Teses / dissertações sobre o tema "Cycle d'azote"
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Texier, Michèle. "Régulation des transferts d'azote dans la rhizosphère de plantes non fixatrices d'azote (cas du blé)". Montpellier 2, 1990. http://www.theses.fr/1990MON20042.
Texto completo da fonteNiboyet, Audrey. "Impact des changements globaux sur le cycle de l'azote". Paris 11, 2008. http://www.theses.fr/2008PA112264.
Texto completo da fonteIn my PhD thesis, I investigated the impact of global change on nitrogen (N) cycle and more specifically on nitrification and denitrification. Impacts of global change were assessed through two experimental designs: a greenhouse experiment in which monocultures of Dactylis glomerata were grown under the interactive effects of elevated CO2 and N supply, and an in situ experiment in which grassland plots were exposed to elevated CO2, temperature, precipitation, N deposition and all their combinations. In addition, the interactive effects of a wildfire and treatments were explored. An interesting result is the non-responsiveness of gross nitrification to global change treatments despite the large effects of N treatments on potential nitrification. The two steps of nitrification also showed contrasting responses to global change treatments: ammonia oxidation increased under high N deposition, while nitrite oxidation decreased in the elevated precipitation treatment. Changes in the abundance and structure of the microbial communities involved could be responsible for these responses. Potential denitrification increased under high N and high precipitation conditions, probably because of higher N availability and lower soil oxygen content. Finally, one of the most striking results of this study was the large impact of fire on soil emissions of N2O, a potent greenhouse gas, especially in the elevated CO2 and increased N deposition plots
Ferrière, Gérard. "Mouvements naturels des éléments dans une prairie : quantification des échanges d'azote entre lombriciens, sol et plantes". Lyon 1, 1986. http://www.theses.fr/1986LYO10026.
Texto completo da fonteBurlet-Godinot, Sophie. "Le monoxyde d'azote (NO) dans la régulation du cycle veille-sommeil : approches voltamétrique, polygraphique, neuroanatomique et pharmacologique chez le rat". Lyon 1, 1998. http://www.theses.fr/1998LYO1T185.
Texto completo da fonteMartinez-Rey, Jorge. "Impact du changement climatique et l’acidification des océans sur le cycle océanique de l’azote". Thesis, Versailles-St Quentin en Yvelines, 2015. http://www.theses.fr/2015VERS009V/document.
Texto completo da fonteThe marine nitrogen cycle is responsible for two climate feedbacks in the Earth System. Firstly, it modulates thefixed nitrogen pool available for phytoplankton growth and hence it modulates in part the strength of thebiological pump, one of the mechanisms contributing to the oceanic uptake of anthropogenic CO2. Secondly, thenitrogen cycle produces a powerful greenhouse gas and ozone (O3) depletion agent called nitrous oxide (N2O).Future changes of the nitrogen cycle in response to global warming, ocean deoxygenation and oceanacidification are largely unknown. Processes such as N2-fixation, nitrification, denitrification and N2Oproduction will experience changes under the simultaneous effect of these three stressors. Global oceanbiogeochemical models allow us to study such interactions. Using NEMO-PISCES and the CMIP5 modelensemble we project changes in year 2100 under the business-as-usual high CO2 emissions scenario in globalscale N2-fixation rates, nitrification rates, N2O production and N2O sea-to-air fluxes adding CO2 sensitivefunctions into the model parameterizations. Second order effects due to the combination of global warming intandem with ocean acidification on the fixed nitrogen pool, primary productivity and N2O radiative forcingfeedbacks are also evaluated in this thesis
Côté, Jean-Sébastien. "Flux biologiques d'azote dans la glace de mer de l'archipel Arctique canadien". Master's thesis, Université Laval, 2015. http://hdl.handle.net/20.500.11794/26544.
Texto completo da fonteL'objectif principal de cette étude était de quantifier, à la base de la glace de mer de première année dans l’archipel Arctique canadien, la variabilité spatiale des principales réactions biologiques du cycle de l'azote, soit l'assimilation du nitrate et de l'ammonium, la nitrification, l'ammonification et la fixation de N₂ afin d’en comparer les taux et de les relier à la variabilité des conditions environnementales du milieu. Les flux d'azote quantifiés ont démontré une grande variabilité selon les conditions biologiques, physiques et chimiques de la glace. La productivité du milieu, estimée par la concentration en biomasse, modulait un grand nombre de ces flux, dont l’intensité relative était généralement semblable pour l'ensemble des sites échantillonnés malgré la variabilité des conditions environnementales. L’ammonification s’est avérée particulièrement importante, favorisant une assimilation conséquente de l’ammonium et une production essentiellement régénérée. Les résultats de cette étude approfondissent la compréhension des mécanismes régulant les flux biologiques d’azote dans la glace de mer et pourront servir à l’élaboration de scénarios futurs en resserrant la paramétrisation des modèles biogéochimiques.
