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Asociace polymerů s amfifilními sloučeninami (surfaktanty) ve vodných roztocích / Self-assembly of polymers with amphiphilic compounds (surfactants) in aqueous solutionsDelisavva, Foteini January 2017 (has links)
Title: Self-assembly of polymers with amphiphilic compounds (surfactants) in aqueous solutions Abstract: This PhD Thesis is devoted to the co-assembly in systems containing electrically charged polymers (polyelectrolytes and block copolymers containing polyelectrolyte sequences). I studied the interactions between block copolymers and oppositely charged surfactants in aqueous solutions, and the structure and properties of co-assembled nanoparticles by a combination of several experimental methods. I found that the spontaneous formation, solubility and stability of complex nanoparticles depend not only on the electrostatic attractive forces but also on the hydrophobic effects. In a major part of my Thesis, I studied the interaction of polyelectrolytes with oppositely charged gemini surfactants (containing two charged head-groups interconnected by a short linker and two hydrophobic tails) which is a relatively new topic - much less studied than the co-assembly with conventional single tail surfactants. Better understanding of the formation and properties of complexes containing gemini surfactants and polymers provides knowledge that should lead to novel tailor-made nanoparticles with desired properties for applications in medicine and new technologies (including nano-technologies). We have shown that the...
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Development of Non-Conventional Microwave Devices Based on Substrate-Integrated Technology for Advanced ApplicationsNova Giménez, Vicente 26 February 2024 (has links)
[ES] El uso masivo de los sistemas de comunicaciones inalámbricas y móviles ha tenido un impacto significativo en nuestra sociedad. Estas tecnologías han experimentado una amplia adopción en el mercado, volviéndose totalmente indispensables en nuestro día a día y provocando un aumento notable en la demanda de movilidad y ancho de banda. Esto ha llevado a la rápida aparición de nuevos sistemas de comunicación y a la progresiva saturación del espectro radioeléctrico, lo que conlleva un constante aumento en los requisitos de los sistemas de radiofrecuencia. Como resultado, los dispositivos que forman parte de estos sistemas se ven sometidos a especificaciones cada vez más restrictivas. Estas restricciones se han visto fuertemente incrementadas en las comunicaciones espaciales, donde los nuevos sistemas basados en satélite de alta capacidad y grandes constelaciones fuerzan la reducción de costes a la vez que requieren de altas prestaciones.
Con el fin de satisfacer las crecientes demandas de los sistemas inalámbricos, se busca el desarrollo de dispositivos de comunicación que ofrezcan altas prestaciones a bajo costo. Estos dispositivos también deben ser compactos, ligeros y fáciles de integrar con diversas tecnologías de guiado de ondas (guías de ondas, cables coaxiales y tecnologías planares). En respuesta a estas necesidades, han surgido dos soluciones tecnológicas: los circuitos integrados en sustrato (SIC) y la fabricación aditiva (AM).
La tecnología SIC permite combinar tecnologías de guiado planares y no planares en un mismo sistema, lo que resulta en unas prestaciones híbridas entre ambas tecnologías. Además, ofrece una notable reducción de peso y una gran miniaturización y su naturaleza planar permite una integración nunca vista.
Por otro lado, la fabricación aditiva permite crear dispositivos con geometrías complejas y bajo peso, lo que proporciona menos limitaciones en el diseño. Esto permite el desarrollo de dispositivos con características avanzadas y la integración de los diferentes bloques de una cadena de radiofrecuencia en un único dispositivo, mejorando así las especificaciones del sistema y reduciendo su complejidad.
Tanto la tecnología SIC como la fabricación aditiva son de gran interés para el sector espacial. Sin embargo, la aplicación de estas tecnologías en el agresivo entorno espacial aún no ha sido estudiada. Por ello, el objetivo principal de esta tesis es precisamente investigar la aplicación de estas tecnologías al diseño de dispositivos de microondas para aplicaciones espaciales. Con este estudio, se busca obtener un mayor conocimiento de las capacidades y limitaciones de estas tecnologías en el contexto espacial, y así explorar su potencial para mejorar y optimizar los dispositivos utilizados en este tipo de sistemas.
