1,721,374 research outputs found
Evidence of evolution of the black hole mass function with redshift
Full text linkAims. We investigate the observed distribution of the joint primary mass, mass ratio, and redshift of astrophysical black holes using the gravitational wave events detected by the LIGO-Virgo-KAGRA collaboration and included in the third gravitational wave transient catalogue. Methods. We reconstructed this distribution using Bayesian non-parametric methods, which are data-driven models able to infer arbitrary probability densities under minimal mathematical assumptions. Results. We find evidence that both the primary mass and mass-ratio distribution evolve with redshift: our analysis shows the presence of two distinct subpopulations in the primary massa redshift plane, with the lighter population, 20 M-, disappearing at higher redshifts, za >a 0.4. The mass-ratio distribution shows no support for symmetric binaries. Conclusions. The observed population of coalescing binary black holes evolves with look-back time, suggesting a trend in metallicity with redshift and/or the presence of multiple redshift-dependent formation channels
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
Survey of Orion Disks with ALMA (SODA). III. Disks in wide binary systems in L1641 and L1647
Full text linkContext. Observations of protoplanetary disks within multiple systems in nearby star-forming regions (SFRs) have shown that the presence of a neighboring object influences the evolution of dust in disks. However, the size of the available sample and the separation range covered are insufficient to fully understand the dust evolution in binary systems.
Aims. The goal of this work, based on the Survey of Orion Disks with ALMA (SODA), is to comprehensively characterize the impact of stellar multiplicity on Class II disks in the L1641 and L1647 regions of Orion A (∼1–3 Myr). We characterized the protostellar multiplicity using the Atacama Large Millimeter/submillimeter Array (ALMA), the ESO-VISTA, and the Hubble Space Telescope. The resulting sample of 65 multiple systems is the largest catalog of wide binary systems to date (projected separation ≥1000 AU) and enables a more robust statistical characterization of the evolution and properties of protoplanetary disks.
Methods. The disk population was observed in the continuum with ALMA at 225 GHz, with a median rms of 1.5 M⊕. We combined these data (resolution of ∼1.1′′) with the ESO-VISTA near-infrared survey of the Orion A cloud (resolution of ∼0.7′′). From this dataset, multiple-star systems were selected using an iterative inside-out search in projected separation (≥1000 AU).
Results. We identify 61 binary systems, 3 triple systems, and 1 quadruple system. The separation range is between 1000 and 104 AU. The dust mass distributions inferred via the Kaplan-Meier estimator yield a median mass of 3.23−0.4+0.6 M⊕ for primary disks and 3.88−0.3+0.3 M⊕ for secondary disks.
Conclusions. Combining our data with those available for the Lupus and Taurus disks, we identify a threshold separation of about 130 AU, beyond which the previously observed positive correlation between millimeter flux (and hence dust mass) and projected separation is lost. Recent theoretical models confirm that pre- and post-threshold systems are the result of different star formation processes, such as the fragmentation of gravitationally unstable circumstellar disks, the thermal fragmentation of infalling cores, or the turbulent fragmentation of molecular clouds. We can rule out the dependence on different SFRs: the cumulative mass distributions of multiples in SFRs of similar ages are statistically indistinguishable. This result strengthens the hypothesis that there is a universal initial mass distribution for disks
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