Clément, Pierre. "Implication du monoxyde d'azote dans les altérations du cycle veille-sommeil apparaissant au cours du vieillissement chez le rat". Lyon 1, 2002. http://www.theses.fr/2002LYO1T096.
Texto completo da fonteSereno, Denis. "Chimiosensibilité et chimiorésistance chez "Leishmania" : transmission au cours du cycle de développement parasitaire "in vitro"". Montpellier 2, 1997. http://www.theses.fr/1997MON20060.
Texto completo da fonteKnauf, Claude. "Mise en évidence d'une libération spontanée, pulsatile et cyclique de monoxyde d'azote (NO) par l'éminence médiane au cours du cycle oestral : implication des capillaires du plexus porte hypothalamo-hypophysaire dans la libération de la GnRH". Lille 1, 2001. https://pepite-depot.univ-lille.fr/LIBRE/Th_Num/2001/50376-2001-277.pdf.
Texto completo da fonteKnauf, Claude Croix Dominique. "Mise en évidence d'une libération spontanée, pulsatile et cyclique de monoxyde d'azote (NO) par l'éminence médiane au cours du cycle oestral implication des capillaires du plexus porte hypothalamo-hypophysaire dans la libération de la GnRH /". [S.l.] : [s.n.], 2001. http://www.univ-lille1.fr/bustl-grisemine/pdf/extheses/50376-2001-277-278.pdf.
Texto completo da fonteMinjeaud, Laura. "Flux d'azote dans les sédiments marins sous influence de la conchyliculture et processus microbiens associés". Aix-Marseille 2, 2008. http://theses.univ-amu.fr.lama.univ-amu.fr/2008AIX22051.pdf.
Texto completo da fonteThe excess of nitrate and ammonium in coastal sediment can have as consequences an important phytoplanctonic development with potential production of toxin causing the stopping of shellfish sales due to health risks and so can have adverse economic repercussions. The study of the microbial processes allowing the entrance or the elimination of nitrogen from ecosystems was therefore undertaken in two coastal shellfish zones: Fos and Arcachon Gulf. Processes implicated in nitrogen fluxes were determined by using a new method of isotope paring developed in this study and taking into account not only denitrification but also nitrification and Anammox process. Theoretical data was validated by experiments. The application of this method on the sediment of the Carteau gulfe (Gulf of Fos) studied in the course of an annual cycle allowed us to show that the denitrification, that is the main process of elimination of nitrogen in this zone, saw its activity multiplying by 20 in the course of last ten years to reach its maximum potentiality, in present time. In present time, out going nitrogen fluxes remain higher than N2 fixation rate, having as consequence the elimination of nitrate from sediment. The nitrification and Anammox being only occasionally detected, the ammonium of sediment is not efficiently eliminated by bacterial processes. In the basin of Arcachon, shellfish zone subjected to the tide, studied in the course of two missions, Anammox could constitute up to 58 % of the production of N2 although denitrification process remained majority in most cases. An effect of the tide and of the year on the N2 production has been noticed without notable variation of qualitative or quantitative structure of the denitrifying community. In the same way, the number of nitrifying or N2-fixing prokaryotes did not show important variation. In this area, the N2-fixation activity was more intense and has lead to positive flux in 2005. A Nitrous oxide production, a by product of denitrification, has been highlighted showing this kind area, under certain condition, could emit this green house gas
Huguenin, Sandra Jaurand Marie-Claude. "Étude du potentiel anti-tumoral de molécules anti-inflammatoires non stéroïdiennes donneuses d'oxyde nitrique sur des lignées tumorales humaines de vessie et de prostate". Créteil : Université de Paris-Val-de-Marne, 2004. http://doxa.scd.univ-paris12.fr:80/theses/th0216491.pdf.
Texto completo da fonteAyraud, Virginie. "Détermination du temps de résidence des eaux souterraines : application au transfert d'azote dans les aquifères fracturés hétérogènes". Phd thesis, Université Rennes 1, 2005. http://tel.archives-ouvertes.fr/tel-00088100.
Texto completo da fonteL'hydrochimie de ces aquifères est fortement liée à l'hétérogénéité physique des roches avec une variabilité spatiale beaucoup plus grande que la variabilité temporelle dans ces bassins-versants. Dans ces milieux, le cycle de l'azote et du soufre sont intimement liés au travers de la dénitrification par oxydation des sulfures. La potentialité d'une dénitrification par oxydation du fer dans les roches cristallines a été mise en évidence au travers d'expérimentations en batch. L'interprétation des données concernant les isotopes du soufre et de l'oxygène des sulfates montrent une cohérence entre la localisation spatiale et le processus mis en jeu quel que soit le site étudié. L'ensemble de ces résultats met en avant l'existence dans la zone profonde de ces aquifères, de solutés d'origine ancienne conservés dans la microporosité et qui contribuent à la chimie des eaux circulant dans les fractures connectées à cette microporosité.
