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 42 for “"Diffusion measurements"”.
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NMR Studies of Solid-Supercritical Fluid Mixtures and a New Technique for NMR Diffusion Measurements
Solid solubilities of naphthalene in supercritical carbon dioxide have been measured near the upper critical end point of the binary mixture by using a novel, in situ NMR technique. The pressure-temperature trace of the solid-liquid-gas phase line that terminates at the upper critical end point was …
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Microscopic diffusion measurements with nanoporous materials: complementary benefits of infrared microimaging and pulsed field gradient NMR
… on the subject of two microscopic techniques of diffusion measurement, namely infrared (IR) microimaging and pulsed field gradient (PFG) NMR. The dissertation contains mainly five chapters. The first chapter introduces diffusion phenomena in general and concisely explains the importance and the …
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Flow and diffusion measurements on complex fluids using dynamic NMR microscopy : a thesis presented in partial fulfilment of the requirements for the degree of Doctor of Philosophy in Physics at Massey University
… measure the temperature dependence of the self-diffusion coefficient of polystyrene in semi-dilute cyclohexane solutions near the de-mixing transition over a wide range of molar masses. The temperature dependence can be described by a Williams-Landel-Ferry (WLF) equation, characteristic of a …
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Nmr and Polarization Microscopy Studies of Sodium Alkyl Carboxylate Solids and Melts
… and Fourier transform NMR. Both the ('1)H self-diffusion measurements and the ('23)Na spin-lattice relaxation time, T(,1), and quadrupole coupling constant,
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Diffusion of organic liquids : pressure, temperature studies
… cell has been designed and used for self-diffusion measurements at pressures up to 1500 x 10⁵ Nm⁻² and for a temperature range from 283.2 K to 328.2K. It has been shown how the bulk flow that occurs in the cell can be calculated and the diffusion coefficient obtained. Self-diffusion …
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Diffusion of organic liquids : pressure, temperature studies
… cell has been designed and used for self-diffusion measurements at pressures up to 1500 x 10⁵ Nm⁻² and for a temperature range from 283.2 K to 328.2K. It has been shown how the bulk flow that occurs in the cell can be calculated and the diffusion coefficient obtained. Self-diffusion …
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Transport properties of micellar solutions and microemulsions.
… phase diagram was confirmed.Conductivity measurements were made in the isotropic liquid regions of these systems and self-diffusion measurements were made in the isotropic liquid regions of the C[12]E[4]-water and C[13]E[6]-water systems, in order to elucidate the structures of these …
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Magnetic Resonance Studies of Three-Phase Heterogeneous Catalytic Hydrogenation Reactions
… and spatially resolved 2D NMR relaxation and diffusion measurements were used to characterize reaction species. Experiments were carried out on the species in their pure state as bulk liquids and imbibed in the catalyst material (Pd/Al2O3). Single component liquids as well as mixtures were …
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Magnetic resonance diffusion imaging and spectral localization: New methods and their quantitative applications
… interest, in recent years, in the measurement of diffusion of water and metabolites in living systems by magnetic resonance (MR) techniques. Knowledge of the diffusion coefficients of the molecules can yield unique information about microstructure and function of tissue. We have developed a method …
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Diffusion and Evaporation of Nitrogen on Tungsten (100)
Surface diffusion and evaporation from a layer of nitrogen chemisorbed on the (100) plane of tungsten has been examined using Auger spectroscopy. The initial localized deposit required for diffusion measurements in a concentration gradient is created by a highly collimated molecular beam. The …
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Defect Engineering for Controlling Semiconductor Diffusion
… toward the surface and results in increased diffusion. The second mechanism involves direct creation and generation of defects at the surface bonds. We show through self-diffusion measurements in silicon that defect concentrations deep in the semiconductor bulk can be varied controllably over …
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Investigation of material properties by NMR in low and high magnetic fields
… of NMR. The mobile sensors developed lately make measurements possible at remote locations for some historical buildings or measuring rocks at the drilling platform minutes after the extraction. In this work the experiments have been performed at both low and high field. The experiments cover …
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Advanced characterization of transport and microstructural properties in membrane materials
… These modifications impact water and salt diffusion as well as microstructural characteristics in the membrane materials, yet the detailed relationships between membrane performance, processing conditions, and transport properties remain to be fully characterized. Although extensive …
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Learning motion patterns using hierarchical Bayesian models
… similar to learning motion patterns arise. Diffusion Tensor Magnetic Resonance Imaging (DT-MRI) is one of the first methods to visualize and quantify the organization of white matter in the brain in vivo. Using methods of tractography segmentation, one can connect local diffusion …
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Radiation-enhanced diffusion of oxygen-18 in uranium dioxide thin films
Anion radiation enhanced diffusion (RED) and thermal diffusion of a buried 18O tracer layer in thin film UO2 was measured using Secondary-Ion Mass Spectroscopy (SIMS). Thin films were grown using a dedicated magnetron sputtering chamber. Samples were irradiated with 1.8 MeV Kr+ over a temperature …
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Examining the Association between Brain MRI Measures at 7 Tesla and cognition following COVID-19 Infection
… COVID-19 illness and determined whether advanced diffusion magnetic resonance imaging measures within subcortical brain structures of the limbic system were related to neurological, respiratory, psychiatric, and gastric symptoms experienced during the acute phase of illness. Cognitive and …
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Investigating transport of charged nanoparticles by multiphoton fluorescence correlation spectroscopy (MPFCS)
… utilization to probe the effect of charge on the diffusion of quantum dot (QD) nanocrystals in collagen and collagen-hyaluronan (HA) composite gel models of human colon adenocarcinoma (LS174T). The MPFCS system was integrated with a multiphoton laser-scanning microscope (MPLSM) to enable …
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NMR-Studien an grenzflächenaktiven Verbindungen in kosmetisch relevanten Systemen
… The results of the T1 and T2 relaxation time measurements indicate a restricted motion of the molecules which is dependent on the oil droplet size in the emulsions. This was verified by NMR pulsed gradient spin echo (PGSE) self-diffusion measurements on emulsions with different droplet sizes. …
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Probing Transport of Ion Dense Electrolytes using Electrophoretic NMR
… and ion motion. The combination of mobilities measurements and diffusion measurements provides some new insight of ion aggregation. We explore ion transport of ionic liquids inside the ionic polymer Nafion as a function of hydration level. When ionic liquids diffuse inside ionic polymers, …
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Structure and Dynamics of Associative Polymer Gels
… which governs their properties such as self-diffusion, relaxation, and creep. In this thesis, a combined experimental and computation approach was used to provide new insight into the structure and dynamics of associative networks on various length and time scales, with the goal of …
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