Invariance Properties of Inviscid Fluids of Grade n

Revisited and completed version, 18 pages and 2 figures.International audienceFluids of grade n are continuous media in dynamic changes of phases avoiding the surfaces of discontinuity and representing the capillary layers in liquid-vapour interfaces. We recall the thermodynamic form of the equation of motion for inviscid fluids of grade n. First integrals and theorems of circulation are deduced. A general classification of flows is proposed

Positive Feedback, Memory and the Predictability of Earthquakes

We review the "critical point" concept for large earthquakes and enlarge it in the framework of so-called "finite-time singularities". The singular behavior associated with accelerated seismic release is shown to result from a positive feedback of the seismic activity on its release rate. The most important mechanisms for such positive feedback are presented. We introduce and solve analytically a novel simple model of geometrical positive feedback in which the stress shadow cast by the last large earthquake is progressively fragmented by the increasing tectonic stress. Finally, we present a somewhat speculative figure that tends to support a mechanism based on the decay of stress shadows. This figure suggests that a large earthquake in Southern California of size similar to the 1812 great event is maturing.Comment: PostScript document of 18 pages + 2 eps figure

Maîtrise de la reproduction du loup en captivité : application pratique sur une meute du parc Alpha (Parc du Mercantour)

Ce travail décrit tout d’abord la biologie de la reproduction du loup (Canis lupus), en soulignant les différences physiologiques et comportementales avec le chien. Dans une seconde temps, après un rappel des différentes méthodes contraceptives et abortives utilisées chez le chien, l’auteur étudie leur utilisation sur des loups captifs. L’utilisation de méthodes définitives (chirurgicales), bien qu'aisée, entraîne une perte du potentiel reproductif et une diminution de la diversité génétique. Pour les méthodes temporaires (médicales), différents traitements hormonaux sont disponibles tels que les progestatifs et les analogues agonistes de la GnRH. Le choix des différentes voies d’administration et leur faisabilité en parc zoologique sont ensuite discutés. L’interruption de gestation, plus difficile à mettre en oeuvre, permet de conserver le comportement de reproduction des animaux et d’éviter les répercussions sur l’organisation sociale. Pour finir, l’auteur décrit les alternatives disponibles pour contrôler la taille d’une meute captive : la division de la meute, la séparation des mâles et des femelles et l’euthanasie des louveteaux

A model for the formation and evolution of traffic jams

In this paper, we establish and analyze a traffic flow model which describes the formation and dynamics of traffic jams. It consists of a pressureless gas dynamics system under a maximal constraint on the density and is derived through a singular limit of the Aw-Rascle model. From this analysis, we deduce the particular dynamical behavior of clusters (or traffic jams), defined as intervals where the density limit is reached. An existence result for a generic class of initial data is proved by means of an approximation of the solution by a sequence of clusters. Finally, numerical simulations are produced

Création littéraire et photographie argentique

Le présent mémoire de maîtrise s'intéresse à la question de l'image et en propose une exploration placée sous le signe du double. Entre recherche et création, poésie et photographie, éclatement formel et méditation ontologique, ce mémoire ouvre des dialogues pour tenter de comprendre, en deux temps, la mécanique des confluences et leur intérêt sur le plan des processus créateurs. À la croisée des notions qu'il embrasse : l'image ; et le faisceau de ses manifestations, qu'elles soient de l'ordre de l'empreinte (trace), de l'archive (souvenir) ou encore de l'aura (lumière). Fruit d'un travail à quatre mains, Empreintes invite tout d'abord à entrer en immersion dans un monde duel où le fond comme la forme participent de la perte des repères. Présenté dans un format hors norme (deux fois 66 pages disposées tête-bêche) , le recueil photo-poétique joue avec l'espace et le temps, proposant d'arpenter en cinq tableaux les paysages laissés par des êtres qui ont été aimés, qui ont été perdus. Une parole s'élève des blessures et du silence pour retrouver leur trace , se dégage peu à peu de ses propres ruines pour naître à elle-même – puis mourir à nouveau – en un cycle sans fin. Empreintes laisse ainsi sourdre la parole vivante en abordant, par le thème de l'eau, le deuil sous toutes ses formes. Pour soutenir ce recueil, la partie Création littéraire et photographie argentique : intermédialité pour une poétique de l'image offre ensuite une réflexion en deux parties . Un rapport de laboratoire permet de remonter le fil du processus créateur pour mieux saisir, par l'archivage, la genèse du recueil. Il présente les trois méthodes de création intermédiatiques expérimentées entre écriture et photographie. Un essai lyrique sur la photographe franco-canadienne Alix Cléo Roubaud (1952-1983) aborde enfin la magie du nu féminin pour clore cette quête de l'image en pleine lumièreThis Master's thesis deals with the topic of images and leads its exploration with a dual-view. Midway between research and creation, poetry and photography, formal fragmentation and ontological meditation, this memoir opens dialogues in a two-stage attempt to understand the mechanics of confluences and their relevance with regard to creative processes. At the crossroads of notions covered : images ; and the irrange of manifestation, whether in terms of footprints (trace), archives (memory) or aura (light). Fruit of a four-hands work, Empreintes is first of all an invitation to immerse oneself in a dual world where both substance and form contribute to a loss of bearings. Presented in a non-standard size (twice 66 pages arranged head to tail), the photo-poetic collection plays with space and time, offering a five-step walk among landscapes deserted by beings once beloved, now forever lost . A Word rises from wounds and silence to recount them, emerges gradually from its own ruins to self- originate - then die again - in an endless cycle. Empreintes then lets the living Word arise in addressing mourning in all its forms by the theme of water. To support this collection, the Création littéraire et photographie argentique : intermédialité pour une poétique de l'image part then offers a reflection in two stages. A lab report traces back the thread of the creative process to better understand, via archiving, the genesis of the collection. It presents three methods of intermedia creation experienced between writing and photography. A lyrical essay on the French-Canadian photographer Alix Cléo Roubaud (1952-1983) eventually addresses the magic of the female nude in order to end this quest for images in full light

