 800 amphibian species, we demonstrate that, after controlling for allometry, amphibians with direct development and those that lay eggs in terrestrial environments have larger eggs and smaller clutches, while different care behaviors and adaptations vary in their effects on the trade-off. Specifically, among the 11 care forms we considered at the egg, tadpole and juvenile stage, egg brooding, male egg attendance, and female egg attendance increase egg size; female tadpole attendance and tadpole feeding decrease egg size, while egg brooding, tadpole feeding, male tadpole attendance, and male tadpole transport decrease clutch size. Unlike egg size that shows exceptionally high rates of phenotypic change in just 19 branches of the amphibian phylogeny, clutch size has evolved at exceptionally high rates in 135 branches, indicating episodes of strong selection; egg and tadpole environment, direct development, egg brooding, tadpole feeding, male tadpole attendance, and tadpole transport explain 80% of these events. By explicitly considering diversity in parental care and offspring habitat by stage of offspring development, this study demonstrates that more favorable conditions for offspring development promote the evolution of larger offspring in smaller broods and reveals that the diversity of parental care forms influences the trade-off in more nuanced ways than previously appreciated.


Dr Nina Dethlefs, 2022, Physics-informed machine learning for rapid fatigue assessments in offshore wind farms, Supergen ORE Hub Project Summary, link: https://supergen-ore.net/uploads/resources/Physics-informed-machine-learning-for-rapid-fatigue-assessments-in-offshore-wind-farms-Final-report.pdf

Abstract

Offshore wind energy is key in the UK’s plan to deliver the legally binding Net Zero 2050 targets, quadrupling the capacity by 2030. First-generation offshore wind monopiles are rapidly approaching their end of designed life. The next-generation of wind turbines are significantly larger, yet still monopile support structures dominate. Accurate estimation of accumulated monopile fatigue is essential now, to inform decommissioning decisions, and optimise future design and maintenance. Due to unpredictable offshore environments, and the difficulty of taking structural measurements, fatigue predictions are subject to significant error.

This project proposes an industry-compatible step-change advance in accumulated fatigue assessment via novel integration of physical modelling and machine learning. The proposed model provides intuitive prediction of the level of fatigue for any turbine within the farm, at any point of its lifetime from distinct operational and environmental conditions, verifiable against physical models, yet with increased efficiency and fidelity of lifetime fatigue estimation.

https://supergen-ore.net/uploads/resources/Physics-informed-machine-learning-for-rapid-fatigue-assessments-in-offshore-wind-farms-Final-report.pdf

https://supergen-ore.net/projects/machine-learning-for-fatigue-assessments-offshore-wind-farms



2021 (36 outputs)

Johannes Menath, Jack Eatson, Robert Brilmayer, Annette Andrieu-Brunsen, D. Martin A. Buzza, and Nicolas Vogel, 2021-12-28, Defined core-shell particles as the key to complex interfacial self-assembly, Proceedings of the National Academy of Sciences (PNAS), doi: 10.1073/pnas.2113394118

Abstract

The two-dimensional self-assembly of colloidal particles serves as a model system for fundamental studies of structure formation and as a powerful tool to fabricate functional materials and surfaces. However, the prevalence of hexagonal symmetries in such self-assembling systems limits its structural versatility. More than two decades ago, Jagla demonstrated that core-shell particles with two interaction length scales can form complex, nonhexagonal minimum energy configurations. Based on such Jagla potentials, a wide variety of phases including cluster lattices, chains, and quasicrystals have been theoretically discovered. Despite the elegance of this approach, its experimental realization has remained largely elusive. Here, we capitalize on the distinct interfacial morphology of soft particles to design two-dimensional assemblies with structural complexity. We find that core-shell particles consisting of a silica core surface functionalized with a noncrosslinked polymer shell efficiently spread at a liquid interface to form a two-dimensional polymer corona surrounding the core. We controllably grow such shells by iniferter-type controlled radical polymerization. Upon interfacial compression, the resulting core-shell particles arrange in well-defined dimer, trimer, and tetramer lattices before transitioning into complex chain and cluster phases. The experimental phase behavior is accurately reproduced by Monte Carlo simulations and minimum energy calculations, suggesting that the interfacial assembly interacts via a pairwise-additive Jagla-type potential. By comparing theory, simulation, and experiment, we narrow the Jagla g-parameter of the system to between 0.9 and 2. The possibility to control the interaction potential via the interfacial morphology provides a framework to realize structural features with unprecedented complexity from a simple, one-component system.


Lawson, Thomas V and Pignatari, Marco and Stancliffe, Richard J and den Hartogh, Jacqueline and Jones, Sam and Fryer, Chris L and Gibson, Brad K and Lugaro, Maria, 2021-12-22, Radioactive nuclei in the early Solar system: analysis of the 15 isotopes produced by core-collapse supernovae, Monthly Notices of the Royal Astronomical Society, doi: 10.1093/mnras/stab3684

Abstract

Short-lived radioactive isotopes (SLRs) with half-lives between 0.1 and 100 Myr can be used to probe the origin of the Solar system. In this work, we examine the core-collapse supernovae production of the 15 SLRs produced: 26Al, 36Cl, 41Ca, 53Mn, 60Fe, 92Nb, 97Tc, 98Tc, 107Pd, 126Sn, 129I, 135Cs, 146Sm, 182Hf, and 205Pb. We probe the impact of the uncertainties of the core-collapse explosion mechanism by examining a collection of 62 core-collapse models with initial masses of 15, 20, and 25 M⊙, explosion energies between 3.4 × 1050 and 1.8 × 1052 erg and compact remnant masses between 1.5 and 4.89 M⊙. We identify the impact of both explosion energy and remnant mass on the final yields of the SLRs. Isotopes produced within the innermost regions of the star, such as 92Nb and 97Tc, are the most affected by the remnant mass, 92Nb varying by five orders of magnitude. Isotopes synthesized primarily in explosive C-burning and explosive He-burning, such as 60Fe, are most affected by explosion energies. 60Fe increases by two orders of magnitude from the lowest to the highest explosion energy in the 15 M⊙ model. The final yield of each examined SLR is used to compare to literature models.


M. J. Bennett, I. Dobson, D. M. Benoit, M. G. Francesconi, 2021-12-08, Utilisation of CO₂ as “Structure Modifier” of Inorganic Solids, Chemistry – A European Journal, doi: 10.1002/chem.202103608

Abstract

Utilisation of CO₂ as a chemical reagent is challenging, due to the molecule’s inherent chemical stability. However, CO₂ reacts promptly at high temperature (~1000 °C) with alkaline-earth oxides to form carbonates and such reactions are used towards capture and re-utilisation. In this work, this concept is extended and CO₂ is utilised as a reagent to modify the crystal structure of mixed-metal inorganic solids. Modification of the crystal structure is a “tool” used by materials scientists to tailor the physical property of solids. CO₂ gas was reacted with several isostructural mixed-metal oxides Sr₂CuO₃, Sr₁.₈Ba₀.₂CuO₃ and Ba₂PdO₃. These oxides are carefully selected to show anion vacancies in their crystal structure, to act as host sites for CO₂ molecules, leading to the formation of carbonate anions, (CO₃)²⁻. The corresponding oxide carbonates were formed successfully and the favourable formation of SrCO₃ as secondary phase was minimised via an innovative, yet simple synthetic procedure involving alternating of CO₂ and air. We also derived a simple model to predict the kinetics of the reactions for the cuprates, using first-principles density functional theory and assimilating the reaction to a gas-surface process.


Graham S. Sellers, Daniel C. Jeffares, Bex Lawson, Tom Prior, David H. Lunt, 2021-12-01, Identification of individual root-knot nematodes using low coverage long-read sequencing, PLOS One, doi: 10.1371/journal.pone.0253248

Abstract

Root-knot nematodes (RKN; genus Meloidogyne) are polyphagous plant pathogens of great economic importance to agriculturalists globally. These species are small, diverse, and can be challenging for accurate taxonomic identification. Many of the most important crop pests confound analysis with simple genetic marker loci as they are polyploids of likely hybrid origin. Here we take a low-coverage, long-read genome sequencing approach to characterisation of individual root-knot nematodes. We demonstrate library preparation for Oxford Nanopore Technologies Flongle sequencing of low input DNA from individual juveniles and immature females, multiplexing up to twelve samples per flow cell. Taxonomic identification with Kraken 2 (a k-mer-based taxonomic assignment tool) is shown to reliably identify individual nematodes to species level, even within the very closely related Meloidogyne incognita group. Our approach forms a robust, low-cost, and scalable method for accurate RKN species diagnostics.


Najeeb Shah, Harshal Deshmukh, Emma G. Wilmot, Jane Patmore, Pratik Choudhary, Peter Christian, Roselle Herring, Niall Furlong, Simon Saunders, Parth Narendran, Dennis J. Barnes, Chris Walton, Robert E.J. Ryder, Thozhukat Sathyapalan, 2021-12, Previous structured education attendance and the relationship with HbA1c and hypoglycaemia awareness in people living with type 1 diabetes mellitus using FreeStyle Libre: insights from the Association of British Clinical Diabetologists (ABCD) Nationwide Audit, The British Journal of Diabetes, doi: 10.15277/bjd.2021.308

Abstract

Background: Dose Adjustment For Normal Eating (DAFNE) is the gold standard National Institute for Health and Care Excellence (NICE) recommended structured education programme that promotes self-management in people living with type 1 diabetes (T1D). We have recently shown that FreeStyle Libre (FSL) is associated with improved haemoglobin A1c (HbA1c) and hypoglycaemia awareness.

Aims: To explore the effect of structured education including DAFNE on HbA1c and GOLD score when combined with FSL use.

Methods: The ABCD national audit data on FSL users were used to conduct this prospective longitudinal study. The Student’s t test was used to compare the baseline and follow-up HbA1c and a change in the GOLD score for hypoglycaemia awareness. The baseline demographic and clinical characteristics of the study population were compared using ANOVA. Linear regression analysis identified predictors of change in HbA1c with FSL use.

Results: The study consisted of 14,880 people living with insulin-dependent diabetes mellitus (IDDM), 97% of whom had T1D, of which 50% were female, with a mean±SD baseline HbA1c of 70±18 mmol/mol and baseline body mass index (BMI) of 25.3±6.2 kg/m2. Follow-up data for HbA1c were available for 6,446 participants while data for GOLD score were available for 5,057 participants. The study population was divided into three groups: 6,701 people with no prior structured education (Group 1), 3,964 with other structured education (Group 2), and 4,215 had previously attended DAFNE structured education (Group 3). Groups 2 and 3 who had previously attended structured education had a lower initial HbA1c than those in Group 1 (p<0.0001). However, there was a significant but similar magnitude of the fall in HbA1c across all groups (−8.10 mmol/mol vs −6.61 mmol/mol vs −6.22 mmol/mol in Groups 1, 2 and 3, respectively), with p (ANOVA)=0.83. Similarly, the decline in GOLD score was comparable in Groups 1, 2 and 3 (−0.33 vs −0.30 vs −0.34, respectively), with p (ANOVA)=0.43. Linear regression analysis identified higher baseline HbA1c (β=0.585, p<0.0001), number of FSL scans over 14 days (β=−0.026, p=0.00135) and other structured education (β=−1.207, p=0.02483) as predictors of HbA1c reduction. Prior DAFNE training was not associated with improved HbA1c reduction in the linear regression model.

Conclusions: FSL use was associated with improvements in HbA1c and GOLD score. Although DAFNE is an evidence-based intervention to improve outcomes in those with T1D, DAFNE attendance prior to commencing FSL did not influence HbA1c or GOLD score outcomes when compared with FSL use alone. Other structured education was identified as a predictor of HbA1c reduction when combined with FSL use.


Mikkel Theiss Kristensen, Kevin A. Pimbblet, Brad K. Gibson, Samantha J. Penny, and Sophie Koudmani, 2021-11-25, Merger Histories and Environments of Dwarf AGN in IllustrisTNG, The Astrophysical Journal, doi: 10.3847/1538-4357/ac236d

Abstract

The relationship between active galactic nuclei (AGN) activity and environment has been long discussed, but it is unclear if these relations extend into the dwarf galaxy mass regime—in part due to the limits in both observations and simulations. We aim to investigate if the merger histories and environments are significantly different between AGN and non-AGN dwarf galaxies in cosmological simulations, which may be indicative of the importance of these for AGN activity in dwarf galaxies, and whether these results are in line with observations. Using the IllustrisTNG flagship TNG100-1 run, 6771 dwarf galaxies are found with 3863 (~57%) having some level of AGN activity. In order to quantify environment, two measures are used: (1) the distance to a galaxy’s 10th nearest neighbor at six redshifts and (2) the time since last merger for three different minimum merger mass ratios. A similar analysis is run on TNG50-1 and Illustris-1 to test for the robustness of the findings. Both measures yield significantly different distributions between AGN and non-AGN galaxies; more non-AGN than AGN galaxies have long term residence in dense environments, while recent (≤4 Gyr) minor mergers are more common for intermediate AGN activity. While no statements are made about the micro or macrophysics from these results, it is nevertheless indicative of a non-negligible role of mergers and environments.


Ota, S. and Christian, G. and Catford, W. N. and Lotay, G. and Pignatari, M. and Battino, U. and Bennett, E. A. and Dede, S. and Doherty, D. T. and Hallam, S. and Herwig, F. and Hooker, J. and Hunt, C. and Jayatissa, H. and Matta, A. and Moukaddam, M. and Rao, E. and Rogachev, G. V. and Saastamoinen, A. and Scriven, D. and Tostevin, J. A. and Upadhyayula, S. and Wilkinson, R., 2021-11-24, (6Li,d) and (6Li,t) reactions on 22Ne and implications for s-process nucleosynthesis, Physical Review C, doi: 10.1103/PhysRevC.104.055806

Abstract

We studied {alpha} cluster states in ^{26}Mg via the ^{22}Ne(^{6}Li},d{gamma})^{26}Mg reaction in inverse kinematics at an energy of 7 MeV/nucleon. States between E_{x} = 4–14 MeV in ^{26}Mg were populated and relative {alpha} spectroscopic factors were determined. Some of these states correspond to resonances in the Gamow window of the ^{22}({alpha}n)^{25}Mg reaction, which is one of the main neutron sources in the astrophysical s-process. Using our new ^{22}Ne(h{alpha}n)^{25}Mg and ^{22}Ne({alpha},{gamma})^{26}Mg reaction rates, we performed new s-process calculations for massive stars and asymptotic giant branch stars and compared the resulting abundances with the abundances obtained using other ^{22}Ne+{alpha} rates from the literature. We observe an impact on the $s$-process abundances up to a factor of three for intermediate-mass AGB stars and up to a factor of ten for massive stars. Additionally, states in ^{25}Mg at E_{x} < 7.5 MeV are identified via the ^{22}Ne(^{6}Li,t)^{25}Mg reaction for the first time. We present the (^{6}Li, t) spectroscopic factors of these states and note similarities to the (d,p) reaction in terms of reaction selectivity.


Katharina C. Wollenberg Valero, Joan Garcia-Porta, Iker Irisarri, Lauric Feugere, Adam Bates, Sebastian Kirchhof, Olga Jovanovic Glavas, Panayiotis Pafilis, Sabrina F. Samuel, Johannes Muller, Miguel Vences, Alexander P. Turner, Pedro Beltran-Alvarez, Kenneth B. Storey, 2021-10-25, Functional genomics of abiotic environmental adaptation in lacertid lizards and other vertebrates, Journal of Animal Ecology, doi: 10.1111/1365-2656.13617

Abstract

1. Understanding the genomic basis of adaptation to different abiotic environments is important in the context of climate change and resulting short-term environmental fluctuations. ; 2. Using functional and comparative genomics approaches, we here investigated whether signatures of genomic adaptation to a set of environmental parameters are concentrated in specific subsets of genes and functions in lacertid lizards and other vertebrates. ; 3. We first identify 200 genes with signatures of positive diversifying selection from transcriptomes of 24 species of lacertid lizards and demonstrate their involvement in physiological and morphological adaptations to climate. To understand how functionally similar these genes are to previously predicted candidate functions for climate adaptation and to compare them with other vertebrate species, we then performed a meta-analysis of 1100 genes under selection obtained from -omics studies in vertebrate species adapted to different abiotic environments. ; 4. We found that the vertebrate gene set formed a tightly connected interactome, which was 23% enriched in previously predicted functions of adaptation to climate, and to a large part (18%) involved in organismal stress response. We found a much higher degree of identical genes being repeatedly selected among different animal groups (43.6%), a higher degree of functional similarity, and posttranslational modifications than expected by chance, and no clear functional division between genes used for ectotherm and endotherm physiological strategies. 171 out of 200 genes of Lacertidae were part of this network. ; 5. These results highlight an important role of a comparatively small set of genes and their functions in environmental adaptation and narrows the set of candidate pathways and markers to be used in future research on adaptation and stress response related to climate change.


S. Q. Hou, T. Kajino, T. C. L. Trueman, M. Pignatari, Y. D. Luo, and C. A. Bertulani, 2021-10-25, New Thermonuclear Rate of ⁷Li(d,n)2⁴He Relevant to the Cosmological Lithium Problem, The Astrophysical Journal, doi: 10.3847/1538-4357/ac1a11

Abstract

Accurate ⁷Li(d,n)2⁴He thermonuclear reaction rates are crucial for precise prediction of the primordial abundances of lithium and beryllium and to probe the mysteries beyond fundamental physics and the standard cosmological model. However, uncertainties still exist in current reaction rates of ⁷Li(d,n)2⁴He widely used in big bang nucleosynthesis (BBN) simulations. In this work, we reevaluate the ⁷Li(d,n)2⁴He reaction rate using the latest data on the three near-threshold ⁹Be excited states from experimental measurements. We present for the first time uncertainties that are directly constrained by experiments. Additionally, we take into account for the first time the contribution from the subthreshold resonance at 16.671 MeV of ⁹Be. We obtain a ⁷Li(d,n)2⁴He rate that is overall smaller than the previous estimation by about a factor of 60 at the typical temperature of the onset of primordial nucleosynthesis. We implemented our new rate in BBN calculations, and we show that the new rates have a very limited impact on the final light element abundances in uniform density models. Typical abundance variations are in the order of 0.002%. For nonuniform density BBN models, the predicted ⁷Li production can be increased by 10% and the primordial production of light nuclides with mass number A > 7 can be increased by about 40%. Our results confirm that the cosmological lithium problem remains a long-standing unresolved puzzle from the standpoint of nuclear physics.


Diego Turrini, Claudio Codella, Camilla Danielski, Davide Fedele, Sergio Fonte, Antonio Garufi, Mario Giuseppe Guarcello, Ravit Helled, Masahiro Ikoma, Mihkel Kama, Tadahiro Kimura, J. M. Diederik Kruijssen, Jesus Maldonado, Yamila Miguel, Sergio Molinari, Athanasia Nikolaou, Fabrizio Oliva, Olja Pani., Marco Pignatari, Linda Podio, Hans Rickman, Eugenio Schisano, Sho Shibata, Allona Vazan & Paulina Wolkenberg, 2021-10-15, Exploring the link between star and planet formation with Ariel, Experimental Astronomy, doi: 10.1007/s10686-021-09754-4

Abstract

The goal of the Ariel space mission is to observe a large and diversified population of transiting planets around a range of host star types to collect information on their atmospheric composition. The planetary bulk and atmospheric compositions bear the marks of the way the planets formed: Ariel’s observations will therefore provide an unprecedented wealth of data to advance our understanding of planet formation in our Galaxy. A number of environmental and evolutionary factors, however, can affect the final atmospheric composition. Here we provide a concise overview of which factors and effects of the star and planet formation processes can shape the atmospheric compositions that will be observed by Ariel, and highlight how Ariel’s characteristics make this mission optimally suited to address this very complex problem.


Ling Qin and Barbara M. Maciejewska and Tungky Subroto and Justin A. Morton and Kyriakos Porfyrakis and Iakovos Tzanakis and Dmitry G. Eskin and Nicole Grobert and Kamel Fezzaa and Jiawei Mi, 2021-10-07, Ultrafast synchrotron X-ray imaging and multiphysics modelling of liquid phase fatigue exfoliation of graphite under ultrasound, Carbon, doi: 10.1016/j.carbon.2021.10.014

Abstract

Ultrasound-assisted liquid phase exfoliation is a promising method for manufacturing of 2D materials in large scale and sustainable manner. A great number of studies using ex-situ nano/micro structure characterization techniques have been made to investigate the underlying mechanisms and understand the exfoliation dynamics. Due to the complex multiphysics and multi-length nature of the process, those ex-situ methods cannot provide full scale real-time dynamic information for understanding how exactly layer exfoliation starts and grows under ultrasound. Here, we used the ultrafast synchrotron-X-ray phase-contrast imaging (a combined temporal resolution of 3.68 us and a spatial resolution of 1.9 um/pixel) to study the exfoliation dynamics in real time. We revealed, for the first time, the fatigue exfoliation phenomenon at the graphite surface caused by the imploding ultrasonic bubbles occurring cyclically in line with the ultrasound frequency. A multiphysics numerical model was also developed to calculate the shock wave produced at bubble implosion and the resulting cyclic and impulsive tensile and shear stresses acting on the graphite surface. The research reveals that layer exfoliation rate and efficiency are predominantly determined by the number of imploding bubbles inside the effective cavitation bubble zone. The findings are valuable for developing upscaling strategies for ultrasound processing of 2D materials.


B. Barbuy, E. Cantelli, L. Muniz, S. O. Souza, C. Chiappini, R. Hirschi, G. Cescutti, M. Pignatari, S. Ortolani, L. Kerber, F. F. S. Maia, E. Bica and E. Depagne, 2021-10-05, UVES analysis of red giants in the bulge globular cluster NGC 6522, Astronomy & Astrophysics, doi: 10.1051/0004-6361/202140815

Abstract

NGC 6522 is a moderately metal-poor bulge globular cluster ([Fe/H] ~ .1.0), and it is a well-studied representative among a number of moderately metal-poor blue horizontal branch clusters located in the bulge. The NGC 6522 abundance pattern can give hints on the earliest chemical enrichment in the central Galaxy. NGC 6522 is a moderately metal-poor bulge globular cluster ([Fe/H] ~ .1.0), and it is a well-studied representative among a number of moderately metal-poor blue horizontal branch clusters located in the bulge. The NGC 6522 abundance pattern can give hints on the earliest chemical enrichment in the central Galaxy.


S. Q. Yan, X. Y. Li, K. Nishio, M. Lugaro, Z. H. Li, H. Makii, M. Pignatari, Y. B. Wang, R. Orlandi, K. Hirose et al, 2021-09-28, The 59Fe (n,γ) 60Fe Cross Section from the Surrogate Ratio Method and Its Effect on the 60Fe Nucleosynthesis, The American Astronomical Society, doi: 10.3847/1538-4357/ac12ce

Abstract

The long-lived 60Fe (with a half-life of 2.62 Myr) is a crucial diagnostic of active nucleosynthesis in the Milky Way galaxy and in supernovae near the solar system. The neutron-capture reaction 59Fe(n,γ)60Fe on 59Fe (half-life = 44.5 days) is the key reaction for the production of 60Fe in massive stars. This reaction cross section has been previously constrained by the Coulomb dissociation experiment, which offered partial constraint on the E1 γ-ray strength function but a negligible constraint on the M1 and E2 components. In this work, for the first time, we use the surrogate ratio method to experimentally determine the 59Fe(n,γ)60Fe cross sections in which all the components are included. We derived a Maxwellian-averaged cross section of 27.5 ± 3.5 mb at kT = 30 keV and 13.4 ± 1.7 mb at kT = 90 keV, roughly 10%-20% higher than previous estimates. We analyzed the impact of our new reaction rates in nucleosynthesis models of massive stars and found that uncertainties in the production of 60Fe from the 59Fe(n,γ)60Fe rate are at most 25%. We conclude that stellar physics uncertainties now play a major role in the accurate evaluation of the stellar production of 60Fe.


Igor Menezes , Ana Cristina Menezes , Elton Moraes , Pedro P. Pires, 2021-09-28, Measuring organizational climate via psychological networks analysis, International Journal of Organization Theory & Behavior, doi: 10.1108/IJOTB-08-2020-0142

Abstract

This study investigates organizational climate under the thriving at work perspective using a network approach. The authors demonstrate how organizational climate functions as a complex system and what relationships between variables from different dimensions are the most important to characterize the construct.


Victoria H J Clark, David M Benoit, 2021-09-20, The vibrational properties of benzene on an ordered water ice surface, Monthly Notices of the Royal Astronomical Society, doi: 10.1093/mnras/stab2670

Abstract

We present a hybrid CCSD(T)+PBE-D3 approach to calculating the vibrational signatures for gas phase benzene and benzene adsorbed on an ordered water-ice surface. We compare the results of our method against experimentally recorded spectra and calculations performed using PBE-D3-only approaches (harmonic and anharmonic). Calculations use a proton ordered XIh water-ice surface consisting of 288 water molecules, and results are compared against experimental spectra recorded for an ASW ice surface. We show the importance of including a water ice surface into spectroscopic calculations, owing to the resulting differences in vibrational modes, frequencies and intensities of transitions seen in the IR spectrum. The overall intensity pattern shifts from a dominating ν11 band in the gas-phase to several high-intensity carriers for an IR spectrum of adsorbed benzene. When used for adsorbed benzene, the hybrid approach presented here achieves an RMSD for IR active modes of 21 cm-1, compared to 72 cm-1 and 49 cm-1 for the anharmonic and harmonic PBE-D3 approaches, respectively. Our hybrid model for gaseous benzene also achieves the best results when compared to experiment, with an RMSD for IR active modes of 24 cm-1, compared to 55 cm-1 and 31 cm-1 for the anharmonic and harmonic PBE-D3 approaches, respectively. To facilitate assignment, we generate and provide a correspondence graph between the normal modes of the gaseous and adsorbed benzene molecules. Finally, we calculate the frequency shifts, Δν, of adsorbed benzene relative to its gas phase to highlight the effects of surface interactions on vibrational bands and evaluate the suitability of our chosen dispersion-corrected density functional theory.


