Search

Small-conductance Ca2+-activated K+ channels (SK, KCa²) are gated solely by intracellular microdomain Ca2+. The channel has emerged as a therapeutic target for cardiac arrhythmias. Calmodulin (CaM) interacts with the CaM binding domain (CaMBD) of the SK channels, serving as the obligatory Ca2+ sensor to gate the channels. In heterologous expression systems, phosphatidylinositol 4,5-bisphosphate (PIP2) coordinates with CaM in regulating SK channels. However, the roles and mechanisms of PIP2 in regulating SK channels in cardiomyocytes remain unknown. Here, optogenetics, magnetic nanoparticles, combined with Rosetta structural modeling, and molecular dynamics (MD) simulations revealed the atomistic mechanisms of how PIP2 works in concert with Ca2+-CaM in the SK channel activation. Our computational study affords evidence for the critical role of the amino acid residue R395 in the S6 transmembrane segment, which is localized in propinquity to the intracellular hydrophobic gate. This residue forms a salt bridge with residue E398 in the S6 transmembrane segment from the adjacent subunit. Both R395 and E398 are conserved in all known isoforms of SK channels. Our findings suggest that the binding of PIP2 to R395 residue disrupts the R395:E398 salt bridge, increasing the flexibility of the transmembrane segment S6 and the activation of the channel. Importantly, our findings serve as a platform for testing of structural-based drug designs for therapeutic inhibitors and activators of the SK channel family. The study is timely since inhibitors of SK channels are currently in clinical trials to treat atrial arrhythmias. [ABSTRACT FROM AUTHOR]

Solid-state nanopore devices with plasmonic nanoantennas are powerful tools that allow for working with individual particles and molecules in solution as well as providing light-induced control of ionic current flow through them. However, the ionic current flow manipulation by light still requires high power densities and, thus, results in the optical heating of the nanopore. Here, we solve this problem by using a 5 nm nanopore in the gap of a plasmonic bow-tie nanoantenna on a SiNx membrane irradiated by a broadband spectrum of incident light. In this regime, photons are not only strongly localized around the nanopore but also efficiently excite and trap charge carriers on defect states in the band gap of the material of the nanopore walls. As a result, ionic current flow modulation is achieved with several orders of magnitude lower power densities (around 0.035 W/cm²) from a white-light lamp than in previous works employing spectrally narrow laser sources (100-105 W/cm²). The lamp irradiation causes a 21% increase in conductivity for a nanopore without a nanoantenna and a 35% increase in conductivity for a nanoantenna-decorated nanopore at the same power of irradiation. The revealed low-intensity approach for ionic current control is preferable for the study of biological objects. [ABSTRACT FROM AUTHOR]

Aims. We study a new mechanism of dust accumulation and planetesimal formation in a gravitationally unstable disk with suppressed magnetorotational instability and we compare it with the classical dead zone in a layered disk model. Methods. We used numerical hydrodynamics simulations in the thin-disk limit (FEOSAD code) to model the formation and long-term evolution of gravitationally unstable disks, including dust dynamics and growth. Results. We found that in gravitationally unstable disks with a radially varying strength of gravitational instability (GI), an inner region (of several astronomical units) of low mass and angular momentum transport is formed. This region is characterized by a low effective value for the αGI parameter, often used to describe the efficiency of mass transport by GI in young protoplanetary disks. The inner region is also similar in terms of characteristics to the dead zone in the layered disk model. As the disk forms and evolves, the GI-induced dead zone accumulates a massive dust ring, which is susceptible to the development of the streaming instability. The model and observationally inferred dust masses and radii may differ significantly in gravitationally unstable disks with massive inner dust rings. Conclusions. The early occurrence of the GI-induced dust ring, followed by the development of the streaming instability suggest that this mechanism may be behind the formation of the first generation of planetesimals in the inner terrestrial zone of the disk. The proposed mechanism, however, crucially depends on the susceptibility of the disk to gravitational instability and requires the magnetorotational instability to be suppressed. [ABSTRACT FROM AUTHOR]

The works in the field of radiation materials science of target materials of neutron sources based on the subcritical assemblies controlled by linear accelerators of electrons or protons, so-called accelerator driven systems (ADS), are reviewed. Now, electronuclear ADS systems are the prototype of safe nuclear reactors of the 5th generation. In connection with the physical start-up of the neutron source facility of the National Scientific Centre 'Kharkiv Institute of Physics and Technology' of the N.A.S. of Ukraine (NSC 'KhIPT' NASU), the target of which is fabricated from powdered tungsten covered with tantalum, the issues of preparation technology, construction, and physical and mechanical properties of W-Ta materials of targets in non-irradiated and irradiated states are considered. The nuclear-physical processes of radiation damage to the target during co-irradiation of it with both neutrons of a subcritical assembly and high-energy e- and g-beams are analyzed. The target resources of ADS systems are estimated. As noted, the difficulty of predicting the 'survivability' of the W-Ta target also relates to the fact that, except for the works carried out at the NSC 'KhIPT' NASU in 70-90th of the last century, there are no experimental works in the world on the radiation damage of reactor materials by high-energy electrons with an energy of 100 MeV and above. [ABSTRACT FROM AUTHOR]

Ground-based laser surveys of the upper parts (from the ridge crests to the border of closed forests) of six steppe slopes of the mountains of the Southern and Northern Kraka massifs (Southern Urals) on a total area of 20.82 hectares were carried out. As a result, 3584 trees were identified in all studied areas, their morphometric parameters (crown height and size) and exact geographical position were assessed with an accuracy of 3–10 cm. It was shown that the closure and density of tree stands are extremely low in the upper third of the surveyed altitudinal profiles, and a local increase in these indicators is observed only on some slopes. It is also widely noted that these characteristics of forest stands increase sharply at a distance of about 2/3rd of the length of the profiles from the ridge crests. Measurements of the depth of the soil layer showed that the soils in the upper parts of the slopes are thin (on average 7–12 cm), and their average depth reaches 29 cm only on some slopes in places where the density of forest stands increases. Soil depth on sections of profiles remote from the ridge crests 1/4th to 2/3rd of their length gradually increases and reaches average values of 20–30 cm. We associate both local and stable (in the lower part) increase in the density of forest stands in the forest–mountain steppe transition zone with the increase in the thickness of the soil layer and the volume of moisture retained by it. [ABSTRACT FROM AUTHOR]

