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An investigation is performed of the effect the treatment of a pulsed plasma flow has on samples of two shapes (flat and cylindrical) made of structural steels (St45, 40Kh, 65G, ShKh15, 40KhN2MA). Processing is done under different conditions with varying parameters (pulse duration, capacitor bank charging voltage, and the type of working gas). Data show that after treatment, corrosion resistance increases for most of the considered grades of steel. The most effective processing parameters are established for each grade of steel. [ABSTRACT FROM AUTHOR]

The structure is considered for a typical system to control electron beam welding deposition with supplying feed (wire). This approach is used today to implement additive technologies. The main features of the process are described. It is shown that the temperature of the underlying layer changes during surface deposition; therefore, it destabilizes the process through changing the temperature of the melt bath as well as the transverse dimensions of the formed layer. The need to use a feedback control system to stabilize the temperature of the welded layer is substantiated and an approach to its technical implementation is described. The results obtained for a prototype of a temperature stabilizer based on a microcontroller are presented. The fundamental potential is demonstrated to ensure the repeatability of the height of the welded layer and to prevent the wire from detaching the liquid melt bath during welding deposition of a multilayer cylindrical contour made of 316L steel. [ABSTRACT FROM AUTHOR]

Studies of variations in the parameters of various geophysical fields during the preparation of destructive earthquakes that occurred in Turkey in February 2023 with magnitudes of 6 ≤ M ≤ 7.8 are carried out using satellite data. It has been found that anomalies of these parameters manifested themselves from 34 to 25 days before the earthquakes as a sharp decrease in the values of relative humidity (RHS) and outgoing longwave radiation (OLR), as well as in an increase in the density of local lineaments. An increase in the surface skin temperature (SST), surface air temperature (SAT), RHS, and OLR, as well as in the values of the aerosol optical depth (AOD) and ionospheric total electron content (TEC), was revealed 19–9 days before the analyzed seismic events. In the period from 5 to 2 days before these earthquakes, a decrease in the SST, SAT, the flux of OLR, and the ionospheric TEC, as well as an increase in RHS and in the length of the secants of the rose diagrams of regional lineaments, were recorded. Quantitative characteristics of these anomalies are determined. [ABSTRACT FROM AUTHOR]

A comprehensive methodology for designing a magnetic deflection system for a technological electron gun is proposed. The feasibility of using deflection systems with an internal magnetic circuit and toroidal coil sections to form deflection fields that ensure azimuth beam rotation with a constant angle of deviation from the vertical axis is substantiated. The potential of computer modeling is shown both at the stage of calculating the deflection field and beam displacement and at the stage of creating the design of the system frame for its subsequent manufacture based on 3D printing. The main coil parameters are determined, and the circuit diagram of a current stabilizer with external control from a digital-to-analog converter is developed. Dependences are presented showing the relationship between control signals and deflection angles in the developed unit prototype. It is shown that the proposed technique is universal and can be used to create electron-optical gun elements providing deflection, scanning, parallel transfer or adjustment of technological electron beams. [ABSTRACT FROM AUTHOR]

Abstract—A combined restoration–hardening method by the formation of beads with a hardness of about 60 HRC using a T-590 electrode is applied to achieve the maximum wear resistance and overhaul life. [ABSTRACT FROM AUTHOR]

Modern industry requires that the surface layers of bearing components made of ShKh15 steel be modified to increase their service life. This effect is obtained by enhancing the microhardness. Currently, the pulsed plasma flow treatment method is being intensively studied. The applicability of this method to bearing steel is limited by high requirements for the surface roughness of manufactured products. In this work, the effect of pulsed plasma flow treatment modes on the roughness and microhardness of ShKh15 steel at different thermal loads and numbers of pulses is studied. The goal was to determine the optimum treatment parameters for obtaining a combination of the maximum hardening with the minimum roughness change. According to the results obtained, after pulsed plasma flow treatment at certain parameters, a fourfold increase in microhardness can be achieved. In addition, when the melting threshold is reached, the roughness of the samples sharply grows. In addition, a series of experiments has been carried out to determine the impact of a number of pulses on the investigated characteristics. It has been found that, under irradiation of ShKh15 steel by several pulses, an increase in the number of impacts on the material provokes a decrease in the microhardness due to a change in the quantitative ratio between the phases. The roughness index varies within 10‒40%, while the values fluctuate chaotically. [ABSTRACT FROM AUTHOR]

A new method of nanostructuring of the surface by electrospark alloying method (ESA) using special processing media (SPM) with carbon nanotubes is proposed. The influence on the ESA regimes and the composition of the SPM on the microstructure and hardness of the coatings has been considered. While processing the Armco iron, with an increase in the discharge energy, the thickness and continuity of the coating increase. In the microstructures, the nanoscale phases of 40 nm to 1300 nm are detected, and they are evenly distributed in the coatings. Adding nanotubes helps to increase the continuity, thickness and hardness. Because of the ESA process, coatings with a uniform distribution of molybdenum are formed. Carbon, apparently in the form of the carbon nanotubes, is concentrated on the surfaces of the samples being processed, regardless of the discharge energy during the ESA process. The use of the proposed ESA method has a positive effect on the quality parameters of the coating. [ABSTRACT FROM AUTHOR]

