Dissertations / Theses on the topic 'Concentrated interactions'

I consider the Virtual Power framework for Continuum Mechanics, which has recently gained considerable attention, mainly in connection with its applicability to non-classical models for materials. I introduce a geometrical approach to possibly infinite dimensional dynamical systems, based on the theory of Banach manifolds, which has not yet been fully exploited in Continuum Mechanics, though it has been used in some particular cases. This theory generalizes the Virtual Power framework, being even more flexible and allowing for the construction of continuum mechanical models on non-Euclidean domains. I studied the mathematical properties of a general linear isotropic incompressible second-gradient fluid. Constitutive prescriptions for these fluids are discussed, together with the constraints imposed by thermodynamical considerations. The key features of the analyzed model are the possibility of describing the adherence interaction of a three-dimensional fluid with one-dimensional structures immersed in it, and also of including concentrated interactions. A presentation of higher-gradient theories is provided, using the general framework proposed for dynamical systems. They turn out to be a particular class of continuum mechanical models, arising from precise assumptions on the kinematics of the descriptors of the system. Higher-order powers are defined as integral representations of elements of the cotangent bundle on the Banach manifold of the descriptors. Exploiting equivalent integral representations for powers of arbitrary order, the appearance of boundary interactions with a non-standard structure is described. The differential problems associated with the pressure-driven flow of a second-order linear liquid, which adheres to a one-dimensional structure, is considered. Existence and uniqueness of solution are established, also for the situation in which the one-dimensional structure drags the three-dimensional fluid, producing the motion. Finally, some examples are provided, in order to give explicit solutions, to show how the concentrated stresses, if present, can be computed, and to suggest possible interpretations for the physical meaning of the higher-order material parameters.

La situation énergétique actuelle impose le développement de technologies qui utilisent des énergies renouvelables pour limiter la dépendance aux ressources fossiles et diminuer l’impact de l’activité humaine sur le changement climatique. Parmi ces technologies, le solaire thermodynamique utilise l’énergie solaire pour chauffer un absorbeur, l’énergie de cet absorbeur étant alors convertie en électricité à travers un cycle thermodynamique classique. L’amélioration des performances de cette technologie passe par la conception d’absorbeurs capables de fonctionner efficacement à haute température. Dans ce travail de thèse, nous explorons deux voies différentes dans ce but.La première est basée sur la conception de structures multicouches optimisées par algorithme génétique. Nous montrons que ces structures permettent d’obtenir un rendement supérieur à 80 %, valeur très proche des limites fondamentales, démontrant ainsi leur fort potentiel pour le solaire thermodynamique.La seconde voie est basée sur l’optimisation des interactions électromagnétiques dans des structures plasmoniques à base de nanoparticules métalliques. Ces structures sont le siège d’effets coopératifs qui peuvent exalter très fortement les pertes dans la structure. Ces mécanismes sont mis à profit pour concevoir des absorbeurs à base de réseaux binaires de nanoparticules d’or et d’argent dispersées dans une matrice transparente
The current energy situation requires the development of technologies that use renewable energy sources to reduce the dependence on fossil fuels and the impact of human activity on climate change. Among these technologies, thermodynamic solar power uses solar energy to heat an absorber, whose heat is then converted into electricity through a classical thermodynamic cycle. The improvement of the performances of this technology requires the design of absorbers able to operate strongly at high temperature. In this thesis, we explore two different ways for this purpose.The first is based on the design of multilayer structures optimized by a genetic algorithm.We will see that these structures lead to an efficiency higher than 80 %, very close to the fundamental limits, demonstrating so their strong potential for thermodynamic solar technology. The second way is based on the optimization of electromagnetic interactions inside plasmonic nanostructures composed of metal nanoparticles. These structures are the site of cooperative effects between nanoparticles that can exalt strongly losses inside the structure. These mechanisms are exploited to design absorbers based on binary networks made with nanoparticles of gold and silver dispersed in a transparent matrix

Thesis (MTech (Chemical Engineering))--Cape Peninsula University of Technology, 2012.
Emulsion explosives are classified as highly concentrated Water-in-Oil emulsions with an internal phase volume fraction of approximately 94%, i.e. far beyond the close packing limit of spherical droplets of 74%. These emulsions are thermodynamically unstable compounds and their instability is related to the crystallisation in the dispersed phase, which is a supersaturated solution of ammonium nitrate salt in water. This presents a problem, because the emulsion weakens or becomes unstable, which results in droplet crystallisation, so that the explosive generally loses at least some of its sensitivity to detonation. Considerable effort has been applied to the improvement of emulsion stability by explosive manufacturers, but important aspects such as the effect of salt and surfactant content/type in emulsions are not fully understood and described in the literature. The purpose of this study was to investigate these shortcomings and to focus on the effect of surfactant nature and concentration and electrolyte concentration/type on the interfacial properties and interactions in emulsion explosives. Interfacial properties (interfacial tension and interfacial elasticity), thermal behaviour (freezing temperatures) of emulsions and rheological aspects (viscoelastic and flow properties) were investigated in terms of surfactant-electrolyte interactions.

