INFLUENCE OF THE SHAPE OF HYDROGEN-CONTAINING INCLUSIONS ON THE INTERGRANULAR CORROSION PROCESS OF THE AL - SI ALLOY SYSTEM

It is known that the surface of aluminum alloys is characterized by the formation of pitting (point damage), which can subsequently cause intergranular corrosion. This corrosion damage is dangerous in that it is almost impossible to detect it visually, since it extends from surface into interior of the material. The effect of the form of hydrogen inclusions on the corrosion resistance of an Al – Si alloy is investigated. For the tests on intergranular corrosion were selected uncoated samples of silumin AK12 (ENAC-AlSi12(a), A04130) with different forms of hydrogen inclusions — atomic and molecular. The content of dissolved hydrogen in all samples is 0.2 cm3/100 g. The duration of methodical tests in special solution of sodium chloride (NaCl) and hydrochloric acid (HCl) is 24 hours. Additionally, two samples from each series were exposed to a solution of another 48 hours. Evaluation of the effects of intergranular corrosion on silumin samples was performed by metallographic method. Given the fact that the data on the loss of mass over a certain period of time are less reliable, in comparison with the data on the structure change over the same time. Then, the effect of intergranular corrosion on the mechanical properties of silumin was evaluated using the electromechanical universal testing machine. During the research was found that at the equal content of the dissolved hydrogen samples with molecular inclusions are more subject to intergranular destruction. This follows from the considerable depth of corrosion propagation and the decrease in the mechanical properties of silumin relative to the results for samples with atomic hydrogen. Wherein the analysis of the level of mechanical properties showed that after intergranular corrosion, the tensile strain decreases to a considerable extent. The work was carried out within the project 14.578.21.0193 “Development of theoretical and technological solutions for hydrogen reduction in aluminum and lowalloyed aluminum alloys” of the Federal Target Program “Researches and developments in the priority directions of progress of Scientific and Technological Complex of Russia for 2014–2020” with the financial support of the Ministry of Education and Science of the Russian Federation. The unique identifier of agreement RFMEFI57816X0193

Investigation of Structure, Chemical and Phase Composition of Silicon Spring Steel Scale

The article presents the results of investigation of structure, chemical and phase composition of scale formed on siliceous spring steels during high-temperature heating prior to rolling. It is established that in 40S2 steel, the hematite layer bordering furnace atmosphere has a minimum thickness of about 40–60 μm, the magnetite layer has thickness of 250 ± 280 μm, the largest thickness of 800 ± 900 μm has wustite layer with secondary ferriferous oxide released during cooling, bordering the steel surface. The scale layer adjacent to the steel surface is characterized by a much greater macrostructural, chemical, and phase inhomogeneity. In addition towustite–ferriferous oxide mixture, iron silicates with an increased silicon content are present. Approaching the steel surface, the number of zones enriched with silicon increases. When 60S2ChA steel is heated to 1180–1200∘С, zones enriched with silicon are observed in the scale at a distance of 200 ± 250 μm from the metal surface, and when heated to temperatures of 1310 ± 1315∘C at a much larger distance, reaching700–800 μm. Keywords: scale, steel heating, siliceous springs steel, scale microstructur

Non-natural nucleosides based on 1,2,4-triazolo[5,1-c][1,2,4]triazin-4(6H)- ones

Two regioselective methods for the synthesis of nucleosides in the series of 3-phenyl- and 3- ethoxycarbonyl-1,2,4-triazolo[5,1-c][1,2,4]triazin-4-ones were developed. The first route involves a Vorbrüggen glycosylation reaction. The second one is based on condensation of 1,2,4- triazolo[5,1-c][1,2, 4]triazin-4-one sodium salts with protected 1-bromo-sugar derivatives

A Numerical Model of an Electrostatic Precipitator

This paper presents a Computational Fluid Dynamics (CFD) model for a wire-plate electrostatic precipitator (ESP). The turbulent gas flow and the particle motion under electrostatic forces are modelled using the CFD code FLUENT. Numerical calculations for the gas flow are carried out by solving the Reynolds-averaged Navier-Stokes equations and turbulence is modelled using the k-ε turbulence model. An additional source term is added to the gas flow equation to capture the effect of electric field. This additional source term is obtained by solving a coupled system of the electric field and charge transport equations. The particle phase is simulated by using Discrete Phase Model (DPM). The results of the simulation are presented showing the particle trajectory inside the ESP under the influence of both aerodynamic and electrostatic forces. The simulated results have been validated by the established data. The model developed is useful to gain insight into the particle collection phenomena that takes place inside an industrial ESP

The rationality of using DNA diagnostics in sports cardiology

NGS is becoming an integral part of medical practice, including in cardiology. The role of genes in the formation of diseases of the cardiovascular system has been actively studied for the last 20 years. Currently, heart diseases with a hereditary component are usually divided into two large groups: monogenic syndromes that lead to an unfavorable outcome, including sudden cardiac death at a young age, and polygenic conditions that manifest after 35 years and are accompanied by deterioration in the quality of life. In professional sports, changes in the myocardium are almost inevitable, however, the first phenotypic signs of hereditary myocardial disease may be hidden behind adaptive changes, which are commonly called “athlete’s heart”. The carriage of causative genes radically changes the approach to the management of an athlete: his admission to training and competitive activities is reviewed, the volume of permissible load and the frequency of visits to a cardiologist are discussed. In this paper, we tried to identify clinical markers — «red flags» that would indicate the need for genetic testing on the example of athletes who underwent an in-depth medical examination in 2021–2022

