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King, Martin D. "Kinetics and mechanisms of reactions of NOâ†3 with some biogenic species." Thesis, University of Oxford, 1998. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.299017.
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Pfrang, Christian. "Nitrate radicals in the atmosphere : reactions with man-made and stress-induced plant emissions, and with peroxy radicals." Thesis, University of Oxford, 2006. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.427757.
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Flugge, Mark. "Laboratory studies of reactions of nitrate radicals with species of atmospheric importance." Thesis, University of Oxford, 2004. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.413082.
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Mattei, Coraline. "Réactivité hétérogène de pesticides adsorbés sur des particules atmosphériques : influence des paramètres environnementaux sur les cinétiques." Thesis, Aix-Marseille, 2019. http://www.theses.fr/2019AIXM0181.
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La contamination de l’environnement par les pesticides est ubiquiste et les preuves d’impacts sanitaires et environnementaux s’accumulent. Après application, une fraction des pesticides passe dans l’atmosphère où ils sont répartis entre les phases gazeuse, aqueuse et particulaire. La plupart des pesticides utilisés aujourd’hui sont semi-volatils et sont donc en partie adsorbés en surface de particules atmosphériques où ont lieu des réactions hétérogènes. La réactivité en phase gazeuse des pesticides est documentée contrairement à celle en phase particulaire qui est mal décrite. Ce travail expérimental a permis d’étudier l’influence de paramètres environnementaux (humidité relative, nature des particules, taux de recouvrement) sur la réactivité hétérogène de 8 pesticides (cyprodinil deltaméthrine difénoconazole fipronil oxadiazon pendiméthaline perméthrine tétraconazole). Ces composés étaient adsorbés sur des particules minérales (silices hydrophobe et hydrophile, sable d’Arizona) et ont été exposés aux principaux oxydants atmosphériques (ozone, radicaux hydroxyles (OH) et nitrates (NO3)). Les résultats ont montré que l’humidité relative, la nature des particules et le taux de recouvrement peuvent influencer les cinétiques de dégradation hétérogène par l’ozone et les radicaux OH. Ils ont aussi permis de mettre en évidence l’efficacité des radicaux NO3 pour la dégradation hétérogène des pesticides (temps de demi-vie hétérogène avec NO3 : 2 à 16 j contre 0,4 à >800 j avec l’ozone et 3 à >100 j avec OH). Ces résultats permettent une meilleure compréhension du devenir atmosphérique des pesticides et contribueront à la prédiction de la pollution de l’air par les pesticidesEnvironmental contamination by pesticides is ubiquitous and induces health and environmental impacts. Once applied, some of the pesticides reach the atmosphere, where they distribute between the aqueous, gaseous and particle phases. Most of the currently used pesticides are semi-volatiles and are therefore partially adsorbed on the atmospheric particle surfaces and undergo heterogeneous degradation reactions. If their reactivity in the gaseous phase is often known, their reactivity in the particle phase remains poorly described. This experimental work allowed studying the influence of environmental parameters (relative humidity, type of particles, pesticides surface concentration) on the reactivity of eight pesticides (cyprodinil, deltamethrin, difenoconazole, fipronil, oxadiazon, pendimethalin, permethrin, tetraconazole). They were adsorbed on mineral surfaces mimicking mineral aerosol particles (hydrophobic and hydrophilic silica, Arizona sand) to simulate atmospheric degradation by the mains atmospheric oxidants (ozone, hydroxyl radicals (OH) and nitrate radicals (NO3)). Results showed that relative humidity, particle type, and pesticide concentration can influence the heterogeneous degradation of pesticides with ozone and OH radicals. They also showed the efficiency of NO3 radicals for the atmospheric heterogeneous degradation of pesticides (half-lives in the particle phase from 2 to 16 d with NO3 compared to 0.4 to > 800 d with ozone and to 3 to > 100 d with OH). Results obtained allow a better understanding of the atmospheric fate of pesticides and will contribute to predict of atmospheric contamination
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Zhang, Yafen. "Ultrahigh Vacuum Studies of the Reaction Kinetics and Mechanisms of Nitrate Radical with Model Organic Surfaces." Diss., Virginia Tech, 2015. http://hdl.handle.net/10919/78003.
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Detailed understanding of the kinetics and mechanisms of heterogeneous reactions between gas-phase nitrate radicals, a key nighttime atmospheric oxidant, and organic particles will enable scientists to predict the fate and lifetime of the particles in the atmosphere. In an effort to acquire knowledge of interfacial reactions of nitrate radical with organics, model surfaces are created by the spontaneous adsorption of methyl-/vinyl-/hydroxyl-terminated alkanethiols on to a polycrystalline gold substrate. The self-assembled monolayers provide a well-defined surface with the desired functional group (-CH3, H2C=CH-, or HO-) positioned precisely at the gas-surface interface. The experimental approach employs in situ reflection-absorption infrared spectroscopy (RAIRS) to monitor bond rupture and formation while a well-characterized flux of NO3 impinges on the organic surface. Overall, the reaction kinetics and mechanisms were found to depend on the terminal functional group of the SAM and incident energy of the nitrate radical (NO3). For reactions of the H2C=CH-SAM with NO3, the surface reaction kinetics obtained from RAIRS reveals that the consumption rate of the terminal vinyl groups is nearly identical to the formation rate of a surface-bound nitrate species and implies that the mechanism is one of direct addition to the vinyl group rather than hydrogen abstraction. Upon nitrate radical collisions with the surface, the initial reaction probability for consumption of carbon-carbon double bonds was determined to be (2.3 ± 0.5) -- 10-3. Studies of reactions of HO-SAM with the effusive source of NO3 suggest that the reaction between NO3 and the HO-SAM is initiated by hydrogen abstraction at the terminal - 'CH2OH groups with the initial reaction probability of (6 ± 1)-- 10-3. An Arrhenius plot was obtained to measure the activation energy of the H abstraction from the HO-SAM. Further, for reactions of the HO-SAM with the high incident energy of NO3 molecules created by molecular beam, the reaction probability for H abstraction at the hydroxyl terminus was determined to be ~0.4. The significant increase in the reaction probability was attributed to the promotion in the ability of NO3 abstracting hydrogen atom at the methylene groups along hydrocarbon chains. The reaction rates of NO3 with the model organic surfaces that have been investigated are orders of magnitude greater than the rate of ozone reactions on the same surfaces which suggests that oxidation of surface-bound organics by nighttime nitrate radicals may play an important role in atmospheric chemistry despite their relative low concentration. X-ray photoelectron spectroscopy (XPS) data suggests that oxidation of the model organic surfaces by NO3 leads to the production of organic nitrates, which are stable for a period time. In addition, the effect of background gases on reactions of NO3 with model organic surfaces needs further investigations at atmospheric pressures. The results presented in this thesis should help researchers to predict the fate and environmental impacts of organic particulates with which nitrate radicals interact.Ph. D.
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Zhang, Yafen. "Fundamental Studies of Reactions between NO3 Radicals and Organic Surfaces." Thesis, Virginia Tech, 2012. http://hdl.handle.net/10919/42372.
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Ultrahigh vacuum (UHV) surface science experiments were designed to study reaction kinetics and mechanisms of gas-phase NO3 radicals with well-organized, highly characterized, organic thin films. The surface reactions were monitored in situ with reflection-absorption infrared spectroscopy (RAIRS). The oxidation states of
surface-bound molecules were identified with X-ray photoelectron spectroscopy (XPS). Consumption of vinyl groups was observed concurrently with formation of organic nitrates in RAIRS. XPS spectra showed little oxidation of sulfur head groups. The observed rate constant was determined based on the consumption of carbon-carbon double bonds and the formation of organic nitrates. Using this rate constant, the initial reaction probability was determined to be (3 ± 1) X 10-3. This reaction probability is approximately two orders of magnitude higher than that for the
reactions between the same surface and pure O3, which is due to the higher electron affinity of NO3 relative to O3. These results led to the development of a proposed mechanism that involves electrophilic addition of NO3 to the double bonds. Reactions between NO3 and a methyl-terminated SAM were also monitored in situ with RAIRS. In the CH3-SAM studies, hydrogen abstraction was observed during NO3 exposure. The results presented in this thesis should help develop an understanding of the
fundamental interfacial reaction dynamics of NO3 radicals with organic surfaces.Master of Science
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Kalalian, Carmen. "Réactivité atmosphérique des composés organiques volatils oxygénés biogéniques (aldéhydes et alcools insaturés). Etudes cinétiques de la réaction entre les radicaux peroxyles et le radical nitrate." Thesis, Reims, 2018. http://www.theses.fr/2018REIMS023/document.
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Les composés organiques volatils d’origine biogénique (COVB) contribuent à plus de 90% des émissions des COV dans l'atmosphère. Ces composés sont éliminés de l’atmosphère par réaction avec les photo-oxydants (OH, NO3, Cl et O3) et par photolyse. Ces processus sont gouvernés par un mécanisme en chaîne dont les porteurs sont des radicaux libres tels que les radicaux peroxyles RO2 qui jouent un rôle clé dans la dégradation atmosphérique des COV. Dans ce contexte, cette thèse se concentre d’une part sur l’étude cinétique en température et mécanistique de la réaction d’ozonolyse, la détermination des spectres UV et la photolyse de six COV oxygénés insaturés (trans-2-pentènal, trans-2-hexènal, 2-méthyl-2-pentènal, 1-pentèn-3-ol, cis- 2-pentèn-1-ol et trans-3-hexèn-1-ol), et d’autre part l’étude de la réactivité de trois radicaux peroxyles (CH3OCH2O2, CH3C(O)CH2O2 et (CH3)2C(OH)CH2O2) vis-à-vis des radicaux nitrates à différentes températures. Trois dispositifs expérimentaux sont utilisés : une chambre de simulation atmosphérique couplée à une spectroscopie infrarouge à transformée de Fourier (FTIR) et à une chromatographie en phase gazeuse associée à une spectrométrie de masse (GC/MS), un dispositif de mesure des spectres UV-Visible et la photolyse laser couplée à une spectrométrie UV-visible et diode laser. Ces dispositifs associés à des méthodes de traitement permettent d'extraire des données cinétiques en température, mécanistiques et spectroscopiques. Les paramètres cinétiques obtenus sont utilisés pour estimer les durées de vie atmosphériques des espèces étudiées. Les résultats mécanistiques sont utilisés pour élaborer les mécanismes d’ozonolyse de ces composés. Toutes ces données permettent d’enrichir les bases de données cinétiques, mécanistiques et spectroscopiques qui alimentent les modèles atmosphériquesBiogenic volatile organic compounds (BVOC) account for 90% of VOC emissions in the atmosphere. These VOCs can be removed from the atmosphere by reaction with photo-oxidants (OH, NO3, Cl and O3) as well as by photolysis. All these processes are governed by a chain mechanism whose carriers are mainly free radicals such as peroxy radicals RO2. Hence the importance of characterizing the reactivity of these species that play a key role in the atmospheric degradation of VOCs. In this context, this thesis focuses on the determination of the temperature dependent kinetic data as well as the mechanism of the ozonolysis reaction and the UV absorption spectra along the photolysis of six unsaturated oxygenated VOCs (trans- 2-pentenal, trans-2-hexenal, 2-methyl-2-pentenal, 1-penten-3-ol, cis-2-penten-1-ol and trans-3-hexen-1-ol). Likewise, the temperature dependent kinetic parameters of the reaction of three peroxy radicals (CH3OCH2O2, CH3C(O)CH2O2 et (CH3)2C(OH)CH2O2) with nitrate radicals were also determined. Three experimental setups coupled to treatment methods were used to extract these data: an atmospheric simulation chamber coupled to both a Fourier-transform infrared spectroscopy (FTIR) and a gas chromatography connected to a mass spectrometry (GC/MS), a device for measuring UV-Visible spectra and a laser photolysis coupled with UV-visible spectrometry and laser diode spectroscopy. The kinetic parameters were used to estimate the atmospheric lifetimes of the studied species. While the mechanistic data were used to establish their ozonolysis mechanisms. All the collected data enrich kinetic, mechanistic and spectroscopic databases, improving atmospheric models specially those involving VOCs
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Allan, Beverley. "A spectroscopic study of radical chemistry in the troposphere." Thesis, University of East Anglia, 1998. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.266729.
