1,721,005 research outputs found
Measurements of photosynthesis in mixtures reveal allelopathy between a dinoflagellate (Amphidinium carterae) and a diatom (Thalassiosira pseudonana)
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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
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
Le NPQ chez les diatomées pennées : un phénomène simple et un outils pour étudier l'orchestration des régulations de la photosynthèse
No full textLes recherches sur la photosynthèse des microalgues marines s'appuient traditionnellement sur des modèles dérivés d'études sur les plantes et microalgues vertes. Cependant, ces modèles ne distinguent pas entre endosymbiotes primaires et secondaires. Cette divergence est particulièrement criante dans l'étude de l'extinction non photochimique (NPQ) de la fluorescence de la chlorophylle a, un mécanisme de régulation essentiel qui protège le photosystème II de l'excès de lumière. Chez les diatomées pennées, le NPQ dépend strictement de deux composants moléculaires: le pigment xanthophylle déépoxydé diatoxanthine (DT) et les protéines de la famille Lhcx. Malgré le lien évident entre le NPQ et DT chez les diatomées, plusieurs modèles contradictoires existent, souvent basé sur des modèles provenant d'organismes verts, inutilement complexes. Cette thèse vise à atteindre deux objectifs principaux. Premièrement, l'étude vise à comprendre la nature et le mécanisme du NPQ chez la diatomée pennée modèle Phaeodactylum tricornutum en examinant les rôles de la DT et de Lhcx1. Deuxièmement, elle vise à fournir une compréhension globale de la manière dont le NPQ influence la chaîne de transfert d'électrons photosynthétique et comment celle-ci, à son tour, affecte le NPQ. Dans la première partie de l'étude, 14 souches de Phaeodactylum tricornutum, dont le sauvage et 13 lignées transgéniques avec une expression variable de Lhcx1, ont été étudiées. Les niveaux de DT ont été modulés par un stress lumineux de courte durée, permettant de créer des matrices Lhcx1-DT. Ces matrices ont démontré que le NPQ est proportionnel au produit de la concentration de Lhcx1 et de DT dans le pool de xanthophylles. Cela suggère que l'interaction entre la DT et Lhcx1, probablement par la liaison de la DT à Lhcx1, forme un quencheur Stern-Volmer homogène responsable du NPQ. De plus, l'unité photosynthétique des diatomées pennées semble suivre un modèle dit «lake», et les divergences dans la relation NPQ-photochimie proviennent potentiellement de variables non prises en compte, telles que l'hétérogénéité cellulaire. La deuxième partie de la thèse s'appuie sur ces résultats pour développer un «contrôleur de photoprotection » en utilisant divers mutants Lhcx1. Cette approche permet d'explorer comment le NPQ influence la photochimie de la photosynthèse tout en maintenant les autres conditions constantes. Les résultats ont montré des relations claires entre le NPQ et d'autres processus photosynthétiques. Notamment, le NPQ était corrélée linéairement au flux cyclique d'électrons et inversement à la photoinhibition. Cette approche peut être considérée comme une étape préliminaire vers la compréhension de l'orchestration plus large des modules régulateurs de la photosynthèse, qui représente une frontière dans la recherche sur la photosynthèse. Elle a permis d'explorer la manière dont les signaux photosynthétiques impactent l'expression des gènes à l'échelle du génome, révélant qu'environ la moitié des gènes réagissaient à des conditions de forte luminosité de manière dépendante du NPQ. Le regroupement de ces gènes en fonction de l'exposition à la lumière et du NPQ déployé a permis de distinguer les groupes à expression invariante (e.g. cycle cellulaire), ceux significativement influencés par la photoprotection (e.g. ribosomaux et liés à la photoprotection) et ceux régulés strictement par la lumière (e.g. liés à l'absorption de la lumière).Enfin, une nouvelle méthode non invasive a été développée pour mesurer la valeur absolue de la force motrice du proton et sa division en ses composantes électriques et osmotiques, ΔpH. Cette nouvelle méthode, basée sur le déplacement électrochromique des pigments photosynthétiques, facilitera les études sur la manière dont la chaîne électronique photosynthétique affecte les