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Voltage imaging in cells requires high-speed recording of small fluorescent signals, often leading to low signal/noise ratios. Because voltage indicators are membrane bound, their orientations are partially constrained by the plane of the membrane. We explored whether tuning the linear polarization of excitation light could enhance voltage indicator fluorescence. We tested a panel of dye- and protein-based voltage indicators in mammalian cells. The dye BeRST1 showed a 73% increase in brightness between the least and most favorable polarizations. The protein-based reporter ASAP1 showed a 22% increase in brightness, and QuasAr3 showed a 14% increase in brightness. In very thin neurites expressing QuasAr3, improvements were anomalously large, with a 170% increase in brightness between polarization parallel versus perpendicular to the dendrite. Signal/noise ratios of optically recorded action potentials were increased by up to 50% in neurites expressing QuasAr3. These results demonstrate that polarization control can be a facile means to enhance signals from fluorescent voltage indicators, particularly in thin neurites or in high-background environments.

The high-rate convergence of copper cylindrical shells with a diameter of 48 mm and a wall thickness of 4 mm is studied at various intensities of explosive loading. Two structural mechanisms of the loss of stability of the radial deformation front are described. A diagram of structural changes reflecting the successive stages of the convergence process is presented. An interrelation is found between the number of protrusions on the shell surfaces during their corrugation at the intensity of explosive loading. It was found that high-rate longitudinal deformation during convergence has a pulsating character. It was found that the temperature rises to ~500°С in the center of the converged shell and that it can be higher than 1000°С at a high rate of spall-pore collapse.

The microstructure and mechanical properties of chromium–nickel austenitic stainless steel fabricated by selective laser melting using a Realizer SLM100 3D printer have been investigated in this work. The structure of the studied specimens has been formed by the complete melting of the initial powder and high-speed cooling of the melt. Cooling of the melt initially leads to the formation of δ ferrite, and then, polymorphic δ → γ transformation results in the formation of the final austenitic structure. The structure of δ ferrite which formed during melt crystallization has been found to exhibit a clear pattern of periodicity. The periodicity depends on the parameters of the melting process, such as the distance between neighboring bands formed during laser-beam traveling (intertrack distance) and the step of platform feeding (distance between layers). The polymorphic δ → γ transformation takes place by a disordered mechanism and no austenite texture forms. However, some structural heredity remains. It can be seen in the orientational relationship between some austenite grains and δ-ferrite grains. The steel fabricated by laser melting is shown to have high mechanical properties such as the yield strength, the ultimate tensile strength, and the tensile elongation at a strain rate of 10–2 s–1, which are 320, 765 MPa, and 50%, respectively. The yield strength and ultimate tensile strength of the specimens under dynamic compression by the Hopkinson–Kolskii technique at an average strain rate of 103 s–1 are 550 and 945 MPa, respectively.

An experiment is performed for explosive convergence (collapse) of a cylindrical shell of low carbon steel with a ferrite-perlite structure. It is revealed that during ultra-rapid heating caused by high-speed deformation austenite formation occurs in an unusual sequence: first, free ferrite is converted, then pearlite. The decrease in free ferrite transformation temperature is explained by action of high pressure, as well as by varying degrees of heating steel structural constituents. An effect of barothermal quenching is observed, as a result of which a pearlite-martensite structure forms.

The recrystallization process in copper subjected to high-rate compression deformation by collapsing a massive cylindrical shell into a cylinder has been studied in this work. Recrystallization occurs in two stages due to the peculiarities of the deformation structure. At the first low-temperature stage, regions with deformation-induced highly-misoriented (over 15 degrees) grains are recrystallized. At the second stage, regions containing deformation-induced cells with low angular boundaries are recrystallized. Recrystallization in copper after loading with a plane shock wave is investigated for comparison. The recrystallization occurs via migration of grain boundaries to form one step.

Systematic analysis of the state and prospects of the development of additive technologies for computer-aided production is conducted to show a new paradigm of their evolution. An approach determining the additive methods as synergy technologies that provide self-organization of surface phenomena is suggested. The new approach is used for choosing the most efficient energy sources and materials for the technologies of layer-by-layer synthesis of articles. It is shown that stabilization of the thickness of the formed layers correlates with the processes of self-organization of surface phenomena and design features of the articles.

