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  • About
  • The Global ETD Search service is a free service for researchers to find electronic theses and dissertations. This service is provided by the Networked Digital Library of Theses and Dissertations.
    Our metadata is collected from universities around the world. If you manage a university/consortium/country archive and want to be added, details can be found on the NDLTD website.
51

Genetic Modifiers of Cystic Fibrosis Pulmonary Disease

Darrah, Rebecca J. 06 July 2010 (has links)
No description available.
52

DEVELOPMENT AND EVALUATION OF EXTENDED-RELEASE BUMETANIDE TABLETS

TILLOTSON, JOHN KING 02 July 2004 (has links)
No description available.
53

Applications of modifiers in supercritical fluid extraction and chromatograph

Mulcahey, Leah J. 28 July 2008 (has links)
The use of modifiers in supercritical fluid chromatography and extraction has become quite common due to the inability of pure carbon dioxide alone to solvate many of the compounds of interest. The effects of modifiers in supercritical fluid chromatography have been more thoroughly studied than the effects of modifier in supercritical fluid extraction. The effects of modifier on trapping efficiencies for off-line supercritical fluid extraction have been evaluated in this work. Sorbent and solid phase traps were investigated with pure carbon dioxide in order to determine the effect of stationary phase identity, pretreatment, and rinse solvent on the recoveries of a test mixture of compounds of varying vapor pressure and molecular weight. The solid phase traps, which were polyethylene frits, performed as well as the sorbent traps in most cases, and significantly better than the sorbent traps in many cases. The ability to cool these traps to -20°C allowed for efficient trapping of volatile compounds without the benefit of sorptive interactions. Sorbent and solid phase traps were then studied with the addition of 1%, 2%, 4%, and 8% methanol to the mobile phase. The sorbent trap explored consisted of 40 µm ODS packing material, while the solid phase trap consisted of 100 yum stainless steel beads. In this work trap temperatures ranged from 5-80°C. It was found that trap temperature, modifier concentration, and trap type influenced recoveries of the test mixture components. Applications of these solid phase and sorbent traps explored were the extraction of polychlorinated biphenyls from river sediment and the extraction of the active components from a drug formulation. The separation of some compounds of pharmaceutical interest was also explored, where the addition of modifier, and in some cases an additive, was required to elute compounds from the chromatographic column. / Ph. D.
54

Pluronic® block-copolymers in medicine: from chemical and biological versatility to rationalisation and clinical advances

Pitto-Barry, Anaïs, Barry, Nicolas P.E. 24 March 2014 (has links)
Yes / This mini-review highlights the latest advances in the chemistry and biology of Pluronic® triblock copolymers. We focus on their applications in medicine, as drug delivery carriers, biological response modifiers, and pharmaceutical ingredients. Examples of drug delivery systems and formulations currently in clinical use, clinical trials or preclinical development are highlighted. We also discuss the role that Pluronic® copolymers may play in the innovative design of new nanomedicines in the near future. / We thank the Leverhulme Trust (Early Career Fellowship no. ECF-2013-414 to NPEB), the University of Warwick (Grant no. RDF 2013-14 to NPEB) and EPSRC (EP/G004897/1 to APB) for support.
55

The role of renin-angiotensin-aldosterone system (RAAS) genes in the development of hypertrophy in hypertrophic cardiomyopathy (HCM)

