Dissertationen zum Thema „Swelling stresses“

Cette étude se focalise sur l’influence du dioxyde de titane sur le comportement d’une résine polymère époxy modèle. Les systèmes considérés sont des composites constitués d’un pigment, le dioxyde de titane TiO2 à des taux massiques de 10% et 20%, et de résine DGEBA-DAMP. Tout d’abord, les propriétés mécaniques et thermiques de films libres complètement réticulés sont mesurées par DSC et DMA. Les résultats des composites sont comparés à ceux de la résine pure pour mieux comprendre l’impact du TiO2. Les films libres de composites sont ensuite immergés dans de l’eau pure à différentes températures (30, 40, 50 et 60 °C) pour étudier la prise en eau et les coefficients de diffusion par gravimétrie. L’évolution des propriétés de nos systèmes est aussi étudiée pour avoir accès à l’influence de l’eau sur leur comportement. Dans un second temps, les composites sont réticulés sur des plaques d’acier et certaines sont soumises à des contraintes mécaniques externes. Ces revêtements sont alors plongés dans une solution saline et l’absorption d’eau est suivie par SIE. Une dernière étape de ce travail consiste à suivre le gonflement des revêtements composites par SECM. Finalement, la comparaison des résultats de la résine pure et des composites obtenus pour les films libres et les revêtements permet de mettre en avant l’impact du TiO2 sur la durabilité de ces systèmes, essentiellement dû au développement de contraintes internes
This study focuses on the influence of titanium dioxide on the behavior of a model epoxy polymer resin. The considered systems are composites which contain titanium dioxide TiO2 as pigment and DGEBA-DAMP as epoxy resin. The studied amounts of titanium dioxide are 10 wt.% and 20 wt.%. Firstly, mechanical and thermal properties of totally cured free films are studied by DSC and DMA. The results of the composites are compared to those of the resin alone to better understand the impact of the titanium dioxide. Then, composite free films are immersed in pure water at different temperatures (30, 40, 50 and 60 °C) to investigate water uptake and diffusion coefficients by gravimetry. At each step of ageing, measurements of the properties are carried out to show the influence of water on our systems behaviors. Then, composites of epoxy resin and pigment are applied on steel panels and some samples are submitted to external mechanical stresses. These coatings are submitted to an environment of NaCl 3 wt.% saline solution and water uptake is followed by Electrochemical Impedance Spectroscopy (EIS). Swelling of composites coatings is followed by SECM in a last step of this work. Finally, a comparison of the results of pure resin and of composite gives access to the impact of titanium dioxide on the durability of these systems. It is mainly due to the presence of internal stresses

