Academic literature on the topic 'Catalyseur supporté'
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Journal articles on the topic "Catalyseur supporté"
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Zalma, Roger, Lionel Bonneau, Jeanine Fournier, Joëlle Guignard, Françoise Borg, and Henri Pezerat. "Hydrodésazotation de l'indole sur catalyseur fer supporté sur amiante." Canadian Journal of Chemistry 65, no. 3 (March 1, 1987): 523–27. http://dx.doi.org/10.1139/v87-091.
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The aim of this study is to examine hydrodenitrogenation (HDN) of indole on asbestos catalysts (chrysotile and crocidolite) under hydrogen pressure. HDN is carried out according to two competitive pathways, either via ortho-ethylaniline or via ortho-toluidine. This reaction is assisted by increase of temperature and pressure and by pre-reduction of the asbestos. Particles of Fe0on the fibre surface are formed from the original material. Their presence plays a role in the initial breaking of the C—N bond and in the hydrogenation reaction.
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Bensaddik, A., B. Ernst, F. Garin, G. Maire, and A. Kiennemann. "Etude in situ par EXAFS de la réductibilité d'un catalyseur Fischer-Tropsch à base de cobalt supporté sur silice." Le Journal de Physique IV 06, no. C4 (July 1996): C4–545—C4–552. http://dx.doi.org/10.1051/jp4:1996451.
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Jaeger, Philippe. "Préparation de catalyseurs supportés. Preparation of supported catalysts." Sciences Géologiques. Bulletin 46, no. 1 (1993): 281–89. http://dx.doi.org/10.3406/sgeol.1993.1911.
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DEVYNCK, J., and F. BEDIOUI. "Catalyse électrochimique à l'aide de catalyseurs immobilisés sur support organique ou minéral." Le Journal de Physique IV 04, no. C1 (January 1994): C1–131—C1–146. http://dx.doi.org/10.1051/jp4:1994109.
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Bachari, Khaldoun, Rabah Bouarab, and Ouiza Chérifi. "Production d’Hydrogène via le Procédé Catalytique CH4 + CO2." Journal of Renewable Energies 4, no. 2 (December 31, 2001): 101–5. http://dx.doi.org/10.54966/jreen.v4i2.1002.
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La réaction de reformage du méthane par le CO2 en gaz de synthèse (H2, CO) a été étudiée sur catalyseurs à base de nickel, cobalt et de terres rares supportés. Les solides catalytiques ont été préparés par imprégnation sèche et caractérisés par absorption atomique et par la diffraction des rayons-X. La production d’hydrogène est remarquablement influencée par la nature de la phase métallique et des supports utilisés. L’ordre décroissent des conversions de CO2 et de CH4 ainsi que la production d’hydrogène des catalyseurs supportés sur silice est : Ru, Ni, Rh, Pt, Co. En revanche, l’activité des catalyseurs supportés sur l’alumine suit la séquence suivante : Rh , Ru, Pt.
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Mauret, P., P. Alphonse, and M. Ramalanjaona. "Désactivation de catalyseurs au nickel non supporté." Journal de Chimie Physique 84 (1987): 895–99. http://dx.doi.org/10.1051/jcp/1987840895.
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Jouve, Andrea, Stefano Cattaneo, Sofia Capelli, Marta Stucchi, Claudio Evangelisti, Alberto Villa, and Laura Prati. "CNF-Functionalization as Versatile Tool for Tuning Activity in Cellulose-Derived Product Hydrogenation." Molecules 24, no. 2 (January 16, 2019): 316. http://dx.doi.org/10.3390/molecules24020316.
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Carbon nanofibers (CNFs) have been functionalized by introducing O, N, and P containing groups in order to investigate the effect of support functionalization in Ru catalysed hydroxymethyl furfural (HMF) and levulinic acid (LA) hydrogenation. In the case of HMF, despite the fact that no effect on selectivity was observed (all the catalysts produced selectively gamma-valerolactone (GVL)), the functionalization strongly affected the activity of the reaction. O-containing and N-containing supports presented a higher activity compared to the bare support. On the contrary, in HMF hydrogenation, functionalization of the support did not have a beneficial effect on the activity of a Ru-catalysed reaction with respect to bare support and only CNFs-O behaved similarly to bare CNFs. In fact, when CNFs-N or CNFs-P were used as the supports, a lower activity was observed, as well as a change in selectivity in which the production of ethers (from the reaction with the solvent) greatly increased.
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Triki, H., H. Batis, and A. Katrib. "Propriétés acido-basiques des catalyseurs LaCrO3 supportés." Journal de Chimie Physique et de Physico-Chimie Biologique 95, no. 9 (October 1998): 2015–33. http://dx.doi.org/10.1051/jcp:1998351.
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Hong, Hui, Yuhui Sun, Yongjun Zhou, Emily Stephens, Markiyan Samborskyy, and Peter F. Leadlay. "Evidence for an iterative module in chain elongation on the azalomycin polyketide synthase." Beilstein Journal of Organic Chemistry 12 (October 11, 2016): 2164–72. http://dx.doi.org/10.3762/bjoc.12.206.
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The assembly-line synthases that produce bacterial polyketide natural products follow a modular paradigm in which each round of chain extension is catalysed by a different set or module of enzymes. Examples of deviation from this paradigm, in which a module catalyses either multiple extensions or none are of interest from both a mechanistic and an evolutionary viewpoint. We present evidence that in the biosynthesis of the 36-membered macrocyclic aminopolyol lactones (marginolactones) azalomycin and kanchanamycin, isolated respectively from Streptomyces malaysiensis DSM4137 and Streptomyces olivaceus Tü4018, the first extension module catalyses both the first and second cycles of polyketide chain extension. To confirm the integrity of the azl gene cluster, it was cloned intact on a bacterial artificial chromosome and transplanted into the heterologous host strain Streptomyces lividans, which does not possess the genes for marginolactone production. When furnished with 4-guanidinobutyramide, a specific precursor of the azalomycin starter unit, the recombinant S. lividans produced azalomycin, showing that the polyketide synthase genes in the sequenced cluster are sufficient to accomplish formation of the full-length polyketide chain. This provides strong support for module iteration in the azalomycin and kanchanamycin biosynthetic pathways. In contrast, re-sequencing of the gene cluster for biosynthesis of the polyketide β-lactone ebelactone in Streptomyces aburaviensis has shown that, contrary to a recently-published proposal, the ebelactone polyketide synthase faithfully follows the colinear modular paradigm.
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Stines-Chaumeil, Claire, François Talfournier, and Guy Branlant. "Mechanistic characterization of the MSDH (methylmalonate semialdehyde dehydrogenase) from Bacillus subtilis." Biochemical Journal 395, no. 1 (March 15, 2006): 107–15. http://dx.doi.org/10.1042/bj20051525.
