Hybrid binomial Langevin-multiple mapping conditioning modeling of a reacting mixing layer

A novel, stochastic, hybrid binomial Langevin-multiple mapping conditioning (MMC) model—that utilizes the strengths of each component—has been developed for inhomogeneous flows. The implementation has the advantage of naturally incorporating velocity-scalar interactions through the binomial Langevin model and using this joint probability density function (PDF) to define a reference variable for the MMC part of the model. The approach has the advantage that the difficulties encountered with the binomial Langevin model in modeling scalars with nonelementary bounds are removed. The formulation of the closure leads to locality in scalar space and permits the use of simple approaches (e.g., the modified Curl’s model) for transport in the reference space. The overall closure was evaluated through application to a chemically reacting mixing layer. The results show encouraging comparisons with experimental data for the first two moments of the PDF and plausible results for higher moments at a relatively modest computational cost

Superconvergent Perturbation Method in Quantum Mechanics

An analogue of Kolmogorov's superconvergent perturbation theory in classical mechanics is constructed for self adjoint operators. It is different from the usual Rayleigh--Schr\"odinger perturbation theory and yields expansions for eigenvalues and eigenvectors in terms of functions of the perturbation parameter.Comment: 11 pages, LaTe

The NILE Project — Advances in the Conversion of Lignocellulosic Materials into Ethanol

NILE ("New Improvements for Lignocellulosic Ethanol") was an integrated European project (2005-2010) devoted to the conversion of lignocellulosic raw materials to ethanol. The main objectives were to design novel enzymes suitable for the hydrolysis of cellulose to glucose and new yeast strains able to efficiently converting all the sugars present in lignocellulose into ethanol. The project also included testing these new developments in an integrated pilot plant and evaluating the environmental and socio-economic impacts of implementing lignocellulosic ethanol on a large scale. Two model raw materials – spruce and wheat straw – both preconditioned with similar pretreatments, were used. Several approaches were explored to improve the saccharification of these pretreated raw materials such as searching for new efficient enzymes and enzyme engineering. Various genetic engineering methods were applied to obtain stable xylose- and arabinose-fermenting Saccharomyces cerevisiae strains that tolerate the toxic compounds present in lignocellulosic hydrolysates. The pilot plant was able to treat 2 tons of dry matter per day, and hydrolysis and fermentation could be run successively or simultaneously. A global model integrating the supply chain was used to assess the performance of lignocellulosic ethanol from an economical and environmental perspective. It was found that directed evolution of a specific enzyme of the cellulolytic cocktail produced by the industrial fungus, Trichoderma reesei, and modification of the composition of this cocktail led to improvements of the enzymatic hydrolysis of pretreated raw material. These results, however, were difficult to reproduce at a large scale. A substantial increase in the ethanol conversion yield and in specific ethanol productivity was obtained through a combination of metabolic engineering of yeast strains and fermentation process development. Pilot trials confirmed the good behaviour of the yeast strains in industrial conditions as well as the suitability of lignin residues as fuels. The ethanol cost and the greenhouse gas emissions were highly dependent on the supply chain but the best performing supply chains showed environmental and economic benefits. From a global standpoint, the results showed the necessity for an optimal integration of the process to co-develop all the steps of the process and to test the improvements in a flexible pilot plant, thus allowing the comparison of various configurations and their economic and environmental impacts to be determined. <br> Le projet NILE, acronyme de "New Improvements for Lignocellulosic Ethanol", était un projet européen (2005-2010) consacré à la conversion des matières premières lignocellulosiques en éthanol. Ses principaux objectifs étaient de concevoir de nouvelles enzymes adaptées à l’hydrolyse de la cellulose en glucose et de nouvelles souches de levure capables de convertir efficacement tous les sucres présents dans la lignocellulose en éthanol. Une autre partie du projet consistait à tester ces nouveaux systèmes dans une installation pilote et à évaluer les impacts environnementaux et socio-économiques de la production et utilisation à grande échelle d’éthanol lignocellulosique. Deux matières premières modèles (l’épicéa et la paille de blé) prétraitées de façon semblable, ont été étudiées. Différentes approches ont été tentées pour améliorer la saccharification de ces matières premières, par exemple, la recherche de nouvelles enzymes efficaces ou l’ingénierie d’enzymes. Plusieurs stratégies d’ingénierie génétique ont été utilisées pour obtenir des souches stables de Saccharomyces cerevisiae capables de fermenter le xylose et l’arabinose, et de tolérer les composés toxiques présents dans les hydrolysats lignocellulosiques. L’installation pilote pouvait traiter 2 tonnes de matières sèches par jour, et l’hydrolyse et la fermentation pouvaient être menées successivement ou simultanément. Un modèle global intégrant la chaîne d’approvisionnement en matière première a servi à évaluer les performances économiques et environnementales de la production d’éthanol lignocellulosique. L’évolution dirigée d’une enzyme du cocktail cellulolytique produit par le champignon Trichoderma reesei, et la modification de la composition de ce cocktail améliorent l’hydrolyse enzymatique des matières premières prétraitées. Cependant, ces résultats n’ont pu être reproduits à grande échelle. Le rendement de conversion et la productivité spécifique en éthanol ont été sensiblement augmentés grâce à l’ingénierie métabolique des souches de levure et au développement d’un procédé optimal de fermentation. Les essais en pilote ont confirmé le bon comportement de ces souches de levure en conditions industrielles ainsi que la possibilité d’utiliser les résidus riches en lignine comme combustible. Le coût de production de l’éthanol et le bilan des émissions de gaz à effet de serre étaient très dépendants des sources d’énergie utilisées. D’un point de vue plus global, les résultats ont montré que l’optimisation du procédé nécessite de codévelopper toutes les étapes de façon intégrée et de valider les améliorations dans une installation pilote, afin notamment de pouvoir comparer différentes configurations et d’en déterminer les effets sur l’économie du procédé et ses impacts environnementaux

