Dissertations / Theses: 'OX2'

1

Augustsson, Adam. "Reindeer Husbandry and Wind Power : Discourses surrounding the construction of IKEA's wind park on Glötesvålen and its local effects on reindeer husbandry." Thesis, Malmö universitet, Malmö högskola, Institutionen för Urbana Studier (US), 2021. http://urn.kb.se/resolve?urn=urn:nbn:se:mau:diva-42460.

Full text

Abstract:

The exploitation of land in Northern Sweden has caused a significant depletion of grazing grounds for semi-domesticated reindeer. This is a threat to the indigenous Sami reindeer herders of Sweden, who rely on the grazing ground in order to sustainably feed their herds. In the last decade, a significant amount of grazing land has been lost due to the construction of wind power parks (WPP) in important grazing regions. This thesis examines the discourse surrounding a WPP built in Härjedalen for IKEA. The WPP was built on Glötesvålen, a unique highland used for grazing by Mittådalen, a local herding community. Through a dissection of electronic sources and semi-structured interviews, the author conducts a discourse analysis to identify the most prevalent narratives surrounding the construction of IKEA’s WPP on Glötesvålen. An inductive approach is used to identify underlying ideologies present in the discourse through a relevant theoretical framework. The results show a pervasive enthusiasm for the WPP as a pivot towards renewable energy which mirrors the ideology of ecological modernization. The results also find a critical narrative which lifts the uneven power dynamic experienced by reindeer herders. This narrative is understood through the lens of Spivak’s (2010) “Can the Subaltern Speak?”. An additional discourse found is the symbolic issue between industrial ecological transitioning and the right to reindeer husbandry as a cultural heritage.
Exploateringen av mark i norra Sverige har orsakat en betydande förlust av betesmarker för renskötare. Detta hotar den svensk-samiska rennäringen, som förlitar sig på betesmarken för att hållbart mata sina hjordar. Under det senaste decenniet har en betydande mängd betesmark gått förlorad på grund av den ökande mängden vindkraftsparker (WPP) på, eller intillrenbetesmarker. Denna avhandling undersöker diskursen kring en WPP byggd i Härjedalen för IKEA. WPP byggdes på Glötesvålen, ett låg-fjäll som tidigare haft strategiskt viktiga betesmarker för samebyn Mittådalen. Genom en dissektion av elektroniska källor och halvstrukturerade intervjuer genomför författaren en diskursanalys för att identifiera de vanligaste narrativen om IKEAs vindkraftpark på Glötesvålen. En induktiv metod används för att identifiera underliggande ideologier som finns i diskursen genom ett relevant teoretisk ramverk. Resultaten visar en genomgripande entusiasm för vindkraft som ett steg mot förnybar energi. Detta narrativ speglar ideologin för ekologisk modernisering. Resultaten hittar också ett kritisk narrativ som lyfter den ojämna maktdynamiken som renskötarna upplever. Detta förstås genom Spivaks (2010) "Kan den underordnade tala?". Ytterligare en diskurs som upptäcks är symbolfrågan mellan industriell ekologisk omställning och bevarandet av renskötseln som kulturarv.

APA, Harvard, Vancouver, ISO, and other styles

2

Thuo, Njeri. "The synthesis and characterization of poly[oxo(2-chloro-1, 4-phenylene) oxy terephthaloyl-co-(2chloro-1, 4-oxy carbonyl methylene oxo terephthayoly-co oxy(2-chloro-1, 4-phenylene methylene oxy oxy terephthaloyl]." DigitalCommons@Robert W. Woodruff Library, Atlanta University Center, 1992. http://digitalcommons.auctr.edu/dissertations/1617.

Full text

Abstract:

Two copolyesters were prepared in the melt from terephthalic acid, 1,4- phenylenediacetic acid, 2-chlo~ 1,4-phenylenediacetate and CXCX -diacetoxy-I ,4- phenylene. Neither polymer is observed to exhibit liquid crystalline properties. Polymer I has an inherent viscosity of O.39g/dl while polymer 2 has an inherent viscosity of O.64g/dl. The Thermal properties of both polymers are obtained. Thermogravimetric analysis result indicate that polymer I starn to loose weight at 2750 C, while polymer 2 which is more thermally stable only losses less than 5% of it's weight at 3500 C. Both polymers were characterized by FT-IR, lH NMR and 13c NMR, POM, DSC, TGA and viscosity.

APA, Harvard, Vancouver, ISO, and other styles

3

Boscaro, Mateus Eugenio. "Determinação de elementos químicos em plásticos biodegradáveis naturais e sintéticos." Universidade de São Paulo, 2014. http://www.teses.usp.br/teses/disponiveis/64/64134/tde-26012015-144429/.

Full text

Abstract:

Preocupações com o acúmulo de lixo plástico e seu consequente impacto ambiental levaram os cientistas e a indústria química, nas últimas décadas, a uma busca por plásticos biodegradáveis e plásticos produzidos com matérias-primas de fontes renováveis. Entre eles, encontram-se o poli(ácido lático), o poli(?-caprolactona), os poli(hidroxialcanoatos), os polímeros de amido e os polímeros sintéticos que recebem aditivos que facilitam a degradação, conhecidos como oxi-biodegradáveis. Em decorrência dos processos de produção e uso de aditivos e corantes, os plásticos podem conter constituintes que não fazem parte das moléculas do polímero. Por esta razão, o objetivo do trabalho foi determinar os elementos químicos presentes em amostras de polímeros biodegradáveis, sacolas oxi-biodegradáveis e sacolas de amido distribuídas em supermercados, empregando-se análise por ativação neutrônica instrumental (INAA) e espectroscopia de fluorescência de raios X (XRF). A identificação dos polímeros das sacolas de supermercado foi realizada por espectroscopia de absorção no infravermelho com transformada de Fourier (FTIR). Os resultados das análises químicas dos polímeros não processados evidenciaram baixas concentrações dos elementos químicos. Já os plásticos das sacolas apresentaram altas concentrações de cálcio, sódio, zinco e titânio, provenientes do uso de cargas minerais, corantes e outros aditivos. Em algumas amostras, as concentrações de zinco, cobalto, cromo, molibdênio e chumbo excederam os limites estabelecidos pela norma ABNT NBR 15448-2:2008 para polímeros biodegradáveis. As análises também indicaram que os aditivos pró-oxidantes utilizados nas sacolas oxi-biodegradáveis são baseados em compostos químicos que contêm ferro. Os resultados obtidos comprovam que os plásticos biodegradáveis podem ser utilizados de forma segura em embalagens e outras aplicações, desde que se evitem os aditivos contendo elementos químicos tóxicos e outras substâncias perigosas
Concerns about the accumulation of plastic waste and its consequent environmental impact have led scientists and chemical industry, in recent decades, to search for biodegradable plastics and plastics made with renewable raw materials. Among them are included poly (lactic acid), polycaprolactone, polyhydroxyalkanoates, starch polymers and synthetic polymers having additives which facilitate degradation, known as oxo-biodegradable. Due to production processes and use of additives and dyes, plastics may contain small amounts of chemical elements that are not part of the polymer molecules. For this reason, the objective of this study was to determine chemical elements in samples of biodegradable polymers, oxy-biodegradable and starch bags distributed in supermarkets by instrumental neutron activation analysis (INAA) and X-ray fluorescence spectroscopy (XRF). The polymers of plastic bags were identified by Fourier transform infrared spectroscopy (FTIR). Results of chemical analysis of unprocessed polymers have shown low concentrations of chemical elements. On the other hand, plastic bags have high concentrations of calcium, sodium, zinc and titanium, from the use of mineral fillers, dyes and other additives. In some bag samples, the concentration of zinc, cobalt, chromium, molybdenum and lead exceeded the limits established by the ABNT NBR 15448-2:2008 for biodegradable polymers. The analysis also indicated that the pro-oxidant additives used in the oxy-biodegradable bags are based on chemical compounds that contain iron. These results demonstrate that biodegradable plastics can be safely used in packaging and other applications, provided additives containing toxic chemical elements and other hazardous substances are avoided

APA, Harvard, Vancouver, ISO, and other styles

4

Benincasa, Fabio. "DETERMINAÇÃO RÁPIDA E AUTOMÁTICA DE AÇÚCARES REDUTORES EM CALDO DE CANA-DE-AÇÚCAR." Universidade do Oeste Paulista, 2012. http://bdtd.unoeste.br:8080/tede/handle/tede/404.

Full text

Abstract:

Made available in DSpace on 2016-01-26T18:56:25Z (GMT). No. of bitstreams: 1 FABIO_BENINCASA_Agronomia_02_07_2012.pdf: 854058 bytes, checksum: 5977b7bda5f28c21b5060e650a4e9387 (MD5) Previous issue date: 2012-05-21
The monosaccharides (glucose and fructose) present in the sugarcane are reducing sugars because they have free carbonyl group, able to oxidize in the presence of oxidizing agents. The classical analytical methods (Lane-Eynon, Benedict, EDTA complexometric-, the Luff-Schoorl method, Musson-Walker, Somogyi-Nelson) based on the reduction of copper ions in alkaline solutions. Some industries use sucroalcooleiras methodology Lane-Eynon, other apparatus REDUTEC®, and others perform the calculation of RS (reducing sugar). The aim of this study was to understand the relationship between the variation of electric conductivity measurement in millivolts, mass wears and concentration of RS, with equipment similar to that proposed by Horii and Gonçalves, properly adapted, tested mathematical models with broth of sugar cane and held the automation of analyses. We used the apparatus REDUTEC ®, digital scales, peristaltic pump, digital camcorder, graphics and mathematical programs. It is concluded that there is a mathematical correlation between electrical conductivity (mv), RS. The mathematical model is statistically efficient solution of low concentration of RS (<0.3%).
Os monossacarídeos (glicose e frutose) presentes na cana-de-açúcar são açúcares redutores por possuírem grupo carbonílico livres, capazes de se oxidarem na presença de agentes oxidantes. Os métodos analíticos clássicos (Lane-Eynon, Benedict, complexométrica-EDTA, Luff-Schoorl, Musson-Walker, Somogyi-Nelson) baseiam-se na redução de íons cobre em soluções alcalinas. Algumas indústrias sucroalcooleiras utilizam a metodologia de Lane-Eynon, outras o aparelho REDUTEC® e outras realizam o calculo de AR (açúcares redutores). O objetivo do presente estudo foi compreender a relação entre a variação da condutividade elétrica medida em milivoltagem, massa gasta e concentração de AR, com aparelho semelhante ao proposto por Horii e Gonçalves, devidamente adaptado, testou-se modelos matemáticos com caldos de cana-de-açúcar e realizou-se a automação das análises. Utilizou-se o aparelho REDUTEC®, balança digital, bomba peristáltica, câmera de vídeo digital, programas matemáticos e gráficos. Conclui-se que existe uma correlação matemática entre condutividade elétrica (mv), massas gasta e AR, O modelo matemático gerado é eficiente estatisticamente, para solução de baixa concentração de AR (< 0,3%).

APA, Harvard, Vancouver, ISO, and other styles

5

Langlet, Abraham. "Nitration of Oxo-pyramidines and Oxo-imidazoles." Doctoral thesis, KTH, Kemi, 2006. http://urn.kb.se/resolve?urn=urn:nbn:se:kth:diva-601.

Full text

Abstract:

This thesis is mainly focused on the reactions of oxo-pyrimidines and oxo-imidazoles with nitric acid in sulfuric acid and properties of the gem-dinitro products formed in this process. Low temperature nitrations of 2-methylimidazoles produced – in addition to the known 2-methyl-5(4)-nitroimidazole – 2-(dinitromethylene)-5,5-dinitro-4-imidazolidinone and parabanic acid. This tetranitro compound was also obtained via nitration of 2-methyl-4,4-dihydro-(1H)-5- imidazolone. Thermal decomposition of 2-(dinitromethylene)-5,5-dinitro-4-imidazolidinone yielded 2-(dinitromethylene)-4,5-imidazolidinedione, which also was the product from the nitration of the new compound 2-methoxy-2-methyl-4,5-imidazolidienedione. Treatment of 2- (dinitromethylene)-5,5-dinitro-4-imidazolidinone with aqueous ammonia resulted in the previously unknown 1,1-diamino-2,2-dinitroethylene (Paper I). The nitration of some 2-substituted pyrimidine-4,6-diones in sulfuric acid, which afforded previously unknown 5,5-gem-dinitro-pyrimidine-4,6-diones in high yields, was studied. Alloxane was prepared in a one-step procedure by thermal decomposition of 5,5-dinitrobarbituric acid in hot acetic acid. The gem-dinitro products were found to be easily attacked by nucleophiles with concomitant formation of gem-dinitroacetyl derivatives, which in turn could be further hydrolysed to salts of dinitromethane and triureas (Papers II and III). Nitration of 4,6-dihydroxypyrimidine in sulfuric acid yielded nitroform as the sole product. This behaviour was tentatively explained by the formation of an intermediate, 5,5-dinitro-4,6- dihydroxypyrimidine, which underwent hydrolysis in the nitrating acid into gem-dinitroacetyl formamidine. This compound was further nitrated in the same reaction mixture into trinitroacetylformamidine, which finally underwent hydrolytic cleavage into nitroform. It was also demonstrated that gem-dinitroacetylureas could produce nitroform upon nitration. The structures of the proposed trinitroacetylureas were confirmed by the isolation of one of their derivatives (Paper IV).
QC 20100907

APA, Harvard, Vancouver, ISO, and other styles

6

Langlet, Abraham. "Nitration of oxo-pyrimidines and oxo-imidazoles /." Stockholm, 2006. http://urn.kb.se/resolve?urn=urn:nbn:se:kth:diva-601.

