Lecture assistée par ordinateur en otolithométrie : application à l'étude de l'âge de Lutjanus sebae (Cuvier, 1828) aux Seychelles

La présente étude porte sur la détermination otolithométrique de l'âge d'un poisson exploité sur le plateau des Seychelles, #Lutjanus sebae$ (Cuvier, 1828). Les observations ont été effectuées sur des coupes transversales d'otolithes sagitta incluses à l'aide d'un dispositif d'analyse d'image. En raison des particularités du matériel biologique étudié, une approche originale du rétrocalcul de la taille des poissons est envisagée. Une partie du plan de coupe est modélisée par une ellipse permettant ainsi de s'affranchir de la contrainte d'un axe standard de lecture. Parallèlement à l'acquisition des données, une mise au point de l'appareillage utilisé est effectuée. Ainsi l'expérience acquise lors des différentes observations permet de discuter des limites de la technique du point de vue de l'extraction de l'information et de son traitement ultérieur. Les résultats de lectures réalisées suggèrent la formation de deux annuli par an. Le principe du comptage des stries supposées journalières par la méthode de la densité est exposé pour ce qui concerne son application à l'espèce étudiée, et les résultats préliminaires obtenus sont présentés. (Résumé d'auteur

Integrated hydrological modelling of a managed coastal Mediterranean wetland (Rhone delta, France): initial calibration

This paper presents a model of a heavily managed coastal Mediterranean wetland. The hydrosystem studied , called ``Ile de Camargue', is the central part of the Rhone river delta. It comprises flat agricultural drainage basins, marshes, and shallow brackish lagoons whose connection to the sea is managed. This hydrosystem is subject to strong natural hydrological variability due to the combination of a Mediterranean climate and the artificial hydrological regime imposed by flooded rice cultivation. To quantify the hydrological balance at different spatial and temporal scales, a simplified model is developed — including the basin and the lagoons — using a time step that enables the temporal dynamic to be reproduced that is adapted to data availability. This modelling task takes into account the functioning of the natural and anthropogenic components of the hydrosystem. A conceptual approach is used for modelling drainage from the catchment, using a GIS to estimate water input for rice irrigation. The lagoon system is modelled using a two-dimensional finite element hydrodynamic model. Simulated results from the hydrodynamic model run under various hydro-climatic forcing conditions (water level, wind speed and direction, sea connection) are used to calculate hydraulic exchanges between lagoon sub units considered as boxes. Finally, the HIC ('Hydrologie de l’Ile de Camargue') conceptual model is applied to simulate the water inputs and exchanges between the different units, together with the salt balance in the hydrosystem during a calibration period.</p> <p style='line-height: 20px;'><b>Keywords: </b>water management,conceptual hydrological model, hydrodynamic model, box model, GIS, Rhone delta, Camargue

Modeling of a managed coastal Mediterranean wetland with TELEMAC-2D: the Vaccarès lagoons system (Rhone delta, Camargue, France)

Water Qualit

EVASPA (EVapotranspiration Assessment from SPAce) Tool: An overview

AbstractEvapotranspiration (ET) is a fundamental variable of the hydrological cycle and its estimation is required for irrigation management, water resources planning and environmental studies. Remote sensing provides spatially distributed cost-effective information for ET maps production at regional scale. We have developed EVASPA too for mapping ET from remote sensing data at spatial and temporal scales relevant to hydrological or agronomica studies.EVASPA includes several algorithms for estimating evapotranspiration and various equations for estimating the required input information (net radiation, ground heat flux, evaporative fraction…), which provides a way to assess uncertainties in the derivation of ET. The tool integrates data from various remote sensing sensors and it can be easily adapted to new sensors. To test the tool, evapotranspiration maps have been produced for the Crau-Camargue pilot site (south-eastern France), where several energy balance stations deployed in contrasted areas provide ground measurements. An overall description of the tool and first results of performance asse sment (comparison to ground data) are presented here

Sterilization of Exopolysaccharides Produced by Deep-Sea Bacteria: Impact on Their Stability and Degradation

Polysaccharides are highly heat-sensitive macromolecules, so high temperature treatments are greatly destructive and cause considerable damage, such as a great decrease in both viscosity and molecular weight of the polymer. The technical feasibility of the production of exopolysaccharides by deep-sea bacteria Vibrio diabolicus and Alteromonas infernus was previously demonstrated using a bioproduct manufacturing process. The objective of this study was to determine which sterilization method, other than heat sterilization, was the most appropriate for these marine exopolysaccharides and was in accordance with bioprocess engineering requirements. Chemical sterilization using low-temperature ethylene oxide and a mixture of ionized gases (plasmas) was compared to the sterilization methods using gamma and beta radiations. The changes to both the physical and chemical properties of the sterilized exopolysaccharides were analyzed. The use of ethylene oxide can be recommended for the sterilization of polysaccharides as a weak effect on both rheological and structural properties was observed. This low-temperature gas sterilizing process is very efficient, giving a good Sterility Assurance Level (SAL), and is also well suited to large-scale compound manufacturing in the pharmaceutical industry

Les affiches d'art à l’école. Puvis de Chavannes éducateur

Chauvelon Émile. Les affiches d'art à l’école. Puvis de Chavannes éducateur. In: La revue pédagogique, tome 36, Janvier-Juin 1900. pp. 301-312