Numerical simulation of the dynamic response in pulse-loaded fibre-metal-laminated plates

This article presents a three-dimensional constitutive model to replicate the dynamic response of blastloaded fibre–metal laminates made of 2024-0 aluminium alloy and woven composite (glass fibre–reinforced polypropylene). Simulation of the dynamic response is challenging when extreme localised loads are of concern and requires reliable material constitutive models as well as accurate modelling techniques. It is well known that back layers in a fibre–metal laminate provide structural support for front layers; thus, proper modelling of constituent failure and degradation is essential to understanding structural damage and failure. The improved developed model to analyse damage initiation, progression and failure of the composite is implemented in finite element code ABAQUS, and a good correlation is observed with experimental results for displacements of the back and front faces as presented by other researchers. The model was also able to predict accurately the tearing impulses. Finally, the concepts of the ‘efficiency of the charge’ and ‘effectiveness of the target’ are proposed in the context of localised blast loading on a structure. Dimensionless parameters are introduced to quantify these parameters

Phonons from neutron powder diffraction

The spherically averaged structure function \soq obtained from pulsed neutron powder diffraction contains both elastic and inelastic scattering via an integral over energy. The Fourier transformation of \soq to real space, as is done in the pair density function (PDF) analysis, regularizes the data, i.e. it accentuates the diffuse scattering. We present a technique which enables the extraction of off-center phonon information from powder diffraction experiments by comparing the experimental PDF with theoretical calculations based on standard interatomic potentials and the crystal symmetry. This procedure (dynamics from powder diffraction(DPD)) has been successfully implemented for two systems, a simple metal, fcc Ni, and an ionic crystal, CaF$_{2}$. Although computationally intensive, this data analysis allows for a phonon based modeling of the PDF, and additionally provides off-center phonon information from powder neutron diffraction

Using a neural network approach to accelerate disequilibrium chemistry calculations in exoplanet atmospheres

In this era of exoplanet characterisation with JWST, the need for a fast implementation of classical forward models to understand the chemical and physical processes in exoplanet atmospheres is more important than ever. Notably, the time-dependent ordinary differential equations to be solved by chemical kinetics codes are very time-consuming to compute. In this study, we focus on the implementation of neural networks to replace mathematical frameworks in one-dimensional chemical kinetics codes. Using the gravity profile, temperature-pressure profiles, initial mixing ratios, and stellar flux of a sample of hot-Jupiters atmospheres as free parameters, the neural network is built to predict the mixing ratio outputs in steady state. The architecture of the network is composed of individual autoencoders for each input variable to reduce the input dimensionality, which is then used as the input training data for an LSTM-like neural network. Results show that the autoencoders for the mixing ratios, stellar spectra, and pressure profiles are exceedingly successful in encoding and decoding the data. Our results show that in 90% of the cases, the fully trained model is able to predict the evolved mixing ratios of the species in the hot-Jupiter atmosphere simulations. The fully trained model is ~1000 times faster than the simulations done with the forward, chemical kinetics model while making accurate predictions.Comment: 13 pages, 9 figures, accepted for publication at MNRA

Orbital selectivity causing anisotropy and particle-hole asymmetry in the charge density wave gap of 2H2H-TaS2_2

We report an in-depth Angle Resolved Photoemission Spectroscopy (ARPES) study on $2H$-TaS$_2$, a canonical incommensurate Charge Density Wave (CDW) system. This study demonstrates that just as in related incommensurate CDW systems, $2H$-TaSe$_2$ and $2H$-NbSe$_2$, the energy gap ($\Delta_{\text{cdw}}\,$) of $2H$-TaS$_2$ is localized along the K-centered Fermi surface barrels and is particle-hole asymmetric. The persistence of $\Delta_{\text{cdw}}\,$ even at temperatures higher than the CDW transition temperature $\it{T}_{\text{cdw}}\,$ in $2H$-TaS$_2$, reflects the similar pseudogap (PG) behavior observed previously in $2H$-TaSe$_2$ and $2H$-NbSe$_2$. However, in sharp contrast to $2H$-NbSe$_2$, where $\Delta_{\text{cdw}}\,$ is non-zero only in the vicinity of a few "hot spots" on the inner K-centered Fermi surface barrels, $\Delta_{\text{cdw}}\,$ in $2H$-TaS$_2$ is non-zero along the entirety of both K-centered Fermi surface barrels. Based on a tight-binding model, we attribute this dichotomy in the momentum dependence and the Fermi surface specificity of $\Delta_{\text{cdw}}\,$ between otherwise similar CDW compounds to the different orbital orientations of their electronic states that are involved in CDW pairing. Our results suggest that the orbital selectivity plays a critical role in the description of incommensurate CDW materials.Comment: 6 pages, 4 figure

Investigation of the spin-glass regime between the antiferromagnetic and superconducting phases in Fe1+y_{1+y}Sex_xTe1−x_{1-x}