Zhenhao Li, Ling Qin, Baisong Guo, Junping Yuan, Zhiguo Zhang, Wei Li & Jiawei Mi, 2021-09-12, Characterization of the Convoluted 3D Intermetallic Phases in a Recycled Al Alloy by Synchrotron X-ray Tomography and Machine Learning, Acta Metallurgica Sinica (English Letters), doi: 10.1007/s40195-021-01312-3

Abstract

Fe-rich intermetallic phases in recycled Al alloys often exhibit complex and 3D convoluted structures and morphologies. They are the common detrimental intermetallic phases to the mechanical properties of recycled Al alloys. In this study, we used synchrotron X-ray tomography to study the true 3D morphologies of the Fe-rich phases, Al2Cu phases and casting defects in an as-cast Al-5Cu-1.5Fe-1Si alloy. Machine learning-based image processing approach was used to recognize and segment the different phases in the 3D tomography image stacks. In the studied condition, the .-Al9Fe2Si2 and .-Al7Cu2Fe are found to be the main Fe-rich intermetallic phases. The .-Al9Fe2Si2 phases exhibit a spatially connected 3D network structure and morphology which in turn control the 3D spatial distribution of the Al2Cu phases and the shrinkage cavities. The Al3Fe phases formed at the early stage of solidification affect to a large extent the structure and morphology of the subsequently formed Fe-rich intermetallic phases. The machine learning method has been demonstrated as a powerful tool for processing big datasets in multidimensional imaging-based materials characterization work.


M. Baratella, V. D’Orazi, V. Sheminova, L. Spina, G. Carraro, R. Gratton, L. Magrini, S. Randich, M. Lugaro, M. Pignatari et al, 2021-09-08, The Gaia -ESO Survey: a new approach to chemically characterising young open clusters: II. Abundances of the neutron-capture elements Cu, Sr, Y, Zr, Ba, La, and Ce, Astronomy & Astrophysics, doi: 10.1051/0004-6361/202141069

Abstract

Young open clusters (ages of less than 200 Myr) have been observed to exhibit several peculiarities in their chemical compositions. These anomalies include a slightly sub-solar iron content, super-solar abundances of some atomic species (e.g. ionised chromium), and atypical enhancements of [Ba/Fe], with values up to ~0.7 dex. Regarding the behaviour of the other s-process elements like yttrium, zirconium, lanthanum, and cerium, there is general disagreement in the literature: some authors claim that they follow the same trend as barium, while others find solar abundances at all ages. In this work we expand upon our previous analysis of a sample of five young open clusters (IC 2391, IC 2602, IC 4665, NGC 2516, and NGC 2547) and one star-forming region (NGC 2264), with the aim of determining abundances of different neutron-capture elements, mainly Cu.I, Sr.I, Sr.II, Y.II, Zr.II, Ba.II, La.II, and Ce.II. For NGC 2264 and NGC 2547 we present the measurements of these elements for the first time.


Harshal Deshmukh, Emma G. Wilmot, Pratik Choudhary, Parth Narendran, Najeeb Shah, Dennis Barnes, Shafie Kamruddin, Rumaisa Banatwalla, Peter Christian, Simon Saunders, Alistair Lumb, Roselle Herring, Jane Patmore, Chris Walton, Robert E.J. Ryder, Thozhukat Sathyapalan, 2021-09, Impaired Awareness of Hypoglycemia and Severe Hypoglycemia in Drivers With Diabetes: Insights From the Association of British Clinical Diabetologists Nationwide Audit, Diabetes Care, doi: 10.2337/dc21-1181

Abstract


Deshmukh H, Wilmot EG, Gregory R, Barnes D, Narendran P, Saunders S, Furlong N, Kamaruddin S, Banatwalla R, Herring R, Kilvert A, Patmore J, Walton C, Ryder REJ, Sathyapalan T., 2021-06-29, Predictors of diabetes-related distress before and after FreeStyle Libre-1 use: Lessons from the Association of British Clinical Diabetologists nationwide study, Diabetes, Obesity and Metabolism: A Journal of Pharmacology and Therapeutics, doi: 10.1111/dom.14467

Abstract

Aim: To identify the baseline demographic and clinical characteristics associated with diabetes-related distress (DRD) and factors associated with improvement in DRD after initiating use of the FreeStyle Libre (FSL) in people living with type 1 diabetes (T1D). Methods: The study was performed using baseline and follow-up data from the Association of British Clinical Diabetologists nationwide audit of people with diabetes who initiated use of the FSL in the United Kingdom. DRD was assessed using the two-item diabetes-related distress scale (DDS; defined as the average of the two-item score .3). People living with T1D were categorized into two groups: those with high DRD, defined as an average DDS score .3 and those with lower DRD, defined as a DDS score <3. We used a gradient-boosting machine-learning (GBM) model to identify the relative influence (RI) of baseline variables on average DDS score. Results: The study population consisted of 9159 patients, 96.6% of whom had T1D. The median (interquartile range [IQR]) age was 45.1 (32-56) years, 50.1% were women, the median (IQR) baseline body mass index was 26.1 (23.2-29.6) kg/m2 and the median (IQR) duration of diabetes was 20 (11-32) years. The two components of the DDS were significantly correlated (r2 = 0.73; P.<.0.0001). Higher DRD was prevalent in 53% (4879/9159) of people living with T1D at baseline. In the GBM model, the top baseline variables associated with average DDS score were baseline glycated haemoglobin (HbA1c; RI = 51.1), baseline Gold score (RI = 23.3), gender (RI = 7.05) and fear of hypoglycaemia (RI = 4.96). Follow-up data were available for 3312 participants. The top factors associated with improvement in DDS score following use of the FSL were change in Gold score (RI = 28.2) and change in baseline HbA1c (RI = 19.3). Conclusions: In this large UK cohort of people living with T1D, diabetes distress was prevalent and associated with higher HbA1c, impaired awareness of hypoglycaemia and female gender. Improvement in glycaemic control and hypoglycaemia unawareness with the use of the FSL was associated with improvement in DRD in people living with T1D.


Peter J. Watson, Alana C. Sharp, Tarun Choudhary, Michael J. Fagan, Hugo Dutel, Susan E. Evans & Flora Groning, 2021-06-23, Computational biomechanical modelling of the rabbit cranium during mastication, Scientific Reports, doi: 10.1038/s41598-021-92558-5

Abstract

Although a functional relationship between bone structure and mastication has been shown in some regions of the rabbit skull, the biomechanics of the whole cranium during mastication have yet to be fully explored. In terms of cranial biomechanics, the rabbit is a particularly interesting species due to its uniquely fenestrated rostrum, the mechanical function of which is debated. In addition, the rabbit processes food through incisor and molar biting within a single bite cycle, and the potential influence of these bite modes on skull biomechanics remains unknown. This study combined the in silico methods of multi-body dynamics and finite element analysis to compute musculoskeletal forces associated with a range of incisor and molar biting, and to predict the associated strains. The results show that the majority of the cranium, including the fenestrated rostrum, transmits masticatory strains. The peak strains generated over all bites were found to be attributed to both incisor and molar biting. This could be a consequence of a skull shape adapted to promote an even strain distribution for a combination of infrequent incisor bites and cyclic molar bites. However, some regions, such as the supraorbital process, experienced low peak strain for all masticatory loads considered, suggesting such regions are not designed to resist masticatory forces.


Richard J Stancliffe, 2021-06-21, The formation of barium giants via mass accretion in binary systems, Monthly Notices of the Royal Astronomical Society, doi: 10.1093/mnras/stab1734

Abstract

We examine the composition of barium stars in the context of mass transfer from an asymptotic giant branch (AGB) companion. We accrete between 0.01 and 0.5.M. of AGB ejecta on to low-mass companions of [Fe/H] = .0.25 at the ages expected for the end of the lives of AGB stars of 2.5, 3, and 4.M.. In each case, we form a star of 2.5.M. that is thought to be a typical barium star mass. We discuss the extent of dilution of accreted material as the star evolves, and describe the impact on the surface abundances. For accretion from a 2.5.M. primary, if the secondary’s initial mass is 2.45.M. or more, accretion takes place when the secondary is undergoing core helium burning. Using data from the sample of De Castro et al., we attempt to fit the observed properties of 74 barium giants using the models we have computed. We find that all but six of these objects are best fit using ejecta from 2.5.M. (32 objects) or 3.M. (36 objects) AGB stars. Higher accretion masses are typically required when accreting from a lower mass companion. We find accretion masses that are broadly consistent with recent hydrodynamical simulations of wind mass transfer, though the accretion efficiency is towards the upper limit found in these simulations. For the 18 stars with reported orbital periods, we find no strong correlations between period and accretion mass.


G Vasilopoulos, Q L Quan, D R Parsons, S E Darby, V P D Tri, N N Hung, I D Haigh, H E Voepel, A P Nicholas and R Aalto, 2021-06-16, Establishing sustainable sediment budgets is critical for climate-resilient mega-deltas, Environmental Research Letters, doi: 10.1088/1748-9326/ac06fc

Abstract

Many of the world’s major river deltas face a sustainability crisis, as they come under threat of increases in salinity and the extent of tidal zones forced by combinations of sea-level rise, changes in river discharge and channel geometry. The relative contribution of these factors to future increases in tidal extent remains unconstrained, with most prior work emphasising the role of climate-driven sea-level rise. Here we use new field data from the Mekong delta to measure variations of river discharge and changes of channel geometry, and project them into the future. We combine these with projections of future sea-level rise into a 2D hydrodynamic numerical model and quantify the influence of the different driving factors on future tidal extension into the delta. We show that within the next two decades, tidal extension into the Mekong delta will increase by up to 56 km due to channel deepening (92%), dominantly driven by anthropogenic sediment starvation. Furthermore, even under strong mitigation scenarios, sediment starvation still drives a long-term commitment to future tidal extension. Specifically, by 2098 eustatically rising sea-levels are predicted to contribute only modestly to the projected extension. These findings demonstrate the urgent need for policy makers to adopt evidence-based measures to reverse negative sediment budgets that drive tidal extension into sediment starved deltas.


Chongchitnan, S., Chantavat, T., Zunder, J., 2021-05-21, Extreme primordial black holes, Astronomische Nachrichten (Astronomical Notes), doi: 10.1002/asna.202113826

Abstract

We present a formalism for calculating the probability distribution of the most massive primordial black holes (PBHs) expected within an observational volume. We show how current observational upper bounds on the fraction of PBHs in dark matter translate to constraints on extreme masses of primordial black holes. We demonstrate the power of our formalism via a case study, and argue that our formalism can be used to produce extreme-value distributions for a wide range of PBH formation theories.


Jianguo Wang, Philip Rubini, Qin Qin, 2021-05-20, A porous media model for the numerical simulation of acoustic attenuation by perforated liners in the presence of grazing flows, Applied Sciences, doi: 10.3390/app11104677

Abstract

In this paper, a novel model is proposed for the numerical simulation of noise-attenuating perforated liners. Effusion cooling liners offer the potential of being able to attenuate combustion instabilities in gas turbine engines. However, the acoustic attenuation of a perforated liner is a combination of a number of interacting factors, resulting in the traditional approach of designing perforated combustor liners relying heavily on combustor rig tests. On the other hand, direct computation of thousands of small-scale holes is too expensive to be employed as an engineering design tool. In recognition of this, a novel physical velocity porous media (PVPM) model was recently proposed by the authors as a computationally less demanding approach to represent the acoustic attenuation of perforated liners. The model was previously validated for the normal incidence of a sound wave by comparison with experimental data from impedance tubes. In this paper, the model is further developed for configurations where the noise signal propagates in parallel with the perforated liners, both in the presence and absence of a mean flow. The model is significantly improved and successfully validated within coexisting grazing and bias flow scenarios, with reference to a series of well-recognized experimental data.


Schirrmacher, P., Roggatz, C.C., Benoit, D.M. et al, 2021-05-20, Ocean Acidification Amplifies the Olfactory Response to 2-Phenylethylamine: Altered Cue Reception as a Mechanistic Pathway?, Journal of Chemical Ecology, doi: 10.1007/s10886-021-01276-9

Abstract

With carbon dioxide (CO2) levels rising dramatically, climate change threatens marine environments. Due to increasing CO2 concentrations in the ocean, pH levels are expected to drop by 0.4 units by the end of the century. There is an urgent need to understand the impact of ocean acidification on chemical-ecological processes. To date, the extent and mechanisms by which the decreasing ocean pH influences chemical communication are unclear. Combining behaviour assays with computational chemistry, we explore the function of the predator related cue 2-phenylethylamine (PEA) for hermit crabs (Pagurus bernhardus) in current and end-of-the-century oceanic pH. Living in intertidal environments, hermit crabs face large pH fluctuations in their current habitat in addition to climate-change related ocean acidification. We demonstrate that the dietary predator cue PEA for mammals and sea lampreys is an attractant for hermit crabs, with the potency of the cue increasing with decreasing pH levels. In order to explain this increased potency, we assess changes to PEA’s conformational and charge-related properties as one potential mechanistic pathway. Using quantum chemical calculations validated by NMR spectroscopy, we characterise the different protonation states of PEA in water. We show how protonation of PEA could affect receptor-ligand binding, using a possible model receptor for PEA (human TAAR1). Investigating potential mechanisms of pH-dependent effects on olfactory perception of PEA and the respective behavioural response, our study advances the understanding of how ocean acidification interferes with the sense of smell and thereby might impact essential ecological interactions in marine ecosystems.


N. J. Hubbard, C. Aa. Diget, S. P. Fox, H. O. U. Fynbo, A. M. Howard, O. S. Kirsebom, A. M. Laird, M. Munch, A. Parikh, M. Pignatari, and J. R. Tomlinson, 2021-05-05, New Experimental 23Na(α, p)26Mg Reaction Rate for Massive Star and Type Ia Supernova Models, The Astrophysical Journal, doi: 10.3847/1538-4357/abee91

Abstract

The 23Na(α, p)26Mg reaction has been identified as having a significant impact on the nucleosynthesis of several nuclei between Ne and Ti in Type Ia supernovae, and of 23Na and 26Al in massive stars. The reaction has been subjected to renewed experimental interest recently, motivated by high uncertainties in early experimental data and in the statistical Hauser-Feshbach models used in reaction rate compilations. Early experiments were affected by target deterioration issues and unquantifiable uncertainties. Three new independent measurements instead are utilizing inverse kinematics and Rutherford scattering monitoring to resolve this. In this work we present directly measured angular distributions of the emitted protons to eliminate a discrepancy in the assumptions made in the recent reaction rate measurements, which results in cross sections differing by a factor of 3. We derive a new combined experimental reaction rate for the 23Na(α, p)26Mg reaction with a total uncertainty of 30% at relevant temperatures. Using our new 23Na(α, p)26Mg rate, the 26Al and 23Na production uncertainty is reduced to within 8%. In comparison, using the factor of 10 uncertainty previously recommended by the rate compilation STARLIB, 26Al and 23Na production was changing by more than a factor of 2. In Type Ia supernova conditions, the impact on production of 23Na is constrained to within 15%.


Morgan, S. O. and Fox, J. and Lowe, C. and Adawi, A. M. and Bouillard, J.-S. G. and Stasiuk, G. J. and Horozov, T. S. and Buzza, D. M. A., 2021-04-12, Adsorption trajectories of nonspherical particles at liquid interfaces, Physical Review E, doi: 10.1103/PhysRevE.103.042604

Abstract

The adsorption of colloidal particles at liquid interfaces is of great importance scientifically and industrially, but the dynamics of the adsorption process is still poorly understood. In this paper we use a Langevin model to study the adsorption dynamics of ellipsoidal colloids at a liquid interface. Interfacial deformations are included by coupling our Langevin dynamics to a finite element model while transient contact line pinning due to nanoscale defects on the particle surface is encoded into our model by renormalizing particle friction coefficients and using dynamic contact angles relevant to the adsorption timescale. Our simple model reproduces the monotonic variation of particle orientation with time that is observed experimentally and is also able to quantitatively model the adsorption dynamics for some experimental ellipsoidal systems but not others. However, even for the latter case, our model accurately captures the adsorption trajectory (i.e., particle orientation versus height) of the particles. Our study clarifies the subtle interplay between capillary, viscous, and contact line forces in determining the wetting dynamics of micron-scale objects, allowing us to design more efficient assembly processes for complex particles at liquid interfaces.


Zhiguo Zhang and Chuangnan Wang and Billy Koe and Christian M. Schleputz and Sarah Irvine and Jiawei Mi, 2021-03-14, Synchrotron X-ray imaging and ultrafast tomography in situ study of the fragmentation and growth dynamics of dendritic microstructures in solidification under ultrasound, Acta Materialia, doi: 10.1016/j.actamat.2021.116796

Abstract

High speed synchrotron X-ray imaging and ultrafast tomography were used to study in situ and in real time the fragmentation and growth dynamics of dendritic microstructures of an Al-15%Cu alloy in solidification under ultrasound. Under the studied condition, a strong swirling acoustic flow of ∼0.3 m/s was observed, resulting in efficient dendrite fragmentation due to thermal perturbation remelting plus mechanical fracture and separation effects. Acoustic flow fatigue impact and phase collision effects were found to play a minor role in causing dendrite fragmentation. Just 10 s of ultrasound application at the early stage of solidification produced ∼100% more dendrite fragments compared to the case without ultrasound, resulting in 20∼25% reduction in the average grain size in the solidified samples. Furthermore, the dendrite morphology and tip growth velocity were mainly affected by the initial dendrite fragment number density and their distribution. The systematic and real-time datasets obtained in near operando conditions provided valuable 4D information for validation of numerical models and assistance in developing optimisation strategy for ultrasound melt processing in industry.


Cordova-Castro, R. M., Krasavin, A. V., Nasir, M. E., Wang, P., Bouillard, J. S. G., McPolin, C. P. T., & Zayats, A. V, 2021-03, Mode Engineering in Large Arrays of Coupled Plasmonic-Dielectric Nanoantennas, Advanced Optical Materials, doi: 10.1002/adom.202001467

Abstract

Strong electromagnetic field confinement and enhancement can be readily achieved in plasmonic nanoantennas, however, this is considerably more difficult to realize over large areas, which is essential for many applications. Here, dispersion engineering in plasmonic metamaterials is applied to successfully develop and demonstrate a coupled array of plasmonic-dielectric nanoantennas offering an ultrahigh density of electromagnetic hot spots (10 cm ) over macroscopic, centimeter scale areas. The hetero-metamaterial is formed by a highly ordered array of vertically standing plasmonic dipolar antennas with a ZnO gap and fabricated using a scalable electrodeposition technique. It supports a complex modal structure, including guided, surface and gap modes, which offers rich opportunities, frequently beyond the local effective medium theory, with optical properties that can be easily controlled and defined at the fabrication stage. This metamaterial platform can be used in a wide variety of applications, including hot-electron generation, nanoscale light sources, sensors, as well as nonlinear and memristive devices.


Cote, Benoit and Eichler, Marius and Yague Lopez, Andres and Vassh, Nicole and Mumpower, Matthew R. and Vilagos, Blanka and Soos, Benjamin and Arcones, Almudena and Sprouse, Trevor M. and Surman, Rebecca and Pignatari, Marco and Peto, Maria K. and Wehmeyer, Benjamin and Rauscher, Thomas and Lugaro, Maria, 2021-02-26, 129I and 247Cm in meteorites constrain the last astrophysical source of solar r-process elements, Science, doi: 10.1126/science.aba1111

Abstract

The composition of the early Solar System can be inferred from meteorites. Many elements heavier than iron were formed by the rapid neutron capture process (r-process), but the astrophysical sources where this occurred remain poorly understood. We demonstrate that the near-identical half-lives (≃15.6 million years) of the radioactive r-process nuclei iodine-129 and curium-247 preserve their ratio, irrespective of the time between production and incorporation into the Solar System. We constrain the last r-process source by comparing the measured meteoritic ratio 129I/247Cm = 438 ± 184 with nucleosynthesis calculations based on neutron star merger and magneto-rotational supernova simulations. Moderately neutron-rich conditions, often found in merger disk ejecta simulations, are most consistent with the meteoritic value. Uncertain nuclear physics data limit our confidence in this conclusion.


James D Keegans, Richard J Stancliffe, Lawrence E Bilton, Claire R Cashmore, Brad K Gibson, Mikkel Theiss Kristensen, Thomas V Lawson, Marco Pignatari, Iraj Vaezzadeh, Benoit Cote, 2021-02-11, Project ThaiPASS: international outreach blending astronomy and Python, Physics Education, doi: 10.1088/1361-6552/abdae7

Abstract

We present our outreach program, the Thailand-UK Python+Astronomy Summer School (ThaiPASS), a collaborative project comprising UK and Thai institutions and assess its impact and possible application to schools in the United Kingdom. Since its inception in 2018, the annual ThaiPASS has trained around 60 Thai high-school students in basic data handling skills using Python in the context of various astronomy topics, using current research from the teaching team. Our impact assessment of the 5 day summer schools shows an overwhelmingly positive response from students in both years, with over 80% of students scoring the activities above average in all activities but one. We use this data to suggest possible future improvements. We also discuss how ThaiPASS may inspire further outreach and engagement activities within the UK and beyond.


Jaehyun Lee and Jihye Shin and Owain N. Snaith and Yonghwi Kim and C. Gareth Few and Julien Devriendt and Yohan Dubois and Leah M. Cox and Sungwook E. Hong and Oh-Kyoung Kwon and Chan Park and Christophe Pichon and Juhan Kim and Brad K. Gibson and Changbom Park, 2021-02-08, The Horizon Run 5 Cosmological Hydrodynamical Simulation: Probing Galaxy Formation from Kilo- to Gigaparsec Scales, The Astrophysical Journal, doi: 10.3847/1538-4357/abd08b

Abstract

Horizon Run 5 (HR5) is a cosmological hydrodynamical simulation that captures the properties of the universe on a Gpc scale while achieving a resolution of 1 kpc. Inside the simulation box, we zoom in on a high-resolution cuboid region with a volume of 1049 x 119 x 127 cMpc3. The subgrid physics chosen to model galaxy formation includes radiative heating/cooling, UV background, star formation, supernova feedback, chemical evolution tracking the enrichment of oxygen and iron, the growth of supermassive black holes, and feedback from active galactic nuclei in the form of a dual jet-heating mode. For this simulation, we implemented a hybrid MPI-OpenMP version of RAMSES, specifically targeted for modern many-core many-thread parallel architectures. In addition to the traditional simulation snapshots, lightcone data were generated on the fly. For the post-processing, we extended the friends-of-friend algorithm and developed a new galaxy finder PGalF to analyze the outputs of HR5. The simulation successfully reproduces observations, such as the cosmic star formation history and connectivity of galaxy distribution, We identify cosmological structures at a wide range of scales, from filaments with a length of several cMpc, to voids with a radius of ~100 cMpc. The simulation also indicates that hydrodynamical effects on small scales impact galaxy clustering up to very large scales near and beyond the baryonic acoustic oscillation scale. Hence, caution should be taken when using that scale as a cosmic standard ruler: one needs to carefully understand the corresponding biases. The simulation is expected to be an invaluable asset for the interpretation of upcoming deep surveys of the universe.


Abdullah O. Hamza, Francesco N. Viscomi, Jean-Sebastien G. Bouillard, and Ali M. Adawi, 2021-02-03, Förster Resonance Energy Transfer and the Local Optical Density of States in Plasmonic Nanogaps, The Journal of Physical Chemistry Letters, doi: 10.1021/acs.jpclett.0c03702

Abstract

Förster resonance energy transfer (FRET) is a fundamental phenomenon in photosynthesis and is of increasing importance for the development and enhancement of a wide range of optoelectronic devices, including color-tuning LEDs and lasers, light harvesting, sensing systems, and quantum computing. Despite its importance, fundamental questions remain unanswered on the FRET rate dependency on the local density of optical states (LDOS). In this work, we investigate this directly, both theoretically and experimentally, using 30 nm plasmonic nanogaps formed between a silver nanoparticle and an extended silver film, in which the LDOS can be controlled using the size of the silver nanoparticle. Experimentally, uranin–rhodamine 6G donor–acceptor pairs coupled to such nanogaps yielded FRET rate enhancements of 3.6 times. This, combined with a 5-fold enhancement in the emission rate of the acceptor, resulted in an overall 14-fold enhancement in the acceptor’s emission intensity. By tuning the nanoparticle size, we also show that the FRET rate in those systems is linearly dependent on the LDOS, a result which is directly supported by our finite difference time domain (FDTD) calculations. Our results provide a simple but powerful method to control FRET rate via a direct LDOS modification.


Hugo Dutel, Flora Groning, Alana C. Sharp, Peter J. Watson, Anthony Herrel, Callum F. Ross, Marc E. H. Jones, Susan E. Evans, Michael J. Fagan, 2021-01-27, Comparative cranial biomechanics in two lizard species: impact of variation in cranial design, Journal of Experimental Biology, doi: 10.1242/jeb.234831

Abstract

Cranial morphology in lepidosaurs is highly disparate and characterized by the frequent loss or reduction of bony elements. In varanids and geckos, the loss of the postorbital bar is associated with changes in skull shape, but the mechanical principles underlying this variation remain poorly understood. Here, we seek to determine how the overall cranial architecture and the presence of the postorbital bar relate to the loading and deformation of the cranial bones during biting in lepidosaurs. Using computer-based simulation techniques, we compare cranial biomechanics in the varanid Varanus niloticus and the teiid Salvator merianae, two large, active foragers. The overall strain magnitudes and distribution across the cranium is similar in both species, despite lower strain gradients in Varanus niloticus. In Salvator merianae, the postorbital bar is important for the resistance of the cranium to feeding loads. The postorbital ligament, which partially replaces the postorbital bar in varanids, does not affect bone strain. Our results suggest that the reduction of the postorbital bar impaired neither biting performance nor the structural resistance of the cranium to feeding loads in Varanus niloticus. Differences in bone strain between the two species might reflect demands imposed by feeding and non-feeding functions on cranial shape. Beyond variation in cranial bone strain related to species-specific morphological differences, our results reveal that similar mechanical behaviour is shared by lizards with distinct cranial shapes. Contrary to mammals, the morphology of the circumorbital region, calvaria and palate appears to be important for withstanding high feeding loads in these lizards.


