Том 50, № 2 (2016)

A computational study has been performed on the radiolysis of an aqueous solution that has the chemical composition and irradiation parameters typical of the primary coolant of pressurized water reactors. In this work, in contrast to previous studies on this subject, it has been taken into account that temporary fluctuations of the reactor radiation parameters, such as the composition of reactor n, γ]-radiation and the absorbed dose rate in the coolant, may occur in an actual real reactor during irradiation. The feasibility of spontaneous switching of the radiation-chemical system from one steady state with low concentrations of oxidizing products of radiolysis to another state with high concentrations resulting from a spike of the reactor radiation dose rate against the background of constant dose rate before and after the spike has been shown. The event triggering the switch is an increase in the concentration of oxygen and HO₂ (O₂^–) radicals during the spike, after which the positive feedback does not allow the system to return back to the initial steady state. In practice, this effect can be caused by phenomena associated with local irregularities in the reactor core: the composition and dose rate of reactor radiation, the presence of steam–gas bubbles due to local subcooled nucleate boiling of the coolant in the core, and the perturbation of the water radiolysis mechanism at the surface of fuel rods because of an increased contribution of heterogeneous reactions etc.

The molecular–topological structure of a terpolymer based on vinylidene fluoride, hexafluoropropylene, and tetrafluoroethylene has been studied for the first time with the use of thermomechanical spectrometry. A five-block topologically amorphous and crystalline pseudo-network structure with crystallites, which have different initial melting temperatures, as branching points has been detected in the terpolymer at temperatures from–100 to 250°C. When γ-irradiated at a dose of 30 kGy, the crystalline blocks of high-temperature modifications assimilated into one cluster block with the formation of a pseudo-network with a 1.5fold increase in the block-average molecular weight and a decreased initial molecular flow temperature.

The endothermic associative ionization reaction N(²D) + O(³P) → NO** → NO(¹Σ⁺) +e^- in slow collisions of the atoms has been considered in terms of the multichannel quantum defect theory. The dependences of the partial and total cross sections of the reaction on the energy of the colliding atoms in the range of 0–0.3 eV have been calculated. It has been shown that the cross sections have a pronounced resonance structure, which is formed as a result of the multichannel interaction of autoionization states of the intermediate Rydberg complex NO** with dissociative states. The temperature dependence of the reaction rate constant is presented. The results are compared with those of other calculations and available experimental data.

The paper presents the results of analysis of the effect of a high-affinity peptide (HAP) homologous to a fragment of the nicotinic acetylcholine receptor (nAChR) on the absorption and fluorescence spectra of thiazole orange and thioflavin T complexes with cucurbit[8]uril in aqueous solution. In the presence of HAP, a change in the absorption spectra of the dye complexes and a drop in the fluorescence intensity occur; for thiazole orange, the fluorescence intensity is restored to the initial level in the presence of α-bungarotoxin capable of high-affinity binding to nAChR. The proposed method make it possible to detect the presence of α-bungarotoxin.

Magnetic, relaxation, and dynamic parameters of polarons P₁^·+, trapped in p-toluenesulfonic aciddoped polyaniline, polarons P₂^·+, and fullerene radical anions photoinduced in the poly(3-dodecylthiophene)/methanofullerene composite and in mixtures of these composites have been investigated using the EPR technique. It has been shown that spin charge carriers P₂^·+ during diffusion along poly(3-dodecylthiophene) chains interact with P₁^·+ trapped on adjacent polymer chains of polyaniline. The exchange interaction and spin relaxation in the ternary composites is determined by the activated hopping mobility of polarons P₂^·+ and depends on the composition of the material.

Level-to-level rate constants of single-photon vibration–translation and vibration–vibration exchange have been calculated for the N₂–O₂ system in the temperature range of 300–800 K in terms of the generalized Schwartz–Slawsky–Herzfeld theory using exact relationships and the most commonly used approximations. It has been shown that the quality of the approximation is improved with an increase in temperature and deteriorates with an increase in the vibrational quantum number. The calculated distributions of vibrationally excited species over levels for the low-pressure glow-discharge conditions substantially depend on the rate constants used in the calculation, especially in the area of high vibrational levels.

The degradation of chitin and chitosans of different molecular weights stimulated by electronbeam plasmas of different gases has been experimentally studied. Biologically active water-soluble lowmolecular-weight chitooligosaccharides are formed as a result of plasma-beam treatment. It has been found that the degradation is a controlled process and products with a necessary molecular weight can be obtained by appropriately choosing plasma-beam treatment parameters (chemical composition of the plasma gas and treatment time and temperature).

Investigation of the activating effect of low-frequency ultrasonic waves on both fiber-forming polymer and chemicals and reagents used in bleaching processes of textile materials is an important objective. Comprehensive experimental studies on determination of the ratio of the treatment time and power of ultrasonic waves have been carried out in order to reach the optimal rate of hydrogen peroxide decomposition. The experimental results have shown that the optimal hydrogen peroxide degradation rate during ultrasoundassisted bleaching is observed at an ultrasonic power of 3 kW and a treatment time of 15–20 min.