1,721,058 research outputs found
Supernova remnants' interactions with the inter-stellar medium
Get PDFAll-sky data at a number of different wavelengths are used to examine the Giant Radio Loops. The x-ray emission of Loop I is modelled as being due to a Supernova Remnant (SNR) that has evolved in a hot, homogeneous, quasi-isotropic medium. The shock is found to weaken towards higher latitudes, and this is attributed to an increase in the ambient gas temperature away from the galactic plane. Other evolutionary possibilities are examined. Radio spectral index maps from 38 to 1420MHz of the northern celestial hemisphere are produced, and the spectra of loops I and III are modelled on the assumption that the energy distribution of electrons accelerated in the shocks will have an upper energy cut-off due to the finite age of the remnants. It is found that the steepening spectra can be fitted by such a model. The electron distribution below the cut-off of order l0GeV is found to fit best if a flatter spectrum than predicted by simple shock theory is assumed. The idea that shocks. Interacting with clouds can explain this flatter spectrum and enhance the soft x-ray emission is put forward as an alternative evolutionary possibility, bringing together the two separate x-ray and radio emission mechanisms. Other galactic SNR are examined to support this idea, including a newly discovered SNR that exists inside the error circle of the COS-B source 2CG342-02. Although this remnant’s association with the γ-ray source cannot be excluded, no firm evidence is found to identify it as the source
On the Age of the Globular Cluster M4
No full textVery deep images of the Galactic globular cluster M4 through the F606W and F814W filters were taken in 2001 with the WFPC2 on board the HST. A first published analysis of this data set produced the result that the age of M4 is 12.7+/-0.7 Gyr thus setting a robust lower limit to the age of the universe. In view of the great astronomical importance of getting this number right we have subjected the same data set to the simplest possible photometric analysis that avoids uncertain assumptions about the origin of the detected sources. This analysis reveals both a thin main sequence and a white dwarf (WD) sequence extending all the way down to the 5 sigma detection limit at I~27. The WD sequence is abruptly terminated at exactly this limit as expected by detection statistics. Using our theoretical WD models to obtain the expected WD sequence for different ages in the observed bandpasses we find that these data allow one only to set a lower limit to the age of M4 of ~9 Gyr. Thus the problem of determining the absolute age of a globular cluster and therefore the onset of GC formation with cosmologically significant accuracy remains completely open
Going Beyond Counting First Authors in Author Co-citation Analysis
Get PDFThe 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
Get PDF“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
Get PDFWe 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
Get PDFWe 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
koamabayili/VECTRON-author-checklist: VECTRON author checklist
No full textWe have done our best to complete the author checklist relating to the use of animals in the hut study. Note that the objective for the hut study was to evaluate the IRS treatment applications for residual efficacy against Anopheles mosquitoes, including the local An. coluzzii mosquito population. Cows were only used to attract mosquitoes into the huts and no tests were carried out directly on the cows. The author checklist is intended for use with studies where experiments are carried out on animals, which is why we have had such difficulty in completing this for the hut study, as many of the questions do not relate to how the cows were used
Author-wise bibliometric analysis based on entropy.
No full textAuthor-wise bibliometric analysis based on entropy.</p
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