Volume 18, Nº 2 (2022)

The problem of constructing a model and carrying out numerical calculations of the bulk strain energy density values in multi-component polymeric frictional composites is solved, taking into consideration the composition, shape, orientation and volume content of fillers, as well as the type of external mechanical impact applied to the material. Composites based on an epoxyphenol binder reinforced with short fibers of E-glass randomly oriented in the space of the material and dispersed additives of rubber, alumina, graphite and barite are considered. Modeling is based on the generalized singular approximation of the random field theory and the concept of the stress concentration operator (fourth rank tensor), which relates the local (internal) values of the stress tensor with average (external) stresses over the material. The dependences of the values of the bulk strain energy density in the elements of inhomogeneity of polymeric frictional composites on variations in the volume concentrations of fillers – E-glass fibers, dispersed rubber inclusions, and mineral powder consisting of alumina, graphite and barite in equal volume fractions have been studied. Two cases of external compressive action, axial and volumetric, are considered. As a result of the numerical model calculations, it was found that an increase in the volume fractions of both E-glass fibers and mineral powder leads to a decrease and convergence of the values of the bulk strain energy density in the components of all types of polymeric frictional composites under consideration. Modeling also showed that an increase in the volume fraction of rubber inclusions leads to an increase and a divergence in the values of the bulk strain energy density in the elements of heterogeneity of all types of polymeric frictional composites under study.

The BiFeO3/Sr0.6Ba0.4Nb2O6 two-layer heterostructure have been sputtered onto a (001)MgO single-crystal substrate by high-frequency sputtering in an oxygen atmosphere. The layers of the heterostructure were obtained epitaxially, where the lower Sr0.6Ba0.4Nb2O6 layer was obtained with the formation of two types of orientational domains, and the upper BiFeO3 layer was obtained in the full parallel orientation ratio with the substrate. According to atomic force microscopy the surface of the heterostructure is a block structure with a low value of the root-mean-square surface roughness. The study of magnetic force microscopy of the heterostructure surface showed the presence of a response at the grain boundaries associated only with the BiFeO3 layer. The causes of the revealed effects are discussed.

A description of the integrated autonomous GPS geodynamic station in the area of the bridge across the Kerch Strait, located in the seismically active zone of the Kerch-Taman region with the maximum possible level of shaking up to 9 points, is presented. The danger to this complex engineering structure is the deep Kerch fault, the seismic activity of which was recorded in numerous historical records and data of the modern industrial period. Geodynamic aseismic movements, mud volcanism and other hazardous geological processes, which can cause damage to the bridge structure and create emergency situations at this particularly important object, are also dangerous. In 2021, in order to monitor the seismogeodynamic activity of the bridge area across the Kerch Strait, the Southern Scientific Centre of the Russian Academy of Sciences (SSC RAS) and Yuzhmorgeologiya JSC installed an autonomous satellite geodynamic station (SGS) as part of the SGS network on the Taman Peninsula. The receiving ground design of the GPS antenna device is made taking into account the recommendations of the international geodynamic service IGS and consists of a special base and a forced centering device. Measurements at the geodynamic station are performed by the GPS Trimble 5700 receiver and the MR-107 radon indicator. The operation of all SGS devices is controlled by a fanless XCY industrial computer based on the Windows 7 operating system. The electrical characteristics of the uninterruptible power supply circuit were determined by the method of UNAVCO (University NAVSTAR Consortium, USA). Measurement data are received every day via the Internet at the monitoring center of the SSC RAS. After primary processing, GPS measurements are sent for secondary processing to the geodynamic program GAMIT v. 7. The data obtained after processing contain the coordinates of the receiving antenna of the SGS with an horizontal accuracy of 2–3 mm and vertical accuracy of 6–8 mm. The secondary processing ends with the Matlab program package developed at the SSC RAS.

The breeding ecology of pied flycatchers Ficedula hypoleuca (Pallas, 1764) was examined on the birds nesting in artificial nests. The material was gathered from 1986 to 1996 and from 2012 to 2021 in the Voronezh State Nature Biosphere Reserve (50°21ʹ–52°02ʹ N, 39°21ʹ–39°47ʹ E). Five hundred twelve nests were observed. The spring bird arrival varies over the years from the 12th of April to the 5th of May. The average date is the 23th of April (n = 34), the time frame of the bird arrival correlates with the temperature in April (r = −0.42, p < 0.05). Oviposition begins in a narrow time range from the 5th to the 9th of May. The beginning and the synchronism of oviposition negatively correlate with the air temperature in the first ten days of May (r = −0.72, −0.81, p < 0.01). The long-term dynamics of bird arrival and oviposition time frames lack any linear trends. The clutch size varies from 3 to 9 eggs, 6.63 ± 0.05 on average (n = 466). The proportion of successful breeding attempts is 15–96.3%, the general breeding success is 9.8–93.2%; the average number of fledglings per one breeding attempt is 4,41. The major factor of egg and nestling mortality is predation of a forest dormouse Dryomys nitedula Pallas, 1778 in deciduous forests. In the current century the level of predation lowered substantially. The embryonic mortality proportion is 0.8–14.5% and negatively correlates with the air temperature during the oviposition period (r = −0.7, p < 0.05). The population in the south of the range is marked by a high density of the artificial nests colonization in pine forests, stable breeding time frames and high breeding productivity. The inter-annual fluctuations of climatic variables have no crucial bearing on the breeding time frames and productivity. The climate grows warmer mainly due to the temperature rise in winter and in the first half of spring, that means little for the researched species as it is a late migrant breeding in May and June.

The results of approbation are analyzed and the experience of biofeedback application which was earlier worked out in somnological practice in the course of positional therapy for treatment of obstructive apnea type breathing disorders by optimizing the patients’ position during treatment for COVID-19 infection is summarized. These patients are advised to adhere to the face-down prone position. Failure to adhere to the recommended position when the supine position (face-up) is abused, invariably leads to a worsening of the course of the disease. However, while staff can monitor COVID-19 patients’ compliance with the prone position during the day, it is not possible at night. Accordingly, in order to facilitate prone positions the patients in the red zone were helped by a miniature device fixed on the chest by means of an elastic band and giving a vibration signal in case of violation of the recommended position. By developing a stable conditioned reflex, excluding any position other than the recommended prone position, the patients found it easier to observe the positioning therapy, which had a positive effect on the patients’ well-being, their physiological state, and accelerated recovery from the COVID-19 disease.