


Vol 43, No 9 (2024)
Элементарные физико-химические процессы
Metastable methane dimers in collisions with inert gas atoms: study by the method of classical trajectories
Abstract
The formation of collision complexes, also called quasi–complexes (QC), metastable dimers or Feshbach resonances, has been studied for CH4 – He, Ne, Ar systems by the method of classical trajectories. The calculations used exact 3D classical Hamilton equations in the action–angle variables and non-empirical surfaces of the interaction potential energy. The selection of collision parameters was carried out by the Monte Carlo method. A statistical analysis of the QCs parameters is performed. It is shown that QCs can be both short-lived and long-lived and are characterized by a variety of interparticle separations. Among the total number of collisions, the fraction of QCs increases rapidly with a decrease of temperature. Formulas are given that reveal the contribution of QCs to the cross sections of the rotational RT- relaxation of CH4. It is shown that in methane mixtures considered RT- relaxation in QC- type collisions is much more effective than in ordinary inelastic collisions.



СТРОЕНИЕ ХИМИЧЕСКИХ СОЕДИНЕНИЙ, КВАНТОВАЯ ХИМИЯ, СПЕКТРОСКОПИЯ
Non-covalent interaction of carbon, silicon and germanium atoms
Abstract
From first principles (electron gas approximation) the calculation of non-covalent interaction potentials for homo- and heteroatomic pairs of carbon, silicon and germanium without the formation of valence chemical bonds was carried out. The calculations took into account the coulomb, kinetic, exchange, and correlation contributions to the interaction energy. The electron density was set taking into account the shell structure of atoms in the Hartree-Fock approximation. The parameters of the Lennard-Jones and Morse potentials and the constants of the dispersion interaction are calculated for all cases. It is shown that for non-covalent interaction the known empirical rules of Lorentz-Berthelot combination for potential parameters are not always fulfilled. Based on the calculations a new generalized potential is proposed that can be used in molecular dynamics and Monte Carlo simulations, as well as in constructing equations of state. Calculations of the second virial coefficient for monatomic carbon vapor are carried out.



Kinetics and mechanism of chemical reactions, catalysis
Quantum chemical simulation of reactions involved in electrically enhanced reduction of nickel and copper nano-oxides with carbon monoxide
Abstract
Quantum chemical calculations are performed to determine the heats of reduction with CO of the simplest electrically neutral or electrically charged oxides of nickel (Ni2O2, Ni2O) and copper (Cu2O2, Cu2O). Also calculated are the heats of conversion of neutral or charged copper oxides to active isomers with an O radical. Based on the calculated results, an explanation is proposed for the change in the rates of reduction of nickel and copper nano-oxides with carbon monoxide caused by applying an electrical voltage to the oxides.



Antioxidant activity of catecholamines during the oxidation of methyl linoleoate in Triton X-100 micelles
Abstract
The effect of catecholamines on the oxidation of methyl linoleate in Triton X-100 micelles was studied. It has been established that catecholamines do not inhibit oxidation at a pH 7.4. Inhibition is only possible in the presence of the superoxide dismutase enzyme or at lower pH levels. The reason for this effect is the interaction of anionic forms of phenols and phenoxyl radicals with oxygen with the formation of superoxide anions. High values of inhibition coefficients for catecholamines in the presence of superoxide dismutase are due to the reactions of the resulting ortho-quinones, leading to the regeneration of OH groups.



Study of the oxidation process of magnetite fluxed pellets by various methods of physical and chemical analysis
Abstract
In order to obtain the most complete information about the processes occurring during the oxidative roasting of magnetite iron ore pellets, comprehensive studies were carried out using various methods of physicochemical analysis. To approximate the assessment of the most probable reactions occurring in pellets during oxidative heating, a thermodynamic analysis was performed. Based on the sign of the isobaric potential, determined from the equation of the isotherm of a chemical reaction, we judged the possibility of a particular chemical reaction occurring in the direction under consideration. The influence on the dissociation reaction of calcium carbonate has been established by the formation of calcium silicates and ferrites, which facilitate its occurrence, as well as the reaction of interaction of iron oxide with calcium carbonate, which, on the contrary, inhibits its occurrence. A technique has been developed for thermographic analysis of solid-gas systems filtered through a layer of granular material, which was implemented on an installation that allows experiments with pellets in a gas flow with different oxygen contents, temperatures and heat treatment durations. It has been experimentally established that decarbonization of pellets occurs most completely and quickly in an atmosphere of inert monatomic gas, as well as in a mixture of gases that do not contain carbon dioxide. The data obtained are in good agreement with the data of thermodynamic analysis. Mineralogical studies were carried out on samples of magnetite fluxed pellets in a wide temperature range. The pellets were heated in accordance with a differential heating curve to certain temperatures, and then cooled in order to fix the structure formed by the time the specified temperature was reached. The results obtained on the considered processes of magnetite oxidation, decomposition of carbonates and formation of ferrites and silicates are in fairly good agreement with the data of the thermodynamic analysis. The results obtained in this work are of particular interest to specialists involved in the development of technologies that ensure the production of pellets with high metallurgical properties.



