Thesis (Ph. D.)--University of Washington, 2004. / Vita. Includes bibliographical references (p. 153-161).

Thesis (Ph.D.)--Hong Kong University of Science and Technology, 2009. / Includes bibliographical references (p. 261-275).

Thesis (Ph.D.)--University of Delaware, 2007. / Principal faculty advisor: Kausik Sarkar, Dept. of Mechanical Engineering. Includes bibliographical references.

Στην παρούσα εργασία μελετήθηκαν φυσικά πηκτώματα κατά συστάδων συμπολυμερών σε ιοντικό υγρό. Τα συμπολυμερή που μελετήθηκαν ήταν το τρισυσταδικό συμπολυμερές πολυ(αιθυλενοξείδιο)-πολυ(στυρόλιο)-πολυ(αιθυλενοξείδιο) (PEO-PS-PEO) και το αστεροειδές συμπολυμερές πολυ(στυρόλιο)-πολυ(αιθυλενοξείδιο) (PS10PEO10) στο ιοντικό υγρό εξαφθοροφωσφορούχο 1-βουτυλο-3-μεθυλιμιδαζόλιο [BMIM][PF6], το οποίο είναι "καλός" διαλύτης για το PEO και "κακός" διαλύτης για το PS. Αρχικά πραγματοποιήθηκε μοριακός χαρακτηρισμός των συμπολυμερών PEO-PS-PEO και PS10PEO10 μέσω των τεχνικών χρωματογραφίας αποκλεισμού μεγεθών (SEC) και της φασματοσκοπίας πυρηνικού μαγνητικού συντονισμού (1H-NMR). Στη συνέχεια πραγματοποιήθηκε η μελέτη των συμπολυμερών σε αραιά διαλύματα μέσω των τεχνικών της δυναμικής σκέδασης φωτός (DLS) και της ιξωδομετρίας. Παρατηρήθηκε πως τα συμπολυμερή PEO-PS-PEO και PS10PEO10 δημιουργούν πολυμοριακά και μονομοριακά "μαλακά" νανοσωματίδια μικκυλιακού τύπου, αντίστοιχα. Από τη DLS προσδιορίστηκε η υδροδυναμική ακτίνα, Rh, των σωματιδίων. Μέσω της τεχνικής της ιξωδομετρίας AMVn υπολογίστηκε η κρίσιμη συγκέντρωση επικάλυψης, c*, στην οποία τα σωματίδια αρχίζουν να εφάπτονται μεταξύ τους. Σε υψηλές συγκεντρώσεις των πολυμερών παρατηρείται η δημιουργία φυσικών πηκτωμάτων λόγω της πλήρωσης του όγκου του διαλύματος από τα σωματίδια. Μέσω ρεολογικών μελετών προσδιορίστηκε η κρίσιμη συγκέντρωση σχηματισμού πηκτώματος, cgel. Παρατηρήθηκε μεγάλη εξάρτηση του σχετικού ιξώδους από τη συγκέντρωση του συμπολυμερούς καθώς και η αύξηση της ισχύος (μέτρου αποθήκευσης) και του χρόνου χαλάρωσης των φυσικών πηκτωμάτων με την αύξηση της συγκέντρωσης. Τέλος, πραγματοποιήθηκε σύγκριση μεταξύ των συστημάτων PEO-PS-PEO/[BMIM][PF6] και PS10PEO10/[BMIM][PF6]. Διαπιστώθηκε πως το PS10PEO10 παρουσιάζει μεγαλύτερη cgel από το PEO-PS-PEO λόγω της μικρότερης πυκνότητας των αλυσίδων στην κορώνα του αστεροειδούς από αυτή του τρισυσταδικού με αποτέλεσμα τα σωματίδια του αστεροειδούς να διεισδύουν πολύ περισσότερο μεταξύ τους για να επιτευχθεί το φαινόμενο του συνωστισμού. / In the present study the properties of physical gels formed by block copolymers in an ionic liquid were studied. The triblock poly(ethylene oxide)-poly(styrene)-poly(ethylene oxide) (PEO-PS-PEO) and the star polystyrene-polyethylene (PS10PEO10) copolymers were studied in 1-butyl-3-methylimadazolium hexafluapophoshate, [BMIM][PF6], which is a good solvent for the PEO blocks and bad solvent for the PS blocks. Initially, the copolymers were characterized by size exclusion chromatography (SEC) and neutron magnetic resonance (1H-NMR). At a next step the study of the polymers in dilute solutions was followed by dynamic light scattering (DLS) and AMVn viscometry. It was found that PEO-PS-PEO and PS10PEO10 self assemble into multimolecular and monomolecular, micellar type soft nanoparticles, respectively. The size of the particles was calculated by DLS. From the AMVn viscometry, the critical overlap concentration at which the formed nanoparticles start adhering to each other, c*, was calculated. At high polymer concentrations, the formation of gels was observed which was due to the jamming of the particles in the total volume of the solution. Through rheological studies, the critical gelation concentration, cgel, was determined. Above cgel a dramatic viscosity rise was observed. At the same time, the storage modulus Go and the relaxation time τR of the system increased also with increasing concentration. Finally, the comparison between the PEO-PS-PEO/[BMIM][PF6] and PS10PEO10/[BMIM][PF6] systems was discussed. It was concluded that the PS10PEO10 copolymer exhibits a higher value of cgel than that of PEO-PS-PEO copolymer due to the lower density of the chains in the corona of the star nanoparticles.

