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1
Lefèvre, Xavier. « Grafting of ‘push-pull’ systems on germanium : towards the electric passivation ». Palaiseau, Ecole polytechnique, 2012. https://theses.hal.science/tel-00782709.
Texte intégralRésumé :
Les excellentes propriétés électroniques du germanium limitées par la faible qualité isolante de son oxyde rendent le développement de nouveaux matériaux diélectriques nécessaires. En outre, la sensibilité du germanium requiert la création d'une couche passivante de surface pour le protéger. Bien que de nombreuses études soient réalisées pour le développement de nouveaux diélectriques inorganiques, ce projet de recherche en rupture concerne la conception, la réalisation et le développement de film mince diélectrique organique passivant sur le germanium pour des applications en nanoélectronique. Le travail réalisé porte principalement sur la synthèse de nouvelles molécules " push-pull " (systèmes conjugués linéaires portant de part et d'autres un groupe donneur et un groupe accepteur) et sur la fonctionnalisation du germanium. Plusieurs nouveaux systèmes donneur-accepteur ainsi que des systèmes conjugués linéaires contenant une fonction d'ancrage ont été synthétisés selon de nouvelles voies. En particulier, une série de dérivés azobenzène contenant différents accepteurs (groupes fluorés, pyridinium, nitro) et donneurs (amines, alcoxyl) ainsi que des fonctions d'ancrage variées (thiol, acide carboxylique, sel de diazonium, triazene) a été obtenue. En parallèle, la préparation et la fonctionnalisation de surfaces de germanium ont été étudiées. Un nouveau procédé permettant d'enlever l'oxyde natif de la surface et d'obtenir des surfaces halogénées de faible rugosité a été développé. Les substrats de germanium ont été fonctionnalisés par des thiols mais également par des sels de diazonium. Ce nouveau processus de greffage spontané a permis d'abaisser considérablement le temps de réaction (15 minutes de greffage spontané des sels de diazonium contre 3 jours pour la formation de monocouches auto-assemblées de thiols) tout en travaillant dans des conditions douces. Les films minces ainsi obtenus présentent une stabilité comparable à celles des monocouches de thiols. Des systèmes conjugués linéaires ont été greffés à la fois sous forme de thiol et sous forme de sels de diazonium afin de déterminer l'influence du noyau aromatique sur la formation du film et sur ses propriétés. Enfin, les systèmes " push-pull " ont également été greffés. Des premières études électroniques sur or avec les systèmes conjugués linéaires ont été réalisées. Ces études ont été étendues au germanium et laissent envisager des résultats significatifs avec les molécules " push-pull "Despite its excellent electronic properties, germanium is limited by the low passivation of its oxide. Therefore, new dielectrics must be developed. Furthermore, germanium sensitivity requires the creation of a passivation layer on the surface. Even if numerous studies were carried out on new inorganic dielectrics, this research project concerns the design, the realization and the development of thin passivating organic dielectric films on germanium for nanoelectronics applications. This work principally involves the synthesis of new push-pull molecules (π-conjugated systems bearing a donor and an acceptor part) and germanium functionalization. New donor-acceptor systems and π-conjugated linear systems containing an anchoring group were synthesized through new ways. In particular, a series of azobenzene derivatives with different acceptors (fluorinated groups, pyridinium, nitro) and donors (amines, alkoxyl) and various anchoring groups (thiol, carboxylic acid, diazonium salt, triazene) was obtained. Meanwhile, preparation and functionalization of germanium surfaces was studied. A new process to etch the native oxide and obtain halogenated surfaces with low roughness was developed. Germanium substrates were then functionalized with thiol but also with diazonium salts. This new spontaneous grafting process considerably decreased the reaction time (15 minutes spontaneous grafting of diazonium salts against 3 days for self-assembled monolayers of thiol formation) in mild conditions. Thin films obtained present stability similar to the one of thiol monolayers. Π-conjugated linear systems were grafted both as thiol and diazonium salt to probe the influence of the aromatic core on the film formation and properties. Finally, push-pull systems were also grafted. Electronic studies on gold with π-conjugated systems were realized. These studies were extended to germanium and allow expecting significant results with push-pull molecules
2
Bergman, Robert Loring. « Matrix Metalloproteinases 2 and 9 in Normal Canine Cerebrospinal Fluid ». Thesis, Virginia Tech, 2001. http://hdl.handle.net/10919/33750.
Texte intégralRésumé :
Cerebrospinal fluid (CSF) analysis is a standard part of a diagnostic evaluation. Commonly evaluated components include the cell count, protein concentration, glucose, and cytology. CSF analysis can be diagnostic in some diseases such as fungal infections and CNS lymphoma. Often, CSF analysis is not specific, but more information can be obtained. Matrix Metalloproteinases (MMPs) are enzymes that have been found in human CSF. They are calcium and zinc dependent endoproteinases with overlapping substrates. They hydrolyze at least one component of tissue extracellular matrix (ECM), such as collagen or elastin. They are important in normal physiologic processes such as angiogenesis, reproduction and wound healing. One class of MMPs, the gelatinases, degrade gelatins and type IV collagen include MMP 2 and MMP 9. MMPs are important in many pathological processes that involve unregulated matrix destruction such as arthritis, neoplasia and CNS diseases. MMP2 is known to be constituitively produced in CSF while MMP 9 is present only in certain pathologic conditions such as multiple sclerosis, neoplasia and inflammatory diseases. We hypothesize that MMP2 is present in normal canine CSF while MMP 9 is absent.
Cerebrospinal fluid samples were taken from 23 normal dogs that were being used for other research purposes. Each CSF sample was evaluated immediately for red blood cells (RBCs), white blood cells (WBCs), protein, and glucose, and then stored at -70°C. Cytological examination was also performed. CSF samples were considered normal if the protein was less than 25 mg/dl, WBCs were less than 6 µl, and RBCs were less than 25 µl. Each dog was euthanized and the brains processed for routine histopathology. MMP analysis was done using gelatin zymography and an enzyme linked immunosorbent assay (ELISA). Bands of enzyme activity were visible following staining due to enzyme degradation of the gelatin. A commercially available polyclonal sandwich ELISA was used to identify the pro form of MMP2.
The mean WBC count for the CSF samples was 0.96 WBC/ml with a range of 0-3 WBC/ml. The mean protein was 12 mg/dl, with a range of 8-17 mg/dl. The mean RBC count was 3.65 RBC/ml with a range of 0-21 RBC/ml. All normal samples of CSF contained a band of clearing that corresponded to the human commercial standard of proMMP2. No other major bands of clearing were noted on normal samples. The commercial human standards also contained ProMMP2. Other bands were present, but were faint and variable. Using a polyclonal antibody based sandwich ELISA, with samples run in triplicate, the mean pro MMP 2 levels were determined to be 5.61 ng/ml with a range of 3.36 - 10.83 ng/ml.
We conclude that normal CSF values are narrower than what has been previously reported for protein concentration and WBC count. Also, the pro form of MMP 2 is present in normal canine CSF based on results of gelatin zymography and ELISA.Master of Science
3
Al-Mugheiry, Mohammed Adil Said. « MRI studies of fluids permeating porous media ». Thesis, University of Nottingham, 1996. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.321376.
Texte intégral
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Valkov, Boris Ivanov. « A blurred interface formulation of The Reference Map Technique for Fluid-Solid Interactions and Fluid-Solid-Solid Interactions ». Thesis, Massachusetts Institute of Technology, 2014. http://hdl.handle.net/1721.1/92123.
Texte intégralRésumé :
Thesis: S.M., Massachusetts Institute of Technology, Department of Mechanical Engineering, 2014.Cataloged from PDF version of thesis.
Includes bibliographical references (pages 143-144).
In this work we present a blurred interface method for Fluid-Solid Interactions (FSI) and multiple solids immersed in a fluid or FSSI (Fluid-Solid-Solid Interactions) based on the reference map technique as presented by Kamrin and Rycroft. I will follow the chain of thought which lead from the initial sharp interface technique to the newer blurred interface one. We will present its capabilities of doing fully-coupled simulations of a compressible Navier-Stokes fluid and highly non-linear solid undergoing large deformations all performed on a single Eulerian grid with no Lagrangian particles whatsoever. The Reference Map Technique (RMT) provides an Eulerian simulation framework allowing to compute fully coupled fluid/soft-solid interactions. However, due to the extrapolations inherent to the Ghost Fluid Method (GFM) for fluid/fluid interactions, on which the RMT is based, numerical artifacts get created in the resulting pressure and velocity fields whenever the levelset defining the interface crosses a gridpoint from the fixed cartesian grid utilized in this method. We will therefore follow the creation and propagation of these artifacts as well as analyze how the blurred technique solves or avoids these problems.
by Boris Ivanov Valkov.
S.M.
5
Aydar, Gokhan. « A new magneto-rheological fluid (MRF) washing machine damper and a novel two-way-controllable MRF valve ». abstract and full text PDF (free order & ; download UNR users only), 2006. http://0-gateway.proquest.com.innopac.library.unr.edu/openurl?url_ver=Z39.88-2004&rft_val_fmt=info:ofi/fmt:kev:mtx:dissertation&res_dat=xri:pqdiss&rft_dat=xri:pqdiss:1441431.
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Davies, Colin John Stephen. « MRI studies of complex fluids and microchannel flows ». Thesis, University of Cambridge, 2009. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.598355.
Texte intégralRésumé :
This thesis considers the use of NMR (Nuclear Magnetic Resonance) in investigating both the formulation, using microchannels, and characterisation of complex fluids using NMR techniques. Multiphase microchannel flows have many applications and understanding the hydrodynamics and mass transfer is essential for developing such systems. Time-averaged velocity images of the parallel flow of PDMS (polydimethylsiloxane) and water in a 500 μm x 250 μm microchannel were compared with an analytical solution and simulations. This was extended into imaging multiphase flows in a smaller (250 μm x 100 μm) microchannel. Poor signal-to-noise levels in this geometry led to the adoption of a spatially- and chemical-shift-resolved propagator acquisition. This was used to differentiate two different flow regimes: parallel flow and droplet production. RheoNMR is the use of NMR techniques in the study of rheology. Time-averaged velocity imaging was used to image a shear-banding micellar solution, cetylpyridinum chloride with sodium salicylate (CPyC1 / NaSal) in sodium chloride brine, in a variety of standard rheological geometries. The fast velocity measurement sequence GERVAIS was used to measure starting and stopping of flows of the CPyC1 / NaSal solution in a wide-gap Couette cell; these were compared to similar experiments performed using PDMS. The propagation of an elastic wave across the cell was seen during start-up and an unusual rebounding oscillation was evident in the stopped flow experiments in the CPyC1 sample. The fast diffusion measurement sequence, Difftrain, was modified to reduce the achievable incremental observation time (at the expense of slightly reduced chemical resolution). This was applied to two case studies: measuring the surface-to-volume ratio of a model porous medium and the droplet sizing of oil-in-water emulsions manufactured with fast-diffusing oils. Finally, NMR relaxometry and diffusometry were used to investigate a phase transition in the structure of a sample of a commercial face cream.
7
Balasubramanian, Ganapathi Raman. « Low-order coupled map lattices for estimation of wake patterns behind vibrating flexible cables ». Link to electronic thesis, 2003. http://www.wpi.edu/Pubs/ETD/Available/etd-0908103-105504.
Texte intégralRésumé :
Thesis (Ph. D.)--Worcester Polytechnic Institute.Keywords: fluid-structure interaction; low dimensional models; coupled map lattices; vortex shedding; cylinder wake patterns; flow control; multi-variable least squares algorithm; neural networks; adaptive estimation. Includes bibliographical references (p. 147-149).
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Johnson, Kevin Robert. « In Vivo Coronary Wall Shear Stress Determination Using CT, MRI, and Computational Fluid Dynamics ». Diss., Georgia Institute of Technology, 2007. http://hdl.handle.net/1853/14482.
Texte intégralRésumé :
Wall shear stress (WSS) has long been identified as a factor in the development of atherosclerotic lesions. Autopsy studies have revealed a strong tendency for lesion development at arterial branch sites and along the inner walls of curvature areas that, in theory, should experience low WSS. Calculations of coronary artery WSS have typically been based upon average models of coronary artery geometry with average flow conditions and then compared to average lesion distributions. With all the averaging involved, a more detailed knowledge of the correlation between WSS and atherosclerotic lesion development might be obscured. Recent advancements in hemodynamic modeling now enable the calculation of WSS in individual subjects. An image-based approach for patient-specific calculation of in vivo WSS using computational fluid dynamics (CFD) would allow a more direct study of this correlation. New state-of-the-art technologies in multi-detector computed tomography (CT) and 3.0 Tesla magnetic resonance imaging (MRI) offer potential improvements for the measurement of coronary artery geometry and blood flow.
