1,720,954 research outputs found
Towards a breakthrough effluent treatment process : use of cyanobacteria selectively precipitating strontium versus calcium
No full textMes travaux de thèse s’inscrivent dans le programme « FOCUSDEM» du CEA qui a pour but de développer sur le long terme des procédés en rupture dans le contexte du démantèlement, et notamment pour le traitement des effluents liquides et la diminution de leur volume. Le ⁹⁰Sr, un isotope radioactif du strontium, est un produit de fission de l’uranium et du plutonium généré dans les centrales nucléaires. Cet élément toxique à vie longue est retrouvé dans les effluents liquides de l’industrie électronucléaire qui doivent être décontaminés avant rejet. Le Sr et le calcium font partie de la famille des alcalino-terreux et possèdent donc des propriétés chimiques similaires. Les procédés de traitement actuels, basés sur des techniques physico-chimiques, sont de ce fait peu sélectifs et peuvent être une source de volumes importants de déchets secondaires. L’objectif de ce projet consistait à comprendre et exploiter la capacité exceptionnelle de la cyanobactérie Gloeomargarita lithophora à accumuler le Sr sélectivement par rapport au Ca à l’intérieur des cellules sous forme de granules de carbonates. Plusieurs axes de recherche ont été développés pour (i) optimiser les conditions de croissance de cet organisme photosynthétique ; (ii) décrypter les mécanismes moléculaires impliqués dans l’accumulation sélective du Sr et (iii) développer un procédé biotechnologique de décontamination d’effluents du nucléaire.Après avoir criblé différents paramètres, une amélioration de la production de biomasse a pu être obtenue en augmentant la concentration en fer et en carbonate d’un milieu minéral classiquement utilisé pour la culture en milieu liquide des cyanobactéries. Pour comprendre les mécanismes moléculaires impliqués dans la biominéralisation intracellulaire du Sr par une approche génétique, il était important d’axéniser la souche, de trouver des conditions pour obtenir des colonies et d’identifier les antibiotiques à utiliser pour la sélection. Après être parvenu à une axénisation partielle et à l’obtention de colonies sur boites, les premiers essais de conjugaison ont été réalisés. Bien que des colonies aient été obtenues, il reste à montrer que le plasmide se maintient dans les cellules. Les résultats ont montré qu’en milieu minéral G. lithophora peut accumuler rapidement (en moins de 3 jours) une dose de ⁹⁰Sr similaire à celle retrouvée dans les effluents et ce de façon stable dans le temps. De plus, l’accumulation intracellulaire de ce radionucléide, qui est un émetteur de rayonnements β, n’affecte pas la survie des cellules. L’activité photosynthétique joue un rôle dans ce mécanisme car l’inhibition de l’appareil photosynthétique provoque un ralentissement de l’accumulation suivi d’un relargage du ⁹⁰Sr par les cellules. Enfin, nos expériences indiquent que G. lithophora pourrait être utilisée dans un procédé de bioremédiation du ⁹⁰Sr pour traiter des effluents ayant une composition similaire à celle d’effluents traités dans une installation nucléaire.My thesis work is part of the CEA's "FOCUSDEM" program, which aims to develop long-term breakthrough processes in the context of dismantling, particularly for liquid effluent treatment and volume reduction. ⁹⁰Sr, a radioactive strontium isotope, is a fission product of uranium and plutonium generated in nuclear power plants. This long-lived toxic element is found in liquid effluents from the nuclear power industry, which must be decontaminated before discharge. Sr and calcium belong to the alkaline earth family and have similar chemical properties. Current treatment processes, based on physico-chemical techniques, are thus not very selective and can be a source of large volumes of secondary waste. The aim of this project was to understand and exploit the exceptional ability of the cyanobacterium Gloeomargarita lithophora to accumulate Sr selectively with respect to Ca inside its cells in the form of carbonate granules. Several lines of research were developed to (i) optimize the growth conditions of this photosynthetic organism; (ii) decipher the molecular mechanisms involved in the selective accumulation of Sr; and (iii) develop a biotechnological process for decontaminating nuclear effluents. After screening various parameters, an improvement in biomass production was achieved by increasing the iron and carbonate concentration of a mineral medium conventionally used for liquid culture of cyanobacteria. To understand the molecular mechanisms involved