Efthimiou, Nikos and Wright, John D. and Clayton, Luke and Renard, Isaline and Zagni, Federico and Caribe, Paulo R.R.V. and Archibald, Stephen J. and Cawthorne, Christopher J., 2021-01-12, Influence of Multiple Animal Scanning on Image Quality for the Sedecal SuperArgus2R Preclinical PET Scanner, Frontiers in Physics, doi: 10.3389/fphy.2020.531662

Abstract

Background: Increased throughput in small animal preclinical studies using positron emission tomography leads to reduced costs and improved efficiency of experimental design, however the presence of multiple off-centre subjects, as opposed to a single centered one, may affect image quality in several ways. Methods: We evaluated the count rate performance using a NEMA scatter phantom. A Monte Carlo simulation of the system was validated against this dataset and used to simulate the count rate performance for dual scatter phantoms. NEMA NU4 image quality phantoms were then scanned in the central and offset positions, as well as in the offset position next to a uniform activity phantom. Uniformity, recovery coefficients and spillover ratios were then compared, as were two time frames for acquisition. Results: Count rate performance assessed with a single NEMA scatter phantom was in line with previous literature, with simulated data in good agreement. Simulation of dual scatter phantoms showed an increase in scatter fraction. For the NEMA Image Quality phantom, uniformity and Recovery coefficients were degraded in the offset, and dual phantom cases, while spillover ratios were increased, notably when the chamber was placed nearest the gantry. Image quality metrics were comparable between the 20- and 10 min timeframes. Conclusion: Dual animal scanning results in some loss of image quality on the Sedecal Argus PET scanner; however, this degradation is within acceptable limits.


Nina Dethlefs and Annika Schoene and Heriberto Cuayahuitl, 2021-01-05, A divide-and-conquer approach to neural natural language generation from structured data, Neurocomputing, doi: 10.1016/j.neucom.2020.12.083

Abstract

Current approaches that generate text from linked data for complex real-world domains can face problems including rich and sparse vocabularies as well as learning from examples of long varied sequences. In this article, we propose a novel divide-and-conquer approach that automatically induces a hierarchy of “generation spaces” from a dataset of semantic concepts and texts. Generation spaces are based on a notion of similarity of partial knowledge graphs that represent the domain and feed into a hierarchy of sequence-to-sequence or memory-to-sequence learners for concept-to-text generation. An advantage of our approach is that learning models are exposed to the most relevant examples during training which can avoid bias towards majority samples. We evaluate our approach on two common benchmark datasets and compare our hierarchical approach against a flat learning setup. We also conduct a comparison between sequence-to-sequence and memory-to-sequence learning models. Experiments show that our hierarchical approach overcomes issues of data sparsity and learns robust lexico-syntactic patterns, consistently outperforming flat baselines and previous work by up to 30%. We also find that while memory-to-sequence models can outperform sequence-to-sequence models in some cases, the latter are generally more stable in their performance and represent a safer overall choice.



2020 (28 outputs)

Efthimiou, Nikos and Kratochwil, Nicolaus and Gundacker, Stefan and Polesel, Andrea and Salomoni, Matteo and Auffray, Etiennette and Pizzichemi, Marco, 2020-12-31, TOF-PET image reconstruction with multiple timing kernels applied on Cherenkov radiation in BGO, IEEE Transactions on Radiation and Plasma Medical Sciences, doi: 10.1109/TRPMS.2020.3048642

Abstract

Today Time-Of-Flight (TOF), in PET scanners, assumes a single, well-defined timing resolution for all events. However, recent BGO-Cherenkov detectors, combining prompt Cherenkov emission and the typical BGO scintillation, can sort events into multiple timing kernels, best described by Gaussian mixture models. The number of Cherenkov photons detected per event impacts directly the detector time resolution and signal rise time, which can later be used to improve the coincidence timing resolution. This work presents a simulation toolkit which applies multiple timing spreads on the coincident events and an image reconstruction that incorporates this information. A full cylindrical BGO-Cherenkov PET model was compared, in terms of contrast recovery and contrast-to-noise ratio, against an LYSO model with a time resolution of 213 ps. Two reconstruction approaches for the mixture kernels were tested; mixture Gaussian and decomposed simple Gaussian kernels. The decomposed model used the exact mixture component applied during the simulation. Images reconstructed using mixture kernels provided similar mean value and less noise than the decomposed. However, typically, more iterations were needed. Similarly, the LYSO model, with a single TOF kernel, converged faster than the BGO-Cherenkov with multiple kernels. The results indicate that model complexity slows down convergence. However, due to the higher sensitivity, the contrast-to-noise ratio was 26.4% better for the BGO model.


S. S. Rana and X. Ma and W. Pang and E. Wolverson, 2020-12-28, A Multi-Modal Deep Learning Approach to the Early Prediction of Mild Cognitive Impairment Conversion to Alzheimer’s Disease, 2020 IEEE/ACM International Conference on Big Data Computing, Applications and Technologies (BDCAT), doi: 10.1109/BDCAT50828.2020.00013

Abstract

Mild cognitive impairment (MCI) has been described as the intermediary stage before Alzheimer’s Disease – many people however remain stable or even demonstrate improvement in cognition. Early detection of progressive MCI (pMCI) therefore can be utilised in identifying at-risk individuals and directing additional medical treatment in order to revert conversion to AD as well as provide psychosocial support for the person and their family.This paper presents a novel solution in the early detection of pMCI people and classification of AD risk within MCI people. We proposed a model, MudNet, to utilise deep learning in the simultaneous prediction of progressive/stable MCI classes and time-to-AD conversion where high-risk pMCI people see conversion to AD within 24 months and low-risk people greater than 24 months. MudNet is trained and validated using baseline clinical and volumetric MRI data (n = 559 scans) from participants of the Alzheimer’s Disease Neuroimaging Initiative (ADNI). The model utilises T1-weighted structural MRIs alongside clinical data which also contains neuropsychological (RAVLT, ADAS-11, ADAS-13, ADASQ4, MMSE) tests as inputs.The averaged results of our model indicate a binary accuracy of 69.8% for conversion predictions and a categorical accuracy of 66.9% for risk classifications.


Zhiguo Zhang and Jia Chuan Khong and Billy Koe and Shifeng Luo and Shi Huang and Ling Qin and Silvia Cipiccia and Darren Batey and Andrew J. Bodey and Christoph Rau and Yu Lung Chiu and Zhu Zhang and Jean-Christophe Gebelin and Nick Green and Jiawei Mi, 2020-11-01, Multiscale characterization of the 3D network structure of metal carbides in a Ni superalloy by synchrotron X-ray microtomography and ptychography, Scripta Materialia, doi: 10.1016/j.scriptamat.2020.10.032

Abstract

Synchrotron X-ray microtomography and ptychography were used to characterize the 3D network structure, morphology and distribution of metal carbides in an as-cast IN713LC Ni superalloy. MC typed carbides were found to distribute mainly on the grain boundary between the matrix γ and γ’ phase. The differences in solidification cooling rate had a minor influence on the volume fraction of the MC type carbides, but significantly affected the carbide size, distribution and network morphology. Depending on the local composition of the remaining liquid phase and geometric constraints, the carbides can form either spherical or strip or network morphologies. The research demonstrated clearly the advantage and technical potential of using the two complementary tomography techniques synergistically to characterize non-destructively complex multiple-phase structures in three dimensional space with a spatial resolution of ~30 nm.


Efthimiou, Nikos and Kratochwil, Nicolaus and Gundacker, Stefan and Polesel, Andrea and Salomoni, Matteo and Auffray, Etiennette and Pizzichemi, Marco, 2020-10-31, Time-Of-Flight PET Image Reconstruction with Complex Timing Kernels: The Case of BGO Cherenkov Photons, 2020 IEEE Nuclear Science Symposium and Medical Imaging Conference (NSS/MIC), doi: 10.1109/NSS/MIC42677.2020.9508046

Abstract

Time-of-Flight (TOF) reconstruction in Positron Emission Tomographic (PET) scanners uses a single kernel to reconstruct all events. However, recently developed detectors combining prompt emission and typical scintillation signal produce output events with different timing spreads. One such detectors technology is based on BGO crystals with Cherenkov photons. Thanks to fast silicon photo-multipliers sensitive in the near-ultraviolet and high-frequency electronic readout, the faint Cherenkov signal produced by the interaction of 511 keV gamma photons can be detected as faster pulse rise times. We present initial results from a Monte Carlo simulation and image reconstruction platform for detectors with multiple timing resolutions in this work. Simulated timing spreads show excellent agreement with the experimental measurements. In addition, the reconstruction software can reconstruct images using listmode and projection data. In terms of contrast recovery, the proposed multi-kernel model with BGO-Cherenkov detectors presents a similar recovery as a typical Gaussian model with LYSO detectors and timing resolution 213 ps. To the best of our knowledge, the use of multiple complex TOF kernels in image reconstruction has not been investigated in the past. However, further optimisations are needed in order to obtain the best possible results.


Clark, Victoria H.J. and Benoit, David M., 2020-10-12, The vibrational signatures of polyaromatic hydrocarbons on an ice surface, Proceedings of the International Astronomical Union, doi: 10.1017/S174392131900944X

Abstract

We use quantum chemical techniques to model the vibrational spectra of small aromatic molecules on a proton-ordered hexagonal crystalline water ice (XIh) model. We achieve a good agreement with experimental data by accounting for vibrational anharmonicity and correcting the potential energy landscape for known failures of density functional theory. A standard harmonic description of the vibrational spectra only leads to a broad qualitative agreement.


T. Mishenina, E. Shereta, M. Pignatari, G. Carraro, T. Gorbaneva, C. Soubiran, 2020-10-07, Molybdenum in the open cluster stars, Journal of Physical Studies, doi: 10.30970/jps.24.3901

Abstract

Molybdenum abundances in the stars from 13 different open clusters have been determined. High-resolution stellar spectra have been obtained using the VLT telescope equipped with the UVES spectrograph on Cerro Paranal, Chile. The Mo abundances have been derived in the LTE approximation from the Mo I lines at 5506 A and 5533 A. A comparative analysis of the behaviour of molybdenum in the sampled stars of open clusters and Galactic disc show similar trends of decreasing Mo abundances with increasing metallicities; such a behaviour pattern suggests a common origin of the examined populations. On the other hand, the scatter of Mo abundances in the open cluster stars is slightly greater, 0.14 dex versus 0.11 dex. The results are discussed, considering the abundance trends with the age of clusters and distances from the center of the Galaxy.


J. Chatterjee and N. Dethlefs, 2020-09-28, A Dual Transformer Model for Intelligent Decision Support for Maintenance of Wind Turbines, 2020 International Joint Conference on Neural Networks (IJCNN), doi: 10.1109/IJCNN48605.2020.9206839

Abstract

Wind energy is one of the fastest-growing sustainable energy sources in the world but relies crucially on efficient and effective operations and maintenance to generate sufficient amounts of energy and reduce downtime of wind turbines and associated costs. Machine learning has been applied to fault prediction in wind turbines, but these predictions have not been supported with suggestions on how to avert and fix faults. We present a data-to-text generation system utilising transformers for generating corrective maintenance strategies for faults using SCADA data capturing the operational status of turbines. We achieve this in two stages: a first stage identifies faults based on SCADA input features and their relevance. A second stage performs content selection for the language generation task and creates maintenance strategies based on phrase-based natural language templates. Experiments show that our dual transformer model achieves an accuracy of up to 96.75% for alarm prediction and up to 75.35% for its choice of maintenance strategies during content-selection. A qualitative analysis shows that our generated maintenance strategies are promising. We make our human- authored maintenance templates publicly available, and include a brief video explaining our approach.


Zeng, Qingmao and Ma, Xinhui and Cheng, Baoping and Zhou, Erxun and Pang, Wei, 2020-09-18, GANs-Based Data Augmentation for Citrus Disease Severity Detection Using Deep Learning, IEEE Access, doi: 10.1109/ACCESS.2020.3025196

Abstract

Recently, many Deep Learning models have been employed to classify different kinds of plant diseases, but very little work has been done for disease severity detection. However, it is more important to master the severities of plant diseases accurately and timely, as it helps to make effective decisions to protect the plants from being further infected and reduce financial loss. In this paper, based on the Huanglongbing (HLB)-infected leaf images obtained from PlantVillage and crowdAI , we created a dataset with 5,406 citrus leaf images infected by HLB. Then six different kinds of popular models were trained to perform the severity detection of citrus HLB with the goal to find which types of models are more suitable to detect HLB severity with the same training circumstance. The experimental results show that the Inception_v3 model with epochs=60 can achieve higher accuracy than that of other models for severity detection with an accuracy of 74.38% due to its highly computational efficiency and small number of parameters. Additionally, aiming for evaluating whether GANs-based data augmentation can contribute to improve the model learning performance, we adopted DCGANs (Deep Convolutional Generative Adversarial Networks) to augment the original training dataset up to two times itself. Finally, a new training dataset with 14,056 leaf images composed by the original training images and the augmented ones were used to train the Inception_v3 model. As a result, we achieved an accuracy of 92.60%, about 20% higher than that of the Inception_v3 model trained by the original training dataset, which suggested that the GANs-based data augmentation is very useful to improve the model learning performance.


Deshmukh H, Papageorgiou M, Aye M, England J, Abdalla M, Sathyapalan T., 2020-09-18, Hyperthyroidism and bone mineral density: Dissecting the causal association with Mendelian randomization analysis, Clinical Endocrinology, doi: 10.1111/cen.14330

Abstract

Introduction: Untreated hyperthyroidism is associated with accelerated bone turnover, low bone mineral density (BMD) and increased susceptibility to fragility fractures. Although treatment appears to improve or even reverse some of these adverse skeletal effects, there is limited guidance on routine BMD assessment in hyperthyroid patients following treatment. By using Mendelian randomization (MR) analysis, we aimed to assess the causal association of hyperthyroid thyroid states with BMD and fractures using the UK Biobank. Methods: This MR analysis included data from 473 818 participants (women: 54% of the total sample, the median age of 58.0 years (IQR = 50-63 years), median body mass index (BMI) of 26.70 (IQR + 24.11-29.82 kg/m2) as part of the UK Biobank study. The study outcomes were heel BMD assessed by quantitative ultrasound of the heel and self-reported fractures. Beta-weighted genetic risk score analysis was performed using 19 single nucleotide polymorphisms (SNPs) for Graves’ disease, 9 SNPs for hyperthyroidism and 11 SNPs for autoimmune thyroiditis. Since the unadjusted risk score MR is equivalent to the inverse-variance weighted method, the genetic risk score analysis was adjusted for age, gender and BMI. Sensitivity analyses were conducted using the Mendelian randomization-Egger (MR-Egger) and the inverse-variance weighted estimate methods. Replication analysis was performed using the GEnetic Factors for Osteoporosis (GEFOS) consortium data. Results: MR analysis using beta-weighted genetic risk score showed no association of genetic risk for Graves’ disease (Beta = .0.01, P-value = .10), autoimmune thyroiditis (Beta = .0.006 P-value = .25) and hyperthyroidism (Beta = .0.009, P-value = .18) with heel ultrasound BMD. MR-Egger and inverse-variance MR methods in UK Biobank and GEFOS consortium confirmed these findings. The genetic risk for these hyperthyroid conditions was not associated with an increased risk of fractures. Conclusion: Our study shows that excess genetic risk for Graves’ autoimmune thyroiditis and hyperthyroidism does not increase the risk for low BMD and is not associated fractures in the Caucasian population. Our findings do not support routine screening for osteoporosis following definitive treatment of hyperthyroid states.


Meyer, A. and de Sereville, N. and Laird, A. M. and Hammache, F. and Longland, R. and Lawson, T. and Pignatari, M. and Audouin, L. and Beaumel, D. and Fortier, S. and Kiener, J. and Lefebvre-Schuhl, A. and Pellegriti, M. G. and Stanoiu, M. and Tatischeff, V., 2020-09-09, Evaluation of the 13N(α,p)16O thermonuclear reaction rate and its impact on the isotopic composition of supernova grains, Physical Review C, doi: 10.1103/PhysRevC.102.035803

Abstract

Background: It has been recently suggested that hydrogen ingestion into the helium shell of massive stars could lead to high 13C and 15N excesses when the shock of a core-collapse supernova passes through its helium shell. This prediction questions the origin of extremely high 13C and 15N abundances observed in rare presolar SiC grains which is usually attributed to classical novae. In this context the 13N(α,p)16O reaction plays an important role since it is in competition with 13Nβ+ decay to 13C.


Liu, Z and Stancliffe, R, 2020-09, A closer look at non-interacting He stars as a channel for producing the old population of type Ia supernovae, Astronomy & Astrophysics, doi: 10.1051/0004-6361/202038443

Abstract

The nature of the progenitors of type Ia supernovae (SNe Ia) remains a mystery. Binary systems consisting of a white dwarf (WD) and a main-sequence (MS) donor are potential progenitors of SNe Ia, in which a thermonuclear explosion of the WD may occur when its mass reaches the Chandrasekhar limit during accretion of material from a companion star. In the present work, we address theoretical rates and delay times of a specific MS donor channel to SNe Ia, in which a helium (He) star + MS binary produced from a common envelope event subsequently forms a WD + MS system without the He star undergoing mass transfer by Roche lobe overflow. By combining the results of self-consistent binary evolution calculations with population synthesis models, we find that the contribution of SNe Ia in this channel is around 2.0.×.10-4.yr-1. In addition, we find that delay times of SNe Ia in this channel cover a range of about 1.0-2.6.Gyr, and almost all SNe Ia produced in this way (about 97%) have a delay time of ~>1.Gyr. While the rate of SN Ia in this work is about 10% of the overall SN Ia rate, the channel represents a possible contribution to the old population (1-3.Gyr) of observed SNe Ia.


U Battino, M Pignatari, C Travaglio, C Lederer-Woods, P Denissenkov, F Herwig, F Thielemann, T Rauscher, 2020-08-13, Heavy elements nucleosynthesis on accreting white dwarfs: building seeds for the p-process, Monthly Notices of the Royal Astronomical Society, doi: 10.1093/mnras/staa2281

Abstract

The origin of the proton-rich trans-iron isotopes in the Solar system is still uncertain. Single-degenerate thermonuclear supernovae (SNIa) with n-capture nucleosynthesis seeds assembled in the external layers of the progenitor’s rapidly accreting white dwarf (RAWD) phase may produce these isotopes. We calculate the stellar structure of the accretion phase of five white dwarf (WD) models with initial masses ≥ 0.85 M⊙ using the stellar code MESA The near-surface layers of the 1, 1.26, 1.32 and 1.38 M⊙ models are most representative of the regions in which the bulk of the p nuclei are produced during SNIa explosions, and for these models we also calculate the neutron-capture nucleosynthesis in the external layers. Contrary to previous RAWD models at lower mass, we find that the H-shell flashes are the main site of n-capture nucleosynthesis. We find high neutron densities up to several 1015 cm−3 in the most massive WDs. Through the recurrence of the H-shell flashes these intermediate neutron densities can be sustained effectively for a long time leading to high-neutron exposures with a strong production up to Pb. Both the neutron density and the neutron exposure increase with increasing the mass of the accreting WD. Finally, the SNIa nucleosynthesis is calculated using the obtained abundances as seeds. We obtain solar to supersolar abundances for p-nuclei with A > 96. Our models show that SNIa are a viable p-process production site.


Richter, W. A. and Brown, B. A. and Longland, R. and Wrede, C. and Denissenkov, P. and Fry, C. and Herwig, F. and Kurtulgil, D. and Pignatari, M. and Reifarth, R., 2020-08-04, Shell-model studies of the astrophysical rp-process reactions 34S(p,γ)35Cl and 34g,mCl(p,γ)35Ar, Physical Review C, doi: 10.1103/PhysRevC.102.025801

Abstract

Background: Dust grains condensed in the outflows of presolar classical novae should have been present in the protosolar nebula. Candidates for such presolar nova grains have been found in primitive meteorites and can in principle be identified by their isotopic ratios, but the ratios predicted by state-of-the-art one-dimensional hydrodynamic models are uncertain due to nuclear-physics uncertainties.


Maria Lugaro, Borbala Cseh, Blanka Vilagos, Amanda I. Karakas, Paolo Ventura, Flavia Dell’Agli, Reto Trappitsch, Melanie Hampel, Valentina D’Orazi, Claudio B. Pereira, Giuseppe Tagliente, Gyula M. Szabo, Marco Pignatari, Umberto Battino, Ashley Tattersall, Mattias Ek, Maria Schonbachler, Josef Hron, and Larry R. Nittler, 2020-07-28, Origin of Large Meteoritic SiC Stardust Grains in Metal-rich AGB Stars, The Astrophysical Journal, doi: 10.3847/1538-4357/ab9e74

Abstract

Stardust grains that originated in ancient stars and supernovae are recovered from meteorites and carry the detailed composition of their astronomical sites of origin. We present evidence that the majority of large (μm-sized) meteoritic silicon carbide (SiC) grains formed in C-rich asymptotic giant branch (AGB) stars that were more metal-rich than the Sun. In the framework of the slow neutron captures (the s process) that occur in AGB stars, the lower-than-solar ${}^{88}$Sr/${}^{86}$Sr isotopic ratios measured in the large SiC grains can only be accompanied by Ce/Y elemental ratios that are also lower than solar and predominately observed in metal-rich barium stars – the binary companions of AGB stars. Such an origin suggests that these large grains represent the material from high-metallicity AGB stars needed to explain the s-process nucleosynthesis variations observed in bulk meteorites. In the outflows of metal-rich, C-rich AGB stars, SiC grains are predicted to be small (sime0.2 μm); large (simeμm-sized) SiC grains can grow if the number of dust seeds is 2-3 orders of magnitude lower than the standard value of 10−13 times the number of H atoms. We therefore predict that with increasing metallicity, the number of dust seeds might decrease, resulting in the production of larger SiC grains.


Deshmukh H, Wilmot EG, Gregory R, Barnes D, Narendran P, Saunders S, Furlong N, Kamaruddin S, Banatwalla R, Herring R, Kilvert A, Patmore J, Walton C, Ryder REJ, Sathyapalan T., 2020-07-15, Effect of Flash Glucose Monitoring on Glycemic Control, Hypoglycemia, Diabetes-Related Distress, and Resource Utilization in the Association of British Clinical Diabetologists (ABCD) Nationwide Audit, Diabetes Care, doi: 10.2337/dc20-0738

Abstract

Objective: The FreeStyle Libre (FSL) flash glucose-monitoring device was made available on the U.K. National Health Service (NHS) drug tariff in 2017. This study aims to explore the U.K. real-world experience of FSL and the impact on glycemic control, hypoglycemia, diabetes-related distress, and hospital admissions.


Scacchi, A., Somerville, W. R. C., Buzza, D. M., & Archer, A. J., 2020-07, Quasicrystal formation in binary soft matter mixtures, Physical Review Research, doi: 10.1103/PhysRevResearch.2.032043

Abstract

Using a strategy that may be applied in theory or in experiments, we identify the regime in which a model binary soft matter mixture forms quasicrystals. The system is described using classical density functional theory combined with integral equation theory. Quasicrystal formation requires particle ordering with two characteristic length scales in certain particular ratios. How the length scales are related to the form of the pair interactions is reasonably well understood for one-component systems, but less is known for mixtures. In our model mixture of big and small colloids confined to an interface, the two length scales stem from the range of the interactions between pairs of big particles and from the cross big-small interactions, respectively. The small-small length scale is not significant. Our strategy for finding quasicrystals involves tuning locations of maxima in the dispersion relation, or equivalently in the liquid state partial static structure factors.


Efthimiou, N., Thielemans, K., Emond, E. et al, 2020-06-19, Use of non-Gaussian time-of-flight kernels for image reconstruction of Monte Carlo simulated data of ultra-fast PET scanners, EJNMMI Physics (European Journal of Nuclear Medicine and Molecular Imaging), doi: 10.1186/s40658-020-00309-8

Abstract

Time-of-flight (TOF) positron emission tomography (PET) scanners can provide significant benefits by improving the noise properties of reconstructed images. In order to achieve this, the timing response of the scanner needs to be modelled as part of the reconstruction process. This is currently achieved using Gaussian TOF kernels. However, the timing measurements do not necessarily follow a Gaussian distribution. In ultra-fast timing resolutions, the depth of interaction of the γ-photon and the photon travel spread (PTS) in the crystal volume become increasingly significant factors for the timing performance. The PTS of a single photon can be approximated better by a truncated exponential distribution. Therefore, we computed the corresponding TOF kernel as a modified Laplace distribution for long crystals. The obtained (CTR) kernels could be more appropriate to model the joint probability of the two in-coincidenceγ-photons. In this paper, we investigate the impact of using a CTR kernel vs. Gaussian kernels in TOF reconstruction using Monte Carlo generated data.