The overall objective of this research was to evaluate the quantitative accuracy of multi-detector CT and 3.0 Tesla MRI and incorporate those imaging modalities into a patient-specific CFD model of coronary artery WSS. Using a series of vessel motion phantoms, it has been shown that 64-detector CT can provide accurate measurements of coronary artery geometry for heart rates below 70 beats per minute. A flow phantom was used to validate the use of navigator-echo gated, phase contrast MRI at 3.0 Tesla to measure velocity of coronary blood flow. Patient-specific, time-resolved CFD models of coronary WSS were created for two subjects. Furthermore, it was determined that population-average velocity curves or steady state velocities can predict locations of high or low WSS with high degrees of accuracy compared to the use of patient-specific blood flow velocity measurements as CFD boundary conditions. This work is significant because it constitutes the first technique to non-invasively calculate in vivo coronary artery WSS using image-based, patient-specific modeling.
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Alrwaili, Amgad, et Martin Bencsik. « Quantification of MRI sensitivity for mono-disperse microbubbles to measure subatmospheric fluid pressure changes ». Diffusion fundamentals 18 (2013) 4, S. 1-5, 2013. https://ul.qucosa.de/id/qucosa%3A13710.
Texte intégralRésumé :
It would be very beneficial to perform MRI of fluids and sense the fluid pressure changes. Our aim is to demonstrate a contrast agent capable of MR sensitivity to sub-atmospheric pressure changes. To achieve this, monodisperse microbubbles were prepared with an optically measured mean radius of 1.4 ± 0.8 μm. A repeated pressure change cycle was applied on the microbubble contrast agent, until it produced an MR signal change solely due to the bubble radius change. The bubbles’ contribution to the relaxation rate before and after applying sub-atmospheric pressure changes was estimated and its echo time dependence modelled, so as to inform the mean radius change. The periodic subatmospheric pressure change was further applied until the MR signal change was only due to the bubble radius change. An excellent MR sensitivity of 28 % bar-1 is demonstrated, bubble radii of 2.4 and 1.8 μm are numerically estimated before and after the application of pressure, and the simulations are further used to estimate the optimum bubble radius maximising the MR sensitivity to a small change in radius.
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Alrwaili, Amgad, et Martin Bencsik. « Quantification of MRI sensitivity for mono-disperse microbubbles to measure subatmospheric fluid pressure changes ». Universitätsbibliothek Leipzig, 2015. http://nbn-resolving.de/urn:nbn:de:bsz:15-qucosa-184234.
Texte intégralRésumé :
It would be very beneficial to perform MRI of fluids and sense the fluid pressure changes. Our aim is to demonstrate a contrast agent capable of MR sensitivity to sub-atmospheric pressure changes. To achieve this, monodisperse microbubbles were prepared with an optically measured mean radius of 1.4 ± 0.8 μm. A repeated pressure change cycle was applied on the microbubble contrast agent, until it produced an MR signal change solely due to the bubble radius change. The bubbles’ contribution to the relaxation rate before and after applying sub-atmospheric pressure changes was estimated and its echo time dependence modelled, so as to inform the mean radius change. The periodic subatmospheric pressure change was further applied until the MR signal change was only due to the bubble radius change. An excellent MR sensitivity of 28 % bar-1 is demonstrated, bubble radii of 2.4 and 1.8 μm are numerically estimated before and after the application of pressure, and the simulations are further used to estimate the optimum bubble radius maximising the MR sensitivity to a small change in radius.
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Saber, Nikoo Rezazadeh. « CFD modelling of blood flow in the human left ventricle based on magnetic resonance imaging data ». Thesis, Imperial College London, 2001. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.390806.
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Benitez, Mendieta Jessica. « Patient-specific computational biomechanical analysis of carotid atherosclerotic plaques based on MRI ». Thesis, Queensland University of Technology, 2021. https://eprints.qut.edu.au/213840/1/Jessica_Benitez%20Mendieta_Thesis.pdf.
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This thesis focuses on the biomechanical analysis of carotid atherosclerosis based on medical imaging. The rupture of carotid atherosclerotic plaques is the leading cause of acute cardiovascular events, such as stroke. For this analysis, patient-specific and image-based carotid models were developed for computational analysis to assess factors associated with plaque development and rupture. This study provided further knowledge in areas such as fluid dynamics of carotid arteries with stenosis, the role of the carotid plaque components, and a new technique for structural analysis of carotid plaques. These approaches will help clinicians in the diagnosis and treatment of carotid atherosclerosis.
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Morris, Robert H. « Advanced design and experimental validation of MRI contrast agents for fluid pressure mapping using microbubbles ». Thesis, Nottingham Trent University, 2009. http://irep.ntu.ac.uk/id/eprint/330/.
Texte intégralRésumé :
This work is related to monitoring fluid pressure using Magnetic Resonance Imaging or MRI and includes numerical simulations and experimental MRI. The nature of this study is such that techniques other than MRI have been extensively used to assess the contrast agent for its physical behaviour. These techniques include rheometry, light scattering, optical and scanning electron microscopy. Six MRI experiments in total were performed: The first two experiments use standard spin echo imaging techniques to test various lipid preparations which are then used as a contrast agent to pressure in a porous medium. The remaining experiments are performed using a fast imaging technique and investigate various improvements to the contrast agent which resulted in the development of an agent exhibiting an unprecedented level of sensitivity. A variety of lipid preparations are utilised throughout the experiments. Initial testing reveals that the DSPC lipid offers the greatest stability, although a fluorinated lipid is used in a later study for an improved synergy between the shell and gas microbubble components. Having assessed the microbubble stability, preparations are prepared as in the work previously published in the area. This preparation is tested in two porous media to investigate the sensitivity of the contrast agent to changes in pressure. A sensitivity of 20% signal change per bar is found in porous media although a drift of 11%h-1 is also observed. An improved preparation was then developed by using an alternative polysaccharide gel, gellan gum. This medium allows a large increase in viscosity without compromising the diffusion coeffcient of water throughout the gel network which is of key importance to the sensitivity of the technique. The suitability of the new preparation is assessed using viscosity, turbidity, diffusion and MRI measurements. The results show that a very stable contrast agent, demonstrating a sensitivity of 38% signal change per bar and negligible drift has been produced. The contrast agent is then developed further to produce a soft solid for potential applications in granular dynamics. By cross linking another polysaccharide gel, carageenan gum, into which the microbubbles have been mixed, a contrast agent has been successfully tested. This agent is again assessed using diffusion and elastic stress measurements which demonstrate its suitability to monitor pressure. Abstract 12 Using a wide range of techniques including time lapse photography, rheology, diffusion NMR and MR imaging, contrast agents have been produced which meet specific applications. Contrast agents in both solid and liquid phases have been produced to allow measurements in porous media and in granular dynamic systems. These contrast agents have been optimised in terms of the lipids used for the microbubbles, the chemistry used for production of the suspending media, the protocols for production, assessment and application of each agent and MRI sequences used to collect images. In doing so a reliable method for tailoring contrast agents to pressure has been developed leading to novel experimental measurements which may be applicable to oil recovery and medicine alike.
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THYAGARAJ, SURAJ. « In Vitro Investigation Of Cerebrospinal Fluid Dynamics In Chiari Malformation By 4D Phase Contrast MRI ». University of Akron / OhioLINK, 2016. http://rave.ohiolink.edu/etdc/view?acc_num=akron1462548992.
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Heidari, Pahlavian Soroush. « Non-Invasive Assessment of Cerebrospinal Fluid and Brain Tissue Biomechanics using MRI and Computational Modeling ». University of Akron / OhioLINK, 2018. http://rave.ohiolink.edu/etdc/view?acc_num=akron1522060187703491.
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Renner, Johan. « Towards Subject Specific Aortic Wall Shear Stress : a combined CFD and MRI approach ». Doctoral thesis, Linköpings universitet, Mekanisk värmeteori och strömningslära, 2011. http://urn.kb.se/resolve?urn=urn:nbn:se:liu:diva-65910.
Texte intégralRésumé :
The cardiovascular system is an important part of the human body since it transports both energy and oxygen to all cells throughout the body. Diseases in this system are often dangerous and cardiovascular diseases are the number one killer in the western world. Common cardiovascular diseases are heart attack and stroke, which origins from obstructed blood flow. It is generally important to understand the causes for these cardiovascular diseases. The main causes for these diseases are atherosclerosis development in the arteries (hardening and abnormal growth). This transform of the arterial wall is believed to be influenced by the mechanical load from the flowing blood on the artery and especially the tangential force the wall shear stress. To retrieve wall shear stress information in arteries invivo is highly interesting due to the coupling to atherosclerosis and indeed a challenge. The goal of this thesis is to develop, describe and evaluate an in-vivo method for subject specific wall shear stress estimations in the human aorta, the largest artery in the human body. The method uses an image based computational fluid dynamics approach in order to estimate the wall shear stress. To retrieve in-vivo geometrical descriptions of the aorta magnetic resonance imaging capabilities is used which creates image material describing the subject specific geometry of the aorta. Magnetic resonance imaging is also used to retrieve subject specific blood velocity information in the aorta. Both aortic geometry and velocity is gained at the same time. Thereafter the image material is interpreted using level-set segmentation in order to get a three-dimensional description of the aorta. Computational fluid dynamics simulations is applied on the subject specific aorta in order to calculate time resolved wall shear stress distribution at the entire aortic wall included in the actual model. This work shows that it is possible to estimate subject specific wall shear stress in the human aorta. The results from a group of healthy volunteers revealed that the arterial geometry is very subject specific and the different wall shear stress distributions have general similarities but the level and local distribution are clearly different. Sensitivity (on wall shear stress) to image modality, the different segmentation methods and different inlet velocity profiles have been tested, which resulted in these general conclusions: The aortic diameter from magnetic resonance imaging became similar to the reference diameter measurement method. The fast semi-automatic level-set segmentation method gave similar geometry and wall shear stress results when compared to a reference segmentation method. Wall shear stress distribution became different when comparing a simplified uniform velocity profile inlet boundary condition with a measured velocity profile. The method proposed in this thesis has the possibility to produce subject specific wall shear stress distribution in the human aorta. The method can be used for further medical research regarding atherosclerosis development and has the possibility for usage in clinical work.
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Gunatilaka, Chamindu C. « Neonatal Airway Analysis Using Magnetic Resonance Imaging and Computational Fluid Dynamics ». University of Cincinnati / OhioLINK, 2021. http://rave.ohiolink.edu/etdc/view?acc_num=ucin1623165127485093.
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Hannas, Angélica Reis. « Determinação da expressão de MMP-2 e MMP-9 na saliva de pacientes portadores de lesões cervicais não cariosas e da influência das MMPs sobre lesões radiculares artificiais através de EDX ». Universidade de São Paulo, 2007. http://www.teses.usp.br/teses/disponiveis/25/25131/tde-30032009-155558/.