En primer lugar, se ha llevado a cabo una comparación de diferentes topologías de filtros implementados en tecnología SIC, los cuales han sido sometidos a pruebas ambientales que simulan las condiciones reales de operación en el espacio.
En segundo lugar, se ha estudiado la aplicación de técnicas de fabricación aditivas al desarrollo de dispositivos de microondas. Para ello, se ha desarrollado un novedoso método de metalización y un sistema de integración de filtros de montaje superficial. Con estas tecnologías se han desarrollado una serie de filtros paso banda que han sido sometidos a pruebas de ambiente espacial, incluyendo: ciclado térmico, pruebas de vibración y test de efecto multipactor.
Por último, se ha estudiado el uso de cristal líquido para agregar capacidades de reconfigurabilidad a dispositivos SIC. Se han analizado las características mecánicas y electromagnéticas de estos materiales mediante dos métodos de caracterización basados en elementos resonantes. Además, se ha desarrollado un demostrador tecnológico basado en la tecnología ESICL. / [CA] L'ús massiu dels sistemes de comunicacions sense fils i mòbils ha tingut un impacte significatiu en la nostra societat. Aquestes tecnologies han experimentat una àmplia adopció en el mercat, perquè s'han tornat totalment indispensables en el nostre dia a dia i han provocat un augment notable en la demanda de mobilitat i amplada de banda. Al seu torn, això ha portat a la ràpida aparició de nous sistemes de comunicació i a la progressiva saturació de l'espectre radioelèctric, la qual cosa comporta un constant augment en els requisits dels sistemes de radiofreqüència. Com a resultat, els dispositius que formen part d'aquests sistemes es veuen sotmesos a especificacions cada vegada més restrictives. Aquestes restriccions s'han vist fortament incrementades en les comunicacions espacials.
Amb la finalitat de satisfer les creixents demandes dels sistemes sense fils, se cerca el desenvolupament de dispositius de comunicació que oferisquen altes prestacions a baix cost. Aquests dispositius també han de ser compactes, lleugers i fàcils d'integrar amb diverses tecnologies de guia d'ones (guies d'ones, cables coaxials i tecnologies planar). En resposta a aquestes necessitats, han sorgit dues soluciones tecnològiques: els circuits integrats en substrat (SIC) i la fabricació additiva (AM).
La tecnología SIC permet combinar tecnologies de guiatge planars i no planars en un mateix sistema, la qual cosa resulta en unes prestacions híbrides. A més, ofereix una notable reducció de pes i una gran miniaturització i la seua naturalesa planar permet una integració no vista mai abans.
D'altra banda, la fabricació additiva permet crear dispositius amb geometries complexes i baix pes, la qual cosa proporciona menys limitacions en el disseny. Això permet el desenvolupament de dispositius amb característiques avançades i la integració dels diferents blocs que conformen la cadena de radiofreqüència, que millora així les especificacions del sistema i en redueix la complexitat.
Tant la tecnologia SIC com la de fabricació additiva són de gran interès per al sector espacial. Tanmateix, l'aplicació d'aquestes tecnologies en l'agressiu entorn espacial encara no ha sigut estudiada. Per això, l'objectiu principal d'aquesta tesi és investigar l'aplicació d'aquestes tecnologies en el disseny de dispositius de microones per a aplicacions espacials. A través d'aquest estudi, se cerca obtenir un major coneixement sobre les capacitats i limitacions d'aquestes tecnologies en el context espacial.
En primer lloc, s'ha dut a terme una comparació de diferents topologies de filtres implementats en tecnologia SIC, els quals han sigut sotmesos a proves ambientals que simulen les condicions reals d'operació a l'espai.
En segon lloc, s'ha estudiat l'aplicació de tècniques de fabricació additives al desenvolupament de dispositius de microones. Per a això, s'ha desenvolupat un nou mètode de metal·lització autocatalític i un sistema d'integració de filtres de muntatge superficial. Aquestes tecnologies s'han combinat per a desenvolupar una sèrie de filtres passabanda de muntatge superficial. Finalment, aquests filtres han sigut sotmesos a proves d'ambient espacial, incloent-hi: ciclatge tèrmic, proves de vibració i test d'efecte multipactor.