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Homotetrameric MSDH (methylmalonate semialdehyde dehydrogenase) from Bacillus subtilis catalyses the NAD-dependent oxidation of MMSA (methylmalonate semialdehyde) and MSA (malonate semialdehyde) into PPCoA (propionyl-CoA) and acetyl-CoA respectively via a two-step mechanism. In the present study, a detailed mechanistic characterization of the MSDH-catalysed reaction has been carried out. The results suggest that NAD binding elicits a structural imprinting of the apoenzyme, which explains the marked lag-phase observed in the activity assay. The enzyme also exhibits a half-of-the-sites reactivity, with two subunits being active per tetramer. This result correlates well with the presence of two populations of catalytic Cys302 in both the apo- and holo-enzymes. Binding of NAD causes a decrease in reactivity of the two Cys302 residues belonging to the two active subunits and a pKapp shift from approx. 8.8 to 8.0. A study of the rate of acylation as a function of pH revealed a decrease in the pKapp of the two active Cys302 residues to approx. 5.5. Taken to-gether, these results support a sequential Cys302 activation process with a pKapp shift from approx. 8.8 in the apo-form to 8.0 in the binary complex and finally to approx. 5.5 in the ternary complex. The rate-limiting step is associated with the β-decarboxylation process which occurs on the thioacylenzyme intermediate after NADH release and before transthioesterification. These data also indicate that bicarbonate, the formation of which is enzyme-catalysed, is the end-product of the reaction.
Dissertations / Theses on the topic "Catalyseur supporté"
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Marchand-Cury, Hélène. "Analyse de l'interface catalyseur supporté-milieu aqueux dans l'oxydation d'espèces dissoutes." Vandoeuvre-les-Nancy, INPL, 1997. http://www.theses.fr/1997INPL034N.
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Le rôle de l'adsorption a été étudié dans l'oxydation catalytique hétérogène des molécules organiques et du sulfure d'hydrogène en présence d'oxyde métallique supporté. Les propriétés physiques et superficielles des supports ont été mesurées avant et après dispersion du catalyseur. Ensuite, on a étudié le comportement des catalyseurs et des supports vis-à-vis des ions minéraux rencontrés dans une eau naturelle type Méry-sur-Oise (hydrogénocarbonate de sodium et chlorure de calcium). La connaissance approfondie des propriétés superficielles des catalyseurs supportés et de leur affinité vis-à-vis des ions minéraux a permi de préciser le rôle du catalyseur et du support dans l'adsorption de quatre molécules organiques et de connaître les mécanismes de l'adsorption du salicylate (modèle des substances humiques) sur deux supports. Le rôle de l'adsorption dans l'oxydation catalytique a été par la suite estimé à l'aide d'expérimentation faite en présence d'ozone. Il apparaît que l'oxydation peut se produire lorsque la molécule est adsorbée ou non. Les mécanismes de l'oxydation catalytique restent proches de ceux connus de la phase homogène donc ils sont très sensibles au pH. Le catalyseur et les supports adsorbent l'ozone et participent à sa décomposition initiale en présence d'ions hydroxyle ou de peroxyde. La vitesse d'initiation radicalaire est certainement accélérée grâce au catalyseur mais pas suffisament pour éviter des réactions d' adsorption ou d'oxydation directe. L'étude sur l'oxydation catalytique du sulfure d'hydrogène met en évidence son adsorption-oxydation sous trois formes. Deux sont aisément réversibles et représentent la majorité du soufre adsorbé dans des conditions de concentration en sulfure faible. La forme la plus stable, un sulfure métallique, correspond à un empoisonnement limité de l'oxyde. Le support du catalyseur est inerte vis-à-vis des sulfures et des sulfates lorsque l'oxyde métallique est présentThe role of the adsorption was studied in the heterogeneous catalytic oxidation of the organic molecule and hydrogen sulfide with the dispersed support metal oxide. The physical and superficial properties was measured before and after dispersion of metal oxide. We have studied the catalyst behavior with the natural water mineraI ions. The knowledge of the superficial properties of metal oxide or support and their affinities for mineraI ions has allowed for clarifying their role in the adsorption of four organic molecules. It has also allowed for knowing the adsorption mecanisms of the salicylate (humic matter model) on two supports. Then, the role of the adsorption in catalytic oxidation was estimated with ozonation experimentations. It appears that the catalytic oxidation is happening whether the molecule is adsorbed or not. The mecanisrns of catalytic oxidation are similar to the ones of homogeneous oxidation and therefore pH sensitive. The metal oxide and supports have adsorbed ozone and have participated at its initial decomposition in presence of hydroxile or peroxide ions. The kinetic of this reaction is slow and the adsorption or direct oxidation are possible. The study of catalytic oxidation of hydrogen sulfide shows three adsorption-oxidation forms. Two forms are easily reversible and represent the major adsorbed sulfur for low values of concentration. The most stable form, metallic sulfide, corresponds at a weak poisonning of the metal oxide. The catalyst support is inert in regards to hydrogen sulfur when the metal oxide is present
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Wafer, Caroline. "Oxydation de composés oléochimiques à l'aide d'un catalyseur ou d'un oxydant supporté." Master's thesis, Université Laval, 2017. http://hdl.handle.net/20.500.11794/27464.
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Pour s'affranchir partiellement des ressources pétrolières coûteuses et non-renouvelables, il devient de plus en plus avantageux d'introduire des composés biosourcés dans les matériaux pétrochimiques. Dans ce contexte, les molécules d'origine oléagineuse issues des huiles végétales non-comestibles s'avèrent une ressource de choix, étant à la fois renouvelables et ayant un impact moindre sur l'environnement. Elles sont d'ailleurs disponibles en quantités industrielles et avec une bonne pureté, en plus de présenter une possibilité de fonctionnalisation via leurs fonctions alcools, esters et alcènes. Afin de faire de ces huiles des composés à valeur ajoutée, nous avons décidé, dans le cadre de ce projet, de nous concentrer sur l'oxydation de leur liaison double, en utilisant comme composé modèle l'oléate de méthyle. Puisqu'il est important, pour diminuer les coûts, de minimiser les réactifs nécessaires et de limiter les purifications, l'emploi de la catalyse hétérogène est tout indiqué pour parvenir à oxyder les acides gras. L'hémine est une porphyrine connue comme le centre catalytique de nombreuses familles de protéines actives en oxydation. Les travaux de Xue et al. (Angew. Chem. Int. Ed. 2012) ont montré que l'hémine liée de façon non-covalente à l'oxyde de graphène réduit peut oxyder sélectivement certains composés d'intérêt. Le but de ce projet est donc de vérifier l'applicabilité d'un catalyseur d'hémine-graphène pour l'oxydation des acides gras en industrie. À la lumière des résultats obtenus, la fonctionnalisation covalente de l'hémine à l'oxyde de graphène, ainsi qu'à une silice mésoporeuse ont également été testées. Les performances se montrant peu reproductibles, des travaux sur l'utilisation d'acides percarboxyliques supportés sur silice comme oxydant réutilisable des acides gras ont ensuite été effectués.