Using bulk magnetization along with elastic and inelastic neutron scattering techniques, we have investigated the phase diagram of Fe$_{1+y}$Se$_{x}$Te$_{1-x}$ and the nature of magnetic correlations in three nonsuperconducting samples of Fe$_{1.01}$Se$_{0.1}$Te$_{0.9}$, Fe$_{1.01}$Se$_{0.15}$Te$_{0.85}$ and Fe$_{1.02}$Se$_{0.3}$Te$_{0.7}$. A cusp and hysteresis in the temperature dependence of the magnetization for the $x=0.15$ and 0.3 samples indicates spin-glass (SG) ordering below $T_{\rm sg} = 23$K. Neutron scattering measurements indicate that the spin-glass behavior is associated with short-range spin density wave (SDW) ordering characterized by a static component and a low-energy dynamic component with a characteristic incommensurate wave vector of ${\bf Q}_m = (0.46, 0, 0.50)$ and an anisotropy gap of $\sim$ 2.5 meV. Our high ${\bf Q}$-resolution data also show that the systems undergo a glassy structural distortion that coincides with the short-range SDW order

Aspects of environmental impacts of seawater desalination : Cyprus as a case study

Acknowledgements The authors are grateful to the European Commission for supporting the activities carried out in the framework of the H2020 European project ZERO BRINE (project under grant agreement No. 730390). The authors would equally like to thank the TOTAL Foundation (Project “Diversity of brown algae in the Eastern Mediterranean”) and the UK Natural Environment Research Council for their support to FCK (program Oceans 2025 – WP 4.5 and grants NE/D521522/1 and NE/J023094/1). This work also received support from the Marine Alliance for Science and Technology for Scotland pooling initiative. MASTS is funded by the Scottish Funding Council (grant reference HR09011) and contributing institutions. The authors would also like to thank representatives from competent authorities in Cyprus providing data, and specifically Nicoletta Kythreotou from the Department of Environment, George Ashikalis from the Transmission System Operator, Dr. DinosPoullis and Lia Georgiou from the Water Development Department.Peer reviewedPublisher PD

Bacterial diversification through geological time

Numerous studies have estimated plant and animal diversification dynamics; however, no comparable rigorous estimates exist for bacteria—the most ancient and widespread form of life on Earth. Here, we analyse phylogenies comprising up to 448,112 bacterial lineages to reconstruct global bacterial diversification dynamics. To handle such large phylogenies, we developed methods based on the statistical properties of infinitely large trees. We further analysed sequencing data from 60 environmental studies to determine the fraction of extant bacterial diversity missing from the phylogenies—a crucial parameter for estimating speciation and extinction rates. We estimate that there are about 1.4–1.9 million extant bacterial lineages when lineages are defined by 99% similarity in the 16S ribosomal RNA gene, and that bacterial diversity has been continuously increasing over the past 1 billion years (Gyr). Recent bacterial extinction rates are estimated at 0.03–0.05 per lineage per million years (lineage^(–1) Myr^(–1)), and are only slightly below estimated recent bacterial speciation rates. Most bacterial lineages ever to have inhabited this planet are estimated to be extinct. Our findings disprove the notion that bacteria are unlikely to go extinct, and provide a valuable perspective on the evolutionary history of a domain of life with a sparse and cryptic fossil record

Orbital and spin chains in ZnV2O4

Our powder inelastic neutron scattering data indicate that \zvo is a system of spin chains that are three dimensionally tangled in the cubic phase above 50 K due to randomly occupied $t_{2g}$ orbitals of V$^{3+}$ ($3d^2$) ions. Below 50 K in the tetragonal phase, the chains become straight due to antiferro-orbital ordering. This is evidenced by the characteristic wave vector dependence of the magnetic structure factor that changes from symmetric to asymmetric at the cubic-to-tetragonal transition

Larval food quantity affects the capacity of adult mosquitoes to transmit human malaria

Adult traits of holometabolous insects are shaped by conditions experienced during larval development, which might impact interactions between adult insect hosts and parasites. However, the ecology of larval insects that vector disease remains poorly understood. Here, we used Anopheles stephensi mosquitoes and the human malaria parasite Plasmodium falciparum, to investigate whether larval conditions affect the capacity of adult mosquitoes to transmit malaria. We reared larvae in two groups; one group received a standard laboratory rearing diet, whereas the other received a reduced diet. Emerging adult females were then provided an infectious blood meal. We assessed mosquito longevity, parasite development rate and prevalence of infectious mosquitoes over time. Reduced larval food led to increased adult mortality and caused a delay in parasite development and a slowing in the rate at which parasites invaded the mosquito salivary glands, extending the time it took for mosquitoes to become infectious. Together, these effects increased transmission potential of mosquitoes in the high food regime by 260-330%. Such effects have not, to our knowledge, been shown previously for human malaria and highlight the importance of improving knowledge of larval ecology to better understand vector-borne disease transmission dynamics