A reaeração superficial é um importante fenômeno físico responsável pela transferência de massa do oxigênio atmosférico para o curso de água, através da interface ar-água. Esse fenômeno é caracterizado quantitativamente pelo coeficiente de reaeração superficial (K2). O K2 pode ser influenciado por diversos fatores naturais, em especial, a turbulência, que é afetada pelas características físicas, hidrológicas e hidráulicas do escoamento da água. Este coeficiente é comumente utilizado em modelos ambientais de qualidade da água, o que implica na necessidade da sua correta estimativa. A estimativa do K2 pode ser realizada por meio de métodos e modelos de predição, entre os métodos destacam-se o traçador gasoso e a sonda solúvel flutuante. O objetivo principal desta pesquisa foi verificar a variabilidade espacial e temporal do K2 em cinco trechos de quatro riachos tropicais localizados no município de São Carlos-SP, em um ano de amostragem. Nesses trechos foram mensuradas as principais variáveis químicas, físicas, hidrológicas e hidráulicas do escoamento da água, além do K2 e a velocidade de dissolução de uma sonda solúvel flutuante (VS). A estimativa do K2 ocorreu pelo método do traçador gasoso, sendo o SF6 e o NaCl os traçadores utilizados. A estimativa do VS ocorreu pelo método da sonda solúvel flutuante, confeccionada com ácido oxálico dihidratado e no formato esférico. Análises estatísticas de correlação (Spearman, r) e variância (Kruskal-Wallis) foram realizadas, e modelos de regressão linear simples (RLS) e múltipla (RLM) foram desenvolvidos. Os trechos apresentaram profundidades e larguras médias inferiores a 0,42 m e 3,27 m, respectivamente. A vazão e a velocidade (U) média variaram de 0,001 m3.s-1 a 0,110 m3.s-1 e de 0,01 m.s-1 a 0,33 m.s-1, respectivamente. Os números de Reynolds e Froude (Fr) foram inferiores a 34070 e 0,36, respectivamente. Os K2 variaram de 16,90 dia-1 a 373,80 dia-1 e os VS, de 0,08 mm.min-1 a 0,77 mm.min-1. Os resultados demonstraram variação espacial significativa e temporal não significativa para as variáveis físicas, hidrológicas, hidráulicas, e também para o K2 e VS. U e Fr foram as principais variáveis que se correlacionaram com o K2 (r > 0,68). Um adequado modelo RLM de predição do K2 (R² = 0,75), baseado em todas as variáveis físicas, hidrológicas e hidráulicas e no VS, foi obtido. O modelo RLS, baseado apenas na relação entre K2 e VS, não foi adequado (R² = 0,43) para a predição do K2. A razão entre os fenômenos da reaeração superficial e dissolução da sonda solúvel flutuante não foi constante, e foi afetada pela turbulência na interface ar-água, o que indicou que o método da sonda solúvel flutuante ainda precisa ser aprimorado. Espera-se que, além de gerarem dados sobre um método (sonda solúvel flutuante) e tema (reaeração superficial) ainda relativamente pouco estudados em riachos tropicais, as informações apresentadas sobre as principais variáveis intervenientes no fenômeno de reaeração superficial e dissolução em riachos possam oferecer direcionamentos a estudos ambientais, especialmente àqueles que versam sobre a qualidade dos recursos hídricos. / Surface reaeration is an important physical phenomenon responsible for the transfer of atmospheric oxygen mass into the water course through the air-water interface. This phenomenon is quantitatively characterized by the surface reaeration coefficient (K2). K2 can be influenced by several natural factors, especially turbulence, which is affected by the physical, hydrologic and hydraulic characteristics of the watercourse. This coefficient is commonly used in environmental models of water quality, which implies the need for its correct estimation. The estimation of K2 can be performed by models of prediction and methods, among the methods the gas tracer and the floating soluble probe stand out. The aim of this research was to verify the spatial and temporal variability of K2 in five stretches of four tropical streams located in the city of São Carlos-SP, in a year of sampling. In these stretches the main chemical, physical, hydrological and hydraulic variables of the watercourse were measured, besides K2 and the dissolution rate of the floating soluble probe (VS). The estimation of K2 occurred by the gas tracer method, with SF6 and NaCl being the tracers used. The VS estimation was carried out by the floating probe method, made with oxalic acid dihydrate and in spherical format. Statistical analyzes of correlation (Spearman, r) and variance (Kruskal-Wallis) were performed, and simple linear regression (SLR) and multiple linear regression models (MLR) were developed. The stretches presented mean depths and widths of less than 0.42 m and 3.27 m, respectively. The flow rate and average velocity (U) ranged from 0.001 m3 s-1 to 0.110 m3s-1 and from 0.01 m.s-1 to 0.33 m.s-1, respectively. The Reynolds and Froude (Fr) numbers were less than 34070 and 0.36, respectively. The K2 ranged from 16.90 day-1 to 373.80 day-1 and the VS, from 0.08 mm.min-1 to 0.77 mm.min-1. The results showed significant spatial variation and a non-significant temporal variation for the physical, hydrological and hydraulic variables, as well as for K2 and VS. U and Fr were the main variables that correlated with K2 (r > 0.68). A suitable MLR prediction model of K2 (R² = 0.75), based on all physical, hydrological and hydraulic variables and VS, was obtained. The SLR model, based only on the relationship between K2 and VS, was not adequate (R² = 0.43) for K2 prediction. The ratio between the phenomena of surface reaeration and dissolution of the floating soluble probe was not constant and was affected by turbulence at the air-water interface, which indicated that the floating soluble probe method still needs to be improved. It is expected that, in addition to generating data on a method (floating soluble probe) and surface (surface reaeration) that are still relatively little studied in tropical streams, the information presented on the main variables involved in the phenomenon of surface reaeration and dissolution in streams may offer environmental studies, especially those dealing with the quality of water resources.