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Khodadadi, Mohamad Reza. "Étude de la réaction d'aziridination au cuivre supporté par des nanoparticules magnétiques." Thesis, Amiens, 2018. http://www.theses.fr/2018AMIE0045/document.
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L'introduction d'atomes d'azote sur des squelettes organiques reste une étape clé pour la synthèse de molécules bioactives alcaloïdes. Depuis quelques années, l'insertion catalytique de nitrène sur les alcènes ou pour la fonctionnalisation des liaisons C-H est devenue un outil indéniable pour une telle introduction. Cependant, les systèmes catalytiques homogènes habituellement utilisés pour cette transformation présentent des inconvénients tels que la stabilité ou la séparation après réaction. Des catalyseurs supportés recyclables sont alors apparus comme une alternative intéressante pour surmonter ces problèmes. Dans le cadre de notre intérêt continu pour le développement de méthodologies durables, nous avons conçu de nouveaux catalyseurs valorisables efficaces, conformes aux principes de la chimie verte. Ici, la première insertion de nitrène pour l'aziridination en utilisant une nanoferrite chargée de cuivre réutilisable comme catalyseur sera présentée. Les propriétés magnétiques des nanoparticules permettent une récupération facile de ces catalyseurs avec un simple aimant externe. Nous montrerons que les catalyseurs peuvent être réutilisés 5 fois avec une conversion totale du styrène et de bons rendements, même après 5 essais. Les investigations après caractérisation complète ont montré une réduction de la charge de cuivre au fur et à mesure des cycles, ce qui peut être dû à un ancrage faible. Ce résultat nous incite à explorer différents linkers entre les nanoparticules magnétiques et le cuivre afin de diminuer cette lixiviation. Plusieurs lieurs présentant des fonctions différentes d'ancrage MNP et de chélation de Cu seront présentés. En outre, l'extrapolation réussie de cette méthodologie à des dérivés de styrène substitués pauvres en électrons ou riches en électrons sera démontrée, ainsi que l'aziridination d'oléfines à longue chaîne qui seront exposéesIntroduction of nitrogen atoms onto organic skeletons remains a key step for the synthesis of alkaloid bioactive molecules. Since a few years, catalytic nitrene insertion on alkenes or for C-H bond functionalization has emerged as an undeniable tool for such introduction. However, homogeneous catalytic systems usually used for this transformation present some drawbacks such as stability, or separation after reaction. Recyclable supported catalysts have then arisen as a valuable alternative to overcome these issues.As part of our continued interest for the development of sustainable methodologies, we designed new and efficient recoverable catalysts fitting by the way the green chemistry principles. Here, the first nitrene insertion for aziridination using a reusable copper-loaded nanoferrite as catalyst will be presented. Magnetic properties of the nanoparticles allow an easy retrieval of those catalysts with a simple external magnet. We will show that the catalysts could be reused for 5 times with total conversion of styrene and good yields, even after 5 runs.Investigations after full characterization showed a reduction of copper loading as the runs, which can be due to a weak anchoring. This result prompts us to explore different linkers between magnetic nanoparticles and copper in order to decrease this leaching. Several linkers exhibiting different MNP-anchoring and Cu-chelating functions will be presented. Also, the successful extrapolation of this methodology to electron-poor or electron-rich substituted styrene derivatives will be demonstrated as well as the aziridination of long chain olefins which will be exhibited
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Bochard, Frédérique. "Réactivité des chloroformiates en présence de chlorure d'hexaalkylguanidinium, supporté ou non, comme catalyseur." Lyon 1, 1996. http://www.theses.fr/1996LYO10232.
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Afin d'etudier la reactivite des chloroformiates en presence de chlorure d'hexabutylguanidinium supporte sur silice macroporeuse (sigcl) ou non (gcl), nous avons, dans un premier temps, realise une etude cinetique de la decomposition des chloroformiates aliphatiques en chlorures et des chloroformiates aromatiques en carbonates. La comparaison avec des chlorures d'ammonium et de phosphonium a confirme la meilleure activite catalytique de gcl. Une etude mecanistique a partir de chloroformiates optiquement actifs a ensuite montre que gcl decompose le (s)-chloroformiate de 2-octyle avec une excellente enantioselectivite (ee=96%), selon un mecanisme de type s#n2. Dans un deuxieme temps, nous avons elabore de nouveaux produits par reaction dechloroformiates avec des epoxydes en presence de gcl. Les carbonates chloromethyles obtenus resultent majoritairement d'une attaque de l'ion chlorure du catalyseur sur le carbone le moins encombre de l'epoxyde. Cette reaction a alors ete etendue a des composes analogues des chloroformiates: les chlorures de carbamoyle qui conduisent aux carbamates chloromethyles et le dioxyde de carbone qui permet d'obtenir des carbonates cycliques
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Madani, Behrang. "Synthèse de Fischer-Tropsch sur catalyseur à base de cobalt supporté sur carbure de Silicium." Université Louis Pasteur (Strasbourg) (1971-2008), 2005. https://publication-theses.unistra.fr/public/theses_doctorat/2005/MADANI_Behrang_2005.pdf.
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La synthèse de Fischer-Tropsch (SFT) conduit à une grande diversité de produits, principalement des alcanes ainsi que des oléfines et des alcools et ce à partir d'un mélange précis de CO et H2. Actuellement le gaz naturel est brûlé au niveau des puits de pétrole, ce qui entraîne non seulement une perte économique non négligeable mais aussi une pollution atmosphérique due au dégagement de CO2. La réaction de FT est une des voies permettant de valoriser le gaz naturel après transformation de celui-ci en gaz de synthèse (mélange de CO et H2). La réaction SFT est exothermique et nécessite une évacuation rapide de la chaleur hors du site catalytique afin d'éviter le problème de formation de points chauds et les problèmes de craquage des produits formés. Les supports utilisés traditionnellement pour la SFT sont souvent des supports isolants tels que l'alumine et la silice qui ne permettent pas une bonne évacuation de la chaleur. Dans ce travail, nous avons remplacé le support isolant par un support conducteur à base de β-SiC, ce qui permet une meilleure homogénéisation de la température dans le lit catalytique. Dans le cadre de cette étude, différents paramètres réactionnels, comme la teneur en Co, la pression totale et le temps de contact ont été optimisés pour obtenir les meilleures activité, sélectivité et stabilité du catalyseur. Nous avons étudié également l'influence de la morphologie du support sur la performance du catalyseur. Parmi les différentes formes de support testé à base de β-SiC (grain, extrudé et mousse), le support sous forme de mousse semble d'avoir la meilleure performance. Nous avons mis au point les procédures de régénération du catalyseur ainsi que le dopage par le molybdène. Les catalyseurs ainsi obtenus présentent de meilleures activité et sélectivitéThe Fischer-Tropsch synthesis (FTS) leads to various products, mainly alkanes as well as olefins and alcohols, starting with precise mixture of CO and H2. Currently, natural gas is recovered as a by-product of oil extraction and directly burnt, which leads a non negligible economic loss as well as an atmospheric pollution due to the production of CO2. The reaction of FTS is one of the ways permitting valorisation of natural gas after its transformation in gas of synthesis (mixture of CO and H2). The SFT reaction is exothermique and requires fast evacuation of heat from the catalytic sites in order to avoid the problem of hot spots formation and subsequent cracking of formed products. The supports used traditionally for the FTS are insulating supports, such as alumina and silica, which does not permit a good evacuation of heat. In this work, we replaced the insulating support by a conducting support based on SiC, which permits a better homogenisation of the temperature in the catalytic bed. In this study, different reaction parameters- the Co content, the total pressure and contact time, have been optimized in order to obtain the best activity, selectivity and stability of the catalysts. We also studied the influence of the morphology of the support on the catalyst performance. Among the different shapes of support based on SiC (grain, extrudes and foam), the support as foam seems to have the best performance. We finalised the procedures of regeneration of the catalyst as well as the doping by molybdenum. The thus obtained catalysts present the best activity and selectivity
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Audirac, Aude. "Contribution à la mise en oeuvre du procédé d'ozonation catalytique à partir d'un catalyseur supporté." Thesis, Poitiers, 2013. http://www.theses.fr/2013POIT2316/document.
