Response of periodic structures due to moving loadsRéponse de structures périodiques à des charges mobiles

A method is proposed to calculate the response of periodic structures subjected to moving loads. It is based on the Floquet decomposition which allows the restriction of the analysis for the overall system to a generic cell. The main contribution of the approach presented hereafter is that the response is directly deduced from transfer functions in the space-wavenumber domain calculated in an unbounded generic cell. Moreover, the equivalence of this new solution with the response of invariant structures obtained using Fourier transforms is established. To cite this article: H. Chebli et al., C. R. Mecanique 334 (2006).     

Relaxation in Unsaturated Polyester Resins Studied by Thermally Stimulated Depolarization Currents

Investigations involving thermally stimulated depolarization currents were performed on unsaturated polyester resins cured with styrene. Samples containing different amounts of Co octoate promoter were studied. The complex spectra revealed the classical β and the α dipolar relaxations. The peak characterizing the α dipolar relaxation was overlapped by a ρ peak of appreciable magnitude, due to the presence of impurities in the promoter solution [1]. However, study of the elementary spectra as concerns both α and β peaks for various samples containing different amounts of Co octoate demonstrated that the relaxation kinetics, and particularly the values of the apparent activation energies, do not depend on these impurities. This revised version was published online in August 2006 with corrections to the Cover Date.     

Spectral functions of singular differential operators with matricial coefficients

We study the asymptotic behavior of the Harish-Chandra function associated to a singular second order differential operator with matricial coefficients. The study is based on a detailed analysis of the asymptotic behavior of some eigenvectors of the operator from which results on the asymptotic behavior of the spectral function and the scattering matrix are derived.     

New Surfactants with Sugar-Based Polar Heads Derived from Bile Acids: The N-Ursocholyl-d-glucosamine and N-Dehydrocholyl-d-glucosamine

Abstract

A simple route to new surfactants with a sugar-based polar head group coupled to a steroidal hydrophobic group is described. These compounds, N-ursocholyl-d-glucosamine and N-dehydrocholyl-d-glucosamine, were obtained in a three stage process by acylation of d-glucosamine with N-acylthiazolidine-2-thiones derived from ursocholic and dehydrocholic acids.     

Amperometric Determination of Hydrogen Peroxide and its Mathematical Simulation for Horseradish Peroxidase Immobilized on a Sonogel Carbon Electrode

A mathematical model of a horseradish peroxidase biosensor was applied to simulate the amperometric response for the detection of hydrogen peroxide. The development of the mathematical model was based on the Michaelis–Menten equation and Fick’s Second Law. The theoretical study is based on the determination of physico-chemical and geometric parameters of a horseradish peroxidase biosensor as well as the kinetic parameters of reaction mechanism such as diffusion coefficients of hydrogen peroxide, the thickness of enzymatic layer, and the Michaelis–Menten kinetic constant. The theoretical analysis provides an accurate estimate of parameters affecting the biosensor performance such as the diffusion coefficient of hydrogen peroxide in the biomembrane that was estimated to be 56?×?10^?12 m²/s. The thickness of diffusion layer was estimated to be 80–100?µm and the biomembrane 7.5?µm. The experimental and numerical values of kinetic parameters were 0.92 and 0.98?µM for the Michaelis–Menten constants and 0.010 and 0.012?µM/s for the catalytic activity rates. The model was validated for hydrogen peroxide detection and exhibited a good agreement with the experimental measurements.     

Structural,magnetic and thermal characterization of Fe50Se50 powders obtained by mechanical alloying

Journal of Thermal Analysis and Calorimetry - In this paper, Fe50Se50 alloy powders were synthesized from pure elemental powder by mechanical allowing. The structure, microstructure, morphology,...     

Metallic complexes from 2-furaldehyde semicarbazone and 5-methyl-(2-furaldehyde) semicarbazone

The synthesis and characterization of CoII, NiII, CuII and CdII complexes with 2-furfuralsemicarbazone (FSC) and 5-methyl 2-furfuralsemicarbazone (MFSC) are reported. These ligands lead to the complexes: [ML2X2] or [MLX2] (L = FSC or MFSC) whose structures were determined using elemental analysis, molar conductivity, magnetic measurements, i.r., far i.r. and electronic spectra as well as by n.m.r. FSC and MFSC act as bidentate ligands in most of the CoII, NiII, CuII and CdII complexes. MFSC is a monodentate ligand in [NiBr2(MFSC)4].