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Agriculture based on the massive use of non-renewable resources and the intensification of production systems show its limits, which question this development path. Yet this agricultural model has been developed in the Saïs plain, particularly in family farms. This development has resulted in the development of income-generating sectors that are intensively managed, with few technical supports. This dynamic has led to a groundwater overexploitation and pollution, and price fluctuations of agricultural products. The sustainability of family farms is questioned, especially since Moroccan agricultural policy encourages an intensive development path. This issue has been studied based on three sub-questions, each addressing the sustainability of family farms from a different perspective. These sub-questions were investigated thanks to a sample of 40 farms, chosen for their diversity of production systems. We used different tools for the data analysis.The first sub-question dealt with the sustainability of farms related to their evolving dynamics over the past 60 years. Seven pathways were identified based on several internal and external drivers. These pathways have resulted currently in three main farm types, differing in their production activities. T1 includes farms close to the original traditional system, based on land without a groundwater access; T2 gather farms cultivating a diversity of irrigated productions; T3 gather specialized farms.The second sub-question aims to evaluate the sustainability of family farms and to formalize its determinants, by mobilizing a research viewpoint. This analysis was based on a sustainability assessment tool (IDEA), adapted to the context of Saïs. Environmental sustainability depends on the diversification of activities and farm autonomy degree; socio-territorial sustainability is linked to the degree of farmer involvement in the territorial dynamics; and economic sustainability depends on the production system and the farm’ structural factors. However, general trend shows an ...

In order to study the action of alcohol on the oral mucosa, Sprague-Dawley female rats, receiving an alcohol rich diet, were sacrifical as well as their controls, 98, 200 and 290 days after the experiment start and their oral mucosa studied histochemically and ultrastructurally. In the alcoholic animal, 1) the epithelium was thickened from day 98 on and SS and SH groups were detected in the keratin; 2) at this time interval, positive acid phosphatase areas were noted. Under the electron microscope, myelin figures were observed phosphatase areas were noted. Under the electron microscope, myelin figures were observed between cells on days 98 and 200. Cells undergoing autolysis could explain the lysosomial enzyme activity; 3) the DNA activity assessed by methyl-pyronine green stain was increased after 200 and 290 days. This activity was correlated at these time intervals with the increase of the mitosis number; 4) succinodeshydrogenase showed an increased activity on days 200 and 290. The mitochondria often of large size showed no ultrastructural changes even on day 290; 5) the vessels, already on day 98, then on days 200 and 290, showed a decrease in alkaline phosphatase reactivity with occasional thinnings of the wall. These modifications suggested that alcohol was able to modify the integrity of oral mucosa cells in the rat, perhaps by modifying the quality of the cell walls.

This thesis deals with a methodology to assess the capabilities of future spaceborne instruments. The case study is the Flexible Combined Imager (FCI) of the future Meteosat Third Generation Imaging mission (MTG - I), and in particular its ability to detect variations in load of desert aerosols in a realistically variable atmosphere. A better understanding of the behavior of these aerosols is part of regularly expressed needs for the study of the climate, weather forecast or assessment of the solar resource in arid areas such as the Sahara. This type of aerosols is abundant in the atmosphere. Their physical and chemical properties make them distinguishable from other types of aerosols such as those resulting from anthropogenic pollution, especially as they are emitted in areas protected from contamination by these other types. They therefore represent a simple case study to validate the methodology developed in this thesis.The methodology is to provide a simulator of the view of the instrument to perform a large number of simulations of the radiance measured under different atmospheric conditions and ground albedo, to analyze the results in order to quantify the influence of each variable in the variation of radiance, and then conclude on the capabilities of detection through a test of detectability taking into account the characteristics of the instrument.The developed simulator was validated by comparison against actual measurements of the SEVIRI instruments onboard Meteosat Second Generation satellites. The main innovation lies in the use of the global sensitivity analysis approach (GSA). The latter quantifies the influence of each variable separately as well as their crossed terms. Cumulative distribution functions were computed from actual observations and allow a realistic sensitivity analysis of the instrument. The GSA is also used to compute functional representation of the influence of one or more variables on the variability of the observed signal. The usefulness of such representations is discussed ...

