Current research within the field of ultrasound contrast agents (UCAs) aims at developing capsules which are not only acoustically active, but also have a chemically modifiable surface. This enables use in new areas, including targeted drug delivery and theranostics. For such purposes, air-filled microbubbles (MBs) with a polyvinyl alcohol (PVA) shell are being studied. Ultrasound imaging velocimetry (UIV) is a technique used to evaluate various types of liquid flows by tracking patterns caused by UCAs across ultrasound images, and has shown great potential for flow measurements in terms of accuracy. The aim of this thesis was to implement a basic UIV program in Matlab to investigate the flow behavior of air-filled PVA MBs being pumped through a phantom, mimicking a blood vessel. The images were acquired using the programmable Verasonics research system by plane wave imaging with coherent compounding, and UIV was implemented as a post-processing technique. Three parameters were varied to study how the UIV performance and flow behavior of the MBs were affected: the concentration of MBs, the flow velocity, and the transducer voltage. The resulting velocity vector fields showed that it is possible to track PVA MBs using the implemented UIV program, and that the concentration 5·106 MBs/ml gave the best results out of the five concentrations tested. The generated velocity vector fields indicated a turbulent and pulsatile flow behavior, which was in line with the predicted flow behavior, although there was a disparity between the measured average flow velocity of the MBs and the predicted flow velocity. It was also observed that the MBs were increasingly pushed in the axial direction with increasing voltage, as according to theory. Even though a more advanced UIV algorithm could improve the accuracy of the velocity measurements, the results show possible use of air-filled PVA MBs in combination with UIV. / Nuvarande forskning inom ultraljudskontrastmedel syftar till att utveckla kapslar som inte bara är akustiskt aktiva, utan som även har en kemiskt modifierbar yta. Detta möjliggör användning inom nya områden, så som målinriktade läkemedel och theanostics. För detta syfte studeras luftfyllda mikrobubblor med ett skal av polyvinylalkohol (PVA). Ultrasound imaging velocimetry (UIV) är en teknik som används för att analysera olika typer av vätskeflöden genom att spåra mönster orsakade av ultraljudskontrastmedel över ett antal ultraljudsbilder. Metoden har visats ha stor potential för flödesmätningar, och hög noggrannhet har uppnåtts. Detta projekt syftade till att implementera ett grundläggande UIV-program i Matlab för att undersöka flödesbeteenden hos luftfyllda PVA-mikrobubblor som pumpas genom en modell av ett blodkärl. Ultraljudsbilderna togs med hjälp av det programmerbara forskningssystemet Verasonics, genom att använda planvågsavbildning och coherent compounding, och UIV implementerades som ett efterbearbetningsprogram. Tre parametrar varierades för att studera hur prestandan av UIV-programmet och flödesbeteendet hos mikrobubblorna påverkades: koncentrationen av mikrobubblor, flödeshastigheten, och spänningsamplituden hos ultraljudsproben. De resulterande hastighetsvektorfälten visade det möjligt att evaluera flödesbeteenden hos PVA-mikrobubblor med hjälp av det implementerade UIV-programmet. Bäst resultat erhölls genom att använda koncentrationen 5·106 mikrobubblor/ml, av de fem testade koncentrationerna. De genererade hastighetsvektorfälten indikerade ett turbulent och pulserande flöde, vilket överensstämde med teorin, trots att det fanns skillnader mellan genomsnittliga uppmätta flödeshastigheter och den beräknade flödeshastigheten. Det kunde också observeras att mikrobubblorna trycktes i den axiella riktningen när spänningsamplituden ökade, vilket överensstämde med teorin. Trots att metodens noggrannhet skulle kunna ökas genom att använda ett mer avancerat UIV-program, visade resultaten på möjligheten att använda luftfyllda PVA-mikrobubblor i kombination med UIV.

The purpose of this study was to investigate the effects and interactions of lead, frequency, amplitude of slip, humidity, and film thickness of polyvinyl chloride on fretting corrosion. In particular, this study describes the effects of these parameters on the polymer film life and also on the wear of the metal surfaces after metallic contact had occurred. The two levels that were used for each parameter are: load, 15.6 and 31.1 N (3.5 and 7.0 lb); amplitude of slip, 165 and 330 μm (6.5 and 13 mils); frequency of slip, 20 and 40 Hz; humidity of air, 16.6 percent, and 58.4 percent relative humidity; and PVC film thickness, 20 and 37 μm (0.8 and 1.45 mils). The 52100 steel balls were loaded against a 1045 steel disk that was coated with PVC. This configuration was then subjected to a two-level, five-factor experiment comprised of the above levels of conditions. / M.S.