The microstructure, phase composition, and microhardness of the cast high-entropy VNb2TaCrMoW alloy with the addition of titanium diboride were studied. The initial VNb2TaCrMoW alloy consisted of two bcc solid solutions, slightly differing in lattice parameters (a = 0.3139 nm and 0.3200 nm). The addition of boron as titanium diboride and repeated remelting led to a bcc solid solution with a larger lattice parameter (a = 0.3217 nm) and a boride with W3.5Fe2.5B4 structure (a = 0.6054 nm and c = 0.3256 nm). The bcc solid solution was the first to crystallize, and the boride was part of the eutectic grains and precipitated from the last melt portions, forming a closed network. The resulting alloy was applied to a carbon steel substrate as a coating using electrospark deposition employing an Elitron-24A installation with varying electrical pulse energy. Higher pulse energy during coating deposition increased the layer thickness and surface roughness but did not influence the phase composition. The microstructure of the coatings was more uniform compared to the cast alloys, and X-ray diffraction showed that the coatings contained bcc solid solutions, Fe7W6 intermetallic compound, and a small amount of TaO2 oxide. The coatings had a hardness of about 10 GPa and were 11–15 μm and 16–20 μm thick at discharge energies of 0.52 and 1.1 J, respectively. A comparative analysis of the phase composition, hardness, and microstructure of the cast alloy and associated coatings was carried out. The coatings deposited at a discharge energy of 0.52 J were subjected to laser processing. Laser processing of the coatings resulted in a thermally affected zone, while the surface layer hardness hardly changed. The wear resistance of the coatings deposited at a discharge energy of 0.52 J was analyzed. Wear resistance testing was conducted for three counterface materials (VK6, Al2O3, and Si3N4) in quasistatic and dynamic loading modes. Laser processing of the electrospark coatings changed the wear mechanism and significantly increased the wear resistance regardless of the counterface material and loading mode. [ABSTRACT FROM AUTHOR]

Differentiation is critical for cell fate decisions, but the signals involved remain unclear. The kidney proximal tubule (PT) cells reabsorb disulphide-rich proteins through endocytosis, generating cystine via lysosomal proteolysis. Here we report that defective cystine mobilization from lysosomes through cystinosin (CTNS), which is mutated in cystinosis, diverts PT cells towards growth and proliferation, disrupting their functions. Mechanistically, cystine storage stimulates Ragulator-Rag GTPase-dependent recruitment of mechanistic target of rapamycin complex 1 (mTORC1) and its constitutive activation. Re-introduction of CTNS restores nutrient-dependent regulation of mTORC1 in knockout cells, whereas cell-permeant analogues of L-cystine, accumulating within lysosomes, render wild-type cells resistant to nutrient withdrawal. Therapeutic mTORC1 inhibition corrects lysosome and differentiation downstream of cystine storage, and phenotypes in preclinical models of cystinosis. Thus, cystine serves as a lysosomal signal that tailors mTORC1 and metabolism to direct epithelial cell fate decisions. These results identify mechanisms and therapeutic targets for dysregulated homeostasis in cystinosis. Cystinosis is a lysosomal storage disease that affects the kidney. Here, the authors use preclinical models and advanced profiling techniques to discover the mechanism by which defective cystine mobilization from lysosomes disrupts kidney cell function, offering insights into potential therapies. [ABSTRACT FROM AUTHOR]

Pulsed plasma flow treatment of materials has been insufficiently studied, which makes it impossible to estimate the main parameters of the modified layer. Thus, the treatment mode is selected experimentally for each individual material to obtain the optimal hardening layer thickness and microhardness. In this scientific study, structural steels 45, 20Kh and 40KhN2MA were irradiated for different durations and number of pulses, followed by investigation of the elemental and phase composition, microhardness and thickness of the hardening layer. [ABSTRACT FROM AUTHOR]

Anomalous variations in various geophysical fields (lineament systems, thermal fields, and ionospheric parameters) during the earthquake with the magnitude M = 5.6, which took place near Lake Baikal on September 22, 2020, and during its preparation, are studied. Features of the geophysical fields are described. Combined analysis of anomalous variations in the geophysical fields in the lithosphere, atmosphere, and ionosphere during the earthquake preparation is carried out. Based on the analysis results, we detect anomalous variations in the lineament systems 15 and 6 days before; in the thermal fields 15 and 14 days before; and in the ionospheric parameters 8, 7, and 6 days before the earthquake. Correspondences are found between the occurrence of the maxima of the lineament systems and the thermal fields 15 and 6 days before the earthquake and changes in the state of the ionosphere and thermal fields 9–10 days and 4 days before the earthquake. [ABSTRACT FROM AUTHOR]