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Cette thèse a pour objet de contribuer au développement du procédé de dépollution des eaux usées industrielles par ozonation catalytique hétérogène mettant en oeuvre un catalyseur poudre breveté, déposé sur des mousses de différents matériaux. Pour cela, une molécule modèle réfractaire, l'acide succinique a été ozonée en présence de catalyseur dans un réacteur lors d'expériences au cours desquelles plusieurs paramètres d'importance pour l'efficacité du procédé ont été modifiés (localisation du catalyseur, configuration du réacteur, introduction d'ozone...).Dans un premier temps la cinétique réactionnelle a été déterminée en faisant varier les concentrations initiales en acide succinique et en catalyseur.Par la suite, l'influence de la localisation du catalyseur supporté au sein du système réactionnel et du mode d'introduction de l'ozone gaz a été étudiée.La variation du temps de séjour de la solution par variation d'une part du débit d'entrée et d'autre part du volume de solution dans le système a permis (i) la confirmation de la loi cinétique et (ii) la détermination d'un volume limite à partir duquel l'efficacité de la réaction est affectée.Les résultats obtenus ont aboutis à la proposition d'un mécanisme d'ozonation catalytique hétérogène en plusieurs étapes et à la définition de paramètres de dimensionnement en vue d'une application industrielleThis study aims at developing an industrial wastewater treatment process based on heterogeneous catalytic ozonation implementing a patented powder catalyst stuck on stainless steel and ceramic foam. A refractory model compound, succinic acid, was chosen to be ozonated in the presence of the catalyst while different operating parameters were varied.Kinetic of the catalytic reaction was determined varying initial concentrations of succinic acid and catalyst.The influence of solid catalyst within the reaction system and of the way of introduction of ozone gas was also investigated.The variation of the solution Hydraulic Retention Time through (i) inlet flow rate variation and (ii) volume of solution in the reaction system variation, allowed the confirmation of the kinetic law and the determination of a threshold volume below which the reaction efficiency decreased.The results obtained allowed the proposition of heterogeneous catalytic ozonation mechanism comprising several steps and the definition of design parameters
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Lutun, Stéphane. "Synthèses d'hétérocycles à l'aide de métaux de transition : préparation d'oxadiazoles : synthèse et utilisation d'un catalyseur supporté." Lille 1, 1997. http://www.theses.fr/1997LIL10072.
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Depuis plus d'un siecle, de nombreux procedes d'heterocyclisation ont ete publies. Des la fin des annees 60, le palladium a ete utilise au cours de ces syntheses. Le laboratoire de chimie organique et environnement (lcoe) de lille i y a contribue en developpant une nouvelle voie d'acces aux furannes par action de palladium(ii) sur des alcoolsinsatures. Nous nous sommes inspires de ces travaux et nous avons mis au point une nouvelle synthese de 1,3,4-oxadiazoles par heterocyclisation de n,n'-diacylhydrazines. Les meilleurs resultats sont obtenus avec le palladium(0)tetrakis(triphenylphosphine). L'utilisation de catalyseurs metalliques supportes par un polymere devient d'utilisation courante tant au laboratoire qu'en industrie. En effet, ces supports polymeriques permettent une extraction aisee du metal en fin de manipulation. Celui-ci peut, alors, etre facilement reutilise lors de reactions ulterieures. Notre attention s'est portee sur la possibilite de produire un polymere, comportant des motifs de type 1,10-phenanthroline, permettant la complexation du palladium(0). Pour cela, nous avons synthetise un derive vinylique de cet agent complexant qui a ete copolymerise en presence de styrene. Sur le polymere obtenu, nous avons complexe le palladium(0) et l'efficacite de ce systeme a pu etre verifiee lors de la cyclisation de la n-acetyl,n'-benzoylhydrazine.
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Carneiro, Da Rocha De Almeida Maria da Graça. "Combustion catalytique du méthane au contact de palladium supporté : étude de l'activation du catalyseur pendant la réaction." Lyon 1, 1995. http://www.theses.fr/1995LYO10054.
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L'oxydation totale du methane, conduite a basses temperatures, en presence d'un catalyseur heterogene, permet a la fois d'eliminer l'hydrocarbure non-brule dans des effluents gazeux issus de procedes thermiques ou industriels, ainsi que d'eviter la production d'oxydes d'azote no#x. L'oxydation du ch#4 a ete etudiee en reacteur a lit fixe sur des catalyseurs a base de pd supporte sur deux alumines de transition et une alumine alpha. L'objectif de cette etude est de determiner les facteurs responsables de l'obtention d'un catalyseur stable et actif ainsi que de suivre l'evolution du catalyseur dans cet etat final, de facon a apprehender les caracteristiques de la phase active. Une methodologie statistique de plan d'experiences a ete utilisee pour determiner l'influence des facteurs de preparation et de pretraitement des catalyseurs sur leur activite catalytique. Le role de differentes atmospheres de pretraitement (o#2, n#2, h#2, ch#4+o#2) a aussi ete evalue. L'activation du catalyseur sous milieu reactionnel est observee, et de type du support est un facteur tres important sur l'activite catalytique. Les catalyseurs les plus actifs pour l'oxydation totale de ch#4 sont peu charges en pd (0,5%), le support est une alumine delta. Les traitements a hautes temperatures sous melange reactionnel ont conduit a l'obtention des catalyseurs les plus actifs pour une temperature optimale de pretraitement comprise entre 700 et 900c. Une exaltation de l'activite catalytique est observee malgre un filtrage important des particules de palladium. Des echantillons des catalyseurs normalisees, issus de divers traitements ont ete caracterisees par titrages h#2-o#2, analyses en temperature programmee (tpr, tpo, tpd), microscopies electronique (tem et sem) et a champ proche (afm), xps, drx et spectroscopie infrarouge de co adsorbe. Les resultats de ces analyses indiquent que le traitement de la phase active sous differentes atmospheres conduit a des morphologies de surface nettement differenciees. Les especes existantes a la surface changent avec la reaction, ainsi que la composition massique des catalyseurs qui sont constitues par pdo et pd, leurs concentrations en surface dependent peu de la nature du traitement. La reaction d'oxydation entraine une fragmentation importante de la surface de la phase active, celle-ci est constitue par pdo et pd metallique dont les proportions sont en constante evolution. L'oxyde de palladium se forme sur les sites les plus actifs
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Locatelli, François. "Etude du mécanisme de rupture des liaisons carbone-carbone endo et exocycliques sur catalyseur iridium supporté sur silice." Lyon 1, 1999. http://www.theses.fr/1999LYO10229.
