Asymptotic stability of the numerical solution for an integrodifferential reaction-diffusion system

This paper presents the study of the numerical solution of a reaction-diffusion system involving a reaction term of integral type arising from biological models. By means of a monotone approach we introduce upper and lower solutions and then we show the existence and the asymptotic behavior of nonnegative numerical solutions. To this end, we require the positivity of the numerical scheme and so we can use some properties of positive and M-matrices. Finally we give some sufficient conditions to verify the asymptotic stability of the numerical solution.     

Relaxation dynamics of a broadband nanosecond acoustic pulse in a bubbly medium

The first experimental observation of the propagation dynamics of a short broadband acoustic pulse in a resonance medium with gas bubbles is carried out. The probing pulse is generated using the optoacoustic effect. It is shown that the theory of short pulse propagation in media with generalized resonance relaxation adequately and accurately describes the dynamics of short pulse dispersion. A possibility to determine the relaxation and resonance parameters of media by the pulsed testing technique is demonstrated.     

Characterization of GaAs layers grown on polycrystalline GaAs by LPE and current controlled LPE

It is the purpose of this paper to investigate the suitability and effectiveness of growth of thin GaAs layers on polycrystalline GaAs substrates by liquid phase epitaxy (LPE) and current controlled LPE (CCLPE). During each growth run LPE and CCLPE were used to grow thin GaAs layers on two large-grain polycrystalline GaAs substrates cut from the same wafer and simultaneously placed in the same growth system. The grain boundary was exposed by cleaving the samples perpendicular to the grain boundary. Notnarski contrast, SEM, C-V and Hall measurements were performed in order to determine the surface morphology, discontinuity of epilayer at the grain boundary, epilayer thickness unform-ity, resistivity (in directions parallel and perpendicular to the grain boundary), and dopant concentration. The CCLPE system was carefully designed so that growth would take place only by electrotransport in the absence of convection or Peltier cooling. The results indicate that CCLPE yields layers with improved surface morphology and thickness uniformity as compared to those grown by LPE. In some samples the epilayer was discontinuous at certain grain boundaries. Results are presented on CCLPE growth rate dependence upon grain orientation, current density, and continuity of the epilayer at the grain boundary.     

Analysis of a TEM Cell with Septum on a Dielectric Slab

A quasi-TEM approach based on conformal transformation is used for the determination of the characteristic impedance of a rectangular coaxial line (TEM cell) having a symmetrically located inner conductor (septum) supported on a dielectric slab of equal width. The method of determination of the capacitance of the dielectric-filled portion is discussed. The results on characteristic impedance for two values of dielectric constant are presented.     

Spatial regularities in the effect of locking of photon echo signals and associative optical memory

The efficiency of suppression of the generation of a photon echo response depending on the mutual spatial orientation of gradients of external nonumform electric fields acting on a resonant medium is studied. The possibility of creating an associative memory where the mutual orientation of the gradients of external electric fields is an associative key is discussed.     

Two-stream-like mechanism of zonal-flow generation by Rossby waves in a shallow rotating fluid

It is shown that the small-scale Rossby waves in a shallow rotating fluid placed in a gravitational field can generate large-scale zonal flows by means of a two-stream-like mechanism. This mechanism is revealed under the conditions when the Lighthill instability criterion is not satisfied. The text was submitted by the authors in English.     

Reaction of furan compounds with hydrogen peroxide in the presence of vanadium catalysts

The reactions of furan and a number of its derivatives (furfural, furan-2-carboxylic acid, 2-furfuryl alcohol, and others), in systems containing H₂O₂ and vanadium compounds, proceed through a mechanism of radical hydoxylation of the furan ring with the formation of 5-hydroxy-2(5H)-furanone and maleic acid. The total yield and ratio of the synthesized compounds depend on the reaction conditions.Translated from Khimiya Geterotsiklicheskikh Soedinenii, No. 11, pp. 1462–1467, November, 1991.