Die Magnetresonanzelastographie (MRE) stellt ein nichtinvasives Verfahren dar, welches die Bestimmung der in vivo Scherelastizität weicher Gewebe ermöglicht. Im Rahmen diese Arbeit wurden Methoden zur Bestimmung isotroper und anisotroper Scherelastizitäten anhand von MRE Wellenbildern entwickelt und evaluiert. Alle in dieser Arbeit vorgestellten Methoden basieren auf planarer MRE, d.h. auf der Aufnahme einer einzelnen Auslenkungskomponente innerhalb der Bildschicht. Dadurch wird die MRE erheblich beschleunigt. Allerdings stellen sich dadurch auch besondere Anforderungen an die Datenauswertung zur Bestimmung aussagekräftiger elastischer Kenngrößen. Anhand von planaren MRE-Experimenten an Gewebephantomen und menschlicher Skelettmuskulatur sowie mittels numerischer Simulation wird gezeigt, dass bei Beachtung weniger experimenteller Randbedingungen und einer darauf abgestimmten Datenauswertung, korrekte Elastizitäten ermittelt werden können. Ein besonderer Schwerpunkt der Arbeit liegt in der Analyse experimenteller Einflüsse wie Bildrauschen und -auflösung auf die ermittelten elastischen Kenngrößen. Des Weiteren werden Methoden zur Bestimmung anisotroper Elastizitäten sowie zur Analyse von Streueffekten im MRE-Wellenbild vorgestellt. Die behandelten Einflüsse auf die Amplituden und Wellenlängen im MRE-Bild, werden vergleichend diskutiert und zusammengefasst, um ein einfaches Verfahrensprotokoll zur Analyse experimenteller in vivo MRE-Daten zu entwickeln. Alle in dieser Arbeit verwendeten Methoden und Programme sind im Anhang zusammengefasst und auf Anforderung erhältlich. / Magnetic resonance elastography (MRE) is a noninvasive method that allows the determination of in vivo shear elasticity of soft tissues. In this thesis methods for the determination of isotropic and anisotropic shear elasticities from MRE wave data were developed and evaluated. All methods presented in this work are based on planar MRE, i.e. they are based on the measurement of a single displacement component in the image plane. This way measurement time in MRE is greatly reduced. However, this imposes specific requirements on data evaluation in order to determine significant elastic constants. On the basis of planar MRE experiments on tissue mimicking gels, human skeletal muscle and numerical simulations it is demonstrated that correct shear elasticities can be determined, taking into account a small set of experimental boundary conditions as well as the employment of complementary data evaluation strategies. This thesis is particularly focussed on the analysis of noise and image resolution on the determined elastic constants. Moreover, methods for determining anisotropic elasticity and analyzing shear wave scattering effects on MRE wave data are introduced. The investigated influences on wave amplitudes and wave lengths are compared and discussed to develop a simple measurement protocol for the evaluation of in vivo MRE data. All methods employed in this work are summarized in the appendix along with the corresponding computer code, which is available on demand.

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En nous concentrant sur les valeurs du module de cisaillement l’équilibre Geq pour le modèle bien connu des polymères vitrifiables (echantillionné par le biais de la MD), nous avons adressé la question générale de en quoi les propriétées méchaniques des couches mince diffères de la phase volumique. Il a été démontrè que dans les deux cas Geq de manière non ambigus sèpare l’état fluide (Geq = 0) de l’état vitreux (Geq > 0). Nous avons aussi insisté sur le fait que Geq pour la couche mince dépend de lépaisseur du film h mais aussi de de la pression tangentielle qui est un résultante de la procédure de préparation de la couche mince / Focusing on the equilibrium shear modulus Geq of well-known glass-forming polymer model system (sampled by means of MD), we have addressed the general question of how the mechanical properties of the thin polymer films differs from the bulk. Using ”stress fluctuation” formalism we obtained Geq(T) for the bulk and films. It has been demonstrated that in both cases Geq unambiguously separates the fluid state (Geq = 0) from the glass (Geq > 0). We also stressed that Geq for the film does not only depend on film thickness h, but also on tangential pressure that is a consequence of the film preparation procedure.