Carstens, N. 03 1900 (has links)
Thesis (MScMedSc (Biomedical Sciences. Molecular Biology and Human Genetics))--University of Stellenbosch, 2009. / Hypertrophic cardiomyopathy (HCM), an inherited primary cardiac disorder mostly caused by defective sarcomeric proteins, is considered a model for studying left ventricular hypertrophy (LVH) in the absence of increased external loading conditions. The disease manifests extreme variability in the degree and pattern of LVH, even in HCM patients with the same causal mutation. The clinical phenotype of HCM can therefore be viewed as a product of the effect of sarcomere dysfunction and of additional genetic modifiers. Components of the renin-angiotensin-aldosterone system (RAAS) are plausible candidate modifiers because of their effect on blood pressure and their direct hypertrophic effect on cardiomyocytes. The present study investigated genes encoding components of the RAAS for association with cardiac hypertrophy traits, in 353 individuals comprised of genetically and echocardiographically affected and unaffected family members, belonging to 22 HCM families with HCM founder mutations by employing a multi-SNP approach with TaqMan allelic discrimination technology. Gene-gene interaction analysis was also performed to investigate the effect of epistasis on hypertrophy. Candidate genes for analysis included the angiotensin II type 2 receptor (AT2 receptor), renin, renin-binding protein (RnBP), the (pro)renin receptor, the mineralocorticoid receptor as well as genes encoding subunits of the epithelial sodium channels (ENaC) and Na+/K+-ATPase that showed evidence for cardiac expression. The present study demonstrates for the first time that variations in the renin and RnBP genes play a role in modulating hypertrophy in HCM, independent of blood pressure and confirms the involvement of the AT2 receptor in hypertrophy in HCM. Additionally we report an association between Na+/K+-ATPase α1- and β1-subunits as well as the ENaC α- and β-subunits and hypertrophy. Significant evidence for epistasis was found between renin and downstream RAAS effectors, suggesting a complex interplay between these RAAS variants and the hypertrophic phenotype in HCM. The identification of such modifiers for HCM may offer novel targets for hypertrophy research and ultimately antihypertrophic therapy.
56

Escalas no Guarani Paraguaio: uma análise do modificador de grau -pa / Scales in Paraguayan Guarani: an analysis of degree modifier - pa

Frutos, Lara 05 December 2011 (has links)
Este trabalho apresenta uma análise semântica dos verbos e adjetivos do Guarani Paraguaio baseada nos pressupostos da Semântica Formal. Mais especificamente, este trabalho se propõe a analisar a interação de verbos e adjetivos com um morfema de grau da língua, a partícula . São analisados neste trabalho adjetivos, verbos e construções causativas com verbos deadjetivais a partir de suas possíveis leituras com o morfema . Demonstra-se aqui que o morfema funciona como um modificador da relação de predicação entre o adjetivo ou o evento e um argumento nominal. Essa relação está dada em termos de uma estrutura de graus, de acordo com a semântica escalar proposta por Kennedy (1999b) e Kennedy & McNally (2005). Essas teorias partem do pressuposto de que adjetivos mapeiam entidades em graus de estruturas abstratas de uma propriedade, as escalas, e por isso adjetivo contém uma variável de grau d em sua entrada lexical. Essa variável é quantificada através de um morfema de grau. Proponho aqui que além do modificador que satura a variável de grau dada no seu léxico, o