French Roadmap for complex Systems 2008-2009

This second issue of the French Complex Systems Roadmap is the outcome of the Entretiens de Cargese 2008, an interdisciplinary brainstorming session organized over one week in 2008, jointly by RNSC, ISC-PIF and IXXI. It capitalizes on the first roadmap and gathers contributions of more than 70 scientists from major French institutions. The aim of this roadmap is to foster the coordination of the complex systems community on focused topics and questions, as well as to present contributions and challenges in the complex systems sciences and complexity science to the public, political and industrial spheres

Présentation de l'architecture et des fonctionnalités de l'application ORI-OAI ; conception et développement en réseau

International audienc

Femtosecond coherent anti-Stokes raman spectroscopy: experiences and modelisation in the case of the low-pressure H-2-N-2 compound

International audienc

Revisiting a theorem by Folkman on graph colouring

International audienceWe give a short proof of the following theorem due to Jon H. Folkman (1969): The chromatic number of any graph is at most 2 plus the maximum over all subgraphs of the difference between the number of vertices and twice the independence number

How heat controls fracture: the thermodynamics of creeping and avalanching cracks

International audienceWhile of paramount importance in material science, the dynamics of cracks still lacks a complete physical explanation. The transition from their slow creep behavior to a fast propagation regime is a notable key, as it leads to full material failure if the size of a fast avalanche reaches that of the system. We here show that a simple thermodynamics approach can actually account for such complex crack dynamics, and in particular for the non-monotonic force-velocity curves commonly observed in mechanical tests on various materials. We consider a thermally activated failure process that is coupled with the production and the diffusion of heat at the fracture tip. In this framework, the rise in temperature only affects the sub-critical crack dynamics and not the mechanical properties of the material. We show that this description can quantitatively reproduce the rupture of two different polymeric materials (namely, the mode I opening of polymethylmethacrylate (PMMA) plates, and the peeling of pressure sensitive adhesive (PSA) tapes), from the very slow to the very fast fracturing regimes, over seven to nine decades of crack propagation velocities. In particular, the fastest regime is obtained with an increase of temperature of thousands of kelvins, on the molecular scale around the crack tip. Although surprising, such an extreme temperature is actually consistent with different experimental observations that accompany the fast propagation of cracks, namely, fractoluminescence (i.e.,\,the emission of visible light during rupture) and a complex morphology of post-mortem fracture surfaces, which could be due to the sublimation of bubbles

Itinéraires de Roberto Rossellini

« Il faut en permanence mettre en marche quelque chose de nouveau » déclarait Roberto Rossellini à l'occasion d'un colloque organisé en marge de sa présidence du Festival de Cannes 1977, quelques semaines avant sa mort. Le présent recueil, en associant esthétique et fabrique, plutôt que de penser les films de Rossellini au miroir de la seule société italienne ou en fonction de la prétendue césure entre cinéma et télévision, se propose de suivre ses multiples itinéraires. Les déplacements géographiques s'associent à des trajectoires historiques et temporelles complexes. Ce livre envisage aussi comment les films se font l'écho des sculptures, des textes poétiques, des créations théâtrales, des textes philosophiques que le cinéaste croise sur son parcours. L'autre piste, et cet enjeu est considérable, concerne l'empreinte des idées cinématographiques de Rossellini sur le cinéma moderne et contemporain, qui poursuit en quelque sorte les chemins tracés tout en les réinventant. Autrement dit, les films de Rossellini continuent leur fabrique