Óxido e fosfato de nióbio, calcinados em diferentes temperaturas, foram usados como catalisadores na reação de desidratação de 1-butanol, onde o efeito da temperatura de reação, da massa de catalisador e da vazão de butanol sobre a conversão e seletividade a butenos foram avaliadas através de um plano experimental. Foram caracterizadas as propriedades cristalográficas dos catalisadores. A maioria dos catalisadores apresentaram uma estrutura amorfa, mas algumas amostras apresentaram uma estrutura cristalina quando calcinadas em maiores temperaturas, 500 e 850 °C para o NbO e NbP, respectivamente. Nos testes reacionais, observou-se que o aumento da temperatura de calcinação dos catalisadores reduziu a conversão de 1-butanol. O catalisador fosfato de nióbio apresentou maior atividade, já que foi obtida uma conversão similar à do óxido de nióbio com uma massa 5 vezes menor, indicando a presença de sítios ácidos mais ativos. Além disso, a variável reacional que teve maior efeito na conversão foi a vazão de alimentação de 1-butanol; e seu aumento causou um decréscimo nos valores de conversão. Este comportamento indicou que a ordem aparente da reação é menor que um, o que foi confirmado por um modelo cinético baseado em lei de potência, o qual ajustado aos dados experimentais resultou em uma ordem aparente em torno de zero Equações fenomenológicas de velocidade de reação baseadas no modelo LHHW foram desenvolvidos. O teste estatístico F de Fisher foi utilizado para comparar os modelos fenomenológicos obtidos: para o óxido de nióbio calcinado em 400 °C o modelo heterogêneo que leva em conta apenas a adsorção de butanol foi considerado o mais adequado; para o fosfato de nióbio calcinado em 400 °C o modelo heterogêneo que leva em conta a adsorção de butanol e de água foi o mais adequado. Para ambos os catalisadores, com exceção do NbO calcinado em 500 °C, foi observada uma significativa isomerização de 1-buteno a 2-buteno, principalmente nas condições que foi obtida uma maior conversão de butanol. Este fato comprova a elevada força ácida destes catalisadores. A seletividade a 2-buteno foi maior ou igual a 1-buteno em todas as temperaturas e condições de reação com fosfato de nióbio. Para o óxido de nióbio, a seletividade a 2-buteno foi maior em poucas condições reacionais. / Niobium oxide and phosphate, calcined at different temperatures, were used as catalysts in the 1-butanol dehydration reaction, where the effect of reaction temperature, catalyst mass and butanol flow rate on conversion and selectivity to butenes were evaluated through an experimental design. The catalysts crystallographic properties were characterized. Most catalysts presented an amorphous structure, but some samples presented a crystalline structure when calcined at higher temperatures, 500 and 850 °C for NbO and NbP, respectively. In the reaction testes, it was observed that the increase in the catalysts calcination temperature decreased the 1-butanol conversion. The niobium phosphate catalyst presented higher activity, since it was obtained a similar conversion to that of niobium oxide with a mass 5 times lower, indicating the presence of more active acidic sites. Furthermore, the reaction variable that had the highest effect on the conversion was in the 1-butanol feeding flow rate; and its growth caused a decrease in the conversion values. This behavior indicated that the apparent reaction order is lower than one, which was confirmed through a kinetic model based on power law, which adjusted to the experimental data resulted in an apparent order around zero Phenomenological equations of reaction rate based on the LHHW model were developed. The Fisher statistical test was used to compare the phenomenological models obtained: for the niobium oxide calcined at 400 °C the heterogeneous model that takes into account only the adsorption of butanol was considered the most adequate; for the niobium phosphate calcined at 400 °C the heterogeneous model that takes into account the adsorption of butanol and of water was the most adequate. For both catalysts, with the exception of NbO calcined at 500 °C, a significant isomerization of 1-butene to 2-butene was observed, mainly in the conditions that were obtained a higher conversion of butanol. This fact proves the elevated acid strength of these catalysts. The selectivity to 2-butene was higher or equal to 1-butene at all reaction temperature and conditions where niobium phosphate was employed. For the niobium oxide, the selectivity to 2-butene was higher in a few reaction conditions.