Made available in DSpace on 2014-06-11T19:23:33Z (GMT). No. of bitstreams: 0 Previous issue date: 2011-02-23Bitstream added on 2014-06-13T18:09:48Z : No. of bitstreams: 1 moraes_jdd_me_arafcf.pdf: 2965279 bytes, checksum: e4b88e85e5a2c07402cdd99a87bdd614 (MD5) / Coordenação de Aperfeiçoamento de Pessoal de Nível Superior (CAPES) / Universidade Estadual Paulista (UNESP) / Diversos antioxidantes demonstram considerável efeito na prevenção do câncer por reduzir o estresse oxidativo causado por uma ampla variedade de ataques: biológicos, químicos e físicos, dentre os quais a radiação solar ultravioleta (UV) é o estresse físico ambiental descrito entre os mais freqüentes ataques que ocorrem sobre a pele, o qual está associado no desenvolvimento na maioria das doenças, incluindo o câncer. Vários componentes da dieta podem ser utilizados sozinhos ou em combinação com fármacos convencionais para prevenir doenças. Ainda, a busca por metodologias alternativas à experimentação com animais para o teste de eficácia de formas cosméticas de uso tópico é devido à pressão pública existente neste sentido, introduzida principalmente pela Comunidade Européia (93/95/EC). O presente estudo teve por objetivo avaliar a atividade do ácido alfa– lipóico em cultura de células, além do estudo de estabilidade de emulsões O/A e seu comportamento reológico. Para isto, foram utilizadas culturas de células como modelo experimental, na tentativa de desenvolver um método alternativo à experimentação com animais que poderá ser utilizado pela indústria cosmética. Foram utilizadas culturas de células HepG2 (metabolizadoras de xenobióticos) e cultura de células HaCaT (queratinócitos) / Several antioxidants show significant effect in preventing cancer by reducing oxidative stress caused by a wide variety of attacks: biological, chemical and physical agents, amongst which the sun's ultraviolet (UV) is the most physical stress environment described among the most frequent attacks that occur on the skin, which is associated with development in most diseases, including cancer. Several dietary components can be used alone or in combination with conventional drugs to prevent disease. Still, the search for alternative methods to animal testing to test the efficacy of topical cosmetic forms is due to public pressure that exists in this sense, introduced mainly by the European Union (93/95/EC). This study aims to assess the activity of alpha-lipoic acid in cultured cells, in addition to studying the stability of O / W emulsions and their rheological behavior. For this, cell cultures are used as experimental models in an attempt to develop an alternative method to animal testing that may be used by the cosmetics industry. Will be used HepG2 cell cultures (xenobiotic metabolizing) and cell culture of HaCaT (keratinocytes)

Made available in DSpace on 2014-06-11T19:27:13Z (GMT). No. of bitstreams: 0 Previous issue date: 2008-12-11Bitstream added on 2014-06-13T20:35:22Z : No. of bitstreams: 1 reis_jfa_me_ilha.pdf: 4095503 bytes, checksum: 7b68949931b17d9ea9723fac44c2e518 (MD5) / As propriedades reológicas do concreto no seu estado fresco são importantes principalmente no período em que o material é lançado nas fôrmas e podem ser determinadas em qualquer momento durante o período de indução da hidratação do cimento. Entretanto, o uso da reologia para estudar a taxa de fluidez ou trabalhabilidade do concreto não é muito comum. Geralmente, o abatimento de tronco de cone é o único parâmetro medido e, mesmo em laboratório, os estudos raramente fornecem informações adicionais sobre o comportamento ao escoamento desses materiais. O ensaio do tronco