A technology has been developed for the destruction of polycomponent materials from the apatite-nepheline ore of the Khibiny deposit to increase the completeness of the extraction of the target component. Heating particles of apatite-nepheline ore to a temperature of 600°C and then rapidly cooling them with water to a temperature of 105°C leads to the formation of a vast network of micro- and macrocracks. These cracks form along the boundaries where the components connect, effectively separating them. Under shock loading of the multicomponent material in a cascade jet mill, powerful stress concentrations arise at the bond boundaries of individual components. This stress leads to the destruction of the material precisely along these bond boundaries. These findings open up the prospect of creating a new technology for the dry processing of phosphate ores. [ABSTRACT FROM AUTHOR]

The formation of solid macroscopic grains (pebbles) in protoplanetary discs is the first step towards planet formation. We aim to study the distribution of pebbles and the chemical composition of their ice mantles in a young protoplanetary disc. We use the two-dimensional hydrodynamical code feosad in the thin-disc approximation, which is designed to model the global evolution of a self-gravitating viscous protoplanetary disc taking into account dust coagulation and fragmentation, thermal balance, and phase transitions and transport of the main volatiles (H2O, CO2, CH4, and CO), which can reside in the gas, on small dust (⁠|$\lt 1\, \mu\mathrm{ m}$|⁠), on grown dust (⁠|$\gt 1\, \mu\mathrm{ m}$|⁠) and on pebbles. We model the dynamics of the protoplanetary disc from the cloud collapse to the 500 kyr moment. We determine the spatial distribution of pebbles and composition of their ice mantles and estimate the mass of volatiles on pebbles, grown dust, and small dust. We show that pebbles form as early as 50 kyr after the disc formation and exist until the end of simulation (500 kyr), providing prerequisites for planet formation. All pebbles formed in the model are covered by icy mantles. Using a model considering accretion and desorption of volatiles on to dust/pebbles, we find that the ice mantles on pebbles consist mainly of H2O and CO2, and are carbon-depleted compared to gas and ices on small and grown dust, which contain more CO and CH4. This suggests a possible dominance of oxygen in the composition of planets formed from pebbles under these conditions. [ABSTRACT FROM AUTHOR]

Numerical results are presented for the low-temperature serrated deformation process in tension induced by a suspended load of 03Kh20N16AG6 austenitic steel and AMg5 aluminum alloy specimens in liquid helium at 4 K. In practice, large loads at cryogenic temperatures are met with liquefied gas tanks, in particular in hydrogen tanks of launch vehicles. The local one-dimensional multiparametric nonlinear mathematical model of the low-temperature serrated metal deformation process was constructed, with its adequate display and quantitative estimates based on mechanical material properties and loading system characteristics. This effect manifests the local thermomechanical metal deformation instability under adiabatic conditions. The mathematical problem was formulated as a nonlinear differential equation of second order with certain initial and other conditions. It represents the dynamic equilibrium of the specimen-loading device system and describes the process of serrated specimen deformation as the system motion. The model is specified for 03Kh20N16AG6 steel and AMg5 aluminum alloy specimens creep-tested in liquid helium. The numerical experiment demonstrated adequate accuracy with the computational method. The qualitative similarity of the process was revealed for the materials of different classes, with the strain levels achieved differing markedly. Comparative computations established that potential energy of the gravitational field induced a much larger localized deformation of the specimen than potential elastic energy, even in combination with additional factors, viz operation of an electric or hydraulic drive, when the deformation rate is two orders of magnitude higher than the standard one for static metal tests in tension. A very large strain arising and localized under slow loading relaxation inevitably fails before the serrated process is complete. [ABSTRACT FROM AUTHOR]

The sustainable development of Ulaanbaatar is closely connected with the solution of issues caused by negative environmental impacts. The findings obtained as part of the Russian Foundation for Basic Research project, a review of the literature and reference materials, and an expeditionary survey revealed the problems and prospects of the natural resource supply of the territory and the need to change the socioeconomic and geoecological situation in Ulaanbaatar. The methodology of an integrated approach, covering socioeconomic, climatic, landscape-geochemical, and water-ecological studies, enabled us to identify the heterogeneity of the suburbanized space, the risks of sociodemographic development, water supply, air pollution and soil cover, which have an adverse impact on the social and economic development of the territory. The process of expanding the suburban area of Ulaanbaatar differs from similar processes in the cities and agglomerations of Russia and Europe and is more similar to the formation of slums in the cities of Africa, Asia, and Latin America. The suburban yurt zones being created in Ulaanbaatar do not have any transport or social or engineering infrastructure, and residents suffer from diseases caused by environmental pollution and coal heating. The sustainable development of Ulaanbaatar and the surrounding area requires the development of a scheme for monitoring natural and anthropogenic changes, improving the protection system, optimizing the use of natural resources, and improving the system of settlement and management of urban areas. [ABSTRACT FROM AUTHOR]

The malfunctioning of the brain synucleins is associated with pathogenesis of Parkinson's disease. Synucleins' ability to modulate various pre-synaptic processes suggests their modifying effects on the electroencephalogram (EEG) recorded from different brain structures. Disturbances in interrelations between them are critical for the onset and evolution of neurodegenerative diseases. Recently, we have shown that, in mice lacking several synucleins, differences between the frequency spectra of EEG from different brain structures are correlated with specificity of synucleins' combinations. Given that EEG spectra are indirect characteristics of inter-structural relations, in this study, we analyzed a coherence of instantaneous values for EEGs recorded from different structures as a direct measure of "functional connectivity" between them. Methods: EEG data from seven groups of knock-out (KO) mice with combined deletions of alpha, beta, and gamma synucleins versus a group of wild-type (WT) mice were compared. EEG coherence was estimated between the cortex (MC), putamen (Pt), ventral tegmental area (VTA), and substantia nigra (SN) in all combinations. Results: EEG coherence suppression, predominantly in the beta frequency band, was observed in KO mice versus WT littermates. The suppression was minimal in MC-Pt and VTA-SN interrelations in all KO groups and in all inter-structural relations in mice lacking either all synucleins or only beta synuclein. In other combinations of deleted synucleins, significant EEG coherence suppression in KO mice was dominant in relations with VTA and SN. Conclusion: Deletions of the synucleins produced significant attenuation of intra-cerebral EEG coherence depending on the imbalance of different types of synucleins. [ABSTRACT FROM AUTHOR]

