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Going Beyond Counting First Authors in Author Co-citation Analysis
Get PDFThe 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
Get PDF“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
Get PDFWe 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
Get PDFWe 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
Frontispiece: Iron/Brønsted Acid Catalyzed Asymmetric Hydrogenation: Mechanism and Selectivity‐Determining Interactions
No full textFull Reaction Mechanism of Nitrile Hydratase: A Cyclic Intermediate and an Unexpected Disulfide Switch
No full textCobalt–Bis(imino)pyridine-Catalyzed Asymmetric Hydrogenation: Electronic Structure, Mechanism, and Stereoselectivity
No full textAcademic
and industrial efforts aim at replacing precious metal
catalysts with cheaper and more environmentally friendly base metal
variants. Two cobalt–bis(imino)pyridine (CoBIP) complexes were
recently reported as promising candidates for asymmetric hydrogenation
[Monfette, S.; et al. J. Am. Chem. Soc. 2012, 134, 4561–4564]. A comprehensive quantum mechanical analysis
of these complexes is reported here, including electronic structures,
preferred conformations, and mechanisms of activation. The full asymmetric
hydrogenation mechanism is analyzed, and the origin of the observed
enantioselectivities with both CoBIP catalysts is evaluated. A key
finding is that CoBIP complexes catalyze a competing alkene isomerization
reaction, which can have crucial implications for the yield and the
stereochemical outcome of alkene hydrogenation
Full Reaction Mechanism of Nitrile Hydratase: A Cyclic Intermediate and an Unexpected Disulfide Switch
No full textThe
full reaction mechanism of nitrile hydratase has remained elusive,
despite extensive theoretical and experimental studies. A novel reaction
mechanism for nitrile hydratase is proposed here, with remarkable
features and very feasible barriers. Our results, obtained on the
basis of large quantum-mechanical active site models, identify Cys-SO– as the nucleophile, performing a direct nucleophilic
attack on the metal-coordinated nitrile. This implies the formation
of an intriguing cyclic intermediate, which subsequently is cleaved
through attack of the axial cysteine on the sulfenate, thereby forming
a disulfide bond. In this mechanism, nitrile hydration occurs without
directly involving a water molecule. Subsequent water-mediated disulfide
cleavage regenerates the active site. This is the first example of
a disulfide switch directly implicated in an enzymatic reaction mechanism
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