Óxido e fosfato de nióbio, calcinados em diferentes temperaturas, foram usados como catalisadores na reação de desidratação de 1-butanol, onde o efeito da temperatura de reação, da massa de catalisador e da vazão de butanol sobre a conversão e seletividade a butenos foram avaliadas através de um plano experimental. Foram caracterizadas as propriedades cristalográficas dos catalisadores. A maioria dos catalisadores apresentaram uma estrutura amorfa, mas algumas amostras apresentaram uma estrutura cristalina quando calcinadas em maiores temperaturas, 500 e 850 °C para o NbO e NbP, respectivamente. Nos testes reacionais, observou-se que o aumento da temperatura de calcinação dos catalisadores reduziu a conversão de 1-butanol. O catalisador fosfato de nióbio apresentou maior atividade, já que foi obtida uma conversão similar à do óxido de nióbio com uma massa 5 vezes menor, indicando a presença de sítios ácidos mais ativos. Além disso, a variável reacional que teve maior efeito na conversão foi a vazão de alimentação de 1-butanol; e seu aumento causou um decréscimo nos valores de conversão. Este comportamento indicou que a ordem aparente da reação é menor que um, o que foi confirmado por um modelo cinético baseado em lei de potência, o qual ajustado aos dados experimentais resultou em uma ordem aparente em torno de zero Equações fenomenológicas de velocidade de reação baseadas no modelo LHHW foram desenvolvidos. O teste estatístico F de Fisher foi utilizado para comparar os modelos fenomenológicos obtidos: para o óxido de nióbio calcinado em 400 °C o modelo heterogêneo que leva em conta apenas a adsorção de butanol foi considerado o mais adequado; para o fosfato de nióbio calcinado em 400 °C o modelo heterogêneo que leva em conta a adsorção de butanol e de água foi o mais adequado. Para ambos os catalisadores, com exceção do NbO calcinado em 500 °C, foi observada uma significativa isomerização de 1-buteno a 2-buteno, principalmente nas condições que foi obtida uma maior conversão de butanol. Este fato comprova a elevada força ácida destes catalisadores. A seletividade a 2-buteno foi maior ou igual a 1-buteno em todas as temperaturas e condições de reação com fosfato de nióbio. Para o óxido de nióbio, a seletividade a 2-buteno foi maior em poucas condições reacionais. / Niobium oxide and phosphate, calcined at different temperatures, were used as catalysts in the 1-butanol dehydration reaction, where the effect of reaction temperature, catalyst mass and butanol flow rate on conversion and selectivity to butenes were evaluated through an experimental design. The catalysts crystallographic properties were characterized. Most catalysts presented an amorphous structure, but some samples presented a crystalline structure when calcined at higher temperatures, 500 and 850 °C for NbO and NbP, respectively. In the reaction testes, it was observed that the increase in the catalysts calcination temperature decreased the 1-butanol conversion. The niobium phosphate catalyst presented higher activity, since it was obtained a similar conversion to that of niobium oxide with a mass 5 times lower, indicating the presence of more active acidic sites. Furthermore, the reaction variable that had the highest effect on the conversion was in the 1-butanol feeding flow rate; and its growth caused a decrease in the conversion values. This behavior indicated that the apparent reaction order is lower than one, which was confirmed through a kinetic model based on power law, which adjusted to the experimental data resulted in an apparent order around zero Phenomenological equations of reaction rate based on the LHHW model were developed. The Fisher statistical test was used to compare the phenomenological models obtained: for the niobium oxide calcined at 400 °C the heterogeneous model that takes into account only the adsorption of butanol was considered the most adequate; for the niobium phosphate calcined at 400 °C the heterogeneous model that takes into account the adsorption of butanol and of water was the most adequate. For both catalysts, with the exception of NbO calcined at 500 °C, a significant isomerization of 1-butene to 2-butene was observed, mainly in the conditions that were obtained a higher conversion of butanol. This fact proves the elevated acid strength of these catalysts. The selectivity to 2-butene was higher or equal to 1-butene at all reaction temperature and conditions where niobium phosphate was employed. For the niobium oxide, the selectivity to 2-butene was higher in a few reaction conditions.

