1,720,991 research outputs found
R.j. Protheroe
No full textI give a brief critical review of the predicted intensity of diffuse high energy neutrinos of astrophysical origin over the energy range from ¸ 10 12 eV to ¸ 10 24 eV. Neutrinos from interactions of galactic cosmic rays with interstellar matter are guaranteed, and the intensity can be reliably predicted to within a factor of 2 up to 10 17 eV. Somewhat less certain are intensities in the same energy range from cosmic rays escaping from normal galaxies or active galactic nuclei (AGN) and interacting with intracluster gas. At higher energies, neutrinos will be produced by interactions of extragalactic cosmic rays with the microwave background. Other sources, such as AGN, in particular blazars, and topological defects, are more speculative. However, searches for neutrinos from all of these potential sources should be made because their observation would have important implications for high energy astrophysics and cosmology. 1 Introduction The technique for constructing a large area ..
R.j. Protheroe
No full textIn this lecture I give an overview of shock acceleration, interactions of high energy cosmic rays with, and propagation through, the background radiation, and the resulting electron-photon cascade. I argue that while the origin of the highest energy cosmic rays is still uncertain, it is not necessary to invoke exotic models such as emission by topological defects to explain the existing data. It seems likely that shock acceleration at Fanaroff-Riley Class II radio galaxies can account for the existing data. However, new cosmic ray data, as well as better estimates of the extragalactic radiation fields and magnetic fields will be necessary before we will be certain of the origin of the highest energy particles occurring in nature. 1 Introduction Cosmic rays with energies up to 100 TeV are thought to arise predominantly through shock acceleration by supernova remnants (SNR) in our Galaxy [1]. A fraction of the cosmic rays accelerated should interact within the supernova remnant and prod..
A lunar radio experiment with the Parkes radio telescope for the LUNASKA project
No full textAbstract not availableJ.D. Bray, R.D. Ekers, P. Roberts, J.E. Reynolds, C.W. James, C.J. Phillips, R.J. Protheroe, R.A. McFadden, M.G. Aartse
Going Beyond Counting First Authors in Author Co-citation Analysis
Get PDFThe 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
Get PDF“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
Get PDFWe 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
A hadronic model for gamma-ray loud quasars
No full text©2003 by Universal Academy PressWe discuss the spectral energy distribution (SED) of quasars in a hadronic model having both internal and external target photon fields. The high energy part of the SED results from a cascade initiated by electrons from charged pion decay and Bethe-Heitler pair production and gamma-rays from neutral pion decay, and involves synchrotron radiation, inverse-Compton scattering and photonphoton pair production. We apply this model to 3C 273.R.J. Protheroe, A.-C. Done
Dispelling the Myths Behind First-author Citation Counts
Get PDFWe 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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