Sohag Kabir, Koorosh Aslansefat, Ioannis Sorokos, Yiannis Papadopoulos, Savas Konur, 2020-05-22, A Hybrid Modular Approach for Dynamic Fault Tree Analysis, IEEE Access, doi: 10.1109/ACCESS.2020.2996643

Abstract

Over the years, several approaches have been developed for the quantitative analysis of dynamic fault trees (DFTs). These approaches have strong theoretical and mathematical foundations; however, they appear to suffer from the state-space explosion and high computational requirements, compromising their efficacy. Modularisation techniques have been developed to address these issues by identifying and quantifying static and dynamic modules of the fault tree separately by using binary decision diagrams and Markov models. Although these approaches appear effective in reducing computational effort and avoiding state-space explosion, the reliance of the Markov chain on exponentially distributed data of system components can limit their widespread industrial applications. In this paper, we propose a hybrid modularisation scheme where independent sub-trees of a DFT are identified and quantified in a hierarchical order. A hybrid framework with the combination of algebraic solution, Petri Nets, and Monte Carlo simulation is used to increase the efficiency of the solution. The proposed approach uses the advantages of each existing approach in the right place (independent module). We have experimented the proposed approach on five independent hypothetical and industrial examples in which the experiments show the capabilities of the proposed approach facing repeated basic events and non-exponential failure distributions. The proposed approach could provide an approximate solution to DFTs without unacceptable loss of accuracy. Moreover, the use of modularised or hierarchical Petri nets makes this approach more generally applicable by allowing quantitative evaluation of DFTs with a wide range of failure rate distributions for basic events of the tree.


Vasilopoulos, G., Le Quan, Q., R. Parsons, D., E. Darby, S., N. Hung, N., P. D. Tri, V., Haigh, I., Voepel, H., Aalto, R., and Nicholas, A, 2020-05, Sediment starvation is the primary factor of tidal ingress in the Mekong delta, EGU General Assembly 2020, doi: 10.5194/egusphere-egu2020-15155

Abstract

The Vietnamese Mekong Delta (VMD) is home of 18 million people, provides enough food to cover 50% of the country’s nutritional needs and underpins the welfare of the rapidly growing population of the wider region. The longer-term future sustainability of this great delta, formed over millennia, is uncertain. The region is threatened by climate change induced eustatic sea-level rise (SLR), and by severe land loss. The latter is the result of a number of factors that are, in their majority, driven by human activities. They include dam impoundment that reduces the amount of sediment reaching and slowly building up the delta, sand mining which rapidly depletes the delta from its slowly accumulated sediment reserves and ground water extraction which enhances sediment compaction and accelerates delta subsidence. In May 2018 we undertook a delta-scale survey to map the bathymetry of all of the main distributary channels of the VMD. Comparisons of these survey data with existing datasets from 1998 and 2018 reveal major increases of channel depth. They show that between 1998 and 2008 the VMD lost in excess of 370 million cubic meters of sediment, while the respective value for the period between 2008 and 2018 is 635 million cubic meters, suggesting an accelerating trend of sediment loss from the system. We assume a ‘business as usual’ scenario for delta management practices and propagate delta degradation into the future, generating delta analogues for years 2028 and 2038. We combine these delta analogues with projections of SLR for the region for up to year 2098 and a number of boundary condition scenarios into a delta-scale hydraulic model. The fluvial-tidal interactions resolved in our numerical modelling simulations reveal that channel deepening is the key driver of tidal ingress into the delta plain for the next few decades. For the longer-term future (2098), the combined effects of predicted SLR and channel incision can lead to an increase of tidal ingress by 20%. This may destabilise delta bifurcations, is likely to increase bank erosion and flood risk into the future and can have sever implications for saline intrusion into the delta plains.


Gottschalk, Hannes C. and Poblotzki, Anja and Fatima, Mariyam and Obenchain, Daniel A. and Perez, Cristobal and Antony, Jens and Auer, Alexander A. and Baptista, Leonardo and Benoit, David M. and Bistoni, Giovanni and Bohle, Fabian and Dahmani, Rahma and Firaha, Dzmitry and Grimme, Stefan and Hansen, Andreas and Harding, Michael E. and Hochlaf, Majdi and Holzer, Christof and Jansen, Georg and Klopper, Wim and Kopp, Wassja A. and Krasowska, Malgorzata and Kroger, Leif C. and Leonhard, Kai and Mogren Al-Mogren, Muneerah and Mouhib, Halima and Neese, Frank and Pereira, Max N. and Prakash, Muthuramalingam and Ulusoy, Inga S. and Mata, Ricardo A. and Suhm, Martin A. and Schnell, Melanie, 2020-04-30, The first microsolvation step for furans: New experiments and benchmarking strategies, The Journal of Chemical Physics, doi: 10.1063/5.0004465

Abstract

The site-specific first microsolvation step of furan and some of its derivatives with methanol is explored to benchmark the ability of quantum-chemical methods to describe the structure, energetics, and vibrational spectrum at low temperature. Infrared and microwave spectra in supersonic jet expansions are used to quantify the docking preference and some relevant quantum states of the model complexes. Microwave spectroscopy strictly rules out in-plane docking of methanol as opposed to the top coordination of the aromatic ring. Contrasting comparison strategies, which emphasize either the experimental or the theoretical input, are explored. Within the harmonic approximation, only a few composite computational approaches are able to achieve a satisfactory performance. Deuteration experiments suggest that the harmonic treatment itself is largely justified for the zero-point energy, likely and by design due to the systematic cancellation of important anharmonic contributions between the docking variants. Therefore, discrepancies between experiment and theory for the isomer abundance are tentatively assigned to electronic structure deficiencies, but uncertainties remain on the nuclear dynamics side. Attempts to include anharmonic contributions indicate that for systems of this size, a uniform treatment of anharmonicity with systematically improved performance is not yet in sight.


Brook, Chris B and Kawata, Daisuke and Gibson, Brad K and Gallart, Carme and Vicente, Andres, 2020-04-15, Explaining the chemical trajectories of accreted and in-situ halo stars of the Milky Way, Monthly Notices of the Royal Astronomical Society, doi: 10.1093/mnras/staa992

Abstract

The Milky Way underwent its last significant merger ten billion years ago, when the Gaia-Enceladus-Sausage (GES) was accreted. Accreted GES stars and progenitor stars born prior to the merger make up the bulk of the inner halo. Even though these two main populations of halo stars have similar durations of star formation prior to their merger, they differ in [./Fe]-[Fe/H] space, with the GES population bending to lower [./Fe] at a relatively low value of [Fe/H]. We use cosmological simulations of a ’Milky Way’ to argue that the different tracks of the halo stars through the [./Fe]-[Fe/H] plane are due to a difference in their star formation history and efficiency, with the lower mass GES having its low and constant star formation regulated by feedback whilst the higher mass main progenitor has a higher star formation rate prior to the merger. The lower star formation efficiency of GES leads to lower gas pollution levels, pushing [./Fe]-[Fe/H] tracks to the left. In addition, the increasing star formation rate maintains a higher relative contribution of Type II SNe to Type Ia SNe for the main progenitor population that formed during the same time period, thus maintaining a relatively high [./Fe]. Thus the different positions of the downturns in the [./Fe]-[Fe/H] plane for the GES stars are not reflective of different star formation durations, but instead reflect different star formation efficiencies.


Chatterjee, Joyjit and Dethlefs, Nina, 2020-04-13, Deep learning with knowledge transfer for explainable anomaly prediction in wind turbines, Wind Energy, doi: 10.1002/we.2510

Abstract

The last decade has witnessed an increased interest in applying machine learning techniques to predict faults and anomalies in the operation of wind turbines. These efforts have lately been dominated by deep learning techniques which, as in other fields, tend to outperform traditional machine learning algorithms given sufficient amounts of training data. An important shortcoming of deep learning models is their lack of transparency—they operate as black boxes and typically do not provide rationales for their predictions, which can lead to a lack of trust in predicted outputs. In this article, a novel hybrid model for anomaly prediction in wind farms is proposed, which combines a recurrent neural network approach for accurate classification with an XGBoost decision tree classifier for transparent outputs. Experiments with an offshore wind turbine show that our model achieves a classification accuracy of up to 97\%. The model is further able to generate detailed feature importance analyses for any detected anomalies, identifying exactly those components in a wind turbine that contribute to an anomaly. Finally, the feasibility of transfer learning is demonstrated for the wind domain by porting our “offshore” model to an unseen dataset from an onshore wind farm. The latter model achieves an accuracy of 65% and is able to detect 85% of anomalies in the unseen domain. These results are encouraging for application to wind farms for which no training data are available, for example, because they have not been in operation for long.


J. Silva-Rodriguez and M. Pineiro-Fiel and S. J. Archibald and P. Aguiar and N. Efthimiou, 2020-04-09, A SimSET-STIR hybrid Monte Carlo model for the Philips Vereos Digital PET, 2019 IEEE Nuclear Science Symposium and Medical Imaging Conference (NSS/MIC), doi: 10.1109/NSS/MIC42101.2019.9059645

Abstract

The aim of this study was to develop an accurate simulation and reconstruction model for the Philips Vereos digital whole-body PET/CT scanner. The model was developed using the SimSET Monte Carlo (MC) simulation code, storing all detected photons in SimSET list-mode (LM) format (history files). LM processing, binning and image reconstruction were performed using STIR recently added LM capabilities. In order to accurately process the listmode files generated by SimSET, a new interface between SimSET and STIR was developed. The performance of our MC model was evaluated using the NEMA NU2-2012 standard. Spatial resolution was in good agreement with published results(±12%). Count-rate performance was accurate overall, with NEC rates accurate for both low (32.5% vs. 31.7% at ≈ 5 KBq/mL), and high counts (146.2 kcps vs 153.4 at ≈ 55 KBq/mL), and consistent prompts for all the activity concentrations. LM-MLEM reconstruction including scatter and attenuation correction was performed to validate the SimSET-STIR developed interface.


N. Efthimiou and A. C. Whitehead and M. Stockhoff and C. Thyssen and S. J. Archibald and S. Vandenberghe, 2020-04-09, Preliminary investigation of the impact of Axial Ring Splitting on Image Quality for the Cost Reduction of Total-Body PET, 2019 IEEE Nuclear Science Symposium and Medical Imaging Conference (NSS/MIC), doi: 10.1109/NSS/MIC42101.2019.9059650

Abstract

Recently, the first TB-PET scanner was unveiled and the initial results were nevertheless impressive. However, the cost of a TB-PET scanner is prohibiting for many institutions around the globe. Therefore here we investigate a cost reduction strategy incorporating a flexible detector arrangement. The proposed arrangement increases the axial field of view while keeping the overall cost at lower levels. We propose the axial ring splitting, which separates the full rings, of a compact PET scanner, to an expanded scanner with rings having only even or only odd numbered detectors. In this paper some preliminary performance results using Monte Carlo simulations, will be presented. In this comparison three configurations were considered (a) full rings PET (b) half-split rings TB-PET (c) full-split rings TBPET. In addition in this investigation the effects of a varying coincidence window are demonstrated. The preliminary results suggest that Config.A demonstrated the highest Noise Equivalent count rate using either a fixed or a varying coincidence window. The main reasons were the absence of gaps and better handling of background radiation. However, reconstructed images for a single bed, from a whole body acquisition, suggested that due to the longer single bed acquisition of the full-split rings geometry the images present better noise properties.


Benjamin Wehmeyer and Carla Frohlich and Benoit Cote and Marco Pignatari and Friedrich-Karl Thielemann, 2020-03-27, Could Failed Supernovae Explain the High r-process Abundances in Some Low Metallicity Stars?, Proceedings of the 15th International Symposium on Origin of Matter and Evolution of Galaxies (OMEG15), doi: 10.7566/JPSCP.31.011063

Abstract

Rapid neutron capture process (r-process) elements have been detected in a large number of metal-poor halo stars. The observed large abundance scatter in these stars suggests that r-process elements have been produced in a site that is rare compared to core-collapse supernovae (CCSNe). Although being rare, neutron star mergers (NSM) alone have difficulties explaining the observations, especially at low metallicities. In this paper, we present a complementary scenario: Using black hole – neutron star mergers (BHNSMs) as additional r-process site. We show that both sites together are able to explain the observed r-process abundances in the Galaxy.


Benoit Cote, Samuel Jones, Falk Herwig and Marco Pignatari, 2020-03-27, Chromium Nucleosynthesis and Silicon Carbon Shell Mergers in Massive Stars, The Astrophysical Journal, doi: 10.3847/1538-4357/ab77ac

Abstract

We analyze the production of the element Cr in galactic chemical evolution (GCE) models using the NuGrid nucleosynthesis yields set. We show that the unusually large [Cr/Fe] abundance at [Fe/H] ~ 0 reported by previous studies using those yields and predicted by our Milky Way model originates from the merging of convective Si-burning and C-burning shells in a 20 Mo. model at metallicity Z = 0.01, about an hour before the star explodes. This merger mixes the incomplete burning material in the Si shell, including 51V and 52Cr, out to the edge of the carbon/oxygen (CO) core. The adopted supernova model ejects the outer 2 Mo. of the CO core, which includes a significant fraction of the Cr-rich material. When including this 20 Mo. model at Z = 0.01 in the yields interpolation scheme of our GCE model for stars between 15 and 25 Mo., we overestimate [Cr/Fe] by an order of magnitude at [Fe/H] ~ 0 relative to observations in the Galactic disk. This raises a number of questions regarding the occurrence of Si-C shell mergers in nature, the accuracy of different simulation approaches, and the impact of such mergers on the presupernova structure and explosion dynamics. According to the conditions in this 1D stellar model, the substantial penetration of C-shell material into the Si shell could launch a convective-reactive global oscillation if a merger does take place. In any case, GCE provides stringent constraints on the outcome of this stellar evolution phase.


Billy Koe and Colin Abraham and Chris Bailey and Bob Greening and Martin Small and Thomas Connolley and Jiawei Mi, 2020-03-14, A novel electromagnetic apparatus for in-situ synchrotron X-ray imaging study of the separation of phases in metal solidification, HardwareX, doi: 10.1016/j.ohx.2020.e00104

Abstract

As a part of a research into new techniques for purifying recycled aluminium alloys, a novel electromagnetic apparatus had been developed for investigating in real-time the separation mechanisms of detrimental inclusions in aluminium alloy melts under alternating magnetic fields. The magnetic coil was designed based on the Helmholtz coil design. A viewing gap was designed for in-situ imaging studies using synchrotron X-rays. The gap was designed to maintain a uniform magnetic field in the central region where a sample is positioned. The current setup for the magnetic coil pair is able to produce a peak magnetic flux density of ~10 mT at a frequency of 25 kHz. A separate electrical resistance furnace, designed to concentrically fit within the magnetic coils, was used to control the heating (up to ~850°C) and cooling of the samples. After a series of systematic tests and commissioning, the apparatus was used in a number of in-situ and ex-situ experiments.


Somerville, Walter R. C. and Law, Adam D. and Rey, Marcel and Vogel, Nicolas and Archer, Andrew J. and Buzza, D. Martin A., 2020-03-11, Pattern formation in two-dimensional hard-core/soft-shell systems with variable soft shell profiles, Soft Matter, doi: 10.1039/D0SM00092B

Abstract

Hard-core/soft shell (HCSS) particles have been shown to self-assemble into a remarkably rich variety of structures under compression due to the simple interplay between the hard-core and soft-shoulder length scales in their interactions. Most studies in this area model the soft shell interaction as a square shoulder potential. Although appealing from a theoretical point of view{,} the potential is physically unrealistic because there is no repulsive force in the soft shell regime{,} unlike in experimental HCSS systems. To make the model more realistic{,} here we consider HCSS particles with a range of soft shell potential profiles beyond the standard square shoulder form and study the model using both minimum energy calculations and Monte Carlo simulations. We find that by tuning density and the soft shell profile{,} HCSS particles in the thin shell regime (i.e.{,} shell to core ratio ) can form a large range of structures{,} including hexagons{,} chains{,} squares{,} rhomboids and two distinct zig-zag structures. Furthermore{,} by tuning the density and r1/r0{,} we find that HCSS particles with experimentally realistic linear ramp soft shoulder repulsions can form honeycombs and quasicrystals with 10-fold and 12-fold symmetry. Our study therefore suggests the exciting possibility of fabricating these exotic 2D structures experimentally through colloidal self-assembly.



2019 (29 outputs)

Borbala Cseh, Maria Lugaro, Valentina D’Orazi, Denise B. de Castro, Claudio B. Pereira, Amanda I. Karakas, Laszlo Molnar, Emese Plachy, Robert Szabo, Marco Pignatari and Sergio Cristallo, 2019-12-30, The composition of Barium stars and the s-process in AGB stars, Proceedings of the International Astronomical Union, doi: 10.1017/S1743921318005100

Abstract

Using abundances from the available largest, homogeneous sample of high resolution Barium (Ba) star spectra we calculated the ratios of different hs-like to ls-like elemental ratios and compared to different AGB nucleosynthesis models. The Ba star data show an incontestable increase of the hs-type/ls-type element ratio (for example, [Ce/Y]) with decreasing metallicity. This trend in the Ba star observations is predicted by low mass, non-rotating AGB models where 13C is the main neutron source and is in agreement with Kepler asteroseismology observations.


Eva Tarazona, Christoph Hahn, Lluis Franch-Gras, Eduardo M. Garcia-Roger, Maria Jose Carmona and Africa Gomez, 2019-12-23, Ecological genomics of adaptation to unpredictability in experimental rotifer populations, Scientific Reports, doi: 10.1038/s41598-019-56100-y

Abstract

Elucidating the genetic basis of phenotypic variation in response to different environments is key to understanding how populations evolve. Facultatively sexual rotifers can develop adaptive responses to fluctuating environments. In a previous evolution experiment, diapause-related traits changed rapidly in response to two selective regimes (predictable vs unpredictable) in laboratory populations of the rotifer Brachionus plicatilis. Here, we investigate the genomic basis of adaptation to environmental unpredictability in these experimental populations. We identified and genotyped genome-wide polymorphisms in 169 clones from both selective regimes after seven cycles of selection using genotyping by sequencing (GBS). Additionally, we used GBS data from the 270 field clones from which the laboratory populations were established. This GBS dataset was used to identify candidate SNPs under selection. A total of 76 SNPs showed divergent selection, three of which are candidates for being under selection in the particular unpredictable fluctuation pattern studied. Most of the remaining SNPs showed strong signals of adaptation to laboratory conditions. Furthermore, a genotype-phenotype association approach revealed five SNPs associated with two key life-history traits in the adaptation to unpredictability. Our results contribute to elucidating the genomic basis for adaptation to unpredictable environments and lay the groundwork for future evolution studies in rotifers.


Peter Hoppe, Richard J. Stancliffe, Marco Pignatari, and Sachiko Amari, 2019-12-05, Isotopic Signatures of Supernova Nucleosynthesis in Presolar Silicon Carbide Grains of Type AB with Supersolar 14N/15N Ratios, The Astrophysical Journal, doi: 10.3847/1538-4357/ab521c

Abstract

We report high-resolution C, N, Al, Si, and S isotope data of 38 presolar SiC grains of type AB. Seventeen of these grains are of subtype AB1 (14N/15N < 440 = solar) and 20 of subtype AB2 (14N/15N ≥ 440), previously proposed to be mainly from supernovae (AB1) and J-type carbon stars (AB2), respectively. Our data are compatible with previously obtained isotope data of AB grains, except that 26Al/27Al ratios of AB1 grains span a narrower range. The data are compared with predictions from supernova models that consider H ingestion into the He shell during the pre-supernova phase. In these models a mixture of explosive H and He burning occurs at the bottom of the He shell during passage of the supernova shock, forming the so-called O/nova zone. Mixing matter from the O/nova zone with matter from the overlying He/C zone and the stellar envelope shows that the isotopic compositions and trends of both AB1 and AB2 grains can be matched within the model uncertainties. This demonstrates that supernovae should be considered as potential sources of AB2 grains, in addition to J-type carbon stars and born-again asymptotic giant branch stars, as previously proposed.


Vasilopoulos, G.; Parsons, D. R.; Quan, L. Q.; Aalto, R. E.; Nicholas, A. P.; Van, T. P. D., Jr.; Hung, N. N.; Voepel, H.; Darby, S.E., 2019-12, Erosion of the Distributary Channels of the Mekong Delta is a Key Driver for Tidal Ingress, AGU Fall Meeting Abstracts, doi:

Abstract

The Mekong delta, home to 18 million people, floods annually during the Monsoon, sustaining a suite of ecosystem services that underpin the welfare of the rapidly growing population of the wider area. The longer-term future sustainability of the region is uncertain. The delta is threatened by climate change induced sea-level rise, and by severe land loss. The latter is the result of a number of factors that are, in their majority, driven by human activities, including sand mining, dam impoundment and, a combination of natural and anthropogenic driven delta subsidence. In May 2018 we undertook a delta scale survey mapping the bathymetry of all of the main distributary channels of the Vietnamese Mekong delta. Comparisons of these rich datasets with existing bathymetric data from 1998 and 2008 reveal major changes of channel mean depths and significant loss of sediment. Moreover this trend appears to worsen with time, with the estimated volume loss, and average channel deepening, for the 2008 – 2018 period being almost twice its 1998 – 2018 equivalent. Assuming a ‘business as usual’ scenario for delta management and continued trajectory, we propagate delta degradation into the future and generate a series of future analogues for the delta and its system functioning. These are combined with projections of sea-level rise (RCP 4.5 and 8.5) for the region and a number of boundary condition scenarios, into a delta-scale hydraulic model. The fluvial-tidal interactions resolved in our numerical modelling simulations reveal that channel bed erosion is a key driver of tidal ingress into the delta plain, which in turn drives salinity intrusion and is likely to destabilise delta bifurcations and likely enhance bank erosion into the future.


Molla, M.; Wekesa, S.; Cavichia, O.; Diaz, A. I.; Gibson, B. K.; Rosales-Ortega, F. F.; Ascasibar, Y.; Wamalwa, D. S.; Sanchez, S. F., 2019-11-01, 2D-Galactic chemical evolution: the role of the spiral density wave, Monthly Notices of the Royal Astronomical Society, doi: 10.1093/mnras/stz2537

Abstract

We present a 2D chemical evolution code applied to a Milky Way type Galaxy, incorporating the role of spiral arms in shaping azimuthal abundance variations, and confront the predicted behaviour with recent observations taken with integral field units. To the usual radial distribution of mass, we add the surface density of the spiral wave and study its effect on star formation and elemental abundances. We compute five different models: one with azimuthal symmetry which depends only on radius, while the other four are subjected to the effect of a spiral density wave. At early times, the imprint of the spiral density wave is carried by both the stellar and star formation surface densities; conversely, the elemental abundance pattern is less affected. At later epochs, however, differences among the models are diluted, becoming almost indistinguishable given current observational uncertainties. At the present time, the largest differences appear in the star formation rate and/or in the outer disc (R ≥ 18 kpc). The predicted azimuthal oxygen abundance patterns for t ≤ 2 Gyr are in reasonable agreement with recent observations obtained with VLT/MUSE for NGC 6754.


Furness, Andrew I., Capellini, Isabella, 2019-10-17, The evolution of parental care diversity in amphibians, Nature Communications, doi: 10.1038/s41467-019-12608-5

Abstract

Parental care is extremely diverse across species, ranging from simple behaviours to complex adaptations, varying in duration and in which sex cares. Surprisingly, we know little about how such diversity has evolved. Here, using phylogenetic comparative methods and data for over 1300 amphibian species, we show that egg attendance, arguably one of the simplest care behaviours, is gained and lost faster than any other care form, while complex adaptations, like brooding and viviparity, are lost at very low rates, if at all. Prolonged care from the egg to later developmental stages evolves from temporally limited care, but it is as easily lost as it is gained. Finally, biparental care is evolutionarily unstable regardless of whether the parents perform complementary or similar care duties. By considering the full spectrum of parental care adaptations, our study reveals a more complex and nuanced picture of how care evolves, is maintained, or is lost.


Donatella Romano, Francesco Calura, Annibale D’Ercole and C. Gareth Few, 2019-10-08, High-resolution three-dimensional simulations of gas removal from ultrafaint dwarf galaxies, Astronomy & Astrophysics, doi: 10.1051/0004-6361/201935328

Abstract

Context. The faintest Local Group galaxies found lurking in and around the Milky Way halo provide a unique test bed for theories of structure formation and evolution on small scales. Deep Subaru and Hubble Space Telescope photometry demonstrates that the stellar populations of these galaxies are old and that the star formation activity did not last longer than 2 Gyr in these systems. A few mechanisms that may lead to such a rapid quenching have been investigated by means of hydrodynamic simulations, but these have not provided any final assessment so far.
Aims. This is the first in a series of papers aimed at analyzing the roles of stellar feedback, ram pressure stripping, host-satellite tidal interactions, and reionization in cleaning the lowest mass Milky Way companions of their cold gas using high-resolution, three-dimensional hydrodynamic simulations.
Methods. We simulated an isolated ultrafaint dwarf galaxy loosely modeled after Bootes I, and examined whether or not stellar feedback alone could drive a substantial fraction of the ambient gas out from the shallow potential well.
Results. In contrast to simple analytical estimates, but in agreement with previous hydrodynamical studies, we find that most of the cold gas reservoir is retained. Conversely, a significant amount of the metal-enriched stellar ejecta crosses the boundaries of the computational box with velocities exceeding the local escape velocity and is, thus, likely lost from the system.
Conclusions. Although the total energy output from multiple supernova explosions exceeds the binding energy of the gas, no galactic-scale outflow develops in our simulations and as such, most of the ambient medium remains trapped within the weak potential well of the model galaxy. It seems thus unavoidable that to explain the dearth of gas in ultrafaint dwarf galaxies, we will have to resort to environmental effects. This will be the subject of a forthcoming paper.


C. C. Roggatz, N. Fletcher, D. M. Benoit, A. C. Algar, A. Doroff, B. Wright, K. C. Wollenberg Valero & J. D. Hardege, 2019-10-07, Saxitoxin and tetrodotoxin bioavailability increases in future oceans, Nature Climate Change, doi: 10.1038/s41558-019-0589-3

Abstract

Increasing atmospheric CO2 levels are largely absorbed by the ocean, decreasing surface water pH1. In combination with increasing ocean temperatures, these changes have been identified as a major sustainability threat to future marine life2. Interactions between marine organisms are known to depend on biomolecules, although the influence of oceanic pH on their bioavailability and functionality remains unexplored. Here we show that global change substantially impacts two ecological keystone molecules3 in the ocean, the paralytic neurotoxins saxitoxin and tetrodotoxin. Increasing temperatures and declining pH increase the abundance of their toxic forms in the water. Our geospatial global model predicts where this increased toxicity could intensify the devastating impact of harmful algal blooms, for example through an increased incidence of paralytic shellfish poisoning. Calculations of future saxitoxin toxicity levels in Alaskan clams, Saxidomus gigantea, show critical exceedance of limits safe for consumption. Our findings for saxitoxin and tetrodotoxin exemplify potential consequences of changing pH and temperature on chemicals dissolved in the sea. This reveals major implications not only for ecotoxicology, but also for chemical signals that mediate species interactions such as foraging, reproduction or predation in the ocean, with unexplored consequences for ecosystem stability and ecosystem services.