L'attention de la communauté scientifique, ainsi que le développement, pour les bioprocédés dédiés à la culture et à l'expansion de cellules souches mésenchymateuses (MSCs) pour la thérapie cellulaire et la médecine régénérative a considérablement grandi pendant ces dernières décennies. Une plus ample compréhension du lien entre la structure, la fonction et les propriétés des suspensions de cellules mésenchymateuses est devenue de première importance. Dans cette thèse, nous présentons tout d'abord les résultats d'une étude expérimentale portant sur l'écoulement de suspensions concentrées de cellules vivantes d'origine mésenchymateuse pour une grande gamme de concentration cellulaire. Nous caractérisons l'évolution de la viscosité relative en fonction de la contrainte de cisaillement appliquée pour des fractions volumiques cellulaires allant de 20 à 60%. Ces matériaux ont des empreintes rhéologiques compliquées mais très reproductibles, incluant des comportements de fluide à seuil, rhéofluidifiants ainsi que des fractures liées à la contrainte de cisaillement. Les propriétés rhéologiques de la suspension sont ensuite étudiées avec l'addition d'acide hyaluronique (HA), une biomolécule avec des séquences d'adhésion pour des récepteurs à la surface des cellules étudiées. Nous montrons que l'addition d'acide hyaluronique modifie substantiellement le comportement de la suspension et nous permet de contrôler les propriétés d'écoulement de la suspension à toutes les fractions volumiques. Cytométrie de flux et imagerie confocal à l'appui, nous montrons que l'effet observé est dû à un important changement dans la formation d'agrégats cellulaires dans la suspension, et donc dans l'envergure du réseau correspondant. La troisième partie de cette thèse porte sur l'ajout de polyéthylène glycol, une molécule qui n'est pas naturellement présente dans l'organisme mais fréquemment utilisée dans la formulation d'hydrogel. En utilisant trois types de PEG, l'influence de la charge des molécules est étudiée. Les résultats montrent que la charge est un paramètre important dans le contrôle des propriétés d'écoulement de suspensions cellulaires, car déterminant dans la formation et la compacité des agrégats. En considérant les agrégats comme des objets fractals, nous montrons qu'en prenant en compte les modifications de fractions volumiques avec le cisaillement, nous pouvons obtenir une courbe maitresse pour l'ensemble des conditions testées, et en extraire la force d'adhésion moyenne entre les cellules, au travers une population de plusieurs millions de cellules. Cette étude livre de nouveaux aspects sur la complexité des propriétés en écoulement de suspensions de cellules méchymateuses, adhérentes et concentrées, sur leur sensibilité à l'ajout de molécules, qu'elles soient naturellement présentes dans les tissues ou non, ainsi qu'une nouvelle méthode pour mesurer la force d'adhésion entre les cellules.

Nationwide, housing authorities demolish public housing communities and relocate the existing residents in an attempt to create more favorable neighborhood environments and to promote safer and more efficacious social interactions for public housing residents. Yet, studies of public housing relocation do not find strong evidence of beneficial social interaction occurring between relocated residents and new neighbors. Despite increased safety and relative increase in neighborhood economic standing, studies find relocated residents socialize outside of their new neighborhoods or else limit existing neighborhood interactions as compared to living in public housing communities. This raises the question of why relocated residents either do or do not choose to interact with their new neighbors within their new residential settings. In an effort to answer this question, I have conducted a study focused on neighborhood social interactions using public housing residents relocated from six of Atlanta, Georgia’s public housing communities. As a backdrop to the study, I present relevant literature concerning both the study of neighborhoods and the study of prior relocation endeavors. I argue that neighborhoods do provide important social landscapes for attempting to benefit public housing residents, though more research and a different framework of analysis are needed in order to manifest theorized outcomes of relocation for all residents involved. I then employ the use of both quantitative survey data from 248 relocated residents and qualitative in-depth interview data from 40 relocated residents to provide further insight into social interaction patterns after relocation from Atlanta’s public housing. This research finds that prior to relocation residents in public housing communities differed in terms of their ideal zones of action and preferred levels of inclusion and engagement in the neighborhood setting and in terms of their surrounding community scene. By examining these different ideal-types of residents in detail, I argue that prior to moving the residents, a better fit between resident and neighborhood can be constructed by housing authorities such that more beneficial social interaction outcomes can be achieved overall in the relocation process.

Using a two-dimensional hybrid simulation, we study the physics of the interaction of the solar wind with a localized magnetic field concentration, or “magcon,” on the Moon. Our simulation treats the solar wind protons kinetically and the electrons as a charge-neutralizing fluid. This approach is necessary because the characteristic scale of the magcon is of the same order or smaller than the proton inertial length—the characteristic scale in the hybrid simulation. Specifically, we consider a case in which the incident solar wind flows exactly normal to the lunar surface, and the magcon is represented by a simple dipole whose moment is parallel to the surface, with a center just below it. We find that while the magcon causes the solar wind to be deflected and decelerated, it does not completely shield the lunar surface anywhere. However, protons which impact the surface in the center of the magnetic anomaly have energies well below the solar wind ram energy. Thus, in this region, any backscattered neutral particles resulting from the interaction of solar wind protons with the lunar regolith would have energies lower than that of the solar wind. Moreover, very few neutrals, if any, would emanate from within the magcon with energies comparable to the solar wind energy. This may explain recent observations of lunar energetic neutral atoms associated with a strong crustal magnetic anomaly. Our study also finds that a significant fraction of the incoming solar wind protons are reflected back into space before reaching the surface. These particles are reflected by a strong electrostatic field which results from the difference in the proton and electron inertia. The reflected particles are seen at very high altitudes above the Moon, over 200 km, and over a much broader spatial scale than the magcon, several hundred kilometers at least. Our simulation also revealed a second population of reflected particles which originate from the side of the magcon where the interplanetary and magcon magnetic fields are directed opposite to one another, leading to a magnetic topology much like magnetic reconnection. As previously reflected particles move through this region, they are deflected upward, away from the surface, forming a second component. Our simulation has a number of similarities to recent in situ spacecraft observations of reflected ions above and around magcons.

