Running characteristics of rubber coating bearing

International audienc

Finite element dependence of stress evaluationfor human trabecular bone

International audienceNumerical simulation using finite element models (FEM) has become more and moresuitable to estimate the mechanical properties of trabecular bone. The size and kind ofelements involved in the models, however, may influence the results. The purpose of thisstudy is to analyze the influence of hexahedral elements formulation on the evaluation ofmechanical stress applied to trabeculae bone during a compression test simulation.Trabecular bone cores were extracted from 18 L2 vertebrae (12 women and 6 men, meanage: 76711, BV/TV¼7.571.9%). Samples were micro-CT scanned at 20 mm isotropic voxelsize. Micro-CT images have been sub-sampled (20, 40 and 80 mm) to create 5.6mm cubicFEM. For each sample, a compression test FEM has been created, using either 8-nodeslinear hexahedral elements with full or reduced integration or 20-nodes quadratichexahedral elements fully integrated, resulting in nine models per samples. Bonemechanical properties have been assumed isotropic, homogenous and to follow a linearelastic behavior law (Young modulus: 8 GPa, Poisson ratio: 0.3).Despite micro-architecture modifications (loss of connectivity, trabeculae thickening)due to voxel size increase, apparent mechanical properties calculated with low resolutionmodels are significantly correlated with high resolution results, no matter the elementformulation. However, stress distributions are more sensitive to both resolution andelement formulation modifications. With linear elements, increasing voxel size leads toan alteration of stress concentration areas due to stiffening errors. On the opposite, the useof reduced integration induces severe smoothing and underestimation of stress fieldsresulting in stress raisers loss. Notwithstanding their high computational cost, quadraticelements are most appropriate for stress prediction in low resolution trabecular bone FEM.These observations are dependent on trabecular bone micro-architecture, and are moresignificant for low density sample displaying low trabecular thickness.In conclusion, we found that element formulation is almost important as element sizewhen evaluating trabecular bone mechanical behavior at trabeculae scale. Therefore,element type should be chosen carefully when evaluating trabecular bone behaviorusing FEM

Couplage de l'IRM Haute Résolution à la spectroscopie optique au moyen d'une sonde endoluminale bimodale pour le diagnostic précoce du cancer colorectal: Développement instrumental, études sur fantôme et premiers résultats in-vivo sur le lapin

National audienc

Optimization of maturation of Radio-cephalic Arteriovenous Fistula using a Model Relating Energy Loss Rate and Vascular Geometric Parameters

International audienceThe main reason for the early failure of radio-cephalic arteriovenous fistula (RCAVF) is non-maturity, which means that the blood flow rate in the fistula cannot increase to the expected value for dialysis. From a mechanical perspective, the vascular resistance at the artificially designed anastomosis causes an energy loss that affects blood flow rate growth and leads to early failure. This research studied how to maximize the RCA VF maturity and primary patency by controlling the energy loss rate. We theoretically analyzed and derived a model that evaluates the energy loss rate Eavf in RCAVF as a function of its blood vessel geometric parameters (GPs) for given flow rates. There was an aggregate of five controllable GPs in RCAVF: radial artery diameter (Dra), cephalic vein diameter (Dcv), blood vessel distance between artery and vein (h), anastomotic diameter (Da), and anastomotic angle (). Through this analysis, it was found that Eavf was inversely proportional to Dra, Dcv, Da, and , whereas proportional to h. Therefore, we recommended surgeons choose the vessels with large diameters , close distance, and increase the diameter and angle of the anastomosis to decrease the early failure of RCAVF. Simultaneously, we could explain the results of many clinical empiricisms with our formula. We found that increasing Dcv and were more significant in reducing Eavf than increasing Dra and Da. Based on our model, we could define two critical energy loss rates (CELa, CELb) to help surgeons evaluate the blood vessels and choose the ideal range of . Help them design the preoperative RCAVF plan for each patient to increase the maturity and the primary patency of RCAVF

The Mediterranean region under climate change

This book has been published by Allenvi (French National Alliance for Environmental Research) to coincide with the 22nd Conference of Parties to the United Nations Framework Convention on Climate Change (COP22) in Marrakesh. It is the outcome of work by academic researchers on both sides of the Mediterranean and provides a remarkable scientific review of the mechanisms of climate change and its impacts on the environment, the economy, health and Mediterranean societies. It will also be valuable in developing responses that draw on “scientific evidence” to address the issues of adaptation, resource conservation, solutions and risk prevention. Reflecting the full complexity of the Mediterranean environment, the book is a major scientific contribution to the climate issue, where various scientific considerations converge to break down the boundaries between disciplines