The diploma thesis deals with self-healing of concrete composite. In the theoretical part, it represents the effect of polymer microfibers on reducing the development of cracks and on improving self-healing properties. It also describes the most commonly used types of bacteria used to enhance the self-healing process and their effect both alone and in interaction with fibers, calcium sources and absorbent additives. It also represents auxiliary additives in the form of superabsorbent polymers. In the practical part, it verifies the influence of the above elements and describes how much the self-healing of concrete has been enhanced by the use of combinations of fibers, absorbent polymers and a source of calcium in the form of calcium lactate. It also indicates whether the self-healing properties used were not improved at the expense of deteriorating the mechanical properties of the composite.

Les copolymères poly (acétate de vinyle-co-alcool vinylique), désignés par PVA, sont des tensioactifs macromoléculaires obtenus par hydrolyse partielle de poly (acétate de vinyle)(PVAc). Si les propriétés tensioactives des PVA ont pu être corrélées aux caractéristiques moléculaires il n'en est par de même en ce qui concerne les associats du type nanogels présents dans les solutions aqueuses. L'objectif de cette thèse était de caractériser les nanogels par des techniques telles que la diffusion dynamique de la lumière, la chromatographie d'exclusion stérique et la viscosimétrie. 9 PVA, de degrés d'hydrolyse de 73 à 88 mole% et de degrés de polymérisation de 650 à 2500 ont été étudiés. Il est apparu que les nanogels présent dans les PVA de DH =73 mole% et formés par interactions hydrophobe-hydrophobe entre séquences acétate ont des tailles entre 20-40 nm, avec des fractions volumiques de l'ordre de 20-30%. La désagrégation des nanogels par formation de complexes avec des tensioactifs anioniques du type SDS et SDBS a ensuite été démontrée. En faisant appel à la technique de fractionnement par « point de trouble » il est apparu que les chaînes les plus riches en acétate et en particulier celles ayant des longueurs des séquences acétate importantes complexent plus de SDS.Des « copolymères modèles » du type copolymères diblocs PVAc-b-PVOH comportant une séquence hydrophobe PVAc et une hydrophile PVOH ont pu être préparés par polymérisation RAFT, suivie par une réaction click. Une étude préliminaire de la micellisation de tels copolymères a permis de montrer la très grande analogie entre micelles de copolymères à blocs PVAc-b-PVOH et les nanogels de PVA examinés précédemment. / Poly (vinyl acetate-co-vinyl alcohol) copolymers, designated by PVA, are macromolecular surfactants obtained by partial hydrolysis of poly (vinyl acetate) (PVAc). If the surfactant properties of PVA have been correlated with molecular characteristics it is not the same for the colloidal aggregates in aqueous solutions so-called nanogels. The objective of this thesis was to characterize the nanogels using techniques such as dynamic light scattering, size exclusion chromatography and viscometry.9 PVA with degrees of hydrolysis between 73 and 88 mole% and polymerization degrees of 650 to 2500 were studied. It appeared that the nanogels, formed by hydrophobic-hydrophobic interactions between acetate sequences, are the size in the range of 20 to 40 nm with volume fractions between 20 and 30%. The disaggregation of nanogels by complex formation with anionic surfactants such as SDS and SDBS was further demonstrated. By using the "cloud point" fractionation technique it appeared that SDS is complexed by the sequences with high acetate content and in particular those with significant lengths of acetate sequences.As a model system diblock copolymers PVAc-b-PVOH containing a PVAc hydrophobie sequence and a PVOH hydrophilic sequence were prepared by RAFT polymerization, followed by a click reaction. A preliminary micellization study of these copolymers showed a very strong analogy between PVAc-b-PVOH block copolymer micelles and PVA nanogels discussed above.

