1,720,981 research outputs found
Epitaxial films of “bscco” grown from liquid kcl solutions onto several substrates
No full textUsing liquid phase epitaxy growth technique (LPE) we have obtained truly epitaxial BSCCO films on SrTiO3 and LaGaO3 substrates. Single-phase samples have been grown both of the 2201 and of the 2212 phase. The growth liquid is a saturated solution of the BSCCO constituent oxides in KCl, and a suitable thermal gradient allows chemical transport from the solute to the substrate. The films have mirror-like surface, small mosaic spread and thickness up to a few microns. The as-grown samples are fully superconducting.The typical resistance vs temperature curve shows a metallic behavior down to about 80 K, followed by a narrow superconducting transition, with zero resistance reached at about 75 K.The transport properties of the films have been investigated, and found to be heavily dependent on the substrate chosen: in particular, films grown on LaGaO3 have much higher resistivities and much lower critical currents than those grown on SrTiO3 substrates. These differences are shown to be due to the presence of weak links occurring in correspondance with twinning domain boundaries of the LaGaO3 substrates
THE CHEMICAL BASIS OF THE C-H-O PHASE-DIAGRAM IN DIAMOND PLASMA DEPOSITIONS
No full textThe chemical origin of the C-H-O phase diagram of diamond plasma deposition methods has been presented. According to the suggested chemical reactions, in almost all C-H-O-gas-containing plasmas the principal reactions begin with carbon removal by oxygen to the very stable CO. The rest of the gases during diamond deposition can be regarded as basically the same with the first successful diamond plasma consisting of a Few per cent of hydrocarbons diluted in hydrogen gas. The suggested reactions result in successful diamond depositions only above the H-CO line in the C-H-O phase diagram
CH5 PRECURSOR MECHANISM FOR DIAMOND GROWTH
No full textDeposition rates of polycrystalline diamond films are investigated as a function of concentration of water vapor in a microwave chemical vapor deposition (CVD) apparatus. For CH4:H-2 = 2%: 98% gas composition the measured deposition rates are compared with mass spectroscopic data published in the literature and predictions suggested by the widely accepted methyl radical (CH3) diamond growth model. Our results do not confirm the CH3 model, but a good correlation is found between the concentration of CH5+ radicals and the deposition rates of diamond. The main reaction paths leading to diamond deposition from CH5+ are also presented
Effect of Ba, Ca and Pb on the c-lattice parameter of BSCCO films
No full textThe Liquid Phase Epitaxy (LPE) technique has been used to grow epitaxial, single-phase BSCCO films of both the 2201 and the 2212 phase. The possibility to introduce in the BSCCO structure ions different from the basic constituent ones by simply adding new elements to the melt has been explored. The effects on the c-lattice parameter of Ba and Pb doping in the 2212 BSCCO structure, and of Ca doping in the 2201 structure have been determined
Compositional dependence of properties of Bi2-yPb ySr3-xCaxCu2O8+z films grown by liquid phase epitaxy
No full textThe growth of Bi2-yPbySr3-xCaxCu2O8+z filsm by liquid phase epitaxy is illustrated. Films are shown to be good single crystals epitaxial relative to the substrate. Films stoichiometry was varied changing the melt composition. The effects of the Ca and Pb stoichiometry on both the structural and superconducting properties are discussed. The c lattice parameter of the films was found to increase linearly with the Ca content per formula unit with a slope of 0.3 A each 0.5 Ca atoms per formula unit. No sizeable changes in the superconducting properties were found for films with a Ca content between 0.8 and 1.3 atoms per formula unit. Lead doping is shown to decrease the transition temperature without broadening the transition itself. 0.4 lead atoms per formula unit decreased the transition temperature down to 69 K
Effects of reducing and oxidizing thermal treatments on the transport critical current density in epitaxial Bi2Sr3-xCa xCu2O8+y films
No full textWe have studied the effects of oxidizing and reducing thermal treatments on the critical current density in epitaxial Bi2Sr3-xCaxCu2O8+y films. Reducing treatments, while increasing the transition temperature up to 94 K, reduces the critical current density relative to the as-grown value in the whole range of reduced temperatures. On the contrary, oxidizing treatments, while decreasing the transition temperature, increases the critical current density. Such effects are shown to be fully reversible under a final air annealing. Such effects are attributed to a decrease of the Bi2Sr3-xCaxCu2O8+y anisotropy which occurs in connection with the increase of the oxygen content in the compound
Growth of epitaxial films of Bi2Sr2CaCu 2O8+x onto SrTiO3 substrates from liquid KCl solution
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Going Beyond Counting First Authors in Author Co-citation Analysis
Full text linkThe present study examines one of the fundamental aspects of author co-citation analysis (ACA) - the way co-citation
counts are defined. Co-citation counting provides the data on which all subsequent statistical analyses and mappings
are based, and we compare ACA results based on two different types of co-citation counting - the traditional type that
only counts the first one among a cited work's authors on the one hand and a non-traditional type that takes into
account the first 5 authors of a cited work on the other hand. Results indicate that the picture produced through this non-traditional author co-citation counting contains more coherent author groups and is therefore considerably clearer. However, this picture represents fewer specialties in the research field being studied than that produced through the traditional first-author co-citation counting when the same number of top-ranked authors is selected and analyzed. Reasons for these effects are discussed
Variations on the Author
Full text link“Variations on the Author” discusses two of Eduardo Coutinho’s recent films (Um Dia na Vida, from 2010, and Últimas Conversas, posthumously released in 2015) and their contribution to the general question of documentary authorship. The director’s filmography is characterized by a consistent yet self-effacing form of authorial self-inscription: Coutinho often features as an interviewer that rather than express opinions propels discourses; an interviewer that is good at listening. This mode of self-inscription characterizes him as an author who is not expressive but who is nonetheless markedly present on the screen. In Um Dia na Vida, however, Coutinho is completely absent form the image, while Últimas Conversas, on the contrary, includes a confessional prologue that moves the director from the margins to the center of his films. This article examines the ways in which these works stand out in the filmography of a director who offers new insights into the notion of cinematic authorship
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