Les mousses extinctrices sont utilisées sur les feux de catégorie B (solvants inflammables). L’efficacité des mousses actuelles contenant des agents moussants fluorés est apportée par la formation d’un film aqueux à la surface du carburant enflammé. Les entreprises recherchent et développent de nouveaux agents moussants sans fluor car ce type de tensioactif est nocif pour l’environnement et la santé. Des mousses très stables sont nécessaires pour qu'une couche épaisse de mousse résiste aux températures élevées et au démoussage par le solvant et évite ainsi la ré-inflammation.Dans ce travail, l’amélioration de la stabilité de la mousse a été réalisée en utilisant des épaississants dans une solution moussante avec des tensioactifs non fluorés. Des polysaccharides tels que la gomme xanthane ont été utilisés et ses interactions avec des tensioactifs ont été étudiés. Les complexes formés par ces interactions ont été utilisés dans le but d’améliorer la stabilité de la mousse et sa résistance aux flammes. Ceci engendre des mousses de plus faible moussabilité mais de plus grande stabilité. Des tests à échelle réduite ont été réalisés selon la norme EN1568 et ont montré l’efficacité de l’addition de gomme xanthane. Ces formulations innovantes associant des polysaccharides et des agents moussants sont de bonnes alternatives aux formules contenant des tensioactifs fluorés. Le mécanisme d’action des hydrotropes améliorant la moussabilité a aussi été étudié
Firefighting foams are used on class B fires (flammable solvents). The efficiency of currently used foams containing fluorinated foaming agents is ensured by the formation of an aqueous thin film on top of the burning solvent. The formation of such film requires the use of fluorinated surfactants that specifically adsorb at the water-air interface. Companies currently develop fluorine-free products for firefighting foams because this kind of surfactants is harmful for the environment and health. Very stable foams are necessary to the formation of a thick layer of foam that resists high temperatures and defoaming by the solvent, preventing fire re-ignition.In this work, improved foam stability was achieved by using thickeners in the foaming fluid together with the non-fluorinated surfactants. Polysaccharides such as xanthan gum were used and their interactions with surfactants were investigated. Complex species formed by such interactions were used in order to improve foam stability and resistance against flames. This causes a lower foamability but higher stability of foams. Small scale fires extinguishing experiments performed following the standard EN1568 showed the efficiency of xanthan gum addition. These innovative formulations combining polysaccharides and foaming agents are suitable alternatives to those containing fluorinated surfactants. The action mechanism of hydrotropes improving foamability has also been studied

Orientador: Carlos Raimundo Ferreira Grosso
Dissertação (mestrado) - Universidade Estadual de Campinas, Faculdade de Engenharia de Alimentos
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Resumo: O objetivo deste trabalho foi produzir micropartículas capazes de resistir ao ambiente gástrico e liberar o material encapsulado em ambiente intestinal. As partículas foram produzidas pela gelificação iônica da pectina de baixo teor de esterificação amidada com íons cálcio e posteriormente recobertas com proteínas utilizando soluções de diferentes concentrações de concentrado proteíco do soro do leite (WPC), submetidas ou não a tratamento térmico. A condição de adsorção das proteínas sobre a superfície das partículas de pectina foi definida a partir da análise da carga livre total das soluções de proteína e polissacarídeos e assim a definição de pH e a relação entre eles foi usada para produção das micropartículas. As micropartículas obtidas foram caracterizadas com relação a sua carga elétrica de forma a se obter as condições de pH e a relação de concentração de polissacarídeo : proteína em solução em que a interação eletrostática entre os biopolímeros fosse possível. Foram testados 5 níveis de proteína em soluções ( 2, 4, 6, 8 e 12%) associados a proteína sem tratamento térmico (STT) e tratada termicamente (TT), desnaturação a 80ºC por 15 minutos, sendo que as partículas obtidas foram caracterizadas com relação a morfologia, teor de proteína e conteúdo de umidade. A partir deste estudo preliminar foram selecionados dois tipos de partículas, uma partícula recoberta com proteína STT e outra partícula recoberta com proteína TT, utilizando como critério de seleção as soluções proteícas onde foram obtidas partículas com o maior teor de proteína adsorvida. As partículas selecionadas foram avaliadas com relação à resistência ao ambiente gástrico e capacidade de liberação do material encapsulado em ambiente intestinal, sendo que, para isso, as micropartículas foram submetidas a uma simulação das condições gastrointestinais in vitro, avaliando sua integridade nestas condições e quantificando-se o teor de proteína solubilizada em ambiente gástrico simulado. Também foi avaliada a estabilidade das partículas em diferentes pHs, tamanho médio, morfologia interna e externa e capacidade de reidratação pós liofilização. As concentrações de proteína em solução em que foram obtidos os mais altos valores de proteína adsorvida foram de 4 a 6%, com adsorção de 49,2 ± 1,0 % para partículas com WPC - STT e 27,6 ± 1,8% para solução de WPC - TT. Variações de tamanho das micropartículas após sua inserção em diferentes pHs assim como em suco gástrico artificial, foram de 224,8 µm a 342,9 µm. As partículas liofilizadas e reidratadas readquiriram forma e tamanho original após uma hora de inserção em água além de apresentarem estabilidade às variações de pH. As partículas permaneceram íntegras em ambiente gástrico e desintegraram-se em meio intestinal, entretanto durante a simulação das condições gástricas houve uma alta solubilização da proteína em suco gástrico quando o pH foi ajustado a 1,2 com a presença de pepsina, enquanto menor solubilização foi observada quando o pH do suco gástrico foi ajustado para 3, também em presença de pepsina
Abstract: The aim of this study was to produce microparticles able to resist the gastric environment and after releasing the encapsulated material in the gut environment. Particles were produced by ionic gellling using low methoxyl amidated pectin with calcium ions and coated with protein using solutions of different concentrations of whey protein concentrated (WPC), submitted or not submitted to thermal treatment. The condition of the protein adsorption on the surface of pectin particles was defined as the analysis of free charge total protein and polysaccharide solutions and thus defining the relationship between pH and ratio used for the production of particles. The particles obtained were characterized with to their electrical change so as to obtain conditions of pH and the concentration of polysaccharide to protein in solution in which the electrostatic interaction between the biopolymer possible. Five levels of protein in solution (2, 4, 6, 8 e 12%) associated with non-denatured (STT) and denatured (TT) protein in a water bath at 80°C for 15 minutes were tested, and the resulting particles were characterized with respect to their morphology, protein and moisture content. From this preliminary study were selected two types of particles, one particle with STT protein and another with TT protein, using as a standard the conditions of protein in solution which produced the highest level of protein adsorbed. The particles selected were evaluated with respect to resistance to the environment of the stomach and ability to release encapsulated material in intestinal environment, and for that, the microparticles were subjected to a simulated gastrointestinal conditions in vitro evaluating its integrity in these conditions and the protein solubilized in the simulated gastric environment quantified. The stability of the particles at different pHs, average size, internal and external morphology and capacity to rehydration after freeze drying were also evaluated. The concentration of protein in solution where the highest values of protein adsorbed was obtained was 4 ¿ 6%, with adsorption of 49.2 ± 1.0% for particles with WPC - STT and 27.6 ± 1.8 % for the solution contained WPC - TT. The size of the microparticles after their insertion at different pHs as well as in artificial gastric juice, ranging from 224,8 µm to 342,9. The microparticles freeze dried and rehydrated regained the shape and original size after one hour of insertion in water and were stable against changes in pH. The particles remained intact in the environment of the stomach and disintegrated at the intestinal environment, however during the simulation of gastric conditions the was a high concentration of protein in gastric juice while the pH was adjusted to 1.2 with the presence of pepsin while smaller solubilization was observed then the pH of gastric juice was adjusted to 3, also in the presence pepsin
Mestrado
Nutrição Experimental e Aplicada à Tecnologia de Alimentos
Mestre em Alimentos e Nutrição