A reaeração superficial é um importante fenômeno físico responsável pela transferência de massa do oxigênio atmosférico para o curso de água, através da interface ar-água. Esse fenômeno é caracterizado quantitativamente pelo coeficiente de reaeração superficial (K2). O K2 pode ser influenciado por diversos fatores naturais, em especial, a turbulência, que é afetada pelas características físicas, hidrológicas e hidráulicas do escoamento da água. Este coeficiente é comumente utilizado em modelos ambientais de qualidade da água, o que implica na necessidade da sua correta estimativa. A estimativa do K2 pode ser realizada por meio de métodos e modelos de predição, entre os métodos destacam-se o traçador gasoso e a sonda solúvel flutuante. O objetivo principal desta pesquisa foi verificar a variabilidade espacial e temporal do K2 em cinco trechos de quatro riachos tropicais localizados no município de São Carlos-SP, em um ano de amostragem. Nesses trechos foram mensuradas as principais variáveis químicas, físicas, hidrológicas e hidráulicas do escoamento da água, além do K2 e a velocidade de dissolução de uma sonda solúvel flutuante (VS). A estimativa do K2 ocorreu pelo método do traçador gasoso, sendo o SF6 e o NaCl os traçadores utilizados. A estimativa do VS ocorreu pelo método da sonda solúvel flutuante, confeccionada com ácido oxálico dihidratado e no formato esférico. Análises estatísticas de correlação (Spearman, r) e variância (Kruskal-Wallis) foram realizadas, e modelos de regressão linear simples (RLS) e múltipla (RLM) foram desenvolvidos. Os trechos apresentaram profundidades e larguras médias inferiores a 0,42 m e 3,27 m, respectivamente. A vazão e a velocidade (U) média variaram de 0,001 m3.s-1 a 0,110 m3.s-1 e de 0,01 m.s-1 a 0,33 m.s-1, respectivamente. Os números de Reynolds e Froude (Fr) foram inferiores a 34070 e 0,36, respectivamente. Os K2 variaram de 16,90 dia-1 a 373,80 dia-1 e os VS, de 0,08 mm.min-1 a 0,77 mm.min-1. Os resultados demonstraram variação espacial significativa e temporal não significativa para as variáveis físicas, hidrológicas, hidráulicas, e também para o K2 e VS. U e Fr foram as principais variáveis que se correlacionaram com o K2 (r > 0,68). Um adequado modelo RLM de predição do K2 (R² = 0,75), baseado em todas as variáveis físicas, hidrológicas e hidráulicas e no VS, foi obtido. O modelo RLS, baseado apenas na relação entre K2 e VS, não foi adequado (R² = 0,43) para a predição do K2. A razão entre os fenômenos da reaeração superficial e dissolução da sonda solúvel flutuante não foi constante, e foi afetada pela turbulência na interface ar-água, o que indicou que o método da sonda solúvel flutuante ainda precisa ser aprimorado. Espera-se que, além de gerarem dados sobre um método (sonda solúvel flutuante) e tema (reaeração superficial) ainda relativamente pouco estudados em riachos tropicais, as informações apresentadas sobre as principais variáveis intervenientes no fenômeno de reaeração superficial e dissolução em riachos possam oferecer direcionamentos a estudos ambientais, especialmente àqueles que versam sobre a qualidade dos recursos hídricos. / Surface reaeration is an important physical phenomenon responsible for the transfer of atmospheric oxygen mass into the water course through the air-water interface. This phenomenon is quantitatively characterized by the surface reaeration coefficient (K2). K2 can be influenced by several natural factors, especially turbulence, which is affected by the physical, hydrologic and hydraulic characteristics of the watercourse. This coefficient is commonly used in environmental models of water quality, which implies the need for its correct estimation. The estimation of K2 can be performed by models of prediction and methods, among the methods the gas tracer and the floating soluble probe stand out. The aim of this research was to verify the spatial and temporal variability of K2 in five stretches of four tropical streams located in the city of São Carlos-SP, in a year of sampling. In these stretches the main chemical, physical, hydrological and hydraulic variables of the watercourse were measured, besides K2 and the dissolution rate of the floating soluble probe (VS). The estimation of K2 occurred by the gas tracer method, with SF6 and NaCl being the tracers used. The VS estimation was carried out by the floating probe method, made with oxalic acid dihydrate and in spherical format. Statistical analyzes of correlation (Spearman, r) and variance (Kruskal-Wallis) were performed, and simple linear