Enhanced light emission from Carbon Nanotubes integrated in silicon micro-resonator

Single-wall carbon nanotube are considered a fascinating nanomaterial for photonic applications and are especially promising for efficient light emitter in the telecommunication wavelength range. Furthermore, their hybrid integration with silicon photonic structures makes them an ideal platform to explore the carbon nanotube instrinsic properties. Here we report on the strong photoluminescence enhancement from carbon nanotubes integrated in silicon ring resonator circuit under two pumping configurations: surface-illuminated pumping at 735 nm and collinear pumping at 1.26 {\mu}m. Extremely efficient rejection of the non-resonant photoluminescence was obtained. In the collinear approach, an emission efficiency enhancement by a factor of 26 has been demonstrated in comparison with classical pumping scheme. This demonstration pave the way for the development of integrated light source in silicon based on carbon nanotubes

Community organizing : une méthode « résolument américaine » ?

Le community organizing dans ses multiples variantes est une méthode d'intervention sociale étiquetée anglo-saxonne. Le concept a gagné en popularité en France et en Europe depuis l'élection de Barack Obama, mais le débat insiste constamment sur sa nature « fondamentalement américaine ». La généalogie du community organizing développée par Alinsky permet cependant de définir la méthode indépendamment du contexte social dans lequel elle s'est appliquée (les quartiers américains). Dans cet article, l'auteur la décrit comme le fruit d'un mariage improbable entre la sociologie urbaine et le syndicalisme. Le développement du community organizing s'est basé, d'une part, sur la compréhension fine des dynamiques communautaires, la reconnaissance et l'activation des phénomènes de leadership ou des identités collectives et, d'autre part, sur l'utilisation systématique de l'action directe, le développement de tactiques de pression du type de celles des syndicats face à l'employeur, mais aussi sur l'art de la négociation pour obtenir des compromis qui seront célébrés comme des avancées et donc des victoires. Une fois comprise et intégrée cette double dimension, les réflexions sur l'importation de ces méthodes pour irriguer le mouvement social européen prennent un nouvel essor.Community organizing is often labelled and denigrated as an anglo-saxon practice of social intervention. Still, since the Obama election, the concept has become increasingly popular in France and in Europe though the discussion consistently centers on its "inherently american". Through the genealogy of community organizing as developed by Alinsky, one can theorize the method independently from the social context in which it was formed (American neighborhoods). In this article, I describe community organizing as the fruit of an improbable union between urban sociology and union organizing. Alinsky based community organizing methods, on the one hand, on a detailed understanding of community dynamics, on the recognition and on the stimulation of leadership and/or collective identities and, on the other hand, on the systematic use of direct action, on the development of pressure point strategies similar to the ones of a union facing its employer, and also on the art of negotiation to achieve compromises. These will be celebrated as a * forward, and thus a victory. Understanding this double dimension of community organizing sheds a new light on the debates as regards the importation of these methods to stimulate the European social movement

Light Emission in Silicon from Carbon Nanotubes

The use of optics in microelectronic circuits to overcome the limitation of metallic interconnects is more and more considered as a viable solution. Among future silicon compatible materials, carbon nanotubes are promising candidates thanks to their ability to emit, modulate and detect light in the wavelength range of silicon transparency. We report the first integration of carbon nanotubes with silicon waveguides, successfully coupling their emission and absorption properties. A complete study of this coupling between carbon nanotubes and silicon waveguides was carried out, which led to the demonstration of the temperature-independent emission from carbon nanotubes in silicon at a wavelength of 1.3 {\mu}m. This represents the first milestone in the development of photonics based on carbon nanotubes on silicon

Inorganic Chemistry in the Mountain Critical Zone : Are the mountain water towers of contemporary society under threat by trace contaminants ?

Potentially harmful trace elements (PHTEs) do not accumulate homogeneously over mountainous area. Generally, highland areas receive more wet deposition, aerosols, and ions than surrounding lowlands ones, mainly due to orographic enhancement. Within mountainous areas, however, the accumulation of PHTEs is much more complex. Direct cloud deposition of contaminants could act as an important pathway of deposition either from a regional low-altitude, cloud level, orographic clouds, or haze whose frequency of occurrence is much higher than surrounding lowlands areas. The accumulation legacy of PHTEs from local human activities should also be considered when investigating PHTE distribution in mountainous areas. Combined with other phenomena, the PHTE accumulation patterns could be highly variable depending on local topography, dominant winds, and vegetation cover, as well as present and past local practices. Despite their remoteness, mountain ecosystems are highly sensitive to PHTEs loadings

Three-dimensional analysis of a tensile test on a propellant with digital volume correlation

International audienceA full three-dimensional study of a tensile test on a sample made of polymerbonded propellant is presented. The analysis combines different tools, namely, X-ray microtomography of an in situ experiment, image acquisition and treatment, 3D volume correlation to measure three-dimensional displacement fields. It allows for global and local strain analyses prior to and after the peak load. By studying the correlation residuals, it is also possible to analyze the damage activity during the experiment

Profilométrie par déphasage en mouvement pour applications industrielles

National audienceLa profilométrie par déphasage est une méthode éprouvée pour reconstruire des surfaces de manière dense et précise. Par contre la scène doit rester immobile pendant l'acquisition d'une séquence de plusieurs images. De plus, il existe des méthodes de stéréo active qui s'affranchissent de la contrainte d'immobilité de la scène mais qui imposent d'autres limitations comme par exemple la continuité de la surface et de la texture ou une résolution de reconstruction considérablement réduite. Nous présentons une nouvelle technique de reconstruction aussi dense et précise que la profilométrie par déphasage et qui permet une translation de la scène pendant l'acquisition de la séquence d'images. Cela la rend intéressante pour des applications industrielles. Nous étudions sa performance à l'aide de simulations et donnons une démonstration sur un exemple réel