Finalment, s'ha estudiat l'ús de cristall líquid per a agregar capacitats de reconfigurabilitat a dispositius de microones integrats en substrat. S'han analitzat les característiques mecàniques i electromagnètiques d'aquests materials mitjançant dos mètodes de caracterització basats en elements ressonants. A més, s'ha desenvolupat un demostrador tecnològic basat en la tecnologia ESICL. / [EN] The widespread use of wireless and mobile communication systems has had a significant impact on our society. These technologies have been widely adopted in the market, becoming essential in our daily lives and leading to a notable increase in the demand for mobility and bandwidth. Consequently, new communication systems are rapidly emerging, and the radio frequency spectrum is becoming increasingly crowded, resulting in continuously rising requirements for radio frequency systems. As a result, radio frequency devices are subjected to ever more stringent specifications. These restrictions are particularly heightened in space communications.
To meet the growing demands of wireless systems, there is a need to develop communication devices that offer high performance at a low cost. Additionally, these devices should be compact, lightweight, and easily integrable with various waveguide technologies (waveguides, coaxial cables, and planar technologies). In response to these needs, two technological solutions have emerged: Substrate Integrated Circuits (SIC) and Additive Manufacturing (AM).
SIC technology combines planar and non-planar guiding technologies in a single system, resulting in hybrid performance between both technologies. It significantly reduces weight and miniaturisation, and its planar nature allows for unprecedented integration.
On the other hand, additive manufacturing enables the creation of devices with complex geometries and low weight, providing fewer design limitations. This allows for the development of devices with advanced features and the integration of different blocks of the radio frequency chain, thereby enhancing the performance of the entire system and reducing its complexity.
Both SIC and AM are of great interest to the space sector. However, the application of these technologies in the harsh space environment has not been thoroughly studied. The main objective of this thesis is to investigate the application of these technologies in the design of microwave devices for space applications. This study aims to gain a deeper understanding of the capabilities and limitations of these technologies in the space context and explore their potential for improving and optimising devices used in such systems.
The thesis first involves the design and comparison of different filter topologies implemented using SIC technology, which has been subjected to environmental tests simulating real space operation conditions.
Secondly, the application of additive manufacturing techniques to the development of microwave devices has been studied. For this purpose, a novel metallisation method and a system for surface-mounted filter integration have been developed. These technologies were combined to develop a series of surface-mounted bandpass filters. Finally, these filters were subjected to space environmental tests, including thermal cycling, vibration tests, and multipactor effect tests.
Lastly, the use of liquid crystal to add reconfigurability capabilities to substrate-integrated microwave devices has been investigated. The mechanical and electromagnetic characteristics of these materials have been analysed using two resonant element-based characterisation methods. Additionally, a technological demonstrator based on ESICL technology has been developed. / Nova Giménez, V. (2024). Development of Non-Conventional Microwave Devices Based on Substrate-Integrated Technology for Advanced Applications [Tesis doctoral]. Universitat Politècnica de València. https://doi.org/10.4995/Thesis/10251/202844
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Hydrodynamic Diffuse Interface Models for Cell Morphology and MotilityMarth, Wieland 05 July 2016 (has links) (PDF)
In this thesis, we study mathematical models that describe the morphology of a generalized biological cell in equilibrium or under the influence of external forces. Within these models, the cell is considered as a thermodynamic system, where streaming effects in the cell bulk and the surrounding are coupled with a Helfrich-type model for the cell membrane. The governing evolution equations for the cell given in a continuum formulation are derived using an energy variation approach. Such two-phase flow problems that combine streaming effects with a free boundary problem that accounts for bending and surface tension can be described effectively by a diffuse interface approach. An advantage of the diffuse interface approach is that models for e.g. different biophysical processes can easily be combined. That makes this method suitable to describe complex phenomena such as cell motility and multi-cell dynamics. Within the first model for cell motility, we combine a biological network for GTPases with the hydrodynamic Helfrich-type model. This model allows to account for cell