de cone modificado proposto de LARRARD permite avaliar a tensão crítica e a viscosidade plástica do concreto, de maneira simples e sem grandes custos, uma vez que reômetros de laboratórios são aparelhos sofisticados e relativamente com custos elevados. Este estudo avalia a tensão de escoamento e a viscosidade plástica obtida pelo teste de abatimento de tronco de cone modificado para dois tipos distintos de concreto, a saber: o concreto fresco convencional e o concreto de alto desempenho (CAD), elaborados com cimento CPV ARI-Plus. E também foi realizado correlações entre o ensaio de abatimento de tronco de cone modificado e o ensaio de reometria clássica. Os resultados obtidos mostraram-se bastante satisfatórios para o cálculo da tensão e da viscosidade dos concretos avaliados. / The concrete rheological properties in fresh state are mainly important in the period that the material is thrown in the molds and it can be certain in any moment during the induction period of the cement hydration. However, the use of the rheology to study the fluidity rate or concrete workability is not very common. Usually, the slump is just an unique measured parameter and, even in laboratory, the studies rarely supply additional information about the flow behavior of those materials. The slump modified test proposed by LARRARD it allows to evaluate the critical tension and concrete plastic viscosity so simply and without significant costs, because rheometers of the laboratories are very sophisticated and relatively expensive apparels. This study evaluates the yield stress and the viscosity obtained by the slump modified test for two different types of concrete, like to: the conventional fresh concrete and the concrete of high acting (CAD), elaborated with cement CPV ARIPlus. And it was done to test the correlation between slump modified test and test classical rheometer. For the concretes of high performed starting from the specific line the addictive volume addition superplastificante was varied obtaining initial slumps that varied between 100mm and 260mm. The initial results obtained have proved very satisfactory in tension and viscosity calculus of the evaluated concretes.

Novel solutions to offset thermal degradation of polyamide-6 (PA-6) and organoclay (organically modified layered silicates) nanocomposites during melt compounding have been investigated. In this research, a novel chain extender (Joncryl ADR 3400) has been used to improve thermal stability of PA-6 and PA- 6/organoclay nanocomposites during melt compounding. The materials were compounded using a linear twin extruder and various laboratory scale mixers. The effects of organoclay and chain extender were studied using both processing methods. In order to replicate large scale production used in industry, a comprehensive plan of experimental work was carried out under different processing conditions (extrusion temperature and screw speed), organoclay and chain extender loading using a linear twin screw extruder. Rheology, mechanical and thermal properties were analysed and selected samples were also characterised by TEM and FTIR. Process induced degradation of PA-6 during the melt compounding was found to have significant influence on the rheological and mechanical properties. Rheological and mechanical characterisation clearly showed showed that incorporation of the chain extender minimised thermal degradation of PA-6 and nanocomposites during melt processing. Visual analysis of selected nanocomposites using TEM confirmed that chain extender increased the dispersion of nanoclays in the PA- 6 matrix. The crystallinity of the PA-6 was slightly affected by addition of organoclay and chain extender. The samples obtained by linear twin screw extrusion showed higher rheological properties than the samples from laboratory scale mixers suggesting better mixing and less thermal degradation during extrusion.

