17 research outputs found
An autosomal dominant major gene confers predisposition to pulmonary tuberculosis in adults
The molecular basis of genetic predisposition to pulmonary tuberculosis in adults remains largely elusive. Few candidate genes have consistently been implicated in tuberculosis susceptibility, and no conclusive linkage was found in two previous genome-wide screens. We report here a genome-wide linkage study in a total sample of 96 Moroccan multiplex families, including 227 siblings with microbiologically and radiologically proven pulmonary tuberculosis. A genome-wide scan conducted in half the sample (48 families) identified five regions providing suggestive evidence (logarithm of the odds [LOD] score >1.17; P < 0.01) for linkage. These regions were then fine-mapped in the total sample of 96 families. A single region of chromosome 8q12-q13 was significantly linked to tuberculosis (LOD score = 3.49; P = 3 Ă 10â5), indicating the presence of a major tuberculosis susceptibility gene. Linkage was stronger (LOD score = 3.94; P = 10â5) in the subsample of 39 families in which one parent was also affected by tuberculosis, whereas it was much lower (LOD score = 0.79) in the 57 remaining families without affected parents, supporting a dominant mode of inheritance of the major susceptibility locus. These results provide direct molecular evidence that human pulmonary tuberculosis has a strong genetic basis, and indicate that the genetic component involves at least one major locus with a dominant susceptibility allele
Ătude de l'absorption des gaz acides dans des solvants mixtes : dĂ©veloppement d'une approche expĂ©rimentale originale et modĂ©lisation des donnĂ©es par une Ă©quation d'Ă©tat d'Ă©lectrolytes
The aim of this study is the characterisation of VLE and chemical equilibria for the systems CO2/Diethanolamine-(DEA)/H2O/MeOH and CO2/Diethanolamine-(DEA)/H2O/PEG400. The effect of physical solvent composition on CO2 absorption has been studied using four compositions (from 0% to 30wt% of alcohol with a fixed composition-30%- of DEA), the measurement being made at T=298.15K and at various CO2 loading (0 to 0.9). The experimental measures concerned a both solubility data and liquid phase analysis was obtained. The effect of MeOH composition has been studied using the original experimental device developed previously (Sidi-Boumedine, 2003). For the system with PEG 400, a new experimental device excluding the pressure limitation of the precedent experimental device was developed. The original data base obtained, including the new solubility data and the liquid phase composition, allows the modelling of the system CO2/DEA/H2O/MeOH using an electrolyte equation of state (FĂŒrst, 1993) representing the equilibrium properties of the system and the liquid phase speciation.Le but du prĂ©sent travail est la caractĂ©risation des Ă©quilibres chimiques et des ELV pour les systĂšmes CO2/Diethanolamine(DEA)/H2O/MeOH et CO2 /Diethanolamine (DEA)/H2O/ PEG400. L'effet de composition du solvant physique sur l'absorption du CO2 a Ă©tĂ© Ă©tudiĂ© en utilisant quatre compositions (de 0% Ă 30% en masse d'alcool avec une composition fixe - 30% - de DEA), les mesures Ă©tant rĂ©alisĂ©es Ă une tempĂ©rature de 298,15K et Ă divers taux de charge en CO2 (de 0 Ă 0,9). Les mesures expĂ©rimentales rĂ©alisĂ©es concernaient Ă la fois des donnĂ©es de solubilitĂ© et des donnĂ©e de spĂ©ciation. Ainsi, L'effet de composition de MeOH a Ă©tĂ© Ă©tudiĂ© en utilisant le dispositif expĂ©rimental original dĂ©jĂ utilisĂ© pour l'analyse des systĂšmes Eau-DEA-CO2 (Sidi-Boumedine, 2003). Pour le systĂšme avec PEG 400, un nouvel dispositif expĂ©rimental permettant d'Ă©carter la limitation de pression du prĂ©cĂ©dent dispositif a Ă©tĂ© dĂ©veloppĂ©. La base de donnĂ©es originale obtenue comprenant des nouvelles donnĂ©es de solubilitĂ© et de composition de la phase liquide a permis la modĂ©lisation du systĂšme CO2/DEA/H2O/CH3OH en utilisant une Ă©quation d'Ă©tat d'Ă©lectrolyte dĂ©veloppĂ©e au laboratoire (FĂŒrst, 1993) reprĂ©sentant ainsi les propriĂ©tĂ©s d'Ă©quilibre du systĂšme que la spĂ©ciation en phase liquide