Here we present a simulation of the crust's stress–strain state in the period prior to the 2019 Ridgecrest (M = 7.1) earthquake in Southern California. In the framework of the geomechanical model accounting for the ongoing weak seismicity, the pattern of the spatial and temporal distributions of anomalous shear strains has been revealed. It has also been shown that the source was formed as an alternate development of fractures at the ends of the future rupture, which manifested itself as an anomalous deformation of a dumbbell shape. Unlike previous theoretical and laboratory studies, here we examine the temporal development of a process that had not been considered before. It has been found that analysis of the displacement vector plays a significant role in identification of the zone of source formation. The source is effectively formed only when these directions are stabilized and close to the direction of the shear in the source of a future earthquake, which is determined from satellite monitoring data. [ABSTRACT FROM AUTHOR]

We present the results of studying anomalous variations in the lineament system during the preparation to the M = 5.6 earthquake that occurred on September 21, 2020, near Lake Baikal, 21 km from the settlement of Kultuk, at a depth of 10 km. The study method, based on the automated lineament analysis of satellite imagery, is described. Peculiarities of the Baikal rift zone structure and its seismic activity are analyzed. Schemes of hatch elongation lines, schemes of regional lineaments, and rose diagrams of lineaments are constructed on the basis of processed series of satellite imagery obtained by Terra (MODIS) in the period from May 25 to October 6, 2020. The total lengths of local lineaments and ratios of their lengths for various directions are calculated. All the data have allowed us to reveal anomalous variations in lineament systems 14 and 5 days before the earthquake of September 21, 2020. It is concluded that these anomalies are geodynamic precursors of the mentioned earthquake. [ABSTRACT FROM AUTHOR]

This paper is devoted to studying the capabilities of modern neural networks in image processing for solving the problem of monitoring the state of steel and reinforced concrete structures. The article presents a method for solving monitoring problems based on the use of a combination of several neural networks focused on recognizing a fragment of a structure and parts of a structure. Methods for training neural networks on small training samples are proposed. The results of the operation of the algorithms on real images are presented, showing the consistency and efficiency of the proposed solution. [ABSTRACT FROM AUTHOR]

The special features of thick combined electrospark coatings (СESC) formed on cylindrical 12Kh18N10T stainless steel samples are analyzed. The samples were carbonized with the help of combined electrospark alloying (CЕSA) using an Elitron-52A device and aluminized with the help of electrospark alloying (ESA) using an EIL-9 automated device at a discharge energy of Wd = 3.4 J. The coatings were deposited on the aluminized surfaces with the help of the T15K6 hard alloy using the same device at Wd = 0.9 and 3.4 J. The СESC roughness was reduced by means of ball rolling and applying a metal–polymer material (MPM) reinforced with the VK6 hard-alloy powder. A new technology to recover parts, such as rotation bodies, has been proposed for practical applications. It made it possible to form the СESC on 12Kh18N10T steel in the following sequence: CЕSA → ESA Al → ESA T15K6 → MPM (reinforced with VK6), with a thickness up to 1.5 mm, a continuity of 100%, a microhardness of ∼10 100–9500 MPa, and a roughness of Ra = 1.2 μm. [ABSTRACT FROM AUTHOR]

Results are presented from using satellite data to study anomalies of different geophysical fields due to the interaction of the lithosphere, atmosphere, and ionosphere. The anomalies are mid- and short-term precursors of strong earthquakes in California that occurred on July 4 and 5, 2019 (M = 6.4 and M = 7.1). Precursory changes in the lithosphere are analyzed using lineament system characteristics obtained by processing satellite imagery (Terra/Aqua satellites and MODIS instrument), along with variations in the Earth's surface temperature (the Aqua satellite and the AIRS instrument). Fluctuations in the temperature of the near-surface atmospheric layer are studied to detect atmospheric anomalies during preparation of seismic events, as are fluctuations in the air temperature now at an altitude of 1000 hPa and changes in outgoing longwave radiation recorded by the AIRS instrument on the Aqua satellite. Variations in the ionospheric electron density in the F2-layer maximum are studied with GPS data to reveal ionospheric anomalies during the precursors and occurrence of earthquakes. Joint analysis of anomalies in different geophysical fields, identified via satellite monitoring, allow precursory changes in the lithosphere to be detected a month before strong earthquakes. Precursory changes in the atmosphere and ionosphere can be detected 3–6 days and 3–5 or 10 days before earthquakes, respectively. [ABSTRACT FROM AUTHOR]

