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Auswahl der wissenschaftlichen Literatur zum Thema „Catalyse plasma“
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Zeitschriftenartikel zum Thema "Catalyse plasma"
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Fernandez, F. A., M. R. Buchanan, J. Hirsh, J. W. Fenton II und F. A. Ofosu. „Catalysis of Thrombin Inhibition Provides an Index for Estimating the Antithrombotic Potential of Glycosaminoglycans in Rabbits“. Thrombosis and Haemostasis 57, Nr. 03 (1987): 286–93. http://dx.doi.org/10.1055/s-0038-1651118.
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SummaryPrevious studies have demonstrated that standard anticoagulant tests are poor indices of the antithrombotic potential of glycosaminoglycans which are weak catalysts of the thrombinantithrombin III reaction. In this study we investigated whether the catalysis of thrombin inhibition by plasma could serve as a reliable index for assessing the antithrombotic effectiveness of glycosaminoglycans. Equal volumes of 125I-thrombin and control or test plasma were incubated for up to 10 min at 37° C. Inactivation of thrombin was then determined after 7.9% SDS-polyacrylamide gel electrophoresis and subsequent autoradiography. Increasing concentrations of heparin (>0.066 μg/mL or 0.01 USP units/mL) and dermatan sulfate (>0.1 μg/mL) could be readily demonstrated in undiluted plasma by enhanced formation of complexes of thrombin with antithrombin III and heparin cofactor II respectively. However, the detection of any catalytic effect of the two glycosaminoglycans decreased significantly with increasing plasma dilutions. When ex vivo plasmas obtained from rabbits that had been injected with the minimum dose of any one of seven glycosaminoglycans required to achieve their optimal antithrombotic effect were assessed for their ability to catalyse thrombin inhibition, there was approximately a 2-fold increase in the amount of thrombin inactivated 30 s after the thrombin had been added to the plasma. The enhanced inhibition of thrombin was achieved by catalysis of antithrombin III and/or heparin cofactor II activities. These results suggest that measurement of the catalysis of thrombin inactivation in undiluted plasma is a sensitive and reliable index for estimating the antithrombotic potential of glycosaminoglycans in rabbits.
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Ljungdahl, Per O. „Amino-acid-induced signalling via the SPS-sensing pathway in yeast“. Biochemical Society Transactions 37, Nr. 1 (20.01.2009): 242–47. http://dx.doi.org/10.1042/bst0370242.
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Yeast cells rely on the SPS-sensing pathway to respond to extracellular amino acids. This nutrient-induced signal transduction pathway regulates gene expression by controlling the activity of two redundant transcription factors: Stp1 and Stp2. These factors are synthesized as latent cytoplasmic proteins with N-terminal regulatory domains. Upon induction by extracellular amino acids, the plasma membrane SPS-sensor catalyses an endoproteolytic processing event that cleaves away the regulatory N-terminal domains. The shorter forms of Stp1 and Stp2 efficiently target to the nucleus, where they bind and activate transcription of selected genes encoding a subset of amino acid permeases that function at the plasma membrane to catalyse the transport of amino acids into cells. In the present article, the current understanding of events in the SPS-sensing pathway that enable external amino acids to induce their own uptake are reviewed with a focus on two key issues: (i) the maintenance of Stp1 and Stp2 latency in the absence of amino acid induction; and (ii) the amino-acid-induced SPS-sensor-mediated proteolytic cleavage of Stp1 and Stp2.
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Ofosu, F. A., G. J. Modi, M. A. Blajchman, M. R. Buchanan und E. A. Johnson. „Increased sulphation improves the anticoagulant activities of heparan sulphate and dermatan sulphate“. Biochemical Journal 248, Nr. 3 (15.12.1987): 889–96. http://dx.doi.org/10.1042/bj2480889.
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Heparan sulphate and dermatan sulphate have both antithrombotic and anticoagulant properties. These are, however, significantly weaker than those of a comparable amount of standard pig mucosal heparin. Antithrombotic and anticoagulant effects of glycosaminoglycans depend on their ability to catalyse the inhibition of thrombin and/or to inhibit the activation of prothrombin. Since heparan sulphate and dermatan sulphate are less sulphated than unfractionated heparin, we investigated whether the decreased sulphation contributes to the lower antithrombotic and anticoagulant activities compared with standard heparin. To do this, we compared the anticoagulant activities of heparan sulphate and dermatan sulphate with those of their derivatives resulphated in vitro. The ratio of sulphate to carboxylate in these resulphated heparan sulphate and dermatan sulphate derivatives was approximately twice that of the parent compounds and similar to that of standard heparin. Anticoagulant effects were assessed by determining (a) the catalytic effects of each glycosaminoglycan on the inhibition of thrombin added to plasma, and (b) the ability of each glycosaminoglycan to inhibit the activation of 125I-prothrombin in plasma. The least sulphated glycosaminoglycans were least able to catalyse the inhibition of thrombin added to plasma and to inhibit the activation of prothrombin. Furthermore, increasing the degree of sulphation improved the catalytic effects of glycosaminoglycans on the inhibition of thrombin by heparin cofactor II in plasma. The degree of sulphation therefore appears to be an important functional property that contributes significantly to the anticoagulant effects of the two glycosaminoglycans.
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Atkinson, Helen M., Tracy A. Mewhort-Buist, Leslie R. Berry und Anthony K. C. Chan. „Anticoagulant mechanisms of covalent antithrombin-heparin investigated by thrombelastography“. Thrombosis and Haemostasis 102, Nr. 07 (2009): 62–68. http://dx.doi.org/10.1160/th08-11-0769.
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SummaryWe have developed an antithrombin-heparin covalent complex (ATH) which inhibits coagulation enzymes by two mechanisms: directly, or by catalytic activation of plasma antithrombin (AT). Anticoagulation by ATH was compared to unfractionated heparin (UFH) or low-molecular-weight heparin (LMWH) using a blood-based, tissue factor (TF)-activated thrombelastography (TEG) assay. Simplified TEG assays with plasma or purified plasma components were used to determine the contribution of the direct and catalytic mechanisms to ATH efficacy. Low anti-Xa concentrations of UFH inhibited clot formation significantly more than equivalent concentrations of ATH or LMWH in blood and plasma. ATH had reduced ability to catalyse AT-mediated thrombin (IIa) inhibition compared to UFH. However, at high anti-Xa concentrations, ATH had similar anticoagulant activity to UFH. ATH and non-covalent AT+UFH directly inhibited clotting to a similar degree in AT-deficient plasma. IIa-ATH complexes, which are limited to catalytic inhibition, displayed impaired anticoagulation compared to free ATH, and the magnitude of this effect increased significantly as anticoagulant concentration increased. Kinetic experiments indicated that the rate of reaction of AT with IIa is lower when catalysed by ATH versus UFH. In conclusion, at low anti-Xa doses catalytic inhibition is the primary mechanism of ATH anticoagulation, and the catalytic potential of ATH is reduced relative to UFH. However, the direct inhibitory activity of ATH is comparable to noncovalent AT+UFH, and at high anti-Xa doses the direct inhibitory activity of ATH may play a larger role in anticoagulation.
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Gutteridge, John M. C. „Plasma ascorbate levels and inhibition of the antioxidant activity of caeruloplasmin“. Clinical Science 81, Nr. 3 (01.09.1991): 413–17. http://dx.doi.org/10.1042/cs0810413.
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1. The copper-containing protein caeruloplasmin has several oxidase activities. 2. Its ability to catalyse the oxidation of ferrous ions to the ferric state (ferroxidase activity) makes it an important antioxidant in vivo. 3. Recent reports have suggested that oral supplementation with vitamin C can inhibit the oxidase activities of caeruloplasmin. 4. As expected, damage to DNA and membrane lipids was stimulated by mixtures of iron salt and ascorbate, and this damage could be inhibited by caeruloplasmin provided the molar ratio of ascorbate to caeruloplasmin was kept sufficiently low. 5. When the molar ratio of ascorbate to caeruloplasmin was greater than 200 substantial loss of ferroxidase antioxidant activity occurred. 6. It is unlikely, however, that oral supplementation with vitamin C can raise plasma levels sufficiently to inhibit caeruloplasmin activity in vivo.
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Day, Joanna M., Paul A. Foster, Helena J. Tutill, Fabien Schmidlin, Christopher M. Sharland, Jonathan D. Hargrave, Nigel Vicker, Barry V. L. Potter, Michael J. Reed und Atul Purohit. „STX2171, a 17β-hydroxysteroid dehydrogenase type 3 inhibitor, is efficacious in vivo in a novel hormone-dependent prostate cancer model“. Endocrine-Related Cancer 20, Nr. 1 (06.11.2012): 53–64. http://dx.doi.org/10.1530/erc-12-0231.
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17β-Hydroxysteroid dehydrogenases (17β-HSDs) catalyse the 17-position reduction/oxidation of steroids. 17β-HSD type 3 (17β-HSD3) catalyses the reduction of the weakly androgenic androstenedione (adione) to testosterone, suggesting that specific inhibitors of 17β-HSD3 may have a role in the treatment of hormone-dependent prostate cancer and benign prostate hyperplasia. STX2171 is a novel selective non-steroidal 17β-HSD3 inhibitor with an IC50 of ∼200 nM in a whole-cell assay. It inhibits adione-stimulated proliferation of 17β-HSD3-expressing androgen receptor-positive LNCaP(HSD3) prostate cancer cells in vitro. An androgen-stimulated LNCaP(HSD3) xenograft proof-of-concept model was developed to study the efficacies of STX2171 and a more established 17β-HSD3 inhibitor, STX1383 (SCH-451659, Schering-Plough), in vivo. Castrated male MF-1 mice were inoculated s.c. with 1×107 cells 24 h after an initial daily dose of testosterone propionate (TP) or vehicle. After 4 weeks, tumours had not developed in vehicle-dosed mice, but were present in 50% of those mice given TP. One week after switching the stimulus to adione, mice were dosed additionally with the vehicle or inhibitor for a further 4 weeks. Both TP and adione efficiently stimulated tumour growth and increased plasma testosterone levels; however, in the presence of either 17β-HSD3 inhibitor, adione-dependent tumour growth was significantly inhibited and plasma testosterone levels reduced. Mouse body weights were unaffected. Both inhibitors also significantly lowered plasma testosterone levels in intact mice. In conclusion, STX2171 and STX1383 significantly lower plasma testosterone levels and inhibit androgen-dependent tumour growth in vivo, indicating that 17β-HSD3 inhibitors may have application in the treatment of hormone-dependent prostate cancer.
