1,720,966 research outputs found
X-RAY PHOTOIONIZED ACCRETION DISKS - UV AND X-RAY CONTINUUM SPECTRA AND POLARIZATION
No full textWe calculate the UV and X-ray continuum spectrum and polarization from an accretion disc centrally illuminated by X-rays. The calculation of the ionization structure of the disc is performed by using the numerical code described by Ross & Fabian, while the inclination effects and the polarization are calculated by solving the transfer equation for polarized radiation. The general relativistic effects in the Schwarzschild metric are also taken into account. The spectra we obtain can explain the X-ray observation for some active galactic nuclei and several Galactic black hole candidates, for which both the iron-line intensity and the shape of the reflection continuum appear to be inconsistent with reprocessing from neutral matter. We find that the degree and angle of polarization vary strongly with the energy; this fact should be testable by future observations. We also suggest, on the basis of earlier works by Loskutov & Sobolev, that the absorption opacity solution of the polarization problem for thin discs can reconcile theory with observations, since even a small absorption opacity can strongly reduce the polarization degree to very low, if observable, values
IRON K-ALPHA LINES FROM X-RAY PHOTOIONIZED ACCRETION DISKS
No full textThe properties of the iron Kalpha line emitted by an accretion disc illuminated by an external X-ray source are calculated for different values of the disc accretion rate m, and for two different source geometries: a point source located on the disc axis and an extended source above the innermost part of the disc. We find that for large values of rh the matter can be significantly ionized, and the iron line equivalent width can reach values as high as 250 eV for the point source, and up to about 400 eV for the extended source; the line centroid energy, in the emitting rest frame, is significantly higher than 6.4 keV, the value for neutral iron. A further increase of m leads to a strong decrease of the line intensity, because the iron becomes fully stripped in the inner region of the disc. The line profiles in the Schwarzschild metric are also calculated, and for the point source they appear much more complex than those obtained assuming neutral matter
Iron K fluorescent lines from relativistic, ionized discs
No full textWe present detailed Monte Carlo calculations of the iron K alpha lines from X-ray photoionized, relativistic accretion discs. The vertical ionization structure of the matter has been taken into account, and Compton scattering and resonant absorption have been treated in detail. We find that the ratio of lines emitted by different iron ions depends, apart from the ionization parameter, on the disc inclination angle. The line profiles with relativistic corrections have also been calculated; they can be used to distinguish between different source geometries
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
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
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