1,720,985 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
Ancrage des parasites moléculaires sur la chromatine inactive dans le noyaux des eucaryotes
No full textLes plasmides naturels sont courants chez les procaryotes, mais peu ont été documentés chez les eucaryotes. Le plasmide naturel 2µ présent dans la levure bourgeonnante Saccharomyces cerevisiae est l'un des mieux caractérisés. Cet élément génétique très stable coexiste avec son hôte depuis des millions d'années, ségrégeant efficacement à chaque division cellulaire par un mécanisme qui reste mal compris. En utilisant la ligature de proximité (Hi-C, Micro-C) pour cartographier les contacts entre le plasmide 2µ et les chromosomes de levure dans des dizaines de conditions biologiques différentes, nous avons constaté que le plasmide 2µ se fixe préférentiellement sur des régions à faible activité transcriptionnelle, correspondant souvent à de longs gènes inactifs. Les acteurs communs de la structure des chromosomes, tels que les membres des complexes de maintenance structurale des chromosomes (SMC), ne sont pas impliqués dans ces contacts qui dépendent plutôt d'un signal nucléosomique associé à une déplétion de l'ARN Pol II. Ces contacts sont stables tout au long du cycle cellulaire et peuvent être établis en quelques minutes. Cette stratégie peut aussi être trouvée dans d'autres types de molécules d'ADN et d'autres espèces que S. cerevisiae, comme le suggère le schéma de liaison du plasmide naturel le long des régions silencieuses des chromosomes de Dictyostelium discoideum.Natural plasmids are common in prokaryotes but few have been documented in eukaryotes. The natural 2µ plasmid present in budding yeast Saccharomyces cerevisiae is one of the most well characterized. This highly stable genetic element coexists with its host for millions of years, efficiently segregating at each cell division through a mechanism that remains poorly understood. Using proximity ligation (Hi-C, MicroC) to map the contacts between the 2µ and yeast chromosomes under dozens of different biological conditions, we found that the plasmid tether preferentially on regions with low transcriptional activity, often corresponding to long inactive genes, throughout the cell cycle. Common players in chromosome structure such as members of the structural maintenance of chromosome complexes (SMC) are not involved in these contacts, and depend instead on a nucleosomal signal associated with a depletion of RNA Pol II. These contacts are highly stable, and can be established within minutes. Our data show that the plasmid segregates by binding to transcriptionally silent regions of the host chromosomes. This strategy may concern other types of DNA molecules and species beyond S. cerevisiae, as suggested by the binding pattern of the natural Ddp5 plasmid along Dictyostelium discoideum chromosomes’ silent regions
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
Aspects temporel et spatial dans des systèmes de régulation génétique
Full text linkThis thesis deals with several aspects concerning genetic regulation on theoretical and experimental points of view. A first work in the field of modelisation of biological systems, proposes to find simple regulatory networks which have the ability to optimise their response when they are submitted to a periodic stimulation. The network called ``Incoherent Feed Forward Loop'' appeared to have the interesting property to let pass trains of pulses which have a particular temporal pattern. Some extensions of this motif (``Diamond'', ``Double Diamond''...) are proposed to also have interesting properties to process more complex time-dependent signals. Next, a work of review and observation concerning DNA looping is presented. After pointing out some common points in systems of DNA looping already known, we have examined the data bases to see if other regulatory regions have the same characteristics. We propose a list of several genes which might be good candidates to be regulated thanks to a DNA looping mechanism. An experimental work of molecular biology is then presented. It tackles a hypothesis found in several works from bioinformatics and statistical physics. The question is the following: can transcription factors bind to binding sites belonging not to a unique regulatory region of one gene (like in the lac operon) but to binding sites belonging to different genes? We tested this hypothesis on the Pel regulatory system which rules the entry into virulence of the enterobacteria Erwinia chrysanthemi. Experiments reproduced and carried out in various physiological conditions lead to the conclusion that the deleted regulatory regions do not seem to act on other genes by a DNA looping mechanism. The last chapter proposes an experimental method to search for such interactions in a broader way inside a bacterial genome. The method is based on molecular biology techniques commonly used, like the random mutagenesis or alpha-complementation. It uses the enhancer system of the promoter of glnA of Escherichia coli and aims at finding significant 3D interactions between DNA segments in a prokaryote genome.Cette thèse s'intéresse à plusieurs aspects concernant la régulation génétique sur les plans théorique et expérimental. Un premier travail théorique qui s'inscrit dans le cadre de la modélisation des systèmes biologiques se propose de trouver des réseaux de régulation simples qui puissent répondre de manière optimale lorsqu'ils sont soumis à une stimulation périodique. Le réseau appelé ``Incoherent Feed Forward Loop'' s'est avéré présenter la propriété intéressante de laisser passer des trains de pulses au profil temporel particulier. Des extensions de ce motif (``Diamond'', ``Double Diamond''...) ont été suggérées pouvant également présenter des propriétés intéressantes pour traiter des signaux plus complexes. Un travail de revue et d'observations concernant les boucles d'ADN est ensuite présenté. Après avoir observé des points communs dans les systèmes de boucle d'ADN déjà connus, nous avons interrogé les bases de données pour savoir quelles étaient les régions de régulation présentant les mêmes caractéristiques. Nous proposons une liste de plusieurs opérons qui mériteraient une démarche expérimentale pour la mise en évidence d'une boucle d'ADN. Un travail expérimental de biologie moléculaire est ensuite présenté. Il s'est attaqué à tester une hypothèse présente dans plusieurs travaux de bioinformatique ou de physique statistique. La question testée est la suivante: est-ce que des facteurs de transcription pourraient se lier à des sites de liaison appartenant non pas à la même région de régulation d'un gène (comme dans le cas de l'opéron lac) mais à des sites de liaison appartenant à des gènes différents? Nous avons testé cette hypothèse sur le système de régulation d'entrée en virulence de la bactérie Erwinia chrysanthemi. Les expériences reproduites et réalisées dans plusieurs conditions physiologiques différentes ont abouti à la conclusion que les régions de régulation supprimées ne semblent pas agir sur d'autres gènes par le mécanisme de boucle d'ADN. Le dernier chapitre propose une méthode expérimentale pour rechercher de telles interactions de façon large dans un génome de bactérie. La méthode est basée sur des techniques de biologie moléculaire couramment utilisées comme la mutagénèse aléatoire ou l'alpha-complémentation. Elle utilise le système enhancer du promoteur de glnA d'Escherichia coli et vise à trouver des interactions 3D significatives entre segments d'ADN au sein d'un génome de procaryote
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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