Fatty Acid Hydroperoxides Biotransformation By Potato Tuber Cell-Free Extracts

peer reviewe

Sensitivity of the liquid bridge hydrodynamics to local capillary contributions

International audienceIn the usual models of thermocapillary flows, a vorticity singularity occurs at the contact free surface-solid boundaries. The steady axisymmetric hydrodynamics of the side-heated liquid bridge of molten metal is addressed here for its sensitivity to the size delta of a length scale explicitly introduced to regularize the problem. By linear stability analysis of the flows, various stable steady states are predicted: The already known steady states which are reflection-symmetric about the mid-plane, but also others which do not possess this property. The thresholds in Ma of the associated bifurcations are strongly dependent on delta, and converge with delta-->0 towards low values. Published data give these results some physical relevance. (C) 2002 American Institute of Physics

Bioconversion of potatoes residues or surplus potatoes to ethanol under non axenic conditions [abstract]

Biofuels can offer an alternative to fossil fuels in the context of climate change and fossil reserves depletion. With 3 million tons of potatoes produced in 2007 and a high yield per hectare of 47 tons, Belgium is the 19th largest producer in the world. The residual and surplus potatoes could be used to produce bioethanol by fermentation. We examined the feasibility of a simple ethanol fermentation process under non axenic conditions. The substrate was pretreated with commercial amylases or by adding as low as 10% FM (Fresh Matter) barley malt. It was then fermented with Saccharomyces cerevisiae. Ethanol and volatile fatty acids were analyzed by GC-FID and soluble sugars were analyzed with the Anthrone method. Starch from potatoes was hydrolyzed to soluble sugars. Hydrolysis seems to continue with 10% FM of barley malt after 48 h while the hydrolysis stopped or decelerated with commercial enzymes. With 10% FM of malt, 3 h of hydrolysis and 7 days of fermentation, an ethanol concentration of 42 g.l-1 was obtained and the conversion yield was 139 gethanol.kg-1 DM. The fermentation conversion yield of soluble sugars to ethanol was > 82% and the endogenous competition was limited. However, starch hydrolyzing seems to be a limiting step under the conditions tested. Commercial enzymes did not provide better results under the same conditions

Systemic analysis of production scenarios for bioethanol produced from ligno-cellulosic biomass [abstract]

Defining alternatives for non-renewable energy sources constitutes a priority to the development of our societies. One of these alternatives is biofuels production starting from energy crops, agricultural wastes, forest products or wastes. In this context, a "second generation" biofuels production, aiming at utilizing the whole plant, including ligno-cellulosic (hemicelluloses, cellulose, lignin) fractions (Ogier et al., 1999) that are not used for human food, would allow the reduction of the drawbacks of bioethanol production (Schoeling, 2007). However, numerous technical, economical, ethical and environmental questions are still pending. One of the aims of the BioEtha2 project, directed by the Walloon Agricultural Research Centre, is to define the position of bioethanol produced from ligno-cellulosic biomass among the different renewable energy alternatives that could be developed in Wallonia towards 2020. With this aim, and in order to answer the numerous questions in this field, the project aims at using tools and methods coming from the concept of "forecasting scenarios" (Sebillotte, 2002; Slegten et al., 2007; For-learn, 2008). This concept, based on a contemporary reality, aims to explore different possible scenarios for the future development of alternative sources of energy production. The principle is to evaluate, explore, possible futures of the studied problematic, through the establishment of possible evolution trajectories. We contribute to this prospective through a systemic approach (Vanloqueren, 2007) that allows lightening the existing interactions within the system "ligno-cellulosic biomass chain" without isolating it from its environment. We explain and sketch the two contexts needed to identify primary stakes. The global context includes inter-dependant and auto-regulating fields such as society, politics, technology and economy. These four fields influence each part of the "chain" with specific tools. However, the interest and possible action fields lay within the intermediary context representing the "resources" such as agriculture, forestry, "driving" elements such as mobility, mediation elements such as territories and environment and concurrent elements such as non-cellulosic biomass, the energy mix and the non-energy valorization

