Flux des particules grossières de matière organique allochtone et autochtone dans un bras mort du Rhône

Les flux de matière organique particulaire allochtone et autochtone ont été suivis dans la Lône des Pêcheurs. Leur estimation quantitative et qualitative rend compte de l'impact de l'écotone rives sur le fonctionnement du système aquatique. Dans ce bras mort, les apports allochtones semblent plus importants que dans d'autres systèmes, comme les ruisseaux forestiers mentionnés par la littérature.Pour l'estimation des flux de matière organique particulaire nous avons utilisé, comme moyen d'échantillonnage, des bacs de plastique rectangulaires déposés sur le fond; en plus nous avons procédé à des prélèvements par benne.Le plus grand apport de feuilles terrestres a lieu en novembre, le plus grand apport de bois et autres débris en avril et dans les mois qui suivent, probablement par suite des crues. Au niveau de la lône, on note une différence entre les parties amont et aval.A surface égale, les apports grossiers (feuilles mortes et bois) sont plus abondants en amont, les éléments en voie de désintégration sont, au contraire, plus nombreux en aval. Cette différence est principalement due à la proportion des rives par rapport à la surface du plan d'eau et probablement aussi à la vitesse de dégradation de ces apports dans les deux stations. Ceci nous amène donc à penser qu'il existerait un gradient décroissant de matière organique grossière de l'amont de la lône vers l'aval.La biocénose aquatique est alimentée d'abord par les macrophytes immergés à décomposition rapide (été, automne), puis par les feuilles terrestres et les macrophytes émergés (hiver, printemps).L'analyse de la structure des invertébrés aquatiques montre la relation entre ces apports, particutièrement les feuilles mortes, et la biomasse des dilacérateurs et des collecteurs.This study concerns a side arm of the River Rhone, 20 km upstream from the city of Lyons, southeastern France. The arm opens into the channel of the river downstream, but it is closed and fed by groundwater upstream. Terrestrial particulate organic matter enters the water through the ecotone of the banks. This flow and that of carbon, nitrogen and phosphorus were measured, using sediment traps and a grab, by the monthly sedimentation of allochthonous organic matter on the bottom, corrected for the time of exposure under the water. The input seemed to be somewhat greater than in the temperate woodland streams described in the literature.The greatest input of terrestrial leaves occurred in November, the greatest input of wood and other debris in April, presumably as a consequence of the flooding of the undergrowth. The arm was narrower upstream than downstream (respectively 10-25 and 60-80 m in width). Though the banks were equally and densely forested, the bottom sediment received more coarse particulate matter upstream, and this matter was equally distributed. In contrast, less organic matter was deposited along the banks downstream and still less in the middle of the arm, where partially, decomposed matter was more abundant. These differences may be explained by the ratio between the banks and the water area, by a certain transport during the floods, and by the faster processing of particulate matter closer to the channel. Hence there seems to be a decreasing gradient of particulate organic matter as one goes downstream along the arm.The heterotrophic communities in the arm were fed successively by the decay of autochthonous submerged macrophytes such as Potamogeton in summer and autumn, then by that of terrestrial leaves (mostly alder, poplar and willow with respectively fast, medium and slow processing velocities) and emergent macrophytes such as Phragmites, during winter and spring.A comparison of invertebrate biomass and community structure shows that shredders and collectors are more numerous in winter and spring, white terrestrial leaves are being processed

Intelligent IT Governance Platform: Strategic level

The objective of this work is the implementation of a new IT governance platform adaptable to any type of Information system architecture and any kind of business. The proposed platform is intelligent and independent to understand the business needs continuously changing, is distributed to involve all stakeholders and heterogeneous components, and scalable to accumulate the know-how of the company's IT Governance through a learning asset

Empirical Study on the Status of Moroccan Information Systems and Proposition of Approach for Choice of Best Practices for Good IT Governance

Today, the function of the chief information officer (CIO) has become part of the flow charts of many Moroccan companies [1]. Based on this statement, we did an empirical study in the first part of this work on the state of information systems (IS) Moroccan to know their strengths and weaknesses. The aim of the second part is to propose an approach based on the IT (information technology) frameworks helping CIOs to form their own repository of good practices to be applied in order to have good IT governance

An Empirical Study on the information systems in the Moroccan organizations: An explanatory model to decide differently and to optimize the IT governance

An information system, it's the key point of the success of companies [5] [6]. Where from the necessity of investing to develop information systems, these investments concern to infrastructures, application software's, set up systems, and existing processes. Companies have to follow policies to manage well their investment of information systems in an economic and optimal way, it is the subject of this paper. To validate our subject, our hypothesis, a study of ground was necessary. We opted for an empirical study on the information systems of the high-level Moroccan organizations in various sectors, by basing itself on scientific foundations. The study and the data analysis allowed us to propose new simplified models

From atomistic structure to thermodynamics and mechanical properties of epoxy/clay nanocomposites: Investigation by molecular dynamics simulations

International audienc

Uptake and distribution of heavy metals in agricultural production irrigated by raw wastewater

Une expérience au champ a été réalisée pour déterminer les concentrations en fer, cuivre, zinc, nickel, cadmium et plomb dans le sol du champ d’épandage d’eaux usées et dans les tissus de divers plantes de grande importance économique: fève (Aphis fabae L.), carotte (Daucus carota L.), petit pois (Pisum sativum L.), laitue (Lactuca sativa L.), blé tendre (Triticum vulgare L.) et avoine (Avena sativa L.). Les parcelles irriguées par les eaux usées présentent des taux de matière organique largement supérieurs à celui de la parcelle témoin. Les concentrations en métal (cuivre, zinc, plomb et cadmium) dans les parcelles irriguées par les eaux usées sont supérieures à celles de la parcelle témoin (Po) et des sols pollués par les métaux lourds. Dans les tissus des plantes irriguées par ces eaux usées, les teneurs en métaux sont élevées par rapport aux valeurs normales rencontrées chez les espèces végétales

Wave packet dynamics of potassium dimers attached to helium nanodroplets

The dynamics of vibrational wave packets excited in K$_2$ dimers attached to superfluid helium nanodroplets is investigated by means of femtosecond pump-probe spectroscopy. The employed resonant three-photon-ionization scheme is studied in a wide wavelength range and different pathways leading to K$^+_2$-formation are identified. While the wave packet dynamics of the electronic ground state is not influenced by the helium environment, perturbations of the electronically excited states are observed. The latter reveal a strong time dependence on the timescale 3-8 ps which directly reflects the dynamics of desorption of K$_2$ off the helium droplets