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Bagoly, Zsuzsa, Vera Sheptovitsky, Rima Dardik, Judith Lahav, Eli Karniel und Aida Inbal. „Coagulation factor XIII serves as protein disulfide isomerase“. Thrombosis and Haemostasis 101, Nr. 05 (2009): 840–44. http://dx.doi.org/10.1160/th08-09-0605.
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SummaryTissue transglutaminase was reported to act as protein disulfide isomerase (PDI). We studied whether plasma transglutaminase – coagulation factor XIII (FXIII) – has PDI activity as well. PDI activity was measured by determining the ability to renature reduced-denatured RNase (rdRNase). We found that FXIII can re-nature rdRNase, with efficiency comparable to commercial PDI. This PDI activity was inhibited by bacitracin. Like tissue transglu-taminase, FXIII-mediated PDI activity is independent of its transglutaminase activity and is located on the A subunit. Surface-associated PDI has been previously shown to catalyse two distinct functions: transnitrosation with subsequent release of intracellular nitric oxide and disulfide bond rearrangement during platelet integrin ligation. Our results imply that FXIII-PDI activity may have a role in platelet function.
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Wang, Zhen, Dong Hao Wang, Yuliya Goykhman, Yuanyuan Yan, Peter Lawrence, Kumar S. D. Kothapalli und J. Thomas Brenna. „The elongation of very long-chain fatty acid 6 gene product catalyses elongation of n-13 : 0 and n-15 : 0 odd-chain SFA in human cells“. British Journal of Nutrition 121, Nr. 3 (03.01.2019): 241–48. http://dx.doi.org/10.1017/s0007114518003185.
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AbstractNormal odd-chain SFA (OCSFA), particularly tridecanoic acid (n-13 : 0), pentadecanoic acid (n-15 : 0) and heptadecanoic acid (n-17 : 0), are normal components of dairy products, beef and seafood. The ratio of n-15 : 0:n-17 : 0 in ruminant foods (dairy products and beef) is 2:1, while in seafood and human tissues it is 1:2, and their appearance in plasma is often used as a marker for ruminant fat intake. Human elongases encoded by elongation of very long-chain fatty acid (ELOVL)1, ELOVL3, ELOVL6 and ELOVL7 catalyse biosynthesis of the dominant even-chain SFA; however, there are no reports of elongase function on OCSFA. ELOVL transfected MCF7 cells were treated with n-13 : 0, n-15 : 0 or n-17 : 0 (80 µm) and products analysed. ELOVL6 catalysed elongation of n-13 : 0→n-15 : 0 and n-15 : 0→n-17 : 0; and ELOVL7 had modest activity toward n-15 : 0 (n-15 : 0→n-17 : 0). No elongation activity was detected for n-17 : 0→n-19 : 0. Our data expand ELOVL specificity to OCSFA, providing the first molecular evidence demonstrating ELOVL6 as the major elongase acting on OCSFA n-13 : 0 and n-15 : 0 fatty acids. Studies of food intake relying on OCSFA as a biomarker should consider endogenous human metabolism when relying on OCSFA ratios to indicate specific food intake.
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SIGAL, Yury J., Mark I. McDERMOTT und Andrew J. MORRIS. „Integral membrane lipid phosphatases/phosphotransferases: common structure and diverse functions“. Biochemical Journal 387, Nr. 2 (05.04.2005): 281–93. http://dx.doi.org/10.1042/bj20041771.
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Phospholipids and sphingolipids play critical roles in signal transduction, intracellular membrane trafficking, and control of cell growth and survival. We discuss recent progress in the identification and characterization of a family of integral membrane proteins with central roles in bioactive lipid metabolism and signalling. These five groups of homologous proteins, which we collectively term LPTs (lipid phosphatases/phosphotransferases), are characterized by a core domain containing six transmembrane-spanning α-helices connected by extramembrane loops, two of which interact to form the catalytic site. LPT family members are localized to all major membrane compartments of the cell. The transmembrane topology of these proteins places their active site facing the lumen of endomembrane compartments or the extracellular face of the plasma membrane. Sequence conservation between the active site of the LPPs (lipid phosphate phosphatases), SPPs (sphingosine phosphate phosphatases) and the recently identified SMSs (sphingomyelin synthases) with vanadium-dependent fungal oxidases provides a framework for understanding their common catalytic mechanism. LPPs hydrolyse LPA (lysophosphatidic acid), S1P (sphingosine 1-phosphate) and structurally-related substrates. Although LPPs can dephosphorylate intracellularly generated substrates to control intracellular lipid metabolism and signalling, their best understood function is to regulate cell surface receptor-mediated signalling by LPA and S1P by inactivating these lipids at the plasma membrane or in the extracellular space. SPPs are intracellularly localized S1P-selective phosphatases, with key roles in the pathways of sphingolipid metabolism linked to control of cell growth and survival. The SMS enzymes catalyse the interconversion of phosphatidylcholine and ceramide with sphingomyelin and diacylglycerol, suggesting a pivotal role in both housekeeping lipid synthesis and regulation of bioactive lipid mediators. The remaining members of the LPT family, the LPR/PRGs (lipid phosphatase-related proteins/plasticity-related genes) and CSS2s (type 2 candidate sphingomyelin synthases), are presently much less well studied. These two groups include proteins that lack critical amino acids within the catalytic site, and could therefore not use the conserved LPT reaction mechanism to catalyse lipid phosphatase or phosphotransferase reactions. In this review, we discuss recent ideas about their possible biological activities and functions, which appear to involve regulation of cellular morphology and, possibly, lipid metabolism and signalling in the nuclear envelope.
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WEIJL, N. I., T. J. ELSENDOORN, R. M. W. MOISON, E. G. W. M. LENTJES, R. BRAND, H. M. BERGER und S. OSANTO. „Non-protein bound iron release during chemotherapy in cancer patients“. Clinical Science 106, Nr. 5 (01.05.2004): 475–84. http://dx.doi.org/10.1042/cs20030271.
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Non-protein bound iron (NPBI) is able to catalyse oxidative reactions, causing damage to vital structures. Adverse effects induced by cisplatin seem, in part, to be mediated by free radicals. In the present study, we have measured plasma NPBI, various other iron parameters and antioxidants in 28 cancer patients undergoing cisplatin-based chemotherapy at various time points before and during chemotherapy. No NPBI was present prior to therapy, but within 1–4 days following the first administration of chemotherapy, mean NPBI rose significantly to 10.6±6.6 µmol/l (range, 0.6–21.3 µmol/l) in 18 (64.3%) of the 28 patients measured. The rise in NPBI was accompanied by a significant rise in total plasma iron and ferritin and a marked decrease in the latent iron-binding capacity. Concomitantly, plasma vitamins C and E decreased significantly, indicating consumption of antioxidants. Similar observations were also made during the fourth chemotherapy cycle. The increase in NPBI preceded and correlated significantly with chemotherapy toxicity, such as a decrease in leucocyte count and haemoglobin, with a transient rise in various liver enzymes and with known cisplatin-related toxicity, i.e. the loss of renal and hearing function. In conclusion, cisplatin chemotherapy induces oxidative damage which rapidly leads to release of iron from intracellular proteins and the appearance of NPBI. Bone marrow, red blood cells, liver and kidney seem to be a likely source of NPBI. The observed high levels of NPBI may be a major causative determinant in chemotherapy-induced toxicity.
Dissertationen zum Thema "Catalyse plasma"
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Jia, Zixian. „Elaboration des matériaux composites nanostructurés Ag, Au/TiO² pour la dépollution des effluents gazeux avec une activation par plasma“. Thesis, Paris 13, 2013. http://www.theses.fr/2013PA132050.
