1,721,189 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
Very Metal-poor Stars in the Solar Vicinity: Kinematics and Abundance Analysis
Full text linkVery metal-poor stars contain crucial information on the Milky Way’s infancy. In our previous study we derived a mean age of ∼13.7 Gyr for a sample of these stars in the Sun’s vicinity. In this work, we investigate the chemical and kinematic properties of these stars with the goal of obtaining some insights into their origin and their parent population. We did not find any Al-Mg anticorrelation, which leads us to the conclusion that these stars did not form in globular clusters, while the detailed analysis of their orbital parameters reveals that these stars are most probably associated with the pristine bulge of the Milky Way. We then sketch a scenario for the formation of the Milky Way in which the first structure to form was the bulge through rapid collapse. The other components have grown later on, with a significant contribution of accreted structures
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
Uncovering Multiple Populations with Washington Photometry. I. The Globular Cluster NGC 1851
Full text linkThe analysis of multiple populations (MPs) in globular clusters (GCs) has become a forefront area of research in astronomy. Multiple red giant branches (RGBs), subgiant branches (SGBs), and even main sequences (MSs) have now been observed photometrically in many GCs, while broad abundance distributions of certain elements have been detected spectroscopically in most, if not all, GCs. UV photometry has been crucial in discovering and analyzing these MPs, but the Johnson U and the Stromgren and Sloan u filters that have generally been used are relatively inefficient and very sensitive to reddening and atmospheric extinction. In contrast, the Washington C filter is much broader and redder than these competing UV filters, making it far more efficient at detecting MPs and much less sensitive to reddening and extinction. Here, we investigate the use of the Washington system to uncover MPs using only a 1 m telescope. Our analysis of the well-studied GC NGC 1851 finds that the C filter is both very efficient and effective at detecting its previously discovered MPs in the RGB and SGB. Remarkably, we have also detected an intrinsically broad MS best characterized by two distinct but heavily overlapping populations that cannot be explained by binaries, field stars, or photometric errors. The MS distribution is in very good agreement with that seen on the RGB, with ~30% of the stars belonging to the second population. There is also evidence for two sequences in the red horizontal branch, but this appears to be unrelated to the MPs in this cluster. Neither of these latter phenomena have been observed previously in this cluster. The redder MS stars are also more centrally concentrated than the blue MS. This is the first time MPs in an MS have been discovered from the ground, and using only a 1 m telescope. The Washington system thus proves to be a very powerful tool for investigating MPs, and holds particular promise for extragalactic objects where photons are limited
Chemical evolution of the metal-poor globular cluster NGC 6809
No full textWe present the abundances analysis for a sample of 11 red giant branch stars in the metal-poor globular cluster NGC 6809 based on high-resolution spectra. Our main goals are to characterize its chemical composition and analyse this cluster’s behaviour associated with the Multiple Populations (MPs) phenomenon. In our work, we obtained the stellar parameters and chemical abundances of 24 elements (O, Na, Mg, Al, Si, Ca, Ti, V, Cr, Mn, Fe, Co, Sc, Ni, Cu, Zn, Y, Zr, Ba, La, Ce, Eu, Nd, and Dy). We found a radial velocity of 174.7 ± 3.2 km/s and a mean iron content of [Fe/H] = −2.01 ± 0.02 in good agreement with other studies. Moreover, we found a large spread in the abundances of the light elements O, Na, and Al confirming the presence of an Na–O anticorrelation or an Na–Al correlation. The Mg–Al anticorrelation is also present in our cluster. The α and iron-peak elements show good agreement with the halo field star trend. The heavy elements are dominated by the r-process
Metal Abundances in Extremely Distant Galactic Old Open Clusters. II. Berkeley 22 and Berkeley 66
Full text linkWe report on high-resolution spectroscopy of four giant stars in the Galactic old open clusters Berkeley 22 and Berkeley 66 obtained with HIRES at the Keck telescope. We find that [Fe/H] = -0.32 ± 0.19 and -0.48 ± 0.24 for Be 22 and Be 66, respectively. Based on these data, we first revise the fundamental parameters of the clusters and then discuss them in the context of the Galactic disk radial abundance gradient. We found that both clusters nicely obey the most updated estimate of the slope of the gradient from the work of Friel and coworkers and are genuine Galactic disk objects. © 2005. The American Astronomical Society. All rights reserved
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