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Seligman, Kelly. "Importancia do radical oxido nitrico no processo de floração utilizando-se Arabidopsis thaliana L. como modelo." [s.n.], 2008. http://repositorio.unicamp.br/jspui/handle/REPOSIP/314346.
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Orientadores: Ione Salgado, Cecilia Alzira Pinto-MaglioDissertação (mestrado) - Universidade Estadual de Campinas, Instituto de Biologia
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Resumo: O radical óxido nítrico (NO), que pode ser produzido nos organismos pela oxidação de arginina ou redução de nitrito, é uma importante molécula sinalizadora em plantas atuando como modulador de diversos processos metabólicos e de desenvolvimento. Recentemente foi identificado como um dos sinais envolvidos no processo de floração. A transição da fase de crescimento vegetativo para a fase reprodutiva é atrasada em plantas mutantes que superproduzem NO, enquanto que a floração é precoce em plantas mutantes deficientes na síntese deste radical. O principal objetivo deste trabalho foi identificar os sítios de produção de NO durante o desenvolvimento floral de Arabidopsis thaliana L. Foram utilizados os indicadores fluorescentes 4,5-diacetato de diaminofluoresceína (DAF-2 DA) e 1,2-diaminoantraquinona (1,2-DAA) para localizar in situ, por microscopia de fluorescência, a produção de NO em botões florais de A. thaliana em diferentes estágios de desenvolvimento. Ainda, a produção de NO pelas estruturas florais foi comparada entre plantas do tipo selvagem e mutante duplo defectivo para os genes estruturais da enzima nitrato redutase - NR - (nia1 nia2) que apresentam conteúdo reduzido de aminoácidos e nitrito e, consequentemente, de NO em suas folhas. Foi analisado também o efeito do seqüestrador de NO, CPTIO, na prevenção da emissão de fluorescência. Os resultados mostraram que o NO é sintetizado em células e tecidos específicos da estrutura floral e que sua produção aumenta com o desenvolvimento floral até a antese: a fluorescência dos indicadores, prevenida pelo seqüestrador de NO, ficou restrita às papilas estigmáticas em gineceus imaturos e a grãos de pólen produzidos pela antera no estame. Plantas mutantes de A. thaliana nia1 nia2 apresentaram o mesmo padrão de emissão de NO nos órgãos florais que o tipo selvagem. Sépalas e pétalas não apresentaram produção significativa de NO em ambos os genótipos analisados. A validação dos resultados obtidos por microscopia foi feita através da incubação de tecidos florais intactos com DAF-2, quantificando-se, por espectrofluorimetria, o composto DAF-2T resultante da reação do indicador com o NO emitido pelos tecidos. Os dados obtidos por espectrofluorimetria mostraram que a intensidade de fluorescência emitida por botões florais foi maior durante o estágio 11 de desenvolvimento, corroborando os dados obtidos de localização por microscopia de fluorescência. Ainda, foi possível quantificar que as plantas do tipo selvagem apresentam, em média, maior intensidade de fluorescência emitida, que plantas nia1 nia2: 1,39 e 1,89 vezes maior nas fases 11 e 13 de desenvolvimento, respectivamente. Um segundo objetivo deste trabalho foi avaliar o papel da enzima NR na indução floral. Os dados obtidos revelam que plantas nia1 nia2 possuem floração precoce, 6 dias em média, quando comparadas com plantas do tipo selvagem. Para verificar se a floração precoce no mutante nia1 nia2 era conseqüência apenas da deficiência do radical NO, ou também da deficiência de aminoácidos, foram analisados os parâmetros de indução floral em plantas nia1 nia2 tratadas com os aminoácidos arginina ou glutamina, para a recuperação dos níveis basais de aminoácidos. A floração neste mutante permaneceu precoce, sugerindo que o fenótipo de floração precoce é conseqüência da deficiência de NO nestas plantas durante a fase vegetativa. Estes resultados sugerem que o NO pode ter um importante papel no processo de floração e no sucesso da reprodução vegetal
Abstract: The radical nitric oxide (NO), that can be produced in the organism by arginine oxidation or nitrite reduction, is an important signaling molecule in plants acting as modulator of several metabolic and developmental processes. Recently NO was identified as one of several signals involved in flowering. The transition from vegetative to reproductive growth is delayed in mutant plants that overproduce NO, while this process is precocious in mutant plants deficient in NO synthesis. The main objective of this study was to identify the sites of NO production during floral development of Arabidopsis thaliana. The fluorescent probes, 4,5-daminofluorescein diacetate and 1,2-diaminoanthraquinone, were utilized to localize in situ, by fluorescence microsopy, the NO production in floral buds of A. thaliana at different stages of development. Still, NO production by the floral structures was compared between wild-type and double defective mutant plants for structural genes of nitrate reductase enzyme - NR - (nia1 nia2) which have reduced content of amino acids and nitrite and, consequently, of NO in their leaves. It was also analyzed the effect of the NO scavenger, CPTIO, in preventing the fluorescence emission. The results showed that NO is synthesized in specific cells and tissues in the floral structure and its production increases with the floral development until anthesis: the fluorescence of the indicators, prevented by NO scavenger, was restricted to the stigmatic papillae, in the gynoecium, and to pollen grains produced by anther in stamen. Mutant plants of A. thaliana nia1 nia2 showed the same pattern of NO emission by the floral organs to that observed in the wild type genotype. Sepals and petals showed no significant NO production in both genotypes analyzed. Validation of the results obtained by fluorescence microscopy was realized by incubating floral tissues with DAF-2 and quantifying, by spectrofluorimetry, the DAF-2T resulted from reaction between the probe and the NO emitted by the tissues. Data obtained by spectrofluorimetry showed that the fluorescence intensity emitted by floral buds was higher during stage 11 of development, corroborating localization data obtained by fluorescence microscopy. Additionally, wild type plants showed greater intensity of fluorescence emission, on average, than nia1 nia2 plants: 1,39 and 1,89 times higher in phases 11 and 13 of development, respectively. A second objective of this work was to evaluate the role of the NR enzyme in floral induction. Data obtained revealed that nia1 nia2 plants flowers earlier, 6 days on average, than the wild-type plants. To verify whether the early flowering phenotype in nia1 nia2 was only consequence of the NO deficiency, or was also due to the amino acids deficiency, it were analyzed the parameters of floral induction in nia1 nia2 plants treated with the amino acids arginine or glutamine for the recovery of the amino acids levels. Flowering in this mutant remained precocious, suggesting that the early flowering phenotype is a consequence of NO deficiency in these plants during the vegetative growth. These results suggest that NO may have an important role in the flowering process and to the reproductive success of the plant
Mestrado
Bioquimica
Mestre em Biologia Funcional e Molecular
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Fouqueau, Axel. "Réactivité des terpènes avec le radical nitrate : études cinétique et mécanistique en chambres de simulation atmosphérique." Thesis, Paris Est, 2019. http://www.theses.fr/2019PESC0015.
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Les composés organiques volatils biogéniques (COVB) sont fortement émis dans l’atmosphère par les forêts et les cultures. Très réactifs vis-à-vis du radical nitrate NO3, principal oxydant nocturne dans la troposphère, ils ont une importance majeure dans la chimie atmosphérique. En effet, cette réaction mène à la formation d’un large panel de produits de réaction en phase gazeuse fonctionnalisés (nitrates organiques, composés carbonylés, ...) et une large fraction d’aérosols organiques secondaires. Les nitrates organiques constituent des espèces réservoirs d’oxydes d’azote dans l’atmosphère et influencent directement le bilan d’azote réactif et ainsi les niveaux d’ozone. L’aérosol organique secondaire, de par sa formation, ses propriétés optiques et hygroscopiques ainsi et sa composition chimique a un impact direct et indirect sur le climat. Ce travail a pour but la compréhension de ces processus à l’échelle moléculaire à travers une étude cinétique et mécanistique des réactions d’oxydation de plusieurs COVB par le radical NO3.Ainsi, les réactions d’oxydation par le radical NO3 de trois monoterpènes ((C10H16), γ- et α-terpinène et le terpinolène) et un sesquiterpène ((C15H24), le β-caryophyllène) ont été invesitguées en chambre de simulation atmosphérique. Les composés ont été choisis d’une part pour mettre en évidence l’influence de leur structure chimique sur leur réactivité et d’autre part, pour combler les manques de données expérimentales dans la littérature sur la chimie de ces composés.Pour la partie cinétique, les constantes de vitesse ont été mesurées à la fois par la méthode de cinétique absolue et par celle de cinétique relative. Les réactions chimiques étudiées étant très rapides, cette étude a nécessité au préalable le développement sur la chambre de simulation atmosphérique d’une voie d’analyse spectroscopique IBB-CEAS (Incoherent Broad Band Cavity Enhanced Absorption Spectroscopy) pour la mesure des radicaux nitrates dans la gamme du ppt. Des études mécanistiques ont également été menées afin d’identifier et de quantifier les principaux produits de réaction. Les rendements de nitrates organiques, d’AOS ont été calculés. Les produits détectés ont permis d’établir des mécanismes réactionnelsBiogenic volatile organic compounds (BVOC) are strongly emitted by forests and crops in the atmosphere. They are very reactive towards nitrate radical, the main tropospheric oxidant during the night, and play a key role in atmospheric chemistry. These reactions lead to the formation of a variety of functionalized products (organic nitrates, carbonyl compounds ...) and to large amounts of secondary organic aerosols. Organic nitrates are the main nitrogen oxides reservoir. They directly influence reactive nitrogen and ozone budgets. Secondary organic aerosol has direct and indirect impacts on climate, due to its formation, its optical and hygroscopic properties and its chemical composition. The aim of this work is to understand these processes at the molecular scale, through kinetic and mechanistic studies of NO3 radical oxidation of several BVOCs.Kinetic and mechanistic studies have been performed for three monoterpenes ((C10H16), γ- and α-terpinene and terpinolene) and one sesquiterpene ((C15H24), β-caryophyllene) in atmospheric simulation chambers. These compounds have been chosen to highlight the influence of their chemical structures on their reactivities and to fill the lack of experimental data about their chemistry in the literature.For the kinetic part, rate constants have been measured with both relative and absolute methods. Due to their high reactivities, this study has requiered the development on the simulation chamber of an IBB-CEAS ((Incoherent Broad Band Cavity Enhanced Absorption Spectroscopy) analysis pathway to measure nitrate radical at the ppt level. Mechanistic studies have been also conducted to identify and quantify the main reaction products. Organic nitrates and SOA yields have been calculated. Detected products allowed proposing reaction mechanisms
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Smith, Craig Anthony. "Nitrates in the synthesis of amino acid radicals /." Title page, contents and abstract only, 1996. http://web4.library.adelaide.edu.au/theses/09SM/09sms644.pdf.
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Oliveira, Halley Caixeta de. "Estudo da homeostase do radical óxido nítrico na bionergética mitocondrial e na resposta de defesa vegetal ao ataque de patógenos." [s.n.], 2010. http://repositorio.unicamp.br/jspui/handle/REPOSIP/314338.
