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Zacharia, Nicole S. B. Massachusetts Institute of Technology. "Thermal imaging of quenched microstructural evolution in steel alloys". Thesis, Massachusetts Institute of Technology, 2001. http://hdl.handle.net/1721.1/118566.
Pełny tekst źródłaCataloged from PDF version of thesis.
Includes bibliographical references (page 41).
A method was devised for quenching undercooled samples of Fe-12Cr-16Ni. The samples were levitated in a magnetic field as a way of containerless processing. They were dropped onto a nucleation trigger and then into a quenching bath. This process was successful in producing quenched samples , but the layer of In-Ga wetting their surface showed problematic in the analysis of the samples. Data shows that double recalescence was observed in a few cases. SEM proved inconclusive and was not sensitive enough to detect the small chemical variations expected in the dendrites. Also, across the entirety of the sample there was no significant partitioning of Cr or Ni.
by Nicole Zacharia.
S.B.
Fukutomi, Hikaru. "Neurite imaging reveals microstructural variations in human cerebral cortical gray matter". Kyoto University, 2020. http://hdl.handle.net/2433/253174.
Pełny tekst źródłaHorne, Nikki Renee. "Microstructural white matter changes in Alzheimer's disease a diffusion tensor imaging study /". Diss., Connect to a 24 p. preview or request complete full text in PDF format. Access restricted to UC campuses, 2008. http://wwwlib.umi.com/cr/ucsd/fullcit?p3296903.
Pełny tekst źródłaTitle from first page of PDF file (viewed April 7, 2008). Available via ProQuest Digital Dissertations. Vita. Includes bibliographical references (p. 127-149).
Nguyen, Thanh Tung. "Modeling of complex microcracking in cement based materials by combining numerical simulations based on a phase-field method and experimental 3D imaging". Thesis, Paris Est, 2015. http://www.theses.fr/2015PESC1152/document.
Pełny tekst źródłaAn approach combining numerical simulations and experimental techniques is developed to model complex microcracking in heterogeneous cementitious materials. The proposed numerical model allowed us to predict accurately in 3D the initiation and the propagation of microcracks at the scale of the actual microstructure of a real sample subjected to compression. Its predictions have been validated by a direct comparison with the actual crack network characterized by 3D imaging techniques. In a first part, the numerical simulation tools are developed and tested. More specifically, the phase-field method is applied to microcracking simulations in highly heterogeneous microstructures and its advantages for such simulations are discussed. Then, the technique is extended to account for interfacial cracking, possibly occurring at inclusion/matrix interfaces. In a second part, the experimental methods used and developed in this work are described. The procedures to obtain the evolution of the 3D crack network within the samples by means of X-rays computed microtomography and in-situ mechanical testing are presented. Then, we focus on the developed image processing tools based on digital volume correlation to extract with good accuracy the cracks from the grey level images. In a third part, we compare the predictions of the numerical model with experimental results obtained, first, with a model material made of expanded polystyrene beads embedded in a plaster matrix, and second, to a more complex lightweight concrete. More precisely, we use the experimental data to identify by inverse approaches the local microstructural parameters, and use the experimental displacements measured by digital volume correlation to define boundary conditions to be applied on sub-domains within the sample for the simulations. The obtained direct comparisons of 3D microcrack networks and their evolutions demonstrate the very good predictive capability of the numerical model
Gong, Nanjie, i 龔南杰. "Probing tissue microstructural changes in neurodegenerative processes using non-gaussian diffusion MR imaging". Thesis, The University of Hong Kong (Pokfulam, Hong Kong), 2014. http://hdl.handle.net/10722/208583.
Pełny tekst źródłapublished_or_final_version
Diagnostic Radiology
Doctoral
Doctor of Philosophy
Qian, Wenshu, i 錢文樞. "Detecting microstructural changes in MRI normal-appearing tissues of the central nervous system by diffusion tensor and kurtosis imaging". Thesis, The University of Hong Kong (Pokfulam, Hong Kong), 2013. http://hdl.handle.net/10722/193462.
Pełny tekst źródłapublished_or_final_version
Diagnostic Radiology
Doctoral
Doctor of Philosophy
Hillman, Timothy R. "Microstructural information beyond the resolution limit : studies in two coherent, wide-field biomedical imaging systems". University of Western Australia. School of Electrical, Electronic and Computer Engineering, 2008. http://theses.library.uwa.edu.au/adt-WU2008.0085.
Pełny tekst źródłaRadlinska, Barbara. "«In vivo» imaging of microstructural and molecular neuroplasticity of fibre tracts in human subcortical stroke". Thesis, McGill University, 2013. http://digitool.Library.McGill.CA:80/R/?func=dbin-jump-full&object_id=119394.