Les revêtements d'hydrogel sont des réseaux de polymères transparents et hydrophiles capables d’abosrber plusieurs fois leur épaisseur en eau. Cependant, les contraintes induites par le gonflement du film peuvent entraîner un décollement préjudiciable de l'hydrogel ce qui peut limiter l’utilisation pratique des ces revêtements. Dans cette étude, nous proposons de décrire les mécanismes de décollement de films minces d’hydrogel en fonction de leur densité de greffage à l'interface film/substrat. Le but est de pouvoir contrôler et prédire la dégradation des revêtements hydrogel pendant le gonflement ou sous des contraintes de contact. Dans ce but, nous avons développé une méthodologie permettant de mesurer l'initiation et la propagation de la délamination induite par le gonflement de films minces d’hydrogel à partir de défauts d'interface préexistants bien contrôlés.Des films minces d'hydrogel de poly(diméthylacrylamide) (PDMA) attachés à la surface sont préparés sur des plaquettes de silicium à partir de la réticulation et du greffage simultanés (CLAG) de chaînes polymères fonctionnalisées par la chimie click thiol-ène. Cette stratégie permet de faire varier l'épaisseur du film (0.1 - 2 µm) et de contrôler le taux de gonflement du réseau, ici fixé à 2, tout en assurant une densité de réticulation homogène. Afin de faire varier la résistance de l'interface film/substrat, le substrat en silicium est greffé avec des mélanges de mercaptosilane (réactif) et de propylsilane (inerte) dans différentes proportions avant le dépôt du film mince. Alors que le mercaptosilane est capable de former des liaisons covalentes avec le réseau PDMA, le propylsilane ne réagit pas, ce qui permet de contrôler le taux de greffage du film mince d’hydrogel sur le substrat. Nous caractérisons la fraction de surface de mercaptosilane ainsi obtenue par des analyses XPS et TOF-SIMS. Par ailleurs, toujours à l’interface subtrat/film, des défauts linéaires bien contrôlés ayant une faible adhérence (largeur entre 10 et 100 µm) sont créés sur le substrat en passivant de façon localisée les groupes thiol réactifs par microlithographie. Ces défauts nucléent le décollement des films de façon bien localisée, ce qui permet ensuite de suivre la propagation de la décohésion à partir de ces défauts.Le décollement du film induit par le gonflement est réalisé sous un flux de vapeur constant assurant la saturation du film en eau. En observant le décollement progressif du film à partir des défauts linéaires préexistants, nous retrouvons un motif d’instabilité classique dit de fil de téléphone et nous montrons que le décollement résulte de contraintes de gonflement localisées proche de la ligne de décollement. Nous mesurons la vitesse de propagation du décollement dans la zone où le film est greffé sur le substrat et nous observons qu’elle augmente de deux ordres de grandeur lorsque la quantité de propylsilane dans le mélange de silanes réactifs passe de 0 à 90 %, c’est-à-dire lorsque le taux de greffage du film décroit. Un seuil d'épaisseur pour le décollement est également observé, les films pouvant se décoller étant d’autant plus minces que le taux de greffage du film ets faible. Les mesures de ce seuil sont discutées à partir d'un argument simple de mécanique de la rupture qui permet de rendre compte semi quantitativement de nos mesures
Hydrogel coatings are transparent and hydrophilic polymer networks that absorb a lot of water and can be suitable candidates for anti-mist coatings. However, swelling-induced stresses within the film can result in detrimental debonding of hydrogel and may fail. In this study, these debonding processes are investigated in the relation to the grafting density at the film/substrate interface, so as to control and predict the failure of the coatings during swelling or under contact stresses. For that purpose, we have developed a methodology consisting in monitoring the initiation and the propagation of swelling-induced delamination from well-controlled preexisting interface defects.Surface-attached poly(dimethylacrylamide) (PDMA) hydrogel thin films are prepared on silicon wafers from the simultaneous Cross-Linking And Grafting (CLAG) of functionalized polymer chains by thiol-ene click chemistry. This strategy allows to tune the film thickness (0.1-2 µm) while ensuring a homogeneous crosslinking density. In order to vary the strength of the film/substrate interface, the silicon wafer is grafted by mixing reactive mercaptosilane and unreactive propylsilane in various proportions prior to the formation of the hydrogel film. We characterize the mercaptosilane surface fraction thus obtained by XPS and TOF-SIMS analyses. Well-controlled line defects (width between 2 and 100 µm) are also created to nucleate delamination of the hydrogel from the substrate.Swelling-induced debonding of the film is achieved under a constant vapor flow ensuring water saturation. Optical observations show the progressive debonding of the film from the pre-existing line defects under the action of localized swelling stresses. We obtain a delamination pattern of typical so-called telephone cord instability. We measure the debonding propagation velocity where the hydrogel is grafted to the substrate. The debonding rate is found to decrease over two orders of magnitude when the amount of mercaptosilane in the reactive silane mixture is increased from 10% to 100% while increasing the covalent bonds between hydrogel and substrate. A threshold thickness for debonding is also observed. This threshold thickness increases with the amount of mercaptosilane used to graft the substrate. We derived quantitative values of the interface fracture energy from the measured thickness threshold with a simple fracture mechanics model

