Strain-Hardening Stages and Structure Evolution in Pure Niobium and Vanadium upon High Pressure Torsion

High pressure torsion (HPT) is one of the ways to form nanostructured materials with high strength properties. However, HPT hardening mechanisms vary from material to material and are poorly understood for some BCC metals, particularly niobium and vanadium. This work aims to identify strain hardening stages for Nb and V metals during HPT. Two approaches have been used to identify the deformation stages during high pressure torsion. The approaches are based on the application of a "piecewise" model, taking into account the different deformation mechanisms that determine the type of the forming structure, and on the analysis of the hardness vs. true strain dependence according to the $H$$-$${e}^{0.5}$ law. We compared the identified stages with the results of the electron microscopic study of the structure. Both models describe well the structural changes observed microscopically in HPT-deformed niobium. However, we have shown that only the piecewise model gives an adequate description of the stages of structure development in vanadium. We have provided an explanation for the observed difference in the behavior of niobium and vanadium upon HPT.Comment: 21 pages, 9 figures, 1 tabl

Live Birth of a Healthy Child in a Couple with Identical mtDNA Carrying a Pathogenic c.471_477delTTTAAAAinsG Variant in the MOCS2 Gene.

Molybdenum cofactor deficiency type B (MOCODB; #252160) is an autosomal recessive metabolic disorder that has only been described in 37 affected patients. In this report, we describe the presence of an in-frame homozygous variant (c.471_477delTTTAAAAinsG) in the MOCS2 gene in an affected child, diagnosed with Ohtahara syndrome according to the clinical manifestations. The analysis of the three-dimensional structure of the protein and the amino acid substitutions suggested the pathogenicity of this mutation. To prevent transmitting this mutation to the next generation, we used preimplantation genetic testing for the monogenic disorders (PGT-M) protocol to select MOCS2 gene mutant-free embryos for transfer in an in vitro fertilization (IVF) program. As a result, a healthy child was born. Interestingly, both parents of the proband shared an identical mitochondrial (mt) DNA control region, assuming their close relationship and thus suggesting that both copies of the nuclear rare variant c.471_477delTTTAAAAinsG may have been transmitted from the same female ancestor. Our estimation of the a priori probability of meeting individuals with the same mtDNA haplotype confirms the assumption of a possible distant maternal relationship among the proband's direct relatives

PECULIARITIES OF INTERACTION BETWEEN CITELLOPHILUS TESQUORUM ALTAICUS (IOFF, 1936) FLEA AND YERSINIA PESTIS WITH VARIOUS PLASMID COMPOSITION

Objective of the study is in vitro investigation of mutual relations between Citellophilus tesquorum altaicus and Yersinia pestis with various plasmid composition: influence of the strain on flea alimentary activity and mortality rate, frequency and dynamics of biofilm formation.Materials and methods. C. tesquorum altaicus were infected by three Yersinia pestis strains: virulent triple-plasmid I-3230 isolated in Mongolia, referential for the Tuva focus I-2638 carrying four plasmids (pYT, pYV, pYP, pTP 33) and also selected from it avirulent isogenic clone I-3480 that lost two plasmids (pYV, pYP). Peculiarities of interaction between fleas and Y. pestis strains were estimated through the lens of specimens with «conglomerates» and “blocks” for feeding, the period from infection prior to the beginning of conglomerates’ formation, alimentary activity, and mortality rate of the infected fleas.Results and conclusions. It was revealed that alimentary activity of the infected insects was higher than that of the control group, and the highest – in fleas infected with I-2638 strain. Greater numbers of dead fleas at feeding was noted in specimens inoculated with I-3230 strain. Predominant significance of I-2638 strain was established in C. tesquorum altaicus biofilm formation both as «conglomerates» and “blocks”. I-3480 strain also formed the conglomerates in fleas more actively than I-3230 lacking pTP33 plasmid. Thus, four-plasmid I-2638 strain surpassed triple-plasmid I-3230 and two-plasmid I-3480 strains in reference to all tested indicators except flea mortality rates. It may testify to co-adaptation of Y. pestis and C. tesquorum altaicus from the Tuva plague focus and to the possibility of a pTP33 functional role in enhancement of a biofilm formation in vivo

