1,721,044 research outputs found
Going Beyond Counting First Authors in Author Co-citation Analysis
Get PDFThe 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
Get PDF“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
Cell migration : identification of Arpin, an novel inhibitor of the Arp2/3 complex and molecular mecanisms of its regulation
No full textDans une cellule en migration, la polymérisation d'actine permet de projeter la membrane plasmique dans une structure appelée le lamellipode. Dans le lamellipode, l'actine est polymérisée de manière branchée par le complexe Arp2/3. L'activation du complexe Arp2/3 au lamellipode est sous le contrôle du complexe WAVE. En réponse à une cascade d’activation moléculaire, une des sous-unités du complexe WAVE expose son domaine WCA (WH2-Connecteur-Acide) qui peut alors se lier au complexe Arp2/3 et l’activer afin d'initier la formation d’un nouveau filament d’actine. La voie d’activation du complexe Arp2/3 par le complexe WAVE a été bien étudiée. Cependant la migration cellulaire est finement régulée et cette unique voie de signalisation nous semblait insuffisante. Dans le but de trouver de nouveaux régulateurs de la migration et en particulier de nouvelles protéines se liant au complexe Arp2/3, nous avons réalisé un crible bioinformatique identifiant les protéines contenant un motif Acide. Ce dernier a abouti à l’identification d’une protéine non caractérisée. In vitro, cette protéine n'active pas le complexe Arp2/3. En revanche, elle est capable d'inhiber l'activation du complexe Arp2/3 induite par le domaine WCA d'un activateur et empêche la formation de branches par le complexe Arp2/3. Nous avons appelé cette nouvelle protéine Arpin pour « Arp2/3 Inhibitor ». De manière cohérente avec son rôle inhibiteur in vitro, la déplétion d'Arpin dans différents type de cellules, induit une augmentation de la vitesse de protrusion des lamellipodes et une demi-vie augmentée des lamellipodes. Ces effets se traduisent par une migration plus rapide et plus persistante en direction. Arpin joue donc le rôle d'un frein de la migration cellulaire et permet à la cellule de tourner. Pour jouer ce rôle-là, Arpin nécessite d’être régulée rigoureusement. Dans la cellule, Arpin est inactive et nécessite d’être activée par Rac. Cependant cette régulation n'est probablement pas directe. Pour mieux comprendre la régulation d'Arpin, nous avons donc recherché des protéines partenaires. Nous avons identifié Tankyrase comme protéine interagissant avec Arpin. De façon significative, le motif d’Arpin qui permet son interaction avec Tankyrase se superpose à la séquence Acide nécessaire à son interaction avec le complexe Arp2/3. Nous avons mis en évidence in vitro une compétition entre Tankyrase et le complexe Arp2/3 sur Arpin. Ces résultats suggèrent Tankyrase inhibe la protéine inhibitrice Arpin. En conclusion, nous avons découvert une nouvelle protéine Arpin, qui inhibe le complexe Arp2/3 et qui joue un rôle régulateur important dans la migration cellulaire. Nous avons identifié une protéine régulatrice de son activité, la Tankyrase. Nous nous attendons à ce qu’Arpin soit impliquée dans des nombreux processus physiologiques ou pathologiques, où la migration cellulaire joue un rôle important, en particulier lors de la formation de métastases dans le cancer.In migrating cells, the Arp2/3 complex generates branched actin networks that power protrusion of the leading edge in a structure called lamellipodium. The Arp2/3 complex is activated at the leading edge by the Wave complex which is itself activated by the small GTPase Rac. WAVE which is in an inactive state, then exposes its WCA domain (WH2-Connector-Acidic) that can bind to the Arp2/3 complex and activate it to trigger the formation of a new daughter actin filament. This signalling pathway of the Arp2/3 complex has been well studied. However, cell migration is a fine-tuned process that is probably regulated in a more complex manner.To identify new regulators of cell migration, especially proteins that bind to the Arp2/3 complex, we performed a bioinformatics screen to identify proteins containing an acidic motif at its C-terminus, a characteristic motif of Arp2/3 activators. By this method we retrieved an uncharacterized protein. A combination of in vitro assays revealed, however, that this protein inhibits the Arp2/3 complex by competing