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This paper presents D/H isotopic fractionation factor measurements of water adsorbed on porous silica tubes in isotopic equilibrium with water vapor. The fractionation factor is measured as a function of vapor pressure ranging from 10% to 80% RH (relative humidity) at room temperature. It is shown that the fractionation factor between the adsorption film or nanometrically confined water and vapor is smaller than that between bulk liquid water and vapor. A qualitative analysis relates this deuterium depletion to a modification of the zero-point energy of the water isomers in the adsorbed/confined state. Furthermore, the behavior of the fractionation factor with RH shows two different linear trends. The transition between the two (at 60% RH) may indicate the transition from a two-dimensional adsorbed water to a three-dimensional water network.

We present experimental data acquired by diffuse reflectance infrared spectroscopy in the mid-IR (4000-400 cm(-1)), on micrometric-sized mineral grain powders. The spectral evolution of the OH-stretching band is followed when the adsorbed water film is thinned under dry conditions, from high to low hydration states. The IR bands are found to be characteristic of the degree of adsorption/confinement of the liquid water. The OH-stretching band is shifted toward shorter wavenumbers than in bulk water, showing that a significant portion of adsorbed water has a higher intermolecular bonding energy. Complementary treatment of the kinetics of water desorption, varying with the surface forces in the water film, confirms the relationships of these bands with the constrained water state. We distinguish different water types obeying liquid-liquid interactions (free and capillary water) or dominated by solid-water interactions (confined and adsorbed water). Part of this study is devoted to mesoporous silica MCM-41, of interest due to the restricted geometries of its mesopores (4.7 nm) favouring the confined water state. The methodology allows us to distinguish bulk and adsorbed/confined water, using spectral analysis coupled with an understanding of the dynamic behaviour of the desorption process.

Growth and differentiation of mycelial strands in Rigidoporus lignosus have been shown to depend on suitable combinations of the pH of the media and the nature of the nitrogen and carbon sources. Amino acids as sole nitrogen sources gave rise to vegetative mycelium. At pH 4.5, growth and mycelial strand differentiation required asparagine, as the fungus failed to grow in the absence of this amino acid. However, at pH 6, differentiation of strands occurred appreciably in asparagine-deficient media, suggesting a close balance between pH and amino acid requirements. Ammonium was required for strand differentiation, while nitrate, as a sole nitrogen source, maintained the fungus undifferentiated. Of the carbohydrates tested, only glucose, fructose and mannose supported strand differentiation. Starch was found to be particularly effective in promoting growth of vegetative mycelium. Strand differentiation required more specific conditions than growth of the vegetative mycelium.

International audience; Supercriticalwatergasification (SCWG) is a very efficient process to convert wet biomass into energetic gases. Unfortunately, SCWG reactor may strongly corrode due to the addition of temperature, pressure and the presence of corrosive species. In the present paper, the corrosion of various ceramic materials in subcritical and supercriticalwater (SCW) gasification process was studied in a batch reactor. We compare the corrosion in distillated water and the corrosion in sugar beet slurry that will be gasified under supercritical conditions. The experimental temperatures were 350 °C and 550 °C and the pressure was 25 MPa. Technical ceramics (SiC, alumina, Y stabilized zirconia, Si3N4, BN, aluminosilicate, cordierite-mullite) show poor capability to sustain corrosion whereas graphite and glassy carbon are the highest performance materials in our working conditions.

In the presence of supercritical water, organic materials are converted into energetic gas, with high hydrogen content. In the present application, thermochemical conversion of humid wastes from wine or sugar production is reached at temperatures and pressures up to 550°C and 250 bars. Material is a key point for the development of SCWG process operating in such conditions. In supercritical water the durability of metals and alloys is limited by corrosion, but ceramics and ceramic composites are known to be stable under extreme conditions. For this reason, we have proceeded to an examination of a selection of ceramic materials that could be used as an anticorrosive wall of the gasification reactor. We show that, ultra-high temperature ceramics Si3N4, BN, Al2O3 and SiC are strongly corroded by humid waste, but carbon-based materials are resistant in both subcritical and supercritical conditions in the presence of pure or waste water. As a conclusion, graphite may be a very good material for SCWG reactor.

