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On the activity of mixed oxides towards VOC oxidation studied by a thermal gravimetric method
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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
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
Surface properties of hihgly dispersed catalysts used in reactions of biomass exploitation
No full textDispersed NbOx catalytic phases in silica matrixes : influence of Nb-concentration and preparative route
No full textNiobium oxide catalytic phase was dispersed in/over silica host structures by using different Nb sources (ammonium niobium oxalate complex and niobium pentaethoxide) and methodologies (coprecipitation, sol-gel, and impregnation). Three series of completely amorphous silica-niobia catalysts were obtained with 5, 15, 30, 45, and 60 mass % Nb2O5 by coprecipitation (aqueous route, from ammonium niobium oxalate) and sol-gel (organic route, from niobium pentaethoxide) and with 5, 10, and 20 mass % Nb2O5 by impregnation on a finite silica, from ammonium niobium oxalate. The surface and bulk catalyst properties of all the series of samples were studied by several physicochemical techniques [N2 adsorption/desorption, thermal gravimetric analysis (TGA), scanning electron microscopy coupled with energy-dispersive X-ray spectroscopy (SEM-EDS), X-ray diffraction (XRD), X-ray photoelectron spectroscopy (XPS), UV-vis diffuse reflection spectra (UV-vis DRS), temperature-programmed reduction (TPR)], and the acid properties of the surfaces were investigated by base (2-phenylethylamine, PEA) titration in liquid (cyclohexane). Evidence from both XPS (3d Nb bands and O Is band) and UV-vis DRS (ligand-to-metal charge-transfer transitions (LMCT) from O2- to Nb5+ and edge energies) measurements showed that the Nb dispersion increased with Nb dilution in the host silica structures. The number of coordinated oxygens around the Nb center was 6, for the highest diluted samples, and converged to 2.5, indicating the progressive formation of Nb 2O5 nanodomains. As the Nb2O5 concentration decreased in the catalyst composition, the surface area values expanded and Nb dispersion increased, owing to Nb-O-Si linkage formation. The synthesis by sol-gel permitted accommodating a higher surface concentration of niobia than by the coprecipitation route
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