Using remote sensing data, we study the changes in lineament systems during the preparation and process of strong earthquakes with М = 7.1 and М = 6.4 which occurred in California (United States) in July 2019. The series of satellite images shot from January 1, 2019, to August 12, 2019, and the data on seismic setting in the region are analyzed. The precursory changes are revealed in the lineament systems; these changes are expressed in rose diagrams of regional lineaments and in summarized length of local lineaments of different directions. An abrupt change in quantitative characteristics of rose diagrams of lineaments began to manifest on June 5, 2019 (i.e., a month before the earthquake of July 4 and 5, 2019). It is established that the maximum length of lineaments striking to the northwest and northeast (corresponding to the longitudinal and transverse strikes relative to the main regional structural features) was reported on June 30, 2019 (i.e., several days before the strong earthquakes). [ABSTRACT FROM AUTHOR]

This paper examines the use of high-entropy alloys (HEAs) as materials for electrospark deposition (ESD). This method is known to produce high-quality protective coatings with a long service life. Arc-melted AlCrFeCoNiCux (x = 0 and 2 mole) cast alloys were used in the research. The HEA coatings were applied to steel 45 employing an Elitron-52A unit. The phase composition, hardness, and microstructure of the cast alloys and associated coatings were compared. The starting HEAs were found to have an inhomogeneous microstructure peculiar to the cast alloys and crystallize to form simple solid solutions with bcc and fcc phases. The AlCrFeCoNi alloy has higher hardness (6229 MPa) than the AlCrFeCoNiCu2 alloy does (5814 GPa). Studies of the structure and phase state of the samples showed that they consisted of an upper layer (coating), transition zone, and substrate with a ferrite–pearlite structure. The hardness, thickness, and continuity of the coatings increase with higher discharge energies Wd in ESD. At Wd = 0.13 J, the coating is 20 μm thick and has 70% continuity; at Wd = 4.6 J, the coating becomes 130 μm thick and is 100% continuous. In contrast to the cast alloys, the high-entropy coatings show higher microhardness: 6230 and 7320 MPa for AlCrFeCoNiCu2 and AlCrFeCoNi, respectively, at a discharge energy of 4.6 J. The coating thickness increases when copper is added to the electrode material. Simple solid solutions peculiar to high-entropy alloys form in both the cast alloys and the coatings. Unlike the cast alloys, the coatings are characterized by homogeneous microstructure. [ABSTRACT FROM AUTHOR]

The paper examines how to increase the reliability and service life of dynamic equipment parts operating at high speeds, loads, and temperatures and in corrosive, abrasive, and other environments. Increase in the thickness of the high-hardness layer for friction parts subjected to abrasive and other types of wear is a relevant problem. The research findings and the method developed for protecting steel products against wear by applying a quasimultilayer wear-resistant coating (QWC) onto the wear surface by electrospark deposition (ESD) and increasing the thickness of the high-hardness layer are described. Based on metallography, hardness measurement, electron microprobe analysis, and X-ray diffraction, the regularities of producing the QWC with alternating alloying electrodes by sequential ESD of carbon, aluminum, and T15K6 hardmetal layers onto a 12Kh18N10T steel substrate are established. The coatings deposited in this sequence have the greatest high-hardness area (320–360 μm) and the smallest surface roughness (7.5 μm). The formation of TiC carbides, intermetallic compounds, and a disordered bcc solid solution promotes the maximum microhardness of the surface layer (approximately 11500 MPa). The diffusion zones of carbon and tungsten increase in the process. Electrospark deposition in accordance with the described technique allows the hardness and thickness of the strengthened layer to be increased. The experiments show that the hardness and thickness of the high-hardness layer cannot be increased only with alternating alloying electrodes by successive deposition of carbon and T15K6 layers (without an aluminum sublayer) on a 12Kh18N10T steel substrate. [ABSTRACT FROM AUTHOR]

The morphology of rare cryophilic species of dinoflagellates Borghiella dodgei Moestrup, Hansen & Daugbjerg from Eastern Europe (Kiev, Ukraine) has been studied. Until now, only two locations of this species—freshwater reservoirs in Italy and Portugal—were known. The original description of B. dodgei from the new locality, drawings, and photos are given in this work. The morphological variability, ecology, and distribution of B. dodgei are discussed. [ABSTRACT FROM AUTHOR]

The wear of centrifuge screws, common components in industrial and municipal wastewater treatment plants, is studied. The TN-20 tungsten-free hardmetal serves for protecting screw flights against abrasive wear. The 12Kh18N10T steel is primarily used in the manufacture of centrifuge screws. A combined technique of depositing protective wear-resistant coatings is proposed. The technique includes electrospark deposition of a T15K6 hardmetal electrode, application of a metal polymer material (MPM), and final laser processing. To reinforce the MPM, small portions of a VK6 hardmetal mixture were added to a two-component epoxy system filled with ferrosilicon and thoroughly stirred. The reinforcement content was ~60%. This technique produces coatings up to 600 μm thick, with 7.3–10.0 GPa microhardness and 100% continuity. Abrasive water jet tests of the 12Kh18N10T steel samples with protective coatings show that their wear resistance is 7.5 times higher than that of the uncoated samples. [ABSTRACT FROM AUTHOR]