Laser-induced breakdown spectroscopy (LIBS) provides a rapid, cost-effective, and extra-sensitive analysis of geological samples to make preliminary conclusions about the presence of valuable elements up to the trace levels in the ore. We present the first results of a highly sensitive qualitative analysis of the core samples of geological ore from two boreholes in Latvia (Staicele 1, from a depth range of 794–802 m, and Garsene (Subate) 2A, from a depth range of 1102–1103 m) using LIBS. Our measurements using this technique confirmed the high iron content and indicated traces of rare and high in-demand metals (such as Ti, V, Co, Sm, etc.) in the sample from Staicele, renewing interest in studying boreholes across Latvia. The presented pilot studies demonstrated effectiveness and unique possibility in performing a very sensitive and time-saving qualitative analysis of the composition of samples of ores from the old but still valuable borehole cores by using the LIBS method. We compare these measurements with other methods of sample analysis. [ABSTRACT FROM AUTHOR]

We described the methods of combined hardening of the surface of samples made of die steel grade 3Kh2V8F. To this end, the samples were exposed to thermal-chemical treatment—boroaluminizing, and the resulting diffusion layer was modified by the method of pulse beam treatment using an electron source with a plasma cathode. The study aims to investigate local structural-phase transformations of the boride diffusion layers due to high-speed heating by a millisecond duration electron beam. The diffusion layer structures after boroaluminizing and subsequent pulse beam treatment were compared. In addition, microhardness and surface topography were studied, and the phase state of the diffusion layer was assessed before and after electron beam treatment. [ABSTRACT FROM AUTHOR]

The article presents the results of assessing the effect of humic acids, taken at a concentration of 250 ppm, on the process of induced phytoextraction of heavy metals from soils selected near Norilsk. Phytoextraction was carried out by different types of marigold plants: Tagetes patula and Tagetes erecta. The studies were carried out in greenhouse conditions under controlled spectral illumination (light culture). The experiment lasted 21 days. A time range of vegetation period was chosen due to a short summer period typical of the study region, where it is more rational to keep records of the systemic removal of toxicants from contaminated soils by several cycles of their sowing/cutting per season, already at the juvenile phase of ontogenesis. For elemental analysis, the method of atomic emission spectrometry with inductively coupled plasma was used. To assess the level of efficiency of metal accumulation, the authors developed and used the original computing neural network CompNN, which allows calculating the cognitive significance index (CSI) based on empirical data on the accumulation of toxicants, both in shoots and roots of plants. The study results showed that the introduction of an organic additive in the form of humic acids into the soil led to inhibition of the growth of the above-ground part of T. patula. As for T. erecta, the rate of accumulation of green plant biomass did not change when humic acids were added. The decrease in the biomass of shoots of T. patula plants is explained by an increase in the accumulation of metals for different experiment variants by 91.6% on average. The content of metals in the shoots of T. erecta under the influence of humic acids, on the contrary, decreased by 17.3% on average. A similar result was also observed in the root zone: the trend of change in the fixation of metals for both plant species was 40.8 and 10.8%, respectively. Calculation of CSI indices also showed that the addition of humic acids in T. patula increases the intensity of metal accumulation from the soil in its biomass in all variants, while in T. erecta, on the contrary, it decreases. The performed cluster analysis demonstrated the fixation of metals in the main buffer zone of plants and also made it possible to isolate nickel into a separate homogeneous series. Based the distribution of this element in the shoots during experiment variants, it was shown that it is closely associated with copper. The correlation coefficients of their accumulation with the CSI index in the shoots of both plants were r = 0.82, 0.87 for Cu and r = 0.87, 0.83 for Ni. The proximity of these values indicates the priority nature of the accumulation of these metals in the plant biomass of marigolds and also characterizes the manifestation of certain interactions between them in contaminated soil by the type of antagonism or synergism. [ABSTRACT FROM AUTHOR]

Purpose. Development of a mathematical model for predicting critical deviations of furnace processes during the operation of anthracite boilers converted to burning sub-bituminous coal, including in non-design modes of operation. Verification of the calculation model of the TPP-210A boiler of the 300 MW power unit on the design fuel – anthracite for further analysis of its operation on sub-bituminous coal. Methodology. Modelling of solid fuel combustion was performed with the help of finite-element CFD models of the boiler unit in the ANSYS-Fluent software complex with the determination of the relevant characteristics of the boiler. Findings. Finite-element CFD models were developed according to the working drawings of the TPP-210A boiler and its burner device, reconstructed for burning sub-bituminous coal. Verification of the results of CFD modeling was carried out for the case of burning the design fuel – anthracite in the design operating modes. It is shown that the discrepancy between the results and the experiment does not exceed 6.5 %, which allows the use of the developed computer model for simulating the burning of subbituminous coal, including in non-design operating modes. The obtained results are the basis for further calculations of the operation of the TPP-210A boiler of the 300 MW power unit on sub-bituminous coal with the determination and minimization of the factors of critical deviations of furnace processes that lead to thermal damage of wall screens. Originality. For the first time, CFD modelling has taken into account all the design features of the burner devices of the TPP210A boiler, reconstructed for burning sub-bituminous coal with the introduction of a steam ejector of a high-concentration dust pipe under rarefaction to the central air channel. For the first time, the distribution of thermal resistances has been applied as boundary conditions on the walls of the fuel tank for the case of burning sub-bituminous coal. The validity of these approaches was confirmed by the verification of the results. Practical value. The verified computer model of the TPP-210A boiler of the 300 MW power unit converted to burning sub-bituminous coal will allow determining and minimizing the factors of critical deviations of furnace processes which lead to thermal damage of wall screens. This will contribute to increasing the reliability and improving the technical and economic indicators of the boilers of the Trypilska TPP, where 3 such boilers are operating, and other power plants (Zmiyivska, Kryvorizka, Prydniprovska), where similar anthracite boilers are planned to be converted to sub-bituminous coal. [ABSTRACT FROM AUTHOR]