A artrose, também chamada de osteoartrose ou osteoartrite (OA), é a terceira doença de maior incidência no Mundo. Nesse trabalho, buscou-se criar uma lesão osteocartilaginosa em joelhos de ratos Wistar machos com seis meses de vida, objetivando constituir um modelo animal para estudo da OA humana e, a partir desse modelo, avaliar biomateriais de forma isolada ou associados entre si e avaliados quanto à sua segurança biológica e potencial de reparação tecidual. Além disto, foi analisado o efeito reparador de células-tronco mesenquimais da polpa do dente de leite humano (MSC) isoladamente e em associação com o biomaterial formado por: Titânio + Poli Vinil Álcool + Ac. Hialurônico, nesse estudo denominado de TRIGEL (TRG). O Ac. Hialurônico (HA), por suas propriedades visco elásticas, o pó de Titânio (Ti), devido às suas propriedades biológicas únicas de ostoeintegração e o polímero Poli Vinil Álcool (PVA), com suas propriedades hidrofílicas, promovendo a formação do Hidrogel, os quais associados entre si formam um compósito, o TRG, que foi aplicado sobre uma lesão padrão no joelho da pata pélvica direita de ratos Wistar machos de seis meses de idade. Para a obtenção da lesão padrão, os animais foram divididos em três grupos de cincoanimais e cada grupo foi submetido a uma intervenção cirúrgica em seus joelhos direitos, utilizando três técnicas cirúrgicas diferentes, a saber: Grupo (I): Remoção cirúrgica dos meniscos medial e lateral mais perfuração do platô tibial seguido da aspiração da medula óssea através dessa perfuração por meio de seringa e agulha. Grupo (II): Remoção dos meniscos mais perfuração, sem aspiração, Grupo (III): Apenas a perfuração. Todos os animais foram autopsiados após 30 dias. Os joelhos dos quinze animais que constituíam os três grupos foram devidamente catalogados e enviados para a empresa Histotech, para a confecção das lâminas, tendo sido eleito, por análise histológica, o Grupo (I), por demonstrar menor reparo tecidual espontâneo. Em tese, o TRG teria as seguintes propriedades: Uma fonte de reparação tecidual (visco terapia) dada pelo HA e a capacidade amortecedora e carreadora de células-tronco do polímero PVA, que se hidrata, formando o hidrogel. O Ti, pela sua propriedade de osteointegração formaria um tampão sobre as áreas de matriz óssea exposta o que possibilitaria o afluxo de novos condrócitos, que também pode ocorrer pela ação das células-tronco. Livrar a superfície articular das áreas com exposição da matriz óssea é fundamental para o bloqueio das proteases que perpetuam a fisiopatologia da OA. Após tratamento estatístico dos diversos ensaios, utilizando-se os diversos biomateriais no tratamento da lesão, o TRG foi o biomaterial que apresentou o melhor resultado de força entre os grupos. No estudo histológico, foi evidenciada a presença de tecido cartilaginoso supra- lesional, o que só ocorreu nos animais dos grupos que receberam: apenas TRG, TRG associado com células-tronco e aquele que recebeu apenas MSCs. No entanto, mais estudos, com animais de maior porte e mais velhos, devem ser realizados para melhor analisar a segurança e o potencial terapêutico do compósito Trigel. / Osteoarthritis, or osteoarthritis (OA) is the third most debilitating disease in the world. In this study, we attempted to create an osteocartilaginous lesion in the knees of six months old male Wistar rats, aiming to constitute an animal model for the study of human OA and to use this model to evaluate the therapeutic potential of biomaterials, which are already well known for their biocompatibility properties in the clinical practice. The biomaterials were used in isolation or associated with each other and then evaluated for their biological safety and tissue repair capacity. Mesenchymal stem cells, obtained from human dental pulp from deciduous teeth (MSC) were evaluated alone and in association with the biomaterial formed by: Titanium + Poly Vinyl Alcohol + Ac. Hyaluronic, here called TRIGEL (TRG). Due to its visco-elastic properties, the Ti powder, due to its unique biological properties of ostointegration and the polymer PVA, with its hydrophylic properties, forming a hydrogel, were associated to form the composite named TRIGEL, (TRG), which was applied to a standard knee injury of the right hind leg of male Wistar rats. In order to elect the standard lesion, the animals were divided into three groups with five animals each and each group underwent a surgical intervention in their right knees, with three different surgical techniques being applied, namely: Group (1): Surgical removal ofmedial and lateral meniscus plus perforation of the tibial plateau, followed by aspiration of the bone marrow through this perforation using syringe and needle. Group (2): Removal of the meniscus plus perforation, without aspiration, Group (3): Drilling only. All groups were autopsied 30 days after the procedure and all groups were autopsied at 30 days post-procedure. The knees of the 15 animals that constituted the three groups were analyzed histologically and Group (1) (meniscus removed, perforated and aspirated), was elected as the standard lesion since it demonstrated less spontaneous tissue repair. TRG has the following properties: HA is used as a source of tissue repair (visco therapy) and hydration of the polymer; PVA, forms a hydrogel\", with damping action and as a stem cells carrier, whereas Ti was used due to its ósseo-integration, which would allow coating of the exposed bone matrix and this intra-osseous osteo-integration response would form an intercalating buffer. The healthy cartilage surfaces around this structural buffer would allow the reception of new chondrocytes or the action of the cells on TRG properties. Freeing the articular surface of the areas with bone matrix exposure is critical for blocking the proteases that perpetuate the pathophysiology of OA. In the various biomaterial tests in the treatment of the standard lesions, TRG was statistically shown to be the one that better mimicked the non-injured group. The histological study demonstrated the presence of a supra-lesional cartilagenous tissue, which only occurred in the groups which received: only TRG, mesenchymal stem cells associated with TRG and that which received only MSCs. However, further studies with larger and older animals should be pursued to better assess the safety and therapeutic potential of the Trigel composite.