Texte intégralRésumé :
As metaloproteinases da matriz (MMPs) foram identificadas na saliva, na placa dental, na dentina e no cemento. Este trabalho teve como objetivos: Estudo I (I) - avaliar a expressão de MMP-2 e MMP-9 presentes na saliva total e parotidiana e no fluido gengival crevicular (FGC) de pacientes portadores e não portadores de lesões cervicais não cariosas (LCNC); Estudo II (II) - investigar se a presença de MMP-8 e -9/TIMPs poderia influenciar a remineralização de lesões artificialmente criadas na superfície radicular, com ou sem desgaste por abrasão. Os métodos utilizados foram: (I) Coleta de amostras de saliva e do FGC de 32 pacientes, com (n=16) e sem LCNC (n=16). A atividade gelatinolítica das MMPs foi avaliada através de análise zimográfica e Western Blot. (II): Espécimes de dentina humana radicular foram obtidos. O grupo controle G1(10) não sofreu nenhum tratamento. Os demais segmentos radiculares foram desmineralizados G2(60). O Grupo A não foi submetido à escovação e o Grupo B foi submetido à abrasão por escovação em uma máquina de escovação simulada. G2(10) foi apenas desmineralizado, G3(10) desmineralizado e remineralizado, e os Grupos G4(10), G5(10), G6(10), G7(10) foram desmineralizados e remineralizados em presença de tampão neutro, TIMP, MMP-8 e -9, MMP-8,-9 e TIMP, respectivamente. Para a análise elemental, as concentrações de Ca+2, P, Mg+2 assim como a relação molar Ca/P e Mg/Ca foram determinadas através de uma sonda eletrônica para microanálise (EPMA). A análise qualitativa por retrodispersão (BSE) foi realizada para demonstrar a distribuição global da densidade mineral. Os resultados (I) mostraram que a principal gelatinase presente, tanto na saliva total quanto no FGC, é a proMMP-9. Na saliva secretada pela glândula parótida, não foram detectadas bandas indicando a presença de gelatinases. Os resultados do estudo (II) indicaram que os espécimes escovados apresentaram maior conteúdo de Ca+2 a 20µm e maior conteúdo de Mg+2 a 30 e 50µm. Em presença de TIMPs, ocorreu uma redução do conteúdo de Ca+2 a 20µm. Para os espécimes não escovados, em todas as profundidades, as amostras incubadas com MMPs apresentaram maiores valores de Ca+2. Portanto, pode-se concluir que (I) a comparação entre pacientes com e sem LCNC mostrou não haver diferença estatisticamente significante quanto à atividade gelatinolítica; (II) quando não inibidas pelos TIMPs, as MMPs degradaram o colágeno completamente desmineralizado na superfície radicular, permitindo melhor recalcificação na superfície subjacente. Esse fenômeno foi também facilitado pela abrasão por escovação.Matrix metalloproteinases (MMPs) have been identified in saliva, plaque, gingival crevicular fluid (GCF), dentin and cementum. Study (I) aimed at evaluating the presence and quantity of gelatinases MMP-2 and MMP-9 in total and parotid saliva and in GCF (GCF) of subjects with and without NCCL. Study (II) aimed at investigating whether the presence of matrix metalloproteinase (MMP)-8 and - 9/TIMPs would influence the remineralization of artificial root lesions with and without mechanical wear. (I) Total stimulated saliva, parotid saliva, and GCF from patients with (n=16) and without NCCL (n=16) were collected and assessed for gelatin zymography and for western immunoblot analysis. (II) Human root segments from Group A (n=35) were not brushed and from Group B (n=35) were subjected to machine-controlled brushing, simulating mechanical wear. Specimens from Group 1 (control, n=10) were left untreated. Group 2 (n=10), was just demineralized; Group 3 (n=10) was demineralized and remineralized. The other samples G4 (n=10), G5 (n=10), G6 (n=10), G7 (n=10) were subjected to remineralization with HEPES buffer, tissue inhibitor of matrix metalloproteinase-2 (TIMP-2), activated MMP-8 and MMP-9 and activated MMP-8, MMP-9 and TIMP-2, respectively. Ca+2, P, Mg+2 concentrations as well as Ca/P and Mg/Ca molar ratios were determined through an Electron Probe Microanalyser (EPMA). (I) Densitometric analysis revealed that the main gelatinase was proMMP-9. No statistically significant difference was observed for MMP-2 and MMP-9 levels, separately. In parotid saliva, gelatinolytic activity was very low or absent. Western immunoblots revealed that, while little immunoreactivity was detected for MMP-2, there was positive immunoreaction for MMP-9, both in total saliva and in GCF. Gelatinases do not seem to originate from parotid gland. (II) The results indicated that the brushed specimens presented higher Ca+2 levels at 20 µm and higher Mg+2 content at 30 and 50 µm. Ca+2 content at 20 µm decreased in the presence of TIMPs. For the non-brushed specimens, in all depths, samples incubated with MMPs showed highest Ca+2 values. It can be concluded that (I) the main gelatinase present in the oral cavity is MMP-9. No significant differences were found in total gelatinolytic activity among NCCL+ and NCCL- patients. (II) When not inhibited by TIMPs, MMPs degraded the completely demineralized collagen in the root surface, allowing for better recalcification in the deeper areas. This phenomenon was also facilitated by the brushing procedure.
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Gao, Hao. « Carotid plaque stress analysis by fluid structure interaction based on in-vivo MRI : implications to plaque vulnerability assessment ». Thesis, Brunel University, 2010. http://bura.brunel.ac.uk/handle/2438/4731.
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Stroke is one of the leading causes of death in the world, resulting mostly from the sudden rupture of atherosclerotic plaques. From a biomechanical view, plaque rupture can be considered as a mechanical failure caused by extremely high plaque stress. In this PhD project, we are aiming to predict 3D plaque stress based on in-vivo MRI by using fluid structure interaction (FSI) method, and provide information for plaque rupture risk assessment. Fluid structure interaction was implemented with ANSYS 11.0, followed by a parameter study on fibrous cap thickness and lipid core size with realistic carotid plaque geometry. Twenty patients with carotid plaques imaged by in-vivo MRI were provided in the project. A framework of reconstructing 3D plaque geometry from in-vivo multispectral MRI was designed. The followed reproducibility study on plaque geometry reconstruction procedure and its effect on plaque stress analysis filled the gap in the literature on imaging based plaque stress modeling. The results demonstrated that current MRI technology can provide sufficient information for plaque structure characterization; however stress analysis result is highly affected by MRI resolution and quality. The application of FSI stress analysis to 4 patients with different plaque burdens has showed that the whole procedure from plaque geometry reconstruction to FSI stress analysis was applicable. In the study, plaque geometries from three patients with recent transient ischemic attack were reconstructed by repairing ruptured fibrous cap. The well correlated relationship between local stress concentrations and plaque rupture sites indicated that extremely high plaque stress could be a factor responsible for plaque rupture. Based on the 20 reconstructed carotid plaques from two groups (symptomatic and asymptomatic), fully coupled fluid structure interaction was performed. It was found that there is a significant difference between symptomatic and asymptomatic patients in plaque stress levels, indicating plaque stress could be used as one of the factors for plaque vulnerability assessment. A corresponding plaque morphological feature study showed that plaque stress is significantly affected by fibrous cap thickness, lipid core size and fibrous cap surface irregularities (curvedness). A procedure was proposed for predicting plaque stress by using fibrous cap thickness and curvedness, which requires much less computational time, and has the potential for clinical routine application. The effects of residual stress on plaque stress analysis and arterial wall material property characterization by using in-vivo MRI data were also discussed for patient specific modeling. As the further development, histological study of plaque sample has been combined with conventional plaque stress analysis by assigning material properties to each computational element, based on the data from histological analysis. This method could bridge the gap between biochemistry and biomechanical study of atherosclerosis plaques. In conclusion, extreme stress distributions in the plaque region can be predicted by modern numerical methods, and used for plaque rupture risk assessment, which will be helpful in clinical practice. The combination of plaque MR imaging analysis, computational modelling, and clinical study/ validation would advance our understandings of plaque rupture, prediction of future rupture, and establish new procedures for patient diagnose, management, and treatment.
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Sreevalson, Nair Jaya. « Modular processing of two-dimensional significance map for efficient feature extraction ». Thesis, Mississippi State : Mississippi State University, 2002. http://library.msstate.edu/etd/show.asp?etd=etd-07012002-111746.
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Virhammar, Johan. « Idiopathic Normal Pressure Hydrocephalus : Cerebrospinal Fluid Tap Test and Magnetic Resonance Imaging as Preoperative Prognostic Investigations ». Doctoral thesis, Uppsala universitet, Neurologi, 2014. http://urn.kb.se/resolve?urn=urn:nbn:se:uu:diva-222779.
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Idiopathic normal pressure hydrocephalus (iNPH) is a condition with dilated cerebral ventricles but intracranial pressure within normal limits. The symptoms of gait impairment, cognitive decline and urinary incontinence develop gradually. Treatment with shunt insertion results in improvement in eight out of ten patients. The cerebrospinal fluid tap test (CSF TT) and preoperative magnetic resonance imaging (MRI) are methods used to select patients who may benefit from shunt surgery, but they are performed and interpreted differently in different centers throughout the world. The aim of this thesis was to evaluate the performance of the CSF TT and the underlying mechanisms of improvement in gait function after CSF removal, and to investigate the prognostic value of preoperative MRI scans. Improvement in gait and changes in cerebral blood flow (CBF) after a CSF TT were investigated in two prospective studies that included 39 and 20 patients, respectively. Gait assessment and perfusion MRI were done before and several times during the first 24 hours after a CSF TT. Perfusion was investigated with pseudo-continuous arterial spin labeling. At the group level, gait function was significantly improved at all investigation times, but only one-third of individual CSF TT responders were improved at all investigation times. In patients with increased CBF in lateral and frontal white matter after the CSF TT, gait function improved more than it did in patients with decreased CBF in these regions. However, in the whole sample, there was no significant increase in CBF after CSF removal. Preoperative MRI scans were retrospectively evaluated in 109 patients with iNPH who had undergone shunt surgery. The callosal angle was smaller in shunt responders compared with non-responders. The following findings showed the highest association with a positive outcome after shunting: a small callosal angle, wide temporal horns, and occurrence of disproportionally enlarged subarachnoid space hydrocephalus. In conclusion, CBF in white matter close to the lateral ventricles may play a role in the reversibility of symptoms after CSF removal in patients with iNPH. The CSF TT should be reevaluated if the patient does not initially improve, and preoperative MRI investigations can add prognostic information regarding the selection of shunt candidates.
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Huang, Xueying. « In Vivo MRI-based three-dimensional fluid-structure interaction models and mechanical image analysis for human carotid atherosclerotic plaques ». Worcester, Mass. : Worcester Polytechnic Institute, 2009. http://www.wpi.edu/Pubs/ETD/Available/etd-050409-100213/.
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Dissertation (Ph.D.)--Worcester Polytechnic Institute.Keywords: atherosclerotic plaque; fluid-structure Interaction models; MRI-based; rupture; plaque vulnerability assessment. Includes bibliographical references (leaves 116-127).
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Gholami, Mohammad. « Shear Induced Migration of Particles in a Yield Stress Fluid ». Ohio University / OhioLINK, 2017. http://rave.ohiolink.edu/etdc/view?acc_num=ohiou1502793185991791.
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Montague, James. « Assessing The Probability Of Fluid Migration Caused By Hydraulic Fracturing ; And Investigating Flow And Transport In Porous Media Using Mri ». ScholarWorks @ UVM, 2017. http://scholarworks.uvm.edu/graddis/793.
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Hydraulic fracturing is used to extract oil and natural gas from low permeability formations. The potential of fluids migrating from depth through adjacent wellbores and through the production wellbore was investigated using statistical modeling and predic-tive classifiers. The probability of a hydraulic fracturing well becoming hydraulically connected to an adjacent well in the Marcellus shale of New York was determined to be between 0.00% and 3.45% at the time of the study. This means that the chance of an in-duced fracture from hydraulic fracturing intersecting an existing well is highly dependent on the area of increased permeability caused by fracturing. The chance of intersecting an existing well does not mean that fluid will flow upwards; for upward migration to occur, a pathway must exist and a pressure gradient is required to drive flow, with the exception of gas flow caused by buoyancy. Predictive classifiers were employed on a dataset of wells in Alberta Canada to identify well characteristics most associated to fluid migration along the production well. The models, specifically a random forest, were able to identify pathways better than random guessing with 78% of wells in the data set identified cor-rectly.
Magnetic resonance imaging (MRI) was used to visualize and quantify contami-nant transport in a soil column using a full body scanner. T1 quantification was used to determine the concentration of a contaminant surrogate in the form of Magnevist, an MRI contrast agent. Imaging showed a strong impact from density driven convection when the density difference between the two fluids was small (0.3%). MRI also identified a buildup of contrast agent concentration at the interface between a low permeability ground silica and higher permeability AFS 50-70 testing sand when density driven con-vection was eliminated.
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Dyverfeldt, Petter. « Extending MRI to the Quantification of Turbulence Intensity ». Doctoral thesis, Linköpings universitet, Centrum för medicinsk bildvetenskap och visualisering, CMIV, 2010. http://urn.kb.se/resolve?urn=urn:nbn:se:liu:diva-52561.
