1,721,023 research outputs found
Nutrition of the common hamster (Cricetus cricetus), impact on its biology and link with agricultural practices and biodiversity
No full textLe Grand hamster (Cricetus cricetus), une espèce de rongeur inféodée au milieu agricole en Eurasie, est en danger critique d’extinction. Dans cette thèse, j’étudie son alimentation, les mesures de conservation et les pratiques agricoles à développer, afin d’améliorer l’état de ses populations. J’ai montré que le hamster peut sélectionner sa nourriture en fonction de ses besoins alimentaires, qui sont variés. Cette diversité d’aliments doit lui permettre de pallier les carences des monocultures de blé et maïs notamment. L’association de plusieurs cultures telles que blé et soja permet ainsi d’assurer un succès reproducteur chez cette espèce, le soja apportant les protéines manquantes dans le blé. Favoriser une diversité de plantes et d’insectes dans son environnement permet autant d’apports protéiques pendant la reproduction. Cela est possible en mettant en place des pratiques agricoles durables se basant sur l’agroécologie, telles que l’agriculture de conservation. Ces pratiques bénéficient à la biodiversité dans sa globalité, aux agriculteurs et à la société. La protection du Grand hamster peut être un moteur de cette transition agricole.The common hamster (Cricetus cricetus), a rodent species living in farmlands in Eurasia, is critically endangered. In this thesis, I studied its diet, conservation measures and agricultural practices to develop to improve its population levels. I have shown that the hamster can select its food according to its dietary needs, which are diverse. It needs a variety of foods to supply deficiencies in notably corn and wheat monocultures. The combination of several crops such as wheat with soybean restore a proper reproductive success in that species, soybean compensating for protein deficiency in wheat. Favouring a diversity of plants and insects in its environment is a way to provide sufficient protein intake during reproduction. This can be achieved by implementing sustainable agricultural practices based on agroecology, such as conservation agriculture, which benefits more widely to biodiversity, farmers, and society. The protection of the common hamster can be a driving force for this agricultural transition
Causes et conséquences évolutives de la phénologie de l’hibernation : approches évolutives des changements de phénologie dans le contexte des changements globaux
No full textCette thèse vise à comprendre les causes et conséquences évolutives de la phénologie de l’hibernation. Mes résultats montrent que la phénologie de l’hibernation résulterait d’un compromis entre les bénéfices pour la survie d’hiberner et ceux d’être actif pour la reproduction. Par une approche interspécifique, j’ai aussi montré que la longévité augmentait avec la durée de l’hibernation chez 82 espèces. Par contre, j’ai observé par une approche intraspécifique chez le hamster commun, que l’augmentation de la durée de l’hibernation chez cette espèce serait associée à des traits d’histoire de vie rapide (longévité courte, descendance nombreuse). Mes résultats suggèrent enfin que la longévité des hibernants pourrait être expliqué par la réduction du métabolisme pendant l’hibernation et leur capacité d’élongation des télomères quelle que soit la période de l’année. Cette thèse ouvre donc de nouvelles voies dans la compréhension des réponses des espèces hibernantes au changement global.This thesis aims to better understand the evolutionary causes and consequences of hibernation phenology. My results show that hibernation phenology would be explained by a trade-off between survival benefits of hibernating and benefits of remaining active for reproduction. Using an interspecific approach, I also showed that longer hibernation duration was associated with increased longevity across 82 hibernating species. In contrast to these results, I observed by an intraspecific approach in the common hamster, that the increase in hibernation duration would instead be associated with fast life history traits (short longevity, numerous offspring). My results on the same species also suggest that longevity of hibernators could be explained by the metabolic reduction during hibernation and their ability to elongate telomeres regardless of the time of the year. This thesis therefore opens new avenues in understanding the responses of hibernating species in the context of global change
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
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
Intestinal morphology,cellular dynamics and physiology according to body fuel availability in rats
No full textL'épithélium de l'intestin grêle est atrophié après un jeûne court défini comme phase de mobilisation des réserves lipidiques (phase II), et surtout après un jeûne prolongé caractérisé par un catabolisme protéique élevé (phase III). Au niveau cellulaire cependant, alors que la phase II du jeûne est marquée par une diminution de la prolifération et de la migration cellulaires, la phase III présente une augmentation de ces mécanismes. La phase III se caractérise aussi par un arrêt de l'apoptose intestinale qui permettrait de préserver les entérocytes et donc l'absorption de nutriments dès réalimentation. La reprise de l'activité cellulaire et l'arrêt de l'apoptose en phase III seraient induits par une baisse des cytokines TNF et TGF 1 et du facteur de transcription intestinal Cdx2. L'augmentation de la prolifération cellulaire initiée déjà pendant la phase III du jeûne entraînerait une restauration de l'épithélium intestinal après réalimentation toute aussi rapide qu après un jeûne plus court.L'expression des transporteurs actifs PepT1 et SGLT1 ainsi que l'activité néoglucogénique intestinale sont stimulées au cours de la phase III mais pas pendant la phase II du jeûne. L'augmentation de la protéine SGLT1 pendant la phase III du jeûne permet une absorption immédiate de glucose dès réalimentation. La présence en grande quantité de la protéine PepT1 en phase III du jeûne devrait permettre une absorption de peptides et donc un apport azoté dès réalimentation. La réalimentation enfin, stimule l'expression des transporteurs facilités GLUT5, GLUT2 et FATP4. Lorsque le jeûne se prolonge et que l'animal atteint un seuil critique de déplétion de ses réserves énergétiques, l'activation de mécanismes cellulaires et moléculaires spécifiques entraînerait une optimisation de la capacité d'absorption des nutriments par la muqueuse de l'intestin grêle dès réalimentation.After the early adaptation to fasting (phase I), an atrophy of the intestinal mucosa occurs during the period which is characterized by the mobilization of fat stores and an efficient protein sparing. This atrophy is aggravated during the further rise in protein utilization (phase III). Cell proliferation and migration decrease during phase II, but strongly increase during a phase III fast and may therefore initiate mucosal repair well before food becomes available. Also, a phase III fast induces an arrest in intestinal epithelial apoptosis at the tip of the villi, suggesting preservation of absorptive cells. The lack of apoptosis and initiation of cell proliferation during phase III fasting may be triggered by a decrease in the cytokines TGFb1, and TNF and in the intestine specific transcription factor Cdx2. They are concomitant with a peak of locomotor activity in these animals induced by a rise in plasma corticosterone and reflecting the search for food. Intestinal gluconeogenesis is increased during a phase III fast, when the availability of amino acids used as precursors raises. At the same time, the active glucose and peptide transporters are enhanced. Glucose can then, be immediately absorbed at low concentrations through SGLT1. Glucose and peptides should be used as a source of energy and peptides should also provide body protein precursors. Finally, refeeding following either a phase II or a phase III fast stimulates facilitative fatty acids and glucose transports, so that large amounts of these metabolites can be transported from the intestinal lumen to the blood stream and provides energy. The unaltered and even increased absorption capabilities of the intestine during a phase III fast when the animal reaches a low threshold in nutrient reserves, coincides with a search for food activity and could permit food assimilation immediately after refeeding
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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