Dissertations / Theses on the topic 'MRI NMR'
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1
Highton, Louise Ariadne Ruth. "Using SABRE in NMR and MRI." Thesis, University of Hull, 2013. http://hydra.hull.ac.uk/resources/hull:8323.
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This thesis describes the use of SABRE as a hyperpolarisation technique in both NMR spectroscopy and MRI. Hyperpolarisation is a method of generating enhanced magnetic resonance signals to improve signal to noise, contrast and resolution within those techniques. The primary aim of this thesis was to develop the SABRE method in the context of enabling applicability to biomedical systems. Initial results focus on optimising the SABRE technique through catalyst modifications. The relationship between signal enhancement and a range of dependencies such as temperature, field and substrate choice are examined. Results show that the rate of exchange for hydride and substrate ligands can be the determining factor when optimising conditions. A range of biologically relevant substrate molecules were investigated. The first measurements using the SABRE method utilise NMR spectroscopy, but results in Chapter 4 shows how the method can be applied to hyperpolarised MRI acquisition using phantoms. Chapter 5 discusses the advances obtained in the development of hyperpolarised signals in a biologically compatible solvent system. There are two strands to this chapter, the first being the synthesis of water soluble SABRE pre-catalysts. The second part uses the previously published SABRE catalyst but in aqueous solutions. A possible biologically compatible solvent would be a 30% aqueous ethanol solution and signal enhancement was successfully measured in this. The results shown in Chapter 6 highlight the efforts made to progress the SABRE technique into in-vivo studies. It features both imaging in biologically compatible solvents as well as ex-vivo tissue studies. One notable result is the observation of a long-lived state which was observable for over two minutes. The final result shows an in-vivo MRI measurement without hyperpolarisation, however a clear action plan to complete the first in-vivo SABRE measurement is given as future work.
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Ko, Han-Bong. "NMR und MRI an mechanisch beanspruchten Polyoxymethylenproben." Phd thesis, [S.l. : s.n.], 2005. http://elib.tu-darmstadt.de/diss/000534.
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Hiltunen, S. (Sami). "Puun lahoamisprosessin seuraaminen NMR- ja MRI-menetelmillä." Bachelor's thesis, University of Oulu, 2018. http://urn.fi/URN:NBN:fi:oulu-201801201103.
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Tutkielma käsittelee NMR-spektroskopian ja magneettikuvauksen menetelmiä, joilla lahoavaa puuta voidaan mahdollisesti kuvata ja tutkia. Lisäksi tutkielmassa esitetään tärkeimpiä teoreettisia lähtökohtia puun lahoamiselle, NMR-spektroskopialle sekä magneettikuvaukselle.
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Smart, Sean Christopher. "NMR examinations of control and ischemic rodent brain tissue." Thesis, Queen Mary, University of London, 1995. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.309450.
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R, F. Marques JoseÌ Pedro. "Effects of dipolar fields in NMR and MRI." Thesis, University of Nottingham, 2004. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.416419.
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Zhang, Qilei. "NMR and MRI studies of controlled release drug delivery systems." Thesis, University of Cambridge, 2012. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.610886.
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Choi, Seongjin. "Proton NMR and MRI studies of sub-millimeter sized biological objects." Columbus, Ohio : Ohio State University, 2008. http://rave.ohiolink.edu/etdc/view?acc%5Fnum=osu1204559010.
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Uríča, Jozef. "Chyby v MRI metodách měření difúzních koeficientů." Master's thesis, Vysoké učení technické v Brně. Fakulta elektrotechniky a komunikačních technologií, 2010. http://www.nusl.cz/ntk/nusl-218553.
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Diploma thesis Errors in MRI methods for measuring diffusion coefficients a study of measurement of diffusion NMR methods, specifies the location, causes, origination diffusion coefficients. The main function of the program is to simulate changes parameters measurement of diffusion coefficients and allows for example only one gradient or runs down gradient pulses.
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Vernickel, Peter. "A multi-element transmit system for MRI." Berlin Köster, 2007. http://deposit.d-nb.de/cgi-bin/dokserv?id=3000504&prov=M&dok_var=1&dok_ext=htm.
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Enwere, M'chuks Paulinus. "Evaluation of NMR and MRI techniques for use in special core analysis." Thesis, Imperial College London, 1991. http://hdl.handle.net/10044/1/46761.
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Díaz, Anadón Laura. "Transient hydrodynamics and reaction in trickle-bed reactors using NMR and MRI." Thesis, University of Cambridge, 2007. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.612866.
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Yamaguchi, Makoto, Kazunori Suzuki, and Stephen Altobelli. "Diffusion of water in thermally fractured granite rock cores studied by PFG NMR and MRI: Diffusion of water in thermally fractured granite rock coresstudied by PFG NMR and MRI." Diffusion fundamentals 3 (2005) 24, S. 1-2, 2005. https://ul.qucosa.de/id/qucosa%3A14315.
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Diffusion of water in thermally fractured granite was studied by using pulsed field gradient NMR (PFGNMR) and MRI methods. Two different approaches gave consistent results, indicating that these methods can be applied for materials of low porosity with fracture networks.
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Chen, Dong. "Acceleration of the spatial selective excitation of MRI via sparse approximation." kostenfrei, 2009. https://mediatum2.ub.tum.de/node?id=956913.
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Hua, Jianmin. "Development of NMR/MRI techniques and chemical models for the study of atherosclerosis." Case Western Reserve University School of Graduate Studies / OhioLINK, 1994. http://rave.ohiolink.edu/etdc/view?acc_num=case1057263774.
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Shi, Fan. "NMR/MRI SIGNAL ENHANCEMENT BY REVERSIBLE EXCHANGE (SABRE) AND HETEROGENEOUS SABRE (HET-SABRE)." OpenSIUC, 2015. https://opensiuc.lib.siu.edu/dissertations/994.
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Signal Amplification by Reversible Exchange, or SABRE, is a type of PHIP (ParaHydrogen Induced Polarization) pioneered by Duckett, Green, and co-workers where an organometallic catalyst is used to co-locate parahydrogen (pH2) and a molecular substrate to be hyperpolarized. Like traditional PHIP, SABRE is of interest because it is cost-effective, potentially continuous, scalable, and rapid (achieving polarization enhancement in seconds). However unlike traditional PHIP, SABRE does not require permanent alteration of the substrate to hyperpolarize it. In addition to achieving 1H polarizations of several percent, SABRE in microTesla fields has enabled the creation of ~10% polarization for heteronuclear (15N) spins. I will discuss on a series of novel catalysts that I developed in my Ph.D program. Firstly of all, a heterogeneous SABRE ("HET-SABRE") catalyst where catalytic moieties were tethered to solid supports. Although NMR enhancements were modest (5), this initial work showed the feasibility of the approach. Next, two types of nanoscale catalysts were created to explore SABRE at the interface between heterogeneous and homogeneous conditions. Nanoparticle and polymer comb variants were synthesized by covalently tethering Ir-based catalysts to support materials comprised of TiO2/PMAA (poly methacrylic acid) and PVP (polyvinyl pyridine), respectively, and characterized by AAS, NMR, and DLS. Following pH2 delivery to mixtures containing one type of "nano-SABRE" catalyst, a target substrate, and ethanol, up to ~(-)40-fold and ~(-)7-fold 1H NMR signal enhancements were observed for pyridine using the nanoparticle and polymer comb catalysts, respectively, following transfer to high field (9.4 T). These enhancements appear to result from intact particles and not from any catalyst molecules leaching from their supports. Unlike the case with homogeneous SABRE catalysts, high-field (in situ) SABRE effects were generally not observed with the nanoscale catalysts. The potential for separation and reuse of such catalyst particles is also demonstrated. Besides the effort on green chemistry of SABRE catalyst, I have been investigating the preparation of different variants of the "standard" SABRE catalyst--[IrCl(COD)(IMes)] (IMes = 1,3-bis(2,4,6-trimethylphenyl)imidazol-2-ylidene; COD=cyclooctadiene)]--for performing SABRE in otherwise "pure" aqueous environments. Because of the poor aqueous solubility of SABRE catalysts, previous promising efforts have used co-solvents to achieve SABRE in aqueous/organic mixtures. However, I have found that the chemical changes that accompany this catalyst's activation also endow it with water solubility. Complete removal of the organic solvent following activation and subsequent re-constitution of the activated structure in deuterated water allowed up to ~(-)33-fold 1H signal enhancements to be obtained for nicotinamide. Additionally, I have investigated chemical alteration of the structure of the pre-activated catalyst to endow greater water solubility. PEGylation of the aromatic carbine moiety provided much greater aqueous solubility, but while SABRE-active in organic solutions, the catalyst lost activity in >50% water (an effect under ongoing study). As an alternative approach, synthesis of a di-Ir complex precursor where the COD rings have been replaced by CODDA (1,2-dihydroxy-3,7-cyclooctadiene) permits creation of a water-soluble catalyst [IrCl(CODDA)IMes] that enables aqueous SABRE in a single step without need for any organic co-solvent; the potential utility of the catalyst is demonstrated with the ~(-)32-fold enhancement of 1H signals of pyridine in water with only 1 atm of pH2. Taken together, these results support the utility of rational design for improving SABRE and HET-SABRE for applications varying from fundamental studies of catalysis to biomedical imaging. In the following, I also investigate different aspects of how catalyst structure can affect resulting SABRE enhancements, including the interplay of catalyst structure and temperature for optimal SABRE, as well as the confounding effects on catalyst activation. Results from the "standard" Ir SABRE catalyst (1)--[IrCl(COD)(IMes)] (IMes = 1,3-bis(2,4,6-trimethylphenyl)imidazol-2-ylidene; COD=cyclooctadiene)]--are compared with those obtained with variants respectively created by synthetically replacing the -Cl moiety with 4-amino-pyridine (4AP, 2), (diphenylphosphino)ethylamine (DPPA, 3), triphenyl phosphine (TPP, 4), and tribenzyl phosphine (TBP, 5); a sixth variant (6) was serendipitously created by an alternate synthetic route for (1) that appears to result in a polymorph according to x-ray crystallography. Studies of activation rate found that (4) and (5) activated the fastest under pH2 exposure (~20 s, an order of magnitude faster than (1)); activation rate was inversely correlated with SABRE enhancement, with peak 1H polarization enhancement ( ranging from only ~(-)44 for (4) to nearly ~(-)1900 for (1) (or PH~6%) for pyridine at 9.4 T, and ~(-)240 for nicotinamide. Although (1) gave the overall highest values as expected, other catalysts gave rise to better SABRE performance in other temperature regimes: Optimal temperatures varied significantly, e.g. ~273 K for (2) to ~310-320 K for (1); the optimal temperature for (6) was considerably lower (<273 K) than that for (1), despite the apparent structural similarity. Taken together, these results show that full optimization of SABRE enhancement for a given experiment (with respect to substrate, target nucleus, etc.) may require systematic variation of parameters including catalyst ligand choice and temperature (to modulate binding affinities and off rates with respect to relevant spin-spin couplings), in addition to pH2 partial pressure, flow rate, and magnetic field. Finally, some research on an ssNMR will be represented, to show the potential application of ssNMR on the coating detection.
