1,720,988 research outputs found
Structure of nitrogen – hydrogen complexes from x-ray and synchrotron radiation techniques
No full textThis Chapter illustrates the role played by x-ray techniques, in particular synchrotron radiation-based ones, in the analysis of the structure of nitrogen-hydrogen complexes in dilute nitrides. Para-graph 6.2 introduces the x-ray diffraction experiments which gave the first evidence of a modification of the structure driven by hy-drogenation. Paragraph 6.3 provides a theoretical and experimen-tal framework for understanding the main results presented in this chapter, which were obtained by x-ray spectroscopy; the paragraph explains the physics at the basis of x-ray absorption spectroscopy, with specific reference to the application to the subject of impurities in semiconductors, diffraction anomalous fine structure, and x-ray emission spectroscopy. The possibility of achieving both unidimensional and threedimensional information on the local struc-
ture around the isoelectronic impurities and the structure of the complexes playing on different analysis strategy is explained; the importance of coupling spectroscopy data analysis with state-of-art theoretical calculations described in Chapter 4 is stressed. Para-graph 6.4 shows the experimental results and data analysis of different x-ray spectroscopy experiments performed on hydrogenated dilute nitrides, focusing on the local structural information ob-tained and placing it in its historical context with respect to the results of different characterization techniques reported at Chapters 5 and 7. The complementarity between different technical approaches is emphasized. Paragraph 6.5 draws the main conclusions of the chapter and future perspectives
Detector-related issues
No full textThis chapter focuses on some of the most important issues related to the use of
detectors in X-ray absorption spectroscopy measurements and provides guidelines
on how to correct or reduce distortions via the choice of an optimal setup
and pre-processing of the experimental data
Gallium clustering and structural effects of hydrogenation in InGaN/GaN nanostructures
No full textWe addressed the issue of atomic ordering in a series of In-rich InxGa1−xN epilayers grown on a GaN/AlN/sapphire(0001) epitaxial template by quantitatively measuring the Ga-cation coordination in the second atomic shell of Ga. We used Diffraction Anomalous Fine Structure Spectroscopy (DAFS) at the Ga K-edge to select the signal coming from the Ga atoms in the epilayer and eliminate any contribution from the buffer layer. DAFS measurements were also performed on hydrogenated epilayers in order to investigate the possible formation of Ga-H complexes. We find that deviation from cation random distribution in the form of Ga clustering is present in both untreated and hydrogenated samples and that in the latter ones the second atomic shell around Ga is modified, suggesting an additional perturbation of the cation sublattice related to hydrogen. However, comparing the present results with In K-edge x-ray absorption spectra previously reported, we conclude that the formation of Ga-H complexes vs. In-H ones is unlikely. Cation clustering has to be anyway taken into account as a possible channel playing in the determination of the optical bandgap of these technology-oriented semiconductors
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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