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The article is aimed at examining the impact of the COVID‑19 pandemic on international migration and the immigration policies of the main host countries. The authors distinguish three periods in the response of nation states to the outbreak of the virus. The first one (February–March 2020) was securitization. During this period, the public health imperative was placed above economic considerations. The second period (spring 2020 – autumn 2021) was adaptation. The third, in which we now live, could be called routinization. Many countries, with the exception of those with a zero tolerance policy for COVID‑19, have chosen to coexist with the virus. The authors demonstrate a significant reduction in migration flows as a direct result of the closure of state borders. Different types of migration have been affected differently by the pandemic. Non-labor market migration (family reunification, humanitarian migration, etc.) suffered the most. The new situation reduced the number of asylum applications (though not the number of refugees themselves). Student migration was initially subject to severe restrictions, but by the end of 2020, many of them were lifted. As for labor migration, despite the draconian measures to reduce it, initially taken in a number of countries, it was soon restored to its previous volumes. The pandemic made it evident how deeply the national economies depend on migration. That is why significant changes were made to immigration policy aimed at full access of migrants to social security systems and the settlement of their legal status. In particular, many G‑20 countries, regardless of their political regimes, have introduced measures such as free medical examinations and medical care for migrant workers, including undocumented ones.

Only seven frenulate species are currently known along the Eurasian coast of the Arctic Ocean. We describe a new genus and a new species of frenulates Crispabrachia yenisey, gen. nov. et sp. nov. The morphological analysis involved standard anatomical techniques, semithin sections and scanning electron microscopy (SEM). The molecular study included four markers (partial COI, 16S, 18S and 28S) and implemented Bayesian and Maximum likelihood phylogenetic approaches. The description of Crispabrachia gen. nov. is the first documented finding of frenulates in the Kara Sea at the estuary of the Yenisey River in rather shallow water (28 m). The establishment of a new genus is warranted based on the composition of morphological characters and several specific features including free, comparatively short curly tentacles, a triangular cephalic lobe with amplate base, the valvate extension of the posterior part of the forepart and prominent papillae on the nonmetameric region. The tube structure with prominent frills and the worm’s numerous tentacles, metameric papillae with cuticular plaques and segmental furrow on the forepart indicate that the new genus belongs to the polybrachiid group. Although the type locality in the Yenisey River estuary is unusual for siboglinids in general, the physical conditions here are common for other frenulates habitats, i.e. salinity ~30–33, bottom water temperature –1.5°C. This finding was made in the Yenisey Gulf in the region with the highest methane concentrations in the southern part of the Kara Sea that reflects permafrost degradation under the influence of river flow. Further study of the region would help to understand the factors influencing frenulate distributions and improve our knowledge of their biodiversity.

Emergency situations have a huge impact on various important areas of human life. Every year there are many situations, the elimination of which requires a lot of financial and human resources. Therefore, the ability to reduce the impact of the consequences and increase the speed of their elimination is extremely important. In this article, a multi-level model of a system was proposed that provides support for performing operational tasks in emergency situations in open areas. The most important elements, areas of their responsibility, and interconnection were identified and described in architectural style. The idea of the work is to design asystem that should use Swarm intelligence under the hood to provide continuous support in emergency situations. The system consists of 4 main parts: Cloud, Swarm, Swarm operator, and Swarm Node. The Cloud (Swarm Wamb) is the main decision-maker that provides ETL data pipelines and operates under strategicallytasks. In accordance with the idea, Swarm womb should be a cloud service-like system with the ability to scale over the world. The Swarm is a combined set of multiple Swarm Nodes and only one Swarm Operator. The main task of the Swarm is to provide support in local operational tasks where SN is responsible for the execution and SOis for control. Rescue and search operation after any natural disaster is a target to show the system’s purpose. In practice, the cloud system (Swarm Wamb) receives requests to perform an operation, calculates resources effort first, anddelegates a task to the Swarm. When the swarm reaches the location, it starts executing. Operator with nodes tries to find survivors and collect as much important information as they can. Video, images, recognized objects are continuously sending to the Cloud for additional analysis in real-time. Any information in an emergency situation can help save more humans lives and reduce risks. In this article, the multilayer distributed intelligence system architecture for emergency area scanning was designed and described. The set of terminology was proposed as well. This architecture covers different levels of tactical and operational tasks

