Signal déterministe lié à la transmission d'activité dans un réseau de neurones ponctuels représenté par un graphe dirigé

L'évolution temporelle d'une activité d'ensemble de neurones $s(t)$, définie comme la somme des activités de neurones ponctuels de type ${0, 1}$ sur une durée $\delta$ est analysée dans cette étude. Plusieurs résultats sont obtenus pour différents réseaux de neurones représentés par leurs graphes de connectivité.On montre que des fonctions $s(t) = t^{\alpha}$ avec $\alpha \in \mathbb{R}$ sont générées par ces réseaux, le paramètre $\alpha$ étant réglé par la structure du graphe utilisé

Les arts poétiques en France au XVIIIe siècle

L'auteur définit les positions fondamentales de l'esthétique de Boileau comme «ouverture» et négation du système normatif (néoaristotélicien). L'incompréhension de cette esthétique et sa confusion avec une poétique normative à la La Harpe aboutirait à une diffamation du Stendhal «classiciste» et à une appréciation erronée de sa production de (fragments de) tragédies, comédies, épopées, considérée comme «ratée», et de sa production de «romans» et «contes» comme libération de la contrainte de l'esthétique classique. Or, Stendhal ne cessera jamais d'adhérer à l'esthétique innovatrice de Boileau, qui, unie à l'esthétique shakespearienne-cervantine, aboutit à la production de «textes fleuves» auxquels on a donné le nom de romans.The author regards the fundamental tenets of Boileau's aesthetic as a répudiation of the neo-Aristotelean normative System. A misunderstanding of this aesthetic and its misidentification as normative poetics by La Harpe conduce to a false vision of Stendhal as both a failed classicist (as writer of tragic, comic and epic fragments) and a successful creator of "novels" and "taies" (and as such delivered from the shackles of classical aesthetics). In fact, Stendhal never ceased to adhere to Boileau's innovative aesthetic. Combined with the aesthetics of Shakespeare and Cervantes, it leads him to produce the "textes fleuves" to which the name of novels has been given

Whole genome evaluation of horizontal transfers in the pathogenic fungus Aspergillus fumigatus

<p>Abstract</p> <p>Background</p> <p>Numerous cases of horizontal transfers (HTs) have been described for eukaryote genomes, but in contrast to prokaryote genomes, no whole genome evaluation of HTs has been carried out. This is mainly due to a lack of parametric methods specially designed to take the intrinsic heterogeneity of eukaryote genomes into account. We applied a simple and tested method based on local variations of genomic signatures to analyze the genome of the pathogenic fungus <it>Aspergillus fumigatus</it>.</p> <p>Results</p> <p>We detected 189 atypical regions containing 214 genes, accounting for about 1 Mb of DNA sequences. However, the fraction of atypical DNA detected was smaller than the average amount detected in the same conditions in prokaryote genomes (3.1% vs 5.6%). It appeared that about one third of these regions contained no annotated genes, a proportion far greater than in prokaryote genomes. When analyzing the origin of these HTs by comparing their signatures to a home made database of species signatures, 3 groups of donor species emerged: bacteria (40%), fungi (25%), and viruses (22%). It is to be noticed that though inter-domain exchanges are confirmed, we only put in evidence very few exchanges between eukaryotic kingdoms.</p> <p>Conclusions</p> <p>In conclusion, we demonstrated that HTs are not negligible in eukaryote genomes, bearing in mind that in our stringent conditions this amount is a floor value, though of a lesser extent than in prokaryote genomes. The biological mechanisms underlying those transfers remain to be elucidated as well as the biological functions of the transferred genes.</p