adjetivo também pode receber um modificador de grau quando houver uma escala de quantidade, dada composicionalmente de acordo com o modelo de Bochnak (2010). Nesse sentido, não atuaria sobre a variável de grau dada pelo léxico do adjetivo, mas sobre uma escala de quantidade construída na sintaxe. Em relação a verbos, modificaria a relação de mapeamento do evento sobre entidades, medido por uma estrutura de graus. Uma das vantagens desta proposta é que isso permitiria que adjetivos fossem modificados simultaneamente por e outros modificadores de grau que atuam sobre a escala de intensidade de adjetivos, o que de fato ocorre na língua. Para sustentar minha hipótese de análise, apresento alguns dados do Guarani Paraguaio em que o morfema co-ocorre com outros intensificadores de grau. Em relação aos verbos deadjetivais, mostrarei que estes não possuem uma leitura atélica como os verbos deadjetivais do Inglês e do Português Brasileiro. Isso serve de evidência para concluir que não modifica a escala de propriedade dada pelo adjetivo formador do verbo, mas que atua no mapeamento do evento na estrutura de graus dada por seu argumento nominal. Em suma, este trabalho mostra que opera sempre sobre escalas de quantidade e nunca sobre a variável de grau do léxico de verbos e adjetivos. / This dissertation presents a semantic analysis of verbs and adjectives Paraguayan Guarani based on the assumptions of Formal Semantics. More precisely, this study aims to analyze the interaction of verbs and adjectives with the particle , a degree morpheme of the language studied here. In this dissertation, I analyze adjectives, verbs and causative constructions with deadjectival verbs and the possible readings of the modification of towards these predicates. It is shown here that the morpheme acts as a modifier of the relationship between the adjective or the event and a nominal argument. This relation is described in terms of a degree structure, according to the semantic of scales proposed by Kennedy (1999b) and Kennedy & McNally (2005). This theory is based on the assumption that adjectives map entities onto degrees of abstract structures of properties - the scales and, for this, adjectives have a degree argument in their lexical entry. The degree variable is saturated by a degree morpheme. I propose here that besides the modifier that saturates the degree variable of the lexicon, the adjective can also be modified by another degree modifier that operates on a quantity scale, which is compositionally given, according to Bochnak (2010). In this sense, does not saturate the degree variable given by the lexicon of the adjective or the verb, but it applies to a quantity scale that is built in syntax. Regarding verbs, modifies the mapping of the event onto entities, which is measured by a degree structure. One of the advantages of this account is that it allows that and other degree intensifiers modify adjectives simultaneously. And it actually happens in Guaraní. In order to support my analysis, I present some data of Paraguayan Guaraní that illustrate how combines to other degree modifiers. I also show that deadjectival verbs cannot have an atelic reading similar to Brazilian Portuguese and English deadjectival verbs. This is used as an evidence to point out that does not modify the property scale of the verb introduced by the adjective, but it only acts on the mapping of the event onto the degree structure of its nominal argument. In conclusion, this work shows that always operates on quantity scales and never on the degree variable of the lexicon of verbs and adjectives.
57