The deformation structure in copper that forms upon the convergence of a massive cylindrical shell into a cylinder is studied in this work. The shell in the deformation zone was subjected to high-speed deformation (~104 1/s) with large values of true strain (e varied from 0.8 to 2.0). It is shown that two types of structures were formed under deformation: regions containing disperse grains with high-angle boundaries and twins and regions with deformation cells having low-angle boundaries. It is found that the twins that arose at the early stages of deformation are distorted upon further deformation: their rectilinear boundaries are bent, the orientation relationships with the matrix are violated, and high-angle boundaries of arbitrary orientation are formed.

We introduce a new class of on-chip optical tweezers with high trapping efficiency, compact footprint, and broadband operation by integrating free-form micro-reflectors and micro-lenses to the facets of waveguides to generate the strong three-dimensional optical field gradient for optical trapping. We demonstrate the design, fabrication, and measurement of both reflective and refractive micro-optical tweezers. The reflective tweezers feature a remarkably small trapping threshold power, and the refractive tweezers are handy for multi-particle trapping and inter-particle interaction analysis. This new class of tweezers is promising for on-chip sensing, cell assembly, particle dynamics analysis, and ion trapping.

Using modern ideas about the form of the phase diagram of boron nitride, the paper considers thermodynamic parameters and mechanisms of the synthesis of dense phases of boron nitride under equilibrium and nonequilibrium conditions. It has been verified that nanodiamonds, like fullerenes and carbon nanotubes, have catalytic properties and contribute to the solid-state conversion of graphite-like boron nitride to sphalerite modification at high pressures and temperatures. We propose a mechanism for the interaction of nanodiamond under high pressures with the surface of graphite-like boron nitride, which leads to a change in the type of electronic bond in its lattice from sp2 to sp3 with the formation of boron nitride with a wurtzite structure and its subsequent transformation into sphalerite boron nitride by the shear mechanism. The use of carbon-coated nanodiamonds resulted in an increase in the catalytically active centers of phase transformation in boron nitride in comparison with unmodified nanodiamonds, which was manifested in an increase in the content of sphalerite boron nitride in materials obtained under comparable technological synthesis conditions. Modified nanodiamonds also contribute to the intensification of the synthesis of superhard polycrystals as compared to uncoated nanodiamond additives, both due to the diffusion of carbon atoms along the grain boundaries of sphalerite boron nitride and due to the rearrangement of graphite microgroups into a diamond structure and sintering of the obtained diamond blocks with grains of sphalerite boron nitride. The process parameters of obtaining superhard polycrystals based on sphalerite boron nitride with the addition of detonation nanodiamond powders after chemical cleaning and surface modification with non-diamond forms of carbon were found.

The structural mechanisms of buckling and the deformation behavior of copper and steel cylindrical shells (pipes) during collapse under the action of an explosion are studied. The dependence of deformation behavior on the transverse dimensions of the shell and properties of the loaded material is described. It is established that the stability of radial collapse depends on absolute dimensions of the shell rather than relative dimensions, with the collapse of large-diameter shells occurring more stably. It is demonstrated that the collapse stability is violated due to the formation of a characteristic pattern of localized strain in the sample, consisting of homogeneous, orderly arranged structural elements whose dimension depends little on the material properties and experimental conditions. A criterion for stable radial collapse that relates the characteristic dimensions of the structural element of localized strain and the shell radius is proposed.

Metallography has been used in this study to investigate copper samples cut from cylindrical shells collapsed under shock wave loading. Spallation phenomena (either the shell is divided into concentric rings, or a wide zone with spallation cavities and cracks is formed), which occur in shells under shock wave loading are considered. High-rate deformation during inertial convergence heals pores and cracks. Traces of healing remain in the microstructure. Various cases of nonradial convergence, when a stable circular deformation front is lost, are observed. Bends appear on the thin-walled shell and the shell crumples during its converging. Periodically arranged protrusions form on the inner surface of the thick-walled shells. They subsequently join together, converging to the center of the shell. A wave-shaped relief, protrusions, dents, and corrugation on the outer surface indicate the loss of stability.

