How a plantar pressure-based, tongue-placed tactile biofeedback modifies postural control mechanisms during quiet standing

The purpose of the present study was to determine the effects of a plantar pressure-based, tongue-placed tactile biofeedback on postural control mechanisms during quiet standing. To this aim, sixteen young healthy adults were asked to stand as immobile as possible with their eyes closed in two conditions of No-biofeedback and Biofeedback. Centre of foot pressure (CoP) displacements, recorded using a force platform, were used to compute the horizontal displacements of the vertical projection the centre of gravity (CoGh) and those of the difference between the CoP and the vertical projection of the CoG (CoP-CoGv). Altogether, the present findings suggest that the main way the plantar pressure-based, tongue-placed tactile biofeedback improves postural control during quiet standing is via both a reduction of the correction thresholds and an increased efficiency of the corrective mechanism involving the CoGh displacements

Understanding the regulation of aspartate metabolism using a model based on measured kinetic parameters

The aspartate-derived amino-acid pathway from plants is well suited for analysing the function of the allosteric network of interactions in branched pathways. For this purpose, a detailed kinetic model of the system in the plant model Arabidopsis was constructed on the basis of in vitro kinetic measurements. The data, assembled into a mathematical model, reproduce in vivo measurements and also provide non-intuitive predictions. A crucial result is the identification of allosteric interactions whose function is not to couple demand and supply but to maintain a high independence between fluxes in competing pathways. In addition, the model shows that enzyme isoforms are not functionally redundant, because they contribute unequally to the flux and its regulation. Another result is the identification of the threonine concentration as the most sensitive variable in the system, suggesting a regulatory role for threonine at a higher level of integration

Enrichissement d un ensemble logiciel d exploitation automatique des canaux (extension des bibliothèques de commandes et conception d outils de diagnostics et de reconstitution de mesures)

Le transport de l eau dans les canaux à surface libre pose problème dès lors que la préservation de la ressource devient un enjeu majeur. Le Canal de Provence a mis en place une commande centralisée qui permet de gérer le canal de façon coordonnée et optimisée. Pour cela l exploitation doit s appuyer sur un réseau de mesures et une suite logicielle adaptée. La première partie de ce travail consiste en l'étude du principe physique de la dynamique contrôlée. La régulation nécessite l estimation des volumes en transit et des retards de propagation. La modélisation a été analysée afin d en connaître les incertitudes et les limites. La seconde partie consiste en une nouvelle formalisation informatique et en la mise en place opérationnelle de nouvelles méthodes de contrôle du canal. Enfin, la troisième partie a mené à la conception d outils de reconstruction de mesures basés principalement sur le filtre de Kalman. Les mesures sont en effet la base du processus de contrôle. Ce travail a mené à la mise en place d extensions logicielles qui sont aujourd hui en fonctionnement sur le canal.PARIS-BIUSJ-Thèses (751052125) / SudocPARIS-BIUSJ-Mathématiques rech (751052111) / SudocFONTAINEBLEAU-MINES ParisTech (771862302) / SudocSudocFranceF

Adaptive control of algae detachment in regulated canal networks

Open-channel distribution networks are subject to algal developments that can induce major disturbances such as clogging of hydraulic devices (pipes, weirs, filters, flow meters). Flushes can be used as a strategy to manage these algae developments. A flush is carried out by increasing the hydraulic shear conditions using hydraulic control structures of the canal network. In response to the shear stress increase, a part of the fixed algae is detached, then re-suspended into the water column, and finally transported downstream. This leads to a peak of turbidity that has to be controlled. In this paper, we develop a distributed linear model of the turbidity dynamics that is used for real-time adaptive control of the flushes. Simulations show the effectiveness of the adaptive controller, which can, at the same time, estimate the gain of the system, linked to the amount of initial fixed biomass, and perform a flush without exceeding the turbidity limit

Do climate models underestimate snow accumulation on the Antarctic plateau? A re-evaluation of/from in situ observations in East Wilkes and Victoria Lands

International audienceIt has been suggested that meteorological and climate models underestimate snow accumulation on the Antarctic plateau, because accumulation (or surface mass balance (SMB)) is dominated by clear-sky precipitation while this process is not properly taken into account in the models. Here, we show that differences between model and field SMB data are much reduced when the in situ SMB reports used to evaluate the models are filtered through quality-control criteria and less reliable reports are subsequently left out. We thus argue that, although not necessarily unsupported, model biases and their interpretations in terms of clear-sky vs synoptic precipitation on the Antarctic plateau may have been overstated in the past. To avoid such misleading issues, it is important that in situ SMB reports of insufficient or unassessed reliability are discarded, even at the cost of a strong reduction in spatial sampling and coverage

Influence of Oceanic Boundary Conditions in Simulations of Antarctic Climate and Surface Mass Balance Change during the Coming Century

