1,720,957 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
Dégradation des acides gras exogènes chez Escherichia coli
No full textLes entérobactéries sont capables d'utiliser des acides gras (AG) exogènes comme sources uniques de carbone et d'énergie. Après leur import dans la cellule, les AG sont les substrats des enzymes de dégradation des AG (Fad) du cycle de B-beta;-oxydation. Chez E. coli, en plus de la machinerie FadDEBA canonique, un deuxième groupe d'enzymes FadIJK a été proposé pour fonctionner spécifiquement en anaérobiose. Caractériser une telle B-oxydation en anaérobiose est important pour la compréhension du métabolisme des entérobactéries dans l'intestin. Cependant, depuis les premières observations en 2003, aucune autre étude n'a été menée. Le premier objectif de la thèse était de caractériser le deuxième système Fad et d'identifier les composants manquants. Les gènes ydiO et ydiQRST ont été proposés pour coder respectivement une déshydrogénase anaérobie et une chaîne de transfert d'électrons reliant le cycle de B-oxydation à la chaîne respiratoire. Cependant, nous n'avons pu mettre en évidence aucun phénotype dans la dégradation des AG qui seraient causés par la délétion de ces gènes. De plus, la surproduction de YdiO n'a pas restauré la croissance d'un mutant fadE sur AG +/-O2, et l'acyl-CoA synthase putative anaerobique FadK n'a pas non plus complémenté un mutant fadD. Nous avons ensuite étudié l'implication des facteurs transcriptionnels répondant à la présence d'oxygène ou de la source de carbone disponible. Nous avons montré que l'expression de fadIJ est régulée exactement comme celle des gènes fadDEBA, et surtout que fadIJK ne sont pas induits en -O2. Tous nos résultats montrent donc que les enzymes FadKIJ ne sont pas spécifiques pour la dégradation des AG en -O2, et que YdiO et YdiQRST ne sont pas impliqués dans ce métabolisme. Cependant, nous avons confirmé que FadIJ jouaient un rôle accessoire dans le métabolisme des AG, qui reste à être compris. Un deuxième aspect de la thèse était d'étudier l'enzyme auxiliaire FadH, essentielle pour dégrader les AG poly-insaturés tels que le linoléate. Puisque FadH contient un cluster Fe-S, nous avons supposé que la dégradation des AG dépendant de FadH pourrait être sensible à la carence en fer. En effet, la croissance de la souche sauvage d'E. coli en carence en fer est altérée spécifiquement sur linoléate. De plus, des enzymes eucaryotes effectuant la même réaction que FadH, mais dépourvues du cluster Fe-S, peuvent sauver la croissance de E. coli sur linoléate en carence en fer. Ces résultats ont été complétés par une approche de mutagenèse pour étudier le rôle du cluster Fe-S dans la fonction de FadH et le mécanisme de complémentation par les enzymes eucaryotes. La troisième partie de la thèse concerne la caractérisation du régulateur transcriptionnel YdiP et de son régulon. Le gène ydiP se trouve dans un locus de gènes potentiellement impliqués dans différents aspects du métabolisme carboné : la conversion du shikimate en chorismate, pour la synthèse d'acides aminés aromatiques et de quinones (ydiLMNB-aroD), et une voie alternative potentielle de dégradation des AG (ydiFOP-ydiQRSTfadK). Une analyse transcriptomique a permis de montrer que les gènes ydiLMNBaroD et ydiFO, situés en amont de YdiP, sont fortement induits lors de la surproduction de YdiP. Les données transcriptomiques ont été confirmées aux niveaux transcriptionnel et traductionnel. Tous ces gènes sont transcrits en opéron à partir d'un promoteur unique situé devant ydiL, et activé par YdiP. De plus, par une stratégie de recherche de mutations suppresseurs, nous avons montré que le locus est réprimé par H-NS, suggérant un mécanisme d'anti-silencing de H-NS par YdiP. En parallèle, la caractérisation de la protéine YdiP a permis d'identifier les résidus cruciaux pour sa fonction. De façon intéressante, le régulon de YdiP présente de nombreuses ressemblances avec celui de dégradation de la carnitine, ce qui suggère un rôle du régulon YdiP dans une voie catabolique spécifique mais du même type.Enterobacteria can use exogenous fatty acids (FA) as unique carbon and energy sources. After FA are imported within the cell, they are the substrates of FA degradation (Fad) enzymes of the B-oxidation cycle. In E. coli, in addition to the well-known Fad machinery (FadDEBA), a second set of Fad enzymes (FadIJK) was proposed to work specifically in anaerobiosis. The possibility of B-oxidation in the absence of oxygen is intriguing, and its study can contribute to understanding Enterobacteria metabolism in the gut. However, since the initial observations in 2003, no further studies have been conducted on the subject, and several issues remain unsolved. The first goal of the thesis was to fully characterize the second Fad system and identify its missing components. The ydiO and ydiQRST genes were proposed to encode respectively a potential anaerobic dehydrogenase and an electron transfer chain linking the B-oxidation cycle with the respiratory chain. However, we did not find any phenotypes in FA degradation caused by the deletion ydiO or ydiQRST genes. Furthermore, YdiO overproduction did not rescue the growth of a fadE mutant on FA +/-O2, and the putative anaerobic acyl-CoA synthase FadK did not either rescue a fadD mutant. Then, we investigated the interplay of transcriptional factors responding to the presence of oxygen or the available carbon source. We showed that fadIJ expression is regulated exactly as the fadDEBA genes, and especially fadIJK are not induced in -O2. All our data reveal that FadKIJ are not specifically in charge of FA degradation in -O2, and that YdiO and YdiQRST are not involved in FA metabolism. However, we did confirm that FadIJ enzymes play an accessory role in FA metabolism, that remains to be fully understood. A second aspect of the thesis was to study the FadH auxiliary enzyme specifically required to degrade poly-unsaturated FAs such as linoleate. Because FadH carries an Fe-S cluster, we made the hypothesis that FA degradation relying on FadH may be sensitive to iron starvation. Indeed, we found that the growth of wild type E. coli on linoleate in iron starvation condition is impaired. We further showed that eukaryotic enzymes performing the same reaction as FadH, but lacking the Fe-S cluster, can rescue E. coli growth on linoleate in iron starvation condition. We completed these results by a mutagenesis approach to study the role of the Fe-S cluster in FadH function and the mechanism of complementation by the eukaryotic counterparts. The third part of the thesis concerns the characterization of the AraC-like transcriptional regulator YdiP and its regulon. The ydiP gene lies inside a locus of genes proposed to be involved in different aspects of carbon metabolism: conversion of shikimate to chorismate, which leads to aromatic amino acid and quinone production (ydiLMNB-aroD), and a putative alternative fatty acid degradation pathway (ydiFOP-ydiQRSTfadK). However, this cluster is poorly characterized, and the operon organization is not known. A transcriptomic analysis led to the identification of genes strongly increased upon YdiP overproduction, which are the ydiLMNBaroD and the ydiFO genes, located upstream ydiP. Further analyses confirmed the transcriptomic data at both transcriptional and translational levels. All these genes are found to be transcribed in operon from a single promoter located upstream ydiL, activated by YdiP. Also, via a suppressor mutation strategy, the nucleoid-associated regulator H-NS was found to repress the locus, suggesting a mechanism of H-NS anti-silencing by YdiP. In parallel, the characterization of YdiP protein features permitted the identification of some crucial residues for its biological function. Interestingly, the ydiP regulon shows similarities with the carnitine degradation genes, which together with the observed anaerobic induction of ydiP, suggest a role of this locus in a specific catabolic pathway in -O2
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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