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Au cours de ce travail de thèse, nous avons développé un procédé plasma-catalyse d'élimination de l'acétaldéhyde en utilisant un processus diphasique couplant un catalyseur nano-structuré et a plasma à la pression atmosphérique. L’élaboration du catalyseur nanostructuré a été d'abord étudiée. Puis la performance de dégradation du polluant a été étudiée. Les nanoparticules monodispersées (titane-oxo-alcoxy) sont générées dans le réacteur de sol-gel avec micro-mélange turbulent et déposés sur des plaques de verre ou des billes de verre comme monocouches nanostructurées. Le dépôt de l'argent et de l'or est réalisé par la réduction des ions sous l’irradiation de UV-A. La cinétique de croissance photocatalytiques et de la morphologie des nanoparticules sont étudiés expérimentalement par les méthodes MET, MEB et AFM. Il est également intéressant de discuter du mécanisme de la formation des nanoparticules et d'évaluer son efficacité quantique. Les conclusions expérimentales sont supportées théoriquement par le calcul des spectres d'absorption. Ensuite l'efficacité du processus de couplage d'une décharge à barrière diélectrique et d’un lit fluidisé d'argent et d’or nanostructurés, pour la dégradation d'un polluant modèle (acétaldéhyde CH₃CHO), est étudiée. Dans la première partie, l'efficacité du procédé plasma seul est discutée, en termes de dégradation des polluants et de production de CO et CO₂. Dans la deuxième partie, la dégradation de CH₃CHO ainsi que la production COx sont étudié en fonction du temps de réduction photocatalytique d’Ag+ et d’Au³⁺ ions, qui est liée à la masse d'argent et d’or déposée. Les voies de dégradation des polluants, notamment la chimie homogène dans la phase de plasma et la chimie hétérogène sur la surface, sont discutées. Enfin, la production des sous-produits principaux est présentées et comparées entre les catalyseurs Ag et AuDuring this Phd work, we have developed a plasma-catalytic process of acetaldehyde removal using a diphasic process coupling a nano-structured catalyst and an atmospheric pressure plasma. The elaboration of the nanoparticulate catalyst has been firstly studied. Then its performance coupling with plasma has been investigated. The monodispersed titanium-oxo-alkoxy nanoparticles are generated in the sol-gel reactor with turbulent micromixing and deposited onto glass plates or glass balls as monolayer nanocoatings. The silver and gold deposition is achieved by the ions reduction at UV-A light illumination. The photocatalytic growth kinetics and nanoparticle morphology are studied experimentally by the TEM, SEM and AFM methods. It’s also interesting to discuss the mechanism of the nanoparticles formation and evaluate its quantum efficiency. The drawn conclusions are supported theoretically through the calculation of the absorption spectra. Then the efficiency of the process coupling a dielectric barrier discharge and a fluidized nanostructured silver and gold based bed for the degradation of a model pollutant (acetaldehyde CH₃ CHO) is studied. In the first part, the efficiency of the plasma alone process is discussed, in terms of pollutant removal and CO and CO₂ production. In the second part, CH₃ CHO removal as well as COx production is studied as a function of the photocatalytic reduction time of Ag⁺ and Au³⁺ ions, which is related to the deposited silver and gold mass. The pollutant removal pathways, including homogeneous chemistry in the plasma phase and heterogeneous chemistry on the surface, are discussed. Finally, the production of main by-products is presented and compared between Ag and Au catalysts
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Baudin, François. „Catalyse de NOx assistée par plasma "non thermique"“. Paris 6, 2004. http://www.theses.fr/2004PA066416.
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Nguyen, Dinh Minh Tuan. „Oxydation totale du trichloroéthylène par procédé catalyse post-plasma“. Thesis, Lille 1, 2012. http://www.theses.fr/2012LIL10182/document.
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Cette étude vise à étudier le procédé innovant de catalyse post-plasma pour l’abattement de faibles teneurs de trichloroéthylène (TCE), présent dans des effluents gazeux, à la pression atmosphérique et à la température la plus basse possible de fonctionnement du catalyseur. L’objectif est de trouver une alternative aux méthodes traditionnelles de remédiation de COVs non adaptées dans ces conditions. Le réacteur Plasma Non Thermique (PNT) utilisé dans ce travail est à multipointes-vers-plaque à décharge luminescente à courant continu. Bien qu’attractif pour la décomposition du TCE du fait de sa facilité d’utilisation et de son faible coût de fonctionnement, il conduit cependant à une oxydation incomplète du COV. Le catalyseur doit palier aux insuffisances du PNT. L’ajout d’un catalyseur à base d’oxyde de manganèse en aval du réacteur PNT à 150°C voire à température ambiante améliore significativement l’efficacité du procédé. Les meilleurs formulations catalytiques minimisent les phénomènes inhibiteurs de l’eau et décomposent fortement l’ozoneThis study concerns the innovative post-plasma catalysis process for abatement of low levels of trichloroethylene (TCE) in gaseous exhausts at atmospheric pressure and at the lowest operating temperature of the catalyst. The aim is to find an alternative to the conventional VOCs remediation methods which are not adapted in these conditions. The Non Thermal Plasma (NTP) reactor used in this work is a direct current luminescent glow discharge multipins to plate reactor. Although attractive for TCE decomposition due to its ease of use and its low operating cost, it leads however to incomplete VOC oxidation. The catalyst must overcome the weaknesses of NTP. Adding a manganese oxide type catalyst downstream the NTP reactor at 150°C even at room temperature significantly increases the effectiveness of the process. It has been shown that the best catalytic formulations lower the inhibiting factors of water and are efficient catalysts for ozone decomposition
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Sonar, Shilpa. „Abatement of toluene through storage-regeneration sequential process : application of thermal and plasma assisted catalytic regeneration“. Electronic Thesis or Diss., Université de Lille (2018-2021), 2021. http://www.theses.fr/2021LILUR064.
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Le toluène est un composé organique volatil (COV) toxique présent dans les environnements intérieurs et extérieurs. La dépollution du toluène se fait généralement par adsorption ou oxydation catalytique. Dans ce dernier cas, le toluène est converti en CO2 et H2O, mais des espèces toxiques peuvent s'accumuler sur les catalyseurs, provoquant leur empoisonnement, leur désactivation et leur frittage. Pour surmonter ces inconvénients, nous proposons des procédés hybrides innovants de "stockage-régénération". Il s’agit de procédés séquentiels basés l’adsorption suivie de l'oxydation catalytique activée soit thermiquement (ATC) ou par un plasma (APC). Ces procédés sont divisés en deux étapes : "L'étape de stockage où le toluène gazeux est adsorbé sur la surface du matériau et l'étape d'oxydation où le toluène adsorbé est converti catalytiquement en CO2 et H2O dans un environnement thermique ou plasma. Le processus ATC a été testé sur de l'hopcalite commerciale (CuMnOx), de la Cérine-NR et de l'UiO-66-SO3H. L'hopcalite se distingue des autres par sa grande capacité d'adsorption "utile" et ses propriétés redox, permettant une activité et une sélectivité en CO2 élevées dans l'oxydation du toluène. Dans le procédé APC, la morphologie de la poudre et le manque d'effet de synergie dans la Cérine-NR et l'UiO-66-SO3H ne permettent pas de générer un plasma stable. Ainsi, seule l'Hopcalite a été étudiée de manière approfondie en APC. Il est observé que l'activité d'oxydation du toluène adsorbé est significativement affectée par les variables du procédé. La stabilité du matériau a été étudiée dans les deux cas au moyen de différentes techniques de caractérisation et il a été confirmé que les matériaux Hopcalite sont très stables. L'activité catalytique a été améliorée par l'imprégnation d'une phase active telle que l'argent, ce qui a conduit à une augmentation de la sélectivité et du rendement en CO2 avec une charge d'argent très faible, tant dans l'ATC que dans l'APC. Un examen approfondi du matériau a révélé qu'un bon équilibre entre la capacité d'adsorption et l'activité catalytique (Cu2+,3+ et Mn3+,4+) est nécessaire. De plus, le coût énergétique de l'APC se situe dans une fourchette acceptable (11.6 kWh-m-3), ce qui signifie qu'avec une optimisation supplémentaire des différents paramètres expérimentaux, il peut être facilement mis à l'échelle de manière rentable. L'ATC et l'APC permettent tous deux d'atteindre une efficacité de réduction du toluène et de conversion en CO2 supérieure à 95 % au premier passage et à 75 % pour les matériaux stabilisés. Ces résultats montrent que les deux procédés ATC et APC pourraient être des procédés prometteurs de réduction du toluène, efficaces sur le plan énergétique, et ouvrent la voie à de nouveaux développements et à une mise à l'échelleToluene is a toxic volatile organic compound (VOC) present in indoor and outdoor environments. The abatement of toluene is typically done by adsorption or catalytic oxidation. In the latter case, toluene is converted into CO2 and H2O, but toxic species can build up on catalysts, causing poisoning, deactivation, and sintering. To overcome these drawbacks, we propose innovative “storage-regeneration” hybrid processes based on sequential adsorption-thermal catalytic oxidation (ATC) and sequential adsorption-plasma catalysis (APC). These processes are divided into two steps: “storage step” where gaseous toluene adsorbed on the surface of material and “oxidation step” where the adsorbed toluene species is catalytically converted into CO2 and H2O in thermal or plasma environment. ATC process was tested on commercial Hopcalite (CuMnOx), Ceria-NR and UiO-66-SO3H. Hopcalite stands out from others owing to its high “useful” adsorption capacity and redox properties, allowing a high activity and CO2 selectivity in toluene oxidation. In APC process, the powder morphology and lack of synergy effect in Ceria-NR and UiO-66-SO3H does not allow to generate stable plasma. Thus only Hopcalite has been studied in depth in APC. It is observed that the oxidation activity of the adsorbed toluene is significantly affected by the process variables. The stability of material was investigated in both cases, and it was confirmed that Hopcalite materials are very stable as evidenced by various characterization techniques. The catalytic activity was enhanced by impregnating active phase such as silver which led to improvement in the CO2 selectivity and CO2 yield at very low silver loading in both ATC and APC. A thorough examination of the material revealed that a good balance of adsorption capacity and catalytic activity (Cu2+,3+ and Mn3+,4+) is required. Moreover, the energy cost of APC is in the range of acceptable level (11.6 kWh·m−3) as a result with further optimization in different experimental parameters, it can be easily scalable in cost-effective manner. Both ATC and APC allow to reach toluene abatement efficiency and conversion to CO2 above 95 % on first run and 75% on stabilized materials. These results show that both ATC and APC process could be a promising energy-efficient toluene abatement processes and open the path for further development and scale-up
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Bouchoul, Nassim. „Valorisation du dioxyde de carbone par couplage plasma non-thermique et catalyse“. Thesis, Poitiers, 2019. http://theses.univ-poitiers.fr/62720/2019-Bouchoul-Nassim-These.