Deep-sea hemichordates Torquaratoridae gen. sp. reach high abundance up to 12 spec. m–2 at the depths of 1830–2130 m on the slope of the Volcanologists Massif in the south-western part of the Bering Sea, dominating in the benthic community at these depths. Their abundance exceeds by two orders the values recorded earlier. In order to clarify this phenomenon, we examined the gut contents of Torquaratoridae gen. sp. The detritus particles and frustules of planktonic diatoms Thalassiosira, Coscinodiscus, Actinocyclus, Chaetoceros, Neodenticula, and Grammatophora were the most common in the gut, as well as the remains of skeletons of benthic invertebrates with little admixture of mineral particles. According to obtained data, Torquaratoridae gen. sp. are mobile deposit feeders with high selectivity to fresh phytodetritus, able to compete with holothurians occupying similar trophic niche. Unusually high abundance of acorn worms is apparently related to high organic matter flux to the seafloor as a result of spring phytoplankton bloom in the surface water layer of the Bering Sea.

Curved continuous fiber trajectories for composite plates with a bolted joint corresponding to the lines of maximum principal stresses were designed using the iterative finite-element modeling. On their basis, variable stiffness composite structures were modeled by the finite-element method, when each element was assigned variable material properties depending on the distribution of fiber trajectories. To simulate the progressive failure of the plates, a material property degradation method was employed. An analysis of progressive failure showed that it is possible to significantly increase the ultimate load and reliability of bolted joints of composite structural elements by transition from the unidirectional to a curvilinear reinforcement.

A microwave beam (wavelength 4 mm, power 150–300 kW) generates an ionization wave in air in the subthreshold field in the shape of a conglomerate of thread-like channels that moves toward the beam. The periphery of the beam refracts in the plasma of the non-self-sustained discharge in the UV halo of the thread-like discharges and self-focuses in the recombining plasma behind the front of the plasmoid that consists of thread-like channels. The self-focusing of the peripheral regions of the wave beam causes local bursts of ionization behind the front of the leading plasmoid.

The authors propose a dedicated mobile roof support for underground coal mining. Joint deformation of roof rocks and roof support is analyzed using the finite element method. The shapes and sizes of failure zones and the influence of the support on coal and host rocks are determined. The application area for the mobile roof support in underground mining is outlined, and the essentiality of the current prediction method of dynamic events during mining is substantiated. It is feasible to increase the rate of heading by means of reduction of the heading cycle duration.

This paper presents examples that characterize various aspects of the possibility of determining the phase composition of solid multielement substances and materials containing nanostructured forms of their components by a differential dissolution stoichiographic method. The use of stoichiography makes it possible to detect and quantitatively determine both known and unknown crystalline and amorphous phases of constant and variable composition without standards of solid phases. The use of stoichiographic methods and ideas of nonequilibrium thermodynamics allows one to gain fundamentally new data on solid-state transformations of multielement, multiphase substances and materials.

Abstract The article describes the parameters of maintaining the gutless symbiotrophic annelid Siboglinum fiordicum in laboratory conditions outside the marine environment for 64 days.

Herein we describe the results of our study of plasma chemical process initiated by high-power microwave pulses generated by 75/0.8 gyrotron (frequency 75 GHz, pulse duration up to 12 ms, power up to 550 kW) in mixtures of metal (Mg, Ti, Mo) and dielectric (Al2O3, AlN, B) powders. The process leads to formation of micro- and nanostructured materials and the yield is strongly affected by hydrogen-containing additives (C2B10H12, H3BO3, NaBH4) in the mixture. It was found that the process occurs in three main stages. The first initiation stage is very short (just slightly exceeds the pulse duration) and includes the absorption of microwave irradiation and the discharge proceeded as coulombic explosion. The main stage is much longer and includes decomposition of starting materials and reactions between all the components. All the tested additives prolong the main stage, in some cases by an order of magnitude or even more, and turn it into self-sustaining oscillating mode. The last one is realized most likely due to autothermic effect. As a result, the yield increases sufficiently. Finally, the decay stage is relatively short stage (up to 200 ms) following the main stage and includes irreversible cooling down of the reaction zone and deposition of the particles. The decay stage is not affected by additives. Owing to use the additives we were able to decrease the energy consumption for preparation of the materials below 1 kJ/g, which is 2–3 times lower compared to our previous results. The prepared materials were characterized by SEM, EDS and X-ray diffraction analysis and found to be mainly oxides, nitrides and borides.

