Systèmes d'innovations et dispositifs d'appui pour les agricultures africaines subsahariennes

International audienceLes auteurs analysent les évolutions actuelles des systèmes de production en Afrique, et notamment en zone de savanes d'Afrique de l'Ouest. Ils précisent les caractéristiques de ces innovations en les confrontant avec les théories de l'innovation et présentent les grands déterminants de l'innovation qui marquent ces zones, que ce soit une pression toujours croissante sur les ressources, une ouverture toujours plus marquée vers le marché, ou l'intervention volontaire d'acteurs publics ou privés capables d'impulser des dynamiques de changements. Ils abordent l'évolution des dispositifs d'appui aux producteurs en montrant les limites des approches diffusionnistes et l'émergence de nouvelles manières d'intervenir. Ils proposent une réflexion sur les conditions pour renforcer les processus d'innovation dans un contexte rendu plus difficile qu'autrefois suite au retrait de l'Etat de nombreuses fonctions

Definition of a New Level One Test Case Measurements of Equilibrium Radiation from an Inductively Coupled Plasma in the Near-UV to Near-IR Spectral Region for a Titan-Type N2-CH4 Mixture. Preliminary Results

A test case, using a similar methodology and experimental set-up than previous test case TC5-Level 1 is presented in this paper. An inductively coupled plasma torch, working at atmospheric pressure, is used to create N2-CH4 Titan-like plasma (98%N2 - 2%CH4). The operating frequency and power are 64 MHz and 3 kW respectively. This kind of apparatus allows obtaining plasma in chemical and quasi-thermal equilibrium The spectral measurements cover the [300-800] nm range and are performed inside the induction coil. Each interesting spectrum is calibrated and compared to the line-by-line spectral code SPARTAN used for the simulation of the radiative emission of entry-type plasma. Finally, a discussion is proposed about the nucleation phenomenon which is occurred in the ICP torch with the N2-CH4 plasma. Preliminary studies show the synthesis of nanostructured carbon on the quartz tube.Comment: Radiation of High Temperature Gases in Atmospheric Entry, Heraklion : Greece (2008

Numerical calculation of the transport coefficients in thermal plasmas

-We have performed a new efficient method to calculate numerically the transport coefficients at high temperature. The collision theory was treated to study singularities that occur when evaluating the collision cross section. The transport coefficients (viscosity, diffusion coefficient, thermal and electrical conductivity) depend strongly on nature of the interaction between the particles that form the plasma and that is why it is necessary to determine the interaction potential accurately.Comment: The 9th International Student Conference on Advanced Science and Technology., Dec 2014, Clermont-Ferrand, Franc

ACQUISITION AND MODELING OF A SPECTRUM IN A NON THERMAL EQUILIBRIUM PLASMA FORMED IN AIR WITH WATER

Spectra in the range of 365-385 nm, corresponding to the Schumann-Runge system of O2 (B33u - X33-g) and to the second positive system of N2 (C30u - B30g) are measured by optical emission spectroscopy in a discharge with liquid non-metallic electrodes (DLNME) in air with water at atmospheric pressure. They are simulated theoretically. This discharge generates a non-equilibrium plasma. In this paper, we first describe the experimental set up. Then, we explain the method of spectra simulation. By comparison of measured and simulated spectra, we determine the rotational and vibrational temperature and the ratio between densities of two upper electronic quantum levels of the two considered systems. The possible mechanism of spectra formation is discussed

Strategies to facilitate the development of uncloned or cloned infectious full-length viral cDNAs: Apple chlorotic leaf spot virus as a case study

Background Approaches to simplify and streamline the construction of full-length infectious cDNA clones (FL-cDNAs) are needed. Among desirable improvements are the ability to use total nucleic acids (TNA) extracts from infected hosts (to bypass viral purification limitations) for the direct one-step amplification of large FL-cDNAs, the possibility to inoculate plants with uncloned FL-cDNAs and the simplified cloning of these large molecules. Results Using the 7.55 kb genome of Apple chlorotic leaf spot trichovirus (ACLSV) approaches allowing the rapid generation from TNA extracts of FL-cDNAs under the control of the T7 promoter and the successful inoculation of plants using in vitro transcripts obtained from these uncloned amplification products have been developed. We also show that the yeast homologous recombination system permits efficient cloning of FL-cDNAs and the simultaneous one-step tailoring of a ternary Yeast-Escherichia coli-Agrobacterium tumefaciens shuttle vector allowing efficient inoculation of both herbaceous and woody host plants by agroinfiltration. Conclusions The fast and efficient strategies described here should have broad applications, in particular for the study "difficult" plant viruses, such as those infecting woody hosts, and potentially for other, non plant-infecting viral agents

Les savanes d'Afrique centrale et les grands enjeux du développement

International audienceSynthèse générale du colloqu

Analyses spectroscopiques d'un plasma CO2-N2 (97%-3%), de type atmosphère martienne, par torche ICP

Une torche à plasma à couplage inductif, fonctionnant à la pression atmosphérique, est utilisée pour créer un plasma à partir d'un mélange CO2-N2 reproduisant une atmosphère martienne (97%-3%). La fréquence ainsi que la puissance de fonctionnement de la torche ICP sont respectivement 64 Mhz et 3 kW. Ce type d'outil analytique permet d'obtenir un plasma relativement proche de l'équilibre thermodynamique. La caractérisation du plasma consistera dans un premier temps à déterminer la composition chimique; un code de calcul basé sur la minimisation de l'énergie libre de Gibbs est utilisé. Dans un second temps, les profils de températures seront données à travers les applications de l'inversion d'Abel des systèmes moléculaires considérés. Les mesures spectroscopiques couvrent le domaine [250-800] nm et sont réalisés à l'intérieur des spires inductives. Chaque spectre est ainsi comparé au code SESAM (Simulation de l'Emission Spectrale de l'Atmosphère de Mars)

Monatomic Excitation Temperature in Theoretical Study of Discharge with Liquid Non-Metallic (Tap Water) Electrodes in Air at Atmospheric Pressure

The discharge with liquid non-metallic electrodes under study is out of thermal equilibrium. From probe and micro-wave absorption measurements the electronic concentration has been evaluated. The spectral intensities of N2 and Oxygen triplet have been measured locally. In this work, we propose to compare the results of calculation with the experimental results for two hypotheses on the monatomic excitation temperature. The first is when we assume the monatomic excitation temperature close to heavy particle translational temperature and the second is when we assume the monatomic excitation temperature close to the electronic translational temperature