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Le dioxyde de carbone et le méthane représentent les deux principaux gaz à effet de serre produits par l’Homme. Dans le contexte environnemental actuel, leur valorisation constitue un enjeu scientifique majeur. Cette thèse s’inscrit ainsi dans cet objectif de valorisation du CO2 et du CH4. Pour cela, la réaction de reformage sec du méthane a été réalisée par couplage plasma non-thermique et catalyse. De façon générale, des catalyseurs à base de métaux, comme Ni/Al2O3, sont utilisés lors du couplage plasma-catalyse. Toutefois, les résultats obtenus en termes de conversions et de sélectivités sont très hétérogènes, voire contradictoires. Afin de mieux comprendre les origines de cette disparité, l’influence de la nature du solide présent dans la zone plasma a été étudiée. Pour ce faire, divers oxydes métalliques, tels que γ-Al2O3, α-Al2O3, MgO, CaO, La2O3, ZnO, CeO2, SiO2, BaO, TiO2 ou encore une zéolithe, ont été sélectionnés pour leurs propriétés physico-chimiques distinctes (permittivité, acidité, basicité, surface spécifique). Ces oxydes ont été testés dans des conditions opératoires identiques en utilisant un réacteur plasma à barrière diélectrique (DBD), une puissance de 8W (fréquence 800 Hz, tension de 13 et 16 kV), et un débit total de 40 mL.min-1, l’hélium étant le constituant majoritaire : 75% volumique.L’étude des caractéristiques physiques des catalyseurs a par exemple permis de souligner l’impact de la permittivité ou de la taille des grains des différents matériaux sur la décharge. Une constante diélectrique élevée n’est pas favorable à la réaction. La présence de TiO2 (εr=2903) dans la décharge entraîne une chute des conversions du CH4 et du CO2, qui passent respectivement de 20 et 9 % à vide, à 5 et 2% avec TiO2. Par ailleurs, il a été montré que la présence de grains trop volumineux réduit la surface accessible au plasma, ce qui entraîne une diminution des conversions des réactifs. Ces dernières passent de 30 et 15% respectivement pour CH4 et CO2 pour des grains de petite taille (250-355µm), à 24 et 11% pour les plus gros grains (800-1000µm). De plus, l’étude des propriétés chimiques des catalyseurs a mis en avant l’influence de la basicité sur les conversions du dioxyde de carbone. Il semble que plus le solide possède de sites basiques, plus l’adsorption du CO2 est favorisée. En outre, une étude plus détaillée a été réalisée en couplant plasma et oxyde de calcium, car ce dernier possède non seulement une faible permittivité (εr=2,1), mais également un nombre important de sites basiques. L’influence du ratio CH4/CO2 et de la température sur CaO a permis de mettre en évidence l’apparition de modifications structurales et texturales après décharge plasma. Il a été montré que pour un ratio CH4/CO2 = 2, et à 300°C, la formation d’eau (réaction inverse de gaz à l’eau) favorise la formation de Ca(OH)2 et CaCO3. L’ajout d’eau (0,1g.h-1) au mélange réactionnel a permis de mettre en avant l’hydroxylation de CaO et la carbonatation de Ca(OH)2. Par ailleurs, la carbonatation de l’hydroxyde de calcium hydraté (Ca(OH)2+ 18% H2O) est favorisée sous plasma. L’analyse des gaz en sortie par spectromètre de masse fait ressortir un phénomène d'oscillation lié à l’adsorption du CO2. Un mécanisme réactionnel, au cours duquel l’élimination et l’adsorption de CO2 et H2O s’effectuent successivement, a été proposé. Un plasma peu énergétique (4W) favorise la carbonatation du solide puisque sa composition est initialement : 0,9Ca(OH)2, 0,9 H2O, 0,1 CaCO3 et devient 0,1Ca(OH)2, 0,9CaCO3 après plasma. Par conséquent, il semble que l’application d’un plasma non-thermique favorise la diffusion du CO2 au cœur de Ca(OH)2+ 18% H2O. En outre, la carbonatation de solides, qui constitue une méthode de stockage du CO2, est un procédé lent et le plus souvent limité par la diffusion du dioxyde de carbone. Dans cette étude, il a été montré que le plasma pourrait présenter un grand intérêt, à condition d’augmenter l’efficacité du procédéThe two main greenhouse gases emitted by human activities are carbon dioxide and methane. Within the context of the current environmental crisis, it has become vital to find a method to valorise these gases. Therefore, this thesis has been conducted to be a part of this process: CO2 and CH4 valorisation. To this end, dry reforming of methane was carried out by coupling non-thermal plasma and catalysts. Metal-based catalysts, such as Ni/Al2O3, are usually used for plasma-catalyst. However, the results are often dissimilar, and even contradictory, as far as conversions and selectivities are concerned. In order to better understand the reasons behind this heterogeneity, the influence of the nature of the solid was studied. For this purpose, metal oxides, such as γ-Al2O3, α-Al2O3, MgO, CaO, La2O3, ZnO, CeO2, SiO2, BaO, TiO2, and a zeolite, were selected because of their respective physicochemical properties (permittivity, acidity, basicity, specific surface). These oxides were submitted to identical tests with identical operational conditions, e.g. a dielectric barrier discharge reactor (DBD), 8W power (800 Hz frequency, 13 and 16 kV tension), a total output of 40 mL.min-1 and a CH4/CO2=0,5 ratio.The study of the physical characteristics of catalysts highlighted the impact of the material’s permittivity or of the size of its grains on the discharge. A high dielectric constant hindered the reaction. When TiO2 (εr=2903) was found in the discharge, it led to a decline in CH4 and CO2 conversions, as they decreased from respectively 20 and 9% without catalyst, to 5 and 2% with TiO2. Furthermore, when grains were too large, there was less surface accessible to plasma, which led to a fall in the reagents’ conversions. Indeed, they dropped from respectively 30 and 15% for CH4 and CO2 for small-sized grains (250-355µm), to 24 and 11% for the largest grains (800-1000µm). In addition to this, the study of the catalysts’ chemical properties showed how basicity influenced the conversions of carbon dioxide. It seemed that when there was a great number of basic sites in a solid, CO2 adsorption was likely to be better. Furthermore, a more detailed study was carried out by coupling calcium oxide with non-thermal plasma. Indeed, the former does not only have a low permittivity, but also a high number of basic sites. Structural and textural modifications appeared after plasma. This was shown by examining the influence of the CH4/CO2 ratio and of the temperature on CaO. When there was a CH4/CO2 = 2 ratio, for a temperature of 300°C, the production of water (reverse water-gas shift reaction) tended to result in the formation of Ca(OH)2 and CaCO3.When water (0,1g.h-1) was added to the reaction mixture, CaO hydroxylation and Ca(OH)2 carbonatation were observed. Furthermore, hydrated calcium hydroxide (Ca(OH)2+ 18% H2O) carbonatation is more likely to occur under plasma. The analysis of gases at the outlet by a mass spectrometer revealed an oscillatory phenomenon associated with CO2 adsorption. A reaction pathway, during which CO2 and H2O adsorption and elimination occur successively, was therefore put forward. A low-energy plasma (4W) is likely to cause carbonatation, as the solid is originally composed of 0,9Ca(OH)2, 0,9 H2O, 0,1 CaCO3, and is made of 0,1Ca(OH)2, 0,9CaCO3 after plasma. Thus, applying a non-thermal plasma seems to encourage CO2 diffusion at the core of Ca(OH)2+ 18% H2O. Carbonatation is a method to store CO2 but it is a slow process, which is often hindered by CO2 diffusion. In this study, plasma was proved to be a highly interesting process, provided that its efficiency could be increased
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Sauce, Sonia. „Etude des mécanismes d’activation d’un catalyseur nanostructuré Ag/TiO₂/SiO₂ dans un environnement plasma lors de la décomposition d’un COV modèle : l'acétaldéhyde“. Thesis, Sorbonne Paris Cité, 2015. http://www.theses.fr/2015USPCD079/document.
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Ce travail de thèse s’intéresse aux phénomènes de surface ayant lieu lorsque l’on combine un procédé en phase homogène – contrôlé par la chimie d’un plasma non-thermique – et un procédé en phase hétérogène – contrôlé par la chimie ayant lieu à la surface d’un matériau nanostructuré Ag/TiO₂/SiO₂ – lors de la dégradation de l’acétaldéhyde, CH₃CHO.Il a été montré que le procédé diphasique permet de convertir 100 % de l’acétaldéhyde à traiter avec une SIE de 168 J.L-1 (soit une puissance de 280 mW). Dans ces conditions, CH₃CHO est converti en COx à plus de 60 %. Une telle efficacité n’est pas atteinte avec les procédés en phase homogène et en phase hétérogène seuls. Les processus se déroulant au sein du procédé diphasique mènent donc à une dégradation de CH₃CHO autrement meilleure que l’ensemble des cinétiques mises en oeuvre lors de l’utilisation des deux procédés seuls.Afin de comprendre quels processus physico-chimiques permettent d’obtenir un tel effet de synergie, l’étude de l’interaction acétaldéhyde/surface a été initiée, par spectroscopie infrarouge à réflexion diffuse (DRIFTS), et constitue le coeur de ce travail de thèse. Une attention particulière a été portée à l’étude des modes d’adsorption de l’acétaldéhyde sur Ag/TiO₂/SiO₂ en absence de plasma. Puis, l’effet de l’apport d’une source thermique et d’une espèce à fort pouvoir oxydant (l’ozone) sur l’acétaldéhyde présent en phase adsorbé a été évaluéThis thesis investigates the surface phenomena which occur when combining a homogeneous phase process – governed by the chemistry of a non-thermal plasma – and a heterogeneous phase process – controlled by the chemistry taking place on the surface of a nanostructured Ag/TiO₂/SiO₂ material – during acetaldehyde (CH₃CHO) removal.It has been shown that acetaldehyde can be removed up to 100 % with a 168 J.L-1 SIE consumption, by using the diphasic process. In these conditions, CH₃CHO is converted into 60 % of COx. Such efficiency is not achieved when using the homogeneous and heterogeneous phase processes alone. Thus, the physico-chemical phenomena occurring in the diphasic process allow a higher CH₃CHO removal compared to the whole kinetics involved in the homogeneous and heterogeneous phase processes alone. So as to understand which physico-chemical processes are involved in this synergistic effect, the study of the acetaldehyde/surface interaction has been started, by Diffuse-Reflectance Infrared Fourier Transform Spectroscopy (DRIFTS), in this thesis. The acetaldehyde adsorption modes on the Ag/TiO₂/SiO₂ surface, without plasma, have been pointed out. Moreover, the effect of bringing a thermal energy source or an oxidizing species (like ozone) on adsorbed acetaldehyde has been evaluated
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Alloncle, Guillaume. „Analyse directe de catalyseur par couplage ablation LASER : spectrométrie d'émission atomique dans un plasma à couplage induit“. Lyon 1, 2008. http://www.theses.fr/2008LYO10247.