Avaliação do efeito de moduladores epigenéticos na biossíntese de produtos naturais em fungos / Evaluation of the effect of epigenetic modifiers in the biosynthesis of fungal natural products.

Almeida, Marília Oliveira de 02 July 2014 (has links)
A manipulação seletiva de alvos epigenéticos usando pequenas moléculas inibidoras das enzimas histona-desacetilases (HDACs) e DNA metiltransferases (DNMTs) é uma estratégia para estimular a expressão das vias biossintéticas e a produção de novos metabólitos secundários em fungos. Neste trabalho, inibidores de histonadesacetilases (butirato de sódio, ácido hidroxâmico suberoilanilida e ácido valproico) e inibidores de DNA metiltransferases (5-azacitidina, hidralazina, procaína e procainamida) foram suplementados em culturas líquidas e sólidas dos fungos endofíticos Fusarium oxysporum SS46, Hyphodermella corrugata FLe8.2 e Chaetomium globosum VR10, das linhagens comerciais Fusarium oxysporum ATCC MYA 4623 e Chaetomium globosum ATCC 56726 e do fitopatógeno Botrytis cinerea B0510. O fungo endofítico H. corrugata FLe8.2, em meio PDB, produziu o composto 2-(2-metoxifenil)-4H-piran-4-ona, e sua cultura em meio Czapek suplementada com hidralazina levou ao isolamento de 3-metil-1,2,4-triazolo[3,4-a]-ftalazina. O tratamento de F. oxysporum SS46 e F. oxysporum ATCC MYA 4623 com hidralazina em meio Czapek levou ao isolamento de um novo composto, 2H-[1,2,4]triazino[3,4- a]-ftalazina. Nestas culturas houve biotransformação da hidralazina pelos fungos, provavelmente como mecanismo de desintoxicação. Ainda, a hidralazina teve um efeito inibidor sobre a biossíntese do ciclohexadepsipeptídeo beauvericina em F. oxysporum SS46. Nas culturas de C. globosum VR10 em meio Czapek os inibidores de HDACs e de DNMTs suprimiram a biossíntese de chaetoglobosinas. A adição de ácido valproico na cultura de C. globosum VR10 em meio PDB eliciou a produção da chaetoviridina B. A adição de 5-azacitidina nas culturas de C. globosum VR10 em meio sólido PDA não modificou a produção da chaetoglosina A. A produção de chaetoviridina B por C. globosum ATCC 56726 em meio PDA foi inibida na menor concentração de 5-azacitidina, 50 ?M, e retomada na concentração de 150 ?M. O tratamento de B. cinerea B0510 com ácido hidroxâmico suberoilanilida SAHA levou à biossíntese de um novo composto, ácido 5-benzil-2,3-di-hidroxi-3-isopropil-4- oxotetrahidrofuran-2-carboxílico, o qual também foi isolado da linhagem geneticamente modificada B. cinerea Bc ?STC2. No geral, considerando as linhagens fúngicas estudadas, os resultados mostram que a adição de moduladores químicos que atuam em mecanismos epigenéticos promove mudanças no perfil de metabólitos secundários. / The selective manipulation of epigenetic targets using small molecule inhibitors of histone deacetylase (HDAC) and DNA methyltransferase (DNMT) activities is a strategy to elicit the expression of biosynthetic pathways and production of new secondary metabolites in fungi. In this work, HDAC inhibitors (sodium butyrate, suberohydroxamic acid and valproic acid) and DNMT inhibitors (5-azacitidine, hydralazine, procaine and procainamide) were supplemented in liquid and solid cultures of the endophytic fungi Fusarium oxysporum SS46, Hyphodermella corrugata FLe8.2 and Chaetomium globosum VR10, of the commercial fungal strains Fusarium oxysporum ATCC MYA 4623 and Chaetomium globosum ATCC 56726 and of the phytopathogenic fungus Botrytis cinerea B0510. The endophytic fungus H. corrugata FLe8.2 produced 2-(2-methoxyphenyl)-4H-pyran-4-one in PDB medium, while in the presence of hydralazine in Czapek medium the fungus produced 3- methyl-1,2,4-triazolo[3,4-a]-phthalazine. Treatment of F. oxysporum SS46 and F. oxysporum ATCC MYA 4623 with hydralazine in a Czapek medium led to the isolation of new compound, 2H-[1,2,4]triazino[3,4-a]-phthalazine. Hydralazine was biotransformed by these three fungi probably as a detoxification strategy. In addition, hydralazine also inhibited the biosynthesis of the cyclodepsipeptide beauvericin by F. oxysporum SS46. HDAC and DNMT inhibitors suppressed chaetoglobosins\' biosynthesis by C. globosum VR10 cultures in Czapek medium. The biosynthesis of chaetoviridin B by C. globosum VR10 was elicited by acid valproic in PDB medium. The production of chaetogosin A by C. globosum VR10 in PDA medium has not been affected by 5-azacitidine. The biosynthesis of chaetoviridin B by C. globosum ATCC 56726 in PDA medium was inhibited in the presence of lower concentration 5- azacitidine (50 ?M) and recovered in the higher concentration (150 ?M). Treatment of B. cinerea B0510 with suberohydroxamic acid led to the biosynthesis of the new compound 5-benzyl-2,3-dihydroxy-3-isopropyl-4-oxotetrahydrofuran-2-carboxylic acid, which was also isolated from the genetically modified strain B. cinerea Bc ?STC2. Results showed that chemical compounds that act in epigenetic mechanisms can induce changes in the secondary metabolite profiles in the fungal strains studied in this work.
58

Efeito da suplementação de cultura de leveduras vivas (Saccharomyces cerevisiae 1026), de monensina e da combinação de monensina e levedura sobre o desempenho e características de carcaça de novilhos Nelore confinados com dietas de alto concentrado / Effects of the supplementation of live yeast (Saccharomyces cerevisiae1026), monensin and both additives on the performance and carcass characteristics of Nellore steers in feedlot