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Orientador: Ione SalgadoTese (doutorado) - Universidade Estadual de Campoinas, Instituto de Biologia
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Resumo: O controle da homeostase do óxido nítrico (NO), determinada pelo balanço entre os processos de síntese e degradação, é essencial para suas funções sinalizadoras. O presente estudo teve como objetivo geral buscar um melhor entendimento da homeostase do NO em plantas, enfocando a importância dessa molécula na bioenergética mitocondrial e na resposta de defesa vegetal ao ataque de patógenos. Inicialmente, foi realizada a caracterização de uma atividade de degradação de NO por mitocôndrias isoladas de tubérculos de batata, observando-se um consumo mitocondrial dependente de sua reação com o ânion superóxido, estimulado na presença de NAD(P)H. Ensaios com diferentes substratos e inibidores respiratórios evidenciaram as NAD(P)H desidrogenases externas, além do complexo III, como os principais sítios de geração de ânion superóxido para o consumo de NO. Por outro lado, numa análise comparativa com mitocôndrias isoladas de fígado de rato, uma atividade NAD(P)H oxidase mitocondrial não associada à cadeia respiratória foi detectada como uma fonte de superóxido, em adição ao vazamento de elétrons nos complexos I e III, para o consumo de NO. Em ambos os casos, a existência de mecanismos mitocondriais de degradação de NO mostrou-se importante para o controle de seus efeitos inibitórios sobre a atividade respiratória. Adicionalmente, a importância da síntese de NO para a defesa vegetal foi analisada utilizando-se como modelo a interação Arabidopsis thaliana-Pseudomonas syringae. Trabalhos anteriores já haviam demonstrado que o mutante de A. thaliana duplo-deficiente para a nitrato redutase (nia1 nia2) apresenta reduzida produção de NO e susceptibilidade à P. syringae, o que poderia resultar de sua prejudicada assimilação de nitrogênio. No presente estudo, plantas nia1 nia2 foram cultivadas com glutamina ou arginina para aumentar os níveis foliares de aminoácidos. Entretanto, esse mutante continuou a desenvolver uma baixa emissão de NO e permaneceu susceptível à infecção bacteriana, indicando que a susceptibilidade não resulta do reduzido conteúdo de aminoácidos. Por outro lado, a fumigação com baixas concentrações do gás NO de plantas nia1 nia2 com os níveis de aminoácidos recuperados restabeleceu a resposta de resistência. Coerentemente, uma análise do perfil transcriptômico utilizando microarranjos de DNA mostrou que o tratamento com NO induziu diversos genes relacionados à defesa em folhas nia1 nia2 infectadas, como aqueles relacionados às vias de sinalização do ácido salicílico e do cálcio, as proteínas relacionadas à patogênese, a reorganização da parede celular e a síntese de compostos com atividade antimicrobiana. Ainda, essa análise indicou novos genes como potenciais alvos do NO, sugerindo aspectos até então desconhecidos do papel dessa molécula sinalizadora na interação fitopatogênica e na fisiologia vegetal. Em especial, destacou-se o possível envolvimento do NO na alteração de transcritos relacionados à sinalização hormonal de forma a permitir um controle atenuador de mecanismos da resposta de defesa.
Abstract: The control of nitric oxide (NO) homeostasis, determined by a balance between the rate of synthesis and degradation, is essential for its signaling functions. The present study aimed a better understanding of NO homeostasis in plants, focusing on the importance of this molecule in mitochondrial bioenergetics and in plant defense response to pathogen attack. Initially, we carried out a characterization of an NO degradation activity by mitochondria isolated from potato tubers, observing a superoxide-dependent NO consumption, that was stimulated in the presence of NAD(P)H. Assays with different respiratory substrates and inhibitors evidenced the external NAD(P)H dehydrogenases, in addition to complex III, as the main sites of superoxide anion generation for NO consumption. On the other hand, in a comparative analysis with mitochondria isolated from rat liver, a mitochondrial NAD(P)H oxidase activity, non-associated to the respiratory chain, emerged as a superoxide source, in addition to the electron leakage from complexes I and III, for NO consumption. In both cases, the existence of mitochondrial mechanisms of NO degradation was important for the control of its inhibitory effects on respiratory activity. Additionally, the importance of NO synthesis for plant defense was analyzed using the interaction Arabidopsis thaliana- Pseudomonas syringae as a model. Previous works have shown that the nitrate reductase double-deficient mutant of A. thaliana (nia1 nia2) presents reduced NO production and susceptibility to P. syringae, that could result from its impaired nitrogen assimilation. Here, nia1 nia2 plants were cultivated with glutamine or arginine to increase the leaf amino acid content. Despite this, this mutant continued to develop a low NO emission and remained susceptible to bacterial infection, indicating that the susceptibility does not result from reduced amino acid levels. On the other hand, the fumigation of amino acid-recovered nia1 nia2 plants with low concentrations of NO gas reestablished the resistance response. Accordingly, a transcriptomic analysis using DNA microarrays showed that NO treatment induced diverse defense-related genes in infected nia1 nia2 leaves, as those associated to salicylic acid and calcium signaling pathways, pathogenesis-related proteins, cell wall reorganization and synthesis of antimicrobial compounds. Additionally, this analysis indicated new genes as potential targets of NO action, suggesting previously unknown aspects about the role of this signaling molecule in phytopathogenic interactions. In special, we can highlight the possible involvement of NO in the modulation of transcripts related to hormonal signaling in order to allow an attenuating control of certain mechanisms of the defense response.
Doutorado
Bioquimica
Doutor em Biologia Funcional e Molecular
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Fletcher, Rodney Justin. "Radical cyclisation in routes to cis-fused heterocycles." Thesis, University of Nottingham, 1995. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.283701.
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Kerdouci, Jamila. "Réactivité des composés organiques volatils avec le radical nitrate : développement d’une relation de type structure réactivité." Thesis, Paris Est, 2011. http://www.theses.fr/2011PEST1090.
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Durant la nuit, le radical nitrate (NO3) est le principal oxydant troposphérique des composés organiques. La compréhension de l'implication des composés organiques dans les processus de chimie troposphérique exige donc une connaissance des constantes cinétiques de leurs réactions avec le radical NO3. Toutefois, au regard du nombre considérable de composés organiques émis ou formés dans la troposphère, il est difficilement envisageable d'appréhender la réactivité de chaque composé en nous reposant exclusivement sur des études de laboratoire. Celles-ci se doivent d'être complétées par l'usage de méthodes prédictives. Nous avons donc, au cours de ce travail, développé une relation de type structure-réactivité (SAR) qui permet le calcul des constantes de vitesse des réactions des composés organiques avec le radical nitrate. Cette méthode prédictive empirique permet d'estimer la réactivité d'un composé à partir de sa structure moléculaire et a été élaborée à partir de constantes cinétiques expérimentales publiées dans la littérature. De plus, conjointement au développement de cette SAR, les constantes cinétiques des réactions d'aldéhydes et d'éthers insaturés avec le radical nitrate ont été mesurées au laboratoire. Ces études expérimentales ont ainsi contribué à étoffer la base de données cinétiques sur laquelle repose cette SAR afin de permettre son parachèvement. Cette SAR reproduit, à un facteur deux près, plus de 90% des constantes cinétiques des alcènes et des composés aliphatiques oxygénés saturés et insaturésThe nitrate radical (NO3) is the main oxidant of organic compounds in the night-time troposphere. Thus, comprehension of organic compounds involvement in tropospheric chemical processes requires the knowledge of the rate coefficients for their reactions with the nitrate radical. Nevertheless, considering the wide range of organic compounds emitted or formed in the atmosphere, it is difficult to determine the reactivity of each compound only with laboratory studies. Thereby, these experimental studies have to be completed by predictive methods. In this study, a group-additivity method is therefore used to develop a new Structure-Activity Relationship (SAR) which allows prediction of the rate constants for reactions of organic compounds with the NO3 radical. This empirical method is based on the prediction of a rate constant leaning only on the molecular structure of the organic compound. It relies on experimental rate constants available in the literature. Moreover, the rate constants of unsaturated aldehydes and ethers with the nitrate radical have been measured. Thereby, these experimental studies contribute to expend the kinetic database used for the SAR development and allow its improvement. For saturated and unsaturated oxygenated compounds, more than 90% of the rate constants are reproduced within a factor of two
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Fowles, M. "Kinetics and photochemistry of the nitrate radical (NOsub3) in the gas phase." Thesis, University of Oxford, 1985. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.370252.
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Silva, Robson Pinho da. "Comportamento redox e detecção voltamétrica de neurotransmissores, nitrito, derivados purínicos e nitrofural em sensores eletroquímicos à base de carbono." Universidade de São Paulo, 2012. http://www.teses.usp.br/teses/disponiveis/46/46136/tde-02052013-102258/.
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Sistemas químicos capazes de produzir radicais livres OH• e O2•-, responsáveis por danos no DNA, foram estudados em diversos tipos de eletrodos de carbono previamente modificados. Nitrofural, RNO2, foi reduzido mono eletronicamente ao seu respectivo nitro ânion radical, RNO2•-, em eletrodo de pasta de carbono modificado superficialmente com um filme de guanina. O nitro ânion radical atacou a guanina imobilizada na superfície do eletrodo e, esta interação in situ, resultou na formação de cátions radicais de guanina (G+•), que ao interagirem com a guanina (G), foram identificados pelo pico de oxidação em voltametria pulso diferencial, VPD, nas formas diméricas de guanina na região positiva de potencial. Os outros sistemas estudados se referem ao desenvolvimento de novos eletrodos de carbono modificados ou ainda a utilização procedimentos de modificações desenvolvidas anteriormente, para a detecção de várias moléculas de importância biológica. O ácido ascórbico (AA), ácido úrico (AU), xantina (XA) e hipoxantina (HX) foram detectados simultaneamente em eletrodo de grafite pirolítico, previamente modificado em solução de dopamina (EGPD), utilizando VPD. Os picos de oxidação, obtidos por voltametria cíclica foram detectados em 51; 393; 765 e 1080 mV vs Ag / AgCl, KCl(sat) para AA, AU, XA e HX, respectivamente. O limite de detecção para XA em presença de 5,0 x10-5 mol L-1 de HX foi 2,3 x10-6 mol L-1 (com sensibilidade de 2,8 A mol-1 L cm2), enquanto que o limite de detecção para HX na presença de 5,0 x10-5 mol L-1 de XA foi de 5,6 x10-6 mol L-1 (com sensibilidade de 1,4 A mol-1 L cm-2). XA e HX foram determinadas em amostras de urina e os valores encontrados foram 0,47 µmol L-1 e 5,9 mol L-1, respectivamente. Serotonina (5-HT) e dopamina (DA) foram determinadas simultaneamente em eletrodo de carbono vítreo, previamente modificado em solução de serotonina (GCE - 5HT). A serotonina foi detectada em 379 mV vs Ag / AgCl, KCl(sat), 31 mV menos positivo daquele observado em eletrodo de carbono vítreo (410 mV), enquanto DA foi detectada a 200 mV. Nenhuma interferência foi observada na presença de (AA), tirosina (Tyr), epinefrina (EP) e noradrenalina (NE). Finalmente, na última etapa do presente trabalho lignina, extraída a partir de licor de Kraft, foi solubilizada em acetonitrila / H2SO4 e a solução resultante utilizada para dispersar nanotubos de carbono de parede múltipla, NTCPM. Esta suspensão foi empregada para modificar a superfície de um eletrodo de carbono vítreo, posteriormente utilizado na detecção de nitrito por VPD no intervalo de concentração de 4,0 x 10-6 ≤ [NO2-] ≤ 8, 0 x 10-5 mol L-1. O complexo formado entre neocuproina e Cu (I), um composto em potencial para geração de radicais livres e promoção de lesões no DNA, foi sintetizado e caracterizado.Chemical systems, which are able to produce OH• and O2•- free radicals, responsible for damage in DNA, were studied at different carbon modified electrode surfaces. Guanine carbon paste modified electrode was used to promote the nitrofural (RNO2) monoelectronic reduction to its respective nitro anion radical, RNO2•-, which attacked guanine immobilized on the electrode surface. The interaction in situ promoted the formation of guanine cation radicals (G+•) between guanine (G), after a dimerization process, were detected in the positive potential range by Differential Pulse Voltammetry, DPV. The other studied systems refer to development of new carbon modified electrodes or utilization of carbon modified electrodes, previously described, for the detection of several important biological molecules. Ascorbic acid (AA), uric acid (UA), xanthine (XA) and hypoxanthine (HX) were simultaneously detected at pyrolytic graphite electrode, previously modified into dopamine solution (EGPD), using DPV. The oxidation peak potentials, were obtained by cyclic voltammetry at 51; 393; 0.765 and 1080 mV vs Ag/AgCl, KCl(sat) for AA, UA, XA and HX, respectively. The detection limit for XA in presence of 5.0 x10-5 mol L-1 HX was 2.3 x10-6 mol L-1 (with sensibility of 2.8 A mol-1 L cm-2), while the detection limit for HX in presence of 5.0 x10-5 mol L-1 XA was 5.6 x10-6 mol L-1 (with sensibility of 1.4 A mol-1 L cm-2). XA and HX were determined in urine samples and the values founded were 0.47 µM e 5.9 µM, respectively. Serotonin (5-HT) and dopamine (DA) were simultaneously detected at glassy carbon electrode, previously modified in serotonin solution (ECV - 5HT). Serotonin was detected at 379 mV vs Ag/AgCl, KCl (sat), 31 mV less positive potential than that observed at bare glassy carbon electrode (410 mV), while DA was detected at 200 mV. No interference was observed in presence of (AA), tyrosine (Tyr), epinephrine (EP) and noradrenaline (NE). Finally, in the last stage of this work, lignin, extracted from Kraft liqueur, was solubilized in acetonitrile/H2SO4 and used to disperse multi-wall carbon nanotubes, MWNTC. This suspension was used to modify the glassy carbon electrode surface and nitrite was detected, by DPV in the concentration range of 4,0 x 10-6≤ [NO2-] ≤ 8,0 x 10-5 mol L-1. The complex formed between neocuproina and Cu (I), a compound which can produce free radicals and thereby cause damage to DNA, was synthesized and characterized.
