Impact sédimentaire des travaux d'aménagement de l'estuaire de la Loire

The planning works realized in the Loire estuary (France) during the course of the twentieth century have brought about an important inflow of sea water to this site. The consequences can be observed through important changes in the location of the extreme limits of both the dynamic tide and the salinity front at 0.5‰; the dynamic tide has progressed from 63?km from the river mouth in 1903 to 100?km in 1992 and the salinity front from 38?km in 1948 to 70?km in 1991. Modifications of the hydraulic conditions have also affected the dynamics of the cohesive sediments present in the estuary. The purpose of this study is to determine the impact of the past and future planning works in the Loire estuary on the erosion and deposition of cohesive sediments in relation to hydraulic conditions. The principal sedimentary processes (transportation, deposition, settlement, erosion) are simulated by simplified models from measurements carried out both in situ and in the laboratory. The dynamics of the cohesive sediment in the Loire estuary are linked with the fortnightly cycle of the tide as follows: when the tidal coefficient falls below 70, almost all the suspended matter is quickly deposited and collects near the estuary bed to form a lens-shaped body of fluid mud which consolidates during 6?days of neap tides. Finally, as soon as the tide coefficient rises above 75, this body of fluid mud is taken again into suspension and only the fraction that was highly concentrated in the course of the settlement remains on the bottom. The sediments remaining on the estuary bed in the course of a fortnightly cycle of the tide represent the residual sedimentation rate over this period. Knowledge of the maximum tide current velocities in the estuary permits the determination of the maximum hydrodynamic stress on the bottom and the critical concentration of the mud susceptible to being eroded by this current, taking into account the yield stress of the mud. In other respects, the quantity of mud that is greater than this critical concentration per surface unit and time unit can be calculated according to a theoretical model developed by Sanchez and Grovel. This methodology allows the evaluation of the residual sedimentation rate representing a layer of 0.08?m per year in front of the harbour of Montoir for the hydraulic conditions of 1976, with a maximum current velocity on the surface of 2.40?m?s^–1. Following the dredging works realized between St-Nazaire and Donges after 1976, the level of the bottom has changed from –10.00 to –13.25?m (with respect to the hydrographic datum). These works have brought about a reduction in maximum velocities of 15% and an increase in the residual sedimentation rate of about 100%. This increase is in agreement with the theoretical estimation of this study. This study also describes the high sedimentation rate observed in a locally dredged berth and located in the zone of the estuary where a lens-shaped body of fluid mud is formed during slack tides. The sedimentation rate depends then on the frequency of the dredging works because the dredged zone can be filled up in a few days. Finally, a methodology is developed in order to estimate the erosion rate induced by an increase in current velocities. This methodology takes into account the vertical concentration gradient in the bed resulting from consolidation, the hydrodynamic stress linked to current velocity, the yield stress of sediment which varies with concentration and the critical hydrodynamic stress for erosion estimated from experimental measurements in laboratory. All the methodologies presented in this paper have been applied only to the estuary of the river Loire. Application to any other similar site is possible after laboratory experiments on local sediments in order to adjust the behavioural laws used to evaluate the permeability coefficient, the effective stress and the yield stress. This study shows that knowledge of hydraulic conditions and local sedimentary processes is very important for predicting the impact of planning works in an estuary.     

Fast computation of the multivariable stability margin for realinterrelated uncertain parameters

An alternative implementation of an algorithm for the computation of the multivariable stability margin to check the robust stability of feedback systems with real parametric uncertainty is proposed. This method eliminates the need for the frequency search by reducing it to the testing of a finite number of conditions. These conditions have a special structure that allows a significant improvement in the speed of computation     

Incorporating amylopectin in poly(lactic acid) by melt blending using poly(ethylene‐co‐vinyl alcohol) as a thermoplastic carrier. (I) morphological characterization

In this study, the possibility of using a biodegradable grade of thermoplastic poly(ethylene‐co‐vinyl alcohol) with high (71 mol %) vinyl alcohol (EVOH‐29), as a carrier to incorporate the renewable and biodegradable component amylopectin (AP) into poly(lactic acid) (PLA) through melt blending, was investigated. The effect of using a plasticizer/compatibilizer (glycerol) in the blend systems was also investigated. In a first step, the EVOH/AP blends were produced and thereafter, in a second step, these were mixed with PLA. In this first study, the blend morphology was investigated using optical microscopy, scanning electron microscopy and Raman imaging spectroscopy and the thermal properties were measured by differential scanning calorimetry. Despite the fact that EVOH and AP are both highly polar, their blends were immiscible. Still, the blends exhibited an excellent phase dispersion on a micron level, which was enhanced further by the addition of glycerol. A good phase dispersion was finally observed by incorporation of the latter blends in the PLA matrix, suggesting that the proposed blending route can be successfully applied for these systems. Finally, the Differential scanning calorimetry (DSC) data showed that the melting point of EVOH dropped in the EVOH/AP blends, but the properties of the PLA phase was still relatively unaffected as a result of blending with the above components. © 2009 Wiley Periodicals, Inc. J Appl Polym Sci, 2010     

From relative to absolute quantification of tryptic peptides with tandem mass tags: application to cerebrospinal fluid

Quantification is a major task in proteomics. Among the different analytical strategies to enable peptide and protein quantification, tagging with isotopic labels has emerged as a practical, versatile, and efficient alternative. In particular, isobaric labels, such as TMT or iTRAQ, are now widely employed to make relative comparison of the protein amounts in separate biological samples with tandem mass spectrometry (MS/MS). We used herein a shotgun proteomic approach based on labelling with tandem mass tags (TMTs) for the relative quantification of proteins, and the absolute quantification of their tryptic peptides in human cerebrospinal fluid (CSF). First, the comparison of ante- and post-mortem CSF samples was carried out for the discovery of protein marker candidates of brain-damage disorders. Second, tryptic peptides representative of these candidates were measured in CSF using reporter-ion calibration curves. These works highlighted the advantages and limitations of such strategies for quantification purposes in proteomics.     