CFTR and Ca2+ Signaling in Cystic Fibrosis

Among the diverse physiological functions exerted by calcium signaling in living cells, its role in the regulation of protein biogenesis and trafficking remains incompletely understood. In cystic fibrosis (CF) disease the most common CF transmembrane conductance regulator (CFTR) mutation, F508del-CFTR generates a misprocessed protein that is abnormally retained in the endoplasmic reticulum (ER) compartment, rapidly degraded by the ubiquitin/proteasome pathway and hence absent at the plasma membrane of CF epithelial cells. Recent studies have demonstrated that intracellular calcium signals consequent to activation of apical G-protein-coupled receptors by different agonists are increased in CF airway epithelia. Moreover, the regulation of various intracellular calcium storage compartments, such as ER is also abnormal in CF cells. Although the molecular mechanism at the origin of this increase remains puzzling in epithelial cells, the F508del-CFTR mutation is proposed to be the onset of abnormal Ca2+ influx linking the calcium signaling to CFTR pathobiology. This article reviews the relationships between CFTR and calcium signaling in the context of the genetic disease CF

« L’Atelier de David » : désir, création, histoire

C’est en écrivant son second livre, consacré à « l’atelier de David » que Thomas Crow a « plus vivement senti ce qu’est une communauté intellectuelle », et ces premiers mots des traditionnels « remerciements » reçoivent tout leurs poids après la lecture de ce bel ouvrage. L’histoire de l’art y mobilise en effet, dans un esprit d’interdisciplinarité de bon aloi, une abondante information – dont témoignent la bibliographie et la copieuse annotation – historique mais aussi littéraire (sur l’ento..

Hisayasu Nakagawa, Mémoires d’un « moraliste passable »

C’est un honneur et une joie que d’avoir à rendre compte du dernier livre de H. Nakagawa, « mémoires » où se révèle l’ancrage existentiel de l’activité intellectuelle exigeante et multiforme de ce « pantophile ». La deuxième partie, « Trois autoportraits », nous était déjà connue puisqu’elle reprend le chapitre consacré au savant japonais par le recueil de S. Karp Être dix-huitiémiste, dans le sillage de la table ronde organisée en 1995 par M. Delon et J. Schlobach, à quelques modifications p..

Implications of paleomagnetic results from the Permian Rodez basin for the late Variscan tectonics in the southern French massif Central.

A paleomagnetic study has been carried out on three sedimentary formations of the Permian Rodez basin in the southern France. Two of them yield paleomagnetic poles of Saxonian and Thuringian age showing counterclockwise rotation of moderate amplitude, during or after the Thuringian deposition. For the French Massif Central, contrary to its stable southern (Lodève basin) and eastern (Largentière basin) borders, on its southwestern border, in a large area including the Rodez, Saint-Affrique and perhaps Brive basins suffered rotations due to the extensional tectonics during the Late Variscan period

Evidence and effects of fluid circulation on organic matter in intramontane coalfields (Massif Central, France)

Recent evidence for a Late Carboniferous hydrothermal event responsible for Au-As mineralization within the Variscan belt of the French Massif Central adds a supplementary episode to the already rather complex thermal history of this area. To better understand this history, 45 coal samples from various sites in the Massif Central were studied petrographically (reflectance analysis) and geochemically (Rock-Eval pyrolysis). The results of this study suggest that the studied coal was buried to 1500 m and that the coalification took place within 25 Ma, probably ending at the boundary between the Early and Late Permian (marked by the Saalic orogeny). Two thermal end-members basins were identified: (i) the Carboniferous of Bosmoreau-les-Mines (Limousin) and West Graissessac (Montagne Noire) showing geothermal paleoflow values between 150 and 180 mW m−2, and (ii) the Stephanian of Argentat and Détroit de Rodez (SW Massif Central) with values estimated at between 100 and 120 mW m−2. By plotting the Tmax and Ro values on a diagram, the samples were grouped into two populations, the first showing a positive correlation between Ro and Tmax and the second with higher Tmax values than expected after Ro values. Selected samples of the second group are also characterized by a high Oxygen Index (OI) that increases with Tmax. These divergence between Ro and Tmax associated with a high OI may be the result of the circulation of slightly oxidizing hot fluids subsequent to coalification. The other kind of Ro-Tmax divergence seems to be linked to local, particularly high thermal activity, especially in Graissessac and Bosmoreau basins. It is interpreted as being due to a difference in response of these two maturity indicators, respectively to the intensity and duration of the thermal events (e.g., short-lived hydrothermal circulation and thermal domes of regional extent)