A presente tese tem por objetivo contribuir para o conhecimento do comportamento dependente do tempo das rochas de anidrita e gipso. O maior interesse é fornecer argumentos convincentes sobre os mecanismos físicos responsáveis pelas deformações lentas observadas em algumas escavações subterrâneas realizadas em maciços dessas rochas na Europa, aspecto este que hoje está bastante confuso e escassamente estudado. A hipótese central desta pesquisa é que o comportamento dependente do tempo das rochas de anidrita e gipso deve-se parcial e/ou totalmente às propriedades reológicas (fluência) e não exclusivamente a expansão decorrente da transformação anidrita – gipso como a maioria dos autores sustenta. Este problema será analisado a partir de uma perspectiva experimental através de ensaios específicos. Os ensaios de expansão axial livre em rochas de anidrita permitiram concluir que quando submersas em água destilada, experimentam diminuição de volume por dissolução. Já as amostras de anidrita em contato com solução saturada em 'CA'SO IND.4' mostram uma relação não linear entre deformação axial e o tempo indicando uma taxa de expansão que decresce com o tempo. As taxas de expansão axial variam entre 0,3 e 2,4%/ano. A novidade é que esta expansão se deve à deposição de uma camada contínua formada por neocristais de gipso e não a expansão por hidratação da anidrita como acontece com os argilominerais. O mecanismo de transformação consiste na dissolução da anidrita e posterior precipitação do gipso em condições de sobre-saturação da solução. A transformação mineralógica acontece, na natureza, em condições propícias de temperatura e saturação da solução com íons 'CA POT.2+' e 'SO IND.4'POT.2-'. Propõe-se uma teoria alternativa sobre deformações lentas de maciços sulfáticos baseada na força de cristalização decorrente da deposição de cristais de gipso nas juntas do maciço rochoso. Propõe-se utilizar as formulações termodinâmicas propostas para expansão de concretos por crescimento de etringita e gipso. Os ensaios de fluência uniaxial sob compressão axial constante mostram que ambos os tipos de rochas sulfáticas apresentam comportamentos elasto-visco-plásticos e taxas de deformação axial e lateral da ordem de '10 POT.-12' a '10 POT.-10' 'S POT.-1'. A deflagração da fluência secundária acontece sob tensões de 4 – 6 MPa para gipsitas e de 25 – 40 MPa para anidritas. As análises sobre os possíveis mecanismos de deformação por fluência foram inconsistentes e nenhuma conclusão definitiva foi atingida. Aparentemente a baixas tensões atuariam mecanismos de difusão e dissolução por pressão. A tensões intermediárias dominariam mecanismos de deslocamentos intra e intercristalinos e a altas tensões as rochas deformariam por propagação de microfissuramento. Ensaios de fluência acoplados a sensores de emissão acústica mostram a manifestação de eventos microssísmicos que usualmente se atribuem à propagação de microfraturas mas que podem dever-se a outros mecanismos. Tanto as taxas de expansão axial como de fluência são compatíveis com as taxas de convergência medidas em algumas obras subterrâneas escavadas em maciços sulfáticos, verificando a hipótese central da pesquisa
The purpose of this thesis is to contribute for the knowledge of time-dependent behavior of sulfatic rocks of anhydrite and gypsum. Emphasis is given to provide straightforward arguments about physical mechanisms responsible for creep observed in some underground excavations in those rocks in Europe. Explanation for this phenomena is not clear yet and studies about them are still scarce. The backbone idea behind this research is that the time-dependent behavior of anhydrite and gypsum is totally or at least partially due to rheological properties, and not exclusively due to swelling resulting from the anhydritegypsum transformation. This problem was investigated experimentally with specific tests. Free swelling tests on anhydrite led to the conclusion that when immersed into distilled water, volume decrease due to dissolution is observed. Anhydrite samples in contact with a saturated solution of 'CA'SO IND.4' present a nonlinear relationship between axial strain and time, indicating swelling rate decreasing with time. Axial swelling rates vary between 0,3% and 2,4%/year. The new concept is that this swelling is due to the deposition of a continuous layer of gypsum composed by gypsum neo-crystals, and not due to hydration swelling of anhydrite, a usual with clay minerals. The transformation mechanism consists of anhydrite dissolution and later precipitation of gypsum under over-saturation condition of the solution. The mineralogical transformation takes place in nature under favorable conditions of temperature and solution saturation with 'CA POT.2+' and 'SO IND.4'POT.2-' ions. An alternative theory is proposed about creep of sulfatic rock masses based on crystallization forces resulting from the deposition of gypsum crystals in the rock masses joints. The use of thermodynamic formulations is proposed for concrete swelling due to the growth of ettringite and gypsum. Uniaxial compression creep tests show that both types of sulfatic rocks present elasto-visco-plastic behavior and axial and lateral strain rates of the order of '10 POT.-12' to '10 POT.-10' 'S POT.-1'. Triggering of secondary creep takes places under stresses of the order of 4 – 6 MPa for gypsum and 25 – 40 MPa for anhydrite. The analyses about the possible creep mechanisms were not consistent and no definite conclusion has been reached get. Apparently under low stresses diffusion and pressure dissolution mechanism dominate. Under intermediate stresses, intra- and inter crystalline displacement mechanisms seem to dominate, and under high stresses rock deform due to microcrack propagation. Creep tests monitored with acoustic emission devices show the occurrence of microseismic events attributed to microcrack propagation. Both axial swelling and creep rock are compatible with convergence rocks measured in some underground works excavated in sulfatic rock masses, following the central idea of this thesis

