Le vieillissement normal est associé à une réorganisation cérébrale qui peut être influencée par plusieurs facteurs. Des théories comme la réserve cognitive de Stern (2002) tentent d’expliquer les effets de ces différents facteurs. Certains, le niveau de scolarité par exemple, sont encore mal connus. Pourtant, le niveau de scolarité est connu pour avoir un impact sur les performances cognitives tout au long de la vie. Le but de ce mémoire est d’étudier les effets du niveau de scolarité sur l’oxygénation cérébrale de personnes âgées en santé lors d’une tâche d’évocation lexicale orthographique et sémantique. Chaque tâche est divisée selon un critère « plus productive » et « moins productive ». Les âgés faiblement scolarisés produisent moins de mots que les âgés fortement scolarisés. De plus, la différence de mots produits entre le critère plus productif et moins productif est plus grande pour la tâche sémantique que pour la tâche orthographique. Du point de vue hémodynamique, les deux groupes ont des activations semblables, contredisant le phénomène HAROLD. De plus, les participants peu scolarisés tendent à activer de façon plus importante l’hémisphère gauche, peu importe la tâche ou la condition. Par contre, les activations varient selon la tâche et la condition dans le cas du groupe fortement scolarisé. / Normal aging is associated with cerebral reorganisation which can be influenced by many factors. For example, the theory cognitive reserve (Stern, 2002) is trying to explain how those factors can have an impact on the reorganization. However, some factors, such as educational level, are known to have an impact on cognitive performance. The aim of this dissertation is to study the effect of educational level in cerebral oxygenation of healthy older adults during both phonologic and semantic verbal fluency tasks. Each task is divided into two criteria: more productive and less productive. Behavioural data showed that less educated elderly generate fewer words than more educated ones for both tasks. Moreover, the differences between the number of words for the more productive criterion and the less productive one are higher for the semantic than for the phonologic task. NIRS data showed that both groups activated prefrontal cortex, without difference between them. In addition, less educated participants tend to have bigger activations in the left hemisphere regardless of the task and the criterion. On the other hand, higher educated participants’ activations vary according to the task and the criterion unlike the HAROLD model’s predictions.

L’étude du cerveau humain est un domaine en plein essor et les techniques non-invasives de l’étudier sont très prometteuses. Afin de l’étudier de manière non-invasive, notre laboratoire utilise principalement l’imagerie par résonance magnétique fonctionnelle (IRMf) et l’imagerie optique diffuse (IOD) continue pour mesurer et localiser l’activité cérébrale induite par une tâche visuelle, cognitive ou motrice. Le signal de ces deux techniques repose, entre autres, sur les concentrations d’hémoglobine cérébrale à cause du couplage qui existe entre l’activité neuronale et le flux sanguin local dans le cerveau. Pour être en mesure de comparer les deux signaux (et éventuellement calibrer le signal d’IRMf par l’IOD), où chaque signal est relatif à son propre niveau de base physiologique inconnu, une nouvelle technique ayant la capacité de mesurer le niveau de base physiologique est nécessaire. Cette nouvelle technique est l’IOD résolue temporellement qui permet d’estimer les concentrations d’hémoglobine cérébrale. Ce nouveau système permet donc de quantifier le niveau de base physiologique en termes de concentrations d’hémoglobine cérébrale absolue. L’objectif général de ma maîtrise était de développer un tel système afin de l’utiliser dans une large étude portant sur la condition cardiovasculaire, le vieillissement, la neuroimagerie ainsi que les performances cognitives. Il a fallu tout d’abord construire le système, le caractériser puis valider les résultats avant de pouvoir l’utiliser sur les sujets de recherche. La validation s’est premièrement réalisée sur des fantômes homogènes ainsi qu’hétérogènes (deux couches) qui ont été développés. La validation des concentrations d’hémoglobine cérébrale a été réalisée via une tâche cognitive et appuyée par les tests sanguins des sujets de recherche. Finalement, on présente les résultats obtenus dans une large étude employant le système d’IOD résolue temporellement en se concentrant sur les différences reliées au vieillissement. / Our understanding of the functional organization of the human brain has been greatly influenced by the development of new medical imaging techniques. Pr. Hoge’s research has focused on the use of functional magnetic resonance imaging (fMRI) and continuous diffuse optical imaging (DOI) for non-invasive localization and quantification of brain activity associated with behavioral stimuli or tasks (e.g. cognitive, motor or visual). The respective signals of both techniques are based on cerebral haemoglobin concentrations because of the coupling that exists between neuronal activity and cerebral blood flow. Relating BOLD fMRI signals with those acquired using DOI has been complicated by the fact that fMRI yields fractional change values, while the majority of DOI methods have provided absolute changes from an unknown baseline. To address this, we adopted a newer technique known as time-resolved DOI, which allows absolute quantification of cerebral haemoglobin concentrations. Time-resolved DOI thus has the capacity to quantify the subject’s resting hemoglobin concentrations in absolute micromolar units. The main objective of my masters’ project was to implement and optimize a time-resolved DOI system for use in a large study exploring the links between cardiovascular fitness, aging, neuroimaging markers, and cognitive performance. In this thesis we describe the fabrication of the system, followed by its characterisation and validation using solid optical phantoms (homogeneous and heterogeneous) developed for this purpose. Haemoglobin concentrations obtained non-invasively with the system are validated against blood draws, while the sensitivity to variations in concentration are assessed during a cognitive task. Finally, we present the results of a large study in which the time-resolved DOI system was used to characterize age-related vascular changes in the brain.

