Vol 21, No 3 (2025)

For the first time, an accurate solution of the contact problem of the action of a rigid wedgeshaped die having a solution in the range of 270-360° is constructed. The stamp acts on a layer of composite material having an arbitrary anisotropy. A homeomorphic mapping of the topological space of the bearer of this stamp onto the topological space of the first quadrant is used, followed by the construction of a fractal and the application of an exact solution of the two-dimensional Wiener-Hopf integral equation for a wedgeshaped stamp with a right angle. In comparison with strip stamps, the solution contains an additively additional term describing the concentration of contact stresses at the angular point of the stamp. The calculation of the characteristic of the contact stress concentration at this point is close to the values obtained by approximate numerical methods in a number of studies. In the area considered away from the top of the stamp, the exact solution becomes the solution for the case of a semi-infinite stamp. The developed method is applicable to composites of arbitrary anisotropies occurring in linearly elastic materials and crystals of any cross-section. It can be useful in engineering practice when assessing the concentrations of contact stresses in the zones of the comer points of stamps having similar angles. In seismology, this approach is applicable for estimating stress concentrations in lithospheric plates in the zones of transition of a mountain ridge to a plain in the presence of angular zones of the specified range.

An effective method of low-frequency non-destructive testing of the medium stratification process by changing the parameters of surface waves excited by pulse (impact) action on the tested object is proposed. The method consists of analog control of the characteristics of the surface wave field accompanying the change in the stratification parameters by measuring the acceleration of specified points on the surface of the tested object, converting the analog signal into a digital one and its subsequent mathematical processing. The latter consists of a special transformation of the recorded signal by using original mathematical methods into a two-dimensional image. This approach allows for visualization of signal change control by converting the original amplitude-time signal into a certain point in two-dimensional space. Any change in the wave field parameters leads to a change in the position of the point on the plane. This implements the possibility of visual control of the change in stratification parameters by the position of the point in two-dimensional space. As an example, an experiment was conducted to control the movement of an inclusion in a crack simulating the dynamic process of stratification of a composite material. A vibration table simulating an impact effect was used as a source of oscillations. A crack is defined as an elongated through-thickness fissure in a specimen. The wave field was monitored at two points on the object’s surface: above the crack and after it. The information content of control by changing the parameters of the transmitted field, and the change in the resonant behavior of the “inclusion-crack” system was studied. The study showed a fairly high sensitivity of the method.

The liquid-phase gradient epitaxy method was used to obtain Al^Ga^Inj _ AszPj _z layers doped with tellurium with thicknesses of 500-1000 pm at synthesis temperatures of 800-900 °C. The Hall coefficients were determined by etching the surface of graded-gap layers at a weak magnetic field with a strength of H— 2.4 • 105 A/m. The dependence of the distribution of the content of the majority charge carriers over the thickness of the layers was calculated and plotted using the Runge-Kutta method. When the undoped liquid zone of A1 - Ga - As - P - In moves in the forward direction, its source is InAs : Те, and when the solution-melt doped with tellurium moves in the opposite direction, the source is the graded-gap crystal of AlGalnAsP. For this reason, as well as because of the high value of the tellurium diffusion coefficient, after passing the zone in the opposite direction, there is no equalization of the Те impurity content in the layer. Due to the high diffusion coefficient of aluminum and phosphorus, the features of the redistribution of these components in the graded-gap layers of AlGalnPAs grown on InAs substrates are discussed. The high concentration of A1 and P atoms in the layers adjacent to the heterointerface, the diffusion of Te from InAs into the layer during the growth of the heterostructure contribute to a higher cleaning depth of the AlGalnPAs layer from tellurium impurities in comparison with the layers of the substrate material. A decrease in the concentration of the majority charge carriers in the layer near the substrate is probably due to structural defects at the layer-substrate boundary.

The task of ensuring the safety of drinking water use is relevant due to the existing environmental risks associated with the deterioration of water quality under the influence of man-made and natural factors, which is noted in numerous foreign and domestic studies. This problem is especially acute in rural areas when using decentralized water sources for household and drinking needs, which, as a rule, are not covered by the state system for monitoring water quality assessment. The purpose of the study was to assess the safety of drinking water use of the population of the Voronezh region from decentralized sources based on sanitary and chemical indicators of water quality. Sampling of water from decentralized sources (springs, wells, separate water intake wells) was carried out in the period from 2024 to 2025 (total 302 samples). The research included the determination of total hardness by titrimetric method, mineralization by conductometric method, total iron and nitrate content by colorimetric method. The results of the water analyses were compared with current hygiene standards. It is established that the indicators of the total iron content and hardness meet sanitary and hygienic standards. However, most water samples are classified as “hard”. The average indicators of water mineralization, depending on the aquifer complex used, range from 517.2 mg/1 (Upper Cretaceous) to 586.0 mg/1 (Neogene-Quatemary) and are assessed as elevated. The facts of exceeding the hygroscopic standards of nitrate content from 1.1 times in mixed-type waters to 1.25 times in waters of the Neogene-quatemary complex have been revealed. Based on the results of the study, proposals have been substantiated to improve the drinking water quality monitoring system in terms of including water quality control from decentralized sources, as well as informing the public about the need to use household water purification filters.