Photoactivated genetically encoded voltage indicators (GEVIs) have the potential to enable optically sectioned voltage imaging at the intersection of a photoactivation beam and an imaging beam. We developed a pooled high-throughput screen to identify archaerhodopsin mutants with enhanced photoactivation. After screening ~105 cells, we identified a novel GEVI, NovArch, whose one-photon near-infrared fluorescence is reversibly enhanced by weak one-photon blue or two-photon near-infrared excitation. Because the photoactivation leads to fluorescent signals catalytically rather than stoichiometrically, high fluorescence signals, optical sectioning, and high time resolution are achieved simultaneously at modest blue or two-photon laser power. We demonstrate applications of the combined molecular and optical tools to optical mapping of membrane voltage in distal dendrites in acute mouse brain slices and in spontaneously active neurons in vivo.

We introduce a new class of on-chip optical tweezers with high trapping efficiency, compact footprint, and broadband operation by integrating free-form micro-reflectors to the facets of waveguides.

A bulky copper cylindrical shell with an internal diameter of 118 mm and a wall thickness of 5.9 mm has been exposed to an explosion of a cylindrical explosive charge uniformly distributed around it. A cylinder with a diameter of 57–58 mm has been obtained as a result of high-speed deformation caused by the explosion. A metallographic analysis of the cylinder structure shows that the shell collapses under the influence of axially symmetric radial deformation, which is accomplished by both twinning and sliding mechanisms. It is determined that axial deformation occurs along with the radial deformation. The microstructure of the cross-section consists of three zones. A wide annular deformation zone is formed on the outside, an annular recrystallization zone is formed closer to the center, and a circular region with a dendritic structure is formed at the center. The presence of dendrites indicates that the temperature at the boundary of this region reaches the melting point of copper. The temperature change along the radius of the cylinder has been calculated.

The effect of the preliminary high strain-rate deformation, performed via the method of dynamic channel-angular pressing (DCAP), and subsequent annealings on the tribological properties of a dispersionhardened Cu–0.092 wt % Cr–0.086 wt % Zr alloy has been investigated. It has been shown that the surfacelayer material of the alloy with a submicrocrystalline (SMC) structure obtained by the DCAP method can be strengthened using severe plastic deformation by sliding friction at the expense of creating a nanocrystalline structure with crystallites of 15–60 nm in size. It has been shown that the SMC structure obtained by the high strain-rate DCAP deformation decreases the wear rate of the samples upon sliding friction by a factor of 1.4 compared to the initial coarse-grained state. The maximum values of the microhardness and minimum values of the coefficient of friction and shear strength have been obtained in the samples preliminarily subjected to DCAP and aging at 400°С. The attained level of microhardness is 3350 MPa, which exceeds the microhardness of the alloy in the initial coarse-grained state by five times.

A technology for manufacturing a steam turbine blade packet made of heat-resistant high-alloy hard-to-weld steel of a martensitic class is offered. The advantage of electron-beam welding use at the assembly of a blade packet instead of a common electric arc welding method in protective environment is described. A technological tooling specially designed essential for welding process automation is considered. There are shown results of laser scanning a blade packet geometry with the aid of NikonMetrology MCAx40+ coordinate measuring arm with the further computer analysis of results obtained in applied Focus software which has shown that thermal deformations are within the limits of a tolerance for the mentioned operation and exclude completely further processing. The application of electron-beam welding at manufacturing a blade packet allows increasing assembly quality, decreasing defects and cost price of an engineering process.