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Smith, Nicola. "A spectroscopic study of the role of the nitrate radical in the troposphere." Thesis, University of East Anglia, 1995. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.297008.
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Ranaweera, Ranaweera Arachchilage Ajantha Upul. "Photo-induced Nitrogen and Carbon Based Radicals; A study on triplet nitrenes, triplet 1,2 and 1,3-biradicals." University of Cincinnati / OhioLINK, 2012. http://rave.ohiolink.edu/etdc/view?acc_num=ucin1337887740.
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Torabi, Abbas. "An investigation of the kinetics and excited state dynamics of the nitrate free radical." Diss., Georgia Institute of Technology, 1985. http://hdl.handle.net/1853/28024.
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Bones, David Lawrence. "Liquid Aerosol Photochemistry." Thesis, University of Canterbury. Chemistry, 2008. http://hdl.handle.net/10092/1500.
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Aerosols of nitrate solutions were irradiated in the presence of radical scavengers in an attempt to measure the yield of hydroxyl radical in both the aqueous phase and the gas phase. Carbon monoxide, benzoic acid, benzene and cyclohexane were used as scavengers to trap hydroxyl radical. The products from the reaction of these scavengers with hydroxyl radical were analysed with High Performance Liquid Chromatography and mass spectrometry. The radiant flux in the chamber was measured via ferrioxalate actinometry, both with bulk liquid and aerosol droplets. Many quantitative results were obtained but several anomalies were found. This suggests that Mie theory is not capable of predicting rates of photochemical reactions within droplets.
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El, Dib Gisèle Chakir Abdelkhaleq. "Dégradation atmosphérique des composés organiques volatils carbonyles (amides, aldéhydes aromatiques) par le radical nitrate et l'atome de chlore et réactivité atmosphérique du radical benzylperoxyle." Reims : S.C.D. de l'Université, 2006. http://scdurca.univ-reims.fr/exl-doc/GED00000952.pdf.
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El, Dib Gisèle. "Dégradation atmosphérique des composés organiques volatils carbonyles (amides, aldéhydes aromatiques) par le radical nitrate et l’atome de chlore et réactivité atmosphérique du radical benzylperoxyle." Reims, 2006. http://theses.univ-reims.fr/exl-doc/GED00000952.pdf.
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L’objectif de la thèse est de définir le devenir atmosphérique de quelques COV utilisés dans différents secteurs industriels ou produits directement dans la troposphère lors de l’oxydation d’autres COV. Nous avons étudié la dégradation du radical benzylperoxyle, d’une série d’amides (N-diméthyl formamide, N-diméthyl acétamide, N-méthylpyrrolidinone, N-diméthyl proprionamide) et d’une série d’aldéhydes aromatiques (2,4-diméthyl benzaldéhyde, 2,5-diméthyl benzaldéhyde, 2,6-diméthyl benzaldéhyde, 3,4-diméthyl benzaldéhyde et 3,5-diméthyl benzaldéhyde). Pour réaliser ce travail différentes techniques expérimentales ont été utilisées. Nous avons déterminé le spectre d’absorption UV du radical benzylperoxyle et les constantes de vitesse des réactions mutuelle et croisée avec HO2 en fonction de la température (298-353 K) en utilisant la technique de photolyse laser couplée à une détection spectroscopie UV-visible. La constante de vitesse de la réaction des amides avec le radical NO3 a été déterminée en fonction de la température (277-353 K), en utilisant la même technique. Ce travail présente la première étude cinétique des amides avec NO3 en fonction de la température. Les sections efficaces d’absorption des aldéhydes ont été mesurées par spectrométrie d’absorption UV-Visible. La constante de vitesse de la réaction des aldéhydes avec l’atome Cl a été déterminée à température ambiante en utilisant la Chambre de Simulation Atmosphérique. Les analyses ont été réalisées par Chromatographie en Phase Gazeuse (CPG). Il s’agit d’une première détermination de ces constantes de vitesse. L’ensemble des résultats est discuté et nous a permis d’évaluer les implications atmosphériques de ces COV (durée de vie et impact sur l’environnement)The purpose of this thesis is to determine the atmospheric fate of a number of VOCs widely used in different applications or directly produced into the troposphere by degradation of other VOCs. We have studied the degradation of benzylperoxy radical, a series of amides (N-dimethyl formamide, N-dimethyl acetamide, N-methylpyrrolidinone, N-dimethyl proprionamide) and a series of aromatic adehydes (2,4-dimethyl benzaldehyde, 2,5-dimethyl benzaldehyde, 2,6-dimethyl benzaldehyde, 3,4-dimethyl benzaldehyde and 3,5-dimethyl benzaldehyde). This work has been realised using several experimental techniques. We have determined the UV spectrum of benzylperoxy radical and the rate constants of the self reaction and the cross reaction with HO2 as a function of temperature (298-353 K) by using the laser photolysis technique with time resolved absorption UV-visible spectroscopy. The reaction rate constants of amides with NO3 radical have been determined as a function of temperature (277-353 K), by using the laser photolysis technique. This work provides the first kinetic study for the reaction of amides with NO3 as function of temperature. The absorption cross sections of aldehydes have been measured by UV-Visible spectrometry. The rate constants of the reaction of aldehydes with Cl atom have been determined at room temperature by using smog chambers. The analyses have been realized by Gas phase chromatography. This work represents the first reported kinetic study of the reaction of Cl atoms with these aldehydes. The whole results are discussed in order to assess the atmospheric implications of the compounds investigated (lifetimes and environmental impact)
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Scarfogliero, Michaël. "Étude en atmosphère simulée de la chimie troposphérique nocturne de composés organiques volatils oxygénés." Thesis, Paris Est, 2008. http://www.theses.fr/2008PEST0010.
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L’oxydation troposphérique des composés organiques volatils (COV) constitue une contribution importante à la formation de photooxydants. L’évaluation de l’impact environnemental des COV rend indispensable d’acquérir une bonne compréhension des processus en jeu. Ce travail porte donc sur l’étude en atmosphère simulée de la réactivité troposphérique avec le radical nitrate (NO3) de COV oxygénés appartenant à une série homogène d’éthers vinyliques aliphatiques (méthyl, éthyl, propyl et butyl vinyl éthers), et à une série de trois esters (acétates d’isopropényle, de vinyle, et d’allyle), auxquelles s’ajoute le 2,3,2 méthylbutènol (MBO). Pour tous ces composés, des études cinétiques (destinées à mesurer la constante d’oxydation par NO3 des produits étudiés) ont été menées selon la méthode relative, et pour certains composés selon la méthode absolue. Des études mécanistiques (destinées à identifier et quantifier les produits de la réaction, et à élucider le mécanisme réactionnel) ont également été menées. Une réévaluation de la constante cinétique d’oxydation du propène par NO3, qui a été mesurée selon la méthode absolue, a également été faite. Les expériences ont été menées dans la chambre de simulation atmosphérique du LISA, à température ambiante et à pression atmosphérique. Les durées de vie des composés étudiés vis-à-vis de NO3 ont été calculées, et comparées à celles vis-à-vis du radical OH et de l’ozone. Les résultats montrent que NO3 peut constituer un puits majeur pour les COV les plus réactifs, comme les éthers vinyliques. Par ailleurs, les apports de nos résultats aux règles de réactivité des COV ont été discutésThe tropospheric oxidation of the volatile organic compounds (VOC) constitutes an important contribution to the formation of photooxydants. It is necessary to acquire a good comprehension of the concerned chemical processes in order to correctly evaluate the environmental impact of the VOC. This work thus concerns the study under simulated conditions of the tropospheric reactivity with the nitrate radical (NO3) of oxygenated VOC pertaining to a homologous series of aliphatic vinyl ethers (methyl, éthyl, propyl and butyl vinyl ethers), and to a series of three esters (allyl and vinyl, isopropenyl acetates). In addition, the 2,3,2 méthylbutènol (MBO) has been studied too. For all these compounds, kinetic studies (in order to measure the rate constant of NO3 oxidation of the studied products) were performed according to the relative rate method, and for some compounds according to the absolute method. Mechanistic studies (in order to identify and quantify the reaction products, and to elucidate the chemical mechanism) were also performed. A revaluation of the rate constant of NO3 oxidation of propene, which was measured according to the absolute method, was also performed. The experiments were carried out in the LISA atmospheric simulation chamber, at room temperature and atmospheric pressure. The lifetimes of the studied compounds with respect to NO3 were calculated, and were compared to those with respect to OH radical and to ozone. The results show that NO3 can be a major sink for the most reactive VOC, like the vinyl ethers. In addition, the contributions of our results to the rules of reactivity of the VOC were discussed
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Semones, Molly Catherine. "Dynamics in the reactivity and photochemical production of hydroxyl radical in treated wastewater effluent and aquatic dissolved organic matter." The Ohio State University, 2017. http://rave.ohiolink.edu/etdc/view?acc_num=osu1482849720513842.
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Ohta, Hiroyuki, Atsushi Nagashima, Masafumi Ito, Masaru Hori, and Toshio Goto. "Formation of silicon nitride gate dielectric films at 300 ℃ employing radical chemical vapor deposition." American Institute of Physics, 2000. http://hdl.handle.net/2237/7102.
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Doussin, Jean-Francois. "Etudes cinétiques et mécanistiques des processus d'oxydation des composés organiques volatils d'importance atmosphérique induits par le radical nitrate en atmosphères simulées." Phd thesis, Université Paris-Diderot - Paris VII, 1998. http://tel.archives-ouvertes.fr/tel-00002792.
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L'étude des mécanismes des transformations chimiques des composés organiques dans l'atmosphère exige de pouvoir mener des expériences en phase gazeuse dont les résultats peuvent être d'une part interprétables et d'autre part fiablement extrapolables aux conditions physico-chimiques de l'atmosphère. Ces deux contraintes impliquent donc de pouvoir s'affranchir de la complexité et de la variabilité de la composition atmosphérique et simultanément de pouvoir travailler dans des domaines de pression, de température et de concentrations proches de celles rencontrées dans l'atmosphère. La simulation expérimentale permet de remplir ces objectifs. Ce travail de doctorat porte donc sur la mise en œuvre de techniques de simulation atmosphérique expérimentale dans le cadre d'études de la réactivité du radical nitrate vis-à-vis de composés organiques volatils d'intérêt troposphérique. L'utilisation de cette méthode nous a conduit à développer une chambre de simulation atmosphérique. Des méthodes d'analyse par spectrométrie optique UV-visible (DOAS UV-visible) et infrarouge à transformées de Fourier (IRTF) à très long trajet optique ont été adoptées ce qui nous a conduit au développement d'un nouveau type de cellule multi-reflexion infrarouge stabilisée. Les résultats qui ont été obtenus portent sur l'étude des mécanismes d'oxydation initiés par NO3 vis-à-vis du formaldéhyde, de l'acétaldéhyde, du propionaldéhyde, du benzène et du toluène. Nos résultats ont permis de décrire complètement le schéma d'oxydation des aldéhydes et de déterminer les constantes cinétiques associées à ces espèces. Nos expériences ont aussi confirmé l'existence d'une réaction entre les radicaux peroxyacyles et NO3 et permis son étude sous conditions atmosphériques simulées. La discussion de son impact atmosphérique montre qu'il pourrait être considérable. Plus généralement, l'importance la chimie des radicaux nitrate vis-à-vis des espèces radicalaires secondaires apparaissant au cours du processus d'oxydation a été démontré. Le radical nitrate étant l'une des espèces-clefs de la troposphère nocturne, ces résultats intéressent la compréhension de l'évolution des polluants atmosphériques durant la nuit. Il résulte de ces recherches que l'utilisation d'une chambre de simulation, équipée de puissants moyens d'analyse spectrométrique in-situ, permet de mener des études mécanistiques avec des bilans complets ainsi que des études portant sur la génération et l'évolution de composés radicalaires intermédiaires.
