1,720,980 research outputs found
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
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
Torpor and timing: impact of endogenously controlled hypothermia on the circadian system of two hamster species
No full textL’influence des saisons est extrêmement marquée au niveau des hautes latitudes du globe, avec des variations des conditions environnementales très prononcées. Les Mammifères vivant dans de telles conditions drastiques, ont développés différentes formes d’hibernation (ou torpeur) pour réduire les coûts métaboliques pendant ces périodes rudes lorsque les ressources énergétiques se font rares.
Les Mammifères hibernants comme le Hamster d´Europe (Cricetus cricetus), dont la température corporelle (Tb) diminue pendant plusieurs jours pour atteindre des niveaux voisins de la température ambiante (Ta), peuvent ainsi préserver au maximum leurs réserves d’énergie. Au contraire, quelques petits Mammifères comme le Hamster de Djungarie (Phodopus sungorus) montrent des hypothermies journalières de moindre amplitude. Ils utilisent les quelques heures de leur temps de repos circadien pour effectuer avec précision des hypothermies contrôlées, et diminuer leur Tb jusqu’à un seuil minimal de 15 °C. De telles Tb basses qui se prolongent, peuvent avoir des conséquences sur l’activité du système nerveux central (SNC). Il est donc crucial que l’intégralité fonctionnelle du SNC soit maintenue, ainsi, la limitation de la durée d’hypothermie permet un « réveil » régulier à des Tas basses. Pendant la torpeur, un des systèmes régulateurs importants serait le système circadien, car il réagit à la photopériode et synchronise les phénomènes internes sur une base de temps circadienne. Dans ce travail de thèse, nous avons pu montrer, pour la première fois, que la machinerie moléculaire de « l’horloge » biologique endogène reste active pendant la torpeur chez le Hamster de Djungarie mais une chute de la Tb diminue l’amplitude de l’expression des gènes de « l’horloge » biologique circadienne. La diminution de l’expression des protéines pendant l’hypothermie, induirait une diminution du rétrocontrôle de la transcription pendant et après une période de torpeur.
Pour mieux comprendre les changements d’expression de ces gènes, nous avons déterminé par microdialyse trans-pineal les sécrétions de mélatonine (hormone reflétant l’activité de la principale sortie de « l’horloge »), pendant une longue durée. Cette méthode, qui a été adaptée pour la première fois au Hamster de Djungarie (animal de petite taille), s’avère être un bon outil pour étudier les signaux saisonniers comme la mélatonine chez les animaux hibernants.
Pendant l’hibernation du Hamster d´Europe, la diminution de la Tb atteint ~8 °C pendant quelques jours dans nos conditions expérimentales. A basse température, nous n’avons pas pu observer de rythme de l’expression des gènes de « l’horloge » biologique ce qui indiquerait dans ces conditions un arrêt des oscillations. A partir de nos résultats, nous avons conclu que « l’horloge » circadienne semble compenser les effets d’une diminution de la Tb dans un large gradient mais au delà d’un certain seuil de température les oscillations sont arrêtées.Seasonal influences become increasingly important at high latitudes, where variations in external conditions are most pronounced. Mammals living in such drastic conditions have developed different forms of torpor to reduce metabolic costs in harsh periods when energy is rare. Deep hibernators like the European hamster (Cricetus cricetus) regularly decrease their body temperature (Tb) for several days to temperatures approaching ambient temperature (Ta) and thereby save a maximum of energy. In contrast some small mammals like the Djungarian hamster (Phodopus sungorus) undergo shallower bouts of daily torpor. Induced by short photoperiod they spontaneously use their daily resting time for only a few hours of precisely timed hypothermia during which their body temperature decreases to minimum 15°C. Invariably low Tbs go along with a depression of CNS activity. Nevertheless it is crucial that functional integrity is maintained, which is why systems of vital importance during hypothermia are supposed to remain active at those low Tbs.
One of the important keys during torpor is believed to be the circadian system. It measures photoperiod and thereby determines the onset of the torpor season and moreover synchronizes internal processes on a circadian basis. In this thesis we could for the first time demonstrate that the clock´s molecular machinery is still active during daily torpor in Djungarian hamsters. Alterations in phase and amplitude of clock gene expression rhythms however, point to temperature sensitivity. Decrease in protein expression during hypothermia, hence a decreased feedback might be responsible for transcriptional alterations during and after a torpor bout.