Full text

APA, Harvard, Vancouver, ISO, and other styles

7

Pohlmann, Juliana Gonçalves. "Avaliação da reatividade ao CO2 de chars obtidos em atmosferas convenional (O2/N2) e de oxi-combustão (O2/CO2) com vistas à aplicação no alto-forno." reponame:Biblioteca Digital de Teses e Dissertações da UFRGS, 2010. http://hdl.handle.net/10183/27923.

Full text

Abstract:

A injeção de carvão pulverizado - PCI - é praticada nas ventaneiras dos altos-fornos com o objetivo de substituir parcialmente o coque, provendo energia e gases redutores ao processo. Em geral, as melhorias desse processo ocorrem no sentido de diminuir o fuel rate e aumentar a produtividade do alto-forno. A tecnologia de oxi-combustão consiste na queima de carvão em uma atmosfera livre de N2, o qual é substituído por um gás rico em CO2. Visando a possibilidade de aplicação desta tecnologia em PCI, chars de três carvões de diferentes ranks utilizados para injeção e chars de um coque de petróleo foram obtidos em atmosferas convencional (O2/N2) e de oxi-combustão (O2/CO2) em forno de queda livre O objetivo do presente trabalho foi avaliar a reatividade ao CO2 desses chars por termogravimetria via método isotérmico a 1000°C. Resultados de eficiência da combustão (burnout), de área superficial e a morfologia dos chars antes da gaseificação auxiliaram a análise da reatividade. A reatividade foi, em geral, mais alta quanto mais baixo o rank do carvão e tendeu a aumentar com o burnout, o qual foi associado ao aumento na área superficial BET. Em geral, as reatividades ao CO2 dos chars de atmosferas O2/N2 e O2/CO2, obtidos com o mesmo teor de oxigênio, não apresentaram diferenças significativas. Apenas no caso dos chars do carvão de mais baixo rank e obtidos em maior teor de oxigênio é que as amostras de oxi-combustão foram mais reativas.
Pulverized coal injection (PCI) is used in the blast furnace tuyeres attempting to provide energy and reducing gases to the process. New technologies have been studied to improve PCI and to make ironmaking process suitable to environmental requirements. Oxy-fuel combustion technology consists of burning coal in a N2-free atmosphere, which is exchanged by a CO2-rich gas. Aiming at a possible application of oxy-fuel combustion in blast furnace, chars of three typical PCI coals of different ranks were obtained under conventional (O2/N2) and oxy-fuel (O2/CO2) atmospheres in drop tube furnace. The aim of this work was to evaluate the CO2 reactivity of these chars via thermogravimetric analysis by isothermal method at 1000ºC. Coals burnouts, BET surface areas of chars and chars morphology before gasification gave support in the reactivity results analyse. In general, the higher reactivities were observed for the lower rank coal chars. Reactivity increased when coal burnouts and chars BET surface areas also increased. The CO2 reactivities of conventional and oxy-fuel chars, obtained under the same oxygen content, have not shown significant differences.

APA, Harvard, Vancouver, ISO, and other styles

8

Franco, Alexandre. "Nitro- e oxi-HPA no material particulado atmosférico: algumas contribuições para uma abordagem integrada." Universidade de São Paulo, 2006. http://www.teses.usp.br/teses/disponiveis/46/46133/tde-05122006-144151/.

Full text

Abstract:

Os derivados nitrados e oxigenados de hidrocarbonetos policíclicos aromáticos, nitro-HPA e oxi-HPA, podem ser encontrados no material particulado atmosférico e são provenientes da queima de combustíveis fósseis e biomassa, ou de reações dos HPA com gases atmosféricos. Determinados nitro-HPA e oxi-HPA apresentam mutagenicidade mais elevada do que a dos seus HPA precursores. O presente trabalho teve como objetivo avaliar os níveis de nitro-HPA e oxi-HPA nos extratos orgânicos do material particulado atmosférico das cidades de São Paulo, Araraquara, Paulínia e Piracicaba, durante períodos com e sem a queima da palha da cana-de-açúcar, verificar a possível existência de transporte de poluentes entre as regiões estudadas e determinar a mutagenicidade do material particulado. O material particulado atmosférico foi coletado em amostrador de grande volume com filtro de fibra de quartzo e extraído em Soxhlet. Os extratos foram submetidos à separação por HPLC, obtendo as frações de HPA, nitro-HPA e oxi-HPA, as quais foram analisadas por GC-MS. Tanto as frações como os extratos brutos foram submetidos a determinações gravimétricas e testes biológicos. Os nitro-compostos específicos, 1-nitropireno (1-NPir), 3-nitrofluoranteno (3-NFlt) e 6-nitrocriseno (6-NCri), para os quais há disponibilidade de padrões, foram analisados sendo que o 6-NCri não foi detectado em nenhuma amostra. Os níveis dos nitro-HPA encontrados (concentração máxima = 0,86 ngm-3) foram similares aos níveis reportados na literatura para diferentes cidades do mundo e o 3-NFlt apresentou níveis mais altos do que o 1-NPir em todas as amostras. Dentre os sítios estudados, São Paulo apresentou, em geral, níveis mais altos do que Araraquara, Piracicaba e Paulínia, apesar das concentrações altas de material particulado encontradas nesses três sítios. Em todos os sítios estudados houve um aumento nos níveis dos nitro-HPA no inverno, e não foi possível verificar se as emissões provenientes da queima da palha da cana-de-açúcar contribuem para os níveis desses poluentes. Na cidade de São Paulo, sítio mais estudado, foi observada uma variação sazonal evidenciada pelo aumento dos nitro-HPA no inverno de 2002. Níveis similares de nitro-HPA foram observados nos invernos de 2001 a 2004, exceto em 2003, onde os níveis foram mais altos devido provavelmente ao período longo de estiagem e às condições meteorológicas favoráveis à estagnação dos poluentes. Relacionando-se os níveis dos nitro-HPA com as trajetórias das massas de ar verificou-se um possível transporte de poluentes de uma região para outra em um único caso, de um total de 15. Dentre os oxi-HPA identificados (5H-fenantro(4,5-bcd)pirano-5-ona, 1-ácido fenantrenocarboxílico, 4H-ciclopenta(def)criseno-4-ona, 9,10-antracenodiona e benzantrona) a 9,10-antracenodiona e a benzantrona são comprovadamente mutagênicos. A benzantrona foi a mais freqüentemente encontrada nas amostras. Os níveis mais altos de oxi-HPA foram encontrados nas amostras de Araraquara e Piracicaba. Por final, pode-se concluir também, que as mutagenicidades das frações nitro- e oxi-HPA são as principais responsáveis pela mutagenicidade do extrato bruto, uma vez que a mutagenicidade das frações HPA praticamente não contribuiu para a mutagenicidade total.
Nitrated and oxygenated derivatives of polycyclic aromatic hydrocarbons, nitro-PAH and oxi-PAH, can be found in the atmospheric particulate matter from the combustion of fossil fuel and biomass or as result of PAH reactions with atmospheric gases. Some nitro-PAH and oxi-PAH compounds present higher mutagenicity than their parent PAH. The objective of this research was to evaluate the nitro- and oxi-PAH levels in organic extracts of atmospheric particulate matter collected at the cities of Sâo Paulo, Araraquara, Piracicaba and Paulinia, over periods with and without sugar cane burning, to analyze the possible transport of pollutants at these regions and to determine the mutagenicity of the particulate matter . The atmospheric particulate matter was collected by high volume sampler over quartz fiber filter and extracted with soxhlet. Extracts were submited to HPLC to obtain PAH, nitro-PAH and oxi-PAH fractions, which were analyzed by the GC-MS. Both fractions and extracts were subjected to gravimetric determinations and biological tests. Specific compounds, 1-nitropyrene (1-NPir), 3-nitrofluoranthene (3-NFlt) and 6-nitrocrisene (6-NCri) were analyzed and only 6-NCri was not detected in any of the samples. The determined levels of nitro-PAH (maximum concentration = 0,86 ngm-3) were similar to that reported in the literature for other cities of the world. In all samples, the 3-NFlt level was higher than that of 1-NPir. Among the studied areas, São Paulo presented, in general, higher levels than Araraquara, Piracicaba and Paulinia, despite the high concentration of particulate matter found at these areas. All the studied sites presented higher levels of nitro-PAH during the winter, and it was not possible to verify if the emissions of sugar cane burning contribute to the levels of these pollutants. An increase of the nitro-PAH during the winter of 2002 was observed in São Paulo, the more deeply studied site, showing a seasonal variation. Similar levels of nitro-PAH were observed in the winter of 2001, 2002 and 2004. In 2003, the levels were even higher probably due to the long period without rain and favorable meteorological conditions to the stagnation of pollutants. Relating the nitro-PAH levels with the air masses trajectories, it was observed that the pollutants were transported from a region to another in only one out of the 15 studied cases. Among the oxi-PAH identified (5H-phenanthro(4,5-bcd)pyran-5-one, 1-phenanthene carboxylic acid, 4H-ciclopenta(def)crisene-4-one, 9,10-anthracenedione and benzanthrone), the 9,10-anthracenedione and benzanthrone are mutagenic and were found in the most of the samples. Finally, the mutagenicity of the nitro-PAH and oxi-PAH fractions accounted for the mutagenicity of the organic extract, due to the fact that the mutagenicity of the PAH fractions was very low and its contribution to the total mutagenicity was negligible.

APA, Harvard, Vancouver, ISO, and other styles

9

Pereira, Daniela Cristina de Almeida. "Poluição em ambientes internos. Caracterização de espécies no material particulado de atmosferas escolares." Universidade de São Paulo, 2018. http://www.teses.usp.br/teses/disponiveis/46/46136/tde-12042018-094059/.

Full text

Abstract:

Atualmente a poluição do ar é um assunto relevante para a população e para os órgãos governamentais, em razão dos efeitos na saúde e no clima. Tão importante quanto a quantidade de material particulado na atmosfera, é também, a sua composição. O objetivo deste estudo foi determinar a concentração de MP10 e espécies orgânicas e inorgânicas em amostras coletadas em ambientes internos e externos de três escolas do Estado de São Paulo, para avaliar a qualidade do ar. As concentrações de MP10 foram determinadas por gravimetria, depois foram submetidas à extração, rotaevaporação, fracionamento em coluna, e os compostos foram determinados através da cromatografia gasosa acoplada ao espectrômetro de massas; o carbono elementar e o carbono orgânico foram determinados pelo método termo-óptico, pelo sistema desenvolvido na Universidade de Aveiro; o carbono grafítico foi determinado por refletometria e os metais por EDXRF e algumas amostras foram analisadas por cromatografia de íons, no instituto de Astronomia, Geofísica e Ciências Atmosféricas da Universidade de São Paulo. As amostras de MP10 foram coletadas nos seguintes sítios: (i) escola de Aplicação, dentro da Cidade Universitária, de área urbana que sofre influência de via de grande movimento de veículos e da vegetação local; (ii) escola Madalena de Almeida do Cais, na cidade de Nova Granada localizada a cerca de 475 quilômetros da cidade de São Paulo, com baixa população e poucos veículos; (iii) escola particular em bairro residencial da zona oeste, que sofre a influência de avenida com grande fluxo de veículos. Os resultados indicaram que a concentração do MP10 foi mais alta em ambiente interno que externo na escola dentro da USP. Na escola particular, a concentração mediana apontou que o ambiente externo apresentou concentração de MP10 superior ao ambiente interno. Para os hidrocarbonetos policíclicos aromáticos, observou-se que tanto na escola do interior quanto na escola do campus, houve maior concentração em ambiente interno, e alguns de maior peso molecular, atribuídos às emissões veiculares, foram mais altos em ambiente externo. As razões diagnósticas indicaram queima de combustíveis fósseis ao redor dos sítios amostrados. As amostras coletadas nas escolas apresentaram baixos riscos à saúde. Os compostos 2- metilantraquinona e benzo(a)antraceno-7,12-diona foram encontrados nas amostras, denotando a influência da exaustão veicular. A fração carbonácea (EC + OC) apresentou maior concentração em ambiente externo, e a razão OC/EC para o ambiente externo apontou para a queima de biomassa. A fonte de carbono grafítico corroborou a influência do tráfego. Para a maioria dos elementos, com exceção do cromo, manganês e ferro, as concentrações obtidas em ambiente interno foram as mais altas, majoritariamente oriundos da ressuspensão do solo. O cromo e o manganês estão relacionados com a emissão dos veículos que utilizaram a mistura gasolina e etanol; o ferro, com a crosta terrestre. Para os íons, a concentração média para ambientes externos apresentou a seguinte tendência: SO42- > NO3- > Ca2+ > NH4+ > Na+ > K+> Mg2+ > Cl- e para ambientes internos foi Ca2+ > SO42- > NO3- > Na+ > NH4+ > K+ > Cl- > Mg2+ > F-. A maioria das espécies apresentou a influência da ressuspensão do solo; o nitrato e o sulfato foram atribuídos à emissão veicular, e o cátion amônio foi formado por reações a partir da degradação da matéria orgânica e dos processos que ocorrem nos catalisadores veiculares.
Nowadays, air pollution is a relevant issue for people and government agencies because of the health and climate effects. As important as the amount of particulate matter in the atmosphere, is also, its composition. The object of this study was to determine the concentration of PM10 and organic and inorganic species in samples collected in indoor and outdoor environment of three schools in the State of São Paulo, to evaluate air quality. The concentrations of PM10 were determined by gravimetry, then the samples were subjected to extraction, rotary evaporation, column fractionation, and the compounds were determined by gas chromatography coupled to the mass spectrometer; elemental carbon and organic carbon were determined by the thermooptical method, by the system developed at the University of Aveiro; the graphitic carbon was determined by reflectometry and the metals by EDXRF and some samples were analyzed by ion chromatography, at the Institute of Astronomy, Geophysics and Atmospheric Sciences of the University of São Paulo. PM10 samples were collected at the following sites: (i) school of Application, within the University City, an urban area that is influenced by a large vehicular route and local vegetation; (ii) Madalena de Almeida do Cais school, in the city of Nova Granada located about 475 kilometers from the city of São Paulo, with low population and few vehicles; (iii) private school in a residential neighborhood in the western zone, which suffers the influence of avenue with a large flow of vehicles. The results indicated that PM10 concentration was higher in indoor than outdoor environment in the school within USP. In the private school, the median concentration indicated that the outdoor environment presented a concentration of PM10 higher than the indoor environment. For the polycyclic aromatic hydrocarbons, it was observed that both countryside school and campus school, a higher concentration of compounds in the indoor environment was found, only some high molecular weight compounds, attributed to vehicular emissions, were higher in the external environment. Diagnostic ratios indicated the burning of fossil fuels around the sites sampled. Samples collected in schools presented low health risks. 2-methylanthraquinone and benzo(a)anthracene-7,12-dione were found in the samples, denoting the influence of vehicle exhaust. The carbonaceous fraction (EC + OC) presented higher concentration in the outdoor environment and OC/EC ratio for the outdoor environment pointed to biomass burning. The graphite carbon source corroborated the traffic influence. For most of the elements, except for chromium, manganese and iron, the concentrations obtained in indoor environment were the highest, mainly derived from soil resuspension. Chromium and manganese are related to the emission of the vehicles that used the mixture gasoline and ethanol; iron is from the terrestrial crust. For the ions, the average concentration for outdoor environments presented the following trend: SO42-> NO3-> Na+> NH4+> Na+> K+> Mg2+> Cl- and for indoor environments was Ca2+> SO42-> NO3-> Na+ > NH4+> K+ > Cl-> Mg2+> F-. Most of the species showed the influence of soil resuspension; nitrate and sulfate were attributed to human activities, i. e., vehicular emission, and, the ammonium cation was formed by reactions from the degradation of the organic matter and the processes that occur in vehicular catalysts.