The research is devoted to study the swelling behaviour in tunnels. A new triaxial testing procedure is developed, which is able to quantify the swelling behaviour of soft rocks and stiff soils. The Caneva Clay is tested both by conventional oedometer swelling tests and by the new triaxial test. The swelling parameters of the clay are quantified for predictive analyses of the swelling behaviour at the tunnel scale.

The purpose of this manuscript is to establish a unified theory of porohyperelasticity with transport and growth and to demonstrate the capability of this theory using a finite element model developed in MATLAB. We combine the theories of volumetric growth and mixed porohyperelasticity with transport and swelling (MPHETS) to derive a new method that models growth of biological soft tissues. The conservation equations and constitutive equations are developed for both solid-only growth and solid/fluid growth. An axisymmetric finite element framework is introduced for the new theory of growing MPHETS (GMPHETS). To illustrate the capabilities of this model, several example finite element test problems are considered using model geometry and material parameters based on experimental data from a porcine coronary artery. Multiple growth laws are considered, including time-driven, concentrationdriven, and stress-driven growth. Time-driven growth is compared against an exact analytical solution to validate the model. For concentration-dependent growth, changing the diffusivity (representing a change in drug) fundamentally changes growth behavior. We further demonstrate that for stress-dependent, solid-only growth of an artery, growth of an MPHETS model results in a more uniform hoop stress than growth in a hyperelastic model for the same amount of growth time using the same growth law. This may have implications in the context of developing residual stresses in soft tissues under intraluminal pressure. To our knowledge, this manuscript provides the first full description of an MPHETS model with growth. The developed computational framework can be used in concert with novel in-vitro and in-vivo experimental approaches to identify the governing growth laws for various soft tissues.

Most of the water fed into a paper machine is removedmechanically in the forming and press sections. One of thefactor which has an important influence on mechanicaldewatering, i.e. in both forming and pressing, is thestress-strain behaviour of the fibre network.

The focus of this thesis is on the development of improvedmathematical descriptions of the stress-strain behaviourexhibited by fibre networks in the forming and press sections.The first part of the thesis presents a physically based modelof the forming and densification of fibre mats in twin-wireformers. The model can calculate the ecect of the applicationof a varied load through the forming section. It was developedfrom mass and momentum balances of the fibre and liquid phases,the fibre mat stress-porosity relation and an expression forthe permeability as a function of the porosity. The fibre-matstress-porosity relation used is rate-independent and presentshysteresis. Simulations have been conducted to study theeffects of roll pressure, blade pulses, wire tension andbeating. The effect of sequential blade pressure pulses afterthe forming roll on the dewatering and the concentrationgradients could be characterised. The simulations alsoexhibited rewetting by expansion when the fibre mats left theforming roll. Increasing wire tension resulted in increaseddewatering, but the rate of increase diminished rapidly withincreasing tension. The simulation results also indicated thatbeating has a large influence on dewatering.

