1,720,986 research outputs found
Global review of 137Cs and 210Pbxs fallout used for dating sediment cores
No full textThis data collection was based on the synthesis of 1351 individual dating sediment cores published between 1977 and 2020. This database provides the locations where 137Cs fallout events were detected. These included the thermonuclear bomb testing peak in 1963, the Chernobyl accident in 1986, the Fukushima accident in 2011, and 25 additional events that led to local radioactive releases. When Lead-210 in excesses (210Pbxs) records were used along with Caesium-137 (137Cs) data, detailed information on the 210Pbxs surface activities and age depth model were also synthesized. Multiple information including the core collection method, sediment properties, radionuclide measurement techniques, sedimentation rates and catchment characteristics were also compiled
Amélioration de la chronologie des retombées initiales de radionucléides pour reconstruire les taux de redistribution de sol dans les bassins versants agricoles d’Amérique du Sud
No full textLa Révolution Verte des années 1960 a conduit à une augmentation significative des surfaces cultivées au détriment des écosystèmes naturels en Amérique du Sud. Cette mise en culture a accéléré les processus d’érosion des sols et de transport de particules fines à travers les paysages, menaçant la durabilité des systèmes agricoles et favorisant l’envasement des cours d’eau et des retenues des barrages hydroélectriques. Cependant, très peu de données sont disponibles à l’échelle de ce continent pour quantifier l’impact de ces phénomènes et promouvoir des stratégies de lutte efficaces visant à réduire les pertes en sol. Pour pallier ce manque de quantification, ce projet doctoral a synthétisé toutes les données relatives aux retombées de radionucléides artificiels (137Cs, plutonium) dans les sols, survenues en Amérique du Sud entre 1952 et 1980 suite aux essais nucléaires atmosphériques.Ces substances, qui marquent durablement les sols, permettent en effet d’établir a posteriori des « bilans » d’érosion et de dater les archives sédimentaires. Une spatialisation des inventaires de 137Cs dans les sols à l’échelle du sous-continent est proposée, ainsi qu’une stratégie d’échantillonnage pour améliorer cette carte à l’avenir. Ensuite, le potentiel de l’analyse du rapport isotopique 240Pu/239Pu dans les sols et sédiments pour affiner ces reconstructions temporelles est démontré. Enfin, en guise d’application, une nouvelle approche d’échantillonnage et d’analyse du 137Cs dans 80 profils de sol collectés à travers un bassin versant (800 km²) représentatif d’une région intensément cultivée du Brésil pour la période 1970-2020 est proposée, et ses limites sont discutées.The Green Revolution of the 1960s led to a significant increase in cultivated land at the expense of natural ecosystems in South America. Consequently, soil erosion processes have rapidly increased, threatening the sustainability of agricultural systems and leading to the siltation of rivers and reservoir siltation. However, only limited information is available at the scale of this continent to quantify the impact of soil erosion and promote effective management strategies to reduce soil losses. To overcome this lack of data, this doctoral project synthesised all the data related to the artificial radionuclide fallout (137Cs, plutonium) in soils of South America between 1952 and 1980 following atmospheric nuclear weapon testing.Fallout radionuclides bound to fine-grained sediment are widely used to date sedimentary sequences and reconstruct soil redistribution rates a posteriori. A spatialization of 137Cs inventories in soils at the sub-continental scale of South America is proposed, as well as a sampling strategy to improve this map in the future. Then, the potential of 240Pu/239Pu atom ratio analyses in soils and sediment to refine these temporal reconstructions is demonstrated. Finally, as an application, a novel approach to sample and analyse 137Cs in 80 soil profiles collected across a representative 800-km² catchment of an intensively cultivated region of Brazil for the period 1970-2020 is proposed, and its limitations are discussed
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
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
Author-wise bibliometric analysis based on entropy.
No full textAuthor-wise bibliometric analysis based on entropy.</p
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