Denissenkov, Pavel A; Herwig, Falk; Woodward, Paul; Andrassy, Robert; Pignatari, Marco; Jones, Samuel, 2019-09-21, The i-process yields of rapidly accreting white dwarfs from multicycle He-shell flash stellar evolution models with mixing parametrizations from 3D hydrodynamics simulations, Monthly Notices of the Royal Astronomical Society, doi: 10.1093/mnras/stz1921

Abstract

We have modelled the multicycle evolution of rapidly accreting CO white dwarfs (RAWDs) with stable H burning intermittent with strong He-shell flashes on their surfaces for 0.7 ≤ MRAWD/M⊙ ≤ 0.75 and [Fe/H] ranging from 0 to −2.6. We have also computed the i-process nucleosynthesis yields for these models. The i process occurs when convection driven by the He-shell flash ingests protons from the accreted H-rich surface layer, which results in maximum neutron densities Nn, max ≈ 1013–1015 cm−3. The H-ingestion rate and the convective boundary mixing (CBM) parameter ftop adopted in the one-dimensional nucleosynthesis and stellar evolution models are constrained through three-dimensional (3D) hydrodynamic simulations. The mass ingestion rate and, for the first time, the scaling laws for the CBM parameter ftop have been determined from 3D hydrodynamic simulations. We confirm our previous result that the high-metallicity RAWDs have a low mass retention efficiency (⁠η≲10 per cent⁠). A new result is that RAWDs with [Fe/H] ≲−2 have η≳20 per cent⁠; therefore, their masses may reach the Chandrasekhar limit and they may eventually explode as SNeIa. This result and the good fits of the i-process yields from the metal-poor RAWDs to the observed chemical composition of the CEMP-r/s stars suggest that some of the present-day CEMP-r/s stars could be former distant members of triple systems, orbiting close binary systems with RAWDs that may have later exploded as SNeIa.


den Hartogh, J. W. and Hirschi, R. and Lugaro, M. and Doherty, C. L. and Battino, U. and Herwig, F. and Pignatari, M. and Eggenberger, P., 2019-09-16, The s process in rotating low-mass AGB stars – Nucleosynthesis calculations in models matching asteroseismic constraints, Astronomy & Astrophysics, doi: 10.1051/0004-6361/201935476

Abstract

Aims. We investigate the s-process during the AGB phase of stellar models whose cores are enforced to rotate at rates consistent with asteroseismology observations of their progenitors and successors.
Methods. We calculated new 2 M. ,Z = 0.01 models, rotating at 0, 125, and 250 km s-1 at the start of main sequence. An artificial, additional viscosity was added to enhance the transport of angular momentum in order to reduce the core rotation rates to be in agreement with asteroseismology observations. We compared rotation rates of our models with observed rotation rates during the MS up to the end of core He burning, and the white dwarf phase.
Results. We present nucleosynthesis calculations for these rotating AGB models that were enforced to match the asteroseismic constraints on rotation rates of MS, RGB, He-burning, and WD stars. In particular, we calculated one model that matches the upper limit of observed rotation rates of core He-burning stars and we also included a model that rotates one order of magnitude faster than the upper limit of the observations. The s-process production in both of these models is comparable to that of non-rotating models.
Conclusions. Slowing down the core rotation rate in stars to match the above mentioned asteroseismic constraints reduces the rotationally induced mixing processes to the point that they have no effect on the s-process nucleosynthesis. This result is independent of the initial rotation rate of the stellar evolution model. However, there are uncertainties remaining in the treatment of rotation in stellar evolution, which need to be reduced in order to confirm our conclusions, including the physical nature of our approach to reduce the core rotation rates of our models, and magnetic processes.


Joan Garcia-Porta, Iker Irisarri, Martin Kirchner, Ariel Rodriguez, Sebastian Kirchhof, Jason L. Brown, Amy MacLeod, Alexander P. Turner, Faraham Ahmadzadeh, Gonzalo Albaladejo, Jelka Crnobrnja-Isailovic, Ignacio De la Riva, Adnane Fawzi, Pedro Galan, Bayram Gocmen, D. James Harris, Octavio Jimenez-Robles, Ulrich Joger, Olga Jovanovic Glavas, Mert Karis, Giannina Koziel, Sven Kunzel, Mariana Lyra, Donald Miles, Manuel Nogales, Mehmet Anil Oguz, Panayiotis Pafilis, Lois Rancilhac, Noemi Rodriguez, Benza Rodriguez Concepcion, Eugenia Sanchez, Daniele Salvi, Tahar Slimani, Abderrahim S’khifa, Ali Turk Qashqaei, Anamarija Zagar, Alan Lemmon, Emily Moriarty Lemmon, Miguel Angel Carretero, Salvador Carranza, Herve Philippe, Barry Sinervo, Johannes Muller, Miguel Vences & Katharina C. Wollenberg Valero, 2019-09-09, Environmental temperatures shape thermal physiology as well as diversification and genome-wide substitution rates in lizards, Nature Communications, doi: 10.1038/s41467-019-11943-x

Abstract

Climatic conditions changing over time and space shape the evolution of organisms at multiple levels, including temperate lizards in the family Lacertidae. Here we reconstruct a dated phylogenetic tree of 262 lacertid species based on a supermatrix relying on novel phylogenomic datasets and fossil calibrations. Diversification of lacertids was accompanied by an increasing disparity among occupied bioclimatic niches, especially in the last 10 Ma, during a period of progressive global cooling. Temperate species also underwent a genome-wide slowdown in molecular substitution rates compared to tropical and desert-adapted lacertids. Evaporative water loss and preferred temperature are correlated with bioclimatic parameters, indicating physiological adaptations to climate. Tropical, but also some populations of cool-adapted species experience maximum temperatures close to their preferred temperatures. We hypothesize these species-specific physiological preferences may constitute a handicap to prevail under rapid global warming, and contribute to explaining local lizard extinctions in cool and humid climates.


M.P. Taggart and C. Akers and A.M. Laird and U. Hager and C. Ruiz and D.A. Hutcheon and M.A. Bentley and J.R. Brown and L. Buchmann and A.A. Chen and J. Chen and K.A. Chipps and A. Choplin and J.M. D’Auria and B. Davids and C. Davis and C.Aa. Diget and L. Erikson and J. Fallis and S.P. Fox and U. Frischknecht and B.R. Fulton and N. Galinski and U. Greife and R. Hirschi and D. Howell and L. Martin and D. Mountford and A.St.J. Murphy and D. Ottewell and M. Pignatari and S. Reeve and G. Ruprecht and S. Sjue and L. Veloce and M. Williams, 2019-08-28, A direct measurement of the 17O(α,γ)21Ne reaction in inverse kinematics and its impact on heavy element production, Physics Letters B, doi: 10.1016/j.physletb.2019.134894

Abstract

uring the slow neutron capture process in massive stars, reactions on light elements can both produce and absorb neutrons thereby influencing the final heavy element abundances. At low metallicities, the high neutron capture rate of 16O can inhibit s-process nucleosynthesis unless the neutrons are recycled via the 17O(α,n)20Ne reaction. The efficiency of this neutron recycling is determined by competition between the 17O(α,n)20Ne and 17O(α,γ)21Ne reactions. While some experimental data are available on the former reaction, no data exist for the radiative capture channel at the relevant astrophysical energies. The 17O(α,γ)21Ne reaction has been studied directly using the DRAGON recoil separator at the TRIUMF Laboratory. The reaction cross section has been determined at energies between 0.6 and 1.6 MeV Ecm, reaching into the Gamow window for core helium burning for the first time. Resonance strengths for resonances at 0.63, 0.721, 0.81 and 1.122 MeV Ecm have been extracted. The experimentally based reaction rate calculated represents a lower limit, but suggests that significant s-process nucleosynthesis occurs in low metallicity massive stars.


U Battino, A Tattersall, C Lederer-Woods, F Herwig, P Denissenkov, R Hirschi, R Trappitsch, J W den Hartogh, M Pignatari, (The NuGrid Collaboration), 2019-08-20, NuGrid stellar data set – III. Updated low-mass AGB models and s-process nucleosynthesis with metallicities Z= 0.01, Z = 0.02, and Z = 0.03, Monthly Notices of the Royal Astronomical Society, doi: 10.1093/mnras/stz2158

Abstract

The production of the neutron-capture isotopes beyond iron that we observe today in the Solar system is the result of the combined contribution of the r-process, the s-process, and possibly the i-process. Low-mass asymptotic giant branch (AGB) (1.5 < M/M⊙ < 3) and massive (M > 10 M⊙) stars have been identified as the main site of the s-process. In this work we consider the evolution and nucleosynthesis of low-mass AGB stars. We provide an update of the NuGrid Set models, adopting the same general physics assumptions but using an updated convective-boundary-mixing model accounting for the contribution from internal gravity waves. The combined data set includes the initial masses MZAMS/M⊙ = 2, 3 for Z = 0.03, 0.02, 0.01. These new models are computed with the MESA stellar code and the evolution is followed up to the end of the AGB phase. The nucleosynthesis was calculated for all isotopes in post-processing with the NuGrid mppnp code. The convective-boundary-mixing model leads to the formation of a 13C-pocket three times wider compared to the one obtained in the previous set of models, bringing the simulation results now in closer agreement with observations. Using these new models, we discuss the potential impact of other processes inducing mixing, like rotation, adopting parametric models compatible with theory and observations. Complete yield data tables, derived data products, and online analytic data access are provided.


Velez, Zelia and Roggatz, Christina C. and Benoit, David M. and Hardege, Jorg D. and Hubbard, Peter C., 2019-07-03, Short- and Medium-Term Exposure to Ocean Acidification Reduces Olfactory Sensitivity in Gilthead Seabream, Frontiers in Physiology, doi: 10.3389/fphys.2019.00731

Abstract

The effects of ocean acidification on fish are only partially understood. Studies on olfaction are mostly limited to behavioural alterations of coral reef fish; studies on temperate species and/or with economic importance are scarce. The current study evaluated the effects of short- and medium-term exposure to ocean acidification on the olfactory system of gilthead seabream (Sparus aurata), and attempted to explain observed differences in sensitivity by changes in the protonation state of amino acid odorants. Short-term exposure to elevated PCO2 decreased olfactory sensitivity to some odorants, such as L-serine, L-leucine, L-arginine, L-glutamate and conspecific intestinal fluid, but not to others, such as L-glutamine and conspecific bile fluid. Seabream were unable to compensate for high PCO2 levels in the medium-term; after four weeks’ exposure to high PCO2, the olfactory sensitivity remained lower in elevated PCO2 water. The decrease in olfactory sensitivity in high PCO2 water could be partly attributed to changes in the protonation state of the odorants and/or their receptor(s); we illustrate how protonation due to reduced pH causes changes in the charge distribution of odorant molecules, an essential component for ligand-receptor interaction. However, there are other mechanisms involved. At a histological level, the olfactory epithelium contained higher densities of mucus cells in fish kept in high CO2 water, and a shift in pH of the mucus they produced to more neutral. These differences suggest a physiological response of the olfactory epithelium to lower pH and/or high CO2 levels, but an inability to fully counteract the effects of acidification on olfactory sensitivity. Therefore, the current study provides evidence for a direct, medium-term, global effect of ocean acidification on olfactory sensitivity in fish, and possibly other marine organisms, and suggests a partial explanatory mechanism.


A Cote, Benoit; Lugaro, Maria; Reifarth, Rene; Pignatari, Marco; Vilagos, Blanka; Yague, Andres; Gibson, Brad K., 2019-06-25, Galactic Chemical Evolution of Radioactive Isotopes, The Astrophysical Journal, doi: 10.3847/1538-4357/ab21d1

Abstract

The presence of short-lived (̃Myr) radioactive isotopes in meteoritic inclusions at the time of their formation represents a unique opportunity to study the circumstances that led to the formation of the solar system. To interpret these observations, we need to calculate the evolution of radioactive-to-stable isotopic ratios in the Galaxy. We present an extension of the open-source galactic chemical evolution codes NuPyCEE and JINAPyCEE that enable the decay of radioactive isotopes in the interstellar medium to be tracked. We show how the evolution of the isotopic ratio depends on the star formation history and efficiency, star-to-gas mass ratio, and galactic outflows. Given the uncertainties in the observations used to calibrate our model, our predictions for isotopic ratios at the time of formation of the Sun are uncertain by a factor of 3.6. At that time, to recover the actual radioactive-to-stable isotopic ratios predicted by our model, one can multiply the steady-state solution (see Equation (1)) by {2.3}-0.7+3.4. However, in the cases where the radioactive isotope has a half-life longer than ̃200 Myr, or the target radioactive or stable isotopes have mass- and/or metallicity-dependent production rates, or they originate from different sources with different delay-time distributions, or the reference isotope is radioactive, our codes should be used for more accurate solutions. Our preliminary calculations confirm the dichotomy between radioactive nuclei in the early solar system with r- and s-process origin, and that 55Mn and 60Fe can be explained by galactic chemical evolution, while 26Al cannot.


Wehmeyer, B; Frohlich, C; Cote, B; Pignatari, M; Thielemann, F-K, 2019-05-16, Using failed supernovae to constrain the Galactic r-process element production, Monthly Notices of the Royal Astronomical Society, doi: 10.1093/mnras/stz1310

Abstract

Rapid neutron capture process (r-process) elements have been detected in a large fraction of metal-poor halo stars, with abundances relative to iron (Fe) that vary by over two orders of magnitude. This scatter is reduced to less than a factor of 3 in younger Galactic disc stars. The large scatter of r-process elements in the early Galaxy suggests that the r-process is made by rare events, like compact binary mergers and rare sub-classes of supernovae. Although being rare, neutron star mergers alone have difficulties to explain the observed enhancement of r-process elements in the lowest metallicity stars compared to Fe. The supernovae producing the two neutron stars already provide a substantial Fe abundance where the r-process ejecta from the merger would be injected. In this work we investigate another complementary scenario, where the r-process occurs in neutron star-black hole mergers in addition to neutron star mergers. Neutron star-black hole mergers would eject similar amounts of r-process matter as neutron star mergers, but only the neutron star progenitor would have produced Fe. Furthermore, a reduced efficiency of Fe production from single stars significantly alters the age-metallicity relation, which shifts the onset of r-process production to lower metallicities. We use the high-resolution [(20 pc)3/cell] inhomogeneous chemical evolution tool ‘ICE’ to study the outcomes of these effects. In our simulations, an adequate combination of neutron star mergers and neutron star-black hole mergers qualitatively reproduces the observed r-process abundances in the Galaxy.


Cote, Benoit; Eichler, Marius; Arcones, Almudena; Hansen, Camilla J.; Simonetti, Paolo; Frebel, Anna; Fryer, Chris L.; Pignatari, Marco; Reichert, Moritz; Belczynski, Krzysztof; Matteucci, Francesca, 2019-04-22, Neutron star mergers might not be the only source of r-process elements in the Milky Way, The Astrophysical Journal, doi: 10.3847/1538-4357/ab10db

Abstract

Probing the origin of r-process elements in the universe represents a multidisciplinary challenge. We review the observational evidence that probes the properties of r-process sites, and address them using galactic chemical evolution simulations, binary population synthesis models, and nucleosynthesis calculations. Our motivation is to define which astrophysical sites have significantly contributed to the total mass of r-process elements present in our Galaxy. We found discrepancies with the neutron star (NS–NS) merger scenario. When we assume that they are the only site, the decreasing trend of [Eu/Fe] at [Fe/H] > −1 in the disk of the Milky Way cannot be reproduced while accounting for the delay-time distribution (DTD) of coalescence times (∝t −1) derived from short gamma-ray bursts (GRBs) and population synthesis models. Steeper DTD functions (∝t −1.5) or power laws combined with a strong burst of mergers before the onset of supernovae (SNe) Ia can reproduce the [Eu/Fe] trend, but this scenario is inconsistent with the similar fraction of short GRBs and SNe Ia occurring in early-type galaxies, and it reduces the probability of detecting GW170817 in an early-type galaxy. One solution is to assume an additional production site of Eu that would be active in the early universe, but would fade away with increasing metallicity. If this is correct, this additional site could be responsible for roughly 50% of the Eu production in the early universe before the onset of SNe Ia. Rare classes of supernovae could be this additional r-process source, but hydrodynamic simulations still need to ensure the conditions for a robust r-process pattern.


David Lauvergnat, Peter Felker, Yohann Scribano, David M. Benoit, Zlatko Bacic, 2019-04-15, H2, HD, and D2 in the small cage of structure II clathrate hydrate: Vibrational frequency shifts from fully coupled quantum six-dimensional calculations of the vibration-translation-rotation eigenstates, The Journal of Chemical Physics, doi: 10.1063/1.5090573

Abstract

We report the first fully coupled quantum six-dimensional (6D) bound-state calculations of the vibration-translation-rotation eigenstates of a flexible H2, HD, and D2 molecule confined inside the small cage of the structure II clathrate hydrate embedded in larger hydrate domains with up to 76 H2O molecules, treated as rigid. Our calculations use a pairwise-additive 6D intermolecular potential energy surface for H2 in the hydrate domain, based on an ab initio 6D H2-H2O pair potential for flexible H2 and rigid H2O. They extend to the first excited (v = 1) vibrational state of H2, along with two isotopologues, providing a direct computation of vibrational frequency shifts. We show that obtaining a converged v = 1 vibrational state of the caged molecule does not require converging the very large number of intermolecular translation-rotation states belonging to the v = 0 manifold up to the energy of the intramolecular stretch fundamental (≈4100 cm−1 for H2). Only a relatively modest-size basis for the intermolecular degrees of freedom is needed to accurately describe the vibrational averaging over the delocalized wave function of the quantum ground state of the system. For the caged H2, our computed fundamental translational excitations, rotational j = 0 → 1 transitions, and frequency shifts of the stretch fundamental are in excellent agreement with recent quantum 5D (rigid H2) results [A. Powers et al., J. Chem. Phys. 148, 144304 (2018)]. Our computed frequency shift of −43 cm−1 for H2 is only 14% away from the experimental value at 20 K.


Jianguo Wang, Philip Rubini, Qin Qin, Brian Houston, 2019-04-04, A Model to Predict Acoustic Resonant Frequencies of Distributed Helmholtz Resonators on Gas Turbine Engines, Applied Sciences, doi: 10.3390/app9071419

Abstract

Helmholtz resonators, traditionally designed as a narrow neck backed by a cavity, are widely applied to attenuate combustion instabilities in gas turbine engines. The use of multiple small holes with an equivalent open area to that of a single neck has been found to be able to significantly improve the noise damping bandwidth. This type of resonator is often referred to as “distributed Helmholtz resonator”. When multiple holes are employed, interactions between acoustic radiations from neighboring holes changes the resonance frequency of the resonator. In this work, the resonance frequencies from a series of distributed Helmholtz resonators were obtained via a series of highly resolved computational fluid dynamics simulations. A regression analysis of the resulting response surface was undertaken and validated by comparison with experimental results for a series of eighteen absorbers with geometries typically employed in gas turbine combustors. The resulting model demonstrates that the acoustic end correction length for perforations is closely related to the effective porosity of the perforated plate and will be obviously enhanced by acoustic radiation effect from the perforation area as a whole. This model is easily applicable for engineers in the design of practical distributed Helmholtz resonators.


Alex Sheardown and Thomas M. Fish and Elke Roediger and Matthew Hunt and John ZuHone and Yuanyuan Su and Ralph P. Kraft and Paul Nulsen and Eugene Churazov and William Forman and Christine Jones and Natalya Lyskova and Dominique Eckert and Sabrina De Grandi, 2019-03-28, A New Class of X-Ray Tails of Early-type Galaxies and Subclusters in Galaxy Clusters: Slingshot Tails versus Ram Pressure Stripped Tails, The Astrophysical Journal, doi: 10.3847/1538-4357/ab0c06

Abstract

We show that there is a new class of gas tails-slingshot tails-that form as a subhalo (i.e., a subcluster or early-type cluster galaxy) moves away from the cluster center toward the apocenter of its orbit. These tails can point perpendicular or even opposite to the subhalo direction of motion, not tracing the recent orbital path. Thus, the observed tail direction can be misleading, and we caution against naive conclusions regarding the subhalo’s direction of motion based on the tail direction. A head-tail morphology of a galaxy’s or subcluster’s gaseous atmosphere is usually attributed to ram pressure stripping, and the widely applied conclusion is that gas stripped tail traces the most recent orbit. However, during the slingshot tail stage, the subhalo is not being ram pressure stripped (RPS) and the tail is shaped by tidal forces more than just the ram pressure. Thus, applying a classic RPS scenario to a slingshot tail leads not only to an incorrect conclusion regarding the direction of motion but also to incorrect conclusions regarding the subhalo velocity, expected locations of shear flows, instabilities, and mixing. We describe the genesis and morphology of slingshot tails using data from binary cluster merger simulations and discuss their observable features and how to distinguish them from classic RPS tails. We identify three examples from the literature that are not RPS tails but slingshot tails and discuss other potential candidates.


Lyskova, N and Churazov, E and Zhang, C and Forman, W and Jones, C and Dolag, K and Roediger, E and Sheardown, A, 2019-03-02, Close-up view of an ongoing merger between the NGC 4839 group and the Coma cluster – a post-merger scenario, Monthly Notices of the Royal Astronomical Society, doi: 10.1093/mnras/stz597

Abstract

We study a merger of the NGC 4839 group with the Coma cluster using X-ray observations from the XMM-Newton and Chandra telescopes. X-ray data show two prominent features: (i) a long (~600 kpc in projection) and bent tail of cool gas trailing (towards south-west) the optical centre of NGC 4839, and (ii) a ‘sheath’ region of enhanced X-ray surface brightness enveloping the group, which is due to hotter gas. While at first glance the X-ray images suggest that we are witnessing the first infall of NGC 4839 into the Coma cluster core, we argue that a post-merger scenario provides a better explanation of the observed features and illustrate this with a series of numerical simulations. In this scenario, the tail is formed when the group, initially moving to the south-west, reverses its radial velocity after crossing the apocenter, the ram pressure ceases and the ram pressure-displaced gas falls back towards the centre of the group and overshoots it. Shortly after the apocenter passage, the optical galaxy, dark matter, and gaseous core move in a north-east direction, while the displaced gas continues moving to the south-west. The ‘sheath’ is explained as being due to interaction of the re-infalling group with its own tail of stripped gas mixed with the Coma gas. In this scenario, the shock, driven by the group before reaching the apocenter, has already detached from the group and would be located close to the famous relic to the south-west of the Coma cluster.


Alexander Turner and Stephen Hayes, 2019-02-21, The Classification of Minor Gait Alterations Using Wearable Sensors and Deep Learning, IEEE Transactions on Biomedical Engineering, doi: 10.1109/TBME.2019.2900863

Abstract

Objective: This paper describes how non-invasive wearable sensors can be used in combination with deep learning to classify artificially induced gait alterations without the requirement for a medical professional or gait analyst to be present. This approach is motivated by the goal of diagnosing gait abnormalities on a symptom by symptom basis, irrespective of other neuromuscular movement disorders patients may be affected by. This could lead to improvements in treatment and offer a greater insight into movement disorders. Methods: In-shoe pressure was measured for 12 able-bodied participants, each subject to 8 artificially induced gait alterations, achieved by modifying the underside of the shoe. The data were recorded at 100 Hz over 2520 data channels and was analysed using the deep learning architecture, long term short term memory networks. Additionally, the rationale for the decision-making process of these networks was investigated. Conclusion: Long term short term memory networks are applicable to the classification of gait function. The classifications can be made using only 2 seconds of sparse data (82.0% accuracy over 96,000 instances of test data) from participants who were not part of the training set. Significance: This work provides potential for gait function to be accurately classified using non-invasive techniques, and at more regular intervals, outside of a clinical setting without the need for healthcare professionals to be present.


Aurora Simionescu, John ZuHone, Irina Zhuravleva, Eugene Churazov, Massimo Gaspari, Daisuke Nagai, Norbert Werner, Elke Roediger, Rebecca Canning, Dominique Eckert, Liyi Gu & Frits Paerels, 2019-02-19, Constraining Gas Motions in the Intra-Cluster Medium, Space Science Reviews, doi: 10.1007/s11214-019-0590-1

Abstract

he detailed velocity structure of the diffuse X-ray emitting intra-cluster medium (ICM) remains one of the last missing key ingredients in understanding the microphysical properties of these hot baryons and constraining our models of the growth and evolution of structure on the largest scales in the Universe. Direct measurements of the gas velocities from the widths and shifts of X-ray emission lines were recently provided for the central region of the Perseus Cluster of galaxies by Hitomi, and upcoming high-resolution X-ray microcalorimeters onboard XRISM and Athena are expected to extend these studies to many more systems. In the mean time, several other direct and indirect methods have been proposed for estimating the velocity structure in the ICM, ranging from resonant scattering to X-ray surface brightness fluctuation analysis, the kinematic Sunyaev-Zeldovich effect, or using optical line emitting nebulae in the brightest cluster galaxies as tracers of the motions of the ambient plasma. Here, we review and compare the existing estimates of the velocities of the hot baryons, as well as the various overlapping physical processes that drive motions in the ICM, and discuss the implications of these measurements for constraining the viscosity and identifying the source of turbulence in clusters of galaxies.