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In cardiovascular medicine, the assessment of blood flow is fundamental to the understanding and detection of disease. Many pharmaceutical, interventional, and surgical treatments impact the flow. The primary purpose of the cardiovascular system is to drive, control and maintain blood flow to all parts of the body. In the normal cardiovascular system, fluid transport is maintained at high efficiency and the blood flow is essentially laminar. Disturbed and turbulent blood flow, on the other hand, appears to be present in many cardiovascular diseases and may contribute to their initiation and progression. Despite strong indications of an important interrelationship between flow and cardiovascular disease, medical imaging has lacked a non-invasive tool for the in vivo assessment of disturbed and turbulent flow. As a result, the extent and role of turbulence in the blood flow of humans have not yet been fully investigated. Magnetic resonance imaging (MRI) is a versatile tool for the non-invasive assessment of flow and has several important clinical and research applications, but might not yet have reached its full potential. Conventional MRI techniques for the assessment of flow are based on measurements of the mean velocity within an image voxel. The mean velocity corresponds to the first raw moment of the distribution of velocities within a voxel. An MRI framework for the quantification of any moment (mean, standard deviation, skew, etc.) of arbitrary velocity distributions is presented in this thesis. Disturbed and turbulent flows are characterized by velocity fluctuations that are superimposed on the mean velocity. The intensity of these velocity fluctuations can be quantified by their standard deviation, which is a commonly used measure of turbulence intensity. This thesis focuses on the development of a novel MRI method for the quantification of turbulence intensity. This method is mathematically derived and experimentally validated. Limitations and sources of error are investigated and guidelines for adequate application of MRI measurements of turbulence intensity are outlined. Furthermore, the method is adapted to the quantification of turbulence intensity in the pulsatile blood flow of humans and applied to a wide range of cardiovascular diseases. In these applications, elevated turbulence intensity was consistently detected in regions where highly disturbed flow was anticipated, and the effects of potential sources of errors were small. Diseased heart valves are often replaced with prosthetic heart valves, which, in spite of improved benefits and durability, continue to fall short of matching native flow patterns. In an in vitro setting, MRI was used to visualize and quantify turbulence intensity in the flow downstream from four common designs of prosthetic heart valves. Marked differences in the extent and degree of turbulence intensity were detected between the different valves. Mitral valve regurgitation is a common valve lesion associated with progressive left atrial and left ventricular remodelling, which may often require surgical correction to avoid irreversible ventricular dysfunction. The spatiotemporal dynamics of flow disturbances in mitral regurgitation were assessed based on measurements of flow patterns and turbulence intensity in a group of patients with significant regurgitation arising from similar valve lesions. Peak turbulence intensity occurred at the same time in all patients and the total turbulence intensity in the left atrium appeared closely related to the severity of regurgitation. MRI quantification of turbulence intensity has the potential to become a valuable tool in investigating the extent, timing and role of disturbed blood flow in the human cardiovascular system, as well as in the assessment of the effects of different therapeutic options in patients with vascular or valvular disorders.
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Yokoyama, Tomoko. « Association between anti-U1 ribonucleoprotein antibodies and inflammatory mediators in cerebrospinal fluid of patients with neuropsychiatric systemic lupus erythematosus ». Kyoto University, 2014. http://hdl.handle.net/2433/189354.
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Etxegarai, Aldami Etxebarria Maddi. « Etude du couplage hydromécanique dans les roches par analyse d'images obtenues par tomographie neutronique ». Thesis, Université Grenoble Alpes (ComUE), 2019. http://www.theses.fr/2019GREAI010/document.
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Le comportement des roches-réservoirs souterraines est un sujet important pour de nombreuses applications liées à la production d’énergie (extraction d’hydrocarbures, séquestration de CO2, ...). L'une des principales questions posées est celle de l'effet des déformations sur les propriétés de transfert hydraulique de la roche, en particulier en conditions saturées. En effet, la déformation des géomatériaux est rarement homogène en raison de conditions aux limites complexes et de sa tendance intrinsèque à se localiser. Cette non-uniformité spatiale de la déformation produit un champ de perméabilité hétérogène. Cela remet en question la validité (a) des méthodes traditionnelles d'analyse macroscopique et (b) des mesures établies principalement loin des zones de déformation localisée. Ainsi, pour améliorer la caractérisation des géo-matériaux, il est crucial d’avoir des mesures locales de la perméabilité, et de connaître la relation entre la déformation et la perméabilité, qui gouverne leur comportement hydraulique.Cette thèse porte sur l’étude du couplage hydromécanique des roches par tomographie aux neutrons et aux rayons X, ainsi que sur le développement de nouvelles méthodes d'analyse. Même si le recours à l'imagerie par rayons X en géosciences devient de plus en plus accessible, la détection directe des fluides a été très limitée en raison du faible contraste air/eau dans les géomatériaux. Contrairement aux rayons X, les neutrons sont très sensibles à l’hydrogène présent dans l'eau. La radiographie par neutrons permet donc d'obtenir des images où la détection du fluide est bien plus facile. De plus, les neutrons sont sensibles aux isotopes, ce qui veut dire que l’eau lourde et celle normale, qui ont des propriétés physico-chimiques proches, peuvent être distinguées avec une grande précision. Il faut noter que l’imagerie aux neutrons pour les roches est un domaine expérimental qui est essentiellement inexploré, ou limité à des études 2D d'échantillons secs, avec peu ou pas de contrôle sur les conditions aux limites.Dans le cadre de ce travail, nous avons conçu une nouvelle cellule triaxiale, avec un contrôle asservi, pour effectuer des expériences d'écoulement de fluides multiples dans un échantillon de roche saturé et chargé mécaniquement avec acquisition des données neutroniques en 4D. Une autre originalité du projet est l'utilisation d'installations d'imagerie neutroniques à haute performance (CONRAD-2 au Helmholtz Zentrum à Berlin et NeXT à l'Institut Laue-Langevin à Grenoble), profitant de la technologie de pointe et des lignes de faisceaux les plus puissantes du monde. Cela a permis d'acquérir des données à une fréquence optimale pour notre étude.Ce travail présente les résultats de plusieurs campagnes expérimentales couvrant une série de conditions initiales et de conditions aux limites relativement complexes. Pour quantifier le couplage hydromécanique local, nous avons appliqué un certain nombre de procédures de post-traitement standard et nous avons également développé un ensemble de méthodes de mesure, par exemple pour suivre le front d’eau et déterminer les cartes de vitesse 3D. Les résultats montrent que la vitesse du front d’eau entraîné par imbibition dans un échantillon sec est augmentée à l’intérieur d'une bande de cisaillement compactante, tandis que la vitesse d’écoulement entraîné par la pression est réduite dans les échantillons saturés, quelque soit la réponse volumétrique de la bande de cisaillement (compactante / dilatante). La nature des données 3D et des analyses s'est révélée essentielle dans la caractérisation du comportement mécanique complexe des échantillons et de la vitesse d'écoulement qui en résulte.Les résultats expérimentaux obtenus contribuent à la compréhension de l'écoulement dans les matériaux poreux sous chargement, garantissent la pertinence de l'analyse et permettent d’etablir une méthode expérimentale pour d'autres campagnes hydromécaniques in-situThe behaviour of subsurface-reservoir porous rocks is a central topic in resource engineering industry and has relevant applications for hydrocarbon and water production or CO2 sequestration. One of the key open issues is the effect of deformations on the hydraulic properties of the host rock, specifically in saturated environments. Deformation in geomaterials is rarely homogeneous because of the complex boundary conditions they undergo as well as for their intrinsic tendency to localise. This non uniformity of the deformation yields a non uniform permeability field, meaning that the traditional macroscopic analysis methods are outside their domain of validity. These methods are in fact based on measurements taken at the boundaries of a tested sample, under the assumption of internal homogeneity. At this stage, our understanding is in need of direct measurements of the local fluid permeability and its relationship with localiseddeformation.This doctoral dissertation focuses on the acquisition of such local data about the hydro mechanical properties of porous geomaterials in full-field, adopting neutron and x-ray tomography, as well as on the development of novel analysis methods. While x-ray imaging has been increasingly used in geo-sciences in the last few decades, the direct detection of fluid has been very limited because of the low air/water contrast within geomaterials. Unlike x-rays, neutrons are very sensitive to the hydrogen in the water because of their interaction with matter (neutrons interact with the atoms’ nuclei rather than with the external electron shell as x-rays do). This greater sensitivity to hydrogen provides a high contrast compared to the rock matrix, in neutron tomography images that facilitates the detection of hydrogen-rich fluids. Furthermore, neutrons are isotope-sensitive, meaning that water (H 2 0) and heavy water (D20), while chemically and hydraulically almost identical, can be easily distinguished in neutron imaging.The use of neutron imaging to investigate the hydromechanical properties of rocks is a substantially under-explored experimental area, mostly limited to 2D studies of dry, intact or pre-deformed samples, with little control of the boundary conditions. In thiswork we developed a new servocontrolled triaxial cell to perform multi-fluid flow experiments in saturated porous media, while performing in-situ loading and acquiring 4-dimensional neutron data.Another peculiarity of the project is the use of high-performance neutron imaging facilities (CONRAD-2, in Helmholtz Zentrum Berlin, and NeXT-Grenoble, in Institut Laue-Langevin), taking advantage of the world’s highest flux and cutting edge technology to acquire data at an optimal frequency for the study of this processes. The results of multiple experimental campaigns covering a series of initial and boundary conditions of increasing complexity are presented in this work.To quantify the local hydro-mechanical coupling, we applied a number of standard postprocessing procedures (reconstruction, denoising, Digital Volume Correlation) but also developed an array of bespoke methods, for example to track the water front andcalculate the 3D speed maps.The experimental campaigns performed show that the speed of the water front driven by imbibition in a dry sample is increased within a compactant shear band, while the pressure driven flow speed is decreased in saturated samples, regardless of the volumetric response of the shear band (compactant/dilatant). The 3D nature of the data and analyses has revealed essential in the characterization of the complex mechanical behaviour of the samples and the resultant flow speed.The experimental results obtained contribute to the understanding of flow in porous materials, ensure the suitability of the analysis and set an experimental method for further in-situ hydromechanical campaigns
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Thewlis, Jonathan. « Numerical modelling of cerebrospinal fluid flow in the human ventricular system based on 4-dimensional radial basis function interpolation of MRI data ». Thesis, University of Nottingham, 2013. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.606725.
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The function and flow behaviour of cerebrospinal fluid (CSF) within the central nervous system (CNS) has been the source of much discussion within the medical community. Understanding of this area has important implications for the treatment of several pathological conditions. A central area of unresolved debate concerns the driving forces for CSF motion. The relative magnitude and role of pulsation of different regions of the CNS has come under question. Modern magnetic resonance imaging (MRI) methods allow transient measurement of CSF flow velocities. This data may be used in the construction of numerical models of CSF flow. However, the small scale of flow requires high velocity resolution, resulting in reduced spatial and temporal resolution. This places limitations on the accurate formation of boundary conditions. No authors have accurately modelled pulsation of the ventricular walls. There exists therefore a need for a 4-dimensional interpolation technique to produce a continuous temporal and spatial velocity profile of CSF flow. This thesis describes a novel 4-dimensionallocal radial basis function (RBF) software tool for the interpolation of uniformly spaced, small scale MRI data. The .application of the tool is demonstrated firstly on MRI velocity data of CSF flow within the brain. The method is then extended to the interpolation of such data to the inlet boundary cell centres of a numerical model ofCSF flow, constructed from anatomical MRI data. The model is validated through comparison with the MRI results: An algorithm for the removal of rigid body motion effects due to movement of the test subject during scanning is also described. CSF flow variation in the interpolated MRI results indicates a pulsatile flow pattern with expansion and contraction of the lateral ventricles. The results of the numerical simulation show some discrepancy with the MRI data. However, peak flow velocities in the cerebral aqueduct are comparable with the literature. Due to the complex geometrical features of the ventricle system and the limitations of the interpolated MRI data, the numerical simulation has been found to be highly sensitive to the positioning of the inlet boundaries. Rigid body motion effects are found to be negligible for larger scale CSF flow but may affect ventricular wall pulsation. l
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McElroy, Mark Allen. « A Procedure for Generating Finite Element Models (FEM) of Abdominal Aortic Aneurysms with Fluid Boundary Conditions Derived from Magnetic Resonance Imaging (MRI) Velocimetry ». The Ohio State University, 2010. http://rave.ohiolink.edu/etdc/view?acc_num=osu1284670607.
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Hagot, Pascal. « Evaluation de l’interaction fluide-structure dans les Voies Aériennes Supérieures par Imagerie par Résonance Magnétique ». Thesis, Paris 11, 2015. http://www.theses.fr/2015PA112059/document.
