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Now showing items 113 - 128 of 24606

  • Antimicrobial potential and chemical constituent of Mikania micrantha H. B. K.

    Yan, Li; Bin bin, Shen; Jun, Li; Yuan, Li; Xia xia, Wang; Ao cheng, Cao  

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  • DFT study of Al doped cage B(12)H(n) clusters

    Boyukata, Mustafa   Guvenc, Ziya B.  

    Density Functional Theory (DFT) with B3LYP/6-311++g** level has been performed to investigate the electronic structures of cage B(12)H(n) for up to n <= 12 and AlB(12)H(n) for up to n <= 13. Moreover, the computations has been extended to the charged clusters of [B(12)H(12)](q), [AlB(12)H(12)](q) and [AlB(12)H(13)](q) where (q = +/- 1 and +/- 2). Their energetics are calculated and structural analysis have been carried out. Cage form of the B(12) remains stable against to hydrogen adsorptions. Copyright (C) 2011, Hydrogen Energy Publications, LLC. Published by Elsevier Ltd. All rights reserved.
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  • Detection of a 1.59 h period in the B supergiant star HD 202850

    Kraus, M.   Tomic, S.   Oksala, M.E.   Smole, M.  

    Context. Photospheric lines of B-type supergiants show variability in their profile shapes. In addition, their widths are much wider than can be accounted for purely by stellar rotation. This excess broadening is often referred to as macroturbulence. Both effects have been linked to stellar oscillations, but B supergiants have not been systematically searched yet for the presence of especially short-term variability caused by stellar pulsations. Aims. We have started an observational campaign to investigate the line profile variability of photospheric lines in a sample of Galactic B supergiants. These observations aim to improve our understanding of the physical effects acting in the atmospheres of evolved massive stars. Methods. We obtained four time-series of high-quality optical spectra for the Galactic B supergiant HD 202850. The spectral coverage of about 500 A around Halpha encompasses the Si II lambdalambda6347, 6371, and the He I lambda6678 photospheric lines. The line profiles were analysed by means of the moment method. Results. The time-series of the photospheric Si II and He I lines display a simultaneous, periodic variability in their profile shapes. Proper analysis revealed a period of 1.59 h in all three lines. This period is found to be stable with time over the observed span of 19 months. This period is much shorter than the rotation period of the star and might be ascribed to stellar oscillations. Since the star seems to fall outside the currently known pulsational instability domains, the nature of the discovered oscillation remains unclear.
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  • Remarks on B(H) circle times B(H)

    Pisier, Gilles  

    We review the existing proofs that the min and max norms are different on B(H) x B(H) and give a shortcut avoiding the consideration of non-separable families of operator spaces.
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  • K. H. B. Wood

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  • K. H. B. Wood

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  • B–H bond iodination of polyhedral dimolybdaborane and dimolybdathiaborane clusters

    Chakrahari, Kiran Kumarvarma   Thakur, Arunabha   Anju, V.P.   Ghosh, Sundargopal  

    Reaction of [Cp*MoCl4] (Cp*-eta(5)-C5Me5) with excess of [LiBH4 center dot thf] followed by pyrolysis with NaI yielded BeI inserted [(Cp*Mo)(2)B5H9-I-n(n)], 1-3 (1: n = 1; 2: n = 2; 3: n = 3). In parallel to the formation of 1-3, the reaction also produced known [(Cp*Mo)(2)B5H9] and [(Cp*Mo)(2)(mu-I)(4)] in good yields. Under the similar reaction conditions, dimolybdathiaborane [(Cp*Mo)(2)B4H4S2] yielded iodine substituted dimolybdathiaboranes, [(Cp*Mo)(2)B4S2H4-I-n(n)], 4 and 5 (4: n = 2; 5: n = 3) in good yields. All the new compounds have been characterized in solution by IR, H-1 and B-11 NMR as simple substituted derivatives of [(Cp*Mo)(2)B5H9] and [(Cp*Mo)(2)B4H4S2]. The solid state structures were established unambiguously by crystallographic analysis of compounds 1-5. (C) 2013 Elsevier B. V. All rights reserved.
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  • PHYSICAL PROPERTIES OF THE B AND Be STAR POPULATIONS OF h AND chi PERSEI