motility driven by membrane protrusion as a result of actin polymerization. Within the second model, we moreover extend the Helfrich-type model by an active gel theory to account for the actin filaments in the cell bulk. Caused by contractile stress within the actin-myosin solution, a spontaneous symmetry breaking event occurs that lead to cell motility. In this thesis, we further study the dynamics of multiple cells which is of wide interest since it reveals rich non-linear behavior. To apply the diffuse interface framework, we introduce several phase field variables to account for several cells that are coupled by a local interaction potential. In a first application, we study white blood cell margination, a biological phenomenon that results from the complex relation between collisions, different mechanical properties and lift forces of red blood cells and white blood cells within the vascular system. Here, it is shown that inertial effects, which can become of relevance in various parts of the cardiovascular system, lead to a decreasing tendency for margination with increasing Reynolds number. Finally, we combine the active polar gel theory and the multi-cell approach that is capable of studying collective migration of cells. This hydrodynamic approach predicts that collective migration emerges spontaneously forming coherently-moving clusters as a result of the mutual alignment of the velocity vectors during inelastic collisions. We further observe that hydrodynamics heavily influence those systems. However, a complete suppression of the onset of collective migration cannot be confirmed. Moreover, we give a brief insight how such highly coupled systems can be treated numerically using finite elements and how the numerical costs can be limited using operator splitting approaches and problem parallelization with OPENMP. / Diese Dissertation beschäftigt sich mit mathematischen Modellen zur Beschreibung von Gleichgewichts- und dynamischen Zuständen von verallgemeinerten biologischen Zellen. Die Zellen werden dabei als thermodynamisches System aufgefasst, bei dem Strömungseffekte innerhalb und außerhalb der Zelle zusammen mit einem Helfrich-Modell für Zellmembranen kombiniert werden. Schließlich werden durch einen Energie-Variations-Ansatz die Evolutionsgleichungen für die Zelle hergeleitet. Es ergeben sie dabei Mehrphasen-Systeme, die Strömungseffekte mit einem freien Randwertproblem, das zusätzlich physikalischen Einflüssen wie Biegung und Oberflächenspannung unterliegt, vereinen. Um solche Probleme effizient zu lösen, wird in dieser Arbeit die Diffuse-Interface-Methode verwendet. Ein Vorteil dieser Methode ist, dass es sehr einfach möglich ist, Modelle, die verschiedenste Prozesse beschreiben, miteinander zu vereinen. Dies erlaubt es, komplexe biologische Phänomene, wie zum Beispiel Zellmotilität oder auch die kollektive Bewegung von Zellen, zu beschreiben. In den Modellen für Zellmotilität wird ein biologisches Netzwerk-Modell für GTPasen oder auch ein Active-Polar-Gel-Modell, das die Aktinfilamente im Inneren der Zellen als Flüssigkristall auffasst, mit dem Multi-Phasen-Modell kombiniert. Beide Modelle erlauben es, komplexe Vorgänge bei der selbst hervorgerufenen Bewegung von Zellen, wie das Vorantreiben der Zellmembran durch Aktinpolymerisierung oder auch die Kontraktionsbewegung des Zellkörpers durch kontraktile Spannungen innerhalb des Zytoskelets der Zelle, zu verstehen. Weiterhin ist die kollektive Bewegung von vielen Zellen von großem Interesse, da sich hier viele nichtlineare Phänomene zeigen. Um das Diffuse-Interface-Modell für eine Zelle auf die Beschreibung mehrerer Zellen zu übertragen, werden mehrere Phasenfelder eingeführt, die die Zellen jeweils kennzeichnen. Schließlich werden die Zellen durch ein lokales Abstoßungspotential gekoppelt. Das Modell wird angewendet, um White blood cell margination, das die Annäherung von Leukozyten an die Blutgefäßwand bezeichnet, zu verstehen. Dieser Prozess wird dabei bestimmt durch den komplexen Zusammenhang zwischen Kollisionen, den jeweiligen mechanischen Eigenschaften der Zellen, sowie deren Auftriebskraft innerhalb der Adern. Die Simulationen zeigen, dass diese Annäherung sich in bestimmten Gebieten des kardiovaskulären Systems stark vermindert, in denen die Blutströmung das Stokes-Regime verlässt. Schließlich wird das Active-Polar-Gel-Modell mit dem Modell für die kollektive Bewegung vom Zellen kombiniert. Dies macht es möglich, die kollektive Bewegung der Zellen und den Einfluss von Hydrodynamik auf diese Bewegung zu untersuchen. Es zeigt sich dabei, dass der Zustand der kollektiven gerichteten Bewegung sich spontan aus der Neuausrichtung der jeweiligen Zellen durch inelastische Kollisionen ergibt. Obwohl die Hydrodynamik einen großen Einfluss auf solche Systeme hat, deuten die Simulationen nicht daraufhin, dass Hydrodynamik die kollektive Bewegung vollständig unterdrückt. Weiterhin wird in dieser Arbeit gezeigt, wie die stark gekoppelten Systeme numerisch gelöst werden können mit Hilfe der Finiten-Elemente-Methode und wie die Effizienz der Methode gesteigert werden kann durch die Anwendung von Operator-Splitting-Techniken und Problemparallelisierung mittels OPENMP.
