AC field induced quantum rectification effect in tunnel junctions

We study the appearance of directed current in tunnel junctions, quantum ratchet effect, in the presence of an external ac field f(t). The current is established in a one-dimensional discrete inhomogeneous "tight-binding model". By making use of a symmetry analysis we predict the right choice of f(t) and obtain the directed current as a difference between electron transmission coefficients in opposite directions, $\Delta T = T^{LR}-T^{RL}$. Numerical simulations confirm the predictions of the symmetry analysis and moreover, show that the directed current can be drastically increased by a proper choice of frequency and amplitudes of the ac field f(t).Comment: 4 pages, 3 figures, to be published in Physical Review

Radiation Pressure Quantization

Kepler's observation of comets tails initiated the research on the radiation pressure of celestial objects and 250 years later they found new incarnation after the Maxwell's equations were formulated to describe a plethora of light-matter coupling phenomena. Further, quantum mechanics gave birth to the photon drag effect. Here, we predict a novel universal phenomenon which can be referred to as quantization of the radiation pressure. We develop a microscopic theory of this effect which can be applied to a general system containing Bose-Einstein-condensed particles, which possess an internal structure of quantum states. By analyzing the response of the system to an external electromagnetic field we find that such drag results in a flux of particles constituting both the condensate and the excited states. We show that in the presence of the condensed phase, the response of the system becomes quantized which manifests itself in a step-like behavior of the particle flux as a function of electromagnetic field frequency with the elementary quantum determined by the internal energy structure of the particles.Comment: Manuscript: 4 pages, 3 figure

Incommensurate dynamics of resonant breathers in Josephson junction ladders

We present theoretical and experimental studies of resonant localized resistive states in a Josephson junction ladder. These complex breather states are obtained by tuning the breather frequency into the upper band of linear electromagnetic oscillations of the ladder. Their prominent feature is the appearance of resonant steps in the current-voltage (I-V) characteristics. We have found the resonant breather-like states displaying incommensurate dynamics. Numerical simulations show that these incommensurate resonant breathers persist for very low values of damping. Qualitatively similar incommensurate breather states are observed in experiments performed with Nb-based Josephson ladders. We explain the appearance of these states with the help of resonance-induced hysteresis features in the I-V dependence.Comment: 5 pages, 6 figure

Wave scattering by discrete breathers

We present a theoretical study of linear wave scattering in one-dimensional nonlinear lattices by intrinsic spatially localized dynamic excitations or discrete breathers. These states appear in various nonlinear systems and present a time-periodic localized scattering potential for plane waves. We consider the case of elastic one-channel scattering, when the frequencies of incoming and transmitted waves coincide, but the breather provides with additional spatially localized ac channels whose presence may lead to various interference patterns. The dependence of the transmission coefficient on the wave number q and the breather frequency Omega_b is studied for different types of breathers: acoustic and optical breathers, and rotobreathers. We identify several typical scattering setups where the internal time dependence of the breather is of crucial importance for the observed transmission properties.Comment: 17 pages, 19 figures, submitted to CHAOS (Focus Issue

ВПЛИВ ЗАНЯТЬ СПОРТОМ НА ФУНКЦІОНАЛЬНІ МОЖЛИВОСТІ СЕРЦЕВО-СУДИННОЇ СИСТЕМИ ДІВЧАТ 17-21 РОКІВ ПОДІЛЬСЬКОГО РЕГІОНУ

In this article considers the effectiveness of the impact of sports on the functionality of the cardiovascular system of girls 17-21 years old living within the Podolsk region. The function of the cardiovascular system of girls was evaluated by the ability to recover after termination of work (by the parameters of heart rate). Classes cycling and playing sports (performance of muscle work of which is connected with the mixed mode of power supply) and martial arts (performance of muscular work is associated with anaerobic (lactate) mode of power supply) contribute to improvement the functional possibilities of the cardiovascular system. This is manifested by the acceleration of recovery of heart rate after metered physical loads of 1 watts and 2 watts per 1 kg of body weight. The smallest percentage of person with a slow recovery of heart rate were detected among athletes, volleyball players and representatives of complex coordination sports. These individuals are involved in the performing of physical exercise with anaerobic (alactate) processes of metabolism.In this article considers the effectiveness of the impact of sports on the functionality of the cardiovascular system of girls 17-21 years old living within the Podolsk region. The function of the cardiovascular system of girls was evaluated by the ability to recover after termination of work (by the parameters of heart rate). Classes cycling and playing sports (performance of muscle work of which is connected with the mixed mode of power supply) and martial arts (performance of muscular work is associated with anaerobic (lactate) mode of power supply) contribute to improvement the functional possibilities of the cardiovascular system. This is manifested by the acceleration of recovery of heart rate after metered physical loads of 1 watts and 2 watts per 1 kg of body weight. The smallest percentage of person with a slow recovery of heart rate were detected among athletes, volleyball players and representatives of complex coordination sports. These individuals are involved in the performing of physical exercise with anaerobic (alactate) processes of metabolism

