1,720,955 research outputs found
Bulk, surface and double layer properties of zirconia polymorphs subjected to mechanical treatments
No full textZirconia (ZrO2) may exist in different polymorphs. At low pressures and for temperatures as high as ∼-1150 °C only the stable phase has the monoclinic structure; tetragonal and cubic oxides form however, as metastable phases together with the monoclinic in the lower temperature region (up to ca. 600 - 800 °C). By combining stages of calcination (of a hydrothermal precursor) with severe grinding treatments of the powders it was possible to obtain pure phase monoclinic oxides (S. Ardizzone, G. Bassi, G. Liborio, Colloids and Surfaces 51 (1990) 207). This paper reports results concerning the effects specifically induced by the severe grinding on the phase composition, on the state of the surface and on the interfacial electrostatic reactivity of the powders. The effects produced by ageing, calcinations and further mechanical treatments of the samples are also examined by the same techniques i.e. by X-ray diffraction, XPS determinations and surface charge measurements. © 1991
INTERACTION OF CARBON-MONOXIDE WITH RU-GAMMA-AL2O3 - AN ELECTRON-SPIN-RESONANCE INVESTIGATION
No full textInteraction of carbon monoxide with Ru/ γ-Al2O3 leads to the formation of RuI and RuIII carbonyl derivatives. The relative amounts of the two species are a function of the temperature used in decarbonylating the Ru3(CO)12/ γ-Al2O3 precursor. The thermal and vacuum stabilities of the RuI derivative [g⊥ = 2.050, g∥ = 1.992, A∥(99Ru, 101Ru) = 28 G] and the RuIII derivative (g∥ = 2.046, g⊥ = 2.005) are different, the RuIII species being the more stable. The Ru-CO bond strength of these carbonyls is high in comparison with that of the analogous Rh/ γ-Al2O3 carbonyl derivatives. The enhanced bond strength may account for the difference in the catalytic behaviour between the Ru and Rh systems
ELECTRON-SPIN RESONANCE INVESTIGATION OF ZRO2-SUPPORTED RUTHENIUM - EVIDENCE OF STRONG METAL-SUPPORT INTERACTION
No full textAn e.s.r investigation of Ru/ZrO2 has shown that Ru centres are present in different oxidation states, two of which are paramagnetic: RuIII and RuI. The assignment of the electronic configuration follows from the results of the interaction of Ru/ZrO2 with CO, for the identification of RuIII and RuI, and with NO for the identification of RuII. Magnetic tensor components allow recognition of an RuIII-CO adduct (g∥ = 2.039, g⊥ = 2.003) and an RuI-CO adduct (g = 2.05) An RuII-NO species was also identified [g⊥ = 2.00, g∥ = 1.91, A⊥ (N) = 40 G]. The results of the interaction with O2 also have been discussed in order to give a fuller description of the electronic configuration of the surface ruthenium centres and of the interaction effects between metal and support centres. It appears that at the Ru-ZrO2 interface occurs an interaction stronger than in the Ru-γ-Al2O3 case, the strength depending also on the temperature of the pyrolysis used to obtain Ru/ZrO2 from the Ru3(CO)12/ZrO2 metal precursor. Also the analogous Rh/ZrO2 system was considered with respect to interaction with NO in order to compare the variation in the metal-support interaction owing to differences in the supported metal
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
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