Orientador: David Mendez Soares / Tese (doutorado) - Universidade Estadual de Campinas, Instituto de Física Gleb Wataghin / Made available in DSpace on 2018-08-17T17:51:55Z (GMT). No. of bitstreams: 1 Gomide_AndrezaBarbosa_D.pdf: 5782130 bytes, checksum: 73ea74eba4132f68eced1394071826de (MD5) Previous issue date: 2011 / Resumo: Frente à complexidade estrutural e funcional das membranas biológicas, a construção de membranas modelo sobre suporte sólido surge como uma resposta para o estudo daquelas. Para acessar as propriedades estruturais e funcionais de uma membrana biológica é fundamental que a membrana modelo seja capaz de refletir a interface membrana/ambiente aquoso. Portanto, foi feito um estudo da água frente à superfície sólida e verificou-se que a água frente a superfícies pode apresentar estrutura e propriedades físicas como densidade, viscosidade, constante dielétrica, etc. diferentes da águas da massa líquida (bulk water). Também investigamos a formação de filmes de fosfolipídios sobre o eletrodo de ouro a partir de soluções de lipossomos. A microbalança de cristal de quartzo (QCM) mostrou os processos de adsorção de lipossomos à superfície do eletrodo de ouro, de ruptura e formação de filmes. Usando a técnica de filmes de Langmuir, determinamos a densidade de fosfolipídios em uma membrana modelo e comparamos com os resultados gravimétricos obtidos com a QCM. Com a técnica de miscroscopia de força atômica (AFM) usando medidas de força vs. distância, detectamos a espessura do filme de DMPC (6 nm). Além disso, mostramos que na presença de uma solução 0,5 M de H2SO4 o filme formado apresenta uma rugosidade na superfície que muda conforme o potencial aplicado ao eletrodo / Abstract: Faced with structural and functional complexity of biological membranes, the construction of model membranes on solid support appears as a response to the study of those. To access the structural and functional properties of a biological membrane, it is crucial that the membrane model is able to reflect the interface membrane/aqueous environment. Therefore, a study was made of water contacting a solid surface. It was found that water close to surfaces can have structure and physical properties (as density, viscosity, dielectric constant, etc..) different from bulk water. We also investigated the formation of phospholipid films on the gold electrode from solutions of liposomes. The quartz crystal microbalance (QCM) showed the adsorption of liposomes to the surface of gold electrode, breakdown and formation of a film. Using the technique of Langmuir we determined the density of phospholipids in a membrane model and compared with the gravimetric results obtained with the QCM. With the atomic force microscope (AFM) using the force vs. distance measurement we detected a 6 nm thick DMPC film on the electrode. Furthermore, we showed that in the presence of a 0.5 M solution of H2SO4 the film formed on the surface has a roughness that changes with the applied potential to the electrode / Doutorado / Físico-Química / Doutora em Ciências