Gomes, Rodrigo da Costa 25 January 2006 (has links)
Preocupações recentes a respeito da resistência de microrganismos a antimicrobianos têm aumentado o interesse por estudos de novos aditivos alimentares para ruminantes, alternativos ao uso dos ionóforos. Assim, objetivou-se com este trabalho avaliar o efeito da suplementação da cultura viva de levedura (Saccharomyces cerevisiae, cepa 1026, 5 x 106 ufc/g, Beef-Sacc®, Alltech, Inc.) e da monensina (Rumensin®, 10% de monensina sódica, Elanco, Inc.) e da combinação dos dois aditivos, sobre as características de desempenho e carcaça de novilhos Nelore confinados. Foram utilizados 72 novilhos da raça Nelore, com peso vivo inicial de 339,5 kg e 20 meses de idade, submetidos a um dos quatro tratamentos: dieta controle (sem aditivos), dieta com levedura (0,6g de Beef Sacc®/kg de matéria seca), dieta com monensina (0,3g de Rumensin®/kg de matéria seca) e dietas com monensina e levedura. Os animais foram alimentados com uma ração contendo bagaço de cana in natura (21%), casca de soja (29%), milho grão moído grosso (39%), farelo de soja (7%) e uréia (1%), por um período médio de 84 dias. Medições individuais de consumo de alimentos foram possibilitadas pelo uso de baias individuais e sistemas de Calan Gates. O pH das carcaças foi medido a 1 e 24 horas após o abate. A meia carcaça esquerda foi dividida em músculos, ossos e aparas para a determinação da porcentagem de porção comestível. A área de olho de lombo e a espessura de gordura subcutânea foram medidas no músculo Longissimus dorsi na região entre as 12ª e 13ª costelas. Bifes daquele músculo foram tirados e maturados por 0, 7 ou 14 dias para mensurações de força de cisalhamento e perdas totais por cozimento. Os tratamentos não influenciaram o ganho de peso, consumo de alimentos ou conversão alimentar dos animais. A suplementação com levedura aumentou o rendimento de carcaça, porém não houve efeitos importantes sobre outras características de carcaça e percentagem de porção comestível. A qualidade da carne também não foi influenciada pelos aditivos. Os aditivos estudados não apresentaram efeitos significativos nas características de desempenho e carcaça de novilhos Nelore alimentados com dietas de alto concentrado em confinamento. / A recent concern about anti-microbial resistance by microorganisms has increased the interest for studies of new feed additives for ruminants, alternatively to ionophores utilization. In this way, It was aimed with this work to evaluate the effects of live yeast culture (Saccharomyces cerevisiae, strain 1026, 5 x 106 cfu/g, Beef Sacc®, Alltech, Inc.), monensin (Rumensin, 10% of sodium monensin, Elanco®, Inc.) and the combination of both additives, on the performance and carcass traits of Nellore steers fed a high concentrate diet in feedlot. Seventy-two animals, with 330 kg of live weight and 20 months of age were allotted to one of four treatments: control (no additives), diet with yeast (0,6g of Beef Sacc®/ kg of dry matter), diet with monensin (0,3g of Rumensin®/ kg of dry matter) and diet with yeast and monensin. Animals were fed ration with sugarcane bagass (21%), soybean hulls (29%), corn ground (39%), soybean meal (7%) and urea (1%), for an 84-day period. Individual feed intake measurements were possible through individual pens and Calan Gates system. Carcass pH was measured at 1 and 24 hours after slaughter. Left half-carcass was split in muscle, bone and fat for retail cuts percentage determination. Rib eye area and subcutaneous fat thickness were measured on Longissimus dorsi muscle in the region between 12th and 13th ribs. Steakes of Longissimus dorsi muscle were taken and aged 0, 7 and 14 days to shear force and cooking total losses measurements. Treatments didn\'t affect weight gain, feed intake or feed efficiency. Yeast increased carcass dressing percentage, but there weren\'t important effects of additives on other carcass traits and on retail cuts percentage. Meat quality wasn\'t influenced by additives. Additives studied showed no significant effects on the performance and carcass traits of Nellore steers fed high concentrate diets in feedlot.
59

Avaliação do efeito de moduladores epigenéticos na biossíntese de produtos naturais em fungos / Evaluation of the effect of epigenetic modifiers in the biosynthesis of fungal natural products.