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Eichner, Cornelius. "Slice-Accelerated Magnetic Resonance Imaging." Doctoral thesis, Universitätsbibliothek Leipzig, 2015. http://nbn-resolving.de/urn:nbn:de:bsz:15-qucosa-184944.
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This dissertation describes the development and implementation of advanced slice-accelerated (SMS) MRI methods for imaging blood perfusion and water diffusion in the human brain. Since its introduction in 1977, Echo-Planar Imaging (EPI) paved the way toward a detailed assessment of the structural and functional properties of the human brain. Currently, EPI is one of the most important MRI techniques for neuroscientific studies and clinical applications. Despite its high prevalence in modern medical imaging, EPI still suffers from sub-optimal time efficiency - especially when high isotropic resolutions are required to adequately resolve sophisticated structures as the human brain. The utilization of novel slice-acceleration methods can help to overcome issues related to low temporal efficiency of EPI acquisitions.
The aim of the four studies outlining this thesis is to overcome current limitations of EPI by developing methods for slice-accelerated MRI. The first experimental work of this thesis describes the development of a slice-accelerated MRI sequence for dynamic susceptibility contrast imaging. This method for assessing blood perfusion is commonly employed for brain tumor classifications in clinical practice. Following up, the second project of this thesis aims to extend SMS imaging to diffusion MRI at 7 Tesla. Here, a specialized acquisition method was developed employing various methods to overcome problems related to increased energy deposition and strong image distortion. The increased energy depositions for slice-accelerated diffusion MRI are due to specific radiofrequency (RF) excitation pulses. High energy depositions can limit the acquisition speed of SMS imaging, if high slice-acceleration factors are employed. Therefore, the third project of this thesis aimed at developing a specialized RF pulse to reduce the amount of energy deposition. The increased temporal efficiency of SMS imaging can be employed to acquire higher amounts of imaging data for signal averaging and more stable model fits. This is especially true for diffusion MRI measurements, which suffer from intrinsically low signal-to-noise ratios. However, the typically acquired magnitude MRI data introduce a noise bias in diffusion images with low signal-to-noise ratio. Therefore, the last project of this thesis aimed to resolve the pressing issue of noise bias in diffusion MRI. This was achieved by transforming the diffusion magnitude data into a real-valued data representation without noise bias. In combination, the developed methods enable rapid MRI measurements with high temporal efficiency. The diminished noise bias widens the scope of applications of slice- accelerated MRI with high temporal efficiency by enabling true signal averaging and unbiased model fits. Slice-accelerated imaging for the assessment of water diffusion and blood perfusion represents a major step in the field of neuroimaging. It demonstrates that cur- rent limitations regarding temporal efficiency of EPI can be overcome by utilizing modern data acquisition and reconstruction strategies.
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Koptyug, Igor V., Anna A. Lysova, Alexey V. Khomichev, and Renad Z. Sagdeev. "27 Al NMR/MRI Studies of the Transport of Granular Al 2 O 3." Universitätsbibliothek Leipzig, 2016. http://nbn-resolving.de/urn:nbn:de:bsz:15-qucosa-194270.
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The NMR/MRI techniques are applicable to the studies of motion of granular solids, providing information on the velocities, effective diffusivities and correlation times of the moving particles. The studies of transport of granular solids reported to-date are based on
the detection of the 1H NMR signal of the liquid phase of liquid-containing solid materials. Yet, the solid phase of many granular solids contains magnetic nuclei, providing in principle an opportunity to study motion of such solids by directly detecting the NMR signal of the solid phase. In this paper, we demonstrate that this can be performed with the use of conventional echo pulse sequences in combination with the conventional motion encoding schemes. The detection of the 27Al NMR signal of the Al2O3 powder
was used to obtain velocity maps of the powder packed in a spinning cylinder, and to measure the velocity distribution (average propagator) for the gravity driven transport of the same powder in a vertical pipe.
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Koptyug, Igor V., Anna A. Lysova, Alexey V. Khomichev, and Renad Z. Sagdeev. "27 Al NMR/MRI Studies of the Transport of Granular Al 2 O 3." Diffusion fundamentals 5 (2007) 2, S. 1-7, 2007. https://ul.qucosa.de/id/qucosa%3A14266.
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The NMR/MRI techniques are applicable to the studies of motion of granular solids, providing information on the velocities, effective diffusivities and correlation times of the moving particles. The studies of transport of granular solids reported to-date are based on
the detection of the 1H NMR signal of the liquid phase of liquid-containing solid materials. Yet, the solid phase of many granular solids contains magnetic nuclei, providing in principle an opportunity to study motion of such solids by directly detecting the NMR signal of the solid phase. In this paper, we demonstrate that this can be performed with the use of conventional echo pulse sequences in combination with the conventional motion encoding schemes. The detection of the 27Al NMR signal of the Al2O3 powder
was used to obtain velocity maps of the powder packed in a spinning cylinder, and to measure the velocity distribution (average propagator) for the gravity driven transport of the same powder in a vertical pipe.
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Tannus, Alberto. "Desenvolvimento da tecnologia de tomografia por ressonância magnética nuclear." Universidade de São Paulo, 1987. http://www.teses.usp.br/teses/disponiveis/54/54132/tde-21052007-164959/.
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Neste trabalho, descrevemos o desenvolvimento do equipamento e o software necessários à implementação da técnica de obtenção de imagens por RMN. Nossos principais objetivos foram a construção de um sistema de controle e aquisição de dados que permitisse operar um espectrômetro de Fourier de RMN pulsada como um tomógrafo de RMN; por outro lado, visamos a construção de um espectrômetro que tivesse seus parâmetros facilmente reconfiguráveis pelo sistema de controle. O resultado foi um sofisticado equipamento que permite, além do proposto, trabalhar com técnicas de espectroscopia de alta resolução e espectroscopia em sólidos. Uma grande ênfase foi dada ao entendimento das técnicas De reconstrução de imagens, desde as convencionais até aquelas que constituem atualmente a fronteira de pesquisa nessa área. Os resultados obtidos com o sistema descrito são considerados bons, comparáveis aos das unidades construídas por empresas que operam comercialmente nessa área, em cooperação com centros localizados em universidades no exterior, pouco devendo a equipamentos similares (protótipos) desenvolvidos naqueles centros.We describe in this work the development of hardware and software necessary to implement the Magnetic Resonance Imaging (MRI) techniques. Our major subjects were the construction of an acquisition and control system which allowed the operation of a pulsed Fourier NMR spectrometer as a NMR Tomograph; further we oriented the developing of a NMR spectrometer whose parameters could be easily reconfigured by the controlling system. As a result we obtained a sophisticated equipment which allows, more than the proposed, working with high resolution spectroscopic techniques and spectroscopy in solids. Since the basic techniques employed in NMR and CT Tomographs are well known, a great emphasis was also given on the understanding of the image reconstruction techniques that constitutes today the frontier of research in this area. The results obtained with the system described here are considered good, comparable to the results from commercial units developed in cooperation with imaging groups located in universities abroad.
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Waiter, Gordon David. "The NMR proton relaxation effectiveness of paramagnetic metal ions and their potential as MRI contrast agents." Thesis, University of Aberdeen, 1995. http://digitool.abdn.ac.uk/R?func=search-advanced-go&find_code1=WSN&request1=AAIU077829.
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Paramagnetic lanthanide ions have been investigated as possible MIR phantom materials and contrast agents. The aim of this study is to determine if it is possible to apply the well known Solomon-Bloembergen equations to solutions of paramagnetic lanthanide ions that have fast electron spin relaxation times, compared to Gadolinium, the most widely used ion for NMR. Studies of the relaxivity, frequency and temperature dependence, show that there is a considerable difference in those properties over the series. Chelation of the ions to EDTA and DTPA resulted in a decrease in the relaxivity which was directly proportional to the decrease in the number of water molecules in the inner co-ordination sphere. The fit of the Solomon-Bloembergen equations to the variable frequency and temperature relaxation times showed that theory is valid for the fast electron spin ions and allowed the calculation of the electron spin relaxation times. This showed that there is a difference of 5 orders of magnitude between Gadolinium, the ion demonstrated to have a slow electron spin relaxation time, and the remaining ions. The addition of EDTA chelated forms of these ions to agarose gels produced NMR phantom materials with relaxation time characteristics that could be chosen to fulfil a desired application. The biodistribution of Gd-DTPA was investigated using ESR and NMR. The concentration of Gd-DTPA in excised rat tissue, 20 minutes after intraperitoneal injection, was determined, by the change in NMR water proton relaxation time from that of a control tissue, and by ESR from direct measurement of the microwave power absorbed by the sample, which is directly proportional to the number of unpaired electron spins in the sample. The results from these two methods of determining contrast agent concentration agree well with each other both in the order of biodistribution and on the absolute concentrations.