Siya Jin, Ron J.Patton, Bingyong Guo, 2019-02-15, Enhancement of wave energy absorption efficiency via geometry and power take-off damping tuning, Energy, doi: 10.1016/j.energy.2018.12.074

Abstract

In this work a three dimensional computational fluid dynamic (CFD) model has been constructed based on a 1/50 scale heaving point absorber wave energy converter (PAWEC). The CFD model is validated first via wave tank tests and then is applied in this study to investigate the joint effects of device geometry and power take-off (PTO) damping on wave energy absorption. Three PAWEC devices are studied with the following geometrical designs: a cylindrical flat-bottom device (CL); a hemispherical streamlined bottom design (CH) and a 90°-conical streamlined bottom structure (CC). A PTO force via varying damping coefficient is applied to compare the power conversion performances of the aforementioned devices. Free decay, wave-PAWEC interaction and power absorption tests are conducted via the CFD model. The results show that for CH and CC designs the added mass and hydrodynamic damping decrease by up to 60% compared with the CL device. Moreover, the CC design is the best of the three structures since its amplitude response increases by up to 100% compared with the CL. Applying an appropriate PTO damping to the CC device prominently increases the achievable optimal power by up to 70% under both regular and irregular waves (compared with the CL device).


Mishenina, T; Pignatari, M; Gorbaneva, T; Bisterzo, S; Travaglio, C; Thielemann, F. K.; Soubiran, C, 2019-02-08, Enrichment of the Galactic disc with neutron capture elements: Sr, Monthly Notices of the Royal Astronomical Society, doi: 10.1093/mnras/stz178

Abstract

The enrichment history of heavy neutron-capture elements in the Milky Way disc provides fundamental information about the chemical evolution of our Galaxy and about the stellar sources that made those elements. In this work we give new observational data for Sr, the element at the first neutron-shell closure beyond iron, N=50, based on the analysis of the high resolution spectra of 276 Galactic disc stars. The Sr abundance was derived by comparing the observed and synthetic spectra in the region of the Sr I 4607Ã…4607Ã… line, making use of the LTE approximation. NLTE corrections lead to an increase of the abundance estimates obtained under LTE, but for these lines they are minor near solar metallicity. The average correction that we find is 0.151 dex. The star that is mostly affected is HD 6582, with a 0.244 dex correction. The behavior of the Sr abundance as a function of metallicity is discussed within a stellar nucleosynthesis context, in comparison with the abundance of the heavy neutron-capture elements Ba (Z=56) and Eu (Z=63). The comparison of the observational data with the current GCE models confirm that the s-process contributions from Asymptotic Giant Branch stars and from massive stars are the main sources of Sr in the Galactic disc and in the Sun, while different nucleosynthesis sources can explain the high [Sr/Ba] and [Sr/Eu] ratios observed in the early Galaxy.


Keegans, James D.; Fryer, Chris L.; Jones, Samuel W.; Cote, Benoit; Belczynski, Krzysztof; Herwig, Falk; Pignatari, Marco; Laird, Alison M.; Diget, Christian Aa., 2019-02-06, Nucleosynthetic yields from neutron stars accreting in binary common envelopes, Monthly Notices of the Royal Astronomical Society, doi: 10.1093/mnras/stz368

Abstract

Massive-star binaries can undergo a phase where one of the two stars expands during its advanced evolutionary stage as a giant and envelops its companion, ejecting the hydrogen envelope and tightening its orbit. Such a common envelope phase is required to tighten the binary orbit in the formation of many of the observed X-ray binaries and merging compact binary systems. In the formation scenario for neutron star binaries, the system might pass through a phase where a neutron star spirals into the envelope of its giant star companion. These phases lead to mass accretion onto the neutron star. Accretion onto these common-envelope-phase neutron stars can eject matter that has undergone burning near to the neutron star surface. This paper presents nucleosynthetic yields of this ejected matter, using population synthesis models to study the importance of these nucleosynthetic yields in a galactic chemical evolution context. Depending on the extreme conditions in temperature and density found in the accreted material, both proton-rich and neutron-rich nucleosynthesis can be obtained, with efficient production of neutron rich isotopes of low Z material at the most extreme conditions, and proton rich isotopes, again at low Z, in lower density models. Final yields are found to be extremely sensitive to the physical modeling of the accretion phase. We show that neutron stars accreting in binary common envelopes might be a new relevant site for galactic chemical evolution, and therefore more comprehensive studies are needed to better constrain nucleosynthesis in these objects.


Donatus O. Onwuli and Sabrina Francesca Samuel and Pagona Sfyri and Kevin Welham and Martin Goddard and Yasir Abu-Omar and Mahmoud Loubani and Francisco Rivero and Antonios Matsakas and David M. Benoit and Mark Wade and John Greenman and Pedro Beltran-Alvarez, 2019-01-31, The inhibitory subunit of cardiac troponin (cTnI) is modified by arginine methylation in the human heart, International Journal of Cardiology, doi: 10.1016/j.ijcard.2019.01.102

Abstract

The inhibitory subunit of cardiac troponin (cTnI) is a gold standard cardiac biomarker and also an essential protein in cardiomyocyte excitation-contraction coupling. The interactions of cTnI with other proteins are fine-tuned by post-translational modification of cTnI. Mutations in cTnI can lead to hypertrophic cardiomyopathy.


Thielemann, F. K.; Mishenina, T.; Pignatari, M.; Gorbaneva, T.; Travaglio, C.; Cote, B.; Thielemann, F.K; Soubiran, C., 2019-01-01, Enrichment of the Galactic disc with neutron-capture elements: Mo and Ru, Monthly Notices of the Royal Astronomical Society, doi: 10.1093/mnras/stz2202

Abstract

We present new observational data for the heavy elements molybdenum (Mo, Z = 42) and ruthenium (Ru, Z = 44) in F-, G-, and K-stars belonging to different substructures of the Milky Way. The range of metallicity covered is -1.0 < [Fe/H] < + 0.3. The spectra of Galactic disc stars have a high resolution of 42 000 and 75 000 and signal-to-noise ratio better than 100. Mo and Ru abundances were derived by comparing the observed and synthetic spectra in the region of Mo I lines at 5506, 5533 Ã… for 209 stars and Ru I lines at 4080, 4584, 4757 Ã… for 162 stars using the LTE approach. For all the stars, the Mo and Ru abundance determinations are obtained for the first time with an average error of 0.14 dex. This is the first extended sample of stellar observations for Mo and Ru in the Milky Way disc, and together with earlier observations in halo stars it is pivotal in providing a complete picture of the evolution of Mo and Ru across cosmic time-scales. The Mo and Ru abundances were compared with those of the neutron-capture elements (Sr, Y, Zr, Ba, Sm, Eu). The complex nucleosynthesis history of Mo and Ru is compared with different Galactic Chemical Evolution (GCE) simulations. In general, present theoretical GCE simulations show underproduction ofMo and Ru at all metallicities compared to observations. This highlights a significant contribution of nucleosynthesis processes not yet considered in our simulations. A number of possible scenarios are discussed.


A Molla, M.; Diaz, A. I.; Cavichia, O.; Gibson, B. K.; Maciel, W. J.; Costa, R. D. D.; Ascasibar, Y.; Few, C. G., 2019-01-01, The time evolution of the Milky Way’s oxygen abundance gradient, Monthly Notices of the Royal Astronomical Society, doi: 10.1093/mnras/sty2877

Abstract

We study the evolution of oxygen abundance radial gradients as a function of time for the Milky Way Galaxy obtained with our MULCHEM chemical evolution model. We review the recent data of abundances for different objects observed in our Galactic disc. We analyse with our models the role of the growth of the stellar disc, as well as the effect of infall rate and star formation prescriptions, or the pre-enrichment of the infall gas, on the time evolution of the oxygen abundance radial distribution. We compute the radial gradient of abundances within the disc, and its corresponding evolution, taking into account the disc growth along time. We compare our predictions with the data compilation, showing a good agreement. Our models predict a very smooth evolution when the radial gradient is measured within the optical disc with a slight flattening of the gradient from ̃-0.057 dex kpc-1 at z = 4 until values around ̃-0.015 dex kpc-1 at z = 1 and basically the same gradient until the present, with small differences between models. Moreover, some models show a steepening at the last times, from z = 1 until z = 0 in agreement with data which give a variation of the gradient in a range from -0.02 to -0.04 dex kpc-1 from t = 10 Gyr until now. The gradient measured as a function of the normalized radius R/Reff is in good agreement with findings by CALIFA and MUSE, and its evolution with redshift falls within the error bars of cosmological simulations.



2018 (23 outputs)

Zlatko Bacic, David Benoit, Matthieu Besemer, Joel Bowman, Stephen Bradforth, David Clary, Robert Donovan, Ingo Fischer, Francesco Gianturco, Majdi Hochlaf, Paul Houston, Peter Knowles, Stephen Leone, Roberto Linguerri, Uwe Manthe, Anne B. McCoy, Jens Petersen, Jeremy Richardson, Xiao Shan, Petr Slavicek, Thierry Stoecklin, Krzysztof Szalewicz, Ad van der Avoird, Roland Wester, Graham Worth and Anne Zehnacker-Rentien, 2018-12-03, Precise characterisation of isolated molecules: general discussion, Faraday Discussions, doi: 10.1039/c8fd90050g

Abstract


Lluis Franch-Gras, Christoph Hahn, Eduardo M. Garcia-Roger, Maria Jose Carmona, Manuel Serra & Africa Gomez, 2018-10-30, Genomic signatures of local adaptation to the degree of environmental predictability in rotifers, Scientific Reports, doi: 10.1038/s41598-018-34188-y

Abstract

Environmental fluctuations are ubiquitous and thus essential for the study of adaptation. Despite this, genome evolution in response to environmental fluctuations – and more specifically to the degree of environmental predictability – is still unknown. Saline lakes in the Mediterranean region are remarkably diverse in their ecological conditions, which can lead to divergent local adaptation patterns in the inhabiting aquatic organisms. The facultatively sexual rotifer Brachionus plicatilis shows diverging local adaptation in its life-history traits in relation to estimated environmental predictability in its habitats. Here, we used an integrative approach – combining environmental, phenotypic and genomic data for the same populations – to understand the genomic basis of this diverging adaptation. Firstly, a novel draft genome for B. plicatilis was assembled. Then, genome-wide polymorphisms were studied using genotyping by sequencing on 270 clones from nine populations in eastern Spain. As a result, 4,543 high-quality SNPs were identified and genotyped. More than 90 SNPs were found to be putatively under selection with signatures of diversifying and balancing selection. Over 140 SNPs were correlated with environmental or phenotypic variables revealing signatures of local adaptation, including environmental predictability. Putative functions were associated to most of these SNPs, since they were located within annotated genes. Our results reveal associations between genomic variation and the degree of environmental predictability, providing genomic evidence of adaptation to local conditions in natural rotifer populations.


Deshmukh, Harshal and Barker, Emma and Ambarasan, Thineshkrishna and Levin, Daniel and Bell, Samira and Witham, Miles D and George, Jacob, 2018-10-29, Calcium channel blockers are associated with improved survival and lower cardiovascular mortality in patients with renovascular disease, Cardiovascular Therapeutics, doi: 10.1111/1755-5922.12474

Abstract

Background and objective Results of interventional trials in renovascular hypertension have been disappointing and medical therapy is the current recommended gold standard. However, the comparative long-term benefits of different antihypertensive drug classes in atherosclerotic renal artery stenosis are not known. We aim to assess the effect of different antihypertensive drug classes on outcomes in renovascular hypertension Design, setting, participants, and measurements Using Tayside Health Informatics Centre database, anonymised data over a 6-year period was analysed. Biochemistry, prescribing data, morbidity, mortality and demographic data were accessed via hospital medical records and electronic data stored in the Tayside Health Informatics Centre Safe Haven. General Registrar’s Office data was used to identify patients who died from cardiovascular disease. Independent predictors of survival in each group were analyzed using Kaplan-Meier survival curves and Cox proportional hazard models, adjusted for a range of covariates, using Time-Updated Drug Analysis. Blood pressure data was obtained from primary and secondary care clinic blood pressure records for each patient. Adjustments for mean systolic blood pressure over the follow-up period and baseline blood pressure were made. Results 579 patients with Atherosclerotic Renal Artery Stenosis were identified. In the unilateral renal artery stenosis cohort, Calcium Channel Blockers but not ACE inhibitors/ARBs, were associated with a significant reduction in all-cause (HR=0.45, CI= 0.31, 0.65; P=<0.0001) and Cardiovascular ((HR= 0.51, CI =0.29-0.90 P=0.019). This was maintained after adjustment for blood pressure. In the bilateral renal artery stenosis cohort, both classes of drugs reduced all-cause but not cardiovascular mortality. Patients with moderate disease benefitted more than those with mild or severe disease. Conclusions Calcium Channel Blockers are associated with significantly increased survival and lower cardiovascular mortality particularly in patients with moderate RAS disease. This article is protected by copyright. All rights reserved.


Deshmukh, Harshal and Papageorgiou, Maria and Kilpatrick, Eric S. and Atkin, Stephen L. and Sathyapalan, Thozhukat, 2018-10-19, Development of a novel risk prediction and risk stratification score for polycystic ovary syndrome, Clinical Endocrinology, doi: 10.1111/cen.13879

Abstract

Summary Objective The aim of this study was to develop a simple phenotypic algorithm that can capture the underlying clinical and hormonal abnormalities to help in the diagnosis and risk stratification of polycystic ovary syndrome (PCOS). Methods The study consisted of 111 women with PCOS fulfilling the Rotterdam diagnostic criteria and 67 women without PCOS. A Firth’s penalized logistic regression model was used for independent variable section. Model optimism, discrimination and calibration were assessed using bootstrapping, area under the curve (AUC) and Hosmer-Lemeshow statistics, respectively. The prognostic index (PI) and risk score for developing PCOS were calculated using independent variables from the regression model. Results Firth penalized logistic regression model with backward selection identified four independent predictors of PCOS namely free androgen index [β 0.30 (0.12), P = 0.008], 17-OHP [β = 0.20 (0.01), P = 0.026], anti-mullerian hormone [AMH; β = 0.04 (0.01) P < 0.0001] and waist circumference [β = 0.08 (0.02), P < 0.0001]. The model estimates indicated high internal validity (minimal optimism on 1000-fold bootstrapping), good discrimination ability (bias corrected c-statistic = 0.90) and good calibration (Hosmer-Lemeshow χ2 = 3.7865). PCOS women with a high-risk score (q1 + q2 + q3 vs q4) presented with a worse metabolic profile characterized by a higher 2-hour glucose (P = 0.01), insulin (P = 0.0003), triglycerides (P = 0.0005), C-reactive protein (P < 0.0001) and low HDL-cholesterol (P = 0.02) as compared to those with lower risk score for PCOS. Conclusions We propose a simple four-variable model, which captures the underlying clinical and hormonal abnormalities in PCOS and can be used for diagnosis and metabolic risk stratification in women with PCOS.


Cseh, B.; Lugaro, M.; D’Orazi, V.; de Castro, D. B.; Pereira, C. B.; Karakas, A. I.; Molnar, L.; Plachy, E.; Szabo, R.; Pignatari, M.; Cristallo, S., 2018-10-17, The s process in AGB stars as constrained by a large sample of barium stars, Astronomy & Astrophysics, doi: 10.1051/0004-6361/201834079

Abstract

Barium (Ba) stars are dwarf and giant stars enriched in elements heavier than iron produced by the slow neutron-capture process (s process). These stars belong to binary systems in which the primary star evolved through the asymptotic giant branch (AGB) phase. During this phase the primary star produced s-process elements and transferred them onto the secondary, which is now observed as a Ba star. Aims. We compare the largest homogeneous set of Ba giant star observations of the s-process elements Y, Zr, La, Ce, and Nd with AGB nucleosynthesis models to reach a better understanding of the s process in AGB stars. Methods. By considering the light-s (ls: Y and Zr) heavy-s (hs: La, Ce, and Nd) and elements individually, we computed for the first time quantitative error bars for the different hs-element to ls-element abundance ratios, and for each of the sample stars. We compared these ratios to low-mass AGB nucleosynthesis models. We excluded La from our analysis because the strong La lines in some of the sample stars cause an overestimation and unreliable abundance determination, as compared to the other observed hs-Type elements. Results. All the computed hs-Type to ls-Type element ratios show a clear trend of increasing with decreasing metallicity with a small spread (less than a factor of 3). This trend is predicted by low-mass AGB models in which 13C is the main neutron source. The comparison with rotating AGB models indicates the need for the presence of an angular momentum transport mechanism that should not transport chemical species, but significantly reduces the rotational speed of the core in the advanced stellar evolutionary stages. This is an independent confirmation of asteroseismology observations of the slow down of core rotation in giant stars, and of rotational velocities of white dwarfs lower than predicted by models without an extra angular momentum transport mechanism.


Pan Wang, Alexey V. Krasavin, Francesco N. Viscomi, Ali M. Adawi, Jean-Sebastien G. Bouillard, Lei Zhang, Diane J. Roth, Limin Tong, Anatoly V. Zayats, 2018-10-02, Metaparticles: Dressing Nano-Objects with a Hyperbolic Coating, Laser & Photonics Reviews, doi: 10.1002/lpor.201800179

Abstract

The ability to engineer the optical response of a plasmonic nano-object is highly desired to achieve better control over light-matter interactions. Due to the sensitivity of plasmon resonances to the surrounding media, isotropic dielectric coating is an easy approach to modify the optical properties of a plasmonic nanostructure. However, the choice of coatings and the provided tunability is limited by the range of refractive indices of available materials. Here, it is shown that coating of plasmonic nano-objects with an anisotropic metamaterial, which displays a hyperbolic dispersion and allows the design of refractive index on demand, provides greater flexibility in engineering their interaction with light. This is experimentally demonstrated by coating Au nanospheres with alternating SiO2 and Au multishells. This creates rich and highly tunable plasmonic modes covering a broad wavelength range (≈400-2200 nm) and produces high local field intensity enhancement (≈500-fold). The concept is extended to hyperbolic coating of dielectric nano-objects, confirming the nature of the modes to be related to the resonances in the hyperbolic layer. The implemented approach using a coating with an engineered effective refractive index may find applications in plasmon-enhanced spectroscopy, nanolasers, design of nonlinear phenomena, photothermal conversions, and hot-electron generation.


Alex Sheardown and Elke Roediger and Yuanyuan Su and Ralph P. Kraft and Thomas Fish and John A. ZuHone and William R. Forman and Christine Jones and Eugene Churazov and Paul E. J. Nulsen, 2018-09-28, The Recent Growth History of the Fornax Cluster Derived from Simultaneous Sloshing and Gas Stripping: Simulating the Infall of NGC 1404, The Astrophysical Journal, doi: 10.3847/1538-4357/aadc0f

Abstract

We derive the recent growth history of the Fornax Cluster, in particular the recent infall of the giant elliptical galaxy NGC 1404. We show, using a simple cluster minor merger simulation tailored to Fornax and NGC 1404, that a second or more likely third encounter between the two reproduces all the main merger features observed in both objects; we firmly exclude a first infall scenario. Our simulations reveal a consistent picture: NGC 1404 passed by NGC 1399 about 1.1–1.3 Gyr ago from the northeast to the southwest and is now almost at the point of its next encounter from the south. This scenario explains the sloshing patterns observed in Fornax—a prominent northern cold front and an inner southern cold front. This scenario also explains the truncated atmosphere, the gas-stripping radius of NGC 1404, and its faint gas tail. Independent of the exact history, we can make a number of predictions. A detached bow shock south of NGC 1404 should exist, which is a remnant of the galaxy’s previous infall at a distance from NGC 1404 between 450 and 750 kpc with an estimated Mach number between 1.3 and 1.5. The wake of NGC 1404 also lies south of the galaxy with enhanced turbulence and a slight enhancement in metallicity compared to the undisturbed regions of the cluster. Southwest of NGC 1404, there is likely evidence of old turbulence originating from the previous infall. No scenario predicts enhanced turbulence outside of the cold front northwest of the cluster center.


Al-Qaissi, Ahmed and Papageorgiou, Maria and Deshmukh, Harshal and Madden, Leigh A. and Rigby, Alan and Kilpatrick, Eric S. and Atkin, Stephen L. and Sathyapalan, Thozhukat, 2018-09-28, Effects of acute insulin-induced hypoglycaemia on endothelial microparticles in adults with and without type 2 diabetes, Diabetes, Obesity and Metabolism: A Journal of Pharmacology and Therapeutics, doi: 10.1111/dom.13548

Abstract

Aims To assess whether endothelial microparticles (EMPs), novel surrogate markers of endothelial injury and dysfunction, are differentially produced in response to acute insulin-induced hypoglycaemia in adults with and without type 2 diabetes. Materials and methods A prospective, parallel study was conducted in individuals with type 2 diabetes (n = 23) and controls (n = 22). Hypoglycaemia (<2.2 mmoL/L: <40 mg/dL) was achieved by intravenous infusion of soluble insulin. Blood samples were collected at baseline and at 0, 30, 60, 120, 240 minutes and 24 hours after hypoglycaemia and analysed for CD31+ (platelet endothelial cell adhesion molecule-1), CD54+ (intercellular adhesion molecule 1), CD62-E+ (E-selectin), CD105+ (endoglin), CD106+ (vascular cell adhesion molecule 1) and CD142+ (tissue factor) EMPs by flow cytometry. The peak elevations (% rise from 0 minutes after hypoglycaemia) in EMP within 240 minutes after insulin-induced hypoglycaemia were modelled using a regression model, with adjustment for relevant covariates. All EMPs were expressed as percentage from 0 minutes hypoglycaemia for each time point and total areas under the curve (AUC0min–24h) were calculated. Results Following insulin-induced hypoglycaemia, levels of circulating EMPs were maximal at 240 minutes (P < 0.001) and returned to baseline values within 24 hours for both groups. The peak elevations (% rise from 0 minutes following hypoglycaemia) seen in CD31+, CD54+, CD62-E+, CD105+ and CD142+ EMPs within 240 minutes were associated with diabetes status after adjustments for all relevant covariates. Individuals with type 2 diabetes showed increased CD31+ EMPs AUC0min–24h (P = 0.014) and CD105+ EMPs AUC0min–24h (P = 0.006) compared with controls, but there were no differences for CD54+ (P = 0.91), CD62-E+ (P = 0.14), CD106+ (P = 0.36) or CD142+ (P = 0.77) EMPs AUC0min–24h. Conclusions The associations between peak elevations within 240 minutes after insulin-induced hypoglycaemia for CD31+, CD54+, CD62-E+, CD105+ and CD142+ and diabetes status indicate that the assessment of a panel of EMPs within this timeframe would identify a hypoglycaemic event in this population. The greater overall responses over time (AUCs) for apoptosis-induced CD31+ and CD105+ EMPs suggest that hypoglycaemia exerts greater endothelial stress in type 2 diabetes.


W.R.C. Somerville, J.L. Stokes, A.M., T.S. Horozov, A.J. Archer and D.M.A. Buzza, 2018-09-13, Density functional theory for the crystallization of two-dimensional dipolar colloidal alloys, Journal of Physics: Condensed Matter, doi: 10.1088/1361-648X/aaddc9

Abstract

Two-dimensional mixtures of dipolar colloidal particles with different dipole moments exhibit extremely rich self-assembly behaviour and are relevant to a wide range of experimental systems, including charged and super-paramagnetic colloids at liquid interfaces. However, there is a gap in our understanding of the crystallization of these systems because existing theories such as integral equation theory and lattice sum methods can only be used to study the high temperature fluid phase and the zero-temperature crystal phase, respectively. In this paper we bridge this gap by developing a density functional theory (DFT), valid at intermediate temperatures, in order to study the crystallization of one and two-component dipolar colloidal monolayers. The theory employs a series expansion of the excess Helmholtz free energy functional, truncated at second order in the density, and taking as input highly accurate bulk fluid direct correlation functions from simulation. Although truncating the free energy at second order means that we cannot determine the freezing point accurately, our approach allows us to calculate ab initio both the density profiles of the different species and the symmetry of the final crystal structures. Our DFT predicts hexagonal crystal structures for one-component systems, and a variety of superlattice structures for two-component systems, including those with hexagonal and square symmetry, in excellent agreement with known results for these systems. The theory also provides new insights into the structure of two-component systems in the intermediate temperature regime where the small particles remain molten but the large particles are frozen on a regular lattice.


Annika M Schoene and Nina Dethlefs, 2018-08-20, Unsupervised suicide note classification, Proceedings of the 7th KDD Workshop on Issues of Sentiment Discovery and Opinion Mining (WISDOM), link: https://sentic.net/wisdom2018schoene.pdf

Abstract

With the greater availability of linguistic data from public social media platforms and the advancements of natural language processing, a number of opportunities have arisen for researchers to analyse this type of data. Research efforts have mostly focused on detecting the polarity of textual data, evaluating whether there is positive, negative or sometimes neutral content. Especially the use of neural networks has recently yielded significant results in polarity detection experiments. In this paper we present a more fine-grained approach to detecting sentiment in textual data, particularly analysing a corpus of suicide notes, depressive notes and love notes. We achieve a classification accuracy of 71.76% when classifying based on text and sentiment features, and an accuracy of 69.41% when using the words present in the notes alone. We discover that while emotions in all three datasets overlap, each of them has a unique ‘emotion profile’ which allows us to draw conclusions about the potential mental state that is reflects. Using the emotion sequences only, we achieve an accuracy of 75.29%. The results from unannotated data, while worse than the other models, nevertheless represent an encouraging step towards being able to flag potentially harmful social media posts online and in real time. We provide a high-level corpus analysis of the data sets in order to demonstrate the grammatical and emotional differences.