The article presents the results of studies of the content of mobile forms of phosphates and the activity of the phosphatase in the soils of agricultural lands of the Donetsk People’s Republic. It was revealed that the lowest content of mobile forms of phosphorus was noted in sites with the cultivation of grain crops (1.27-2.17 mg /100 g of soil), where this indicator did not exceed 42% compared to the control. When cultivating vegetable crops, the maximum supply of phosphates (3.44-4.59 mg / 100 g of soil) was characterized by the plot under tomatoes, while the content of mobile phosphorus in the A horizon of the fields under onions and eggplants was 36-38% lower compared to the control indicators. All underlying horizons had a reduced content of mobile phosphates and activity of the phosphatase compared to arable ones, which is typical of the chernozem type of soil formation. The removal of phosphorus with commercial agricultural crops led to a decrease in the content of mobile phosphates in the soil of all sites after harvesting. The most significant decrease of this indicator was noted in the arable horizon of plots under grain crops, amounting to more than 65% compared to the control. During the period of active formation of vegetative mass, the maximum phosphatase activity was observed in plots under grain crops and amounted to 70-86% relative to the control. The assessment of phosphatase activity in the soil according to the Gaponyuk and Malakhov scale showed that sites under grain crops is characterized by a high degree, and all other sites are of medium degree. A strong negative correlation was established between the content of mobile phosphates and phosphatase activity (r from -0.83 to -0.92).

The data on ichthyological studies in the eastern part of the Taganrog Bay and the mouth of the Don River in the period from January to July 2025 are presented. During this period, 43 fish species belonging to 13 families were caught. Such previously common species as sabrefish, vimba, shemaya began to be encountered individually or their catches decreased significantly. The most common catch in terms of the number of species included 21 fish species (common carp, silver crucian carp, kutum, white bream, mullet, rudd, pike perch, roach, needlefish, etc.). Our daily monitoring confirms that in addition to sturgeon, the Azov semi-anadromous populations of pike perch, bream and sabrefish are on the verge of extinction. The number of other valuable commercial fish - carp, roach, vimba - has also sharply decreased.

Despite significant progress in understanding the molecular mechanisms of cancer initiation and development, there has been a steady increase in the incidence of malignant neoplasms. In this regard, the identification of molecular markers and molecular targets of human cancer diseases, new diagnostic markers of the initiation, development and progression of malignant tumors remains a priority area of research. The renin-angiotensin cascade is a physiological pathway that promotes the proliferation of tumor cells, angiogenesis and inflammatory response in tumor tissue, invasion and metastasis. (Pro)renin receptor ((P)RR)/MAP kinase is an alternative pathway of regulation of the renin-angiotensin system (RAS). The purpose of the review is to analyze the role of the (pro)renin receptor in the molecular mechanisms of carcinogenesis, to assess its prospects for role of a new biomarker and a potential therapeutic target for the diagnosis, treatment and prognosis of cancer. The (pro)renin receptor has been identified as a new member of the local RAS. However, our knowledge of (P)RR was mainly limited to its role in physiological processes, in cardiovascular diseases and kidney diseases. In recent years, it has been convincingly proven that (P)RR is aberrantly expressed and contributes to the development of various types of cancer. The review analyzes the potential role of (P)RR in the molecular mechanisms of initiation and progression of various types of cancer. It is shown that (P)RR plays an important role in cancer-associated signaling pathways such as Wnt/p-catenin, RAS, MAPK/ERK, and PI3K/AKT/mTOR. The relationship between the expression level of (P)RR and its soluble form (s(P)RR) with the development of malignant neoplasms has been established. s(P)RR may be a new non-invasive biomarker for malignancies, but further research is needed to determine its diagnostic value. Thus, the (pro)renin receptor, including its full-size form in tumor tissues and its soluble form in blood, has significant potential as a new biomarker for the diagnosis of malignant neoplasms.