Russian Journal of Physical Chemistry B最新文献

Abstract

First-principles calculations using first-principles calculations have been performed to investigate the structural, elastic, and electronic properties of chalcogenide perovskite CaZrS₃ under different pressures. The calculated structural parameters and elastic constants show a good agreement with the other theoretical values. The details of pressure dependences of the structural parameters and elastic constants are also presented and discussed. According to our calculation, we found that the deformation resistances along the axial direction are stronger than the deformation resistances in shape. It is also found, the elastic constant C₁₁ is always bigger than the C₃₃ at the same pressure, showing that it is easier to compress along the c-axis than along the a-axis. For the calculated results of the pressure dependence of the electronic band structure, the total density of states and partial density of states of orthorhombic CaZrS₃. We found that the band gap decreases with the pressure, which provide some additional information about these chalcopyrite semiconductors under pressure to fundamental material physics.

Abstract

The effect of the ratio of the reagents on a stabilized cool flame (CF) of rich propane-oxygen mixtures is investigated. It is found that with an increase in the initial concentration of propane in the mixture, its consumption, as well as the concentration of propylene, has a maximum at a ratio of C₃H₈ : O₂ = 1 : 1. In this case, the selectivity of propylene formation reaches a maximum at a ratio of C₃H₈ : O₂ = 4 : 1. It is shown that an increase in the initial propane concentration in the mixture increases the yield of methane, but reduces the yield of propylene, ethylene, hydrogen, CO, CO₂, methanol, formaldehyde and acetaldehyde. At a ratio of C₃H₈ : O₂ = 6 : 1, ethane was also found in the reaction products. The possibility of ethanol formation in the reactions of ethoxyl and hydroxyethyl radicals with acetaldehyde is analyzed using the CBS-QB3 quantum-chemical method.

Abstract

This article studies the structural-functional damage of fibrinogen (FG) treated with hypochlorous acid (HOCl) in the concentration range (10–100 µM). Using tandem mass spectronomy (the MS/MS method), 15 modified amino acid residues with a dose-dependent susceptibility to the oxidizing agent are detected. Using turbidity measurements and confocal laser scanning microscopy (CLSM), it is shown that FG oxidation by 25–100 µM HOCl leads to the formation of a denser fibrin gel, a delayed onset of polymerization, and a decrease in the slope of the polymerization curve, presumably due to the conformational changes in the protein. At lower a HOCl concentration (10 µM), at least six amino acid residues are substantially modified (9–29%), but functionally such modified protein was not distinguishable from the native one. The detected amino acid residues are assumed to be scavengers of the reactive oxygen species (ROS), which prevent the alteration of FG functions.

Abstract

The results of thermogravimetric and Fourier transform infrared (FTIR) analysis of polymer composite materials (PCMs) based on polyethylene (PE) and polycarbonate (PC) are presented and compared to PE and PC polymers. Empirical data are obtained for mathematical modeling, including the amount of solid residue upon pyrolysis, volatile yield, and ash content of the studied PCMs and polymers. The results of the mathematical modeling of the pyrolysis process at a temperature of 600°C are presented to quantitatively assess the composition of pyrolysis gas.

Abstract

Composite film samples of polylactide-natural rubber with a rubber content of 5, 10, and 15 wt % were obtained by the solution method. The study of their morphology shows the presence of rubber inclusions in the form of drops in the polylactide matrix. The thermophysical characteristics are determined by differential scanning calorimetry (DSC). It is determined that when rubber is added and the peak of cold crystallization of polylactide (PLA) disappears on the melting thermograms, the melting temperature decreases by 1–4°C compared to 100% PLA. The structure of the obtained compositions is studied by nuclear magnetic resonance, electron paramagnetic resonance (EPR), and X-ray diffraction. The diffraction patterns of the samples contain reflections characteristic of the crystalline α-form of PLA.

