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 26 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 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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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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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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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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Fabrication and Device Applications of Self Assembled Nanostructures
… The phase decoheres in a time known as the transverse relaxation time or T2 time. We have carried out a measurement of the ensemble-averaged transverse spin relaxation time (T2*) in bulk and few molecules of the organic semiconductor tris-(8-hydroxyquinolinolato aluminum) or Alq3. The Alq3 …
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Synthesis, Characterization and Structure-Property Relationships of Polymer-Stabilized Nanoparticles Containing Imaging and Therapeutic Agents
… the polymer, and substantial increase in the NMR transverse relaxation rates was noted. Controlled clusters of primary iron oxide nanoparticles stabilized by the biodegradable block copolymer, poly(ethylene oxide-b-D,L-lactide) were fabricated by a scalable, rapid precipitation technique using a …
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Developing Magnetic Resonance Based Analytics to Support Continuous Bioprocess
… protein concentration on diffusion coefficients, relaxation times and spectral peak area are explored. The possibility of developing calibration curves for concentration determination are shown through both the use of 1D 1H WATERGATE spectra and the water-proton transverse relaxation rate …
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Characterising Adsorption and Mass Transfer in Porous Media
… been introduced for their prevention. The NMR relaxation behaviour of water saturating the pore space of silica was observed to correlate strongly with independent measurements of the activation energy of dehydroxylation, thus establishing NMR relaxometry as a tool for directly probing the …
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Application of MRI and low-field NMR in biopharmaceutical development
… a protein sample was developed, called Diffusion-Relaxation water NMR (DRwNMR). This utilises the water proton signal, exploiting the change in transverse relaxation rate [R₂(¹H₂O)] and diffusion coefficient [D(¹H₂O)] to give this information. Importantly, the DRwNMR method overcomes the inherent …
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