A method for production of Sn–Sb–Cu alloy (babbitt) based composite coatings reinforced with micron-sized SiC and B4C particles on a steel substrate has been developed. A combined action of uniformly distributed high-modulus reinforcements and plastic matrix increases the strength and durability, reduces the wear rate, and significantly improves the antifriction properties of the coating. The surfacing rods based on B83 babbit containing reinforcing particles for arc welding of coatings on steel substrate were produced by the extrusion method. These rods were characterized by lack of porosity and discontinuities in the internal volume as well as by defect-free surface. The density and hardness of the rods are comparable with the same characteristics of the cast babbitt. Arc welding of coatings was performed in the AC mode with a non-consumable tungsten electrode in an argon atmosphere. Welding current I = 160–170 А, arc voltage U = 16–18 V, welding rate Vw = 4.2 m/h, and protective gas (Ar) flow rate VAr = 12–14 L/min. The structure and tribological properties of the composite rods and coatings deposited were investigated with the help of electron and optical microscopy methods and under dry sliding friction tribological tests. The size of SnSb intermetallic compounds in the rods after extrusion and in the coatings deposited was determined. It was found that the size of intermetallic phases decreased by a factor of two after introduction of SiC and B4C particles into the babbitt alloy. The results of wear tests show that reinforcing and modifying the structure of the surfacing rods by introduction of high-strength micron- and submicron-sized ceramic SiC and B4C particles improves the antifriction properties of surfaced composite coatings. The friction coefficient of the composite coating was the same throughout the load interval, while for the unmodified babbit coating its value was by two times higher than that for the composite coating under a load up to 39 N and 20% higher under loads greater than 39 N. The coatings with high-strength SiC and B4C particles have a low coefficient of friction (0.4) and a high coefficient of the friction process stability (0.8).

The deformation behavior and the properties of copper alloyed with chromium and zirconium (0.04–0.14 wt %) are studied during high-rate deformation (~105 s–1) by dynamic channel angular pressing (DCAP). The sequence of the decomposition of the α solid solution of copper accompanied by the precipitation of second-phase nanoparticles and recrystallization in annealing (aging) is determined. The influence of DCAP and aging on the mechanical and physical properties of the copper alloys is investigated.

Since its advent in the 1970s, optical tweezers have been widely deployed as a preferred non-contact technique for manipulating microscale objects. On-chip integrated optical tweezers, which afford significant size, weight, and cost benefits, have been implemented, relying upon near-field evanescent waves. As a result, these tweezers are only capable of manipulation in near-surface regions and often demand high power since the evanescent interactions are relatively weak. We introduce on-chip optical tweezers based on freeform micro-optics, which comprise optical reflectors or refractive lenses integrated on waveguide end facets via two-photon polymerization. The freeform optical design offers unprecedented degrees of freedom to design optical fields with strong three-dimensional intensity gradients, useful for trapping and manipulating suspended particles in an integrated chip-scale platform. We demonstrate the design, fabrication, and measurement of both reflective and refractive micro-optical tweezers. The reflective tweezers feature a remarkably low trapping threshold power, and the refractive tweezers are particularly useful for multiparticle trapping and interparticle interaction analysis. Our integrated micro-optical tweezers uniquely combine a compact footprint, broadband operation, high trapping efficiency, and scalable integration with planar photonic circuits. This class of tweezers is promising for on-chip sensing, cell assembly, particle dynamics analysis, and ion trapping.

An experiment has been performed on the collapse of a thick-walled shell (tube) made of steel 20 (Fe–0.2 wt % C) to a continuous cylinder under the action of explosion. The changes of the microstructure of the cylinder have been investigated that arise under the effect of two factors, i.e., a shock wave, which causes the initial pulse to the collapse, and high-strain-rate deformation upon the subsequent inertial convergence of the shell walls. Changes in the time-dependent temperature distribution in the cylinder have been calculated. As a result of the deformation, the new structure has been obtained in steel 20 due to barothermic quenching that consists of fine crystals of the α phase, which arise during the quenching at the place of free ferrite, and of regions of the retained initial pearlite. It has been shown that the uncommon order of the occurrence of the α → γ transformation is explained by the different degree of heating of the structural constituents of the steel (free ferrite; and pearlite). The conclusion has been drawn that the high-strain-rate deformation that occurs in this experiment can be used as the method that makes it possible not only to differently deform but also to differently heat the different structural components of multiphase materials.

The decomposition of supersaturated solid solution in the Cu–0.06 wt% Zr alloy has been investigated. Upon aging of the initially quenched alloy the homogeneous precipitation of particles is dominating. The decomposition begins from the precipitation of a metastable copper–zirconium phase, the particles of which have the shape of nanodimensional disks. An increase in the aging temperature results in the formation of coarser rodlike particles of the Cu5Zr equilibrium phase. Aging of the deformed alloy is characterized by the predominance of the heterogeneous precipitation of particles at subboundaries and dislocations, and the decomposition begins at a lower temperature. The particle size is less by an order of magnitude than that in the quenched state. The precipitation of nanodimensional particles at dislocations retards the formation of recrystallization centers.