in the intracellular biomineralization of Sr using a genetic approach, it was important to axenize the strain, find conditions for obtaining colonies and identify the antibiotics to be used for selection. After achieving partial axenization and obtaining colonies on plates, the first conjugation trials were carried out. Although colonies were obtained, it remains to be shown that the plasmid is maintained in the cells. The results showed that in mineral medium, G. lithophora can rapidly accumulate (in less than 3 days) a dose of ⁹⁰Sr similar to that found in effluents, and in a stable manner over time. Moreover, intracellular accumulation of this radionuclide, which is a β-emitter, does not affect cell survival. Photosynthetic activity plays a role in this mechanism, as inhibition of the photosynthetic apparatus slows down accumulation, followed by release of ⁹⁰Sr from the cells. Finally, our experiments indicate that G. lithophora could be used in a ⁹⁰Sr bioremediation process to treat effluents with a composition similar to that of effluents treated in a nuclear facility
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
Author Under Sail The Imagination of Jack London, 1893-1902
No full textIn Author Under Sail, Jay Williams offers the first complete literary biography of Jack London as a professional writer engaged in the labor of writing. It examines the authorial imagination in London's work, the use of imagination in both his fiction and nonfiction, and the ways he defined imagination in the creative process in his business dealings with his publishers, editors, and agents. In this first volume of a two-volume biography, Williams traverses the years 1893 to 1902, from London's "Story of a Typhoon" to The People of the Abyss. The Jack London who emerges in the pages of Author Under Sail is a writer whose partnership with publishers, most notably his productive alliance with George Brett of Macmillan, was one of the most formative in American literary history. London pioneered many author models during the heyday of realism and naturalism, blurring the boundaries of these popular genres by focusing on absorption and theatricality and the representation of the seen and unseen. London created an impassioned, sincere, and extremely personal realism unlike that of other American writers of the time. Author Under Sail is a literary tour de force that reveals the full range of London as writer, creative citizen, and entrepreneur at the same time it sheds light on the maverick side of machine-age literature.Intro -- Title Page -- Copyright Page -- Dedication -- Contents -- Acknowledgments -- Introduction -- 1. Spirit Truth -- 2. From Absorption to Theatricality and Back Again -- 3. "I Will Build a New Present" -- 4. Sons as Authors -- 5. Fathers as Publishers -- 6. The Daughter as Author -- 7. Lovers as Authors -- 8. At Sea with the Family -- 9. Yellow News, Yellow Stories -- 10. The Return Home -- Notes -- Bibliography -- Index -- About Jay WilliamsIn Author Under Sail, Jay Williams offers the first complete literary biography of Jack London as a professional writer engaged in the labor of writing. It examines the authorial imagination in London's work, the use of imagination in both his fiction and nonfiction, and the ways he defined imagination in the creative process in his business dealings with his publishers, editors, and agents. In this first volume of a two-volume biography, Williams traverses the years 1893 to 1902, from London's "Story of a Typhoon" to The People of the Abyss. The Jack London who emerges in the pages of Author Under Sail is a writer whose partnership with publishers, most notably his productive alliance with George Brett of Macmillan, was one of the most formative in American literary history. London pioneered many author models during the heyday of realism and naturalism, blurring the boundaries of these popular genres by focusing on absorption and theatricality and the representation of the seen and unseen. London created an impassioned, sincere, and extremely personal realism unlike that of other American writers of the time. Author Under Sail is a literary tour de force that reveals the full range of London as writer, creative citizen, and entrepreneur at the same time it sheds light on the maverick side of machine-age literature.Description based on publisher supplied metadata and other sources.Electronic reproduction. Ann Arbor, Michigan : ProQuest Ebook Central, YYYY. Available via World Wide Web. Access may be limited to ProQuest Ebook Central affiliated libraries
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