1,721,092 research outputs found
Parameters of ventilatory function in chronic bronchitis [Comportement de quelques paramètres fonctionnels ventilatoires dans la bronchite chronique.]
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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
Advances in position-sensitive photodetectors for PET applications
No full textThis paper presents a brief review of the use of position-sensitive detectors in positron emission tomography (PET) together with an overview of the near-future perspectives. Special attention is given to the development of a new class of magnetic field-compatible solid state photodetectors, the so-called silicon photomultipliers (SiPM). (C) 2009 Elsevier B.V. All rights reserved
Development and validation of RAYDOSE: a Geant4-based application for molecular radiotherapy.
No full textWe developed and validated a Monte-Carlo-based application (RAYDOSE) to generate patient-specific 3D dose maps on the basis of pre-treatment imaging studies. A CT DICOM image is used to model patient geometry, while repeated PET scans are employed to assess radionuclide kinetics and distribution at the voxel level. In this work, we describe the structure of this application and present the tests performed to validate it against reference data and experiments. We used the spheres of a NEMA phantom to calculate S values and total doses. The comparison with reference data from OLINDA/EXM showed an agreement within 2% for a sphere size above 2.8 cm diameter. A custom heterogeneous phantom composed of several layers of Perspex and lung equivalent material was used to compare TLD measurements of gamma radiation from (131)I to Monte Carlo simulations. An agreement within 5% was found. RAYDOSE has been validated against reference data and experimental measurements and can be a useful multi-modality platform for treatment planning and research in MRT
Studies of silicon photomultipliers at cryogenic temperatures
No full textWe investigate the behavior of silicon photomultipliers (SiPMs) at low temperatures: I-V characteristics, breakdown voltage, dark noise, afterpulsing, crosstalk, pulse shape, gain and photon detection efficiency are studied as a function of temperature in the range 50K < T < 320 K. We discuss our measurements on the basis of the temperature dependent properties of silicon and of the models related to carrier generation, transport and multiplication in high electric field. We conclude that SiPMs provide an excellent alternative to vacuum tube photomultipliers (PMTs) in low temperature environments, even better than in room temperature ones: in particular they excel in the interval 100K < T < 200K. (C) 2010 Elsevier B.V. All rights reserved
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