Contamination Des Laits Importes Au Mali Par La Melamine

Au Mali l’insuffisance de données scientifiques sur la contamination des aliments en général et du lait en particulier par la Mélamine a motivé la conduite de la présente étude.Dans ce travail, nous avions recherchés la Mélamine dans les laits importés au Mali.Un total de 150 échantillons de laits importés, a été récolté dans le District de Bamako.La détermination de la Mélamine a été effectuée par Immuno-affinité/Méthode ELISA. Les résultats des analyses ont montré que 38 échantillons sur les 150 de laits importés étaient contaminés par la Mélamine. Chez les importateurs, 8 échantillons sur 18 des laits importés étaient contaminés, les taux de contamination variaient de 0,03mg/kg à 0,91 mg/kg. Chez les demi-grossistes 19 échantillons sur 66 des laits importés, étaient contaminés par la Mélamine. Les taux de contamination variaient de 0,01 à 1,14mg/kg. Chez les détaillants, 11 échantillons sur 66 des laits importés étaient contaminés avec des taux de contamination qui variaient de 0,01 à 1,00mg/kg. Les taux moyens de contamination des laits pour les importateurs, les demi-grossistes et les détaillants sont respectivement de (0,20 ; 0,26 ; 0,26) mg/kg. Il est a noté que les taux obtenus sont inférieurs à la norme du Codex Alimentarius qui fixe la limite maximale pour le lait et les aliments contenant le lait à 2,5mg/kg

Contamination Des Laits Importes Au Mali Par Les Radionucléides

 Au Mali l’insuffisance de données scientifiques sur la contamination des aliments en général et du lait en particulier par les radionucléides a motivé la conduite de la présente étude.Dans ce travail, nous avions recherchés les radionucléides (134Cs, 137Cs, 90Sr) dans les laits importés au Mali.Un total de 150 échantillons de laits (18 chez les importateurs, 66 chez les vendeurs demi-grossistes, 66 échantillons chez les détaillants) a été récolté dans le District de Bamako.La détermination du 90Sr a été effectuée par le Compteur à gaz proportionnel selon la norme NF EN ISO 13160.La détermination des Césiums (134Cs, 137Cs) a été effectuée par Spectrométrie Gamma selon la norme NF ISO 10703.Les analyses des 150 échantillons des laits importés, n’ont détecté aucune trace des césiums (134Cs, 137Cs) et du Strontium (90Sr). Tous les résultats obtenus sont conformes aux normes du Codex Alimentarius

Low cycle fatigue of 316L stainless steel processed by surface mechanical attrition treatment (SMAT)

International audienceIn this work, the effect of surface mechanical attrition treatment (SMAT) on the cyclic behaviour of a 316L stainless steel under low cycle fatigue (LCF) is investigated. The LCF results are presented in the form of cyclic stress amplitude evolution for both untreated and SMATed samples. In order to better understand the microstructure change due to cyclic loading, electron backscatter diffraction (EBSD) is used to characterize the microstructure of the SMATed samples before and after fatigue tests. A microstructure gradient is highlighted for samples after SMAT from the top surface layer in nanocrystalline grains to the interior region non-affected by impacts. Under LCF loading, new slip systems are activated in the work hardened region, whereas no plastic slip is activated in the nanostructured layer. The residual stresses generated by SMAT are measured using X-ray diffraction (XRD), and their relaxations under cyclic loading are studied by taking into account the microstructure change. The cyclic behaviour of the samples in different material states is interpreted based on these investigations

Modelling matrix damage and fibre-matrix interfacial decohesion in composite laminates via a multi-fibre multi-layer representative volume element (M²RVE)

AbstractA three-dimensional multi-fibre multi-layer micromechanical finite element model was developed for the prediction of mechanical behaviour and damage response of composite laminates. Material response and micro-scale damage mechanism of cross-ply, [0/90]ns, and angle-ply, [±45]ns, glass-fibre/epoxy laminates were captured using multi-scale modelling via computational micromechanics. The framework of the homogenization theory for periodic media was used for the analysis of the proposed ‘multi-fibre multi-layer representative volume element’ (M2RVE). Each layer in M2RVE was represented by a unit cube with multiple randomly distributed, but longitudinally aligned, fibres of equal diameter and with a volume fraction corresponding to that of each lamina (equal in the present case). Periodic boundary conditions were applied to all the faces of the M2RVE. The non-homogeneous stress–strain fields within the M2RVE were related to the average stresses and strains by using Gauss’ theorem in conjunction with the Hill–Mandal strain energy equivalence principle. The global material response predicted by the M2RVE was found to be in good agreement with experimental results for both laminates. The model was used to study effect of matrix friction angle and cohesive strength of the fibre–matrix interface on the global material response. In addition, the M2RVE was also used to predict initiation and propagation of fibre–matrix interfacial decohesion and propagation at every point in the laminae

Electromechanical models of ferroelectric materials

Models of the electromechanical behaviour of ferroelectric materials are reviewed. Starting from the constitutive relationships for piezoelectrics and estimates of the response of piezoelectric composites, the development of models is traced from the macro-scale through to the micro-scale. Derivations of models based on extensions of classical plasticity and crystal plasticity theory are given, following the literature, and example applications of these models are shown. The formation of domain patterns is discussed and minimum energy methods based on the concept of compatibility are used to derive typical domain patterns for tetragonal and rhombohedral ferroelectrics. Methods for modelling the evolution of domain patterns are described. Finally the outlook for future directions in modelling of ferroelectrics is discussed

Conceptual design of BabyIAXO, the intermediate stage towards the International Axion Observatory

International audienceThis article describes BabyIAXO, an intermediate experimental stage of the International Axion Observatory (IAXO), proposed to be sited at DESY. IAXO is a large-scale axion helioscope that will look for axions and axion-like particles (ALPs), produced in the Sun, with unprecedented sensitivity. BabyIAXO is conceived to test all IAXO subsystems (magnet, optics and detectors) at a relevant scale for the final system and thus serve as prototype for IAXO, but at the same time as a fully-fledged helioscope with relevant physics reach itself, and with potential for discovery. The BabyIAXO magnet will feature two 10 m long, 70 cm diameter bores, and will host two detection lines (optics and detector) of dimensions similar to the final ones foreseen for IAXO. BabyIAXO will detect or reject solar axions or ALPs with axion-photon couplings down to g$_{aγ}$ ∼ 1.5 × 10$^{−11}$ GeV$^{−1}$, and masses up to m$_{a}$ ∼ 0.25 eV. BabyIAXO will offer additional opportunities for axion research in view of IAXO, like the development of precision x-ray detectors to identify particular spectral features in the solar axion spectrum, and the implementation of radiofrequency-cavity-based axion dark matter setups.[graphic not available: see fulltext