Heat and moisture diffusion in spruce and wood panels computed from 3-D morphologies using the Lattice Boltzmann method

International audienceIn this paper, the Lattice Boltzmann method is used to simulate heat and mass diffusion in bio-based building materials. The numerical method is presented and the methodology developed to reduce the calculation time is described. The 3-D morphologies of spruce and wood fibers are obtained using synchrotron X-ray micro-to-mography. Equivalent macroscopic properties (heat conductivity and mass diffusivity) are therefore determined from the real micro-structure of the materials. The results reveal the anisotropy of the studied materials. The computed equivalent heat conductivity varies from − − 0.036 W m K 1 1 to − − 0.52 W m K 1 1 and the computed di-mensionless mass diffusivity varies from 0.0088 to 0.78 depending on the materials and on the diffusion directions. Using these results, morphology families are identified and simple expressions are proposed to predict the equivalent properties as a function of phase properties and solid fraction

Changes in Cognitive Function Over 96 weeks in Naïve Patients Randomised to Darunavir-ritonavir plus either Raltegravir or Tenofovir-Emtricitabine: a substudy of the NEAT001/ANRS143 trial

BACKGROUND: Improvements in cognitive function are described after initiation of combination antiretroviral therapy (cART), with sparse data on differences between cART strategies. METHODS: We assessed changes in cognition, over 96 weeks, in therapy naïve HIV-positive adults randomised to darunavir/ritonavir (800/100mg once daily) with either raltegravir (400mg twice daily, Arm1) or tenofovir/emtricitabine (245/200mg once daily, Arm2). Seven cognitive tests were administered at baseline and week 96. Changes from baseline in individual cognitive test scores and composite score (NPZ) were assessed. Comparisons between treatment arms were by intention-to-treat and associations with immunological and virological parameters by regression models. FINDINGS: Of 343 subjects enrolled, 208 completed the week 96 cognitive assessment. Baseline median (IQR) CD4+ count and plasma HIV RNA was 348(282-398) cells/uL and 4.7(4.2-5.1) log10 copies/mL, respectively. At week 96, numbers with plasma HIV RNA undetectable and remaining on randomised cART were 85(92%) and 110(96%), and 84(90%) and 107(93%) in Arm1 and Arm2, respectively. Overall, performance significantly improved by week 96 in 5 of 7 individual tests and in NPZ. Mean change in NPZ was 0.28 versus 0.21 for Arm1 and 2, respectively (p=0.37). No statistically significant differences between study treatment arms were observed in individual cognitive domains apart from attention (greater improvement in Arm1, p=0.0499). At week 96, NPZ-score increase was associated with increase in CD4+ (p=0.001) but not HIV RNA area-under-curve (p=0.60). INTERPRETATION: Subsequent to the initiation of cART, immunological recovery rather than type of antiretroviral therapy is the major driver of changes in cognitive function

IMAGING TECHNIQUES FOR UNDERSTANDING PHYSICO-MECHANICAL MODIFICATIONS OF LIGNOCELLULOSIC BIOMASS DUE TO HYDROTHERMAL PRETREATMENT

International audienceSteam explosion is a promising lignocellulosic biomass pretreatment for improving carbohydrates accessibility to enzymatic hydrolysis. The mechanical properties degradation during hydrothermal step is a key parameter for the process efficiency. In this work, two imaging techniques were used to assess changes in ultrastructural characteristics of poplar cell wall caused by hydrothermal pretreatment. Firstly, anatomical changes on the cell wall structure were observed by X-ray nano-tomography. Secondly, chemical changes in the different layers of the cell wall before and after pretreatment were observed by two-dimensional chemical mapping through Raman micro-spectrometry. The comparison between pretreated and raw biomass revealed shrinkage and thinning of cell wall as well as sub-parietal chemical changes

Fluage du bois "vert" à haute température (120 degrés C) : expérimentation et modélisation à l'aide d'éléments de Kelvin thermo-activés

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Mesures de coefficients de retrait d'un groupe de cellules de bois par imagerie à rayons X

International audienceAn experimental device has been developed to perform numerical X-ray images by direct projection of samples made of a group of wood cells. This device consists of a micro-focus X-rays source, a scintillator and a cooled CCD camera. The dimensions are adapted to anatomical structure of wood. A speci®c climatic chamber has been conceived to control the moisture content of the sample. Experiments consist in imaging the sample at different humidity conditions. After pre-processing, a program compares two images and allows the bidimensional strain field to be determined. The shrinkage coef®cients obtained by this protocol are representative of the unrestrained shrinkage properties of the wood sample