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Ceccarelli, Mattia. "Optimization and applications of deep learning algorithms for super-resolution in MRI." Master's thesis, Alma Mater Studiorum - Università di Bologna, 2020. http://amslaurea.unibo.it/21694/.
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The increasing amount of data produced by modern infrastructures requires instruments of analysis more and more precise, quick, and efficient. For these reasons in the last decades, Machine Learning (ML) and Deep Learning (DL) techniques saw exponential growth in publications and research from the scientific community. In this work are proposed two new frameworks for Deep Learning: Byron written in C++, for fast analysis
in a parallelized CPU environment, and NumPyNet written in Python, which provides a clear and understandable interface on deep learning tailored around readability. Byron will be tested on the field of Single Image Super-Resolution for NMR imaging of brains (Nuclear Magnetic Resonance) using pre-trained models for x2 and x4 upscaling which exhibit greater performance than most common non-learning-based algorithms. The
work will show that the reconstruction ability of DL models surpasses the interpolation of a bicubic algorithm even with images totally different from the dataset in which they were trained, indicating that the generalization abilities of those deep learning models can be sufficient to perform well even on biomedical data, which contain particular shapes and textures. Ulterior studies will focus on how the same algorithms perform with different conditions for the input, showing a large variance between results.
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Pecháček, Libor. "Optimalizace parametrů akvizice MR signálu pro měření malých objektů." Master's thesis, Vysoké učení technické v Brně. Fakulta elektrotechniky a komunikačních technologií, 2010. http://www.nusl.cz/ntk/nusl-218233.
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The subject of my thesis is a design of the methods optimizing, the acquisition of MR signals when small objects measure. The thesis is divided into several parts in order to give a deeper knowledge of the problem. The first part focuses on the theory associated with NMR (Nuclear Magnetic Resonance) and SNR (signal-to-noise ratio). The practical verification of the theory follows. The conclusion of this work is focused on MR images filtering by use of wavelet transform to suppress a noise in the image. The method optimization of MR acquisition parameters for the measurement of small objects is then distributed to the entire work.
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Yamaguchi, Makoto, Kazunori Suzuki, and Stephen Altobelli. "Diffusion of water in thermally fractured granite rock cores studied by PFG NMR and MRI." Universitätsbibliothek Leipzig, 2016. http://nbn-resolving.de/urn:nbn:de:bsz:15-qucosa-194883.
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Diffusion of water in thermally fractured granite was studied by using pulsed field gradient NMR (PFGNMR) and MRI methods. Two different approaches gave consistent results, indicating that these methods can be applied for materials of low porosity with fracture networks.
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Mashni, Jamil Assad. "DEVELOPMENTS IN SIGNAL AMPLIFICATION BY REVERSIBLE EXCHANGE (SABRE) OF 15N AND 13C NUCLEI TOWARDS APPLICATIONS IN MRI." OpenSIUC, 2019. https://opensiuc.lib.siu.edu/theses/2516.
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Signal Amplification by Reversible Exchange (SABRE) is a hyperpolarization technique that utilizes parahydrogen for the NMR signal enhancement of nuclear spins. SABRE is related to Parahydrogen Induced Polarization (PHIP), another means of hyperpolarization using parahydrogen; PHIP achieves hyperpolarization via chemical reduction. Although PHIP and SABRE share many similarities in experimentation, PHIP ultimately requires the presence of an unsaturated chemical bond as well as pairwise-addition of parahydrogen. No permanent chemical change occurs during SABRE, and instead may be considered as a merely physical exchange between molecules with sites on a catalyst. PHIP and SABRE may be compared to Dynamic Nuclear Polarization (DNP), arguably the most well-known and researched method for hyperpolarization; despite all that has been achieved with DNP, PHIP and SABRE offer vastly more-rapid, less-expensive, and more-simplified approaches for achieving hyperpolarization. The focus of this work is experimentation with SABRE processes and methods designed to overcome certain experimental challenges associated with this technique.
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Hussain, Rehan. "NMR studies of carbon dioxide sequestration in porous media." Thesis, University of Cambridge, 2015. https://www.repository.cam.ac.uk/handle/1810/248877.
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Carbon dioxide (CO2) sequestration in the sub-surface is a potential mitigation technique for global climate change caused by greenhouse gas emissions. In order to evaluate the feasibility of this technique, understanding the behaviour of CO2 stored in geological rock formations over a range of length- and time-scales is crucial. The work presented in this dissertation contributes to the knowledge in this field by investigating the two-phase flow and entrapment processes of CO2, as well as other relevant fluids, in porous media at the pore- and centimetre-scales using a combination of lab-based nuclear magnetic resonance (NMR) experimental techniques and lattice Boltzmann (LB) numerical simulation techniques. Pulsed field gradient (PFG) NMR techniques were used to acquire displacement distributions (propagators) of brine flow through a model porous medium (100 µm glass bead packing) before and after the capillary (residual) trapping of gas-phase CO2 in the pore space. The acquired propagators were compared quantitatively with the corresponding LB simulations. In addition, magnetic resonance imaging (MRI) techniques were used to characterise the extent of CO2 trapping in the bead pack. The acquired NMR propagators were compared to LB simulations applied to various CO2 entrapment scenarios in order to investigate the pore morphology in which CO2 becomes entrapped. Subsequently, MRI drop shape analysis techniques were used to identify a pair of analogue fluids which matched certain key physical properties (specifically interfacial tension) of the supercritical CO2/water system in order to extend the work to conditions more relevant to CO2 sequestration in the sub-surface, where CO2 is likely to be present in the supercritical phase. As before, NMR propagator measurements and MRI techniques, along with LB simulations, were used to characterise the capillary trapping of the CO2 analogue phase in glass bead packs, as well as two different types of rock core plugs – relatively homogeneous Bentheimer sandstone, and heterogeneous Portland carbonate. In addition to capillary trapping, the effect of vertical permeability heterogeneity, such as is often present in underground rock formations, was investigated for the flow of miscible (water/brine) gravity currents in model porous media (glass bead packs), using MRI techniques such as 2D spin-echo imaging and phase-shift velocity imaging. Finally, a preliminary investigation was made into the effect of particle- and pore-size distributions on the gas/liquid (air/water) interface for porous media consisting of glass bead and sand packs of different average particle size using quantitative MRI techniques.
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He, Ping. "NOVEL EXPERIMENTAL APPROACHES AND THEORETICAL MODELS FOR IMPROVING SENSITIVITY AND INFORMATION CONTENT OF NMR AND MRI SPECTROSCOPY." OpenSIUC, 2013. https://opensiuc.lib.siu.edu/dissertations/757.
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The ongoing effort to improve the sensitivity and information content of NMR spectroscopy and MRI has important implications in scientific research and medical diagnostics. In this dissertation, a variety of approaches have been investigated and expanded on in an effort to contribute to this field. First, cryptophanes are cage-shaped molecules that have previously been used to encapsulate molecules of interest for a number of potential applications--including gas sensing and biosensing. In one set of studies, encapsulation of molecular hydrogen gas (H2) has shown different behavior compared to other small organic molecules in C111 (up until now, the smallest cryptophane). The transient, non-covalent binding was studied by variable-temperature NMR at different fields up to 950 MHz. A mathematical model that considers multiple-H2 binding was developed to better understand the physics and binding process, with predictions compared to experimental data (and rationalized in light of quantum chemical calculations on possible H2@C111 complexes). To our knowledge, C111 is the only system to reversibly trap multiple H2 gas molecules non-covalently under mild conditions. In a second series of studies, the interaction of laser-polarized xenon and a water-soluble cryptophane was studied. Despite the low concentration of xenon in aqueous solution, it was possible to achieve polarization transfer from xenon to cryptophane spins via the SPINOE (spin-polarization induced nuclear Overhauser effect). The SPINOE enhancements, along with the 129Xe NMR spectra, provide information about the interaction of the Xe-cryptophane complex (variants of which are now used in so-called xenon biosensors). This was our first in-house successful application of hyperpolarized xenon as a signal source for the spins of other molecules, leading the way to a number of ongoing studies. Although the absolute NMR enhancements obtained via the SPINOE were small, much larger enhancements were studied in a technique that uses para-hydrogen (pH2)--a spin isomer of normal molecular hydrogen)--as the source of spin order. As with the xenon experiments (and the H2 binding experiments), pH2 must be delivered as a gas to a sealed sample prior to performing the NMR experiments. Parahydrogen-induced polarization (PHIP) is an emerging field in enhancing the sensitivity in NMR experiments and may play an important role in MRI studies. Within this field a very recent phenomena of signal amplification by reversible exchange (SABRE) was investigated. The reproducibility of this recent discovery has been examined and new conclusions about the mechanism of this technique are delineated. NMR signal enhancements of nearly ~400-fold are reported. Moreover, a new water soluble NHC-Iridium catalyst was synthesized and investigated in SABRE related studies. We also report the first studies of SABRE-enhancement in biologically tolerable solvents--opening a door to the development of SABRE-hyperpolarized metabolic contrast agents for subsecond molecular imaging in the body. Although much of the above work was motivated by the desire to improve NMR/MRI sensitivity enhancement, other efforts concerned the other side of the equation--improving NMR/MRI information content. The next section concerns our efforts to investigate use of Variable-Angle (VA) NMR to study composite liquid crystal (LC) media comprised of stretched polyacrylamide gels (SAG) and embedded bacteriophage Pf1 particles. This in situ combination exploited the apparent interference between the different solute-aligning properties of the two LC components--yielding composite media with alignment properties that can differ in a tunable manner from those obtained with each medium alone. Characterization of alignment of both large and small molecules provides more insight into the nature of solute alignment that those composite phases introduce--with the goal of developing this approach as a new technique for studying molecular structure and dynamics via the dipolar and quadrupolar couplings that are restored in liquid-crystalline media. Finally the use of SPIONS--superparamagnetic iron oxide nanoparticles--as contrast agents is a relatively new approach to enhance information content in MRI studies; this is particularly true for SPIONs that have been surface-functionalized to achieve an environment-sensitive MR response. Novel surface-functionalized SPIONs were investigated by examining their effect on nuclear spin relaxation in aqueous environments simulating bodily tissues. More specifically, the pH and ionic strength dependent properties of selected dendron-functionalized and polymer-functionalized SPIONs have been examined. Of particular interest to this dissertation is how environment-mediated transient clustering of the SPIONs gives rise to changes in so-called transverse (homogeneous) spin relaxation rates as measured by following the decay of MR signals detected after the application of a series of radio-frequency (RF) pulses. In order to better understand these effects in the context of the SPIONs' behavior, a mathematical model is under development whose predictions are compared with experimental data. Aspects of the model are also compared to transmission electron micrography (TEM) and dynamic light scattering (DLS).
