1,721,062 research outputs found
Triaxial strong-lensing analysis of the z > 0.5 MACS clusters: the mass-concentration relation
No full textThe high concentrations derived for several strong-lensing clusters present a major inconsistency between theoretical ? cold dark matter (?CDM) expectations and measurements. Triaxiality and orientation biases might be at the origin of this disagreement, as clusters elongated along the line of sight would have a relatively higher projected mass density, boosting the resulting lensing properties. Analyses of statistical samples can probe further these effects and crucially reduce biases. In this work we perform a fully triaxial strong-lensing analysis of the 12 Massive Cluster Survey (MACS) clusters at z > 0.5, a complete X-ray-selected sample, and fully account for the impact of the intrinsic 3D shapes on their strong-lensing properties. We first construct strong-lensing mass models for each cluster based on multiple images, and fit projected ellipsoidal NavarroFrenkWhite haloes with arbitrary orientations to each mass distribution. We then invert the measured surface mass densities using Bayesian statistics. Although the Einstein radii of this sample are significantly larger than those predicted by ?CDM, here we find that the massconcentration relation is in full agreement with results from N-body simulations. The z > 0.5 MACS clusters suffer from a moderate form of the orientation bias as may be expected for X-ray-selected samples. Being mostly unrelaxed, at a relatively high redshift, with high X-ray luminosity and notable substructures, these clusters may lie outside the standard concentrationEinstein radius relation. Our results remark the importance of triaxiality and properly selected samples for understanding galaxy clusters properties and suggest that for higher-z, unrelaxed low-concentration clusters form a different class of prominent strong gravitational lenses. Arc redshift confirmation and weak-lensing data in the outer region are needed to further refine our analysis
A Pilot Survey for C III] Emission in the Reionization Era: Gravitationally Lensed Z ∼ 7–8 Galaxies in the Frontier Fields Cluster Abell 2744
Full text linkWe report results of a search for C iii] 1907, 1909 Å emission using Keck's MOSFIRE spectrograph in a sample of 7 candidates () lensed by the Hubble Frontier Field cluster Abell 2744. Earlier work has suggested the promise of using the C iii] doublet for redshift confirmation of galaxies in the reionization era given that Lyα (λ1216 Å) is likely attenuated by the neutral intergalactic medium. The primary challenge of this approach is the feasibility of locating C iii] emission without advanced knowledge of the spectroscopic redshift. With an integration time of 5 hr in the H band, we reach a median flux limit (in between the skylines) of ergs cm−2 s−1 but no convincing C iii] emission was found. We also incorporate preliminary measurements from two other CLASH/HFF clusters in which, similarly, no line was detected, but these were observed to lesser depth. Using the known distribution of OH emission and the photometric redshift likelihood distribution of each lensed candidate, we present statistical upper limits on the mean total C iii] rest-frame equivalent width (EW) for our sample. For a signal-to-noise ratio of 5, we estimate that the typical C iii] doublet rest-frame EW is, with 95% confidence, Å. Although consistent with the strength of earlier detections in brighter objects at , our study illustrates the necessity of studying more luminous or strongly lensed examples prior to the launch of the James Webb Space Telescope
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
Author-wise bibliometric analysis based on entropy.
No full textAuthor-wise bibliometric analysis based on entropy.</p
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