Durability and generalization of attribution-based feedback following failure: Effects on expectations and behavioral persistence

Objective: This experiment investigated, following perceived failure, the immediate, long-term (i.e., durability), and cross-situational (i.e., generalization) effects of attribution-based feedback on expectations and behavioral persistence. Design: We used a 3×2 (Group×Time) experimental design over seven weeks with attributions, expectations of success, and persistence as dependent measures. Method: 49 novice participants were randomly assigned to one of three treatment (attributional feedback) groups: (a) functional (i.e., controllable and unstable); (b) dysfunctional (i.e., uncontrollable and stable); or (c) no feedback. Testing involved three sessions, in which participants completed a total of five trials across two performance tasks (golf-putting and dart-throwing). In order to track whether the attributional manipulation conducted within the context of the golf-putting task in Session 2 would generalize to a new situation, participants performed a dart-throwing task in Session 3, and their scores were compared with those recorded at baseline (in Session 1). Results: Analysis of pre- and post-intervention measures of attributions, expectations, and persistence revealed that the functional attributional feedback led to more personally controllable attributions following failure in a golf-putting task, together with increases in success expectations and persistence. In contrast, dysfunctional attributional feedback led to more personally uncontrollable and stable attributions following failure, together with lower success expectations and reduced persistence. These effects extended beyond the intervention period, were present up to four weeks post intervention, and were maintained even when participants performed a different (i.e., dart-throwing) task. Conclusions: The findings demonstrate that attributional feedback effects are durable over time and generalize across situations

Metabolic processes and carbon nutrient exchanges between host and pathogen sustain the disease development during sunflower infection by Sclerotinia sclerotiorum.

International audienceInteractions between the necrotrophic fungus Sclerotinia sclerotiorum and one of its hosts, Helianthus annuus L., were analyzed during fungal colonization of plant tissues. Metabolomic analysis, based on (13)C- and (31)P-NMR spectroscopy, was used to draw up the profiles of soluble metabolites of the two partners before interaction, and to trace the fate of metabolites specific of each partner during colonization. In sunflower cotyledons, the main soluble carbohydrates were glucose, fructose, sucrose and glutamate. In S. sclerotiorum extracts, glucose, trehalose and mannitol were the predominant soluble carbon stores. During infection, a decline in sugars and amino acids was observed in the plant and fungus total content. Sucrose and fructose, initially present almost exclusively in plant, were reduced by 85%. We used a biochemical approach to correlate the disappearance of sucrose with the expression and the activity of fungal invertase. The expression of two hexose transporters, Sshxt1 and Sshxt2, was enhanced during infection. A database search for hexose transporters homologues in the S. sclerotiorum genome revealed a multigenic sugar transport system. Furthermore, the composition of the pool of reserve sugars and polyols during infection was investigated. Whereas mannitol was produced in vitro and accumulated in planta, glycerol was exclusively produced in infected tissues and increased during colonization. The hypothesis that the induction of glycerol synthesis in S. sclerotiorum exerts a positive effect on osmotic protection of fungal cells and favors fungal growth in plant tissues is discussed. Taken together, our data revealed the importance of carbon-nutrient exchanges during the necrotrophic pathogenesis of S. sclerotiorum