Rotational kinetics of absorbing dust grains in neutral gas

We study the rotational and translational kinetics of massive particulates (dust grains) absorbing the ambient gas. Equations for microscopic phase densities are deduced resulting in the Fokker-Planck equation for the dust component. It is shown that although there is no stationary distribution, the translational and rotational temperatures of dust tend to certain values, which differ from the temperature of the ambient gas. The influence of the inner structure of grains on rotational kinetics is also discussed.Comment: REVTEX4, 20 pages, 2 figure

On costa variation in leaves of fossil permian protoshagnalean mosses

Leaves of extinct mosses of the order Protosphagnales are studied with the special attention to their different developmental stages. A previously unknown morphotypes without costa and with very short costa are revealed in this group. It is characteristic for young small leaves of Kosjunia and Intia , but apparently does not occur in other genera of this fossil order. The present collection allows restore a heteroblastic series in these leaves and associated with it differentiation of laminal areolationyesBelgorod State National Research Universit

New Bryokhutuliinia species (bryophyta) with sporophytes from the upper jurassic of Transbaikalia

A new species of the moss genus Bryokhutuliinia, B. crassimarginata is described from the Upper Jurassic deposits from the Olov, Transbaikal Area of South Siberia. Its excellent preservation demonstra- tes that the leaves were not only complanate, but truly distichous. In addition to anatomically pre- served gametophytes, sporophytes on short lateral branches were found, although carbonized and not exhibiting structural details. Possible relationships with pleurocarpous mosses and with Fissidentaceae are discussedyesBelgorod State National Research Universit

Interaction between dust grains near a conducting wall

The effect of the conducting electrode on the interaction of dust grains in a an ion flow is discussed. It is shown that two grains levitating above the electrode at the same height may attract one another. This results in the instability of a dust layer in a plasma sheath.Comment: 9 pages. 3 figures. Submitted to Plasma Physics Report

Effect of ionization/recombination processes on the electrical interactions between positively charged particles in highly collisional plasmas

The effect of ionization and recombination processes on the electrical interactions between a pair of small charged particles in highly collisional plasmas is discussed. In particular, it is shown that these processes suppress the long-range attraction between positively charged particles. The condition corresponding to the vanishing of attraction is derived. The role of the effect for conditions of existing experiments is estimated

On the leaf morphogenesis of palaeozoic mosses of protosphagnales

New fossil moss collections with an excellently preserved anatomy, forming the Permian deposits of the Pechora Coal Basin, allow study leaves at different stages of development, thus revealing morphogenetic patterns of their lamina differentiation. In some respects, these patterns are different from those of modern mossesyesBelgorod State National Research Universit

Stationary Velocity and Charge Distributions of Grains in Dusty Plasmas

Within the kinetic approach velocity and charge distributions of grains in stationary dusty plasmas are calculated and the relations between the effective temperatures of such distributions and plasma parameters are established. It is found that the effective temperature which determines the velocity grain distribution could be anomalously large due to the action of accelerating ionic bombarding force. The possibility to apply the results obtained to the explanation of the increasing grain temperature in the course of the Coulomb-crystal melting by reduction of the gas pressure is discussed. This paper was received by Phys.Rev.Lett. on 11 August 1999. As potential referees the authors offered to Editor the following persons: V.N.Tsytovich, Russia; R.Bingham, UK; D.Resendes, Portugal; G.Morfill, P.Shukla, Y.M.Yu., Germany.Comment: 8 pages, no figure

Superlattice with hot electron injection: an approach to a Bloch oscillator

A semiconductor superlattice with hot electron injection into the miniband is considered. The injection changes the stationary distribution function and results in a qualitative change of the frequency behaviour of the differential conductivity. In the regime with Bloch oscillating electrons and injection into the upper part of the miniband the region of negative differential conductivity is shifted from low frequencies to higher frequencies. We find that the dc differential conductivity can be made positive and thus the domain instability can be suppressed. At the same time the high-frequency differential conductivity is negative above the Bloch frequency. This opens a new way to make a Bloch oscillator operating at THz frequencies.Comment: RevTeX, 8 pages, 2 figures, to be published in Phys. Rev. B, 15 Januar 200