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Codd, Terrance Joseph. "Spectroscopic Studies of the A2E'' State of NO3." The Ohio State University, 2014. http://rave.ohiolink.edu/etdc/view?acc_num=osu1405984270.
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Djehiche, Mokhtar. "Développement d’un couplage cw-CRDS – chambre de simulation pour la mesure in situ du radical HO2 et d’espèces d’intérêt atmosphérique." Thesis, Lille 1, 2011. http://www.theses.fr/2011LIL10045/document.
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La spectroscopie cw-CRDS (continuous wave-Cavity Ring-Down Spectroscopy) est une technique d’absorption très sensible utilisée pour identifier et quantifier des espèces en phase gazeuse à des concentrations faibles et avec un temps de réponse très court. Nous avons développé une chambre de simulation atmosphérique (110 L) équipée d’un spectromètre cw-CRDS dans le proche IR (~ 1,5 µm), permettant la détection in situ du radical hydroperoxyle HO2, et d’autres espèces d’intérêt atmosphérique. Nous avons démontré les performances de ce dispositif original en étudiant deux systèmes réactionnels. Le premier système étudié est la photolyse du méthyle nitrite (CH3ONO), qui génère des radicaux OH. Le HONO issu de la réaction OH + CH3ONO a été identifié et quantifié pour la première fois, ce qui constitue une avancée importante dans la connaissance de cette réaction. La formation du HONO et du CH2O, produit majoritaire de la photolyse, a été étudiée dans différentes conditions expérimentales. Dans un deuxième temps, l’oxydation du méthanol dans l’air par les atomes de chlore Cl a été étudiée. Le radical HO2 a été observé pour la première fois par cw-CRDS in situ dans une chambre de simulation atmosphérique. La cinétique de disparition de HO2 a été étudiée, confirmant la valeur de la constante de vitesse de la réaction mutuelle ; une perte significative sur les parois de réacteur a été observée à très basse pression. La mesure des taux de photolyse du NO2, du CH3ONO et du Cl2 par différentes méthodes a permis de caractériser le dispositif expérimental développé dans ce travailThe continuous wave-Cavity Ring-Down Spectroscopy (cw-CRDS) is a very sensitive absorption technique used to selectively identify and quantify gaseous species at low concentrations and with a short acquisition time. We have developed an environmental chamber (110L) coupled with a near-IR cw-CRDS spectrometer for the detection of HO2 and other gaseous species. In order to demonstrate the performance of this setup, we have investigated two reaction systems. The first study concerns the methyl nitrite (CH3ONO) photolysis, which is known to generate OH radicals. The HONO product in the OH + CH3ONO reaction has been identified and quantified for the first time, which represents a very important step in the comprehension of this reaction. The formation of HONO and CH2O (a major product in the CH3ONO photolysis) has been studied under different experimental conditions. Secondly, the oxidation of methanol in air by chlorine atoms has been investigated. The HO2 radical has been observed for the first time by in-situ cw-CRDS in an environmental chamber. The kinetics of HO2 disappearance has been studied and the results confirm the rate constant value of the HO2 self reaction. A rather significant loss of HO2 on the walls of reactor has been observed at low pressure. Finally, the measurement of the photolysis frequencies of NO2, CH3ONO and Cl2 by various methods has allowed characterizing the experimental device developed in this work
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Doussin, Jean François. "Etudes cinetiques et mecanistiques des processus d'oxydation de composes organiques volatils d'importance tropospherique induits par le radical nitrate en atmosphere simulee." Paris 7, 1998. http://www.theses.fr/1998PA077040.
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L'etude des mecanismes des transformations chimiques des composes organiques dans l'atmosphere exige de pouvoir mener des experiences en phase gazeuse dont les resultats peuvent etre d'une part interpretables et d'autre part fiablement extrapolables aux conditions physico-chimiques de l'atmosphere. Ces deux contraintes impliquent donc de pouvoir s'affranchir de la complexite et de la variabilite de la composition atmospherique et simultanement de pouvoir travailler dans des domaines de pression, de temperature et de concentrations proches de celles rencontrees dans l'atmosphere. La simulation experimentale permet de remplir ces objectifs. Ce travail de doctorat porte donc sur la mise en uvre de techniques de simulation atmospherique experimentale dans le cadre d'etudes de la reactivite du radical nitrate vis-a-vis de composes organiques volatils d'interet tropospherique. L'utilisation de cette methode nous a conduit a developper une chambre de simulation atmospherique. Des methodes d'analyse par spectrometrie optique uv-visible (doas uv-visible) et infrarouge a transformees de fourier (irtf) a tres long trajet optique ont ete adoptees ce qui nous a conduit au developpement d'un nouveau type de cellule multi-reflexion infrarouge stabilisee. Les resultats qui ont ete obtenus portent sur l'etude des mecanismes d'oxydation inities par no#3 vis-a-vis du formaldehyde, de l'acetaldehyde, du propionaldehyde, du benzene et du toluene. Nos resultats ont permis de decrire completement le schema d'oxydation des aldehydes et de determiner les constantes cinetiques associees a ces especes. Nos experiences ont aussi confirme l'existence d'une reaction entre les radicaux peroxyacyles et no#3 et permis son etude sous conditions atmospheriques simulees. La discussion de son impact atmospherique montre qu'il pourrait etre considerable. Plus generalement, l'importance la chimie des radicaux nitrate vis-a-vis des especes radicalaires secondaires apparaissant au cours du processus d'oxydation a ete demontre. Le radical nitrate etant l'une des especes-clefs de la troposphere nocturne, ces resultats interessent la comprehension de l'evolution des polluants atmospheriques durant la nuit. Il resulte de ces recherches que l'utilisation d'une chambre de simulation, equipee de puissants moyens d'analyse spectrometrique in-situ, permet de mener des etudes mecanistiques avec des bilans complets ainsi que des etudes portant sur la generation et l'evolution de composes radicalaires intermediaires.
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Karoui, Hakim. "Synthèse d'une nouvelle nitrone phosphorylée : la 5-diéthoxyphosphoryl-5-méthyl-1-pyrroline N-oxyde (DEPMPO). Applications au piégeage in vitro et in vivo des radicaux libres centrés sur l'oxygène." Aix-Marseille 3, 1994. http://www.theses.fr/1994AIX30019.
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Un nouveau piege a radicaux, la 5-diethoxyphosphoryl-5-methyl-1-pyrroline n-oxyde (depmpo) a ete synthetise via une voie synthetique comprenant 2 etapes et son utilisation pour pieger des radicaux libres oxygenes en milieu biologique a ete etudiee. Le spin trapping in vitro des radicaux hydroxyle et superoxyde a ete effectue en solution tampon phosphate 0,1 m et les constantes de couplage hyperfin des adduits de spin obtenus ont ete determinees. Les constantes de vitesse de piegeage des radicaux hydroxyle et superoxyde avec la depmpo sont similaires a celles trouvees avec la 5,5-dimethyl-1-pyrroline n-oxide (dmpo). Cependant nous avons trouve que l'adduit de spin depmpo-superoxyde etait plus persistant (15 fois a ph 7) que l'adduit dmpo-superoxyde. Pour la premiere fois, en utilisant la depmpo, la production de radicaux superoxyde pendant la reperfusion de curs de rats isoles au cours d'une ischemie myocardique provoquee a ete clairement caracterisee
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Ohta, Hiroyuki, Atsushi Nagashima, Masaru Hori, and Toshio Goto. "Effect of ions and radicals on formation of silicon nitride gate dielectric films using plasma chemical vapor deposition." American Institute of Physics, 2001. http://hdl.handle.net/2237/7099.
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Svejstrup, Thomas. "Visible light-mediated synthesis of nitrogen-containing molecules : photoredox generation of amidyl and aminium radicals and nitrile oxides." Thesis, University of Manchester, 2018. https://www.research.manchester.ac.uk/portal/en/theses/visible-lightmediated-synthesis-of-nitrogencontaining-molecules-photoredox-generation-of-amidyl-and-aminium-radicals-and-nitrile-oxides(c8134c85-2bcd-4441-84da-0553a2769477).html.
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Nitrogen-centred radicals (NCRs) are a versatile class of reaction intermediates that can lead to useful synthetic transformations. Classical generation of NCRs requires pre-functionalised precursors that can be difficult to access and requires harsh reaction conditions in the formation of the NCR itself, which had limited synthetic application and interest. With the emergence of visible-light mediated photoredox catalysis as a method for the generation of radicals, interest in NCRs has been renewed. In this thesis, the generation of amidyl and aminium radicals is demonstrated and their application for the advancement of NCR chemistry has been achieved. Initial work utilised electron-poor O-aryl hydroxamic acids as suitable precursors for hydroamidation reactions, activated via single-electron reduction under photoredox conditions. These precursors are accessible by a variety of routes using commercially available reagents. This transformation was a transition metal-free protocol, made possible by using the organic dye eosin Y as the photocatalyst. The use of electron-poor O-aryl electrophores was then extended to the generation of aminium radicals from easy-to-make O-aryl hydroxylamines. The synthesis of arylamines was achieved by polarised radical addition of the aminium radical to arenes. This was achieved in the presence of Ru(bpy)3, blue light, and a strong acid, HClO4. This methodology was applied in the synthesis of a wide range of arylamines with examples in the late stage modification of drugs. Additionally, visible-light photoredox catalysis enabled the synthesis of biologically relevant isoxazolines and isoxazoles from nitrile oxides. This is achieved by two sequential oxidative single electron transfers with hydroxyimino acids, which are bench stable and can easily be synthesised by a simple condensation reaction, to generate the desired nitrile oxide intermediate. These nitrile oxides undergo [3+2] cycloadditions and this methodology shows broad functional group compatibility and provides a new route able to an important class of compounds.
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Le, Giang Truong. "Influence des ions chlorure, nitrate et sulfate sur les vitesses de décomposition de H2O2 et d'oxydation de composés organiques par les systèmes Fe(II)/H2O2 et Fe(III)/H2O2 : étude spectrophotométrique et modélisation cinétique." Poitiers, 2003. http://www.theses.fr/2003POIT2290.
