Effect of Co substitution on Ni2_{2}MnGe Heusler alloy: ab initio study

Ab initio calculations shown that the Co substitution instead of Ni in Ni$_{2}$MnGe with the L2$_{1}$ crystallographic structure leads to a decrease of the lattice constant and an increase of the total magnetic moment of the Ni$_{2-x}$Co$_{x}$MnGe compounds. The Mn(B) has the largest local moment above $3~\mu_{B}$ coupled parallel to moments on the Ni(A,C) and Co(A,C), which are found in the ranges of $0.19\div0.26~\mu_{B}$ for Ni(A,C) and $1.03\div0.97~\mu_{B}$ for Co(A,C) for studied range of $x$. Using the results stemming from the total energy calculations, the values of bulk modulus and its pressure derivatives are estimated according to the Murnaghan EOS.Comment: 3 pages, 3 figures; The European Conference Physics of Magnetism 2017; submitted to Acta Physica Polonica

Orthorhombic phase of La0.5_{0.5}Bi0.5_{0.5}NiO3_{3} studied by first principles

The aim of presented first principles study of La$_{0.5}$Bi$_{0.5}$NiO$_{3}$ is to investigate electronic structure of orthorhombic phase Pbnm. The calculations show that metallicity and magnetism of the system are strongly related with hybridization between Ni 3d and O 2p. To improve the quality of the electronic structure description of the system, especially the treatment of correlation for the Ni 3d, we employ GGA, LDA, and GGA+U, LDA+U. The LSDA results give good agreement with experiment. Thus, the screening effects originating from the hybridized 3d and O 2p electrons are sufficiently strong that they reduce the electronic correlations in the La$_{0.5}$Bi$_{0.5}$NiO$_{3}$, making it a weakly correlated metal.Comment: 4 pages, 3 figures; The European Conference Physics of Magnetism 2017, submitted to Acta Physica Polonica

Macroscopic Properties of Open-Cell Foams Based on Micromechanical Modelling

This paper presents a micromechanical analysis for the assessment of macroscopic behaviour of threedimensional open-cell solid foams. The analysis is based on material properties of a solid phase and topological arrangement of cell structure. A foam structure consists of idealized tetrahedral unit cells, which are built of four identical half-struts forming a diamond-like structure and identified as Plateau borders. Such a unit cell represents the essential microstructural features of foam. An analytical formulation of force-displacement relations for struts can be found by considering the affinity of node displacements in tensile, bending, and shear deformation. The elements of the stiffness matrix for a single cell are expressed as functions of the compliance coefficients for stretching and bending of struts. The effective elastic constants for metallic foam considered as isotropic material are determined as functions of foam relative density and compared with available results. In this paper we define an energy-based limit condition of linear elasticity for open-cell foams and calculate the critical energy density pertinent to a particular orthogonal energy state accounting for elementary interactions in a microstructure. The study based on the assumption of linear elasticity leads to simple analytical formulas. Nevertheless, it should be stressed that the proposed theoretical basis of micromechanical modelling could be also applied for the analysis of nonlinear elastic behaviour, plasticity, and failure of foams. Such problems require, however, a more complex numerical approach

Fundamental stellar and accretion disc parameters of the eclipsing binary DQ Velorum

To add to the growing collection of well-studied double periodic variables (DPVs) we have carried out the first spectroscopic and photometric analysis of the eclipsing binary DQ Velorum to obtain its main physical stellar and orbital parameters. Combining spectroscopic and photometric observations that cover several orbital cycles allows us to estimate the stellar properties of the binary components and the orbital parameters. We also searched for circumstellar material around the more massive star. We separated DQ Velorum composite spectra and measured radial velocities with an iterative method for double spectroscopic binaries. We obtained the radial velocity curves and calculated the spectroscopic mass ratio. We compared our single-lined spectra with a grid of synthetic spectra and estimated the temperature of the stars. We modeled the V-band light curve with a fitting method based on the simplex algorithm, which includes an accretion disc. To constrain the main stellar parameters we fixed the mass ratio and donor temperature to the values obtained by our spectroscopic analysis. We obtain donor and gainer masses, the radii, and temperatures for the stellar components. We find that DQ Vel is a semi-detached system consisting of a B3V gainer and an A1III donor star plus an extended accretion disc around the gainer. The disc is filling 89% of the gainer Roche lobe and it has a concave shape that is thicker at its edge than at its centre. We find a significant sub-orbital frequency of 0.19 d^{-1} in the residuals of the V-band light curve, which we interpret as a pulsation of an slowly pulsating B-type (SPB) of a gainer star. We also estimate the distance to the binary (3.1 kpc) using the absolute radii, apparent magnitudes, and effective temperatures of the components found in our study.Comment: 12 pages, 13 Postscript figure