Ces aquifères peuvent être décomposés en trois compartiments principaux que sont les zones de recharge, la zone altérée et la zone profonde. Dans chacun de ces compartiments les temps de résidence sont homogènes à l'échelle de la Bretagne : eaux récentes dans les zones de recharge, eaux anciennes (>50 ans) dans la zone profonde et un temps de résidence moyen de 18 ± 2 ans dans la zone altérée. Ces données indiquent que la gestion de ces aquifères doit prendre en compte l'échelle du temps de résidence de l'eau dans la zone altérée, réservoir de soutien des cours d'eau (supérieur à la dizaine d'années).
Prévot, Vincent. "Étude sur la modulation de la sécrétion de GnRH dans la zone externe de l'éminence médiane : implication d'une plasticité stéroïdo-dépendante et rôle du monoxyde d'azote". Lille 1, 1999. https://pepite-depot.univ-lille.fr/LIBRE/Th_Num/1999/50376-1999-141.pdf.
Texto completo da fonteMartinez-Rey, Jorge. "Impact du changement climatique et l’acidification des océans sur le cycle océanique de l’azote". Electronic Thesis or Diss., Versailles-St Quentin en Yvelines, 2015. http://www.theses.fr/2015VERS009V.
Texto completo da fonteThe marine nitrogen cycle is responsible for two climate feedbacks in the Earth System. Firstly, it modulates thefixed nitrogen pool available for phytoplankton growth and hence it modulates in part the strength of thebiological pump, one of the mechanisms contributing to the oceanic uptake of anthropogenic CO2. Secondly, thenitrogen cycle produces a powerful greenhouse gas and ozone (O3) depletion agent called nitrous oxide (N2O).Future changes of the nitrogen cycle in response to global warming, ocean deoxygenation and oceanacidification are largely unknown. Processes such as N2-fixation, nitrification, denitrification and N2Oproduction will experience changes under the simultaneous effect of these three stressors. Global oceanbiogeochemical models allow us to study such interactions. Using NEMO-PISCES and the CMIP5 modelensemble we project changes in year 2100 under the business-as-usual high CO2 emissions scenario in globalscale N2-fixation rates, nitrification rates, N2O production and N2O sea-to-air fluxes adding CO2 sensitivefunctions into the model parameterizations. Second order effects due to the combination of global warming intandem with ocean acidification on the fixed nitrogen pool, primary productivity and N2O radiative forcingfeedbacks are also evaluated in this thesis
Prieur, Vincent. "Modélisation du cycle terrestre de l'azote et estimation des émissions de N2O à l'échelle de la France et de l'Europe". Paris 6, 2012. http://www.theses.fr/2012PA066269.
Texto completo da fonteThe growing demand in agricultural surfaces and the intensification of agricultural practices, consequences of an increase in world population and of changes in consumption modes associated to the development of emerging countries on the one hand and on the development of agrofuels on the other hand, represents an increasing pressure for the ecosystems and an important source of greenhouse gases (GHG) which must be taken into account in the framework of climate change studies. The agriculture represents 10 to 12% of global GHG emissions and in particular 60% of the emissions of nitrous oxide (N2O) which possesses a radiating power 310 times higher than the one of CO2 at a 100 years horizon. This thesis provides an estimation of the emissions of N2O from crop lands at the scale of Europe using the global land surface and vegetation dynamics model O-CN. This model originally developed to estimate carbon fluxes between the biosphere and the atmosphere allows to study the emissions of nitrogen gases thanks to the recent addition of a modelling of nitrogen cycle in the biosphere and of the dynamics of inorganic nitrogen in soils. Sensitivity tests of estimated N2O emissions to internal parameters of the model and to environmental factors have been performed. Application of the model to experimental sites and comparisons to observations allows to evaluate emissions simulations. The results obtained are put into perspective through comparison at the scale of France with estimations from the agro-environmental CERS-EGC model and at the scale of Europe with GEIA, EDGAR 3. 2 et IER databases
Huguenin, Sandra. "Étude du potentiel anti-tumoral de molécules anti-inflammatoires non stéroi͏̈diennes donneuses d'oxyde nitrique sur des lignées tumorales humaines de vessie et de prostate". Paris 12, 2004. https://athena.u-pec.fr/primo-explore/search?query=any,exact,990002164910204611&vid=upec.
Texto completo da fonteNon Steroidal anti-inflammatory Drugs (NSAIDs) are well known anti-inflammatory molecules. Their anti-tumoral potential has recently been identified. Unfortunately, their secondary effects, particularly on the gastrointestinal tract, are limiting their use. Using the gastroprotective properties of nitric oxide (NO), a new class of molecules has been developed: the NO-donating Non Steroidal anti-inflammatory Drugs (NO-NSAIDs). The aim of this work was to identify, among several NO-NSAIDs obtained from different NSAIDs, the most active nitro-derivatives and to determinate if these new molecules were able to induce apoptosis and to inhibit the proliferation in human tumoral bladder and prostate cell lines. The results emphasized the potential interest of NO-NSAIDs, and particularly the NO-sulindac (NCX 1102), as therapeutic agents against urological cancers
Perrin, Aurélie. "Evaluation environnementale des systèmes agricoles urbains en Afrique de l'Ouest : Implications de la diversité des pratiques et de la variabilité des émissions d'azote dans l'Analyse du Cycle de Vie de la tomate au Bénin". Thesis, Paris, AgroParisTech, 2013. http://www.theses.fr/2013AGPT0080/document.
