1,721,028 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
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
Molecular mechanisms involved during plant seed germination in response to strigolactones
No full textLes graines des plantes parasites obligatoires de racines des genres Orobanche, Phelipanche et Striga, pathogènes de grandes cultures, ont adopté au cours de leur évolution vers l’hétérotrophie, une modalité de germination plus spécialisée que celle des plantes autotrophes, puisqu’elle nécessite la perception de stimulants de germination (GS) exsudés par leurs hôtes. Les strigolactones (SL) ont notamment été identifiés comme induisant chez Phelipanche ramosa l’expression d’un gène de catabolisme de l’acide abscissique (ABA) : PrCYP707A1. Ces travaux de thèse montrent que l’amélioration de la germination des plantes parasites et d’Arabidopsis par différents GS, est systématiquement corrélée à la régulation d’un ou plusieurs gènes de la famille CYP707A, dont l’expression requiert la voie canonique de signalisation SL décrite chez des plantes autotrophes modèles. Les plantes parasites nécessitent cependant une période de conditionnement débutant à l’imbibition, au cours de laquelle les GS n’induisent pas l’expression des gènes CYP707A ni la germination. Chez P. ramosa, nous observons une diminution globale de la méthylation de l’ADN, jusqu’à un seuil nécessaire à l’induction de l’expression de PrCYP707A1. Une région de 78 pb de son promoteur est par ailleurs déméthylée. Nous nous sommes alors intéressés à l’implication d’autres marques épigénétiques dans la germination de P. ramosa. Si nous n’avons pas pu détecter d’effet des modifications post-traductionnelles des histones lors du conditionnement, leur état d’acétylation influence la réponse aux SL. Cet effet semble notamment lié à la modulation de l’homéostasie de l’ABA suite à l’induction des gènes CYP707A par les SL.Many cultivated species are threatened by obligate root parasitic plants from the Orobanche, Phelipanche and Striga genera, whose germination processes evolved during their transition to heterotrophy, until becoming fully dependent on germination stimulants (GS) exuded by surrounding host roots. Most notably, strigolactones (SL) were previously identified as inducing the expression of an abscisic acid (ABA) catabolism encoding gene in Phelipanche ramosa: PrCYP707A1. During this thesis, we show that germination enhancement upon various GS, in Arabidopsis as in obligate root parasitic plants, is always correlated to the up-regulation of one or more CYP707A genes, whose expression requires the canonical SL signaling pathway described in autotrophic model plants. Nevertheless, an important feature of obligate root parasitic plants germination still lies in the existence of a conditioning period beginning at imbibition. In P. ramosa, it is defined as the time needed by seeds to up-regulate PrCYP707A1 in response to GS, then germinate. During this process, we observe a strong decrease in the global DNA methylation that has to reach a necessary threshold to induce the expression of this gene. Most importantly, a 78 bp-region of its promoter is demethylated. We then wondered whether other epigenetic processes could be involved during P. ramosa germination. Although we could not detect any effect of histones post-translational modifications on the conditioning period, their acetylation status strongly affects the strigolactone response. This effect seems to be intimately linked to the modulation of ABA homeostasis following the SL-induced CYP707A upregulation
Transcriptomics and functional genetics in the parasitic plant Phelipanche ramosa
No full textLes plantes sont connues pour être des organismes autotrophes mais au cours de l’évolution certaines d’entre elles ont opté pour un mode vie parasitaire. La clé de cette transition repose sur l’apparition d’un organe permettant la mise en place de l’interaction entre la plante parasite et la plante hôte : l’haustorium. La formation de cet organe chez les Orobanchaceae hémiparasites (photosynthétiques) peut être induite en réponse à des facteurs inducteurs d’haustorium (HIF) issus de la dégradation des parois racinaires de l’hôte. Chez les holoparasites (non photosynthétiques) tels que les orobanches, l’induction haustoriale demeure un processus mal compris du fait de l’absence d’activité des HIF connus. Ces travaux de thèse montrent que l’haustoriogenèse chez l’Orobanchaceae holoparasite Phelipanche ramosa est induite par des molécules contenues dans les exsudats racinaires de son hôte, le colza. L’établissement d’un transcriptome de référence et une analyse de la réponse transcriptomique globale des graines germées de P. ramosa en réponse aux exsudats de colza suggèrent l’établissement d’une signalisation hormonale. Le fractionnement HPLC ainsi que des analyses UPLC-MS montrent la présence d’un composé de type cytokinine dans la fraction la plus active des exsudats. En parallèle, l’activité inductrice d’haustorium des cytokinines a été démontrée proposant un rôle majeur de ces phytohormones lors de l’haustoriogenèse chez P. ramosa. Ce travail de thèse a également permis de cultiver P. ramosa en l’absence de l’hôte par la mise en place de lignées de cals, et également d’établir une méthode de transformation génétique permettant des approches de validation fonctionnelle.Although plants are known to be autotrophic