The excretory system ultrastructure and immunocytochemistry have been investigated in the plerocercoid Pyramicocephalus phocarum. It has been shown that P. phocarum has independent terminal cells, cyrtocytes. The entire canal system is a single undivided syncytium, which includes nephridial funnels of the terminal tubules, and peripheral and central canals. The nephridial funnel and cyrtocyte form a filtration complex of the protonephridial type. In the caudal region, several peripheral canals open into a deep fold of the tegument, the urinary bladder. The excretory pores are separated from the tegument by annular septate desmosomes. There are no cell junctions inside the excretory system. The presence of the F-actin ring and the expression of non-synaptic serotonin in the collar area have been detected in cyrtocytes by immunocytochemistry methods.

The article shows the urgency of technological advance in coal mining in difficult geological conditions and describes the application prospects for an integrated multi-function platform in underground mining of different minerals. The international practice of mobile roof support design and creation of a work environment in mines is reviewed. The authors propose an integrated multi-function platform as a walking roof support module which ensures safe and efficient mining in difficult geological conditions. Within R&D project supported by the Foundation for Assistance to Small Innovative Enterprises in Science and Technology, Project No. 2566GS1/41340, the kinematics of the platform is developed so that to ensure uniform loading of the walking support systems owing to constructional linkage between the support units, and to provide stability of the support system on a composite topography floor thanks to four couples of hinge supports with adjustability of height and position. Arrangement of structural elements is proposed, and their kinematic linkage is described. The walking support advance algorithm is developed in the form of a working cycle. Within R&D project supported by the Russian Foundation for Basic Research, Project No. 18-37-00356, the control operation algorithm and control automation circuit are developed for the walking roof support. The automated control is integrable in the standard electrohydraulic control system of mine roof supports. As a result, the walking roof support with the automated control can be considered as a framework (a platform solution) for the robotic system engineering for safe and efficient underground mining of stratified deposits and diamond placers. The study was supported by the Russian Foundation for Basic Research, Project No. 19-35-90075-19.

The tubeworm Riftia pachyptila is a key primarily producer in hydrothermal vent communities due to the symbiosis with sulphur-oxidizing bacteria, which provide nourishment to the worm from sulphides, oxygen and carbon dioxide. These substances diffuse from the vent water into the bloodstream of the worm through their tentacular crowns, and then to the bacteria, hosted in a specialized organ of the worm, called a trophosome. The uptake rates of these substances depend on the surface/volume relationship of the tentacles. We here describe two morphotypes, ‘fat’ and ‘slim’, respectively, from the basalt sulphide-rich vents at 9 °N and 21 °N at the East Pacific Rise, and the highly sedimented, sulphide-poor vents at 27 °N in the Guaymas Basin. The ‘fat’ morphotype has a thicker body and tube, longer trunk and smaller tentacular crowns, whereas the ‘slim’ morphotype has shorter trunk, thinner body and tube, and presents longer tentacular crowns and has a higher number of tentacular lamellae. Given the dependence on sulphides for the growth of R. pachyptila, as well as high genetic connectivity of the worm’s populations along the studied localities, we suggest that such morphological differences are adaptive and selected to keep the sulphide uptake near to the optimum values for the symbionts. ‘Fat’ and ‘slim’ morphotypes are also found in the vestimentiferan Ridgeia piscesae in similar sulphide-rich and poor environments in the northern Pacific.

The task of resource saving is relevant for all transport companies and many world communities of scientists and engineers are engaged in search for ways to solve it. World railway companies, and especially large ones such as Russian Railways, are large consumers of energy resources and the problem of saving is the most urgent for them. One of directions for solving this task can be the use of an optimal energy regulation system for traction of each train – an operational rationing system. Such a task can only be solved by modelling the process of movement through the dynamic programming method. In modern conditions of development of engineering and technology, it has become possible to develop such operational standardization systems endowed with important properties: high performance, multitasking, solution accuracy, ease of use and maintenance. These requirements impose certain restrictions on the architecture of the operational rationing system. Typical system architecture should be built around a centralized node, which will act as a solver and storage, nodes for input and output of information can be geographically separated. The method of dynamic programming can be improved by using it in the process of training artificial neural networks, which will form not only a priori estimates of energy consumption for traction, but also an a posteriori estimate of train control (by a train driver or auto-driving system). Also, the use of artificial neural networks will allow us to continuously improve the method due to training using the accumulated amount of data from real trips, which will allow us to clarify the norms of energy consumption and to plan our costs in the future. The prototype of the operational standardization system was developed at the department of traction rolling stock of Russian Open Academy of Transport of Russian University of Transport and the results obtained allow us to state that the chosen approach to solving the problem of energy saving has been chosen correctly.