To prevent the global surface temperature from increasing past the 2 oC target, it is necessary to address CO2 emissions from small point sources. Within Canada’s heavy oil industry, SAGD facilities use natural gas combustion to produce the large amounts of steam required for the process, which produces approximately 0.5-2 Mtonnes of CO2 per annum. A suitable technology for CO2 mitigation from a SAGD facility is Pressurized Chemical Looping Combustion. PCLC is an oxy-combustion, carbon capture technology with a relatively low predicted energy penalty of 3-4%. The process requires a dual, interconnected fluidized bed reactor system with circulating solids. Natural gas is converted in the fuel reactor via a solid metal oxide, which is then circulated to the air reactor for reoxidation with air. As the cost of air compression is significant, the economical feasibility of the process is reliant on air reactor performance. The objective of this study is to investigate the oxidation reaction and derive a kinetic model for reactor design and performance assessment purposes. Ilmenite ore was chosen as the metal oxide, as it is low cost and has desirable oxygen transport properties for PCLC. Pressurized TGA tests were conducted to study the effects of oxygen concentration, temperature and pressure on the rate of the oxidation reaction. The total pressure was varied from 1-16 bara at 900 oC with air. The oxygen concentration was varied from 2.5-21 vol%, and the temperature from 800-1000 oC at 8 bar. Temperatures below 850 oC resulted in segregation of the Fe and Ti phase in the ilmenite ore, leading to a reduction in the overall oxygen carrying capacity. Crack formation was observed at higher oxygen partial pressures, resulting in increased surface area for reaction and a fast reaction rate. At lower oxygen partial pressures, a solid-state diffusion controlled regime was observed due to the absence of fissures. A dual mechanistic oxidation kinetic model was derived at 8 bar, with 2nd order random nucleation dominating at lower conversions, and Jander’s solid state diffusion model dominating at higher conversions. The transition from the nucleation and growth to the diffusion-controlled portion occurred at higher conversions with higher oxygen partial pressure. The activation energy was 16.6 kJ/mol and 48.7 kJ/mol while the order of reaction with respect to oxygen was 0.3 and 1.3 for respectively the nucleation and growth, and diffusion-controlled regimes. A preliminary air reactor model is constructed as a turbulent bed. The turbulent bed is modelled as an axial dispersion reactor for a basic performance assessment.

The elucidation of molecular function of proteins encoded by genes is a major challenge in biology today. Genes regulate the amount of proteins (enzymes) needed to catalyse a metabolic reaction. There are several works on either the modelling of gene expression or metabolic network. However, an integrative model of both is not well understood and researched. The integration of both gene expression and metabolic network could increase our understanding of cellular functions and aid in analysing the effects of genes on metabolism. It is now possible to build genome-scale models of cellular processes due to the availability of high-throughput genomic, metabolic and fluxomic data along with thermodynamic information. Integrating biological information at various layers into metabolic models could also improve the robustness of models for in silico analysis. In this study, we provide a software tool for the in silico reconstruction of genome-scale integrative models of gene expression and metabolic network from relevant database(s) and previously existing stoichiometric models with automatic generation of kinetic equations of all reactions involved. To reduce computational complexity, compartmentalisation of the cell as well as enzyme inhibition is assumed to play a negligible role in metabolic function. Obtaining kinetic parameters needed to fully define and characterise kinetic models still remains a challenge in systems biology. Parameters are either not available in literature or unobtainable in the lab. Consequently, there have been numerous methods developed to predict biological behaviour that do not require the use of detailed kinetic parameters as well as techniques for estimation of parameter values based on experimental data. We present an algorithm for estimating kinetic parameters which uses fluxes and metabolites to constrain values. Our results show that our genetic algorithm is able to find parameters that fit a given data set and predict new biological states without having to re-estimate kinetic parameters.

Gaining a quantitative understanding of metabolic behaviour has long been a major scientific goal. Beginning with crude mass balance experiments and progressing through enzyme kinetics, single-pathway models and collaborative efforts such as a community- based yeast reconstruction and onwards to the digital human. The primary goal of this research was to generate a large-scale kinetic metabolic model of yeast metabolism. As a community our ability to produce large-scale dynamic metabolic models has typically been limited by the time and cost involved in obtaining exact measurements of all relevant kinetic parameters. Attempts have been made to bring about a greater understanding by using computational approaches such as flux balance analysis, and also laboratory approaches such as metabolic profiling. Unfortunately these approaches alone do not go far enough to allow for a rich understanding of the metabolic behaviour.Methods were developed that allowed known data such as fluxes, equilibrium constants and metabolite concentrations to be used in first-approximation strategies. These made possible the construction of a thermodynamically consistent model that was reflective of the organism and growth conditions under which the known data were measured. Efforts were made to improve the strategy by developing already known dynamic flux measurement techniques so they were more reflective of the type of data required for constructing the metabolic model. The model constructed, using data from a specific yeast strain in a continuous culture environment, and included 284 reactions. The model showed a reasonable reproduction of system behaviour after perturbations of extracellular glucose above and below the operating conditions, after identification and substitution of just two exact rate laws of reactions that showed high control over the system. The methods developed require little knowledge beyond the stoichiometric matrix in the first instance, and as such, are applicable to any organism that has a reasonably comprehensive network reconstruction available.