Texto completo da fonteUrban agriculture provides opportunities to reduce poverty and ensure food safety for cities inhabitants in West Africa. The general objective of this thesis is producing representative inventories and a robust environmental assessment for those production systems using the Life Cycle Assessment (LCA) methodology. Our case study was the tomato production in urban gardens in Benin. Our state of the art identified the integration of the diversity of systems and the variability of field emissions as two major challenges for the LCA of vegetable products. We therefore developed a typology-based protocol to collect cropping systems data that includes their diversity and an approach combining a nitrogen budget and the use of a biophysical model to estimate nitrogen field emissions. We created inventories for 6 cropping system types and one weighted mean representative for the urban tomato growers in Benin. The analysis of the agronomical performances of these systems highlighted the important yield variability and the variable and often excessive use of pesticides and fertilizers. The investigation of nitrogen fluxes variability at plot and crop cycle scales led to the identification of 4 major influencing factors: water use, nitrogen input, soil pH and field capacity. Using favorable and unfavorable scenarios for nitrogen emissions for each of these 4 factors, we demonstrated that the LCA results were sensitive to their variations. The implementation of LCA using those contrasted data showed that one hectare of tomato production in Benin was more impacting than European vegetable productions. The benefits from the favorable climate for producing out-of-season tomatoes were hampered by the low efficiency of irrigations systems, the frequent use of insecticides and large nitrogen emissions. Measured data and new knowledge on these systems are needed to validate and refine our conclusions
Mocquet, Christophe. "Interférence entre les processus mitotiques et la prise d'azote chez Thalassiosira weissflogii. Implications en modélisation et sur les flux globaux". Phd thesis, Université Pierre et Marie Curie - Paris VI, 2009. http://tel.archives-ouvertes.fr/tel-00472581.
Texto completo da fonteChandra, Varunesh. "Nitrous oxide and ammonia emissions from crop residue decomposition in soils". Electronic Thesis or Diss., Sorbonne université, 2021. https://accesdistant.sorbonne-universite.fr/login?url=https://theses-intra.sorbonne-universite.fr/2021SORUS204.pdf.
Texto completo da fonteCrop residues are organic inputs to soil that enhance soil carbon stocks. Although, their decomposition in soils have been showed to cause higher nitrous oxide and ammonia emissions. On analysing related literature, we found that the position of residue incorporation affects these gaseous emissions. We carried out laboratory experiments with three different soil - small particled sandy, calcareous clayey and slightly calcareous clayey soils, with red clover and wheat residues incorporated in them. The residues were incorporated in three positions in soil microcosms - on the surface, mixed in the top layer and layered between two soil layers, to simulate real world scenarios. We found that surface placed residues on soil had the highest ammonia fluxes. While layered and mixed residues had higher nitrous oxide fluxes. The fluxes from red clover residue were higher than wheat owing to high nitrogen in the former. We used this flux data obtained to test a constructed nitrous oxide and and ammonia emission model by coupling CANTIS, NOE and ammonia volatilisation models. We found that the model simulations were underestimated although they were corresponding well qualitatively with the experimental observations
Lescure, Chantal. "Relation bassin versant-étang : étude quantitative de l'azote inorganique dans les échanges atmosphère-sol-eau". Lyon 1, 1987. http://www.theses.fr/1987LYO11740.
Texto completo da fonteHasson-Mouchel, Virginie. "Étude des impacts toxicologiques d'émissions de moteur Diesel en cycle réglementaire : influence de la régénération du filtre à particules et de la qualité du carburant". Rouen, 2010. http://www.theses.fr/2010ROUES009.
Texto completo da fonteThe quality of air is right in the centre of population concerns in terms of health and environment. Motorized traffic is one of the main production sources of anthropogenic origin of atmospheric pollution. To reduce health and environmental impact different regulations were set up (Euro norms, biodiesel blending). To answer these norms the constructors developed different strategies and notably some post-treatment systems among which we can name the Diesel particle filter. However this filter is progressively going to become obstructed, it is necessary to clean it by the soot combustion : it's the regeneration. Therefore, our work consisted in developing a biological tool for assessing in regulation cycle (NEDC) the toxicological impact of Diesel and particularly the impact of regeneration but also the of a biodiesel. Our experiments accomplished on Diesel exhaust of an approved Diesel and a biodiesel in presence with or without regeneration did not allow to notice difference of the pollutant level : regulated and not regulated pollutants. However the biological answer varies according to used Diesel and with or without regeneration of Diesel particulate filter. Approved Diesel exhausts induce a restricted toxic impact while biodiesel leads to a moderate oxidative stress. The presence of regeneration does not change the answer with approved combustible while biodiesel we noticed a major oxidative stress as well as a loss of viability. In vivo, with biodiesel in presence or not of regeneration anti-oxidizing defences allowed to compensate attacks, it was not noticed difference of answers in presence or not of regeneration. To conclude, we developed a discriminating tool able of assessing the biological impact of Diesel exhaust in regulation cycle. Our results show that the only one measure of regulated pollutants do not allow to understand completely the health impact of complex atmosphere
Ndiaye, Mamadou. "Contribution des légumineuses arbustives à l'alimentation azotée du maïs (Zea mays l. ) : cas d'un système de culture en allées dans le centre-sud Sénégal". Vandoeuvre-les-Nancy, INPL, 1997. http://docnum.univ-lorraine.fr/public/INPL_T_1997_NDIAYE_M.pdf.
