1,720,986 research outputs found
Integrative approach to deconditioning induced by dry immersion and prolonged bed rest as models of microgravity
No full textL’exposition à la microgravité entraine des changements multi-systémiques chez l’être humain, pouvant être délétères sur le long terme ou lors d’un retour rapide à une gravité plus élevée. L’objectif de ce travail de thèse est triple 1) mieux décrire les effets physiologiques induits par le modèle d’immersion sèche, 2) tester des contremesures mécaniques et d’exercices physiques, et 3) proposer une approche de physiologie intégrative multi systèmes des changements dus aux transferts liquidiens, à l’inactivité physique aiguë et à la décharge globale du corps et enfin initier une comparaison homme-femme. Nous présentons ici des simulations de microgravité avec 3 études d’immersion sèche de courte durée : une immersion de 3 jours (n=12) et de 5 jours chez les hommes (n=18, avec contremesure mécanique), et une de 5 jours chez les femmes (n=18). Enfin, une simulation par alitement prolongé anti orthostatique de 90 jours chez les hommes est aussi présentée (n=22, avec contremesures d’exercice physique aérobiques ou résistifs). Ces deux modèles de microgravité sont complémentaires, l’immersion mimant plus fidèlement les effets rapides et l’alitement permettant d’étudier les systèmes présentant une cinétique d’évolution plus lente.Exposure to microgravity induces multisystemic changes in humans, which can be deleterious in the long term or during a rapid return to higher gravity. The objective of this thesis work is threefold: 1) better describe the physiological effects induced by the dry immersion model, 2) test mechanical and physical exercise countermeasures, 3) propose a multi-systems integrative physiology approach of changes due to fluid shifts, acute physical inactivity and global unloading of the body, and finally initiate a male-female comparison. We present here microgravity simulations with 3 short-duration dry immersion studies : One immersion lasting 3 days (n=12) and one lasting 5 days in men (n=18, with mechanical counter measure), and one lasting 5 days in women (n=18, first time strict). Finally, one simulation by prolonged anti-orthostatic bedrest in men is also presented (n=22, with aerobic or resistive exercise countermeasures). These two microgravity models are complementary, as immersion mimics rapid effects more faithfully and bed rest allows the study of systems with slower evolution kinetics
MECANISMES DE LA DYSFONCTION VASCULAIRE INDUITE PAR DES MODELES DE MICROGRAVITE
No full textGravitational stimulation is an inherent part of terrestrial environment. Modified gravity changes functioning of numerous body systems, including cardiovascular system. The aim of this work was to study the mechanisms of vascular modifications induced by modeled microgravity. The human studies were performed using dry immersion. This model is considered as one of the most appropriate to reproduce the effects of prolonged microgravity and especially to mimic the lack of support. We found that dry immersion induces microcirculatory impairment with endothelial dysfunction (study of circulating microparticles) and impaired skin vasodilation (study by iontophoresis of vasoactive substances coupled with laser Doppler flowmetry). This vascular impairment is integrated to more general cardiovascular deconditioning syndrome. The global deconditioning was also considered in this work, including the rapid reset of water and sodium balance to a new steady state. During the recovery period, we observed a significant increase of plasmatic NT-proBNP which might reflect the degree of cardiovascular deconditioning. Our studies with animal models of horizontal and antiorthostatic hypokinesia suggest that increased endotoxin translocation and reduced energy metabolism in microgravity could contribute to endothelial impairment. Endothelial dysfunction may be regarded as one of the therapeutic targets for pathologies associated with physical inactivity and microgravity.La gravité est une stimulation permanente pour l'organisme sur terre. La microgravité induit des modifications de nombreuses fonctionnalités, y compris celles du système cardio-vasculaire. Le but de ce travail était d‟étudier les mécanismes des modifications vasculaires induites par les modèles de microgravité. Nous avons conduit nos études chez l‟homme à l‟aide de l‟immersion sèche qui est considérée comme un des modèles reproduisant au mieux la