1,720,976 research outputs found
Suppressing the lower multipoles in the CMB anisotropies
No full textThe Cosmic Microwave Background (CMB) anisotropy power on the largest angular scales observed both by WMAP and COBE DMR appears to be lower than the one predicted by the standard model of cosmology with almost scale free primordial perturbations arising from a period of inflation. One can either interpret this as a manifestation of cosmic variance or as a physical effect that requires an explanation. We discuss various mechanisms that could be responsible for the suppression of such low l multipoles. Features in the late time evolution of metric fluctuations may do this via the integral Sachs–Wolfe effect. Another possibility is a suppression of power at large scales in the primordial spectrum induced by a fast rolling stage in the evolution of the inflaton field at the beginning of the last 65 e-folds of inflation. We illustrate this effect in a simple model of inflation and fit the resulting CMB spectrum to the observed temperature–temperature (TT) power spectrum. We find that the WMAP observations suggest a cutoff at kc = 4.9+1.3−1.6 × 10^{−4} Mpc^{−1} at 68% confidence, but only an upper limit of kc < 7.4 × 10−4 Mpc^{−1} at 95%. Thus, although it improves the fit of the data, the presence of a cutoff in power spectrum is only required at a level close to 2σ. This is obtained with a prior which corresponds to equal distribution w.r.t. kc. We discuss how other choices (such as an equal distribution w.r.t. lnkc, which is natural in the context of inflation) can affect the statistical interpretation
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
Probing Early and Late Inflations Beyond Tilted LambdaCDM
No full textThe topic of this thesis is about cosmic inflations, including the early-universe inflation
that seeds the initial inhomogeneities of our universe, and the late-time cosmic acceleration triggered by dark energy. The two inflationary epochs have now become part of
the standard ΛCDM cosmological model. In the standard paradigm, dark energy is a
cosmological constant or vacuum energy, while the early-universe inflation is driven by
a slowly rolling scalar field. Currently the minimal ΛCDM model with six parameters
agrees well with cosmological observations.
If the greatest achievement of the last twenty golden years of cosmology is the ΛCDM
model, the theme of future precision cosmology will be to search for deviations from
the minimal ΛCDM paradigm. It is in fact expected that the upcoming breakthroughs
of cosmology will be achieved by observing the subdominant anomalies, such as nonGaussianities in the Cosmic Microwave Background map. The aim of this thesis is then
to make theoretical predictions from models beyond ΛCDM, and confront them with
cosmological observations. These models include: 1) a new dark energy parametrization
based on quintessence models; 2) reconstructing early-universe inflationary trajectories,
going beyond the slow-roll assumption; 3) non-Gaussian curvature fluctuations from preheating after the early-universe inflation; 4) infra-red cascading produced by particle
production during inflation; 5) preheating after Modular inflation; 6) decaying cold dark
matter. We update the cosmological data sets – Cosmic Microwave Background, Type Ia supernova, weak gravitational lensing, galaxy power spectra, and Lyman-α forest – to
the most current catalog, and run Monte Carlo Markov Chain calculations to obtain the
likelihood of parameters. We also simulate mock data to forecast future observational
constraints.Ph
Author-wise bibliometric analysis based on entropy.
No full textAuthor-wise bibliometric analysis based on entropy.</p
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