Climate change is one of the biggest global threats of the 21st century. Fossil fuels constitute by far the most important energy source for transportation and the different governments are starting to take action to promote the use of cleaner fuels. Biomass-derived fuels are a promising alternative for diversifying fuel sources, reducing fossil fuel dependency and abating greenhouse gas emissions. The research interest has quickly shifted from first-generation biofuels, obtained from food commodities, to second-generation biofuels, produced from non-food resources. The subject of this PhD thesis is the production of second-generation biofuels via thermochemical conversion: biomass is first gasified to synthesis gas, a mixture of mainly H2 and CO; synthesis gas can then be catalytically converted to different fuels. This work summarizes six publications, which are focused on the synthesis gas conversion step. Two processes are principally examined in this summary. The first part of the PhD thesis is devoted to the synthesis of ethanol and higher alcohols, which can be used as fuel or fuel additives. The microemulsion technique is applied in the synthesis of molybdenum-based catalysts, achieving a yield enhancement. Methanol cofeeding is also studied as a way of boosting the production of longer alcohols, but a negative effect is obtained: the main outcome of methanol addition is an increase in methane production. The second part of the PhD thesis addresses wax hydroconversion, an essential upgrading step in the production of middle-distillate fuels via Fischer-Tropsch. Bifunctional catalysts consisting of noble metals supported on silica-alumina are considered. The deactivation of a platinum-based catalyst is investigated, sintering and coking being the main causes of decay. A comparison of platinum and palladium as catalyst metal function is also carried out, obtaining a fairly different catalytic performance of the materials in terms of conversion and selectivity, very likely due to dissimilar hydrogenation power of the metals. Finally, a kinetic model based on the Langmuir-Hinshelwood-Hougen-Watson formalism is proposed to describe the hydroconversion reactions, attaining a good fitting of the experimental data. / Klimatförändringarna är ett av de största globala hoten under det tjugoförsta århundradet. Fossila bränslen utgör den helt dominerande energikällan för transporter och många länder börjar stödja användning av renare bränslen. Bränslen baserade på biomassa är ett lovande alternativ för att diversifiera råvarorna, reducera beroendet av fossila råvaror och undvika växthusgaser. Forskningsintresset har snabbt skiftat från första generationens biobränslen som erhölls från mat-råvaror till andra generationens biobränslen producerade från icke ätbara-råvaror. Ämnet för denna doktorsavhandling är produktion av andra generationens biobränslen via termokemisk omvandling. Biomassa förgasas först till syntesgas, en blandning av i huvudsak vätgas och kolmoxid; syntesgasen kan sedan katalytiskt omvandlas till olika bränslen. Detta arbete sammanfattar sex publikationer som fokuserar på steget för syntesgasomvandling. Två processer är i huvudsak undersökta i denna sammanfattning. Den första delen av doktorsavhandlingen ägnas åt syntes av etanol och högre alkoholer som kan användas som bränsle eller bränsletillsatser. Mikroemulsionstekniken har använts vid framställningen av molybden-baserade katalysatorer, vilket gav en höjning av utbytet. Tillsatsen av metanol har också studerats som ett sätt att försöka få en högre koncentration av högre alkoholer, men en negativ effekt erhölls: huvudeffekten av metanoltillsatsen är en ökad metanproduktion. Den andra delen av doktorsavhandlingen handlar om vätebehandling av vaxer som ett viktigt upparbetningssteg vid framställning av mellandestillat från Fischer-Tropsch processen. Bifunktionella katalysatorer som består av ädelmetaller deponerade på silica-alumina valdes. Deaktiveringen av en platinabaserad katalysator undersöktes. Sintring och koksning var huvudorsakerna till deaktiveringen. En jämförelse mellan platina och palladium som funktionella metaller genomfördes också med resultatet att det var en ganska stor skillnad mellan materialens katalytiska egenskaper vilket gav olika omsättning och selektivitet, mycket sannolikt beroende på olika reaktionsmönster hos metallerna vid vätebehandling. Slutligen föreslås en kinetisk modell baserad på en Langmuir-Hinshelwood-Hougen-Watson modell för att beskriva reaktionerna vid vätebehandling. Denna modell ger en god anpassning till experimentella data. / El cambio climático es una de las mayores amenazas del siglo XXI. Los