1,720,967 research outputs found
Exploring the Universe through the astrophysical gravitational-wave background
Full text linkThis thesis is dedicated to the theoretical modelling of the stochastic gravitational-wave background (SGWB) originating from coalescing stellar compact binaries, and its characterization as a tool for studying the properties of binary populations, their host galaxies, and the broader Universe. I defined a general pipeline to obtain theoretical predictions for both the intensity and the anisotropies of the SGWB based on state-of-the-art binary population synthesis codes, empirical prescriptions for galactic physics and a Boltzmann solver for computing the evolution of cosmological perturbations. A key step in the process is the characterization of the SGWB as a tracer of the large-scale structure (LSS), by defining its redshift distribution, bias and magnification bias. Then, I used this pipeline to simulate full-sky maps of the SGWB, taking into account both clustering properties and the discreteness of sources in space and time, which causes the presence of a shot noise that is typically orders of magnitude larger than the intrinsic anisotropies induced by the LSS. An effective way to reduce the impact of shot noise is to cross-correlate the SGWB with other tracers of the LSS. In this thesis, I focused on the cross-correlation with CMB lensing and studied the detectability of the SGWB anisotropies, evaluating the signal-to-noise ratio for the angular power spectrum of both the auto- and cross-correlation, with networks of present and forthcoming gravitational-wave detectors. Finally, I studied how the high-frequency peak of the SGWB produced by coalescing binaries can be used as an observable to constrain a selection of astrophysical and cosmological parameters
Intensity and anisotropies of the stochastic gravitational wave background from merging compact binaries in galaxies
No full textWe investigate the isotropic and anisotropic components of the Stochastic Gravitational
Wave Background (SGWB) originated from unresolved merging compact binaries in
galaxies. We base our analysis on an empirical approach to galactic astrophysics that allows
to follow the evolution of individual systems. We then characterize the energy density of
the SGWB as a tracer of the total matter density, in order to compute the angular power
spectrum of anisotropies with the Cosmic Linear Anisotropy Solving System (CLASS) public
code in full generality. We obtain predictions for the isotropic energy density and for the
angular power spectrum of the SGWB anisotropies, and study the prospect for their observations
with advanced Laser Interferometer Gravitational-Wave and Virgo Observatories
and with the Einstein Telescope. We identify the contributions coming from different type
of sources (binary black holes, binary neutron stars and black hole-neutron star) and from
different redshifts. We examine in detail the spectral shape of the energy density for all types
of sources, comparing the results for the two detectors. We find that the power spectrum of
the SGWB anisotropies behaves like a power law on large angular scales and drops at small
scales: we explain this behavior in terms of the redshift distribution of sources that contribute
most to the signal, and of the sensitivities of the two detectors. Finally, we simulate a high
resolution full sky map of the SGWB starting from the power spectra obtained with CLASS
and including Poisson statistics and clustering properties
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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