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Aursand, Ida Grong. "Low-field NMR and MRI studies of fish muscle : Effects of raw material quality and processing." Doctoral thesis, Norges teknisk-naturvitenskapelige universitet, Institutt for bioteknologi, 2009. http://urn.kb.se/resolve?urn=urn:nbn:no:ntnu:diva-5706.
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The present thesis aims at using non-invasive and non-destructive NMR techniques to contribute to a further understanding of fish tissue composition and its characteristics. Moreover, it aims at investigating the water dynamics and the distribution of fat and salt in fish as affected by species, raw material quality and processing from both the chemical and the physical angle at the same time. The applicability of low-field NMR as a tool for the fish processing industry was investigated. The bench top low-field NMR instrument was found suitable for fat and water determination in small Atlantic salmon (Salmo salar) samples, whereas the portable low-field NMR surface scanner (ProFiler) was appropriate for rapid fat determination in minced muscle. Thus, low-field NMR was proven to be good measuring technique, and with the introduction of the NMR surface scanner concept, online quality control may become feasible in the future. Transversal (T2) NMR relaxometry has been demonstrated to contain valuable information about water dynamics in Atlantic salmon and Atlantic cod (Gadus morhua) tissue. The thesis contributes to a further understanding of the relationship between water distribution and microstructure of fish flesh. It has been established that the method is sensitive to fish species, ante-mortem handling, rigor status, freezing/thawing, heating, and brine salting. The tissue T2 relaxation characteristics have been linked to microstructure, salt distribution and salt uptake. It is shown that T2 relaxation components correlate well with water holding capacity during salting. It has been suggested that entrapped and free water, and fat when present, give rise to the main relaxation components in fish muscle tissue. The understanding of the tissue water distribution and dynamics has been improved. However, the clarification of the relaxation characteristics in fish flesh is still an active area of research. In fatty fish, both fat and water contributes to the T2 NMR relaxation signal. A two dimensional map of the diffusion versus T2 relaxation proved to be a good technique to increase the understanding of water and fat distribution in salmon muscle tissue, by clear separation of the NMR signals from water and fat components into different populations. MR imaging was probed for investigation of fat and salt distribution. 1H MRI was successfully applied to produce separate quantitative water and fat images. Combined 1H and 23Na imaging of brine salted Atlantic salmon revealed that the uptake and distribution of salt in the tissue was highly dependent on the spatial fat distribution. An evident relation was observed between T2 relaxation characteristics of salmon flesh and the sodium distribution in salted fillets. T2 relaxaometry and MR imaging gave further insight into the microstructure and water distribution of fish tissue of different quality and its effect on salt distribution. The combination of these NMR techniques is considered to be a useful tool to increase the understanding of the tissue water distribution and dynamics and for optimization of salting processes.
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Li, Wei. "Study of Cardiac Function and Energetics in Mouse Models of Cardiomyopathies by MRI and NMR Spectroscopy." Case Western Reserve University School of Graduate Studies / OhioLINK, 2010. http://rave.ohiolink.edu/etdc/view?acc_num=case1269983160.
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Nunes, Dourado de Carvalho Victor. "Dipolar order relaxation (T1D) in myelin : a combined inhomogeneous MT (ihMT) MRI and Jeener-Broekaert NMR approach." Thesis, Aix-Marseille, 2020. http://www.theses.fr/2020AIXM0195.
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Le transfert d’aimantation inhomogène (ihMT) est une technique IRM qui permet d’accéder in vivo au contenu de myéline dans le système nerveux central. La technique ihMT met en évidence des effets d’ordre dipolaire pondérés par le temps de relaxation dipolaire, T1D. T1D est modulé par la dynamique moléculaire, fournissant néanmoins une sensibilité plus accrue aux processus liés aux mouvements lents. Accéder aux valeurs de T1D représente une nouvelle voie d’investigation dans la caractérisation des tissus biologiques et des pathologies associées. IhMT est hautement spécifique de la myéline, et pourrait être utilisée in vivo pour aider au diagnostic et au suivi des patients atteints de sclérose en plaques. Des expériences ont suggéré l’existence de plusieurs composantes T1D dans les tissus myélinisés probablement due à une mobilité moléculaire hétérogène. Une méthode de RMN, technique Jeener-Broekaert, a été utilisée dans ce travail afin de mieux appréhender la relaxation T1D dans les membranes. Avec cette séquence, une relaxation T1D multi-composante a été observé dans des membranes lipidiques synthétiques, simulant la myéline. Ce travail propose un nouveau modèle quantitatif ihMT permettant de considérer plusieurs composantes T1Ds. Des cartes T1D quantitatives ont ainsi été générées. L’application du modèle proposé a permis de révéler l’existence de deux composantes T1Ds, une courte de l’ordre de 500 μs et une longue de l’ordre de 10 ms, dans la moelle épinière de rat. La mesure combinée de T1D par RMN JB et IRM ihMT permettra de caractériser plus précisément les composantes de composition, structure et dynamique moléculaire des membranes contribuant au signal ihMTInhomogeneous magnetization transfer (ihMT) is a MRI technique that enables accurate measurement of myelin content in the central nervous system in vivo. ihMT highlights the dipolar order effects and is weighted by the associated relaxation time T1D. T1D is modulated by molecular dynamics, however it provides additional sensitivity to slow motional processes. Hence assessing T1D is important to add new information to characterize biological tissues and associated pathophysiology. ihMT and other MRI techniques can be used to evaluate myelin in vivo, and help diagnosis and follow-up of multiple sclerosis patients. New experiments have suggested that myelinated tissues and membranes would exhibit multiple T1D components probably due to a heterogeneous molecular mobility and relatively slow magnetization mixing mechanisms. To better understand T1D relaxation, the presented work uses a NMR method, the Jeener-Broekaert sequence. With this sequence, multi-T1D relaxation was observed on synthetic lipid membranes, surrogate models of myelin. This work proposes a new ihMT model with two dipolar order reservoirs and associated T1Ds. Quantitative T1D maps were generated. Implementation of the proposed model found short and long T1D on the order of 500 μs and 10 ms, respectively, in fixed rat spinal cord. Combining NMR and MRI assessments of T1D may help understand what states of myelin, in terms of composition, structure and molecular dynamics, contribute to the ihMT signal in vivo
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Haga, Kristin Kerr. "The combined application of 'H MRI and '19F MRS to the study of cerebroprotection." Thesis, University of London, 2000. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.312006.
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Kekkonen, P. (Päivi). "Characterization of thermally modified wood by NMR spectroscopy:microstructure and moisture components." Doctoral thesis, Oulun yliopisto, 2014. http://urn.fi/urn:isbn:9789526206127.