combustibles fósiles constituyen actualmente la fuente de energía más importante para el transporte, por lo que los diferentes gobiernos están empezando a tomar medidas para promover el uso de combustibles más limpios. Los combustibles derivados de biomasa son una alternativa prometedora para diversificar las fuentes de energía, reducir la dependencia de los combustibles fósiles y disminuir las emisiones de efecto invernadero. Los esfuerzos de los investigadores se han dirigido en los últimos años a los biocombustibles de segunda generación, producidos a partir de recursos no alimenticios. El tema de esta tesis de doctorado es la producción de biocombustibles de segunda generación mediante conversión termoquímica: en primer lugar, la biomasa se gasifica y convierte en gas de síntesis, una mezcla formada mayoritariamente por hidrógeno y monóxido de carbono; a continuación, el gas de síntesis puede transformarse en diversos biocombustibles. Este trabajo resume seis publicaciones, centradas en la etapa de conversión del gas de síntesis. Dos procesos se estudian con mayor detalle. En la primera parte de la tesis se investiga la producción de etanol y alcoholes largos, que pueden ser usados como combustible o como aditivos para combustible. La técnica de microemulsión se aplica en la síntesis de catalizadores basados en molibdeno, consiguiendo un incremento del rendimiento. Además, se introduce metanol en el sistema de reacción para intentar aumentar la producción de alcoholes más largos, pero los efectos obtenidos son negativos: la principal consecuencia es el incremento de la producción de metano. La segunda parte de la tesis estudia la hidroconversión de cera, una etapa esencial en la producción de destilados medios mediante Fischer-Tropsch. Los catalizadores estudiados son bifuncionales y consisten en metales nobles soportados en sílice-alúmina. La desactivación de un catalizador de platino se investiga, siendo la sinterización y la coquización las principales causas del problema. El uso de platino y paladio como componente metálico se compara, obteniendo resultados catalíticos bastante diferentes, tanto en conversión como en selectividad, probablemente debido a su diferente capacidad de hidrogenación. Finalmente, se propone un modelo cinético, basado en el formalismo de Langmuir-Hinshelwood-Hougen-Watson, que consigue un ajuste satisfactorio de los datos experimentales. / <p>QC 20160308</p>

Thesis (PhD (Biochemistry))--University of Stellenbosch, 2009. / ENGLISH ABSTRACT: The sugarcane stalk, besides being the main structural component of the plant, is also the major storage organ for carbohydrates. Sucrose forms the bulk of stored carbohydrates. Previous studies have modelled the sucrose accumulation pathway in the internodal storage parenchyma of sugarcane using kinetic models cast as systems of ordinary differential equations. Typically, results were analysed with methods such as metabolic control analysis. The present study extends those original models within an advection-diffusion-reaction framework, requiring the use of partial differential equations to model sucrose metabolism coupled to phloem translocation. Let N be a stoichiometric matrix, v a vector of reaction rates, s a vector of species concentrations and r the gradient operator. Consider a coupled network of chemical reactions where the species may be advected with velocities, U, or diffuse with coefficients, D, or both. We propose the use of the dynamic system, s + r (Us) + r (Drs) = Nv; for a kinetic model where species can exist in different compartments and can be transported over long distances in a fluid medium, or involved in chemical reactions, or both. Darcy’s law is used to model fluid flow and allows a simplified, phenomenological approach to be applied to translocation in the phloem. Similarly, generic reversible Hill equations are used to model biochemical reaction rates. These are also phenomenological equations, where all the parameters have operationally defined interpretations. Numerical solutions to this formulation are demonstrated with time-courses of two toy models. The first model uses a simple “linear” pathway definition to study the impact of the system geometry on the solutions. Although this is an elementary model, it is able to demonstrate the up-regulation of photosynthesis in response to a change in sink demand. The second model elaborates on the reaction pathway while keeping the same geometry definition as the first. This pathway is designed to be an abstracted model of sucrose metabolism. Finally, a realistic model of sucrose translocation, metabolism and accumulation is presented, spanning eight internodes and