The effect of thermal exposure under high vacuum conditions on the chemical composition of the surface layers of the VT6 alloy with the mixed implantation of N+ ions by a carbon film is investigated. It is shown that under the conditions of thermal exposure the change in the concentration profiles of the distribution of elements is determined by the processes of chemical interaction, in which the diffusion of carbon and nitrogen into deeper layers does not occur. On the contrary, their concentration decreases and this is due to the formation of volatile compounds CO, CO2, or (CH)2 under thermal exposure. Titanium in the surface analyzed layer is in an oxidized state with various degrees of oxidation. Up to a depth of about 10 nm, the oxidation states of titanium are Ti4+ and Ti3+; in the transition region of the film/substrate, Ti2+. [ABSTRACT FROM AUTHOR]

Simple Summary: This study addresses the global healthcare challenge of cancer by investigating hereditary cancer syndromes (HCS) and their genetic underpinnings. Using a multigene hereditary cancer panel, we examined Russian patients with suspected HCS, revealing that 21.6% had pathogenic or likely pathogenic genetic variants. Predominant mutations were found in BRCA1/BRCA2, CHEK2, and ATM genes, and we identified 16 previously undescribed variants in MUTYH, GALNT12, MSH2, MLH1, MLH3, EPCAM, and POLE genes. Our findings underscore the importance of comprehensive genetic testing for personalized cancer prevention and treatment. This research contributes essential genetic insights, particularly in regions like Russia where epidemiological data are limited, establishing the way for improved understanding and management of hereditary cancer syndromes. Cancer is a major global public health challenge, affecting both quality of life and mortality. Recent advances in genetic research have uncovered hereditary cancer syndromes (HCS) that predispose individuals to malignant neoplasms. While traditional single-gene testing has focused on high-penetrance genes, the past decade has seen a shift toward multigene panels, which facilitate the analysis of multiple genes associated with specific HCS. This approach reveals variants in less-studied gene regions and improves our understanding of cancer predisposition. In a study composed of Russian patients with clinical signs of HCS, we used a multigene hereditary cancer panel and revealed 21.6% individuals with pathogenic or likely pathogenic genetic variants. BRCA1/BRCA2 mutations predominated, followed by the CHEK2 and ATM variants. Of note, 16 previously undescribed variants were identified in the MUTYH, GALNT12, MSH2, MLH1, MLH3, EPCAM, and POLE genes. The implications of the study extend to personalized cancer prevention and treatment strategies, especially in populations lacking extensive epidemiological data, such as Russia. Overall, our research provides valuable genetic insights that give the way for further investigation and advances in the understanding and management of hereditary cancer syndromes. [ABSTRACT FROM AUTHOR]

The article presents a numerical technique for solving equations that describe the process of radiative transfer in protostellar disks. The proposed method expands the previously developed original computational gas-dust model of the star formation process using multi-level nested grids, which takes into account thermal radiation. In this article, we will consider three numerical schemes for three model equations describing the heat equation, the equilibrium and nonequilibrium radiative transfer models. All three model equations are parabolic, which, with the requirement to use a hydrodynamic time step, leads to the use of implicit schemes. In this work, to solve systems of linear algebraic equations, we used a fairly robust BiCGStab scheme with Jacobi preconditioning. Model problems demonstrate the robustness of the developed methodology. [ABSTRACT FROM AUTHOR]

Direct imaging observations of planets revealed that wide-orbit (>10 au) giant planets exist even around subsolar-metallicity host stars and do not require metal-rich environments for their formation. A possible formation mechanism of wide-orbit giant planets in subsolar-metallicity environments is the gravitational fragmentation of massive protoplanetary discs. Here, we follow the long-term evolution of the disc for 1 Myr after its formation, which is comparable to disc lifetime, by way of a two-dimensional thin-disc hydrodynamic simulation with the metallicity of 0.1  |$\rm {Z}_{\odot }$|⁠. We find a giant protoplanet that survives until the end of the simulation. The protoplanet is formed by the merger of two gaseous clumps at ∼0.5 Myr after disc formation, and then it orbits ∼200 au from the host star for ∼0.5 Myr. The protoplanet's mass is ∼10 MJ at birth and gradually decreases to 1 MJ due to the tidal effect from the host star. The result provides the minimum mass of 1 MJ for the protoplanet in our simulation. We anticipate that the mass of a protoplanet experiencing reduced mass loss thanks to the protoplanetary contraction in higher resolution simulations can increase to ∼10 MJ. We argue that the disc gravitational fragmentation would be a promising pathway to form wide-orbit giant planets with masses of ≥1 MJ in subsolar-metallicity environments. [ABSTRACT FROM AUTHOR]

Using the example of an electron source with a plasma cathode based on a low-pressure arc discharge with grid stabilization of the cathode/emission plasma boundary and an open anode/beam plasma boundary, a mechanism is described for increasing the electrical strength of a high-voltage accelerating gap by introducing a series negative current feedback (NCF) in the accelerating interval, which makes it possible to level out uncontrolled bursts of the beam current during its pulse. The introduction of NCF is achieved by using a special electrode in the space of the plasma emitter connected through a resistance to the anode of the arc discharge, and the main task of which is to intercept accelerated ions penetrating into the emitter from the high-voltage accelerating gap, due to which the current of electron emission from the arc discharge plasma decreases by a value proportional to the ion current in the accelerating gap. Since most sources and accelerators of electrons with plasma cathodes based on discharges of various types have a similar principle of operation, the use of this method will not only expand the limiting parameters of the generated electron beams, but also increase the stability of the operation of such electron sources, and, accordingly, beam irradiation of various materials and products. [ABSTRACT FROM AUTHOR]

In a source with a plasma grid cathode based on a low-pressure arc with layer stabilization of the emission plasma boundary, a method of combined control of the electron beam current during a submillisecond pulse of its generation has been developed. A diagram of power supplies and their connection to the electrodes of the electron source is presented, as well as oscillograms demonstrating the possibility of an extended range of control of the power of the electron beam by changing the concentration of the emission plasma by adjusting the discharge current, with a simultaneous change in the width of the ion layer at the surface of the emission grid due to grid control when applying a potential bias to an additional grid electrode. Expanding the power range of the generated beam opens up new opportunities for the use of electron sources of this class for both scientific and industrial purposes. [ABSTRACT FROM AUTHOR]