O presente trabalho visou preparar e caracterizar eletrólitos poliméricos (EP) à base de poli(vinil butirato) (PVB) com diferentes sais de lítio (LiClO4, LiCF3SO3 e LiI/I2), com ou sem o plastificante g-butirolactona (GBL), além de viabilizar a aplicação dos mesmos em dispositivos eletrocrômicos e células solares. Observou-se, através das análises por espectroscopia de impedância eletroquímica, que o PVB é capaz de solvatar no máximo 40% de sal de lítio em massa. Foi verificado que as condutividades iônicas dessas amostras, em função do aumento da temperatura, podem ser explicadas pelo modelo Vogel-Tammann-Fulcher, e que o eletrólito PF04 (PVB com 40% de LiCF3SO3) possui o maior valor de condutividade (1,5´10-4 S/cm) com relação às outras amostras. Os espectros de infravermelho das amostras estudadas mostraram um deslocamento nos picos correspondentes às carbonilas da matriz polimérica em resposta à coordenação das mesmas com íons Li+. Os resultados da espectroscopia Raman comprovaram a presença do par redox (I3-/I-) no eletrólito com LiI/I2. Os difratogramas de raios-X do PVB evidenciaram um pico largo centrado em 20º (2q) com 800 c.p.s. de intensidade, a adição de LiI/I2 e LiCF3SO3 ao polímero reduziu as intensidades para 750 e 700 c.p.s respectivamente, ao contrário do observado com LiClO4, onde se nota que o sal não foi completamente solvatado pelo polímero. A micrografia obtida por microscopia eletrônica de varredura (SEM) do eletrólito com 23% de LiClO4 (amostra P04) mostraram evidências de aglomerados iônicos na superfície. As análises por calorimetria exploratória diferencial (DSC) mostraram que um aumento na concentração de sal adicionado ao polímero causou uma diminuição na temperatura de transição vítrea (Tg), e que os eletrólitos possuem em torno de 44% de cristalinidade. Os eletrólitos P04 e PF04 foram aplicados em janelas eletrocrômicas, apresentando uma diferença de 10,5 e 9,3% respectivamente entre os estados colorido e descolorido. O eletrólito com LiI/I2 foi aplicado em célula solar gerando uma fotocorrente máxima de 1,09 mA/cm2 e eficiência de 0,41% sob a irradiação de 100 mW/cm2. Eletrólitos géis com adição de 90% γ-butirolactona também foram aplicados em células solares, os valores de fotocorrente e eficiência foram incrementados (5,82 mA/cm2 e 2,1%, respectivamente). / The aim of the present study was to prepare and characterize polymer electrolytes (EP) based on poly(vinyl butyrate) (PVB) with different lithium salts (LiClO4, LiCF3SO3 and LiI/I2) and/or containing g-butyrolactone (GBL), and to apply them in electrochromic devices and solar cells. It was observed through electrochemical impedance spectroscopy that the PVB is able to solvate up to 40% in weight of lithium salt. It was found that the ionic conductivity of these samples, as a function of temperature, can be explained by Vogel-Tammann-Fulcher model, and the electrolyte PF04 (PVB with 40% of LiCF3SO3) had the highest conductivity value of 1,5´10-4 S/cm when compared to other samples. Infrared spectra of the samples showed a shift in the peaks corresponding to the carbonyl groups of the polymer matrix in response to their coordination with Li+ ions. The results of Raman spectroscopy confirmed the presence of the redox couple (I3-/I-) in the electrolyte with LiI/I2 (PVB04). The X-ray diffractograms of the PVB showed a broad peak centered at 20 (2q) com intensity of 800 cps. The addition of LiI/I2 and LiCF3SO3 to the polymer matrix decreased the intensities to 750 and 700 cps respectively, but not after the LiClO4 addition, which was explained by its not complete solvatation by the polymer matrix. The Scanning Electron Microscopy (SEM) pictures of electrolyte with 23% of LiClO4 (P04 sample) showed evidences of ion clusters on the surface. The analyzes via Differential Scanning Calorimetry (DSC) showed that an increase in the concentration of the salt added to the polymer matrix caused a decrease in glass transition temperature (Tg), and that electrolytes are about 44% crystalline. The electrolytes P04 and PF04 were applied to electrochromic windows (ECDs) and showed a transmittance difference of 10.5 and 9.3%, respectively between the colored and discolored states. The electrolyte with LiI/I2 was applied to dye sensitized solar cell (DSSC) generating a maximum photocurrent of 1.09 mA/cm2 and 0.41% of efficiency under irradiation of 100 mW/cm2. Gel electrolytes containing 90% of γ-butyrolactone were applied to DSSC and showed 5.82 mA/cm2 of photocurrent and 2.1% of efficiency.