Pełny tekst źródłaContexte Les recherches dans le domaine de la récupération suite à un accident vasculaire cérébral (AVC) suggèrent que les changements morphologiques comme moléculaires sont associés à des résultats cliniques. Ces changements peuvent être mesurés de façon non invasive chez l'être humain grâce à l'utilisation de l'Imagerie par Tenseur de Diffusion (ITD) et de la Tomographique par Émission de Positrons (TEP). Au travers de quatre études prospectives contrôlées, cette thèse s'attache à décrire les changements microstructuraux et neuroinflammatoires au cours de leur progression le long des fibres du Faisceau Pyramidal (FP) affectées par un AVC sous-cortical ischémique. Méthodes Des patients présentant un AVC ischémique sous-cortical, qu'il affecte le Faisceau Pyramidal (groupe FP) ou non (groupe NonFP), ainsi que des participants contrôles ayant présenté un Accident Ischémique Transitoire (AIT) se sont vu proposer des examens de ITD et TEP11C-[R]-PK11195 3 semaines et 6 mois après leur AVC. Concernant les données issues de l'examen par ITD, le FP (affecté directement par l'AVC), les Fibres Calleuses Motrices (FCM; affectées indirectement par l'AVC) et les Fibres Calleuses Occipitales (FCO; non affectées par l'AVC) furent délimitées grâce à l'utilisation de la tractographie. Les ratios (l'hémisphère affecté/non affecté) déterminés par l'Anisotropie Fractionnelle (AF) furent calculés. Ces ratios (rAFFP;rAFFCM; rAFFCO) furent comparés à 3 semaines puis 6 mois post-AVC et également analysés selon leur orientation (antérograde ou rétrograde) par rapport à la lésion, et mis en relation avec des résultats cliniques. Concernant les données issues de l'examen de TEP, le ratio d'absorption de la dose traceuse fut déterminé pour un ensemble de zones d'intérêt standardisées le long du FP. Ces marqueurs moléculaires de neuroinflammation furent mis en relation avec l'intégrité des faisceaux, ainsi qu'avec des résultats cliniques. Résultats Les analyses de l'ITD ont révélé que le ratio moyen rAFFP dans le groupe FP était significativement moins élevé que pour les groupes NonFP comme AIT, à 3 semaines et à 6 mois de l'AVC, et que cela était corrélé à des résultats cliniques. Le ratio rAFFCM du groupe FP a décru avec le temps. 6 mois post AVC, le ratio rAFFCM du groupe FP était significativement moins élevé que celui du groupe NonFP comme celui rAFFCO du groupe FP. Le ratio rAFFCM du groupe FP à 6 mois était corrélé à celui rAFFP rétrograde de la zone lésée. Les analyses des données issues de l'examen de TEP ont révélé que les ratios d'absorption du traceurétaient significativement plus élevés au niveau de la zone lésée et dans le sens antérograde 3 semaines post-AVC pour le groupe FP, mais uniquement dans le sens antérograde à la lésion 6 mois post-AVC. Les ratios dans le sens antérograde étaient corrélés avec le ratio rAFFP antérograde 3 semaines post-AVC, alors que les ratios dans la lésion étaient corrélés avec le ratio antérograde rAFFP seulement 6 mois post-AVC. Après avoir contrôlé la présence de dommages sur le faisceau pyramidal, les ratios initiaux d'absorption au niveau du tronc cérébral présentèrent une corrélation positive avec les résultats cliniques, bien que les ratios au niveau de la lésion tendaient à être négativement corrélés. Conclusions Dans l'ensemble, des changements significatifs concernant les fibres affectées directement ou indirectement par un AVC sous-cortical ischémique peuvent être observés au niveau morphologique comme moléculaire grâce à la neuroimagerie. Des changements dans l'intégrité de la fibre, comme démontrés par l'ITD, sont mis en évidence dans les directions antrérograde comme rétrograde à la zone cérébrale lésée, contestant ainsi la notion qu'une faible Anisotropie Fractionnelle reflète une dégénération Wallérienne. Les marqueurs moléculaires de neuroinflammation sont présents uniquement dans la zone lésée elle-même, et dans les fibres antérogrades.
Gongvatana, Assawin. "Microstructural white matter integrity in HIV-infected individuals in the HAART era a diffusion tensor imaging study /". Diss., Connect to a 24 p. preview or request complete full text in PDF format. Access restricted to UC campuses, 2008. http://wwwlib.umi.com/cr/ucsd/fullcit?p3316192.
Pełny tekst źródłaTitle from first page of PDF file (viewed September 4, 2008). Available via ProQuest Digital Dissertations. Vita. Includes bibliographical references (p. 81-94).
Chappell, Michael Hastings. "Developments in the use of diffusion tensor imaging data to investigate brain structure and connectivity". Thesis, University of Canterbury. Physics and Astronomy, 2007. http://hdl.handle.net/10092/1476.
Pełny tekst źródłaYoung, Bob Neill. "Experimental neuropsychological tests of feature ambiguity, attention and structural learning : associations with white matter microstructural integrity in elderly with amnesic and vascular mild cognitive impairment". Thesis, University of Canterbury. Psychology, 2014. http://hdl.handle.net/10092/9367.
Pełny tekst źródłaYang, Zheyi. "Numerical methods to estimate brain micro-structure from diffusion MRI data". Electronic Thesis or Diss., Institut polytechnique de Paris, 2023. http://www.theses.fr/2023IPPAE016.