APA, Harvard, Vancouver, ISO, and other styles

10

Yau, K. C. "The asymmetric synthesis of oxo-piperidines and oxo-pyrrolidines." Thesis, University College London (University of London), 2014. http://discovery.ucl.ac.uk/1451240/.

Full text

Abstract:

Chapter 1 describes the attempts to synthesize piperidin-2-ones via an aza-Michael-Michael annulation, which were unsuccessful. A general route for the synthesis of piperidin-2,4-diones from β-keto esters via a Dieckmann cyclisation was proposed and five piperidin-2,4-diones with different substituents at positions-5 and -6 were prepared. An asymmetric route to 1-unsubstituted piperidin-2,4-diones was also developed which involved the use of Davies' chiral auxiliary to induce an asymmetric Michael addition. Chapter 2 describes a new approach to the synthesis of codeine. The piperidin-4-one ring was prepared by a Dieckmann cyclisation; a Robinson annulation was performed to construct the cyclohexenone ring and the key bicyclic intermediate was made. However, attempts to prepare the corresponding benzomorphan via a Grewe cyclisation of the α,β-unsaturated ketone were not successful. Synthesis of various 2,3-disubstituted piperidin-4-ones using the same strategy as the codeine synthesis was attempted; six different piperidin-4-ones with alkyl and aryl substituents at the 2-position were prepared. Chapter 3 describes the attempts to synthesize 1,2-dihydropyrrol-3-ones employing the same strategy used to make piperidin-4-ones in Chapter 2. Seven different diester intermediates were successfully prepared but attempts for Dieckman cyclisation failed. The focus was changed to prepare 5-substituted pyrrolidin-3-ones by the protocol used to make piperidin-2,4-diones in chapter 1 and four pyrrolidin-3-ones were made. Enantioselective syntheses using the Davies' chiral auxiliary were attempted and enantiopure 5-methylpyrrolidin-3-one was prepared.

APA, Harvard, Vancouver, ISO, and other styles

11

Rudolph, Martin. "Synthesis and characterization of magnetron-sputtered Ta₃N₅ thin films for the photoelectrolysis of water." Thesis, Université Paris-Saclay (ComUE), 2017. http://www.theses.fr/2017SACLS094/document.

Full text

Abstract:

Le Ta₃N₅ fait partie des matériaux les plus prometteurs pour la photo-électrolyse de l’eau. En effet, la bande de valence et la bande de conduction sont situées autour du potentiel d’évolution de l’hydrogène et de l’oxygène et son petit gap (2.1eV) permet l’absorption d’une grande partie du spectre solaire. Par contre la synthèse de ce matériau est difficile à cause de la structure riche en azote (faible diffusion) et de l’état d’oxydation élevé du Ta (+5) dans le cristal de Ta₃N₅. Sa synthèse par pulvérisation cathodique est peu exploitée à ce jour, malgré que cette technique de dépôt permette d’augmenter le rapport ion-neutre arrivant sur le film en croissance et donc de fournir de l’énergie supplémentaire à la surface du film favorisant ainsi la cristallisation. Lors cette thèse, des couches minces de Ta₃N₅ ont été déposées par pulvérisation cathodique dans une atmosphère réactive. Il y est montré que la pulvérisation d’une cible de Ta produit des Ar rétrodiffusés avec des énergies élevées qui augmentent l’incorporation de défauts dans la couche lorsque la polarisation de la cible est élevée. Des films de Ta₃N₅ ont été déposés en mode continu ce qui a permis de maintenir une polarisation faible. Il a été mis en évidence que l’oxygène incorporé dans le cristal joue un rôle crucial pour la déposition du film de Ta₃N₅. De plus, l’oxygène influence fortement les propriétés des couches minces, notamment les propriétés optiques et électroniques. Un nouveau système, augmentant le flux d’ions vers le substrat, a été installé dans le réacteur de dépôt ce qui a augmenté le degré de cristallisation de la phase Ta₃N₅. Les connaissances acquises lors de cette thèse ont été utilisées pour préparer des photoanodes à partir de Ta₃N₅ et leur aptitude à décomposer l’eau sous l’illumination du soleil a été démontrée
Ta₃N₅ is one of the most promising candidates for efficient water splitting using sunlight due to its band positions with respect to the oxygen and hydrogen evolution potentials and its small band gap of 2.1eV. Its synthesis, however, is challenging given its high content of nitrogen, with its low diffusivity, and the Ta metal atom in a high oxidation state. Few investigations into its synthesis by magnetron sputtering exist to date although this technique offers the possibility of tuning the ion-to-neutral flux ratio onto the growing film. This can change the supply of energy onto its surface and therefore promote the crystallization. In this thesis, reactive magnetron sputtering is investigated for the preparation of Ta₃N₅ thin films. It is shown that sputtering of a Ta target in an Ar atmosphere produces energetic backscattered Ar neutrals at high target potentials. To keep the potential low, Ta₃N₅ is deposited by sputtering in DC mode. The growth of the Ta₃N₅ phase requires the incorporation of oxygen into the lattice. It is shown that optical and electronic properties of these samples vary strongly with the precise amount of oxygen in the thin film. Samples with a high degree of crystallinity are obtained by increasing the N₂⁺ flux onto the substrate by changing the form of the magnetic field of the magnetron. The highly crystalline samples prepared by this method are proven to work as photoanodes for the splitting of water under illumination

APA, Harvard, Vancouver, ISO, and other styles

12

Colim, Alexsandro Nunes. "Avaliação de adsorventes sólidos para a remoção de derivados de HPAs em solução." Universidade Federal de Santa Maria, 2014. http://repositorio.ufsm.br/handle/1/10565.

Full text

Abstract:

Polycyclic aromatic hydrocarbons, nitrogen and oxygen (Nitro-PAHs and Oxy-PAHs) compose the class of compounds where a hetero atom of nitrogen and oxygen, respectively, is present in the constitution of the HPA. The inclusion of a heteroatom leads to increased mobility and increased toxicological potential. In this work were investigated adsorbent materials for removal of Nitro-PAH and Oxy-PAH from aqueous solutions. For this purpose, activated carbon (AC), polyurethane foam (PUF), quartz fiber (QF), high density polyethylene (PEHD), polytetrafluoroethylene Teflon (PTFE), Amberlite XAD-2 (XAD-2) and silica gel (Si), were evaluated as potential solid substrates, as well as its use as an alternative to XAD -2 for making personal samplers type lapel. Quinoline, 1-nitronaphthalene, Acridine, Phenazine, 2-nitrofluorene, 9-nitroanthracene and 1-nitropyrene were chosen as representatives of the class of compounds Nitro-PAHs. 2-naphthol, 2-hydroxyfluorene, Phenanthrene-9-carboxaldehyde, 9,10-anthraquinone, and 1-hydroxypyrene were chosen as representatives of the class of compounds Oxy-PAHs. The results were obtained by batch tests. For Nitro-PAHs, the adsorbents with the highest removal rates were: XAD-2 (100% removal on XAD-2, except for Quinoline - 80%) and activated carbon (around 90% for all reviews compounds). For Oxy-PAHs, the highest removal rates were provided by adsorbents: polyurethane foam and activated carbon, both with rates higher than 90% of removal. Due to the low solubility of the compounds, the presence of a co-solvent is required. The lowest temperature (20 ⁰C) favored the adsorption of the compounds. In general, both (Nitro-PAHs and Oxy-PAHs) classes have their removal influenced by increasing the concentration of the solute in solution.
Hidrocarbonetos policíclicos aromáticos nitrogenados e oxigenados (Nitro-HPAs e Oxi-HPAs) compõem a classe de compostos onde um heteroátomo de nitrogênio e oxigênio, respectivamente, esta presente na constituição do HPA. A inserção do heteroátomo acarreta numa maior mobilidade e aumento do potencial toxicológico. Neste trabalho foram investigados materiais adsorventes para a remoção de Nitro-HPAs e Oxi-HPAs a partir de soluções aquosas. Para isto, carvão ativado, espuma de poliuretano, fibra de quartzo, polietileno de alta densidade, politetrafluoretileno (teflon), Amberlite XAD-2 e sílica gel, foram avaliados como possíveis substratos sólidos. Quinolina, 1-nitronaftaleno, Acridina, Fenazina, 2-nitrofluoreno, 9-nitroantraceno e 1-nitropireno foram escolhidos como representantes à classe de compostos Nitro-HPAs. 2-naftol, 2-hidroxifluoreno, Fenantreno-9-carboxaldeído, 9,10-antraquinona e 1-hidroxipireno foram escolhidos como representantes à classe de compostos Oxi-HPAs. Os resultados foram obtidos através de ensaios em batelada. Para os Nitro-HPAs estudados, os adsorventes que apresentaram as maiores taxas de remoção foram: XAD-2 (100% de remoção em XAD-2, exceto pra Quinolina 80%) e carvão ativado (em torno de 90% para todos os compostos avaliados). Para os Oxi-HPAs estudados, as maiores taxas de remoção foram proporcionadas pelos adsorventes: espuma de poliuretano e carvão ativado, ambos com taxas de remoção superiores a 90%. Devido à baixa solubilidade dos compostos, a presença de um co-solvente se faz necessária. A temperatura mais baixa (20 ⁰C) favoreceu a adsorção dos compostos. De modo geral, ambas as classes (Nitro-HPAs e Oxi-HPAs) tem sua remoção influenciada pelo aumento da concentração do soluto em solução.

APA, Harvard, Vancouver, ISO, and other styles

13

Kuan, Fong Sheen, and mikewood@deakin edu au. "Organotin-Oxo Clusters." Deakin University. School of biological and chemical sciences, 2002. http://tux.lib.deakin.edu.au./adt-VDU/public/adt-VDU20051125.084244.