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Abstract Wood is an essential material that has many applications in the fields of engineering and especially in the forest industry, which is particularly important in Fennoscandia. Among the various modification methods for wood, thermal modification has grown substantially over the past decades. It is an environmentally friendly method for increasing the lifetime and usability of timber. The aim of this thesis is to characterize the properties of thermally modified wood as well as to obtain new information on the changes taking place in pinewood due to the thermal modification process. Several NMR methods were used to gain information on the effect of thermal modification on the microstructure and moisture components of Pinus sylvestris pinewood. Pinewood samples thermally modified at different temperatures were studied and compared to corresponding unmodified wood samples. Diffusion of water and methane was studied using pulsed-field-gradient stimulated-echo measurements to determine the highly anisotropic size distribution of pores in different cell structures of pinewood. NMR cryoporometry and relaxometry measurements were conducted to gain information on the amounts and environments of both the bound and free water absorbed into the wood samples. Cryoporometry measurements resulted in an upper limit value for the size of bound water sites and the combination of cryoporometry and relaxometry data enabled the size determination of cell wall micropores. Magnetic resonance imaging was used to visualize the spatial distribution of absorbed free water in the studied samples. Together these methods give a broad overall picture of the effects of the modification process. The results of this work give new insight into the microstructure of thermally modified pinewood and its relationship to moisture, which is of importance for both wood science as well as industry. The applicability of the NMR techniques used here to the study of wood is also proven in this work. Using the techniques developed, it is possible to determine the optimal modification temperature, which is high enough to obtain the desired effects, but low enough not to destroy the microstructure of woodTiivistelmä Puuta pystytään hyödyntämään useilla eri aloilla ja se on materiaalina tärkeä etenkin Fennoskandiassa merkittävälle metsäteollisuudelle. Useiden erilaisten puun käsittelymenetelmien joukossa lämpökäsittely on kasvattanut voimakkaasti suosiotaan viime vuosikymmeninä. Kyseessä on ympäristöystävällinen menetelmä, jolla voidaan pidentää puun käyttöikää sekä käytettävyyttä erilaisissa sovelluskohteissa. Tämän väitöskirjan päämääränä on ollut lämpökäsitellyn puun ominaisuuksien tutkiminen ja uuden tiedon saaminen puussa lämpökäsittelyprosessin myötä tapahtuvista muutoksista. Työssä käytettiin useita eri NMR-menetelmiä lämpökäsitellyn mäntypuun (Pinus sylvestris) mikrorakenteen sekä puussa olevan kosteuden aiheuttamien vaikutusten tutkimiseksi. Työssä tutkittiin eri lämpötiloissa käsiteltyjä mäntypuunäytteitä, joita verrattiin vastaaviin käsittelemättömiin näytteisiin. Veden ja metaanin diffuusiota tutkittiin PGSTE-menetelmällä puun erittäin anisotrooppisen solurakenteen sisältämien huokosten mittojen määrittämiseksi. NMR-kryoporometria- ja -relaksometriamittaukset antoivat tietoa puuhun imeytyneen sidotun ja vapaan veden määrästä ja esiintymisympäristöstä. Kryoporometria-mittausten tuloksista saatiin yläraja sidotun veden esiintymispaikkojen koolle, ja kryoporometria- ja relaksometriamittausten tuottaman tiedon yhdistäminen mahdollisti soluseinämien mikrohuokosten koon määrittämisen. Magneettikuvausta käytettiin näytteisiin absorboituneen veden avaruudellisen jakauman määrittämiseen. Käytetyt menetelmät tarjoavat laajan kokonaiskuvan lämpökäsittelyprosessin vaikutuksista puulle. Tämän työn tulokset antavat puutiedettä ja -teollisuutta hyödyttävää uutta tietoa lämpökäsitellyn männyn mikrorakenteesta sekä sen suhteesta kosteuteen. Väitöskirja myös osoittaa käytettyjen NMR-menetelmien soveltuvan hyvin puun tutkimiseen. Tämän tutkimuksen myötä kehitettyjen menetelmien avulla voidaan määrittää mm. optimaalinen lämpökäsittelylämpötila, joka on riittävän korkea haluttujen ominaisuuksien kannalta aiheuttamatta kuitenkaan puun mikrorakenteen hajoamista
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Ayala, Julio Enqrique II. "A 200-MHz fully-differential CMOS front-end with an on-chip inductor for magnetic resonance imaging." Texas A&M University, 2005. http://hdl.handle.net/1969.1/4729.
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Recently, there is a growing interest in applying electronic circuit design for
biomedical applications, especially in the area of nuclear magnetic resonance (NMR).
NMR has been used for many years as a spectroscopy technique for analytical chem-
istry. Previous studies have demonstrated the design and fabrication of planar spiral
inductors (microcoils) that serve as detectors for nuclear magnetic resonance mi-
crospectroscopy.
The goal of this research was to analyze, design, and test a prototype integrated
sensor, which consisted of a similar microcoil detector with analog components to
form a multiple-channel front-end for a magnetic resonance imaging (MRI) system to
perform microspectroscopy. The research has succeeded in producing good function-
ality for a multiple-channel sensor. The sensor met expectations compared to similar
one-channel systems through experiments in channel separation and good signal-to-
noise ratios.
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Randtke, Edward Alexander. "Development and Evaluation of Exchange Rate Measurement Methods." Diss., The University of Arizona, 2013. http://hdl.handle.net/10150/314652.
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Exchange rate determination allows precise modeling of chemical systems, and allows one to infer properties relevant to tumor biology such as enzyme activity and pH. Current exchange rate determination methods found via Contrast Enhanced Saturation Transfer agents are not effective for fast exchanging protons and use non-linear models. A comparison of their effectiveness has not been performed. In this thesis, I compare the effectiveness of current exchange rate measurement methods. I also develop exchange rate measurement methods that are effective for fast exchanging CEST agents and use linear models instead of non-linear models. In chapter 1 I review current exchange rate measurement methods. In chapter 2 I compare several of the current methods of exchange rate measurement, along with several techniques we develop. In chapter 3 I linearize the Quantifying Exchange through Saturation Transfer (QUEST) measurement method analogously to the Omega Plot method, and compare its effectiveness to the QUEST method. In chapter 4, I compare the effectiveness of current exchange rate theories (Transition State Theory and Landau-Zener theory) in the moderate coupling regime, and propose our own combined Eyring-Landau-Zener theory for this intermediate regime. In chapter 5 I discuss future directions for method development and experiments involving exchange rate determination.
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Amor, Nadia [Verfasser]. "Novel methods and applications of NMR and MRI : low-power RF excitation and hyperpolarized xenon-129 / Nadia Amor." Aachen : Hochschulbibliothek der Rheinisch-Westfälischen Technischen Hochschule Aachen, 2012. http://d-nb.info/1021937592/34.
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Bush, Isabelle. "NMR studies of enhanced oil recovery core floods and core analysis protocols." Thesis, University of Cambridge, 2019. https://www.repository.cam.ac.uk/handle/1810/290145.
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With conventional oil reserves in decline, energy companies are increasingly turning to enhanced oil recovery (EOR) processes to extend the productive life of oilfield wells. Laboratory-scale core floods, in which one fluid displaces another from the pore space of a rock core, are widely used in petroleum research for oilfield evaluation and screening EOR processes. Achieving both macro- and pore-scale understandings of such fluid displacement processes is central to being able to optimise EOR strategies. Many of the mechanisms at play, however, are still poorly understood. In this thesis nuclear magnetic resonance (NMR) has been used for quantitatively, non-invasively and dynamically studying laboratory core floods at reservoir-representative conditions. Spatially-resolved relaxation time measurements (L-T1-T2) have been applied to studying a special core analysis laboratory (SCAL) protocol, used for simulating reservoir oil saturations following initial oil migration (primary drainage) and characterising core samples (capillary pressure curves). Axial heterogeneities in pore filling processes were revealed. It was demonstrated that upon approaching irreducible water saturation, brine saturation was reduced to a continuous water-wetting film throughout the pore space; further hydrocarbon injection resulted in pore pressure rise and wetting film thinning. L-T1-T2 techniques were also applied to a xanthan gum polymer-EOR flood in a sandstone core, providing a continuous measurement of core saturation and pore filling behaviours. A total recovery of 56.1% of the original oil in place (OOIP) was achieved, of which 4.9% was from xanthan. It was demonstrated that deposition of xanthan debris in small pores resulted in small-pore blocking, diverting brine to larger pores, enabling greater oil displacement therein. L-T1-T2, spectral and pulsed field gradient (PFG) approaches were applied to a hydrolysed polyacrylamide (HPAM)-EOR flood in a sandstone core. A total recovery of 62.4% of OOIP was achieved, of which 4.3% was from HPAM. Continued brine injection following conventional recovery (waterflooding) and EOR procedures demonstrated most moveable fluid saturation pertained to brine, with a small fraction to hydrocarbon. Increases in residual oil ganglia size was demonstrated following HPAM-EOR, suggesting HPAM encourages ganglia coalescence, supporting the "oil thread/column stabilisation" mechanism proposed in the literature. NMR relaxometry techniques used for assessing surface interaction strengths (T1/T¬2) were benchmarked against an industry-standard SCAL wettability measurement (Amott-Harvey) on a water-wet sandstone at magnetic field strengths comparable to reservoir well-logging tools (WLTs). At 2 MHz, T1/T2 was demonstrated to be weakly sensitive to the core wettability, although yielded wettability information at premature stages of the Amott-Harvey cycle. This suggests the potential for NMR to deliver faster wettability measurements, in SCAL applications or downhole WLT in situ reservoir characterisation.
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Fuhrer, Erwin [Verfasser], and J. G. [Akademischer Betreuer] Korvink. "Advanced interfaces for biomedical engineering applications in high- and low field NMR/MRI / Erwin Fuhrer ; Betreuer: J. G. Korvink." Karlsruhe : KIT-Bibliothek, 2019. http://d-nb.info/1195049161/34.
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Cassidy, Maja. "Hyperpolarized Silicon Particles as In-vivo Imaging Agents." Thesis, Harvard University, 2012. http://dissertations.umi.com/gsas.harvard:10649.
