Functional characteristics of Bi2Sr2Ca2Cu3O10 + δ/ZrN composites

We present the results of investigation of the magnetic, transport, structural, and mechanical properties of composites obtained by introducing finely dispersed zirconium nitride into a matrix of a Bi₂Sr₂Ca₂Cu₃O_{10 + δ} (Bi2223) high-temperature superconductor. It is established that the introduction of ZrN particles in the range of very small concentrations (0.1–0.3 wt %) leads to a significant (more than threefold) increase in the critical current density of Bi2223 and increases the density of the composite, while the microhardness of the superconducting phase remains unchanged.     

Calculation of the size-distribution function for quantum dots at the kinetic stage of growth

A theoretical model for calculating the distribution of quantum dots in size in the case of growth according to the Stranski-Krastanow mechanism in the lattice-mismatched heteroepitaxial systems is suggested. The model is based on the general theory of the islands’ nucleation at the first-order phase transition, in which situation the role of the metastable phase is played by the overstressed wetting layer, while the elastically stressed three-dimensional islands act as nuclei of the new phase. The suggested model clarifies and generalizes a number of the results reported previously. The theory can be used at the kinetic stage of formation of quantum dots, in which case their ensemble is noninteracting. An example of calculation of the kinetics for formation of hut-shaped clusters in the heteroepitaxial Ge/Si(100) system is given.     

A mechanism of charge transport in electroluminescent structures consisting of porous silicon and single-crystal silicon

Electroluminescent structures that emit in the visible region of the spectrum and are based on porous silicon (por-Si) formed on the p-Si substrate electrolytically using an internal current source are fabricated. The photoluminescent and electroluminescent properties, as well as the current-and capacitance-voltage characteristics of the structures are studied. Electroluminescence is observed only if the forward bias voltage is applied to the structure; the electroluminescence mechanism is based on the injection and is related to the radiative recombination of electrons and holes in quantum-dimensional Si nanocrystals. The injection of holes is controlled by the condition of their accumulation in the space-charge region of p-Si and by a comparatively low concentration of electronic states at the por-Si/p-Si interface. The charge transport in por-Si is caused by the direct tunneling of charge carriers between the quantum-mechanical levels, which is ensured by an appreciable number of quantum-dimensional Si nanocrystals. The leakage currents are low as a result of a small variance in the sizes of Si nanocrystals and the absence of comparatively large nanocrystals.     

Magnetotransport properties of type II heterojunctions based on GaInAsSb/InAs and GaInAsSb/GaSb

The results of detailed study of the magnetotransport properties of broken-gap type II heterojunctions in a GaInAsSb/InAs(GaSb) system are reported. An electron channel with a high charge-carrier mobility (as high as 50000–60000 cm²/(V s)) is observed and studied for the first time in an isotype broken-gap p-GaInAsSb/p-InAs heterostructure. The effects of electron-channel depletion and semimetal-semiconductor transition in the case of heavy doping of the quaternary alloy with acceptors are studied. Magnetotransport properties at temperatures of 4.2–200 K are studied in detail. Data on the energy spectrum and parameters of two-dimensional charge carriers at the heteroboundary are obtained. It is ascertained experimentally that, depending on the composition, either staggered (at x = 0.85) or broken-gap (at x = 0.95) heterojunctions can be formed in the Ga_1?x In_xAs_ySb_1?y /GaSb, which is confirmed by theoretical calculations. The anomalous Hall effect and negative magnetoresistance were observed in GaInAsSb/InAs:Mn grown on substrates doped heavily with Mn magnetic acceptor impurity so that the hole concentration was as high as p > 5 × 10¹⁸ cm^?3; these phenomena are caused by exchange interaction of Mn ions in InAs with high-mobility charge carriers in the electron channel at the heterointerface.     

Investigation of the safety of the product "Rialam."

The data on safety investigation of product "Rialam", which is proposed as biologically active food supplement are presented. Chronic experiment and single generation experiment were made on Wistar rats. It is shown that diet "Rialam" in dose 100 mg/kg of body weight didn't influence negatively on growth and development of rats blood parameters, immune status, internal organs morphology, metabolism, hadn't embryotoxic, gonadotoxic and teratogenic action.     

