Computational study of structural and elastic properties of random AlGaInN alloys

In this work we present a detailed computational study of structural and elastic properties of cubic AlGaInN alloys in the framework of Keating valence force field model, for which we perform accurate parametrization based on state of the art DFT calculations. When analyzing structural properties, we focus on concentration dependence of lattice constant, as well as on the distribution of the nearest and the next nearest neighbour distances. Where possible, we compare our results with experiment and calculations performed within other computational schemes. We also present a detailed study of elastic constants for AlGaInN alloy over the whole concentration range. Moreover, we include there accurate quadratic parametrization for the dependence of the alloy elastic constants on the composition. Finally, we examine the sensitivity of obtained results to computational procedures commonly employed in the Keating model for studies of alloys

A comparative DFT study of electronic properties of 2H-, 4H- and 6H-SiC(0001) and SiC(000-1) clean surfaces: Significance of the surface Stark effect

Electric field, uniform within the slab, emerging due to Fermi level pinning at its both sides is analyzed using DFT simulations of the SiC surface slabs of different thickness. It is shown that for thicker slab the field is nonuniform and this fact is related to the surface state charge. Using the electron density and potential profiles it is proved that for high precision simulations it is necessary to take into account enough number of the Si-C layers. We show that using 12 diatomic layers leads to satisfactory results. It is also demonstrated that the change of the opposite side slab termination, both by different type of atoms or by their location, can be used to adjust electric field within the slab, creating a tool for simulation of surface properties, depending on the doping in the bulk of semiconductor. Using these simulations it was found that, depending on the electric field, the energy of the surface states changes in a different way than energy of the bulk states. This criterion can be used to distinguish Shockley and Tamm surface states. The electronic properties, i.e. energy and type of surface states of the three clean surfaces: 2H-, 4H-, 6H-SiC(0001), and SiC($000 \bar{1}$) are analyzed and compared using field dependent DFT simulations.Comment: 18 pages, 10 figures, 4 table

Ordering in ternary nitride semiconducting alloys

We present a thorough theoretical study of ordering phenomena in nitride ternary alloys GaInN, AlInN, and AlGaN. Using the Monte Carlo approach and energetics based on the Keating model we analyze the influence of various factors on ordering in bulk crystals and epitaxial layers. We characterize the degree of both short range order (SRO) and long ranger order (LRO) for different compositions, temperatures and for substrates associated with different epitaxial strain. For the description of the SRO the Warren-Cowley parameters related to the first four coordination shells are used. The LRO is detected by means of the introduced sim-LRO parameter, based on the Bragg-Williams approach. The description of the observed long-range ordering patterns and conditions for their occurrence follows

A crowdsourced analysis to identify ab initio molecular signatures predictive of susceptibility to viral infection

The response to respiratory viruses varies substantially between individuals, and there are currently no known molecular predictors from the early stages of infection. Here we conduct a community-based analysis to determine whether pre- or early post-exposure molecular factors could predict physiologic responses to viral exposure. Using peripheral blood gene expression profiles collected from healthy subjects prior to exposure to one of four respiratory viruses (H1N1, H3N2, Rhinovirus, and RSV), as well as up to 24 h following exposure, we find that it is possible to construct models predictive of symptomatic response using profiles even prior to viral exposure. Analysis of predictive gene features reveal little overlap among models; however, in aggregate, these genes are enriched for common pathways. Heme metabolism, the most significantly enriched pathway, is associated with a higher risk of developing symptoms following viral exposure. This study demonstrates that pre-exposure molecular predictors can be identified and improves our understanding of the mechanisms of response to respiratory viruses

Need to use advance notice for urban public transport drivers

The article presents the results of a pilot survey conducted among public transport drivers, including of buses and trolleybuses, in three cities in Poland. The research was aimed at checking the existence of the need for advance notice systems concerning traffic light signal changes. This issue was examined using information on these drivers’ vehicles from countdown timers and traffic lights other than those for the lane in which the vehicles were moving. The respondents also indicated their proposals for advance notice systems for traffic light signal changes

Density Functional Studies of Nonlinear Elastic Properties for Zinc-Blende Nitrides

In this paper we present a method of calculating third-order elastic constants C$\text{}_{ijk}$ and its application to zinc-blende nitrides AlN, GaN, and InN. Our approach is based on accurate ab initio calculations of both energy and stress as a function of applied strain. Ab initio computations are performed within density functional theory framework. To assess the reliability of the presented method, we compare our theoretical findings for GaAs with experimental results for C$\text{}_{ijk}$ available for this material

Theoretical Calculations of Cohesive and Electronic Properties of Quaternary AlGaInN Alloys

We present theoretical studies of the AlGaInN nitride quaternary alloys. The studies are based on ab initio calculations performed within the density functional theory and virtual crystal approximation. The equilibrium lattice constants, bulk moduli, and elastic constants were calculated for the whole possible range of concentrations of the alloy constituents. The theoretical values were then fitted with second- and third-order polynomials. For all properties studied, the considerable bowing was observed

Plasma interleukin-1α and interleukin-8 in female dogs with non-metastatic and metastatic malignant mammary gland tumours

In this study plasma concentrations of IL-1α and IL-8 in 29 female dogs with malignant mammary gland tumours (19 without metastasis and 10 with metastasis) and in 10 healthy control animals were determined. Concentrations of IL-1α and IL-8 were analysed using a specific canine ELISA assay. Mean plasma concentrations of IL-1α and IL-8 were significantly higher (p<0.05) in female dogs with both non-metastatic and metastatic malignant tumours compared to the healthy animals. The concentrations of both tested cytokines were significantly increased (p<0.05) in the dogs with metastasis. In female dogs with mammary carcinomas, the plasma concentration of IL-1α was significantly higher (p<0.05) in the animals with grade 3 tumours compared to the dogs with grade 1 tumours. The concentration of IL-8 was significantly higher (p<0.05) in the dogs with grade 3 tumours compared to that found in the animals with grade 1 and grade 2 tumours. A moderate correlation (r=0.433) was found between IL-1α and IL-8 concentrations in the female dogs. These findings suggest that increased malignancy and invasiveness of canine mammary tumours is associated with an increased production of IL-1α and IL-8 in the tumour microenvironment, which, in turn, leads to an increase in their circulating levels. This may indicate that circulating levels of the cytokines investigated could be considered as diagnostic and prognostic markers in canine malignant mammary tumours. However, further studies in this fields are needed