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Synthèse contrôlée et auto-organisation de glycopolymères amphiphiles à greffons polymères mésogènes, destinés à la vectorisation de principes actifs / Controlled synthesis and self-assembly of amphiphilic glycopolymers with polymeric mesogen grafts, in view of drug delivery applicationsFerji, Khalid 08 October 2013 (has links)
De nouveaux glycopolymères greffés aux paramètres macromoléculaires contrôlés [dextrane-g-poly(acrylate de diéthylène glycol cholestéryle), Dex-g-PADEGChol] ont été préparés en quatre étapes via la stratégie de synthèse « grafting from». L'originalité de ces glycopolymères réside dans la combinaison, et pour la première fois, d'une dorsale polysaccharide hydrophile biocompatible/ biodégradable et de greffons polymères hydrophobes à caractère mésogène. L'ATRP a été utilisée pour contrôler la croissance des greffons PADEGChol en milieu homogène à partir d'un macroamorceur dérivé de dextrane (DexAcBr). Les conditions de polymérisation avaient été préalablement ajustées en étudiant l'homopolymérisation du monomère ADEGChol en présence d'un amorceur modèle et de plusieurs systèmes catalytiques CuIBr/(PMDETA ou OPMI) dans différents solvants (THF ou toluène). Le caractère amphiphile de ces glycopolymères a été évalué et leurs propriétés mésomorphes ont été étudiées par calorimétrie différentielle à balayage, microscopie optique à lumière polarisante et par diffraction des rayons X. Des études préliminaires par microscope électronique à transmission et diffusion dynamique de la lumière polarisée ont démontré que ces glycopolymères adoptent une morphologie vésiculaire appelée « polymersome » en phase aqueuse, lorsque le DMSO est utilisé comme co-solvant. Ces nano-objets pourront être testés ultérieurement pour la formulation d'un nouveau type de vecteurs de principes actifs / New graft glycopolymers with well-defined parameters [dextran-g-poly(diethylene glycol cholesteryl ether acrylate) (Dex-g-PADEGChol)] have been prepared in four steps using the "grafting from" strategy. Challenge of this work arises from the combination for the first time of a hydrophilic, biocompatible/biodegradable polysaccharide backbone with mesogen hydrophobic polymeric grafts. Controlled growth of the grafts (PADEGChol) was obtained using ATRP initiated in homogeneous medium from a dextran derivative (DexAcBr). In order to find the best polymerization conditions, homopolymerization of ADEGChol monomer was investigated using an initiator model and various catalytic systems CuIBr/(PMDETA or OPMI) in two solvents (Toluene and THF). The amphiphilic properties of such glycopolymers were evaluated and their mesomorphic properties have been studied by thermal polarizing optical microscopy, differential scanning calorimetry and X-ray scattering. Using transmission electron microscopy and dynamic light scattering, vesicular morphology called "polymersome" was observed in aqueous medium when DMSO was used as co-solvent. These polymersomes could be tested as new drug delivery systems
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Hydrodynamic Diffuse Interface Models for Cell Morphology and MotilityMarth, Wieland 27 May 2016 (has links)
In this thesis, we study mathematical models that describe the morphology of a generalized biological cell in equilibrium or under the influence of external forces. Within these models, the cell is considered as a thermodynamic system, where streaming effects in the cell bulk and the surrounding are coupled with a Helfrich-type model for the cell membrane. The governing evolution equations for the cell given in a continuum formulation are derived using an energy variation approach. Such two-phase flow problems that combine streaming effects with a free boundary problem that accounts for bending and surface tension can be described effectively by a diffuse interface approach. An advantage of the diffuse interface approach is that models for e.g. different biophysical