1,720,995 research outputs found
Vanadium-doped TiO2 catalysts. A unifying picture of powders and suspensions
No full textAnatase powders, both pure and vanadium-doped, were subjected to acid-base leaching cycles. The different samples were characterized with respect to chemical composition, morphology and surface area. The effects of the different treatments on the chemical state of the surface and on the electrification at the solid-solution boundary were investigated, respectively, by X-ray photoelectron spectroscopy and electrophoretic mobility measurements. The stability of the aqueous suspensions was measured by sedimentation tests. The results of the different determinations are cross-compared in order to produce a general description of the catalysts.
Anatase powders, both pure and vanadium-doped, were subjected to acid-base leaching cycles. The different samples were characterized with respect to chemical composition, morphology and surface area. The effects of the different treatments on the chemical state of the surface and on the electrification at the solid-solution boundary were investigated, respectively, by X-ray photoelectron spectroscopy and electrophoretic mobility measurements. The stability of the aqueous suspensions was measured by sedimentation tests. The results of the different determinations are cross-compared in order to produce a general description of the catalysts
ELECTROANALYTICAL STUDY OF THE KINETICS OF THE FAC-MER ISOMERIZATION OF [RECL(CO)3(PME2PH)2]+ IN ACETONITRILE
No full textThe isomerization offac-[ReCl(CO)3(PMe2Ph)2]+ to the corresponding meridional-trans isomer has been studied by electroanalytical techniques in MeCN solvent. Chronoamperometric and cyclic voltammetric data relative to the oxidation offac- andmer-[ReCl(CO)3(PMe2Ph)2] allow the accurate determination of the very high kinetic rate constant for the isomerization and permit discussion of thermodynamic aspects of redox homogeneous chemical reactions involving species of the different redox couples arising from the anodic processes
Voltammetric Behaviour of Technetium99 Complexes with -Accptor Ligands in Aprotic Medium. Part II. Reduction of TcCl3(PMe2Ph)3 and of TcCl4(PMe2Ph)2
No full textThe electrode processes relative to oxidation and reduction of Tc99 compounds, together with the relevant stability potential range are studied, aiming at defining the characteristics suitable for application in diagnostics
Voltammetric Behaviour of Technetium99 Complexes with -Acceptor Ligands in Aprotic Medium. Part I. Oxidation of TcCl3(PMe2Ph2)
No full textThe redox properties of a Tc complex are studied in order to the define the electrode mechanisms and the stability potential rang
Voltammetric behaviour of technetium99 complexes with π-acceptor ligands in aprotic medium. III. Oxidation of technetium(I) complexes with phosphine and carbon monoxide ligands
No full textThe anodic behaviour of TcCl(CO)2(PMe2Ph)3 and TcCl(CO)3(PMe2Ph)2 complexes has been studied in acetonitrile solvent. Both the complex undergo an overall two-electron oxidation process with the formation of Tc(III) species; the electrode mechanism leading to their formation has been studied. In particular the [TcCl(CO)(MeCN)2(PMe2Ph)3][ClO4]2 compound has been isolated and characterized
Characterization and stabilization of Si3N4 suspensions
No full textTwo commercial Si3N4 powders were mixed with Al2O3 and Y2O3 through coprecipitation of the oxides from solutions of nitrates. The samples were characterized by XPS spectroscopy and electrophoretic mobility determinations on the suspensions. Sedimentation tests indicated that an oxylignin-based polyelectrolyte proved effective in the dispersion of the powders. The adsorption of the deflocculant followed Langmuir type isotherms characterized by values of the standard free energy of adsorption in the range typical of physisorption processes. The results of the different characterizations are discussed point by point, and different localizations of the dispersant in the interfacial region of the different samples are proposed
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
Appropriate Similarity Measures for Author Cocitation Analysis
Full text linkWe provide a number of new insights into the methodological discussion about author cocitation analysis. We first argue that the use of the Pearson correlation for measuring the similarity between authors’ cocitation profiles is not very satisfactory. We then discuss what kind of similarity measures may be used as an alternative to the Pearson correlation. We consider three similarity measures in particular. One is the well-known cosine. The other two similarity measures have not been used before in the bibliometric literature. Finally, we show by means of an example that our findings have a high practical relevance.information science;Pearson correlation;cosine;similarity measure;author cocitation analysis
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