Volume 43, Nº 8 (2017)

A magnetic measuring microscope with a spatial resolution of 3 μm in the determination of current dipole coordinates is described. For the primary transducer, a film Hall transducer with sensitive-zone dimensions of 250 × 400 μm is used. The transducer is positioned at a distance of 3 mm from the plane of scanning. Superresolution as compared to the sensor dimensions and distance from the object was reached by using a priori information about the scanned object. A means of calibration of the magnetic microscope and measurement of its metrological characteristics is proposed. The effectiveness and consistency of the obtained estimate of coordinates is shown by comparison of the random error in measurements of current dipole coordinates with the Cramér–Rao bound. The measuring microscope can be applied in studying elements of functional electronics.

Averaged fields of thickness of an isothermal vertically flowing liquid film, obtained by the laserinduced fluorescence method, have been analyzed. The chosen minimum averaging time interval, at which the wave motion is completely averaged, allows one to observe rivulet dynamics in a transverse direction. It is found that short-lived rivulets, which are chains of no less than five to eight waves with similar transverse coordinates, are dominant structures on the film surface at Reynolds number Re > 50.

The possibility of obtaining a stoichiometric Bi₂Se₃ film by vacuum-thermal treatment of a Se/Bi heterostructure is demonstrated for the first time. It was found that a stoichiometric Bi₂Se₃ film can be only produced at a certain ratio of the Se and Bi film thicknesses (d_Se/d_Bi = 3.13). X-ray-diffraction analysis and Raman spectroscopy were used to study the phase transformations in a Se(141 nm)/Bi(45 nm) heterostructure upon its thermal treatment in a vacuum. The phase transition temperatures at which various crystalline phases are formed were determined. It is shown that Bi₂Se₃ crystallizes in the Se(141 nm)/Bi(45 nm) heterostructure heated to 493 K in conformity with an exponential law, with a characteristic time in which the equilibrium state is attained equal to 20 min.

The variation of interatomic interaction energy during allotropic transition in titanium is established by analyzing the stress and temperature dependences of durability. This energy is ≈458 kJ/mol in bodycentered β-Ti at a temperature of T > 1155 K, which agrees well with the titanium sublimation heat, and ≈305 kJ/mol in hexagonal close-packed α-Ti at T < 1155 K. Literature data confirming the conclusions drawn are discussed.

Hybrid particles with a core–shell structure have been obtained in the form of monodisperse spherical mesoporous silica particles filled with magnetite and covered with a mesoporous silica shell functionalized with a luminescent dye. The particles have a small root-mean-square size deviation (at most 10%), possess a specific surface area and specific pore volume of up to 250 m²/g and 0.15 cm³/g, respectively, and exhibit visible luminescence peaked at a wavelength of 530 nm. The particles can be used in diagnostics of cancerous diseases, serving simultaneously for therapeutic (magnetic hyperthermia and targeted drug delivery) and diagnostic (contrast agent for magnetic-resonance tomography and luminescent marker) purposes.

The compaction behavior is studied in Al₂O₃ ceramics with a pore space volume in the range from 35 to 60% and with the following three types of hierarchical pore structure: coarse porosity with a size of 80 to 100 μm, fine porosity with a size of 14 to 15 μm, and intermediate interblock porosity comprised of elongated (110–120 μm) porous microchannels formed as a result of zonal isolation during sintering. It is shown that the obtained hierarchical porous structure causes the formation of a hierarchical deformation structure in the volume of ceramics and leads to a decrease in the extent of destruction processes from the macroscopic scale in the case of unimodal ceramics to the microscale destruction comparable with the sizes of the blocks formed during sintering.

We present the results of investigation of the tensoresistive characteristics of crystals of TlIn_1–xCo_xSe₂ solid solutions with compositions in the interval of cobalt concentrations within 0 ≤ x ≤ 0.5. In addition, the temperature dependence of the tensometric sensitivity of crystals has been studied at 300 K ≤ T ≤ 410 K. The crystals under consideration proved to be promising materials for semiconductor tensometry.

Threshold values of an electric field for anisotropic spinodal decomposition of water in a supercritical region at T = 670 K and at a low temperature of about 350 K have been calculated. This threshold depends on the second derivative of the dielectric permittivity with respect to density. The dependence of the permittivity of medium on its density was determined by studying fluctuations of the polarization vector in a broad range of densities at the given temperatures. Time series of fluctuations of the polarization vector of ensembles of water molecules were constructed by the method of molecular dynamics.

We describe a device for obtaining cold plasma in air at atmospheric pressure using a system of positive high-voltage pin electrodes, which is intended for the treatment of skin and soft-tissue injuries in animals. Plasma is generated due to the development of periodic pulsed discharge of nanosecond duration at current pulse amplitudes 10–20 mA, characteristic frequencies 10–20 kHz, and applied voltages within 8–10 kV. The high efficacy of the proposed device and method is confirmed by the good clinical results of treating large domestic animals with traumatic injuries.

Nonlinear dynamics of a charged particle in a radiofrequency multipole ion trap has been studied for the first time by the method of direct averaging over rapid field oscillations. An expression for the twodimensional effective potential of this trap is obtained, and regions of ion localization are determined. A Poincaré section is presented that clearly demonstrates the nonlinear character of ion dynamics in the multipole trap.

We propose to stabilize the azimuthal structure of superradiance pulses using two-dimensional (2D) periodic Bragg structures that simultaneously play the role of a slow-wave system. Analysis performed in the framework of a quasi-optical approach is confirmed by the results of 3D particle-in-cell modeling that demonstrates the possibility of using the proposed system for generating multi-GW nanosecond radiation pulses in the millimeter waveband.

We report the basic possibility of creating a micro fuel cell (MFC) with a monolithic silicon-based membrane–electrode assembly (MEA), which employs a porous three-layer framework structure manufactured by two-sided anodic etching of a 500-μm-thick silicon wafer. A technology of MEAs for MFCs is described.

We have studied the characteristics of the structure, composition, and electrocatalytic properties of thin MoS_x films obtained by pulsed laser deposition using an Mo target ablated in H₂S reactive-gas medium. The laser plume during deposition was directed tangentially and normally to the substrate, which allowed amorphous films to be obtained with different local atomic packings in an amorphous matrix consisting of Mo₃–S clusters. It is established that the orientation of Mo₃–S clusters influences charge transport in the catalyst and determines the type and surface density of catalytically active sites in the reaction of hydrogen evolution. For small, approximately equal amounts of Mo and Pt (~4 μg/cm²) laser-deposited on glassy carbon substrates, the MoS_x films were inferior to a Pt film with respect to hydrogen overvoltage (by about 90 mV) in acid solution, but the efficiency of thin-film MoS_x catalysts at elevated cathode potentials exceeded that of a thin Pt film.