1,721,012 research outputs found
A search for time dependent neutrino emission from microquasars with the ANTARES telescope
No full textResults are presented on a search for neutrino emission from a sample of six microquasars, based on the data collected by the ANTARES neutrino telescope between 2007 and 2010. By means of appropriate time cuts, the neutrino search has been restricted to the periods when the acceleration of relativistic jets was taking place at the microquasars under study. The time cuts have been chosen using the information from the X-ray telescopes RXTE/ASM and Swift/BAT, and, in one case, the gamma-ray telescope Fermi/LAT. No statistically significant excess has been observed, thus upper limits on the neutrino fluences have been derived and compared to the predictions by models. Constraints have been put on the ratio of proton to electron luminosity in the jets
Light Concentrators for Silicon Photomultipliers
No full textAbstractPhotosensitive devices represent a key solution for several current and future categories of experiments in which photon detection is the crucial point for the observation of physical phenomena. Astro particle experiments for instance, one of the most promising observation channels for High Energy Physics, typically study energetic phenomena in which charged particles originating from the interactions or decays of primary particles radiate Cherenkov or fluorescence light, which is then detected by photosensitive devices. In these fields of applications, the Silicon Photomultipliers (SiPM) devices based on the limited Geiger-mode avalanche (generally G-APD, Geiger Avalanche Photons Detectors), are extensively under study. Unfortunately, applications of SiPMs are very limited by their small sensitive surfaces. In order to overcome the limits of the small dimensions of the sensitive area of SiPM devices, different solutions are reported. In particular it is discussed the use of Optical Concentrators with the correct refraction index, characteristic and geometry for the improvement of the sensitive surface dimensions of a SiPM device
High Gain Hybrid Photomultipliers Based on Solid State p-n Junctions in Geiger Mode and Their use in Astroparticle Physics
No full textAbstractIn astroparticle physics photomultiplier tubes play a crucial role in the detection of fundamental physical processes. After about one century of standard technology (photocathode and dynode electron multiplication chain), the recent strong development of modern silicon devices has brought to maturity a new generation of photodetectors based on an innovative, high-quality, cost effective technology. In particular the most promising development in this field is represented by the rapidly emerging CMOS p-n Geigermode avalanche photodiode technology (G-APD or SiPM), for high-speed single photon detection with high gain and linearity. Most applications will require collection of light from even larger surfaces or volumes, so it is necessary to increase the active surface and the angular acceptance of SiPMs while keeping high sensitivity. The main purpose of this research is, therefore, to provide an attractive solution to overcome this problem. The idea is to realize a hybrid detector (Vacuum Silicon PhotoMulTiplier,VSiPMT), where the dynodes structure of a classical Vacuum PhotoMultiplier Tube (VPMT) is replaced by an array of G-APDs, which collects the photoelectrons emitted by photocathode and acts as an electron multiplier
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
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