EN alone is often insufficient, or occasionally contraindicated, in critically ill patients and results in growing energy and protein deficit. The cost benefit of using early PN in patients with short-term relative contraindications to EN has been reported. In selected patients SPN has been associated with a decreased risk of infection, a reduced duration of mechanical ventilation, a shorter stay in the ICU. Altogether four studies have investigated the costs associated with these interventions since 2012: two of them from Australia and Switzerland have shown that optimization of energy provision using SPN results in cost reduction, conflicting with other studies. The latter encouraging findings require further validation

Extrait des Oeuvres de Lavoisier

Neutron stars are at the origin of some of the most extreme phenomena in the universe because of their ultra-intense electromagnetic fields accelerating the surrounding particles to ultra-relativistic speeds. To better understand these stars, different models have been developed but all have limitations, that is why "particles in cells" numerical simulations have been performed by various teams, but using algorithms not well suited to intense fields, implying a scaling and velocities of particles well below reality.In this thesis, to overcome the limitations of other algorithms, we have developed a code based on successive analytical solutions to the equation of motion of a particle in constant fields (with and without radiation reaction). We have injected up to 8192 test particles around neutron stars, in the Deutsch field, and studied their velocities and positions. The code is functional, shows expected results and demonstrates the importance of the radiation reaction but is limited by the absence of interaction between particles. ; Les étoiles à neutrons sont à l’origine de phénomènes parmis les plus extrêmes de l’univers en raison de leurs champs électromagnétiques ultra-intenses accélérant les particules alentours à des vitesses ultra relativistes. Pour mieux comprendre ces astres, différents modèles ont été élaborés mais tous ont des limites, c’est pourquoi des simulations numériques «particles in cells» ont été réalisées par diverses équipes, mais en utilisant des algorithmes peu adaptés aux champs intenses, impliquant un scaling et des vitesses de particules bien en dessous de la réalité.Dans cette thèse, pour dépasser les limites des autres algorithmes, nous avons développé un code basé sur des solutions analytiques successives à l’équation du mouvement d’une particule en champs constants (avec et sans réaction de rayonnement). Nous avons injecté jusqu’à 8192 particules test autours d’étoiles à neutrons, dans le champ de Deutsch, et avons étudié leurs vitesses et leurs positions. Le code est ...

