1,721,177 research outputs found
Destexhe Alain, Amérique centrale. Enjeux politiques
No full textLempérière-Roussin Annick. Destexhe Alain, Amérique centrale. Enjeux politiques. In: Vingtième Siècle, revue d'histoire, n°25, janvier-mars 1990. Dossier : le Brésil au pluriel. p. 128
Destexhe Alain, Amérique centrale. Enjeux politiques
No full textLempérière-Roussin Annick. Destexhe Alain, Amérique centrale. Enjeux politiques. In: Vingtième Siècle, revue d'histoire, n°25, janvier-mars 1990. Dossier : le Brésil au pluriel. p. 128
Biologically Realistic Mean-Field Models of Conductance-Based Networks of Spiking Neurons with Adaptation
No full textAccurate population models are needed to build very large-scale neural models, but their derivation is difficult for realistic networks of neurons, in particular when nonlinear properties are involved, such as conductance-based interactions and spike-frequency adaptation. Here, we consider such models based on networks of adaptive exponential integrate-and-fire excitatory and inhibitory neurons. Using a master equation formalism, we derive a mean-field model of such networks and compare it to the full network dynamics. The mean-field model is capable of correctly predicting the average spontaneous activity levels in asynchronous irregular regimes similar to in vivo activity. It also captures the transient temporal response of the network to complex external inputs. Finally, the mean-field model is also able to quantitatively describe regimes where high- and low-activity states alternate (up-down state dynamics), leading to slow oscillations. We conclude that such mean-field models are biologically realistic in the sense that they can capture both spontaneous and evoked activity, and they naturally appear as candidates to build very large-scale models involving multiple brain areas
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
La complexité cachée des réseaux de neurones biologiquement réalistes : propriétés émergentes et comportements dynamiques
No full textCette thèse étudie la dynamique neuronale pendant l'éveil attentif, en se concentrant spécifiquement sur le type de dynamique "asynchrone et irrégulière" (AI) observée dans le cortex cérébral. Cette recherche vise à mieux comprendre les comportements des réseaux neuronaux, en mettant l'accent sur deux modèles : le modèle « Adaptive Exponential » (AdEx) « integrate and fire » et le modèle Hodgkin-Huxley (HH), avec un accent particulier sur le modèle AdEx. La thèse met en évidence des différences intrigantes entre des réseaux neuronaux apparemment similaires. Dans une première partie, elle met en lumière la façon dont les réseaux neuronaux répondent aux stimuli externes, en particulier dans le contexte de l'épilepsie, en examinant pourquoi certains systèmes contrôlent et éteignent l'entrée paroxystique alors que d'autres la reproduisent et la propagent. Dans une seconde partie, la thèse explore comment des réseaux de neurones AdEx ou HH faiblement connectés peuvent présenter des états AI de deux manières distinctes : des états AI auto-entretenus (Self-sustained) ou des états AI nécessitant une entrée externe (Driven).Pour élucider ces différences, une combinaison de techniques classiques de traitement du signal, d'analyse structurelle de la configuration du réseau et d'outils de systèmes dynamiques - y compris les exposants de Lyapunov et la dissipation du système - est employée. L'étude utilise également des modèles de champ moyen des réseaux AdEx pour comprendre comment les variantes Self-sustained et Driven se manifestent à un niveau global. L'exploration de ces propriétés et de ces variations nous permet de mieux comprendre les propriétés émergentes complexes et les comportements dynamiques distincts qui existent au sein des réseaux de neurones biologiques apparemment similaires.This thesis investigates the neural dynamics during attentive wakefulness, specifically focusing on the "asynchronous and irregular" (AI) type of dynamics observed in the cerebral cortex. The research aims to gain a deeper understanding of neural network behavior, with a primary emphasis on two models: the Adaptive Exponential (AdEx) integrate and fire model, and the Hodgkin-Huxley (HH) model, with a particular focus on the AdEx model. The thesis uncovers intriguing differences among seemingly similar neural networks. In a first part, it will shed light on how neural networks respond to external stimuli, particularly in the context of epilepsy, examining why certain systems control and kill the paroxysmal input while others reproduce and propagate it.In a second part, the thesis explores how sparsely connected networks of AdEx or HH neurons can exhibit AI states in two distinct ways: self-sustained AI states, or AI states requiring external input (Driven). To unravel those differences, a combination of classical signal processing techniques, structural analysis of the configuration of the network, and dynamical systems tools - including Lyapunov exponents and system dissipation - are employed. The investigation also makes use mean-field models of AdEx networks to comprehend how self-sustained and driven variants manifest at a global level.Exploring these properties and variations enhances our understanding of the complex emergent properties and distinct dynamical behavior that exist within apparently similar biological neural networks
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
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