La diffusion multiple de la lumière(DWS) est une technique qui permet de sonder la dynamique interne de milieux opaques et concentrés à des fréquences élevées. Elle a été utilisée pour déterminer les propriétés viscoélastiques de ces milieux. Elle a l'avantage d'être non destructive, rapide et sensible. Ce travail a pour objectif l'étude des tissus biologiques mous par DWS. La première étape est la mise en place du dispositif expérimental. Afin d'évaluer les limites de la technique, des études successives ont été réalisées sur des matériaux de complexité croissante (une suspension, le lait et une mousse) tendant vers la complexité structurale des tissus biologiques. Pour la suspension et le lait, la théorie de DWS peut s'appliquer et permet de mesurer avec une bonne précision leur viscosité. Les limites de DWS pour évaluer la viscosité sont atteintes avec la mousse dont la structure complexe est proche de celle des tissus biologiques. Enfin, le cortex rénal, le parenchyme hépatique et le cerveau de porc ont été étudiés. La théorie appliquée pour les milieux précédents ne permet pas de remonter à leur viscosité. Mais la DWS a permis de suivre leur microstructure au cours de la déshydratation et de la dégénérescence. Pour tous ces milieux la répétabilité, la reproductibilité, la variabilité et l'effet des conditions expérimentales ont été évalués. La DWS pourrait être utilisée pour étudier l'effet de la température et de la congélation sur le spectre de DWS des tissus biologiques ou combinée à la rhéologie pour suivre l'évolution des spectres de DWS au cours d'un cisaillement / Diffusing Wave Spectroscopy (DWS) is a technique that allows to probe the internal dynamics of opaque media and concentrated at high frequencies. It has been used to determine the viscoelastic properties of these media. It has the advantage of being nondestructive, rapid and sensitive. This work aims to study soft biological materials by DWS. The first step is setting up of the experimental device. To evaluate the limits of the art, successive studies were conducted on materials of increasing complexity (a suspension, milk and a foam) tending to the structural complexity of biological tissues. Concerning the suspension and milk, two concentrated media, and mono-dispersed in which the particles are in Brownian motion, DWS allowed to measure with good precision their viscosity. The limits of DWS to evaluate the viscosity of the medium are achieved with the foam which the complex structure is similar to that of soft biological tissues. Finally, the renal cortex, the hepatic parenchyma and porcine brain were studied. The theory applied to previous media does not allow to calculate viscosity. But the DWS allowed us to follow their microstructure during dehydration and degeneration. For all these media, repeatability, reproducibility, variability and effect of experimental conditions were evaluated. The DWS could be used to study the effect of temperature and freezing on the DWS spectrum of biological tissues, or combined with rheology to monitor the evolution spectra DWS during shear

The subject of this diploma thesis is a study of the influence of cellulose ethers on the rheological properties of lime. The theoretical part focuses on rheological parameters, techniques and test equipment used in rheology measurements. Various types of cellulose ethers and their influence on the rheological properties of fresh mortars are described. The practical part deals with the study of the influence of different types and quantities of cellulose ethers on the properties of fresh lime pastes and mortars. The results were obtained from measurements on a rotational rheometer with a special geometry for building materials. Measuring methods used were flow and oscillatory tests. Yield stress, viscosity and flow index were determined by the flow measurement. The stability and stiffness of fresh materials were determined during the oscillation measurements. The measured results are then evaluated and compared.

The Diploma thesis is focus on polymer modified bitumen for warm mix asphalt. The theoretical part of the thesis describes additives which influence the properties of bitumen for their use and reduction of production and service temperatures. Further, the theoretical part describes the conclusions from the researches. This part also describes empirical and functional tests of bituminous binders. The practical part presents the results of individual tests. Tests were performed on samples of non-aged, aged by RTFOT and RTFOT + PAV methods. The results of the work and the assessment of the suitability of bituminous binders are summarized at the end of the thesis.

The diploma thesis is focused on polymer modified binders with different polymer doses. The theoretical part describes the history of the use of bitumen, the extraction of bitumen from oil and behavious of the polymer type SBS/SB, which is used in the diploma thesis on modified binders. Further, the theoretical part describes the empirical and functional tests of bitumen binders. In the practical part the results of indidual tests are presented and compared with the standard ČSN 65 7222-1. At the end of the diploma thesis are summarized results of work and evaluation of binders with the best achieved properties.

The comparison of rheological properties (complex shear modulus and phase angle and dynamic viscosity) of four paving bitumens and two polymer modified bitumens is performed in this diploma thesis. Furthermore, the empirical tests (needle penetration and softening point) were determined on these binders. Effect of asphalt binders aging was modeled using RTFOT test and modified RTFOT test (3 x RTFOT).

Diploma thesis is particularly focused on ageing of asphalt mixtures and asphalt binders. In the theoretical part an array of methods simulating short term and long term ageing consequently is introduced. The main objective of the practical part was to carry out the long-term ageing test method BSA (Braunschweiger Alterung). Thereafter, specimens testing for stiffness properties according to CSN EN 12697-26 were made. After conducting the measurement on those, asphalt binder was extracted and processed to follow-up testing. The testing consisted of a range of methods – Penetration CSN EN 1426, Ring and Ball test CSN EN 1427, Determination of the Frass breaking point CSN EN 12593, Determination of complex shear modulus CSN EN 14770 and Dynamic viscosity using a dynamic shear rheometer (DSR). The given results were assessed in the last part in order to evaluate the rate of the binder degradation caused by the method BSA.