regression (SLR) and multiple linear regression models (MLR) were developed. The stretches presented mean depths and widths of less than 0.42 m and 3.27 m, respectively. The flow rate and average velocity (U) ranged from 0.001 m3 s-1 to 0.110 m3s-1 and from 0.01 m.s-1 to 0.33 m.s-1, respectively. The Reynolds and Froude (Fr) numbers were less than 34070 and 0.36, respectively. The K2 ranged from 16.90 day-1 to 373.80 day-1 and the VS, from 0.08 mm.min-1 to 0.77 mm.min-1. The results showed significant spatial variation and a non-significant temporal variation for the physical, hydrological and hydraulic variables, as well as for K2 and VS. U and Fr were the main variables that correlated with K2 (r > 0.68). A suitable MLR prediction model of K2 (R² = 0.75), based on all physical, hydrological and hydraulic variables and VS, was obtained. The SLR model, based only on the relationship between K2 and VS, was not adequate (R² = 0.43) for K2 prediction. The ratio between the phenomena of surface reaeration and dissolution of the floating soluble probe was not constant and was affected by turbulence at the air-water interface, which indicated that the floating soluble probe method still needs to be improved. It is expected that, in addition to generating data on a method (floating soluble probe) and surface (surface reaeration) that are still relatively little studied in tropical streams, the information presented on the main variables involved in the phenomenon of surface reaeration and dissolution in streams may offer environmental studies, especially those dealing with the quality of water resources.

O fungo de podridão branca Ceriporiopsis subvermispora é seletivo na degradação de lignina em estágios curtos de colonização de madeira e dessa forma tem sido uma das espécies mais estudadas em biopolpação, que consiste em um tratamento biológico de cavacos de madeira que antecede etapas convencionais de polpação. Para degradar a lignina na parede celular vegetal esse fungo secreta a enzima manganês-peroxidase (MnP), a qual necessita de ácido oxálico para transportar o íon Mn3+ oriundo do seu ciclo catalítico. O complexo quelante-Mn3+ gerado degrada apenas porções fenólicas da lignina. Porém, por meio da peroxidação de lipídeos por Mn3+, radicais livres são gerados e apresentam potencial de oxidação suficiente para degradar estruturas não-fenólicas da lignina. Com base nesses aspectos, o presente trabalho avaliou a importância desses mediadores da MnP, ácido oxálico e lipídeos, no processo degradativo quanto à adição ou à supressão dessas substâncias nos cultivos. Em cultivos com madeira in natura ou extraídas com etanol (provavelmente isento de lipídeos) não ocorreu diferença significativa quanto à produção de metabólitos extracelulares (enzimas, ácido oxálico), à degradação de lignina e à atividade redutora de Fe3+ (envolvida na geração de radicais OH pela reação de Fenton). A formação de TBARS (substâncias que reagem com o ácido tiobarbitúrico), que serve como indício de reações de peroxidação de lipídeos, também foi semelhante, demonstrando que mesmo a partir de madeira livre de extrativos essas reações ocorrem. Com o avanço do biotratamento, a lignina foi despolimerizada por meio da diminuição de ligações ?-O-4, os teores de OH alifáticas e fenólicas foram diminuídos, enquanto o teor de grupos carboxila aumentou. Embora a degradação de celulose em madeira tenha sido baixa, cartões de holocelulose (livres de lignina) adicionados nesses cultivos foram despolimerizados. Nos cultivos em que houve a adição de uma fonte extra de lipídeos (óleo de soja), a produção de enzimas e degradação de lignina foram similares, enquanto a produção de ácido oxálico e TBARS foi estimulada por esse co-substrato. A maior concentração de óleo de soja adicionado (10,4 g/kg de madeira) fez com que a lignina presente na madeira residual apresentasse o mesmo teor de ligações ?