Vol 43, No 7 (2024)

The kinetics of thermal decomposition of FOX-7 compound at 155 °C under semi-open conditions in vessels with a volume of V = 0.8–0.9 cm³ in an air atmosphere and the degree of filling of the vessel with substances m/V = 0.03–0.72 g/cm³ has been studied by gravimetric method. It was found that at the largest m/V, an induction period is observed at the early stages of the reaction, during which the rate of mass loss of the sample is ten times less than the rate of decomposition of FOX-7 in the solid phase. With a decrease in m/V, the induction period is shortened and at m/ V = 0.04 g/cm³ disappears altogether. The appearance of the induction period is due to the fact that nitronic acid, which is the only product of the first stage of decomposition of FOX-7, is well adsorbed on the surface of FOX-7 crystals. At the same time, it almost completely loses its reactivity. As a result, until the end of the adsorption process, the decomposition of FOX-7 proceeds without the formation of gaseous products, and the reaction rate is not fixed by the gravimetric method suitable for studying the kinetics of the reaction at the early stages of decomposition FOX-7.

To verify the hypothesis of electrical hot spots – channels of local electrical breakdowns – the analysis of the electrical properties of condensed explosives and the evaluation of the electric field strength in shock-loaded dielectrics were carried out. It is established that conditions for electrical breakdowns can be created in the compressed zone of explosives due to polarization phenomena (electric field) and shock-induced electrical conductivity (free electrons). The position of the electric model of detonation kinetics are formulated. The results of experiments with liquid nitromethane and monocrystalline PENT are explained.

The results of modeling the radiation characteristics of air behind the front of a strong shock wave, performed using the Direct Simulation Monte Carlo method, are presented. The model used takes into account various physical and chemical processes occurring in shock-heated air, including translational-rotational and translational-vibrational energy exchange, kinetics of chemical reactions, excitation of electronic levels of atoms and molecules, as well as emission and absorption processes for a discrete spectrum. As a result of the calculations, timeintegrated spectrograms of the volumetric radiation power of shock-heated air were obtained in absolute units in the range of shock wave velocities from 7.4 to 10.7 km/s at a gas pressure in front of the shock wave front of 0.25 Torr. The calculation data are compared with experimental data obtained on the double-diaphragm shock tube DDST-M of the Institute of Mechanics of Moscow State University.

Numerical simulations of autoignition of lean (6% H₂), stoichiometric, and rich (90% H₂) hydrogen–air mixtures have been performed to examine the influence of third-body efficiency (chaperon efficiency, CE) on the value of ignition delay, τ. The temperature ranges explored in the computations are 850–1000 K for P₀ = 1 bar and 1000–1200 K for P₀ = 6 bar. By using a detailed kinetic mechanism, it has been found that the sensitivity of ignition delay to CE is the highest for the reaction step H + O₂ + M = HO₂ + M, which can lead to a variation in τ by a factor of 2 to 3. A pressure increase or deviation from stoichiometry reduces the sensitivity. The influence of CE is qualitatively different and weaker for the reaction step OH + OH + M = H₂O₂ + M.

A study on the neutralization of sulfur compounds during the filtration combustion of model mixture compositions containing iron sulfide or copper sulfate by adding marble (CaCO₃) was carried out. It has been experimentally shown that during burning model charge compositions with additions of both iron sulfide and copper sulfate, replacing chemically inert sapphire with marble leads to a decrease in combustion temperature by approximately 150–200 °C. At the same time, the content of CO₂ in gaseous products increases, and the concentrations of CO and H₂ decrease. The greatest effect on the absorption of sulfur-containing substances when adding marble was shown in experiments where sulfur was present in the fuel in sulfide form: the addition of 50% marble made it possible to capture 72% of the initial sulfur content, and for compositions with 90% marble in the charge, 85%. The absorption of sulfur compounds formed during the combustion of model mixture compositions with copper sulfate is much worse. When the charge contains 50% and 85% marble, sulfur-containing compounds were absorbed by only 19% and 24%, respectively.

The structural organization of DNA in “stressed” (with increased stress resistance), anabiotic and mummified cells obtained by introducing 4-hexylresorcinol in different concentrations at different stages of cell culture growth was studied using the synchrotron radiation diffraction technique. Experimental studies allow us to conclude that 4-hexylresorcinol is the initiator of the transition of cells into an anabiotic and mummified state in the stationary stage of growth. In the prestationary stage, in the studied concentration range, 4-hexylresorcinol initiates the transition of cells into a mummified state, but not into an anabiotic state, which indicates that DNA is unprepared for the crystallization process in these bacteria. The structure of DNA inside a cell in an anabiotic dormant state (almost complete absence of metabolism) and dormant state (starvation stress) coincide (form nanocrystalline structures). Data indicate the universality of DNA condensation or the universality of DNA protection by the Dps protein in the dormant state, regardless of the type of stress. The mummified state (complete absence of metabolism, irreversible to life) is very different in structure (has no order within the cell).

A new method for mixing solutions and suspensions containing thermodynamically immiscible dispersion media based on the use of ultrasonic dispersion and thermally stimulated microwave heating has been proposed. The results of a study of a number of functional composites obtained by mixing solutions of biodegradable polymers in chloroform with aqueous suspensions of natural polymers are presented. The possibility of obtaining polymer composites doped with magnetic nanoparticles and drugs by this method is considered. It has been established that the proposed method of mixing makes it possible to combine suspensions of polymers of different nature in the composition of composites suitable for creating porous, hygroscopic and magnetically controlled materials for biomedical and environmental applications.