Experimental setup to study catalysts by combined pulse microcatalytic and ESR spectroscopic methods

A setup consisting of an ESR spectrometer and a pulse microcatalytic installation is suggested for simultaneous kinetic and spectral measurements directly in catalytic processes.

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Nonlinear Current-Voltage Curves for Thin-Film Gas-Sensitive Structures

Current-voltage curves for sensor structures based on thin tin oxide films are examined in various gases. Conditions favoring symmetrical nonlinear curves in the voltage range −30 to 30 V are found.__________Translated from Elektrokhimiya, Vol. 41, No. 6, 2005, pp. 735–737.Original Russian Text Copyright © 2005 by Simakov.Published on the basis of a report delivered at the VII Meeting on Fundamental Problems in Solid-State Ionics (Chernogolovka-2004).     

Calculation of the drag and heat transfer from a sphere in the gas flow in a cylindrical channel

A numerical experiment on the simulation of heat transfer from a sphere to a gas flow in a cylindrical channel in the Stokes and transient flow regimes has been described. Radial and axial profiles of the gas temperature and the dependences of drag coefficient C_d of the body and Nusselt number Nu on Reynolds number Re have been calculated and analyzed. The problem of the influence of the early drag crisis for a sphere on its heat transfer to the gas flow has been considered. The estimation of this phenomenon has shown that the early drag crisis of the sphere in a strongly turbulent flow causes a reduction in heat transfer from the sphere to the gas by three to six times (in approximately the same proportion as for its drag coefficient).     

Calculations of the flow resistance and heat emission of a sphere in the laminar and high-turbulent gas flows

An early drag crisis can occur at high turbulence of incoming gas flow to a sphere. To study the influence of a crisis on heat transfer from a sphere to gas, a numerical experiment was carried out in which the free gas flow around a sphere with a temperature lower than the sphere temperature was simulated for two cases. The flow was laminar in the first case and highly turbulent in the second case. To take into account turbulence, the kinematic coefficient of turbulent viscosity with a value, which is much higher (up to 2000 times) than that for physical viscosity, was introduced. The results of calculations show that the early drag crisis occurs at Reynolds numbers of about 100 and results in considerable (by four to seven times) decrease in the hydrodynamic force and sphere drag coefficient C _d . The early drag crisis is also accompanied by the crisis of heat transfer from a sphere to gas with a decrease in Nusselt numbers Nu by three to six times.     

Synthesis and some properties of 4-oxo-3,4-dihydro- and 2,4-dioxo-1,2,3,4-tetrahydropyrimido[5,4-b]indoles

The condensation of N-(2-ethoxycarbonylindol-3-yl)-N,N-dialkylamidines with ammonia, primary amines, and hydrazines has given a series of 4-oxopyrimido[5,4-b] indoles which have been converted into the 4-chloro and then into the 4-methoxy, 4-dialkylamino, and 4-mercapto derivatives. 2,4-Dioxopyrimido[5,4-b]indoles have been synthesized by the successive action of chloroformic ester and then methylamine, hydrazine, or ethylhydrazine on 3-amino-2-ethoxycarbonylindoles differing by their substituents in position 5.Translated from Khimiya Geterotsiklicheskikh Soedinenii, No. 5, pp. 635–639, May, 1985.     

Mass spectrometric study of the overheated vapor over Ni(II), Cu(II), and Zn(II) N,N′-ethylenebis(acetylacetoniminato) complexes

A mass spectrometric study of the overheated vapor over the complexes Ni(acacen), Cu(acacen), and Zn(acacen) (H₂acacen = N,N′-ethylenebis(acetylacetonimine)) has been carried out in the temperature range of 180–760°C. Irrespective of the degree of overheating, the vapor phases over all of these compounds contain no ions heavier than the molecular ion [MO₂N₂C₁₂H₁₈]⁺. The existence of molecular ions in the overheated vapor in the double-chamber two-temperature effusion cell is evidence of the high thermal stability of the complexes. The onset temperature of the thermal decomposition of Ni(acacen), Cu(acacen), and Zn(acacen) is 690, 610, and 560°C, respectively. The way of fragmentation of the chelates under electron impact ionization depends on the nature of the metal.     

The sorption of molybdenum by polymeric chelate-forming sorbents with the o-hydroxy?1-Azo-1′?o′-hydroxy functional group

The sorption of molybdenum by synthesized polymeric chelate-forming sorbents (PCSs) based on hydroxypolystyrene and a structural fragment with o-〈1-azo-1′〉o′-hydroxybenzene was studied. A mechanism of the sorption of molybdenum(VI) was suggested and substantiated. Qualitative correlations between the most important physicochemical parameters of the sorbent, sorption process, and sorbate (chelate) were established and described. The correlations can be used to quantitatively predict the physicochemical parameters of sorbents and their chelates for the purposes of synthesis, the use of PCSs for the concentration and isolation of elements, and physicochemical studies.