Bulletin of the Russian Academy of Sciences: Physics最新文献

We studied the dynamics of a microsphere with a double-layer shell embedded in a polymeric matrix under the impact of a shock wave. Deformation and destruction mechanisms of the microsphere’s shell are considered, as well as the influence of the polymer matrix properties on the transmission of shock loads. In the first part of the study, using computer models, a series of numerical experiments was conducted to analyze processes of shock wave propagation through the composite material, considering differences in mechanical properties between the shell layers and the polymer medium. It was shown that the double-layered shell structure promotes effective absorption of the impact energy and formation of fibrous structures. In the second stage of the research, modeling of the stress–strain state of the heterogeneous material under the influence of a relativistic electron beam (REB) was carried out. For this purpose, a procedure for averaging the physical and mechanical properties of the composite components was implemented, allowing an accurate description of the material response to high-energy external loading. The obtained results demonstrate the promise of applying numerical averaging methods for predicting the behavior of heterogeneous materials under extreme conditions. The results of this work can be used for optimizing the properties of composite materials employed under dynamic load conditions such as shock waves and exposure to intense charged particle beams.

The safe treatment and reliable immobilization of waste generated during the reprocessing of spent nuclear fuel remain critical challenges for nuclear power. This study evaluates the feasibility of a plasma-based route that converts liquid reprocessing residues into chemically stable metal-oxide powders and then immobilizes these products into durable matrices suitable for long-term storage. The approach combines thermodynamic modeling with laboratory-scale experiments. Modeling was used to determine adiabatic combustion temperatures and equilibrium phase compositions for water–salt–organic feeds under plasma exposure. Experiments with a high-frequency plasma generator confirmed that, under optimized conditions near 1200°C, organic constituents are completely oxidized, and finely dispersed oxides are formed. The resulting powders include simple and complex oxides of iron, molybdenum, zirconium, neodymium, cerium, strontium, and yttrium; the phase balance depends on the plasma-cooling regime. Post-processing by gravitational and magnetic separation improves powder recovery and purity. For final conditioning, the oxides were incorporated into chloride-based melts, yielding dense, chemically and thermally stable solid forms after solidification. These results demonstrate that plasma treatment can integrate waste destruction, oxidation, and immobilization within a single technological workflow, reducing external heat demand and enabling robust products for storage or further use. The findings provide an engineering basis for scaling plasma systems for radioactive-waste management with an emphasis on safety, efficiency, and sustainability.

In this paper the conditions for runaway electrons generation in streamer discharges are both theoretically and experimentally investigated. The discharge ignition is performed in a long quartz tube with external ring electrodes filled with low-pressure air. Gas pressure of 1 Torr is corresponding to the sea-level altitude of ≈47 km and falls within a range of 40–90 km, typical for red sprites observation. It is shown that the streamer discharge is ignited on the front of dielectric barrier discharge and plasma diffuse jet propagating towards the grounded collector is formed. The conditions for runaway electrons generation in gas-filled dielectric tube with external electrodes have been implemented. The spatio-temporal distribution of electron density, as well as energy distribution of electrons along the symmetry axis of tube, are obtained. It is shown that the highest values of reduced electric field and of electron kinetic energy are observed on the front of streamer at the trailing edge of voltage pulse.

We presented experimental studies on the synthesis of tungsten carbide powder by the vacuum-free electric arc method. The optimal parameters of plasma processing of the tungsten–carbon system were determined based on the results of temperature field distribution during vacuum-free electric arc synthesis. Temperature conditions are ensured in the reaction zone at certain parameters—the power supply current is 250–300 A, ensuring a temperature mode of 1700°C. The study of the mass balance showed that the greatest mass losses are observed with an increase in current to 300–350 A. X-ray phase analysis of the synthesized material revealed the predominance of the crystalline phase of tungsten carbide WC.

An experimental study was performed to analyze the emission of runaway electrons in atmospheric gaps in the presence of an advanced pulse, preceding the subnanosecond leading edge of the main voltage pulse, during which the electric field at the cathode reaches a strength sufficient for the occurrence of runaway electrons. The pulses of the runaway electron current vary due to the appearance and dynamics of the cathode plasma layer from the boundary of which the electrons run away. Plasma is generated by ionization of the gas by field emission electrons as early as during the advance pulse. It is shown that the characteristics of the runaway electron flow depend on the amplitude and duration of this pulse, as well as on the presence of an interval between it and the leading edge of the main voltage pulse.

