Décharges Sparks dans les liquides diélectriques : caractérisation et application à la synthèse de nanoparticules

Ce projet de recherche s’inscrit dans le parcours international de la maitrise de Physique (option plasma) de l’Université de Montréal en collaboration avec l’Université Paul Sabatier de Toulouse (France). Il concerne la caractérisation des décharges électriques (Sparks) dans les liquides diélectriques et ses applications dans la synthèse de nanoparticules. L’objectif est d’amélioré la connaissance des conditions de formation des nanoparticules. Cela implique de caractériser l’ensemble du système expérimental et de développer sa métrologie d’une part, et d’autre part d’obtenir l’évolution des paramètres plasma lors de la synthèse. Dans un premier temps, sur le site du LAPLACE (UMR5213), Toulouse, il a fallu développer une alimentation électrique impulsionnelle destinée à réaliser des décharges dans les liquides. En se basant sur un dispositif existant qui fût amélioré, le fonctionnement a été caractérisé du point de vue électrique (courant - tension). L’application à la synthèse de nanoparticules a été ensuite abordée pour différentes conditions expérimentales, en considérant l’aspect énergétique (bilan d’énergie, caractéristiques de la décharge…). Les travaux se sont poursuivis à l’Université de Montréal, où un circuit électrique équivalent du système expérimental est réalisé afin de visualiser l’évolution temporelle des paramètres plasma (température et densité électronique) en fonction des paramètres électriques choisis. Aussi, la synthèse de nanoparticules de Co et Ni par la décharge a été évaluée et les nanoparticules formées sont caractérisées à l’aide du microscope électronique à Transmission de Polytechnique Montréal.This research project is part of the international master's program in Physics (plasma option) between Université de Montréal and Université Paul Sabatier - Toulouse (France). It concerns the synthesis of nanoparticles by pulsed electrical discharges in liquids. The objective is to develop the synthesis process while improving the knowledge of the formation conditions of nanoparticles. This involves characterizing the entire experimental system and developing its metrology on the one hand, and on the other hand obtaining the evolution of plasma parameters during synthesis. Initially, at the LAPLACE lab (UMR5213), Toulouse, it was necessary to develop a pulsed electrical supply to produce discharges in liquids. Based on an existing device that, after being improved, the discharge process is characterized from the electrical point of view (current, voltage). The application of the device in the synthesis of nanoparticles was tested under different experimental conditions, considering the energy aspect (energy balance, characteristics of the discharge, etc.). The second part was conducted at Université de Montréal, where the synthesized nanoparticles are characterized using the transmission electron microscope of Polytechnique Montreal. Also, the electrical circuit equivalent to the experimental system was determined to visualize the time evolution of the plasma parameters (Temperature and Electron Density) based on the electrical characteristics

Intensify pastures for livestock production: vermicompost use, an agro-ecological practice

The intensification of animal production at pasture is essential to meet the growing demand for animal products but also for other functions, the maintenance of areas, livelihoods and well-being of populations. This intensification must also take into account the reduction of agricultural land, promote positive interactions with the environment and biodiversity, while ensuring the supply of populations. The use of vermicompost involving the action of earthworms is an example of agro-ecological practices, to participate in the intensification of grassland and which has been studied in the context of a call to project, AGRIBIO3. Besides the fact that this practice makes it possible to achieve a proper recycling and recovery of various manures, it improves the quality of organic soil, nutrient bioavailability, and grassland biomass while having a nematophagous action, beneficial to a lesser gastrointestinal parasitism of grazing small ruminants. The biological and financial advantages of this practice in the longer term, and their use to various grassland systems must be quantified

The role of WNK in modulation of KCl cotransport activity in red cells from normal individuals and patients with sickle cell anaemia