four compartments. Most of the parameters and species concentrations used as initial values were obtained from experimental measurements. To analyse the models, a method of sensitivity analysis called the Fourier Amplitude Sensitivity Test (FAST) is employed. FAST calculates the contribution of the possible variation in a parameter to the total variation in the output from the model, i.e. the species concentrations and reaction rates. The model predicted that the most important factors affecting sucrose accumulation are the synthesis and breakdown of sucrose in futile cycles and the rate of cross-membrane transport of sucrose. The models also showed that sucrose moves down a concentration gradient from the leaves to the symplast, where it is transported against a concentration gradient into the vacuole. There was a net gain in carbohydrate accumulation in the realistic model, despite an increase in futile cycling with internode maturity. The model presented provides a very comprehensive description of sucrose accumulation and is a rigorous, quantitative framework for future modelling and experimental design. / AFRIKAANSE OPSOMMING: Benewens sy strukturele belang, is die suikerrietstingel ook die primêre bergingsorgaan vir koolhidrate. Die oorgrote meerderheid van hierdie koolhidrate word as sukrose opgeberg. Studies tot dusver het die metabolisme rondom sukroseberging in die parenchiem van die onderskeie stingellitte as stelsels gewone differensiaalvergelykings gemodelleer. Die resultate is ondermeer met metaboliese kontrole-analise geanaliseer. Hierdie studie brei uit op die oorspronklike modelle, deur gebruik te maak van ’n stromings-diffusie-reaksie-raamwerk. Parsiële differensiaalvergelykings is geformuleer om die metabolisme van sukrose te koppel aan die vloei in die floëem. Gestel N is ’n stoichiometriese matriks, v ’n vektor van reaksiesnelhede, s ’n vektor van spesie-konsentrasies en r die differensiaalvektoroperator. Beskou ’n netwerk van gekoppelde reaksies waar die onderskeie spesies stroom met snelhede U, of diffundeer met koëffisiënte D, of onderhewig is aan beide prosesse. Dit word voorgestel dat die dinamiese stelsel, _s + r (Us) + r (Drs) = Nv; gebruik kan word vir ’n kinetiese model waar spesies in verskeie kompartemente kan voorkom en vervoer kan word oor lang afstande saam met ’n vloeier, of kan deelneem aan chemiese reaksies, of albei. Darcy se wet word gebruik om die vloeier te modeller en maak dit moontlik om ’n eenvoudige, fenomenologiese benadering toe te pas op floëem-vervoer. Eweneens word generiese, omkeerbare Hill-vergelykings gebruik om biochemiese reaksiesnelhede te modelleer. Hierdie vergelykings is ook fenomenologies van aard en beskik oor parameters met ’n duidelike fisiese betekenis. Hierdie omvattende raamwerk is ondermeer gedemonstreer met behulp van numeriese oplossings van twee vereenvoudigde modelle as voorbeelde. Die eerste model het bestaan uit ’n lineêre reaksienetwerk en is gebruik om die geometrie van die stelsel te bestudeer. Alhoewel hierdie ’n eenvoudige model is, kon dit die toename in fotosintese as gevolg van ’n verandering in metaboliese aanvraag verklaar. Die tweede model het uitgebrei op die reaksieskema van die eerste, terwyl dieselfde stelselgeometrie behou is. Hierdie skema is ontwerp as ’n abstrakte weergawe van sukrosemetabolisme. Ten slotte is ’n realistiese model van sukrosevervoer, metabolisme en berging ontwikkel wat agt stingellitte en vier kompartemente omvat. Die meeste parameters en konsentrasies van biochemiese spesies wat as aanvanklike waardes in die model gebruik is, is direk vanaf eksperimentele metings verkry. Die Fourier Amplitude Sensitiwiteits-Toets (FAST) is gebruik om die modelle te analiseer. FAST maak dit moontlik om die bydrae van parameters tot variasie in modeluitsette soos reaksiesnelhede en die konsentrasies van chemiese spesies te bepaal. Die model het voorspel dat sintese en afbraak van sukrose in ’n futiele siklus, asook transmembraan sukrosevervoer, die belangrikste faktore is wat sukrose-berging beïnvloed. Die model het ook getoon dat sukrose saam met ’n konsentrasiegradiënt beweeg vanaf die blare tot by die stingelparenchiem-sitoplasma, van waar dit teen ’n konsentrasiegradiënt na die vogselholte (vakuool) vervoer word. Volgens die realistiese model was daar ’n netto toename in die totale hoeveelheid koolhidrate, ten spyte van ’n toename in die futile siklus van sukrose in die ouer stingellitte. Die model wat in hierdie proefskrif voorgestel word verskaf ’n uitgebreide, omvattende beskrywing van sukroseberging. Voorts stel dit ’n rigiede kwantitatiewe raamwerk daar vir toekomstige modellering en eksperimentele ontwerp.

