Nauka Yuga Rossii

Buckling under external loads often becomes the cause of collapse for various buildings and engineering structures. Due to this, the problem of stability analysis for modern layered composites, which are widely used in many industries, is quite relevant. They often have a complex microstructure and contain internal stresses that can appear in the process of assembling a composite due to plastic strains, heating and phase transitions, or be created artificially. In the present paper, within the framework of the general theory of stability for three-dimensional bodies, we have studied the equilibrium bifurcation of a thick multilayer spherical shell under internal and external pressure. It was assumed that its layers could be preliminary deformed and contain initial (residual) stresses. To describe the behavior of the considered spherical shell, the model of a micropolar medium was applied which made it possible to take into account the effect of microstructure on buckling. Using the representations of the constitutive relations with respect to different reference configurations, in the case of a physically linear micropolar material model, equations of neutral equilibrium were derived that describe the behavior of a layered shell with prestressed parts in a perturbed state. By applying a special substitution based on Legendre polynomials, the stability analysis of a thick А-layer micropolar spherical shell in the case of axisymmetric perturbations was reduced to solving a linear homogeneous boundary value problem for a system of 6А ordinary differential equations. Given the material parameters of the layers, their thickness and initial strains, this boundary value problem can be quite easily solved numerically using the finite-difference method.

A multilayer YMnO3/BiFeO3/SrTiO3 heterostructure on a single-crystal Al2O3(0001) substrate obtained by RF-cathode sputtering in an oxygen atmosphere has been fabricated. The thickness of each layer was estimated based on the sputtering time and did not exceed 300 nm. The complex structural investigations of the YMnO3/BiFeO3/SrTiO3/Al2O3(0001) heterostructure were carried out. It was found that its surface has good quality without any inclusions, inhomogeneities, or impurities. Each layer of the films grows by islands type according to the Volmer-Weber mechanism. Statistical analysis of the topology of heterostructure surface showed the absence of bimodality of growth blocks, their shape is predominantly oval in habit, and their average size is ~110 nm. The surface layer of YMnO3 has a relatively low roughness of about 14.7 nm. A target consisting of the main pure hexagonal phase of yttrium manganite was used for sputtering the upper layer. According to the results of X-ray structural analysis, each layer of the heterostructure was found to be formed with a pseudocubic crystal lattice. Thus, the deposited YMnO3 layer of thin film has an orthorhombic structure, which in bulk materials is stabilized under more complex conditions with the simultaneous application of high pressure and temperature. Studies of Raman spectra at room temperature confirmed that for the upper YMnO3 layer, the main mode at 680 cm-1, which is characteristic of the hexagonal symmetry in bulk materials, is absent. The spectrum consists of at least 6 well-resolved peaks, the most intense of which is at 605 cm-1. This also confirms that the upper layer of the YMnO3 multiferroic is formed in a crystal structure different from its target.

A rhodamine-hydroxyphenylimidazole conjugate has been synthesized, which is an ion-controlled molecular switch of optical and fluorescent properties. According to IR-, 1H and 13C NMR spectroscopy, electron absorption spectroscopy and fluorescence analysis, it is in the spirolactam form. The electronic absorption spectra of the conjugate in solvents of different polarity contain absorption bands at 315 nm, while fluorescence is observed in the significantly longer-wavelength region of 455-465 nm with an anomalous Stokes shift (up to 10240 cm-1). Using model compounds 2-(4,5-diphenyl-LH-imidazol-2-yl)-5-methylphenol and 2-(2-methoxyphenyl)-4,5-diphenyl-fH-imidazole, which do not have a free proton, it was established that this emission is due to rapid intramolecular O^N proton transfer in the terminal imidazole fragment in the excited state. The synthesized conjugate in acetonitrile under the action of Zn2+, Cd2+, Co2+, Cu2+ and Hg2+ ions demonstrates a contrast naked-eye effect with the formation of a new long-wave absorption band in the region of 550-555 nm and coloring the solution pink. At the same time, intense fluorescence appears in the region of 580-590 nm. The possibility of reversible switching of the indicated spectral characteristics of the conjugate in toluene with the sequential addition of trifluoroacetic acid and triethylamine is shown. In the presence of acid, a new long-wave absorption band with a maximum at 560 nm is formed, indicating the opening of the spirolactam cycle, and a naked-eye effect is also observed due to the coloration of the colorless solution in pink. In the fluorescence spectrum of the conjugate, instead of a band with a maximum at 465 nm, a band with a maximum at 582 nm appears. Upon subsequent addition of triethylamine to the resulting solution, the absorption band with a maximum at 560 nm disappears and the original absorption and fluorescence pattern is restored.

Soils in arid territories such as Kalmykia are particularly vulnerable to pyrogenic impacts due to pre-existing environmental stressors like droughts and salinization. Changes in the physical, chemical and biological properties of soils in various regions of Kalmykia after fires were studied. The relevance of this study stems from the increasing frequency of wildfires in steppe and semi-desert regions, driven by climate change and anthropogenic activities. The study material consisted of samples of southern chernozem, light chestnut, and brown semi-desert soils collected in the Gorodovikovsk, Tselinny, and Chernozemelskiy districts of Kalmykia. The methods included determination of pH, organic carbon content, macroelements, ions, and enzymatic activity using standard soil-chemical techniques. The findings revealed that wildfires cause a significant increase in mineral element content (20-60 %) and soil alkalinization (pH rise of 0.2-0.6 units), associated with ash deposition. Enzymatic activity decreases by 30-70 % immediately after fires but partially recovers within three months, particularly in chernozems. The most pronounced changes were observed in brown semi-desert soils, where recovery processes proceed more slowly due to extreme environmental conditions. Due to the long-term impact of fires on soil ecosystems, monitoring soil salinization and developing reclamation measures for arid regions is necessary.