Oxidation of the Styrene Epoxide – Hydroquinone – Copper(II) Chloride Ternary System in a Methanol Solution
Abstract
The consumption of styrene epoxide (SE) and hydroquinone (HQ) in a ternary TrS system (SE – HQ – Cu(II)) in an oxygen atmosphere in a methanol solution was studied. Oxygen uptake by the triple system SE – HQ – CuCl2 was studied manometrically. Expression of velocity in terms of reagent concentrations V = k [Cu(II)]1 [HQ]0 [SE]0, the effective oxidation rate constant k = 1.82×105 exp(– 40 kJ mol-1/RT) s-1, (308–323) K. The mechanism of oxidation of TrS is discussed.



Chemical physics of biological processes
Biological activity of carnitine 2-ethyl-6-methyl-3-hydroxypyridine
Abstract
The antiradical properties and biological activity of carnitine 2-ethyl-6-methyl-3-hydroxypyridine (СP) were investigated. The drug had high antiradical activity. In the concentration range 10-6–10-9M, CP prevented the activation of lipid peroxidation in the membranes of mouse liver mitochondria incubated in a hypotonic medium. Such an incubation caused a change in the fatty acid (FA) composition of the lipid component of mitochondrial membranes: the total relative percentage of 18:2ω6, 18:1ω9 and 22:6ω3 – the main FAs that make up cardiolipin decreased by 8.1%. The introduction of CP into the incubation medium led not only to the restoration of the pool of these FAs, but also to an increase in their content by 15%, which, possibly, contributed to an increase in the efficiency of mitochondrial functioning and an increase in the body’s resistance to stress.



Adhesion of mold spores to polymer materials during their deposition in the air
Abstract
The features of the adhesive interaction of spores of various types of mold fungi deposited in a stationary air environment with polymeric materials are investigated. It is shown that regardless of the type of material, its angle of inclination and the type of fungus, all spores that have reached the polymer surface remain on it. The location of the sample relative to the source of spore propagation and the mechanism of their supply to the surface determine the number of spores retained on the material, characterizing the microbiological component of the air environment (the content and specific consumption of fungal spores in it). An algorithm for estimating this characteristic is proposed. It is advisable to take the research results into account when developing methods for testing the resistance of polymer materials to infection and damage by biodegradable fungi.



Chemical physics of polymeric materials
Stabilization of silver iodide sols particles by acetate and N-scucinil of chitosan
Abstract
The article is devoted to the study of the regularities of stabilization of colloidal particles of silver iodide sols by polymeric stabilizers – chitosan acetate and sodium salt of chitosan N-succinyl. The relevance of the work is due to the fact that the creation of stable polymer-colloidal dispersions based on water-soluble derivatives of chitosan and inorganic colloidal particles with antiseptic properties is one of the ways to create hybrid gel-like and film materials for biomedical purposes. It was proved that in the presence of chitosan acetate polycation with a concentration of 0.1% mas. adsorption of similarly charged macroions on the particles of the dispersed phase leads to an increase in the stability of the AgI sol with positively charged colloidal particles using measurements of electrokinetic potential. The AgI sol with positively charged particles is recharged and the electrokinetic potential of the AgI sol with negatively charged particles increases with a simultaneous increase in the aggregative stability of the sols in the presence of the polyanion – N-succinyl chitosan. Using potentiometric titration have shown that the increase in the aggregative stability of silver iodide sols at higher concentrations of chitosan acetate and chitosan N-succinyl is more associated not with the adsorption of macromolecules on the sol surface, but with an increase in the viscosity of solution with increasing polymer concentration (structural-mechanical barrier according to Rehbinder). Data of optical spectroscopy and viscometry indicate that the mixing of silver iodide sols with solutions of polymers of chitosan acetate and N-succinyl chitosan is accompanied by the formation of stable polymer-colloidal dispersions, the components of which interact with each other, and do not represent mechanical mixtures of a polymer solution and a colloidal solution.



ДИНАМИКА ТРАНСПОРТНЫХ ПРОЦЕССОВ
Accumulation of disordered perturbations of density, velocity and pressure in an unstable system
Abstract
A numerical study of the behavior of disordered perturbations of density, velocity and pressure in the problem of flow around a stationary solid sphere is carried out. Regular equations of multimoment hydrodynamics supplemented with stochastic components are used for the study. The statistical properties of stochastic components are identified with the statistical properties of disordered perturbations arising in the incoming flow due to external influence. It was found that the loss of stability is accompanied by the accumulation of disordered perturbations of density, velocity and pressure in the wake behind the sphere. It is shown that high values of the turbulence coefficient provide a significant accumulation of disordered disturbances, which leads to a strong distortion of the laminar flow pattern. It is found that high values of pressure and density pulsation coefficients provide an equally significant accumulation of disordered perturbations in the pressure and density.



The effect of disordered perturbations on the entropy of an unstable system
Abstract
The contribution of disordered perturbations in density, velocity and pressure to the pair entropy of an unstable system, which sets the direction of its evolution, is estimated. Disordered perturbations arising in the incoming flow due to external influence are calculated by numerical integration of regular equations of multimoment hydrodynamics supplemented with stochastic components. The calculation of the distortion of the pair entropy of the system due to disordered perturbations is performed in the problem of flow around a stationary solid sphere. It is established that disordered perturbations of density, velocity and pressure do not have any noticeable effect on the parameters of the vortex street in the wake behind the sphere.