An Erratum to this paper has been published: https://doi.org/10.1134/S1063785024340030 [ABSTRACT FROM AUTHOR]

The possibility of using the dynamics of lineament systems as precursors of seismic events has been studied based on the example of strong earthquakes (M ≥ 5) in California (United States), Peru, Iran, Turkey, Transbaikalia, and Kamchatka, as well as in other regions. The pattern and time intervals of changes in lineament systems during earthquake preparation and occurrence are analyzed. It is shown that the features of changes in rose diagrams, ratios of total lengths of local lineaments (strokes) of different directions, orientation of elongation lines of rose diagram of strokes, and other characteristics that were revealed using satellite images can be used as mid- and short-term precursors of seismic events. A methodology for the automated lineament analysis of satellite images is suggested and prospects of its development for monitoring seismically dangerous areas are determined. [ABSTRACT FROM AUTHOR]

This paper presents the results of studying the precursor cyclic stress-strain state of the lithosphere during the preparation of significant seismic events using the automated lineament analysis of multitemporal space images. The proposed method has been tested by the example of a number of strong and devastating earthquakes over the past decade in different parts of the world. The identified precursor cyclical dynamics of lineament systems has a period of 1 to 3 months and makes it possible to predict the time, place, and possible magnitude of earthquakes. [ABSTRACT FROM AUTHOR]

Residual-photoconductivity spectra (RPS) are studied for HgTe/CdHgTe quantum-well heterostructures of n- and p-type conduction at T = 4.2 K. RPS is shown to be both positive (an increase in the carrier concentration in the quantum well) and negative depending on the illumination wavelength. The RPS maxima in the sample with n-type conduction in general correspond to the RPS minima in the p-type samples and vice versa. It is found for p-type samples that illumination at specific wavelengths leads to the "freezing" of free carriers in the quantum well (QW) but not to a change in the conduction type. This fact indicates the important role of the built-in electric field in the RPS mechanism; this field is "switched-off" upon QW neutralization. [ABSTRACT FROM AUTHOR]

This work analyzes the manufacturing process of an electron-beam additive form by heating as a result of remelting the supplied filler wire as a control object. Control actions and output values are designated that can be used in constructing a control systems with feedback. A mathematical modeling technique is used to study heat transfer in a nonstationary formulation, taking into account the influence of the latent heat of fusion. The transient processes of temperature changes were studied at points, whose values can be used to estimate the extension of the weld pool and the degree of metal overheating. An analysis of the results of computational experiments is carried out, and the range of variations of control actions are shown. The possibility of an independent temperature control in the range of the beam and the extension of the liquid bath is also justified. Recommendations are given for the technical implementation of the system and the option of implementing local regulators, types of sensors, and their installation. [ABSTRACT FROM AUTHOR]

Abstract: The article describes the formation features of short- and mid-term strong (M ≥ 6) earthquake precursors detected from space. A database has been created that contains parameter variations for the ionospheric, geodynamic, and thermal fields detected from space during the preparation and occurrence of significant seismic events. This database is an important element of a unified integrated system for monitoring catastrophic natural disasters. We present a technique for the collection and systematization of satellite and related information, as well as data processing methods to obtain information on irregular variations of various geophysical fields in seismic regions. This database contains general information on more than 4000 earthquakes, as well as the characteristics of 80 strong earthquakes (magnitudes from 6.0 to 9.1) that occurred in various world regions between 1990 and 2017. We also present examples from the database of visualization and analysis of data for various precursors of an earthquake that occurred in Italy on August 24, 2016 (M = 6.2). [ABSTRACT FROM AUTHOR]

Abstract: The effects of the residual photoconductivity in HgTe/CdHgTe (013) double quantum-well heterostructures are studied at T = 4.2 K. It is shown that the residual photoconductivity in this system has a bipolar character, i.e., both positive and negative persistent photoconductivity is present depending on the illumination wavelength. [ABSTRACT FROM AUTHOR]

Methods are considered for improving the quality of babbit sliding bearings by applying individual elements to their surface with electrospark alloying of soft antifriction metals. Numerical values are determined for the adhesion force between metals during formation of an antifriction layer using traditional (Fe-Sn) and suggested technology (Fe-Cu and Fe-Cu-Sn). The expediency of using an intermediate copper layer for improving sliding bearing running in is confirmed by calculation. [ABSTRACT FROM AUTHOR]

