1,721,157 research outputs found
Measuring the cosmological parameters with the Ep,i-Eiso correlation of gamma-ray bursts
No full textWe have used the Ep,i-Eiso correlation of gamma-ray bursts (GRBs) to measure the cosmological parameter ΩM. By adopting a maximum likelihood approach which allows us to correctly quantify the extrinsic (i.e. non-Poissonian) scatter of the correlation, we constrain (for a flat universe) ΩM to 0.04-0.40 (68 per cent confidence level), with a best-fitting value of ΩM ~ 0.15, and exclude ΩM = 1 at >99.9 per cent confidence level. If we release the assumption of a flat universe, we still find evidence for a low value of ΩM (0.04-0.50 at 68 per cent confidence level) and a weak dependence of the dispersion of the Ep,i-Eiso correlation on ΩΛ (with an upper limit of ΩΛ ~ 1.15 at 90 per cent confidence level). Our approach makes no assumptions on the Ep,i-Eiso correlation and it does not use other calibrators to set the `zero' point of the relation, therefore our treatment of the data is not affected by circularity and the results are independent of those derived via Type Ia supernovae (or other cosmological probes). Unlike other multi-parameters correlations, our analysis grounds on only two parameters, then including a larger number (a factor of ~3) of GRBs and being less affected by systematics. Simulations based on realistic extrapolations of ongoing (and future) GRB experiments (e.g. Swift, Konus-Wind, GLAST) show that: (i) the uncertainties on cosmological parameters can be significantly decreased and (ii) future data will allow us to get clues on the `dark energy' evolution
Prospects for multi-messenger extended emission from core-collapse supernovae in the Local Universe
No full textMulti-messenger emissions from SN1987A and GW170817/GRB170817A suggest a Universe rife with multi-messenger transients associated with black holes and neutron stars. For LIGO-Virgo, soon to be joined by KAGRA, these observations promise unprecedented opportunities to probe the central engines of core-collapse supernovae (CC-SNe) and gamma-ray bursts. Compared to neutron stars, central engines powered by black hole-disk or torus systems may be of particular interest to multi-messenger observations by the relatively large energy reservoir E-J of angular momentum, up to 29% of the total mass in the Kerr metric. These central engines are expected from relatively massive stellar progenitors and compact binary coalescence involving a neutron star. We review prospects of multi-messenger emission by catalytic conversion of EJ by a non-axisymmetric disk or torus. Observational support for this radiation process is found in a recent identification of E similar or equal to (3.5 +/- 1)%M(circle dot)c(2) in Extended Emission to GW170817 at a significance of 4.2 sigma concurrent with GRB170817A. A prospect on similar emissions from nearby CC-SNe justifies the need for all-sky blind searches of long duration bursts by heterogeneous computing
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
Nova LMC 1991 : evidence for a super-bright nova population
Full text linkWe discuss the recent outburst of nova LMC 1991. By comparing its magnitude at maximum and rate of decline with those of 14 historical LMC novae, we show that nova LMC 1991 represents the first detection of a super-bright nova in the Large Magellanic Cloud. We have critically reviewed the photometric properties of the nova population in the Galaxy, M31, LMC and Virgo Cluster, and find that 9 objects deviate systematically from the Magnitude at Maximum vs. Rate of Decline relation by about one magnitude. This result may imply the existence of a distinct family of super-bright novae
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