Trapped radiation in injection lasers

The effect of trapped radiation on the stimulated emission threshold and power in injection lasers is investigated theoretically and experimentally. The density of trapped radiation is determined by the relation between the gain and the loss coefficients for this radiation in the active region. The last value depends upon treatment of the cavity sidewalls and laser diode geometry. The absorption of spontaneous emission in the active diode region provides for an additional optical excitation of the crystal and can result in a decrease of threshold current. The GaAs laser diodes with Fabry-Perot cavities and four-ended resonators were studied. The lasing threshold for the axial modes is increased with the diode width and that for the nonaxial radiating modes is decreased with it. The luminescence spectra from the cavity ends and sidewalls are investigated as a function of diode length and current density. It is shown that the gained luminescence can be an essential source of energy losses in injection lasers and leads to limitations of dimensions of laser diodes with planar p-n-junctions. Various methods for suppression of harmful radiation and for increase of the stimulated emission power in injection lasers are discussed.     

Correlation energy and the superconductivity of polyvalent metals

The size effects in the correlation energy of the electron subsystem of metals are found to be related to the superconductivity of polyvalent metals. This relation can be used as a criterion for distinguishing superconducting from nonsuperconducting materials.     

Nitrogen concentration in ZnO films grown by magnetron sputtering in an Ar-NO plasma

Nitrogen-doped ZnO films are grown on (0001)-oriented sapphire substrates by magnetron RF sputtering in an Ar-NO plasma at a pressure of about 10 mTorr and Ar-to-NO flow-rate ratios of 0–90. It is revealed that the nitrogen concentration in the films depends on the Ar-to-NO flow-rate ratios as well as on the nitrogen concentration in the process environment. The highest doping level of nitrogen (4.3 at %) is achieved in films deposited at a substrate temperature of 300°C and an Ar-to-NO flow-rate ratio of 90:1. These films are found to contain Zn-N bonds, but not N-O bonds.     

Effect of nature of fibrous substrate of composite membranes on their structure,conductive properties,and selectivity

The effect of fibers selected for investigation on the kinetics of synthesis and curing of the polymer matrix has been revealed; structural features of Polikon K materials formed on polyacrylonitrile, polyester, and novolac phenol–formaldehyde fibers have been studied; and the performance characteristics of the materials have been determined.     

Fusarium sibiricum sp. nov, a novel type A trichothecene-producing Fusarium from northern Asia closely related to F. sporotrichioides and F. langsethiae

Production of type A trichothecenes has been reported in the closely related species Fusarium langsethiae and F. sporotrichioides. Here, we characterized a collection of Fusarium isolates from Siberia and the Russian Far East (hereafter Asian isolates) that produce high levels of the type A trichothecene T-2 toxin and are similar in morphology to the type A trichothecene-producing F. langsethiae, and to F. poae which often produces the type B trichothecene nivalenol. The Asian isolates possess unique macroscopic and microscopic characters and have a unique TG repeat in the nuclear ribosomal intergenic spacer (IGS rDNA) region. In Asian isolates, the TRI1-TRI16 locus, which determines type A versus type B trichothecene production in other species, is more similar in organization and sequence to the TRI1-TRI16 locus in F. sporotrichioides and F. langsethiae than to that in F. poae. Phylogenetic analysis of the TRI1 and TRI16 gene coding regions indicates that the genes in the Asian isolates are more closely related to those of F. sporotrichioides than F. langsethiae. Phylogenetic analysis of the beta-tubulin, translation elongation factor, RNA polymerase II and phosphate permease gene sequences resolved the Asian isolates into a well-supported sister lineage to F. sporotrichioides, with F. langsethiae forming a sister lineage to F. sporotrichioides and the Asian isolates. The Asian isolates are conspecific with Norwegian isolate IBT 9959 based on morphological and molecular analyses. In addition, the European F. langsethiae isolates from Finland and Russia were resolved into two distinct subgroups based on analyses of translation elongation factor and IGS rDNA sequences. Nucleotide polymorphisms within the IGS rDNA were used to design PCR primers that successfully differentiated the Asian isolates from F. sporotrichioides and F. langsethiae. Based on these data, we formally propose that the Asian isolates together with Norwegian isolate IBT 9959 comprise a novel phylogenetic species, F. sibiricum, while the two subgroups of F. langsethiae only represent intraspecific groups.     

Mixed lipid-protein films of bacterial photosynthetic reaction centres. II. Mixed multilayers on solid supports

The cytokine interleukin 8 (IL-8) has been shown to be a potent mediator of leukocyte recruitment and neovascularization in inflammatory and neoplastic diseases. In this study we hypothesize that IL-8 produced in the nasal polyp microenvironment is responsible for the leukocyte recruitment seen in nasal polyposis. To test this hypothesis we evaluated nasal polyps for distribution and content of IL-8 antigen with immunohistochemical techniques and radioimmunoassay to determine tissue levels of IL-8. The immunohistochemical results demonstrated that IL-8 antigen staining occurred predominantly within inflammatory cells and epithelium. IL-8 was detected in all nasal polyp tissue homogenates (a mean value of 1767 +/- 1633 pg/mg total protein (TP) with a range of 134 to 3668 pg/mg TP vs control specimens with a mean value of 77 pg/mg TP with a range of 0.09 to 255 pg/mg TP). These data demonstrate the presence and distribution and levels of IL-8 antigen in nasal polyps in vivo, supporting our hypothesis that local production of IL-8 could be an important factor in the sustained recruitment of leukocytes in nasal polyposis. Thus IL-8 likely plays a significant role in the pathogenesis of this disease process and therefore is a potential target for therapeutic intervention.     

Application of the majority connectedness carrier for computing the reliability of complex systems

A computational method for probability of majority connectedness of the two-pole network of a random graph is stated when the union of circuits is used as a connectedness carrier of node-poles. Formal rules for calculations of this type illustrated by the corresponding examples are given.