Pełny tekst źródłaDiffusion magnetic resonance imaging (diffusion MRI) is a widely used non-invasive imaging modality to probe the micro-structural properties of biological tissues below the spatial resolution, by indirectly measuring the diffusion displacement of water molecules. Due to the geometrical complexity of the brain and intricate diffusion MRI mechanism, it is challenging to directly link the received signals to meaningful biophysical parameters, such as axon radii or volume fraction.In recent years, several biophysical models have been introduced to address the issue of weak interpretability. These models represent the diffusion MRI signals as a mixture of analytical signals under certain assumptions, e.g. impermeable membranes, of various disconnected simple geometries, such as spheres and sticks. Subsequently, they aim to extract the parameters of these geometries, which correlate with biophysical parameters, by inverting the analytical expression.However, the validity of these assumptions remains undetermined in actual experiments.The objective of this thesis is to improve the microstructure estimation reliability and efficiency from two perspectives. First, to facilitate the quantitative study of the valid range of biophysical models and the effect of geometrical deformation and cell membrane permeability via simulation, we proposed two reduced models derived from the Bloch-Torrey equation, respectively. For the case of the presence of permeable membranes, a new simulation approach using impermeable Laplace eigenbasis is proposed. As for the geometrical deformation, we use an asymptotic expansion with respect to the deformation angles to approximate the signal. These two reduced models enable efficient computation of signals for various values of deformation/permeability. Numerical simulations reveal that these two models can fast compute the signals within a reasonable error level compared to existing methods. Several studies have been conducted about the effects of permeability and deformation on the signals or the apparent diffusion coefficient (ADC), using the proposed models.Second, instead of inverting a simplified geometries model, we present a novel approach to associate soma size in gray matter by intermediary biomarkers. Numerical simulations identify a correlation between the volume-weighted soma radius/volume fraction and the inflection point of direction-averaged signals at high b-values (b>2500s/mm^2), offering insights for microstructure estimation. We fit a fully connected neural network using these biomarkers and compared to biophysical models, this approach offers comparable results on both synthetic and in vivo data and fast estimation since no inversion is involved
Schmitz, Birte [Verfasser], Xiaoqi [Akademischer Betreuer] Ding i Karin [Akademischer Betreuer] Weißenborn. "Investigation of metabolic and microstructural alterations in human brain under physiological and pathological conditions by using magnetic resonance imaging and 1H and 31P magnetic resonance spectroscopy / Birte Schmitz ; Akademische Betreuer: Xiaoqi Ding, Karin Weißenborn ; Institut für Diagnostische und Interventionelle Neuroradiologie". Hannover : Bibliothek der Medizinischen Hochschule Hannover, 2020. http://d-nb.info/1225413656/34.
Pełny tekst źródłaZhang, Zhongping, i 张忠平. "Quantitative in vivo assessment of tissue microstructure using diffusion tensor and kurtosis imaging". Thesis, The University of Hong Kong (Pokfulam, Hong Kong), 2011. http://hub.hku.hk/bib/B4694395X.
Pełny tekst źródłaO'Connell, Mary Kathleen. "Understanding abdominal aortic aneurysm progression through three-dimensional microstructure imaging /". May be available electronically:, 2007. http://proquest.umi.com/login?COPT=REJTPTU1MTUmSU5UPTAmVkVSPTI=&clientId=12498.
Pełny tekst źródłaWinkler, Amy. "OPTICAL METHODS FOR MOLECULAR SENSING: SUPPLEMENTING IMAGING OF TISSUE MICROSTRUCTURE WITH MOLECULAR INFORMATION". Diss., The University of Arizona, 2010. http://hdl.handle.net/10150/195176.
Pełny tekst źródłaPan, Yi. "Terahertz time-domain spectroscopy and near-field imaging of microstructured waveguides". Thesis, University of Bath, 2013. https://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.607613.
Pełny tekst źródłaMa, Lin. "Multi-scale 3D imaging of the microstructure in organic-rich shales". Thesis, University of Manchester, 2016. https://www.research.manchester.ac.uk/portal/en/theses/multiscale-3d-imaging-of-the-microstructure-in-organicrich-shales(514544f2-39f8-4fe2-b8f4-fecb27380c10).html.
Pełny tekst źródłaHiremath, Pranoti. "Identifying Changes in Myocardial Microstructure via a Novel Sonographic Imaging Algorithm". Thesis, Harvard University, 2015. http://nrs.harvard.edu/urn-3:HUL.InstRepos:15821586.
Pełny tekst źródłaHudson, Kristen Kay. "Development of imaging methods to quantify the laminar microstructure in rat hearts". Thesis, Texas A&M University, 2004. http://hdl.handle.net/1969.1/1271.
Pełny tekst źródłaDoherty, Sharon Marie. "Advanced imaging and 3D measurement of microstructure in food emulsions and foams". Thesis, University of Ulster, 2010. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.551598.
Pełny tekst źródłaPanagiotaki, E. "Geometric models of brain white matter for microstructure imaging with diffusion MRI". Thesis, University College London (University of London), 2011. http://discovery.ucl.ac.uk/1310435/.
Pełny tekst źródłaStephenson, David E. "Microstructure and Transport Properties of Porous Li-ion Electrodes". BYU ScholarsArchive, 2011. https://scholarsarchive.byu.edu/etd/2752.
Pełny tekst źródłaRazavi, Mohammad Reza. "Characterization of microstructure and internal displacement field of sand using X-ray computed tomography". Online access for everyone, 2006. http://www.dissertations.wsu.edu/Dissertations/Fall2006/M_Razavi_121206.pdf.