Orientador: Carlos Raimundo Ferreira Grosso
Dissertação (mestrado) - Universidade Estadual de Campinas, Faculdade de Engenharia de Alimentos
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Resumo: O objetivo deste trabalho foi produzir micropartículas com multicamadas contendo alto teor de proteínas, capazes de serem estáveis a condições adversas do meio e resistentes ao ambiente gástrico. Na primeira parte deste estudo, interações eletrostáticas entre o alginato e proteínas do concentrado proteico do soro do leite (WPC) foram avaliadas em relação às condições de pH (3,5 e 3,75) e proporções de polissacarídeo e proteína. A formação de coacervados com os biopolímeros alginato e WPC foi caracterizada quanto à aparência, tamanho médio e carga superficial. Esta análise permitiu definir as condições em que a interação entre proteínas e partículas de alginato pudesse ocorrer. Assim, micropartículas de alginato produzidas por gelificação iônica foram posteriormente recobertas por interação eletrostática com proteínas, utilizando soluções de diferentes concentrações de concentrado proteico do soro do leite, em dois pHs. Foram testadas três concentrações de proteína em solução para cada pH de recobrimento, sendo 0,6, 3 e 4% para o pH 3,5 e 1,7, 3 e 4% para o pH 3,75. As partículas obtidas foram caracterizadas com relação ao teor total de proteína, conteúdo de umidade, tamanho e morfologia. As maiores adsorções proteicas foram obtidas com a maior concentração de proteína em solução (4%) em ambos pHs. A partir deste estudo preliminar, selecionou-se a amostra de micropartículas com o maior teor de proteína adsorvida para se construir multicamadas em sua superfície através da interação eletrostática. Na segunda parte do estudo, foram produzidas multicamadas de alginato e proteínas do concentrado proteico do soro do leite sobre a superfície da partícula de alginato. Essas partículas foram caracterizadas igualmente as anteriores. A proteína total adsorvida na partícula foi alta, variou de 51,20% a 64,91%, sendo 33,24% dessa proteína encontrada na primeira camada (AlgPart1). Na terceira camada (AlgPart3), também foram encontradas elevados teores proteicos, variando de 17,96% a 31,67%. Uma relação proporcional entre a concentração de alginato e WPC com o aumento da adsorção proteica nesta camada foi observada. A formação das multicamadas (AlgPart1 e AlgPart3) sobre a superfície das partículas provocou uma diminuição significativa no teor de umidade das partículas (AlgPart), ao contrário do que foi observado com o tamanho. Observações realizadas por MEV revelaram que as camadas produzidas com alginato tendem a ter superfícies mais lisas, e com WPC, tendem a ser rugosas. A amostra de micropartículas com multicamadas que apresentou a maior adsorção proteica foi avaliada quanto à estabilidade em temperatura de esterilização (121 ºC, por 15 minutos),pH (2, 4, 6 e 8), concentração de sal (0, 50, 100, 150 e 200 mM) e em condições gastrointestinais (in vitro). Além disso, foram caracterizadas em relação ao tamanho médio, solubilidade proteica e morfologia. Partículas multicamadas úmidas permaneceram íntegras à temperatura de esterilização, apresentaram uma diminuição significativa de tamanho e um acréscimo significativo na solubilidade da camada proteica para o meio em pH 2, e permaneceram estáveis em pHs 4, 6 e 8. A perda de proteína das multicamadas da partícula aumentou significativamente com o aumento da força iônica do meio. As partículas com multicamadas se mostraram parcialmente resistentes às condições gástricas, com uma liberação de 30,5% da proteína presente na partícula e, foram sensíveis à atividade proteolítica em ambiente intestinal simulado promovendo a desintegração das multicamadas e a liberação de praticamente toda proteína da partícula. Considerando os resultados obtidos, conclui-se que é possível a formação de multicamadas de alginato e WPC sobre a superfície de partículas de gelificação iônica com alta adsorção proteica, capazes de serem estáveis em condições adversas do meio e parcialmente resistente às condições gástricas
Abstract: The objective of this work was to produce microparticles with multilayer containing high protein content, capable of being stable to harsh conditions of the environment and resistant to the gastric environment. In the first part of this study, the electrostatic interaction between the alginate and protein of concentrate whey protein (WPC) was evaluated in relation to pH conditions (3.5 and 3.75) and ratio of polysaccharide: protein. The formation of coacervates between the alginate and WPC was characterized as the visual appearance, medium size and surface charge. This analysis allowed us to define the conditions in which the interaction between proteins and alginate particles could occur. Thus alginate microparticles produced by ionic gelation were subsequently coated by electrostatic interaction with proteins, using solutions with different concentrations of whey protein at two pHs. Three concentrations were tested with respect to the protein concentration, being 0.6, 3 and 4% for pH 3.5 and 1.7, 3 and 4% for pH 3.75. The particles were characterized with respect to the total protein content, moisture content, size and morphology. The highest protein adsorption were obtained with the higher concentration of protein solution (4%) by both pH. From this preliminary study, we selected the particle with the highest level of protein adsorbed to construct multilayer using electrostatic interaction on its surface. In the second part of the study, were produced multilayers of alginate and WPC were produced on the surface of the particle of alginate. These particles were characterized in relation to protein adsorption, moisture content, medium size and morphology. The total protein adsorbed on the particle was high, varied from 51.20% to 64.91%, being 33.24% of this protein found in the first layer (AlgPart1). In the third layer (AlgPart3), were also found elevated protein levels, varying from 17.96% to 31.67%. A proportional relationship between the concentration of alginate and WPC with increased protein adsorption was observed in this layer. The formation of multilayers (AlgPart1 and AlgPart3) on the particle surface caused a significant decrease in moisture content of the particles (AlgPart), contrary to what was observed with the size. Observations made by SEM revealed that layers produced with alginate tend to have most smooth surfaces, and WPC tend to be rough. The particle multilayers that presented the highest protein adsorption was evaluated as to the stability at sterilization temperature (121 º C for 15 minutes), pH (2, 4, 6 and 8), salt concentration (0, 50, 100, 150 and 200 mM) and in gastrointestinal conditions. Furthermore were characterized with respect to medium size, protein solubility and morphology. Moist Multilayer particles have remained stable against the temperature of sterilization, showing a significant decrease in size and a significant increase in the solubility of the protein layer into the medium at pH 2, and remain stable at pH 4, 6 and 8. The loss of protein from multilayer particle increased as ionic strength increased. The particles with multilayer were partially resistant to gastric conditions, with a release of 30.49% of the protein in the particle, and were susceptible to proteolytic activity in simulated intestinal environment promoting the particle disintegration and the release of all protein recovering the particles. Considering the results obtained, it is concluded that it is possible the formation of multilayer alginate and WPC on the surface of particles obtained ionic gelation using high protein adsorption, capable of being stable in adverse conditions of the environment (temperature, pH, ionic strength) and resistant to gastric conditions
Mestrado
Consumo e Qualidade de Alimentos
Mestra em Alimentos e Nutrição