Improved sugar yields from biomass sorghum feedstocks: comparing low-lignin mutants and pretreatment chemistries

Additional file 4. R script to calculate overall sugar yields from ASE350 optimal temperature data using NU method

Ophioglossum polyphyllum A. Braun in Seub. (Ophioglossaceae, Pteridophyta), a rare potherb in south central Tibet (T.A.R., P.R.China)

peer reviewe

Etude experimentale et modelisation du stockage thermique de longue duree en lit de cailloux enterre, ventile

SIGLECNRS T 58674 / INIST-CNRS - Institut de l'Information Scientifique et TechniqueFRFranc

Instabilités 3D de convection thermocapillaire en zone-flottante

Nous étudions numériquement la stabilité d'un écoulement 2D en zone-flottante vis-à-vis de perturbations 3D. La zone- flottante est une partie liquide mantenue par capillarité entre deux barreaux cylindriques coaxiaux isothermes et est soumise à un flux thermique latéral dont le profil est fixe. Sa surface libre est ici considérée comme plane et indéformable. Les solutions numériques sont obtenues par méthode de collocation spectrale. Les écoulements stationnaires sont obtenus par méthode de Newton et une méthode d'Arnoldi est utilisée pour l'étude de la stabilité linéaire. La recherche a été menée sur une large gamme de nombres de Prandtl (Pr), allant de 0.001 à 100. Le mode stabilisant est le mode 2 aux faibles Pr et le mode 1 pour les grands Pr. Le mécanisme de déstabilisation est analysé en observant le taux de croissance de l'énergie de la perturbation, mettant en évidence le caractère hydrodynamique de la perturbation aux faibles Pr et hydrothermal aux grands Pr. L'utilisation d'un nouvel outil d'analyse, le système adjoint, permet d'identifier les zones sensibles de l'écoulement à des perturbations impulsionnelles. Cet outil a été utilisé pour étudier les perturbations bidimensionnelles. La localisation des zones sensibles permet d'identifier des structures dans l'écoulement qui, à bas Pr, répondent au critère de Fjørtøft. Cependant ce critère ne s'applique, comme tous les critères de stabilité, qu'à des écoulements non visqueux. A hauts Pr, le lieu sensible à une perturbation thermique se situe dans les zones de fort gradient thermique sur la surface libre, proche des fronts solides. La structure d'écoulements 3D faiblements non linéaires a aussi été décrite.We study numerically the stability of the 2D flow in floating-zone with respect to 3D perturbations. The floating-zone is a liquid bridge maintained thanks to capillarity between two coaxial isothermal rods and is laterally heated. The free surface is straight and non-deformable. The numerical solutions are calculated with spectral collocation method. Stationary flows are obtained with Newton method and their stability is determined through an Arnoldi method. The study has been performed over a large range of Prandtl (Pr) number values, from 0.001 to 100. The mode 2 is the most dangerous at low Pr whereas the mode 1 is the most dangerous at high Pr. We analyze the destabilisation mechanism through the perturbation energy growth rate. It appears that the perturbation is hydrodynamical at low Pr and hydrothermal at high Pr. A new tool, the adjoint system, allows us to localize the most sensitive regions of the flow with respect to impulse perturbations. It was used to study the 2D stationary flows. The low Pr stationary flow structure in the most sensitive regions satisfies the Fjørtøft stability criteria. Nevertheless, this criteria is, like the other stability criteria, only for inviscid fluids. For high Pr, the most sensitive region to temperature disturbance is located on the free surface, near the walls where thermal gradients is strong. The 3D structure of weakly non linear flows has also been described.ORSAY-PARIS 11-BU Sciences (914712101) / SudocNANCY/VANDOEUVRE-INPL (545472102) / SudocSudocFranceF