École normale supérieure de Cachan

About: École normale supérieure de Cachan is a education organization based out in Cachan, Île-de-France, France. It is known for research contribution in the topics: Decidability & Nonlinear system. The organization has 2717 authors who have published 5585 publications receiving 175925 citations.

Strong exciton–photon coupling at room temperature in microcavities containing two-dimensional layered perovskite compounds

Abstract: We have realized Perot–Fabry microcavities containing a two-dimensional layered perovskite-type semiconductor: (C6H5C2H4–NH3)2PbI4 between a dielectric mirror and a metallic mirror. A strong coupling regime between the perovskite exciton and the confined photon mode has been evidenced at room temperature from angular-resolved reflectivity experiments, anticrossings as large as 190 meV are observed between the excitonic and cavity modes. We have shown that the design of the microcavity can be varied at will, so that the detuning or the Rabi splitting can be precisely chosen. The emission of the polaritonic low energy branch has been observed.

Identification of cation-binding sites on actin that drive polymerization and modulate bending stiffness.

Abstract: The assembly of actin monomers into filaments and networks plays vital roles throughout eukaryotic biology, including intracellular transport, cell motility, cell division, determining cellular shape, and providing cells with mechanical strength. The regulation of actin assembly and modulation of filament mechanical properties are critical for proper actin function. It is well established that physiological salt concentrations promote actin assembly and alter the overall bending mechanics of assembled filaments and networks. However, the molecular origins of these salt-dependent effects, particularly if they involve nonspecific ionic strength effects or specific ion-binding interactions, are unknown. Here, we demonstrate that specific cation binding at two discrete sites situated between adjacent subunits along the long-pitch helix drive actin polymerization and determine the filament bending rigidity. We classify the two sites as “polymerization” and “stiffness” sites based on the effects that mutations at the sites have on salt-dependent filament assembly and bending mechanics, respectively. These results establish the existence and location of the cation-binding sites that confer salt dependence to the assembly and mechanics of actin filaments.

Second-harmonic generation from coupled plasmon modes in a single dimer of gold nanospheres.

Abstract: We show that a dimer made of two gold nanospheres exhibits a remarkable efficiency for second-harmonic generation under femtosecond optical excitation. The detectable nonlinear emission for the given particle size and excitation wavelength arises when the two nanoparticles are as close as possible to contact, as in situ controlled and measured using the tip of an atomic force microscope. The excitation wavelength dependence of the second-harmonic signal supports a coupled plasmon resonance origin with radiation from the dimer gap. This nanometer-size light source might be used for high-resolution near-field optical microscopy.