École Polytechnique

About: École Polytechnique is a education organization based out in Palaiseau, France. It is known for research contribution in the topics: Laser & Plasma. The organization has 18995 authors who have published 39265 publications receiving 1225163 citations. The organization is also known as: Ecole Polytechnique & Polytechnique.

Flow pattern in the scour hole around a cylinder

Abstract: Local scour around a bridge pier (cylinder) is a problem of much concern to hydraulic engineers. This is a complex phenomenon resulting from the interaction of the three-dimensional turbulent flow field around the cylinder and the mobile channel bed (see Fig. 1). In the vicinity of the cylinder, scouring is the consequence. In this paper, the three-dimensional flow held in an established (equilibrium) scour hole is experimentally investigated. An acoustic-Doppler velocityprofiler (ADVP) was used to measure instantaneously the three components of the velocities in the vertical symmetry (stagnation) plane of the flow before and after the cylinder. The vorticity of the flow field was calculated. Results of the study show, that a vortex-system is established in the front and a trailing wake-vortex system of strong turbulence is formed in the rear of the cylinder.

Functionalized fluorescent oxide nanoparticles: Artificial toxins for sodium channel targeting and imaging at the single-molecule level

Abstract: Lanthanide ion-doped oxide nanoparticles were functionalized for use as fluorescent biological labels. These nanoparticles are synthesized directly in water, which facilitates their functionalization, and are remarkably photostable without emission intermittency. Nanoparticles functionalized with guanidinium groups act as artificial toxins and specifically target sodium channels. They are individually detectable in live cardiac myocytes, revealing a heterogeneous distribution of sodium channels. Functionalized oxide nanoparticles appear to be a novel tool that is particularly attractive for long-term single-molecule tracking.

Quantitative Measurement of Transmission, Reflection, and Diffraction of Two-Dimensional Photonic Band Gap Structures at Near-Infrared Wavelengths

Abstract: We present quantitative measurements of the interaction between a guided optical wave and a two-dimensional photonic crystal using spontaneous emission of the material as an internal point source. This is the first analysis at near-infrared wavelengths where transmission, reflection, and inplane diffraction are quantified at the same time. Low transmission coincides with high reflection or in-plane diffraction, indicating that the light remains guided upon interaction. Also, good qualitative agreement is found with a two-dimensional simulation based on the transfer matrix method. [S0031-9007(97)04591-2]