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Le catalyseur ir/sio 2, caracterise par infrarouge, volumetrie d'adsorption, analyse elementaire et microscopie electronique, est prepare par oxydation puis reduction d'ir(acac) 3 depose sur silice. Cette etude a permis de proposer des conditions operatoires necessaires a l'obtention d'un catalyseur avec une distribution de taille de particules etroite. La reaction catalytique d'un melange de cyclohexane et d'hydrogene sur un catalyseur a base d'iridium supporte sur silice a ete etudie dans des conditions permettant de s'affranchir totalement de l'aromatisation. L'hydrogenolyse est alors la seule reaction observee. La reaction d'hydrogenolyse a egalement ete etudiee en partant de l'ethane ou du n-hexane afin de clarifier le mecanisme de l'hydrogenolyse. Nous avons alors propose un mecanisme n'impliquant que des etapes elementaires connues en chimie organometallique classique. La difference de distribution observee dans les produits de reaction permet de discuter les vitesses relatives des differentes reactions a la surface du catalyseur. Des cycloalcanes substitues ont egalement ete etudies (1,4-dimethylcyclohexane, 1,2-cis dimethylcyclohexane, ethylcyclohexane et decaline). L'aromatisation reste dans ce cas possible a 200\c sous pression atmospherique malgre un tres large exces d'hydrogene. Parmi les produits d'hydrogenolyse, ceux issus d'une seule coupure c-c sont majoritaires (>70%), mais il se forme egalement des produits issus d'au moins deux coupures c-c. En se basant sur le mecanisme propose pour l'hydrogenolyse du cylohexane, des intermediaires de type dimetallacycle ont ete proposes pour expliquer la formation des produits primaires observes. Afin de rendre compte des selectivites observees, la stabilite des especes de surface a alors ete discutee.
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Tonnerre, Jean-Marc. "Étude de la structure locale d'un catalyseur d'hydrodésulfuration Ni-Mo non supporté par la diffusion anomale des RX." Paris 11, 1989. http://www.theses.fr/1989PA112284.
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Ce mémoire est consacré à l'étude, par la diffusion anomale des RX, de la phase "NiMoS" de type MoS2 d'un catalyseur d'hydrodésulfuration Ni-Mo non supporté. L'activité catalytique de ces systèmes multiphasiques est reliée à la présence d'une phase NiMoS qui apparaît sous forme de petites cristallites présentant une structure de type MoS2. Afm de l'isoler, nous avons étudié un échantillon avec une faible concentration en Ni (7%). Au sein de cette phase, la position des atomes promoteurs Ni est le sujet de controverses. Pour certains auteurs, ils s'insèrent entre les feuillets S-Mo-S sur le bord des cristallites dans des sites "pseudo intercalés"; pour d'autres, ils se substituent aux Mo sur le pourtour des feuillets. Afm de lever l'ambiguïté, liée au manque d'informations sur les seconds voisins, nous avons utilisé la diffusion anomale différentielle pour sonder l'ordre local sur plusieurs sphères de coordination autour de chaque espèce métallique. Les résultats au seuil d'absorption K du Mo montrent que cette technique, initialement développée pour la caractérisation structurale de matériaux désordonnés, s'applique à l'étude de matériaux mal-cristallisés. Les distances et les nombres de coordination des premiers voisins, sont corrects respectivement à ±0. 02 A et 10%. Au seuil K du Ni, la faible concentration des atomes promoteurs conduit à un signal différentiel très faible (ôl/1-3%). Les résultats sont plus bruyants et le traitement des données a nécessité un soin particulier. Ils montrent clairement que le Ni est dans un site Mo et donc élimine le modèle de "pseudo-intercalation". L'analyse des nombres de coordinence ne permet pas de préciser directement la localisation des Ni. Deux situations substituées (dans le volume, sur les bords) ont été testées en simulant les fonctions de distribution différentielle. Le meilleur accord modèle expérience s'établit pour la localisation sur les bords. Enfin l'analyse d'expériences EXAFS au seuil du Ni semble indiquer la présence de corrélations possédant une distance Ni-Ni très proches de celle des corrélations Ni-Sen premier voisin.
Books on the topic "Catalyseur supporté"
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Clean Synthesis Using Porous Inorganic Solid Catalysts and Supported Reagents (RSC Clean Technology Monographs). Royal Society of Chemistry, 2000.
Find full textBook chapters on the topic "Catalyseur supporté"
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Heikkinen, Anna, Johanna Kujala, and Annika Blomberg. "Outlining Stakeholder Engagement in a Sustainable Circular Economy." In Stakeholder Engagement in a Sustainable Circular Economy, 1–15. Cham: Springer International Publishing, 2023. http://dx.doi.org/10.1007/978-3-031-31937-2_1.
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AbstractA circular economy is considered one of the most pertinent solutions to contemporary socioeconomic and environmental sustainability challenges, such as climate change, biodiversity loss and resource depletion. The transition from a linear to a circular economy requires the support and participation of various organisations and institutions as well as stakeholders at all levels of society. This edited volume examines the role and importance of stakeholder engagement in a sustainable circular economy from multiple theoretical and practical perspectives. We understand a sustainable circular economy as a pathway to a more environmentally friendly and socially inclusive society and stakeholder engagement as an important tool to catalyse this journey. This volume provides an in-depth, research-based overview of how stakeholder engagement can catalyse the transition towards a sustainable circular economy and foster and support sustainable change. It provides an up-to-date discussion of theoretical and practical advances that is intended for researchers, policymakers and practitioners working on the circular economy.
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Chan, T. S., M. Moridani, A. Siraki, H. Scobie, K. Beard, M. A. Eghbal, G. Galati, and P. J. O’Brien. "Hydrogen Peroxide Supports Hepatocyte P450 Catalysed Xenobiotic/Drug Metabolic Activation to form Cytotoxic Reactive Intermediates." In Advances in Experimental Medicine and Biology, 233–36. Boston, MA: Springer US, 2001. http://dx.doi.org/10.1007/978-1-4615-0667-6_34.