Orientador: Vera Lúcia Borges Isaac / Banca: Marcos Antonio Corrêa / Banca: Pedro Alves da Rocha Filho / Resumo: Diversos antioxidantes demonstram considerável efeito na prevenção do câncer por reduzir o estresse oxidativo causado por uma ampla variedade de ataques: biológicos, químicos e físicos, dentre os quais a radiação solar ultravioleta (UV) é o estresse físico ambiental descrito entre os mais freqüentes ataques que ocorrem sobre a pele, o qual está associado no desenvolvimento na maioria das doenças, incluindo o câncer. Vários componentes da dieta podem ser utilizados sozinhos ou em combinação com fármacos convencionais para prevenir doenças. Ainda, a busca por metodologias alternativas à experimentação com animais para o teste de eficácia de formas cosméticas de uso tópico é devido à pressão pública existente neste sentido, introduzida principalmente pela Comunidade Européia (93/95/EC). O presente estudo teve por objetivo avaliar a atividade do ácido alfa- lipóico em cultura de células, além do estudo de estabilidade de emulsões O/A e seu comportamento reológico. Para isto, foram utilizadas culturas de células como modelo experimental, na tentativa de desenvolver um método alternativo à experimentação com animais que poderá ser utilizado pela indústria cosmética. Foram utilizadas culturas de células HepG2 (metabolizadoras de xenobióticos) e cultura de células HaCaT (queratinócitos) / Abstract: Several antioxidants show significant effect in preventing cancer by reducing oxidative stress caused by a wide variety of attacks: biological, chemical and physical agents, amongst which the sun's ultraviolet (UV) is the most physical stress environment described among the most frequent attacks that occur on the skin, which is associated with development in most diseases, including cancer. Several dietary components can be used alone or in combination with conventional drugs to prevent disease. Still, the search for alternative methods to animal testing to test the efficacy of topical cosmetic forms is due to public pressure that exists in this sense, introduced mainly by the European Union (93/95/EC). This study aims to assess the activity of alpha-lipoic acid in cultured cells, in addition to studying the stability of O / W emulsions and their rheological behavior. For this, cell cultures are used as experimental models in an attempt to develop an alternative method to animal testing that may be used by the cosmetics industry. Will be used HepG2 cell cultures (xenobiotic metabolizing) and cell culture of HaCaT (keratinocytes) / Mestre

Polymer extrusion is an energy intensive process whereby the simultaneous action of viscous shear and thermal conduction are used to convert solid polymer to a melt which can be formed into a shape. To optimise efficiency, a homogeneous melt is required with minimum consumption of process energy. In this work, in-process monitoring techniques have been used to characterise the thermal dynamics of the single screw extrusion process with real-time quantification of energy consumption. Thermocouple grid sensors were used to measure radial melt temperatures across the melt flow at the entrance to the extruder die. Moreover, an infrared sensor flush mounted at the end of the extruder barrel was used to measure non-invasive melt temperature profiles across the width of the screw channel in the metering section of the extruder screw. Both techniques were found to provide useful information concerning the thermal dynamics of the extrusion process; in particular this application of infrared thermometry could prove useful for industrial extrusion process monitoring applications. Extruder screw geometry and extrusion variables should ideally be tailored to suit the properties of individual polymers but in practise this is rarely achieved due the lack of understanding. Here, LDPE, LLDPE, three grades of HDPE, PS, PP and PET were extruded using three geometries of extruder screws at several set temperatures and screw rotation speeds. Extrusion data showed that polymer rheology had a significant effect on the thermal efficiency on the extrusion process. In particular, melt viscosity was found to have a significant effect on specific energy consumption and thermal homogeneity of the melt. Extruder screw geometry, set extrusion temperature and screw rotation speed were also found to have a direct effect on energy consumption and melt consistency. Single flighted extruder screws exhibited poorer temperature homogeneity and larger fluctuations than a barrier flighted screw with a spiral mixer. These results highlighted the importance of careful selection of processing conditions and extruder screw geometry on melt homogeneity and process efficiency. Extruder scale was found to have a significant influence on thermal characteristics due to changes in surface area of the screw, barrel and heaters which consequently affect the effectiveness of the melting process and extrusion process energy demand. In this thesis, the thermal and energy characteristics of two single screw extruders were compared to examine the effect of extruder scale and processing conditions on measured melt temperature and energy consumption. Extrusion thermal dynamics were shown to be highly dependent upon extruder scale whilst specific energy consumption compared more favourably, enabling prediction of a process window from lab to industrial scale within which energy efficiency can be optimised. Overall, this detailed experimental study has helped to improve understanding of the single screw extrusion process, in terms of thermal stability and energy consumption. It is hoped that the findings will allow those working in this field to make more informed decisions regarding set conditions, screw geometry and extruder scale, in order to improve the efficiency of the extrusion process.