Flexible Nanosomes (SECosomes) Enable Efficient siRNA Delivery in Cultured Primary Skin Cells and in the Viable Epidermis of Ex Vivo Human Skin

The extent to which nanoscale‐engineered systems cross intact human skin and can exert pharmacological effects in viable epidermis is controversial. This research seeks to develop a new lipid‐based nanosome that enables the effective delivery of siRNA into human skin. The major finding is that an ultraflexible siRNA‐containing nanosome—prepared using DOTAP, cholesterol, sodium cholate, and 30% ethanol—penetrates into the epidermis of freshly excised intact human skin and is able to enter into the keratinocytes. The nanosomes, called surfactant‐ethanol‐cholesterol‐osomes (SECosomes), show excellent size, surface charge, morphology, deformability, transfection efficiency, stability, and skin penetration capacity after complexation with siRNA. Importantly, these nanosomes have ideal characteristics for siRNA encapsulation, in that the siRNA is stable for at least 4 weeks, they enable highly efficient transfection of in vitro cultured cells, and are shown to transport siRNA delivery through intact human skin where changes in the keratinocyte cell state are demonstrated. It is concluded that increasing flexibility in nanosomes greatly enhances their ability to cross the intact human epidermal membrane and to unload their payload into targeted epidermal cells.     

Structure and Technofunctional Properties of Protein-Polysaccharide Complexes: A Review

Food proteins and polysaccharides are the two key structural entities in food materials. Generally, interactions between proteins and polysaccharides in aqueous media can lead to one- or two-phase systems, the latter being generally observed. In some cases of protein-polysaccharide net attraction, mainly mediated through electrostatic interactions, complex coac-ervation or associative phase separation occurs, giving rise to the formation of protein-polysac-charide complexes. Physicochemical factors such as pH, ionic strength, ratio of protein to polysaccharide, polysaccharide and protein charge, and molecular weight affect the formation and stability of such complexes. Additionally, the temperature and mechanical factors (pressure, shearing rate, and time) have an influence on phase separation and time stability of the system. The protein-polysacchaide complexes exhibit better functional properties than that of the proteins and polysaccharides alone. This improvement could be attributed to the simultaneous presence of the two biopolymers, as well as the structure of the complexes. Consequently, the interesting hydration (solubility, viscosity), structuration (aggregation, gelation) and surface (foaming, emulsifying) properties of these complexes can be used in a number of domains. Among others, these could be macromolecular purification, microencapsulation, food formulation (fat replacers, texturing agents), and synthesis of biomaterials (edible films, artificial grafts).     

Realistic model for the multiple‐input floating‐gate transistor

Multiple‐input floating‐gate transistor (FGMOS) circuit designers face a serious problem along the design process: the lack of a realistic simulation model. For this reason, a solution that properly predicts the initial voltage at the floating gates is presented in this paper. In order to assess the performance of the proposal, a comparison is made against a test circuit fabricated in a 0.5‐µm On‐Semiconductor CMOS process. Based on this comparison, the proposed model is shown to be a fundamental tool in the design of FGMOS circuits. © 2014 Institute of Electrical Engineers of Japan. Published by John Wiley & Sons, Inc.     

Experimental study on micro EDM-drilling of Ti6Al4V using helical electrode

There is a growing interest in the machining of micro-holes with high aspect-ratio in difficult-to-machine alloys for the aerospace industry. Processes based on electro discharge machining (EDM) and developed for the manufacture of both micro-electrode and micro-hole are actually used, but most of them involve micro-EDM machines. In this work, the influence of EDM parameters on material removal rate, electrode wear, machining time and micro-hole quality when machining Ti6Al4V is studied. Due to an inefficient removal of debris when increasing hole depth, a new strategy based on the use of helical-shaped electrodes has been proposed. The influence of helix angle and flute depth with respect to process performance has been addressed. Main results include 37% reduction in machining times (hole diameter 800 μm) when using electrode helix angle of 45° and flute-depth of 50 μm, and an additional 19% with flute-depth of 150 μm. Holes of 661 μm diameter and as much as 6.81 mm depth, which yields in aspect ratio of 10:1, have successfully been machined in Ti6Al4V.     

Hot turning of a difficult-to-machine steel (sae xev-f) aided by infrared radiation

This paper discusses how to improve the position precision of a semi-closed loop servo system. A support vector regression algorithm is chosen to model and predict position error. The predicted error is then fed back to the input entry to compensate the error. Fuzzy PID control is introduced to adjust the controlling rule of the PID controller in the semi-closed loop servo system so as to improve the dynamic response characteristics of the servo system and reach a high degree of position precision. A case study is implemented. The simulation and experimental results show that combining the improved fuzzy control with predicted position error feedback ensures a high degree of position precision and a high degree of dynamic response characteristics.