1,720,957 research outputs found
CHARACTERIZATION OF COPPER-MANGANESE MIXED OXIDES
No full textCopper-manganese mixed oxides were obtained by decomposition at 723 K for 24 h, in nitrogen and in air, of hydroxycarbonate and/or carbonate precursors containing both Cu(II) and Mn(II) ions in the same structure. It is shown that even at this relatively low temperature a spinel phase, Cu(I)xCu(II)1-xMn(III)2-xMn(IV)xO4, is formed. The redox equilibrium Cu(II) + Mn(III) = Cu(I) + Mn(IV) is shifted toward right or left when the samples are decomposed in air or in nitrogen, respectively . In Situ XRD and XPS reduction studies have demonstrated that: (i) the final products of reduction are metallic copper and MnO; (ii) if in the initial mixed oxide composition CuO is present in larger amount than CuMn2O4 the N2-treated product is more reducible than the air-treated one; (iii) when the CuMn2O4 spinel phase predominates the sample as a whole becomes less reducible; (iv) the N2-treated sample which contains the spinel Cu(II)Mn(III)2O4 is less reducible than the corresponding air-treated one containing the spinel with all Cu(I), Cu(II), Mn(III) and Mn(IV) species
Characterization of copper-manganese hydroxysalts and oxysalts
No full textCopper-manganese oxysalts of various Cu:Mn atomic ratios (from Cu:Mn = 100:0 to 0:100 in steps of 10) have been prepared by coprecipitation, at constant pH, from solutions of copper and manganese nitrates added to a solution of NaHCO3; the structure and chemical nature of the Cu-Mn oxysalts have been investigated by several complementary techniques such as XRD, magnetic susceptibility, reflectance spectroscopy and XPS to obtain information both on their bulk and on their surface properties. At high Cu:Mn atomic ratios the materials consist of Mn-containing malachite while at low Cu:Mn atomic ratios the product is Cu-containing rhodochrosite. For intermediate compositions a mixture of both phases is obtained. The introduction of Mn2+ into the malachite lattice gives a smaller cell volume increase than that expected from the difference between the ionic radii of octahedral Cu2+ and Mn2+; this is probably due to less octahedral site distortion. The presence of Cu2+ (d9) in the rhodochrosite lattice shows a much bigger cell volume decrease than that expected from ionic radii difference, the plausible reason for this behaviour being a higher covalent metal-oxygen bond character and/or octahedral site distortion. The Mn-malachite phase shows a surface enrichment in Mn; in this case it is suggested that the strain-energy contribution, arising from size effects, determines the segregation of manganese. There is homogeneity between the Cu:Mn compositional ratios in the bulk and at the surface only if the Cu-rhodochrosite phase is present. The surface appears enriched in copper when the two phases are both present; in this case the manganese-malachite phase probably tends to cover the copper-rhodochrosite one
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
Dispelling the Myths Behind First-author Citation Counts
Full text linkWe conducted a full-scale evaluative citation analysis study of scholars in the XML research field to explore just how different from each other author rankings resulting from different citation counting methods actually are, and to demonstrate the capability of emerging data and tools on the Web in supporting more realistic citation counting methods. Our results contest some common arguments for the continued
use of first-author citation counts in the evaluation of scholars, such as high correlations between author rankings by first-author citation counts and other citation
counting methods, and high costs of using more realistic citation counting methods that are not well-supported by the ISI databases. It is argued that increasingly available digital full text research papers make it possible for citation analysis studies to go beyond what the ISI databases have directly supported and to employ more
sophisticated methods
koamabayili/VECTRON-author-checklist: VECTRON author checklist
No full textWe have done our best to complete the author checklist relating to the use of animals in the hut study. Note that the objective for the hut study was to evaluate the IRS treatment applications for residual efficacy against Anopheles mosquitoes, including the local An. coluzzii mosquito population. Cows were only used to attract mosquitoes into the huts and no tests were carried out directly on the cows. The author checklist is intended for use with studies where experiments are carried out on animals, which is why we have had such difficulty in completing this for the hut study, as many of the questions do not relate to how the cows were used
Author-wise bibliometric analysis based on entropy.
No full textAuthor-wise bibliometric analysis based on entropy.</p
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