Texto completo da fonteLehuger, Simon. "Modélisation des bilans de gaz à effet de serre des agro-écosystèmes en Europe". Phd thesis, AgroParisTech, 2009. http://tel.archives-ouvertes.fr/tel-00438077.
Texto completo da fonteHameed, Hassan Rasheed. "Transformation et translocation de l'azote sous influence lombricienne et microbienne : modèles et validation écologiques". Montpellier 2, 1989. http://www.theses.fr/1989MON20243.
Texto completo da fonteGutknecht, Élodie. "Interactions côte-large dans le système de l'upwelling du Benguela par modélisation couplée physique/biogéochimique". Toulouse 3, 2011. http://thesesups.ups-tlse.fr/2713/.
Texto completo da fonteThe main objective of this PhD thesis is the study of the shelf/offshore interactions in the Benguela upwelling system, off South African and Namibian coasts, using a numerical model as well as satellite and in-situ data. A Biogeochemical model adapted for the Benguela Upwelling System (BioBUS), taking into account the main processes linked with eastern boundary upwelling systems and associated oxygen minimum zones, has been developed and coupled with the ROMS hydrodynamical model, in order to implement a realistic configuration in the Namibian upwelling system (Northern Benguela), the studied area of this PhD thesis. This PhD thesis contributes to the improvement of the physical/biogeochemical couplings as well as the understanding of the Eastern Boundary Upwelling Systems (EBUS) and their local and regional impact. Nitrogen inputs from the upwelling area to the South Atlantic oligotrophic gyre were estimated (0. 38 molN. M-2. Yr-1) and are of the same order as other possible N sources (such as atmospheric deposition, biological fixation,. . . ) sustaining primary production in the subtropical gyre (from 0. 01 to 0. 24 molN. M-2. Yr-1). Nitrogen losses by denitrification and anammox processes linked with the oxygen minimum zone (2. 2 108 molN. Yr-1) have the same order of magnitude than N2O outgasing to the atmosphere (5. 5 108 molN. Yr-1), however they are underestimated when compared with in-situ estimations. Air-sea N2O fluxes are clearly significant in this area for the atmospheric N2O budget. Indeed, even if this area represents 1. 2% of the EBUS, its estimated N2O emission contributes to 4% of the EBUS emissions. Furthermore, this PhD thesis shows the important role of mesoscale processes in the nitrogen total transport off the Namibian continental shelf
Gelaude, Armance. "Rôle de gazotransmetteurs au cours de la reprise de méiose et du développement précoce de Xenopus laevis". Thesis, Lille 1, 2015. http://www.theses.fr/2015LIL10076/document.
Texto completo da fonteGazomediators family is composed by nitric oxyide, hydrogen sulfide and carbon monoxide. This family is involved in many cellular process like cell cycle regulation. During, this thesis we have investigated the effect of nitric oxide and hydrogen sulfide on meiosis resumption, cell cycle progression and fecundation of Xenopus oocytes (a recognized model for cell cycle researchs) and on early development of Xenopus embryos. We have demonstrated that the two gazomediators inhibited the meiosis resumption of Xenopus oocytes. The Cdc25C phosphatase was a key target for this effect. In a specific way, nitric oxide had an effect on spindle morphogenesis while hydrogen sulfide targeted protein synthesis. Surprisingly, a study conducted in collaboration with the University of Prague demonstrated a positive effect of hydrogen sulfide on the meiosis resumption of pig oocytes and discriminated key targets for this effect such as the MAPK pathway. Hydrogen sulfide also induced a decrease of fecundation rate and seemed to disrupt early development of xenopus embryos. This work allows to expand the knowledge linking gazomediators and reproduction
Guérin, Dachkevitch Nathalie. "Emissions de N2 O par les sols cultivés : effets de la teneur en nitrate et de la température". Dijon, 1999. http://www.theses.fr/1999DIJOS081.
Texto completo da fonteCaffin, Mathieu. "Devenir de la fixation d'azote et export de carbone dans l'océan Pacifique tropical sud-ouest". Thesis, Aix-Marseille, 2018. http://www.theses.fr/2018AIXM0475/document.