Pełny tekst źródłaCuevas, Assunta Mariela. "Microstructure characterization of friction-stir processed nickel-aluminum bronze through orientation imaging microscopy". Thesis, Monterey, Calif. : Springfield, Va. : Naval Postgraduate School ; Available from National Technical Information Service, 2002. http://library.nps.navy.mil/uhtbin/hyperion-image/02sep%5FCuevas.
Pełny tekst źródłaMcHugh, Damien Joseph. "The effect of tumour microstructure on diffusion-weighted MRI measurements". Thesis, University of Manchester, 2015. https://www.research.manchester.ac.uk/portal/en/theses/the-effect-of-tumour-microstructure-on-diffusionweighted-mri-measurements(9821717e-df69-4dd0-baf7-51cf27a18aa2).html.
Pełny tekst źródłaNovello, Lisa. "Towards Improving the Specificity of Human Brain Microstructure Research with Diffusion-Weighted MRI". Doctoral thesis, Università degli studi di Trento, 2022. http://hdl.handle.net/11572/342277.
Pełny tekst źródłaYang, Xuan. "Three-dimensional Characterization of Inherent and Induced Sand Microstructure". Diss., Georgia Institute of Technology, 2005. http://hdl.handle.net/1853/7557.
Pełny tekst źródłaLacerda, Luis Miguel Rosa Sousa Prado De. "Quantitative white matter metrics : diffusion imaging and advanced processing for detailed investigation of brain microstructure". Thesis, King's College London (University of London), 2017. https://kclpure.kcl.ac.uk/portal/en/theses/quantitative-white-matter-metrics(9058c64a-93a0-4db0-9799-c0bba7bd55fe).html.
Pełny tekst źródłaRan, Peipei. "Imaging and diagnostic of sub-wavelength micro-structures, from closed-form algorithms to deep learning". Electronic Thesis or Diss., université Paris-Saclay, 2020. http://www.theses.fr/2020UPASG061.
Pełny tekst źródłaElectromagnetic probing of a gridlike, finite set of infinitely long circular cylindrical dielectric rods affected by missing ones is investigated from time-harmonic single and multiple frequency data. Sub-wavelength distances between adjacent rods and sub-wavelength rod diameters are assumed throughout the frequency band of operation and this leads to a severe challenge due to need of super-resolution within the present micro-structure, well beyond the Rayleigh criterion. A wealth of solution methods is investigated and comprehensive numerical simulations illustrate pros and cons, completed by processing laboratory-controlled experimental data acquired on a micro-structure prototype in a microwave anechoic chamber. These methods, which differ per a priori information accounted for and consequent versatility, include time-reversal, binary-specialized contrast-source and sparsity-constrained inversions, and convolutional neural networks possibly combined with recurrent ones
Gibb, Matthew Michael James. "Myocardial microstructure and its role in propagation dynamics". Thesis, University of Oxford, 2012. http://ora.ox.ac.uk/objects/uuid:69a1a65e-9a71-422c-86e8-c347cfabf21a.
Pełny tekst źródłaChao, Chien-Wei. "An Improved Dynamic Particle Packing Model for Prediction of the Microstructure in Porous Electrodes". BYU ScholarsArchive, 2015. https://scholarsarchive.byu.edu/etd/5632.
Pełny tekst źródłaLi, Shiu Fai Frankie. "Imaging of Orientation and Geometry in Microstructures: Development and Applications of High Energy X-ray Diffraction Microscopy". Research Showcase @ CMU, 2011. http://repository.cmu.edu/dissertations/59.
Pełny tekst źródłaGuo, Zhen. "Insights of Taste Masking from Molecular Interactions and Microstructures of Microspheres". Thesis, University of Bradford, 2017. http://hdl.handle.net/10454/17420.
Pełny tekst źródłaSquarcina, Letizia. "Diffusion tensor imaging and fiber tractography: new approaches to study altered microstructure and evaluation in different pathologies". Doctoral thesis, Università degli studi di Padova, 2010. http://hdl.handle.net/11577/3422176.
Pełny tekst źródłaL'imaging da tensore di diusione (diffusion tensor imaging) è una tecnica di risonanza magnetica (magnetic resonance imaging, MRI) non invasiva, che permette di ottenere informazioni riguardanti la direzionalità della struttura microscopica cerebrale. In questa tesi vengono presentati dei nuovi algoritmi sviluppati con lo scopo di migliorare l'analisi e la comprensione delle caratteristiche microstrutturali e dell'organizzazione del cervello in vivo. In particolare, viene esposto un nuovo algoritmo di trattografia per la valutazione delle caratteristiche microstrutturali e di diffusione delle lesioni della materia bianca causate da sclerosi multipla, e una nuova tecnica per lo studio di alterazione nella connettività talamo corticale in pazienti colpiti da traumi cranici.
Beaujoin, Justine. "Post mortem inference of the human brain microstructure using ultra-high field magnetic resonance imaging with strong gradients". Thesis, Université Paris-Saclay (ComUE), 2018. http://www.theses.fr/2018SACLS448/document.
