Evaluation de nanocomposites polypropylène/silicate pour l'isolation électrique : étude des phénomènes de polarisation, de conduction et des propriétés optiques

Ce travail de thèse porte sur des nanocomposites -NC- à matrice polyoléfine. Le but est d'apporter des éléments d'interprétation sur leurs propriétés macroscopiques. Nous avons étudié les propriétés électriques, optiques et physicochimiques de matériaux composites à base de matrices de polypropylène iso- et syndio-tactique; les dispersions appartiennent à la classe générique des silicates. Les moyens mis en œuvre concernent des mesures en analyse diélectrique dynamique, de courant dans le domaine temps, d'électroluminescence, de photoluminescence et de spectroscopie UV-visible. Une méthode d'inversion temps-fréquence a été mise en place : elle permet d'expliquer les transitoires de courants observés à partir des données fréquentielles et d'identifier les régimes de champ où des phénomènes non linéaires se produisent.This thesis focuses on polyolefin matrix nanocomposite. The goal is to provide an interpretation on their macroscopic properties. We studied electrical properties, optical and chemicophysical properties of composite materials based on iso- and syndiotactic polypropylene matrix and dispersions belong to the generic class of silicates. The means employed on measures dynamic dielectric analysis, current in the time domain, electroluminescence, photoluminescence and UV-visible spectroscopy. A method of time-frequency inversion was implemented : it allows to explain the transient currents observed from the frequency data and identify the regimes of field where nonlinear phenomena occur

Role of ethylene on various ripening pathways and on the development of sensory quality of Charentais cantaloupe melons

Charentais melons (Cucumis melo L., var cantalupensis Naud.) in which ethylene biosynthesis has been suppressed by an antisense ACC oxidase gene have been used to better understand the role of ethylene in the regulation of the ripening process of climacteric fruit and on the development of sensory qualities. We have shown that a number of biochemical and molecular processes associated with the ripening of climacteric fruit are ethylene-independent. In some cases, such as softening of the flesh, the same pathway comprises both ethylene-dependent and -independent components. The various ethylene-dependent events exhibit differential sensitivity to ethylene. The threshold level for degreening of the rind is 1 ppm, while 2.5 ppm are required to trigger the ethylene-dependent component of the softening process. The saturating level of ethylene for all these events is less than 5 ppm, which is by far lower than the internal ethylene concentrations found in the fruit at the climacteric peak (around 100 ppm). Detachment of the fruit influences the development of respiratory climacteric. Fruit remaining attached to the vine, although producing higher levels of ethylene, exhibit a reduced climacteric rise in respiration as compared to detached fruit. The response of antisense ACO fruit to exogenous ethylene in terms of respiration is higher in detached than in attached fruit. Ethylene-suppressed melons show a severe reduction of aroma volatiles production, particularly in ester production. In the biosynthetic pathway of aliphatic esters, the dehydrogenation of fatty acids and aldehydes appears to be ethylene-dependent. In contrast, alcohol acetylation comprises ethylene-dependent and ethylene-independent components, probably corresponding to differentially regulated alcohol acetyl transferases. In terms of sensory quality, these data show that the extension of shelf-life through the inhibition of ethylene production has some beneficial effects on texture and sugar accumulation but is detrimental for the generation of aroma

Production of γ-decalactone by Yarrowia lipolytica : insights into experimental conditions and operating mode optimization

BACKGROUND γ-Decalactone production from ricinoleic acid biotransformation derived from the triglycerides in castor oil by Yarrowia lipolytica, has been widely described in literature in studies concerning lipidic metabolism that leads to lactones production, interactions of cells with the lipid substrate, toxicity of produced metabolites, selection of over-producing mutants and selection of environmental conditions. RESULTS In order to improve technological aspects of γ-decalactone production, oxygen transfer rate (OTR), cell density and oil concentration effects were investigated, in batch and step-wise fed-batch cultures of Yarrowia lipolytica W29. The best γ-decalactone concentration of 5.4 ± 0.5 g L-1 was obtained for batch cultures with 60 g L-1 of cells and substrate concentration. CONCLUSION The direct influence of aeration and agitation rates, thus of OTR, on production of γ-decalactone has been demonstrated. γ-Decalactone productivity of 215 ± 19 mg L-1 h-1 was obtained with 60 g L-1 of cells and castor oil concentration in batch and step-wise fed-batch cultures of Yarrowia lipolytica. The results obtained suggest that these two strategies are good alternatives for industrial production processes.The authors thank the Project 'BioInd - Biotechnology and Bioengineering for improved Industrial and Agro-Food processes, REF. NORTE-07-0124-FEDER-000028' co-funded by the Programa Operacional Regional do Norte (ON. 2 - O Novo Norte), QREN, FEDER and Fundacao para a Ciencia e a Tecnologia (FCT) (SFRH/BD/63701/2009 PhD grant to Adelaide Braga) for the financial support provided and FCT Strategic Project PEst-OE/EQB/LA0023/2013

Phenyltransferase compartmentation in cells of Vitis vinifera cultivated in vitro

International audienc

The 10th Weurman flavour research symposium : book of abstracts

International audienc

Les scores de prédiction clinique des thromboses veineuses profondes et des embolies pulmonaires (revue de la littérature et résultats de l'étude Toulousaine STVP ( Stratégie pour le diagnostic des Thromboses veineuses profondes))

La maladie veineuse thromboembolique est la troisième cause de mortalité en France. Une revue exhaustive de la littérature a permis de répertorier les différents scores de prédiction clinique validés concernant les embolies pulmonaires et les thromboses veineuses profondes. Elle montre qu' ils constituent la première étape d'une démarche diagnostique scientifique en accord avec les bonnes pratiques médicales. Les différents scores de Wells semblent être les plus performants. Ces scores sont inclus dans une stratégie diagnostique bien codifiée hiérarchisant les examens complémentaires. Ils diminuent le recours aux examens radiologiques de 20 à 30%. Selon les premiers résultats de l'étude Toulousaine STVP (Stratégie pour le diagnostic des Thromboses Veineuses Profondes), le score de Wells présente une excellente valeur prédictive négative. Ces résultats préliminaires demandent à être confirmés après examen des 400 patients qui doivent être inclus.TOULOUSE3-BU Santé-Centrale (315552105) / SudocPARIS-BIUM (751062103) / SudocSudocFranceF