1,720,972 research outputs found
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
Is helium the key parameter in the extended colour spread of the first generation stars in M3?
No full textThe study of the 'chromosome maps' of Galactic globular clusters has shown that the stars identified as 'first generation' often define an extended sequence in the mF275W. mF814W colour, whose straightforward interpretation, by comparison with synthetic spectra, is that they are inhomogeneous in helium content. The cluster M3 (NGC 5272) is one of the most prominent example of this phenomenon, since its first generation is distributed on an extended colour range, formally corresponding to a large helium enhancement (~0.1). It is necessary to ask whether the bulk of photometric observations available for this cluster supports or falsifies this interpretation. For this purpose, we examine the horizontal branch morphology, the period and magnitude distributions of the RR Lyrae variables, and the main sequence colour distribution. Simulating the first generation stars with such internal variation of helium content we cannot meet all the observational constraints at the same time, concluding that the origin of the first generation colour spread is still without a straightforward explanation
The C+N+O abundances and the splitting of the subgiant branch in the globular cluster NGC 1851
No full textAmong the newly discovered features of multiple stellar populations in globular clusters (GCs), the cluster NGC 1851 harbours a double subgiant branch (SGB), that can be explained in terms of two stellar generations, only slightly differing in age, the younger one having an increased total C+N+O abundance. Thanks to this difference in the chemistry, a fit can be made to the SGBes, roughly consistent with the C+N+O abundance variations already discovered two decades ago, and confirmed by recent spectroscopic data. We compute theoretical isochrones for the main sequence turnoff (TO), by adopting four chemical mixtures for the opacities and nuclear reaction rates. The standard mixture has Z = 10-3 and [α/Fe] = 0.4, the others have C+N+O, respectively, equal to 2, 3 and 5 times the standard mixture, according to the element abundance distribution described in the text. We compare tracks and isochrones, and show how the results depend on the total CNO abundance. We note that different initial CNO abundances between two clusters, otherwise similar in metallicity and age, may lead to differences in the TO morphology that can be easily attributed to an age difference. We simulate the main sequence and SGB data for NGC 1851 and show that an increase of C+N+O by a factor of ~3 best reproduces the shift between the SGBes. According to spectroscopic data by Yong et al., the C+N+O abundance in this cluster appears correlated with the abundance of s-process elements, Na and Al, and this makes massive asymptotic giant branches (AGBs) the best progenitors of the C+N+O enriched population. We compare the main sequence width in the colour mF336W-mF814W with models, and find that the maximum helium abundance compatible with the data is Y ~= 0.29. We consider the result in the framework of the formation of the second stellar generation in GCs, for the bulk of which we estimate a helium abundance of Y <~ 0.26. The precise value depends on which are the AGB masses from which the C+N+O enriched matter originates, and on the amount of dilution with the pristine gas
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
The puzzle of metallicity and multiple stellar populations in the globular clusters in Fornax
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