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Le Syndrome d’Apnée Obstructive du Sommeil affecte 4 à 6 % de la population en France soit près de 3 millions de personnes. Toutefois, les techniques de diagnostic usuelles ne permettent pas de déterminer de façon précise les sites d’occlusion ni de décrire les interactions fluide-paroi qui jouent un rôle important dans les processus de fermeture des voies aériennes supérieures. Au cours de ce travail, un ensemble d’outil a été mis en œuvre pour explorer les mécanismes sous-jacents conduisant à une apnée obstructive. La détermination géométrique et la caractérisation mécanique des voies aériennes supérieures, d’une part, la mesure des écoulements dans ces dernières, d’autre part, ont été réalisées par imagerie par résonance magnétique de l’hydrogène, pour les tissus, de l’hélium-3 et du fluor-19 pour les gaz. Les données obtenues ont été exploitées tout d’abord dans un modèle numérique statique pour estimer les lois d’état locales et caractériser la compliance des voies aériennes supérieures, puis, dans un modèle monodimensionnel, prenant en compte l’interaction fluide-structure et la limitation de débit au cours de l’inspiration, pour localiser les sites potentiellement responsables d’un éventuel collapsus. Par ailleurs, les écoulements de gaz d’hélium-3 et d’hexafluorure de soufre ont été simulés afin de déterminer le potentiel de ces deux modalités d’imagerie de gaz pour l’étude des obstructions des voies aériennes. La faisabilité d’une imagerie statique et dynamique par résonance magnétique du fluor a été démontrée. Avec une densité du gaz traceur bien plus importante, cette dernière technique présente une plus grande sensibilité à l’obstruction. Cette thèse ouvre ainsi une nouvelle voie de diagnostic et de guide thérapeutique personnalisé pour ce syndromeObstructive Sleep Apnea (OSA) is a common disorder occurring in almost 3 million French people. However, current diagnosis methods are not sufficient to precisely define obstructing sites and doesn't take into account the fluid structure coupling which plays an important role during upper airway closing. During this thesis, we developed a series of tools exploring upper airway closing process. On the one hand, a screening tool of the structure and the mechanical properties of the upper airway, and on the other hand, a screening tool exploring with dynamic images of inert gases flow into the upper airway, were obtained using conventional hydrogen MRI coupled to magnetic resonance elastography (MRE) and helium-3 or fluor-19 gases MRI, respectively. Geometric and biomechanical data obtained using MRI/MRE are injected into a numerical model given the compliance and the state law of upper airway. Contributions of anatomical restriction on airway collapse are also investigated using a multi-compartmental two-dimensional fluid structure interaction model during a breath inspiration to predicted airway mechanical changes and collapse pressures. Furthermore, helium 3 and sulfur hexafluoride flow was modeled at steady state using commercial finite volume software to evaluate potential feasibility to image upper airway collapsibility during OSA. First dynamic MR imaging using sulfur hexafluoride (SF6) was obtained showing the feasibility of this technique. Using SF6, 6 times denser than air, shows a higher sensibility to upper airway obstruction. This thesis opens a new imaging modality to probe and to diagnose upper airway obstruction
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Wåhlin, Anders. « Cerebral blood flow and intracranial pulsatility studied with MRI : measurement, physiological and pathophysiological aspects ». Doctoral thesis, Umeå universitet, Radiofysik, 2012. http://urn.kb.se/resolve?urn=urn:nbn:se:umu:diva-55424.
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During each cardiac cycle pulsatile arterial blood inflates the vascular bed of the brain, forcing cerebrospinal fluid (CSF) and venous blood out of the cranium. Excessive arterial pulsatility may be part of a harmful mechanism causing cognitive decline among elderly. Additionally, restricted venous flow from the brain is suggested as the cause of multiple sclerosis. Addressing hypotheses derived from these observations requires accurate and reliable investigational methods. This work focused on assessing the pulsatile waveform of cerebral arterial, venous and CSF flows. The overall aim of this dissertation was to explore cerebral blood flow and intracranial pulsatility using MRI, with respect to measurement, physiological and pathophysiological aspects. Two-dimensional phase contrast magnetic resonance imaging (2D PCMRI) was used to assess the pulsatile waveforms of cerebral arterial, venous and CSF flow. The repeatability was assessed in healthy young subjects. The 2D PCMRI measurements of cerebral arterial, venous and CSF pulsatility were generally repeatable but the pulsatility decreased systematically during the investigation. A method combining 2D PCMRI measurements with invasive CSF infusion tests to determine the magnitude and distribution of compliance within the craniospinal system was developed and applied in a group of healthy elderly. The intracranial space contained approximately two thirds of the total craniospinal compliance. The magnitude of craniospinal compliance was less than suggested in previous studies. The vascular hypothesis for multiple sclerosis was tested. Venous drainage in the internal jugular veins was compared between healthy controls and multiple sclerosis patients using 2D PCMRI. For both groups, a great variability in the internal jugular flow was observed but no pattern specific to multiple sclerosis could be found. Relationships between regional brain volumes and potential biomarkers of intracranial cardiac-related pulsatile stress were assessed in healthy elderly. The biomarkers were extracted from invasive CSF pressure measurements as well as 2D PCMRI acquisitions. The volumes of temporal cortex, frontal cortex and hippocampus were negatively related to the magnitude of cardiac-related intracranial pulsatility. Finally, a potentially improved workflow to assess the volume of arterial pulsatility using time resolved, four-dimensional phase contrast MRI measurements (4D PCMRI) was evaluated. The measurements showed good agreement with 2D PCMRI acquisitions. In conclusion, this work showed that 2D PCMRI is a feasible tool to study the pulsatile waveforms of cerebral blood and CSF flow. Conventional views regarding the magnitude and distribution of craniospinal compliance was challenged, with important implications regarding the understanding of how intracranial vascular pulsatility is absorbed. A first counterpoint to previous near-uniform observations of obstructions in the internal jugular veins in multiple sclerosis was provided. It was demonstrated that large cardiac- related intracranial pulsatility were related to smaller volumes of brain regions that are important in neurodegenerative diseases among elderly. This represents a strong rationale to further investigate the role of excessive intracranial pulsatility in cognitive impairment and dementia. For that work, 4D PCMRI will facilitate an effective analysis of cerebral blood flow and pulsatility.
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Salameh, Wassim. « Imagerie par Résonance Magnétique pour la vélocimétrie d’un fluide en milieu poreux ». Thesis, Vandoeuvre-les-Nancy, INPL, 2011. http://www.theses.fr/2011INPL034N/document.
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Cette étude présente la mise au point de mesures de porosité et de vitesse d’écoulement faites par IRM dans des colonnes de billes de verre et de polymère de différentes granulométries saturées en eau. L’avantage des billes en polymère est qu’elles ne contiennent pas d’éléments ferro ou paramagnétiques, contrairement aux billes de verre qui perturbent le champ magnétique créant des artéfacts sur les images IRM. La séquence d’IRM utilisée pour l’étude des écoulements en milieu poreux a été préalablement paramétrée à l’aide d’une étude sur un écoulement de Poiseuille. Deux situations ont été examinées : d’une part, l’observation des écoulements interstitiels entre les billes permet de minimiser les effets de volume partiel et de faciliter la correction du phénomène de repliement de phase. D’autre part, la mesure de vitesses moyennes (Darcy) nécessite d’utiliser simultanément les images de vitesse et les images de porosité. Dans ce cas, il est préférable d’ajuster la puissance des gradients d’encodage de vitesse de façon à éviter tout phénomène de repliement de phase. La géométrie du dispositif utilisé a permis une comparaison rigoureuse des mesures de débit de façon intrinsèque uniquement par IRM (débit en milieu poreux et dans l’espace annulaire) et aussi à partir de la mesure directe du débit (pesée)This study presents the development of measurement of porosity and velocity of flow made by MRI in packed beds with glass and polymer beads of various size saturated in water. The advantage of polymer beads is that they do not contain elements ferro or paramagnetics, contrary to the glass beads which disrupt the magnetic field creating artifacts on the MRI images. The calibration of the MRI velocity measurements was achieved from Poiseuille flow in a tube at different flow rates. Two situations were examined: first, the observation of interstitial flows between the beads minimizes partial volume effects and facilitates the correction of the phenomenon of phase aliasing. On the other hand, the measurement of average interstitial velocity (Darcy) requires using simultaneous velocity image and porosity image. In this case, it is preferable to adjust the strength of magnetic field gradient in the velocimetry sequence in a way to avoid any phase aliasing. The geometry of the flow cell was chosen to enable comparison by the MRI method between volume flow rates of water in the porous media and in the outer annulus
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Kurzen, Matthew James. « Discretization Error Estimation and Exact Solution Generation Using the 2D Method of Nearby Problems ». Thesis, Virginia Tech, 2010. http://hdl.handle.net/10919/31239.
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This work examines the Method of Nearby Problems as a way to generate analytical exact solutions to problems governed by partial differential equations (PDEs). The method involves generating a numerical solution to the original problem of interest, curve fitting the solution, and generating source terms by operating the governing PDEs upon the curve fit. Adding these source terms to the right-hand-side of the governing PDEs defines the nearby problem.
In addition to its use for generating exact solutions the MNP can be extended for use as an error estimator. The nearby problem can be solved numerically on the same grid as the original problem. The nearby problem discretization error is calculated as the difference between its numerical solution and exact solution (curve fit). This is an estimate of the discretization error in the original problem of interest.
The accuracy of the curve fits is quite important to this work. A method of curve fitting that takes local least squares fits and combines them together with weighting functions is used. This results in a piecewise fit with continuity at interface boundaries. A one-dimensional Burgersâ equation case shows this to be a better approach then global curve fits.
Six two-dimensional cases are investigated including solutions to the time-varying Burgersâ equation and to the 2D steady Euler equations. The results show that the Method of Nearby Problems can be used to create realistic, analytical exact solutions to problems governed by PDEs. The resulting discretization error estimates are also shown to be reasonable for several cases examined.Master of Science
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Holubář, Oldřich. « Analýza šíření tlakové vlny v aortě ». Master's thesis, Vysoké učení technické v Brně. Fakulta strojního inženýrství, 2011. http://www.nusl.cz/ntk/nusl-229831.
Texte intégralRésumé :
This master thesis is focused on usage of monitoring pulse wave propagation in aortic system in a field of diagnostic abdominal aortic aneurysm (AAA). There is a description of cardio-vascular system and its pathology in a form of AAA. A summarization of temporary diagnostic method was created and some new methods were proposed. This new methods presume monitoring of pulse wave propagation. Fluid structure interaction (FSI) analyses of pulse wave propagation were performed on simplified models of geometry which representing specific sections of aorta. The goal of these analyses was to prove usage of FSI method in a future development of proposed diagnostic methods.
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Tavares, Ludmyla Santos. « Padronização e validação analítica dos métodos DPX-RAM/LC-MS e MIP-PSI-MS para análise de cocaína em fluido oral ». Universidade Federal de Goiás, 2017. http://repositorio.bc.ufg.br/tede/handle/tede/7385.
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Coordenação de Aperfeiçoamento de Pessoal de Nível Superior - CAPES
The analysis of drugs of abuse in non-conventional biological fluids is attracting a lot of interest due to recent legislation changes in Brazil and a greater police surveillance. However, complex matrix samples have a large amount of endogenous, exogenous and other interfering compounds that make direct analysis impossible in analytical systems. In this way, sample preparation has been presented as an important tool for rapid and sensitive analytical methods. The miniaturized sample preparation technique called disposable pipette extraction (DPX) has shown to be promising once it integrates the clean-up and pre-concentration of samples. Restricted access materials (RAM) are a class of materials that allow the exclusion of endogenous compounds and the extraction of analytes in a single step. In this manner, in this work a RAM extraction phase has been developed for DPX applied to the analysis of cocaine in oral fluid via liquid chromatography coupled with mass spectrometry (DPX-RAM/LC-MS). The proposed method was optimized using a 24 factorial design. According to the results obtained, the better efficiency of extraction was obtained in the following conditions: pH 9, 10 extractions cycles (draw/eject), 3 desorption cycles (draw/eject) and acetonitrile as desorption solvent. The DPX-RAM/LC-MS method showed to be linear from 10 to 100 ng.mL-1 and have R2 = 0,999. As an alternative to sample preparation and a previous separation step, it was also evaluated in this work, a direct injection system for the mass spectrometer (MS) employing an ambient ionization source called Paper Spray Ionization (PSI). For this purpose, molecularly imprinted polymers (MIP) for the analysis of cocaine were synthetized directly on the surface of a cellulose membrane and employed as paper in a PSI system. The membrane containing MIP showed to be more selective and had a greater intensity of signal when compared to the chromatographic paper normally used for PSI. MIP-PSI method showed to be linear from 1 to 100 ng.mL-1 and have R2 = 0,998.The methods proposed are precise and accurate with obtained values bellow 15%, recovery above 80% and the limits of detection and quantification are lower than the ones found in the literature. Both techniques were standardized and validated according to ANVISA’s normative.