Full text

Abstract:

This thesis reports on the development and expansion of reliable synthetic di-and multi-tin precursors for the assembly of oligomeric organotin-oxo compounds in which the shape, dimension and tin nuclearity can be controlled. The reaction of polymeric diorganotin oxides, (R2SnO)m (R = Me, Et, n-Bu, n-Oct, c-Hex, i-Pr, Ph), with saturated aqueous NH4X solutions (X = F, Cl, Br, I, OAc) in refluxing 1,4-dioxane afforded in high yields dimeric tetraorganodistannoxanes, [R2(X)SnOSn(X)R2]2, and in a few cases diorganotin dihalides or diacetates, R2SnX2. This method appears to be particularly good for the synthesis of halogenated tetraorganodistannoxanes but a less suitable method for the preparation of dicarboxylato tetraorganodistannoxanes. Identification of [R2(OH)SnOSn(X)R2]2 (R = n-Bu; X = Cl, Br) and [R2(OH)SnOSn(X)R2][R2(X)SnOSn(X)R2] suggest a serial substitution mechanism starting from [R2(OH)SnOSn(OH)R2]2. A series of α, ω -bis(triphenylstannyl)alkanes, [Ph3Sn]2(CH2)n (n = 3-8, 10, 12) and some of their derivatives were synthesised and characterised. These α, ω-bis(triphenylstannyl)alkanes, [Ph3Sn]2(CH2)n were converted to the corresponding halides [R(Cl)2Sn]2(CH2)n (R = CH2SiMe3) and subsequently to the polymeric oxides {[R(0)Sn]2(CH2)n}m. Reaction of {[R(O)Sn]2(CH2)n}m with [R(Cl)2Sn]2(CH2)n. (n = 3, n' = 4 and n = 4, n' = 3) in toluene at 100°C results in a mixture of symmetric and asymmetric double ladders, where different spacer chain lengths (n and n') provide the source of asymmetry. The coexistence at high temperature of separate 119Sn NMR signals belonging to symmetric and asymmetric double ladders suggests an equilibrium that is slow on the 119Sn NMR time scale and the position of which is temperature dependent. However, 119Sn NMR spectroscopic experiments of {[R(0)Sn]2(CH2)3}m with [R(Cl)2Sn]2(CH2)n for longer spacers (n - 5, 6, 8, 10, 12) reveal that molecular self-assembly of symmetric spacer-bridged di-tin precursors of equal chain length is preferred over asymmetric species. An ether-bridged di-tin tetrachloride [R(Cl)2Sn(CH2)3]2O (R = CH2SiMe3) and its corresponding polymeric oxide {[R(O)Sn(CH2)3]2O}m were synthesised and characterised. Reaction of [R(Cl)2Sn(CH2)3]2O with {[R(O)Sn(CH2)3]2O}m results in a unique functionalised double ladder {{[RSn(Cl)](CH2)3O(CH2)3[RSn(Cl)]}O}4 whose structure in the solid state was determined by X-ray analysis. Identification of tetrameric functionalised double ladder as well as dimeric and monomeric species suggest the existence of an equilibrium in solution. The feasibility of the functionalised double ladder to form host-guest complexes with a variety of metal cations is investigated using electrospray mass spectrometry (ESMS). Evidence for such complexes is found only for sodium cations. The reaction between {[R(O)Sn]2(CH2)n}m (n = 3, 4, 8, 10) and triflic acid is described. The initial formed products [RSn(CH2)nSnR](OTf)4 are easily hydrolysed. For n = 3, self-assembly leads to a discrete double ladder type structure, {{[RSn(OH)](CH2)3[RSn(H2O)]}O}44OTf, which is the first example of a cationic double ladder. For n ≥ 3, hydrolysis gives polymeric products, as demonstrated by the crystal structure of {[(H2O)(OH)RSn]2(CH2)4-2OTf2H2O}m. Two spacer-bridged terra-tin octachlorides [R(Cl)2Sn(CH2)3Sn(Cl)2]2(CH2)n (R = CH2SiMes; n = 1, 8) and their corresponding polymeric oxides {[R(O)Sn(CH2)3Sn(O)]2(CH2)n}m were successfully synthesised and characterised. Attempts were made to synthesise quadruple ladders from these precursors. Reactions of [R(Cl)2Sn(CH2)3Sn(Cl)2]2CH2 with {[R(O)Sn(CH2)3Sn(O)]2CH2}m or (Y-Bu2SnO)3 result in, mostly insoluble, amorphous solids. Reactions of [R(Cl)2Sn(CH2)3Sn(Cl)2]2(CH2)8 with {[R(O)Sn(CH2)3Sn(O)]2(CH2)8}m or (t-Bu2SnO)s result in new tin-containing species which are presumably oligomeric. The synthesis of a series of alkyl-bridged di-tin hexacarboxylates [(RCO2)3Sn]2(CH2)n (n = 3, 4; R = Ph, c-C6H11, CH3, C1CH2) is also reported. The hydrolysis of these compounds is facile and complex. There appears to be no correlation between spacer chain length and hydrolysis product. However, the conjugate acid strength of the carboxylate does appear to be important. In general only insoluble amorphous polymeric organotin-oxo compounds were obtained.

APA, Harvard, Vancouver, ISO, and other styles

14

Werneck, Jessica Sanchez de Freitas [UNIFESP]. "Estudo da Similaridade Genética de Amostras de Acinetobacter baumannii Produtoras de Carbapenemases do Tipo OXA Isoladas em Diversos Hospitais Brasileiros." Universidade Federal de São Paulo (UNIFESP), 2010. http://repositorio.unifesp.br/handle/11600/9536.

Full text

Abstract:

Made available in DSpace on 2015-07-22T20:50:06Z (GMT). No. of bitstreams: 0 Previous issue date: 2010-09-29
Centro de Integração Empresa Escola (CIEE)
Conselho Nacional de Desenvolvimento Científico e Tecnológico (CNPq)
Fundação de Amparo à Pesquisa do Estado de São Paulo (FAPESP)
Fundação de Apoio e Desenvolvimento ao Ensino, Pesquisa e Extensão Universitária no Acre (FUNDAPE)
Nesta dissertação são apresentados dois estudos envolvendo isolados clínicos de Acinetobacter baumannii que apresentaram mecanismos enzimáticos de resistência aos carbapenêmicos, a produção de carbapenemases do tipo OXA. O primeiro estudo avalia a relação genética de amostras de A. baumannii multirresistentes produtoras de OXA-23 provenientes de distintas cidades brasileiras. 91 amostras clínicas de A. baumannii foram isoladas em 17 centros médicos localizados nas cidades de São Paulo (SP), Rio de Janeiro (RJ), Belo Horizonte (MG), Porto Alegre (RS), Blumenau (SC), Curitiba (PR), São Luiz (MA) e Salvador (BA). Nesta coleção observamos altas taxas de resistência aos carbapenêmicos (91.2%) e presença do gene blaOXA-23-like em 83,5% dos isolados. O elemento de insersão ISAba1 à montante ao gene blaOXA-23 foi detectado em todos os 76 isolados de A. baumannii produtores de OXA-23. Nove grupos de genótipos foram observados entre os 76 isolados produtores de OXA-23. Nossos achados sugerem que o gene blaOXA-23 presente nestes isolados estava localizado DNA cromossomal. Três principais grupos (A, B e D) foram observados circulando em seis cidades das regiões sudeste e sul do Brasil, sendo que o genótipo predominante (A) apresentou relação clonal àquele primeiramente descrito na cidade de Curitiba, em 2003. Em contrapartida foi encontrado um único genótipo de A. baumannii produtor de OXA-23 na cidade de São Luís. Embora existam estudos brasileiros prévios reportando a disseminação de clones de A. baumannii pordutores de OXA-23 localmente, nenhum estudo brasileiro demonstrou antes, i) a análise comparativa dos genótipos originários de diferentes e distantes cidades brasileiras, ii) a provável localização do gene blaOXA-23 e iii) a presença do elemento ISAba1 à montante ao gene blaOXA-23,o que pode ter levado ao alto grau de resistência aos carbapenens observado. Desta maneira, o estudo demonstra a circulação de clones de A. baumannii produtores de OXA-23 no Brasil e enfatiza que medidas de controle de infecção são urgentemente necessárias para reduzir tanto a disseminação de isolados multirresistenes quanto o número de infecções causadas por este patógeno. O segundo estudo trata de um relato de caso de um paciente internado em um hospital da cidade de São Paulo, que apresentou uma infecção por A. baumannii produtor de OXA-72. O isolado em questão, A 30235, apresentou resistência a todos os antimicrobianos testados, com excessão à ampicilina/sulbactam tendo apresentado redução da sensibilidade a esta associação. Foi realizada com sucesso a transformação do plasmídeo presente no isolado A30235 na cepa de A. baumannii ATCC 19606. A confirmação da presença do gene blaOXA-72 no transformante evidenciou a localização plasmidial deste determinante de resistência. O plasmídio contendo o gene blaOXA-72 apresentou um peso molecular de aproximadamente 86 Kb. Neste estudo identificamos pela primeira vez no Brasil, um isolado clínico de A. baumannii produtor de OXA-72. A presença deste determinante de resistência codificado por um gene localizado em um elemento genético móvel demonstra a crescente diversidade de carbapenemase do tipo OXA no Brasil com potencial de disseminação. Medidas de controles adequadas deverão ser tomadas para evitar a disseminação de isolados produtores de OXA-72 entre os hospitais brasileiros, o que tem ocorrido com os isolados de A. baumannii produtor de OXA-23.
In this dissertation we present two studies involving carbapenem-resistant Acinetobacter baumannii clinical isolates due to the production of carbapenems modifying enzymes, the OXA-type carbapenemases. The first study aimed to determine the genetic relationship of multi-drug-resistant A. baumannii producing OXA-23 that was isolated in distinct Brazilian cities. A total of 91 A. baumannii clinical isolates were recovered from 17 medical centers located at eight cities, namely São Paulo (SP), Rio de Janeiro (RJ), Belo Horizonte (MG), Porto Alegre (RS), Blumenau (SC), Curitiba (PR), São Luiz (MA) and Salvador (BA). In this collection we observed high rates of carbapenems resistance (91.2%). Also, the blaOXA- 23-like gene was present in 83.5% of isolates. The insertion sequence ISAba1 was positioned upstream the blaOXA-23 gene in all OXA-23-producing A. baumannii identified. Nine clusters were observed among OXA-23 producers. Our fidings suggest that the blaOXA-23 gene was probably chromosomally-located in all isolates studied. Three clusters (A, B and D) were found in six cities from southeast and southern reagions of Brazil. In addition, the predominant cluster (A) was clonally related to that first described in Curitiba, in2003. In contrast, a single cluster of A. baumannii producing OXA-23 was found in São Luís city. Although there were previous reports regarding the spread of OXA-23-producing A. baumannii in Brazil the following features had not yet been assessed: i) the comparative analysis of OXA-23 producers genotypes originating in distinct and distant Brazilian cities, ii) the genetic location of the blaOXA-23 gene and iii) the presence of ISAba1 upstream blaOXA-23 probably resulting in high degree of carbapenem resistance. Thus, our study demonstrates that the clonal dissemination of OXA-23- producing A. baumannii had occurred in Brazil. These findings emphasize that infection control measures are urgently needed to reduce both the spread of multidrug resistantstrains and the number of infections caused by this pathogen. The second study refers to a case report involving a hospitalized patient that presented an wound infection due to OXA-72-producing A. baumannii. The referred clinical isolate, A 30235, was resistant to most antibiotics tested and showed reduced susctptibility to ampicillin/sulbactam. Successful transformation assays using A. baumannii ATCC 19606 as the recipient strain revealed the plasmid location of the blaOXA-72 gene. This plasmid showed molecular weight of about 86 Kb. We identified for the first time in Brazil, an A. baumannii clinical isolate producing OXA-72. The presence of this resistance determinant encoded by a gene located in a mobile genetic elemet, points out to an increasing diversity of OXA-type carbapenemase in Brazil with potential spread. Appropriate control measures should be taken to prevent the spread of OXA-72 producers among Brazilian hospitals, which it we have experienced with OXA-23- producing-A. baumannii in this country.
TEDE
BV UNIFESP: Teses e dissertações

APA, Harvard, Vancouver, ISO, and other styles

15

Stern, Eric. "Nouveaux agonistes des récepteurs aux cannabinoïdes CB², dérivés de 4-oxo-quinoléines, 4-oxo-naphtyridines et 4-oxo-cinnolines." Lille 2, 2006. http://www.theses.fr/2006LIL2S013.