Electronic structure and X-ray photoelectron spectra of YNi4B compound

The electronic structure of the tern ary Y Ni4 B compoun d, crystalli zin g in the hexagonal CeCo4 B structure ( P 6= m m m space group ), was studied by X -ray photo electron spectroscopy and ab initio calculations. Core levels and the valence band were investigated. T he X- ray photo electron spectroscopy valence band is compared with that obtained from ab initi o calculations. The valence band spectrum at the Fermi level exhibits the domination of the Ni( 3 d ) states, which are hybridized with 4d states of Y and 2p states of B. The theoretical electronic specific heat coeffcient Û derived from N ( E F ) is about 11.33 mJ /(mol K 2 ) for exp erimental lattice parameters. T he calculated bulk modulus is B 0 = 1 :61632 Mbar

Antimicrobial properties of nanostructured surfaces - demonstrating the need for a standard testing methodology

Bioinspired nanostructured materials that exhibit antimicrobial properties are being synthesized and tested at increasing rates for use in healthcare, manufacturing processes, and diagnostics. Although progress has been made in improving and understanding their bactericidal activity, arguably, the biggest problem currently in the field is the lack of a standard testing methodology that allows for optimal characterization and better comparison of emerging nanostructures. Here, we examine two forms of nanostructured silicon that vary in their ability to kill certain bacterial species due to different physical mechanisms and derive guidelines for the comparative testing. We perform a comprehensive evaluation of methodologies used extensively in the field (e.g., colony counting and live dead analysis) and the novel application of high-throughput flow cytometry. The data reveal how the techniques are complementary but not always directly equivalent or correlative. Therefore, comparison of results obtained using different methodologies on different materials can be grossly misleading. We report significant variations in bactericidal efficiencies depending on experimental environments (medium type, etc.) and methodologies employed. In addition, we demonstrate how cytometry is yet another powerful complementary tool that can aid the mechanistic understanding of antimicrobial activities of rough surfaces. Besides standardization for comparison, ultimately, evaluation methods need to consider anticipated applications. Then and only then can the true potential (or limitation) of a novel material be determined for its suitability for advancement in a particular field of use

Effect of multi-component fertilizers on seeds yield, yield components and physiological parameters of winter oilseed rape (Brassica napus L.)

ArticleSubject of the discussed studies was an analysis of the impact of mineral multicomponent fertilizers, from Polish and foreign producers, on the yield and yield components of winter oilseed rape (Brassica napus var. oleifera). Two field experiments were carried out in 2015–2017 in Lipnik. The experimental crop was winter oilseed rape, hybrid cultivar DK EXPLICIT. Two factors were studied in the experiment A: 4 multi-component mineral fertilizers - two Belarusian (1 i 2), one Russian and one Polish (Polifoska 6) and 4 doses of fertilization (250, 500 and 750 kg ha-1 ). In the experiment (B) were compared two factors: 3 multi-component mineral fertilizers - Belarusian, Russian and Polish production - Polifoska 8 and 4 doses of fertilization (200, 400 and 600 kg ha-1 ). The fertilizers applied in the experiments, manufactured in Belarus, Russia and Poland, did not show variations in the amount of yield of winter rape. The number of winter rapeseed plants on the area unit (in autumn and spring) was independent of the type of fertilizers. In the experiment B, higher number of rapeseed siliques was obtained after application of Polifoska 8, than other fertilizers. Rapeseed grown on soil with the fertilizers manufactured in Belarus showed a lower value of greenness index (SPAD) and leaf area index (LAI). As a result of the application of multi-component fertilizers, manufactured in Belarus, Russia and Poland, the recorded differences in the winter rapeseed yield, yield components and physiological parameters did not exceed 10%