1,721,161 research outputs found
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
Study of beta decay of exotic nuclei of interest for reactor physics, nuclear structure and nuclear astrophysics with the Total Absorption Gamma-ray Spectroscopy (TAGS) technique
No full textLa désintégration bêta est impliquée dans de nombreux domaines de la physique nucléaire : physique des réacteurs, structure nucléaire… De nombreuses expériences ont permis d’étudier les propriétés de la désintégration β d’un certain nombre de noyaux, ces derniers étant de plus en plus exotiques au fur et à mesure des avancées technologiques. Mais une partie de ces données souffre de l’effet « Pandemonium ». Connu depuis les années 70, cet effet est lié à l’utilisation des détecteurs haute résolution au Germanium qui ont une faible efficacité de détection des photons de haute énergie. Il en résulte une sous-estimation de l’alimentation des niveaux de haute énergie lors du calcul de l’intensité de désintégration β. Pour pallier cet effet, on utilise une technique de détection de haute efficacité: la Spectroscopie Gamma par Absorption Totale (TAGS). Dans cette thèse, nous nous sommes focalisés sur l’étude de trois noyaux mesurés auprès de l’accélérateur IGISOL en Finlande avec le détecteur DTAS. Nous présentons les résultats expérimentaux ainsi que l’intensité bêta obtenue, et la comparons aux résultats extraits des bases de données. Cette comparaison montre qu’une quantité non négligeable d’intensité β n’était pas détectée auparavant pour les trois noyaux étudiés. Nous discutons ensuite des impacts de cette différence dans le domaine des réacteurs nucléaires, et étudions l’alimentation β des états de haute énergie dans les noyaux fils qui pourraient constituer des résonances pygmées dans ces noyaux. Des comparaisons de nos résultats expérimentaux avec un modèle microscopique de QRPA sont également présentées afin d’aider à l’interprétation des données.Beta decay is involved in many topics in nuclear physics : reactor physics, nuclear astrophysics, nuclear structure… Many experiments have investigated the properties of beta decay of a number of nuclei, the latter being more and more exotic along with technological advances. But in some cases, data suffer from the “Pandemonium” effect. Known since the seventies, this effect is due to the use of high-resolution germanium detectors which have a very low efficiency to detect high energy photons. This may lead to an underestimation of the beta-intensity feeding the high energy levels. To overcome the problem, we use a technique with high intrinsic and geometric efficiencies: the Total Absorption Gamma-ray Spectroscopy (TAGS). In this work, we will focus on the study of three nuclei, measured at IGISOL in Finland, with the fragmented detector DTAS. We present the experimental results and the associated betaintensities, and compared them with the existing databases. This comparison shows a non-negligeable amount of beta-intensity that was not detected before for the three studied nuclei. Then we discuss the impacts of these new results on the reactor calculations (antineutrino spectra, decay heat), and analyze the β-feeding of the high energy levels in the daughter nuclei to study Pygmy Dipole Resonances (PDR or low lying resonances). Lastly, our experimental β-strengths are compared with the Gamow-Teller strengths obtained with a QRPA model
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
Mesure et étude théorique des propriétés de désintégration bêta des produits de fission pour la structure et l'astrophysique nucléaires et les applications
No full textLes domaines de physique dans lesquels la désintégration bêta des noyaux joue un rôle sont nombreux. Cette thèse s’intéresse à deux d’entre eux : la nucléosynthèse et la physique des réacteurs. Les propriétés radioactives des produits de fission sont des ingrédients essentiels pour le processus de nucléosynthèse de capture rapide de neutrons, appelé le processus r, à l’origine de la moitié des éléments plus lourds que le Fer dans l’univers. Par ailleurs, le processus de désintégration bêta est à l’origine de l’émission des antineutrinos et de la puissance résiduelle des réacteurs nucléaires. Les transitions bêta interdites non-uniques constituent entre un tiers et la moitié des transitions bêta qui entrent dans les calculs des chemins du processus r ou des spectres en énergie des antineutrinos des réacteurs. Leur impact n’a pas encore pu être quantifié à ce jour et nécessite en amont des nouvelles mesures et des développements théoriques des modèles existants. Ce travail de thèse a porté sur la détermination de facteurs de forme de transitions bêta premières interdites de noyaux riches en neutrons par des études théoriques et expérimentales. Sur le plan théorique, les opérateurs de désintégration bêta première interdite avec un modèle microscopique de pnQRPA auto-cohérente avec symétrie axiale utilisant l'interaction de Gogny ont été calculés et inclus au modèle. L’effet de leur prise en compte sur les distributions de force des opérateurs, les alimentations bêta et les demi-vies a été quantifié sur la chaîne isotopique des noyaux de Germanium riches en neutrons de A=75 à 83. L’analyse d’une expérience de Spectroscopie Gamma par Absorption Totale (TAGS) menée auprès du dispositif IGISOL à l’université de Jyväskylä, a conduit à l’obtention de l’alimentation bêta d’un noyau, le 99Zr, contributeur important à la puissance résiduelle des réacteurs et au spectre en énergie des antineutrinos des réacteurs. En outre, l’expérience eShape, menée en 2022 à IGISOL ayant pour but de déterminer la forme des spectres en énergie des électrons issus des transitions bêta premières interdites, a été calibrée pour l’exploitation future des données.The fields of physics in which the beta decay of nuclei plays a role are numerous. This thesis focuses on two of them: nucleosynthesis and reactor physics. The radioactive properties of fission products are essential ingredients in the process of rapid neutron capture nucleosynthesis, known as the r-process, which is responsible for half of the elements heavier than iron in the universe. The beta decay process is also responsible for the emission of antineutrinos and the decay heat of nuclear reactors. Non-unique forbidden beta transitions account for between a third and a half of the beta transitions used in rprocess path calculations or in the energy spectra of reactor antineutrinos. Their impact has yet to be quantified, and requires new measurements and theoretical developments of existing models. This thesis work focused on the determination of form factors of first forbidden beta transitions of neutron-rich nuclei through theoretical and experimental studies. On the theoretical side, the first forbidden beta decay operators with a microscopic selfconsistent pnQRPA model with axial symmetry using the Gogny interaction were calculated and included in the model. The effect of taking them into account on operator strength distributions, beta feeds and half-lives has been quantified on the isotopic chain of neutron-rich Germanium nuclei from A=75 to 83. Analysis of a Total Absorption Gamma Spectroscopy (TAGS) experiment carried out at the IGISOL device at the University of Jyväskylä, has led to the extraction of the beta feeding of a nucleus, 99Zr, an important contributor to the decay heat of reactors and to the energy spectrum of reactor antineutrinos. In addition, the eShape experiment, carried out at IGISOL in 2022 to determine the shape of electron energy spectra from forbidden first beta transitions, has been calibrated for future data exploitation. oc
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
koamabayili/VECTRON-author-checklist: VECTRON author checklist
No full textWe have done our best to complete the author checklist relating to the use of animals in the hut study. Note that the objective for the hut study was to evaluate the IRS treatment applications for residual efficacy against Anopheles mosquitoes, including the local An. coluzzii mosquito population. Cows were only used to attract mosquitoes into the huts and no tests were carried out directly on the cows. The author checklist is intended for use with studies where experiments are carried out on animals, which is why we have had such difficulty in completing this for the hut study, as many of the questions do not relate to how the cows were used
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