Synthesis of acyclic nucleoside analogues by one-step Vorbrüggen glyco-sylation of 1,2,4-triazolo[1,5-a]pyrimidine-7-ones

New analogues of acyclovir have been prepared by reacting 1,2,4 -triazolo[1,5-a]pyrimidin-7-ones 1а-i and (2-acetoxyethoxy)methyl acetate 2 in the presence of trimethylsilyl trifluoromethanesulfonate as a catalyst. The interaction between the compounds 1а-е and 2 has led to a mixture of N3 and N4 isomers. In contrast, the reaction of compounds 1g-i and 2 proceeded selectively to form N3 isomers. In the case of compounds 1a-c the predominant product is the one with the acyclic moiety in azine ring (N4 isomer). Interaction between 1d-f and 2 has led to mixtures comprising mainly N3 isomer. It has been found that the ratio of glycosylation products 1 and 2 are thermodynamically controlled. The structure of the obtained compounds has been proved by 1Н, 13С, two-dimensional 1Н-13С NMR spectroscopy and X-ray analysis

Estimate of rock mass stability in surface-borehole mining of high-grade iron ore

Under consideration is the estimate of rock mass stability around underground openings generated as a result of hydraulic borehole mining of iron ore. The authors use analytical solutions of two plane elasticity problems on stress state of infinite media with the zone of weakening in the form of one or two circular holes, given initial stresses are set in the study domain

Hemolysis and ATP release from human and rat erythrocytes under conditions of hypoxia: a comparative study

Red blood cells are involved not only in transportation of oxygen and carbon dioxide but also in autoregulation of vascular tone by ATP release in hypoxic conditions. Molecular mechanisms of the ATP release from red blood cells in response to a decrease in partial oxygen pressure still remain to be elucidated. In this work we have studied effects of hypoxia on red blood cell hemolysis in humans and rats and compared the effects of inhibitors of ecto-ATPase and pannexin on the release of ATP and hemoglobin from rat erythrocytes. The 20-min hypoxia at 37°C increased hemolysis of red blood cells in humans and rats 1.5- and 2.5-fold, respectively. In rat erythrocytes a significant increase in hypoxia-induced extracellular ATP level was found only in the presence of ecto-ATPase inhibitor ARL 67156. In these conditions we observed a positive correlation (R2 = 0.5003) between the increase in free hemoglobin concentration and the ATP release. Neither carbenoxolon nor probenecid, the inhibitors of low-selectivity pannexin channels, altered the hypoxia-induced ATP release from rat erythrocytes. The obtained results indicate a key role of hemolysis in the ATP release from red blood cells

Influence of various parameters on the vegetable raw material pelleting process and pellets quality (review)

Determining the regularities of the process of pelleting vegetable raw materials is relevant for the improvement of technologies and technical equipment in order to reduce energy intensity and improve the quality of pellets. The generalization of the results of the research aimed at studying the influence of various parameters on the process of pelleting vegetable raw materials and the quality of feed and biofuel pellets is the purpose of the research. A selection and systematic review of the scientific literature on the subject of the study for the period of 2007-2022 has been carried out. The analysis has proved that heat pre-treatment and moistening of vegetable raw materials, as well as their composition and particle size are the factors that have the greatest impact on the quality of feed and biofuel pellets. Increasing the pressure in the range of 20...200 MPa results in increasing the pellets durability. A die temperature of around 100°C is optimum for obtaining dense pellets of highquality from vegetable raw materials. The design parameters of the pelletizer play an important role in obtaining high-quality pellets when processing vegetable raw materials. The design of the inlet in the form of a tapering cone helps to reduce energy consumption and pelleting pressure. An increase in the ratio of the die channel length to its diameter exponentially increases the pelleting pressure and its energy intensity. The interplay between the physical processes occurring in the pelletizer makes it difficult to interpret the impact of each parameter on the pelleting process, so different authors have different assessments of the contribution of individual factors in producing high-quality pellets. Therefore, the interaction between the individual pelleting parameters and their influence on the results of the process should be examined more precisely

Approaches to the classification of sports disciplines, taking into account their influence on the biochemical profile of an athlete

There are many classifications of sports disciplines, which base on various approaches, which separately take into account the patterns of training activity, physiology, the risk of collision and injury, etc. In our opinion, it most fully reflects the specifics of sports changes that occur in the body of athletes under the influence of intense physical activity, at the level of biochemical processes. The classification of sports disciplines proposed by us takes into account the influence of the nature of the training process, the specifics of sports loads, the leading type of energy supply of sports work on the biochemical profile of an athlete, which makes it possible to identify the key features that occur in the body of an athlete under the influence of a specific load