processes can easily be combined. That makes this method suitable to describe complex phenomena such as cell motility and multi-cell dynamics. Within the first model for cell motility, we combine a biological network for GTPases with the hydrodynamic Helfrich-type model. This model allows to account for cell motility driven by membrane protrusion as a result of actin polymerization. Within the second model, we moreover extend the Helfrich-type model by an active gel theory to account for the actin filaments in the cell bulk. Caused by contractile stress within the actin-myosin solution, a spontaneous symmetry breaking event occurs that lead to cell motility. In this thesis, we further study the dynamics of multiple cells which is of wide interest since it reveals rich non-linear behavior. To apply the diffuse interface framework, we introduce several phase field variables to account for several cells that are coupled by a local interaction potential. In a first application, we study white blood cell margination, a biological phenomenon that results from the complex relation between collisions, different mechanical properties and lift forces of red blood cells and white blood cells within the vascular system. Here, it is shown that inertial effects, which can become of relevance in various parts of the cardiovascular system, lead to a decreasing tendency for margination with increasing Reynolds number. Finally, we combine the active polar gel theory and the multi-cell approach that is capable of studying collective migration of cells. This hydrodynamic approach predicts that collective migration emerges spontaneously forming coherently-moving clusters as a result of the mutual alignment of the velocity vectors during inelastic collisions. We further observe that hydrodynamics heavily influence those systems. However, a complete suppression of the onset of collective migration cannot be confirmed. Moreover, we give a brief insight how such highly coupled systems can be treated numerically using finite elements and how the numerical costs can be limited using operator splitting approaches and problem parallelization with OPENMP. / Diese Dissertation beschäftigt sich mit mathematischen Modellen zur Beschreibung von Gleichgewichts- und dynamischen Zuständen von verallgemeinerten biologischen Zellen. Die Zellen werden dabei als thermodynamisches System aufgefasst, bei dem Strömungseffekte innerhalb und außerhalb der Zelle zusammen mit einem Helfrich-Modell für Zellmembranen kombiniert werden. Schließlich werden durch einen Energie-Variations-Ansatz die Evolutionsgleichungen für die Zelle hergeleitet. Es ergeben sie dabei Mehrphasen-Systeme, die Strömungseffekte mit einem freien Randwertproblem, das zusätzlich physikalischen Einflüssen wie Biegung und Oberflächenspannung unterliegt, vereinen. Um solche Probleme effizient zu lösen, wird in dieser Arbeit die Diffuse-Interface-Methode verwendet. Ein Vorteil dieser Methode ist, dass es sehr einfach möglich ist, Modelle, die verschiedenste Prozesse beschreiben, miteinander zu vereinen. Dies erlaubt es, komplexe biologische Phänomene, wie zum Beispiel Zellmotilität oder auch die kollektive Bewegung von Zellen, zu beschreiben. In den Modellen für Zellmotilität wird ein biologisches Netzwerk-Modell für GTPasen oder auch ein Active-Polar-Gel-Modell, das die Aktinfilamente im Inneren der Zellen als Flüssigkristall auffasst, mit dem Multi-Phasen-Modell kombiniert. Beide Modelle erlauben es, komplexe Vorgänge bei der selbst hervorgerufenen Bewegung von Zellen, wie das Vorantreiben der Zellmembran durch Aktinpolymerisierung oder auch die Kontraktionsbewegung des Zellkörpers durch kontraktile Spannungen innerhalb des Zytoskelets der Zelle, zu verstehen. Weiterhin ist die kollektive Bewegung von vielen Zellen von großem Interesse, da sich hier viele nichtlineare Phänomene zeigen. Um das Diffuse-Interface-Modell für eine Zelle auf die Beschreibung mehrerer Zellen zu übertragen, werden mehrere Phasenfelder