173,636 research outputs found

    Enhanced crystallinity of low temperature deposited silicon films on graphite subtrates

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    The previously developed technique of a sandwich coating for silicon crystallinity enhancement in silicon films deposited at low temperature is applied to graphite substrates. The measured increase in silicon crystallinity is comparable to that observed earlier using a quartz substrate. The distribution of aluminum in the silicon films is determined using Auger spectroscopic depth profiling. Carbon diffusion from the substrate into the silicon film is shown to be negligible at a substrate temperature of 600 C

    Dopant gas effect on silicon chemical vapor depositions: A surface potential model

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    A surface potential model is proposed to consistently explain the known dopant gas effects on silicon chemical vapor deposition. This model predicts that the effects of the same dopant gases on the diamond deposition rate using methane and carbon tetrachloride should be opposite and similar to those of silane, respectively. Available data are in agreement with this prediction

    Hadronic production of the PP-wave excited BcB_c-states (BcJ,L=1B_{cJ,L=1}^*)

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    Adopting the complete αs4\alpha_s^4 approach of the perturbative QCD (pQCD) and updated parton distribution functions, we have estimated the hadronic production of PP-wave excited BcB_c-states (BcJ,L=1B_{cJ,L=1}^*). In the estimate, special care on the relation of the production amplitude to the derivative of wave function at origin of the potential model is payed. For experimental references, main uncertainties are discussed, and the total cross sections and the distributions of the production with reasonable cuts at the energies of Tevatron and LHC are computed and presented. The results show that PP-wave production may contribute to the BcB_c-meson production indirectly by a factor about 0.5 of the direct production, and with such a big cross section, it is worth further to study the possibility to observe the PP-wave production itself experimentally.Comment: 23 pages, 9 figures, to replace for revising the misprints ec

    Высшее образование в Китае и России: сходство и отличие

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    В статье дана сравнительная характеристика высшего образования в странах Китай и Россия.The article gives a comparative description of higher education in China and Russia

    On first-order expressibility of satisfiability in submodels

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    Let κ,λ\kappa,\lambda be regular cardinals, λκ\lambda\le\kappa, let φ\varphi be a sentence of the language Lκ,λ\mathcal L_{\kappa,\lambda} in a given signature, and let ϑ(φ)\vartheta(\varphi) express the fact that φ\varphi holds in a submodel, i.e., any model A\mathfrak A in the signature satisfies ϑ(φ)\vartheta(\varphi) if and only if some submodel B\mathfrak B of A\mathfrak A satisfies φ\varphi. It was shown in [1] that, whenever φ\varphi is in Lκ,ω\mathcal L_{\kappa,\omega} in the signature having less than κ\kappa functional symbols (and arbitrarily many predicate symbols), then ϑ(φ)\vartheta(\varphi) is equivalent to a monadic existential sentence in the second-order language Lκ,ω2\mathcal L^{2}_{\kappa,\omega}, and that for any signature having at least one binary predicate symbol there exists φ\varphi in Lω,ω\mathcal L_{\omega,\omega} such that ϑ(φ)\vartheta(\varphi) is not equivalent to any (first-order) sentence in L,ω\mathcal L_{\infty,\omega}. Nevertheless, in certain cases ϑ(φ)\vartheta(\varphi) are first-order expressible. In this note, we provide several (syntactical and semantical) characterizations of the case when ϑ(φ)\vartheta(\varphi) is in Lκ,κ\mathcal L_{\kappa,\kappa} and κ\kappa is ω\omega or a certain large cardinal

    Current developments in LC-MS for pharmaceutical analysis

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    The current developments in liquid chromatography-mass spectrometry (LC-MS) and its applications to the analysis of pharmaceuticals are reviewed. Various mass spectrometric techniques, including electrospray and nanospray ionization, atmospheric pressure chemical ionization and photoionization and their interface with liquid chromatographic techniques are described. These include high performance liquid chromatography, capillary electrophoresis and capillary electrochromatography and the advantages and disadvantages of each technique are discussed. The applications of LC-MS to the studies of in vitro and in vivo drug metabolism, identification and characterization of impurities in pharmaceuticals, analysis of chiral impurities in drug substances and high-throughput LC-MS-MS systems for applications in the “accelerated drug discovery” process are described
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