Relativistic backward wave oscillator using a selective mode converter

A new version of the relativistic backward wave oscillator (BWO) is proposed and investigated experimentally, where the cutoff (for the working mode mode) taper at the cathode end is replaced by a selective Bragg-type mode converter. In the experimental BWO model, which operates in the three-centimeter range and is equipped with a mode converter based on a slightly corrugated waveguide, a radiated power of 700 MW in pulses of duration up to 100 ns with an output spatial structure similar to a Gaussian wave beam is obtained at an accelerating potential of 0.8 MV and a focusing magnetic field of 7 kOe. Zh. Tekh. Fiz. 69, 102–105 (November 1999)     

Double Electric Layer of a Helium Discharge in Modulation Mode

Russian Physics Journal - The positive column of a helium gas discharge in modulation mode has been investigated. It has been revealed that the contribution of the stepwise ionization to population...     

Formylation of 1,2,3,4-tetrahydro-2,4,5-trimethylpyrrolo-1-2,c]pyrimidine. Its conversions to the 7-formyl derivative with opening of the tetrahydropyremidine ring

We have optimized the method for obtaining 1,2,3,4-tetrahydro-2,4,5-trimetkylpyrrolo[1,2-c]pyrimidine. We carried out the reactions of quaternization, forinylation, and opening of the tetrahydropyrinddine ring of its 7-formyl derivative and the oxime of this carbonyl compound.Russian University of International Friendship, Moscow 117923. Translated from Khimiya Geterotsiklicheskikh Soedinenii, No. 4, pp. 534–539, April, 1995. Original article submitted March 14, 1995.     

Influence of ethylene and some defoliants on the dynamics of the change in the protein spectrum in cotton plant shoots

Translated from Khimiya Prirodnykh Soedinenii, No. 1, pp. 177–178, January-February, 1995. Original article submitted October 17, 1994.     

Isolation and characterization of neurotoxins from the venom of the spiderAnemesia sp.

Three neurotoxin fractions have been isolated from the venom of the spider Anemesia sp. On interacting with a presynaptic membrane, two of them (An4 and Any) caused an enhancement of the secretion of the mediator and exhaustion of its reserves, while the third (An7) caused suppression of the amplitude of the synaptic potentials.Institute of Physiology and Biophysics, Academy of Sciences of the Republic of Uzbekistan, 700095, Tashkent, ul. Niyazova, 1. Translated from Khimiya Prirodnykh Soedinenii, No. 3, pp. 471–473, May–June, 1995. October 24, 1994.     

Unstructured adaptive remeshing finite element method for dusty shock flow

The passage of planar shocks in a dusty gas was investigated to note effects due to particle loading and initial shock Mach number. Two-phase flow equations have been added to a conservative, monotonic flow solver to allow study of compressible particle and droplet flows, which are of importance for shock propagation in two-phase flows and spray propulsion systems. The formulation developed herein employed a conservative Eulerian treatment for the gas and particle phases. The computations were performed using the finite element method-flux corrected transport (FEM-FCT) scheme, which has shown excellent predictive capability of various compressible flows which include both strong and weak shocks. The flux limiting technique was modified to provide monotonic particle velocity fields to increase the scheme's computational stability. Adaptive unstructured methodology based on adapting to high gradients of both the fluid and particle densities was used in conjunction with the conservative shock-capturing scheme to adequately resolve strong flowfield gradients. The shock attenuation of this scheme was then compared with previous experimental and numerical results and was found to yield robust predictions. Various interphase coupling terms were also considered to note their effect on the shock attenuation.This article was processed using Springer-Verlag t_ex Shock Waves macro package 1.0 and the AMS fonts, developed by the American Mathematical Society.     

Kinetic anomalies of crystal growth: Development of methodical approaches and interpretations

Crystal growth rate in solutions is characterized by the so-called anomalies in the form of maxima and minima alternating with a change in temperature. This phenomenon was discovered by Sipyagin and Chernov in 1967. To date, it has been found for all thoroughly investigated materials. In this paper, the kinetic anomalies of electrochemical deposition of metals (Cu and Hg) from CuSO₄ and Hg(NO₃)₂ solutions are described for the first time. The data on the growth of CuSO₄ · 5H₂O crystals in a solution are reported. On the basis of comparison of the characteristics of anomalies for Cu-CuSO₄ · 5H₂O and Cu-Hg pairs, with due regard for the expected general and different features of the structure of solutions and adsorption layers, it is concluded that this phenomenon is caused by the structural alterations in the bulk of the solution with a significant influence of the adsorption layer.     

Formation of GaAs nanowhisker arrays by magnetron sputtering deposition

The possibility is demonstrated of fabricating arrays of cone-shaped GaAs nanowhiskers with a surface number density of up to 10⁹ cm^-2, a characteristic height ranging from 300 to 10000 nm, and a transverse size of approximately 200 nm at the base and from 200 to 10 nm or smaller at the top. The characteristic height of GaAs nanowhiskers varies in direct proportion to the effective thickness of the deposited material layer and in inverse proportion to the transverse nanowhisker size at the top. The growth of GaAs nanowhiskers is studied as a function of the deposition rate, the temperature, and the crystallographic orientation of the substrate. From an analysis of the obtained dependences of the nanowhisker size on these parameters, it is concluded that GaAs nanowhiskers are formed through the diffusion mechanism.