An approach considering additive methods as synergic techniques ensuring self-organization of surface phenomena is offered. On the basis of the approach the energy sources and material for the techniques of layered synthesis of products are chosen. The thickness stabilization of layers formed is connected with the processes of surface phenomena self-organization and design peculiarities of parts.

Structural self-organization of metals and alloys has been analyzed and the mode sustainability of technological and operational processes under intense complex heat and deformation exposure has been determined. The ways of structure formation intensification in the material processing and structure stabilization in material operation that combine control pressure and thermal effects parameters have been proposed.

Changes in the structure and mechanical properties of the low-alloy chromium–zirconium bronze Cu–0.14% Cr–0.04% Zr have been investigated after a high-strain-rate (104–105 s–1) deformation by the method of dynamic channel-angular pressing (DCAP) and following annealings at 300–700°C. A significant increase in the mechanical properties of the investigated bronze after DCAP and after DCAP and subsequent aging at temperatures of 400–450°C has been established. Thus, compared to the initial quenched state the ultimate tensile strength increases by a factor of 2.6 and 2.8 and the yield stress, by a factor of 3.3 and 5.1, respectively, with the retention of satisfactory plasticity. It has been shown that, upon DCAP and subsequent annealings, in the low-alloyed bronze under investigation there occurs a decomposition of the α solid solution with the precipitation of nanosized particles. This leads to a significant strengthening of the bronze and to an increase in its thermal stability compared with the pure copper subjected to DCAP.

The influence of aging and deformation by dynamic channel-angular pressing (DCAP) on the change of the structure and mechanical properties of Cu – 0.14 % Cr – 0.04 % Zr low-alloy chromium-zirconium bronze has been studied. It is shown that, under DCAP and subsequent aging, the studied bronze suffers the decomposition of the alpha-solid solution accompanied by the precipitation of nanosized particles of chromium and the copper-zirconium phase. This hardens the bronze and increases its thermal stability. A substantial increase in the mechanical properties of the bronze after DCAP and subsequent aging has been found. Thus, ultimate strength is increased 2.8 times and yield stress is increased 5.1 times as compared with the initial hardened condition, satisfactory plasticity being maintained.

The effect of high pressures (up to 45 GPa) and frequencies of the alternating-current (ac) electric field (10 Hz–10 MHz) on the electrical properties of multicomponent copper and silver chalcogenides has been studied. The behavior of the direct-current (dc) electrical resistivity of the samples has been analyzed under uniaxial pressure along the measuring electric field.

The effect of the composition of glassy ionic conductors AgGe1 + xAs1–xS3 and the composites based on these materials containing single-walled carbon nanotubes (CNT) AgGe1+xAs1–x(S + CNT)3, on the atomic structure and ionic conductivity is analyzed.

An experiment has been performed on the collapse of a thick steel cylindrical shell into a continuous cylinder under the action of a sliding detonation wave. The process of the collapse has been recorded via X-ray photography, and it has been found that the time of collapse in one section is equal to 30 μs. The average degree of deformation is 77% and the rate of deformation is 104 s−1. The structure of steel 20 in the transverse section of the cylinder consists of three zones. In the outer zone, the initial ferrite-pearlite structure changes under the effect of compressive shock wave and localized shears. The shock wave leads to the formation of a high-pressure ɛ phase and twins. Upon the subsequent inertial collapse of the shell, substantial shear deformations arise in the surface layer, which are localized in directions located at angles of 60° to the cylindrical surface. The structure of the middle zone changes under the action of severe plastic deformation, which occurs predominantly in the radial direction. The deformation leads to the appearance of an internal pressure and to an increase in the temperature. As a result of the action of three factors (pressure, temperature, and deformation), the temperature of the formation of austenite decreases by several hundred kelvins. In the free ferrite, an α → γ transformation occurs and quenching takes place following a subsequent sharp decrease in pressure (barothermic quenching). The pearlitic regions suffer plastic deformation. The microhardness of the steel with this structure is equal to the microhardness of quenched steel. The structure of the third, i.e., central, zone, changes under the action of a significant increase in temperature caused by the further increase in the degree of deformation. The complete transformation of ferrite into austenite occurs at the center of this zone, which means that the temperature in this zone reaches 850–900°C or greater. The microhardness decreases to values typical of annealed steel.