microgravité. L'immersion sèche est le seul modèle de microgravité prolongée à imiter l'absence d‟appui. Notre travail montre que l‟immersion sèche induit une atteinte au niveau microcirculatoire avec une dysfonction endothéliale (étude des microparticules circulantes) et une atteinte de la fonction vasodilatatrice cutanée (étude par iontophorèse couplée au laser Doppler). Cette atteinte vasculaire s'intègre dans un syndrome de déconditionnement cardiovasculaire plus global que nous avons également étudié. Il comprend un nouvel équilibre hydro-sodé qui survient très rapidement, dans les 24 premières heures. Pendant la période de récupération, nous avons observé une augmentation significative du NT-proBNP qui pourrait être un marqueur biologique du déconditionnement cardio-vasculaire. Nos études sur l‟animal avec les modèles d‟hypokinésie et d'inclinaison tête en bas discontinues chroniques suggèrent qu'une translocation augmentée d‟endotoxine et une réduction du métabolisme énergétique en microgravité pourraient participer aux atteintes endothéliales. La dysfonction endothéliale deviendrait ainsi une cible thérapeutique pour des atteintes liées à l‟inactivité physique et à la microgravité
MECANISMES DE LA DYSFONCTION VASCULAIRE INDUITE PAR DES MODELES DE MICROGRAVITE
No full textGravitational stimulation is an inherent part of terrestrial environment. Modified gravity changes functioning of numerous body systems, including cardiovascular system. The aim of this work was to study the mechanisms of vascular modifications induced by modeled microgravity. The human studies were performed using dry immersion. This model is considered as one of the most appropriate to reproduce the effects of prolonged microgravity and especially to mimic the lack of support. We found that dry immersion induces microcirculatory impairment with endothelial dysfunction (study of circulating microparticles) and impaired skin vasodilation (study by iontophoresis of vasoactive substances coupled with laser Doppler flowmetry). This vascular impairment is integrated to more general cardiovascular deconditioning syndrome. The global deconditioning was also considered in this work, including the rapid reset of water and sodium balance to a new steady state. During the recovery period, we observed a significant increase of plasmatic NT-proBNP which might reflect the degree of cardiovascular deconditioning. Our studies with animal models of horizontal and antiorthostatic hypokinesia suggest that increased endotoxin translocation and reduced energy metabolism in microgravity could contribute to endothelial impairment. Endothelial dysfunction may be regarded as one of the therapeutic targets for pathologies associated with physical inactivity and microgravity.La gravité est une stimulation permanente pour l'organisme sur terre. La microgravité induit des modifications de nombreuses fonctionnalités, y compris celles du système cardio-vasculaire. Le but de ce travail était d‟étudier les mécanismes des modifications vasculaires induites par les modèles de microgravité. Nous avons conduit nos études chez l‟homme à l‟aide de l‟immersion sèche qui est considérée comme un des modèles reproduisant au mieux la microgravité. L'immersion sèche est le seul modèle de microgravité prolongée à imiter l'absence d‟appui. Notre travail montre que l‟immersion sèche induit une atteinte au niveau microcirculatoire avec une dysfonction endothéliale (étude des microparticules circulantes) et une atteinte de la fonction vasodilatatrice cutanée (étude par iontophorèse couplée au laser Doppler). Cette atteinte vasculaire s'intègre dans un syndrome de déconditionnement cardiovasculaire plus global que nous avons également étudié. Il comprend un nouvel équilibre hydro-sodé qui survient très rapidement, dans les 24 premières heures. Pendant la période de récupération, nous avons observé une augmentation significative du NT-proBNP qui pourrait être un marqueur biologique du déconditionnement cardio-vasculaire. Nos études sur l‟animal avec les modèles d‟hypokinésie et d'inclinaison tête en bas discontinues chroniques suggèrent qu'une translocation augmentée d‟endotoxine et une réduction du métabolisme énergétique en microgravité pourraient participer aux atteintes endothéliales. La dysfonction endothéliale deviendrait ainsi une cible thérapeutique pour des atteintes liées à l‟inactivité physique et à la microgravité
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
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