eingeführt, die die Zellen jeweils kennzeichnen. Schließlich werden die Zellen durch ein lokales Abstoßungspotential gekoppelt. Das Modell wird angewendet, um White blood cell margination, das die Annäherung von Leukozyten an die Blutgefäßwand bezeichnet, zu verstehen. Dieser Prozess wird dabei bestimmt durch den komplexen Zusammenhang zwischen Kollisionen, den jeweiligen mechanischen Eigenschaften der Zellen, sowie deren Auftriebskraft innerhalb der Adern. Die Simulationen zeigen, dass diese Annäherung sich in bestimmten Gebieten des kardiovaskulären Systems stark vermindert, in denen die Blutströmung das Stokes-Regime verlässt. Schließlich wird das Active-Polar-Gel-Modell mit dem Modell für die kollektive Bewegung vom Zellen kombiniert. Dies macht es möglich, die kollektive Bewegung der Zellen und den Einfluss von Hydrodynamik auf diese Bewegung zu untersuchen. Es zeigt sich dabei, dass der Zustand der kollektiven gerichteten Bewegung sich spontan aus der Neuausrichtung der jeweiligen Zellen durch inelastische Kollisionen ergibt. Obwohl die Hydrodynamik einen großen Einfluss auf solche Systeme hat, deuten die Simulationen nicht daraufhin, dass Hydrodynamik die kollektive Bewegung vollständig unterdrückt. Weiterhin wird in dieser Arbeit gezeigt, wie die stark gekoppelten Systeme numerisch gelöst werden können mit Hilfe der Finiten-Elemente-Methode und wie die Effizienz der Methode gesteigert werden kann durch die Anwendung von Operator-Splitting-Techniken und Problemparallelisierung mittels OPENMP.
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Characterization of heterogeneous diffusion in confined soft matterTäuber, Daniela 26 October 2011 (has links) (PDF)
A new method, probability distribution of diffusivities (time scaled square displacements between succeeding video frames), was developed to analyze single molecule tracking (SMT) experiments. This method was then applied to SMT experiments on ultrathin liquid tetrakis(2-ethylhexoxy)silane (TEHOS) films on Si wafer with 100 nm thermally grown oxide, and on thin semectic liquid crystal films. Spatial maps of diffusivities from SMT experiments on 220 nm thick semectic liquid crystal films reveal structure related dynamics. The SMT experiments on ultrathin TEHOS films were complemented by fluorescence correlation spectroscopy (FCS). The observed strongly heterogeneous single molecule dynamics within those films can be explained by a three-layer model consisting of (i) dye molecules adsorbed to the substrate, (ii) slowly diffusing molecules in the laterally heterogeneous near-surface region of 1 - 2 molecular diameters, and (iii) freely diffusing dye molecules in the upper region of the film. FCS and SMT experiments reveal a strong influence of substrate heterogeneity on SM dynamics. Thereby chemisorption to substrate surface silanols plays an important role. Vertical mean first passage times (mfpt) in those films are below 1 µs. This appears as fast component in FCS autocorrelation curves, which further contain a contribution from lateral diffusion and from adsorption events. Therefore, the FCS curves are approximated by a tri-component function, which contains an exponential term related to the mfpt, the correlation function for translational diffusion and a stretched exponential term for the broad distribution of adsorption events. Lateral diffusion coefficients obtained by FCS on 10 nm thick TEHOS films, thereby, are effective diffusion coefficients from dye transients in the focal area. They strongly depend on the substrate heterogeneity. Variation of the frame times for the acquisition of SMT experiments in steps of 20 ms from 20 ms to 200 ms revealed a strong dependence of the corresponding probability distributions of diffusivities on time, in particular in the range between 20 ms and 100 ms. This points to average dwell times of the dye molecules in at least one type of the heterogeneous regions (e.g. on and above silanol clusters) in the range of few tens of milliseconds.