Eucalyptus macarthurii is one of the cold tolerant eucalypt species grown in South Africa for pulp and paper. However, little research has been done on this species’ growth performance. A study was therefore initiated to: i) analyse growth characteristics of Eucalyptus macarthurii at two sites and to calculate genetic parameters (genetic and phenotypic correlations, heritabilities and genetic gains), ii) develop a non-destructive near infrared calibration model to predict whole tree pulp yield of Eucalyptus macarthurii, and iii) screen a second generation Eucalyptus macarthurii breeding population, using the developed near infrared calibration model on core samples, to predict screened pulp yield and to rank and identify families with superior pulping properties. Eucalyptus macarthurii population growth data (diameter under bark, diameter over bark, bark thickness, bark stripping, height, basic wood density and stem form) were measured at Pinewoods and Vlakkloof sites and their respective genetic parameters calculated. Genotype by environment interaction was found in this population, indicating that different populations should perhaps be developed independently of each other for the two sites. Genetic and phenotypic correlations between diameter over bark and diameter under bark were, 0.96 and 0.98 for Pinewoods and 0.98 and 0.99 for Vlakkloof, respectively. These correlations indicated that selection of diameter over bark would lead to a positive indirect selection for diameter under bark. The heritability estimates also ranged from 0.03 to 0.23 at both sites, which indicated a reasonable response to selection. The predicted gains for all traits found at Pinewoods were higher than those at Vlakkloof for progeny trials E76/P1, except height for progeny trial E76/P2, which was 2.09m at Pinewoods site and 3.52m at Vlakkloof site which showed that, selection for taller trees will be more effective at Vlakkloof site. A preliminary study was undertaken from eleven second generation trees (2007 tree collection) to investigate if the radial strip core taken at breast height predicts the whole tree wood properties. Correlations found between laboratory Kraft pulping of whole tree wood discs and whole tree NIR spectra with that of the radial strip core NIR spectra were 0.9472 and 0.9506, respectively. These results confirmed that NIR spectra of the radial strip core at breast height predict the whole tree wood properties. A non-destructive near infrared calibration model using wood samples was obtained from Eucalyptus macarthurii felled trees. The wood samples were chipped into wood chips, pulped using Kraft pulping (reference method) and a sub-sample of wood chips of the same trees were ground into sawdust samples and analysed through near infrared spectroscopy for screened pulp yield. The screened pulp yield values obtained from both processes had a narrow screened pulp yield range of 40 to 48%. The Eucalyptus macarthurii screened pulp yield values obtained from both processes, as well as from values obtained from other eucalypt species, were subjected to Vision® Software for calibration and validation of the near infrared calibration model. The results indicated a strong calibration correlation coefficient of 94%, between Kraft pulping and near infrared spectroscopy with a validation coefficient of 89%. The strong correlation and validation coefficient indicated that a reliable non-destructive near infrared model to predict screened pulp yield was successfully developed. The successful development of the valid calibration model required a wider range of other eucalypts species, which improved the development of the model. The developed calibration model was applied to the second generation breeding population planted in KwaZulu-Natal and Mpumalanga provinces, using wood core samples obtained from standing trees for the prediction of screened pulp yield. The highest screened pulp yield achieved was 48%, which compared well to that found for Kraft pulping, which confirmed the success of the development of the calibration model. There was a wide scope of growth variation found amongst traits, which will be useful in selecting superior trees for the next generation. The development of the nondestructive near infrared calibration model was a success due to the strong correlation coefficients found between the screened pulp yields obtained from Kraft pulping and near infrared spectroscopy processes, which was achieved by the inclusion of other eucalypt species in the dataset. The calibration model can be used to select the top performing individual and family trees for the next generation based on screened pulp yield. Tree improvement trials can now be conserved for further breeding, without felling the trees for determination of pulping properties. / Thesis (M.Sc.)-University of KwaZulu-Natal, Pietermaritzburg, 2008.