Robust voltage imaging in tissue remains a technical challenge. Existing combinations of genetically encoded voltage indicators (GEVIs) and microscopy techniques cannot simultaneously achieve sufficiently high voltage sensitivity, background rejection, and time resolution for highresolution mapping of sub-cellular voltage dynamics in intact brain tissue. We developed a pooled high-throughput screening approach to identify Archaerhodopsin mutants with unusual photophysical properties. After screening ~105 cells, we identified a novel GEVI, NovArch, whose 1-photon near infrared fluorescence is reversibly enhanced by weak 2-photon excitation. Because the 2-photon excitation acts catalytically rather than stoichiometrically, high fluorescence signals, optical sectioning, and high time resolution are achieved simultaneously, at modest 2-photon laser power. We developed a microscopy system optimized for NovArch imaging in tissue. The combination of protein and optical engineering enhanced signal contrast sufficiently to enable optical mapping of back-propagating action potentials in dendrites in acute mouse brain slice.

Предложено оценивать параметры механических свойств поверхностного слоя рабочих элементов из поликристаллических сверхтвердых композитов на основе кубического нитрида бора режущих инструмент по результатам анализа сканограмм, полученных методом склерометрирования. Представлено теоретическое обоснование метода и рассмотрены термодинамические показатели механических свойств поверхностного слоя – величину активационного барьера запуска процесса производства энтропии и способность к производству энтропии при приложении дозированного воздействия. Приведены результаты экспериментальных исследований работоспособности режущих инструментов из сверхтвердых композитов, полученные при точении закаленных сталей, подтверждающие теоретические выкладки., It was proposed to evaluate the parameters of surface layer’s mechanical properties of the working elements of the cuttingtools from polycrystalline superhard composites based on cubic boron nitride on the basis of the results of scratch tests. The theoretical rationale of the method was represented and the thermodynamical indicators of mechanical properties of surface layer (the value of the activation barrier of the entropy production start and its production ability when dozed impact was applied) were considered. There were showed the results of the experimental researches of the working capability of the cutting tools from superhard composites, obtained then machining the hardened steels which affirm the theoretical calculation.

Chalcogenides Cu1-xAgxGeAsSe3 (x = 0.55–0.65) are synthesized, and their electrical properties are studied at temperatures of 78–400 K and pressures of 15–45 GPa. The compounds are found to be mixed electronic-ionic conductors. Increasing the fraction of silver lead to an increase conductivity and shifts the region of considerable change in electrical properties at high pressures toward even higher pressures.

Methods of magnetic powder patterns (Bitter technique), optical microscopy, and transmission electron microscopy have been used to study the formation of martensite in a spherical sample of 12Kh18N10T steel upon loading by quasi-spherical converging shock waves. Prior to loading, the steel exhibited carbide banding (TiC and Cr23C6 carbides were located in bands along the axis of the initial sample). It has been shown that, upon loading, disperse crystals of martensite are formed in these carbide-containing bands. No martensite was formed in the central part of the solid sphere, in the surface layers, and in the Altshuler-pattern rays. It has been concluded that, in these regions, the temperature exceeded the M d temperature, above which the deformation does not cause a martensitic transformation.

The results of the investigations of a ceramic composite sintered from ZrO2-based powders produced by ultrasonic spray pyrolysis have been considered. The scratch tests and microcutting with a single diamond grain have been used to evaluate the strength and deformation properties of surface layers of the resultant composite. The possibility to apply these composites in finishing products of non-ferrous metals has been discussed.

The use of systematic approaches ensures significant development of the conventional methods of materials science and efficient use of these methods for objects having complex multidimensional structure, including nanostructured materials. The application of wavelet-based multifractal analysis and multidimensional physicochemical analysis for qualitative and quantitative description of material structures, which allows one to detect that differences that cannot be detected using other individual methods, is shown. The system characteristics of material structures are assessed. The self-organization processes in structures are characterized.

