Coherent acoustic vibration of metal nanoshells

Using time-resolved pump-probe spectroscopy we have performed the first investigation of the vibrational modes of gold nanoshells. The fundamental isotropic mode launched by a femtosecond pump pulse manifests itself in a pronounced time-domain modulation of the differential transmission probed at the frequency of nanoshell surface plasmon resonance. The modulation amplitude is significantly stronger and the period is longer than in a gold nanoparticle of the same overall size, in agreement with theoretical calculations. This distinct acoustical signature of nanoshells provides a new and efficient method for identifying these versatile nanostructures and for studying their mechanical and structural properties.Comment: 5 pages, 3 figure

Phase transitions between single- and double-layered smectic structures in binary mixtures of cyano-mesogens

Binary mixtures of mesogens which exhibit respectively single-layered (A 1), double layered (A2) and partially double layered (A d) smectic phases show abrupt A2-A1 or A2-Ad transitions as a function of concentration. Double layered structures imply the formation of dimerized entities and the possibility of dimerization is discussed in terms of the amphiphilic nature of the molecules in the binary mixture (symmetrical and dissymmetrical polar mesogens). The results are analysed with respect to the thermal stability of the A 2 phase when defects are introduced in the polar interface by adding non-polar symmetrical mesogens.Des mélanges binaires de mésogènes présentant respectivement des phases smectiques monocouches (A1), bicouches (A2) et partiellement bicouches (Ad) permettent de mettre en évidence en fonction de la concentration des transitions brusques A2-A1 ou A 2-Ad. La structure bicouche implique un processus de dimérisation des entités mésogènes qui est discuté en fonction du caractère amphipathique des molécules (molécules polaires symétriques et dissymétriques). La stabilité de la phase bicouche est également analysée lorsque l'on introduit une perturbation au niveau de l'interface polaire par adjonction de molécules non polaires

Barometric pumping of a fractured porous medium

International audienceBarometric pumping plays a crucial role in the release of trace gases from fractured porous media to the atmosphere, and it requires a rigorous and complete modeling in order to go beyond the approximate schemes available in the literature. Therefore, a coupled set of convection and convection-diffusion equations for a slightly compressible fluid in unsteady conditions should be solved. The numerical methodology is presented, and it is applied to conditions close to the ones of the Roselend Natural Laboratory (France). The precision of the code is assessed and the mechanism of barometric pumping is explained. The usual schematization by simple vertical fractures is shown to be only qualitative. Finally, barometric pumping is shown to be efficient in a narrow range of parameter values; its efficiency is a decreasing function of the matrix porosity and of the fracture density

Quotient Categories and Phases

We study properties of a category after quotienting out a suitable chosen group of isomorphisms on each object. Coproducts in the original category are described in its quotient by our new weaker notion of a 'phased coproduct'. We examine these and show that any suitable category with them arises as such a quotient of a category with coproducts. Motivation comes from projective geometry, and also quantum theory where they describe superpositions in the category of Hilbert spaces and continuous linear maps up to global phase. The quotients we consider also generalise those induced by categorical isotropy in the sense of Funk et al.Comment: Fixed typos, added discussion of isotropy, expanded introductio

Structure bicouche des mésophases SA et SB du 4-cyanobutoxybenzylidene-4-octylaniline

In order to analyze the mesomorphic behavior of molecules containing a highly dipolar endgroup mechanically decoupled from the rigid moiety, the 4-cyanobutoxybenzylidene-4-octylaniline was synthesized. The first observations made (polarizing microscopy, differential scanning calorimetry, and X-ray diffraction) suggest the présence of two smectic mesophases, of B and A type respectively. The structure of these would correspond to double layers : in each sub-layer, the molecular arrangement would be of the ferro-type, and the stacking of the sub-layers would be of the antiferro-type. However, it is impossible to definitely specify the spatial extension of the order described, on the basis of the experimental data obtained so far.Pour analyser le comportement mésomorphe de molécules contenant un groupe fortement dipolaire découplé mécaniquement du tronçon rigide, nous avons synthétisé le 4-cyanobutoxybenzylidène-4-octylaniline. Les premières observations (microscope polarisant, enthalpimétrie différentielle, diffraction des rayons X) indiquent la présence de deux mésophases smectiques, l'une de type B et l'autre de type A. Celles-ci auraient une structure bicouche : dans chaque sous-couche, les molécules seraient arrangées de manière ferro- et les sous-couches, elles-mêmes, seraient superposées de manière antiferro- . Cependant, les données expérimentales obtenues ne permettent pas encore de se prononcer définitivement sur l'étendue spatiale de ce type d'ordre