T.L. Lee, J. Mi, S. Ren, S. Zhao, J. Fan, S. Kabra, S. Zhang, and P.S. Grant, 2018-05-26, Modelling and neutron diffraction characterization of the interfacial bonding of spray formed dissimilar steels, Acta Materialia, doi: 10.1016/j.actamat.2018.05.055

Abstract

The spray forming of thick, dissimilar steel clad tubes with the objective of achieving a high integrity metallurgical bond across the cladding-substrate interface able to withstand residual stresses and subsequent thermo-mechanical processing was investigated by large scale experiments, modelling and extensive microstructural characterization including microscopy, X-ray tomography, neutron scattering and mechanical testing. The simulated residual stress distributions across the cladding-substrate interface, accounting for any as-sprayed porosity and the distribution of martensitic and retained austenite phases, were compared with neutron diffraction measurements and differences used to infer the load transfer behaviour and thus the mechanical integrity of the interface. The mechanical properties of the interfaces were then also measured directly by shear testing. The link between substrate pre-heating, the spray forming temperature, and the resulting preform temperature, porosity, phase fractions, residual stress, strength and integrity of the interface were established and quantified explicitly.


Benoit, David M. and Lauvergnat, David and Scribano, Yohann, 2018-05-25, Does cage quantum delocalisation influence the translation-rotational bound states of molecular hydrogen in clathrate hydrate?, Faraday Discussions, doi: 10.1039/C8FD00087E

Abstract

In this study, we examine the effect of a flexible description of the clathrate hydrate framework on the translation-rotation (TR) eigenstates of guest molecules such as molecular hydrogen. Traditionally, the water cage structure is assumed to be rigid, thus ignoring the quantum nature of hydrogen nuclei in the water framework. However, it has been shown that protons in a water molecule possess a marked delocalised character in many situations, ranging from water clusters to proton transfer in the bulk. In the case of water clathrates, all previous TR bound-state calculations of guest molecules consider that the caging water molecules are fixed at their equilibrium geometry. Only recently, a static investigation of the role of proton configurations was performed by Bacic and co-workers by sampling a very large number of different static structures of water clathrates. Here, we investigate the importance of the rotational degrees of freedom of the water cage on the TR levels of the guest molecule using an efficient adiabatic decoupling scheme. Our approach combines rigid body diffusion Monte Carlo calculations for the description of the rotational degree of freedom of water molecules surrounding the guest molecular hydrogen to an efficient Smolyak sparse-grid technique for the calculation of the TR levels. This approach allows us to take into account the highly anharmonic nature of the rotational water motions in a high-dimensional system. The clathrate-induced splittings of the j = 1 rotational levels are much more sensitive to the quantum hydrogen delocalisation than the translational transitions. This result is in good agreement with the previous static study of Bacic and co-workers.


Daniela Carollo and Patricia B. Tissera and Timothy C. Beers and Dmitrii Gudin and Brad K. Gibson and Ken C. Freeman and Antonela Monachesi, 2018-05-18, The Origin of the Milky Way’s Halo Age Distribution, The Astrophysical Journal, doi: 10.3847/2041-8213/aac2dc

Abstract

We present an analysis of the radial age gradients for the stellar halos of five Milky Way (MW) mass-sized systems simulated as part of the Aquarius Project. The halos show a diversity of age trends, reflecting their different assembly histories. Four of the simulated halos possess clear negative age gradients, ranging from approximately .7 to .19 Myr kpc.1, shallower than those determined by recent observational studies of the Milky Way’s stellar halo. However, when restricting the analysis to the accreted component alone, all of the stellar halos exhibit a steeper negative age gradient with values ranging from .8 to .32 Myr kpc.1, closer to those observed in the Galaxy. Two of the accretion-dominated simulated halos show a large concentration of old stars in the center, in agreement with the Ancient Chronographic Sphere reported observationally. The stellar halo that best reproduces the current observed characteristics of the age distributions of the Galaxy is that formed principally by the accretion of small satellite galaxies. Our findings suggest that the hierarchical clustering scenario can reproduce the MW’s halo age distribution if the stellar halo was assembled from accretion and the disruption of satellite galaxies with dynamical masses less than ~109.5 M ., and a minimal in situ contribution.


Chalupa, David and Hawick, Ken A. and Walker, James A., 2018-04-16, Hybrid Bridge-Based Memetic Algorithms for Finding Bottlenecks in Complex Networks, Big Data Research, doi: 10.1016/j.bdr.2018.04.001

Abstract

We propose a memetic approach to find bottlenecks in complex networks based on searching for a graph partitioning with minimum conductance. Finding the optimum of this problem, also known in statistical mechanics as the Cheeger constant, is one of the most interesting NP-hard network optimisation problems. The existence of low conductance minima indicates bottlenecks in complex networks. However, the problem has not yet been explored in depth in the context of applied discrete optimisation and evolutionary approaches to solve it. In this paper, the use of a memetic framework is explored to solve the minimum conductance problem. The approach combines a hybrid method of initial population generation based on bridge identification and local optima sampling with a steady-state evolutionary process with two local search subroutines. These two local search subroutines have complementary qualities. Efficiency of three crossover operators is explored, namely one-point crossover, uniform crossover, and our own partition crossover. Experimental results are presented for both artificial and real-world complex networks. Results for Barabasi-Albert model of scale-free networks are presented, as well as results for samples of social networks and protein-protein interaction networks. These indicate that both well-informed initial population generation and the use of a crossover seem beneficial in solving the problem in large-scale.


Chen, Long; Vivier, Elodie; Eling, Charlotte J.; Babra, Tahkur S.; Bouillard, Jean Sebastien G.; Adawi, Ali M.; Benoit, David M.; Hartl, Frantisek; Colquhoun, Howard M.; Efremova, Olga A.; Greenland, Barnaby W., 2018-04-07, Conjugated, rod-like viologen oligomers: Correlation of oligomer length with conductivity and photoconductivity, Synthetic Metals, doi: 10.1016/j.synthmet.2018.03.019

Abstract

An iterative synthesis has been used to produce conjugated, monodisperse, viologen-based aromatic oligomers containing up to 12 aromatic/heterocyclic rings. The methoxy-substituted oligomers were soluble in common organic solvents and could be processed by spin coating. The conductivities of the resulting films (30–221 nm thick) increased by more than one order of magnitude as the oligomer length increased from unimer (1, 2.20 × 10 −11 S cm- 1 ) through dimer (2) to trimer (3, 6.87 × 10 -10 S cm -1 ). The bandgaps of the materials were estimated from the absorption spectra of these thin films. The longest oligomer, 3, exhibited a noticeably narrower bandgap (2.3 eV) than the shorter oligomers (1 and 2 both 2.7 eV). Oligomer 3 also showed photoconductivity under irradiation across a wide range of wavelengths in the visible spectral region. In conjunction with DFT calculations of these systems our results suggest that structurally related viologen-type oligomers may find use in optoelectronic devices.


Bing Wang, Dongyue Tan, Tung Lik Lee, Jia Chuan Khong, Feng Wang, Dmitry Eskin, Thomas Connolley, Kamel Fezzaa, Jiawei Mi, 2018-04, Data and videos for ultrafast synchrotron X-ray imaging studies of metal solidification under ultrasound, Data in Brief, doi: 10.1016/j.dib.2018.01.110

Abstract

The data presented in this article are related to the paper entitled ‘Ultrafast synchrotron X-ray imaging studies of microstructure fragmentation in solidification under ultrasound’ [Wang et al., Acta Mater. 144 (2018) 505-515]. This data article provides further supporting information and analytical methods, including the data from both experimental and numerical simulation, as well as the Matlab code for processing the X-ray images. Six videos constructed from the processed synchrotron X-ray images are also provided.


Roggatz, Christina C. and Lorch, Mark and Benoit, David M., 2018-03-22, Influence of Solvent Representation on Nuclear Shielding Calculations of Protonation States of Small Biological Molecules, Journal of Chemical Theory and Computation, doi: 10.1021/acs.jctc.7b01020

Abstract

In this study, we assess the influence of solvation on the accuracy and reliability of isotropic nuclear magnetic shielding calculations for amino acids in comparison to experimental data. We focus particularly on the performance of solvation methods for different protonation states, as biological molecules occur almost exclusively in aqueous solution and are subject to protonation with pH. We identify significant shortcomings of current implicit solvent models and present a hybrid solvation approach that improves agreement with experimental data by taking into account the presence of direct interactions between amino acid protonation state and water molecules.


Y. Zhao and W. Du and B. Koe and T. Connolley and S. Irvine and P.K. Allan and C.M. Schleputz and W. Zhang and F. Wang and D.G. Eskin and J. Mi, 2018-03-15, 3D characterisation of the Fe-rich intermetallic phases in recycled Al alloys by synchrotron X-ray microtomography and skeletonisation, Scripta Materialia, doi: 10.1016/j.scriptamat.2017.12.010

Abstract

Synchrotron X-ray microtomography and skeletonisation method were used to study the true 3D network structures and morphologies of the Fe-rich intermetallic phases in recycled Al-5.0%Cu-0.6%Mn alloys with 0.5% and 1.0% Fe. It was found that, the Fe-phases in the 1.0%Fe alloy have node lengths of 5–25μm; while those in the 0.5%Fe alloy are of 3–17μm. The Fe-phases in the 1.0%Fe alloy also developed sharper mean curvature with wider distribution than those in the 0.5%Fe alloy. Combining SEM studies of the deeply-etched samples, the true 3D structures of 4 different type Fe phases in both alloys are also revealed and demonstrated.


Travaglio, C.; Rauscher, T.; Heger, A.; Pignatari, M.; West, C., 2018-02-07, Role of core-collapse supernovae in explaining Solar System abundances of p nuclides, The Astrophysical Journal, doi: 10.3847/1538-4357/aaa4f7

Abstract

The production of the heavy stable proton-rich isotopes between 74Se and 196Hg—the p nuclides—is due to the contribution from different nucleosynthesis processes, activated in different types of stars. Whereas these processes have been subject to various studies, their relative contributions to Galactic chemical evolution (GCE) are still a matter of debate. Here we investigate for the first time the nucleosynthesis of p nuclides in GCE by including metallicity and progenitor mass-dependent yields of core-collapse supernovae (ccSNe) into a chemical evolution model. We used a grid of metallicities and progenitor masses from two different sets of stellar yields and followed the contribution of ccSNe to the Galactic abundances as a function of time. In combination with previous studies on p-nucleus production in thermonuclear supernovae (SNIa), and using the same GCE description, this allows us to compare the respective roles of SNeIa and ccSNe in the production of p-nuclei in the Galaxy. The γ process in ccSN is very efficient for a wide range of progenitor masses (13 M ⊙–25 M ⊙) at solar metallicity. Since it is a secondary process with its efficiency depending on the initial abundance of heavy elements, its contribution is strongly reduced below solar metallicity. This makes it challenging to explain the inventory of the p nuclides in the solar system by the contribution from ccSNe alone. In particular, we find that ccSNe contribute less than 10% of the solar p nuclide abundances, with only a few exceptions. Due to the uncertain contribution from other nucleosynthesis sites in ccSNe, such as neutrino winds or α-rich freeze out, we conclude that the light p-nuclides 74Se, 78Kr, 84Sr, and 92Mo may either still be completely or only partially produced in ccSNe. The γ-process accounts for up to twice the relative solar abundances for 74Se in one set of stellar models and 196Hg in the other set. The solar abundance of the heaviest p nucleus 196Hg is reproduced within uncertainties in one set of our models due to photodisintegration of the Pb isotopes 208,207,206Pb. For all other p nuclides, abundances as low as 2% of the solar level were obtained.


Bing Wang and Dongyue Tan and Tung Lik Lee and Jia Chuan Khong and Feng Wang and Dmitry Eskin and Thomas Connolley and Kamel Fezzaa and Jiawei Mi, 2018-02-01, Ultrafast synchrotron X-ray imaging studies of microstructure fragmentation in solidification under ultrasound, Acta Materialia, doi: 10.1016/j.actamat.2017.10.067

Abstract

Ultrasound processing of metal alloys is an environmental friendly and promising green technology for liquid metal degassing and microstructural refinement. However many fundamental issues in this field are still not fully understood, because of the difficulties in direct observation of the dynamic behaviours caused by ultrasound inside liquid metal and semisolid metals during the solidification processes. In this paper, we report a systematic study using the ultrafast synchrotron X-ray imaging (up to 271,554 frame per second) technique available at the Advanced Photon Source, USA and Diamond Light Source, UK to investigate the dynamic interactions between the ultrasonic bubbles/acoustic flow and the solidifying phases in a Bi-8%Zn alloy. The experimental results were complimented by numerical modelling. The chaotic bubble implosion and dynamic bubble oscillations were revealed in-situ for the first time in liquid metal and semisolid metal. The fragmentation of the solidifying Zn phases and breaking up of the liquid-solid interface by ultrasonic bubbles and enhanced acoustic flow were clearly demonstrated and agreed very well with the theoretical calculations. The research provides unambiguous experimental evidence and robust theoretical interpretation in elucidating the dominant mechanisms of microstructure fragmentation and refinement in solidification under ultrasound.


Marco Pignatari and Peter Hoppe and Reto Trappitsch and Chris Fryer and F.X. Timmes and Falk Herwig and Raphael Hirschi, 2018-01-15, The neutron capture process in the He shell in core-collapse supernovae: Presolar silicon carbide grains as a diagnostic tool for nuclear astrophysics, Geochimica et Cosmochimica Acta, doi: 10.1016/j.gca.2017.06.005

Abstract

Carbon-rich presolar grains are found in primitive meteorites, with isotopic measurements to date suggesting a core-collapse supernovae origin site for some of them. This holds for about 1-2% of presolar silicon carbide (SiC) grains, so-called Type X and C grains, and about 30% of presolar graphite grains. Presolar SiC grains of Type X show anomalous isotopic signatures for several elements heavier than iron compared to the solar abundances: most notably for strontium, zirconium, molybdenum, ruthenium and barium. We study the nucleosynthesis of zirconium and molybdenum isotopes in the He-shell of three core-collapse supernovae models of 15, 20 and 25 M☉ with solar metallicity, and compare the results to measurements of presolar grains. We find the stellar models show a large scatter of isotopic abundances for zirconium and molybdenum, but the mass averaged abundances are qualitatively similar to the measurements. We find all models show an excess of 96Zr relative to the measurements, but the model abundances are affected by the fractionation between Sr and Zr since a large contribution to 90Zr is due to the radiogenic decay of 90Sr. Some supernova models show excesses of 95,97Mo and depletion of 96Mo relative to solar. The mass averaged distribution from these models shows an excess of 100Mo, but this may be alleviated by very recent neutron-capture cross section measurements. We encourage future explorations to assess the impact of the uncertainties in key neutron-capture reaction rates that lie along the n-process path.


Peter Hoppe and Marco Pignatari and Janos Kodolanyi and Elmar Groner and Sachiko Amari, 2018-01-15, NanoSIMS isotope studies of rare types of presolar silicon carbide grains from the Murchison meteorite: Implications for supernova models and the role of 14C, Geochimica et Cosmochimica Acta, doi: 10.1016/j.gca.2017.01.051

Abstract

We have conducted a NanoSIMS ion imaging survey of about 1800 presolar silicon carbide (SiC) grains from the Murchison meteorite. A total of 21 supernova (SN) X grains, two SN C grains, and two putative nova grains were identified. Six particularly interesting grains, two X and C grains each and the two putative nova grains were subsequently studied in greater detail, namely, for C-, N-, Mg-Al-, Si-, S-, and Ca-Ti-isotopic compositions and for the initial presence of radioactive 26Al (half life 716,000 yr), 32Si (half life 153 yr), and 44Ti (half life 60 yr). Their isotope data along with those of three X grains from the literature were compared with model predictions for 15 M. and 25 M. Type II supernovae (SNe). The best fits were found for 25 M. SN models that consider for the He shell the temperature and density of a 15 M. SN and ingestion of H into the He shell before the explosion. In these models a C- and Si-rich zone forms at the bottom of the He burning zone (C/Si zone). The region above the C/Si zone is termed the O/nova zone and exhibits the isotopic fingerprints of explosive H burning. Satisfactory fits of measured C-, N-, and Si-isotopic compositions and of 26Al/27Al ratios require small-scale mixing of matter originating from a region extending over 0.2 M. for X and C grains and over 0.4 M. for one of the putative nova grains, involving matter from a thin Si-rich layer slightly below the C/Si zone, the C/Si zone, and the O/nova zone. Simultaneous fitting of 14N/15N and 26Al/27Al requires a C-N fractionation of a factor of 50 during SiC condensation. This leads to preferential incorporation of radioactive 14C (half life 5700 yr) over directly produced 14N and can account for the 14N/15N along with 26Al/27Al ratios as observed in the SiC grains. The good fit for one of the putative nova grains along with its high 26Al/27Al points towards a SN origin and supports previous suggestions that some grains classified as nova grains might be from SNe. Apparent problems with the small-scale mixing scheme considered here are C/O ratios that are mostly <1 if C-, N-, and Si-isotopic compositions and 26Al/27Al ratios are simultaneously matched, underproduction of 32Si, and overproduction of 44Ti. This confirms the limitations of one-dimensional hydrodynamical models for H ingestion and stresses the need to better study the convective-boundary mixing mechanisms at the bottom of the convective He shell in massive star progenitors. This is crucial to define the effective size of the C/Si zone formed by the SN shock. The comparison between the Si isotope data of the SN grains and the models gives a hint that the predicted 30Si is too high at the bottom of the He burning shell.


Hannes C. Gottschalk and Anja Poblotzki and Martin A. Suhm and Muneerah M. Al-Mogren and Jens Antony and Alexander A. Auer and Leonardo Baptista and David M. Benoit and Giovanni Bistoni and Fabian Bohle and Rahma Dahmani and Dzmitry Firaha and Stefan Grimme and Andreas Hansen and Michael E. Harding and Majdi Hochlaf and Christof Holzer and Georg Jansen and Wim Klopper and Wassja A. Kopp and Leif C. Kroger and Kai Leonhard and Halima Mouhib and Frank Neese and Max N. Pereira and Inga S. Ulusoy and Axel Wuttke and Ricardo A. Mata, 2018-01-01, The furan microsolvation blind challenge for quantum chemical methods: First steps, The Journal of Chemical Physics, doi: 10.1063/1.5009011

Abstract

Herein we present the results of a blind challenge to quantum chemical methods in the calculation of dimerization preferences in the low temperature gas phase. The target of study was the first step of the microsolvation of furan, 2-methylfuran and 2,5-dimethylfuran with methanol. The dimers were investigated through IR spectroscopy of a supersonic jet expansion. From the measured bands, it was possible to identify a persistent hydrogen bonding OH–O motif in the predominant species. From the presence of another band, which can be attributed to an OH-π interaction, we were able to assert that the energy gap between the two types of dimers should be less than or close to 1 kJ/mol across the series. These values served as a first evaluation ruler for the 12 entries featured in the challenge. A tentative stricter evaluation of the challenge results is also carried out, combining theoretical and experimental results in order to define a smaller error bar. The process was carried out in a double-blind fashion, with both theory and experimental groups unaware of the results on the other side, with the exception of the 2,5-dimethylfuran system which was featured in an earlier publication.



2017 (18 outputs)

Vorotnikova, Natalya A. and Vorotnikov, Yuri A. and Novozhilov, Igor N. and Syrokvashin, Mikhail M. and Nadolinny, Vladimir A. and Kuratieva, Natalia V. and Benoit, David M. and Mironov, Yuri V. and Walton, Richard I. and Clarkson, Guy J. and Kitamura, Noboru and Sutherland, Andrew J. and Shestopalov, Michael A. and Efremova, Olga A., 2017-12-22, 23-Electron Octahedral Molybdenum Cluster Complex [{Mo6I8}Cl6], Inorganic Chemistry, doi: 10.1021/acs.inorgchem.7b02760

Abstract

Photoactive transition metal compounds that are prone to reversible redox reactions are important for myriad applications, including catalysis, optoelectronics, and sensing. This article describes chemical and electrochemical methods to prepare cluster complex (Bu4N)[{Mo6I8}Cl6], a rare example of a 23 e- cluster complex within the family of octahedral clusters of Mo, W, and Re. The low temperature and room temperature crystal structures; electronic structure; and the magnetic, optical, and electrochemical properties of this complex are described.


Ruiz-Lara, T., Few, C. G., Florido, E., Gibson, B. K., Perez, I., Sanchez-Blazquez, P., 2017-12-15, The role of stellar radial motions in shaping galaxy surface brightness profiles, Astronomy & Astrophysics, doi: 10.1051/0004-6361/201731485

Abstract

Aims: The physics driving features such as breaks observed in galaxy surface brightness (SB) profiles remains contentious. Here, we assess the importance of stellar radial motions in shaping their characteristics. Methods: We use the simulated Milky Way-mass cosmological discs from the Ramses Disc Environment Study (RaDES) to characterise the radial redistribution of stars in galaxies displaying type-I (pure exponentials), II (downbending), and III (upbending) SB profiles. We compare radial profiles of the mass fractions and the velocity dispersions of different sub-populations of stars according to their birth and current location. Results: Radial redistribution of stars is important in all galaxies regardless of their light profiles. Type-II breaks seem to be a consequence of the combined effects of outward-moving and accreted stars. The former produce shallower inner profiles (lack of stars in the inner disc) and accumulate material around the break radius and beyond, strengthening the break; the latter can weaken or even convert the break into a pure exponential. Further accretion from satellites can concentrate material in the outermost parts, leading to type-III breaks that can coexist with type-II breaks, but situated further out. Type-III galaxies would be the result of an important radial redistribution of material throughout the entire disc, as well as a concentration of accreted material in the outskirts. In addition, type-III galaxies display the most efficient radial redistribution and the largest number of accreted stars, followed by type-I and II systems, suggesting that type-I galaxies may be an intermediate case between types II and III. In general, the velocity dispersion profiles of all galaxies tend to flatten or even increase around the locations where the breaks are found. The age and metallicity profiles are also affected, exhibiting different inner gradients depending on their SB profile, being steeper in the case of type-II systems (as found observationally). The steep type-II profiles might be inherent to their formation rather than acquired via radial redistribution.


Jianguo Wang, Philip Rubini, Qin Qin, 2017-12-01, Application of a porous media model for the acoustic damping of perforated plate absorbers, Applied Acoustics, doi: 10.1016/j.apacoust.2017.07.003

Abstract

Perforated panel, or plate, absorbers are commonly employed to reduce sound pressure levels across a broad range of applications including the built environment, industrial installations and propulsion devices. The acoustic performance of a perforated plate absorber depends upon a number of parameters such as physical geometry of the absorber, acoustic spectrum and sound pressure level of the acoustic source. As a consequence, experimental determination of acoustic properties is often required on an individual basis in order to optimise performance. Computational simulation of a perforated plate absorber would alleviate the necessity for experimental characterisation. Fundamentally this can be achieved by the direct numerical solution of the underlying governing equations, the compressible form of the Navier-Stokes equations. The numerical methodology is available and routinely implemented as a Computational Fluid Dynamics solver. However, the numerical simulation of flow through a perforated plate with a large number of very small orifices would require significant computational resource, not routinely available for engineering design simulations. In this paper, a porous media model, implemented as a sub-model within a CFD solver, is investigated and validated against a number of well-acknowledged acoustic experiments undertaken in an impedance tube, for a sound pressure wave incident normal to a perforated plate. The model expresses the underlying governing equations within the perforated plates in terms of a pseudo-physical velocity representation. Comparison between three dimensional, compressible, laminar flow CFD simulations and experimental data, demonstrate that the porous model is able to represent acoustic properties of perforated plate absorbers in linear and non-linear absorption regimes and also the inertial effect in the presence of a mean bias flow. The model significantly reduces the computational resource required in comparison to full geometric resolution and is thus a promising tool for the engineering design of perforated plate absorbers.


Addison R. L. Marshall, Jamie Stokes, Francesco N. Viscomi, John E. Proctor, Johannes Gierschner, Jean-Sebastien G. Bouillard and Ali M. Adawi, 2017-10-04, Determining molecular orientation via single molecule SERS in a plasmonic nano-gap, Nanoscale, doi: 10.1039/C7NR05107G

Abstract

In this work, plasmonic nano-gaps consisting of a silver nanoparticle coupled to an extended silver film have been fully optimized for single molecule Surface-Enhanced Raman Scattering (SERS) spectroscopy. The SERS signal was found to be strongly dependent on the particle size and the molecule orientation with respect to the field inside the nano-gap. Using Finite Difference Time Domain (FDTD) simulations to complement the experimental measurements, the complex interplay between the excitation enhancement and the emission enhancement of the system as a function of particle size were highlighted. Additionally, in conjunction with Density Functional Theory (DFT), the well-defined field direction in the nano-gap enables to recover the orientation of individual molecules.


Szitenberg A, Salazar-Jaramillo L, Blok VC, Laetsch DR, Joseph S, Williamson VM, et al., 2017-09-25, Comparative genomics of apomictic root-knot nematodes: hybridization, ploidy, and dynamic genome change, Genome Biology and Evolution, doi: 10.1093/gbe/evx201

Abstract

The Root-Knot Nematodes (RKN; genus Meloidogyne) are important plant parasites causing substantial agricultural losses. The Meloidogyne incognita group (MIG) of species, most of which are obligatory apomicts (mitotic parthenogens), are extremely polyphagous and important problems for global agriculture. While understanding the genomic basis for their variable success on different crops could benefit future agriculture, analyses of their genomes are challenging due to complex evolutionary histories that may incorporate hybridization, ploidy changes, and chromosomal fragmentation. Here we sequence 19 genomes, representing five species of key RKN collected from different geographic origins. We show that a hybrid origin that predated speciation within the MIG has resulted in each species possessing two divergent genomic copies. Additionally, the apomictic MIG species are hypotriploids, with a proportion of one genome present in a second copy. The hypotriploid proportion varies among species. The evolutionary history of the MIG genomes is revealed to be very dynamic, with non-crossover recombination both homogenising the genomic copies, and acting as a mechanism for generating divergence between species. Interestingly, the automictic MIG species M. floridensis differs from the apomict species in that it has become homozygous throughout much of its genome.


