Fine Purification of Monoisotopic Silanes 28SiH4 , 29SiH4 , and 30SiH4 via Distillation

High-purity isotopically enriched (99.98% ²⁸Si, 99.57% ²⁹Si, and 99.83% ³⁰Si) silane samples are prepared for the first time. The total hydrocarbon content of the samples is no higher than 0.1–0.3 ppm. The concentration of electroactive impurities in the silicon prepared from the purified monoisotopic silane is below 10¹⁵ cm^–3.     

Multifrequency gyrotron with high-efficiency synthesized waveguide converter

The results of numerical simulation and experimental investigation of a prototype of a megawatt multifrequency gyrotron for controlled thermonuclear fusion facilities are presented. In experiments, the gyrotron has operated at six frequencies in the range 105–152 GHz with small diffraction losses in the internal quasi-optical system and a high Gaussian mode content in the output beam.     

The orthogenesis of atherosclerosis]

It has been ascertained that myofibroblasts penetrating the aortal intima from the medium layer because of its compensatory rearrangements in sites of wear and pull of the vascular wall when a fibrous plaque becomes a lipid one, get transformed in stages. Ordinarily elongated orderly arranged cells become spider-like ones, polymorphous, disintegrated cells. Lipid drops get accumulated in their cytoplasma. The above myofibroblasts were identified as Langhans' cells. Changes are reported in aortal intima plaques identical to those occurring in cell culture near the Ge?flik's [correction of Geuflick's] line. It means that accumulation of lipids in aortal plaques and atheromatous degeneration of the latter may be related to aging and necrosis of myofibroblasts which reach the Ge?flik's [correction of Geuflick's] line too soon in such sites of their compensatory proliferation as enlargements of fibrous tissue in the intima. Thus, atherosclerosis is to be regarded as quite a natural process, as reaction of re-arrangements of the vascular wall in sites of its premature wear. Prophylaxis of atherosclerosis is a problem of major social concern, which may be solved only through providing adequate conditions of work and life, cultivating a healthy life style.     

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.     

Vibratory comminution of A12O3 powders

Translated from Poroshkovaya Metallurgiya, No. 8(332), pp. 6–9, August, 1990.     

Precision determination of252Cf half-life and the time dependence of the neutron flux of a Ra - Be(α, n) source

Scientific-Industrial Association D. I. Mendeleev All-Union Scientific-Research Institute of Metrology. Translated from Atomnaya Énergiya, Vol. 73, No. 6, pp. 502-504, December, 1992.