-O-4 que o controle, enquanto maior degradação de OH alifáticas e menor formação de grupos carboxila foram observadas nessas ligninas. Em outro ciclo de cultivos, íons Ca2+ foram adicionados para precipitar o ácido oxálico produzido pelo fungo. Nos cultivos com a mais alta carga de cálcio (1400 mg/kg) houve diminuição na formação de ácido oxálico e consequentemente uma inibição na degradação de todos os componentes da madeira. Ao serem realizados cultivos com ácido oxálico exógeno, o fungo atuou de forma a igualar a concentração de ácido oxálico livre em relação a um cultivo sem esse suplemento, tanto por catabolismo quanto por precipitação desse ácido. Para as máximas cargas de cálcio, ácido oxálico e óleo de soja foram realizados outros cultivos sobre madeira em biorreatores para realização de ensaios de polpação. A polpação quimiotermomecânica sulfito alcalino dessas amostras de madeira biodegradada mostrou que os cultivos adicionados de Ca2+ e os não suplementados foram os que proporcionaram os maiores benefícios atribuídos ao biotratamento. Por outro lado, a adição de ácido oxálico anulou o benefício oriundo do biotratamento. A busca de correlações entre os níveis de metabólitos extracelulares com os benefícios do biotratamento para a polpação quimiotermomecânica não apresentaram tendências claras que indiquem a relevância de um metabólito em especial. Pelo contrário, aparentemente deve haver um compromisso entre todas as atividades extracelulares para que um determinado benefício seja obtido. / The white-rot fungus Ceriporiopsis subvermispora degrades lignin selectively during the initial stages of wood colonization and in this way it has been one of the most studied species in biopulping. This process consists of a biological treatment of wood chips that precedes conventional pulping stages. To degrade lignin in the plant cell wall this fungus secretes the enzyme manganese-peroxidase (MnP), which needs oxalic acid to transport the Mn3+ ion formed in the catalytic cycle of the enzyme. The oxalate-Mn3+ complex degrades only lignin phenolic portions. However, through lipid peroxidation intiated by Mn3+, free radicals are generated and they present enough oxidation potential to degrade nonphenolic lignin structures. With basis in these aspects, the present work evaluated the importance of these mediators of MnP, oxalic acid and lipids, in the degradative process either by their addition or suppression in wood-containing cultures. In cultivations with in natura wood or ethanol extracted wood (probably free of lipids) thre was no significant difference in the production of extracelular metabolites (enzymes, oxalic acid), or in the lignin degradation and the Fe3+-reducing activity (involved in the OH radicals generation by the Fenton´s reaction). The formation of TBARS (thiobarbituric acid reactive substances), that ii indicative of lipid peroxidation reactions, was also similar in both cultivations systems, demonstrating that even starting from extractives-free wood, these reactions can occur. With the progress of the biotreatment, the lignin was depolymerized through the decrease of ?-O-4 bonds, the contents of aliphatic and phenolic OH decreased, while carboxyl groups content increased. Although the cellulose degradation in wood has been low, holocellulose cards (free from lignin) added in these cultures were depolymerized. In the cultures where lipids were added (soy-bean oil), the enzyme production and lignin degradation were similar, while the oxalic acid and TBARS productions was stimulated by this co-substrate. With the highest concentration of soy-bean oil added (10,4 g/kg wood), the lignin in the residual wood presented the same content of ?-O-4 bonds as compared to the control, while higher degradation of aliphatic OH and lower formation of carboxyl groups were observed in these lignins. In another cycle of cultivations, Ca2+ ions were added to precipitate oxalic acid produced by the fungus. In the cultivations with the highest load of calcium (1400 mg/kg) there was a decrease in the oxalic acid formation and consequently an inhibition in the degradation of all the wood components. To the cultivations accomplished with exogenous oxalic acid, the fungus acted to equalize the concentration of free oxalic acid either by catabolism or by precipitation of this acid. For the highest loads of calcium, oxalic acid andsoy-bean oil, other cultivations were accomplished on 20 L-biorreactors to produce biotreated wood samples suitable for pulping experiments. The alkaline-sulfite chemitermomechanical pulping of these samples showed that the biotreated wood in Ca2+-ammended and nonsupplemented cultures were the ones that provided the highest benefits. On the other hand, the oxalic acid addition annulled the benefit originated from the biotreatment. The search for correlations among the levels of extracelular metabolites with the benefits of the biotreatment for the chemitermomechanical pulping did not present clear tendencies to indicate the relevance of a metabolite in special. On the contrary, probably there is a commitment among all of the extracellular activities, so that a certain benefit would be obtained.