Abstract: Abnormal activity of red cell KCl cotransport (KCC) is involved in pathogenesis of sickle cell anaemia (SCA). KCC-mediated solute loss causes shrinkage, concentrates HbS, and promotes HbS polymerisation. Red cell KCC also responds to various stimuli including pH, volume, urea, and oxygen tension, and regulation involves protein phosphorylation. The main aim of this study was to investigate the role of the WNK/SPAK/OSR1 pathway in sickle cells. The pan WNK inhibitor WNK463 stimulated KCC with an EC50 of 10.9 ± 1.1 nM and 7.9 ± 1.2 nM in sickle and normal red cells, respectively. SPAK/OSR1 inhibitors had little effect. The action of WNK463 was not additive with other kinase inhibitors (staurosporine and N-ethylmaleimide). Its effects were largely abrogated by pre-treatment with the phosphatase inhibitor calyculin A. WNK463 also reduced the effects of physiological KCC stimuli (pH, volume, urea) and abolished any response of KCC to changes in oxygen tension. Finally, although protein kinases have been implicated in regulation of phosphatidylserine exposure, WNK463 had no effect. Findings indicate a predominant role for WNKs in control of KCC in sickle cells but an apparent absence of downstream involvement of SPAK/OSR1. A more complete understanding of the mechanisms will inform pathogenesis whilst manipulation of WNK activity represents a potential therapeutic approach

Discovery of 9-Cyclopropylethynyl-2-((S)-1-[1,4]dioxan-2-ylmethoxy)-6,7-dihydropyrimido[6,1-a]isoquinolin-4-one (GLPG1205), a unique GPR84 negative allosteric modulator undergoing evaluation in a phase II clinical trial

GPR84 is a medium chain free fatty acid-binding G-protein-coupled receptor associated with inflammatory and fibrotic diseases. As the only reported antagonist of GPR84 (PBI-4050) that displays relatively low potency and selectivity, a clear need exists for an improved modulator. Structural optimization of GPR84 antagonist hit 1, identified through high-throughput screening, led to the identification of potent and selective GPR84 inhibitor GLPG1205 (36). Compared with the initial hit, 36 showed improved potency in a guanosine 5′-O-[γ-thio]triphosphate assay, exhibited metabolic stability, and lacked activity against phosphodiesterase-4. This novel pharmacological tool allowed investigation of the therapeutic potential of GPR84 inhibition. At once-daily doses of 3 and 10 mg/kg, GLPG1205 reduced disease activity index score and neutrophil infiltration in a mouse dextran sodium sulfate-induced chronic inflammatory bowel disease model, with efficacy similar to positive-control compound sulfasalazine. The drug discovery steps leading to GLPG1205 identification, currently under phase II clinical investigation, are described herein

Le cas des antillais et des surinamiens, l'immigration aux Pays-Bas

Les Antilles néerlandaises et le Suriname ont des relations étroites avec les Pays-Bas en raison de leur histoire coloniale. Pourtant ce n'est qu'à partir des années soixante-dix que les Antillais et les Surinamiens émigrent massivement vers les Pays-Bas, en cela comparables à l'immigration d'outre-mer vers la France métropolitaine. Ces populations ont souvent un faible niveau socio-économique et sont confrontées à des problèmes d'intégration que le gouvernement néerlandais tente, encore à l'heure actuelle, de résoudre.Merciris Jean-Philippe. Le cas des antillais et des surinamiens, l'immigration aux Pays-Bas. In: Hommes et Migrations, n°1274, Juillet-août 2008. L’espace caribéen : institutions et migrations depuis le XVIIe siècle. pp. 144-154

Rôle des métalloprotéases matricielles ostéoblastiques et du facteur de transcription Runx2 dans l'action anabolique de la parathormone in vivo

PARIS7-Bibliothèque centrale (751132105) / SudocSudocFranceF

Leaf-Cutting Ants, Biology and Control

International audienc

Soil aggregation in a laboratory experiment : interactions between earthworms, woodlice and litter palatability

Interactions between soil invertebrate functional groups are still poorly understood. In this study, the effect of the soil dwelling earthworm Aporrectodea caliginoso and the woodlouse Porcellio scaber (litter inhabitant), atone or in combination, on soil aggregation was investigated in laboratory microcosms with litter of different quality (Quercus robur and Fagus sylvatica). After 4 months of incubation, the aggregate size distribution was measured using a dry-sieving method. A. caliginosa played an important role in the formation of large aggregates (> 2 mm), whereas P scaber greatly influenced litter disappearance. A. caliginosa individuals formed a greater number of large aggregates when fed with beech leaves compared to oak leaves even though they preferred the latter. In the presence of beech and P scaber, A. caliginosa produced significantly fewer large aggregates than expected