Isochoric thermal conductivity of solid nitrogen

The isochoric thermal conductivity of solid nitrogen has been investigated on four samples of different densities in the temperature interval from 20 K to the onset of melting. In alfa-N2 the isochoric thermal conductivity exhibits a dependence weaker than 1/T; in beta-N2 it increases slightly with temperature. The experimental results are discussed within a model in which the heat is transported by low-frequency phonons or by "diffusive" modes above the mobility boundary. The growth of the thermal conductivity in beta-N2 is attributed to the decreasing "rotational" component of the total thermal resistance, which occurs as the rotational correlations between the neighboring molecules become weaker.Comment: Postscript 12 pages, 3 figures, 1 table. To be published in 200

On the Analysis of Chemical Composition of Moon's Surface by Direct Methods

Proportional counter for X ray emission detection and chemical analysis of lunar surface element

Photon-induced vanishing of magnetoconductance in 2D electrons on liquid He

We report on a novel transport phenomenon realized by optical pumping in surface state electrons on helium subjected to perpendicular magnetic fields. The electron dynamics is governed by the photon-induced excitation and scattering-mediated transitions between electric subbands. In a range of magnetic fields, we observe vanishing longitudinal conductivity sigma_xx. Our result suggests the existence of radiation-induced zero-resistance states in the nondegenerate 2D electron system.Comment: 4 pages, 5 figure

Revision of Agraptocoris Reuter (Heteroptera: Miridae: Phylinae), with description of five new species and a review of aedeagal terminology

The predominantly Central Asian genus Agraptocoris Reuter is revised. Eight valid species are recognized, five of those being described as new to science, namely A. eugeniae, A. nigrisetosus, A. pallescens, A. subconcolor (all Mongolia), and A. pamiricus (Tajikistan and Kyrgyzstan). A phylogenetic analysis based on 37 morphological characters is presented for all Agraptocoris species and 13 outgroup taxa. This analysis establishes Agraptocoris as monophyletic and rendered the subtribes Phylina and Oncotylina as non-monophyletic. The differential diagnosis for the genus and a key to all species are given. Habitus photographs, illustrations of male genitalic structures, scanning micrographs of morphological structures, host and distributional information are provided for all species. Homologies and terminology of the aedeagal structures in the subfamily Phylinae are discussed

Causal signal transmission by quantum fields. IV: The causal Wick theorem

Wick's theorem in the Schwinger-Perel-Keldysh closed-time-loop formalism is written in a form where the place of contractions is taken by the linear response function of the field. This result demonstrates that the physical information supplied by Wick's theorem for operators is propagation of the free field in space and time.Comment: Final version, to appear in Phys Rev

Sliding of Electron Crystal of Finite Size on the Surface of Superfluid He-4 Confined in a Microchannel

We present a new study of the nonlinear transport of a two-dimensional electron crystal on the surface of liquid helium confined in a 10 micrometer-wide channel in which the effective length of the crystal can be varied from 10 to 215 micrometers. At low driving voltages, the moving electron crystal is strongly coupled to deformation of the liquid surface arising from resonant excitation of surface capillary waves, ripplons, while at higher driving voltages the crystal decouples from the deformation. We find strong dependence of the decoupling threshold of the driving electric field acting on the electrons, on the size of the crystal. In particular, the threshold electric field significantly decreases when the length of the crystal becomes shorter than 25 micrometers. We explain this effect as arising from weakening of surface deformations due to radiative loss of resonantly-excited ripplons from an electron crystal of finite size, and we account for the observed effect using an instructive analytical model.Comment: 5 figure