An experimental and theoretical study is carried out to control the distribution of electron beam current density in a SOLO source with a plasma cathode based on a low-pressure arc discharge with grid stabilization of the emission plasma boundary. It has been shown experimentally and numerically that using a control electrode in the form of a disk (disks) in the plasma cathode and a leading magnetic field, it is possible to change the distribution of the emission current density and, accordingly, the energy density of the electron beam on the collector. Theoretical study using the envelope method, "particle-in-cells" method and drift-diffusion models shows good agreement with experiment. [ABSTRACT FROM AUTHOR]

The results of experiments on the generation of a radially converging electron beam in a source with a multiarc grid plasma cathode are presented. The beam was generated at an accelerating voltage of up to 50 kV, a discharge current of 50–300 A, a pulse duration of 50–500 μs, and a pressure of 20–50 mPa. The operation modes of the electron source are compared, and the design of the plasma emitter is modernized to increase the current density to a level sufficient to modify the surface of the collector material. [ABSTRACT FROM AUTHOR]

The results of measuring the current density distribution of a wide-aperture electron beam outputted into the atmosphere and generated in an accelerator based on a non-self-sustaining high-voltage glow discharge (HVGD) are described. A self-sustained glow wire discharge with a hollow cathode was used to generate the emission plasma. A comparison was made of the inhomogeneity of the beam current density in the atmosphere in continuous and pulse-periodic emission generation modes. [ABSTRACT FROM AUTHOR]

On the example of an electron source with a plasma cathode based on a low-pressure arc discharge with grid stabilization of the cathode/emission plasma boundary and an open anode/beam plasma boundary, a new method of electron beam formation is described, in which an additional auxiliary arc discharge is ignited in the anode region of the source. Initiation of the discharge was carried out by the electron beam, and the discharge itself was supported by an additional power source, which represented a low-impedance artificial forming line included in the collector circuit. The dependence of the current in the accelerating gap on the current flowing in the collector circuit was obtained in the absence of the arc discharge current of the plasma cathode. [ABSTRACT FROM AUTHOR]

Some physical principles and design solutions that were used in the creation and modernization of electron sources with grid plasma emitters and which made it possible to improve their parameters and operational properties are considered. As an example, the main characteristics of modernized low-energy (up to 25 keV), medium-energy (up to 100 keV) and relatively high-energy (up to 200 keV) electron sources with grid plasma emitters are given, which are distinguished by a unique set of basic parameters, which allows them to be used both in scientific, and for technological purposes. The prospects for further development of such sources are shown and the scope of their application is considered. [ABSTRACT FROM AUTHOR]

In a source based on a non-self-sustaining high-voltage glow discharge with the extraction of a large cross section electron beam (2900 cm2) into the atmosphere, the dynamics of the anode plasma during the generation period of an auxiliary glow wire discharge with a hollow cathode is demonstrated. A repetitively pulsed generation mode with a frequency of 10 kHz was used. The features of the formation and evolution of the auxiliary discharge anode plasma were studied by measuring the distribution of the electron beam current density in the atmosphere. By applying a negative potential bias to the anode grid by (50–200 V) relative to the walls of the vacuum chamber, the possibility of increasing the electron beam extraction coefficient into the atmosphere during the discharge generation pause is shown. New modes of electron beam generation and its more efficient extraction into the atmosphere open new prospects for using electron sources of this type both in science and in industrial applications. [ABSTRACT FROM AUTHOR]

We consider the possibility of modifying the adhesive properties of polyethylene films by an electron beam in the atmosphere to produce composite materials. The modification was carried out on a wide-aperture (750 × 150 mm) low-energy (up to 200 keV) electron accelerator DUET with a grid plasma cathode based on a low-pressure arc and the output of a submillisecond beam of large cross-section into the atmosphere. By the method of studying the wetting edge angle, it was determined that the modification of polyethylene films in various radiation intervals improves adhesive properties, and the edge angle was reduced from 101° of the original to 65° of the modified ones. Infrared spectroscopy and scanning electron microscopy revealed the formation of oxygen-containing (C=O, C–O) functional groups and an increase in the relative intensity of the absorption bands, which indicates a chemical change in the structure of the surface of the material, contributing to the improvement of adhesive properties. The method of atomic force microscopy revealed a decrease in the greatest height of profile irregularities from 125 to 40.4 nm, which contributes to an increase in the contact area of the adhesive with the surface. Experiments on modification of polyethylene films by a large-section electron beam with atmospheric discharge confirm the possibility of using installations of this type to improve adhesive properties and create composite materials based on them. [ABSTRACT FROM AUTHOR]

The effect of salts of humic (HA) and fulvic (FA) acids extracted from ultradispersed humate-sapropel suspension on the growth and development of four basil varieties used for medicinal purposes, as well as on the content of microelements in the above-ground parts of these plants, was studied under conditions of a complete photoculture and a poor nutrient provision. The experiment included midripening Green Large and early-ripening Emily, Lemona, and Marian basil varieties. Plants were grown in a closed grow box for 50 days. Seeds were sown in a soil mix consisting of vermiculite (50%) and peaty-gley soil (50%). The total content of organic matter and Ntotal in this soil mix was 30.4 and 1.4%, respectively; the content of labile forms of P2O5 and exchange K2O was 88.0 and 82.0 mg/kg, respectively; pHKCl was 5.57. The experimental scheme included the following variants: control (1.0 N Knop's solution) and 0.01% solutions of HA or FA salts. The treatment of plants was performed by a single under-root application and a weekly spraying of leaves. According to the performed morphometric and chemical analyses, the best results were shown by var. Lemona plants, whose height and biomass in the treated variant did not differ from the control values (29.75 and 29.00 mg, respectively). Treated plants of this variety also demonstrated insignificant reduction of their photosynthesis efficiency measured by a SPAD optic chlorophyll counter (31.98 relative units on average vs. 35.54 relative units in the control) that indicated the presence of a variety-specific response to the use of such an approach. The least differences between the experimental and control variants observed for the var. Lemona evidenced to the ability of both humic acid fractions to mobilize microelements for the growth of a plant biomass and change of its biochemical composition. [ABSTRACT FROM AUTHOR]