O fungo de podridão branca Ceriporiopsis subvermispora é seletivo na degradação de lignina em estágios curtos de colonização de madeira e dessa forma tem sido uma das espécies mais estudadas em biopolpação, que consiste em um tratamento biológico de cavacos de madeira que antecede etapas convencionais de polpação. Para degradar a lignina na parede celular vegetal esse fungo secreta a enzima manganês-peroxidase (MnP), a qual necessita de ácido oxálico para transportar o íon Mn3+ oriundo do seu ciclo catalítico. O complexo quelante-Mn3+ gerado degrada apenas porções fenólicas da lignina. Porém, por meio da peroxidação de lipídeos por Mn3+, radicais livres são gerados e apresentam potencial de oxidação suficiente para degradar estruturas não-fenólicas da lignina. Com base nesses aspectos, o presente trabalho avaliou a importância desses mediadores da MnP, ácido oxálico e lipídeos, no processo degradativo quanto à adição ou à supressão dessas substâncias nos cultivos. Em cultivos com madeira in natura ou extraídas com etanol (provavelmente isento de lipídeos) não ocorreu diferença significativa quanto à produção de metabólitos extracelulares (enzimas, ácido oxálico), à degradação de lignina e à atividade redutora de Fe3+ (envolvida na geração de radicais OH pela reação de Fenton). A formação de TBARS (substâncias que reagem com o ácido tiobarbitúrico), que serve como indício de reações de peroxidação de lipídeos, também foi semelhante, demonstrando que mesmo a partir de madeira livre de extrativos essas reações ocorrem. Com o avanço do biotratamento, a lignina foi despolimerizada por meio da diminuição de ligações ?-O-4, os teores de OH alifáticas e fenólicas foram diminuídos, enquanto o teor de grupos carboxila aumentou. Embora a degradação de celulose em madeira tenha sido baixa, cartões de holocelulose (livres de lignina) adicionados nesses cultivos foram despolimerizados. Nos cultivos em que houve a adição de uma fonte extra de lipídeos (óleo de soja), a produção de enzimas e degradação de lignina foram similares, enquanto a produção de ácido oxálico e TBARS foi estimulada por esse co-substrato. A maior concentração de óleo de soja adicionado (10,4 g/kg de madeira) fez com que a lignina presente na madeira residual apresentasse o mesmo teor de ligações ?-O-4 que o controle, enquanto maior degradação de OH alifáticas e menor formação de grupos carboxila foram observadas nessas ligninas. Em outro ciclo de cultivos, íons Ca2+ foram adicionados para precipitar o ácido oxálico produzido pelo fungo. Nos cultivos com a mais alta carga de cálcio (1400 mg/kg) houve diminuição na formação de ácido oxálico e consequentemente uma inibição na degradação de todos os componentes da madeira. Ao serem realizados cultivos com ácido oxálico exógeno, o fungo atuou de forma a igualar a concentração de ácido oxálico livre em relação a um cultivo sem esse suplemento, tanto por catabolismo quanto por precipitação desse ácido. Para as máximas cargas de cálcio, ácido oxálico e óleo de soja foram realizados outros cultivos sobre madeira em biorreatores para realização de ensaios de polpação. A polpação quimiotermomecânica sulfito alcalino dessas amostras de madeira biodegradada mostrou que os cultivos adicionados de Ca2+ e os não suplementados foram os que proporcionaram os maiores benefícios atribuídos ao biotratamento. Por outro lado, a adição de ácido oxálico anulou o benefício oriundo do biotratamento. A busca de correlações entre os níveis de metabólitos extracelulares com os benefícios do biotratamento para a polpação quimiotermomecânica não apresentaram tendências claras que indiquem a relevância de um metabólito em especial. Pelo contrário, aparentemente deve haver um compromisso entre todas as atividades extracelulares para que um determinado benefício seja obtido. / The white-rot fungus Ceriporiopsis subvermispora degrades lignin selectively during the initial stages of wood colonization and in this way it has been one of the most studied species in biopulping. This process consists of a biological treatment of wood chips that precedes conventional pulping stages. To degrade lignin in the plant cell wall this fungus secretes the enzyme manganese-peroxidase (MnP), which needs oxalic acid to transport the Mn3+ ion formed in the catalytic cycle of the enzyme. The oxalate-Mn3+ complex degrades only lignin phenolic portions. However, through lipid peroxidation intiated by Mn3+, free radicals are generated and they present enough oxidation potential to degrade nonphenolic lignin structures. With basis in these aspects, the present work evaluated the importance of these mediators of MnP, oxalic acid and lipids, in the degradative process either by their addition or suppression in wood-containing cultures. In cultivations with in natura wood or ethanol extracted wood (probably free of lipids) thre was no significant difference in the production of extracelular metabolites (enzymes, oxalic acid), or in the lignin degradation and the Fe3+-reducing activity (involved in the OH radicals generation by the Fenton´s reaction). The formation of TBARS (thiobarbituric acid reactive substances), that ii indicative of lipid peroxidation reactions, was also similar in both cultivations systems, demonstrating that even starting from extractives-free wood, these reactions can occur. With the progress of the biotreatment, the lignin was depolymerized through the decrease of ?-O-4 bonds, the contents of aliphatic and phenolic OH decreased, while carboxyl groups content increased. Although the cellulose degradation in wood has been low, holocellulose cards (free from lignin) added in these cultures were depolymerized. In the cultures where lipids were added (soy-bean oil), the enzyme production and lignin degradation were similar, while the oxalic acid and TBARS productions was stimulated by this co-substrate. With the highest concentration of soy-bean oil added (10,4 g/kg wood), the lignin in the residual wood presented the same content of ?-O-4 bonds as compared to the control, while higher degradation of aliphatic OH and lower formation of carboxyl groups were observed in these lignins. In another cycle of cultivations, Ca2+ ions were added to precipitate oxalic acid produced by the fungus. In the cultivations with the highest load of calcium (1400 mg/kg) there was a decrease in the oxalic acid formation and consequently an inhibition in the degradation of all the wood components. To the cultivations accomplished with exogenous oxalic acid, the fungus acted to equalize the concentration of free oxalic acid either by catabolism or by precipitation of this acid. For the highest loads of calcium, oxalic acid andsoy-bean oil, other cultivations were accomplished on 20 L-biorreactors to produce biotreated wood samples suitable for pulping experiments. The alkaline-sulfite chemitermomechanical pulping of these samples showed that the biotreated wood in Ca2+-ammended and nonsupplemented cultures were the ones that provided the highest benefits. On the other hand, the oxalic acid addition annulled the benefit originated from the biotreatment. The search for correlations among the levels of extracelular metabolites with the benefits of the biotreatment for the chemitermomechanical pulping did not present clear tendencies to indicate the relevance of a metabolite in special. On the contrary, probably there is a commitment among all of the extracellular activities, so that a certain benefit would be obtained.