Epicycles and Poincar\'{e} Resonances in General Relativity

The method of geodesic deviations provides analytic approximations to geodesics in arbitrary background space-times. As such the method is a useful tool in many practical situations. In this note we point out some subtleties in the application of the method related to secular motions, in first as well as in higher order. In particular we work out the general second-order contribution to bound orbits in Schwarzschild space-time and show that it provides very good analytical results all the way up to the innermost stable circular orbit.Comment: 24 pages, 4 figure

Pressure transduction and fluid evacuation during conventional negative pressure wound therapy of the open abdomen and NPWT using a protective disc over the intestines

<p>Abstract</p> <p>Background</p> <p>Negative pressure wound therapy (NPWT) has gained acceptance among surgeons, for the treatment of open abdomen, since very high closure rates have been reported with this method, compared to other kinds of wound management for the open abdomen. However, the method has occasionally been associated with increased development of fistulae. We have previously shown that NPWT induces ischemia in the underlying small intestines close to the vacuum source, and that a protective disc placed between the intestines and the vacuum source prevents the induction of ischemia. In this study we compare pressure transduction and fluid evacuation of the open abdomen with conventional NPWT and NPWT with a protective disc.</p> <p>Methods</p> <p>Six pigs underwent midline incision and the application of conventional NPWT and NPWT with a protective disc between the intestines and the vacuum source. The pressure transduction was measured centrally beneath the dressing, and at the anterior abdominal wall, before and after the application of topical negative pressures of -50, -70 and -120 mmHg. The drainage of fluid from the abdomen was measured, with and without the protective disc.</p> <p>Results</p> <p>Abdominal drainage was significantly better (p < 0. 001) using NPWT with the protective disc at -120 mmHg (439 ± 25 ml vs. 239 ± 31 ml), at -70 mmHg (341 ± 27 ml vs. 166 ± 9 ml) and at -50 mmHg (350 ± 50 ml vs. 151 ± 21 ml) than with conventional NPWT. The pressure transduction was more even at all pressure levels using NPWT with the protective disc than with conventional NPWT.</p> <p>Conclusions</p> <p>The drainage of the open abdomen was significantly more effective when using NWPT with the protective disc than with conventional NWPT. This is believed to be due to the more even and effective pressure transduction in the open abdomen using a protective disc in combination with NPWT.</p

Key principle of the efficient running, swimming, and flying

Empirical observations indicate striking similarities among locomotion in terrestrial animals, birds, and fish, but unifying physical grounds are lacking. When applied to efficient locomotion, the analytical mechanics principle of minimum action yields two patterns of mechanical similarity via two explicit spatiotemporal coherent states. In steady locomotory modes, the slow muscles determining maximal optimum speeds maintain universal intrinsic muscular pressure. Otherwise, maximal speeds are due to constant mass-dependent stiffness of fast muscles generating a uniform force field, exceeding gravitation. Being coherent in displacements, velocities and forces, the body appendages of animals are tuned to natural propagation frequency through the state-dependent elastic muscle moduli. Key words: variational principle of minimum action (04.20.Fy), locomotion (87.19.ru), biomechanics (87.85.G-).Comment: Submitted to the Europhysical Letter

A preliminary study of the effect of closed incision management with negative pressure wound therapy over high-risk incisions

Background Certain postoperative wounds are recognised to be associated with more complications than others and may be termed high-risk. Wound healing can be particularly challenging following high-energy trauma where wound necrosis and infection rates are high. Surgical incision for joint arthrodesis can also be considered high-risk as it requires extensive and invasive surgery and postoperative distal limb swelling and wound dehiscence are common. Recent human literature has investigated the use of negative pressure wound therapy (NPWT) over high-risk closed surgical incisions and beneficial effects have been noted including decreased drainage, decreased dehiscence and decreased infection rates. In a randomised, controlled study twenty cases undergoing distal limb high-energy fracture stabilisation or arthrodesis were randomised to NPWT or control groups. All cases had a modified Robert-Jones dressing applied for 72 h postoperatively and NPWT was applied for 24 h in the NPWT group. Morphometric assessment of limb circumference was performed at six sites preoperatively, 24 and 72 h postoperatively. Wound discharge was assessed at 24 and 72 h. Postoperative analgesia protocol was standardised and a Glasgow Composite Measure Pain Score (GCPS) carried out at 24, 48 and 72 h. Complications were noted and differences between groups were assessed. Results Percentage change in limb circumference between preoperative and 24 and 72 h postoperative measurements was significantly less at all sites for the NPWT group with exception of the joint proximal to the surgical site and the centre of the operated bone at 72 h. Median discharge score was lower in the NPWT group than the control group at 24 h. No significant differences in GCPS or complication rates were noted. Conclusions Digital swelling and wound discharge were reduced when NPWT was employed for closed incision management. Larger studies are required to evaluate whether this will result in reduced discomfort and complication rates postoperatively