with the activators. We called this protein Arpin for “Arp2/3 inhibitor”. Depletion of Arpin in different kind of cells, such as mammalian cells or amoeba, induces lamellipodia to protrude faster and to last longer, consistent with its inhibitory role on Arp2/3 complex activity. These effects observed lead to an increased velocity and a more directional migration in random migration assay. The function of the Arp2/3 inhibitory protein Arpin is thus to slow down and steer cell migration.In the cell, Arpin has been shown to be inactive until it is activated by Rac, most likely by an indirect manner. We identified Tankyrase as an interactor of Arpin. Interestingly, the binding motif of Arpin to Tankyrase overlaps the acidic motif required for the binding to the Arp2/3 complex. By a biochemistry approach, we showed a competition between Tankyrase and the Arp2/3 complex for the binding to Arpin. This observation suggests that Tankyrase inhibits the inhibitory protein Arpin in the cell. To conclude, we identified a new protein, Arpin which inhibits the Arp2/3 complex and plays an important role in the control of cell migration. We identified a protein which regulated its activity, Tankyrase. Thus, we can imagine that Arpin could be implicated in numerous physiological and pathological processes where cell migration is involved, particularly during metastases formation in cance
Clathrin is required for Scar/Wave mediated lamellipodium formation
No full textLe complexe Scar/WAVE génère la formation des lamellipodes par l'intermédiaire du complexe Arp2/3 responsable de la polymérisation de réseaux d'actine branchés. Dans le but d'identifier de nouveaux régulateurs du complexe Scar/WAVE, nous avons conduit un crible en cellules de Drosophiles combinant une approche protéomique à une approche de génomique fonctionnelle. La chaîne lourde de la clathrine a été identifiée au cours de ce crible comme une protéine interagissant avec le complexe Scar/WAVE et dont la déplétion affecte la formation des lamellipodes. Ce rôle de la clathrine dans la formation des lamellipodes peut être découplé de son rôle classique dans le transport vésiculaire en utilisant différentes approches. De plus, la clathrine est localisée au lamellipode en l'absence d'adapteurs et des protéines accessoires de l'endocytose. La surexpression de la clathrine affecte le recrutement membranaire du complexe WAVE réduisant ainsi la vélocité des protrusions membranaire et la migration cellulaire. Par opposition, lorsque la clathrine est envoyée artificiellement à la membrane plasmique par une fusion à une séquence myristoylée, on observe une augmentation du recrutement membranaire du complexe Scar/WAVE, de la vélocité des protrusions membranaires et de la migration cellulaire. L'ensemble de ces résultats montrent que la clathrine envoie le complexe Scar/WAVE à la membrane plasmique et donc contrôle la formation des lamellipodes en plus de son rôle plus classique dans le traffic membranaire.The Scar/Wave complex (SWC) generates lamellipodia through Arp2/3-dependent polymerization of branched actin networks. In order to identify new SWC regulators, we conducted a screen in Drosophila cells combining proteomics with functional genomics. This screen identified Clathrin Heavy Chain (CHC) as a protein that binds to the SWC and whose depletion affects lamellipodium formation. This role of CHC in lamellipodium formation can be uncoupled from its role in membrane traffic by several experimental approaches. Furthermore, CHC is detected in lamellipodia in the absence of the adaptor and accessory proteins of endocytosis. We found that CHC overexpression decreased membrane recruitment of the SWC, resulting in reduced velocity of protrusions and reduced cell migration. In contrast, when CHC was targeted to the membrane by fusion to a myristoylation sequence, we observed an increase in membrane recruitment of the SWC, in protrusion velocity and in cell migration. Together these data suggest that CHC brings the SWC to the plasma membrane, thereby controlling lamellipodium formation, in addition to its classical role in membrane traffic
Appropriate Similarity Measures for Author Cocitation Analysis
Get PDFWe 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
Get PDFWe 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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