The aim of the present study is to assess and compare various processes aiming at recover CO2 from power plants fed with natural gas (NGCC) and pulverized coal (PC). These processes are post-combustion CO2 capture using chemical solvents, natural gas reforming for pre-combustion capture by methanol and oxy-fuel combustion with cryogenic recovery of CO2. These processes were evaluated using the process software Aspen PlusTM to give some clues for choosing the best option for each type of power plant. With regard to post-combustion, an aqueous solution based on a mixture of amines (N-methyldiethanolamine (MDEA) and triethylene tetramine (TETA)) was developed. Measurements of absorption were carried out between 298 and 333 K in a Lewis cell. CO2 partial pressure at equilibrium, characteristic of its solubility in the solvent, was determined up to 393 K. The solvent performances were compared with respect to more conventional solvents such as MDEA and monoethanolamine (MEA). For oxy-fuel combustion, a recovery process, based on a cryogenic separation of the components of the flue gas, was developed and applied to power plants. The study showed that O2 purity acts on the CO2 concentration in the flue gas and thus on the performances of the recovery process. The last option is natural gas reforming with CO2 pre-combustion capture. Several configurations were assessed: air reforming and oxygen reforming, reforming pressure and dilution of the synthesis gas. The comparison of these various concepts suggests that, in the short and medium term, chemical absorption is the most interesting process for NGCC power plants. For CP power plants, oxy-combustion can be a very interesting option, as well as post-combustion capture by chemical solvents. La présente étude a pour objectif d'évaluer et de comparer entre eux divers procédés de captage du CO2 appliqués aux centrales thermiques alimentées en gaz naturel (NGCC) et au charbon pulvérisé (CP). Ces procédés consistent en un captage du CO2 des fumées en post-combustion par des solvants chimiques, une décarbonisation du gaz naturel avec captage du CO2 en pré-combustion par un solvant physique et l'oxy-combustion du combustible avec séparation frigorifique du CO2. Ces procédés ont été évalués à l'aide du logiciel de procédés Aspen PlusTM pour aider à choisir la meilleure option pour chaque type de centrale. Pour la post-combustion, une solution aqueuse basée sur un mélange d'amines (N-méthyldiéthanolamine (MDEA) et triéthylène tétramine (TETA)) a été évaluée. Des mesures d'absorption ont été réalisées entre 298 et 333 K dans un réacteur fermé type cellule de Lewis. La pression partielle du CO2 à l'équilibre, caractéristique de la solubilité du CO2 dans le solvant, a été déterminée jusqu'à 393 K. Les performances sont comparées vis à vis de solvants plus conventionnels tels que la MDEA et la monoéthanolamine (MEA). Pour l'oxy-combustion, un procédé de captage, basé sur une séparation des composants des fumées à faible température, a été développé et appliqué aux centrales NGCC et CP. L'étude a montré que la pureté du flux d'O2 avait une influence non négligeable sur la concentration en CO2 dans les fumées et donc sur les performances du procédé de séparation. La dernière option étudiée est le reformage du gaz naturel qui permet un captage du CO2 en amont du système de production de l'électricité. Plusieurs configurations ont été évaluées : reformage à l'air ou à l'oxygène, pression de reformage et dilution du gaz de synthèse. La comparaison de ces différents concepts suggère que, à court et moyen terme, l'absorption chimique soit le procédé le plus intéressant pour la centrale NGCC. Pour la centrale CP, l'oxy-combustion peut être une option très intéressante, au même titre que le captage en post-combustion par absorption chimique.

The Aquitanian coast, as well as most coastal regions, is influenced by several hydrodynamical factors. Those factors can be modified by climate change. This study aims at studying climate change impact mainly on wave conditions which affect the Aquitanian coast.Using dynamical downscaling, waves are modelled from the North Atlantic Ocean towards the Bay of Biscay at a 10 km spatial resolution exclusively from wind fields. Waves are simulated with WAVEWATCH III spectral wave model, for the present climate (wind fields issued from the ERA-40 reanalysis) and for a control scenario and three future greenhouse gas emission scenarios (A2, A1B, B1) (wind fields issued from the RETIC simulations of ARPEGE-Climat). The database calibration and validation are based on local buoy measurements. Wind fields issued from climate model present systematic biases, therefore, a quantile-quantile correction is applied to wave projections.Wave climate evolution analysis is done in two steps. Firstly, present wave climate (1958-2001) is investigated regarding multi-decadal trends and interannual variability. A significant increase of summer wave height is identified on the period 1970-2001 (0.54 cm/y at the Biscay buoy). Concerning largest wave heights, a significant shift of directions is noticed for autumn (up to −0.47°/y from 1974 to 2001 at the Biscay buoy) and spring (0.3°/y from 1958 to 2001 at the Biscay buoy). The strong interannual variability of wave conditions is correlated to several general atmospheric circulation preferential modes (teleconnexion patterns and weather regimes). This underlines a strong link between local wave conditions and climate. For instance, the winter wave height and direction anomalies within the Bay of Biscay are strongly correlated to the North Atlantic Oscillation and the East Atlantic teleconnection pattern indices. Secondly, wave condition changes between present climate (1961-2000) and future scenarios (2061-2100) are investigated and analysed. A general decrease of wave heights is noticed ...