Vol 63, No 8 (2018)

The process of diffusional phase transformation described by the two-phase Stefan-type model with the free boundary has been considered. In terms of this model, an inverse problem of boundary conditions that provide the displacement of the free boundary by a given law has been stated. The problem has been solved numerically using a computational algorithm that exploits the front rectification method and a variational approach with local regularization.

We report on the results of mathematical simulation of the interaction of various sequences of proteins Mdm2, P53, and Nap1 in accordance with the developed algorithms that were used for identifying the region of binding of various proteins during the formation of biological complexes P53–Mdm2, Mdm2–Mdm2, and Nap1–Nap1. The approach developed in this work will make it possible to determine active regions of binding of polypeptide chains of various proteins and to choose and synthesize highly selective peptides that will be bound in the active center of a protein and will lead to its activation or inhibition and blocking of its biological functions.

Electric field that extracts ions from polar solutions to gas phase is calculated for membrane interface with electrode located on the vacuum surface of the membrane. Such a structure can be used to significantly decrease the voltage that provides efficient emission of ions from solution filling the membrane channel and, hence, improve the characteristics of membrane interface.

The results of investigation of discharge characteristics of the Penning plasma source are presented. Volt-ampere characteristics (VAC), energy distribution, and mass-charge composition of ions emitted from the discharge under different modes of its combustion were measured. The connection between the discharge current bursts and increase in the potential drop (up to 50% of the anode voltage) is established. The measured VACs agree well with the theoretical dependencies. It is shown that the content of atomic hydrogen ions increases from 5 to 10% with an increase in the anode voltage from 1 to 3.5 kV and the power applied in the discharge (from 0.2 to 3 W).

We have analyzed the beam instability taking into account nonpotential effects in a completely magnetized plasma with a density varying slowly with time. It is shown that a frequency shift appears in the amplified signal (during the propagation in such an electrodynamic system); analytic relations determining this shift have been obtained.

Basic magnetic characteristics (coercive force H_c, residual magnetization M_r, magnetization M, and saturation magnetization M_s) of solid solutions of type (CuInSe₂)_1–x(MeSe)_x (Me = Mn, Fe) have been investigated in a wide temperature interval (100–300 K). The existence of a magnetic phase transition has been established for all studied solid solutions at low temperatures, and the Néel temperatures have been determined from the temperature dependences of the magnetization. It is shown that the temperature dependences of coercive force H_c and of magnetization M can be described using the thermal relaxation (fluctuation) theory.

We report on the results of investigation of anisotropy of the nonlinear magnetoelectric current effect in M-type hexaferrites with a collinear magnetic ordering at room temperature. It is found that as a result of the passage of a direct electric current in a plane perpendicular to the hexagonal axis of the strontium hexaferrite sample, the saturation magnetization and the anisotropy constant of the material decrease. The change in the magnetic parameters measured using radio spectroscopic methods is found to be proportional to the supplied electric power density; the determined proportionality factors turn out to be several times larger than in the case when the current passes along the axis. We propose a phenomenological theory that explains the observed effects qualitatively.

A multilayer system of ohmic contacts for GaAs/AlGaAs photovoltaic converters has been developed. A method of ohmic contact blackening is suggested with the aim of improving the coefficient of optical signal reflection from an Ag/Au/Ag multilayer contact. Owing to blackening, the reflection coefficient has been decreased more than tenfold.

Double-layer thin-film compositions with a TiN coating based on a ferromagnetic Ni–5 at % W alloy and a paramagnetic Ni–9.5 at % W alloy have been prepared. Texturing in both components of the Ni–W/TiN system has been studied using X-ray diffraction analysis. It has been found that the coating layer causes crystal planes in the Ni–9.5 at % W strip to reorient and thereby enhances the cube texture in the substrate. It has been shown that under certain growth conditions, a thin TiN coating above the Ni–9.5 at % W/TiN substrate grows quasi-single-crystalline with a cube texture.

The possibility for using the ferrite-garnet magnetooptical films with a band domain structure has been considered with the aim of visualization of the spatial distribution of a magnetic flux near sensitive elements of a high-temperature superconductor matrix. The methods that enhance the efficiency of magnetooptical conversion have been suggested.

A quasi-plausible algorithm is synthesized for detection of ultrawideband quasi-radio-signal with arbitrary shape and unknown amplitude, initial phase and duration. Statistical characteristics of the efficiency of the proposed algorithm (false-alarm and signal-omission probabilities) are determined. A decrease in the detection efficiency due to a priori ignorance of the signal parameters is characterized.

The use of an electronic cooling system at the High Intensity heavy ion Accelerator Facility (HIAF) accelerator complex, which is being developed at the Institute of Modern Physics (China), to improve the efficiency of ion injection into the accelerator and reduce the spread of ion pulses in the beam has been proposed. Electron cooling of the ion beam was carried out due to the interaction of ions with a continuous electron beam with a current of up to 3 A, energy of up to 450 keV, and energy stability at the level of 10^–4 or better. The electron beam energy recuperation was carried out at the expense of a power source with a power of 5–15 kW, which was located at the top of a high-voltage column—a high-voltage terminal. The operation of a prototype of power transmission system, which was based on a cascade transformer with a volumetric coil, has been considered. Such a transformer has a relatively low scattering inductance, which can significantly reduce the number of capacitors to compensate for it. It has been shown that this design made it possible to transfer power of up to 40 kW at small dimensions of the transformer and heat dissipation in it was not more than 10 kW.

Iron nanopowders and iron and aluminum micropowders exposed to microwave radiation with a frequency of 9.4 GHz and a power density of 80 W/cm² at a pulse repetition rate of 400 Hz have been investigated. According to the results of differential thermal analysis, the microwave radiation caused nonmonotonic changes in the thermal properties of the A1 and Fe powders. After irradiation of the iron nanopowder, the temperature of the onset of its oxidation increased from 150.01 to 158.75°C; in the case of the micropowder, the temperature nonmonotonically changed from 150.00 to 275.38°C. The specific heat of oxidation of the Fe nanopowder increased by 17.3% at maximum, while in the Fe micropowder the maximum attained increase was 13%. For the Al micropowder, the maximum increase in the specific heat of oxidation was found to be 59.7%. Microwave irradiation leads to the formation of electron avalanches, which reduce metal ions in their oxides. At the same time, at certain irradiation doses the generated electron flows oxidize the reduced metals, which is reflected in the nonmonotonic variation in the properties of a material. The increase in the specific heat of oxidation is related to the participation of energy-saturated states of the metals in the oxidation processes.

The surface of silicon substrates has been studied experimentally and theoretically by the method of atomic force microscopy spreading resistance imaging, and measuring techniques for the spreading resistance of semiconductors have been developed based on these data. It has been shown that the resistivity of silicon can be determined reliably if the force with which the probe is pressed against the substrate exceeds some threshold. The influence of the environment on the values of currents in the probe–substrate system has been studied. It has been found that the electrical performance of semiconductors can be properly determined by atomic force microscopy spreading resistance imaging under high-vacuum conditions.