Radiation Pressure Quantization

Kepler's observation of comets tails initiated the research on the radiation pressure of celestial objects and 250 years later they found new incarnation after the Maxwell's equations were formulated to describe a plethora of light-matter coupling phenomena. Further, quantum mechanics gave birth to the photon drag effect. Here, we predict a novel universal phenomenon which can be referred to as quantization of the radiation pressure. We develop a microscopic theory of this effect which can be applied to a general system containing Bose-Einstein-condensed particles, which possess an internal structure of quantum states. By analyzing the response of the system to an external electromagnetic field we find that such drag results in a flux of particles constituting both the condensate and the excited states. We show that in the presence of the condensed phase, the response of the system becomes quantized which manifests itself in a step-like behavior of the particle flux as a function of electromagnetic field frequency with the elementary quantum determined by the internal energy structure of the particles.Comment: Manuscript: 4 pages, 3 figure

Time-dependent spectral-feature variations of stars displaying the B[e] phenomenon III. HD 50138

We analyse spectroscopic observations of the B[e] star HD 50138 (MWC 158, V743 Mon, or IRAS 06491-0654), a member of the FS CMa group, obtained over the last twenty years. Four different epochs are identified in the observational data, where the variability of the spectral features is substantially different. Additionally, two long periods of (3 000 +/- 500) and (5 000 +/- 1000) days are found in the variations of the equivalent widths of the H alpha and [OI] 6300 A lines and radial velocities of the H alpha line violet peak. Modest signatures of a regular period of ~34 days in the radial velocities of the H alpha red peak and H beta central depression are found in the season 2013/2014. The H alpha V/R changes indicate a periodicity of ~50 days. The correlations between individual spectral features significantly restricts the model of the object and suggest that it is most likely a binary system with a highly distorted disc with spiral arms around the primary component. At the same time, no obvious signs of the secondary component has been found in the object's spectrum

CONCEPTUAL ASPECTS AND APPLIED MEANS OF STRUCTURAL TRANSFORMATIONS OF THE RUSSIAN ECONOMY IN TERMS OF EXTERNAL CONSTRAINTS

The theoretical and economic study of various aspects of the impact of external restrictions on the Russian economy in recent years has become one of the actively developing areas of scientific research. External constraints create special conditions in which the structural transformation of the Russian economy can get an additional boost. Effective implementation of the relevant opportunities involves expanding the space of scientific research and overcoming interdisciplinary boundaries. The representation of external constraints as a stable component of the system phenomenon of “new economic reality”, which arose in the conditions of deep technological changes; specific opportunities arising in the process of structural transformations in the conditions of external constraints; development of applied means of structural transformations in the conditions of external constraints have been studied in the article. Through the prism of external constraints, the key problem nodes and contradictions of structural transformations have been considered; the effects arising at different levels of this process have been evaluated; tools for solving the problems that arise here have been proposed. Recommendations for improvement of the state economic policy in the field of structural transformations have been given. The heuristic resources of a number of modern scientific theories: socio-economic transformations, state economic policy, cognitive economics have been used in the research

Classification of medical images of patients with Covid-19 using transfer learning technology of convolutional neural network

The paper shows an approach to solving the problem of classifying X-ray images of the chest part of a healthy person and with the presence of COVID-19. The method is a trainable convolutional neural network. The results obtained allow improving existing approaches and methods in the field of classification of medical images with COVID-19, as well as obtaining an auxiliary mechanism for detecting COVID-19 in patient

Application of multivariate analysis to identify relationships among useful agronomic characters of cowpea and differentiation of cultivars for vegetable and grain uses

Background. Сowpea (Vigna unguiculata (L.) Walp.) is a thermophilic crop; in most countries it is grown for grain and vegetable uses. Positive results of open-field cowpea production in the southern regions of Russia and the possibility of its cultivation on infertile soils in hot and dry climate imply the need to develop new cultivars suitable for wider introduction into Russian agriculture. It is of paramount importance for cowpea breeders to know the patterns of variability in the relationships among agronomic traits and their characteristics in cultivars grown for different uses (grain and vegetable). Besides, acceleration of the breeding process to a large extent depends on the knowledge of the traits that make it possible to differentiate the source material according to its intended purpose.Materials and methods. For three years, 315 cowpea accessions of various origin from the VIR collection were studied in Astrakhan Province, Russia. Eight useful agronomic characters were examined. The variability and relationships of these characters were assessed in cultivars grown for grain and vegetable purposes using multivariate statistical analyses.Results and discussion. The characters that differentiate grain and vegetable cowpea accessions were identified: the type of seed coat surface, the presence of fiber in ventral and dorsal pod sutures and a sclerenchyma layer in pods valves, and pod length. Discriminant functions were calculated for identification and classification of accessions according to their grain and forage uses. The character (presence of depressions or longitudinal striae on the seed coat surface) diagnosing vegetable cowpea cultivars was pinpointed. Characters associated with high seed yield were identified. For grain cultivars such character is the weight of 1000 seeds, while for vegetable cultivars it is a large-seeded and long-fruit pod