La dynamique et la rhéologie d'une suspension 2D confinée de vésicules (un modèle de RBCs (globules rouges) ) sont étudiées numériquement en utilisant une méthode de Boltzmann sur réseau frontière immergée. Nous analysons d'abord les situations dans lesquelles les vésicules effectuent le mouvement de chenille de char. Des paires de vésicules se placent dans un état d'équilibre avec une distance relative constante et régulée par le confinement. La distance d'équilibre augmente avec l'intervalle entre les parois suivant une relation linéaire. Cependant, aucune distance d'équilibre stable entre deux vésicules en mouvement de tumbling n’est observée. La présence ou l'absence d'une distance d'équilibre entre deux vésicules dicte l'organisation spatio-temporelle de la suspension. L’organisation de la suspension s’accompagne d’assez amples oscillations de la viscosité normalisée variant en fonction de la concentration, tandis que la viscosité effective ne varie pas.Les interactions dans la direction verticale par rapport au plan de cisaillement sont analysées par des simulations en 3D de capsules et des expériences. Nous montrons que dans une suspension confinée de sang, les RBCs s’organisent spontanément en une structure cristalline sous le seul effet de l'interaction hydrodynamique. Il est en outre démontré que lorsque les RBCs sont remplacés par des particules rigides, l'ordre disparait pour laisser place au désordre. Différents ordres cristallins peuvent apparaître selon la concentration et le confinement. La distance intercellulaire de la structure cristalline est une fonction linéaire du confinement. L’ordre apparaît comme une interaction subtile entre la force de portance qui pousse les RBCs des murs vers le centre et l'interaction hydrodynamique dans la verticale du plan d'écoulement de cisaillement. Cette étude introduit un nouveau paradigme dans le domaine des suspensions non-colloïdales diluées où la prévalence des désordres était mise à jour la règle.La répartition des RBCs au niveau d’une bifurcation est abordée dans nos simulations sur ordinateur ainsi que dans des expériences in vitro. Ces études révèlent que la répartition de RBCs dépend fortement du contraste de viscosité entre la viscosité de l'hémoglobine du RBC et le fluide suspendant, tant que l'hématocrite est inférieure à 20%. Pour des dilutions importantes, nos résultats montrent un nouveau phénomène : la branche de faible débit peut recevoir une concentration plus élevé que la branche de haut débit, en opposition à l'effet Zweifach-Fung. Ce phénomène est observé sous confinement modéré et est le résultat d'une structuration particulière de la suspension cellulaire. Nos résultats suggèrent que les différentes propriétés des RBCs doivent être prises en compte et soigneusement analysées afin d'avoir une bonne compréhension de la distribution de RBCs dans la microcirculation et donc de la livraison de l'oxygène dans la microcirculation en général.Enfin, nous réalisons des simulations numériques d'une grande quantité de RBCs, circulant dans un réseau qui est structuré selon un motif en nid d'abeilles. Nos résultats montrent que tant que l'hématocrite est inférieure à 20%, les RBCs dont la membrane est plus rigide présentent un déplacement latéral plus important dans le réseau. En plus, nous découvrons une différence par rapport à la circulation de RBCs dans un tube droit où le débit pour des globules rigides est plus petit. Au contraire, un débit plus important est observé pour les RBCs plus rigides dans le réseau. Enfin, nous présentons la manifestation d'une diffusion longitudinale plus rapide d’une suspension dense de RBCs de faible déformabilité dans le réseau. Nos résultats fournissent des informations intéressantes sur la livraison de RBCs dans le réseau, ce qui pourrait être important non seulement sur la compréhension de la perfusion du sang et le transit de RBC dans la microcirculation, mais aussi sur des