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L'objectif de cette thèse a été d'étudier et de modélise l'influence des ions chlorures et sulfates sur les vitesses de décomposition des H2O2 et d'oxydation de composés organiques par les systèmes Fe(II)/H2O2 et Fe(III)/H2O2 en phase homogène, à pH acide et à 25 ʿC. L'étude du système Fe(II)/H2O2 a permis de montrer que les constantes cinétiques apparentes de réaction de H2O2 sur Fe2+, FeCl+ et FeSO4 sont respectivement égales à 55, 55, 78 M-1 s-1. Pour le système Fe(III)/H2O2, la complexation de Fe(III) par les ions chlorures et sulfates conduit à une diminution de la concentration hydroperoxycomplexes de Fe(III) et explique la diminution des vitesses de décomposition de H2O2 et des vitesse d'oxydation de composés organiques. La formation de radicaux Cl2·- qui sont beaucoup moins réactifs que les radicaux hydroxyles contribue également à la diminution des vitesses d'oxydation des composés organiques. Toutes les vitesses expérimentales ont été correctement modéliséesThe influence of chloride and sulfate ions on the rates of decomposition of H2O2 and of oxidation of organic compounds by the Fe(II)/H2O2 and Fe(III)/H2O2 has been investigated. Experiments were conducted at acidic pH and 25 ʿC. For the Fe(II)/H2O2 system, the rate constants for the reaction of H2O2 with Fe2+, FeCl+ and FeSO4 were found to be equal to 55, 55 ; 78 M-1 s-1. For the Fe(III)/H2O2 system, complexation reactions of Fe(III) by chloride or sulphate inhibit the formation of iron(III) hydroperoxycomplexes and lead to a decrease of the rates of decomposition of H2O2 and of the rates of oxidation of organic compounds. The formation of Cl2·- radicals which are less reactive than hydroxyl radicals also contribute to a decrease of the rates of oxidation of organic compounds. The reaction rates obtained in this study could be predicted well by a kinetic model
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Morin, Julien. "Etudes expérimentales des réactions des radicaux OH et des atomes d’oxygène d’intérêt pour l’atmosphère et la combustion." Thesis, Orléans, 2016. http://www.theses.fr/2016ORLE2034/document.
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L’objectif de ce travail consiste à étudier, d’une part, les réactions des nitrates d’alkyles avec OH qui ont un intérêt atmosphérique, et d’autre part, les réactions des radicaux OH avec les alcanes et des atomes d’oxygène avec les oléfines qui ont un intérêt pour la combustion. Toutes les réactions ont été étudiées dans des réacteurs à écoulement à basse pression, y compris le réacteur à écoulement à haute température mis en place dans le cadre de la thèse, couplés à un spectromètre de masse quadripolaire à ionisation par impact électronique. Pour les réactions OH + nitrate d’alkyle, la dépendance en température de la constante de vitesse a été mesurée pour dix nitrates d'alkyles, dont pour huit nitrates pour la première fois, sur une large plage de température. Pour six nitrates, les produits de la voie réactionnelle menant au recyclage direct de NO₂, arrachement d’atome H de carbone α, ont été observés et leur rendements mesurés. La grande quantité de données obtenues dans ce travail a été utilisée pour une mise à jour de la relation structure-activité (SAR) pour les réactions d'alkyles nitrates avec OH et a permis d'améliorer les modèles atmosphériques actuels. Les études de réactions de radicaux OH avec les trois alcanes et de l'atome O avec l’éthylène et le propène ont permis de déterminer les constantes de vitesse respectives sur une large gamme de température allant de 220 à 900 K. De plus, la distribution des produits de réactions multivoies O + oléfine en fonction de la température a été déterminée pour la première fois. Ces résultats permettront d’améliorer les modèles de combustion actuellement utilisésThe objective of this work was to study the reactions of alkyl nitrates with OH radicals relevant to atmosphere and reactions of OH radical with alkanes and oxygen atoms with olefins of interest for combustion chemistry. All reactions were studied in low pressure flow reactors (including high temperature flow reactor developed during the thesis) coupled to a quadrupole mass spectrometer with electron impact ionization. For OH reaction with nitrates, the temperature dependence of the rate constant was measured in an extended temperature range for ten alkyl nitrates, for eight of them for the first time. For six nitrates, the products of reaction pathway leading to direct recycling of NO₂ (H atom abstraction from α carbon) were observed and their yields were measured. The large amount of data obtained in this work has been used for an update of the structure-activity relation (SAR) for the reactions of alkyl nitrates with OH and will improve existing atmospheric models. For the reactions of OH radicals with three alkanes and O atoms with ethene and propene the rate constants were measured over a wide temperature range, 220-900 K. Moreover, the distribution of the products of the multichannel reactions O + olefin was determined as a function of temperature for the first time. These results are expected to improve current combustion models
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Sarkar, Sujan K. "Reaction Mechanism and Detection of Elusive C, N, and O Centered Radicals and Intermediates in Solution and Solid State." University of Cincinnati / OhioLINK, 2015. http://rave.ohiolink.edu/etdc/view?acc_num=ucin1448037904.
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Wulff, Alfredo. "Mecanismos de sintese e degradação do radical oxido nitrico pela mitocondria de Arabidopsis thaliana." [s.n.], 2008. http://repositorio.unicamp.br/jspui/handle/REPOSIP/314339.
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Orientador: Ione SalgadoDissertação (mestrado) - Universidade Estadual de Campinas, Instituto de Biologia
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Resumo: O objetivo deste trabalho foi estudar os mecanismo s de síntese e de degradação do radical óxido nítrico (NO) pela mitocôndria vegetal, com ênfase à influência das NAD(P)H desidrogenases e da oxidase alternativa (AOX) nestes processos. Os experimentos foram realizados com mitocôndrias isoladas de células em cultura da planta modelo Arabidopsis thaliana. Inicialmente estabeleceu-se um protocolo para o isolamento e purificação de mitocôndrias, cuja integridade funcional foi determinada pelo controle respiratório, potencial elétrico de membrana e transporte eletroforético de cálcio. Os processos de síntese e de degradação de NO foram analisados monitorando-se o consumo de oxigênio e as concentrações de NO no meio de reação, com eletrodos específicos. Os resultados mostraram que o nitrito inibiu a respiração das mitocôndrias de A. thaliana em competição com o oxigênio do meio. Esta inibição foi revertida por cPTIO, um seqüestrador de NO. Quando a AOX foi inibida por n-propilgalato, o efeito inibitório do nitrito na respiração mitocondrial foi aumentado, enquanto que, na presença de myxothiazol, que previne a redução da citocromo c oxidase (COX), o nitrito não teve efeito na respiração. Os efeitos observados do nitrito no consumo de oxigênio sugeriram que NO foi sintetizado pelas mitocôndrias de A. thaliana através de uma atividade redutora de nitrito. Entretanto, a síntese de NO a partir de nitrito foi principalmente detectada em anaerobiose. Em altas concentrações de nitrito (1-5 mM), a produção de NO se mostrou praticamente insensível aos inibidores da cadeia respiratória, enquanto que, em concentrações menores de nitrito (100 -200 ?M) a COX, mas não a AOX, contribuiu para a síntese de NO. A exposição das mitocôndrias ao NO ou ao nitrito causou uma inibição transiente e menor no consumo de oxigênio quando NAD(P)H f oi utilizado como substrato respiratório, em relação ao succinato. Estas inibições foram potencializadas por superóxido dismutase, sugerindo um mecanismo de degradação de NO dependente de NAD(P)He de oxigênio pelas mitocôndrias de A. thaliana. O conjunto dos resultados mostra que o NO pode ser produzido pela mitocôndria de A. thaliana através de uma atividade redutora de nitrito e que as NAD(P)H desidrogenases e a AOX, além da COX, podem interferir nesta produção. Em aerobiose, a quantidade de NO produzido pode ser controlada pelas atividades de degradação das NAD(P)H desidrogenases e pela COX. A AOX contribui de maneira oposta, ajudando a manter a concentração de NO. Em anaerobiose a atividade redutora de nitrito é favorecida sendo o NO produzido nestas condições pela COX e também devido ao estado mais reduzido da cadeia respiratória. Ainda, em anaerobiose, os mecanismos de degradação de NO, dependentes de oxigênio, estão inibidos. Em conclusão, os resultados deste trabalho mostram a importância das proteínas alternativas da cadeia respiratória da mitocôndria para a homeostase do NO na planta
Abstract: The objective of this work was to study the mechanisms of synthesis and degradation of NO by plant mitochondria, with emphasis on the influence of the NAD(P)H dehydrogenases and the alternative oxidase (AOX) in these processes. The experiments were carried out with mitochondria isolated from cells in culture of the model plant Arabidopsis thaliana. Initially, a protocol for the isolation and purification of mitochondria was established, and their functional integrity was determined by respiratory control, electric membrane potential and electrophoretic calcium transport. The processes of synthesis and degradation of NO were analyzed by monitoring oxygen consumption and NO concentration in the reaction medium with specific electrodes. The results showed that nitrite inhibited respiration of A. thaliana mitochondria, in competition with oxygen in the medium. This inhibition was reversed by cPTIO, an NO scavenger. When AOX was inhibited by n-propylgalate, the inhibitory effect of nitrite in mitochondrial respiration was increased, whereas in the presence of myxothiazol, which prevents the reduction of cytochrome c oxidase (COX), nitrite had no effect on respirati on. The observed effects of nitrite in the oxygen consumption suggested that NO was synthes ized by A. Thaliana mitochondria through a nitrite reductase activity. Meanwhile, the synthesis of NO from nitrite was mainly detected under anaerobiosis. At high concentrations of nitrite (1-5 mM), the production of NO was virtually insensitive to inhibitors of the respiratory chain, while at lower concentrations of nitrite (100-200 ?M) COX, but not AOX, contributed for the synthesis of NO. The exposure of mitochondria to NO or nitrite caused a transient and lower inhibition in oxygen consumption when NAD(P)H was used as respiratory substrate, compared to succinate. These inhibitions were enhanced by superoxide dismutase, suggesting an NAD(P)H- and oxygendependent mechanism for NO degradation by mitochondria of A. thaliana. The overall results show that NO can be produced by A. thaliana mitochondria through a nitrite reductase activity and that NAD(P)H dehydrogenases and AOX, in addition to COX, can interfere in this production. In aerobiosis the amount of NO produced can be controlled by the degradation activities of NAD(P)H dehydrogenases and COX. The AOX has an opposite effect, keeping the concentration of NO. In anaerobiosis the nitrite reductase activity is favore d and NO is produced in these circumstances by COX, and also due the more reduced state of the respiratory chain. Additionally, in anaerobiosis, the oxygen -dependent mechanisms of NO degradation are inhibited. In conclusion, the results of this study show the importance of the alternative proteins of the mitochondrial respiratory chain for NO homeostasis in the plant
Mestrado
Bioquimica
Mestre em Biologia Funcional e Molecular
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Huling, Scott Gage 1957. "Microbial and peat effects on the oxidation of alpha-(4-pyridyl-1-oxide)-N-tert-butyl-nitrone by hydroxyl radicals in soil." Diss., The University of Arizona, 1996. http://hdl.handle.net/10150/290654.
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The Fenton reaction involves the reaction between H₂O₂ and ferrous iron that yields a hydroxyl radical (·OH). H₂O₂ has been used to generate ·OH in soil and aquifer material to oxidize undesirable contaminants. However, non-target chemical species, both natural and anthropogenic also react with ·OH. That is, non-target chemical species can "scavenge" ·OH and limit the "oxidation capacity" of the treatment system. A laboratory study was conducted to determine whether soil microbiota or soil organic matter in the form of peat would scavenge ·OH and compete with a probe compound (alpha-(4-pyridyl-1-oxide)-N-tert-butyl-nitrone (4-POBN)) for ·OH. 4-POBN was used because of the numerous advantages regarding its fate in soil and ease of analysis, however, it would be rare to find this probe as a contaminant in ground water or soil. A soil slurry composed of silica sand (SiO₂), goethite (FeOOH), 4-POBN and either a suspension of catalase-positive bacterium (Shewanella putrefaciens) or Pahokee peat was amended with H₂O₂. An analytical technique was used to estimate the steady-state ·OH concentration, the rate of ·OH production, the natural scavenging conditional rate constant, and the rate of ·OH scavenging. The oxidation efficiency was calculated which provided an empirical measure of treatment. Parameter values were compared to evaluate the roles of microbes and peat as determinants of ·OH availability under the conditions of the experiment. Microbes did not significantly effect the rate of ·OH production. The steady-state ·OH concentration was estimated to be approximately the same in the microbial-amended and unamended reactors, and the treatment efficiency was slightly greater in microbial-amended reactors. These results indicate that microbes had a minimal scavenging role. Pahokee peat increased the rate of ·OH production which was partially attributed to the iron contained in the peat. The conditional natural scavenging reaction rate constant was lower in the peat-amended reactors, and the steady-state ·OH concentration was greater in the peat-amended reactors. The rate of ·OH scavenging and the total ·OH scavenged were greater in the peat-amended reactors. Although the conditional natural scavenging rate constant was lower in peat-amended reactors, the rate of scavenging increased. This was attributed to the increased concentration of ·OH. The degradation rate of 2-chlorophenol, a common ground water contaminant, was successfully predicted using 4-POBN transformation data obtained under similar experimental conditions.