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L’analyse élémentaire est indispensable en catalyse hétérogène, mais coûteuse en temps, particulièrement pour les matrices complexes à minéraliser. L’analyse directe d’échantillons par couplage entre l’ablation laser et les plasmas à couplages induit (ICP) apparaît comme une alternative intéressante à la fluorescence X ou à l’ICP. L’ablation laser nécessite cependant une connaissance des mécanismes impliqués lors de l’analyse. L’objectif de cette étude est l’évaluation des performances du couplage entre l’ablation laser et la spectrométrie d’émission atomique dans un plasma à couplage induit (LA-ICP-AES) pour l’analyse des catalyseurs. Une comparaison des stratégies d’étalonnage montre que les performances en termes de linéarité, répétabilité et justesse sont améliorées par l’utilisation d’un étalon interne. Les effets de matrice, ainsi que le fractionnement, sont efficacement compensés par l’étalon interne. Cependant, certains biais sur les concentrations mesurées apparaissent en multipliant les différences entre étalons et échantillons. L’étude des mécanismes impliqués dans l’ablation des catalyseurs a montré que l’aérosol transporté vers l’ICP était issu de la vaporisation de l’échantillon et de sa condensation sous une forme fortement cristalline. La distribution des éléments catalytiques entre les particules formées varie en fonction de leurs tailles. Les différences de composition globale au cours de l’analyse sont mineures pour un catalyseur faiblement chargé en élément et majeures pour un catalyseur fortement chargé en métaux. Malgré ce fractionnement, la mise en place du couplage LA-ICP-AES en catalyse est intéressante pour de nombreuses applicationsInorganic analyses are compulsory in heterogeneous catalysis. Classical techniques are time consuming, especially for alumina or silica matrixes, because of mineralization step. Direct analysis of solids by coupling laser ablation to ICP-AES appears as a promising alternative to XRF or ICP, with a total analysis time of few minutes. Laser ablation, affected by fractionation effects, requires knowledge of mechanisms occurring during ablation. Accurate quantitative analyses require a sufficient matrix matching between samples and standards. The purpose of this work is the evaluation of LA-ICP-AES coupling for the direct analysis of heterogeneous catalysts and the understanding of mechanisms involved. Results, obtained on different kind of catalysts, show that analytical performances in terms of linearity, repeatability and accuracy are significantly improved with the use of an internal standard and are comparable with XRF. Nevertheless, significant bias appears when samples and standards matrixes differ significantly. The study of mechanisms involved in the ablation of catalysts showed that the aerosol transported to the ICP is generated from the vaporization if the sample and its condensation into highly crystalline nano-particles and microparticles. Chemical composition of the aerosol revealed the occurrence of fractionation of elements between the two particles types. Even if fractionation occurs, the use of LA-ICP-AES coupling into the field of heterogeneous catalysis is promising for the quick diagnostic by qualitative analysis, quantitative analysis with appropriate standards, and localized analysis for mapping
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OUMGHAR, AHMED. „Valorisation du methane par un plasma d'air ou d'azote-couplage avec la catalyse heterogene“. Paris 6, 1992. http://www.theses.fr/1992PA066281.
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Les reserves du gaz naturel mises a jour croissent regulierement alors que celles du petrole semblent atteindre un palier. Ceci donne une importance croissante au gaz naturel comme matiere premiere des industries chimiques. La transformation du gaz naturel en produits plus lourds est realisee a l'aide de l'energie electrique: le methane composant majoritaire du gaz naturel reagit avec un plasma d'air ou d'azote cree par un generateur de micro-ondes a 2450 mhz. La reaction aboutit a la formation principalement des produits en c#2(c#2h#6, c#2h#4, c#2h#2), de produit en c#3(c#3h#8), du monoxyde de carbone et de l'hydrogene. L'optimisation de ce procede est realisee en faisant varier plusieurs parametres experimentaux a savoir: stchiometrie de la reaction d'oxydation du methane, temps de sejour, temps au bout duquel le plasma agit sur le methane, pression du milieu reactionnel, puissance. La formation des produits fait l'objet d'une discussion des mecanismes reactionnels. Plusieurs catalyseurs ont ete introduits dans la post-decharge et leurs performances ont ete comparees
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Rahmani, Abdelkader. „Mise en oeuvre de procédé plasma–catalyse destiné à la valorisation du biogaz (CH4+CO2) en carburants liquides. Etude expérimentale et modélisations“. Thesis, Sorbonne Paris Cité, 2018. http://www.theses.fr/2018USPCD041.
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Ce travail de thèse double culture s’inscrit dans le cadre de la Transition Énergétique vers un modèle intégrant les potentiels de production de biogaz. Il est consacré à l’étude de la technologie plasma-catalyse de reformage du méthane en présence du dioxyde de carbone en carburants liquides. Une étude géomatique a été développée afin de réaliser la cartographie des zones agricoles potentiellement productrices de biogaz en France. Les résultats révèlent que la cogénération et l’injection du bio-méthane dans le réseau gazier permettent de valoriser seulement 43% du potentiel total en biogaz issu des déchets agricoles en France. La transformation du biogaz en carburants liquides stockables et transportables, à l’aide d’un dispositif pouvant être installé dans des territoires ruraux éloignés, permettrait de tirer davantage de profit de ce potentiel. Les décharges plasma permettent de développer une réactivité suffisante pour exciter et dissocier les molécules du biogaz dans les conditions requises. Un modèle cinétique a été développé afin de déterminer les paramètres du plasma et l’évolution temporelle des espèces réactives ainsi que les processus de conversion du biogaz. Un procédé de Décharge à Barrière Diélectrique Surfacique a été réalisé pour la transformation de mélange de CH₄ et de CO₂ représentatif du biogaz. Les principaux produits gazeux sont CO, H₂, C₂H₆ et C₂H₄ et les principaux produits liquides, représentant 3% à 8% de la masse de biogaz transformé, sont le méthanol, l’isopropanol, l'éthanol et l'acétaldéhyde. L’efficacité énergétique dépendant des paramètres opératoires et varie entre 2% et 9%. L’Energie Spécifique Injectée est le paramètre le plus influent sur l’efficacité énergétique du procédé ainsi que sur la distribution des produits. L’ajout de la vapeur d'eau, précurseur d’espèces actives telles que : OH, O et O-, apporte une nette amélioration des taux de conversion à un coût énergétique égal à 26 eV/molécule. Nous avons étudié le couplage plasma-catalyse par l’emploi de 12 catalyseurs solides. Nous avons élaboré par le procédé Fluidized Spray Plasma des catalyseurs tels que : X%CuO-Y%ZnO/Al₂O₃, TiO₂/SiO₂ et Ag/TiO₂/SiO₂. Ces catalyseurs, ainsi que des catalyseurs élaborés par d’autres techniques ont été caractérisés et testés dans le réacteur SDBD. Il en ressort que la nature du catalyseur affecte peu la conversion du biogaz mais elle modifie la distribution des produits liquides. La meilleure sélectivité en méthanol a été obtenue en utilisant le Pt/Al₂O₃ (élaboré par voie polyol) puis en utilisant le CuO/Al₂O₃ et le 60%Cu-40%ZnO/Al₂O₃This double culture thesis, merging geography and physics is achieved in the frame of the Energy Transition towards a model integrating biogas production potentials. It is devoted to the study of plasma-catalysis technology for reforming methane in the presence of carbon dioxide to liquid fuels. A geomatic study has been developed to map agricultural areas potentially producing biogas in France. The results reveal that cogeneration and injection of bio-methane into the gas network allows recovering only 43% of the total biogas potential from agricultural waste in France. The transformation of biogas into storable and transportable liquid fuels, using a device that can be installed in remote rural areas, would make more use of this potential. Plasma discharges allows developing sufficient reactivity to excite and dissociate the molecules of the biogas under the required conditions. A kinetic model has been developed to determine plasma parameters and temporal evolution of reactive species as well as biogas conversion processes. A Surface Dielectric Barrier Discharge (SDBD) process was developed for the transformation of CH₄ and CO₂ mixture representative of the biogas. The main gaseous products are CO, H₂, C₂H₆ and C₂H₄ and the main liquid products, representing 3% to 8% of the transformed biogas mass, are methanol, isopropanol, ethanol and acetaldehyde. The energy efficiency depends on the operating parameters and varies between 2% and 9%. Specific Injected Energy is the most influential parameter on the energy efficiency of the process as well as on products distribution. The addition of water vapor, a precursor of active species such as: OH, O and O-, improves the conversion and allows obtaining energy consumption equal to 26 eV/molecule. Plasma-catalysis was also studied by the use of 12 solid catalysts. The Fluidized Spray Plasma process was used to develop catalysts such as X% CuO-Y% ZnO/Al₂O₃, TiO₂/SiO₂ and Ag/TiO₂/SiO₂ by. These catalysts as well as catalysts made by other techniques have been characterized and tested in the SDBD reactor. The main result is that the nature of the catalyst does not affect the conversion of the biogas but it modifies liquid products composition. The best methanol selectivity was obtained using Pt/Al₂O₃ (made by polyol) followed by CuO/Al₂O₃ and then 60% Cu-40% ZnO/Al₂O₃
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Baylet, Alexandre. „Oxydation du méthane à basse et haute température, application de procédés plasma et/ou catalyse“. Poitiers, 2008. http://theses.univ-poitiers.fr/26682/2008-Baylet-Alexandre-These.pdf.