The purpose of this thesis was to explore the potential of near-infrared spectroscopy (NIRS) as an access channel by establishing reliable signal detection to verify the existence of signal differences associated with changes in activity. This thesis focused on using NIRS to measure brain activity from the prefrontal cortex during an auditory Go-No-Go task. A singular spectrum analysis change-point detection algorithm was applied to identify transition points where the NIRS signal properties varied from previous data points in the signal, indicating a change in brain activity. With this algorithm, latency values for change-points detected ranged from 6.44 s to 9.34 s. The averaged positive predictive values over all runs were modest (from 49.41% to 67.73%), with the corresponding negative predictive values being generally higher (48.66% to 78.80%). However, positive and negative predictive values up to 97.22% and 95.14%, respectively, were achieved for individual runs. No hemispheric differences were found.

The purpose of this thesis was to explore the potential of near-infrared spectroscopy (NIRS) as an access channel by establishing reliable signal detection to verify the existence of signal differences associated with changes in activity. This thesis focused on using NIRS to measure brain activity from the prefrontal cortex during an auditory Go-No-Go task. A singular spectrum analysis change-point detection algorithm was applied to identify transition points where the NIRS signal properties varied from previous data points in the signal, indicating a change in brain activity. With this algorithm, latency values for change-points detected ranged from 6.44 s to 9.34 s. The averaged positive predictive values over all runs were modest (from 49.41% to 67.73%), with the corresponding negative predictive values being generally higher (48.66% to 78.80%). However, positive and negative predictive values up to 97.22% and 95.14%, respectively, were achieved for individual runs. No hemispheric differences were found.

Title: Effect of cold water immersion on intermittent isometric forearm flexor contractions to failure in rock climbers Objectives: The aim of this study was to determine the effect of cold water immersion on intermittent isometric forearm flexor contraction to failure in rock climbers. Methods: Thirty-two climbers (15 male and 17 female) completed three intermittent trials to failure, on a climbing-specific handgrip dynamometer, on three separate visits to the laboratory. For each visit a different recovery strategy was employed: passive recovery (PAS), cold water immersion at 8 řC (CWI 8) or 15 řC (CWI 15). The force time integral (FTI - time of contraction multiplied by the force of contraction) was determined to assess intermittent performance. The tissue saturation index (TSI) and total haemoglobin (tHb) during isometric contractions from near-infrared spectroscopy (NIRS) were determined to assess hemodynamic changes. Differences between repeated trials and three recovery protocols, derived parameters NIRS, were assessed using repeated measures ANOVA with Bonferroni corrections. Results: There was no significant difference between conditions after trial one. In response to the PAS recovery condition there was a 10% and 22% decrease in FTI in the second and third trials, respectively. The PAS...