International audienceThis article reports on high-resolution (60 km) atmospheric general circulation model simulations of the Antarctic climate for the periods 1981–2000 and 2081–2100. The analysis focuses on the surface mass balance change, one of the components of the total ice sheet mass balance, and its impact on global eustatic sea level. Contrary to previous simulations, in which the authors directly used sea surface boundary conditions produced by a coupled ocean–atmosphere model for the last decades of both centuries, an anomaly method was applied here in which the present-day simulations use observed sea surface conditions, while the simulations for the end of the twenty-first century use the change in sea surface conditions taken from the coupled simulations superimposed on the present-day observations. It is shown that the use of observed oceanic boundary conditions clearly improves the simulation of the present-day Antarctic climate, compared to model runs using boundary conditions from a coupled climate model. Moreover, although the spatial patterns of the simulated climate change are similar, the two methods yield significantly different estimates of the amplitude of the future climate and surface mass balance change over the Antarctic continent. These differences are of similar magnitude as the intermodel dispersion in the current Intergovernmental Panel on Climate Change (IPCC) exercise: selecting a method for generating boundary conditions for a high-resolution model may be just as important as selecting the climate model itself. Using the anomaly method, the simulated mean surface mass balance change over the grounded ice sheet from 1981–2000 to 2081–2100 is 43-mm water equivalent per year, corresponding to a eustatic sea level decrease of 1.5 mm yr−1. A further result of this work is that future continental-mean surface mass balance changes are dominated by the coastal regions, and that high-resolution models, which better resolve coastal processes, tend to predict stronger precipitation changes than models with lower spatial resolution

Dimethylsulfide (DMS) oceanic emissions around Antarctica in LMD-ZT General Circulation Model

Poste

High-southern latitudes sulfur cycle in an Atmospheric General Circulation Model

PosterThis modeling study (Cosme et al., Sulfur cycle in the high southern latitudes in the LMD-ZT General Circulation Model, submitted to JGR) was motivated by the recent publication of annual time-scale records of dimethylsulfide (DMS) and dimethylsulfoxide (DMSO) in Antarctica, completing the available series of sulfate and methanesulfonic acid (MSA). Sulfur chemistry has been incorporated in the Laboratoire de Météorologie Dynamique Atmospheric General Circulation Model (AGCM), LMD-ZT, with high resolution and improved physics in the high-southern latitudes. The model predicts the concentration of 6 major sulfur species through emissions, transport, wet and dry deposition and chemistry in both gaseous and aqueous phases. Model results are broadly realistic when compared with measurements in air and snow or ice, and to results of other modeling studies, at high- and mid- southern latitudes. Although not corrected in this work, defects are identified and discussed: Atmospheric MSA concentrations are underestimated and DMSO concentrations are overestimated in summer, reflecting the lack of a DMSO sink leading to MSA; the deposition scheme used in the model may not be adapted to polar regions; DMS concentrations are underestimated in winter, and the model does not adequately reproduces interannual variability. Oceanic DMS sources appear deciding for the description of the sulfur cycle in these regions. The model suggests that ground atmospheric DMS concentrations are higher in winter than in summer, in a large part of central Antarctica. In the high-southern latitudes, high loads of DMS and DMSO are found and the main chemical sink of sulfur dioxide (SO2) is aqueous oxidation by ozone (O3), whereas oxidation by hydrogen peroxide (H2O2) dominates at the global scale

The sulfur cycle at high-southern latitudes in the LMD-ZT General Circulation Model

This modeling study was motivated by the recent publication of year-round records ofdimethylsulfide (DMS) and dimethylsulfoxide (DMSO) in Antarctica, completing theavailable series of sulfate and methanesulfonic acid (MSA). Sulfur chemistry has beenincorporated in the Laboratoire de Me´te´orologie Dynamique-Zoom Tracers (LMD-ZT)Atmospheric General Circulation Model (AGCM), with high-resolution and improvedphysics at high-southern latitudes. The model predicts the concentration of six major sulfurspecies through emissions, transport, wet and dry deposition, and chemistry in both gas andaqueous phases. Model results are broadly realistic when compared with measurements inair and snow or ice, as well as to results of other modeling studies, at high- and middlesouthernlatitudes. Atmospheric MSA concentrations are underestimated and DMSOconcentrations are overestimated in summer, reflecting the lack of a DMSO heterogeneoussink leading to MSA. Experiments with various recently published estimates of the rateof this sink are reported. Although not corrected in this work, other defects are identifiedand discussed: DMS concentrations are underestimated in winter, MSA and non-sea-salt(nss) sulfate concentrations may be underestimated at the South Pole, the depositionscheme used in the model may not be adapted to polar regions, and the model does notadequately reproduces interannual variability. Oceanic DMS sources have a majorcontribution to the variability of sulfur in these regions. The model results suggest that in alarge part of central Antarctica ground-level atmospheric DMS concentrations are larger inwinter than in summer. At high-southern latitudes, high loads of DMS and DMSO arefound and the main chemical sink of sulfur dioxide (SO2) is aqueous oxidation by ozone(O3), whereas oxidation by hydrogen peroxide (H2O2) dominates at the global scale. Acomprehensive modeled sulfur budget of Antarctica is provided