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 68 for “"molecular diffusion"”.
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Discrete 3D Model of Molecular Diffusion Through the Nuclear Pore Complex
… the nuclear envelope (NE) of a eukaryotic cell. Molecular cargo travel through the passageways to either import to the nucleus or export to the cytoplasm of the cell. Efficient export of certain cargo is necessary for maintained health of a cell, and hence, the organism. Traditional methods of …
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Magnetic Resonance Imaging by Populations in the Presence of Molecular Diffusion
This work makes extensive use of relaxation theories (chapters 2 through 4) and numerical simulations (chapters 3 and 4) to delineate the physical basis of MRI by populations and predict enhancements of performance. Chapters 3 and 4 predict the resolution of the method for ideal spatial geometries. …
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Application of Taylor Dispersion Technique to Measure Molecular Diffusion Coefficient of Hexane-Bitumen System
… analytic limitations in liquid solvent-bitumen diffusion studies. Taylor dispersion technique has been selected in this work due to its convenient short run-time experiments and reliable data analysis to find molecular diffusion coefficients in hexane-bitumen system. For the first time, the …
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Improved Experimental and Mathematical Techniques for Measurement of Solvent Gas Diffusivity in Heavy Oils
… resources. The solvent based processes rely on molecular diffusion for in situ mixing of the solvent with the oil and generally provide much slower rates of oil production than the thermal processes. This is so because the molecular diffusivity is often much smaller than the thermal diffusivity. …
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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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Nuclear magnetic resonance microscopy
… high resolution (up to 2[mu]m). The effects of molecular diffusion and local variations in the magnetic susceptibility in NMR microscopy are described, which, along with the intrinsic low sensitivity of NMR, are the fundamental limitations to resolution. Molecular diffusion in the presence of a …
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Diffusional effects in magnetic resonance imaging and microscopy
… microscopy. This thesis addresses the role of molecular diffusion in NMR and develops new methods to obtain image contrast and to infer diffusional action.
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Nuclear magnetic resonance studies of structure and dynamics in heterogeneous samples
… in the bulk magnetic susceptibility and molecular diffusion. The correlations between the dipolar and susceptibility fields are used for extracting information on the detailed structure and composition of heterogeneous samples. In the first part of this dissertation, a new method for …
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An investigation of atmospheric turbulence in the 100-105 km region over Cerro Pachón, Chile
… Na mixing ratio, and total constituent diffusion coefficient measurements. Twenty-seven (27) nights of lidar data spanning 2500 hours in the zenith and 2375 hours in the off-zenith directions at 25 m, 6 s resolution were analyzed to determine mean turbulence and instability trends in the …
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Computational Fluid Dynamics Methodologies for Simulation of Chemical Oxygen-Iodine Laser Flowfields
… the addition of a conservative, multicomponent molecular diffusion model to ensure accurate molecular diffusion transport modelling. Additionally, a 13 reaction, 10 species finite rate chemistry model was developed with the GASP thermo-chemical database for use with chemistry modelling …
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Study of the role of differential diffusion and equation of state on the features of stably stratified turbulent channel flow using direct numerical simulations
… content) through an equation of state (EoS). The molecular diffusion of the temperature and salinity in such flows differ substantially, which leads to the presence of a differential diffusion phenomenon. This furthers the complexity of stratified turbulence, where the density stratification is …
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Mapping crossing myofiber populations with Diffusion Spectrum Imaging in simulated and microfabricated model tissues
… issue, we sought to validate the capacity of Diffusion Spectrum Imaging (DSI), an MRI method for assessing molecular diffusion in a confined geometry, to determine fiber alignment in tissues whose myofibers are aligned at varying orientations. By this method, molecular displacement in a tissue …
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Bridging molecular and systems scales in membrane biology
… presented in my thesis use approaches based in molecular simulation, to study the influence of protein-lipid (Chapter 3) and protein-protein interactions (Chapter 4) on molecular diffusion in photosynthetic processes. The next two studies are focused on using non-equilibrium MD methods such as …
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Development of a hydrogel-based biocompatible platform for studying metabolic interactions between algae and bacteria
… between these microbial species based on molecular diffusion processes has been challenging due to a lack of an appropriate co-culture system. In this thesis, a hydrogel-based biocompatible platform is proposed to study the interaction between algae and bacteria in a systematic way. By …
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Resonances and Mixing in Confined Time-dependent Stokes Flows: The experiments, Numerics, and Analytics
… turbulence to be present, and too large for the molecular diffusion to be significant, the chaotic advection presents almost the only mechanism that can lead to mixing. Unfortunately for mixing, the intrinsic symmetries of the flow create invariant surfaces that act as barriers to mixing. Thus, a …
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Numerical Simulation of Thermohaline Convection in the Mixed Layer of the Ocean
… Particular emphasis is given to two-component diffusion resulting from dynamic instabilities in the water column. The conservation equations for salt and heat include the effects of solar heating, horizontal advectlon, and turbulent fluxes at the sea surface, while wind mixing enter through the …
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Air Ingress and Heat-Driven Flow Relaminarization in a Very High Temperature Reactor (VHTR)
… the reactor core of VHTR would result from both molecular diffusion and natural circulation. At low graphite temperatures in the riser, molecular diffusion is the dominating mechanism; however, as the riser temperature increases, natural circulation becomes dominant and the rate of nitrogen …
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Aging Assessment of High Voltage Single Component Room Temperature Vulcanized Silicone Rubber (RTV-1) Subjected to Aqueous Salt
… diffusive hypochlorous acid. Comparatively, a molecular dynamics model was developed to analyze salt ion, water, nitric acid, and hypochlorous acid diffusion through the RTV polymer network, indicating hypochlorous acid as super diffusive, chlorine as diffusive, and water as subdiffusive. …
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Modeling of Biological Activity in Expanded-Bed, Anaerobic Activated Carbon Filters
… concepts of liquid-layer mass transport, biofilm molecular diffusion, and Monod kinetics were incorporated in developing the models. Acetate was the single-stage substrate studied while phenol was examined in parallel and modeled as the two-stage substrate. After 849 days of continuous operation, …
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