Abstract

Catalysts based on high-silica zeolites with Si/Al ratios of 50 and 80 (ZSM-5-50 and ZSM-5-80) modified by Ca, Sr, Cr, Mn, and Sb ions are synthesized and studied in the reaction of the oxidation of benzene to phenol by nitrous oxide. It is shown that catalysts containing about 0.1–0.2 wt % of Sb ions are more active and selective in the reaction of the direct oxidation of benzene to phenol by nitrous oxide. It formally corresponds to the substitution of 1/12 and 1/6 ions of H ions by Sb ions in a ratio of 1 : 1 of the zeolite. In the presence of a sample composed of ZSM-5-50 + 1/12 Sb at a temperature of 450°C and a contact time of 1 s, a phenol yield of 61.2% is achieved with a selectivity of 96%, which is approximately twice as high as the values known in the literature for other for other Me-ZSM-5 catalysts. At the same time, the sample with the composition of ZSM-5-50 + 1/6Sb turns out to be more stable than the other catalysts based on ZSM-5 zeolites. A model is also proposed for the activation of nitrous oxide on single active sites (located at a sufficient distance from each other) of the catalyst, which explains the higher efficiency of nitrous oxide as oxidant than that of molecular oxygen in the reaction of the direct oxidation of benzene to phenol in the presence of Me-ZSM-5 catalysts with a low concentration (less than 0.1%) of Me ions.

Abstract

The possibility of using radiation from a two-frequency pulsed copper vapor laser with wavelengths of 510.6 and 578.2 nm with an exposure of 30 to 120 s to stimulate the development of coniferous trees (spruce, pine, larch) with single seed irradiation is shown. The stimulation effect manifests itself at various early stages of development, such as the awakening of seeds in the aquatic environment in the first hours of the experiment (according to the electron absorption spectroscopy data), seed germination, and seedling growth under stressful cultivation conditions. Possible causes of light exposure to plant seeds are discussed.

Abstract

In this research, spherical and small size gold nanoparticles were successfully prepared by a cost-effective, eco-friendly green approach using mulberry leaf extract as both reducing and stabilizing agent. The reducing potential of mulberry leaf extract was studied for the synthesis of gold nanoparticles without adding any external reducing agents. The formation of gold nanoparticles was confirmed by the change of color. The prepared gold nanoparticles were characterized by UV-visible absorption spectroscopy, dynamic light scattering, scanning electron microscope, transmission electron microscopy, fourier transform infrared and powder X-ray diffraction. The absorbance peak which found at 560 nm in UV-vis spectroscopy demonstrated the generation of gold nanoparticles. The fourier transform infrared elucidated that the gold nanoparticles were capped with various functional groups from extracts, keeping them from agglomeration and oxidation. The X-ray diffraction results illustrated that the particles were highly crystalline in nature. The transmission electron microscopy and scanning electron microscope showed the particles were small and spherical. The effect of reaction temperature, amount of chloroauric acid solution and extracts was also investigated. The results demonstrated that these parameters play vital roles in the production of gold nanoparticles.

Abstract

Advanced nanotechnologies allow synthesizing nanoparticles (NPs) with the given physical and chemical properties providing an opportunity to study the effects and mechanisms of the influence of NPs on plants in order to improve their productivity. In this study, Zn NPs introduced in the polymer coating are used as a preparation for the presowing treatment of pepper seeds. It is found that Zn NPs in concentrations of 10^–5 and 10^–6% in the composition of polymers accelerated plant growth and led to a significant increase in the number of leaves and buds, while the root mass volume increased on average by 10–30% compared to the control plants. After seed treatment with Zn NPs with a concentration of 10^–6%, the proline content in plant leaves increases by 58% (p ≤ 0.05); and the protein content, by 20% (p ≤ 0.05). The treatment of seeds with Zn NPs at a concentration of 10^–5% leads to the sugar content increasing by 36% (p ≤ 0.05), and the chlorophyll content, by 52% (p ≤ 0.05) compared with the control.

A mathematical model of the process of thermal destruction of polymer binders is developed, taking into account the experimentally established dependencies of the decomposition depth on temperature and the amount of coke residue on the heating rate. A method for determining the kinetic parameters of the process by the method of inverse problems is developed. The kinetic parameters of the model for six binders are determined.