As análises de drogas de abuso em fluidos biológicos não convencionais têm atraído muito interesse devido às recentes mudanças nas legislações nacionais e maior fiscalização policial. No entanto, amostras com matrizes complexas apresentam grande quantidade de compostos endógenos, exógenos e outros interferentes que inviabilizam a análise direta em sistemas analíticos. Neste sentido, o preparo de amostras tem se apresentado como importante ferramenta para métodos analíticos rápidos e sensíveis. A técnica miniaturizada de preparo de amostras, conhecida como extração em ponteiras descartáveis (DPX) tem se mostrado promissora uma vez que integra o clean-up e a pré-concentração das amostras. Os materiais de acesso restrito (RAM) são uma classe de materiais que permitem a exclusão dos compostos endógenos e a extração dos analitos de interesse em uma única etapa. Assim sendo, neste trabalho foi desenvolvida uma fase extratora RAM para DPX e aplicada à análises de cocaína em fluido oral por cromatografia líquida acoplada ao espectrômetro de massas (DPX-RAM/LC-MS). O método proposto foi otimizado utilizando um planejamento fatorial 24 e segundo os resultados obtidos, a maior eficiência de extração foi obtida nas seguintes condições: pH 9, 10 ciclos de extração (aspirar/dispensar), 3 ciclos de dessorção (aspirar/dispensar) e acetonitrila como solvente de dessorção. O método DPXRAM/LC-MS mostrou-se linear de 10 a 100 ng.mL-1 com R2 = 0,999. Como alternativa ao preparo de amostras e a separação prévia foi também avaliado, neste trabalho, um sistema para injeção direta no espectrômetro de massas (MS) pela técnica de ionização ambiente conhecida como Paper Spray Ionization (PSI). Para tanto, polímeros molecurlamente impressos (MIPs) para análise de cocaína foram sintetizados diretamente na superfície de uma membrana filtrante e empregados como papel em sistema PSI. A membrana contendo o MIP mostrou ser mais seletiva e apresentou maior intensidade no sinal quando comparada com o papel cromatográfico usualmente utilizado para PSI. O método PSI-MS mostrou-se linear de 1 a 100 ng.mL-1 com R2 = 0,998. Os dois métodos apresentaram valores de exatidão e precisão abaixo de 15%, recuperação acima de 80% e os limites de quantificação e detecção abaixo dos encontrados na literatura. Ambas técnicas foram padronizadas e validadas de acordo com as normativas da ANVISA.
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Taylor, Cassandra Jeanne. « Internal Deformation Measurements and Optimization of Synthetic Vocal Fold Models ». BYU ScholarsArchive, 2018. https://scholarsarchive.byu.edu/etd/8819.
Texte intégralRésumé :
Developing lifelike vocal fold models is challenging due to various associatedbiomechanical complexities. Nevertheless, the development and analysis of improved vocal foldmodels is worthwhile since they are valuable tools for gaining insight into human vocal foldvibratory, aerodynamic, and acoustic response characteristics. This thesis seeks to contribute tothe development of computational and physical vocal fold modeling in two ways. First is byintroducing a method of obtaining internal deformation fields within vibrating synthetic vocal foldmodels; second is by presenting an optimization algorithm coupled with a computational vocalfold model to optimize geometry and stiffness of a synthetic vocal fold model to achieve morerealistic vibration patterns.The method for tracking the internal deformation of self-oscillating vocal fold models isbased on MR imaging. Silicone models scaled to four times life-size to lower the flow-inducedvibration frequency were imbedded with fiducial markers in a coronal plane. Candidate markermaterials were tested using static specimens, and two materials, cupric sulfate and glass, werechosen for testing in the vibrating VF models. The vibrating models were imaged using a gatedMRI protocol wherein MRI acquisition was triggered using the subglottal pressure signal. Twodimensionalimage slices at different phases during self-oscillation were captured, and in eachphase the fiducial markers were clearly visible. The process was also demonstrated using a threedimensionalscan at two phases. The benefit of averaging to increase signal-to-noise ratio wasexplored. The results demonstrate the ability to use MRI to acquire quantitative deformation datathat could be used, for example, to validate computational models of flow-induced VF vibrationand quantify deformation fields encountered by cells in bioreactor studies.A low fidelity, two-dimensional, finite element model of VF flow-induced vibration wascoupled with a custom MATLAB-based genetic algorithm optimizer. The objective was to achievea closed quotient within the normal human physiological range. The results showed that changesin geometry and stiffness would lead to a model that exhibited the desired characteristics. Aphysical model based on optimized parameters was then fabricated and the closed quotient wastested. The physical model successfully vibrated with nonzero closed quotient as predicted by thecomputational model.
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Mendes, Rafael. « Comportement rhéologique et modélisation des bruts paraffiniques en écoulement instationnaire ». Thesis, Paris Est, 2015. http://www.theses.fr/2015PEST1062/document.
Texte intégralRésumé :
Le transport des bruts paraffiniques, et tout particulièrement leur remise en écoulement après un arrêt, dans de longues conduites sous-marines soumises à de basses températures, peut être difficile du fait de l'augmentation de leur viscosité. Le comportement rhéologique d´une huile paraffinique modèle, possédant des propriétés macroscopiques d'écoulement analogues à celles des bruts paraffiniques, est d'abord analysé en utilisant la vélocimétrie par imagerie par résonance magnétique associée à des mesures de contrainte de cisaillement au sein d'une géométrie Couette. Nous montrons que lors d'un écoulement forcé à température constante le matériau subit une déstructuration irréversible qui dépend de l'intensité du cisaillement. Ainsi la contrainte apparente critique permettant l'écoulement du matériau dépend de l'histoire thermique et d'écoulement subie par le matériau. Nous étudions ensuite le comportement rhéologique complet de deux bruts réels à partir de différents types de tests rhéométriques (fluages, redémarrage, régime permanent, changement brusque de vitesse) pour différentes histoires d'écoulement, notamment pendant la période de refroidissement. Le comportement détaillé du matériau en régime transitoire ainsi observé peut alors être modélisé. De plus les variations du seuil de contrainte en fonction de l'histoire thermique et de l'écoulement sont aussi décrites, ce qui nous donne le champ de contrainte seuil dans la conduite à l'état initial. Le modèle dans son ensemble est finalement implémenté dans un code de calcul pour simuler le redémarrage de l´écoulement d'un brut paraffinique dans une conduite réelleTransporting waxy crude oils through long pipelines at low temperatures may be challenging, particularly its flow restart after a pipeline shut-in, due to its viscosity increase. The rheological behavior of a model waxy oil with macroscopic flow properties analogous to waxy crude oils is first analyzed using Magnetic Resonance Imaging velocimetry associated to stress measurements in a Couette geometry. While flowing at constant temperature, major irreversible structure break depending on shear intensity are observed. Thus, the critical apparent shear stress beyond which the material flows depends on the thermal and flow histories of the oil. Next, the rheological behavior of two waxy crude oils is studied using rheometrical tests (creep tests, flow restarts, abrupt changes of shear rate and steady flow) after different flow histories, notably during the cooling process. Then, those experimentally observed trends are modeled. Additionally, a comprehensive study of the yield stress in function of flow and temperature histories is presented. It provides an approach for describing the yield stress field inside the pipeline at the flow restart moment. Finally, the entire rheological model is implemented in the computational code for simulating waxy crude oils flow restart of a real scale pipeline
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Boisly, Martin. « Modellierung des Materialverhaltens Magnetorheologischer Fluide unter Verwendung der Fourier-Transformations Rheologie ». Doctoral thesis, Logos Verlag Berlin GmbH, 2017. https://tud.qucosa.de/id/qucosa%3A32282.
Texte intégralRésumé :
In dieser Dissertation wird das viskoplastische Schubverhalten eines magnetorheologischen Fluids (MRF) modelliert. Mithilfe eines phänomenologischen Modellierungsansatzes auf Basis nichtlinearer rheologischer Elemente können die gemessenen Fließkurven sowie Speicher- und Verlustmoduli abgebildet werden. Ein MRF ist ein Material mit fest-flüssig Übergang. Es besitzt von einem Magnetfeld abhängige Materialeigenschaften. Um diese beschreiben zu können, wird zunächst eine phänomenologische Stoffklassifizierung eingeführt. Auf deren Grundlage teilen sich Stoffe allgemein in Flüssigkeiten, Festkörper und Materialien mit fest-flüssig Übergang auf. Zur Beschreibung des Materialverhaltens von MRF werden drei viskoplastische Modelle formuliert und gegenübergestellt. Zur Identifikation der Materialparameter wird eine Identifikationsstrategie auf der Grundlage charakteristischer Punkte entwickelt. Charakteristische Punkte sind exklusive Punkte von Materialfunktionen, die analytisch beschrieben und ohne Weiteres experimentell ermittelt werden können. Analytische Ausdrücke für charakteristische Punkte der Speicher- und Verlustmoduli werden über das Analogieprinzip unter Verwendung von Lissajous Diagrammen abgeleitet. Infolgedessen können die Materialparameter durch das Auswerten algebraischer Zusammenhänge identifiziert werden, ohne nichtlineare Optimierungsverfahren anwenden zu müssen. Hierbei stellt die Fließspannung einen signifikanten Materialparameter dar. Deswegen werden die Standardverfahren zur Bestimmung der Fließspannung auf rheologische
Modelle angewendet und bewertet.
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Dattola, Tiziano. « Caratterizzazione mediante tecniche di imaging a risonanza magnetica nucleare dello spiazzamento di fluidi non miscibili nei mezzi porosi ». Master's thesis, Alma Mater Studiorum - Università di Bologna, 2020. http://amslaurea.unibo.it/20013/.
Texte intégralRésumé :
L’attività condotta in questo lavoro di tesi è stata rivolta alla caratterizzazione delle proprietà petrofisiche di campioni di roccia, mediante tecniche di imaging a risonanza magnetica (MRI). In particolare il lavoro si è focalizzato sullo studio dello spiazzamento di fluidi non miscibili in campioni di roccia per caratterizzarne le proprietà intrinseche, quale la permeabilità, e al contempo verificare il comportamento del fluido all’interno del mezzo poroso. Le prove di laboratorio classiche, sono state eseguite tramite cella triassiale collegata ad un apparato di flussaggio per determinare le proprietà di trasporto della roccia. Tale apparato, ha permesso anche l’applicazione di metodi a risonanza magnetica nucleare (NMR) per ottenere in modo non invasivo e non distruttivo indicazioni di carattere qualitativo sui mezzi porosi esaminati, attraverso la realizzazione di immagini create col tomografo Artoscan Esaote. Per analizzare le immagini acquisite, in modo anche quantitativo, è stato necessario utilizzare diversi software sviluppati ad hoc. In particolare si menziona il software ARTS per la comparazione quantitativa delle immagini e CorrelaIMG per misurare in modo oggettivo, l’avanzamento del fronte di spiazzamento. Tali analisi,sono state completate su due campioni rocciosi di differente litotipo. L’avanzamento del fronte, per ambedue i campioni, è risultato essere ben descrivibile mediante un semplice modello esponenziale. Il valore dei parametri del modello sono stati valutati mediante regressione non lineare col risolutore Solver di Excel®. I risultati ottenuti mostrano una piena corrispondenza fra le misure classiche e i risultati ottenuti per mezzo delle immagini MRI.
Pertanto, il lavoro di tesi riconferma,come la tecnica MRI sia un ottimo strumento, per valutare le caratteristiche di un mezzo poroso sottoposto a flussaggio, specialmente quando si renda indispensabile minimizzare le alterazioni subite dal campione come conseguenza della tecnica adottata.
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Khalifé, Maya. « Mesure de pression non-invasive par imagerie cardiovasculaire et modélisation unidimensionnelle de l’aorte ». Thesis, Paris 11, 2013. http://www.theses.fr/2013PA112325/document.
Texte intégralRésumé :
L'imagerie par Résonance Magnétique permet de mesurer l'écoulement sanguin. Au niveau cardiovasculaire, elle permet d'acquérir non seulement des images anatomiques du cœur et des gros vaisseaux mais aussi des images fonctionnelles de vitesse par contraste de phase. Cette technique offre des perspectives dans l'étude de la dynamique des fluides et dans la caractérisation des artères, en particulier pour les grosses artères systémiques comme l'aorte dont le rôle est primordial dans la circulation sanguine. Par ailleurs, l'un des paramètres qui entrent en jeu dans la détermination de la fonction cardiaque et du comportement vasculaire est la pression artérielle. La méthode de référence de la mesure de pression dans l'aorte étant le cathétérisme, plusieurs méthodes combinant la modélisation à l'imagerie ont été proposées afin d'estimer un gradient de pression de façon non invasive. Ce travail de thèse propose de mesurer la pression dans un segment d'aorte grâce à un modèle 1D simplifié et en utilisant les données mesurées par IRM et un modèle 0D représentant le réseau vasculaire périphérique comme conditions aux limites. Aussi, afin d'adapter le modèle à l'aorte du patient, une loi de pression exprimant une relation entre la section aortique à la pression et basée sur la compliance a été utilisée. Cette dernière, liée à la vitesse d'onde de pouls (VOP), a été mesurée en IRM sur les ondes de vitesse.Par ailleurs, les séquences de codage de vitesse et d'accélération sont longues et ponctuées d'artéfacts dus au mouvement du patient. Une apnée est requise afin de limiter le mouvement respiratoire. Cependant, la durée de l'apnée atteint 25 à 30 secondes pour de telles séquences, ce qui est souvent impossible à tenir pour les malades. Une technique d'optimisation de séquences dynamiques par réduction du champ de vue est proposée et étudiée. La technique décrit un dépliement des régions repliées par différence complexe de deux images, l'une codée et l'autre non codée en vitesse. Cette méthode réalise une réduction de plus de 25% de la durée d'apnéeMagnetic Resonance Imaging (MRI) is used to measure blood flow. It allows assessing not only dynamic images of the heart and the large arteries, but also functional velocity images by means of Phase Contrast. This promising technique is important for studying fluid dynamics and characterizing the arteries, especially the large systemic arteries that play a prominent role in the blood circulation. One of the parameters used for determining the cardiac function and the vascular behavior is the arterial pressure. The reference technique for measuring the aortic pressure is catheterism, but several methods combining imaging and mathematical modeling have been proposed in order to non-invasively estimate a pressure gradient. This work proposes to measure pressure in an aortic segment through a simplified 1D model using MRI measured flow and 0D model representing the peripheral vascular system as boundary conditions. To adapt the model to the aorta of a patient, a pressure law was used forming a relation between the aortic section area and pressure, based on compliance, which is linked to pulse wave velocity (PWV) estimated on MRI measured flow waves.Scan duration was optimized, as it is often a limitation during image acquisition. Velocity and acceleration sequences require a long time and may cause artifacts. Hence, they are acquired during apnea to avoid respiratory motion. However, for such acquisitions, a subject would have to hold their breath for more than 25 seconds which can pose difficulties for some patients. A technique that allows dynamic acquisition time optimization through field of view reduction was proposed and studied. The technique unfolds fold-over regions by complex difference of two images, one of which is motion encoded and the other acquired without an encoding gradient. By implementing this method, we decrease the acquisition time by more than 25%
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Nury, Catherine. « Développement d’une sonde de photoaffinité pour la détection sensible de formes actives de Métalloprotéases Matricielles dans des systèmes biologiques complexes ». Thesis, Paris 5, 2012. http://www.theses.fr/2012PA05P629/document.