FU Orionis type objects (fuors) are characterized by rapid (tens to hundreds years) episodic outbursts, during which the luminosity increases by orders of magnitude. One of the possible causes of such events is a close encounter between stars and protoplanetary disks. Numerical simulations show that the fuor-like outburst ignition requires a very close encounter ranging from a few to a few tens of astronomical units. In contrast, the observed stellar objects in fuor binaries are usually hundreds of astronomical units apart. Simple mathematical estimates show that if such a close approach took place, the binary stellar components would have an unrealistic relative velocity, at least an order of magnitude greater than the observed velocity dispersion in young stellar clusters. Thus, the bursts are either triggered with a certain delay after passage of the periastron or their ignition does not necessary require a close encounter and hence the outburst is not caused by the primordial gravitational perturbation of the protoplanetary disk. In this work, an encounter of a star surrounded by a protoplanetary disk with a diskless external stellar object was modeled using numerical hydrodynamics simulations. We showed that even fly-bys with a relatively large periastron (at least 500 AU) can result in fuor-like outbursts. Moreover, the delay between the periastron passage and the burst ignition can reach several kyr. It was shown for the first time by means of numerical modeling that the perturbation of the disk caused by the external object can trigger a cascade process, which includes the development of the thermal instability in the innermost disk followed by the magneto-rotational instability ignition. Because of the sequential development of these instabilities, the rapid increase in the accretion rate occurs, resulting in the luminosity increase by more than two orders of magnitude. [ABSTRACT FROM AUTHOR]

Inactivation of the Snca gene in young mice by chronic injections of tamoxifen (TAM), a selective estrogen receptor modifier, has been shown to decrease the level of alpha-synuclein, a key peptide in the pathogenesis of Parkinson's disease. In young mice, different time courses of the effect were observed in different brain areas, meaning associated disturbances in the intracerebral relations, namely in brain function after TAM-induced synucleinopathy. Methods: We analyzed electroencephalogram (EEG) coherence ("functional connectivity") between the cortex (MC), putamen (Pt), and dopamine-producing brain regions (ventral tegmental area, VTA, and substantia nigra, SN) in two groups of two-month-old male mice. We compared EEG coherences in the conditional knockout Sncaflox/flox mice with those in their genetic background (C57Bl6J) one, two, and three months after chronic (for five days) intraperitoneal injections of TAM or the vehicle (corn oil). The EEG coherences in the TAM-treated group were compared with those in the alpha-synuclein knockout mice. Results: A significant suppression of EEG coherence in the TAM-treated mice versus the vehicle group was observed in all inter-structural relations, with the exception of MC-VTA at one and three months and VTA-SN at two months after the injections. Suppressive changes in EEG coherence were observed in the alpha-synuclein knockout mice as well; the changes were similar to those in TAM-treated mice three months after treatment. Conclusion: our data demonstrate a combined time-dependent suppressive effect induced by TAM on intracerebral EEG coherence. [ABSTRACT FROM AUTHOR]

We study the effect of the implantation of N+ ions on the chemical composition and atomic structure of the surface layers of VT6 titanium alloy. Nitrogen is accumulated in the surface layers up to concentrations of 30 at % or more, and chemical compounds of titanium nitride TiN are formed as phase inclusions. Presumably, this phenomenon is attributed to certain chemical processes, particularly, the chemical reactivity of titanium atoms and their propensity to interact with nitrogen atoms. Although the integral concentration of oxygen in the surface layers decreases under ion bombardment due to sputtering, oxidation of the components of the VT6 titanium alloy is observed in deeper layers. Oxygen from both the natural-oxide layer and the residual atmosphere in the vacuum chamber, penetrating deeper into surface layers during irradiation, is involved in the oxidation of titanium-alloy components. The accumulation of nitrogen, the formation of titanium nitrides, and the oxidation of the components of the VT6 titanium alloy testify to the significant role of chemical processes in the formation of the structural-phase state of the surface layers of the VT6 titanium alloy under N+-implantation conditions. [ABSTRACT FROM AUTHOR]

The human ether-a-go-go-related gene (hERG) not only encodes a potassium-selective voltage-gated ion channel essential for normal electrical activity in the heart but is also a major drug anti-target. Genetic hERG mutations and blockage of the channel pore by drugs can cause long QT syndrome, which predisposes individuals to potentially deadly arrhythmias. However, not all hERG-blocking drugs are proarrhythmic, and their differential affinities to discrete channel conformational states have been suggested to contribute to arrhythmogenicity. We used Rosetta electron density refinement and homology modeling to build structural models of open-state hERG channel wild-type and mutant variants (Y652A, F656A, and Y652A/F656 A) and a closed-state wild-type channel based on cryo-electron microscopy structures of hERG and EAG1 channels. These models were used as protein targets for molecular docking of charged and neutral forms of amiodarone, nifekalant, dofetilide, d/l-sotalol, flecainide, and moxifloxacin. We selected these drugs based on their different arrhythmogenic potentials and abilities to facilitate hERG current. Our docking studies and clustering provided atomistic structural insights into state-dependent drug–channel interactions that play a key role in differentiating safe and harmful hERG blockers and can explain hERG channel facilitation through drug interactions with its open-state hydrophobic pockets. [ABSTRACT FROM AUTHOR]

A systematic study of the influence of various types of mechanical action on magnetic properties and energy losses during remagnetization in electrical steels was carried out. Using a specially designed and manufactured experimental setup, samples of various types of electrical steels were studied at magnetization reversal frequencies of up to 5 kHz and magnetic induction amplitudes of up to 1.9 T. It was found that the deterioration of magnetic properties occurs to a lesser extent during the manufacture of samples by waterjet cutting compared to laser processing. It was shown that as a result of heat treatment at 900°C in vacuum, the magnetic properties are restored to their original values. The experimental results of measuring energy losses during frequency magnetization reversal were compared with theoretical models. [ABSTRACT FROM AUTHOR]

The stress-strain state of earth-fill dams with impervious asphalt concrete and clay-cement concrete diaphragms is discussed based on the results of field observations. [ABSTRACT FROM AUTHOR]

Methods for controlling the electron beam power in a source based on a low-pressure arc discharge with layer stabilization of the emission plasma boundary are described. The control is carried out by the method of amplitude and latitude modulation within the duration of the submillisecond beam current pulse with a time resolution of 10 μs. Two ways to control the power of the electron beam are implemented: the first one is based on changing the concentration of the emission plasma by modulating the arc discharge current and the second method uses grid control (the mode of operation of the plasma triode) at the constant discharge current. Simplified diagrams of the power supply sources of the discharge and intergrid control voltage, typical oscillograms of the main currents of the discharge system, a graph of a quick-acting power change, and a control characteristic of a plasma triode are presented. [ABSTRACT FROM AUTHOR]