Full text

Abstract:

Le cancer, deuxième cause de mortalité et de morbidité dans les pays développés après les maladies cardio-vasculaires, résulte d'un dérèglement du programme génétique de la cellule conduisant à son immortalité et à une prolifération anarchique. En France en 2004, 40 000 nouveaux cas de cancer de la prostate ont été diagnostiqués. Le cancer de la prostate touche an général le sujet âgé et représente la deuxième cause de décès par cancer chez l'homme, après le cancer du poumon. Du fait du vieillissement de la population des pays développés, le nombre de patients atteints par le cancer de la prostate ne va cesser d'augmenter. Afin de palier les problèmes liés à l'utilisation des anticancéreux classiques (manque de sélectivité, résistance, échappement. . . ), le développement de nouvelles stratégies thérapeutiques pour traiter le cancer de la prostate s'avère indispensable. Depuis 1997, plusieurs états américains ont autorisé l'utilisation du Δ9-THC ( Δ9 – tétrahydrocannabinol, principe actif du cannabis) et de l'un de ses dérivés dans le contrôle des nausées et des vomissements engendrés par la chimiothérapie anticancéreuse. Actuellement plusieurs dérivés du Δ9-THC sont en phase III de tests cliniques pour le traitement des douleurs associées aux cancers. Depuis la caractérisation du Δ9-THC dans les années 60, de nombreux progrès ont été réalisés dans la compréhension de la pharmacologie des cannabinoïdes, notamment par la découverte, au début des années 90, de deux récepteurs couplés à des protéines G: le récepteur CB1, principalement localisé au niveau du système nerveux central (SNC), et le récepteur CB2, présent au niveau périphérique. L'étude de ces récepteurs, rendue possible par le développement de ligands de synthèse, a permis de mettre en évidence des effets anticancéreux (antiprolifératif, proapoptotique. . . ) liés à leur stimulation. Cependant la stimulation du récepteur CB1 pourrait être à l'origine d'effets secondaires du fait de sa localisation dans le SNC. Il serait dès lors intéressant d'étudier le potentiel anticancéreux de ligands sélectifs du récepteur CB2. Dans le cadre de nos recherches visant à élaborer de nouveaux ligands des récepteurs aux cannabinoïdes CB2, nous avons développé une chimiothèque de 98 composés autour d'un motif central hétérocyclique de type quinoléine, naphtyridine ou encore cinnoline substitué en position 3 par une fonction carboxamide. Lors des tests pharmacologiques, ces composés se sont révélés être des agonistes sélectifs du récepteur CB2. Différentes modulations structurales ont été envisagées, comme l'introduction de substituants en position 2, 5, 6, 7 et 8, le remplacement de la fonction carboxamide par son isomère rétroamide ou par une fonction cétone. La réduction en amine secondaire, ou encore le remplacement de la chaïne latérale hydrophobe par d'autres groupements plus hydrophiles ou aromatiques ont également été envisagés. Le potentiel antiprolifératif de ces ligands sélectifs du récepteur CB2 a ensuite été évalué sur différentes lignées cellulaires issues de cancers de la prostate
Cancer, second cause of mortality nad morbidity in the developed countries, just after cardiovascular diseases, results from a deregulation of the genetic cell program leading to its immortality and its uncontroled proliferation. In France in 2004, about 40,000 new cases of prostate cancer were diagnosed. Prostate cancer reaches in general old people and represents the second cause of death per cancer, after lung cancer. Because of the ageing of the population of developed countries, the number of prostate cancer patients will increase. In order to solve problems related to the use of traditional anti-cancer drugs (lack of selectivity, resistance. . . ), the development of new therapeutic strategies to treat prostate cancer proves to be essential. Since 1997, Δ9-THC ( Δ9 – tétrahydrocannabinol, the major psychoactive component of Cannabis sativa L. ) is currently used to treat nausea and emesis in cancer patient undergoing extensive chemotherapy. Moreover some cannabis-based drugs are in phase three clinical trials for treating pain associated with cancer. Since Δ9-THC characterization in the sixties, many improvements have been made in cannabinoid pharmacology knowledge, particularly, in the nineties with the discovery of two G-protein coupled receptors : the CB1 receptor, which is mainly located in the central nervous system (CNS), and the CB2 receptor which is principally present in the immune system. Thanks to the development of a great variety of new synthetic ligands, the study of these receptors has revealed the anticancer potency of the cannabinoid receptors agonists. CB1 receptor stimulation could induce undesirable effects due to its CNS localization, so we proposed to study the anticancer potency of CB2-selective agonists. In order to develop new potent CB2-selective ligands, a 98-compound library was built using a central heterocyclic ring as quinoleine, naphthyridine or cinnoline, substitued in position 3 by various carboxamido substituents, and hydrophobic side chains in the N1-position. Pharmacological results revealed a strong CB2 selectivity, and an agonist profile for all compounds. Thus, some chemical modulations were next realized as : replacement of the carboxamide link, in position 3, by inverse amide analogue or its reduction in secondary amine ; introduction of differentsubstituents on the position 2, 5, 6, 7 and 8 ; modulation of the N1-position side chain. Anticancer potency of these new potent CB2 receptor ligands was investigated using different prostate cancer cell lines

APA, Harvard, Vancouver, ISO, and other styles

16

Webb, Gordon A. "Radiopharmaceutical applications of technetium 3-oxy-4-pyrones and 3-oxy-4-pyridinones and gallium 3-oxy-4-pyridinones." Thesis, University of British Columbia, 1990. http://hdl.handle.net/2429/29206.

Full text

Abstract:

Ammonium pertechnetate [NH₄][TⅽO₄] was reacted with the following ligands via the reduction route: 3-hydroxy-2-methyl-4-pyrone (maltol), 5-hydroxy-2-hydroxymethyl-4-pyrone (kojic acid), 3-hydroxy-2-methyl-4-pyridinone (Hmpp), 3-hydroxy-l,2-dimethyl-4-pyridinone (Hdpp), 3-hydroxy-2-methyl-l-hexyl-4-pyridinone (Hmhpp), 3-hydroxy-2-methyl-l-undecanato-4-pyridinone (Hmupp), and β-[N-(3-hydroxy-4-pyridinone)]-α-aminopropionic acid (l-mimosine). The products from the reduction route were characterized by mass spectrometry, infrared spectrometry, ultraviolet spectroscopy, and conductivity‧measurements. Initial results indicate the formation of mono-cationic tris-ligand complexes of tin and technetium ([TcL₃]⁺and [SnL₃]⁺). The formation of Tc (V) complexes via a substitution route was also investigated. [Bu₄N][TcOCl₄] was reacted with: 3-hydroxy-2-methyl-4-pyrone (maltol), 5-hydroxy-2-hydroxymethyl-4-pyrone (kojic acid), and β-[N-(3-hydroxy-4-pyridinone)]-α-aminopropionic acid (l-mimosine). The 3-hydroxy-4-pyridinone used in this study (except mimosine) were prepared by the conversion of an oxygen heterocycle, 3-hydroxy-2-methyl-4-pyrone, to the corresponding nitrogen heterocycle by reaction with a primary amine. These potentially bidentate ligands contain an α-hydroxyketone moiety and their conjugate bases form mono-cationic tris-ligand technetium complexes. Hmupp, a new compound, was fully characterized by mass spectrometry, infrared spectrometry, proton NMR, ultraviolet spectroscopy, and elemental analysis. Initial clearance studies were done in a rabbit with the products of the reactions of [⁹⁹(formula omitted)TcO₄]- with Hdpp and Mimosine. Analogous to the synthetic procedure above using [⁹⁹Tc0₄]-, two products are formed ([⁹⁹(formula omitted)TcL3]⁺ and [SnL₃]⁺). The [SnL₃]⁺ complex is not radioactive and is therefore not visualized by the imaging procedure. The observed distribution is therefore that of the [⁹⁹(formula omitted)TcL₃]⁺ complex. The results of the clearance study with [⁹⁹(formula omitted)Tc(dpp)₃]⁺ show a small amount of liver, heart, and gall bladder uptake; however, the majority of the activity is rapidly excreted via the kidneys and bladder. There is also some gut uptake observed, and this is cleared much more slowly. The clearance study conducted with [⁹⁹(formula omitted)Tc(mimo)₃]⁺ shows results similar to those conducted with [⁹⁹(formula omitted)Tc(dpp)₃]⁺; however, less gut uptake and faster bladder clearance are observed with the mimosine complex. In addition to the technetium radiopharmaceutical work, some gallium-67 work was also done. This was done in collaboration with William Nelson and Don Lyster to complete an ongoing study of the in vitro and in vivo coordination chemistry of gallium 3-oxy-4-pyridinones as a model for the biodistribution of aluminum. ⁶⁷Ga-biodistribution studies were conducted with the following 3-hydroxy-4-pyridinone ligands: 3-hydroxy-2-methyl-4-pyridinone (Hrnpp), 3-hydroxy-l,2-dimethyl-4-pyridinone (Hdpp), 3-hydroxy-2-methyl-l-hexyl-4-pyridinone (Hmhpp), and β-[N-(3-hydroxy-4-pyridinone)]-α-aminopropionic acid (l-mimosine). The results of the biodistribution show that under conditions of excess ligand ⁶⁷Ga is redirected from transferrin; however, the ⁶⁷Ga-ligand complexes do not localize in any organs.
Science, Faculty of
Chemistry, Department of
Graduate

APA, Harvard, Vancouver, ISO, and other styles

17

Chesnaud, Anthony. "Oxy-gallates et oxy-germanates de terres rares conducteurs par ions oxygène." Nantes, 2005. http://www.theses.fr/2005NANT2047.

Full text

Abstract:

De nouveaux conducteurs anioniques dérivés de Nd4Ga2O9, Nd4GeO8 et Nd3GaO6, ont été obtenus par substitutions cationiques. Les oxy-Cuspidine Nd4[Ga2(1-x)M2xO7+xٱ1-x]O2 (M=Ge,Ti) ont été préparées par diverses techniques. Avec la substitution, la structure Cuspidine est maintenue jusqu'à x=0,5 et 1,0 pour M=Ge et Ti respectivement. Dans les deux cas, une modulation 1D de la structure est observée pour x  0,15 mais l'effet du substituant sur la conductivité anionique est différent : Ti joue un rôle assez neutre alors que Ge l'améliore. De nouveaux composés ont aussi été préparés par substitution de Ge4+ par Ga3+ dans Nd4GeO8, de Ga3+ par Zn2+, Mg2+, et de Nd3+ par Ca2+, Sr2+ dans Nd3GaO6. Une technique d'auto-combustion a été développée pour synthétiser ces matériaux à 900°C. Il est possible de créer 10% de lacunes d'oxygène dans Nd4GeO8 et moins de 1% dans Nd3GaO6. Cependant, ces taux de substitution relativement faibles induisent une nette augmentation de la conductivité.

APA, Harvard, Vancouver, ISO, and other styles

18

Blättermann, Stefanie [Verfasser]. "Functional characterization of the 5-oxo-ETE receptor OXE-R and identification of the first small molecule antagonist with a novel mechanism of ligand bias / Stefanie Blättermann." Bonn : Universitäts- und Landesbibliothek Bonn, 2011. http://d-nb.info/104484700X/34.

Full text

APA, Harvard, Vancouver, ISO, and other styles

19

Schumacher, Rüdiger. "Reaktivität m-oxo-m-acetato-verbrückter [my-oxo-my-acetato-verbrückter] Eisen- und Mangankomplexe." [S.l. : s.n.], 2001. http://deposit.ddb.de/cgi-bin/dokserv?idn=962378852.

Full text

APA, Harvard, Vancouver, ISO, and other styles

20

Barbieri-Arhancet, Graciela I. "New oxy-dihydrofuran annulation methodology." Diss., This resource online, 1990. http://scholar.lib.vt.edu/theses/available/etd-09162005-115038/.

Full text

APA, Harvard, Vancouver, ISO, and other styles

21

Ledger, Joanne Rachel. "Polycationic and oxo-functionalized cyclophosphazenes." Thesis, University of Liverpool, 2009. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.533993.

Full text

APA, Harvard, Vancouver, ISO, and other styles

22

Mehner, Alexander. "Zwillingspolymerisation von Titan-oxo-Verbindungen." Doctoral thesis, Universitätsbibliothek Chemnitz, 2017. http://nbn-resolving.de/urn:nbn:de:bsz:ch1-qucosa-222231.

Full text

Abstract:

In der vorliegenden Arbeit werden die Synthese und die Charakterisierung neuer Titan-oxo-Monomere beschrieben. Ein weiterer Teil beschäftigt sich mit dem kationischen Polymerisationsverhalten dieser Verbindungen, welche dem Typ der „Zwillingspolymerisationen“ zugeordnet werden kann. Die Charakterisierung der dabei entstehenden nanostrukturierten Hybridmaterialien aus Titandioxid und organischen Polymeren wird beschrieben. Als Vergleich dienen Simultanpolymerisationen von Titanalkoxiden und polymerisierbaren organischen Alkoholen.

APA, Harvard, Vancouver, ISO, and other styles

23

Gauvreau, Danny. "Enantioselective tandem oxy-copeene reaction." Thesis, University of Ottawa (Canada), 2003. http://hdl.handle.net/10393/26374.

Full text

Abstract:

The tandem oxy-Cope/ene reaction allows the rapid construction of complex structures in a few steps. It was notably used in the total synthesis of (+)-arteannium M where the cascade revealed to be highly diastereoselective and enantioselective. The hypothesis that the retention of chirality based on the rigidity of an intermediate atropisomer devoid of stereogenic centers was proposed. This document presents a study of the enantioselectivity of the tandem oxy-Cope/ene reaction and provides an explanation for the decrease in chirality observed during the cascade. Different variables of the reaction and of the starting material were analyzed to explain the retention of chirality.* The efforts of our group in the development of tandem reactions led to the discovery of a novel cascade that involves 4 pericyclic reactions: the oxa-Cope/Claisen/ene/Claisen cascade. This sequence of reactions was briefly investigated to determine its scope and limitations, notably by changing the substituent on the alkyne and on the tertiary alcohol of 150*. *Please refer to dissertation for diagrams.

APA, Harvard, Vancouver, ISO, and other styles

24

Potron, Anaïs. "Résistance aux carbapénèmes médiée par les carbapénèmases de type OXA-48 chez les entérobactéries." Thesis, Paris 11, 2013. http://www.theses.fr/2013PA114850.