Objective: To develop recommendations for the management of snow clearing of street railways in urban settlements. Methods: The article analyzes the Russian regional climatic influence on the management of street railway traffic and the current maintenance of tram tracks, and the indicators to be monitored when planning the work of snow clearing equipment. The requirements for the maintenance of tram tracks in winter in heavy snowfalls and blizzards have been described. An overview of the snow clearing equipment available in the soviet and present times, as well as its application has been discussed. Results: Recommendations for the management of various types of snow clearing equipment for various types of tram tracks are given. The justifying calculations of the size of the snow clearing fleet in relation to regional climatic indicators are presented. Practical importance: The article demonstrates the preference of introduction of special rail snow clearing equipment for the tram track routine maintenance in winter, especially in snow heavy areas, both tram type based on tram dimensions and hybrid road-rail type. Practical recommendations for the conditions for the use of various types of snow clearing equipment have been developed

The study is continued of the temporal changes of the parameters of turbulent plasma density fluctuations during multi-pulse electron cyclotron (EC) heating of the plasma on the L-2M stellarator. The plasma density fluctuations with different wave vectors (k = 30, 20, 2, and 1 cm –1) in different spatial regions of the plasma column were recorded by the method of collective scattering of microwave radiation. The time dependence of plasma density fluctuations, which has a bursty shape, was analyzed, including the discharges in which the gyroresonance region was shifted by 3–4 cm from the center of the plasma column toward the inside of the torus. A comparison was made between the specificities of the evolution of plasma density fluctuations and the evolution of their statistical characteristics. It was found that the kurtosis (M4) of the scattering signals deviates from the value 3, which also occurs in bursts. During a EC heating pulse, three groups of different bursts (of signal intensity, its kurtosis and their increments) were observed. Autocorrelation analysis of density fluctuations and their increment was carried out and it showed that the half-width of the autocorrelation functions changes during multi-pulse EC heating. The probability of the initiation of bursty processes by perturbations in the near-wall plasma region is discussed.

У наведеній статті було оцінено безпеку і можливість виникнення небажаних ефектів транскраніальної магнітної стимуляції (ТМС) під час та після сеансу у хворих на розсіяний склероз (РС). Фундаментальне обстеження 80 хворих на розсіяний склероз показало, що не дивлячись на можливі деякі небажані явища, транскраніальна магнітна стимуляція, як метод неінвазивної нейромодуляції, займає важливе місце в процесі немедикаментозної реабілітації хворих на РС. Безпека ТМС включає ретельний відбір пацієнтів з дотриманням критеріїв показань і протипоказань призначення процедури, згода пацієнта на проведення ТМС, вибір протоколу стимуляції з персоніфікованим підбором параметрів, запобігання побічних явищ і моніторинг стану пацієнта в процесі проведення ТМС.

Time-dependent energy spectra of galactic cosmic rays (GCRs) carry fundamental information regarding their origin and propagation. When observed at the Earth, these spectra are significantly affected by the solar wind and the embedded solar magnetic field that permeates the heliosphere, changing significantly over an 11-year solar cycle. Energy spectra of GCRs measured during different epochs of solar activity provide crucial information for a thorough understanding of solar and heliospheric phenomena. The PAMELA experiment had collected data for almost ten years (15th June 2006 - 23rd January 2016), including the minimum phase of solar cycle 23 and the maximum phase of solar cycle 24. In this paper, we present new spectra for helium nuclei measured by the PAMELA instrument from January 2010 to September 2014 over a three Carrington rotation time basis. These data are compared to the PAMELA spectra measured during the previous solar minimum providing a picture of the time dependence of the helium nuclei fluxes over a nearly full solar cycle. Time and rigidity dependencies are observed in the proton-to-helium flux ratios. The force-field approximation of the solar modulation was used to relate these dependencies to the shapes of the local interstellar proton and helium-nuclei spectra., 9 pages, 5 figures

A way of calculating a directional flux of charged particles in near-Earth space under conditions of high anisotropy of the flux is developed. It can be used for telescope-type spectrometers capable of measuring the direction of incident particle arrival.

