Solidification of the Glass-Forming Al86Ni2Co6Gd6 Melt under High Pressure

High pressures allow the synthesis of new metastable compounds that remain intact for a sufficiently long time at normal conditions. Until now, it has not been fully understood how pressure, glass-forming ability and solidification of liquids are interconnected. We have investigated the structure of the glass-forming eutectic alloy Al86Ni2Co6Gd6 obtained by rapid cooling from the melt having a temperature of 1800 K under a pressure of 10 GPa. X-ray diffraction analysis and electron microscopy show that the samples are homogeneous and dense. The structure is finely dispersed. New stable crystalline phases with cubic (cP4/2) and tetragonal (tI26/1) structures are formed in the alloy. The studies have shown that the average microhardness of the samples obtained at 10 GPa is almost 2 times higher than that of the original sample at atmospheric pressure and is about 1700 MPa. To understand the results, we used ab initio molecular dynamics and studied how the melt changes with pressure. It is shown that at a temperature of 1800 K, high pressure increases the concentration of icosahedral clusters in the melt so that at 10 GPa atoms inside the icosahedra form a percolation cluster, while at atmospheric pressure they do not. Thus, the glass-forming ability of a melt increases at high pressure strongly influencing solidification processes.Comment: 10 pages, 8 figure

About causes of slow relaxation of melted intermetallic alloys

Ascertainment of the nature of the slow relaxation processes observed after melting in glass-forming eutectic melts is the subject of this work. We claim that the diffusion processes nonlinearity in heterogeneous melt with inclusions of refractory stoichiometry is the origin of this phenomenon. The cause for this nonlinearity is the thermodynamic instability similar to one taking place at spinodal decomposition, and indispensable condition is the initially non-homogenous. For confirmation of our devotes, we consider the model of liquid solution of a binary system, which evolution described by the Cahn-Hilliard equation with combined Gibbs potential assuming the presence of remains after melting stoichiometric phase. Exemplified by the Al-Y and Al-Yb alloys, using Gibbs potentials from a standard database we show that subject to initial heterogeneity in these systems the instability can develop leading to the slow relaxation processes, and determine the regions of this instability in the phase diagrams

Size effects in chlorine doped PbSe thin films

The possibility of obtaining strongly degenerate (≈ 3·10²⁰ сm⁻³) PbSe thin films (d = 5 – 220 nm) with n-type conductivity by thermal evaporation in vacuum of PbSe crystals doped with PbCl₂, with subsequent condensation onto (001) KCl substrates was established. It was shown that the films had high homogeneity degree, no grain structure was observed. The thickness dependences of thermoelectric properties (the Seebeck coefficient S, the Hall coefficient RH and the electric conductivity σ) of thin films were obtained. In the thickness range d ≈ 5 ÷ 30 nm, oscillation properties were observed with growth of d that are attributable to electron gas quantization. The calculation of S(d) dependence on the assumption of size quantization with regard to contribution of several subbands and the thickness dependence of the Fermi energy was shown to be in agreement with the experimental data. In the region of d > 30 nm there was growth of S and σ with thickness, which is attributable to manifestation of classical size effect and interpreted in the framework of Fuchs-Sondheimer and Mayer theories

Dependences of thermoelectric properties on the thickness of thin films of indium doped lead telluride

Dependences of thermoelectric properties (the Seebeck coefficient S, the electric conductivity σ, the Hall coefficient RH, the carrier mobilityμ and the thermoelectric power P = S²·σ) on the thickness d (d = 10 – 255 nm) of thin films prepared by vacuum evaporation of indiumdoped PbTe crystals and subsequent condensation on (111) BaF₂ substrates were obtained. With decreasing thickness of films to d ≈ 40 nm, there is n- to p-type inversion of conduction which is related to a change in thermodynamic equilibrium conditions and partial reevaporation of lead and/or indium atoms. Extremes were found on the thickness dependences of properties at d₁ ≈ 20 nm which is indicative of hole gas quantization. In the range of thicknesses with n-type conduction there is a smooth change in thermoelectric properties with thickness which testifies to manifestation of classical size effect and is sufficiently well described in the framework of the Fuchs-Sondheimer theory

Frequency and risk factors of fractures in adolescents and young ADULTS in the population of Irkutsk

The aim of the study was to examine frequency and risk factors of fractures among adolescents and young adults of Irkutsk aged 14 to 24. The results of the study showed that the frequency of fractures was 23.8 %; and boys have fractures significantly more often than girls (p = 0.01). Risk factors for fractures are: male gender (OR = 1.25); body height (> 174 cm for girls (OR = 3.9), > 177 cm for males (OR = 3.5)); body weight (> 60 kg for girls (OR = 2.5), > 66 kg for boys (OR = 2.1)); tenderness to palpation of spinous processes of vertebra (OR = 3.1 for girls, and OR = 2.4 for boys); dietary calcium intake < 500 mg/day (OR = 1.5 for girls, and OR = 2.3 for boys). In addition, back pain (OR = 1.9) and joint hypermobility syndrome (Or = 1.4) were significantly more often found in girls with fractures. There was no statistically significant connection between fractures in adolescents and young adults and hypodynamia, bone mineral density, social factors (single-parent or multi-child family), and parental history of fractures