Structure changes in chromium-zirconium bronze upon high-speed deformation and subsequent annealing have been studied using the methods of metallography and electron microscopy and microhardness measurements. Deformation was performed by the method of dynamic channel-angular pressing in one and three passes. The deformation creates a submicrocrystalline structure and increases the microhardness by 2.4 times. Aging additionally increases the microhardness by 10%. During annealing at temperatures of 400–700°C, aging and recrystallization take place. At early stages of aging, nanosized particles pin dislocations, thus hampering the formation of recrystallization centers. At subsequent stages, chromium particles impede the migration of large-angle boundaries, thereby blocking the development of recrystallization. At the beginning of aging process in the deformed structure, chromium particles are coherent with the copper matrix and have an fcc structure. Upon the coarsening of the particles in the recrystallized structure, they acquire a bcc structure that is typical of chromium.

The deformation behavior and the structural transformations in bulk copper and brass samples subjected to dynamic channel-angular pressing (DCAP) have been studied. The stress-strain state during high-rate deformation is estimated, and the change in the shear in the cross section of the samples during DCAP is determined. A nanostructured state is found to form in the material during DCAP as a result of cyclic processes of fragmentation and dynamic recrystallization.

The effect of high pressure (up to 40 GPa) and alternating electric field frequency (100 Hz-500 kHz) on the electrical properties of synthesized single-crystal proustite Ag3AsS3 is studied. The behavior of real and imaginary parts of impedance upon an increase in pressure confirms earlier data on the closing of valence and conduction zones, and on the material's transition to the metal state at ∼30 GPa. © 2013 Allerton Press, Inc.

We demonstrate thermally limited force spectroscopy using a probe formed by a dielectric microsphere optically trapped in water near a dielectric surface. We achieve force resolution below 1 fN in 100 s, corresponding to a 2 {\AA} rms displacement of the probe. Our measurement combines a calibrated evanescent wave particle tracking technique and a lock-in detection method. We demonstrate the accuracy of our method by measurement of the height-dependent force exerted on the probe by an evanescent wave, the results of which are in agreement with Mie theory calculations., Comment: 5 pages; 4 figures

The evolution of the structure of 99.8%-pure copper during severe plastic deformation by dynamic channel angular pressing and the properties of the produced submicro- and nanocrystalline (SMC + NC) copper have been studied. It is shown that four-pass extrusion forms a copper structure under conditions of repeated processes of fragmentation and dynamic recrystallization. It is found that copper with a mixed nonequilibrium SMC + NC structure consisting of 50–350 nm grains/subgrains exhibits high mechanical properties (HV 1560 MPa, σu = 440 MPa, σ0.2 = 414 MPa, δ = 19%) and is thermally stable on heating to 150°C.

Effects of shock wave interaction and the related phenomena of the localization of plastic deformation, destruction, and mass transfer in metal ball samples subjected to explosive loading at pressures of 36 to 150 GPa are studied. A correlation between the macro- and microstructural changes and the geometrical conditions of loading according to various schemes is found. It is shown that the mass transfer effects are of hydrodynamic origin. The depth penetration of the material was 3.2 mm in narrow channels and 0.3 mm in solid material.

The effect of static pressure on the electric properties of vitreous materials Cu 1 - xAg xGeAsSe 3, where x = 0.95, 0.9, and 0.85 is studied. The pressure dependences of impedance and dielectric loss tangent at pressures 15-45 GPa are analyzed. The ranges of substantial changes in the electrical properties of the samples are found. © Allerton Press, Inc., 2012.

Structural changes in two ball-shaped specimens of a 12Kh18N10T steel that were subjected to symmetric and asymmetric quasi-spherical explosive loading have been investigated by metallography, electron microscopy, and microhardness measurements. Propagation and interaction of converging shock waves, structural transformations in Al’tshuler beams, and the phenomenon of cumulation in the center of the specimens have been analyzed.

The electrical properties of the chalcogenide AgSnSbSe3 have been investigated over a wide range of variations in external parameters, such as the temperature, the pressure, and the frequency of the electric field. It has been found that the temperature dependence of the permittivity and the dependence of the electrical resistivity on the hydrostatic pressure exhibit anomalies that are characteristic of structural phase transitions. The influence of the frequency on dielectric properties of the material has been analyzed.