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This thesis describes the development of hyperpolarized silicon particles as a new type of magnetic resonance imaging (MRI) agent. Silicon particles are inexpensive, non-toxic, biodegradable, targetable, and have unique physical properties that lead to extremely long nuclear polarization times. The \(^{29}Si\) nuclei are hyperpolarized by low temperature dynamic nuclear polarization using naturally occurring defects at the particle surface and directly imaged using \(^{29}Si\) MRI. The imaging window achievable is several orders of magnitude longer than other hyperpolarized imaging agents. The technique requires no additional imaging agent to be incorporated into the silicon, and so toxicity complications are reduced. The construction of a system for low temperature dynamic nuclear polarization and a NMR spectrometer for studying the nuclear polarization dynamics in silicon particles is described. Room temperature nuclear spin relaxation \((T_1)\) times are investigated for a variety of silicon particles spanning five orders of magnitude in mean diameter, from 10nm nanoparticles to mm-scale granules. The nuclear \(T_1\) times of all Si particles are found to be long, ranging from many minutes to several hours at room temperature. \(T_1\) is found to be a function of particle size, dopant concentration, synthesis method and crystallinity. A core-shell model to describe the electron and nuclear spin dynamics in the particles is developed. The decay in nuclear hyperpolarization is studied as a function of ambient magnetic field and temperature, demonstrating that the long spin relaxation times persist despite changing environmental conditions. A new technique is reported for enhancing the dynamic nuclear polarization in silicon particles using modulated microwave irradiation. A theoretical model for understanding this enhanced polarization process is developed. As well as providing an efficient mechanism for polarizing the \(^{29}Si\) nuclei within the particle, the surface defects are also found to be efficient at polarizing \(^1H\) nuclei in frozen solutions surrounding the particles. Several in-vivo applications of hyperpolarized \(^{29}Si\) MRI are demonstrated, including gastrointestinal imaging, intravenous imaging and mapping blood flow in a tumor. The spin relaxation rates are found to be unaffected by surface functionalization, the particles tumbling in solution, or the in-vivo environment.Engineering and Applied Sciences
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Javed, M. A. (Muhammad Asadullah). "Advanced liquid and gas NMR methods for probing topical materials." Doctoral thesis, Oulun yliopisto, 2019. http://urn.fi/urn:isbn:9789526222493.
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Abstract The present thesis exploits advanced liquid and gas NMR methods for the characterization of various interesting materials. The methods used to study the structural properties of thermally modified wood, ionic liquids, cements, shales, and porous organic cages include MRI, NMR cryoporometry, Laplace NMR, multidimensional Laplace NMR, as well as ¹²⁹Xe and ¹⁹F NMR. The commonality factor in all the studies is the usage of either inherent or introduced liquid or gas molecules to probe the topical materials. The MRI method was utilized to visualize the water absorption phenomena in the thermally modified pine wood. High-resolution images made it possible to observe the spatial distribution of free water and the changes in the rate of absorption of water in wood samples modified at different temperatures. The images also helped to resolve the individual resin channels. T₂ maps enabled us to observe the changes in the relaxation values of free water in thermally modified wood as compared to their unmodified reference wood samples. The multidimensional Laplace NMR methods were exploited to study the structural and dynamical properties of a novel halogen-free, boron-based ionic liquid (hf-BIL). NMR self-diffusion (D) experiments showed the presence of two coexisting dynamic phases in hf-BIL. Multidimensional D − T₂ correlation experiments made it possible to determine the T₂ relaxation times of the slow and fast diffusing phases. T₂ − T₂ relaxation exchange measurements allowed quantifying the exchange rates of anions and cations between the phases. Moreover, the theoretical modeling of the experimental data revealed that the slow diffusing phase was composed of anion-cation aggregates, while the fast diffusing phase was comprised of free anions and cations. ¹²⁹Xe NMR analysis of the xenon adsorbed in the cements and shales helped us to determine their porous structures. The method exploits the high sensitivity of the chemical shift of ¹²⁹Xe to its local environment. The chemical shift value of ¹²⁹Xe enabled us to estimate the size of the mesopores in the cement samples. The exchange spectroscopy (EXSY) measurements were used to determine the exchange rates between the free gas and mesopores of the cement samples. ¹²⁹Xe NMR spectra of the shale samples provided information about pore sizes and paramagnetic compounds. ¹H NMR cryoporometry measurements of the shale samples immersed in acetonitrile made it possible to analyze the pore size distribution ranging from 10 to over 100 nm. Moreover, T₂ − T₂ exchange measurements helped us to quantify the exchange rates of acetonitrile in the shale samples. Xenon and SF₆ were used as internal reporters to gain versatile information on adsorption phenomena in the cage and window cavities of the crystalline porous organic cages. ¹²⁹Xe NMR analysis of the adsorbed xenon helped us to determine the diffusion coefficients and activation energy of diffusion as well as thermodynamic parameters. With the help of T₂ relaxation time values, it was possible to estimate the exchange rates between cage and window cavities. Chemical exchange saturation transfer (CEST) experiments resolved a window cavity site, which arises from crystal defects in porous organic cages. In addition, ¹⁹F NMR analysis made it possible to estimate the relaxation rates and diffusion coefficients of SF₆ gas in porous organic cages. Modelling of the T₁, T₂ and diffusion data confirmed that the cage to window exchange is the completely dominating mechanism for ¹²⁹Xe T₂ relaxation. T₁ relaxation is dominated by diffusion modulated dipole-dipole relaxation (DDinter) and chemical shift anisotropy (CSA) relaxation due to local cavity mobility. Whereas, in case of SF₆ T₂ data, the dominating mechanism is diffusion modulated dipole-dipole relaxation and for T₁ the local tumbling of SF₆ in cage cavity is the key dynamics behind the dipole-dipole and CSA mechanismsOriginal papers The original publications are not included in the electronic version of the dissertation. Javed, M. A., Kekkonen, P. M., Ahola, S., & Telkki, V.-V. (2015). Magnetic resonance imaging study of water absorption in thermally modified pine wood. Holzforschung, 69(7), 899–907. https://doi.org/10.1515/hf-2014-0183 Javed, M. A., Ahola, S., Håkansson, P., Mankinen, O., Aslam, M. K., Filippov, A., … Telkki, V.-V. (2017). Structure and dynamics elucidation of ionic liquids using multidimensional Laplace NMR. Chem. Commun., 53(80), 11056–11059. https://doi.org/10.1039/c7cc05493a http://jultika.oulu.fi/Record/nbnfi-fe2017102750335 Javed, M. A., Komulainen, S., Daigle, H., Zhang, B., Vaara, J., Zhou, B., & Telkki, V.-V. (2019). Determination of pore structures and dynamics of fluids in hydrated cements and natural shales by various ¹H and ¹²⁹Xe NMR methods. Microporous and Mesoporous Materials, 281, 66–74. https://doi.org/10.1016/j.micromeso.2019.02.034 http://jultika.oulu.fi/Record/nbnfi-fe2019041712678 Komulainen, S., Roukala, J., Zhivonitko, V. V., Javed, M. A., Chen, L., Holden, D., … Telkki, V.-V. (2017). Inside information on xenon adsorption in porous organic cages by NMR. Chemical Science, 8(8), 5721–5727. https://doi.org/10.1039/C7SC01990D http://jultika.oulu.fi/Record/nbnfi-fe201709288804 Håkansson, P., Javed, M. A., Komulainen, S., Chen, L., Holden, D., Hasell, T., … Telkki, V.-V. (2019). NMR relaxation and modelling study of the dynamics of SF₆ and Xe in porous organic cages. Manuscript
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Williamson, Kathryn Maxine Williamson. "NMR Spectroscopy as a Robust Tool for the Analysis of Lipids in Fish Oil Supplements and Coffee." The Ohio State University, 2018. http://rave.ohiolink.edu/etdc/view?acc_num=osu1523978049728289.
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Adhikari, Rajan Deep. "MRI T2 Signal Changes Indicate Tau Pathophysiology in a Murine Alzheimer's Disease Model." BYU ScholarsArchive, 2017. https://scholarsarchive.byu.edu/etd/6944.
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Pathogenesis, diagnosis and treatment, the essential domains in medical practice, seem helpless to address Alzheimer's disease (AD). With a huge mortality rate, it is looming and threatening the socioeconomic barrier. Despite many different studies, the pathogenesis of AD remains inconclusive. However, growing numbers of studies suggest oxidative stress to contribute to the initiation and progression of AD. We propose an iron hypothesis: iron mediated oxidative damage by reactive oxygen species (ROS), which induces protective roles of amyloid beta and hyper-phosphorylated tau (HP-tau) to sequester iron and limit the disease. We propose to study such mechanism using transgenic mice models for AD, inducing oxidative stress to elevate intracellular iron, and analyze its co-localization with proteins using Magnetic Resonance Imaging (MRI), 1H Nuclear Magnetic Resonance (NMR) spectroscopy and Western blot. We report three primary findings: 1) a significant loss in T2 signal over bilateral hippocampi of transgenic mice compared to the wild types (WT) by three months, corresponding to early disease and the ability of proteins to sequestration iron. Ability of rescue treatments to impede disease progression reflected as preserved T2 signal intensities over these areas throughout our study period of nine months. 2) Concentration of zinc and its dual role in the presence or absence of oxidative stress reflected as loss of 1H NMR T2 measurement showed that higher concentrations of zinc were neuro protective when there was an active oxidative stress inducing condition, but neurotoxic and promote oxidative damage in normal condition. And 3) Different strains of mice, according to their transgene, expressed various proteins associated with AD. However, these expressions were in accordance with our iron-hypothesis.
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Julínek, Michal. "Numerické modelování vlivu magnetické susceptibility na MR obrazy." Master's thesis, Vysoké učení technické v Brně. Fakulta elektrotechniky a komunikačních technologií, 2010. http://www.nusl.cz/ntk/nusl-218616.
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Wang, Xiaoling. "MRI and NMR Investigations of Transport in Soft Materials and Explorations of Electron-Nuclear Interactions for Liquid-State Dynamic Nuclear Polarization." Diss., Virginia Tech, 2015. http://hdl.handle.net/10919/75067.
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The first part of this dissertation (Chapters 1 to 4) describes the use of magnetic resonance techniques for polymeric material characterizations in solutions, with emphasis on methods utilizing magnetic field gradients - magnetic resonance imaging (MRI) and pulsed-field-gradient (PFG) NMR. The second part (Chapter 5) presents enhancements to dynamic nuclear polarization, an intensity enhancement approach for magnetic resonance techniques.