Orientador: Maria Salete Machado Cândido / Banca: José Roberto Cury Saad / Banca: Patricia dos Santos Jardim / Resumo: O objetivo deste trabalho foi o de avaliar comparativamente "in vitro", a resistência de união ao cisalhamento de uma resina composta à dentina bovina em função da combinação de três diferentes sistemas adesivos e de dois diferentes agentes dessensibilizantes. Foram utilizados os sistemas adesivos: Single Bond, Master Bond e Prime & Bond 2.1 e os seguintes agentes dessensibilizantes: o Oxagel e o G. H. F. Dessensibilizador. Para a confecção dos corpos de prova, 90 incisivos bovinos (n=10) foram utilizados, os quais tiveram suas superfícies vestibulares desgastadas, até a exposição dentinária, de tal forma que, a área de adesão padronizada, tivesse 4 mm de diâmetro. Após a realização dos tratamentos de superfície, onde os Grupos controle eram indicados apenas pela aplicação do sistema adesivo, e os Grupos experimentais, pela aplicação dos agentes dessensibilizantes testados após o condicionamento ácido, foram confeccionados cilindros de resina composta Z-100, com o auxílio de uma matriz bipartida. Os corpos-de-prova foram então armazenados em água destilada a 37°C por 24 horas, e submetidos em seguida ao ensaio de cisalhamento, a uma velocidade do atuador de 0,5 mm/min. Os resultados obtidos foram submetidos à análise de variância, e ao teste de Tukey, ao nível de 5% de significância. Observou-se que houve influência dos agentes dessensibilizantes, quando estes eram aplicados na dentina bovina e interagiam com os sistemas adesivos, sendo que o G. H. F. Dessensibilizador aumentou estatisticamente os valores de resistência de união do Single Bond, e do Prime & Bond 2.1, e o Oxagel não influenciou nos valores de resistência de união dos sistemas adesivos testados. / Abstract: The objective of this work was it of evaluating "in vitro" comparatively , the shear bond strength of a resin composed to the bovine dentin in function of the combination of three different adhesive systems and of two different agents dessensitizers. The adhesive systems were used, to know: Single Bond, Master Bond and Prime & Bond 2.1 and the following agents dessensitizers: Oxagel and G. H. F. Desensitizer. For the making of the test bodies, 90 incisive bovine (n=10) they were used, which had its worn away vestibular surfaces, until the exhibition dentin, in such a way that, the area of standardized adhesion, had 4 diameter mm. After the accomplishment of the surface treatments, where the Groups control was just suitable for the application of the adhesive system, and the experimental Groups, for the application of the agents dessensitizers tested after the acid conditioning, cylinders of composed resin were made Z-100, with the aid of a bipartite matrix. The test bodies, they were stored then in water distilled for 37°C by 24 hours, and submitted soon after to the shear bond strength rehearsal, to a crosshead speed of 0,5 mm/min. The obtained results were submitted to the variance analysis, and to the test of Tukey, at the level of 5% of significance. It was observed that there was influence of the agents dessensitizers, when these were applied in the bovine dentin and interagiam with the adhesive systems, and G. H. F. Dessensitizer increased statistically the values of resistance of union of Single Bond, and of the it Prime & Bond 2.1, and Oxagel didn't influence in the values of resistance of union of the tested adhesive systems. / Mestre

This work focuses on the physical properties and crystallization of theophyline co-crystals. Co-crystals of theophylline with oxalic acid, glutaric acid and maleic acid have been investigated. The DSC curves of these co-crystals show that their first endothermic peaks are all lower than the melting temperature of theophylline. The decomposition temperature of theophylline – oxalic acid co-crystal is at about 230 °C, determined by DSC together with TGA. After decomposition, the remaining theophylline melts at about 279 °C, which is higher than the known melting temperature of theophylline, suggesting a structure difference, ie. a new polymorph may have been formed. The formation of hydrogen bonds in theophylline – oxalic acid co-crystal was investigated by FTIR. Changes of FTIR peaks around 3120 cm-1 reflects the hydrogen bond of basic N of theophylline and hydroxyl H of oxalic acid. The solubility of theophylline – oxalic acid co-crystal and theophylline – glutaric acid co-crystal was determined in 4:1 chlroform – methanol and in pure chloroform respectively. At equilibrium with the solid theophylline – oxalic acid co-crystal, the theophylline concentration is only 60 % of the corresponding value for the pure solid theophylline. At equilibrium with the solid theophylline – glutaric acid co-crystal, the theophylline concentration is at least 5 times higher than the corresponding value for the pure solid theophylline. Two phases of theophylline were found during the solubility determination. In the chloroform – methanol mixture (4:1 in volume ratio) the solubility of the stable polymorph of theophylline is found to be about 14 % lower than that of the metastable phase. Various aspects of the phase diagram of theophylline – oxalic acid co-crystal was explored. Theophylline – oxalic acid co-crystal has been successfully prepared via primary nucleation from a stoichiometric solution mixture of the two components in chloroform – methanol mixture. By slurry conversion crystallization, the co-crystal can be prepared in several solvents, and yield and productivity can be significantly increased. Theophylline – glutaric acid can be successfully prepared via both co-grinding of the two components and slow evaporation with seeding. / QC20100608