We presented a description of various configurations of a plasma-chemical reactor for the synthesis of lanthanum hexaboride. The experimental and analytical results of this study demonstrate the possibility of synthesizing lanthanum hexaboride with a cubic crystal lattice. The recommended configuration of an arc reactor for the maximum yield of the desired phase is shown. The characteristics of the energy parameters and X-ray phase analysis data for the obtained synthesis products are presented using two different configurations of the plasma-chemical reactor.

Synthetic glycolipids and similar amphiphils with peptide and other head groups have been designed for labeling/modification of living cells under mild physiological conditions. Under-standing the mechanism of their penetration through the cellular glycocalyx and subsequent insertion into the plasma membrane opens up the prospect of improving the recently found anti-tumor properties of such constructs. In this work, we applied small-angle X-ray scattering (SAXS) technique to characterize structure of nanoparticles formed by self-assembly of synthetic glycolipid A (type 2)-Ad-DE and to estimate its dependence on the glycolipid concentration. The studies were performed at a range of SAXS-applicable concentrations. The obtained results indicate that self-assembly process leads to formation of monodisperse nanoparticles with micelle-like architecture, which is maintained regardless of concentration, indicating absence of the nanoparticle’s positive interaction with their glycopart. We applied ab initio modeling that showed a good agreement with experimental data, and found that the ellipsoid monodisperse nanoparticles have a size of about 14 nm. Quasi-atomic modeling visualised that glycan ligands are well accessed for biological recognition. This knowledge will facilitate further study of the formation of the supramolecular form(s) of A(type 2)-Ad-DE and other glycolipids within the glycocalyx and its further fate in new therapeutic strategies.

We have used a planar magnetron discharge to form emission plasma in a forevacuum plasma electron source (FPES) generating pulsed low-energy (up to 10 keV) electron beam at gas pressure of 4–16 Pa (Ar, N₂). The operation features of the magnetron discharge and emission properties of its plasma in the FPES have been investigated. Initiation voltage and delay time of initiation of the magnetron discharge decrease with increasing accelerating voltage, gas pressure, and acceleration gap length, as well as when Ar is used instead of N₂. The observed decrease in the initiation voltage and delay time is due to influence of a “parasitic” high-voltage glow discharge appearing in an accelerating gap, when high voltage is applied. An increase in pressure leads to higher emission current (beam current), that is typical for FPESs based on other discharge types. This increase in emission current is caused by a “back-streaming” ion flow from beam-produced plasma. Operating voltage of the planar magnetron discharge is lower during electron beam generation at gas pressure more than 4 Pa, which is also due the influence of the “back-streaming” ion flow penetrating into discharge system of the planar magnetron. The use of the planar magnetron discharge in the FPES provides generation of the wide-aperture (with radius of up to about 40 mm) low-energy electron beam with rather high homogeneity, pulse duration up to 10 ms and current up to 15 A.

The products resulting from the oxidative modification of petroleum asphaltenes were studied by Raman spectroscopy. Oxidizing agents such as peroxyacetic acid, potassium dichromate, and ammonium persulfate were used. Raman spectroscopy data indicated that the diameter of the aromatic sheets in asphaltenes varies widely depending on the calculation method applied. During chemical modification, the number of aromatic sheets decreases by several folds compared to native asphaltenes. The average number of aromatic rings per asphaltene sheet was found to be 8–10.

A new method of nonresonant selective spectroscopy was proposed for studying the low-frequency dynamics of molecules in liquids. The method is based on the nonresonant two-pulse laser excitation of the ultrafast optical Kerr effect. The first pulse induces anisotropy of the medium exclusively due to the orientational response of molecules. Theoretical calculations showed that, under these conditions, one can send a second pulse, which excites other vibrational and rotational responses, but suppresses the induced orientational anisotropy. It was shown that this scenario corresponds to conventional single-pulse excitation of the ultrafast optical Kerr effect, which does not include the contribution from orientational anisotropy. This allows for accurate determination of the spectral characteristics of intermolecular dynamics.