applications pratiques. / Dynamics and rheology of a 2D confined suspension of vesicles (a model for RBCs) is studied numerically by using an immersed boundary lattice Boltzmann method (IB-LBM). We pay a special attention to the link between the spatiotemporal organization of the suspension and rheology. We first analyze situations in which vesicles perform tank-treading. The pair of vesicles settles into an equilibrium state with constant relative distance, which is regulated by the confinement. The equilibrium distance increases with the gap between walls following a linear relationship. However, no stable equilibrium distance between two tumbling vesicles is observed. The presence or the lack thereof of an equilibrium distance between two vesicles dictates the spatiotemporal organization of the suspension (order or disorder). Ordering of the suspension is accompanied with quite ample oscillation of normalized viscosity as a function of concentration, while the effective viscosity exhibits plateau. The oscillations amplitude of normalized viscosity is suppressed when disordered pattern prevails.Beside the interactions in the shear plane discussed in 2D framework, the interactions in the vertical direction to the shear plane are also analyzed by 3D simulations of capsules (a model for RBCs) and experiments. We show that in a confined blood suspension RBCs spontaneously organize in a crystalline-like structure under the sole effect of hydrodynamic interaction. It is further shown that when RBCs are substituted by rigid particles order disappears in favor of disorder. Various crystalline orders take place depending on concentration and confinement. The intercellular distance of the crystalline structure is a linear function of confinement. Order appears as a subtle interplay between the lift force that pushes RBCs away from walls towards the center and hydrodynamics interaction in the vertical of shear flow plane. This study introduces a new paradigm in the field of dilute non-colloidal suspensions where the prevalence of disorder was up-to date the rule.The partition of RBCs at the level of bifurcations is addressed in our computer simulations and in vitro experiments, which reveal that the hematocrit partition depends strongly on the viscosity contrast between the viscosities of the RBC hemoglobin and the suspending fluid, as long as hematocrit is less than 20% (which is the normal range in microcirculation). In the extreme hemodilution, our results exhibit a new phenomenon: the low flow rate branch may receive higher hematocrit than the high flow rate branch in opposition to the known Zweifach-Fung effect. This phenomenon is observed under moderate confinement and is the result of a peculiar structuring of the cell suspension. Our findings suggest that the various RBCs properties must be taken into consideration and carefully analyzed in order to have a firm understanding of RBC distribution in microcirculation and thus oxygen delivery in the microcirculation in general.Finally, we carry out numerical simulations of a large number of RBCs flowing in a network that is structured in a honeycomb pattern. Our results reveal that as long as the hematocrit is less than 20% the RBCs with higher membrane rigidity show a larger lateral displacement in the network. Furthermore, we discover a deviation of RBC flux in network from that in straight tube where the more rigid RBCs get the smaller flux. Oppositely, the larger RBC flux is observed for the more rigid RBCs in the network. Finally, we report on the manifestation of a faster longitudinal diffusion of crowded RBCs with smaller deformability in the network. Our results provide interesting information on the RBC delivery in the network, which should be significant not only in the understanding of the blood perfusion and the RBC transit in the microcirculation but also in practical applications such as cell sorting and chemical analysis.