In Chapter 2, I illustrate a characterization method to quantify free polymer chain content in a polymer/DNA complex (polyplex) formulation via one-dimensional proton NMR experiments. This assessment of free polymer quantity has critical impacts on in vivo gene transfection efficiency, cellular uptake, as well as toxicity of polycationic gene delivery vectors. Specifically, I investigated the complexation properties of three different polymeric "theranostic" agents, which combine an imaging functionality on the polymer as well as a DNA/RNA complexation component. These agents are under development to allow real time clinical monitoring of drug delivery and efficacy using MRI. Our NMR method provides simple and quantitative assessment of free and DNA-complexed polymers, including the actual polymer amine to DNA phosphate molar ratio (N/P ratio) within polyplexes. The NMR results are in close agreement with the stoichiometric number of polymer/DNA binding obtained by isothermal titration calorimetry. The noninvasive nature of this method allows broad application to a range of polyelectrolyte coacervates, for understanding and optimizing polyelectrolyte complex formation.
Chapter 3 demonstrates a time-resolved MRI approach for measuring diffusion of drug-delivery polymeric nanoparticles on mm to cm scales as well as monitoring nanoparticle concentration distribution in bulk biological hydrogels. Our results show that as the particle size and surface charge become larger, collagen gel at tumor relevant concentration (1.0 wt.%) presents a more significant impediment to the diffusive transport of negatively charged nanoparticles. These results agree well with those obtained by fluorescence spectroscopies (neutral or slightly positively charged diffusing particles) as well as the proposed electrostatic bandpass theory of tumor interstitium (negatively charged particles). This study provides fundamental information for the design of polymeric theranostic vectors and carries implications that would benefit the understanding of nanoparticle transport in solid tumors. Furthermore, this work takes a significant step toward developing quantitative and real time in vivo monitoring of clinical drug delivery using MRI.
Chapter 4 addresses the application of PFG-NMR for the determination of weight-average molar mass (Mw) for polyanions that have anti-HIV activity through the measurement of polymer diffusion coefficients in solutions. The effective characterization of molecular weights of polyelectrolytes has been a general and growing problem for the polymer industry, with no clear solutions in sight. In this study, we obtained the molar masses (Mw) for two series of sulfonated copolymers using sodium polystyrene sulfonate samples as molecular weight standards. PFG-NMR has notable advantages over conventional techniques for the characterization of charged polymers and shows great promise for becoming an effective alternative to chromatography methods.
Chapter 5 is devoted to experimental and theoretical studies of liquid state dynamic nuclear polarization (DNP) via the Overhauser effect. Based on the adventurous work done by previous Dorn group members, we show that for 1H-nuclide-containing systems, the dipolar DNP enhancement can be significantly improved by decreasing the correlation time of the interaction by utilizing a supercritical fluid (SF CO2) which allows for greater dipolar enhancements at higher magnetic fields. For molecules containing the ubiquitous 13C nuclide, we show that previously unreported sp hybridized (H-C) alkyne systems represented by the phenylacetylene-nitroxide system exhibit very large scalar-dominated enhancements. Furthermore, we show for a wide range of molecular systems that the Fermi contact interaction can be computationally predicted via electron-nuclear hyperfine coupling and correlated with experimental 13C DNP enhancements. For biomedical applications, the enhancement of metabolites in SF CO2 followed by rapid dissolution in water or biological fluids is an attractive approach for future hyperpolarized NMR and MRI applications. Moreover, with the aid of density functional theory calculations, solution state DNP provides a unique approach for studying intermolecular weak bonding interaction of solutes in normal liquids and SF fluids.Ph. D.
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笠井, 純. "超流動3He-Aにおけるカイラルドメイン構造の可視化." Kyoto University, 2019. http://hdl.handle.net/2433/236601.
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Duarte, Mendes Catita Leonor. "Contribution of NMR and Raman imaging for modeling and rationalization of the impregnation process of metallic precursors in porous media." Thesis, Lyon, 2017. http://www.theses.fr/2017LYSE1262/document.
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Cette thèse s’inscrit dans le domaine de la catalyse hétérogène pour des applications en raffinage et en pétrochimie. Plus particulièrement, nous avons choisi d’étudier le cas des catalyseurs d’hydrotraitement largement utilisés dans les procédés de conversion du pétrole en carburant. Ces catalyseurs sont constitués d’une phase métallique sulfurée supporté sur un support poreux inorganique.Dans ce travail, nous nous sommes particulièrement intéressés à la compréhension et la modélisation de la première étape de préparation d’un catalyseur d’hydrotraitement : l’étape d’imprégnation. Une méthodologie innovante basée sur la technique d’imagerie RMN qui permet d’observer operando le transport des précurseurs métalliques dans le support et sur la technique d’Imagerie Raman a été développée. Les résolutions spatiales et temporelles obtenues ont permis de valider cette méthodologie pour caractériser l’étape d’imprégnation en termes de phénomènes physiques (capillarité et diffusion) et chimiques (interaction de surface) et pour identifier les descripteurs clés de cette étape.En conclusion, ces travaux permettront un meilleur contrôle de l'étape d'imprégnation et donc du profil de distribution de la phase active, ce qui aura une forte répercussion sur la performance catalytiqueThe objective of this work is to characterize the impregnation step in terms of physical phenomena (capillarity and diffusion) and chemical phenomena (surface interaction) in order to identify the key descriptors of this step in order to improve the preparation hydrotreating catalysts. This involves monitor spatial and temporally the transport of the species in the impregnation solution within the porosity, more particularly in the case of Ni(Co)MoP/?-Al2O3 catalysts preparation.An original MRI approach has been developed to follow in-situ the impregnation step from a solution of mixed nature with more than one metal precursor in the presence of an additive. MRI provides access to the spatial distribution of all species within the catalyst with a spatial resolution of 39 × 39 µm. Raman imaging allows an identification of the chemical nature of the species in solution with a spatial resolution of 16.2 × 16.2 µm.First, the phenomena involved in the impregnation of model solutions composed of Ni (or Co), were studied by modifying the parameters of the solution. These experiments were then used as the basis for the development of a mathematical model to rationalize the impregnation step. In a second part, this study was extended to the preparation of hydrotreatment catalysts. Several phenomena have been evaluated here, notably the impact of the presence of phosphorus on the transport of Mo species, possible competition of adsorption between P, Co and Mo and the effect of the presence of citric acid.This study allows a better control of the impregnation step and thus of the distribution profile of the active phase, which has an impact on the catalytic performance
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Jeništa, Petr. "Optimalizace metody měření magnetické susceptibility." Master's thesis, Vysoké učení technické v Brně. Fakulta elektrotechniky a komunikačních technologií, 2011. http://www.nusl.cz/ntk/nusl-218874.
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The aim of this thesis is measure the specimens placed in field of MR tomograph, the measured data to evaluace the process and measurement errors. The theoretical part is focused on describing basic parameters of magnetic field, commissioning some older methods of measurement and design methods for the measurement of samples not issuing MR signal. There is performed modeling for the proposed Metod and the 1D, 2D and 3D environments using COMSOL Multiphysics. The practical part is the measurements samples in the tomograph the Institute of Scientific Instruments Academy of Science in Brno. The measured data are processed in Marevisi and Matlab programs. The MATLAB program is written for processing, analysis and data evaluation, after which it is possible to determine the value of the magnetic susceptibility of the selected samples. In conclusion of the work is the quantification accuracy of measurements.
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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/.
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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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Geng, Jianzhao. "Flux pumping for high-Tc superconducting (HTS) magnets." Thesis, University of Cambridge, 2017. https://www.repository.cam.ac.uk/handle/1810/268221.
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High Tc superconductors are enabling in the generation of extremely high magnetic fields. Flux pumping is a promising technology which can be used to operate HTS magnets without significant loss. In this decade, several HTS flux pumps based on travelling magnetic waves have been developed, yet their physics is still unclear. This thesis established a framework in the area of flux pumping for HTS coils. It revealed the underlying physics of existing travelling wave flux pumps, which is an important theoretical contribution. Based on the thorough understanding of flux pumping mechanism, the author proposed two novel types of flux pumps. The new inventions make flux pumping much easier, more controllable, and much less energy consuming. These flux pumps may promote the future applications of HTS magnets. This thesis can be a guidebook for researchers and engineers in developing flux pumps.
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Blanc, Jordy. "Modifications métaboliques lors de l'activation cérébrale : suivi par spectroscopie de résonance magnétique nucléaire du proton et du carbone 13." Thesis, Bordeaux, 2018. http://www.theses.fr/2018BORD0336/document.
