1,721,092 research outputs found
Cosmological Parameters from Galaxy Clusters: An Introduction
Full text linkThis lecture is an introduction to cosmological tests with clusters of galaxies. Here, I do not intend to provide a complete review of the subject, but rather to describe the basic procedures to set up the fitting machinery to constrain cosmological parameters from clusters, and to show how to handle data with a critical insight. I will focus mainly on the properties of X ray clusters of galaxies, showing their success as cosmological tools, to end up discussing the complex thermodynamics of the di?use intracluster medium and its impact on the cosmological tests
Spatial distribution of metals in the ICM. Evolution of the iron excess in relaxed galaxy clusters
Full text linkWe investigate the spatial distribution of iron in the intracluster medium (ICM) in a selected sample of 41 relaxed clusters in the redshift range 0.05 < z < 1.03 using Chandra archival data. We compute the azimuthally averaged, deprojected ZFe profile of each cluster out to ~0.4r500, and identify a peak in the distribution of iron followed by a flatter distribution at larger radii. Due to the steep gradient both in gas density and abundance, we find that the emission-weighted iron abundance within 0.2r500, which entirely includes the iron peak in most of the cases, is on average ~25 per cent higher than the mass-weighted value, showing that spatially resolved analysis and accurate deprojection are key to study the evolution of iron enrichment in the very central regions of cool-core clusters.We quantify the extent of the iron distribution in each cluster with a normalized scale parameter rFe, defined as the radius where the iron abundance excess is half of its peak value. We find that rFe increases by a factor of ~3 from z ~ 1 to z ~ 0.1, suggesting that the spatial distribution of iron in the ICM extends with time, possibly due to the mixing with the mechanical-mode feedback from the central galaxy. We also find that the iron mass excess within 0.3r500, when normalized to the total baryonic mass within the same region, does not evolve significantly, showing that this iron mass component is already established at z ~ 1
Serological methods are able to determine how well influenza vaccines work
No full textIn influenza vaccine efficacy studies, virus identification is considered the ideal end point. This approach, especially if performed in large populations could be difficult to carry out and the results could depend on the level of influenza viruses’ circulation. This is why serological studies are often used as surrogate methods. Here we analyze the antibody response of 181 elderly volunteers (aged ≥65 years) to 2014-15 influenza vaccine to understand if serological data are able to predict the vaccine efficacy. We compared the response of those who have or have not had a serologically evidenced influenza infection after vaccination (the volunteers that had a seroconversion on comparing hemagglutination inhibiting (HI) titers found 1 and 6 months after vaccination were considered positive for serological evidence of recent infection). Before vaccination the infected group showed lower antibody levels than uninfected volunteers, after vaccination these differences increased. Dividing the infected volunteers according to the absence or the presence of influenza like illness (ILI) and to the severity of the ILI, we found that, 1 month after vaccination, 80-90% of volunteers with severe infections or with mild infections, respectively, were unprotected (HI<40). On the other hand, among the infected volunteers not showing ILI and the non-infected volunteers, more than half were found to be protected. Although the validity of using serologic confirmation of infection rather than virus identification to determine vaccine efficacy has been questioned, our results, though obtained analyzing a small population, confirm the validity of the serological approach
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
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