The gill skeleton of the enteropneust Saccoglossus mereschkowskii consists of a series of tridents. The central prong of each trident bifurcates in its ventral end. The most anterior gill skeletal element has a simple horseshoe shape. Homologues of the elements of the enteropneust gill apparatus were found in the structure of the gill apparatus of Cephalochordata. The organization of the gill skeleton of Enteropneusta and Cephalochordata can be derived from the metameric horseshoe-shaped elements. The similarity of the structure of the gill skeleton of Enteropneusta and Cephalochordata contradicts a common "upside-down theory" of the origin of Chordata.

An electronic three-phase fully fiber-optic measuring voltage transformer (FOVT) of accuracy class 0.2 for a nominal voltage of 220 kV with a digital output for operation at power system facilities, including electrical substations, is described. The operation principle of the device is based on the use of a longitudinal linear electro-optical effect (Pockels effect) for measuring AC voltage. The fiber-optic measurement scheme based on low-coherent interferometry is connected via a fiber cable to an optical high-voltage primary converter (HVPC) with an electro-optical crystal placed in it; there are no additional voltage dividers inside. The digital signal processing unit (DPU) contains optical and electronic circuits for generating, detecting, and processing an electro-optical signal. FOVT has a digital interface that complies with the IEC 61950-9-2 LE standard, and can be used as a component for the Digital Substation and Smart Power Grid technologies. The design features of the HVPC and the DPU are described and the results of the metrological characteristics of FOVT-220, based on the data obtained during the certification and pilot operation at the 220 kV electrical substation, are presented.

We present the first results of Mars neutron sounding by FREND instrument onboard ESA’s Trace Gas Orbiter data analysis. Neutron flux mapping is performed with high spatial resolution, which allows to match epithermal neutron flux variation with relief’s geomorphological structures. Local regions with suppressed neutron flux indicate the presence of considerable amount of hydrogen atoms in the surface material, which is supposedly part of water molecules. Local regions in the equatorial latitudes of the planet with significant decrease of neutron flux are discovered, which points to large mass fraction of water ice in the soil material, ranging from tens to 100 $$\%$$ . Considering high water content, these regions are named ice permafrost ‘‘oases.’’ Estimates of ice mass fraction for 7 such regions are obtained based on neutron measurements analysis and end-to-end numerical modeling of the entire physical process of neutron sounding by FREND on Mars orbit. Possible reasons for formation of such ‘‘oases’’ and their significance for future Mars exploration are discussed.

A modeling method of variable stiffness composite structures (VSCSs) with curved fiber trajectories has been developed. The fiber trajectories are aligned in the direction of maximum principal stress, and the VSCSs with variable fiber orientation and the variable fiber volume fraction are modeled on the basis of these trajectories. A material property degradation method taking into account the heterogeneity of material properties of the VSCSs is used to predict the ultimate load and model the progressive failure for a composite plate with a hole under tensile loading. It is shown that a transition from rectilinear reinforcement to curvilinear results in an increase in the ultimate load of the plate. The opportunity for simulation of a continuous fiber path for the VSCSs is presented, and the path could be used to produce the VSCSs by additive manufacturing (3D printing).

Paying attention to the quite wide spreading of precast and cast-in-situ reinforced concrete in Ukraine, it was necessary to expand the scope of application of various butt joints. In particular, the use of loop rebar joints is itself one of the main design decisions that determines the industrial implementation of construction, primarily hydraulic structures. Loop rebar joints connect elements for assembling precast-monolithic reinforced concrete elements without the use of welding. A large territory of south-western and southern parts of Ukraine is classified as seismically dangerous. The use of modern probabilistic technologies at the design and operation stages of construction projects improves the accuracy of hazardous seismic load estimates and allows to optimize the probable losses from the negative impact of earthquakes. The proper assessment of the level of seismic impact depends on knowledge of the pattern in the logarithmic decrement changes as a result of building structures and buildings damage. Available information does not give a clear understanding of this pattern. A comparative analysis of the change in the logarithmic damping decrement of vibrations because of cracking in beams with a loop joint was carried out. The loop joint was located in the clean bending zone of beam, with keyed and keyless execution of the ends of the joined elements. The data for analysis were obtained from the experiment. We use the power method to achieve the objectives − the instant load removal method. As a result the nature of the change in the logarithmic damping decrement of the beam in case of violation of the integrity of the loop joint zone was established. The values of the logarithmic decrement in the beams with key joints were comparable with the similar values obtained for beams without joints. At the same time, the absolute values of the decrement in beams with keyless loop joints were maximum in these studies .