The second part of the thesis presents two models of therate-dependent stress-strain behaviour of the fibre networkthat is observed in wet pressing. The first model was based onthe approach pioneered by Perzyna (1966) for strain-ratedependent plasticity and was quite satisfactory for calculatingthe stress-strain behaviour of the fibre network in singlepress nips. It was successfully applied for studyingdensification and dewatering in both normal wet pressing andhigh temperature wet pressing. However, the first model onlyincludes rate dependence in the compression phase of thecompressionexpansion cycle; the expansion phase is treated asbeing rate independent

The second model of the stress-strain behaviour of the fibrenetwork treats both compression and expansion as being ratedependent, according to experimental observations. It is basedon the idea that the wet fibre web may be conceived as alayered network of restricted swelling gels. A swollen fibre isa restricted gel, the inner swelling pressure in a swollenfibre wall being balanced by the stresses in the fibre wallstructure. The observed rate dependence of wet webs in bothcompression and expansion phases was attributed to the flow ofwater out of and into the fibre walls. The second model gavepredictions that are in good agreement with results fromuniaxial experiments using pressure pulses of arbitrary shapefor both a single pulse and a sequence of pulses. It maytherefore be used as a general model for the rheologicalbehaviour of the wet fibre network in wet pressing, providedthe model parameters are estimated from experimental data withsmall experimental error.

KEYWORDS:Paper, modelling, dewatering, forming, wetpressing, fibre network stress, rheology, hysteresis,intra-fibre water, compressibility, structural stress,stress-strain, restricted gels, swelling.

Recent progress in magnetic resonance imaging (MRI) has opened the way for micron-scale resolution, and thus for imaging biological cells. In this thesis work, we performed magnetic resonance microscopy (MRM) on the nervous system of Aplysia californica, a model particularly suited due to its simplicity and to its very large neuronal cell bodies, in the aim of studying cellular-scale processes with various MR contrasts. Experiments were performed on a 17.2 Tesla horizontal magnet, at resolutions down to 25 µm isotropic. Initial work consisted in conceiving and building radiofrequency microcoils adapted to the size of single neurons and ganglia. The first major part of the project consisted in using the manganese ion (Mn2+) as neural tract tracer in the buccal ganglia of Aplysia. Manganese is an MR contrast agent that enters neurons via voltage-gated calcium channels. We performed the mapping of axonal projections from motor neurons into the peripheral nerves of the buccal ganglia. We also confirmed the existence of active Mn2+ transport inside the neural network upon activation with the neurotransmitter dopamine. In the second major part of the project, we tested the potential of two diffusion MRI sequences for microscopy. On the one hand, we explored a very original mechanism for diffusion weighting, DESIRE (Diffusion Enhancement of SIgnal and REsolution), particularly suited for small samples. The two-dimensional DESIRE sequence was implemented and successfully tested on phantoms. The measured enhancement was consistent with theoretical predictions. Using this sequence to produce diffusion weighted images with an unprecedented contrast in biological tissue remains a challenge. On the other hand, a more "standard" sequence was implemented to measure the apparent diffusion coefficient (ADC) in nervous tissue with MRM. This sequence was a three-dimensional DP-FISP (Diffusion Prepared Fast Imaging with Steady-state free Precession), which met criteria for high resolution in a short acquisition time, with minimal artifacts. Using this sequence, we studied the changes in water ADC at different scales in the nervous system, triggered by cellular challenges. The challenges were hypotonic shock or exposure to ouabain. ADC measurements were performed on single isolated neuronal bodies and on ganglia tissue, before and after challenge. Both types of stress produced an ADC increase inside the cell and an ADC decrease at tissue level. The results favor the hypothesis that the increase in membrane surface area associated with cell swelling is responsible for the decrease of water ADC in tissue, typically measured in ischemia or other conditions associated with cell swelling.

