1,720,975 research outputs found
Oxide electronic polarizabilities and aluminum coordination at the outer surface of zeolites obtained by X-ray photoelectron spectroscopy
No full textAn extension of the simple electrostatic model of the Anger parameter developed a few years ago by Moretti [Surf. Interf. Anal. 16 (1990) 159; 17 (1991) 352] is presented and discussed. It is shown that the Anger parameter is site-sensitive and can bring very useful information about the local chemical environment of core-ionized atoms. In zeolites, the Si and AI Auger parameters permit the direct determination of the in-framework electronic polarizability of the two oxide species Si-O-Si(AI) and Si-OM-Al, where M (H,Na,...) is the counter-cation of the negative charge on Al. The knowledge of these quantities is fundamental to theoretical investigations of the adsorptive properties of zeolites. This approach was previously investigated by Pellenq and Nicholson [J. Chem. Sec. Faraday Trans. 89 (1993) 2499] who, however, due to the limitations of the simple electrostatic model, only obtained averaged oxygen electronic polarizability. The extended model also permits the direct identification of framework tetra- and tri- coordinated Al sites in zeolites (Bronsted and Lewis acid sites), as well as of extra-framework hexa-coordinated Al species in dealuminated zeolites. We applied our model to all the zeolites for which Si and Al Auger parameter data were reported in the literature. (C) 1998 Elsevier Science B.V. All rights reserved
Use of Auger parameter and Wagner plot in the characterization of Cu-ZSM-5 catalysts
No full textThe potentiality of X-ray photoelectron spectroscopy (XPS) in obtaining structural information of Cu-ZSM-5 as a catalyst is presented. The use of XPS determines the insight on both the local electronic and the geometrical structure of copper cations. The use of Auger plot, Wanger plot and simple electrostatic model permits the structural realization. The geometrical structure of copper cations sites obtained by XPS and the result obtained by X-ray absorption fine structure (EXAFS) and X-ray absorption near edge structure (XANES) studies were in agreement
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
Deep versus Shallow Behavior of Intrinsic Defects in Rutile and Anatase TiO2 Polymorphs
No full textThe structural and electronic properties of oxygen vacancies (V-Ox) and titanium interstitials (Ti-(i)) in the bulk of the rutile and anatase forms of TiO2 have been investigated with LSD-GGA+U ab initio simulations. In particular, formation energies of the charged and neutral forms of the V-Ox and Ti-(i) defects as well as the corresponding vertical and thermodynamic transition levels have been estimated. The achieved results can reconcile the apparent inconsistency of experimentally observed deep donor levels with the n-type conductivity observed in reduced TiO2. They show indeed that both defects give rise to vertical transition levels about 1 eV below the conduction band (CB), in agreement with experimental measures, and to thermodynamic transition levels close to the CB. That is, these defects behave as deep donors, when looking at vertical transitions, and as shallow donors, when the effects of the structural relaxations are taken into account. A major part of the explanation of this behavior is played by the polaron-like character of the defect states, which was already noted, but not deepened, in literature. Finally, it is shown that the application of the U correction to both Ti and O species gives qualitatively similar results, but with a better agreement to experimental findings, with respect to the application to Ti only. The former approach gives pretty similar results, for both rutile and anatase bulk properties, to those coming from HSE hybrid functional calculations
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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