Made available in DSpace on 2015-05-14T13:21:32Z (GMT). No. of bitstreams: 1 arquivototal.pdf: 15006665 bytes, checksum: 541b3c9095c1006563486163e559d5fd (MD5) Previous issue date: 2014-02-03 / Coordenação de Aperfeiçoamento de Pessoal de Nível Superior - CAPES / The search for a better quality of life has led to increased consumption of foods with fewer calories, high in fiber and vitamins, and obtained from different forms of cultivation. Amid these foods, there are cereal bars and lettuce, foods that are easily accessible, widely consumed and have high nutritional values. Like any other food, require efficient methods that can ensure its quality. Thus, the need for rapid, accurate analytical methods and low cost, which can help to identify and classify these foods safely arises. Within this perspective, this paper makes use of Near Infrared Spectroscopy (NIR) combined with Linear Discriminant Analysis (LDA) to classify samples of cereal bars and lettuce. A total of 121 samples of cereal bars, three distinct types (conventional, diet and light) and 104 samples of three different types of lettuce cultivation (conventional, organic and hydroponic) was used. The acquisition of the spectra was made on equipment Spectrum 400 (Perkin Elmer) with accessory NIRA (Near Infrared Reflectance Acessory) in the range 10000 - 4000 cm-1. Classification models were constructed by combining the LDA algorithms and variable selection: Stepwise (SW), Successive Projections Algorithm (SPA) and Genetic Algorithm (GA). Strategies for pre - processing data were evaluated and the efficiency of the models was determined from the of correct classification rate (CCR) for the full set of samples and the test set. For both matrices the model that generated a better CCR was the GA-LDA valued 95% to matrix of the cereal bars and 97.1 % for array of lettuces, both based on the total set of samples (training, validation and testing). Regarding the set of test models presented results of CCR with performance of 90.3 % and 95.4 % for matrices of cereal bars and lettuce respectively. / A busca por uma melhor qualidade de vida tem levado ao aumento do consumo de alimentos com menos calorias, ricos em fibras e vitaminas, e obtidos de formas de cultivo diferenciadas. Em meio a esses alimentos, encontram-se as barras de cereais e as alfaces, que são alimentos de fácil acesso, muito consumidos e que possuem altos valores nutricionais. Como qualquer outro alimento, necessitam de métodos eficientes que possam assegurar sua qualidade. Assim, surge a necessidade de métodos analíticos rápidos, precisos e de baixo custo, que possam ajudar a identificar e classificar com segurança a esses alimentos. Dentro desta perspectiva, este trabalho faz uso da Espectroscopia no Infravermelho Próximo (NIR) aliada a Análise Discriminante Linear (LDA) para classificar amostras de barras de cereais e alfaces. Um total de 121 amostras de barras de cereais, de três tipos distintos (convencional, diet e light) e 104 amostras de alface de três diferentes tipos de cultivo (convencional, orgânico e hidropônico) foi utilizado. A aquisição dos espectros foi feita no equipamento Spectrum 400 (Perkin Elmer) com acessório NIRA (Near Infrared Reflectance Acessory) na faixa de 10.000 a 4.000 cm-1. Modelos de classificação foram construídos através da associação da LDA e algoritmos de seleção de variáveis: Stepwise (SW), Algoritmo das Projeções Sucessivas (SPA) e Algoritmo Genético (GA). Estratégias de pré-processamento de dados foram avaliadas e a eficiência dos modelos foi determinada em relação à taxa de classificação correta (TCC), para o conjunto total das amostras e para o conjunto de teste. Para as duas matrizes o modelo que gerou um melhor TCC foi o GA-LDA com valor de 95% para matriz das barras de cereais e 97,1% para matriz das alfaces, ambos baseados no conjunto total das amostras (treinamento, validação e teste). Em relação ao conjunto de teste os modelos apresentaram resultados de TCC com desempenho de 90,3% e 95,4% para as matrizes das barras de cereais e alfaces respectivamente.