La présente étude vise à comprendre le comportement chimico-hydro-mécanique des argiles raides à travers deux formations géologiques, l'argile de Boom et les argiles yprésiennes, qui sont censées être des formations hôtes potentielles pour le stockage de déchets radioactifs en Belgique. Le comportement volumique a été étudié tant à l'état intact qu'à l'état reconstitué, et sous différentes conditions : K0 et isotrope, sous des boucles de chargement - déchargement. Les résultats obtenus montrent que le comportement volumique de ces argiles est gouverné par la compétition entre l'effet physico-chimique et l'effet mécanique, caractérisée par une contrainte seuil qui correspond à la contrainte de gonflement en termes de changements de structure. Une loi de comportement volumique a été ainsi développée afin de décrire cet aspect. La perméabilité a été déterminée, comparée avec les résultats dans la littérature et corrélée avec les paramètres comme l'indice des vides. La variation de la perméabilité avec la profondeur ont mis en évidence le rôle déterminant des macro-pores dans le transfert des fluides. Le comportement volumique et la perméabilité des argiles de Boom et yprésiennes intactes sont aussi influencés par la variation de la composition chimique de l'eau de pore, qui modifie la double couche diffuse et favorise l'agrégation des particules argileuses. Les caractéristiques élastiques, la surface de charge et l'enveloppe de rupture ont été identifiées pour le comportement déviatorique des argiles de Boom et yprésiennes. Un modèle élasto-plastique conceptuel a été développé permettant de tenir compte des effets du gonflement et de la compétition entre l'effet mécanique et l'effet physico-chimique

碩士
中華大學
機械工程學系
106
With the rapid development of modern technology, In this age when almost everyone has a smart phone, It’s not just a mobile phone, but a small computer. Ability to handle many transactions that were handled by previous computers. Surely, Need to plug many features into a smart phone, It is necessary to make many wafers even smaller line is more shorter. Of course, the camera is also one of the important functions of smart phones, and most of them are CMOS lens chip modules. This paper takes CMOS wafer module as the research object. And high efficiency、Wafer-level chip package with high power and high density (Chip Scale Package, CSP) For packaging Is one of the commonly used packaging technologies, But this type of packaging also has its drawbacks. Because such a package is more similar to the wafer structure which uses a variety of polymeric materials, The polymeric material has hygroscopic properties And because of the presence of air in the CMOS image sensor, And the air is not only the thermal expansion system, Its moisture absorption rate is also more obvious than other polymer materials. Therefore, how to effectively prevent the humid air from entering the package is an important issue. This study uses the finite element software ANSYS to establish a finite element model. Simulation and analysis of CMOS image sensor packages, Simulating the diffusion efficiency and moisture distribution of the material in the package when absorbing moisture, Then introduce hygroscopic diffusion data, Analysis of stress and strain caused by different wet expansion coefficients of materials after moisture absorption, And observe the deformation of the structure. In this study, the SOLID226 element in ANSYS software was used to analyze the wet diffusion of the model and the structural parameters were analyzed. In this model, it consists of multiple layers of materials, but not for each material, it has the characteristics of moisture absorption, and structural simulation is needed. SOLID226 can solve this problem, and the diffusion coefficient parameters and structural coefficient parameters of the material. Type it together and analyze it together. The initial state of the boundary condition is to set the external environmental humidity to a saturated state, and the model is set to a completely dry state. After the analysis, the diffusion state of the humidity from the outside and the stress behavior after the wet expansion are observed.

