Global ETD Search
Search theses and dissertations gathered from participating repositories worldwide. Every result links back to the library that holds it. No account is needed.
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Showing 1 to 20 of 33 for “"Transverse relaxation"”.
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Transverse Relaxation Times of Major Brain Metabolites in Gulf War Illness
… changes in metabolite concentrations and T2 relaxation times in GWI. This protocol generated reproducible MRS results, with small inter- and intrasubject variability, on normal controls in the basal ganglia region using single voxel spectroscopy. The second aim of this thesis was to compare …
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Spin coherence and optical properties of alkali-metal atoms in solid parahydrogen
… spectra, optical pumping,and longitudinal relaxation of spins in the ground state. We find a large variation in the magnitude of the ground state spin polarization from one alkali species to another; however, all the species exhibit similar longitudinal relaxation times on the order of 1 s. …
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A new approach to the study of surface phenomena, measurements of diffusion rates, intermolecular distances and electronic properties of CO chemisorbed on supported platinum catalysts by nuclear magnetic resonance
… 4 K to 600 K. He shows that a measurement of transverse relaxation at 77 K can be used to measure relative distances among molecules in the adsorbed layer. His measurements of transverse relaxation and of spin-lattice relaxation are consistent with the geometry of CO layers chemisorbed on …
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NMR of geophysical drill cores with a mobile Halbach scanner
… fast non-destructive measurements of porosity, relaxation time distributions, and estimation of permeability. These properties can be calculated directly from the NMR data using the developed methodology. Any independent measurements of these properties with other methods are not needed. One of …
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Mobile NMR for rock porosity and permeability
… magnetic field. Besides one-dimensional (1D) relaxation measurements which can be performed with all sensors, the second version of the Halbach core-scanner is also suitable for two-dimensional (2D) relaxation measurements on core plugs. 1D transverse relaxation measurements were made on fully …
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NMR characterization of chlorhexidine in lipid-based formulations /
… order parameter profiles, and longitudinal and transverse relaxation times were used to explore the structural phase behaviour of various DMPC/CHG mixtures in the temperature range 5-60°C.
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Magnetic Resonance Microscopy: 1. Four-Dimensional Spectral-Spatial Imaging. 2. Diffusional Effects in Magnetic Resonance Microscopy
… at narrow bandwidths of the order of the transverse relaxation rate, DESIRE results in greatly increased signal-to-noise relative to traditional NMR imaging techniques and has the potential for submicron resolution. Both time-dependent and steady-state simulations and analytic expressions …
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Biomedizinische Anwendungen der NMR-MOUSE
… position of interest. Within a few minutes the transverse relaxation time T2 is measured, which can be correlated to the type of tissue and its condition at the position investigated. The measurement depth can be adjusted from 0 to 5 mm, which allows the examination of not only achilles tendon …
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Non-Invasive Detection of Anaerobic Metabolism in Exercising Muscle Using Proton MRI
… transfer (MT) or other longitudinal relaxation mechanisms. Isolated frog gastrocnemii were treated with iodoacetate (IAA; to inhibit lactate production), NaCN (to maximize lactate production), or left untreated and then performed 60 1s/min maximal isometric contractions. The …
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Hydration and Water Distribution Studies of Heart Muscle by Nuclear Magnetic Relaxation
The multinuclear magnetic relaxation behavior of heart muscle from chicken, pork, and beef is investigated. Nonlinear regression analysis of the $\sp1$H transverse magnetization decay yields the best fit with three exponential components that are likely to correspond to three separate types of …
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Engineered metalloproteins as contrast sensors for molecular fMRI
… device that reversibly enhances NMR transverse relaxation times (T2) by Ca - dependent crosslinking. Second, we show that the T1 contrast effect of a recently proposed family of cytochrome P450-based MRI sensors can be significantly enhanced by substitution of the protein's native …
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Low field NMR for analysis of rubbery polymers
… samples. The NMR measurements were restricted to transverse relaxation of the magnetization and DQ NMR experiments, done on a low field spectrometer (0.5 T) at a proton Larmor frequency of 20 MHz. The measurement temperatures were varied, depending on the glass transition temperature of the …
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Water relations of simple sugar solutions and skim milk powder as studied by nuclear magnetic resonance spectroscopy
… $\sp2$H and $\sp1$H decoupled $\sp{17}$O NMR transverse relaxation rates (R$\sb2$). For all three nuclei, R$\sb2$ increased with increasing sugar concentration with different magnitude and different trends of increases. Comparison of $\sp1$H, $\sp2$H and $\sp{17}$O NMR R$\sb2$ relaxation …
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Profiling of Relaxation Time and Diffusivity Distributions with Low Field NMR
… introduced that allow for the determination of relaxation time or diffusion-relaxation time distributions as a function of sample height. One-dimensional T 2 and D-T 2 profiles can be determined with a low-field Maran Ultra spectrometer by implementing nuclear magnetic resonance imaging …
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Nuclear spin coherence times of HD trapped in solid parahydrogen matrices
… measurements of nuclear spin coherence and relaxation across controlled impurity conditions remain limited. This dissertation describes the design, construction, and operation of an apparatus that addresses the need to improve existing coherence-time measurements. In this dissertation, we …
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Science and history explored by nuclear magnetic resonance
… Proton 1D exchange spectroscopy combined with transverse relaxation measurements offered good insight in the state of water in hydrated SPEEK/SiO2 membranes revealing that concentrations of 5%-10% wt. PEOS could enhance the electrical conductivity of PEM. Hyperpolarized 129Xe NMR spectroscopy …
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Molecular Origins of Phase Stability in Phase-Change Nano-Emulsions for Thermal Energy Storage by NMR Spectroscopy
… of nano-emulsion droplets. <sup>1</sup>H NMR Transverse relaxation times increased at higher shear rates, indicating increased molecular mobility due to shear-induced structural changes.</p> <p>Overall, this dissertation presents the effective and non-invasive applications of NMR spectroscopy, …
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Magnetic resonance microscopy
… at narrow bandwidths of the order of the transverse relaxation rate, DESIRE results in greatly increased signal-to-noise relative to traditional NMR imaging techniques and has the potential for submicron resolution. Both time dependent and steady-state simulations and analytic expressions …
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MRI based cerebral oxygenation measures in humans : technical development for use across lifespan
… effect of residual cerebrospinal fluid signal on transverse relaxation time quantification. The detected change in oxygen extraction fraction in the visual cortex during visual stimulation, demonstrated the technique's suitability for absolute quantitative functional MRI experiments. T2-Relaxation …
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Synthesis and Characterization of Well-Defined Heterobifunctional Polyethers for Coating Magnetite and Their Applications in Biomedicine Resonance Imaging
… agents for MRI imaging. Thus, transverse NMR relaxivities of these complexes were studied as a function of chemical composition and nanostructure size and compared to commercial contrast agents. The amphiphilic polyether-magnetite nanoparticles were shown to be stable in both …
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