Seismo-ionospheric variations during the strong earthquake on February 27, 2010 in Chile have been considered. An analysis of the ionospheric state has been performed using measurements based on a GPS satellite navigation system. The results of processing have shown that the decrease in the electron concentration on February 24, 2010 relative to the preceding day was from 24 to 35%. It has also been noted that, 3 days prior to the seismic event, a substantial drop in the rate of change of in the total electron content was observed near the epicenter zone for 1.5 h. It has been shown that, directly before the earthquake, instantaneous variations in the rate of change in the electron content by an order of value that exceeds normal background behavior was observed. [ABSTRACT FROM AUTHOR]

This paper presents a method of control of the metal-transfer mode during electron-beam surfacing with a filler-wire feed based on simultaneous recording of the potential of the wire and article connected with the apparatus frame through the resistors. The main metal-transfer modes are specified that are observed with a change of the energy-input rate. The importance of the solved problem for additive technologies is shown. A scheme of experimental investigations carried out at the ELA-15I apparatus is given, and the obtained oscillograms are presented. The relation of the characteristics of the registered signals with the operation modes of the equipment and transfer parameters is shown. It is noted that, with a change of only the filler-wire feed rate, a changeover from drop metal transfer to the scattering mode can be triggered. The possibility of detecting the mode of appearance of the shot metal, as well as emergency modes related with stopping the filler-wire feed or excessive increase of its feed rate, is substantiated. The influence of the plasma processes on the registered signals in the developed scheme is analyzed, and it is also shown that, to reduce the influence of these processes, it is necessary to decrease the resistance of the measuring circuit. Photographs of the process corresponding to the certain oscillogram intervals are given. [ABSTRACT FROM AUTHOR]

The structurization of aluminum coatings on steel 20 and 40 substrates produced in different ESD modes is considered. The thickness and microhardness of ‘white’ and transition layers and the surface roughness increase and chemical and phase compositions change with higher discharge energy. The coating formed at low discharge energies mainly consists of α-Fe and aluminum oxides. Electron microprobe analysis shows that the coating produced at high discharge energies consists of iron and aluminum intermetallics and free aluminum. Compared to steel 20, the electrospark-deposited coating on steel 40 has a deeper layer with increased hardness and has greater microhardness. The surface roughness remains virtually the same. To decease roughness and increase integrity of the coatings, we recommend electrospark deposition with the same electrode (aluminum), but at lower discharge energies (Wd = 0.52 J). [ABSTRACT FROM AUTHOR]

Regularities in the influence of processing time and discharge energy on the thickness, microhardness and roughness of carburized cases during electrospark graphite alloying of steel surfaces are studied and quantitative data on them are obtained. The thickness of the strengthened layer increases with gains in discharge energy and alloying time. Specimens of 40Kh, 38KhMYuA, 40KhN2MYuA, 30Kh13, Armco iron, 12Kh18N10T steels and 20 steel, as well as EGe-4 graphite are studied. The tests were carried out using the following devices: EILV-8А, EILV-9, Elitron-22А, and Elitron-52А, which provide discharge energy in the range from 0.1 to 6.8 J. Experiments show that case depth and microhardness under the same process conditions are differ significantly for various steel grades. Case depth increases with higher initial carbon contents in steel. The greater the discharge energy, the greater this difference is. Wear tests show that the method of nonabrasive ultrasonic finish processing after graphite electrospark alloying is effective, and it allows increases in the wear resistance of specimens by a factor of 7.8 for 40Kh steel and by a factor of 11.5 for 12Kh18N10T steel. Research confirms that the stage electrospark alloying of the surface of a specimen after carbonization with a graphite electrode effectively decreases roughness. Discharge energy is lowered at each stage. The stage graphite electrospark alloying of the 38KhMYuA steel case allowed decreases in the surface roughness from Rа = 11.9-14.0 μm to 0.8-0.9 μm. Industrial tests show that graphite electrospark alloying offers can accomplish a number of practical tasks. [ABSTRACT FROM AUTHOR]

The radical-producing activity of human platelets has been studied using the enhanced chemiluminescence method. It is shown that chemiluminescence of isolated platelets is observed only in the presence of lucigenin, a selective probe for superoxide anion; the luminescence is amplified many times upon the addition of NADH and NADPH, the substrates of oxidative chains. The chemiluminescence is not affected by diphenyliodonium, an inhibitor of NADPH oxidase, but it is inhibited in a dose-dependent manner by the oxidative phosphorylation uncouplers dinitrophenol and rotenone. Thus, a superoxide anion radical is the main free radical generated by platelets, and mitochondria are one of the superoxide anion radical sources in platelets. [ABSTRACT FROM AUTHOR]

The conversion of phenylone polymer (poly- m-phenylene isophthalamide) at 293 K under the action of a nitrogen dioxide−oxygen gaseous mixture and nitrogen dioxide and oxygen individually is studied by the ESR method. In the first case, aryliminooxyl and arylacylaminoxyl free radicals are recorded, whereas in the second, diarylaminoxyl and phenoxy free radicals. The presence of phenolic and phenyl benzoate polymeric products in nitrated phenylone is detected by IR spectroscopy. The mechanisms of reactions occurring in both the oxidation modes are considered. [ABSTRACT FROM AUTHOR]