Marília Oliveira de Almeida 02 July 2014 (has links)
A manipulação seletiva de alvos epigenéticos usando pequenas moléculas inibidoras das enzimas histona-desacetilases (HDACs) e DNA metiltransferases (DNMTs) é uma estratégia para estimular a expressão das vias biossintéticas e a produção de novos metabólitos secundários em fungos. Neste trabalho, inibidores de histonadesacetilases (butirato de sódio, ácido hidroxâmico suberoilanilida e ácido valproico) e inibidores de DNA metiltransferases (5-azacitidina, hidralazina, procaína e procainamida) foram suplementados em culturas líquidas e sólidas dos fungos endofíticos Fusarium oxysporum SS46, Hyphodermella corrugata FLe8.2 e Chaetomium globosum VR10, das linhagens comerciais Fusarium oxysporum ATCC MYA 4623 e Chaetomium globosum ATCC 56726 e do fitopatógeno Botrytis cinerea B0510. O fungo endofítico H. corrugata FLe8.2, em meio PDB, produziu o composto 2-(2-metoxifenil)-4H-piran-4-ona, e sua cultura em meio Czapek suplementada com hidralazina levou ao isolamento de 3-metil-1,2,4-triazolo[3,4-a]-ftalazina. O tratamento de F. oxysporum SS46 e F. oxysporum ATCC MYA 4623 com hidralazina em meio Czapek levou ao isolamento de um novo composto, 2H-[1,2,4]triazino[3,4- a]-ftalazina. Nestas culturas houve biotransformação da hidralazina pelos fungos, provavelmente como mecanismo de desintoxicação. Ainda, a hidralazina teve um efeito inibidor sobre a biossíntese do ciclohexadepsipeptídeo beauvericina em F. oxysporum SS46. Nas culturas de C. globosum VR10 em meio Czapek os inibidores de HDACs e de DNMTs suprimiram a biossíntese de chaetoglobosinas. A adição de ácido valproico na cultura de C. globosum VR10 em meio PDB eliciou a produção da chaetoviridina B. A adição de 5-azacitidina nas culturas de C. globosum VR10 em meio sólido PDA não modificou a produção da chaetoglosina A. A produção de chaetoviridina B por C. globosum ATCC 56726 em meio PDA foi inibida na menor concentração de 5-azacitidina, 50 ?M, e retomada na concentração de 150 ?M. O tratamento de B. cinerea B0510 com ácido hidroxâmico suberoilanilida SAHA levou à biossíntese de um novo composto, ácido 5-benzil-2,3-di-hidroxi-3-isopropil-4- oxotetrahidrofuran-2-carboxílico, o qual também foi isolado da linhagem geneticamente modificada B. cinerea Bc ?STC2. No geral, considerando as linhagens fúngicas estudadas, os resultados mostram que a adição de moduladores químicos que atuam em mecanismos epigenéticos promove mudanças no perfil de metabólitos secundários. / The selective manipulation of epigenetic targets using small molecule inhibitors of histone deacetylase (HDAC) and DNA methyltransferase (DNMT) activities is a strategy to elicit the expression of biosynthetic pathways and production of new secondary metabolites in fungi. In this work, HDAC inhibitors (sodium butyrate, suberohydroxamic acid and valproic acid) and DNMT inhibitors (5-azacitidine, hydralazine, procaine and procainamide) were supplemented in liquid and solid cultures of the endophytic fungi Fusarium oxysporum SS46, Hyphodermella corrugata FLe8.2 and Chaetomium globosum VR10, of the commercial fungal strains Fusarium oxysporum ATCC MYA 4623 and Chaetomium globosum ATCC 56726 and of the phytopathogenic fungus Botrytis cinerea B0510. The endophytic fungus H. corrugata FLe8.2 produced 2-(2-methoxyphenyl)-4H-pyran-4-one in PDB medium, while in the presence of hydralazine in Czapek medium the fungus produced 3- methyl-1,2,4-triazolo[3,4-a]-phthalazine. Treatment of F. oxysporum SS46 and F. oxysporum ATCC MYA 4623 with hydralazine in a Czapek medium led to the isolation of new compound, 2H-[1,2,4]triazino[3,4-a]-phthalazine. Hydralazine was biotransformed by these three fungi probably as a detoxification strategy. In addition, hydralazine also inhibited the biosynthesis of the cyclodepsipeptide beauvericin by F. oxysporum SS46. HDAC and DNMT inhibitors suppressed chaetoglobosins\' biosynthesis by C. globosum VR10 cultures in Czapek medium. The biosynthesis of chaetoviridin B by C. globosum VR10 was elicited by acid valproic in PDB medium. The production of chaetogosin A by C. globosum VR10 in PDA medium has not been affected by 5-azacitidine. The biosynthesis of chaetoviridin B by C. globosum ATCC 56726 in PDA medium was inhibited in the presence of lower concentration 5- azacitidine (50 ?M) and recovered in the higher concentration (150 ?M). Treatment of B. cinerea B0510 with suberohydroxamic acid led to the biosynthesis of the new compound 5-benzyl-2,3-dihydroxy-3-isopropyl-4-oxotetrahydrofuran-2-carboxylic acid, which was also isolated from the genetically modified strain B. cinerea Bc ?STC2. Results showed that chemical compounds that act in epigenetic mechanisms can induce changes in the secondary metabolite profiles in the fungal strains studied in this work.
60