In a proposed design for a concentrated solar power tower, sand is irradiated by solar energy and transfers its energy to another fluid stream by means of a finned tube heat exchanger. To maximize heat transfer and minimize potential damage to the heat exchanger, it is desired to have a very uniform flow through the heat exchanger. However, performing full scale flow tests can be expensive, impractical, and depending upon the specific quantities of interest, unsuitable for revealing the details of what it happening inside of the flow stream. Thus, the discrete element method has been used to simulate and study particulate flows. In this project, the flow of small glass beads through a square pyramid shaped hopper and a wedge shaped hopper were studied at the lab scale. These flows were also simulated using computers running two versions of discrete element modeling software – EDEM and LIGGGHTS. The simulated results were compared against the lab scale flows and against each other. They show that, in general, the discrete element method can be used to simulate lab scale particulate flows as long as certain material properties are well known, especially the friction properties of the material. The potential for increasing the accuracy of the simulations, such as using better material property data, non-uniform particle size distributions, and non-spherical particle shapes, as well as simulating heat transfer within a granular flow are also discussed.

Dans un avion, un hélicoptère ou un lanceur actuel, des milliers de capteurs, pour la plupart non critiques sont utilisés pour la mesure de divers paramètres (températures, pressions, positions...) Les résultats sont ensuite acheminés par des fils vers les calculateurs de bord qui les traitent. Ceci implique la mise en place de centaines de kilomètres de câbles (500 km pour un avion de ligne) dont le volume est considérable. Il en résulte une grande complexité de conception et de fabrication, des problèmes de fiabilité, notamment au niveau des connexions, et une masse importante. Par ailleurs l'instrumentation de certaines zones est impossible car leur câblage est difficilement envisageable par manque d'espace. En outre, s'il est souvent intéressant d'installer de nouveaux capteurs pour faire évoluer un aéronef ancien, l'installation des câbles nécessaires implique un démantèlement partiel, problématique et coûteux, de l'appareil. Pour résoudre ces problèmes, une idée innovante a émergé chez les industriels de l'aéronautique : commencer à remplacer les réseaux filaires reliant les capteurs d'un aéronef et leur centre de décision par des réseaux sans fil. Les technologies de communication sans fil sont aujourd'hui largement utilisées dans les marchés de l'électronique de grande consommation. Elles commencent également à être déployées pour des applications industrielles comme l'automobile ou le relevé à distance de compteurs domestiques. Cependant, remplacer des câbles par des ondes représente un défi technologique considérable comme la propagation en milieu confiné, la sécurité, la sureté de fonctionnement, la fiabilité ou la compatibilité électromagnétique. Cette thèse est motivée d'une part par l'avancée non négligeable dans le milieu aérospatial que pourrait être l'établissement d'un réseau sans fil à bord d'aéronefs dans la résolution de problématique classiques comme l'allégement et l'instrumentation. Il en résulterait donc : * Une meilleure connaissance de l'environnement et de la santé de l'aéronef * Un gain sur le poids. * Un gain en flexibilité. * Un gain en malléabilité et en évolutivité. * Un gain sur la complexité. * Un gain sur la fiabilité D'autre part, étant donnée la complexité de la conception de ce réseau de capteur sans fil, il a été nécessaire d'appliquer une méthodologie évolutive et adaptée mais inspirée de l'ingénierie système. Il est envisageable, vu le nombre de sous-systèmes à considérer, que cette méthodologie soit réutilisable pour d'autre cas pratiques. Une étude aussi complète que possible a été réalisée autour de l'existant déjà établi sur le sujet. En effet, on peut en lisant ce mémoire de thèse avoir une idée assez précise de ce qui a été fait. Une liste a été dressée de toutes les technologies sans fil en indiquant leur état de maturité, leurs avantages et leurs inconvénients afin de préciser les choix possibles et les raisons de ces choix. Des projets de capteurs sans fil ont été réalisés, des technologies sans fil performantes et personnalisables ont été développées et arrivent à maturité dans des secteurs variés tels que la domotique, la santé, l'automobile ou même l'aéronautique. Cependant aucun capteur sans fil n'a été véritablement installé en milieu aérospatial car de nombreux verrous technologiques n'ont pas été levés. Fort des expériences passées, et de la maturité qu'ont prise certaines technologies, des conclusions ont été tirées des projets antérieurs afin de tendre vers des solutions plus viables. Une fois identifiés, les verrous technologiques ont été isolés. Une personnalisation de notre solution a été à envisager afin de remédier tant que faire se peut à ces points bloquants avec les moyens mis à disposition. La méthodologie appliquée nous a permis d'identifier un maximum de contraintes, besoins et exigences pour mieux focaliser les efforts d'innovation sur les plus importantes et choisir ainsi les technologies les plus indiquées.