Orientadores: Eduardo Augusto Caldas Batista, Antonio Jose de Almeida Meirelles / Dissertação (mestrado) - Universidade Estadual de Campinas, Faculdade de Engenharia de Alimentos / Made available in DSpace on 2018-08-10T02:56:23Z (GMT). No. of bitstreams: 1 Priamo_WagnerLuiz_M.pdf: 1151319 bytes, checksum: 0c097b45fca5039b53924a7b27cd3e1a (MD5) Previous issue date: 2008 / Resumo: A extração de óleos vegetais com solvente possui a vantagem de operar a temperaturas menores em relação às usadas na extração mecânica, permitindo também a extração de outros compostos desejáveis da semente oleaginosa. Hexana é, geralmente, utilizada para extrair óleo por lixiviação, porém é inflamável e suspeita de causar danos à saúde humana. Alguns estudos surgiram com o intuito de investigar a mudança deste solvente. O processo de refino dos óleos vegetais brutos envolve a dessolventização, degomagem, branqueamento, desacidificação e desodorização. Óleos vegetais podem ser desacidificados por processos convencionais, como o refino químico e físico. O refino químico é aplicado para todos os óleos brutos, entretanto, proporciona grandes perdas de óleo neutro. Para óleo de alta acidez, o refino físico é também uma possibilidade, mas pode causar alterações indesejáveis na cor e na estabilidade oxidativa. Uma alternativa é a desacidificação por extração líquido-líquido, o qual é um processo mais brando, ocorrendo à temperatura ambiente e pressão atmosférica, causando menores perda de óleo neutro. Ainda, destaca-se a produção de biodiesel a partir de matrizes vegetais, onde este pode ser produzido pela transesterificação de triacilgliceróis com metanol ou etanol gerando metil ou etil ésteres. A baixa solubilidade dos triacilgliceróis em álcoois aponta para a necessidade do uso de outros solventes que proporcionem um sistema monofásico e melhorar a difusão dos reagentes. O conhecimento do comportamento de fases destes sistemas compostos por óleo vegetal bruto/solventes à diferentes temperaturas, configura o principal tópico em operações de transferência de massa e catálise. Levando isto em consideração, este trabalho teve por objetivo determinar experimentalmente dados de equilíbrio líquido-líquido de sistemas ternários compostos por óleo de farelo de arroz refinado/etanol anidro/n-hexano e quaternários compostos por óleo de farelo de arroz refinado/ácido oléico comercial/etanol anidro/n-hexano, usando a técnica de espectroscopia por infravermelho próximo para a quantificação dos componentes das fases em equilíbrio. A partir dos resultados obtidos, verificou-se que a solubilidade dos sistemas é afetada pelo teor de ácido graxo livre presente no óleo de farelo de arroz, onde com o aumento deste acarreta numa diminuição da região heterogênea. O mesmo fato ocorreu no estudo realizado para os sistemas ternários, onde o aumento da temperatura promoveu um aumento da solubilidade, devido ao fato de a solubilidade mútua entre o óleo de farelo de arroz e etanol aumentar com o aumento desta variável. Em todos os sistemas, verificaram-se maiores desvios no balanço de massa para o componente ácido oléico comercial e n-hexano, enquanto que para os demais componentes, óleo de farelo de arroz e etanol anidro, seus desvios foram baixos. Através dos dados obtidos nesse trabalho verificou-se que o método proposto pode ser utilizado na quantificação dos componentes nas fases em equilíbrio para sistemas ternários e quaternários apresentando algumas vantagens em relação a outras técnicas, como por exemplo, a cromatografia. Os dados de equilíbrio líquido-líquido foram usados para ajustar os parâmetros do modelo de NRTL, com desvio médio relativo de 1,06 % para os sistemas a 25 ºC e de 0,26 % para o sistema ternário a 40 ºC / Abstract: Solvent extraction has the advantage of operating at lower temperatures and also can extract other desirable components from oilseeds when compared to mechanical extraction. Commercial hexane is the usual solvent to extract oil by leaching, but it is highly flammable and it can cause hazard to human health. Some studies have begun to investigate the change of this solvent. The refining processes of crude vegetable oils involve solvent stripping, degumming, bleaching, deacidification and deodorization. Vegetable oils can be deacidified by conventional processes, such as chemical and physical refining. Chemical refining is applicable for all raw materials; however, it can result in large losses of neutral oil. For high acidity oils, physical refining is also a possibility, but can cause undesirable alterations in color and stability to oxidation. An alternative is the deacidification by