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Niccolai, Gerald P., and Jean-Marie Basset. "New Processes for Carbon-Carbon Bond Activation Catalysed by Oxide Supported Surface Organometallic Complexes." In Catalytic Activation and Functionalisation of Light Alkanes, 111–24. Dordrecht: Springer Netherlands, 1998. http://dx.doi.org/10.1007/978-94-017-0982-8_5.
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Mureithi, Joseph, Saidi Mkomwa, Amir Kassam, and Ngari Macharia. "Research and technology development needs for scaling up conservation agriculture systems, practices and innovations in Africa." In Conservation agriculture in Africa: climate smart agricultural development, 176–88. Wallingford: CABI, 2022. http://dx.doi.org/10.1079/9781789245745.0009.
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Abstract Although the net agricultural production across all regions of Africa has experienced a significant increase, African agriculture has performed below its potential over recent decades. Many aspects have been fronted to curb this situation, including sustainable intensification of farming systems and value-chain transformation through Conservation Agriculture (CA) across Africa. Based on the latest update, Africa has about 2.7 million ha under CA, an increase of 458% over the past 10 years with 2008/09 as baseline. However, this constitutes a mere 1.5% of the global area under CA, and less than 1.4% of the total cropland area in Africa. A combination of modern techniques and the optimization of agroecological processes in CA systems and practices requires that agricultural research plays a bigger role in its evolution and focus in the different regions of Africa. This targeted research should crucially contribute towards making agriculture in Africa more productive, competitive, sustainable and inclusive in terms of its functionality towards the farmer, society and nature. Scientific solutions for agricultural transformation need to be pursued without losing sight of the potentials and fragility of Africa's agricultural environments, the complexity of its agricultural production systems and the continent's rich biodiversity. The agricultural research and development agenda in Africa must build on the rich traditional farming culture, knowledge and practices, supported by coherent longer-vision for investments in science for agricultural development. Most of these investments are expected to come from national public and private sources, with governments also expected to invest in generation of 'public goods' such as the national or global environmental benefits typical of CA, and to also catalyse innovation and support market growth. The absolute imperative is that farmers must shift from outdated conventional tillage-based methods to modern, well-tested and knowledge-based methods of land use. Making this transition will be difficult without the creation of an enabling environment. This chapter discusses the various roles and advances required in CA-based research that will support the adoption of CA systems by millions of smallholder farmers in Africa with a view to enhancing sustainable and effective agricultural development and economic growth.
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Guerrero-Ruiz, A., and I. Rodríguez-Ramos. "Recent Progress in Supported Metal-Catalysed C1 Chemistry." In Supported Metals in Catalysis, 247–300. IMPERIAL COLLEGE PRESS, 2011. http://dx.doi.org/10.1142/9781848166783_0007.
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Guerrero–Ruiz, A., and I. Rodríguez–Ramos. "RECENT PROGRESS IN SUPPORTED METAL CATALYSED C1 CHEMISTRY." In Supported Metals in Catalysis, 155–85. IMPERIAL COLLEGE PRESS, 2005. http://dx.doi.org/10.1142/9781860947476_0005.
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Jacquier, Alain. "RNA-catalysed RNA processi•ng." In Eukaryotic mRNA Processing, 1–36. Oxford University PressOxford, 1997. http://dx.doi.org/10.1093/oso/9780199634187.003.0001.
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Abstract RNA processing reactions, as most chemical reactions occurring in living cells, are greatly accelerated by enzymatic catalysis. Proteins were, for a long time, the only class of molecules known to support enzymatic activity. The discovery, a decade ago, that several RNA processing events could be catalysed by RNA molecules (1, 2) thus revolutionized our views in several areas of biology and, most particularly of course, in the RNA processing field. These catalytic RNA molecules have been called ‘ribozymcs’.
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Mochida, Isao, Takaaki Higashiizumi, Youichi Ishihara, and Hiroshi Fujitsu. "Spillover in catalyses over Co-phthalocyanines supported on titania." In New Aspects of Spillover Effect in Catalysis - For Development of Highly Active Catalysts, Proceedings of the Third International Conference on Spillover, 321–24. Elsevier, 1993. http://dx.doi.org/10.1016/s0167-2991(08)63201-2.
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Berrichi, F. Z. El, B. Louis, L. Cherif, M. J. Ledoux, and C. Pham Huu. "Benzoylation of anisole catalysed by Ga/SBA-15 supported on β-SiC." In Zeolites and related materials: Trends, targets and challenges, Proceedings of the 4th International FEZA Conference, 1307–10. Elsevier, 2008. http://dx.doi.org/10.1016/s0167-2991(08)80129-2.
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Alcántara, A. R., J. V. Sinisterra, C. Torres, J. M. Guisán, M. H. Gil, and A. Williams. "Peptide Synthesis in Organic-Aqueous Media Catalysed by α-Chymotrypsin Immobilised Over Different Supports." In Progress in Biotechnology, 443–50. Elsevier, 1992. http://dx.doi.org/10.1016/b978-0-444-89046-7.50066-7.
Full textConference papers on the topic "Catalyseur supporté"
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F, Rubona, Ibongu E, Bah AJ, Dianouni F, and Wepnyui H. "Formation virtuelle comme catalyser d'amelioration des soins neonataux au centre de sante de reference de douentza au Mali." In MSF Paediatric Days 2024. NYC: MSF-USA, 2024. http://dx.doi.org/10.57740/q5pyocl.
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BACKGROUND AND OBJECTIVES Le Centre de Sante de Référence de Douentza fait face à des nombreux défis des soins néonataux exacerbés par le contexte d’accès très limités. Plusieurs initiatives ont été envisagées notamment le support continu du Pédiatre, analyses des causes des décès et définition des plans d’action, formation au lit des malades. Pour accéder et accompagner le personnel soignant, une formation virtuelle intersectionnelle des soins néonataux a été réalisée pendant 2,5 mois pour une équipe de 7 staffs (infirmières et médecins). Le partage de cette expérience a comme objectif de montrer les bonnes pratiques possibles dans ces contextes. CASE DESCRIPTION Après cette formation virtuelle interactive, l’équipe a pris l’initiative d’identifier les grands défis à relever pour améliorer les soins néonataux à travers une évaluation approfondie (arbre à problèmes) des pratiques de soins dans le projet. La collecte d’informations comprenait des observations sur place à travers des entretiens avec le personnel de santé et avec des accompagnants, des dossiers des patients ainsi que les audits de décès. Définition et implémentation du plan d’amélioration qui a permis : • Réorganisation de la salle de néonatologie en fonction du degré d’urgence : rouge, orange, vert, zone de réanimation. • Meilleure acceptance en interne et sensibilisation sur les soins de la mère kangourou et zéro séparation. • Mise en place et maitrise du protocole de prise en charge (PEC) et de la réanimation néonatale. • Consensus et adoption des critères de PEC (admissions, référence, soins palliatifs). • Travail en amont avec l’équipe de la Promotion de santé et engagement communautaire pour le recours précoce aux soins. CONCLUSIONS La formation virtuelle a permis non seulement d’interagir, d’acquérir des nouvelles connaissances mais aussi l ́analyse et détection des causes profondes du problème, proposer des interventions ciblées à court et moyen terme ; définir le chronogramme d’implémentation ainsi que les indicateurs de suivi. Des changements perceptibles sont opérés et continueront pour des soins néonataux appropriés.
