Simultaneous achievement of polarization attraction and Raman amplification in isotropic optical fibers

We present a theoretical analysis and experimental demonstration of the combined effects of polarization attraction and Raman amplification in isotropic optical fibers. The polarization attraction process is based on four-wave mixing interaction of counterpropagating pump and signal waves. We show that this technique can be used for the design of a highly efficient nonlinear system that permits the simultaneous processing of repolarization and amplification of light waves in dielectric media.     

Contact dynamics in a gently vibrated granular pile

We use multispeckle diffusive wave spectroscopy to probe the micron-scale dynamics of a water-saturated granular pile submitted to discrete gentle taps. The typical time scale between plastic events is found to increase dramatically with the number of applied taps. Furthermore, this microscopic dynamics weakly depends on the solid fraction of the sample. This process is largely analogous to the aging phenomenon observed in thermal glassy systems. We propose a heuristic model where this slowing-down mechanism is associated with a slow evolution of the distribution of the contact forces between particles. This model accounts for the main features of the observed dynamics.     

Cytotoxicity and inflammation in human alveolar epithelial cells following exposure to occupational levels of gold and silver nanoparticles

This study explores the viability of rare earth-doped zirconia nanophosphors as probable candidates for white light emission. Undoped ZrO₂ and single- and double-doped ZrO₂:M (where M?=?Tb³⁺ and Eu³⁺) nanophosphors have been synthesized using a simple sonochemical process. The products were characterized using X-ray diffraction, scanning electron microscopy (SEM), transmission electron microscopy (TEM), high-resolution transmission electron microscopy (HRTEM), energy dispersive X-ray spectroscopy (EDS), and photoluminescence spectrophotometry. The SEM micrographs show that resultant nanoparticles have dendritic shape. TEM and HRTEM studies showed that the size of the majority of the nanoparticles were around 28?±?5?nm. Characteristic blue and green emission from Tb³⁺ ions and red from Eu³⁺ dopant ions were observed. The CIE coordinates of the double-doped ZrO₂:Tb³⁺ (1.2?%):Eu³⁺ (0.8?%) nanophosphor lie in the white light region of the chromaticity diagram and show promise as good phosphor materials for new lighting devices.     

Etude par RMN de la relaxation spin réseau d'un syst`eme AB de noyaux en interconversion lente

Nuclear Overhauser effects allow us to determine all transition probabilities in a two-spin AB system, using a triple resonance apparatus we have constructed. Theoretical and experimental studies of the relaxation in the special case where the nuclei belong to a molecule interconverting slowly between two different conformations have been made, and the exchange ratio has been deduced.     

Mass Spectrometry of Some Benzylidene Imidazolidinediones and Thiazolidinediones. II- chlorobenzyl imidazolidinedione and Fluoro or Chlorobenzyl Thiazolidinedione Compounds

In the present investigation, a study of the electron impact mass spectrometry data is reported for seven compounds of a series of some 3-(4-chlorobenzyl)-5-benzylidene-imidazolidine-2, 4-diones and 3-(4-fluoro or chlorobenzyl)-5-benzylidene-thiazolidine-2, 4-diones previously synthesized.     

Spaces of Tilings, Finite Telescopic Approximations and Gap-Labeling

The continuous Hull of a repetitive tiling T in ℝ^d with the Finite Pattern Condition (FPC) inherits a minimal ℝ^d-lamination structure with flat leaves and a transversal which is a Cantor set. This class of tiling includes the Penrose & the Amman Benkker ones in 2D, as well as the icosahedral tilings in 3D. We show that the continuous Hull, with its canonical ℝ^d-action, can be seen as the projective limit of a suitable sequence of branched, oriented and flat compact d-manifolds. As a consequence, the longitudinal cohomology and the K-theory of the corresponding C*-algebra are obtained as direct limits of cohomology and K-theory of ordinary manifolds. Moreover, the space of invariant finite positive measures can be identified with a cone in the d^th homology group canonically associated with the orientation of ℝ^d. At last, the gap labeling theorem holds: given an invariant ergodic probability measure μ on the Hull the corresponding Integrated Density of States (IDS) of any selfadjoint operators affiliated to takes on values on spectral gaps in the ℤ-module generated by the occurrence probabilities of finite patches in the tiling. Accepted in Revised Form: 7 May 2005     

X-ray absorption study of Cu,Zn SOD under high pressure

Abstract

We have investigated Cu, Zn Superoxide Dismutase (Cu, Zn SOD) metal sites at high pressure using X-ray absorption. XAS (X-ray Absorption Spectroscopy) gives information on local structure and it is particularly suited to metal site investigation. To the best of our knowledge, this is the first time that protein conformational states have been investigated using the high pressure XAS technique. Cu, Zn SOD catalyses the dismutation of toxic oxygen radicals produced in cells; this reaction occurs at the copper metal site. Structural changes around the copper, induced by pressure, can be directly related to protein substates. Their characterisation is thus important in the understanding of protein activity.

The high-pressure device was a Paris-Edinburgh large volume cell.

Experiments were performed on lyophilised Cu, Zn SOD between 0 and 48 kbar at the copper and zinc K-edges. The two metal local atomic environments have a different behaviour as pressure increases: copper exhibits a more flexible environment; on the contrary, zinc shows small structural modifications. We have identified a state, formed between 3 and 8 kbar, which is stable up to 48 kbar.     

The modelling of desk screens by a combined BEM – Source image approach

An original BEM approach is proposed to study the efficiency of desk screens in open plan offices. For large offices the volume geometry can be approximated by two horizontal planes – for floor and ceiling – and the source image approach is used to compute an approximated room Green function. When used in combination with the BEM approach, this allows reducing the discretised boundary to the desks only. The computation of the room Green functions is based on the modelling of the floor and ceiling response by means of the image source approach. The proposed approach is validated both numerically and experimentally. Very significant reductions of computation times have been obtained. The approach is used in an attempt to design efficient desk screens.