1,721,060 research outputs found
Constraints on top-down models for the origin of UHECRs from the Pierre Auger Observatory data
No full textInternational audienceIn the context of the report by the AGASA experiment of an apparent excess in the cosmic ray flux above the energy of the expected GZK feature, a variety of "top-down models" have been proposed for the origin of ultra-high-energy cosmic rays (UHECRs). These models involve the decay of supermassive particles and generically predict high neutrino and photon fluxes at ultra-high energy. Relying on the corresponding flux limits and overall spectrum normalisation obtained by the Pierre Auger Observatory, we set constraints on a wide class of top-down models and their contribution to the UHECR flux
Predictions of ultra-high energy neutrino fluxes
No full textProceedings of the 3rd International Workshop on a Very Large Volume Neutrino Telescope for the Mediterranean SeaInternational audienceThe recent discovery of the cutoff in the spectrum of Ultra-High Energy Cosmic Rays points to an extragalactic astrophysical origin of these cosmic rays. The neutrino flux at the highest energy is expected to come only from energy losses of protons and nuclei during propagation from their sources to the Earth. In this paper we discuss the uncertainties on this flux together with the possibilities of future experiments to discover it. We also briefly review possible Galactic and extragalactic point sources of neutrinos
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
Ultra-high energy nuclei source in the direction to Virgo cluster
No full text4 pages, 3 figuresThe significant anisotropy in the arrival directions of the 69 events with energy E> 55 EeV detected by Pierre Auger collaboration is located in the 20-degree region centered near Cen A. Not only the 2-point, but also the 3-point and 4-point autocorrelation functions are completely saturated by this region. Besides there is an deficit of events in the direction of Virgo cluster. If one assumes that the excess around Cen A is due to heavy nuclei shifted from Virgo, one can explain 20-degree scale of this anomaly. Also location of the highest energy event between the Cen A region and the Virgo cluster supports this idea. Magnitude and direction of the magnetic field is similar in this case to those expected for Galactic models. The existence of nuclei sources in the sky opens the road for a self-consistent description of Auger data
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
Clustering of ultra-high energy cosmic ray arrival directions on medium scales
No full text11 pages, 5 figuresThe two-point autocorrelation function of ultra-high energy cosmic ray (UHECR) arrival directions has a broad maximum around 25 degrees, combining the data with energies above eV (in the HiRes energy scale) of the HiRes stereo, AGASA, Yakutsk and SUGAR experiments. This signal is not or only marginally present analyzing events of a single experiment, but becomes significant when data from several experiments are added. Both the energy dependence and the angular scale might be interpreted as first signature of the large-scale structure of UHECR sources and of intervening magnetic fields
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