1,720,967 research outputs found
Methods of crystallography: powder X-ray diffraction
No full textIn the last twenty-five years, relevant theoretical, methodological and experimental advances have been made in the development and application of the X-ray powder diffraction (XRPD) method. In particular, attention has been devoted to the interpretation of XRPD data. The XRPD approach is used currently in mineralogical as well as in many other scientific fields (solid-state chemistry, pharmacology, materials science, etc.) to address a wide range of scientific purposes: qualitative analysis for the identification of the crystalline phases constituting a powder sample; quantitative analysis for estimating the weight fraction of each phase in a mixture; structure solution; microstructural analysis for the inspection of crystalline domain size effects and lattice defects; investigation of highly complex materials: compounds with incommensurate structures, nanoparticles, amorphous materials; studies at non-ambient conditions, in situ, time-resolved and in operando for the description of thermal or compressional behaviour, phase stability and structural evolution. The aim of this chapter is to provide an overview of some basic principles and significant aspects of the XRPD method and examples of its applications to mineralogical problems
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
Cerium(IV) oxide modification by inclusion of a hetero-atom: A strategy for producing efficient and robust nano-catalysts for methanol carboxylation
No full textCerium(IV) oxide has been reported to catalyse the direct carboxylation of methanol to dimethylcarbonate, DMC. Nevertheless, the life of commercially available catalysts is quite short as after the first cycle the activity decreases and after a few cycles goes to zero. Noteworthy, no reports are in the literature about the stability of catalysts and their life. We have investigated the behaviour of catalysts and their deactivation using either surface techniques, such as XPS, or structural techniques, such as XRD. The reduction of Ce(IV) to Ce(III) and surface modification seem to be responsible for de-activation of the oxide. The results of a detailed study correlating the size and structure of particles to the activity of the catalysts are reported in this paper. In particular, pure commercial CeO(2) is compared, using High Throughput Experiments (HTE), with CeO(2) synthesised in our laboratory and with the latter loaded with Al or Fe at various concentrations. The hetero-metals have a different effect on the stabilization of the Ce-catalyst and on its activity. Al-loaded CeO(2) affords the most interesting results in terms of lifetime and activity. Therefore, the correlation of the structural properties of CeO(2) loaded with Al at a concentration variable between 3 and 40% to the activity in catalysis is discussed in detail. XPS and XRD data have been used for the characterization of the catalyst before and after a catalytic run. Pure synthesised CeO(2) and CeO(2) loaded with Al are able to maintain their activity for several cycles (apparent TON of several tens) or three days of operation without any treatment after recovery, with a much better performance than the commercial catalysts that, conversely, loose their activity after a few cycles. The size of the particles determines the activity of the catalyst and we show that particles having a size 15-60 nm are the most active, while particles sized micrometers are much less active
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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