Full text

Abstract:

Les carbapénèmes constituent le traitement de dernier recours des infections associées à des germes multirésistants producteurs de -lactamases à spectre étendu. Les entérobactéries ont cependant développé des mécanismes de résistance à l’encontre de cette classe d’antibiotiques, notamment par la production de carbapénèmases. La carbapénèmase OXA-48 a rapidement disséminé en Europe et dans le pays du pourtour méditerranéen depuis 2010. Les objectifs de ce travail ont englobé, dans une première partie, la caractérisation de trois variants de la carbapénèmase OXA-48, possédant chacun des particularités phénotypiques ou génétiques. Nous nous sommes ensuite intéressés à l’épidémiologie de la carbapénèmase OXA-48 afin de comprendre ses mécanismes de dissémination puis à la variabilité de son environnement génétique. Le dernier objectif était de déterminer les facteurs génétiques à l’origine de la dissémination de la carbapénèmase OXA-48. Nous avons ainsi montré que les carbapénèmases de type OXA-48 bénéficient de tous les éléments moléculaires pour assurer leur succès : mobilisation par un transposon actif pour certains variants, transfert efficace de plasmides et dissémination clonale de souches
Carbapenems are often the last therapeutic option for treating infections involving multiresistant ESBL-producing bacteria. Nevertheless, enterobacteria have developped resistance mechanisms toward this class of antibiotics, including carbapenemases production. Carbapenemase OXA-48 has rapidly spread throughout Europe and various countries of Mediterranean area since 2010. The aim of this work was first to characterize three variants of the carbapenemase OXA-48, each possessing phenotypic or genetic characteristics. We focused on the epidemiology of carbapenemase OXA-48 in order to understand the mechanisms of its dissemination and on the variability of its genetic environment. The last objective was to determine the genetic factors responsible for the spread of carbapenemase OXA-48. We have shown that the OXA-48-type carbapenemases possess all the molecular elements to ensure its success: mobilization by an active transposon for some variants, efficient transfer of plasmids and clonal spread of strains

APA, Harvard, Vancouver, ISO, and other styles

25

Szuromi, Endre. "Alkene-oxo and alkene-alkene coupling on Pt(II)." Diss., Columbia, Mo. : University of Missouri-Columbia, 2005. http://hdl.handle.net/10355/4156.

Full text

Abstract:

Thesis (Ph. D.)--University of Missouri-Columbia, 2005.
The entire dissertation/thesis text is included in the research.pdf file; the official abstract appears in the short.pdf file (which also appears in the research.pdf); a non-technical general description, or public abstract, appears in the public.pdf file. Title from title screen of research.pdf file viewed on (November 14, 2006) Vita. Includes bibliographical references.

APA, Harvard, Vancouver, ISO, and other styles

26

Clausen, Christian. "Dianionische Oxy-Cope-Umlagerungen durch die Addition von Vinyl-Metall-Reagenzien an 1,2-Diketone." [S.l. : s.n.], 1998. http://deposit.ddb.de/cgi-bin/dokserv?idn=95482346X.

Full text

APA, Harvard, Vancouver, ISO, and other styles

27

黃國賢 and Kwok-yin Wong. "Syntheses, reactivities and electrochemical studies of some high valent oxo complexes of ruthenium." Thesis, The University of Hong Kong (Pokfulam, Hong Kong), 1986. http://hub.hku.hk/bib/B31230763.

Full text

APA, Harvard, Vancouver, ISO, and other styles

28

Wong, Kwok-yin. "Syntheses, reactivities and electrochemical studies of some high valent oxo complexes of ruthenium /." [Hong Kong : University of Hong Kong], 1986. http://sunzi.lib.hku.hk/hkuto/record.jsp?B12322623.

Full text

APA, Harvard, Vancouver, ISO, and other styles

29

Lupart, Saskia. "Syntheses of multinary Lithium (Oxo)nitridosilicates." Diss., lmu, 2012. http://nbn-resolving.de/urn:nbn:de:bvb:19-147249.

Full text

APA, Harvard, Vancouver, ISO, and other styles

30

Ekholm, Marie. "OX1 Orexin Receptor Signalling to Phospholipases." Doctoral thesis, Uppsala universitet, Fysiologi, 2010. http://urn.kb.se/resolve?urn=urn:nbn:se:uu:diva-111138.

Full text

Abstract:

The neuropeptides orexin-A and orexin-B were discovered in 1998 and were first described as regulators of feeding behaviour. Later research has shown that they have an important role in the regulation of sleep. Two G protein-coupled receptors, OX1 and OX2 orexin receptors, mediate the cellular responses to orexins. The overall aim of this thesis was to investigate the OX1 orexin receptors signalling to phospholipases. Previous investigations have determined that orexin receptors induce Ca2+ elevations through both receptor-operated Ca2+ channels (ROCs) and store-operated Ca2+ channels (SOCs). In this thesis we investigated the importance of these influxpathways on orexin-mediated phospholipase (PLC) activation. The results demonstrate that ROC influx is enough to fully support orexin-stimulated PLC activation but that SOC influx has a further amplifying role. We also investigated the metabolites generated after PLC activation, inositolphosphates and diacylglycerol (DAG). The results indicate involvement of two different PLC activities with different substrate specificities one of them leading to DAG production without co-occurring IP3 production at low orexin receptor stimulation. The results also suggest that at even lower orexin receptor stimulation DAG is produced via the activation of phospholipase D. In this thesis we also investigated if the ubiquitous phospholipase A2 (PLA2) signalling system is involved in orexin receptor signalling. The results demonstrate that stimulation of the OX1 orexin receptors leads to arachidonic acid (AA) release. This release is fully dependent on Ca2+ influx, probably through ROC, and at the same time the studies demonstrate that ROC influx is partly dependent on PLA2 activation. At low orexin receptor activation the AA release seemed to in part rely on extracellular signal-regulated kinase. We also devised two methods to aid in these investigations. The first method enabled studies of the receptor-operated Ca2+ influx without interference of the co-occurring store-operated Ca2+ influx. This was done by the expression of IP3-metabolising enzymes IP3-3-kinase-A and IP3-5-phosphatase-I. The second method enables quantification of DAG and IP3 signalling in fixed cells using GFP-fused indicators, leading to a semi-quantitative but easily applicable pharmacological assay.

APA, Harvard, Vancouver, ISO, and other styles

31

Šušnjar, Nevena. "Towards rhodium and iridium oxo complexes." [S.l.] : [s.n.], 2006. http://deposit.ddb.de/cgi-bin/dokserv?idn=979943604.

Full text

APA, Harvard, Vancouver, ISO, and other styles

32

Morris, Susan. "Oxo species of zirconium and yttrium." Thesis, University of Reading, 1994. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.240334.

Full text

APA, Harvard, Vancouver, ISO, and other styles

33

Günyar, Alev Topaloğlu Sözüer Işıl. "Oxo-Imido molybdenum tripyrazolyl borate complexes/." [s.l.]: [s.n.], 2004. http://library.iyte.edu.tr/tezler/master/kimya/T000464.pdf.

Full text

APA, Harvard, Vancouver, ISO, and other styles

34

Weiss, Vitor Correa. "Complexos de vanádio(IV) não oxo." reponame:Repositório Institucional da UFSC, 2012. http://repositorio.ufsc.br/xmlui/handle/123456789/93103.

Full text

Abstract:

Dissertação (mestrado) - Universidade Federal de Santa Catarina, Centro de Ciências Físicas e Matemáticas, Programa de Pós-Graduação em Química, Florianópolis, 2009.
Made available in DSpace on 2012-10-24T16:40:44Z (GMT). No. of bitstreams: 1 273349.pdf: 901411 bytes, checksum: b664df92fc9cf4e20e2e9976ba78a192 (MD5)
A existência de diferentes estados de oxidação é uma característica importante na química dos metais de transição. O potencial de oxirredução de um complexo metálico não depende somente da natureza do íon metálico. A presença de um ligante complexado ao metal altera a densidade eletrônica sobre os centros metálicos e a estabilidade dos mesmos, afetando os potenciais de oxirredução dos íons metálicos. Neste sentido, apresenta-se neste trabalho a síntese e caracterização de quatro novos ligantes H4btben-Br, H4btben-NO2, H4btben e H4btben-CH3, que diferem exclusivamente na presença dos grupos substituintes Br, NO2, H e CH3 nas posições para aos grupos fenolatos, e seus respectivos complexos de vanádio(IV) não-oxo, com o objetivo de estudar a variação no potencial redox do metal devido a presença desses substituintes. Os complexos foram caracterizados pelas técnicas de espectroscopia no infravermelho, UV-Vis e Ressonância Paramagnética Eletrônica (EPR). Os complexos [V(btben-NO2] e [V(btben)] também foram caracterizados através de suas estruturas cristalinas por difração de raios X. Para estudar a influência no potencial redox do íon metálico pelos quatro grupos substituintes Br, NO2, H e CH3, foram realizados estudos eletroquímicos dos complexos através do método de voltametria cíclica a diferentes velocidades de varredura e seus potenciais correlacionados com os parâmetros de Hammett dos respectivos substituintes, onde se observou uma correlação linear, demonstrando uma influência direta dos grupos nos potenciais redox desses complexos.

APA, Harvard, Vancouver, ISO, and other styles

35

Spiegl, Nicolas. "Oxy-fuel gasification in fluidised beds." Thesis, Imperial College London, 2010. http://hdl.handle.net/10044/1/7028.

Full text

Abstract:

Rising energy demand, up coming shortage of natural gas and oil and increasing awareness of the effect of global warming are the driving forces behind the development of new, highly efficient processes with integrated carbon capture and storage, using fuels with predicted long term availability. Gasification and especially fluidised bed gasification is seen as a promising near zero emissions route to utilise low value coal, waste and biomass for energy production via the integrated gasification combined cycle process (IGCC). The integration of a carbon capture and storage (CCS) technology into the design of IGCC plants changes the design framework for the gasification process as a pure stream of CO2 at the downstream end of the plant is now available. Therefore a novel oxy-fuel fluidised bed gasification process is proposed in which the gasifier is operated as part of an IGCC plant with pure O2 and recycled CO2. Steam is used to enhance the carbon conversion if necessary. A laboratory scale fluidised bed gasifier capable to operate up to 1000°C and 20 bar was used to study the implications of oxy-fuel firing on flue gas composition and operability of the gasifier. Maintaining a constant feed rate (1 - 6 g/min) a stable fuel gas composition was obtained for up to 30 min. Using a lignite as feedstock, carbon conversions higher than 95% and a fuel gas with a medium heating value were obtained under oxy-fuel conditions. With the addition of steam, the operating temperature could be reduced from 950°C to 850°C while maintaining the gasification performance. The decrease in carbon conversion with increasing pressure was investigated using experimental data from a wire mesh rector and optical char surface analysis. Strategies to optimize the gasification performance were developed for atmospheric and pressurised operations. Besides the lignite, two bituminous coals and different mixtures of biomass and lignite were tested for their use in an oxy-fuel fluidised bed gasifier. Analysis of the tar, H2S and NH3 content of the fuel gas provided information about the influence of operation conditions on the emissions of pollutants. The results show that oxy-fuel firing of a fluidised bed gasifier could be a promising route to avoid N2 dilution of the fuel gas and reduce the costs of integrating CCS technology. In order to assist further research, the results obtained in this study are used to derive design recommendations for large scale testing facilities.

APA, Harvard, Vancouver, ISO, and other styles

36

Fant, Bruno. "Importance du contexte cellulaire et de la régulation spatio-temporelle de l'expression du facteur de transcription Otx2 dans la modulation de ses fonctions." Thesis, Nice, 2014. http://www.theses.fr/2014NICE4100/document.

Full text

Abstract:

Cette thèse s’intéresse aux mécanismes permettant d’expliquer plusieurs des fonctions de l’homéogène Otx2 au cours du développement. Une première partie étudie l’importance de la régulation de son expression dans la régionalisation du système nerveux central. A la fin de la gastrulation la frontière d’expression postérieure d’Otx2 déterminera la position de l’organiseur isthmique responsable de l’induction du mésencéphale et du métencéphale. Un modèle murin a été mis au point dans lequel cette frontière est abolie au profit d’une présence uniforme du gène. A l’encontre du modèle actuel, l’isthme est alors correctement induit, et est de plus déplacé antérieurement, signe qu’un seuil net de concentration d’Otx2 est nécessaire à sa fonction régionalisante. Une seconde partie étudie l’importance du contexte cellulaire dans les modalités d’action d’Otx2 au niveau de la rétine adulte. Otx2 est exprimé dans les deux tissus qui composent cet organe, la neurorétine et le RPE. Une étude par ChIP-seq dans ces deux tissus a pu montrer que l’homéogène y occupait des sites de fixation très différents, suggérant des fonctions distinctes. L’écrasante majorité des sites occupés par Otx2 dans la neurorétine l’était également par son paralogue Crx, indice d’une redondance fonctionnelle. Une nouvelle lignée de souris a permis l’analyse des partenaires protéiques d’Otx2 dans la neurorétine, et pu démontrer qu’Otx2 ne formait pas d’interactions avec les autres facteurs de ce tissu, faisant en fait de Crx l’acteur principal de la famille Otx. Cette analyse a également dévoilé une série de partenaires jusque-là inconnus d’Otx2, potentiellement associée à de nouvelles fonctions de la protéine
The molecular mechanisms explaining several functions of the homeogene Otx2 during embryonic development are the focus of this work. In a first part the importance of the regulation of its expression in the regionalisation of the central nervous system is studied. At the end of gastrulation the posterior border of Otx2 expression will position the isthmic organizer responsible for the induction of the midbrain and hindbrain. A mouse model was developed where this border is replaced by an ubiquitous expression of the gene. Contrary to the predictions of the current model, the organizer then correctly arises, and is shifted anteriorly. A concentration threshold of Otx2 thus appears necessary to its regionalising function. In a second part the importance of the cellular context in Otx2 function in the adult retina is examined. Otx2 is expressed in both tissues of this organ, the neural retina and RPE. A ChIP-seq analysis performed on both tissues revealed that this homeogene occupies very different sets of binding sites, which suggests distinct functions of the transcription factor. Most Otx2-bound sites in the neural retina were also bound by its paralogue Crx, with which a functional redundancy may therefore exist. A new mouse line finally allowed the study of the complete Otx2 interactome in the neural retina; this analysis showed that Otx2 does not interact with other important transcription factors of this tissue, and that Crx may therefore be the main actor of the Otx family in neural retina function. It also led to the discovery of a series of previously unknown partners of Otx2, which could be associated to new functions of this homeogene

APA, Harvard, Vancouver, ISO, and other styles

37

Marvilliers, Sandrine. "Synthèses, caractérisations et études du comportement en oxydation de complexes dinucléaires fer-oxo et manganèse-oxo d'intérêt biologique." Paris 11, 1999. http://www.theses.fr/1999PA112302.