organisms, some of them have adopted a parasitic lifestyle in the course of evolution. One of the major feature of this transition lies in the apparition of a novel organ, the haustorium, which allows the establishment of the interaction between the parasitic plant and its host. The formation of this organ in hemiparasitic Orobanchaceae (photosynthetic) is induced in response to haustorium inducing factors (HIF) derived from the degradation of host roots cell walls. In holoparasites (not photosynthetic) such as broomrapes, this process remains misunderstood due to the inactivity of the known HIF. This Ph.D. work shows that the haustoriogenesis in the harmful holoparasite Phelipanche ramosa, is induced by molecules contained in root exudates of its host Brassica napus. The establishment of a reference transcriptome and the analysis of the transcriptomic response of germinated seeds of P. ramosa in response to B. napus root exudates both suggest the involvement of hormonal signaling. The HPLC fractionation of root exudates along with UPLC-MS analysis identified a cytokinin-like compound in the most active fraction. Furthermore, this work demonstrates that cytokinins induce haustorium differentiation in vitro, suggesting a major role of this phytohormone during the haustorium formation in P. ramosa. Moreover, this work allowed to set a host-free culture system of P. ramosa by developing calli lines, and to develop of a transformation system allowing functional validation approaches
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
Use of miPEPs to study and control Orobanche cumana - Sunflower interaction
No full textLes orobanches sont des plantes parasites de grandes cultures qui peuvent entraîner une perte de rendement pouvant aller jusqu’à 100%. Il n’existe actuellement aucune méthode de lutte efficace et durable. La biologie des orobanches est complexe car elles ne peuvent se développer en l’absence d’un hôte. La présence de l’hôte va induire deux étapes clés de leur développement : la germination et l’haustoriogenèse. Ces processus biologiques sont induits par la perception de molécules exsudées dans la rhizosphère par les racines de l’hôte. Une meilleure compréhension de leur biologie particulière est un prérequis au développement de nouveaux moyens de lutte plus efficaces. La découverte d’une nouvelle classe de peptides régulateurs appelés miPEPs (mi-RNA encoded peptide) a ouvert de nouvelles perspectives d’étude de la biologie des orobanches, mais aussi de développement de nouveaux agents de biocontrôle. Ces miPEPs sont issus d’ORFs présents sur les précurseurs en amont des séquences des miARNs. Ces miPEPs stimulent spécifiquement l’expression de leurs précurseurs et donc du miARN associé. Le suivi de l’expression des gènes cibles de miARNs à la suite d’un traitement avec le stimulant de germination rac-GR24 a permis d’identifier les miARNs associés potentiellement impliqués dans la germination d’O. cumana. Il a été également montré que l’ajout de miPEPs d’O. cumana et de P. ramosa permet d’inhiber partiellement la germination et d’inhiber et/ou de stimuler la formation des haustoriums. La spécificité d’action de ces miPEPs sur l’expression des gènes cibles des miARNs associés a été mise en évidence par des tests de qRT-PCR à la suite d’un traitement avec des miPEPs. Enfin, deux miPEPs se révèlent être efficaces pour diminuer le nombre de fixations d’O. cumana sur le tournesol lorsqu’ils sont ajoutés à la solution d’arrosage, et sont donc de bons candidats pour être utilisés en tant qu’agent de biocontrôle de ces pathogènes.Broomrapes are parasitic plants of major field crops that can cause a yield loss of up to 100%. Currently, there is no effective and sustainable methods of control. The biology of broomrapes is complex because they cannot develop in the absence of a host. The host presence induces two key developmental stages which are germination and the formation of the haustorium. These biological processes are induced by the perception of molecules exuded in the rhizosphere by the roots of the host. A better understanding of their biology is required to develop new and more effective methods of control. The discovery of a new class of regulatory peptides called miPEPs (mi- RNA encoded peptides) has opened new perspectives for studying their biology, but also for the development of new biocontrol agents. These miPEPs are derived from ORFs present on miRNAs precursors, upstream of the miRNA sequence. These miPEPs specifically stimulate the expression of their precursors and therefore of the associated miRNA. Monitoring the expression of miRNA target genes following treatment with the germination stimulant rac-GR24 allowed the identification of associated miRNAs potentially involved in O. cumana germination. This work also shows that the addition of miPEPs of O. cumana and P. ramosa can partially inhibit germination and inhibit and/or stimulate the haustorium formation. The specificity of action of these miPEPs on the expression of miRNAs associated target genes was demonstrated by qRT-PCR experiments following miPEPs treatment. Finally, two miPEPs have been shown to be effective in reducing the number of O. cumana attachments on sunflowers when added to the irrigation solution and are therefore good candidates for use as a biocontrol agent for these pathogens
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