The band structure and the double metal-insulator-metal phase transition in the conductivity of elastically strained zero-gap Cd<Subscript><Emphasis Type="Italic">x</Emphasis></Subscript>Hg<Subscript>1−<Emphasis Type="Italic">x</Emphasis></Subscript>Te

In the zero-gap Cd _x Hg_1?x Te semiconductor subjected to an axial elastic strain, a band gap is formed between the bottom of the conduction band and the top of the valence band. In the new state, the band structure is found to depend on the initial arrangement of the valence subbands, i.e., on the composition defined by the parameter x. At x < 0.135–0.140, the material becomes a semiconductor with an indirect band gap. If 0.140 < x < 160, the band of light holes at k = 0, Γ₆, is found to be above the Γ₈ band. As a result, the material becomes a direct-gap semiconductor, and a double “metal-semiconductor-metal” phase transition in conductivity occurs. In this case, as the strain is increased, the type of conductivity of the zero-gap semiconductor at low temperatures changes according to the sequence as follows: electron metallic conductivity-electron activation conductivity-hopping conductivity-hole metallic conductivity.     

Oxidative-gravimetric porosimetry of macroporous silicon

A simple nondestructive method to find the internal surface area, porosity, pore diameter, and pore density in macroporous silicon with through channels is suggested and tested. The porosity p is determined from the mass loss upon anodizing, and the surface area per unit volume, S _v , from the mass of SiO₂ formed on the pore surface upon thermal oxidation. The relations are given for calculation of the average pore diameter d and pore density N from the obtained S _v and p. Dependences of the specific surface area and porosity on the resistivity of initial n-Si in the range ρ = 3–25 Θ cm have been studied for samples with ordered and self-organized “lattices” of macropores. The obtained values are within the limits p = 27–50%, S _v = 2800–6000 cm²/cm³, d = 1.9–6.5 μm, and N = 1.4?10 × 10⁶ cm^?2, in agreement with the data fumished by microscopy.     

Demonstrating high-power 30-GHz free-electron maser operation on a resonant load

An effective narrow-band free-electron maser (FEM) with reversed axial guide magnetic field, based on a corrugated high-selectivity Bragg resonator with a jump in the ripple phase, has been constructed and tested. The FEM operates at 30 GHz with characteristics of the output radiation (power, pulse duration, spectrum width) and stability of the generation regime that allow the device to be used in testing electrodynamic components for future electron-positron supercolliders. Experiments have been performed with a high-Q resonator operating on a resonant load, which can be used to model the degradation of an accelerating structure of the CLIC collider (CERN) as a result of thermal fatigue caused by the multiply repeated (∼10⁵ cycles) action of microwave pulses.     

Accessory artificial circulation in complex treatment of experimental acute toxic pulmonary edema

In experiments on 50 dogs with toxic acute edema of the lung, induced with intravenous injection of 0.1% silver nitrate, the authors have studied the efficacy of accessory artificial circulation and "conservative" therapy. During the perfusion a discharge of the right portions, adequate extracorporeal gas metabolism, normalization of blood gas and acid-base balance were noted; an intensity of pulmonary edema is descreased. An intensive therapy for pulmonary edema was found to be more effective in association of "conservative" treatment with venoarterial perfusion and blood oxygenation.     

The peculiaries of the nutrition and immune status of people in the condition of penitentiary establishment

The decrease of calorie in ration content, insufficient consumption of proteins and lipids was found among the patients in the condition of penitentiary establishment, it results in decrease of characteristics of natural immunity and resistibility to various infections agents, to the action of toxic substances, stress and other negative conditions that take place in penitentiary establishment a disbalanse of regulatory subpopulation of cellular consistent of immunity and predominance of suppressive-cytotoxic influence was observed among the patients of the penitentiary establishment (with a reduced ration of nutrition) over halt a year. Considering a health problem, in the establishments of imprisonment one may probably state that a reduced ration of nutrition is one of the main courses of immune homeostasis shift leasing in the basis of specific and non-specific phenomena of morbidity.