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Guseva, Tatiana, Svetlana Panova, Irina Tikhonova, Arina Volosatova, and Chirag Bhimani. "RESOURCE EFFICIENCY ENHANCEMENT AS A COMMON BACKGROUND FOR GREEN TAXONOMIES OF BRICS COUNTRIES." In 23rd SGEM International Multidisciplinary Scientific GeoConference 2023. STEF92 Technology, 2023. http://dx.doi.org/10.5593/sgem2023/5.1/s20.27.
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This article considers various approaches to developing taxonomies of green projects and focusing on common requirements of countries and regions. The article also analyses the standards of the International Organization for Standardization and evaluates options for applying its key principles, while developing support instruments to catalyse green projects in resource-rich countries, such as BRICS. The research proposes a scientific rationale for systematising incomplete and controversial approaches to evaluation of green projects in industry. The authors consider the main criteria for the international standard, including (1) reduction of greenhouse gases emissions and increase of their absorption; (2) climate change adaptation; (3) sustainable water management; (4) circular economy development; (5) pollution prevention and control (based on Best Available Techniques); and (6) biodiversity protection and restoration. The authors underline that projects aimed at the enhancement of resource efficiency of production processes play pivotal role for the sustainable development of the industry. This article analyses current approaches to developing and implementing green projects using the cement sector as an example. This article identifies that in resource-rich countries, the primary focus is on resource efficiency enhancement and implementation of the Best Available Techniques, which allows preventing pollution, reducing greenhouse gas emissions, and contributing towards the circular economy formation.
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Imaoka, T., and T. Asaji. "FUNCTION OF PLATELET 47K PHOSPHOPROTEIN." In XIth International Congress on Thrombosis and Haemostasis. Schattauer GmbH, 1987. http://dx.doi.org/10.1055/s-0038-1644634.
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Secretion of platelet granule constituents is closely associated with the phosphorylation of a cytosol polypeptide that we called P47 of Mr 47,000 (Imaoka, T. and Haslam, R.J., J. Biol. Chem. 258, 11404, 1983), by protein kinase C. Since the identity and function remains to be known, we purified protein kinase C, unphosphorylated and phosphorylated P47 to homogeneity from human platelets. Then precise phosphorylation reaction of P47 in vitro and a biological function of P47 were studied. Protein kinase C catalysed the phosphorylation reaction of P47 protein, platelet myosin light chain, histone III-S with Km of 0.8±0.2, 4.2±0.5, 4.7±0.7μM, and Vmax of 0.312, 0.189, 0.874 nmole/min/mg, respectively. Some data previously obtained in this laboratory and others utilizing histone III-S as substrate are consistent with the synergistic effect by diacylglycerol (DG) in the presence of Ca++ , phosphatidylserine (PS). Using P47 as substrate, the enzyme required both Ca++ and PS, but not DG for activity. 125I labelled unphosphorylated P47 had an ability to bind with platelet membrane fraction in the presense of phosphatidylserine. Effect of diacylglycerol was inhibitory in this PS dependent P47 binding with membrane. Unphosphorylated P47 had a inhibitory activity in platelet actin polymerization. Molar ratio to inhibit actin polymerization was 1:8(P47:actin). These activities were Ca++ independent. Purified 32P-labelled P47 lost the binding ability with membrane, also the inhibitory activity in actin polymerization.Therefore, we propose the hypothesis that unphosphorylated P47 may loosely bind with the inside of plasma membrane of platelet and inhibit actin polymerization as a modulator, when stimulated, protein Kinase C rapidly phosphorylate P47 and induce the activation of cytoskeletal network and subsequently release reaction. On the other hand, whether DG in fact can act as a second messenger remain uncertain, (supported by MESC of Japan)
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Hill, Rodrigo. "Memories and Reveries: photography, memory and diaspora." In LINK 2023. Tuwhera Open Access, 2023. http://dx.doi.org/10.24135/link2022.v4i1.200.
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This presentation aims to explore the intersection of photography with notions of memory and diaspora as catalysers for the development of a lens-based model of representation connected to affect, cultural perception and nostalgia. I will discuss and present my recent creative practice research project titled Desacoplado: Memórias e Devaneios (Displacement: Memories and Reveries) exhibited at the Auckland Museum as part of Toró: é tudo tanto group exhibition from March to October 2023. The project compiles personal archival imagery produced throughout the last twenty years, marking temporal points that preceded or at times ran in parallel with migration experiences to and in Aotearoa. Drawing on Stuart Hall’s notions on diaspora and Svetlana Boym’s take on nostalgia I constructed a theoretical model to support and inform my creative practice developments. Hall asserted that diaspora is surrounded by a sense of loss and connection while Boym discusses nostalgia as a feeling of loss and displacement. These distinctive concepts and views were useful to understand my own condition as an immigrant in Aotearoa, displaced from my home environment and yet part of an ongoing process of becoming. To address these concepts I started a process of reviewing my photographic archive, looking for imagery that could fit a family album of some kind, ranging from snap-shots, family photographs and archival imagery re-worked through montage, cropping, printing and picture framing strategies. This process covered multiple iterative stages and ways of selecting, compiling, curating and presenting the photographs. These methodological stages were useful to shape a model to address the ways notions of nostalgia and diaspora can be discussed and represented through lens-based and curatorial approaches, positioning photography at core as both practice and research methodology. This led to the compilation of 18 photographs, covering various personal moments and responses to diasporic experiences both in Aotearoa and my home country Brasil. My presentation at the 2023 LINK conference will aim to unpack some of the creative decisions, ideas and processes connected to Desacoplado: Memórias e Devaneios, highlighting the value of photography and creative practice as means to address complex research concepts.
Reports on the topic "Catalyseur supporté"
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Taylor, Joe, Peter Taylor, and Louise Clark. Covid Collective Learning Report. Institute of Development Studies, March 2024. http://dx.doi.org/10.19088/cc.2024.001.
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This report provides an overview the Covid Collective research platform, how it was operationalised, and the learning which emerged from the three-year programme. The foundation of the Covid Collective’s theory of change was the network and relationships that were established and developed to harness collaboration and sharing of knowledge across a platform of global research partners. We acknowledged the critical role knowledge sharing, learning and engagement played in creating a culture that could enable and catalyse evidence-based, transformative action in response to Covid-19. The network that was developed in forming the Covid Collective could then facilitate comparative learning and collective action, and generate new insights and knowledge on the factors that support more or less effective responses to Covid-19 and help to build resilience to address future global development challenges.
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Yalovsky, Shaul, and 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, January 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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Henriikka, Henriikka, Naudet Naudet, and Marin Dacos. Building a Global Research Initiative On Open Science. Ministère de l’enseignement supérieur et de la recherche, April 2024. http://dx.doi.org/10.52949/54.