A artrose, também chamada de osteoartrose ou osteoartrite (OA), é a terceira doença de maior incidência no Mundo. Nesse trabalho, buscou-se criar uma lesão osteocartilaginosa em joelhos de ratos Wistar machos com seis meses de vida, objetivando constituir um modelo animal para estudo da OA humana e, a partir desse modelo, avaliar biomateriais de forma isolada ou associados entre si e avaliados quanto à sua segurança biológica e potencial de reparação tecidual. Além disto, foi analisado o efeito reparador de células-tronco mesenquimais da polpa do dente de leite humano (MSC) isoladamente e em associação com o biomaterial formado por: Titânio + Poli Vinil Álcool + Ac. Hialurônico, nesse estudo denominado de TRIGEL (TRG). O Ac. Hialurônico (HA), por suas propriedades visco elásticas, o pó de Titânio (Ti), devido às suas propriedades biológicas únicas de ostoeintegração e o polímero Poli Vinil Álcool (PVA), com suas propriedades hidrofílicas, promovendo a formação do Hidrogel, os quais associados entre si formam um compósito, o TRG, que foi aplicado sobre uma lesão padrão no joelho da pata pélvica direita de ratos Wistar machos de seis meses de idade. Para a obtenção da lesão padrão, os animais foram divididos em três grupos de cincoanimais e cada grupo foi submetido a uma intervenção cirúrgica em seus joelhos direitos, utilizando três técnicas cirúrgicas diferentes, a saber: Grupo (I): Remoção cirúrgica dos meniscos medial e lateral mais perfuração do platô tibial seguido da aspiração da medula óssea através dessa perfuração por meio de seringa e agulha. Grupo (II): Remoção dos meniscos mais perfuração, sem aspiração, Grupo (III): Apenas a perfuração. Todos os animais foram autopsiados após 30 dias. Os joelhos dos quinze animais que constituíam os três grupos foram devidamente catalogados e enviados para a empresa Histotech, para a confecção das lâminas, tendo sido eleito, por análise histológica, o Grupo (I), por demonstrar menor reparo tecidual espontâneo. Em tese, o TRG teria as seguintes propriedades: Uma fonte de reparação tecidual (visco terapia) dada pelo HA e a capacidade amortecedora e carreadora de células-tronco do polímero PVA, que se hidrata, formando o hidrogel. O Ti, pela sua propriedade de osteointegração formaria um tampão sobre as áreas de matriz óssea exposta o que possibilitaria o afluxo de novos condrócitos, que também pode ocorrer pela ação das células-tronco. Livrar a superfície articular das áreas com exposição da matriz óssea é fundamental para o bloqueio das proteases que perpetuam a fisiopatologia da OA. Após tratamento estatístico dos diversos ensaios, utilizando-se os diversos biomateriais no tratamento da lesão, o TRG foi o biomaterial que apresentou o melhor resultado de força entre os grupos. No estudo histológico, foi evidenciada a presença de tecido cartilaginoso supra- lesional, o que só ocorreu nos animais dos grupos que receberam: apenas TRG, TRG associado com células-tronco e aquele que recebeu apenas MSCs. No entanto, mais estudos, com animais de maior porte e mais velhos, devem ser realizados para melhor analisar a segurança e o potencial terapêutico do compósito Trigel. / Osteoarthritis, or osteoarthritis (OA) is the third most debilitating disease in the world. In this study, we attempted to create an osteocartilaginous lesion in the knees of six months old male Wistar rats, aiming to constitute an animal model for the study of human OA and to use this model to evaluate the therapeutic potential of biomaterials, which are already well known for their biocompatibility properties in the clinical practice. The biomaterials were used in isolation or associated with each other and then evaluated for their biological safety and tissue repair capacity. Mesenchymal stem cells, obtained from human dental pulp from deciduous teeth (MSC) were evaluated alone and in association with the biomaterial formed by: Titanium + Poly Vinyl Alcohol + Ac. Hyaluronic, here called TRIGEL (TRG). Due to its visco-elastic properties, the Ti powder, due to its unique biological properties of ostointegration and the polymer PVA, with its hydrophylic properties, forming a hydrogel, were associated to form the composite named TRIGEL, (TRG), which was applied to a standard knee injury of the right hind leg of male Wistar rats. In order to elect the standard lesion, the animals were divided into three groups with five animals each and each group underwent a surgical intervention in their right knees, with three different surgical techniques being applied, namely: Group (1): Surgical removal ofmedial and lateral meniscus plus perforation of the tibial plateau, followed by aspiration of the bone marrow through this perforation using syringe and needle. Group (2): Removal of the meniscus plus perforation, without aspiration, Group (3): Drilling only. All groups were autopsied 30 days after the procedure and all groups were autopsied at 30 days post-procedure. The knees of the 15 animals that constituted the three groups were analyzed histologically and Group (1) (meniscus removed, perforated and aspirated), was elected as the standard lesion since it demonstrated less spontaneous tissue repair. TRG has the following properties: HA is used as a source of tissue repair (visco therapy) and hydration of the polymer; PVA, forms a hydrogel\", with damping action and as a stem cells carrier, whereas Ti was used due to its ósseo-integration, which would allow coating of the exposed bone matrix and this intra-osseous osteo-integration response would form an intercalating buffer. The healthy cartilage surfaces around this structural buffer would allow the reception of new chondrocytes or the action of the cells on TRG properties. Freeing the articular surface of the areas with bone matrix exposure is critical for blocking the proteases that perpetuate the pathophysiology of OA. In the various biomaterial tests in the treatment of the standard lesions, TRG was statistically shown to be the one that better mimicked the non-injured group. The histological study demonstrated the presence of a supra-lesional cartilagenous tissue, which only occurred in the groups which received: only TRG, mesenchymal stem cells associated with TRG and that which received only MSCs. However, further studies with larger and older animals should be pursued to better assess the safety and therapeutic potential of the Trigel composite.