Nitrogen vacancy (NV) centers are a major platform for the detection of nuclear magnetic resonance (NMR) signals at the nanoscale. To overcome the intrinsic electron spin lifetime limit in spectral resolution, a heterodyne detection approach is widely used. However, application of this technique at high magnetic fields is yet an unsolved problem. Here, we introduce a heterodyne detection method utilizing a series of phase coherent electron nuclear double resonance sensing blocks, thus eliminating the numerous Rabi microwave pulses required in the detection. Our detection protocol can be extended to high magnetic fields, allowing chemical shift resolution in NMR experiments. We demonstrate this principle on a weakly coupled 13C nuclear spin in the bath surrounding single NV centers, and compare the results to existing heterodyne protocols. Additionally, we identify the combination of NV-spin-initialization infidelity and strong sensor-target-coupling as linewidth-limiting decoherence source, paving the way towards high-field heterodyne NMR protocols with chemical resolution. Heterodyne detection is vastly used to overcome the intrinsic electron spin lifetime limiting the spectral resolution in NMR experiments based on nitrogen vacancy platforms, but the application of this technique at high magnetic fields is yet a challenge. The authors introduce heterodyne detection method applicable at high magnetic fields. [ABSTRACT FROM AUTHOR]

Cardiac function is tightly regulated by the autonomic nervous system (ANS). Activation of the sympathetic nervous system increases cardiac output by increasing heart rate and stroke volume, while parasympathetic nerve stimulation instantly slows heart rate. Importantly, imbalance in autonomic control of the heart has been implicated in the development of arrhythmias and heart failure. Understanding of the mechanisms and effects of autonomic stimulation is a major challenge because synapses in different regions of the heart result in multiple changes to heart function. For example, nerve synapses on the sinoatrial node (SAN) impact pacemaking, while synapses on contractile cells alter contraction and arrhythmia vulnerability. Here, we present a multiscale neurocardiac modelling and simulator tool that predicts the effect of efferent stimulation of the sympathetic and parasympathetic branches of the ANS on the cardiac SAN and ventricular myocardium. The model includes a layered representation of the ANS and reproduces firing properties measured experimentally. Model parameters are derived from experiments and atomistic simulations. The model is a first prototype of a digital twin that is applied to make predictions across all system scales, from subcellular signalling to pacemaker frequency to tissue level responses. We predict conditions under which autonomic imbalance induces proarrhythmia and can be modified to prevent or inhibit arrhythmia. In summary, the multiscale model constitutes a predictive digital twin framework to test and guide high‐throughput prediction of novel neuromodulatory therapy. Key points: A multi‐layered model representation of the autonomic nervous system that includes sympathetic and parasympathetic branches, each with sparse random intralayer connectivity, synaptic dynamics and conductance based integrate‐and‐fire neurons generates firing patterns in close agreement with experiment.A key feature of the neurocardiac computational model is the connection between the autonomic nervous system and both pacemaker and contractile cells, where modification to pacemaker frequency drives initiation of electrical signals in the contractile cells.We utilized atomic‐scale molecular dynamics simulations to predict the association and dissociation rates of noradrenaline with the β‐adrenergic receptor.Multiscale predictions demonstrate how autonomic imbalance may increase proclivity to arrhythmias or be used to terminate arrhythmias.The model serves as a first step towards a digital twin for predicting neuromodulation to prevent or reduce disease. [ABSTRACT FROM AUTHOR]

Biomodified mineral fertilizers (BMFs) were produced by enriching the ammophos fertilizer with PGPR Bacillus velezensis BS89 with the use of two technologies: BMF 1, the ammophos fertilizer with the addition of spores of Bacillus velezensis BS89 on a dry carrier (diatomite); and BMF2, ammophos granules treated with spores of Bacillus velezensis BS89 in a cell suspension. The effects of BMFs on maize growth and productivity and the rhizosphere bacterial community were assessed. BMFs significantly increased maize growth, dry matter, minerals, starch and protein contents in maize grain. The application of biomodified mineral fertilizers resulted in the significant increase in the yield and some parameters of maize plants such as ear length and number of kernels in the row. The yield was increased by 7.5–7.6%, ear length by 9%, and number of kernels in the row by 6.7–7%, as compared with ammophos. However, we found no considerable differences in the composition of the bacterial community of the maize rhizosphere after the use of BMFs as compared with the use of ammophos at the level of the phyla, which was confirmed by the ecological indices of biodiversity: the Shannon index and the Simpson index. Comparison of the experimental variants with bulk soil showed differences in the microbiome composition of the dominant bacterial phyla. A greater abundance of Proteobacteria and Bacteroidetes and a lower abundance of Chloroflexi was registered in bulk soil as compared with the other experimental variants where maize plants were present. The highest percentage (5.3%) of unidentified taxonomic phyla was also found in bulk soil. Our studies showed that maize is the main structuring factor during formation of the microbiome composition in the rhizosphere. The application of biomodified fertilizers BMF1 and BMF2 considerably increased the abundance of bacteria representing the minority of the community, namely, those from the phyla Verrucomicrobia, Chloroflexi, Planctomycetes, Proteobacteria, Firmicutes and Chlamydiae, as compared with the use of ammophos. Thus, the application of biomodified mineral fertilizers is a promising agronomic and ecological strategy for boosting maize yield and the quality of grain under field conditions. [ABSTRACT FROM AUTHOR]

The potentiodynamic method was used to study the influence of the cadmium complex of nitrilo-tris-methylenephosphonic acid Na4[Cd(H2O)N(CH2PO3)3]·7H2O on the corrosion-electrochemical behavior of low-carbon steel in neutral aqueous media in the presence of Cl ions-. The composition and structure of passive films formed at different potentials and composition of the medium were studied by X-ray photoelectron spectroscopy with layer-by-layer etching. When the content of Cl– ions up to 20 mg/dm3 Na4[Cd(H2O)N(CH2PO3)3]·7H2O at a concentration of 0.025–1.00 g/dm3 acts as a corrosion inhibitor, reducing the current density of anodic dissolution of the metal, and, at a concentration of more than 1.00 g/dm3, encouraging corrosion. The minimum corrosion rate is achieved at a concentration of Na4[Cd(H2O)N(CH2PO3)3]·7H2O 0.15 g/dm3 regardless of the concentration of Cl– ions. At Cl– ion concentrations of 50 mg/dm3 and more, Na4[Cd(H2O)N(CH2PO3)3]·7H2O is ineffective as a corrosion inhibitor. [ABSTRACT FROM AUTHOR]