Texto completo da fonteThis PhD thesis focuses on the quantification of diazotrophy and its influence on biogeochemical cycles in the western tropical South Pacific Ocean, a critically under-sampled region so far. The aim of this work is to (1) quantify N2 fixation and identify the main contributors of diazotrophy in this region, (2) assess the influence of N2 fixation on primary production and carbon export, (3) identify transfer pathways of the fixed nitrogen in the planktonic food web.We have found that the western tropical South Pacific Ocean was a hotspot of N2 fixation. In the western part, the oligotrophic waters of the Melanesian archipelago presented high N2 fixation rates and diazotrophes were dominated by Trichodesmium. In the eastern part, the ultra-oligotrophic waters of the South Pacific gyre presented lower N2 fixation rates, and diazotrophs were dominated by UCYN-B.The nitrogen budgets show that N2 fixation contributed to more than 90 % of the of new nitrogen input in the photic layer. The study of the transfer pathways of the fixed nitrogen has shown that 7 to 15 % of total N2 fixation was transferred to non-diazotrophs.This PhD thesis indicates that diazotrophy sustains the biological pump in the western tropical South Pacific Ocean, and can have a critical influence in the planktonic community structure and in biogeochemical cycles of carbon and nitrogen in oligotrophic regions
Bernadet, Philippe. "Propriétés spectroscopiques de complexes formes entre un hydracide (HCl, HBr, HI)) et l'oxyde d'éthylène (EO) en matrice d'argon et d'azote : analyse du profil de la bande d'absorption HCl des complexes H(D)Cl:EO et H(D)Cl:dimethylether et étude". Paris 6, 1986. http://www.theses.fr/1986PA066355.
Texto completo da fonteLory, Caroline. "Rôle du fer dans le contrôle de la fixation d'azote atmosphérique dans l'océan Pacifique tropical sud-ouest". Electronic Thesis or Diss., Aix-Marseille, 2022. http://www.theses.fr/2022AIXM0221.
Texto completo da fonteThis thesis work focuses on the interactions between diazotrophs and Fe in the Western Tropical South Pacific ocean (WTSP), a hot spot of N2 fixation. The objectives were 1) to identify the main environmental factors that structure the activity and biogeographic distribution of diazotrophs, 2) to quantify in situ their demand for Fe and to compare it with that of the rest of the microbial community, 3) to evaluate the bioavailability of Fe complexed to extracellular polymeric substances (EPS) produced by a diazotroph (Crocosphaera). It has been shown that the N2 fixation rates measured during the TONGA mission are high, especially at the Tonga volcanic arc, and that Fe is the main parameter that structures the activity of diazotrophs between the South Pacific gyre and the WTSP. Using a new 'group specific' approach combining in situ measurements of 55Fe uptake and cell sorting by flow cytometry, we showed that the contribution of diazotrophs to total biological Fe uptake is significant (~30%), although these organisms are not the most abundant, but lower than that of picoplankton (53%, fraction 0.2-2μm). Fe uptake rates and resulting quotas are higher for Trichodesmium than for Crocosphaera, leading to a singular biogeographic distribution of these two phylotypes in the WTSP. Finally, we show that EPS produced by Crocosphaera are weak ligands and supply highly bioavailable Fe. Produced in large quantities, they could contribute to the ecological success of Crocosphaera in Fe-poor waters and provide an additional facet of Crocosphaera's critical role in biogeochemical cycles
Holzmuller, Philippe. "Etude des mécanismes cellulaires et moléculaires impliqués dans l'activité microbicide des molécules de l'immunité protectrice (monoxyde d'azote) et chimiothérapeutique (antimoine) chez Leishmania". Montpellier 2, 2002. http://www.theses.fr/2002MON20149.
Texto completo da fonteBerthelot, Hugo. "Fixation d'azote et son devenir dans l'océan de surface : transfert dans le réseau trophique planctonique et influence sur les cycles biogéochimiques de l'azote et du carbone". Thesis, Aix-Marseille, 2015. http://www.theses.fr/2015AIXM4103/document.
Texto completo da fonteThis PhD thesis, achieved within the framework of the VAHINE project, focuses on the fate of the recently fixed N2 by diazotrophes in the oligotrophic surface ocean.It appears that the release of the recently fixed N2 in the dissolved pool is a process shared between all diazotrophs tested and that the magnitude of this release depend on the environmental contrains rather than on diazotroph involved in fixation.The transfer of the N2 fixed toward non-diazotroph plankton has been investigated using an innovative methodology (coupling of nano-scale mass spectrometry (nanoSIMS) and cell sorting flow cytometry). It appeared that 5 to 20 % of the recently fixed N2 is transferred toward non-diazotroph plankton, mainly through NH4+ release. This transfer is twice more efficient when the N2 is fixed by the filamentous Trichodesmium compared to Crocosphaera and Cyanothece.Particulate export of the fixed N2 has been investigate in large in-situ mesocosms equipped with sediment traps, deployed in the New Caledonian lagoon and enriched with PO43- in order to stimulate N2 fixation. During this experiment, N2 fixation fueled a large part of the new primary production (>90 %) and that fixed N2 was quickly exported. The export has been direct, through the sedimentation of the diazotrophs themselves, and indirect, through the transfer of ~20 % of the recently fixed N2 toward non-diazotrophic plankton that have, in turn, sedimented
Gabrielle, Benoît. "Modélisation des cycles des éléments eau-carbone-azote dans un système sol-plante et application à l'estimation des bilans environnementaux des grandes cultures". Châtenay-Malabry, Ecole centrale de Paris, 1996. http://www.theses.fr/1996ECAP0491.