Autosomal dominant polycystic disease (ADPKD) is the most common hereditary renal disease and is characterized by renal cyst growth and enlargement. Hypertension occurs early when renal function is normal and is characterized by decreased renal blood flow. Accordingly, the measurement of blood flow in the renal arteries can be a valuable tool in evaluating disease progression. In studies performed in conjunction with this work, blood flow was measured through the renal arteries using magnetic resonance imaging (MRI). In order to validate these in vivo measurements, a vascular phantom was created using polyvinyl alcohol (PVA) and also scanned using MRI under controlled steady flow conditions. Ranges of vessel diameters and flow velocities were used to simulate actual flow in a normal and diseased population of adults and children. With the vessel diameters studied in this experiment, minimization of field of view and an increase in spatial resolution is important in obtaining accurate data. However, a significant difference does not exist between the results when using the 160 or 200 mm FOV. An increase in the number of phase encodings provides improved results, although an increase in image acquisition time is observed. Velocity-encoding in all three orthogonal directions does not improve image data. This method of using MRI to measure flow through a vessel is shown to be both accurate and reproducible, and the protocol providing the most correct results is prescribed. Breath-hold phase-velocity encoded MRI proves to be an accurate and reproducible technique in capturing flow and has the potential to be used for the purpose of observing hemodynamic changes in the renal arteries with the progression of ADPKD.

O presente trabalho visou preparar e caracterizar eletrólitos poliméricos (EP) à base de poli(vinil butirato) (PVB) com diferentes sais de lítio (LiClO4, LiCF3SO3 e LiI/I2), com ou sem o plastificante g-butirolactona (GBL), além de viabilizar a aplicação dos mesmos em dispositivos eletrocrômicos e células solares. Observou-se, através das análises por espectroscopia de impedância eletroquímica, que o PVB é capaz de solvatar no máximo 40% de sal de lítio em massa. Foi verificado que as condutividades iônicas dessas amostras, em função do aumento da temperatura, podem ser explicadas pelo modelo Vogel-Tammann-Fulcher, e que o eletrólito PF04 (PVB com 40% de LiCF3SO3) possui o maior valor de condutividade (1,5´10-4 S/cm) com relação às outras amostras. Os espectros de infravermelho das amostras estudadas mostraram um deslocamento nos picos correspondentes às carbonilas da matriz polimérica em resposta à coordenação das mesmas com íons Li+. Os resultados da espectroscopia Raman comprovaram a presença do par redox (I3-/I-) no eletrólito com LiI/I2. Os difratogramas de raios-X do PVB evidenciaram um pico largo centrado em 20º (2q) com 800 c.p.s. de intensidade, a adição de LiI/I2 e LiCF3SO3 ao polímero reduziu as intensidades para 750 e 700 c.p.s respectivamente, ao contrário do observado com LiClO4, onde se nota que o sal não foi completamente solvatado pelo polímero. A micrografia obtida por microscopia eletrônica de varredura (SEM) do eletrólito com 23% de LiClO4 (amostra P04) mostraram evidências de aglomerados iônicos na superfície. As análises por calorimetria exploratória diferencial (DSC) mostraram que um aumento na concentração de sal adicionado ao polímero causou uma diminuição na temperatura de transição vítrea (Tg), e que os eletrólitos possuem em torno de 44% de cristalinidade. Os eletrólitos P04 e PF04 foram aplicados em janelas eletrocrômicas, apresentando uma diferença de 10,5 e 9,3% respectivamente entre os estados colorido e descolorido. O eletrólito com LiI/I2 foi aplicado em célula solar gerando uma fotocorrente máxima de 1,09 mA/cm2 e eficiência de 0,41% sob a irradiação de 100 mW/cm2. Eletrólitos géis com adição de 90% γ-butirolactona também foram aplicados em células solares, os valores de fotocorrente e eficiência foram incrementados (5,82 mA/cm2 e 2,1%, respectivamente). / The aim of the present study was to prepare and characterize polymer electrolytes (EP) based on poly(vinyl butyrate) (PVB) with different lithium salts (LiClO4, LiCF3SO3 and LiI/I2) and/or containing g-butyrolactone (GBL), and to apply them in electrochromic devices and solar cells. It was observed through electrochemical impedance spectroscopy that the PVB is able to solvate up to 40% in weight of lithium salt. It