liquid-liquid extraction, process carried out at room temperature and atmospheric pressure and that causes lower loss of neutral oil. Biodiesel is a renewable energetic source and it is gaining acceptance and market. The most common way to produce biodiesel is by transesterification of triacylglycerols with methanol or ethanol, generating methyl or ethyl esters. The low solubility of triacylglycerols in alcohols presents the necessity of using some another solvent to create a system of one phase and to improve the diffusion of the reagents. The knowledge of the behavior of all these systems of crude vegetable oil / solvents at different temperatures configures the principal topic in mass transfer operations and catalysis. Taking, these points into account, this work aims to determine experimental data for liquid-liquid equilibrium of ternary systems containing refined rice brain oil / anhydrous ethanol / n-hexane and quaternary systems containing refined rice brain oil / commercial oleic acid / anhydrous ethanol / n-hexane, using Near Infrared Spectroscopy (NIR) for quantification of the components in each phase in equilibrium. For the quaternary systems, the increasing in the oleic acid composition in rice brain oil increases the solubility of the systems and decreases the biphasic region. For the ternary systems, the results showed that the increase in the temperature promotes a reduction of the two phase region, given by the increase of the mutual solubility of refined rice brain oil and anhydrous ethanol. In all systems higher deviations of mass balance for the commercial oleic acid and hexane were found, while for the other components, refined rice brain oil and anhydrous ethanol, the deviations were lower. According to the results obtained, we concluded that the Near Infrared Spectroscopy is highly accurate, with some advantage in relation to other analytical methods. The experimental data were correlated using the NRTL model, and for the systems at 298.3 K, the global deviation was 1.06 %; for the ternary system at 313.3 K, the global deviation was 0.26 % / Mestrado / Mestre em Engenharia de Alimentos

Orientador: Rubens Maciel Filho / Dissertação (mestrado) - Universidade Estadual de Campinas, Faculdade de Engenharia Química / Made available in DSpace on 2018-08-16T11:19:21Z (GMT). No. of bitstreams: 1 MartinezArias_EdgarLeonardo_M.pdf: 60155872 bytes, checksum: 6edb8dbfd65cb71ea0a617a741e58925 (MD5) Previous issue date: 2010 / Resumo: A tecnologia da microreação é um importante método de intensificação de processos que oferece numerosos benefícios para a indústria de processos químicos. A elevada razão área superficial-volume aumenta as taxas de transferência de massa e energia, melhorando a eficiência e o desempenho dos reatores, e permitindo um aumento na segurança resultante do baixo hold-up em comparação com o reator convencional. O fluxo de líquidos imiscíveis nos microreatores tem mostrado uma intensificação da transferência de massa através da aplicação de estruturas internas que servem como misturadores passivos, o que aumenta a difusão e, conseqüentemente, aumenta a taxa de reação observada. Nesta dissertação, destaca-se o estudo da hidrodinâmica e da influência dos parâmetros de reação na intensificação da produção contínua de biodiesel em três microreatores com configurações diferentes, através de técnicas experimentais e computacionais. Experimentos foram realizados para caracterizar o óleo de mamona como potencial matéria prima para a produção de biodiesel. Testes reológicos, calorimetria diferencial de varredura (DSC), termogravimetria (TG/DTG) e cromatografia gasosa foram utilizados para determinar as propriedades físicas e químicas do óleo vegetal. Cromatografia de exclusão de tamanho (HPLC/SEC) foi utilizada para avaliar as diferentes variáveis que afetam a reação de transesterificação de óleo de mamona com etanol anidro tendo o hidróxido de sódio como catalisador em um reator em batelada. O efeito da temperatura, razão molar álcool/óleo, concentração de catalisador e tempo de reação foram analisados, observando a variação da composição do meio de reação. Um modelo matemático foi aplicado para descrever a cinética química de transesterificação. Tecnologias de microfabricação convencionais, tais como fotolitografia e litografia macia foram aplicadas na fabricação de microreatores utilizando fotorresiste SU-8 e polidimetilsiloxano (PDMS). Várias dificuldades no processamento do fotorresiste SU-8 para obter estruturas complexas através do processo de fotolitografia foram discutidas. No processo de litografia macia o molde foi fabricado com base