High-resolution dissociative recombination of cold H3+and first evidence for nuclear spin effects

The energy-resolved rate coefficient for the dissociative recombination (DR) of H(3)(+) with slow electrons has been measured by the storage-ring method using an ion beam produced from a radiofrequency multipole ion trap, employing buffer-gas cooling at 13 K. The electron energy spread of the merged-beams measurement is reduced to 500 microeV by using a cryogenic GaAs photocathode. This and a previous cold- measurement jointly confirm the capability of ion storage rings, with suitable ion sources, to store and investigate H(3)(+) in the two lowest, (J,G) = (1,1) and (1,0) rotational states prevailing also in cold interstellar matter. The use of para-H(2) in the ion source, expected to enhance para-H(3)(+) in the stored ion beam, is found to increase the DR rate coefficient at meV electron energies.     

Formation of a system of InGaAs quantum wires in a gallium arsenide matrix

The formation of a system of one-dimensional quantum conductors in porous multilayer In_xGa_1?xAs/GaAs structures with a two-dimensional charge-carrier gas in the In_xGa_1?xAs layers is discussed. The transition from the single-crystalline to porous matrix is studied with scanning atomic force microcopy. A decrease in the dimensionality of the electron-hole gas in the objects, i.e., a transition from the two-dimensional to a one-dimensional system, is established by analyzing the dependences of the position and width of a spectral line in the photoluminescence spectra on the etching time. Both multilayer periodic superlattices and a structure with a single In_xGa_1?xAs layer located near the surface of gallium arsenide are studied. The electrophysical characteristics of electrons in the porous superlattices are measured as functions of temperature. They confirm the formation of a new structure and indicate a change in the mechanism of electron scattering in the quasi-one-dimensional transport channels formed in the system.     

Simulation of pulsed-laser-induced explosive boiling

Bulk evaporation process in absorbing condensed matter irradiated with laser pulses was studied using the one-dimensional thermal model with additional interfaces between different phases. Within this approach, it was shown that the repeated explosive boiling mode can be achieved using nanosecond laser pulses, if the nucleation time is shorter than 0.1 ns. This mode can be observed if the surface pressure is lower than the critical pressure P _c of the liquid-vapor phase transition. The dependences of these processes on the laser pulse intensity and duration, as well as on evaporation kinetics were studied. Explosive boiling and spallation of a transparent liquid film on a pulse-heated absorbing target, as well as the photoacoustic signal in the target before the explosion, were considered.     

Modeling of blood microcirculation processes with allowance for pulse pressure oscillations

Processes of unsteady transcapillary exchange in hemodynamics with allowance for plasma motion in the interstitial space are studied by methods of physical and mathematical modeling. The presence of pulse oscillations of pressure in the network of capillaries is responsible for separation of filtration and re-absorption through capillary walls in space and time. General and specific properties of functioning of the arteriole, intermediate, and venule segments of the capillary network in exchange properties are demonstrated. Pressure oscillations are found to enhance transcapillary exchange.     

One approach to constructing a minimal convex hull

The minimal convex hull of a subset of finite-dimensional space is constructed in a discrete fashion: at each step, we construct a new set that includes the inherited set. The procedure for finding the chain of sets involves geometrically evident constructions. This chain becomes stationary; i.e., from some number onward, all the sets of the chain being constructed coincide with the minimal convex hull. Our approach uses the principal result (Caratheodory’s theorem) underlying the conventional approach to constructing a minimal convex hull.     

On the strong solutions of a regularized model of a nonlinear visco-elastic medium

We consider the initial boundary-value problem for the system of equations describing the motion of a nonlinear visco-elastic medium with memory along the trajectories of the velocity field; the system in question is a generalization of the system of Navier-Stokes equations. We establish existence and uniqueness theorems for strong solutions containing higher derivatives that are square-integrable in the plane case.     

Cyclocondensation of chalcones with 2-amino- and 1,2-diaminobenzimidazoles

2,4-Diaryl-1,4-dihydropyrimido[1,2-a]benzimidazoles were obtained by the reaction of 2-aminobenzimidazole with chalcones, and their heteroaromatization was accomplished. The condensation of 1,2-diaminobenzimidazole with unsymmetrically substituted chalcones, which leads to substituted pyrimido-[1,2-a]benzimidazoles, was studied. The specificity of this reaction was ascertained by means of alternative synthesis.Translated from Khimiya Geterotsiklicheskikh Soedinenii, No. 8, pp. 1071–1075, August, 1989.     

Reaction of diaroylethylenes with ortho-phenylenediamine and its derivatives

Derivatives of 1,2-dihydroquinoxaline were synthesized. The direction of the reaction of unsymmetrical diaroylethylenes with o-phenylenediamine was shown by chemical and spectral methods and the reaction mechanism was discussed.Translated from Khimiya Geterotsiklicheskikh Soedinenii, No. 5 pp. 656–661, May, 1986.