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Le lactate est considéré comme un métabolite déchet depuis de très nombreuses années. Cependant, cette vision semble revisitée depuis quelques temps, avec l'apparition de la notion de glycolyse aérobie et de navettes lactate dans différents types cellulaires (muscle, cerveau et sperme). Concernant le cerveau, des études in vitro, ex vivo et in vivo réalisées ces 20 dernières années ont montré, d'une part, que les astrocytes produisent du lactate et d’autre part que le lactate pouvait être un substrat énergétique pour le système nerveux central (SNC), et plus particulièrement les neurones. Cette notion de navette lactate entre astrocyte et neurone a été proposée pour la première fois en 1994 par Pellerin et Magistretti (ANLS, pour astrocyte-neuron lactate shuttle). Malgré de nombreuses recherches depuis, l'existence d'un transfert net de lactate entre les astrocytes et les neurones n'a toujours pas pu être démontrée in vivo. Dans cet optique, la visualisation de la production de lactate in vivo dans le cerveau activé est essentielle. Le rôle des transporteurs au lactate, MCTs (Monocarboxylate Transporters), dans la détection de ce signal est également un point capital. L’objectif de cette thèse a été de développer la spectroscopie de RMN in vivo localisée dans le cortex somato-sensoriel du rat en condition d’activation cérébrale. Dans un premier temps, un travail de développement a été effectué afin de mettre au point le protocole de stimulation neuronale et d’obtenir un rapport signal sur bruit suffisant pour pouvoir quantifier de façon fiable le lactate. Une fois le protocole établi sur des rats contrôles, l’étude a été réalisée sur des rats modifiés génétiquement et réprimés pour le MCT, soit neuronal, soit astrocytaire. Le but était de déterminer si ce partenaire clef de l’ANLS avait une influence sur les fluctuations de lactate lors de l'activation cérébrale. En plus de la spectroscopie proton in vivo et de l’IRM fonctionnelle, des études de RMN du carbone-13 ont été réalisées ex vivo. Le résultat majeur de cette thèse montre qu’en l’absence du transporteur de lactate neuronal, non seulement on perd l’augmentation de lactate lors de la stimulation cérébrale mais on perd également le signal BOLD sur l’IRMf. Ce résultat suggère, et ce pour la première fois, que l’activité neuronale est fortement dépendante du transporteur au lactateLactate has been considered as a waste metabolite for many years. However, this vision has been reconsidered recently, with the appearance of the notion of aerobic glycolysis and lactate shuttles in different cell types (muscle, brain, and sperm). Concerning the brain, in vitro, ex vivo and in vivo studies carried out over the last 20 years have shown, on the one hand, that astrocytes produce lactate and, on the other hand, that lactate can be an energetic substrate for the central nervous system (CNS), and more particularly neurons. This lactate shuttle between astrocyte and neuron was first proposed in 1994 by Pellerin and Magistretti (called ANLS, for astrocyte-neuron lactate shuttle). Despite many studies since then, the existence of a net transfer of lactate between astrocytes and neurons has still not been demonstrated in vivo. In this regard, visualization of lactate production in vivo in the activated brain is essential. The role of lactate transporters, MCTs (Monocarboxylate Transporters), in detecting this signal is also a key issue. The objective of this thesis was to develop in vivo NMR spectroscopy located in the somato-sensory cortex of rats under brain activation conditions. First, experiments were carried out to develop the neural stimulation protocol and to obtain a sufficient signal-to-noise ratio to be able to quantify lactate. Once the protocol was established on control rats, the study was performed on genetically modified rats and down-regulated for MCT, either neuronal or astrocytic. The aim was to determine whether this key partner of the ANLS has an influence on lactate fluctuations during brain activation. In addition to in vivo proton spectroscopy and functional MRI, carbon-13 NMR studies were performed ex vivo. The major result of this thesis shows that in the absence of the neuronal lactate transporter, not only is the increase in lactate lost during brain stimulation but the BOLD signal on the fMRI is also lost. This result suggests, for the first time, that neural activity is highly dependent on the lactate transporter
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Wang, Biyun. "Application des analyses par RMN/IRM et gammadensimétrie à la réparationdu béton âgé : étude des transferts hydriques, de l’impact sur l’hydratation du mortierde réparation et sur la durabilité du béton réparé." Thesis, Paris Est, 2015. http://www.theses.fr/2015PESC1159/document.
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La zone d'enrobage des aciers des structures en béton armé est soumise au cours de la vie de l'ouvrage à l'action de divers agents agressifs (ions chlorure, dioxyde de carbone, etc.) qui sont susceptibles d'entraîner la corrosion des armatures. Dans le cadre de la maintenance de l'ouvrage, une réparation du béton dégradé est généralement imposée afin d'assurer l'intégrité et la sécurité de la structure, et d'en allonger la pérennité. Cette étude s'attache à explorer les transferts hydriques qui limitent l'efficacité de la réparation au cours de l'hydratation du mortier de réparation. L'évolution microstructural et les profils hydriques sont obtenus par des techniques non-destructives comme l'imagerie résonance magnétique (IRM) et la gamma-densimétrie (GD) depuis très jeune âge à 28 jours. La durabilité du béton réparé est concernée. L'effet du séchage est évité dans cette étude. Le mortier isolé d'une même formulation est préparé pour la comparaison du comportement d'hydratation avec le mortier de réparation. Des diverses techniques classiques aident de compléter les résultats obtenus par IRM et GD. Donc le système de réparation est désigné. Les transferts hydriques à l'interface sont visualisés pendant la réparation (0 - 28 jours), afin de permettre une exploration en profondeur sur les mécanismes des couplages physico-chimiques. La réparation plus efficace donc est déterminée par cette méthodologie, en étudiant divers matériaux de réparation, divers états de support (saturé ou séché) et divers conditions environnementaux, etc. De plus, après la réparation (1 - 2 mois), la porosité totale est mesurée par GD ou la porosimétrie par l'intrusion de mercure (PIM). La distribution poreuse est aussi examinée par PIM selon la hauteur du système de réparation. Les indicateurs de durabilité (Cl- et CO2) après la réparation (> 2 mois) présentent l'empêchement de pénétration des ions chlorures et un effet non-évident pour la pénétration du dioxyde de carbone. L'évolution est suivie au fur et à mesure pendant la pénétration, afin d'explorer l'efficacité de la réparation qui s'adresse à une vie de service prolongée. Cette méthodologie pourra être appliquée aussi sur des autres systèmes, où il existe des transferts hydriques. Par exemple, une couche de protection en Béton Fibré à Ultra-haute Performance (BFUHP) sur le béton ordinaire. En conclusion, cette méthodologie en combinant des techniques non-destructifs et destructifs, est un outil d'étudier le système de réparation par un moyen systématique et quantitatif. C'est intéressant de comparer des divers cas. L'efficacité de réparation est étudiée afin d'assurer une durabilité à long termeThe coating area of steel reinforced concrete structures is subjected during service life time to various aggressive agents (carbon dioxide, chloride ions, etc.), which causes corrosion of steel rebars. Concerning the maintenance, repair works of degraded concrete cover are generally imposed to ensure its integrity and structural safety, and to extend long-term durability. This research aims in exploring moisture transfers which limit the efficiency of repair work during mortar hydration. Microstructure evolution and water profiles are obtained by non-destructive techniques such as Magnetic Resonance Imaging (MRI) and Gamma-Ray Attenuation (GRA) since casting until 28 days. The durability of repaired concrete is involved after the repair procedure. The effect of drying is avoided in this research. Sealed mortar of the same formula is prepared to compare its hydration performance with the repair mortar. Various conventional techniques help to supplement the results obtained by MRI and GRA. The configuration of designed repair systems is shown. Moisture transfers at the interface between the repair mortar and the old concrete are investigated during the repair procedure (0 - 28 days), which allows exploring the mechanisms of physico-chemical couplings. Efficient repair work can be determined for various repair materials, various substrates (initially-saturated or initially-dried), various environmental conditions, etc. Furthermore, total porosity is measured by GRA or by Mercury Intrusion Porosimetry (MIP) after the repair procedure (1 - 2 months). Pore size distribution (PSD) is also investigated by MIP at different positions within the repair systems. Durability indicators (Cl- and CO2) after the repair procedure (> 2 months) present a prevention of chloride penetration and a non-evident influence on carbonation. Evolution is followed during penetration, in order to explore repair efficiency during prolonged service life time. This methodology could also be applied on various systems where exist moisture transfers. For example, a protective layer of Ultra High Performance Fiber-Reinforced Concrete (UHPFRC) on conventional concrete. In conclusion, this methodology is a tool to investigate the repair systems in a systematic and quantitative way, by combining non-destructive and destructive techniques. It is interesting to compare aforementioned systems. Repair efficiency is investigated in order to ensure a long-term durability
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Hamraoui, Khalid. "Contrôle quantique de la rotation moléculaire et de processus de Résonance Magnétique Nucléaire." Thesis, Bourgogne Franche-Comté, 2019. http://www.theses.fr/2019UBFCK020/document.
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L’objectif de cette thèse est d’appliquer des méthodes de contrôle quantique pour manipuler la dynamique rotationnelle de molécules et améliorer l’efficacité de processus en résonance magnétique nucléaire.Ces techniques ont été utilisées théoriquement et expérimentalement pour contrôler l’orientation d’une molécule toupie symétrique à l’aide de champ THz. Cette étude a été généralisée à une grande distance d’interaction entre le champ et l’échantillon. Dans ce cas, la molécule ne peut plus être considérée comme isolée. Nous avons également montré jusqu'à quel point l’évolution temporelle du degré d’orientation pouvait être mise en forme. Des méthodes de contrôle optimal ont permis de déterminer le champ THz pour atteindre cet état à la fois à températures nulle et non-nulle. Un autre chapitre présente un nouvel algorithme d’optimisation pour les dynamiques périodiques. Cet algorithme est appliqué à la maximisation du SNR en RMN. Un dernier chapitre est dédié à un article de vulgarisation sur l’effet de la raquette de tennis. Cet effet géométrique peut être observé dans tout corps rigide suffisamment asymétriqueThe goal of this thesis is to apply quantum control techniques to manipulate molecular rotation and to enhance the efficiency of processes in Nuclear Magnetic Resonance.These techniques have been used theoretically and experimentally to control the orientation of a symmetric top molecule by means of THz laser fields. This study has been extended to the case of a long interaction distance between the field and the sample. In this case, the molecule cannot be approximated as isolated. We have also shown the extend to which the time evolution of the degree of orientation can be shaped. Optimal control techniques were used to design the THz field which allows to reach the corresponding dynamics, both at zero and non zero temperatures. Another chapter proposes a new optimization algorithm in the case of periodic quantum dynamics. We apply this algorithm to the maximization of the SNR in NMR. A last chapter is dedicated to a popular paper about the tennis racket effect. This geometric effect can be observed in any asymetric rigid body