Texte intégralRésumé :
Le développement d’une nouvelle sonde dite « activity-based probe » pour réaliser la détection de formes actives de protéases appartenant à la famille des protéases à zinc de la matrice (MMP) a été réalisé dans ce travail, en partant d’un inhibiteur phosphinique puissant des MMP dans lequel a été introduit un groupement photoactivable de type diazérine. Ce composé se révèle un inhibiteur puissant de plusieurs MMP avec des affinités nanomolaires. Ce composé incubé avec différentes MMP est par ailleurs capables de modifier de façon covalente un grand nombre de MMP au niveau de leur site actif, avec des rendements de modification variant de plus de 50% à 11%, selon la nature des MMP. En ayant choisi comme moyen de détection la radioactivité, nous démontrons qu’avec cette nouvelle sonde qu’il est possible de détecter des formes actives de MMP avec des sensibilités de l’ordre de la femtomole dans des systèmes modèles de protéomes complexes. Appliquée à l’analyse de lavages broncho alvéolaires de souris traitées par voie pulmonaire avec des nanoparticules pour induire une réponse inflammatoire, cette nouvelle sonde permet de mettre en évidence la présence de formes actives du domaine catalytique de la MMP-12, une métalloprotéase à zinc exprimée par les macrophages, mais pas dans les animaux contrôles. En revanche l’analyse de carotides humaines de patients souffrant d’athérosclérose ne nous pas conduit avec cette sonde à la détection de formes actives de MMP. Malgré ce résultat, il est à noter que la détection de forme active de MMP dans un fluide pathologique est une première dans ce domaine. Cette sonde étant validée pour sa capacité à détecter des formes actives de MMP, elle permettra dans l’avenir de tester d’autres fluides pathologiques d’origine humaine ou bien des extraits de tissu comme des tumeurs pour lesquels les MMP pourraient être des marqueurs de ces pathologiesA new activity-based probe able to covalently modify the active site of proteases belonging to the matrix metalloprotease family (MMPs) has been developed in this thesis project. The probe was shown to behave as potent inhibitor of several MMPs, with nanomolar Ki values. This probe was also able to modify specifically only the free active site of MMPs, with particular high yields of cross-linking varying from 50 % to 11 %, depending of the MMPs tested. Using radioactivity as means of detection, this probe was able to detect active form of MMPs with a threshold of 1 femtomole. Applied to the study of bronchoalvelolar fluids (BAL) from mice exposed to nanoparticles by a lung aspiration protocol, this probe revealed the presence of the catalytic domain of MMP-12 under its active form, but not in control animals. When used to detect active form of MMPs from extracts obtained from human arteries of patient suffering from atherosclerosis, the probe was not able to detect such MMP active forms. Despite this negative result, the detection of active form of MMP in pathological fluid like BAL has never been reported before this work. Having validated this novel MMP activity-based probe, it will be possible to use it now for detecting MMPs from other pathological fluids or tissues extracts in which MMPs can be good markers of the pathology
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Mardones, Peñailillo Jeannette. « Expresión de proteína quimiótica de monocitos-3 (MCP-3/CCL7) en fluido gingival crevicular y en lesiones periapicales de dientes con periodontitis apical crónica ». Tesis, Universidad de Chile, 2009. http://repositorio.uchile.cl/handle/2250/136312.
Texte intégralRésumé :
Trabajo de Investigación Requisito para optar al Título de Cirujano DentistaAutor no autoriza el acceso a texto completo de su documento
ntroducción La periodontitis apical crónica (PAC) es una respuesta inmunoinflamatoria causada por la infección bacteriana de la pulpa dental, en la que hay destrucción de los tejidos periapicales. La proteína quimiotáctica de monocitos – 3 (MCP3/CCL7) es una quimioquina que atrae, principalmente, a células del linaje monocito-macrófago, las que son fundamentales durante el desarrollo de la PAC, por lo que podría participar en la patogénesis de las lesiones periapicales (LPAs) y su caracterización en el fluido gingival crevicular (FGC) podría reflejar el estado de salud/enfermedad de los tejidos perirradiculares. El objetivo de este trabajo es comparar la expresión de MCP-3, en FGC de dientes con diagnóstico de PAC y de dientes sanos; y establecer una correlación entre la expresión de MCP-3 en FGC de dientes con PAC y homogeneizados de biopsias de LPAs de dichos dientes. Material y métodos Se seleccionaron 12 pacientes con diagnóstico clínico de PAC e indicación de exodoncia. Se obtuvieron muestras de FGC de dientes con PAC con indicación de exodoncia y libres de enfermedad periodontal, FGC de sus contralaterales sanos y biopsias de las LPAs obtenidas luego de las exodoncias de los dientes con PAC. Para determinar la expresión de MCP-3 se realizó Western blot. La intensidad de las bandas se midió por análisis densitométrico con el programa UN SCAN IT ® 1 Resultados MCP-3 se expresa en FGC de dientes sanos y de dientes con PAC, así también en las LPAs. Los niveles de MCP-3 en FCG de dientes con PAC fueron significativamente mayores que en sanos. Se observó correlación positiva en la expresión de MCP-3 entre FGC de dientes con PAC y homogeneizados de biopsias de LPAs. Conclusiones MCP-3 participaría en la patogénesis de las LPAs, probablemente actuando como quimioatractante de células del linaje monocito-macrófago. La LPA sería la principal fuente de MCP-3. A su vez, nuestros resultados sugieren que el FGC podría ser una herramienta útil en el estudio de la PAC, ya que refleja cambios en su composición de acuerdo al estado de salud/enfermedad de los tejidos periapicales.
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Berry, Matthew James. « Hydrodynamic analysis of the momentum-reversal and lift tidal turbine ». Thesis, University of Exeter, 2017. http://hdl.handle.net/10871/29541.
Texte intégralRésumé :
Tidal energy has the potential to make a valuable contribution to meeting future global energy demands. Converting the energy of tidal streams into useful electricity can be achieved with use of tidal-stream turbines, such as the Momentum-Reversal and Lift (MRL) device. This turbine utilises a blade motion where each blade rotates continuously through 180° about its own axis for every 360° of turbine rotation. The aim of the design is to harness both useful lift and drag forces when rotating at relatively slow speeds. However, no detailed analysis of the time-varying fluid dynamic behaviour of the turbine has been undertaken before this study. The primary aim of this study has been to further understanding of the performance characteristics of the MRL turbine design, focusing on a laboratory- scale device. The study has analysed both the time-averaged and time-varying torque and power output, and the associated fluid-dynamic structure of flow through the turbine. A secondary aim was to generate data that can be used by other researchers who focus on the wake generation of the MRL tidal turbine. This study has used OpenFOAM to develop a time-dependent RANS CFD model and investigate the performance of the MRL turbine. To allow validation of the CFD model, experiments were firstly undertaken in order to measure the cycle-mean torque and power output of the turbine when operating in a laboratory flume. Measurements of the flow velocity at a number of upstream and downstream locations were also taken, in order to allow comparison with the CFD simulation results, where appropriate. Also, in order to allow validation of the CFD approach against time-varying data, the motion of the turbine blades was analysed. This allowed suitable experimental test cases to be identified from the literature and CFD simulation results have been compared to these. A detailed sensitivity analysis of the MRL turbine CFD model was carried out, followed by two-dimensional simulations of the turbine involving a single-blade and three-blades. Three-dimensional simulations were also undertaken, with results compared to the gathered experimental results. Finally, the effect of varying turbine solidity was investigated with the CFD model. Overall it was found that the CFD simulations successfully reproduce the rotational speed at which maximum torque and power are developed. However, the three-dimensional simulations significantly over-predict the magnitude of results in comparison to the gathered experimental results. Regardless, the two- and three-dimensional simulations have allowed detailed analysis of the flow behaviour and structures that are responsible for the development of blade forces and turbine torque.
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Ianev, Deniza [Verfasser]. « Analysis of calprotectin, PMN elastase, MMP-8 and IL-1β in microliter volumes of gingival crevicular fluid - suitability as prognostic factors for the recession after soft tissue management / Deniza Ianev ». Ulm : Universität Ulm, 2017. http://d-nb.info/1137557583/34.
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Rosin, Mark. « Instabilities and transport in magnetized plasmas ». Thesis, University of Cambridge, 2011. https://www.repository.cam.ac.uk/handle/1810/237241.
Texte intégralRésumé :
In a magnetized plasma, naturally occurring pressure anisotropies facilitate instabilities that are expected to modify the transport properties of the system. In this thesis we examine two such instabilities and, where appropriate, their effects on transport. First we consider the collisional (fluid) magnetized magnetorotational instability (MRI) in the presence of the Braginskii viscosity. We conduct a global linear analysis of the instability in a galactic rotation profile for three magnetic field configurations: purely azimuthal, purely vertical and slightly pitched. Our analysis, numerical and asymptotic, shows that the first two represent singular configurations where the Braginskii viscosity's primary role is dissipative and the maximum growth rate is proportional to the Reynolds number when this is small. For a weak pitched field, the Braginskii viscosity is destabilising and when its effects dominate over the Lorentz force, the growth rate of the MRI can be up to 2√2 times faster than the inviscid limit. If the field is strong, an over-stability develops and both the real and imaginary parts of the frequency increase with the coefficient of the viscosity. Second, in the context of the ICM of galaxy clusters, we consider the pressure-anisotropy-driven firehose instability. The linear instability is fast (~ ion cyclotron period) and small-scale (ion Larmor radius ρi) and so fluid theory is inapplicable. We determine its nonlinear evolution in an ab initio kinetic calculation (for parallel gradients only). We use a particular physical asymptotic ordering to derive a closed nonlinear equation for the firehose turbulence, which we solve. We find secular (α t) growth of magnetic fluctuations and a k-||3 spectrum, starting at scales >~ ρi. When a parallel ion heat flux is present, the parallel firehose instability mutates into the new gyrothermal instability. Its nonlinear evolution also involves secular magnetic energy growth, but its spectrum is eventually dominated by modes with a maximal scale ~ρilT/λmfp,(lT is the parallel temperature gradient scale). Throughout we discuss implications for modelling, transport and other areas of magnetized plasma physics.
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Vilaplana, Martínez Eduard. « A biphasic model for cortical structural changes in preclinical AD : a multimodal MRI, CSF and PET study ». Doctoral thesis, Universitat Autònoma de Barcelona, 2017. http://hdl.handle.net/10803/456994.
Texte intégralRésumé :
La enfermedad de Alzheimer (EA) se caracteriza neuropatológicamente por la presencia de depósitos extracelulares de ß-amiloide (Aß) y ovillos neurofibrilares intracelulares (proteína tau fosforilada, p-tau) así como fenómenos inflamatorios. Estos procesos se asocian con atrofia cerebral, pérdida neuronal y alteraciones funcionales que acaban produciendo deterioro cognitivo y eventualmente un síndrome clínico de demencia. El depósito de amiloide comienzan décadas antes de que se pueda hacer un diagnóstico de demencia e incluso de la aparición de los primeros síntomas, y constituyen lo que se conoce como EA preclínica (Sperling et al., 2011).