The development of accelerated test methods can significantly reduce the time required to create reliable equipment. A laboratory setup has been created for the wear testing of samples made from various materials while in motion within an abrasive mass. This method was used to simultaneously evaluate the wear resistance of different materials (steel St. 3, steel 40Kh, steel 45, steel 65G) under identical wear conditions. The dependence of the relative wear resistance of the samples on the rotor speed of the equipment was determined. To assess the influence of regime parameters on material wear, studies were conducted using a centrifugal mill. The wear of the working surface of the mill's accelerating elements occurs due to the material sliding over the blades. Single-factor studies were carried out to determine the intervals and levels of factor variation, and the experiment plan matrix 33 was implemented. Mathematical wear models were derived for the flat radial accelerating elements of the centrifugal mill, all made from steel grades with different hardness levels. Graphical analysis of the mathematical models is presented in the figures. The rotor speed was found to have the greatest influence on the wear intensity of the accelerating elements (blades), followed by the diameter of the initial particles and the grinder's performance. [ABSTRACT FROM AUTHOR]

A new method is presented for increasing the coefficient of electron beam extraction into the atmosphere for accelerators with a non-self-sustained high-voltage glow discharge, which is characterized by high-frequency (tens of kilohertz) generation of an auxiliary discharge. An increase in the efficiency of beam extraction into the atmosphere is achieved by using a pulsed auxiliary glow discharge of the orbitron type, also called wire discharge, and by controlling the pulse duty factor of this discharge while stabilizing the average value of its current. Using the example of the accelerator under study, the possibility of increasing the output coefficient by 0.3 relative to the mode with direct current is shown. [ABSTRACT FROM AUTHOR]

A niobium film on an AISI 5135 steel substrate was exposed to submillisecond pulsed electron-beam irradiation with controlled energy modulation within a pulse to increase the film–substrate adhesion. This modulated irradiation made it possible to dope the steel-surface layer with Nb through film dissolution in the layer, for which optimum irradiation conditions were chosen from experiments and a mathematical simulation. The irradiated system was tested for surface hardness and wear, and its surface structure and elemental composition were analyzed. The results demonstrate that the microhardness of the irradiated system is much higher and that its wear rate is much lower compared to the initial state. [ABSTRACT FROM AUTHOR]

Plant roots secrete various organic substances into the rhizosphere, which are a source of nutrition for microorganisms and largely determine the nature of plant–microbe interactions. The composition of the main fractions of root exudates in ten modern varieties of wheat was determined: the contents of amino acids, organic acids, and sugars were analyzed. Reliable qualitative and quantitative differences between varieties for individual components of exudates were revealed, which determined the peculiarities of cultivar clustering on this trait. Relationships between exudation and the effectiveness of plant interaction with the growth-promoting rhizobacterium Pseudomonas fluorescens SPB2137 and the phytopathogenic fungus Fusarium culmorum 30 in laboratory systems, as well as with the resistance of the varieties to diseases in the field, were found. The number of P. fluorescens SPB2137 in the root zone positively correlated with the amounts of many amino acids, as well as maltose, secreted by the roots. The stimulating effect of rhizobacteria on root growth positively correlated with the amount of released glucose and melibiose. A relationship between the nature of root exudation and root colonization or the susceptibility of the varieties to F. culmorum 30 was not found. An analysis of the correlations between the incidence of wheat varieties in the field and the intensity of exudation of certain substances, as well as with the biocomposition index of amino acid exudation, was carried out. The role of root exudate components in the formation of effective plant-microbial systems is discussed. [ABSTRACT FROM AUTHOR]

The thermal instability of accretion disks is widely used to explain the activity of cataclysmic variables, but its manifestation in gas and dust disks in young stars has been studied in less detail. A semi-analytical stationary model is presented for calculating the equatorial temperature of a gas and dust disk around a young star. The model considers the opacity caused by dust and gas, as well as the evaporation of dust at temperatures above 1000 K. Using this model, the distributions of the equatorial temperature of the gas and dust disk are calculated under various assumptions on the source of opacity and the presence of dust. It is shown that when all the above processes are considered, the thermal balance equation in the region AU has multiple temperature solutions. Thus, the conditions for thermal instability are satisfied in this region. As an illustration of the possible influence of instability on the nature of accretion in a protoplanetary disk, we consider a viscous disk model with -parametrization of turbulent viscosity. It is shown that in such a model a non-stationary mode of disk evolution is realized with alternating phases of accumulation of matter in the inner disk and phases of its rapid accretion onto the star, which leads to a burst character of accretion. The results obtained indicate the need to take this instability into account when modeling the evolution of protoplanetary disks. [ABSTRACT FROM AUTHOR]

The preoperative diagnostics of medullary thyroid carcinoma (MTC), including the measuring of the blood calcitonin level, has a number of limitations. Particular focus has recently been placed on the role of miRNAs in the development of various malignant tumors; a comparative analysis of accuracy of the existing methods for MTC diagnosis with a novel diagnosis method, evaluation of the miRNA-375 expression level, was performed in this study. The expression level of miRNA-375 in cytology samples from 555 patients with the known histological diagnosis, including 41 patients with confirmed postoperative diagnosis of MTC, was assessed. The diagnostic parameters of the basal calcitonin level, calcitonin in wash-out fluid from the FNAB needle, and miRNA-375 were compared. An assessment of the miRNA-375 expression level made it possible to detect all the MTC samples with a 100% accuracy among all the 555 cytology specimens, as well as in non-informative FNAB specimens, and specimens from the ipsilateral thyroid lobe. Parameters such as sensitivity, specificity, PPV, and NPV were 100%. The miRNA-375 level, unlike calcitonin, does not correlate with tumor volume, so it does not have the so-called "gray zone". An assessment of the miRNA-375 expression allows one to accurately distinguish MTC from other malignant and benign thyroid tumors. [ABSTRACT FROM AUTHOR]