Pełny tekst źródłaThe aim of ultra-high field strength (≥7T) and ultra-strong gradient systems (≥300mT/m) is to go beyond the millimeter resolution imposed at lower field and to reach the mesoscopic scale in neuroimaging. This scale is essential to understand the link between brain structure and function. However, despite recent technological improvements of clinical UHF-MRI, gradient systems remain too limited to reach this resolution. This thesis aims at answering the need for mapping the human brain at a mesoscopic scale by the study of post mortem samples. An alternative approach has been developed, based on the use of preclinical systems equipped with ultra-high fields (7T/11.7T) and strong gradients (780mT). After its extraction and fixation at Bretonneau University Hospital (Tours), an entire human brain specimen was scanned on a 3T clinical system, before separating its two hemispheres and cutting each hemisphere into seven blocks that could fit into the small bore of an 11.7T preclinical system. An MRI acquisition protocol targeting a mesoscopic resolution was then set up at 11.7T. This protocol, including anatomical, quantitative, and diffusion-weighted sequences, was validated through the study of two key structures: the hippocampus and the brainstem. From the high resolution anatomical and diffusion dataset of the human hippocampus, it was possible to segment the hippocampal subfields, to extract the polysynaptic pathway, and to observe a positive gradient of connectivity and neuritic density in the posterior-anterior direction of the hippocampal formation. The use of advanced microstructural models (NODDI) also highlighted the potential of these techniques to reveal the laminar structure of the Ammon’s horn. A high resolution anatomical and diffusion MRI dataset was obtained from the human brainstem with an enhanced resolution of a hundred micrometers. The segmentation of 53 of its 71 nuclei was performed at the Bretonneau University Hospital, making it the most complete MR-based segmentation of the human brainstem to date. Major white matter bundles were reconstructed, as well as projections of the locus coeruleus, a structure known to be impaired in Parkinson’s disease. Buoyed by these results, a dedicated acquisition campaign targeting the entire left hemisphere was launched for total scan duration of 10 months. The acquisition protocol was performed at 11.7T and included high resolution anatomical sequences (100/150μm) as well as 3D diffusion-weighted sequences (b=1500/4500/8000 s/mm², 25/60/90 directions, 200μm). In addition, T1-weighted inversion recovery turbo spin echo scans were performed at 7T to further investigate the myeloarchitecture of the cortical ribbon at 300µm, revealing its laminar structure. A new method to automatically segment the cortical layers was developed relying on a Gaussian mixture model integrating both T1-based myeloarchitectural information and diffusion-based cytoarchitectural information. The results gave evidence that the combination of these two contrasts highlighted the layers of the visual cortex, the myeloarchitectural information favoring the extraction of the outer layers and the neuritic density favoring the extraction of the deeper layers. Finally, the analysis of the MRI dataset acquired at 11.7T on the seven blocks required the development of a preprocessing pipeline to correct artifacts and to reconstruct the entire hemisphere using advanced registration methods. The aim was to obtain an ultra-high spatio-angular resolution MRI dataset of the left hemisphere, in order to establish a new mesoscopic post mortem MRI atlas of the human brain, including key information about its structure, connectivity and microstructure
Wang, Lin. "Binary tomography reconstruction of bone microstructures from a limited number of projections". Thesis, Lyon, 2016. http://www.theses.fr/2016LYSEI054/document.
Pełny tekst źródłaDiscrete tomography reconstruction of bone microstructure is important in diagnosis of osteoporosis. One way to reduce the radiation dose and scanning time in CT imaging is to limit the number of projections. This method makes the reconstruction problem highly ill-posed. A common solution is to reconstruct only a finite number of intensity levels. In this work, we investigate only binary tomography reconstruction problem. First, we consider variational regularization methods. Two types of Total Variation (TV) regularization approaches minimized with the Alternate Direction of Minimization Method (ADMM) and two schemes based on Level-set (LS) regularization methods are applied to two experimental bone cross-section images acquired with synchrotron micro-CT. The numerical experiments have shown that good reconstruction results were obtained with TV regularization methods and that level-set regularization outperforms the TV regularization for large bone image with complex structures. Yet, for both methods, some reconstruction errors are still located on the boundaries and some regions are lost when the projection number is low. Local minima were obtained with these deterministic methods. Stochastic perturbations is a useful way to escape the local minima. As a first approach, a stochastic differential equation based on level-set regularization was studied. This method improves the reconstruction results but only modifies the boundaries between the 0 and 1 regions. Then partial stochastic differential equation obtained with the TV regularization semi-norm were studied to improve the stochastic level-set method. The random change of the boundary are performed in a new way with the gradient or wavelet decomposition of the reconstructed image. Random topological changes are included to find the lost regions in the reconstructed images. At the end of our work, we extended the TV regularization method to 3D images with real data on RTK (Reconstruction Toolkit). And we also extended the level-set to the multi-level cases
Fick, Rutger. "Modélisation avancée du signal dMRI pour la caractérisation de la microstructure tissulaire". Thesis, Université Côte d'Azur (ComUE), 2017. http://www.theses.fr/2017AZUR4006/document.