Wrinkles represent a pathway towards the spontaneous generation of ordered surface microstructure for applications in numerous fields. Examples of highly complex ordered wrinkle structures abound in Nature, but the ability to harness this potential for advanced material applications remains limited. This work focuses on understanding the relationship between the patterns on a wrinkled surface and the experimental conditions under which they form. Because wrinkles form in response to applied stresses, particular attention is given to the nature of the stresses in a wrinkling surface. The fundamental insight gained was then utilized to account for observed wrinkle formation phenomena within more complex geometric and kinetic settings. In order to carefully control and measure the applied stresses on a wrinkling film, a swelling-based system was developed using poly(dimethylsiloxane) (PDMS), surface-oxidized with a UV-ozone treatment. The swelling of the oxidized surface upon exposure to an ethanol vapor atmosphere was characterized using beam-bending experiments, allowing quantitative measurements of the applied stress. The wrinkle morphologies were characterized as a function of the overstress, defined as the ratio of the applied swelling stress to the critical buckling stress of the material. A transition in the dominant morphology of the wrinkled surfaces from dimple patterns to ridge patterns was observed at an overstress value of ~2. The pattern dependence of wrinkles on the ratio of the principal stresses was examined by fabricating samples with a gradient prestress. When swollen, these samples exhibited a smooth morphological transition from non-equibiaxial to equibiaxial patterns, with prestrains as low as 2.5% exhibiting non-equibiaxial characteristics. This transition was seen both in samples with low and high overstresses. To explore the impact of these stress states in more complex geometries, wrinkling hemispherical surfaces with radii of curvature ranging from 50-1000 μm were fabricated using the same material system. Upon wrinkling, the hemispheres formed complex hierarchical assemblies reminiscent of naturally occurring structures. The curvature of a surface exhibited a correlation with its critical buckling stress, independent of other factors. This enables the surface curvature to be used as an independent control over the dimple-to-ridge transition which occurs as a function of overstress. As in the flat buckling surfaces, this transition was shown to occur at an overstress value of ~2. Surface curvature was also shown to improve the observed hexagonal ordering of the dimple arrays, resulting in the formation of regular "golf ball" structures. Geometric effects in finite flat plates were also examined. Using circular masks during the oxidation process, plates with radii ranging from 0.4-8.6 mm were created. Upon wrinkling, a dimple-to-ridge transition was observed with increasing plate size, with the morphological switch occurring at a radius of ~2 mm. This observed transition was not found to be due to the inherent mechanics of plates of different sizes, but instead to a reduction in the oxide conversion due to shadowing or stagnation caused by the masking process, which lowered the applied overstress. The shape of the finite plate was found to have little impact on the resulting wrinkle morphologies. Kinetic aspects of wrinkling were qualitatively characterized by observing the wrinkling process over the course of swelling. Wrinkling was observed to frontally propagate across the surface, and the ordering of the patterns which developed showed a qualitative correlation with the degree of uniformity in the advancing wrinkle front. Swelling with different solvents was found to lead to the formation of different patterns, based on the swelling kinetics of the UVO-treated PDMS upon exposure to each solvent.

(EN) The formation of brain oedema, which accompanies ischemic or traumatic brain injuries, originates from a disruption of ionic/neurotransmitter homeostasis that leads to extracellular K+ elevation and neurotransmitter accumulation in the extracellular space. An increased uptake of these osmotically active substances, predominantly provided by astrocytes, is accompanied by intracellular water accumulation via aquaporin-4 (AQP4). Since it has been shown that the removal of perivascular AQP4 via the deletion of α- syntrophin, which is the protein responsible for anchoring AQP4 on the astrocytic membrane (Neely et al. 2001), delays oedema formation and K+ clearance (Amiry-Moghaddam et al. 2003), we aimed to elucidate how the alpha-syntrophin deletion affects astrocyte volume changes in the cortex during pathological states, such as hypoosmotic stress or oxygen- glucose deprivation (OGD), using three-dimensional (3D) confocal morphometry in situ. In order to visualize individual astrocytes that lack alpha-syntrophin, double transgenic mice (GFAP/EGFP/α-Syn-/- ) were generated by crossbreeding GFAP-EGFP mice with α- syntrophin knockout mice. 3D-confocal morphometry revealed that alpha-syntrophin deletion did not alter astrocyte swelling during hypoosmotic stress or their recovery in isotonic solution;...