碩士
國防醫學院
藥學研究所
95
The increased public interest of coadministration of Chinese herbal medicine with Western medicine has raised an important issue of drug interaction. Drug-drug interactions may result a loss in therapeutic efficacy or may induce the toxic effects. Many Chinese herbal medicine and prescription drugs have been found to have interactions. Recently, many studies have indicated that herbal drug interaction is related to Cytochrome P450 (CYP450), the most abundant enzyme in human liver and is highly expressed in the intestinal tract. The purpose of this study is to determine the effects of Chinese herbal medicine on CYP450 and to investigate the possible interactions of Chinese herbal medicine and Western medicine. The 24 concentrated compound Chinese herbal medicines used in this study were referring to the order list of National Social Health Care System and Customs of Medicine use in Taiwan. These 24 concentrated compound Chinese herbal medicines were screened for the activity of CYP3A using human liver microsomes for in vitro study. 10 Chinese herbal medicines were selected for the in vivo test due to their inhibition effects on CYP3A. There were 2 groups for the in vivo study, short term and long term study. The in vivo study was performed by using the Sprague – Dawley (SD) rats. The short term study was carried out by orally administered concentrated compound Chinese herbal medicine to SD rats 3 times daily for 7 days followed by orally administered midazolam, a CYP3A substrate, on the 8th day. Pharmacokinetic parameters (i.e. AUC, Cmax) were observed to determine whether the metabolism of midazolam was affected by the Chinese herbal medicines or had the possible herbal – drug interaction. The SD rats were sacrificed and the livers and intestines were taken for the determination of CYP3A activity using testosterone as a model drug. 5 concentrated compound Chinese herbal medicines were selected for the long term in vivo study. The long term study was performed by giving the 5 concentrated compound Chinese herbal medicines orally to SD rats 3 times daily for 14 days followed by midazolam on the 15th day. The result of short term study showed that the Cmax and AUC of midazolam increased significantly when orally administered Cang Er Zi San and Long-Daan-Shiah-Gan-Tang. The clearance was also increased significantly when orally administered Zhi-Bai-Di-Huang-Wan. On the other hand, the result for the long term study showed that the Cmax and AUC of midazolam decreased significantly when orally administered Jia-Wei-Xiao-Yao-San, Zhi-Bai-Di-Huang-Wan and Ban-Xia-Xie-Xin-Tang. According to the results of short term study, Cmax, AUC, and the activity of CYP3A of liver and intestine showed negative correlations, but the clearance of midazolam showed a positive correlation. Moreover, the ratio of AUC for 1’-OH-midazolam and midazolam and the activity of CYP3A showed significant positive correlation.

碩士
國立臺灣大學
土木工程學研究所
92
The goal of the present study is to develop experimental and computational tools for the study of concentrated dispersions of solid particles interacting with a liquid. The experimental approach developed uses stereo imaging to track the motions of the visible cores of transparent particles bathed in a liquid of identical refractive index. The capability of the approach is demonstrated by measuring the 3D circulation inside a fluidisation of 1,000 spheres. For the computational approach, Lagrangian dynamics is combined with the meshless Method of Fundamental Solutions. This approach is applied to rigid disks moving in a 2D potential flow. The resulting simulations show how liquid inertia influences the particle motions.