Pełny tekst źródłaThis thesis is dedicated to furthering neuroscientific understanding of the human brain using diffusion-sensitized Magnetic Resonance Imaging (dMRI). Within dMRI, we focus on the estimation and interpretation of microstructure-related markers, often referred to as ``Microstructure Imaging''. This thesis is organized in three parts. Part I focuses on understanding the state-of-the-art in Microstructure Imaging. We start with the basic of diffusion MRI and a brief overview of diffusion anisotropy. We then review and compare most state-of-the-art microstructure models in PGSE-based Microstructure Imaging, emphasizing model assumptions and limitations, as well as validating them using spinal cord data with registered ground truth histology. In Part II we present our contributions to 3D q-space imaging and microstructure recovery. We propose closed-form Laplacian regularization for the recent MAP functional basis, allowing robust estimation of tissue-related q-space indices. We also apply this approach to Human Connectome Project data, where we use it as a preprocessing for other microstructure models. Finally, we compare tissue biomarkers in a ex-vivo study of Alzheimer rats at different ages. In Part III, we present our contributions to representing the qt-space - varying over 3D q-space and diffusion time. We present an initial approach that focuses on 3D axon diameter estimation from the qt-space. We end with our final approach, where we propose a novel, regularized functional basis to represent the qt-signal, which we call qt-dMRI. Our approach allows for the estimation of time-dependent q-space indices, which quantify the time-dependence of the diffusion signal
Cropper, Sherrill Lyne. "The influence of native wheat lipids on the rheological properties and microstructure of dough and bread". Diss., Kansas State University, 2015. http://hdl.handle.net/2097/18924.
Pełny tekst źródłaDepartment of Grain Science and Industry
Hulya Dogan
Jon Faubion
Bread quality and final crumb grain are reflective of the ability for wheat flour dough to retain and stabilize gas cells during the baking process. The visco-elastic properties of dough allow for the incorporation of air cells and expansion during fermentation and baking. The gluten-starch matrix provides the backbone support. However, following the end of proofing and during the beginning of baking, the structure weakens due to over-extension and expansion and the matrix begins to separate and eventually break down. Native wheat lipids, which are found in small quantities in wheat flour, provide a secondary support for gas cell stabilization because of their amphiphilic characteristics and ability to move to the interface and form condensed monolayers. The objectives of this research were to evaluate the influence of native wheat lipids on the rheological properties of dough and the microstructure of bread. Native wheat lipids were extracted from straight-grade flour and separated into total, free, bound, nonpolar, glycolipids, and phospholipids using solid-phase extraction (SPE) with polar and nonpolar solvents. Defatted flour was reconstituted using each lipid fraction at a range of levels between 0.2% and 2.8%. Dough and bread were made following AACC Method 10-10.03. Rheological testing of the dough and evaluation of the microstructure of the bread was conducted using small and large deformation testing, C-Cell imaging, and x-ray microtomography analysis to determine changes in visco-elastic properties and gas cell structure and distribution. Rheological assessment through small amplitude oscillatory measurements demonstrated that nonpolar, phospholipids, and glycolipid fractions had a greater interaction with both proteins and starch in the matrix, creating weaker dough. Nonpolar, phospholipids, and glycolipids, varied in their ability to stabilize gas cells as determined by strain hardening index. C-Cell imaging and x-ray microtomograpy testing found that treatments containing higher concentrations of polar lipids (glycolipids and phospholipids) had a greater effect on overall loaf volume, cell size, and distribution. This illustrates that level and type of native wheat lipids influence the visco-elastic properties of dough and gas cell size, distribution, cell wall thickness, and cell stability in bread.
Neto, Henriques Rafael. "Advanced methods for diffusion MRI data analysis and their application to the healthy ageing brain". Thesis, University of Cambridge, 2018. https://www.repository.cam.ac.uk/handle/1810/281993.
Pełny tekst źródłaMohee, Lakshana. "Collagen scaffolds for tissue engineering : the relationship between microstructure, fluid dynamics, mechanics and scaffold deformation". Thesis, University of Cambridge, 2018. https://www.repository.cam.ac.uk/handle/1810/276980.
Pełny tekst źródłaRöling, Christian. "Anwendungsbezogene Weiterentwicklung der abbildenden Ellipsometrie". Doctoral thesis, Niedersächsische Staats- und Universitätsbibliothek Göttingen, 2017. http://hdl.handle.net/11858/00-1735-0000-0023-3F1F-5.
Pełny tekst źródłaMolina, Romero Miguel [Verfasser], Bjoern H. [Akademischer Betreuer] Menze, Marion I. [Gutachter] Menzel i Bjoern H. [Gutachter] Menze. "Disentangling Tissue Microstructure with Magnetic Resonance Imaging / Miguel Molina Romero ; Gutachter: Marion I. Menzel, Bjoern H. Menze ; Betreuer: Bjoern H. Menze". München : Universitätsbibliothek der TU München, 2018. http://d-nb.info/117332271X/34.
Pełny tekst źródłaCarapella, Valentina. "Impact of tissue microstructure on a model of cardiac electromechanics based on MRI data". Thesis, University of Oxford, 2013. http://ora.ox.ac.uk/objects/uuid:69d28c8c-832b-4ac4-aa48-3d0613708515.
Pełny tekst źródłaColeman, Michael Thomas. "The use of backscattered electron imaging mode to assess the effect of fine dispersions on development of superplastic microstructures in Al-Mg alloys". Thesis, Monterey, Calif. : Springfield, Va. : Naval Postgraduate School ; Available from National Technical Information Service, 1993. http://handle.dtic.mil/100.2/ADA272426.
Pełny tekst źródłaMirea, Iulia. "Analyse de la microstructure 3D du tissu cardiaque humain à l’aide de la micro-tomographie à rayons X par contraste de phase". Thesis, Lyon, 2017. http://www.theses.fr/2017LYSEI076/document.
