1,720,978 research outputs found
Internal Dynamics of ABCG 209 at z ~ 0.21
No full textWe report the results about the internal dynamics of the rich galaxy cluster
ABGC209 on the basis of new spectroscopic and photometric data. ABCG209 is a peak of 112 detected member galaxies at z= 0:209, characterised by a high value of the line–of–sight velocity dispersion, 3⁄4v » 1400 km s¡1. The cluster shows evidence of relevant substructure and dynamical segregation, and is characterised by a preferential SE–NW direction. The observational scenario suggests that ABCG209 is a strongly evolving cluster, possibly in an advanced phase of merging
Local disk star counts: observational constraints on the stellar IMF
No full textWe predict the local disk star counts through a galactic code which adopts stellar models (evolutionary tracks up to the white dwarf phase) together with a star formation rate (SFR) and an initial mass function (IMF). Results are compared with the disk luminosity function and the local white dwarf (WD) density to obtain constraints on IMF and SFR. We take into account three different ages (7.5, 9, 12 Gyr) and several star formation histories. Our analysis for a 7.5 Gyr disk and a flat SFR shows that a simple power law IMF (Salpeter like) for M>0.6Msun reproduces both the above observational quantities and the WD luminosity function cut-off. This result doesn't hold for a disk age larger than ~ 9 Gyr. In general, an increase of the disk age determines too many faint WDs. Even a steeper IMF exponent in the WD progenitor mass range cannot lead to agreement with observations
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
Book Review: From the Realm of the Nebulae to Populations of Galaxies: Dialogues on a Century of Research, Astrophysics and Space Science Library, 435
Full text linkThis document is Dr. Oswalt’s review of From the Realm of the Nebulae to Populations of Galaxies : Dialogues on a Century of Research, Astrophysics and Space Science Library, 435. by Mauro D\u27Onofrio, Roberto Rampazzo, and Simone Zaggia Springer, 2016 785p bibl index afp, 9783319310046 219.0
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
The Pisa Evolutionary Library
No full textWe supplement recent evolutionary computations of canonical stellar models (i.e. with inefficient core overshooting) with Z=0.0002, 0.0004, 0.0006, 0.001, 0.004, 0.008 and suitable assumptions about the original He content. Evolutionary results have been compared with observational data in order to properly calibrate the efficiency of the surface convection. On this basis, we follow the evolution of stellar models in the mass range 0.6 to 11 Msun from the Main Sequence (MS) until C ignition or the onset of thermal pulses in the advanced Asymptotic Giant Branch (AGB) phase, presenting cluster isochrones covering the range of ages from 20 Myr to 20 Gyr. To allow a comparison with evolutionary investigations appeared in the recent literature, we computed additional sets of models which take into account moderate core overshooting during the H burning phase (for the metallicities suitable for stars in the Magellanic Clouds: Z=0.004, Z=0.008). Selected predictions constraining the cluster ages are discussed, presenting a calibration of the difference in magnitude between the luminous MS termination and the He burning giants in terms of the cluster age. Both evolutionary tracks and isochrones have been made available at the URL http://gipsy.cjb.net in the ``Pisa Evolutionary Library'' directory
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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