Texto completo da fonteThe field-assessment of the environmental impacts of crop production has emerged as a critical issue, since modern agriculture should be expected not to pose major threats. We have here assessed the nitrogen (N) pollutions, caused by such a crop (oilseed rape), through both experimental and modeling approaches. Two types of pollution were investigated : the leaching of nitrate below the root zone, and the gaseous emissions of ammonia (NH3) and nitrous oxide (N2O) to the atmosphere. The prediction of N fluxes at the boundaries of the soil-crop system requires the use of a model simulating the dynamics of water, carbon and N within this system. Among the approaches of various complexities undertaken in the literature, we chose two models representing either a simple (CERES) or a more theoretical (DAISY) viewpoint. Five data sets corresponding to a range of climate and soil conditions were used to test various options for both models. None of the models clearly outranked the other. DAISY performed better as regards heat and mass transfer in soil, but CERES proved a superiority for the simulation of crop growth. Actually, the precisions of the models were also dependent on the type of medium investigated : we then suggested that a functional classification of soils could serve as a basis for determining the form of model to use, that would offer the best precision for a given set of available inputs. Overall, the modifications we proposed to the soil components of CERES allowed this simple approach to yield a satisfactory accuracy in the prediction of the water, carbon and nitrogen fluxes in the soil-crop system
Sauboua, Emmanuelle. "Modélisation stochastique fonctionnelle du transfert d'eau et d'azote sous culture de maïs : application à l'évaluation de l'impact des pratiques agricoles en plaine de Bièvre". Université Joseph Fourier (Grenoble), 2001. http://www.theses.fr/2001GRE10095.
Texto completo da fonteManuel, Isabelle. "Étude cinétique et modélisation de réactions mises en jeu en calalyse trois-voies". Paris 6, 2002. http://www.theses.fr/2002PA066437.
Texto completo da fonteBezière, Nicolas. "Optimisation du concept d'inhibition de cyclooxygénase dans le traitement du cancer de la prostate". Lille 2, 2008. http://tel.archives-ouvertes.fr/index.php?halsid=q968p6judh55afekbn8rglgem7&view_this_doc=tel-00519646&version=1.
Texto completo da fonteAcetylsalicylic acid, a molecule found in willow bark’s extracts, has been used for thousands of years as an antiinflammatory and analgesic agent. During the 80’s, the discovery of cyclooxygenase as a target for this enzyme inhibitor revived the interest in non steroidal anti-inflammatory drugs (NSAIDs) research. The existence of several isoforms of COX has been proven more recently, and each one has been associated with different effects NSAIDs can have. This led to the emergence of therapeutics targeting a single isoform, in an attempt to lower the side effects of non-specific drugs. Even if still discussed, the usefulness of this new type of molecules in the cancer pathology has recently been showed, particularly on prostate cancer cells. Our study consists in optimizing cyclooxygenase inhibitors to achieve more efficacy in chemotherapy and chemoprevention of this kind of disease. First of all, the use of a peptide vector that can be recognized and cleaved by the prostate specific antigen (a protease active exclusively in the prostate) while carrying a COX-2 inhibitor and capable of, after cleavage followed by intramolecular rearrangement, releasing the active moiety appealed to us in a targeted therapy approach. The conception, synthesis and study of a novel spacer allowing us to link the COX-2 inhibitor to a peptide while permitting a cleaving – rearrangement sequence to occur after PSA recognition were conducted and gave promising results. In parallel, adding to a COX inhibitor an other active moiety under the form of a prodrug was looked into. Nitric oxide (NO), an ubiquitous radical messenger, displays surprising pharmacological properties in a wide array of tissues, be it as a vasodilatator, gastric mucosa protector and even in cancer chemotherapy. The synthesis of a wide panel of innovative compounds, COX-2 selective or not, able to release both NO and the inhibitor seemed interesting, especially when considering the amount of contradictory bibliographic data presenting the mode of action of this type of drugs. Once obtained, the in-depth analysis of the metabolic pathway underwent by our molecules had to be studied in order to shed light on the biological mechanisms underlying their effects. Using various techniques, such as ex vivo vasodilatation experiments on rat aorta strips and electron spin resonance measurements, we were able to access metabolization kinetics of these prodrugs; while classical enzymatic inhibition assays on human whole blood and proliferation assays on human prostatic cancer cell lines revealed the therapeutic interest of our compounds. Finally, combining the peptide vector and the NO donor on a cyclooxygenase inhibitor was attempted
Randall, Benjamin. "Characterisation and quantification of the fluxes of particulate and dissolved nitrogen in the unicellular diazotroph crocosphaera watsonii : towards a closed nitrogen budget". Electronic Thesis or Diss., Sorbonne université, 2019. http://www.theses.fr/2019SORUS685.
