1,720,992 research outputs found
Constraints on the spacetime dynamics of an early dark energy component
Full text linkWe consider an Early Dark Energy (EDE) cosmological model, and perform an analysis which takes into account both background and perturbation effects via the parameters c(eff)(2) and c(vis)(2), representing effective sound speed and viscosity, respectively. By using the latest available data we derive constraints on the amount of dark energy at early times and the present value of the equation of state. Our focus is on the effect that early dark energy has on the Cosmic Microwave Background (CMB) data, including polarization and lensing, in a generalized parameter space including a varying total neutrino mass, and tensor to scalar ratio, besides the 6 standard parameters of the minimal cosmological model. We find that the inclusion of Baryonic Acoustic Oscillations (BAO) data and CMB lensing significantly improves the constraints on the EDE parameters, while other high redshift data like the Quasar Hubble diagram and the Lyman-a forest BAO have instead a negligible impact. We find Omega(eDE) < 0.0039 and w(0) < -0.95 at the 95% C.L. for EDE accounting for its clustering through the inclusion of perturbation dynamics. This limit becomes weaker Omega(eDE) < 0.0034 if perturbations are neglected. The constraints on the EDE parameters are remarkably stable even when Sigma m(v), and r parameters are varied, with weak degeneracies between Omega(eDE) and r or Sigma m(v). In general we expect smaller values for the upper limits on the total amount of EDE with an increasing neutrino mass, while with a decreasing value of the tensor to scalar ratio we expect the 2 sigma upper limits on EDE to increase. We compare this EDE model with a simple wCDM with zero dark energy at early times and we find similar to 1-2% different upper limits on total neutrino mass and similar to 0.1-0.2% difference on the equation of state at the present time. Perturbation parameters are not constrained with current data sets, and tensions between the CMB derived H-0 and sigma(8) values and those measured with local probes are not eased. This work demonstrates the capability of CMB probes to constrain the total amount of EDE well below the percent level
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
Unveiling dark fifth forces with linear cosmology
Full text linkWe initiate the exploration of the cosmology of dark fifth forces: new forces
acting solely on Dark Matter. We focus on long range interactions which lead to
an effective violation of the Equivalence Principle on cosmological scales
today. At the microscopic level, the dark fifth force can be realized by a
light scalar with mass smaller than the Hubble constant today () coupled to Dark Matter. We study the behavior of the
background cosmology and linear perturbations in such a Universe. At the
background level, the new force modifies the evolution of the Dark Matter
energy density and thus the Hubble flow. At linear order, it modifies the
growth of matter perturbations and generates relative density and velocity
perturbations between Dark Matter and baryons that grow over time. We derive
constraints from current CMB and BAO data, bounding the strength of the dark
fifth force to be less than a percent of gravity. These are the strongest
constraints to date. We present potential implications of this scenario for the
Hubble tension and discuss how our results are modified if the light scalar
mediator accounts for the observed density of the Dark Energy. Finally, we
comment on the interplay between our constraints and searches for violations of
the Equivalence Principle in the visible sector.Comment: 54 pages, 15 figures. v2: revision of Section 6, now including atomic
clock constraints; added Table 1 summarizing the main results; extended
discussion of BAO; added several references. Matches version to appear in
JCAP. v3: fixed some incorrect equations, all results and figures unaffected.
Updated with latest experimental constraints from MICROSCOPE and atomic
clock
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
- …