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Les travaux de recherche de cette thèse concernent les problèmes liés à l’oxydation du CH4, gaz à effet de serre notoire provenant dans le cas présent du transport routier, et plus précisément l’élimination du CH4 issu des gaz d’échappement des moteurs de type Diesel. L’oxydation totale du CH4 a été étudiée : - A basse température par procédé Plasma/Catalyse : de tous les systèmes testés, la combinaison d’un système plasma froid de type DBD coaxial associé à un catalyseur Pd/Al2O3 en position POSTplasma permet l’oxydation de 30 % du CH4 avec une énergie déposée de 225 J. L-1 (Q=600 mL. Min-1, N2/O2/CO2/H2O/0,5%CH4, T=250 °C, H=150 mm) tout en minimisant la production de O3 et en ne générant pas de NOx. Cependant, les puissances consommées (> kW) sont trop importantes pour une éventuelle application sur véhicules. - A basse température sur catalyseurs Pd/Al2O3 (température de light-off) : L’étape de ré-oxydation de Pd° est plus rapide sur des petites particules mais l’activation du CH4 y est plus difficile en raison d’une stabilisation plus importante des petites particules de PdO par le support. Une série de pulses réducteurs (CH4 ou C3H6) en conditions isothermes permet d’activer le catalyseur et d’atteindre un maximum de conversion. - A haute température sur catalyseurs Pd/(oxyde modifié) (pics haute température) : la synthèse d’une alumine dopée (La, Sr, Ba, Mn) avec une surface spécifique de l’ordre de 50 m2. G-1 permet d’atteindre des taux de conversion de 90 % du CH4 à 700 °C tout en maintenant une excellente stabilité thermique. Un mécanisme redox de type Mars et van-Krevelen, avec transfert de l’oxygène du support vers les particules de palladium est proposé pour expliquer les différences en termes d’activité catalytique et de stabilité thermique en comparaison au catalyseur de référence Pd/Al2O3This research work deals with CH4 oxidation coming from road transport, CH4 being a well-known greenhouse gas, with CH4 removal from exhaust gas of Diesel engine. Total CH4 oxidation has been studied : - At low temperature by Plasma/Catalysis process : from all the systems tested, the combination of a coaxial DBD non-thermal plasma combined with Pd/Al2O3 catalyst in POST-plasma position allows to convert 30 % of CH4 with an energy of 225 J. L-1 (Q=600 mL. Min-1, N2/O2/CO2/H2O/0. 5%CH4, T=250 °C, H=150 mm) while minimising O3 production and avoiding NOx production. However, the power consumed (> kW) is too significant for prospective vehicle applications. - At low temperature on Pd/Al2O3 catalysts (light-off temperature) : the re-oxidation step of Pd° is faster on small particles but CH4 activation is more difficult due to stabilization of small PdO particles by the support. A series of reductant pulses (CH4 or C3H6) in isothermal conditions allows to activate the catalyst and to reach a maximum of conversion. - At high temperature on Pd/(modified oxide) catalysts (peak at high temperature) : (La, Sr, Ba, Mn) doped alumina preparation with a specific surface area of 50 m2. G-1 allows to reach 90 % of CH4 conversion at 700 °C and to maintain an excellent thermal stability. A Mars and van-Krevelen mechanism, with oxygen transfer from support to palladium particles is proposed in order to explain catalytic activity and thermal stability differences in comparison to the Pd/Al2O3 reference catalyst
Bücher zum Thema "Catalyse plasma"
1
Tu, Xin, J. Christopher Whitehead und Tomohiro Nozaki, Hrsg. Plasma Catalysis. Cham: Springer International Publishing, 2019. http://dx.doi.org/10.1007/978-3-030-05189-1.
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Parvulescu, Vasile I., Monica Magureanu und Petr Lukes, Hrsg. Plasma Chemistry and Catalysis in Gases and Liquids. Weinheim, Germany: Wiley-VCH Verlag GmbH & Co. KGaA, 2012. http://dx.doi.org/10.1002/9783527649525.
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Winter, Lea. Upgrading Carbon and Nitrogen to Fuels and Chemicals Using Heterogeneous and Plasma Catalysis. [New York, N.Y.?]: [publisher not identified], 2020.
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service), SpringerLink (Online, Hrsg. Molecular Catalysts for Energy Conversion. Berlin, Heidelberg: Springer Berlin Heidelberg, 2009.
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Weidler, Natascha. Plasma-enhanced chemical vapor deposition of cobalt-based catalysts for the oxygen evolution reaction. Darmstadt: Universitäts- und Landesbibliothek Darmstadt, 2017.
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Plasma Catalysis. MDPI, 2019. http://dx.doi.org/10.3390/books978-3-03897-751-3.
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Tu, Xin, J. Christopher Whitehead und Tomohiro Nozaki. Plasma Catalysis: Fundamentals and Applications. Springer, 2019.
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Parvulescu, Vasile I., Monica Magureanu und Petr Lukes. Plasma Chemistry and Catalysis in Gases and Liquids. Wiley & Sons, Incorporated, John, 2013.
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Parvulescu, Vasile I., Monica Magureanu und Petr Lukes. Plasma Chemistry and Catalysis in Gases and Liquids. Wiley & Sons, Incorporated, John, 2012.
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Parvulescu, Vasile I., Monica Magureanu und Petr Lukes. Plasma Chemistry and Catalysis in Gases and Liquids. Wiley-VCH Verlag GmbH, 2012.
Den vollen Inhalt der Quelle findenBuchteile zum Thema "Catalyse plasma"
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Kim, Hyun-Ha, Yoshiyuki Teramoto und Atsushi Ogata. „Plasma-Catalyst Interactions“. In Plasma Catalysis, 47–68. Cham: Springer International Publishing, 2019. http://dx.doi.org/10.1007/978-3-030-05189-1_3.
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Chen, Zhitong, und Richard E. Wirz. „Plasma Catalysis“. In Cold Atmospheric Plasma (CAP) Technology and Applications, 83–93. Cham: Springer International Publishing, 2021. http://dx.doi.org/10.1007/978-3-031-79701-9_7.
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Mizuno, Akira, und Michael Craven. „Plasma Catalysis Systems“. In Plasma Catalysis, 21–46. Cham: Springer International Publishing, 2019. http://dx.doi.org/10.1007/978-3-030-05189-1_2.
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Bogaerts, Annemie, und Erik Neyts. „Plasma Catalysis Modeling“. In Plasma Catalysis, 69–114. Cham: Springer International Publishing, 2019. http://dx.doi.org/10.1007/978-3-030-05189-1_4.
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Whitehead, J. Christopher. „Plasma Catalysis: Introduction and History“. In Plasma Catalysis, 1–19. Cham: Springer International Publishing, 2019. http://dx.doi.org/10.1007/978-3-030-05189-1_1.
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Lee, Dae Hoon. „Plasma-Catalytic Reforming of Alcohols“. In Plasma Catalysis, 309–41. Cham: Springer International Publishing, 2019. http://dx.doi.org/10.1007/978-3-030-05189-1_10.
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Whitehead, J. Christopher. „Plasma Catalysis: Challenges and Future Perspectives“. In Plasma Catalysis, 343–48. Cham: Springer International Publishing, 2019. http://dx.doi.org/10.1007/978-3-030-05189-1_11.
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Khacef, Ahmed, und Patrick Da Costa. „Plasma-Catalytic Removal of NOx in Mobile and Stationary Sources“. In Plasma Catalysis, 115–44. Cham: Springer International Publishing, 2019. http://dx.doi.org/10.1007/978-3-030-05189-1_5.
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Cools, Pieter, Nathalie De Geyter und Rino Morent. „Plasma-Catalytic Removal of VOCs“. In Plasma Catalysis, 145–80. Cham: Springer International Publishing, 2019. http://dx.doi.org/10.1007/978-3-030-05189-1_6.
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Yi, Yanhui, Li Wang und Hongchen Guo. „Plasma-Catalytic Decomposition of Ammonia for Hydrogen Energy“. In Plasma Catalysis, 181–230. Cham: Springer International Publishing, 2019. http://dx.doi.org/10.1007/978-3-030-05189-1_7.
Der volle Inhalt der QuelleKonferenzberichte zum Thema "Catalyse plasma"
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Bond, Gary, A. Halman, H. Eccles, R. Mao, S. Pollington, P. Hinde, V. Demidyuk und A. Gkelios. „A COMPARATIVE STUDY OF MICROWAVE AND BARRIER DISCHARGE PLASMA FOR THE REGENERATION OF SPENT ZEOLITE CATALYSTS“. In Ampere 2019. Valencia: Universitat Politècnica de València, 2019. http://dx.doi.org/10.4995/ampere2019.2019.9936.
