The necessity of developing a new design for automatic control of the microwave signal gain to ensure the stability of the output parameters of the atomic frequency standard (AFS) based on rubidium-87 atoms under various external conditions of its operation is substantiated. A new scheme for automatic gain control in the microwave path of the AFS based on rubidium-87 atoms is presented. A signal amplifier that controls the microwave excitation signal is considered, and mathematical modeling of microwave devices included in the microwave path is carried out. The validity of the developed automatic gain control scheme for the atomic frequency standard is confirmed. rubidium - 87.
Show AbstractCardiomyocytes obtained by differentiation from human pluripotent stem cells serve as an indispensable platform for the fundamental study of the mechanisms of cardiovascular diseases. While the possibility of reproducing rare pathologies, individual selection of drugs and other issues related to the electrophysiological properties of single cardiomyocytes have been well studied, little attention has been paid to the properties of the syncytium of differentiated cells. Thus, one of the important properties was the reproduction of homogeneous conductive syncytium when transplanted to a new substrate, which is strictly dependent on the stage of cell differentiation: once on a new substrate, single cells are able to form conductive tissue, but lose this property after 20 days of differentiation. The aim of this work is a theoretical explanation of this dependence based on the morphology of differentiated cells. To simulate the process of tissue formation, the Potts cell model was used, based on immunocytochemical images of single cardiomyocytes at different stages of differentiation. The conduction of the excitation wave through such virtual cardiac layers was reproduced using the ten-Tusscher Panfilov electrophysiological model. According to the results of the work, it was possible to establish a connection between the morphology of single cells and the properties of the tissue formed from them, which allows us to explain the relationship of the differentiation stage with the properties of the tissue transplanted to a new substrate.
Show AbstractIn the magnetohydrodynamics approximation, nonstationary processes in solar coronal structures are considered, which are identified as compression waves. To study the rapid damping of these waves, the effects of heat conduction and radiation losses are applied, more precisely, the effect of the imbalance between heating and energy losses. The behavior of the waves varies greatly depending on the parameters of the coronal loops, which requires accuracy in their determination. The calculation results also depend on the accuracy of the heating/loss function approximation. Depending on these conditions, both the thermal conductivity effect and the imbalance between heating and energy losses can play a decisive role in the attenuation of slow magnetosonic waves. The effects of heat conduction and imbalance between heating and losses lead not only to wave attenuation, but also to its dispersion.
Show AbstractVolcanic seismicity has quite significant differences from tectonic seismicity, consisting in a different nature: here, instead of the mechanism of accumulation and release of stresses, there is destruction of the rock under the pressure of magma, low-frequency seismic waves arising from vibrations of a large volume of magma, as well as events of an explosive nature, when hot gases rush to the surface. Therefore, the study of the regime of volcanic seismicity is of particular interest. The seismic catalog of Iceland from 1995 to 2019 was analyzed in the study. The seismic regime of the Icelandic volcano Bárðarbunga (BAR) during the eruption is significantly different from the rest of the seismicity of the region. Through detailed reports from the Icelandic meteorological service, it was possible to establish that this difference was mainly due to two processes timed to the eruption: the collapse of the central caldera and the outflow of lava along a fissure swarm. Thus, it was possible to identify the nature of some of the events in the catalog as volcanic. As a result of the analysis of variations of b-value for the process of opening cracks under magma pressure, an anomaly of the b-value known from the literature was revealed, which is typical for so-called volcanic swarms. Thus, evidence was obtained in favor of the hypothesis that such anomalies, often preceding eruptions, are associated exactly with processes of this type. Also, using the Zaliapin– Ben-Zion nearest neighbor method, the grouping of events associated with the eruption was analyzed, and a significantly lower clustering of events was found compared to tectonic regimes, which is probably also due to the difference in the nature of these seismicities.
Show AbstractThe experience of teaching general relativity based on the spacetime diagram, or Minkowski diagram, is discussed. Main special relativity effects, such as time dilation and length contraction, deduce easily by geometrical constructions on the diagram and <<event>> and <<measurement>> concepts.
Show AbstractUsing the least squares method, approximating functions for the experimental dependence of the total velocity of the antiferromagnetic vortices on the domain wall velocity were selected. Using the obtained functions and the relation between the vortex velocities and the domain wall velocity, the dependences of the vortex velocity along the domain wall u on the domain wall velocity v were calculated. It was found that if the velocity of the domain wall is less than a certain critical value, the dependence u(v) is not determined. This confirms the earlier conclusion about the impossibility of the antiferromagnetic vortices existence inside the domain wall if it moves at a speed less than the sound velocity.
Show AbstractThis paper considers earthquake anomalies for five strong earthquakes in China (Xinjiang-Yutian earthquake MS7.3, Wenchuan earthquake MS8.0, Lushan earthquake MS7.15, Jiuzhaigou earthquake MS7.2, and Milin earthquake MS7.1). Based on the avalanche unstable fracture formation model (AUF), three different prediction methods are Gutenberg-Richter relation （b-value），regional-time-length algorithm（RTL）and seismogenic rupture concentration (KCP). Spatiotemporal distribution analysis of precursor anomalies before strong earthquakes shows that RTL and Kcp anomalies are detected before all earthquakes, and b-value anomalies are found before 4 earthquakes. The average times between the occurrence of anomalies and the occurrence of earthquakes were: RTL – 2.13 years; b-value - 3.45 years; KCP - 16.75 years. Average distance between the region of the main RTL anomaly and the epicenter: 0.895°. The results show that the seismic prediction method based on the model AUF is applicable to the geological conditions of China and that the time of anomalies preceding an earthquake indicates the probability of an earthquake occurring.
Show AbstractIn this article the seasonal variability of the concentrations of particulate matter PM10 and PM2.5 on average in Moscow for 2017-2021 was investigated. It is shown that particulate matter concentrations vary depending on the season: the maximum values of particulate matter concentrations occur in spring-summer, absolute maximum are typical for April and a seasonal minimum is observed in winter. The differences of the seasonal course in Moscow, London and Beijing are explained by differences in climatic conditions and different anthropogenic sources. Episodes of increased concentrations of particulate matter in the spring are associated with the descent of snow cover and lack of precipitation, unfavorable meteorological conditions, as well as with the introduction of suspended particles into the territory of Moscow from other regions.
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