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Viswanathan, Rajesh. "The development of free radical-mediated aryl amination and its application toward the total synthesis of ambiguine G nitrile." [Bloomington, Ind.] : Indiana University, 2005. http://wwwlib.umi.com/dissertations/fullcit/3177639.
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Thesis (Ph. D.)--Indiana University, Dept. of Chemistry, 2005.Title from PDF t.p. (viewed Dec. 8, 2008). Source: Dissertation Abstracts International, Volume: 66-05, Section: B, page: 2595. Chair: Jeffrey N. Johnston.
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Mishra, S. K. "Detection and analysis of spin trapped radical adducts by using alpha-phenyl-tert-butyl nitrone (PBN) derivatives and GC/MS." Thesis, University of Salford, 2016. http://usir.salford.ac.uk/39302/.
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Paradzinsky, Mark. "Hydrogen Abstraction by the Nighttime Atmospheric Detergent NO3·: Fundamental Principles." Diss., Virginia Tech, 2021. http://hdl.handle.net/10919/103783.
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The nitrate radical (NO3·) was first identified as early as the 1881, but its role in atmospheric oxidation has only been identified within recent decades. Due to its high one-electron reduction potential and its reactivity toward a diverse set of substrates, it dominates nighttime atmospheric oxidation and has since been the subject of much work. Despite this, studies on NO3· hydrogen atom transfer reactions have been somewhat neglected in favor of its more reactive oxidative pathways.
The first section of the dissertation will highlight the role of substrate structure, solvent effects, and the presence of a polar transition state on NO3· hydrogen abstractions from alcohols, alkanes, and ethers. In this work the acquisition of absolute rate constants from previously unexamined substrates was analyzed alongside a curated list of common organic pollutants degraded through hydrogen atom abstraction. It was found that NO3· reacts with low selectivity through an early polarized transition state with a modest degree of charge transfer. Compared to the gas-phase, condensed-phase reactions experience rate enhancement—consistent with Kirkwood theory—as a result of the polarized transition state.
These insights are then applied to abstractions by NO3· from carboxylic acids in the next section. It was found that the rate constants for abstraction of α-carbons were diminished through induction by the adjacent carbonyl compared to the activation seen for the aforementioned substrates. The deactivation of abstraction by the carbonyl was found to be dramatically reduced as the substrate's alkyl chain was lengthened and/or branched. This apparent change in mechanism coincides with hydrogen abstraction of the alkyl chain for sufficiently large carboxylic acids and rules out the possibility of concerted bond breaking elsewhere in the molecule.
Finally, the dissertation will cover some additional projects related to the overall nature of the work including examination of the kinetics of radical clock systems when complexed with metal ions and the examination of a highly oxidative biosourced monomer.Doctor of Philosophy
The nitrate radical (NO3·) was first identified as early as the 1881, but its role in the breakdown of atmospheric pollutants has only been identified within recent decades. Operating primarily at night, NO3· serves as a major atmospheric oxidant—it breaks down pollutants by reactions that involve the removal of electrons from those substrates. This chemistry is particularly important in understanding the consequences of an increasingly industrialized world and the subsequent short-term health and environmental implications. Geographically, these reactions will occur in large concentrations near locations that contribute greatly to atmospheric pollution, such as above coal-powered plants, heavily industrialized areas, above the canopy of large forests, and immediately behind the engines of airplanes as they move through the sky. The proximity of these locations to large population centers has caused the pollutants to greatly impact human health. These contaminants have been linked to several of the leading global causes of death, such as ischemic heart disease, stroke, and respiratory illnesses. The first section of the dissertation will focus on the role of pollutant structure, the medium in which the reaction occurs, and the development of a charged complex when NO3· reacts with alcohols, alkanes, and ethers. These substrates are often found as the result of incomplete combustion when burning fuel or as products of even more sustainable biodiesels. In this work the exact rate constants were found for substrates that were previously unexamined and compared with similar known reaction rates. It was found that NO3· has a low preference for what it reacts with and passes through a modestly charged complex early in the reaction. Compared to gaseous reactions, reactions in a liquid environment proceed faster due to the formation of a charged complex. This was then applied to reactions with carboxylic acids in the next section. Carboxylic acids are often found in large concentrations above the canopy of large forests resulting from the oxidation of isoprenes that are naturally released from broad-leaf trees. It was found that these reactions were slower than reactions with alkanes as the development of the charged complex was inhibited due to the presence of an adjacent dipole. When the carboxylic acid was longer and/or more branched, the formation of the charged complex was no longer inhibited as the reaction site moved further from the dipole. A change in reaction pathway was observed when the acids were sufficiently large. This ruled out the possibility of the reaction occurring simultaneously with a fracturing and rearrangement elsewhere. Finally, the dissertation will cover some additional projects that share some overlap with the work already described including the study of the rates of radical clock systems in the presence of metal ions and the study of naturally sourced monomers that are prone to losing electrons.
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Dassanayake, Rohan S. "Kinetic and Mechanistic Studies on the Reactions of Reactive Nitrogen and Oxygen Species (RNOS) with Vitamin B12 Complexes." Kent State University / OhioLINK, 2014. http://rave.ohiolink.edu/etdc/view?acc_num=kent1416602061.
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Herbig, Charlotte [Verfasser], Thomas [Gutachter] Michely, and Marika [Gutachter] Schleberger. "Ion Irradiation and Carbon Radical Exposure of Graphene and Hexagonal Boron Nitride on Iridium(111) / Charlotte Herbig ; Gutachter: Thomas Michely, Marika Schleberger." Köln : Universitäts- und Stadtbibliothek Köln, 2017. http://d-nb.info/1129872505/34.
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Deletraz, Anaïs. "Développement d'antioxydants de type nitrone comme agents neuroprotecteurs Reactivities of MeO-substituted PBN-type nitrones." Thesis, Avignon, 2019. http://www.theses.fr/2019AVIG0272.
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Le stress oxydant est associé à de nombreuses pathologies humaines telles que les maladies neurodégénératives. Les nitrones sont des antioxydants capables de protéger les cellules contre les dommages induits par un stress oxydant. Elles sont aussi capables de réagir avec les radicaux libres pour former un adduit de spin nitroxyde persistant et détectable en spectroscopie par résonance paramagnétique électronique (RPE). Elles ont été ainsi très largement utilisées comme sondes analytiques afin d’étudier les processus radicalaires se produisant dans des environnements biochimiques. Dans ce travail de thèse, nous nous sommes intéressés à l’α-phenyl-N-tert-butyl nitrone (PBN), une nitrone linéaire possédant de bonnes propriétés de piégeage ainsi qu’une activité protectrice dans des modèles animaux de maladies neurodégénératives. Le but de ce travail était d’étudier l’impact de la nature, de la position et du nombre de substituants de part et d’autre de la fonction nitronyle (cycle phényle et partie N-tert-butyle) sur les propriétés de la nitrone et d’améliorer son activité. Différentes séries de nitrones de type PBN ont ainsi été synthétisées et leur capacité de piégeage du radical hydroxyméthyle (CH2OH) ainsi que leurs propriétés électrochimiques et de neuroprotection ont été évaluées. Il ressort de cette étude que l’introduction d’un groupement électroattracteur en position para du cycle phényle ou sur la partie N-tert-butyle améliore les capacités de piégeage du radical nucléophile CH2OH. Au contraire, la fonctionnalisation de la PBN avec un substituant électrodonneur a tendance à diminuer sa capacité de piégeage. Lorsque des substituants sont introduits à la fois en para du cycle et sur la fonction N-tert-butyle, les effets vont dans le même sens sans pour autant s’additionner complètement. En revanche, l’influence des substituants sur la neuroprotection des nitrones n’a pu être identifiée. Finalement, des nitrones avec des activités de piégeage de radicaux et/ou de neuroprotection prometteuses ont été identifiéesOxidative stress is associated with many human pathologies such as neurodegenerative diseases. Nitrones are antioxidants able to protect the cells against oxidative stress-induced damage in in vitro and in vivo models. They are also able to react with free radicals to form a persistent nitroxide spin adduct, detectable by electron paramagnetic resonance (EPR) spectroscopy. They have thus been widely used as analytical probes to study the radical processes occurring in biochemical environments. In this thesis work, we focused on the α-phenyl-N-tert-butyl nitrone (PBN), a linear nitrone with good spin-trapping properties as well as protective activity in animal models of neurodegenerative diseases. The aim of this work was to study the impact of the nature, the position and the number of substituents on both sides of the nitronyl function (phenyl ring and N-tert-butyl part) on the properties of the nitrone and to improve its activity. Different series of PBN-type nitrones were thus synthesized and their spin-trapping ability towards hydroxymethyl radical (CH2OH), as well as their electrochemical and neuroprotective properties were evaluated. It emerges from this study that the introduction of an electron-withdrawing group in the para position of the phenyl ring or in the N-tert-butyl part improves the trapping capacities of the nucleophilic radical •CH2OH. In contrast, the functionalization of PBN with an electron-donating substituent tends to decrease its spin-trapping ability. When substituents are introduced both in the para position of the phenyl ring and in the N-tert-butyl function, the effects go in the same direction without completely adding up. In contrast, the influence of substituents on the neuroprotection of nitrones could not be identified. Finally, nitrones with promising trapping and/or neuroprotective activities were identified
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Allouch, Ahmad. "Détection du radical HO2. /O2-. : élaboration de pièges de type nitrone-ester ; détermination fiable des constantes de vitesse de piégeage par modélisation cinétique après traitement du signal RPE." Aix-Marseille 1, 2005. http://www.theses.fr/2005AIX11020.
Full textAbstract:
Ces travaux se situent dans le cadre de la recherche de nouveaux pièges à superoxyde et de l'étude de leurs propriétés. Nous avons tout d'abord synthétisé trois nouvelles nitrones linéaires portant un ou deux groupements ethoxycarbonyle. Leur utilisation en milieu aqueux a montré qu'elles piégeaient efficacement divers radicaux carbones et oxygènes, y compris le superoxyde, mais conduisaient avec le radical OH à des adduits trop instables pour être détectés par RPE. La seconde partie de ce travail concerne exclusivement les aspects cinétiques du piégeage du superoxyde. Une nouvelle méthode a été élaborée, fondée sur une compétition entre la réaction de piégeage et la dismutation spontanée du superoxyde en milieu aqueux. Les courbes cinétiques sont obtenues après un traitement numérique du signal de RPE utilisant la décomposition en valeurs singulières (SVD) et une déconvolution par la méthode du pseudo-inverse. Leur simulation permet d'obtenir des valeurs fiables de KP, constante de vitesse de piégeage du superoxyde. L'application de cette méthode à une série de dix composés a montré que l'EMPO (2-éthoxycarbonyle-2-méthyl-3,4-dihydro-2H-pyrrole-1-oxyde) et de la DEPO (2,2-diéthoxycarbonyl-3,4-dihydro-2H-pyrrole-1-oxyde) sont à ce jour les pièges du superoxyde les plus efficaces à pH 7,2.
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Pilli, Aparna. "Atomic Layer Deposition of Boron Oxide and Boron Nitride for Ultrashallow Doping and Capping Applications." Thesis, University of North Texas, 2020. https://digital.library.unt.edu/ark:/67531/metadc1752373/.
Full textAbstract:
The deposition of boron oxide (B₂O₃) films on silicon substrates is of significant interest in microelectronics for ultrashallow doping applications. However, thickness control and conformality of such films has been an issue in high aspect ratio 3D structures which have long replaced traditional planar transistor architectures. B₂O₃ films are also unstable in atmosphere, requiring a suitable capping barrier for passivation. The growth of continuous, stoichiometric B₂O₃ and boron nitride (BN) films has been demonstrated in this dissertation using Atomic Layer Deposition (ALD) and enhanced ALD methods for doping and capping applications.