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Due to their acid characteristics and pore structure, which can induce high product selectivity; zeolite catalysts are used extensively in industry to catalyse reactions involving hydrocarbons. However, these catalysts can suffer from deactivation due to cracking reactions that result in the deposition of carbon leading to poisoning of the acid sites and blocking of the pores [1]. Depending upon the reaction and the particular catalyst involved this deactivation may take place over several months or even years but in some cases occurs in minutes. Therefore, zeolite catalysts are frequently reactivated / regenerated. This generally involves a thermal treatment involving air which results in oxidation of the carbon [2]. However, the oxidation of carbon is highly exothermic, and if not carefully controlled, results in the generation of exceedingly high localized temperatures which can destroy the zeolite structure and result in subsequent loss of catalyst activity. More conservative thermal treatments can result in incomplete regeneration and again a catalyst displaying inferior activity. This paper explores the use of non-thermal plasma which had been either generated using microwaves or via a barrier discharge to regenerate spent zeolite catalysts. The catalyst, H-mordenite, was tested for the disproportionation of toluene (Figure 1) using conventional heating. The spent catalyst was then regenerated using a plasma or conventional thermal treatment before having its activity re-evaluated for the toluene disproportionation reaction as previous. Fig. 1. Reaction Scheme for Toluene Disproportionation. Interestingly, not only is plasma regeneration highly effective but also catalysts can be regenerated in greatly reduced times. There is an additional advantage in that plasma regeneration can impart physical properties that result in a zeolite that is resistant to further deactivation. However, the results are highly dependent upon the experimental conditions involved for plasma regeneration. References Wu J, Leu L., Appl. Catal., 1983; 7:283-294. M. Guisnet and P. Magnoux, Deactivation of Zeolites by Coking. Prevention of Deactivation and Regeneration. In: Zeolite Microporous Solids: Synthesis, Structure, and Reactivity. E.G. Derouane, F Lemos, C. Naccache, F. Ramôa Ribeiro, Eds. Pages 437-456. Springer 1992.
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Ofosu, F. A., G. J. Modi, M. A. Blajchman, M. R. Buchanan und E. A. Johnson. „INCREASED SULFATION IMPROVES THE ABILITY OF VESSEL WALL GLYCOSA-MINOGLYCANS TO REGULATE THROMBIN ACTIVITY AND PROTHROMBIN ACTIVATION IN PLASMA“. In XIth International Congress on Thrombosis and Haemostasis. Schattauer GmbH, 1987. http://dx.doi.org/10.1055/s-0038-1643252.
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Studies have shown that dermatan sulfate (DS), heparan sulfate (HS) and chondroitin-4-sulfate (C4S), have antithrombotic properties. The sulfate to carboxylate ratios of these three glycosaminoglycans (GAGs) are approximately half that of heparin (HEP) and the gravimetric dose of each of the three GAGs required to achieve antithrombotic effects in vivo comparable to HEP can be 10 times or more than that of HEPT Since antithrombotic effects depend on the ability of a GAG to catalyse thrombin inhibition and/or to inhibit prothrombin activation, we determined the relationship between the extent of sulfation of various GAGs and their effects on these two reactions in normal plasma. In addition to the three GAGs, DS, HS and C4S were resulfated in vitro to yield DS-S, HS-S and C4S-S, each with a sulfate to carboxylate ratio comparable to that of heparin. As summarized below, increased sulfation improved the ability of a GAG to catalyse thrombin inhibition and to inhibit prothrombin activation. Increasing the degree of sulfation primarily improved the ability of a GAG to accelerate the inhibition of thrombin by heparin cofactor II. The degree of sulfation, therefore, appears to be an important functional attribute of the ability of vessel wall GAGs to regulate the formation and activity of thrombin in plasma.
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van Hell, Albert J., Dayana Martins Gueth, Manuel Nuno Melo, Siewert Jan Marrink und Marcel Verheij. „Abstract 2750: Short-chain lipids catalyse intracellular drug accumulation by a transient molecular gateway that allows plasma membrane traversal“. In Proceedings: AACR 103rd Annual Meeting 2012‐‐ Mar 31‐Apr 4, 2012; Chicago, IL. American Association for Cancer Research, 2012. http://dx.doi.org/10.1158/1538-7445.am2012-2750.
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Guo, Kun, und Ahalapitiya H. Jayatissa. „Growth of Carbon Nanotubes on Metallic Catalyst by CVD“. In ASME 2006 International Mechanical Engineering Congress and Exposition. ASMEDC, 2006. http://dx.doi.org/10.1115/imece2006-15356.
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The growth of carbon nanotubes was investigated using a filament assisted atmospheric CVD system. The scope of this study is two fold: (i) control the growth of carbon nanotubes by chemical treatment of catalysis surface and temperatures and (ii) study of nanotubes growth for gas sensor applications. We have conducted the growth of carbon nanotubes on surfaces by treatment of metal catalyst surface with different acids and plasma. The treated surfaces were kept in a furnace tube CVD and the nanotubes were grown using a hot filament assisted decomposition of methane (CH4) and argon (Ar) gas mixture. It was found that the growth of carbon nanotubes could be controlled by the catalysts, filament and furnaces temperature.
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Fisher, Galen B., Craig L. DiMaggio und John W. Sommers. „NOx Reactivity Studies of Prototype Catalysts for a Plasma–Catalyst Aftertreatment System“. In International Fuels & Lubricants Meeting & Exposition. 400 Commonwealth Drive, Warrendale, PA, United States: SAE International, 1999. http://dx.doi.org/10.4271/1999-01-3685.
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Polaert, Isabelle, Bachar Alrafei, Jose Delgado-Liriano und Alain Ledoux. „Synergetic effect of microwave plasma and catalysts in CO2 methanation“. In Ampere 2019. Valencia: Universitat Politècnica de València, 2019. http://dx.doi.org/10.4995/ampere2019.2019.9806.
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The reduction of CO2 concentration in our atmosphere consists in a big challenge for researchers, who are trying to explore novel technologies in order to transform CO2 into high added-value products. CO2 conversion into methane using microwave plasma (MWP) manifests as a very promising solution due to the ease of transport of methane and its storage. Microwave plasma represents a source of high-energy electrons, active ions and radicals that enhance or enable chemical reaction. It can be supplied by electricity generated from renewable resources. Then, MWP does not require any electrode to be generated and thus, the cost of those electrodes and of maintenance is reduced compared to glow discharge or DBD plasmas. MWP also can be generated over wide range of pressure (between 10 mbar-1bar). In addition, in the case of MWP, more electrons and active species are produced in comparison with other type of plasma[1–4]. MWP is a very suitable medium for this chemical reaction and leads to an efficient dissociation of CO2. The catalytic reduction of CO2 with H2 using MWP has been investigated in this work and the synergetic effects between the plasma and several catalysts were studied. First, the reaction was carried out without any catalysts and the effect of CO2/H2 ratio, total flow rate and input energy were evaluated. Then, a microwave generated plasma process was coupled with several Nickel catalysts that we prepared and characterized [5] in order to lead the reaction into methane formation. Multiple configurations were studied by changing the position of the catalyst bed. Obtained results were compared with conventional catalytic tests made with the same catalysts. It was found that the conversion of CO2 and energy efficiency increased using plasma assisted catalytic methanation of CO2 in comparison with conventional process. Operating conditions were studied in order to optimize methane production and energy efficiency of Plasma-catalytic process. References Qin, Y., G. Niu, X. Wang, D. Luo, Y. Duan, J. CO2 Util., 2018, 28, 283–291. De la Fuente, J.F., S.H. Moreno, A.I. Stankiewicz, G.D. Stefanidis, Int J Hydrogen Energy, 2016, 41, 21067–21077. Ashford, B., X. Tu, Curr Opin Green Sustain Chem, 2017, 3, 45–49. Vesel, A., M. Mozetic, A. Drenik, M. Balat-Pichelin, Chem Phys., 2011, 382, 127–131. Alrafei, B., I. Polaert, A. Ledoux, F. Azzolina-Jury, Catal. Today, Available online 12 March 2019, In Press, Accepted Manuscript. https://doi.org/10.1016/j.cattod.2019.03.026
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Oukacine, L., F. Gitzhofer, N. Abatzoglou und D. V. Gravelle. „Study of Ni/Al2O3 Deposition on Metallic Surface using RF Plasma Process“. In ITSC2005, herausgegeben von E. Lugscheider. Verlag für Schweißen und verwandte Verfahren DVS-Verlag GmbH, 2005. http://dx.doi.org/10.31399/asm.cp.itsc2005p0545.
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Abstract This work is aimed at acquiring knowledge on successive deposition of alumina and nickel coatings on a metallic substrate using an RF plasma torch. The composition and morphology of various Ni/Al2O3 steam reforming catalysts, prepared by plasma spraying of precursor nickel suspensions, are studied in this work. As Ni/γ-Al2O3 is a well known reforming catalyst it was decided to study the deposition of a particular catalytic formulation on a metallic substrate. The purpose of this study was to find the means of building 2D monolithic catalysts by plasma deposition. Since 2D monolithic catalysts are non-porous, their specific areas available for hosting the catalytic reactions are low. Thus, It is essential to have very good dispersion of the active catalytic sites. Such dispersion is only possible only if the deposit can take place at the nanometer scale. The suspension plasma spraying is assessed for its ability to produce such structures. This method permits the formation of nanocrystalline structures within a few seconds. The main difficulty is the control of the various spraying parameters in order to obtain satisfactory deposition. The Ni/γ-Al2O3 catalysts so obtained are characterized by scanning electron microscopy, field electron microscopy and X-Ray diffraction.
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Zhu, Xinbo, Xiang Gao und Xin Tu. „Plasma-Catalyst Coupling for Enhanced Oxidation of Ethyl Acetate Over V2O5/TiO2 Nanofiber Catalyst*“. In 2017 IEEE International Conference on Plasma Science (ICOPS). IEEE, 2017. http://dx.doi.org/10.1109/plasma.2017.8496225.