Evolution of the structure of pure copper (99.8 %) in the course of severe plastic deformation performed by the new method of dynamic channel-angular pressing (DCAP) and the mechanical properties of the arising mixed SMC+NC structures have been studied. The rate of deformation of the material during DCAP is ∼105 s−1, the duration of the process of deformation is 500 μs, the pressure does not exceed 2 GPa. It has been established that in the course of twofold-fourfold pressing the grains and subgrains of copper become refined by three orders of magnitude. It has been found that a decrease in the inner radius of the profile of the zone of intersection of the channels in the die (R) from 7 mm to 0 leads to the formation in the bulk samples of an SMC+NC structure consisting of grains and subgrains with a size from 50 to 350 nm. It is shown that the high-rate deformation with the use of the DCAP method increases the copper hardness by a factor of 2–2.2; the strength grows by a factor of 1.4; and the plasticity remains high. The estimation of the variation of the value of shear along the cross section of the samples upon DCAP showed that in the scheme with R = 7 mm the relative shear is γ ≤ 1.65; in the scheme with R = 0, γ = 1.8-2.0. In the case of a scheme with R = 0, the DCAP leads to a considerable (in comparison with the initial state) increase in the strength without loss of plasticity even upon single-pass pressing.

Methods of electron microscopy, dilatometry, and microhardness and resistivity measurements have been used to study the effect of annealing on the process of recrystallization of a mixed submicrocrys-talline+nanocrystalline (SMC+NC) structure of 99.8% copper produced by high-rate (∼105 s−1) deformation using dynamic channel angular pressing (DCAP). It has been shown that the SMC+NC structure of copper is thermally stable upon heating to a temperature of 150°C. It has been found that the ρ/ρ0 ratio of copper with an SMC+NC structure at a temperature of 4.2 K is considerably (by 5 times) higher than ρ/ρ0 of copper in the annealed coarse-grained state. This effect is due to a high concentration of defects and a high degree of dispersity of the copper structure after DCAP. Changes in the microhardness and in the resistivity (at a temperature of 4.2 K) of the SMC+NC copper after annealing characterize the level of relaxation processes.

The structure and microhardness of VT1-00 and VT1-0 titanium is studied after dynamic channel angular pressing (DCAP) at 20 and 500°C. It is established that DCAP at 20°C leads to partial fracture of a sample and the accumulation of cracks. DCAP at 500°C allows one to retain samples unfailed and to obtain a mixture of deformed portions and recrystallized 2- to 3-μm grains in their structures.

The macro- and microstructure have been analyzed and the tensile mechanical properties have been measured for commercial titanium subjected to dynamic channel angular pressing (DCAP) at high temperatures using one or two passes, as well as to additional warm rolling and low-temperature annealing. The structure of titanium after DCAP at a high temperature consists of a dispersed mixture of fine recrystallized grains (1 to 2 μm in size) and deformed nonrecrystallized regions. The deformed regions have a subgrain structure with sub-grains 200–300 nm in size. After the second pass, the size of the recrystallized grains becomes less by two times as compared to their size after one-pass DCAP, the subgrains in the deformed regions acquire a more equiaxed shape, and the microstructure becomes more uniform. The warm rolling of the samples subjected to DCAP at high temperatures increases the total density of dislocations and provides a high level of internal stresses. After two-pass DCAP at 530°C, the ultimate strength of titanium was 650MPa and the relative elongation was 19%. Additional rolling to 50% at 300°C and low-temperature annealing increases the ultimate strength to 790 MPa, while the relative elongation is retained at a high level of 15%.

A mathematical model of the process of electrochemical intercalation of a granular graphite bed in nitric and sulfuric acids that takes into account the varying physicochemical properties of the graphite matrix is proposed. The numerical solution of the problem by the finite element method shows that, in agreement with the literature data, the current distribution is nonuniform even for a granular bed of a small height (∼2 × 10−2 m), which results in the synthesis of a nonuniform product. The methods of assessing the nonuniformity of intercalation and its elimination by passing to a multistage process are proposed. The results of numerical methods can be used in predicting the technological characteristics of the final product.