quantités et les activités des acteurs moléculaires impliqués dans le NPQ via le ΔpH, bouclant ainsi la boucle de rétro-action entre le NPQ et la photosynthèse.Research on photosynthesis in marine microalgae has traditionally relied on models derived from studies of green organisms such as Arabidopsis and Chlamydomonas. However, these models do not fully account for the distinctions between primary and secondary endosymbionts. This divergence is evident in the study of non-photochemical quenching (NPQ) of chlorophyll a fluorescence, a key regulatory mechanism that protects photosystem II from excess light. In pennate diatoms, NPQ strictly depends on two key molecular components: the deepoxidized xanthophyll pigment diatoxanthin and Lhcx family proteins, with Lhcx1 being the major constitutive one. Despite the clear link between NPQ and diatoxanthin, several conflicting models of diatom NPQ exist, often unnecessarily borrowing the complexity of models from green organisms. This thesis has two main objectives. First, the study aims to understand the nature and mechanism of NPQ in the model pennate diatom Phaeodactylum tricornutum by examining the roles of diatoxanthin and Lhcx1. Second, it aims to provide a comprehensive understanding of the NPQ regulatory module: how NPQ influences the photosynthetic electron transfer chain and how this, in turn, affects NPQ. In the first part of the study, 14 strains of Phaeodactylum tricornutum, including the wild type and 13 transgenic lines with variable Lhcx1 expression, were grown under two non-stressful light conditions. Diatoxanthin levels were modulated using short-term light stress, which allowed the creation of Lhcx1-diatoxanthin matrices. These matrices demonstrated that NPQ is proportional to the product of Lhcx1 concentration and the proportion of diatoxanthin in the xanthophyll pool. This suggests that the interaction between diatoxanthin and Lhcx1, probably through diatoxanthin binding to Lhcx1, forms a uniform Stern-Volmer quencher responsible for NPQ. Furthermore, the photosynthetic unit of pennate diatoms appears to follow a “lake” model, with discrepancies in the NPQ-photochemistry relationship potentially arising from unaccounted variables, such as cellular heterogeneity. The second part of the thesis builds on these results to develop a “photoprotection dial” using various Lhcx1 mutants and adjusting high light exposure. This approach allows exploring how NPQ influences the photochemical phase of photosynthesis while holding other conditions constant. The results showed clear relationships between NPQ and the redox state of the photosynthetic electron transport chain, photoinhibition, and cyclic electron flow. Non-photochemical losses in photosystem II were found to be linearly correlated with cyclic electron flow and inversely correlated with photoinhibition. This approach is considered a preliminary step toward understanding the broader orchestration of photosynthetic regulatory modules, which represents a frontier in photosynthesis research. It allowed exploring how photosynthetic signals impact gene expression at a genome-wide scale, revealing that approximately half of the genes responded to high light conditions in a Lhcx1 (or NPQ)-dependent manner. Clustering these genes based on time of high light exposure and photoprotective capacity provided insights into groups with invariant expression (e.g., housekeeping and cell cycle genes), those significantly influenced by photoprotection (e.g., proteasomes, ribosomes, and photoprotection-related genes), and those regulated by light independently of Lhcx1 (e.g., genes related to light absorption and photosynthetic complexes). Finally, a novel non-invasive method, based on the electrochromic shift of photosynthetic pigments, was developed to measure the absolute value of the proton motive force and its division into its electrical and osmotic components, ΔpH. This will facilitate studies of how the photosynthetic electron transfer chain affects the quantities and activities of molecular actors involved in NPQ via ΔpH, thus closing the loop of the NPQ regulatory module
Author-wise bibliometric analysis based on entropy.
No full textAuthor-wise bibliometric analysis based on entropy.</p
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