Furthermore, time series of SM spectra from Nile Red in 25 nm thick poly-n-alkyl-methacrylate (PnAMA) films were studied. In analogy to translational diffusion, spectral diffusion (shifts in energetic positions of SM spectra) can be studied by probability distributions of spectral diffusivities, i.e. time scaled square energetic displacements. Simulations were run and analyzed to study contributions from noise and fitting uncertainty to spectral diffusion. Furthermore the effect of spectral jumps during acquisition of a SM spectrum was investigated. Probability distributions of spectral diffusivites of Nile Red probing vitreous PnAMA films reveal a two-level system. In contrast, such probability distributions obtained from Nile Red within a 25 nm thick poly-n-butylmethacrylate film around glass transition and in the melt state, display larger spectral jumps. Moreover, for longer alkyl side chains a solvent shift to higher energies is observed, which supports the idea of nanophase separation within those polymers.
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Characterization of heterogeneous diffusion in confined soft matterTäuber, Daniela 20 October 2011 (has links)
A new method, probability distribution of diffusivities (time scaled square displacements between succeeding video frames), was developed to analyze single molecule tracking (SMT) experiments. This method was then applied to SMT experiments on ultrathin liquid tetrakis(2-ethylhexoxy)silane (TEHOS) films on Si wafer with 100 nm thermally grown oxide, and on thin semectic liquid crystal films. Spatial maps of diffusivities from SMT experiments on 220 nm thick semectic liquid crystal films reveal structure related dynamics. The SMT experiments on ultrathin TEHOS films were complemented by fluorescence correlation spectroscopy (FCS). The observed strongly heterogeneous single molecule dynamics within those films can be explained by a three-layer model consisting of (i) dye molecules adsorbed to the substrate, (ii) slowly diffusing molecules in the laterally heterogeneous near-surface region of 1 - 2 molecular diameters, and (iii) freely diffusing dye molecules in the upper region of the film. FCS and SMT experiments reveal a strong influence of substrate heterogeneity on SM dynamics. Thereby chemisorption to substrate surface silanols plays an important role. Vertical mean first passage times (mfpt) in those films are below 1 µs. This appears as fast component in FCS autocorrelation curves, which further contain a contribution from lateral diffusion and from adsorption events. Therefore, the FCS curves are approximated by a tri-component function, which contains an exponential term related to the mfpt, the correlation function for translational diffusion and a stretched exponential term for the broad distribution of adsorption events. Lateral diffusion coefficients obtained by FCS on 10 nm thick TEHOS films, thereby, are effective diffusion coefficients from dye transients in the focal area. They strongly depend on the substrate heterogeneity. Variation of the frame times for the acquisition of SMT experiments in steps of 20 ms from 20 ms to 200 ms revealed a strong dependence of the corresponding probability distributions of diffusivities on time, in particular in the range between 20 ms and 100 ms. This points to average dwell times of the dye molecules in at least one type of the heterogeneous regions (e.g. on and above silanol clusters) in the range of few tens of milliseconds.
Furthermore, time series of SM spectra from Nile Red in 25 nm thick poly-n-alkyl-methacrylate (PnAMA) films were studied. In analogy to translational diffusion, spectral diffusion (shifts in energetic positions of SM spectra) can be studied by probability distributions of spectral diffusivities, i.e. time scaled square energetic displacements. Simulations were run and analyzed to study contributions from noise and fitting uncertainty to spectral diffusion. Furthermore the effect of spectral jumps during acquisition of a SM spectrum was investigated. Probability distributions of spectral diffusivites of Nile Red probing vitreous PnAMA films reveal a two-level system. In contrast, such probability distributions obtained from Nile Red within a 25 nm thick poly-n-butylmethacrylate film around glass transition and in the melt state, display larger spectral jumps. Moreover, for longer alkyl side chains a solvent shift to higher energies is observed, which supports the idea of nanophase separation within those polymers.
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