Viscous and acoustic properties of AlCu melts

© 2016, Pleiades Publishing, Inc.The atomic dynamics of the binary Al100–xCux system is simulated at a temperature T = 973 K, a pressure p = 1.0 bar, and various copper concentrations x. These conditions (temperature, pressure) make it possible to cover the equilibrium liquid Al100–xCux phase at copper concentrations 0 ≤ x ≤ 40% and the supercooled melt in the concentration range 40% ≤ x ≤ 100%. The calculated spectral densities of the time correlation functions of the longitudinal (Formula Presented) (k, ω) and transverse (Formula Presented) (k, ω) currents in the Al100–xCux melt at a temperature T = 973 K reveal propagating collective excitations of longitudinal and transverse polarizations in a wide wavenumber range. It is shown that the maximum sound velocity in the vL(x) concentration dependence takes place for the equilibrium melt at an atomic copper concentration x = 10 ± 5%, whereas the supercooled Al100–xCux melt saturated with copper atoms (x ≥ 40%) is characterized by the minimum sound velocity. In the case of the supercooled melt, the concentration dependence of the kinematic viscosity ν(x) is found to be interpolated by a linear dependence, and a deviation from the linear dependence is observed in the case of equilibrium melt at x < 40%. An insignificant shoulder in the ν(x) dependence is observed at low copper concentrations (x < 20%), and it is supported by the experimental data. This shoulder is caused by the specific features in the concentration dependence of the density ρ(x)

PREVALENCE OF THE DISEASES OF OSTEOMUSCULAR SYSTEM AND FRACTURES AMONG THE PERSONS OF YOUNG AGE IN IRKUTSK

The purpose of a research was the study of the frequency of arthralgia, prevalence of the diseases of osteomuscular system, and fractures among the persons from 14 to 24 years in Irkutsk. The frequency of arthralgia composed. 22,4 %. The prevalence of the diseases of osteomuscular system composed. 36561 to 100000. Fractures occurred in 23,8 % people at the age of up to 24 years

Study of biofilms by V. cholerae strains on the surfaces of biotic and abiotic substrates using mass spectrometry

Objective: identification and comparative study of protein spectra of Vibrio cholerae biofilms by MALDI-ToF mass spectrometry.Materials and methods: V. cholerae O1 strains isolated from different sources were studied. Methods: bacteriological, mass spectrometry.Results: mass spectrometric analysis showed that it was impossible to identify strains from “plankton” samples and from chitin and plastic plates. After culturing the biofilm and plankton strains, all of them were assigned to the V. cholerae species with a Score above 2,300. A сomparative analysis of MALDI-ToF mass spectra of different variants of V. cholera cultures revealed differences, while general peaks with different intensity were maintained.Conclusions: all samples of V. cholerae cultures taken for analysis aft er culture on a nutrient medium were reliably identified with a high Score. As a result of comparative analysis of protein mass spectra by the m/z value and relative intensity of peaks, no proteins characteristic only for plankton cultures or biofilms of V. cholerae were detected. The stability of the phenotypic properties of V. cholerae regardless of its form of existence and the high reliability of the MALDI-ToF mass spectrometry method for identifying both planktonic and biofilm forms of V. cholerae with the preservation of the research protocol and bacteriological culturation

MALDI MASS-SPECTROMETRIC ANALYSIS FOR TYPING AND INTRASPECIES DIFFERENTIATION OF CHOLERA VIBRIOS ON THE BASE OF CONSTRUCTION OF THE REFERENCE LIBRARY OF PROTEOMIC PROFILES

Purpose: Construction of a personal relevant database on spectra of V. cholerae strains belonging to different biotypes, serological groups and toxigenic levels, which will allow for the identification, differentiation and comparison of bacterial isolates on the base of analysis of V. cholerae ribosomal protein cell fingerprints.Materials and methods: For the construction of the reference library of mass charges m/z 100 passportized strains from museum collection have been used, characterized by the complex of parameters, namely: by serogroup, biotype, object and year of isolation and by the presence of cholera toxin genes (ctxAB+).Results: As the result of the studies performed the personal database has been developed for the expanded collection of Vibrio cholerae protein spectra in addition to MALDI Biotyper (“Bruker Daltonics”) (Certificate of State Registration for database “Proteomic Profiles of Mass-Spectra of Strains Representing V. cholerae Species for MALDI Biotyper Program” No. 2013620585 of 29.04.2013).Summary: The relevant protein spectra database developed provides the possibility to perform interspecies and partial intraspecies differentiation of V. cholerae О1 and О139 strains on the base of analysis of fingerprints of V. cholerae ribosomal protein cells