Effect of methanol addition on waterâCO2âdiethanolamine system: Influence on CO2 solubility and on liquid phase speciation
International audienceThe aim of this study is the characterisation of VLE and chemical equilibria for the system CO2/diethanolamine (DEA)/H2O/methanol. The effect of MeOH composition has been studied using four compositions (from 0 to 30wt% of methanol with a fixed composition (30 wt%) of DEA), the measurement being made at T=298.15 K and at various CO2 loadings (from 0.2 to 0.8). An original experimental device was used. This device combines a FT-IR spectroscopy analysis of the liquid phase with a VLE measurement cell.The data base obtained, including the new solubility data and the liquid phase composition, allows the modelling of the system CO2/DEA/H2O/methanol using an electrolyte equation of state [Furst, W., Renon, H., 1993, Representation of excess properties of electrolyte solutions using a new equation of state, AIChE J, 39(2): 335-343] representing the equilibrium properties of the system and the liquid phase speciation. (C) 2008 The Institution of Chemical Engineers
Influence of dissolved oxygen on the bioleaching efficiency under oxygen enriched atmosphere
International audienceThe use of oxygen enriched air is a common practice in high-temperature bioleaching tests (> 70°C) to overcome oxygen solubility limitation and reduced the energy costs of the process. Air is usually preferred in medium and low-temperature operations mainly for technical and economic constraints. Nevertheless, under high-sulfide loading conditions - high-grade metal sulfide concentrates and high solids concentration - the microbial and chemical demand for oxygen is significantly increased during the bioleaching process. If not satisfied, this high oxygen demand might limit the oxidation efficiency. Therefore it requires the injection of large amounts of air. Sparging with oxygen enriched gas instead of air may offer an interesting alternative process option to improve gas transfer in the bioleaching reactor and to provide an adequate oxygen supply in order to satisfy the oxygen demand. It might be useful to develop innovative alternative to the classical stirred tank reactor (STR) technology. However, the use of such conditions can lead to much higher dissolved oxygen (DO) concentrations than those encountered with air. Very few papers have been devoted to the study of the optimal range of DO concentrations for bioleaching processes. Most of them reported an inhibitory effect of DO concentrations above 5 ppm. The purpose of this study was to investigate the influence of DO on the bioleaching efficiency under oxygen-enriched atmosphere in 21 L stirred tank reactor at 42°C. Bioleaching experiments were performed in continuous mode with sulfide-rich tailings wastes composed mainly of pyrite (51%) and quartz using the âBRGM-KCCâ bacterial consortia. The solid load was close to 20% (w/w). Using various oxygen supply conditions (partial pressure, gas rate), the DO concentration in the reactor varied between 4 and 17 ppm. For a DO ranging from 4 to 13 ppm, a good bacterial oxidizing activity was observed and the sulfide dissolution efficiency increased with the DO concentration. It is assumed that this improvement of the bioleaching efficiency was linked to an increase of the oxygen transfer rate from the gas phase to the liquid phase rather than a direct effect of the DO level. When the DO concentration reached 17 ppm a significant decrease of the microbial activity and consequently of the oxygen consumption was noticed. These results show that there is a critical value above which the DO concentration is detrimental to the activity of the bioleach microorganisms present in the âBRGM-KCCâ consortia but this value is much higher than the one usually mentioned in the literature