L’IRM apporte des informations morphologiques concernant la tumeur, mais également des informations concernant sa micro-vascularisation. En TEP/TDM, l’accumulation de la 18F-FDopa dans les cellules tumorales résulte de l’activité métabolique plus importante que celle des tissus sains. Nous avons étudié 28 gliomes pour lesquels nous avons analysé les données provenant d’IRM et de TEP/TDM. Une méthode de recalage a été développée afin de combiner les informations issues des deux modalités TEP et IRM et d’extraire des volumes d’intérêt sur la base des données conjointes TEP et IRM. L’analyse du contenu de ces volumes d’intérêt par un modèle de mélange gaussien a permis de différencier, dans ces volumes, les tissus tumoraux et les tissus sains, et d’obtenir ainsi des volumes tumoraux et de référence communs pour les modalités TEP et IRM. Des paramètres issus de la TEP ou de l’IRM ont ensuite été calculés dans ces volumes communs aux deux modalités, pour caractériser les tumeurs et les tissus sains. L’analyse discriminante linéaire (ADL) des données TEP/TDM et d’IRM combinées permet de discriminer les différentes classes tissulaires. Les courbes Receiver Operating Characteristic ROC combinées à l’ADL permettent d’évaluer les critères multiples [SUVmax , rCBV] et [rk1 , rCBV] et conduisent à des AUC respectives de 0,88 et 0,92. En considérant les informations combinées [SUVmax , rCBV], nous avons obtenu une sensibilité de détection des tumeurs de haut grade de 95% pour une spécificité correspondante de 60% ainsi qu’une valeur prédictive négative de 52% pour une valeur prédictive positive de 95%. De même, avec le critère [rk1 , rCBV], nous avons obtenu une spécificité de 60% pour 95% de sensibilité de détection des tumeurs de haut grade ainsi qu’une valeur prédictive négative de 60% pour une valeur prédictive positive de 95%. Nos travaux montrent que la fusion des informations microvasculaires et métaboliques est possible. Dans le cas du diagnostic différentiel des gliomes, l’information microvasculaire n’apporte cependant pas d’information plus discriminante que l’information métabolique seule. / MRI provides morphological information about tumour, but also provides information regarding the micro-vascularization of the tumour. In PET/CT, the accumulation of 18F-FDopa in tumour cells results from the metabolic activity greater than that of healthy tissues. We studied 28 gliomas for which we analysed data from MRI and PET/CT. A registration method has been developed to combine information from both PET and MRI and to extract volumes of interest consistent with the information included in the two modalities. In these volumes, the tumour compartment and normal tissue compartment were identified using a Gaussian mixture model. Parameters from PET or MRI data were then calculated in these compartments. ROC analyses combined with linear discriminant analyses were used to assess whether joint observation of standardized uptake value (SUVmax ) and relative Cerebral Blood Volume (rCBV) or of relative rk1 and rCBV could distinguish between low grade and high grade tumours. We found that using this joint analysis, 82.4% of high-grade tumors and 70.0% of low-grade tumors were correctly classified (AUC of 0.88 for [SUVmax , rCBV] and of 0.92 for [rk1 , rCBV]). Considering the [SUVmax , rCBV] combined information, the sensitivity for detecting high-grade tumors was 95% with a specificity of 60%. The negative predictive value was 52% for a positive predictive value of 95%. Similarly, considering the [rk1 , rCBV] combined information, we also a specificity of 60% associated with a 95% sensitivity for detecting high-grade tumors, with a negative predictive value of 60% and positive predictive value of 95%. Our work shows that joint analysis of microvascular and metabolic information is possible by combining PET and MR imaging data. However, we found that, in our patient population, the microvascular information given by MR did not bring information more discriminating than the metabolic information derived from PET only.