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Birmingham, Joseph G., und Donald J. Hammerstrom. „Fouling Prevention Using Plasma Catalysis“. In International Fuels & Lubricants Meeting & Exposition. 400 Commonwealth Drive, Warrendale, PA, United States: SAE International, 1999. http://dx.doi.org/10.4271/1999-01-3641.
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Hoard, John, Paul Laing, M. Lou Balmer und Russ Tonkyn. „Comparison of Plasma-Catalyst and Lean NOx Catalyst for Diesel NOx Reduction“. In International Fuels & Lubricants Meeting & Exposition. 400 Commonwealth Drive, Warrendale, PA, United States: SAE International, 2000. http://dx.doi.org/10.4271/2000-01-2895.
Der volle Inhalt der QuelleBerichte der Organisationen zum Thema "Catalyse plasma"
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Hicks, Jason, William Schneider und David Go. Advancing Sustainable Ammonia Synthesis through Plasma-Assisted Catalysis (Final Report). Office of Scientific and Technical Information (OSTI), Mai 2019. http://dx.doi.org/10.2172/1514853.
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Pearlman, Howard, Matt Giles, Chien-Hua Chen und Max Demydovych. Plasma-Catalysis of CO2 and CH4 to Produce High Value Chemicals. Office of Scientific and Technical Information (OSTI), April 2020. http://dx.doi.org/10.2172/1714373.
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Mulvaney, Paul. High Throughput Spectroscopic Catalyst Screening via Surface Plasmon Spectroscopy. Fort Belvoir, VA: Defense Technical Information Center, Juli 2015. http://dx.doi.org/10.21236/ada626615.
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Kanner, Joseph, Edwin Frankel, Stella Harel und Bruce German. Grapes, Wines and By-products as Potential Sources of Antioxidants. United States Department of Agriculture, Januar 1995. http://dx.doi.org/10.32747/1995.7568767.bard.
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Several grape varieties and red wines were found to contain large concentration of phenolic compounds which work as antioxidant in-vitro and in-vivo. Wastes from wine production contain antioxidants in large amounts, between 2-6% on dry material basis. Red wines but also white wines were found to prevent lipid peroxidation of turkey muscle tissues stored at 5oC. The antioxidant reaction of flavonoids found in red wines against lipid peroxidation were found to depend on the structure of the molecule. Red wine flavonoids containing an orthodihydroxy structure around the B ring were found highly active against LDL and membrane lipid peroxidation. The antioxidant activity of red wine polyphenols were also found to be dependent on the catalyzer used. In the presence of H2O2-activated myoglobin, the inhibition efficiency was malvidin 3-glucoside>catechin>malvidin>resveratol. However, in the presence of an iron redox cycle catalyzer, the order of effectiveness was resveratol>malvidin 3-glucoside = malvidin>catechin. Differences in protein binding were found to affect antioxidant activity in inhibiting LDL oxidation. A model protein such as BSA, was investigated on the antioxidant activity of phenolic compounds, grape extracts, and red wines in a lecithin-liposome model system. Ferulic acid followed by malvidin and rutin were the most efficient in inhibiting both lipid and protein oxidation. Catechin, a flavonal found in red-wines in relatively high concentration was found to inhibit myoglobin catalyzed linoleate membrane lipid peroxidation at a relatively very low concentration. This effect was studied by the determination of the by-products generated from linoleate during oxidation. The study showed that hydroperoxides are catalytically broken down, not to an alcohol but most probably to a non-radical adduct. The ability of wine-phenolics to reduce iron and from complexes with metals were also demonstrated. Low concentration of wine phenolics were found to inhibit lipoxygenase type II activity. An attempt to understand the bioavailability in humans of antocyanins from red wine showed that two antocyanins from red wine were found unchanged in human urine. Other antocyanins seems to undergo molecular modification. In hypercholesterolemic hamsters, aortic lipid deposition was significantly less in animals fed diets supplemented with either catechin or vitamin E. The rate of LDL accumulation in the carotid arteries was also significantly lower in the catechin and vitamin E animal groups. These results suggested a novel mechanism by which wine phenolics are associated with decreased risk of coronary heart diseases. This study proves in part our hypothesis that the "French Paradox" could be explained by the action of the antioxidant effects of phenolic compounds found at high concentration in red wines. The results of this study argue that it is in the interest of public health to increase the consumption of dietary plant falvonoids. Our results and these from others, show that the consumption of red wine or plant derived polyphenolics can change the antioxidant tone of animal and human plasma and its isolated components towards oxidative reactions. However, we need more research to better understand bioavailability and the mechanism of how polyphenolics affect health and disease.
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Yalovsky, Shaul, und Julian Schroeder. The function of protein farnesylation in early events of ABA signal transduction in stomatal guard cells of Arabidopsis. United States Department of Agriculture, Januar 2002. http://dx.doi.org/10.32747/2002.7695873.bard.
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Loss of function mutations in the farnesyltransferase β subunit gene ERA1 (enhanced response to abscisic acid), cause abscisic acid hypersensitivity in seedlings and in guard cells. This results in slowed water loss of plants in response to drought. Farnesyltransferase (PFT) catalyses the attachment of the 15-carbon isoprenoid farnesyl to conserved cysteine residues located in a conserved C-terminal domain designated CaaX box. PFT is a heterodimeric protein comprised of an a and b sununits. The a subunit is shared between PFT and geranylgeranyltransferase-I (PGGTI) which catalyses the attachemt of the 20-carbon isoprenoid geranylgeranyl to CaaX box proteins in which the last amino acid is almost always leucine and in addition have a polybasic domain proximal to the CaaL box. Preliminary data presented in the proposal showed that increased cytoplasmic Ca2+ concentration in stomal guard cells in response to non-inductive ABA treatements. The goals set in the proposal were to characterize better how PFT (ERA1) affects ABA induced Ca2+ concentrations in guard cells and to identify putative CaaX box proteins which function as negative regulators of ABA signaling and which function is compromised in era1 mutant plants. To achieve these goals we proposed to use camelion Ca2+ sensor protein, high throughput genomic to identify the guard cell transcriptome and test prenylation of candidate proteins. We also proposed to focus our efforts of RAC small GTPases which are prenylated proteins which function in signaling. Our results show that farnesyltransferaseprenylates protein/s that act between the points of ABA perception and the activation of plasma membrane calcium influx channels. A RAC protein designated AtRAC8/AtRop10 also acts in negative regulation of ABA signaling. However, we discovered that this protein is palmitoylated and not prenylated although it contains a C-terminal CXXX motif. We further discovered a unique C-terminal sequence motif required for membrane targeting of palmitoylatedRACs and showed that their function is prenylation independent. A GC/MS based method for expression in plants, purification and analysis of prenyl group was developed. This method would allow highly reliable identification of prenylated protein. Mutants in the shared α subunit of PFT and PGGT-I was identified and characterized and was shown to be ABA hypersensitive but less than era1. This suggested that PFT and PGGT-I have opposing functions in ABA signaling. Our results enhanced the understanding of the role of protein prenylation in ABA signaling and drought resistance in plants with the implications of developing drought resistant plants. The results of our studies were published 4 papers which acknowledge support from BARD.
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Schuster, Gadi, und David Stern. Integrated Studies of Chloroplast Ribonucleases. United States Department of Agriculture, September 2011. http://dx.doi.org/10.32747/2011.7697125.bard.
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Gene regulation at the RNA level encompasses multiple mechanisms in prokaryotes and eukaryotes, including splicing, editing, endo- and exonucleolytic cleavage, and various phenomena related to small or interfering RNAs. Ribonucleases are key players in nearly all of these post-transcriptional mechanisms, as the catalytic agents. This proposal continued BARD-funded research into ribonuclease activities in the chloroplast, where RNase mutation or deficiency can cause metabolic defects and is often associated with plant chlorosis, embryo or seedling lethality, and/or failure to tolerate nutrient stress. The first objective of this proposal was to examined a series of point mutations in the PNPase enzyme of Arabidopsis both in vivo and in vitro. This goal is related to structure-function analysis of an enzyme whose importance in many cellular processes in prokaryotes and eukaryotes has only begun to be uncovered. PNPase substrates are mostly generated by endonucleolytic cleavages for which the catalytic enzymes remain poorly described. The second objective of the proposal was to examine two candidate enzymes, RNase E and RNase J. RNase E is well-described in bacteria but its function in plants was still unknown. We hypothesized it catalyzes endonucleolytic cleavages in both RNA maturation and decay. RNase J was recently discovered in bacteria but like RNase E, its function in plants had yet to be explored. The results of this work are described in the scientific manuscripts attached to this report. We have completed the first objective of characterizing in detail TILLING mutants of PNPase Arabidopsis plants and in parallel introducing the same amino acids changes in the protein and characterize the properties of the modified proteins in vitro. This study defined the roles for both RNase PH core domains in polyadenylation, RNA 3’-end maturation and intron degradation. The results are described in the collaborative scientific manuscript (Germain et al 2011). The second part of the project aimed at the characterization of the two endoribonucleases, RNase E and RNase J, also in this case, in vivo and in vitro. Our results described the limited role of RNase E as compared to the pronounced one of RNase J in the elimination of antisense transcripts in the chloroplast (Schein et al 2008; Sharwood et al 2011). In addition, we characterized polyadenylation in the chloroplast of the green alga Chlamydomonas reinhardtii, and in Arabidopsis (Zimmer et al 2009). Our long term collaboration enabling in vivo and in vitro analysis, capturing the expertise of the two collaborating laboratories, has resulted in a biologically significant correlation of biochemical and in planta results for conserved and indispensable ribonucleases. These new insights into chloroplast gene regulation will ultimately support plant improvement for agriculture.
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Plasma Catalysis for NOx Reduction from Light-Duty Diesel Vehicles. Office of Scientific and Technical Information (OSTI), Dezember 2005. http://dx.doi.org/10.2172/940820.
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