    Boyer, Amber N. Marsh   McSwain, M. Virginia   Aragona, Christina   Ou-Yang, Benjamin  

    We present a study of the B and Be star populations of the double cluster h and chi Persei. Blue optical spectroscopy is used to first measure projected rotational velocity, V sin i, effective surface temperature, T-eff, and surface gravity, log g, for B-type sample stars, while available Stromgren photometry is used to calculate T-eff and log g for the Be stars showing emission. In our sample of 104 objects for which we measured these stellar parameters, 28 are known or proposed Be stars. Of these Be stars, 22 show evidence of emission at the times of our observations, and furthermore, we find evidence in our data and the literature for at least 8 transient Be stars in the clusters. We find that the Be stars are not rotating near their critical velocity, contrary to the results of studies of similar open clusters. We compare the results of our analysis with other previous studies and find that the cluster members are more evolved than found by Huang & Gies but still retain much of their initial rotational angular momentum.
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  • Reflections on some groups of B. H. Neumann

    Baumslag, Gilbert   Miller, Charles F., III  

    In 1937, B. H. Neumann constructed a family of continuously many, non-isomorphic two-generator groups. We will prove that none of the infinite groups in this family are finitely presented, describe how to present them and classify their word problems. Other remarkable properties of Neumann's groups are also discussed.
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  • The ESCA Analysis of the B(3)H(8)(-) Anion

    Il'inchik, E. A.   Gulyaev, R. V.   Svintsitskii, D. A.   Myakishev, K. G.   Volkov, V. V.  

    Compounds [Et(4)N](2)B(3)H(8) and CsB(3)H(8) are studied using the ESCA method. The results of analysis of the B1s electron spectra and estimation of the effective charge differences in [Et(4)N](2)B(3)H(8) are compared to the data of theoretical calculations of the B(3)H (8) (-) anion.
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  • Flowers of Mongolia / Mongol orny cėcėgby M. H. Hauck; Z. B. Solongo

    Sabrina Rilke  

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  • Oxidative Dehydrogenation of Propane with CO2Over Cr/H[B]MFI Catalysts

    Qingjun Zhu   Makoto Takiguchi   Tohru Setoyama   Toshiyuki Yokoi   Junko N. Kondo   Takashi Tatsumi  

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  • Enhanced surface blistering of germanium with B +/H + coimplantation

    Xiaobo Ma   Xiaofeng Du   Weili Liu   Chao Chen   Zhitang Song   Chenglu Lin  

    The surface blisters in B +/H + coimplanted germanium (Ge) and H-only-implanted Ge were compared. The surface-blister phenomenon in B +/H + coimplanted Ge emerged after annealing at 330-340degC; but in H-only-implanted Ge, the blistering emerged after annealing at over 400degC. The results indicate that the preimplanted boron can facilitate the coalescence of implanted H into bubbles, and so, it decreases the temperature for surface-blister formation. The exfoliation mechanism of B +/H + coimplanted Ge during the annealing step was investigated. The transmission electron microscopy results indicate that the B +/H + coimplantation creates both (100) and {111} platelet defects, and the nucleation of H bubbles occurs at regions where the (100) defects are concentrated. The bottoms of popped-off blisters show a very rough surface because the (100) and {111} platelets occur at different depths, and the wide distribution of (100) platelets also contributes to this roughness. The results show that boron appears to be one of the choices for prebonding implantation because it reduces the splitting temperature of the H-implanted Ge wafer.
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  • David B. H. Denoon (ed). China, The United States and the Future of Southeast Asia

    Fell   Richard  

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  • Die messtechnische Erfassung von Bodenbewegungen an H?ngen und B?schungen

    Reinfried Pilgram   Gerhard Mayer   Fritz Kremser  

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  • B. Enjolras and K. H. Sivesind (eds): Civil Society in Comparative Perspective

    Aiken   Mike  

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