1,720,957 research outputs found
Spectroscopy of the circumnuclear emission lines regions in Seyfert Galaxies II. NGC 7214
No full textThis paper is the second of a series (Radovich & Rafanelli 1996) devoted to the investigation of the emission line properties of the circumnuclear and extranuclear regions in a sample of nearby Seyfert galaxies. Our aim is to identify star formation regions around the active nucleus and to derive their properties like star formation rate and dust content, and compare them with those observed in non-active galaxies. We show that photoionization models may fit the observed line ratios both in the nuclear and circumnuclear regions of the Sy 1.2 galaxy NGC 7214. In the nucleus, components with different densities must be considered. In the circumnuclear regions, line ratios to projected distances of ~ 2 kpc from the nucleus are typical of ionization by a power law. At higher distances ( ~ 5-8 kpc) they are fitted either by a thermal continuum or assuming that both stars and the non thermal source contribute to the ionization of the gas. A simple interpretation is suggested, in the framework of the unified model for Seyfert galaxies. Evidence for enhanced star formation, maybe related to the ongoing interaction with a close spiral galaxy, is found in only one region. Based on observations collected at ESO - La Silla (Chile)
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
Spectroscopy and BVI Photometry of the young open cluster NGC 6604
Full text linkBVIC photometry and classification spectroscopy is presented
for the young open cluster NGC 6604. Additional Echelle spectroscopy of the
brightest members is used to check the reddening against the interstellar
NaI and KI absorption lines, to measure the cluster radial velocity and to
derive the individual rotational velocities. We obtain 1.7 kpc as the
cluster distance, an age of years and a reddening
EB-V= 1.02 ( from three independent methods). Pre-ZAMS
objects are apparently not detected over the = 8.5 mag
explored range. The cluster radial velocity is in agreement with the Hron (1987) model for the Galaxy disk rotation
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
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