To more precisely investigate phase changes seen in gene expression, we set up a long term microdialysis experiment to continuously measure melatonin, a well defined clock output, in vivo directly in the pineal gland. This method could for the first time be adapted to the very small Djungarian hamster and provides a good tool to study a circadian signal like melatonin in a seasonally heterothermic animal.
During deep hibernation in European hamsters that decreased their Tb for several days to ~8°C in our experimental conditions, we could not observe any rhythmic clock gene expression and thereby show that the clock stops oscillating at those low temperatures. We conclude from our data, that the circadian clock seems to be temperature compensated in a wide temperature range but once a certain low temperature is reached, oscillation is no longer possible
Seasonal cerebral plasticity in two hamster species: the Djungarian hamster (Phodopus sungorus) and the Syrian hamster (Mesocricetus auratus)
No full textL’alternance des saisons est un phénomène astronomique et périodique qui a pour effet de changer les paramètres environnementaux. Par conséquent, les animaux, doivent s’adapter à ces variations en modifiant, par exemple leur poids, leur pelage, ou la période de reproduction. Les animaux utilisent la longueur du jour (la photopériode) pour synchroniser ces fonctions avec les saisons. Les variations jour/nuit sont perçues par le cerveau et transmises à la glande pinéale qui va sécréter la mélatonine uniquement pendant la nuit. Le signal mélatoninergique va diffuser dans l’ensemble de l’organisme dont le cerveau et l’axe hypothalamo-hypophysaire. Les neurones de l’hypothalamus sécrètent le GnRH (gonadotropin-releasing hormone) qui va activer les cellules gonadotropes de l’hypophyse permettant ainsi la libération de la FSH (follicle-stimulating hormone) et de la LH (luteinizing hormone). Ces deux hormones vont réguler la gamétogenèse et la synthèse des hormones sexuelles au niveau des gonades. Les changements saisonniers de la sécrétion de la mélatonine aboutissent donc au repos sexuel de l’animal en hiver. Ces changements saisonniers de l’activité reproductrice affectent donc les niveaux des stéroïdes sexuels circulants. Les stéroïdes sexuels vont rétroagir sur les structures hypothalamiques et extrahypothalamiques. Dans ce contexte, nous avons étudié les effets de ces deux hormones, régulées de façon saisonnière, sur le cerveau, chez deux espèces d’hamsters. Ces travaux ont permis de mettre en évidence des phénomènes de plasticité neuronale et gliale structurale ou neurochimique contrôlés par les deux principaux médiateurs des saisons, la mélatonine et les stéroïdes sexuels.The alternation of seasons is an astronomical and periodical phenomenon which induces changes in environmental parameters. As a consequence, animals have to adapt to these variations and for that different strategies have been developed to save energy in winter, such as variations in body weight, fur or reproductive period. Animals use photoperiod (i.e. day length) to synchronise these functions to the seasons. To decode photoperiod and adapt their physiology and behaviour, mammals rely on their photoneuroendocrine system, which includes the pineal gland and its rhythmic release of melatonin. Melatonin secretion occurs exclusively at night, and transmits the photoperiodic information to the rest of the body including the brain, and the hypothalamo-hypophyseal axis. Neurones in the hypothalamus secrete GnRH (gonadotropin-releasing hormone) which will activate the gonadotropes in the pituitary gland to produce and release FSH (follicle-stimulating hormone) and LH (luteinizing hormone). These hormones will stimulate gametogenesis and the synthesis of sex steroids at the level of the gonads. We know that the lenghtening melatonin signal towards winter leads to reproductive quiescence. Also sex steroids can feedback on the hypothalamic and extrahypothalamic structures. Accordingly, the general goal of this work was to study the effects of these two photoperiodically regulated hormones, on the brain, in two hamster species. Our results showed evidences of neuronal and glial structural or neurochemical plasticity controlled by the principal mediators of seasons, melatonin and sex steroids
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