was found that the ionic conductivity of these samples, as a function of temperature, can be explained by Vogel-Tammann-Fulcher model, and the electrolyte PF04 (PVB with 40% of LiCF3SO3) had the highest conductivity value of 1,5´10-4 S/cm when compared to other samples. Infrared spectra of the samples showed a shift in the peaks corresponding to the carbonyl groups of the polymer matrix in response to their coordination with Li+ ions. The results of Raman spectroscopy confirmed the presence of the redox couple (I3-/I-) in the electrolyte with LiI/I2 (PVB04). The X-ray diffractograms of the PVB showed a broad peak centered at 20 (2q) com intensity of 800 cps. The addition of LiI/I2 and LiCF3SO3 to the polymer matrix decreased the intensities to 750 and 700 cps respectively, but not after the LiClO4 addition, which was explained by its not complete solvatation by the polymer matrix. The Scanning Electron Microscopy (SEM) pictures of electrolyte with 23% of LiClO4 (P04 sample) showed evidences of ion clusters on the surface. The analyzes via Differential Scanning Calorimetry (DSC) showed that an increase in the concentration of the salt added to the polymer matrix caused a decrease in glass transition temperature (Tg), and that electrolytes are about 44% crystalline. The electrolytes P04 and PF04 were applied to electrochromic windows (ECDs) and showed a transmittance difference of 10.5 and 9.3%, respectively between the colored and discolored states. The electrolyte with LiI/I2 was applied to dye sensitized solar cell (DSSC) generating a maximum photocurrent of 1.09 mA/cm2 and 0.41% of efficiency under irradiation of 100 mW/cm2. Gel electrolytes containing 90% of γ-butyrolactone were applied to DSSC and showed 5.82 mA/cm2 of photocurrent and 2.1% of efficiency.

L'étude des phénomènes fondamentaux de<p>transport et de thermodynamique apparaissant lors de l'évaporation<p>en milieu poreux permet l'investigation d'applications pratiques<p>variées. Dans ce travail, nous développons des modèles fondamentaux<p>d'évaporation en milieu poreux que nous appliquons ensuite au<p>séchage en lit fluidisé de deux matériaux granulaires poreux :le<p>PVC et la levure.<p><p>Les modèles mis au point sont réalisés suivant une approche<p>multiéchelle. Nous nous intéressons tout d'abord aux phénomènes se<p>déroulant à l'échelle d'un pore. Les modèles développés à cette<p>échelle sont ensuite exploités dans le cadre d'une étude à l'échelle<p>d'un grain poreux. Le couplage des modèles de grain avec un modèle à<p>l'échelle du réacteur permet alors l'étude des applications<p>industrielles.<p><p>A l'échelle du pore, nous étudions les phénomènes de transport dans<p>un capillaire initialement rempli de liquide qui s'évapore vers<p>l'atmosphère ambiante. L'objectif est de prédire le taux<p>d'évaporation dans cette configuration. Nous nous intéressons<p>successivement à la modélisation du transport de matière par<p>convection-diffusion en phase gazeuse et la modélisation de l'impact<p>de films liquides adsorbés à la paroi du capillaire sur le transport<p>de matière. Ces deux modèles sont confrontés à des expériences<p>d'évaporation en capillaires cylindriques visualisées à l'aide de<p>deux dispositifs optiques. Le premier offre un suivi d'ensemble au<p>cours du temps du capillaire, alors que le second, un interféromètre<p>de Mach-Zehnder, permet une visualisation locale de la région<p>entourant le ménisque.<p><p>Le modèle portant sur le transport de matière par<p>convection-diffusion mène à la définition d'un critère non<p>dimensionnel permettant d'évaluer si la convection dans la phase<p>gazeuse dans le capillaire doit être prise en compte pour évaluer le<p>taux d'évaporation. Le modèle de film permet de prédire l'impact de<p>celui-ci sur l'évaporation en présence d'un gaz inerte lorsque les<p>mouvements convectifs en phase gazeuse sont négligeables. La<p>confrontation de ce modèle avec les profils d'épaisseur des films<p>obtenus à l'aide de interféromètre de Mach-Zehnder ne permet pas de<p>valider le modèle, et ce, suite à une trop grande incertitude sur<p>l'évaluation des interactions entre la paroi et le liquide.<p><p>A l'échelle d'un grain, nous développons un modèle discret par<p>réseau de pores et deux modèles continus pour tenter de prédire le<p>taux d'évaporation et la distribution des phases dans le milieu<p>poreux. Le modèle par réseau de pores prend en compte les transports<p>de matière par diffusion en phase gazeuse, par convection dans les<p>pores remplis de liquide et par convection dans les films liquides.