We report experimental results on incipient dynamics of gravitational destabilization in an immersed granular medium. Two protocols have been used to reach instability: a progressive loading and a dam-break situation. The instability triggering, analyzed by high-speed imaging and CIV post-processing, reveals distinct dynamical behaviours depending on the initial packing fraction of the medium. Two destabilisation modes have been observed: a surface avalanche and a deeper phenomenon that we called circular collapse.

International audience; We report experimental results on the maximum angle of stability, i.e., the so-called avalanche angle, of a granular medium subjected to an inner water flow controlled by a constant pressure drop. A unique avalanche threshold is derived by two alternative theoretical developments, namely a continuum and a discrete approach, and is successfully confronted to many measurements in a large experimental range. A qualitative analysis of the instability triggering reveals different dynamical behaviors depending on whether the water flow is downward or upward in the granular layer, namely stabilizing versus destabilizing regime. Contrary to the purely hydrostatic situation, the free surface following an avalanche departs from a linear shape because the dynamical pressure gradient is no longer constant in the medium. A simple model is proposed that can satisfactorily predict the postavalanche height profile as well as its subsequent evolution for higher inclinations.

Between 1985 and 1988 45 patients with descending thoracic or thoracoabdominal aortic aneurysms underwent selective arteriography of the intercostal and lumbar arteries to delineate preoperatively the artery of Adamkiewicz and the thoracic radicular artery. Identification of these vessels failed in five patients (11%), was considered complete in 31 patients (69%) and incomplete in nine (20%). Selective arteriography classified these patients into four groups: groups A and B--the artery of Adamkiewicz arose respectively above and below the zone of operation; group C--the artery arose directly from the segment to be operated; and group D--origin could not be determined. All 30 patients in group C underwent a spinal cord revascularization procedure (complete in 20 cases, incomplete in 10). Spinal cord complications occurred in 9/45 patients (20%). No spinal cord complications occurred in groups A and B; their incidence was 5% in group C when revascularization was complete, and 50% when revascularization was incomplete; and 60% had complications in group D (p less than 0.01). Spinal cord complications were more frequent (p less than 0.05) when the artery of Adamkiewicz arose from an intercostal or lumbar artery obliterated at its aortic origin but filled through collaterals or when spinal cord circulation was interrupted for more than 45 minutes. This study confirms the importance of preserving arterial supply to the spinal cord during repair of descending thoracic and thoracoabdominal aneurysms. The information obtained from spinal cord arteriography allows the prediction of complications and informs the choice of the appropriate surgical technique.

From October 1973 to April 1985, 81 patients with aneurysms of the descending thoracic or thoracoabdominal aorta underwent surgery. Eight (10%) of these patients were treated by exclusion-bypass. The aneurysm was located in the descending aorta alone in five cases, and in the descending thoracic and thoracoabdominal aorta in three cases. In all cases, the proximal anastomosis of the bypass was performed on the ascending aorta. The site of the distal anastomosis was the supraceliac aorta in two cases, the infrarenal aorta in three cases and the iliac arteries in three other cases. Exclusion was bipolar, at each end of the aneurysm, in six cases, and unipolar, ie. proximal interruption only, in two cases. Two patients died during the first postoperative month, one of rupture of the distal portion of the aortic arch, the second, after onset of secondary paraplegia. There were no other spinal, cardiac or cerebral complications. One patient died three months postoperatively of intercurrent pulmonary infection. The five other surviving patients whose mean follow-up period is 48.1 +/- 25 months, are alive and enjoying good health. Resection and grafting as advocated by Crawford, is the usual treatment proposed for aneurysms of the descending thoracic and thoracoabdominal aorta. Exclusion-bypass may however be preferred in the following cases: elderly patients with compromised respiratory status, aneurysms of the descending thoracic aorta, either voluminous, of infectious origin or associated with aneurysm of the infrarenal abdominal aorta.