Low temperature ALD of B₂O₃ was achieved using BCl₃/H₂O precursors at 300 K. In situ x-ray photoelectron spectroscopy (XPS) was used to assess the purity and stoichiometry of deposited films with a high reported growth rate of ~2.5 Å/cycle. Free-radical assisted ALD of B₂O₃ was also demonstrated using non-corrosive trimethyl borate (TMB) precursor, in conjunction with mixed O₂/O-radical effluent, at 300 K. The influence of O₂/O flux on TMB-saturated Si surface was investigated using in situ XPS, residual gas analysis mass spectrometer (RGA-MS) and ab initio molecular dynamics simulations (AIMD). Both low and high flux regimes were studied in order to understand the trade-off between ligand removal and B₂O₃ growth rate. Optimization of precursor flux was discovered to be imperative in plasma and radical-assisted ALD processes.
BN was investigated as a novel capping barrier for B₂O₃ and B-Si-oxide films. A BN capping layer, deposited using BCl₃/NH₃ ALD at 600 K, demonstrated excellent stoichiometry and consistent growth rate (1.4 Å/cycle) on both films. Approximately 13 Å of BN was sufficient to protect ~13 Å of B₂O₃ and ~5 Å of B-Si-oxide from atmospheric moisture and prevent volatile boric acid formation. BN/B₂O₃/Si heterostructures are also stable at high temperatures (>1000 K) commonly used for dopant drive-in and activation. BN shows great promise in preventing upward boron diffusion which causes a loss in the dopant dose concentration in Si.
The capping effects of BN were extended to electrochemical battery applications. ALD of BN was achieved on solid Li-garnet electrolytes using halide-free tris(dimethylamino)borane precursor, in conjunction with NH₃ at 723 K. Approximately 3 nm of BN cap successfully inhibited Li₂CO₃ formation, which is detrimental to Li-based electrolytes. BN capped Li-garnets demonstrated ambient stability for at least 2 months of storage in air as determined by XPS. BN also played a crucial role in stabilizing Li anode/electrolyte interface, which drastically reduced interfacial resistance to 18 Ω.cm², improved critical current density and demonstrated excellent capacitance retention of 98% over 100 cycles. This work established that ALD is key to achieving conformal growth of BN as a requirement for Li dendrite suppression, which in turn influences battery life and performance.
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Ratajczak, Fabien. "Synthèse et réactivité de nitroxydes chiraux." Université Joseph Fourier (Grenoble), 1997. http://www.theses.fr/1997GRE10134.
Full textAbstract:
Les nitroxydes sont des radicaux libres qui sont reduits en hydroxylamine ou oxydes en sel d'oxoammonium par des processus monoelectroniques reversibles. Les sels d'oxoammonium formes in situ oxydent notamment les alcools primaires et secondaires dans des conditions douces, catalytiques, et sont chimio et regioselectifs. Pour tester leurs potentialites en synthese asymetriques, deux methodes de synthese de nitroxydes chiraux a axe de symetrie c#2 ont ete mises au point. La premiere methode, originale, met en jeu la formation de dienolates en ,' d'aminodiesters suivie de leur reaction avec des electrophiles. Le dedoublement des amines d,l obtenues suivie d'une oxydation mene aux nitroxydes chiraux cycliques (cinq et six chainons) enantiomeriquement enrichis. La seconde strategie comporte deux additions nucleophiles successives sur des nitrones. Les nitroxydes optiquement actifs sont obtenus via un dedoublement d'amines. Une version enantioselective de cette methode a ete developpee a partir de la nitrone issue de la (2r,5r)-dimethylpyrrolidine. La stabilite des sels d'oxoammonium resultant de l'oxydation des nitroxydes prepares a ete etudiee par electrochimie. Ils sont peu stables, mais formes in situ ils catalysent l'oxydation des alcools. Certains d'entre eux sont capables de reconnaissance chirale dans le cas du dedoublement cinetique d'un alcool racemique ou de l'oxydation asymetrique d'un diol meso. Les exces enantiomeriques sont actuellement modestes, mais quelques resultats sont prometteurs. Enfin le nouveau systeme d'oxydation d'alcools primaires par le couple ncs/tempo mis au point presente une chimioselectivite remarquable.
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Rosselin, Marie. "Design of amphiphilic nitrones with improved spin-trapping and antioxidant properties." Thesis, Avignon, 2014. http://www.theses.fr/2014AVIG0258/document.
Full textAbstract:
Le stress oxydant se définit comme un déséquilibre entre la production d’espèces oxygénées et azotés réactives et les défenses antioxydants. Ce phénomène est associé à de nombreuses pathologies telles que des maladies neurodégénératives et cardiovasculaires ou des cancers. Pour contrecarrer les dégâts causés par le stress oxydant, l’utilisation d’antioxydants synthétiques s’est avérée intéressante car il devient alors possible de modifier les propriétés physico-chimiques des antioxydants et de leur assurer un meilleur ciblage cellulaire et tissulaire. Nos travaux de recherche se positionnent dans la recherche de nouveaux agents antioxydants synthétiques. Au cours de cette thèse nous nous sommes focalisés sur l’utilisation de l’alpha-phényl-N-tert-butylnitrone (PBN), qui présente une bonne activité pharmacologique contre les dégâts liés aux radicaux libres, et qui est également largement utilisée en tant que sonde analytique pour l’identification d’espèces radicalaires par la technique de piégeage de spin couplée à la résonance paramagnétique électronique (RPE). Dans la première partie de ces travaux de thèse, nous avons tenté d’améliorer les propriétés intrinsèques de la PBN en greffant divers substituants soit sur le cycle aromatique, soit sur le groupement N-tert-butyl de la fonction nitrone. L’analyse des propriétés physico-chimiques et biologiques de ces composés nous a permis de mesurer l’impact de la nature et de la position des substituants sur les propriétés antioxydantes de la PBN. La seconde partie de ces travaux a consisté à greffer le motif PBN sur des structures moléculaires amphiphiles dérivées d’un acide-aminé. Cette deuxième partie a pour but d’améliorer l’activité biologique et la biodisponibilité des dérivés PBNOxidative stress is defined as an unbalance between the production of free radicals and the antioxidant defenses. The oxidative stress state has been associated with several pathologies such as neurodegenerative and cardiovascular diseases or cancers. To prevent oxidative stress-mediated damage, the use of synthetic antioxidants is attractive as it allows to tune their physico-chemical properties as well as their cellular targeting specificity. Of particular interest is the linear alpha-phenyl-N-tert-butylnitrone (PBN) which exhibits pharmacological activity against radical-mediated pathophysiological conditions and has been widely used as analytical reagent for the identification of radical species by the spin-trapping method coupled to electron paramagnetic resonance (EPR) spectroscopy. In this thesis report, we first tried to improve the intrinsic antioxidant properties of PBN by grafting various substituents either onto the aromatic ring or the N-tert-butyl-group of the nitronyl function. The physico-chemical and biological properties of the compounds were then determined. With optimized nitrone derivatives in hand, the second part of this project consisted in improving the bioactivity and bioavailability of our nitrone agents using amphiphilic carriers or specific targeting ligands
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Aboab, Bettina. "Etude du couplage vibronique dans le cas d'un système XY3Z de symétrie C3V soumis à effet Jahn-Teller : application au calcul du couplage vibronique dans l'état excite 3E du radical methyl-nitrène CH3N." Pau, 1992. http://www.theses.fr/1992PAUU3019.
Full textAbstract:
Notre travail est consacré au traitement du couplage vibronique. Après avoir présenté l'essentiel des méthodes théoriques utilisées pour résoudre ce problème, nous nous sommes intéressé au traitement du couplage vibronique Jahn-Teller dynamique E(3Al+3E) au voisinage du point de symétrie C3V d'un système XY3Z présentant une double dégénérescence d'espace. Nous avons ensuite appliqué ce traitement au calcul du couplage vibronique dans l'état excité 3E du radical méthyl-nitrène Ch3N
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Miersch, Linda. "Synthese und Charakterisierung neuartiger Bismutoxido-Cluster als molekulare Vorstufen für organisch-anorganische Hybridmaterialien." Doctoral thesis, Universitätsbibliothek Chemnitz, 2012. http://nbn-resolving.de/urn:nbn:de:bsz:ch1-qucosa-90797.
Full textAbstract:
In der vorliegenden Arbeit wird die Synthese neuartiger, polynuklearer Bismutoxido-Cluster sowie deren Potential zur Verwendung als Bausteine zum Aufbau organisch-anorganischer Hybridmaterialien beschrieben. Die molekularen Verbindungen werden nach partieller Hydrolyse eines basischen Bismutnitrats in DMSO erhalten. Durch Zugabe von Additiven wie Carbon- und Sulfonsäuren können funktionalisierte Bismutoxido-Cluster erzeugt werden, die eine gute Löslichkeit in organischen polaren Lösungsmitteln besitzen. Die Charakterisierung der Produkte erfolgte mittels Einkristallröntgenstrukturanalyse, NMR- und IR-Spektroskopie sowie ESI-Massenspektrometrie. Erste Untersuchungen zur Synthese röntgenopaker organisch-anorganischer Hybridmaterialien auf der Basis von Bismutoxido-Clustern und Methylmethacrylat wurden durchgeführt. Hierzu wurde der nanoskalige Bismutoxido-Cluster [Bi38O45(OMc)24] als anorganischer Baustein gewählt. Die Oberfläche des Bismut-Sauerstoff-Gerüsts dieser Verbindung ist mit Methacrylat-Liganden bedeckt, welche eine gute Löslichkeit vermitteln und durch ihre polymerisierbaren Funktionalitäten eine kovalente Anbindung z. B. an Vinylmonomere ermöglichen. Die radikalische Copolymerisation von [Bi38O45(OMc)24] mit Methylmethacrylat liefert transparente Komposite, die anhand von Festkörper-NMR-Spektroskopie, IR-Spektroskopie sowie TG- und DSC-Analyse charakterisiert wurden.
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Mak, Jackson. "Heterogeneous reactions between nitrate radicals + organic coatings and nitrate radicals + soot." Thesis, 2006. http://hdl.handle.net/2429/17706.
Full textAbstract:
The reactive uptake of nitrate radicals (NO3) by self-assembled monolayers
(SAM) and methane soot was investigated using a flow tube reactor coupled to a
chemical ionization mass spectrometer (CIMS) as the detector. The detection of NO3
was accomplished by using I⁻ as the reagent ion, and the rate constant for the reaction of
N03 + I⁻ was determined to be (6.5 ± 5.0) x 10⁻¹⁰ cm³ • molecule⁻¹ • s⁻¹. The
performance of the experimental approach was evaluated by measuring the rate constant
for the bimolecular reaction between NO3 and NO. The rate constant for this reaction
was determined to be (2.7 + 0.2) x 10⁻¹¹ cm³ - molecule⁻¹ -s⁻¹, which is in excellent
agreement with the literature data.
Self-assembled monolayers were used as proxies for organic aerosols. The
reactive uptake coefficients were determined to be (8 ± 3) x 10⁻⁴ for octadecanethiol
(ODT) on gold and (1.3 + 0.2) x 10⁻³ for octadecyltrichlorosilane (OTS) on glass.
Although calculations show the loss of NO3 to organic coatings is of minor importance as
a sink of NO3 , they do, however, suggest NO3 is as efficient as OH in processing surfaces
of saturated hydrocarbons. In addition, the surface of an OTS monolayer was probed
with Fourier transform infrared (FTIR) spectroscopy prior to and following exposure to
NO3. The spectra indicate there was no fragmentation of the monolayer.
Heterogeneous reactions between NO3 and methane soot were investigated. From
the experimental results, a lower limit of 0.03 was determined for the reactive uptake
coefficient for this reaction. Calculations show the depletion of NO3 by soot may be an
important NO3 sink in the atmosphere in urban areas. Furthermore, infrared (IR)
absorption spectra show significant changes to the soot surface after exposure to NO3.
Functional groups such as epoxides, carbonyls, organic nitrites and nitrates were
observed after treatment.Science, Faculty of
Chemistry, Department of
Graduate