Thompson, B. B. and Few, C. G. and Bergemann, M. and Gibson, B. K. and MacFarlane, B. A. and Serenelli, A. and Gilmore, G. and Randich, S. and Vallenari, A. and Alfaro, E. J. and Bensby, T. and Francois, P. and Korn, A. J. and Bayo, A. and Carraro, G. and Casey, A. R. and Costado, M. T. and Donati, P. and Franciosini, E. and Frasca, A. and Hourihane, A. and Jofré, P. and Hill, V. and Heiter, U. and Koposov, S. E. and Lanzafame, A. and Lardo, C. and de Laverny, P. and Lewis, J. and Magrini, L. and Marconi, G. and Masseron, T. and Monaco, L. and Morbidelli, L. and Pancino, E. and Prisinzano, L. and Recio-Blanco, A. and Sacco, G. and Sousa, S. G. and Tautvaisiene, G. and Worley, C. C. and Zaggia, S., 2017-09-11, The Gaia-ESO Survey: Matching Chemo-Dynamical Simulations to Observations of the Milky Way, Monthly Notices of the Royal Astronomical Society, doi: 10.1093/mnras/stx2316

Abstract

The typical methodology for comparing simulated galaxies with observational surveys is usually to apply a spatial selection to the simulation to mimic the region of interest covered by a comparable observational survey sample. In this work we compare this approach with a more sophisticated post-processing in which the observational uncertainties and selection effects (photometric, surface gravity and effective temperature) are taken into account. We compare a ‘solar neighbourhood analogue’ region in a model Milky Way-like galaxy simulated with RAMSES-CH with fourth release Gaia-ESO survey data. We find that a simple spatial cut alone is insufficient and that observational uncertainties must be accounted for in the comparison. This is particularly true when the scale of uncertainty is large compared to the dynamic range of the data, e.g. in our comparison, the [Mg/Fe] distribution is affected much more than the more accurately determined [Fe/H] distribution. Despite clear differences in the underlying distributions of elemental abundances between simulation and observation, incorporating scatter to our simulation results to mimic observational uncertainty produces reasonable agreement. The quite complete nature of the Gaia-ESO survey means that the selection function has minimal impact on the distribution of observed age and metal abundances but this would become increasingly more important for surveys with narrower selection functions.


R. J. deBoer, J. Gorres, M. Wiescher, R. E. Azuma, A. Best, C. R. Brune, C. E. Fields, S. Jones, M. Pignatari, D. Sayre, K. Smith, F. X. Timmes, and E. Uberseder, 2017-09-07, The 12C(α,γ)16O reaction and its implications for stellar helium burning, Reviews of Modern Physics, doi: 10.1103/RevModPhys.89.035007

Abstract

The creation of carbon and oxygen in our Universe is one of the forefront questions in nuclear astrophysics. The determination of the abundance of these elements is key to our understanding of both the formation of life on Earth and to the life cycles of stars. While nearly all models of different nucleosynthesis environments are affected by the production of carbon and oxygen, a key ingredient, the precise determination of the reaction rate of 12C(α,γ)16O, has long remained elusive. This is owed to the reaction’s inaccessibility, both experimentally and theoretically. Nuclear theory has struggled to calculate this reaction rate because the cross section is produced through different underlying nuclear mechanisms. Isospin selection rules suppress the E1 component of the ground state cross section, creating a unique situation where the E1 and E2 contributions are of nearly equal amplitudes. Experimentally there have also been great challenges. Measurements have been pushed to the limits of state-of-the-art techniques, often developed for just these measurements. The data have been plagued by uncharacterized uncertainties, often the result of the novel measurement techniques that have made the different results challenging to reconcile. However, the situation has markedly improved in recent years, and the desired level of uncertainty ≈10% may be in sight. In this review the current understanding of this critical reaction is summarized. The emphasis is placed primarily on the experimental work and interpretation of the reaction data, but discussions of the theory and astrophysics are also pursued. The main goal is to summarize and clarify the current understanding of the reaction and then point the way forward to an improved determination of the reaction rate.


Hahn, Christoph and Genner, Martin J and Turner, George F and Joyce, Domino A, 2017-08-29, The genomic basis of cichlid fish adaptation within the deepwater “twilight zone” of Lake Malawi, Evolution Letters, doi: 10.1002/evl3.20

Abstract

Deepwater environments are characterized by low levels of available light at narrow spectra, great hydrostatic pressure, and low levels of dissolved oxygen-conditions predicted to exert highly specific selection pressures. In Lake Malawi over 800 cichlid species have evolved, and this adaptive radiation extends into the “twilight zone” below 50 m. We use population-level RAD-seq data to investigate whether four endemic deepwater species (Diplotaxodon spp.) have experienced divergent selection within this environment. We identify candidate genes including regulators of photoreceptor function, photopigments, lens morphology, and haemoglobin, many not previously implicated in cichlid adaptive radiations. Colocalization of functionally linked genes suggests coadapted “supergene” complexes. Comparisons of Diplotaxodon to the broader Lake Malawi radiation using genome resequencing data revealed functional substitutions and signatures of positive selection in candidate genes. Our data provide unique insights into genomic adaptation within deepwater habitats, and suggest genome-level specialization for life at depth as an important process in cichlid radiation.


D. Chalupa, 2017-07-20, On transitions in the behaviour of tabu search algorithm TabuCol for graph colouring, Journal of Experimental & Theoretical Artificial Intelligence, doi: 10.1080/0952813X.2017.1354082

Abstract

Even though tabu search is one of the most popular metaheuristic search strategies, its understanding in terms of behavioural transitions and parameter tuning is still very limited. In this paper, we present a theoretical and experimental study of a popular tabu search algorithm TabuCol for graph colouring. We show that for some instances, there are sharp transitions in the behaviour of TabuCol, depending on the value of tabu tenure parameter. The location of this transition depends on graph structure and may also depend on its size. This is further supported by an experimental study of success rate profiles, which we define as an empirical measure of these transitions. We study the success rate profiles for a range of graph colouring instances, from 2-colouring of trees and forests to several instances from the DIMACS benchmark. These reveal that TabuCol may exhibit a spectrum of different behaviours ranging from simple transitions to highly complex probabilistic behaviour.


Dethlefs, Nina, 2017-07-18, Domain Transfer for Deep Natural Language Generation from Abstract Meaning Representations, IEEE Computational Intelligence Magazine, doi: 10.1109/MCI.2017.2708558

Abstract

Stochastic natural language generation systems that are trained from labelled datasets are often domain-specific in their annotation and in their mapping from semantic input representations to lexical-syntactic outputs. As a result, learnt models fail to generalize across domains, heavily restricting their usability beyond single applications. In this article, we focus on the problem of domain adaptation for natural language generation. We show how linguistic knowledge from a source domain, for which labelled data is available, can be adapted to a target domain by reusing training data across domains. As a key to this, we propose to employ abstract meaning representations as a common semantic representation across domains. We model natural language generation as a long short-term memory recurrent neural network encoder-decoder, in which one recurrent neural network learns a latent representation of a semantic input, and a second recurrent neural network learns to decode it to a sequence of words. We show that the learnt representations can be transferred across domains and can be leveraged effectively to improve training on new unseen domains. Experiments in three different domains and with six datasets demonstrate that the lexical-syntactic constructions learnt in one domain can be transferred to new domains and achieve up to 75-100% of the performance of in-domain training. This is based on objective metrics such as BLEU and semantic error rate and a subjective human rating study. Training a policy from prior knowledge from a different domain is consistently better than pure in-domain training by up to 10%.


Zhao, Y and Du, W and Koe, B and Connolley, T and Irvine, S and Allan, PK and Schleputz, CM and Zhang, W and Wang, F and Eskin, DG and others, 2017-07, Synchrotron X-ray tomography studies of Fe-rich intermetallic phases in Al alloys, Proceeding of the 6th Decennial International Conference on Solidification Processing, doi:

Abstract

Aluminium (Al) alloys are widely used lightweight metallic materials for land transportation and aerospace vehicles. A common problem in cast and wrought Al alloys is the formation of brittle Fe-rich intermetallic phases which are detrimental to their mechanical properties. In order to better understand the 3-dimensional (3D) morphology of Fe-rich intermetallic phases in Al-Cu casting alloys, Al-5%Cu-0.6%Mn-XFe (X = 0.5 and 1.0%) alloys were prepared. Ultrasonic melt processing (USP) was applied during solidification in order to study its effect on the Fe-rich intermetallic phases. Solidified samples were then scanned using synchrotron X-ray tomography. The tomography scans were segmented and analysed to determine the 3D morphology of the Fe-rich intermetallic phases in samples processed with and without USP. It was found that the size of the Fe-rich intermetallic phases in samples prepared with USP was refined compared to the samples prepared without USP.


Nan Liu and Larry R. Nittler and Marco Pignatari and Conel M. O’D. Alexander and Jianhua Wang, 2017-06-06, Stellar Origin of 15 N-rich Presolar SiC Grains of Type AB: Supernovae with Explosive Hydrogen Burning, The Astrophysical Journal Letters, doi: 10.3847/2041-8213/aa74e5

Abstract

We report C, N, and Si isotopic data for 59 highly 13 C-enriched presolar submicron- to micron-sized SiC grains from the Murchison meteorite, including eight putative nova grains (PNGs) and 29 15 N-rich ( 14 N/ 15 N ≤ solar) AB grains, and their Mg–Al, S, and Ca–Ti isotope data when available. These 37 grains are enriched in 13 C, 15 N, and 26 Al with the PNGs showing more extreme enhancements. The 15 N-rich AB grains show systematically higher 26 Al and 30 Si excesses than the 14 N-rich AB grains. Thus, we propose to divide the AB grains into groups 1 ( 14 N/ 15 N < solar) and 2 ( 14 N/ 15 N ≥ solar). For the first time, we have obtained both S and Ti isotopic data for five AB1 grains and one PNG and found 32 S and/or 50 Ti enhancements. Interestingly, one AB1 grain had the largest 32 S and 50 Ti excesses, strongly suggesting a neutron-capture nucleosynthetic origin of the 32 S excess and thus the initial presence of radiogenic 32 Si ( t 1/2 = 153 years). More importantly, we found that the 15 N and 26 Al excesses of AB1 grains form a trend that extends to the region in the N–Al isotope plot occupied by C2 grains, strongly indicating a common stellar origin for both AB1 and C2 grains. Comparison of supernova models with the AB1 and C2 grain data indicates that these grains came from supernovae that experienced H ingestion into the He/C zones of their progenitors.


Dethlefs, Nina and Turner, Alexander, 2017-05-27, Deep Text Generation — Using Hierarchical Decomposition to Mitigate the Effect of Rare Data Points, Language, Data, and Knowledge: First International Conference, LDK 2017, Galway, Ireland, June 19-20, 2017, Proceedings, doi: 10.1007/978-3-319-59888-8_25

Abstract

Deep learning has recently been adopted for the task of natural language generation (NLG) and shown remarkable results. However, learning can go awry when the input dataset is too small or not well balanced with regards to the examples it contains for various input sequences. This is relevant to naturally occurring datasets such as many that were not prepared for the task of natural language processing but scraped off the web and originally prepared for a different purpose. As a mitigation to the problem of unbalanced training data, we therefore propose to decompose a large natural language dataset into several subsets that “talk about” the same thing. We show that the decomposition helps to focus each learner’s attention during training. Results from a proof-of-concept study show 73% times faster learning over a flat model and better results.


Mishenina, T. and Pignatari, M. and Cote, B. and Thielemann, F.-K. and Soubiran, C. and Basak, N. and Gorbaneva, T. and Korotin, S. A. and Kovtyukh, V. V. and Wehmeyer, B. and Bisterzo, S. and Travaglio, C. and Gibson, B. K. and Jordan, C. and Paul, A. and Ritter, C. and Herwig, F., 2017-05-11, Observing the metal-poor solar neighbourhood: a comparison of galactic chemical evolution predictions, Monthly Notices of the Royal Astronomical Society, doi: 10.1093/mnras/stx1145

Abstract

Atmospheric parameters and chemical compositions for 10 stars with metallicities in the region of -2.2 < [Fe/H] < -0.6 were precisely determined using high-resolution, high signal-to-noise, spectra. For each star, the abundances, for 14-27 elements, were derived using both local thermodynamic equilibrium (LTE) and non-LTE (NLTE) approaches. In particular, differences by assuming LTE or NLTE are about 0.10 dex; depending on [Fe/H], Teff, gravity and element lines used in the analysis. We find that the O abundance has the largest error, ranging from 0.10 and 0.2 dex. The best measured elements are Cr, Fe, and Mn; with errors between 0.03 and 0.11 dex. The stars in our sample were included in previous different observational work. We provide a consistent data analysis. The data dispersion introduced in the literature by different techniques and assumptions used by the different authors is within the observational errors, excepting for HD103095. We compare these results with stellar observations from different data sets and a number of theoretical galactic chemical evolution (GCE) simulations. We find a large scatter in the GCE results, used to study the origin of the elements. Within this scatter as found in previous GCE simulations, we cannot reproduce the evolution of the elemental ratios [Sc/Fe], [Ti/Fe], and [V/Fe] at different metallicities. The stellar yields from core-collapse supernovae are likely primarily responsible for this discrepancy. Possible solutions and open problems are discussed.


Makina, Y. and Mahjoubi, K. and Benoit, D. M. and Jaidane, N.-E. and Al-Mogren, M. Mogren and Hochlaf, M., 2017-05-09, Periodic Dispersion-Corrected Approach for Isolation Spectroscopy of N2 in an Argon Environment: Clusters, Surfaces, and Matrices, The Journal of Physical Chemistry A, doi: 10.1021/acs.jpca.7b00093

Abstract

Ab initio and Perdew, Burke, and Ernzerhof (PBE) density functional theory with dispersion correction (PBE-D3) calculations are performed to study N2-Arn (n <= 3) complexes and N2 trapped in Ar matrix (i.e., N(at)Ar). For cluster computations, we used both Moller-Plesset (MP2) and PBE-D3 methods. For N2(at)Ar, we used a periodic-dispersion corrected model for Ar matrix, which consists on a slab of four layers of Ar atoms. We determined the equilibrium structures and binding energies of N2 interacting with these entities. We also deduced the N2 vibrational frequency shifts caused by clustering or embedding compared to an isolated N2 molecule. Upon complexation or embedding, the vibrational frequency of N2 is slightly shifted, while its equilibrium distance remains unchanged. This is due to the weak interactions between N2 and Ar within these compounds. Our calculations show the importance of inclusion of dispersion effects for the accurate description of geometrical and spectroscopic parameters of N2 isolated, in interaction with Ar surfaces, or trapped in Ar matrices.


Siri Chongchitnan and Matthew Hunt, 2017-03-27, On the abundance of extreme voids II: a survey of void mass functions, Journal of Cosmology and Astroparticle Physics, doi: 10.1088/1475-7516/2017/03/049

Abstract

The abundance of cosmic voids can be described by an analogue of halo mass functions for galaxy clusters. In this work, we explore a number of void mass functions: from those based on excursion-set theory to new mass functions obtained by modifying halo mass functions. We show how different void mass functions vary in their predictions for the largest void expected in an observational volume, and compare those predictions to observational data. Our extreme-value formalism is shown to be a new practical tool for testing void theories against simulation and observation.


Dethlefs, Nina and Hawick, Ken, 2017-02-04, DEFIne: A Fluent Interface DSL for Deep Learning Applications, Proceedings of the 2nd International Workshop on Real World Domain Specific Languages, doi: 10.1145/3039895.3039898

Abstract

Recent years have seen a surge of interest in deep learning models that outperform other machine learning algorithms on benchmarks across many disciplines. Most existing deep learning libraries facilitate the development of neural nets by providing a mathematical framework that helps users implement their models more efficiently. This still represents a substantial investment of time and effort, however, when the intention is to compare a range of competing models quickly for a specific task. We present DEFIne, a fluent interface DSL for the specification, optimisation and evaluation of deep learning models. The fluent interface is implemented through method chaining. DEFIne is embedded in Python and is build on top of its most popular deep learning libraries, Keras and Theano. It extends these with common operations for data pre-processing and representation as well as visualisation of datasets and results. We test our framework on three benchmark tasks from different domains: heart disease diagnosis, hand-written digit recognition and weather forecast generation. Results in terms of accuracy, runtime and lines of code show that our DSL achieves equivalent accuracy and runtime to state-of-the-art models, while requiring only about 10 lines of code per application.


Uberseder, E.; Heil, M.; Kaeppeler, F.; Lederer, C.; Mengoni, A.; Bisterzo, S.; Pignatari, M.; Wiescher, M.;, 2017-02-02, Stellar (n ,gamma) cross sections of 23Na, Physical Review C, doi: 10.1103/PhysRevC.95.025803

Abstract

The cross section of the 23Na(n ,γ )24Na reaction was measured via the activation method at the Karlsruhe 3.7 MV Van de Graaff accelerator. NaCl samples were exposed to quasistellar neutron spectra at k T =5.1 and 25 keV produced via the 18O(p,n )18F and 7Li(p ,n )7Be reactions, respectively. The derived capture cross sections <σ> kT=5 keV=9.1 ±0.3 mb and <σ> kT =25keV=2.03 ±0.05 mb are significantly lower than reported in literature. These results were used to substantially revise the radiative width of the first 23Na resonance and to establish an improved set of Maxwellian average cross sections. The implications of the lower capture cross section for current models of s-process nucleosynthesis are discussed.



2016 (4 outputs)

Liang Zheng, T.L. Lee, Na Liu, Zhou Li, Guoqing Zhang, J. Mi, P.S. Grant, 2016-12-27, Numerical and physical simulation of rapid microstructural evolution of gas atomised Ni superalloy powders, Materials & Design, doi: 10.1016/j.matdes.2016.12.074

Abstract

The rapid microstructural evolution of gas atomised Ni superalloy powder compacts over timescales of a few seconds was studied using a Gleeble 3500 thermomechanical simulator, finite element based numerical model and electron microscopy. The study found that the microstructural changes were governed by the characteristic temperatures of the alloy. At a temperature below the γ’ solvus, the powders maintained dendritic structures. Above the γ’ solvus temperature but in the solid-state, rapid grain spheroidisation and coarsening occurred, although the fine-scale microstructures were largely retained. Once the incipient melting temperature of the alloy was exceeded, microstructural change was rapid, and when the temperature was increased into the solid + liquid state, the powder compact partially melted and then re-solidified with no trace of the original structures, despite the fast timescales. The study reveals the relationship between short, severe thermal excursions and microstructural evolution in powder processed components, and gives guidance on the upper limit of temperature and time for powder-based processes if desirable fine-scale features of powders are to be preserved.


Farre, Albert and Soares, Kaline and Briggs, Rachel A. and Balanta, Angelica and Benoit, David M. and Bonet, Amadeu, 2016-10-26, Amine Catalysis for the Organocatalytic Diboration of Challenging Alkenes, Chemistry – A European Journal, doi: 10.1002/chem.201603979

Abstract

The generation of in situ sp2-sp3 diboron adducts has revolutionised the synthesis of organoboranes. Organocatalytic diboration reactions have represented a milestone in terms of unpredictable reactivity of these adducts. However, current methodologies have limitations in terms of substrate scope, selectivity and functional group tolerance. Here a new methodology based on the use of simple amines as catalyst is reported. This methodology provides a completely selective transformation overcoming current substrate scope and functional/protecting group limitations. Mechanistic studies have been included in this report


Szitenberg, Amir; Cha, Soyeon; Opperman, Charles H.; Bird, David M.; Blaxter, Mark L.; Lunt, David H., 2016-08-26, Genetic drift, not life history or RNAi, determine long term evolution of transposable elements, Genome Biology and Evolution, doi: 10.1093/gbe/evw208

Abstract

Transposable elements (TEs) are a major source of genome variation across the branches of life. Although TEs may play an adaptive role in their host’s genome, they are more often deleterious, and purifying selection is an important factor controlling their genomic loads. In contrast, life history, mating system, GC content, and RNAi pathways, have been suggested to account for the disparity of TE loads in different species. Previous studies of fungal, plant, and animal genomes have reported conflicting results regarding the direction in which these genomic features drive TE evolution. Many of these studies have had limited power, however, because they studied taxonomically narrow systems, comparing only a limited number of phylogenetically independent contrasts, and did not address long-term effects on TE evolution. Here we test the long-term determinants of TE evolution by comparing 42 nematode genomes spanning over 500 million years of diversification. This analysis includes numerous transitions between life history states, and RNAi pathways, and evaluates if these forces are sufficiently persistent to affect the long-term evolution of TE loads in eukaryotic genomes. Although we demonstrate statistical power to detect selection, we find no evidence that variation in these factors influence genomic TE loads across extended periods of time. In contrast, the effects of genetic drift appear to persist and control TE variation among species. We suggest that variation in the tested factors are largely inconsequential to the large differences in TE content observed between genomes, and only by these large-scale comparisons can we distinguish long-term and persistent effects from transient or random changes.


Pignatari, M., Herwig, F., Hirschi, R., Bennett, M., Rockefeller, G., Fryer, C., Timmes, F. X., Ritter, C., Heger, A., Jones, S., Battino, U., Dotter, A., Trappitsch, R., Diehl, S., Frischknecht, U., Hungerford, A., Magkotsios, G., Travaglio, C., Young, P., 2016-08-11, NuGrid Stellar Data Set – I. Stellar Yields from H to Bi for Stars with Metallicities Z = 0.02 and Z = 0.01, The Astrophysical Journal Supplement Series, doi: 10.3847/0067-0049/225/2/24

Abstract

We provide a set of stellar evolution and nucleosynthesis calculations that applies established physics assumptions simultaneously to low- and intermediate-mass and massive star models. Our goal is to provide an internally consistent and comprehensive nuclear production and yield database for applications in areas such as presolar grain studies. Our non-rotating models assume convective boundary mixing (CBM) where it has been adopted before. We include 8 (12) initial masses for Z = 0.01 (0.02). Models are followed either until the end of the asymptotic giant branch phase or the end of Si burning, complemented by simple analytic core-collapse supernova (SN) models with two options for fallback and shock velocities. The explosions show which pre-SN yields will most strongly be effected by the explosive nucleosynthesis. We discuss how these two explosion parameters impact the light elements and the s and p process. For low- and intermediate-mass models, our stellar yields from H to Bi include the effect of CBM at the He-intershell boundaries and the stellar evolution feedback of the mixing process that produces the {}13{{C}} pocket. All post-processing nucleosynthesis calculations use the same nuclear reaction rate network and nuclear physics input. We provide a discussion of the nuclear production across the entire mass range organized by element group. The entirety of our stellar nucleosynthesis profile and time evolution output are available electronically, and tools to explore the data on the NuGrid VOspace hosted by the Canadian Astronomical Data Centre are introduced.



Preprints (10 outputs)

More information

TM Cross, DM Benoit, M Pignatari, BK Gibson, 2024-03, Modelling Triatomic Biosignatures: Ozone and Isotopomers, link: https://arxiv.org/html/2403.05442v1

Lauric Feugere, Claudio Silva de Freitas, Adam Bates, Kenneth B. Storey, Pedro Beltran-Alvarez and Katharina C. Wollenberg Valero, 2023-10-05, Consequences of directly- and indirectly-experienced heat stress in a mutagenic environment, doi: 10.1101/2023.10.03.560724

L. Roberti, M. Pignatari, A. Psaltis, A. Sieverding, P. Mohr, Zs. Fulop, M. Lugaro, 2023-06-20, The γ-process nucleosynthesis in core-collapse supernovae. I. A novel analysis of γ-process yields in massive stars, doi: 10.48550/arXiv.2306.11409

Hannah E. Brinkman and C. L. Doherty and M. Pignatari and O. R. Pols and M. Lugaro, 2023-05, Aluminium-26 from massive binary stars III. Binary stars up to core-collapse and their impact on the early Solar System, doi: 10.48550/arXiv.2305.16787

Dimitrios Manolis, Shirin Hasan, Camille Ettelaie, Anthony Maraveyas, Darragh P. O’Brien, Benedikt M. Kessler, Holger Kramer, Leonid L. Nikitenko, 2023-04, Novel protein interaction network of human calcitonin receptor-like receptor revealed by label-free quantitative proteomics, doi: 10.1101/2023.04.18.537143

Eamon C. Faulkner, Adam A. Moverley, Simon P. Hart, Leonid L. Nikitenko, 2023-04, Altered Heterogeneity of Ageing Lung Endothelium is a Hallmark of Idiopathic Pulmonary Fibrosis, doi: 10.1101/2022.03.08.22272025

Michael R Winter, Adam P Taranto, Henok Zemene Yimer, Alison Coomer Blundell, Shahid Siddique, Valerie M Williamson, David H Lunt, 2023-03, Phased chromosome-scale genome assembly of an asexual, allopolyploid root-knot nematode reveals complex subgenomic structure, doi: 10.1101/2023.03.20.533402

Ryan Ward, David M. Benoit, Francesco Benfenati, 2022-09, A pathway to accurate potential energy curves on NISQ devices, doi: 10.48550/arXiv.2209.11176

Grigorios Vasilopoulos, Quan Quan, Daniel Parsons, Stephen Darby, Van Tri, Nguyen Hung, Ivan Haigh, Hal Voepel, Andrew Nicholas, Rolf Aalto, 2020-10, Anthropogenic sediment starvation forces tidal dominance in a mega-delta, doi: 10.21203/rs.3.rs-81555/v1

Katharina C. Wollenberg Valero, Joan Garcia-Porta, Iker Irisarri, Lauric Feugere, Adam Bates, Sebastian Kirchhof, Olga Jovanovic Glavas, Panayiotis Pafilis, Sabrina F. Samuel, Johannes Muller, Miguel Vences, Alexander P. Turner, Pedro Beltran-Alvarez, Kenneth B. Storey, 2019-08, Abiotic environmental adaptation in vertebrates is characterized by functional genomic constraint, link: https://doi.org/10.1101/726240