em técnicas de fotolitografia, onde o fotorresiste SU-8 foi usado para construir a estrutura dos moldes dos microreatores. Experimentos foram realizados para a análise da influência da geometria do microreator. Três diferentes estruturas foram construídas: T, Omega e Tesla. A mistura dentro dos microreatores para baixos números de Reynolds foi avaliada mediante procedimentos experimentais e simulações de dinâmica de fluidos (CFD). A caracterização qualitativa da mistura foi realizada através da observação da evolução da mistura do óleo de mamona/etanol para diferentes razões de fluxo com base na taxa de transferência de um corante solvatocrômico entre os dois líquidos imiscíveis. Além disso, mediante simulações CFD foi possível caracterizar as circulações internas e capturar o mecanismo de geração de mistura, melhorando a compreensão dos resultados obtidos experimentalmente. Finalmente, a produção contínua de biodiesel foi estudada nos microreatores, a fim de avaliar a influência de parâmetros tais como: geometria, massa de catalisador, temperatura de reação, razão molar etanol/óleo e tempo de residência no rendimento da reação. Os resultados obtidos mostraram que o microreator Tesla exibiu maior mistura e alta conversão para baixos números de Reynolds em comparação com os microreatores T e Omega. Uma conversão de etil ésteres de aproximadamente 98,9% foi obtida no microreator Tesla, enquanto, para os microreatores T e Omega a conversão foi ao redor de 79,1% e 96,2%, respectivamente. Além disso, uma fibra óptica conectada ao espectrômetro portátil no infravermelho próximo foi utilizada para avaliar a possibilidade do monitoramento on-line da reação de transesterificação. / Abstract: Microreactor technology is an important method of process intensification which offers potential benefits to the chemical process industries due to the well-defined high specific interfacial area available for heat and mass transfer, which increases transfer rates, improves efficiency and reactor performance, and enhances safety resulting from low holdups when compared to the conventional reactors. The immiscible liquid-liquid two-phase flow has shown a better intensifying of mass transfer through application of internal structures that serve as passive mixers in microreactors, which enhances diffusive penetration and consequently increases the reaction rates observed. The present work highlights the hydrodynamics and the influence of process parameters in the intensification of the continuous biodiesel production using an alkaline catalyst in three different microreactors through complementary experimental and computational techniques. Initially, experiments were carried out to characterize the castor oil as potential feedstock for biodiesel production. Rheological test, differential scanning calorimetry (DSC), thermogravimetric analysis (TG/DTG) and gas chromatography were performed. Size-exclusion chromatography (SEC) was used to evaluate the different variables that affect the transesterification reaction of castor oil with anhydrous ethanol and sodium hydroxide as catalyst in a jacketed glass batch reactor. The effects of temperature, ethanol/castor oil molar ratio, catalyst concentration, and reaction time were analyzed by observing the variation of the reaction medium composition. A mathematical model was applied to describe chemical kinetic of transesterification based on the reversible mechanism of the reactions. Traditional micromanufacturing technology such as photolithography and soft lithography using SU-8 photoresist and polydimethylsiloxane (PDMS) respectively were employed for fabrication of microreactors. Several difficulties of SU-8 processing to obtain complex structures through the photolithography process have been discussed. In the soft lithography process the mold was fabricated based on photolithography techniques, and SU-8 photoresist was used to construct microreactor structure templates. Experiments were carried out to allow an examination of the influence of reactor path geometry. Three different templates were applied for evaluation: T-, Omega, and Tesla-shaped microreactors. The mixing inside of microreactors at low Reynolds number was evaluated with experimental procedures and computational fluid dynamics simulations (CFD). A qualitative characterization of the mixing was firstly carried out by observing the mixture evolution of castor oil/ethanol at different rate flow ratios on basis of the transfer of a solvatochromatic dye between the two immiscible fluids. In addition, CFD methodologies were developed to characterize internal circulations and to capture the