<p>Les effets visqueux en phase liquide sont également modelisés. Pour<p>la prise en compte de ces derniers, nous montrons l'importance de<p>l'usage d'un algorithme approprié. Nous évaluons ensuite au travers<p>de trois nombres sans dimensions l'impact du transport par film et<p>des effets visqueux sur l'évaporation et la distribution des phases.<p>Cette analyse dimensionnelle est ensuite appliquée à l'étude de<p>réseaux de pores pour lesquels la section des liaisons les<p>constituant est idéalisée par des polygones réguliers. Pour les<p>modèles continus après une vérification simplifiée de<p>l'applicabilité de cette démarche, nous développons deux modèles<p>simples. Dans les deux modèles, l'étape de séchage à vitesse<p>constante est supposée limitée par le transport de matière externe<p>au grain. Le premier modèle, dit à front pénétrant, suppose que<p>l'étape de séchage à vitesse décroissante correspond à l'existence<p>d'un front d'évaporation qui s'enfonce dans la matrice poreuse. Le<p>second modèle, dit à surface d'échange variable, attribue cette même<p>étape du séchage à une diminution progressive de la surface<p>d'évaporation en surface du grain.<p><p>A l'échelle du réacteur, nous présentons deux modèles visant à<p>simuler deux types d'essais différents :le séchage en lit fluidisé<p>et la thermogravimétrie analytique. Ces deux modèles sont couplés<p>aux différents modèles à l'échelle de grain pour étudier le séchage<p>de PVC et de levure tant en lit fluidisé que lors des essais de<p>thermogravimétrie analytique.<p><p>Dans le cas du PVC, le modèle par réseau de pores ne peut pas être<p>appliqué de par la nécessité d'une trop grande puissance de calcul.<p>Au niveau des modèles continus, nous montrons que l'application du<p>modèle à surface d'échange variable permet de reproduire les courbes<p>de séchage expérimentales des essais en lit fluidisé.<p><p>Dans le cas de la levure, nous appliquons le modèle par réseau de<p>pores et le modèle à front pénétrant. L'utilisation du modèle par<p>réseau de pores nécessite une connaissance plus détaillée de la<p>structure poreuse des grains. Le traitement d'une analyse par<p>microtomographie nous permet d'obtenir un réseau de pores<p>expérimental. Celui-ci est utilisé pour montrer que la méthode de<p>caractérisation de la porosité par intrusion de mercure ne semble<p>pas adaptée à un matériau deformable comme la levure. Le même réseau<p>est utilisé pour simuler le séchage de grains de levure à l'aide du<p>modèle par réseau de pores. Les simulations sont réalisées sur des<p>réseaux équivalents à des coupes dans le solide. Le modèle par<p>réseau de pores et le modèle à front pénétrant permettent tous deux<p>de modéliser correctement le séchage de levure en lit fluidisé<p>moyennant l'ajustement de leurs paramètres ajustables,<p>respectivement la conductibilité des films liquide et la tortuosité.<p>Pour l'essai de thermogravimétrie, ils ne parviennent à approcher<p>que la première étape de celui-ci. Les avantages, défauts et<p>complémentarités de ces deux modèles sont discutés.<p><p>Nous évaluons ensuite l'impact du rétrécissement de la levure et des<p>types d'eau sur le séchage de ce matériau. Le rétrécissement est,<p>pour ce faire, mesuré à l'aide d'un stéréomicroscope. Ces premières<p>mesures, exploratoires, mènent à la définition d'un modèle empirique<p>de retrait du solide au cours de son séchage. En le prenant en<p>compte dans les modèles déjà appliqués à la levure, nous montrons<p>que le retrait a un impact significatif sur l'étape de séchage à<p>vitesse décroissante. Cet impact<p> peut cependant être masqué intégralement par la réévaluation<p>des paramètres ajustables des différents modèles. Finalement,<p>l'étude des types d'eau au travers d'un modèle simple appliqué à<p>l'essai de thermogravimétrie analytique montre que les types d'eau<p>ne doivent pas être pris en compte pour modéliser le séchage de<p>levure.<p><p>A l'issue de ce travail, nous disposons donc de modèles fondamentaux<p>d'évaporation en milieu poreux. Ceux-ci peuvent être appliqués à des<p>cas d'intérêt industriel, comme nous le réalisons pour le PVC et la<p>levure. Ils peuvent servir à améliorer la<p>compréhension de ces procédés. Ils représentent donc des<p>outils de choix pour la conception, le dimensionnement et<p>l'optimisation du séchage. / Doctorat en Sciences de l'ingénieur / info:eu-repo/semantics/nonPublished