Pełny tekst źródłaCardiovascular diseases remain one of the most serious health problems, motivating research to deepen our understanding of the myocardial function. To succeed, there is a need to get detailed information about the spatial arrangement of the cardiac tissue components. Currently, our understanding of the cardiac microarcInstitut de Technologie de Harbin - Chineecture is limited by the lack of 3D descriptions of the cardiac tissue at the microscopic scale. This thesis investigates the 3D cardiac tissue microstructure using X-Ray µ-CT phase contrast imaging available at the ESRF. For the first time, 9 human cardiac left ventricle (LV) wall samples are imaged at an isotropic resolution (3.5 µm) and analysed. We focus on the description of the cardiac extracellular matrix (CEM) that is one of the main components of the tissue. The CEM includes: the endomysium that surrounds and separates individual myocytes and capillaries, the perimysium that surrounds groups of myocytes and the epimysium that surrounds the entire heart muscle. Each reconstructed sample is about 30 Gb which represents a large amount of data to process and display. To succeed, we developed an automatic image processing algorithm to binarise each sample by selecting the CEM. We extract statistical features of the ECM, mainly the thickness of the cleavage planes (CP) and the inter-CP distances. The results show that the local 3D arrangement of the CP differs according to their location in the LV (posterior, anterior, septal) and their distance from the apex (more complex). The thickness of the CP extracted from all the samples roughly ranges from 24 µm to 59 µm and the inter-CP distances from 70 µm to 280 µm with significant local variations of the standard deviation. Those new quantitative markers of the ECM of the human cardiac are of main interest for a better understanding of the heart function
Yoo, Thomas. "Application of a Multimodal Polarimetric Imager to Study the Polarimetric Response of Scattering Media and Microstructures". Thesis, Université Paris-Saclay (ComUE), 2018. http://www.theses.fr/2018SACLX106/document.
Pełny tekst źródłaThe work carried out during this thesis was aimed to study the interaction of polarized light from the scattering media and particles. This work is part of a strong collaborative context between the LPICM and various private and public laboratories. A wide variety of aspects have been treated deeply, including instrumental development, advanced numerical simulation and the creation of measurement protocols for the interpretation of complex data.The instrumental part of the thesis was devoted to the development of an innovative instrument, suitable for taking polarimetric images at different scales (from millimeters to microns) that can be quickly reconfigured to offer different imaging modes of the same sample. The two main aspects that characterize the instrument are i) the possibility of obtaining real polarimetric images of the sample and the angular distribution of light scattered by an illuminated zone whose size and position can be controlled, ii) the total control of the polarization state, size and divergence of the beams. These two aspects are not united on any other commercial or experimental apparatus today.The first object of the study using the multimodal imaging polarimeter was to study the effect of the thickness from a scattering medium on its optical response. In medical imaging, there is a broad consensus on the benefits of using different polarimetric properties to improve the effectiveness of optical screening techniques for different diseases. Despite these advantages, the interpretation of the polarimetric responses in terms of the physiological properties of tissues has been obscured by the influence of the unknown thickness of the sample.The objective of the work was, therefore, to better understand the dependence of the polarimetric properties of different scattering materials with the known thickness. In conclusion, it is possible to show that the polarimetric properties of the scattering media vary proportionally with the optical path that the light has traveled inside the medium, whereas the degree of polarization depends quadratically on the optical path. This discovery could be used to develop a method of data analysis that overcomes the effect of thickness variations, thus making the measurements very robust and related only to the intrinsic properties of the samples studied.The second object of study was to study the polarimetric responses from particles of micrometric size. The selection of the particles studied by analogy to the size of the cells that form the biological tissues, and which are responsible for the dispersion of light. By means of the polarimetric measurements, it has been discovered that when the microparticles are illuminated with an oblique incidence with respect to the optical axis of the microscope, they appear to behave as if they were optically active. Moreover, it has been found that the value of this apparent optical activity depends on the shape of the particles. The explanation of this phenomenon is based on the appearance of a topological phase of the beam. This topological phase depends on the path of the light scattered inside the microscope. The unprecedented observation of this topological phase has been done by the fact that the multimodal polarimetric imager allows illumination of the samples at the oblique incidence. This discovery can significantly improve the efficiency of optical methods for determining the shape of micro-objects
Kerdja, Youcef. "Caractérisation 3D et modélisation multi-échelle des matériaux actifs de batteries". Thesis, Université Grenoble Alpes, 2020. http://www.theses.fr/2020GRALI033.