generation mixing mechanism without chemical reaction, improved the understanding of immiscible ethanol/castor oil system. Finally, continuous biodiesel production was studied in the microreactors in order to evaluate the influence of the geometrical parameters, catalyst amount, reaction temperature, molar ratio ethanol to oil, and residence time on performance of the reaction. The Tesla-Shaped microreactor exhibited higher conversions at low Reynolds number when compared with T- and Omega-shaped microreactors. Ethyl ester conversion was about 98.9% in Tesla-shaped microreactor, whereas for T- and Omega-shaped microreactor it was only about 79.1% and 96.2% respectively. On the other hand, fiber-optic near infrared spectroscopy was used to evaluate the possibility of monitoring quantitatively the transesterification reaction on-line. / Mestrado / Desenvolvimento de Processos Químicos / Mestre em Engenharia Química

Orientador: Roberto Jose Maria Covolan / Tese (doutorado) - Universidade Estadual de Campinas, Instituto de Fisica Gleb Wataghin / Made available in DSpace on 2018-08-12T12:47:40Z (GMT). No. of bitstreams: 1 Mesquita_RicksonCoelho_D.pdf: 22300712 bytes, checksum: 11bd3fc16a125afc1c2cd8b4d18bc2e2 (MD5) Previous issue date: 2009 / Resumo: A atividade neuronal relacionada a um determinado estímulo ou tarefa induz uma cadeia de complexos eventos biológicos no cérebro. O aumento no consumo de energia induz um acréscimo na demanda por glicose e oxigênio no tecido extravascular. Fatores bioquímicos e neuronais induzem variações nos vasos sanguíneos que resultam em alterações de uxo sanguíneo, volume e oxigenação. Embora extensivamente investigada, esta cascata de eventos ainda é pouco compreendida. Neste projeto, procuramos descrever o acoplamento entre os níveis celular, metabólico e vascular associado à ativação funcional do cérebro. Usando medidas eletro fisiológicas, modelamos os sistemas neuro-vascular e neuro-metabólico para descrever a hemodinâmica cerebral medida através de técnicas ópticas. Resultados obtidos em ratos durante a estimulação de um fio de bigode mostraram que a determinação de uma função resposta para cada sistema, assumido como linear, descreve bem o comportamento hemodinâmico e possibilita o estudo dos estados vascular e metabólico caracterizados pelos parâmetros medidos. A partir de experimentos multimodais de NIRS e fMRI, desenvolvemos metodologias inovadoras para a determinação de imagens metabólicas, capazes de prever variações do consumo de oxigênio com boa resolução espacial e temporal. Por fim, analisamos a in u^encia de parâmetros fisiológicos no sinal óptico, mostrando a contribuição importante da pressão sanguínea na composição deste. Medidas de correlação temporal foram projetadas para gerar mapas de correlação vascular que podem ser aplicados ao estudo da conectividade vascular cerebral, tanto em indivíduos normais como em pacientes com patologias cerebrais. / Abstract: Task-associated neuronal activity leads to a complex chain of biological events within the brain. The increased energetics gives rise to elevated glucose and oxygen consumption in the tissue. Biochemical and neuronal factors induce changes in blood vessels and variations in blood ow, volume and oxygenation. Although it has been extensively investigated, this cascade of events is still poorly understood and highly debated. In this project, the aim was to describe the coupling among the cellular, metabolic and vascular levels associated to functional brain activation. Using electrophysiological measurements, we modeled the neuro-vascular and neuro-metabolic systems in order to describe cerebral hemodynamics as seen through optical techniques. Results obtained in rats during whisker-barrel stimulation showed that the determination of a response function for each system, assumed as linear, can describe the hemodynamic behavior and allow the study of the vascular and metabolic states characterized by the measurements. From multimodal experiments of NIRS and fMRI, we developed unique methods to the determination of metabolic images, which can predict changes in oxygen consumption with good temporal and spatial resolution. Finally, we analyzed the in uence of the physiology in the optical signal, and showed the importance of taking into account blood pressure oscillations into this signal. Measurements of temporal correlation were projected to generate vascular correlation maps that may be useful to the study of cerebral vascular connectivity, both in normal subjects and in patients with cerebral pathologies. / Doutorado / Metodos Oticos de Analise / Doutor em Ciências