Monte Carlo simulations of segregation in Pt-Re catalyst nanoparticles

We have investigated the segregation of Pt atoms to the surfaces of Pt-Re nanoparticles using the Monte Carlo method and Modified Embedded Atom Method potentials that we have developed for Pt-Re alloys. The Pt75Re25 nanoparticles (containing from 586 to 4033 atoms) are assumed to have disordered fcc configurations and cubo-octahedral shapes (terminated by {l_brace}111{r_brace} and {l_brace}100{r_brace} facets), while the Pt50Re50 and Pt25Re75 nanoparticles (containing from 587 to 4061 atoms) are assumed to have disordered hcp configurations and truncated hexagonal bipyramidal shapes (terminated by {l_brace}0001{r_brace} and {l_brace}101 {bar 1}{r_brace} facets). We predict that due to the segregation process the equilibrium Pt-Re nanoparticles would achieve a core-shell structure, with a Pt-enriched shell surrounding a Pt-deficient core. For fcc cubo-octahedral Pt75Re25 nanoparticles, the shells consist of almost 100 at. percent of Pt atoms. Even in the shells of hcp truncated hexagonal bipyramidal Pt50Re50 nanoparticles, the concentrations of Pt atoms exceed 85 at. percent (35 at. percent higher than the overall concentration of Pt atoms in these nanoparticles). Most prominently, all Pt atoms will segregate to the surfaces in the hcp truncated hexagonal bipyramidal Pt25Re75 nanoparticles containing less than 1000 atoms. We also find that the Pt atoms segregate preferentially to the vertex sites, less to edge sites, and least to facet sites on the shell of Pt-Re nanoparticles

STUDYING THE POSSIBLE MUTAGENIC PROPERTIES OF NEW MEDICINE ON THE BASIS OF COMPLEX LITHIUM CITRATE, ALUMINUM OXIDE AND POLYMETHILSILOXANE

Aim of the study was to investigate the possible mutagenic properties of a new drug based on a lithium-containing substance – a complex of lithium citrate, polymethylsiloxane and aluminum oxide. Material and methods. Methods for testing mutagenicity using chromosomal aberrations in the bone marrow cells of CBA mice and somatic recombination in Drosophila melanogaster were used. Results. It was shown that a single intragastric administration of drug at a dose of 5000 mg/kg and a fivefold course of administration at a dose of 400 mg/kg to CBA mice did not increase the level of cytogenetic disorders in bone marrow cells. The study of the lithium complex drug in a somatic mosaicism test revealed that the preparation at a dose of 2000 mg/kg does not increase the frequency of mutations in Drosophila melanogaster. Conclusion. A single intragastric administration of the studied drug at a dose of 5000 mg/kg and its course administration (400 mg/kg × 5) do not increase the level of cytogenetic disorders in the bone marrow cells of CBA mice. In the somatic recombination (mosaicism) test system on D. melanogaster, no increase in the appearance of mutant setae and spots on the body and head was observed when using yellow and singed markers. The results of the study indicate that the studied drug does not have mutagenic properties

Investigations of Structural-Functional Aspects of Epizootic Process in Natural Plague Foci in Siberia

Comprehensively studied have been structural elements of ecosystems of Siberian natural plague foci, as well as levels of integration among epizootic process components, and ways of their functional interaction. Application of the complex approach to the surveillance over structural-functional elements of the parasitic system along with investigations of epizootic process dynamics has provided for identification of peculiarities as regards epizootics development, transformation and evolution of population and carrier/vector coenosis structure in time and space. Revealed is the genetic diversity of plague microbe circulating within the bounds of separate foci and zones of focality. Determined is a long-lasting anti-epidemic effect (more than 20 years) of the field desinsection in the Saglinsk meso-focus of the Tuva natural plague focus