During the extraction of apple juice an insoluble residue, called apple pomace, is generated. Apple pomace represents the fruit cell wall material, identified as a source of polysaccharides and polyphenols. However, apple pomace is mostly discarded by the industries. In the one hand, this occurs because some polysaccharides and polyphenols still correspond to molecules of unknown applications and structures resulting from oxidation phenomena that occur during juice extraction. On the other hand, the industries lack drying methodologies capable of meeting their needs for valorization of apple pomace compounds. The adoption of different extraction and fractionation methodologies gives an overview of the properties and structures of the compounds that can be available from apple pomace after the implementation of a drying process to preserve the byproduct. Based on this hypothesis, apple pomace was subjected to extractions with water, methanol and acetone:water (60:40; v:v), without or with urea, and microwave superheated water extractions to unravel the existence of phenolic structures other than those naturally occurring in the fresh fruit. Additionally, for identification of chemically modified carbohydrates due to polyphenol oxidation, hot water extractions were performed followed by dialysis (12-14 kDa) and ethanol precipitation. Extraction with hot water, methanol and acetone followed by analysis by liquid chromatography allowed to observe the presence of flavan-3-ols, flavonols, dihydrochalcones and hydroxycinamic acids, totaling 5 g/kg of dry apple pomace. Oxidation products of dihydrochalcones and hydroxycinnamic acids were also detected in apple pomace. Alkaline fusion analysis of water-insoluble material demonstrated the occurrence of non-extractable oxidized procyanidins, whose prevalence was 4-fold higher than in native apple polyphenols. Extraction with microwave superheated water followed by ethanol precipitation of the obtained extracts showed that procyanidins were covalently linked to the pectic polysaccharides, xyloglucans and cellulose present in the water-insoluble material and could account for up to 40% of the polyphenols that can be obtained from apple pomace. Solid phase extraction of the hot water-soluble material using C18 cartridges showed that, along with polyphenols, polysaccharides were also extracted, some of them exhibiting a hydrophobic behavior at pH 7 and/or pH 3. Dialysis followed by ethanol precipitation, alongside with glycosidic linkages analysis by gas chromatography, nuclear magnetic ressonance, size-exclusion chromatography, and alkaline fusion, led to the conclusion that polyphenols covalently linked to polysaccharides are responsible for their hydrophobicity, constituting xyloglucan-polyphenols-pectic polysaccharide and arabinan-polyphenol complexes. To understand the formation of polysaccharide-polyphenol complexes established by covalent bonds, the interactions of arabinans with 5-O-caffeoylquinic acid and phloridzin were studied. Through their diffusion along dialysis membranes in the presence or absence of polysaccharide, linear arabinans showed 10-fold and 2-fold greater retention of 5-O-caffeoylquinic acid and phloridzin than branched arabinans suggesting that a higher degree of branching limits polysaccharides interaction with polyphenols. The same trend was observed for the interaction of arabinans with procyanidins by isothermal titration calorimetry, where linear arabinans presented higher affinity constants (Ka 540 M-1) than branched arabinans (Ka 391 M-1). This approach also demonstrated that the occurrence of covalently linked polyphenols to arabinans restricts further interactions with polyphenols (Ka 85 M-1). The analysis of the material that precipitated after interaction between arabinans and procyanidins showed that procyanidins of higher degree of polymerization and less branched polysaccharides tended to form insoluble aggregates. In order to ensure the stability of apple pomace for further extraction of compounds, this byproduct was dried via microwave hydrodiffusion and gravity (MHG) technology using delivery powers of 300-900 W. MHG drying proved to be a three phases process: heating, drying and burning point phase. This methodology presented an estimated 80% energy efficiency, as well as drying times (1-2.6 h) and water flows (5.1-13.9 mL/min) up to 4-fold higher than those verified by hot air drying (3.6-9.9 he 1-3.5 mL/min). Using MHG drying, it was also possible to obtain extracts composed by polyphenols and polysaccharides. The addition of ethanol during the drying process can increase the obtained extract mass. The dried apple pomace was stable for at least 2 years, after which was possible to obtain extracts rich in polyphenols and polysaccharides. In conclusion, the adoption of different extraction and fractionation procedures allowed a better understanding of the structures and chemical properties of the compounds present in apple pomace, especially those derived from oxidation reactions of polyphenols. This, together with the efficient and rapid drying verified for MHG technology, opens new research perspectives and applications that should culminate in the possible mitigation of apple pomace as an agro-industrial residue.
Durante a extração do sumo de maçã é gerado um resíduo insolúvel denominado bagaço de maçã. O bagaço de maçã representa o material da parede celular do fruto, identificado como fonte de polissacarídeos e polifenóis. No entanto, o bagaço de maçã é maioritariamente descartado pelas indústrias. Por um lado, pelo facto de alguns polissacarídeos e compostos fenólicos corresponderem a moléculas de aplicações e estruturas desconhecidas, resultantes de fenómenos de oxidação que ocorrem durante a extração de sumo. Por outro, as indústrias carecem de metodologias de secagem capazes de corresponder às suas necessidades para valorização dos compostos do bagaço de maçã. A adoção de diferentes metodologias de extração e fracionamento permitem obter uma visão global das propriedades e estruturas dos compostos passíveis de serem recolhidos do bagaço após implementação de um processo de secagem para preservação do subproduto. Com base nesta hipótese, o bagaço de maçã foi submetido a extrações com água, metanol e acetona:água (60:40; v:v), sem ou com ureia, e água superaquecida por micro-ondas com o objetivo de desvendar a existência de outras estruturas fenólicas além daquelas que ocorrem naturalmente no fruto. Adicionalmente, para identificação de carbohidratos quimicamente modificados como consequência da oxidação de polifenóis, foram realizadas extrações com água quente seguidas de fracionamento por diálise (12-14 kDa) e precipitação em etanol. A extração com água quente, metanol e acetona seguida de análise por cromatografia líquida permitiu identificar a presença de flavan-3-óis, flavonóis, di-hidrocalconas e ácidos hidroxicinâmico, totalizando 5 g/kg de bagaço seco. Também foram detectados produtos de oxidação de di-hidrocalconas e ácidos hidroxicinâmicos no bagaço de maçã. A análise por fusão alcalina do material insolúvel em água demonstrou a ocorrência de procianidinas oxidadas não-extractáveis, cuja prevalência foi 4 vezes superior aos compostos fenólicos nativos da maçã. A extração com água superaquecida por micro-ondas seguida de precipitação em etanol dos extratos obtidos mostrou que estas se encontravam covalentemente ligadas aos polissacarídeos pécticos, xiloglucanas e celulose presentes no material insolúvel em água, podendo corresponder até 40% dos compostos fenólicos possíveis de serem obtidos a partir do bagaço de maçã. A extração em fase sólida do material solúvel em água quente, usando cartuchos C18, mostrou que, juntamente com os polifenóis, foram extraídos polissacarídeos, alguns dos quais apresentando um comportamento hidrofóbico a pH 7 e/ou a pH 3. O fracionamento por diálise e precipitação em etanol, e a análise das ligações glicosídicas por cromatografia em fase gasosa, ressonância magnética nuclear, cromatografia de exclusão molecular e fusão alcalina, permitiu inferir que os polifenóis ligados covalentemente aos polissacarídeos são responsáveis pela sua hidrofobicidade, constituindo complexos de xiloglucanas-polifenóis-polissacarídeos pécticos e complexos de arabinanas-polifenóis. Para compreender a formação dos complexos polissacarídeos-polifenóis, estabelecidos por ligações covalentes, foram estudadas as interações de arabinanas com o ácido 5-O-cafeoilquinico e floridzina. Através da sua difusão ao longo de membranas de diálise na presença ou ausência de polissacarídeo, verificou-se que as arabinanas lineares apresentaram 10 a 2 vezes maior retenção do ácido 5-O-cafeoilquinico e da floridzina do que as arabinanas ramificadas sugerindo que um maior grau de ramificação dos polissacarídeos limita a sua interação com os compostos fenólicos. A mesma tendência foi observada para a interação de arabinanas com procianidinas por calorimetria de titulação isotérmica, onde arabinanas lineares apresentaram maiores constantes de afinidade (Ka 540 M-1) do que arabinanas ramificadas (Ka 391 M-1). Esta abordagem demonstrou também que a ocorrência de polifenóis ligados covalentemente a arabinanas restringe possíveis interações adicionais com os polifenóis (Ka 85 M-1). A análise do material que precipitou após interação entre as arabinanas e as procianidinas mostrou que as procianidinas de maior grau de polimerização e os polissacarídeos menos ramificados são as estruturas que tendem a formar os agregados insolúveis. Com o objetivo de garantir a estabilidade do bagaço de maçã para posterior extração de compostos, este subproduto foi secado via tecnologia de micro-ondas por hidrodifusão e gravidade (MHG), utilizando potências de 300-900 W. A secagem por MHG mostrou-se um processo composto por três fases: aquecimento, secagem e ponto de queima. Esta metodologia apresentou uma estimativa de 80% de eficiência energética, bem como tempos de secagem (1-2.6 h) e fluxos de água (5,1-13,9 mL/min) até 4 vezes superiores às verificadas por secagem com ar quente (3,6-9,9 h e 1-3,5 mL/min). Pela técnica MHG foi possível obter em simultâneo com a secagem, extratos constituídos por polifenóis e polissacarídeos. Através da adição de etanol durante o processo de secagem, a massa de extrato foi incrementada. O bagaço secado mostrou-se estável por pelo menos 2 anos, após os quais foi possível obter extratos ricos em compostos fenólicos e polissacarídeos. Em conclusão, a adoção de diferentes mecanismos de extração e de fracionamento permitiu uma maior compreensão das estruturas e propriedades químicas dos compostos presentes no bagaço de maçã, especialmente aquelas derivadas de reações de oxidação dos compostos fenólicos. Isto, em conjunto com a eficiente e rápida secagem verificada pela tecnologia de MHG abre novas perspetivas de investigação e aplicações que podem culminar na possível mitigação do bagaço de maçã como um resíduo agroindustrial.
Programa Doutoral em Ciência e Tecnologia Alimentar e Nutrição