This thesis presents the potential of integrating chemical and biological treatment technologies for the removal of high concentrations of phenol in a bioremediation medium. High concentrations of phenol in wastewater are difficult to remove by purely biological methods. Chemical oxidation is one way to treat high concentrations of phenol but complete oxidation is not always possible or will make the treatment process uneconomical. An experimental design approach, based on central composite rotatable design (CCRD) was used to evaluate the effects of process parameters on phenol oxidation by Fentons reagent and chlorine dioxide. Performance of the chemical oxidation was evaluated by determining the percentage of phenol oxidized at equilibrium. The reaction mechanism for the oxidation of phenol by Fentons reagent was proposed based on identification of the intermediate compounds.<p> The effects of H₂O₂ concentration (2000 to 5000 mg L^-1) and FeSO₄.7H₂O concentration (500 to 2000 mg L^-1) were investigated on phenol oxidation and optimal concentrations of H₂O₂ and FeSO₄.7H₂O for complete oxidation of 2000 mg L^-1 phenol in medium were found to be 4340 mg L^-1 and 1616 mg L^-1, respectively, at 25°C and pH 3. The main oxidation products were identified as catechol, hydroquinone and maleic acid.<p> In the case of phenol oxidation by chlorine dioxide, the effects of chlorine dioxide concentration (500 to 2000 mg L^-1), temperature (10 to 40°C) and pH (3 to 7) on the oxidation of 2000 mg L^-1 of phenol were determined. The optimal concentration of chlorine dioxide to completely oxidize 2000 mg L^-1 of phenol was 2000 mg L^-1. The other parameters did not significantly affect the oxidation over the ranges studied. The main oxidation products were identified as 1,4-benzoquinone and 2-chloro-1,4-benzoquinone.<p> Finally, the biodegradation of 1,4-benzoquinone, the main oxidation product of phenol oxidation by chlorine dioxide, was studied in batch and continuous systems using Pseudomonas putida 17484 in two dose McKinneys medium. The effects of 1,4-benzoquinone concentration and temperature were studied on biodegradation of 1,4-benzoquinone in batch reactors. Under optimal conditions, it was found that 150 mg L^-1 1,4-benzoquinone could be successfully biodegraded at 15°C. In a continuous reactor operating at 15°C the highest removal rate with 500 mg L^-1 of 1,4-benzoquinone was found to be 246 mg L^-1 h^-1. The values of µmax, Ks and yield were also determined as 0.74±0.03 h^-1 and 14.17±3.21 mg L^-1 and 2x10¹³ cell mg^-1, respectively.

This thesis presents the potential of integrating chemical and biological treatment technologies for the removal of high concentrations of phenol in a bioremediation medium. High concentrations of phenol in wastewater are difficult to remove by purely biological methods. Chemical oxidation is one way to treat high concentrations of phenol but complete oxidation is not always possible or will make the treatment process uneconomical. An experimental design approach, based on central composite rotatable design (CCRD) was used to evaluate the effects of process parameters on phenol oxidation by Fentons reagent and chlorine dioxide. Performance of the chemical oxidation was evaluated by determining the percentage of phenol oxidized at equilibrium. The reaction mechanism for the oxidation of phenol by Fentons reagent was proposed based on identification of the intermediate compounds.<p> The effects of H₂O₂ concentration (2000 to 5000 mg L^-1) and FeSO₄.7H₂O concentration (500 to 2000 mg L^-1) were investigated on phenol oxidation and optimal concentrations of H₂O₂ and FeSO₄.7H₂O for complete oxidation of 2000 mg L^-1 phenol in medium were found to be 4340 mg L^-1 and 1616 mg L^-1, respectively, at 25°C and pH 3. The main oxidation products were identified as catechol, hydroquinone and maleic acid.<p> In the case of phenol oxidation by chlorine dioxide, the effects of chlorine dioxide concentration (500 to 2000 mg L^-1), temperature (10 to 40°C) and pH (3 to 7) on the oxidation of 2000 mg L^-1 of phenol were determined. The optimal concentration of chlorine dioxide to completely oxidize 2000 mg L^-1 of phenol was 2000 mg L^-1. The other parameters did not significantly affect the oxidation over the ranges studied. The main oxidation products were identified as 1,4-benzoquinone and 2-chloro-1,4-benzoquinone.<p> Finally, the biodegradation of 1,4-benzoquinone, the main oxidation product of phenol oxidation by chlorine dioxide, was studied in batch and continuous systems using Pseudomonas putida 17484 in two dose McKinneys medium. The effects of 1,4-benzoquinone concentration and temperature were studied on biodegradation of 1,4-benzoquinone in batch reactors. Under optimal conditions, it was found that 150 mg L^-1 1,4-benzoquinone could be successfully biodegraded at 15°C. In a continuous reactor operating at 15°C the highest removal rate with 500 mg L^-1 of 1,4-benzoquinone was found to be 246 mg L^-1 h^-1. The values of µmax, Ks and yield were also determined as 0.74±0.03 h^-1 and 14.17±3.21 mg L^-1 and 2x10¹³ cell mg^-1, respectively.