Pełny tekst źródłaFour NMC type materials having the same chemical composition (LiNi1/3Mn1/3Co1/3O2) but different microstructures were synthesized and then used as positive electrodes to probe the impact of the microstructure over their electrochemical performances. FIB-SEM tomography was used to get 3D images of the synthesized materials, compute their ionic tortuosity and link the results to the observed electrochemical performances. 2D microscopy images were also obtained on the four materials to go beyond tortuosity computation and realize multi-physics simulations at the microstructure scale on real electrodes. To that end, an electrochemical model at the microstructure level has been developed. This model allows the visualization of the electrochemical kinetics’ as well as lithium liquid and solid diffusion’s influences over the global battery capacity and lithiation heterogeneities at the microstructure level. This study was performed, via a sensitivity analysis of the material physical properties, on a ‘template microstructure’ and allowed us to understand and quantify the different influences’ mechanism and the competition between them over the characteristics of the battery at multiple scales. After that, the developed model was used to simulate galvanostatic discharges on two of the previously extracted 2D microstructures. These simulations allowed us to get a real-time visualization of the local current density as well as of the overpotential at active material-electrolyte interface. The real-time visualization helped us to explain how two NMC type materials having the same chemical composition, but different microstructures led to different discharge capacities
Jomaa, Mohamed Hedi. "Elaboration, characterization and modeling of electroactive materials based on polyurethanes and grafted carbon nanotubes". Thesis, Lyon, INSA, 2015. http://www.theses.fr/2015ISAL0053/document.
Pełny tekst źródłaHarvesting systems capable of transforming dusty environmental energy into electrical energy have attracted considerable interest throughout the last decade. Several research efforts have focused on the transformation of the mechanical vibration into electrical energy. Most of these research activities deal with classical piezoelectric ceramic materials, but more recently, a promising new type of materials is represented by electroactive polymers (EAPs). Among the various EAPs, polyurethane (PU) elastomers are of great interest due to the significant electrical-field strains, and due to their attractive and useful properties such as flexibility, light weight, high chemical and abrasion resistance, high mechanical strength and easy processing to large area films as well as their ability to be molded into various shapes and biocompatibility with blood and tissues. In addition, it has recently been shown that the incorporation into a PU matrix of nanofillers, such as carbon nanotubes (CNTs), can greatly enhance the expected strain, or the harvested energy. However, it is well known that CNTs are hardly dispersed in a polymeric matrix, and that the interfacial adhesion strength is generally poor. An effective method to improves both dispersion and adhesion may consist in functionalizing CNTs by grafting polymer chains onto their surfaces. The main objective of this thesis was to develop high-efficiency polymers nanocomposites for harvesting energy and actuation. The key motivation was to use polymer-grafted CNTs to improve dispersion, interfacial adhesion in PU, and understand how this can change the electroactive properties of the PU/CNT nanocomposites. In other words, it was a pluridisciplinary project including an optimization of the elaboration process, physical characterizations ˗ including microstructural, electrical and mechanical behaviors in a wide range of frequencies and temperatures ˗ and the determination of the electroactive properties. A comprehensive study was then carried out first on pure PU to understand how their electroactive properties depend on their microstructure, and then on the nanocomposites to understand how the incorporation of functionalized CNT can improve the electromechanical properties
Saur, Hugo. "Étude des microstructures par tomographie à rayons X : application aux roches clastiques à grain fin". Electronic Thesis or Diss., Pau, 2022. http://www.theses.fr/2022PAUU3005.
Pełny tekst źródłaThe study of the microstructure of rocks is essential for our contemporary and future challenges in energy, engineering and construction. Furthermore, this study allows us to characterize the geological deformation processes that led to the current state of geological formations. Fine-grained clastic rocks, commonly called "shales", represent about two-thirds of all sedimentary rocks. 3D data concerning silt-sized grains or clasts embedded in the porous clay-rich matrix of this type of rock are relatively scarce despite the fact that these data are crucial to understand the anisotropic properties of these rocks at the macroscale but also to evaluate the deformation state of the rock matrix. A better understanding of the microstructure of these rocks would allow us to predict their mechanical or physical properties, which are essential for applications in the energy sector, among others. X-ray computed tomography (XCT) is a non-destructive technique providing a 3D image of the microstructure of any object. A direct geometric characterization of the constituents of fine-grained clastic rocks is possible with this technique. Based on XCT images, this thesis aims first to develop methodological aspects to study the 3D shape fabric of silt particles and their spatial distribution. The moments of inertia of segmented grains from 3D digital images are used for this development. We then present applications on fine-grained rocks with a sedimentary fabric and on deformed fine-grained rocks with a tectonic fabric. The first application part of the thesis focuses on the same lithologic unit having experienced different amounts of deformation. Samples from the South Pyrenean Basin and samples from a historical outcrop in the Central Appalachians were collected. We provide new data on the evolution of the 3D shape of grains and pores at the micrometer scale and their arrangement in the rock matrix with respect to the deformation intensity. The obtained data allow discussing the deformation mechanisms at the grain scale of the different mineralogical phases. However, the limited size of the imaged samples by means of XCT (≤ 2 mm diameter) raises the question of the representativeness of these analyses. On the South Pyrenean site, some samples are studied in more detail to evaluate the homogeneity of the results. We show that the XCT data complement the indirect petrophysical measurements by providing access to localized sub-fabrics that are integrated in a bulk measurement of the rock fabric. The limits are reached when the characteristic length of the deformation structures are on the order of the sample size imaged by XCT. In the second application part, samples from turbiditic systems of the South Pyrenean basin are analyzed. These systems, when deformed in compressive tectonic settings, record the same amount of shortening differently expressed in the various siliciclastic matrices. The results obtained from the shape data of the clasts are compared to our bulk magnetic fabric measurements and show a good consistency. The methodology presented in this work can be extended to other types of porous and granular media for a better understanding of the influence of fabric anisotropy on their macroscopic properties and mechanical behavior