No / Caffeine/oxalic acid 2:1 cocrystal exhibited superior stability to humidity over caffeine, but compressional behavior is not studied yet. To compare compressional properties of caffeine/oxalic acid 2:1 cocrystal obtained by different cocrystallization techniques. Cocrystal was obtained by solvent precipitation and ultrasound assisted solution cocrystallization (USSC) and characterized by X-ray powder diffraction and scanning electron microscopy. Compaction study was carried out at different compaction forces. Compact crushing strength, thickness and elastic recovery were determined. Compaction was in order, caffeine > solvent precipitation cocrystal > USSC cocrystal. Caffeine exhibited sticking and lamination, where solvent precipitation compacts showed advantage. Caffeine and solvent precipitation compacts showed sudden drop in compactability, higher elastic recovery with severe lamination at 20,000 N. This was due to overcompaction. Crystal habit of two cocrystal products was same, but USSC cocrystals were difficult to compact. Uniform needle shaped USSC cocrystals must be difficult to orient in different direction and fracture during compression. Elastic recovery of USSC cocrystals was also more compared to other powders indicating less fracture and poor bonding between particles resulting in poor compaction. Cocrystal formation did not improve compressional property of caffeine. Cocrystals exposed to different crystallization environments in two techniques may have resulted in generation of different surface properties presenting different compressional properties.

Currently at the Savannah River Site (SRS), there are fifteen single-shell, 3.6-million liter tanks containing High Level Waste. To close the tanks, the sludge must be removed. Mechanical methods have had limited success. Oxalic acid cleaning is now being considered as a new technology. This research uses sample results and chemical equilibrium software to develop a preferred flowsheet and evaluate the acceptability of the system impacts. Based on modeling and testing, between 246,000 to 511,000 l of 8 wt% oxalic acid were required to dissolve a 9,000 liter Purex sludge heel. For SRS H-Area modified sludge, 322,000 to 511,000 l were required. To restore the pH of the treatment tank slurries, approximately 140,000 to 190,000 l of 50 wt% NaOH or 260,000 to 340,000 l of supernate were required. When developing the flowsheet, there were two primary goals to minimize downstream impacts. The first was to ensure that the Resultant oxalate solids were transferred to DWPF, without being washed. The second was to transfer the remaining soluble sodium oxalates to the evaporator drop tank, so they do not transfer through or precipitate in the evaporator pot. Adiabatic modeling determined the maximum possible temperature to be 73.5°C and the maximum expected temperature to be 64.6°C. At one atmosphere and at 73.5°C, a maximum of 770 l of water vapor was generated, while at 64.6°C a maximum 254 l of carbon dioxide were generated. Although tank wall corrosion was not a concern, because of the large cooling coil surface area, the corrosion induced hydrogen generation rate was calculated to be as high as 10,250 l/hr. Since the minimum tank purge exhaust was assumed to be 5,600 l/hr, the corrosion induced hydrogen generation rate was identified as a potential concern. Excluding corrosion induced hydrogen, trending the behavior of the spiked constituents of concern, and considering conditions necessary for ignition, energetic compounds were shown not to represent an increased risk Based on modeling, about 56,800 l of Resultant oxalates could be added to a washed sludge batch with minimal impact on the number of additional glass canisters produced. For each sludge batch, with 1 to 3 heel dissolutions, about 60,000 kg of sodium oxalate entered the evaporator system, with most collecting in the drop tank, where they will remain until eventual salt heel removal. For each 6,000 kg of sodium oxalate in the drop tank, about 189,000 l of Saltstone feed would eventually be produced. Overall, except for corrosion-induced hydrogen, there were no significant process impacts that would forbid the use of oxalic acid in cleaning High Level Waste tanks. / MATHEMATICAL SCIENCES / M. Tech. (Chemical Engineering)