Metal-directed columnar phase formation in tetrahedral zinc(II) and manganese(II) metallomesogens

New, non-discoid M(II) complexes [MCl2(L)] {M = Mn, Zn; L = 2,6-diformyl-4- methylphenolbis[3’,4’,5’-tris(hexadecyloxy)phenylimine]} have been prepared and shown to exhibit columnar mesophases, the nature of which was found to be metal-dependent. As analysed by DSC and small-angle X-ray diffraction experiments, the complex [ZnCl2(L)] exhibits a single mesophase with rectangular symmetry (Colr) between 46 and 145 °C, whereas the Mn(II) analogue [MnCl2(L)] displays a purely hexagonal mesophase (Colh) phase between 55 and 285 °C. By combining these results with those obtained from dilatometry, a model for the molecular organisation within the columnar mesophases is proposed. The single-crystal X-ray structure of the related complex [Zn(NO3)(L’)2]NO3.3MeOH {L’ = 2,6-diformyl-4-methylphenolbis[3’,4’,5’-tris(methoxy)phenylimine]} has been determined and supports the proposed mode of binding of the ligand to the metal via only one imine and a phenol

Estime de soi et troubles psychiatriques à l'adolescence.

peer reviewedSelf-esteem refers to the individual's perception of his and her competence, value, and worthiness of respect. The early years are critical in forming a base of self-esteem; it develops as a result of positive or negative experiences during childhood. Self-esteem has been identified as an important parameter of adolescent development. This suggest the importance of considering self-esteem in adolescence. This study examined the different data on self-esteem of well adolescents and psychiatric adolescents. The results are discusse

Arrays of Nano-Electromechanical Biosensors Functionalized by Microcontact Printing

The biofunctionalization of nanoelectromechanical structures is critical for the development of new classes of biosensors displaying improved performances and higher-level of integration. We propose a modified microcontact printing method for the functionalization and passivation of large arrays of nanocantilevers in a single, self-aligned step. Using fluorescence microscopy and resonant frequency measurements, we demonstrate (1) the bioactivity and the anti-fouling property of deposited antibodies and BSA molecules and (2) the preservation of the nanostructures' mechanical integrity.Comment: 20 pages, 5 figure

SoLid : Search for Oscillations with Lithium-6 Detector at the SCK-CEN BR2 reactor

Sterile neutrinos have been considered as a possible explanation for the recent reactor and Gallium anomalies arising from reanalysis of reactor flux and calibration data of previous neutrino experiments. A way to test this hypothesis is to look for distortions of the anti-neutrino energy caused by oscillation from active to sterile neutrino at close stand-off (similar to 6-8m) of a compact reactor core. Due to the low rate of anti-neutrino interactions the main challenge in such measurement is to control the high level of gamma rays and neutron background. The SoLid experiment is a proposal to search for active-to-sterile anti-neutrino oscillation at very short baseline of the SCK center dot CEN BR2 research reactor. This experiment uses a novel approach to detect anti-neutrino with a highly segmented detector based on Lithium-6. With the combination of high granularity, high neutron-gamma discrimination using 6LiF:ZnS(Ag) and precise localization of the Inverse Beta Decay products, a better experimental sensitivity can be achieved compared to other state-of-the-art technology. This compact system requires minimum passive shielding allowing for very close stand off to the reactor. The experimental set up of the SoLid experiment and the BR2 reactor will be presented. The new principle of neutrino detection and the detector design with expected performance will be described. The expected sensitivity to new oscillations of the SoLid detector as well as the first measurements made with the 8 kg prototype detector deployed at the BR2 reactor in 2013-2014 will be reported

Energy Linearity and Resolution of the ATLAS Electromagnetic Barrel Calorimeter in an Electron Test-Beam

A module of the ATLAS electromagnetic barrel liquid argon calorimeter was exposed to the CERN electron test-beam at the H8 beam line upgraded for precision momentum measurement. The available energies of the electron beam ranged from 10 to 245 GeV. The electron beam impinged at one point corresponding to a pseudo-rapidity of eta=0.687 and an azimuthal angle of phi=0.28 in the ATLAS coordinate system. A detailed study of several effects biasing the electron energy measurement allowed an energy reconstruction procedure to be developed that ensures a good linearity and a good resolution. Use is made of detailed Monte Carlo simulations based on Geant which describe the longitudinal and transverse shower profiles as well as the energy distributions. For electron energies between 15 GeV and 180 GeV the deviation of the measured incident electron energy over the beam energy is within 0.1%. The systematic uncertainty of the measurement is about 0.1% at low energies and negligible at high energies. The energy resolution is found to be about 10% sqrt(E) for the sampling term and about 0.2% for the local constant term