Texto completo da fonteDiazotrophy exists as a source of fixed N in the ocean, affecting processes like the marine food web. Important fluxes of the dissolved N phase, which inform the overall N budgets of individual diazotrophs, are poorly understood. This is especially true of recently discovered diazotrophs which may not function under pre-established paradigms. One such diazotroph is Crocosphaera watsonii, which is found widespread throughout sub-tropical oceans. Here we characterise N fluxes consequent to diazotrophy for Crocosphaera, including fluxes of NO3-, NH4+, and dissolved organic N (DON). We also aim to use our results to assess the accuracy of commonly used biological N2 fixation assays. We first assessed the use of NO3- by Crocosphaera. To do this, batch cultures of Crocosphaera were grown long term with NO3-, measuring uptake of NO3- uptake its effect on diazotrophy, culture growth and other important physiological parameters. We found little uptake with no effect on the assessed parameters, including diazotrophy. We next focussed on flux of DON and NH4+ in continuous cultures regulated for conditions such as temperature, light, and pH. We targeted light availability as an important parameter. Between culture conditions of sub-saturating (SSL) and saturating light (SL), we found an increase in N acquisition, C acquisition and cell growth rate in the SL condition. Furthermore, we found an uptake of DON over a 24h period, with greater uptake in the SSL scenario (42% v.s. 7%). There was greater flux of NH4+ into the medium in the SSL. Using an isotopic approach, we found 2.5-3.5% of recently fixed N was exuded 24h. Our assessment of the accuracy of methodology found that 15N2 incubations underestimated N2 fixation while the acetylene reduction assay overestimated. Overall, 15N2 incubations were more reliable when factoring in fluxes of dissolved N. Our findings represent new perspectives into the importance of fluxes of dissolved N to N budgets of Crocosphaera watsonii
Gimenez, Audrey. "Etude des interactions entre diazotrophie, disponibilité nutritive et production planctonique dans l'océan de surface du pacifique tropical sud-ouest par une approche combinant observation et modélisation". Thesis, Aix-Marseille, 2018. http://www.theses.fr/2018AIXM0208/document.
Texto completo da fonteThis work is part of the OUTPACE project which aimed to characterize the western tropical south Pacific (WTSP) in terms of biogeochemical stocks and fluxes and biological diversity of diazotrophs along a West-East longitudinal transect. This work combines an experimental with a modeling approach in order to study the role of diazotrophy in the planktonic dynamics and biogeochemical cycles of the WTSP surface waters. The values measured during the campaign, iespecially those of primary production (PP) and dissolved inorganic phosphate (DIP) turnover time, revealed a West-East gradient of productivity and nutrient availability, closely related to the spatial variability of N$_2$ fixation rates. The use of a mechanistic biogeochemical model (implemented in the Eco3M platform) explicitly including two compartments of diazotrophs and coupled with a vertical 1D physical model, allowed to highlight the fact that the absence / presence of diazotrophy could explain the contrast between the western regions of the Melanesian Archipelago (WMA) and the west of the south Pacific gyre (WGY). ). The model results showed that non-diazotrophic organisms benefited from the new nitrogen supply provided by nitrogen fixers, and that the surface planktonic production depended significantly on diazotroph activity, which is controlled by the phosphate availability in the west and by the iron availability in the east of the WTSP
Botrel, Morgan. "Caractérisation du cycle et des sources d'azote dans les lacs tempérés par l'utilisation d'isotopes stables". Thèse, 2011. http://hdl.handle.net/1866/8359.
Texto completo da fonteWe studied the application of multiple stable isotopes measures with the overall objective of improving our understanding of nitrogen cycling and sources in temperate lakes over different spatial and temporal scales. Results from our study across 65 lakes on a trophic gradient demonstrated that surface sediment nitrogen stable isotope ratio (δ15N) is an indicator of the relative importance of anthropogenic N loads, but that diagenesis can alter this ratio. Nevertheless, sediment core δ15N is a powerful proxy for the determination of longterm changing anthropogenic N loads to lake ecosystems and the causes of lake eutrophication. Results from our second study on multiple stable isotopes seasonal variation in three shallow lakes along a trophic gradient and with different stratification regimes have demonstrated that such an approach is particularly promising in mesotrophic and stratified lakes. In these systems, our results showed that the suspended particulate organic matter (SPOM) δ15N could be used to assess the nitrogen sources assimilated by phytoplankton. However, measurement of carbon stable isotopes (δ13C) and C:N ratios from the SPOM showed that the observed relationships can be altered by watershed derived organic matter. We have also found a deviation from the 1:1 relationship between nitrogen and oxygen stable isotopes (δ18O) of nitrate (NO3-) indicating a simultaneous NO3- assimilation and nitrification in our stratified system. The application of dual nitrate isotopes is promising in the study of nitrification since this process is not well understood in lakes and can increase the severity of eutrophication symptoms.