The present study was aimed at understanding the high pressure (HP) processing-induced interactions of milk proteins in whey protein concentrate (WPC) solutions, in skim milk and in pure protein systems. The changes in milk proteins induced by heat treatments in the same systems under selected conditions were also evaluated. The main approach taken was to elucidate changes in the whey proteins in heat- and pressure-treated samples from common aliquots, under identical conditions, using various one-dimensional (1D) and two-dimensional (2D) polyacrylamide gel electrophoresis (PAGE) techniques in the absence or presence of a disulphide bond reducing agent. In some instances, the samples were also analysed using small deformation rheology, size exclusion chromatography (SEC) and transmission electron microscopy (TEM). The results of the present study indicated that, in general terms, heat treatment and HP treatment had common effects, i.e. denaturation and subsequent aggregation of whey proteins. Both heat treatment and HP treatment generated disulphide-bonded and hydrophobically bonded aggregates of whey proteins. However, the sensitivities of each of the whey proteins to heat treatment [immunoglobulin (Ig) > lactoferrin (LF) > bovine serum albumin (BSA) > β-laetoglobulin B (β-LG B) > β-LG A > α-lactalbumin (α-LA)] and pressure treatment (β-LG B > β-LG A > IgG > LF > BSA > α-LA) were considerably different. Also, HP treatment generated a comparatively greater proportion of smaller aggregates than did heat treatment. The effects of protein concentration, intensity of pressure treatment, holding time and pressurising temperature on whey protein aggregation in WPC solutions were investigated. The rate of aggregation of whey proteins increased with an increase in the concentration of protein in the WPC solution and the pressurising temperature. The combination of low protein concentration, mild pressure treatment (200 MPa) and low pressurising temperature (20°C) led to minimal loss of native-like and SDS-monomeric β-LG, whereas the combination of high protein concentration, severe pressure treatment (600 MPa) and higher pressuring temperature (40°C and higher) led to significant loss of both native-like and SDS-monomeric β-LG. The sensitivity of pressure-resistant whey proteins, such as α-LA and BSA, to the aggregation was significantly increased at pressurising temperatures of 40°C and higher. Self-supporting gels were formed when 8 or 12% (w/v) WPC solutions were pressure treated at 600-800 MPa. 20°C. Detailed analysis of the behaviour of the proteins during the formation of these gels revealed a novel pathway, suggesting that intermolecular disulphide bond formation occurred at high pressure but that hydrophobic association became important after the HP treatment. In the later part of the study, heat- and HP-induced interactions of caseins and whey proteins were studied in a more complex system, i.e. skim milk. With the application of modified PAGE techniques, it was possible to show that the high molecular weight disulphide-bonded aggregates that were formed by HP treatment of skim milk contained disulphide-linked complexes consisting of αS2-casein (αS2-CN) as well as κ-CN, β-LG and other whey proteins. The results showed that the effects of heat treatment and HP on the interactions of the caseins and whey proteins in milk were significantly different. The accessibility of αS2-CN and the formation of complexes involving αS2-CN, κ-CN and whey proteins in the HP-treated milk, as demonstrated using the modified 2D PAGE technique, and as explained by possible proposed reactions of the caseins and whey proteins in pressure-treated milk, was an important finding of the present study. Finally, a study on the effects of HP treatment in model systems using pure proteins in solution, both singly or in binary and ternary combinations, generated very useful information and clarified the role of each protein in pressure-induced aggregation and interactions of milk proteins in complex systems such as WPC and milk. It was found that the reactions of β-LG were not significantly affected by other proteins such as α-LA or BSA, but that the presence of β-LG in the system catalysed the reactions of other proteins such as α-LA or BSA.