The processes associated with the transfer of excitonic excitations between tunnel-uncoupled quantum wells (QW) and the influence of the local electric field were investigated in AlGaAs/GaAs heterostructures by the method of photoluminescence excitation (PLE) spectroscopy at low (4.2 K) temperature. The variation in the intensity of photoluminescence (PL) from the wider QW under resonant excitation of excitonic transition in the adjacent narrow QW has been observed. The difference in the PL maximum position and intensity of the wider QW under resonance excitation of the narrow one is explained by the influence of quantum-confined Stark effect on the process of exciton recombination. [ABSTRACT FROM AUTHOR]

The effect of temperature-rate strain conditions in the free settlement of Cu-2% Ti billets sintered in the 100-700°C temperature range with a strain rate of 0.01 and 0.001 sec on the power process variables and structurization are studied. It is observed some increase in the stress at ~400°C, while the general trend is the decrease in stress with increasing strain temperature. This is due to the dynamic strain age-hardening, accompanied with the release of the intermediate metastable and coherent β′-phase CuTi. It is demonstrated that the intensity of compaction during free settlement increases with increasing temperature, strain rate, and the starting porosity of the samples. It is observed that with increasing degree of strain of the billet, it occurs a monotonic decrease in the average grain size of copper and crushing of titanium particles, whose intensity increases with increasing rate and temperature of the strain. [ABSTRACT FROM AUTHOR]

We report the observation of stimulated emission in heterostructures with double InGaAs/GaAsSb/GaAs quantum wells, grown on Si(001) substrates with the application of a relaxed Ge buffer layer. Stimulated emission is observed at 77 K under pulsed optical pumping at a wavelength of 1.11 μm, i.e., in the transparency range of bulk silicon. In similar InGaAs/GaAsSb/GaAs structures grown on GaAs substrates, room-temperature stimulated emission is observed at 1.17 μm. The results obtained are promising for integration of the structures into silicon-based optoelectronics. [ABSTRACT FROM AUTHOR]

A multifunction setup for coherent optical spectroscopy with excitation of semiconductor structures in a wavelength interval of 750-1800 nm and a time resolution of about 100 fs is presented. Minor adjustments are needed for the measurements of photoluminescence kinetics, photon echo, and four-wave mixing under excitation of samples using time-correlated series of femtosecond laser pulses. Results of optical experiments are presented. [ABSTRACT FROM AUTHOR]

An experimental technique for the acquisition of current-density distributions of continuously operating electron beams with an electron energy of 60 keV is proposed. The measurement results for different cross-sectional areas of the beam with a power of 2.1 kW and a current density around 1 × 10 A/m are given. [ABSTRACT FROM AUTHOR]

The time-resolved photoluminescence of GaAs/AlGaAs quantum-cascade structures under intense pulse excitation is studied. Aside from optical transitions between the ground electron and hole states of a system of two tunnel-coupled quantum wells, the photoluminescence spectrum at short times after the excitation pulse exhibits features corresponding to transitions between the excited states of these wells, which are not observed in time-integrated photoluminescence spectra. It is shown that, due to a high pump level, the electron gas is initially strongly heated, which makes it possible to observe band-to-band transitions between both the ground and excited states. Nonequilibrium carriers cool down with a characteristic relaxation time of ∼125 ps. [ABSTRACT FROM AUTHOR]

We experimentally observed an increase in the intensity of photoluminescence from a wider quantum well (QW) when an exciton transition was induced in the neighboring narrower QW separated from the former one by a tunneling-nontransparent AlGaAs barrier. The dependence of the efficiency of the near-field radiative transfer of excitons on the distance between QWs was studied in heterostructures without coincidence of exciton resonances in the adjacent QWs. Theoretical results were qualitatively consistent with the available experimental data. [ABSTRACT FROM AUTHOR]

The type of heterojunction in the GaAsSb/GaAs heterostructure at x = 0.36 is studied by photoluminescence spectroscopy and time-resolved photoluminescence. A GaAsSb/GaAs heterostructure with an Sb fraction of 15%, for which we can confidently state is a type-I heterojunction, was studied for comparison. It was established from the blue shift of the photoluminescence line depending on the excitation power and relaxation time of the photoluminescence signal from the GaAsSb/GaAs quantum well, which was ∼11 ns, that the GaAsSb/GaAs structure at an Sb content of 36% clearly constitutes a type II heterojunction. This was additionally evidenced by the data obtained for structures with an Sb content of 15%, in which case no shift of the location of the photoluminescence line on the pump power was observed, while the relaxation time of photoluminescence in the region of the signal from the quantum well was ∼1.5 ns. [ABSTRACT FROM AUTHOR]