Full text

Abstract:

Dans la première partie de ce manuscrit, je résume l'étude que j'ai réalisée sur des complexes dinucléaires du fer, modèles structuraux voire fonctionnels du site actif de la méthane monooxygénase. Le chapitre 1 traite des connaissances biochimiques actuelles sur cette enzyme. Dans le chapitre 2 sont étudiés deux complexes dinucléaires du Fe(III) synthétisés avec le ligand tétradente azote bis(MeIm)Me₂en: [L(H₂O)Fe(μ-O)Fe(H₂O)L]⁴⁺ et [L(H₂O)Fe(μ-O)Fe(OH)L]³⁺. Dans le chapitre 3 est présentée la structure du complexe [L(H₂O)Fe(μ-O)Fe(OH)L]³⁺ (L = bispic(Me)₂en; ligand tétradente azoté). En milieu anhydre, ce compose perd spontanément la molécule d'eau ligandant un des deux Fe(III) et le ligand hydroxyde se réarrange en second pont. L’ajout d'eau sur [LFe(μ-O)( μ-OH)FeL]³⁺ permet de réobtenir le composé initial avec une constante d'équilibre de 5,4 M⁻¹. C'est la première fois qu'un tel équilibre est mis en évidence. Le chapitre 4 est consacré à l'étude d'un complexe dinucléaire du fer et de deux précurseurs mononucléaires synthétisés avec un ligand hydrophobe, également tétradente azoté (LBzl₂). Le complexe LFe(μ-O)( μ-OH)FeL]³⁺a été isolé et caractérisé. Dans la deuxième partie, j'expose les résultats de mon étude concernant des complexes dinucléaires du fer et du manganèse, possédant des ligands contenant un groupement phénolate. Nous voulions comparer les propriétés redox de ces complexes à celles de systèmes biologiques analogues : le site actif de la ribonucléotide réductase et le centre de dégagement du dioxygène des plantes. Le chapitre 5 dresse un bilan des connaissances actuelles sur ces deux métalloprotéines. Le chapitre 6 concerne l'étude de deux complexes dinucléaires du fer, synthétisés avec deux ligands pentacoordinants (LaH et LbH, coordination de type N₄O). On a pu montrer que l'oxydation de ces entités conduit à la formation d'un radical phénoxyle qui reste lié à l'entité dinucléaire. Dans le chapitre 7, les deux produits d'oxydation du complexe de manganèse [Lb’Mn(III)(μ-O)Mn(III)Lb’] ²⁺, où Lb’H est la base de Schiff du ligand LbH précédent, ont été étudiés. Le premier est lié à l'oxydation d'un des ions Mn(III). De récentes études (EXAFS, XANES) ont montré que la seconde oxydation concernait le deuxième Mn(III), en formant le premier complexe dinucléaire de Mn(IV) de ce genre. Un intermédiaire possédant un radical phénoxyle a pu être détecté lors de cette seconde oxydation.

APA, Harvard, Vancouver, ISO, and other styles

38

Leedham, Angela Priscilla. "Imido analogues of main group oxo-anions." Thesis, University of Bristol, 2002. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.247865.

Full text

APA, Harvard, Vancouver, ISO, and other styles

39

Kassim, Mohammad B. "Studies of nitrosyl and oxo molybdenum complexes." Thesis, University of Bristol, 2003. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.274612.

Full text

APA, Harvard, Vancouver, ISO, and other styles

40

Green, G. "Transition metal oxo-complexes as organic oxidants." Thesis, Imperial College London, 1985. http://hdl.handle.net/10044/1/37711.

Full text

APA, Harvard, Vancouver, ISO, and other styles

41

Torero, Ibad Raoul. "Otx2 et neuroprotection de la rétine adulte." Paris 6, 2013. http://www.theses.fr/2013PA066203.

Full text

Abstract:

Le facteur de transcription Otx2, homéoprotéine de la famille bicoïd, est exprimé dans la rétine de souris adultes. L’ARNm d’Otx2 est détecté dans les photorécepteurs et les cellules bipolaires. En plus de ces cellules, la protéine Otx2 est également présente dans les cellules ganglionnaires rétiniennes (CGR) où l'ARNm n'est pas détecté. Les résultats récents ont montré que les CGR peuvent internaliser de la protéine Otx2 exogène, soulignant le fait que la protéine Otx2 observée dans les CGR est transférée à partir des cellules bipolaires. De même, l’homéoprotéine Engrailed peut être internalisée par les neurones dopaminergiques et la protéine peut stimuler la survie de ces cellules in vivo et in vitro. Nous montrons ici qu’Otx2 est un facteur de survie pour des neurones adultes. La première partie de cette thèse analyse la structure et la fonction de la rétine chez des souris transgéniques hypomorphes Otx2. Ainsi, on a pu mettre en évidence que l'expression à l'âge adulte de cette protéine est nécessaire pour le maintien de populations neuronales de la rétine. En particulier, une neurodégénérescence des cellules bipolaires et des cônes a été mise en évidence. Cette mort des cellules dépend de la quantité d'Otx2 exprimée. Dans la deuxième partie, nous montrons qu’Otx2 stimule la survie des cellules ganglionnaires rétiniennes adultes dans des modèles de mort cellulaire in vitro et in vivo. Pour cela, nous utilisons des modèles de mise en culture de neurones rétiniens adultes où la protéine recombinante Otx2 augmente significativement la survie des CGR. Cette neuroprotection est aussi démontrée in vivo dans un modèle d’excitotoxicité par injection de NMDA. Enfin, en utilisant un test optocinétique d’acuité visuelle sur souris éveillée, nous démontrons qu’Otx2 protège contre la perte de l'acuité visuelle causée par le NMDA. Enfin, dans la troisième partie, nous montrons qu'en addition d'un effet neuroprotecteur, Otx2 peut stimuler la régénération axonale des CGR adultes in vitro sur des substrats de cultures permissifs et non permissifs. De plus, cette promotion de la régénération est aussi démontrée in vivo dans un modèle d'écrasement du nerf optique chez la souris adulte
The transcription factor Otx2, homeoprotein of the bicoid family is expressed in the retina of adult mice. Otx2 mRNA is detected in photoreceoptors and bipolar cells. In addition to these cells, Otx2 protein is also found in retinal ganglion cells (RGCs) where the mRNA is not detected. Recent results showed that RGCs can take up exogenous Otx2 and thus it is possible that the Otx2 observed in RGCs was transferred from bipolar cells. The Engrailed homeoprotein can be taken up by dopaminergic neurons and can stimulate the survival of these cells both in vivo and in vitro. We demonstrate here that Otx2 is a survival factor for adult neurons. The first part of this report analyses retina structure and function in hypomorphic transgenic Otx2 mice. We show that Otx2 expression during adulthood is necessary for the maintenance of neural populations in the retina. We emphazyse the neurodegeneration of bipolar cells and cone cells related to Otx2 level expression. In the second part, we demonstrate that Otx2 protein stimulates the survival of adult ganglion retinal cells in vitro and in vivo in stressed conditions. We show that recombinant Otx2 protein added to adult RGCs cultures significantly increases survival of the cells. This neuroprotection is also demonstratred in vivo in a model of excitotoxicity by intraocular injection of NMDA. Finally, using the optomotor test of visual acuity in awake behaving mice, we demonstrate that Otx2 protects against the loss of visual acuity caused by NMDA. Finally, in the third part, we show that, in addition to neuroprotective properties, Otx2 stimulates axon regeneration from adult RGC in vitro on permissive and non-permissive substrates. This axon regeneration promoting activity by Otx2 is also demonstrated in vivo in an optic nerve crush model in adult mice

APA, Harvard, Vancouver, ISO, and other styles

42

Burchfield, Nicole Ashley. "Narrow Angle Radiometer for Oxy-Coal Combustion." BYU ScholarsArchive, 2020. https://scholarsarchive.byu.edu/etd/8423.

Full text

Abstract:

A new method of power production, called pressurized oxy-fuel combustion, burns coal with CO2 and oxygen, rather than air, bringing us closer to the end goal of developing zero emission coal-fired utility boilers. However, high-pressure, high-temperature systems such as these are under-studied, and their behavior is difficult to measure. An accurate model for previously untested conditions requires data for validation. The heat release profile of flames and their radiative intensity is one of the key data sets required for model validation of an oxy-coal combustion system. A radiometer can be used to obtain the necessary radiative heat flux data. However, several studies show significant measurement errors of past radiometer designs. This work focuses on developing a narrow angle radiometer that can be used to describe radiative heat transfer from a pressurized oxy-coal flame. The sensitivity of the instrument to outside environmental influences is thoroughly examined, making it possible to obtain the axial radiative heat flux profile of the flame in a 100kW pressurized facility by accurately converting the measured quantities into radiative heat flux. Design aspects of the radiometer are chosen to improve the accuracy of radiative heat flux measurements as well as conform to the physical constraints of the 100kW pressurized facility. The radiometer is built with a 0.079-inch aperture, an 8.63-inch probe internally coated with high emissivity coating, four baffles spaced evenly down the length of the probe, no optic lens, a thermopile as the sensor, argon purge gas, and a water-cooled jacket. The radiometer has a viewing angle of 1.33 degrees. The instrument is calibrated with a black body radiator, and these calibration data are used in combination with radiation models to convert the radiometer signal in mV to radiative heat flux in kW/m2. Environmental factors affecting accuracy are studied. The results of the calibration data show that the radiometer measurements will produce a calculated heat flux that is accurate to within 5.98E-04 kW/m2.

APA, Harvard, Vancouver, ISO, and other styles

43

Treuil-Dussouet, Félix. "Photoconductivity in rare earth metal-oxy-hydrides." Thesis, Uppsala universitet, Materialteori, 2020. http://urn.kb.se/resolve?urn=urn:nbn:se:uu:diva-416695.

Full text

Abstract:

In this project the evolution of resistivity under light exposition in materials like rare earth metal-oxy-hydrides is studied. These materials observe a decrease of the resistance when exposed under the light of a 19,5 W power lamp, and slowly tend to return to their initial resistance. After having developed a resistance measurement setup, the photoconductivity of different samples (Gd, YHO) was measured in function of the oxygen concentration and in different conditions such as the face of illumination.

APA, Harvard, Vancouver, ISO, and other styles

44

錢國輝 and Kwok-fai Chin. "Syntheses, electrochemistry and photophysical and photochemical properties of some high-valent oxo, nitrido and amido complexes ofosmium." Thesis, The University of Hong Kong (Pokfulam, Hong Kong), 1995. http://hub.hku.hk/bib/B31234756.

Full text

APA, Harvard, Vancouver, ISO, and other styles

45

Chin, Kwok-fai. "Syntheses, electrochemistry and photophysical and photochemical properties of some high-valent oxo, nitrido and amido complexes of osmium /." Hong Kong : University of Hong Kong, 1995. http://sunzi.lib.hku.hk/hkuto/record.jsp?B17506128.

Full text

APA, Harvard, Vancouver, ISO, and other styles

46

Blondin, Geneviève. "Interaction d'echange, delocalisation electronique et couplage vibronique dans des complexes fer-soufre, fer-oxo et manganese-oxo d'interet biologique." Paris 11, 1992. http://www.theses.fr/1992PA112015.

Full text

Abstract:

Ce travail comporte trois parties: la premiere partie est consacree a l'interaction d'echange. Tout d'abord au sein de complexes homo et heterodinucleaires comportant le motif m(-o)(-ch#3co#2)#2m#2#+ ou m et m sont des ions trivalents de metaux de la premiere serie des elements de transition (cr, mn, fe). Ensuite, un schema de couplage pour le cluster tetranucleaire manganese-oxo catalysant au sein du photosysteme ii l'oxydation de l'eau en dioxygene, est propose. Ce modele permet d'expliquer le signal r. P. E. Multiligne observe dans l'etat s#2 et converge avec les donnees e. X. A. F. S. La deuxieme partie montre qu'au sein des systemes a valence mixte, delocalisation electronique et interaction d'echange sont intimement liees: couplage antiferromagnetique et transfert electronique sont antagonistes. Les concepts de double echange et d'echange-transfert sont detailles. Dans la troisieme partie, le role des vibrations dans les complexes a valence mixte est etudie. Dans la limite d'un fort couplage vibronique, l'hamiltonien d'heisenberg reste applicable. Un modele est propose pour interpreter les phenomenes de localisation-delocalisation dans les clusters fer-soufre fe#2s#2#1#+ et fe#3s#4#0

APA, Harvard, Vancouver, ISO, and other styles

47

Lima, Francisco das Chagas Alves. "Estudo teórico de propriedades químicas de sistemas hetero-macrocíclos que complexam metais de transição divalentes da primeira e segunda filas." Universidade de São Paulo, 2008. http://www.teses.usp.br/teses/disponiveis/75/75131/tde-23062008-155103/.