The ability of three species of Barents Sea macroalgae to accumulate technogenic radionuclides 137Cs, 60Co и 65Zn from seawater under the same environmental conditions was studied in a laboratory experiment. The relevance of these studies is due to the presence of potential sources of radioactive contamination on the coast of the Kola Peninsula and the growing interest in the use of seaweed in various areas related to the livelihoods of the population. Laboratory experiments have shown that radionuclides bind to algae tissues. Fucuses Fucus vesiculosus and F. serratus absorb from 23 to 100%, Palmaria palmata red algae - from 25 to 97% of the added activity of radionuclides from the water. The average specific activity of 60Co and 65Zn in fucus algae reached an equilibrium value on the 2nd and 3rd days of exposure, and 137Cs was accumulated by plants until the end of the experiment. The viability and functional activity of plants during the experiment was confirmed by a high level of photosynthetic activity and an increase in the biomass of fucus thallomas in experimental vessels and control groups. The study also revealed the possibility of absorption of isotopes 137Cs, 60Co and 65Zn by algae epibionts, as well as dead plant particles. The maximum intensity of isotope absorption by algae was observed on the first day of the experiment. The plants accumulated 60Co and 65Zn from water most efficiently. The absorption of radionuclides by brown and red algae-macrophytes in seawater proceeds by one mechanism. The possibility of using algae for phytoremediation during emergency discharges of radioactive waste into the sea is shown.

Wild garlic Allium longicuspis Regel belongs to rare species. It is both the original form and the progenitor of cultivated sowing garlic A. sativum L. A long-term (2009-2024) study of the biological features (seasonal development rhythm, morphometry, reproductive performance, success of introduction, and resistance to diseases and pests) and biochemistry of wild garlic in culture in the Republic of Bashkortostan (Botanical Garden-Institute, Ufa) is presented. According to the research results, wild garlic has a stable development rhythm. It grows mainly in early April, a flowering shoot appears in late May-early June, and the buds open in mid-July. The flowers do not form seeds, as they are sterile. After a short period of rest, wild garlic begins to renew itself in the fall. It goes into winter in a vegetative state. Analysis of the chemical composition showed a high content of ascorbic acid and other biologically active substances. Wild garlic in the conditions of the study region is characterized as a winterhardy plant, resistant to diseases and pests.

Enhancing plant tolerance to abiotic stresses is a key objective in contemporary molecular biology and plant biotechnology. In this study, we investigated the impact of heterologous expression of the LlBANMT gene, responsible for the biosynthesis of p-alanine-betaine (PAB), on the physiological traits of transgenic Panax ginseng plants subjected to salinity, temperature, and high light stress. It was shown that LlBANMT overexpression was associated with a significant increase in membrane stability index and a decrease in relative electrolyte leakage in P. ginseng leaves under salt and cold stress conditions compared to control plants. In contrast, PAB accumulation had no pronounced effect on these parameters under light stress. Under salinity and cold exposure, transgenic leaves retained higher relative water content. Furthermore, transgenic plants maintained elevated levels of chlorophylls and carotenoids under all stress treatments. These findings indicate a membrane-stabilizing effect of PAB and its capacity to maintain water and ionic homeostasis under abiotic stress, likely due to its osmoprotective and antioxidant properties. Therefore, the LlBANMT gene represents a promising molecular tool for developing stress-tolerant ginseng varieties with enhanced adaptive plasticity to adverse environmental conditions. The results of this study broaden current understanding of pAB functions and demonstrate its potential as an effective metabolic regulator in plant biotechnology

Based on the materials of studying aquatic vegetation collected in 2006-2022 in different watercourses of the Don River basin, aquatic vegetation was classified using the Braun-Blanquet method based on 35 geobotanical descriptions. Five associations were identified: Nymphaeetum albae, Nupharetum luteae,Nymphaeetum candidae, Trapetum natantis, and Nymphoidetum peltatae in the alliance of Nymphaeion albae of the Potamogetonetea class, for which the characteristics are given. The communities of the associations Nymphaeetum albae and Nupharetum luteae are most widespread (found in the delta, lower and middle reaches). Less often - Nymphaeetum candidae.The results of studies of the aquatic vegetation of the river basin are summarized. One hundred eight descriptions were attributed to higher aquatic vegetation (40 - classes Platyhypnidio-Fontinalietea antipyreticae and Lemnetea; 68 - class Potamogetonetea), 19 associations related to 5 alliances were identified (1 - alliance Fontinalion antipyreticae, 3 - alliance Lemnion minoris, 3 - alliance Stratiotion, 7 - alliance Potamogetonion, 5 - alliance Nymphaeion albae). In addition to those identified, according to the presence of diagnostic species in the reservoirs of the region, it is assumed that there are 13 more associations. The most widespread communities of associations are: Ceratophylletum demersi, Hydrocharitetum morus-ranae, Lemnetum minoris, Nymphaeetum albae, Nupharetum luteae, Potamogetonetum pectinati, Potamogetonetum perfoliati. The communities of Ceratophylletum demersi and Lemnetum minoris associations are most often noted.It is shown that the cenotic composition and spatial structure of the aquatic vegetation of the Don River and other rivers of its basin are determined by ecotopic diversity, water mineralization, and climatic factors: in the delta - lower course - middle course series, there is an increase in cenotic diversity - 9-10-18, the number of noted species in the same series - 27-28-38. There are 12 species of plants listed in the Red Book of Rostov Region in aquatic vegetation communities.