<p>This work focuses on the physical properties and crystallization of theophyline co-crystals. Co-crystals of theophylline with oxalic acid, glutaric acid and maleic acid have been investigated.</p><p>The DSC curves of these co-crystals show that their first endothermic peaks are all lower than the melting temperature of theophylline. The decomposition temperature of theophylline – oxalic acid co-crystal is at about 230 °C, determined by DSC together with TGA. After decomposition, the remaining theophylline melts at about 279 °C, which is higher than the known melting temperature of theophylline, suggesting a structure difference, ie. a new polymorph may have been formed. The formation of hydrogen bonds in theophylline – oxalic acid co-crystal was investigated by FTIR. Changes of FTIR peaks around 3120 cm^-1 reflects the hydrogen bond of basic N of theophylline and hydroxyl H of oxalic acid. The solubility of theophylline – oxalic acid co-crystal and theophylline – glutaric acid co-crystal was determined in 4:1 chlroform – methanol and in pure chloroform respectively. At equilibrium with the solid theophylline – oxalic acid co-crystal, the theophylline concentration is only 60 % of the corresponding value for the pure solid theophylline. At equilibrium with the solid theophylline – glutaric acid co-crystal, the theophylline concentration is at least 5 times higher than the corresponding value for the pure solid theophylline. Two phases of theophylline were found during the solubility determination. In the chloroform – methanol mixture (4:1 in volume ratio) the solubility of the stable polymorph of theophylline is found to be about 14 % lower than that of the metastable phase. Various aspects of the phase diagram of theophylline – oxalic acid co-crystal was explored.</p><p>Theophylline – oxalic acid co-crystal has been successfully prepared via primary nucleation from a stoichiometric solution mixture of the two components in chloroform – methanol mixture. By slurry conversion crystallization, the co-crystal can be prepared in several solvents, and yield and productivity can be significantly increased. Theophylline – glutaric acid can be successfully prepared via both co-grinding of the two components and slow evaporation with seeding.</p> / QC20100608

Bayer processing of bauxite employed for production of alumina yield a residue red-mud. The worldwide annual-rate of red-mud generation is approximately 120 million tons, and most of this is stockpiled. Red mud is rich in elements like aluminum, titanium and rare earths, in addition to the major iron-bearing constituents. The objective of this research is to explore such a strategy to extract Iron as fine particulate magnetite. Pyrometallurgical reduction experiments using carbon mixtures and a novel hydrometallurgical route are experimented. Reduction experiments performed with petroleum coke as a reductant resulted in incomplete reduction. The ‘optimal conditionsÂ’ for gaseous state reduction are determined to be: a processing temperature of 540oC ± 10oC, partial pressures CO (g) and CO2 (g) each of 0.070atm (bar) ± 0.001atm.(bar)/ inert diluent-gas: N2 (g), for a conversion-time of 30min. A mathematical-model was developed on the basis of unidirectional-diffusion of CO2 (g) within the CO2 (g)–CO (g)–N2 (g) gas-phase of the porous product-layer. Magnetic separation applied to the optimally reduced sample in: obtaining a magnetic portion with high iron and non-magnetic portion containing nonferrous (Al, Ti) is not successful. This finding was subsequently attributed to the nanometer length-scales crystallites of the predominant iron-containing phase, hydrated ferric-oxide(s) as determined by STEM micrographs. In addition, the presence of substitution for Fe3+ by Al3+ and Ti3+/4+ are determined with the help of MÖssbauer spectrograms. A hydrometallurgical route involving selective leaching and precipitation of iron in red-mud is tried. Red-mud is leached in oxalic acid at: 95˚C, 15 % Pulp density, 2.5 h leaching time, 1.5 pH. Kinetic studies yielded the leaching mechanism to be predominantly fluid film control. Ferric oxalate in the leach liquor is reduced to insoluble ferrous oxalate selectively using Iron powder. The ferrous oxalate formed is ~98 % pure. The precipitated ferrous oxalate is magnetically separated and reduced in Nitrogen atmosphere to form fine particulate magnetite. Additionally an economic feasibility study was conducted for the hydro and pyro alternatives to produce magnetite using Monte Carlo Simulations by imparting uncertainties in various input cost components. A traditional process was also compared to the proposed approaches for Total Capital Investment (TCI), Total Product Cost (TPC), Net Present Value (NPV) and sensitivity analysis. ~52 % reduction in Total product cost, 46 % reduction in Total Capital Investment was achieved for the hydrometallurgical process when compared to the traditional approach.