Estudo do comportamento eletroquímico de carbono Printex 6L modificado com 2-terc-butil-9,10-antraquinona e 2-etil-9,10-antraquinona para a eletrogeração de H2O2 em meio ácido / Study of the electrochemical behavior of carbon Printex 6L modified with 2-tert-butyl-9,10-anthraquinone and 2-ethyl-9,10-anthraquinone for electrogeneration of the H2O2 in acid medium

Valim, Ricardo Bertholo 21 September 2012 (has links)
Neste trabalho foi estudado o comportamento eletroquímico de materiais à base de carbono Printex 6L, sem e com a adição de compostos orgânicos da classe das quinonas (2-terc-butil-9,10-antraquinona (TBA) e 2-etil-9,10-antraquinona (EA)) para a produção de peróxido de hidrogênio (H2O2) a partir da reação de redução do oxigênio gasoso (O2). Na primeira etapa, foi utilizada a técnica de microcamada porosa depositada sobre um eletrodo de disco/anel rotatório, sendo que a partir dos resultados obtidos foram confeccionados eletrodos de difusão gasosa (EDG) para a eletrogeração de H2O2. Os melhores resultados utilizando a microcamada porosa foram para os materiais com a adição dos modificadores, sendo que o material com 1,0% (m/m) de TBA na demonstrou ser o mais eficiente na geração de peróxido de hidrogênio, apresentando eficiência 20% maior comparado ao Printex 6L sem modificador. Com o eletrodo de difusão gasosa confeccionado com o composto orgânico escolhido, na melhor porcentagem de adição mássica de modificador, obteve-se a concentração de 301 mg L-1, sendo que com o eletrodo confeccionado com Printex 6L sem modificador obteve-se a concentração de 175 mg L-1, sob as mesmas condições experimentais. A eficiência cinética também apresentou os mesmos resultados quanto à eficiência dos materiais escolhidos, sendo de 5,94 mg L-1 min-1 para o material com 1,0% de TBA, no potencial de -1,0 V (vs. ECS), e de 3,05 mg L-1 min-1 para o eletrodo de difusão gasosa sem modificador, no potencial de -0,8 V (vs. ECS). / In this work, the electrochemistry behavior of the materials prepared with Printex 6L, with and without addition of organic compounds of the class of quinones, being the compounds: 2-tert-butyl-9,10-anthraquinone (TBA) and 2-ethyl-9,10-anthraquinone (EA). These materials were used to promote the electrogeneration of hydrogen peroxide through the oxygen reduction reaction. In the first phase, it was used the technique of porous microlayer deposited on the rotating ring/disk electrode, and after has been confectioned gas diffusion electrodes (GDE). The best results using the porous microlayer were for the materials with addition of modifiers, and the material with 1.0% (m/m) of 2-terc-butyl-9,10-anthraquinone was demonstrated to be the most efficient in generating hydrogen peroxide, presenting an efficiency 20% higher when compared to Printex 6L without the modifier. The gas diffusion electrode made with the chosen organic compound, in the best massic percentage of modifier, obtained the concentration of 301 mg L-1, and the electrode made with Printex 6L without the modifier obtained the maximum concentration of 175 mg L-1, under the same experimental conditions. The kinect efficiency also demonstrated the same results regarding the efficiency of the chosen materials, which means 5.94 mg L-1 min-1 for the material with 1.0% of 2-terc-butyl-9,10-anthraquinone, in the potential of -1.0 V(vs. SCE), and 3.05 mg L-1 min-1 for the gas diffusion electrode without the modifier, in the potential of -0.8 V (vs. SCE).

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