The spectra and kinetics of the low-temperature interband photoluminescence of epitaxial structures of terahertz quantum cascade lasers is studied under conditions of strong pulsed excitation. Photoluminescence corresponding to transitions between both the ground and excited states of two tunnel-coupled wells is observed at high excitation levels (600 mW; spot diameter ∼200 μm). Kinetic measurements show that the rise and decay times significantly decrease up to the time resolution of the measuring system at wavelengths <770 nm with decreasing photoluminescence observation wavelength. [ABSTRACT FROM AUTHOR]

We report a study into the process of energy transfer between quantum wells divided by 30-nm-thick opaque barriers. It was experimentally observed that the intensity of a photoluminescence signal from a quantum well increased by 15% under resonant excitation of exciton transition in the adjacent quantum well. The quantum wells were 30 nm apart. A radiative mechanism of energy transfer in the near-field region of emitting exciton is proposed. Within this theoretical model, the efficiency of the energy transfer decreases by a power law with greater distance between the quantum wells. The theory is found to be in qualitative agreement with the experimental results. [ABSTRACT FROM AUTHOR]

Processes occurring when a static transverse electric field is applied to a GaAs/AlGaAs n- i- n heterostructure with single quantum wells and asymmetric tunnel-coupled double quantum wells have been investigated by optical methods. The difference between the energies of exciton transitions for quantum wells of different widths makes it possible to attribute the observed photoluminescence peaks to particular pairs of wells or particular single quantum wells. The local electric field for each quantum well has been determined in terms of the Stark shift and splitting of exciton lines in a wide range of external voltage. A qualitative model has been proposed to explain the nonmonotonic distribution of the electric field over the depth of the heterostructure. [ABSTRACT FROM AUTHOR]

Mechanism of nitrogen dioxide interaction with polymers containing amide and imide groups in the main or side chains of macromolecules (polycaproamide, polyvinylpyrrolidone, poly- m-phenylene isophthalamide and polypyromellitimide) is considered. The initiators of conversions of polymers of the given classes are not monoradicals of nitrogen dioxide rather than its equilibrium dimers in the form of nitrosyl nitrate. In primary oxidizing reaction of an electron transfer from donor groups of macromolecules to nitrosyl nitrate, radical cations, nitric oxide and nitrate anion are formed, which in the subsequent reactions give products of nitration and nitrosation. These products are precursors of stable acylalkylaminoxyl, acylarylaminoxyl, iminoxyl macroradicals. The specific interactions of nitrogen dioxide dimers with functional groups of macromolecules determine features of the mechanism of ion-radical conversions of the polymers and the composition of radical and molecular products. The direct detection of radical cations has been realized by ESR method for confirmation of the ion-radical initiation concept using model reaction of nitrogen dioxide with triphenylamine. [ABSTRACT FROM AUTHOR]

Isotherms of mono- and polyelement adsorption of Cu2+, Pb2+, and Zn2+ by an ordinary chernozem were described by the Langmuir equation. The values of the adsorption constant k decreased in the range Cu2+ > Pb2+ ≫ Zn2+ for the monoelement adsorption from nitrate and acetate salt solutions, Cu2+ > Pb2+ > Zn2+ for the polyelement adsorption from nitrate solutions, and Pb2+ > Cu2+ ≫ Zn2+ for the polyelement adsorption from acetate solutions. The maximum adsorption ( Cmax, ∞) of individual cations at the polyelement contamination was always lower than at the monoelement contamination because of the mutual competition. At the same time, the values of k for the polyelement adsorption were higher than those for the monoelement adsorption because heavy metals (HMs) interact with most of the specific adsorption centers. It was shown that the ratio between the content of exchangeable cations displaced from the soil exchangeable complex (SEC) into the solution and the content of adsorbed HMs decreased with the increasing concentration of adsorbed HMs. These values could be higher (for Cu2+), equal, or lower than 1 (for Pb2+ and Zn2+). In the former case, this was due to the dissolution of readily soluble salts at low HM concentrations in the SEC. In the latter case, this was related to the adsorption of associated HMs and the formation of new phases localized on the surface of soil particles at high HM concentrations in the SEC. [ABSTRACT FROM AUTHOR]

The variability of the ionosphere during April–May, 2008, has been analyzed in detail in order to reveal anomalous variations related to seismic activity, initiated by the strongest Wenchuan earthquake ( M = 7.9) in the Sichuan province on May 12, 2008. Information about the total electron content (TEC) from the network of GPS receivers in the earthquake region, the global IONEX TEC maps, and the reconstructed vertical profiles of electron density according to the data of GPS receivers were used as a data source. The spatial and time localization of the observed anomalies, their morphological features, and the absence of geomagnetic disturbances during the observation period undoubtedly demonstrate that the observed variations were caused by seismic activity. [ABSTRACT FROM AUTHOR]