Full text

Abstract:

Um estudo teórico detalhado das estruturas e energias do ligante 1, 7, 11, 17-tetraoxa-2, 6, 12, 16-trazaocicloocsano ([20]aneN4O4) coordenado com íons metálicos de transição Fe2+, Co2+, Ni2+, Ru2+, Rh2+ e Pd2+ foi realizado em nível de teoria B3LYP/Lanl2DZ. As geometrias dos complexos foram totalmente otimizados em simetria Cs com os íons metálicos coordenados com quatro átomos de nitrogênio (complexos 1a e 1aq) ou quatro átomos de oxigênios (complexos 1b e 1bq) e duas moléculas de água. Os arranjos octaédricos (1a e 1b) e quadrado-planares (1aq e 1bq) foram consideremos neste trabalho. A estrutura teórica está em excelente acordo com a estrutura de difração de raio-x experimental determinada para o complexo octaédrico de Ni2+ de [20]AneN4O4. Os cátions M2+ ligam-se preferencialmente aos átomos de nitrogênios com energia de ligação que aumenta na ordem Fe2+ < Ru2+ < Co2+ < Ni2+ < Rh2+ < Pd2+. Para os metais de transição da primeira fila, os complexos de spin alto são mais estáveis que os complexos de spin baixo. Em contraste, para os metais de transição da segunda fila, os estados de spin baixo mostraram-se mais estáveis que os estados de spin alto. As ligações metal-ligante nos complexos foram analisadas em termo das interações covalentes e iônicas e ajudaram a entender porque os complexos (1a e 1aq) são mais estáveis que os complexos (1b e 1bq). Os complexos poliaminas [20]aneN4 e poliéteres [20]aneO4 foram obtidos substituindo os átomos de nitrogênio e oxigênio da posição alfa dos macrociclos [20]aneN4O4 e [20]aneO4N4, respectivamente. O macrociclo [20]aneO4 tem preferência em complexar íons metálicos da primeira fila, enquanto o macrociclo [20]aneN4 prefere complexar os íons metálicos da segunda fila.
A detailed theoretical study of structures and energies of the 1,7,1l,17-tetraoxa-2,6,12,16-tetraaza-cycloeicosane ligand ([20]AneN4O4) coordinated to Fe2+, Co2+, Ni2+, Ru2+, Rh2+ and Pd2+ transition metals ions was carried out with the B3LYP/Lanl2DZ method. The geometries of the complexes were fully optimized in Cs symmetry with the metal ions coordinated either to four atoms nitrogen (complexes 1a e 1b) or to the four atoms oxygen (complexes 1aq e 1bq). The octahedral and square planar arrangements were considered in this work. The theoretical structure is in excellent agreement with the experimental X-ray diffraction structure determination for the [20]AneN4O4 octahedral Ni2+ complex. The M2+ cations bind preferentially to the nitrogen atoms with binding energies that increase in the order Fe2+ < Ru2+ < Co2+ < Ni2+ < Rh2+ < Pd2+. For the first-row transition metals, the highspin complexes are more stable than the low-spin complexes. In contrast, for the second-row of transition metals, the low-spin states were found more stable than the high spin states. The metal-ligand bonds in the complexes were analyzed in terms of the covalent and ionic interactions and helped to understand why complexes (1a e 1aq) are more stable than complexes (1b e 1bq). The polyamines [20]aneN4 and polyethers [20]aneO4 complexes were obtained substituting the atoms N or O of the alfa position of the macrocycles [20]aneN4O4 and [20]aneO4N4, respectively. The macrocycle [20]aneO4 prefers to complex first-row transition metals; however, the macrocycle [20]aneN4 prefers to complex second-row transition metals.

APA, Harvard, Vancouver, ISO, and other styles

48

MacLean, Peter Ross. "Applications of a hydroxy-directed Diels-Alder reaction and further investigation of the tandem oxy-CopeEne, and oxy-CopeEneClaisen reactions." Thesis, University of Ottawa (Canada), 2003. http://hdl.handle.net/10393/26418.

Full text

Abstract:

The recent development of a hydroxy-directed Diels-Alder reaction, which enables control of both regio- and diastereoselectivity, has prompted an investigation of potential applications. Extending the methodology to more complicated dienes, such as those created via the tandem oxy-Cope/Ene reaction, offers the potential for rapid construction of polycyclic molecules with significant stereochemical complexity.* The simplicity and efficiency of this technique has also inspired its employment as the primary disconnection in the production of a library of analogues of the unsaturated dialdehyde Isovelleral.* Also examined herein is the recently discovered tandem oxy-Cope/Ene/Claisen reaction; a highly diastereoselective method for generating trans -decalin systems containing quaternary carbon centers. Showing potential as a tool in diterpene synthesis, the scope and limitations of this reaction were further investigated by attempting the synthesis of a rosane derivative 97, recently isolated from the liverwort Gackstroemia decipiens .* *Please refer to dissertation for diagrams.

APA, Harvard, Vancouver, ISO, and other styles

49

Berger, Erik. "Heterometallic Oxo-Alkoxides of Europium, Titanium and Potassium." Licentiate thesis, Uppsala University, Inorganic Chemistry, 2010. http://urn.kb.se/resolve?urn=urn:nbn:se:uu:diva-121653.

Full text

Abstract:

Coordination compounds of europium and titanium with oxide, ethoxide (OCH₂CH₃), iso-propoxide (OCH(CH₃)₂) and tert-butoxide (OC(CH₃)₃) ligands have been studied. These belong to the general class of oxo-alkoxides, M_xO_y(OR)_z, with alkoxide ligands (OR) containing an organic, aliphatic part R. The R group can be systematically varied, permitting the investigation of the influence of electronic and steric effects on the coordination of metal and oxygen atoms. Their tendency towards hydrolysis and formation of metal-oxygen-metal bridges also makes (oxo)alkoxides interesting as precursors in liquid solution-based or gas phase-based synthesis of many technologically important materials.

The structure of a termetallic oxo-alkoxide of formula Eu₃K₃TiO₂(OH/OCH₃)(OR)₁₁(HOR) (R = C(CH₃)₃) was revealed by a combination of single-crystal X-ray diffraction and IR spectroscopy. Its unusual structure features a facial oxygen-centered Eu₃K₃O octahedron sharing one face with an oxygen-centered K₃TiO tetrahedron. Six-coordination of oxygen by a combination of alkali metal and lanthanoid atoms is not uncommon for alkoxides, but the attachment of a tetrahedron to one of its faces provides a new dimension to the library of oxo-alkoxide structures. The structure was the result of incomplete metathesis in the synthesis attempt of europium-titanium oxo-tert-butoxides.

Eu₄TiO(OR)₁₄ and (Eu_0.5La_0.5)₄TiO(OR)₁₄ (R = CH(CH₃)₂) were found to be isostructural with previously published Ln₄TiO(OR)₁₄ structures (Ln=Sm, Tb_0.9Er_0.1). X-ray diffraction and UV-Vis absorption results show no site preference for La in either the solid state or hexane solution. The Ln₄TiO(OR)₁₄ structure forms part of an interesting group of Ln₄MO(OR)_10+z(HOR)_q structures where M is another lanthanoid (Ln) or a di-, tri- or tetravalent heteroatom, giving either a square pyramidal or a trigonal bipyramid-like coordination of the central oxygen atom, depending on the chemistry and size of M.

Eu₂Ti₄O₂(OR)₁₈(HOR)₂ (R = CH₂CH₃) was deduced from IR data to have the same molecular structure as Er₂Ti₄O₂(OR)₁₈(HOR)₂. UV-Vis measurements are also in agreement with the presence of one symmetry-unique europium site in the molecular structure. Structure determination by single-crystal X-ray diffraction has yet to be performed.

Coordination compounds of europium and titanium with oxide, ethoxide (OCH2CH3), isopropoxide(OCH(CH3)2) and tert-butoxide (OC(CH3)3) ligands have been studied. Thesebelong to the general class of oxo-alkoxides, MxOy(OR)z, with alkoxide ligands (OR)containing an organic, aliphatic part R. The R group can be systematically varied, permittingthe investigation of the influence of electronic and steric effects on the coordination of metaland oxygen atoms. Their tendency towards hydrolysis and formation of metal-oxygen-metalbridges also makes (oxo)alkoxides interesting as precursors in liquid solution-based or gasphase-based synthesis of many technologically important materials.The structure of a termetallic oxo-alkoxide of formula Eu3K3TiO2(OH/OCH3)(OR)11(HOR)(R = C(CH3)3) was revealed by a combination of single-crystal X-ray diffraction and IRspectroscopy. Its unusual structure features a facial oxygen-centered Eu3K3O octahedronsharing one face with an oxygen-centered K3TiO tetrahedron. Six-coordination of oxygen bya combination of alkali metal and lanthanoid atoms is not uncommon for alkoxides, but theattachment of a tetrahedron to one of its faces provides a new dimension to the library of oxoalkoxidestructures. The structure was the result of incomplete metathesis in the synthesisattempt of europium-titanium oxo-tert-butoxides.Eu4TiO(OR)14 and (Eu0.5La0.5)4TiO(OR)14 (R = CH(CH3)2) were found to be isostructuralwith previously published Ln4TiO(OR)14 structures (Ln=Sm, Tb0.9Er0.1). X-ray diffraction andUV-Vis absorption results show no site preference for La in either the solid state or hexanesolution. The Ln4TiO(OR)14 structure forms part of an interesting group of Ln4MO(OR)10+z-(HOR)q structures where M is another lanthanoid (Ln) or a di-, tri- or tetravalent heteroatom,giving either a square pyramidal or a trigonal bipyramid-like coordination of the centraloxygen atom, depending on the chemistry and size of M.Eu2Ti4O2(OR)18(HOR)2 (R = CH2CH3) was deduced from IR data to have the samemolecular structure as Er2Ti4O2(OR)18(HOR)2. UV-Vis measurements are also in agreementwith the presence of one symmetry-unique europium site in the molecular structure. Structuredetermination by single-crystal X-ray diffraction has yet to be performed.

APA, Harvard, Vancouver, ISO, and other styles

50

Hu, Yukun. "CO2 capture from oxy-fuel combustion power plants." Licentiate thesis, KTH, Energiprocesser, 2011. http://urn.kb.se/resolve?urn=urn:nbn:se:kth:diva-48666.

Full text

Abstract:

To mitigate the global greenhouse gases (GHGs) emissions, carbon dioxide (CO2) capture and storage (CCS) has the potential to play a significant role for reaching mitigation target. Oxy-fuel combustion is a promising technology for CO2 capture in power plants. Advantages compared to CCS with the conventional combustion technology are: high combustion efficiency, flue gas volume reduction, low fuel consumption, near zero CO2 emission, and less nitrogen oxides (NOx) formation can be reached simultaneously by using the oxy-fuel combustion technology. However, knowledge gaps relating to large scale coal based and natural gas based power plants with CO2 capture still exist, such as combustors and boilers operating at higher temperatures and design of CO2 turbines and compressors. To apply the oxy-fuel combustion technology on power plants, much work is focused on the fundamental and feasibility study regarding combustion characterization, process and system analysis, and economic evaluation etc. Further studies from system perspective point of view are highlighted, such as the impact of operating conditions on system performance and on advanced cycle integrated with oxy-fuel combustion for CO2 capture. In this thesis, the characterization for flue gas recycle (FGR) was theoretically derived based on mass balance of combustion reactions, and system modeling was conducted by using a process simulator, Aspen Plus. Important parameters such as FGR rate and ratio, flue gas composition, and electrical efficiency etc. were analyzed and discussed based on different operational conditions. An advanced evaporative gas turbine (EvGT) cycle with oxy-fuel combustion for CO2 capture was also studied. Based on economic indicators such as specific investment cost (SIC), cost of electricity (COE), and cost of CO2avoidance (COA), economic performance was evaluated and compared among various system configurations. The system configurations include an EvGT cycle power plant without CO2 capture, an EvGT cycle power plant with chemical absorption for CO2 capture, and a combined cycle power plant. The study shows that FGR ratio is of importance, which has impact not only on heat transfer but also on mass transfer in the oxy-coal combustion process. Significant reduction in the amount of flue gas can be achieved due to the flue gas recycling, particularly for the system with more prior upstream recycle options. Although the recycle options have almost no effect on FGR ratio, flue gas flow rate, and system electrical efficiency, FGR options have significant effects on flue gas compositions, especially the concentrations of CO2 and H2O, and heat exchanger duties. In addition, oxygen purity and water/gas ratio, respectively, have an optimum value for an EvGT cycle power plant with oxy-fuel combustion. Oxygen purity of 97 mol% and water/gas ratio of 0.133 can be considered as the optimum values for the studied system. For optional operating conditions of flue gas recycling, the exhaust gas recycled after condensing (dry recycle) results in about 5 percentage points higher electrical efficiency and about 45 % more cooling water consumption comparing with the exhaust gas recycled before condensing (wet recycle). The direct costs of EvGT cycle with oxy-fuel combustion are a little higher than the direct costs of EvGT cycle with chemical absorption. However, as plant size is larger than 60 MW, even though the EvGT cycle with oxy-fuel combustion has a higher COE than the EvGT cycle with chemical absorption, the EvGT cycle with oxy-fuel combustion has a lower COA. Further, compared with others studies of natural gas combined cycle (NGCC), the EvGT system has a lower COE and COA than the NGCC system no matter which CO2 capture technology is integrated.
QC 20111123

APA, Harvard, Vancouver, ISO, and other styles

Dissertations / Theses on the topic 'OX2'

Create a spot-on reference in APA, MLA, Chicago, Harvard, and other styles