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The Global Research Initiative on Open Science (GRIOS) represents a pioneering effort to systematically evaluate, promote, and implement Open Science practices worldwide. GRIOS will address the critical gaps in our understanding and application of Open Science. This initiative is a direct response to the growing recognition of Open Science's potential to democratise access to research findings, enhance the quality of scientific inquiry, and foster a more inclusive and collaborative research environment. GRIOS will catalyse the global adoption of Open Science by: - Conducting in-depth reviews of existing Open Science research to synthesise current knowledge and identify best practices and challenges. GRIOS will synergise with existing Open Science initiatives and research on open science to create a unique global understanding based on all the available knowledge. - Developing evidence-based recommendations to guide the implementation of Open Science practices and policies. - Creating a comprehensive research agenda to address knowledge gaps and promote further investigation into Open Science. - Establishing a global network of researchers and organisations committed to advancing Open Science, facilitating knowledge exchange, and fostering collaboration. A cornerstone of the GRIOS initiative is its commitment to inclusivity and diversity, ensuring that the full spectrum of the academic ecosystem is represented in its efforts, particularly emphasising the inclusion of knowledge and experience from the Global South and young academics. To achieve this, GRIOS governance reflects a broad range of perspectives and expertise to ensure that the policies, practices, and research agendas it develops are informed by a wide array of experiences and needs. This approach not only enriches the initiative's outputs with diverse insights but also fosters a more equitable and inclusive Open Science landscape. GRIOS represents a critical step forward in realising the full potential of Open Science. By systematically addressing the challenges and opportunities associated with Open Science,the initiative will play a pivotal role in shaping the future of research and its contribution to society. Stakeholders across the research ecosystem are invited to join this collaborative effort to advance Open Science and ensure that it serves the global public good. We urge research institutions, funders, policymakers, and practitioners to support and participate in the GRIOS initiative. Together, we can unlock the transformative power of Open Science and create a more open, inclusive, and impactful research landscape.
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Building Profitable and Sustainable Community Owned Connectivity Networks. Academy of Science of South Africa (ASSAf), 2021. http://dx.doi.org/10.17159/assaf.2019/0065.
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The IID seminar titled “Building Profitable and Sustainable Community Owned Connectivity Networks”, was hosted on 31 August 2020 on Zoom Webinar. The 2019 White Paper on science, technology and innovation (STI) recognise the pivotal enabling role of information and communication technologies (ICTs) in realising an inclusive and prosperous information society and knowledge economy. One of the Department of Science and Innovation (DSI)’s key role is to catalyse the digital ecosystem and develop scalable models for community owned connectivity networks to replicate in other areas. Rural areas provide challenging environment to implement communication infrastructure for data and Internet based services, including high cost of network implementation and lack of customer base, low-income streams, highly scattered and low population density. The DSI has thus partnered with the University of Western Cape (UWC), the Mankosi Village community, with support from the Technology Innovation Agency (TIA) to scaleup the Zenzeleni Community Owned Connectivity Networks (COCN). The Zenzeleni COCN has been in existence since 2012 and provides timely, reliable and affordable Wi-Fi connectivity to the remote rural areas of Mankosi and Zithulele in Mthatha. The webinar, facilitated by Ms Ellen Fischat from Story Room aimed to look at how rural and township wireless connectivity models, including Zenzeleni COCN can be scaled-up to increase the number of people connected in the rural settings, more so in light of the COVID-19 crisis. It is evident from the proceedings the need for community networks to provide access to connectivity and also more importantly, what connectivity enables. Subsequent discussions would need to focus on the users and owners of these community networks to understand how their lives have improved through the deployment of the technology. This will shed light of the financial feasibility and benefit.
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Private sector and food security. Commercial Agriculture for Smallholders and Agribusiness (CASA), 2023. http://dx.doi.org/10.1079/20240191178.
Full textAbstract:
The global community is facing escalating acute food insecurity crises, predominantly in Sub- Saharan Africa, due to climate change, the Russia-Ukraine conflict, and COVID-19 shocks. Related impacts on donor government budgets, domestic conflicts and limited fiscal capacity in countries already experiencing acute food insecurity, often on top of high chronic food insecurity levels, further exacerbate the issue. This policy brief examines the potential of private sector financing to alleviate acute food insecurity, through providing a targeted review of key mechanisms for mobilizing private sector investment in priority regions affected by acute food insecurity. These mechanisms include (1) donor-private sector partnerships, (2) private sector industry initiatives, and (3) standalone investors and institutions. They have been analysed through case studies and stakeholder consultations, to offer insights into the potential of private sector investment to address acute food insecurity challenges. The analysis emphasizes the role of private sector commercial investment, including short-term investments in addressing immediate food supply needs and medium- to long-term investments in enhancing the resilience of local food systems, focusing on geographies experiencing Integrated Food Security Phase Classification (IPC) Acute Food Insecurity Phases 2 and 3.1 These are acute food insecurity contexts where the private sector might still perceive a viable investment opportunity and where such investments can contribute to building more resilient food systems. Based on this initial review of mechanisms to mobilize private sector financing, the brief concludes that private sector financing has a role to play in building the resilience of medium-term food systems in order to prevent future emergencies, but that it is not suitable for addressing short-term, urgent financing needs related to acute food insecurity that is at crisis levels or near to them. Private sector investors also need significant de-risking and blended finance in countries that are most affected by acute food insecurity, as well as policy predictability and demonstrated national commitments to domestic and regional food and agriculture strategies, due to the long timeframes of, and risks for, most agricultural investments. This indicates that substantial additional donor and public sector intervention is needed to catalyse private sector investment and to direct it towards investments that will have the biggest impact on food security. Learnings from the case studies and other documents reviewed for this policy brief, along with interviews with a range of sectoral stakeholders, indicate that initiatives to mobilize private sector investment should prioritize two objectives so as to achieve the most food security impact. These will shift countries that are experiencing acute food insecurity away from exporting unprocessed agricultural production and importing consumable food and towards national and regional processing and value addition for local consumption. First, focus efforts on catalysing private investment in local agricultural processing and value addition. The missing value chain link in many acutely food-insecure countries is local processing and value addition capacity, which would also provide local off-take for domestic agricultural production. Many initiatives to date have not focused on this piece of the equation, but rather on access to inputs and smallholder farmer support. Second, leverage blended financing to mobilize local financial institutional lending to processing and value addition SMEs. Local currency lending is often the type of financing that agricultural SMEs most need: SME financing needs are not well-matched with the types of foreign currency investment that development finance institutions (DFIs) and other international investors offer, especially with regard to ticket size and return expectations. This brief also recognizes the limitations of its approach and the complexity of the dynamics around using private sector investment to alleviate acute food insecurity. Therefore, the brief concludes by highlighting critical questions for further research, including the positioning of smallholder engagement for food security, innovation in blended financing instruments, and enabling trade and agricultural policy frameworks.