1,720,981 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
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
LINEAR-STABILITY OF SPHERICAL COLLISIONLESS STELLAR-SYSTEMS
No full textThe linear stability analysis is presented here in a self-contained form, and several general issues, related to the symmetry properties of the relevant equations and to the boundary conditions are formulated. A numerical code for the study of the linear stability of collisionless spherical stellar systems with no radial truncation is constructed and applied to survey a family of astrophysically interesting anisotropic equilibrium models. The code is flexible, in that it can accept any reasonable initial distribution function f=f(E, J(2)) and is not restricted to a specific mass model. We have focused on the l=2 modes and on the so-called radial orbit instability. Marginal stability has been identified, corresponding to a value of 2K(r)/K-T = 1.58 for the ratio of the total radial to tangential kinetic energy, somewhat on the low side with respect to a generally accepted stability criterion. As the ratio 2K(r)/K-T increases, the number of unstable modes and the value of their growth rates are found to increase considerably, so that for negative-temperature models we have found up to six modes, with a growth rate much higher than the inverse half-mass crossing time and matching the timescales available in the innermost regions of the galaxy. For these negative-temperature models the density perturbations are very concentrated and indicate that the system would evolve rapidly through sizable poloidal motions which are bound to redistribute both the orbits and the mass in the central parts of the galaxy. The results shown are briefly compared with those derived from N-body simulations
Anisotropic stellar systems with tangentially biased velocity dispersion
No full textThis paper provides a simple general procedure to construct self-consistent spherical equilibrium models of stellar systems populated by stars in quasi-circular orbits. The focus on Maxwellian-like distributions in the relevant velocity space and the use of the epicyclic expansion allow us to work with physically intuitive models. Explicit solutions for a sequence of distribution functions with density distribution close to that of isochrone models are produced with varying degrees of pressure anisotropy. These results are meant to be the starting point for extensive stability analyses, and they may also be of interest for the construction of quantities such as projected velocity dispersion and line-of-sight-velocity profiles for comparison with observations of elliptical galaxies
Actinomicosi polmonare. Presentazione di un caso clinico e revisione della letteratura
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