En la actualidad podemos estudiar los mecanismos fisiopatológicos que ocurren en la EA preclínica a través de biomarcadores (Dubois et al., 2016). Entender las relaciones entre biomarcadores en la EA preclínica es esencial para entender la fisiopatología de la enfermedad y poder desarrollar terapias que ralenticen o frenen su curso. Sin embargo, estas relaciones distan de estar claras, por ejemplo, la relación de la amiloidosis y la estructura cortical dista de es controvertida (Fortea et al., 2014).
El objetivo principal de esta tesis fue estudiar las alteraciones corticales estructurales que ocurren en la enfermedad de Alzheimer preclínica. Concretamente, los objetivos fueron 1) estudiar la relación entre Aß y el grosor cortical y sus posibles interacciones con la proteína p-tau, 2) analizar los cambios estructurales corticales longitudinales de la EA preclínica, 3) investigar la microestructura cortical y entender su relación con la macroestructura en el continuum de la enfermedad y, 4) estudiar el impacto local del depósito de amiloide en la estructura cerebral en la EA preclínica.
Para la realización de esta tesis se ha contado con bases de datos públicas americanas (Alzheimer’s Disease Neuroimaging Initiative, http://adni.loni.usc.edu/) y con bases de datos españolas (proyecto SIGNAL, https://www.signalstudy.es/).
Los resultados de la tesis han conducido a la propuesta de un modelo bifásico de cambios corticales estructurales en la EA preclínica. El depósito de amiloide en ausencia de tau patológico se asocia a un incremento del grosor cortical, una ralentización de la atrofia longitudinal a 2 años y descensos de difusión cortical. Posteriormente, en presencia de tau patológica, y como resultado del efecto tóxico sinérgico o interacción entre procesos patológicos, se produciría una aceleración de la atrofia e incrementos de difusión que se extenderían siguiendo un patrón característico que ha sido definido como la huella cortical de la EA (Dickerson et al., 2009).
Los resultados presentados en esta tesis tienen implicación directa en la investigación y en la práctica clínica. En primer lugar, en relación a los modelos de evolución de biomarcadores de la EA (Jack et al., 2013) ya que esta fase temprana de engrosamiento cortical no está contemplada en los modelos actuales. Nuestro modelo ayudaría a integrar los resultados contradictorios previos en la literatura en relación a los efectos del amiloide sobre la estructura cerebral. Los modelos actuales, no contemplan la interacción/sinergia entre biomarcadores que rigen el mencionado proceso bifásico. En segundo lugar, los resultados tienen implicaciones en el diseño de los ensayos clínicos, tanto en la selección de pacientes como en el uso subrogado de la resonancia como marcador de eficacia, ayudando a entender algunos resultados inesperados de los ensayos clínicos previos con inmunoterapia anti-amiloidea. Finalmente, la difusión cortical podría ser un marcador precoz en el curso de la EA. Futuros estudios multimodales de resonancia magnética y líquido cefalorraquídeo que incorporen PET de inflamación y de Tau con seguimientos longitudinales serán claves para seguir estudiando los procesos fisiopatológicos que subyacen la EA preclínica.The Alzheimer’s disease (AD) neuropathological hallmarks are the presence of extracellular amyloid ß (Aß) deposition and intracellular neurofibrillary tangles (hyperphosphorilated tau protein) as well as inflammation phenomena. These processes are associated with cerebral atrophy, neuronal loss and functional alterations which lead to cognitive dysfunction and, eventually, a clinical syndrome of dementia. These pathophysiological processes begin decades before the diagnosis of the clinical dementia even before the appearance of the first clinical symptoms, and constitute the preclinical AD (Sperling et al, 2011). Nowadays we can study the pathophysiological mechanisms that occur in preclinical AD through biomarkers (Dubois et al., 2016). It is crucial to understand the relationships between biomarkers in preclinical AD to further understand the disease pathophysiology and be able to develop treatments that could slow down or stop its course. However, these relationships are not clear, for example, the relationship between brain amyloidosis and brain structure is controversial (Fortea et al., 2014). The objective of this thesis was to study the cortical structural alterations that occur in preclinical AD. Specifically, 1) to study the relationship between Aß and cortical thickness and its potential interactions with p-tau, 2) to analyze the 2-year cortical longitudinal changes in preclinical AD, 3) to investigate cortical microstructure and understand its relationship with brain macrostructure in the disease continuum and, 4) to assess the local impact of amyloid deposition in brain structure in preclinical AD. In this thesis, we have used data from a public American database (Alzheimer’s Disease Neuroimaging Initiative, http://adni.loni.usc.edu/) and from a Spanish multicentric cohort (proyecto SIGNAL, https://www.signalstudy.es/). The results of this thesis have conducted to the proposal of a biphasic model of structural cortical changes in preclinical AD. Amyloid deposition in the absence of pathological tau levels would be associated with increased cortical thickness, less 2-year longitudinal cortical thinning and cortical diffusivity decreases. Then, in the presence of pathological tau levels, and as a result of the synergic toxic effect or interaction between pathologic processes, there would be an atrophy acceleration and cortical diffusivity increases that would spread following a pattern that has been described as the AD-signature (Dickerson et al., 2009). The results presented in this thesis have direct research and clinical implications. First, they impact on the models of biomarker evolution in AD (Jack et al., 2013), as the cortical thickening phase is not contemplated in previous models. Our model would help to understand previous contradictory results in the literature that assessed the effect of amyloid on brain structure. Current models do not take into account the interaction/synergy effect between biomarkers that define the aforementioned biphasic process. Second, our results have relevance in the design of clinical trials, both in the selection of patients and in the use of MRI as a surrogate marker of efficacy, and might help explain some unexpected results in previous anti-amyloid immunotherapy trials. Finally, cortical diffusivity could be an early marker in the AD course. Further multimodal studies that incorporate tau- and inflammation-PET with longitudinal follow-ups are crucial to further investigate the pathophysiological process that underlies preclinical AD.
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Suo, Jin. « Investigation of blood flow patterns and hemodynamics in the human ascending aorta and major trunks of right and left coronary arteries using magnetic resonance imaging and computational fluid dynamics ». Diss., Available online, Georgia Institute of Technology, 2005, 2005. http://etd.gatech.edu/theses/available/etd-01192005-121529/unrestricted/suo%5Fjin%5F200505%5Fphd.pdf.
Texte intégralRésumé :
Thesis (Ph. D.)--Biomedical Engineering, Georgia Institute of Technology, 2005.Giddens, P. Don, Committee Chair ; Vito, P. Raymond, Committee Member ; Taylor, Robert, W., Committee Member ; Oshinski, John, Committee Member ; Bao, Gang, Committee Member. Includes bibliographical references.
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Reiss-Zimmermann, Martin, Michael Scheel, Markus Dengl, Matthias Preuß, Dominik Fritzsch et Karl-Titus Hoffmann. « The influence of lumbar spinal drainage on diffusion parameters in patients with suspected normal pressure hydrocephalus using 3T MRI ». Sage, 2014. https://tud.qucosa.de/id/qucosa%3A35424.
Texte intégralRésumé :
Background: Normal pressure hydrocephalus (NPH) has been an ongoing and challenging field of research for the past decades because two main issues are still not fully understood: the pathophysiologic mechanisms underlying ventricular enlargement and prediction of outcome after surgery. Purpose: To evaluate changes in diffusion tensor imaging (DTI) derived parameters in patients with suspected normal pressure hydrocephalus before and after withdrawal of cerebrospinal fluid (CSF). Material and Methods: Twenty-four consecutive patients with clinical and radiological suspicion of NPH and 14 agematched control subjects were examined with DTI on a clinical 3T scanner. Patients were examined before and 6–36 h after CSF drainage (interval between scans, 5 days). Fifteen patients were finally included in data analysis. Fractional anisotropy (FA) and mean, parallel, and radial diffusivity (MD, PD, RD) were evaluated using a combination of a ROI-based approach and a whole-brain voxel-by-voxel analysis. Results: Alteration of DTI parameters in patients with suspected NPH is regionally different. Compared to the control group, we found an elevation of FA in the subcortical white matter (SCWM) and corpus callosum, whereas the other diffusion parameters showed an increase throughout the brain in variable extent.We also found a slight normalization of RD in the SCWM in patients after lumbar drainage. Conclusion: Our results show that DWI parameters are regionally dependent and reflect multifactorial (patho-) physiological mechanisms, which need to be interpreted carefully. It seems that improvement of gait is caused by a decrease of interstitial water deposition in the SCWM.
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Boräng, Jennifer, et Adam Boucher. « Green tea inhibits proteolytic enzymes in GCF from patients with chronic periodontitis ». Thesis, Malmö högskola, Odontologiska fakulteten (OD), 2012. http://urn.kb.se/resolve?urn=urn:nbn:se:mau:diva-19944.
Texte intégralRésumé :
Kronisk parodontit orsakar vävnadsdestruktion till följd av matrixmetalloproteinasaktivitet. Dessa enzym härrör från värdcellerna och är en del av det immunologiska svaret på bakteriella virulensfaktorer. Grönt te har studerats för sina hälsofrämjande egenskaper, som omfattar bland annat anti-inflammatoriska effekter. Effekten beror delvis på enzyminhibering av tepolyfenoler. Syftet med denna studie var att ytterligare undersöka den inhiberande effekten av grönt te, med fokus på enzymatisk aktivitet i gingivalvätska från patienter med parodontal sjukdom. Patienter med kronisk parodontit valdes ut för att delta i studien. Gingivalvätska extraherades med mikropipetter från patienternas gingivala sulci. Proverna behandlades med grönt te och jämfördes med obehandlade prover från samma försöksperson. Fluorescens proteasanalys med kasein som substrat utfördes på fjorton prover för att detektera skillnader i kaseinolytisk aktivitet. Zymogramanalys med användning av gelatin som substrat utfördes på fyra prover, för att undersöka skillnader i gelatinolytisk aktivitet och analysera molekylvikter för de olika enzymerna. Den fluorometriska analysen visade en signifikant lägre enzymaktivitet i prover med tillsatt grönt te jämfört med obehandlade prover (p<0.001). Zymogramanalysen visade en skillnad i enzymaktivitet som var mest uttalad i banden för molekylär vikt runt 255 kDa, analogt med komplex av matrixmetalloproteinas-9. Sammanfattningsvis har det i denna studie påvisats att grönt te har en hämmande effekt på kaseinolytisk aktivitet och en mindre, mer specifik, hämmande effekt på gelatinasaktivitet.Chronic periodontitis involves tissue destruction by matrix metalloproteinase, derived from the host cells, as part of the immunological response to bacterial virulence factors. Green tea has been studied for its health promoting properties, which includes anti-inflammatory effects. The effect is in part due to enzyme inhibition by tea polyphenols. The aim of this study was to further investigate the inhibitory effect of green tea, focusing on enzymatic activity in gingival crevicular fluid from patients with periodontal disease. Patients with chronic periodontitis were selected for participation in the study. Gingival crevicular fluid was extracted with micropipettes from the gingival sulci of the patients. Samples were treated with green tea and compared with untreated samples from the same subject. Fluorescence protease assay with casein as substrate was made using fourteen samples for detecting differences in caseinolytic activity. Zymogram assay using gelatin as substrate was done using four samples to test gelatinolytic activity and analyse molecular weights of the different enzymes. The fluorometric assay showed a significantly lower enzyme activity in samples mixed with green tea than untreated samples (p<0.001). The zymogram assay showed a difference in band strength which was most pronounced in the bands of molecular weight around 255 kDA, analogous to complexes of matrix metalloproteinase-9. In conclusion, green tea has been shown in this study to have a strong inhibitory effect on caseinolytic activity and a lesser, more specific, inhibitory effect on gelatinase activity.
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Michal, Lukáš. « Zlepšení sedimentační stability MR kapalin použitím bentonitových jílů ». Master's thesis, Vysoké učení technické v Brně. Fakulta strojního inženýrství, 2021. http://www.nusl.cz/ntk/nusl-443152.
Texte intégralRésumé :
The diploma thesis is focused on the issue of sedimentation stability of magnetorheological fluids, whis represents one of the most important characteristics determining the reliability of these fluids. Higher sedimentation stability can by achieved in several ways. Methods that are further examined in the thesis include particle polymerization and the addition of clay mineral additives. Both achieve positive results by schowing increased sedimentation stability. However, in the case of additives, the effect is much higher. In particular, the CLAYTONE 40 additive achieves a lower particle sedimentation rate while maintaining the same viscosity as the commercial LORD-122ED. The results provide significant knowledge in the field and can bring magnetorheological fluids closer to wider commercial use.