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 23 for “"PFG-NMR"”.
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PFG-NMR Untersuchungen zu Skalenverhalten, effektiver Größe und Lösungsverhalten von Dendrimeren
… wurde die gepulste Feldgradienten NMR (PFG-NMR) eingesetzt, um das hydrodynamische Verhalten der Dendrimere in Lösung zu erforschen. Aus der Konzentrationsabhängigkeit des Diffusionskoeffizienten konnte abgeleitet werden, dass das Verhalten der PAMAM-Dendrimere dem von Proteinen …
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Microscopic diffusion measurements with nanoporous materials: complementary benefits of infrared microimaging and pulsed field gradient NMR
… (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 current challenges of the investigation of molecular diffusion in nanoporous …
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NMR Techniques for Measuring Transport Phenomena in Microporous Materials
… Field Gradient Nuclear Magnetic Resonance (PFG NMR). The main body of this work involves the use of weakly adsorbing hydrocarbon gases (CH4, C2H6 and C3H¬8) adsorbed in a large pore β-zeolite structure. This thesis describes the development of a solely PFG NMR based technique for measuring …
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Characterization of catalyst pellets using NMR and MRI: MRI, diffusion and relaxation measurements of liquid imbibed in alumina and titania extrudates
… are studied using Nuclear Magnetic Resonance (NMR) and Magnetic Resonance Imaging (MRI) techniques with the aim of characterizing mass transport in the pellets and exploring the presence of spatial heterogeneities formed in the manufacturing process. Measurements have been done both in bulk, …
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Tuning polymeric chiral surfactants for enhanced enantiomeric recognition in micellar electrokinetic chromatography
… was obtained by use of pulsed field gradient-NMR (PFG-NMR). A superior chromatographic performance in MEKC was demonstrated by the modified polymeric surfactants as compared to the non-modified polymeric surfactants. A correlation between the polarity and the size of the polymeric surfactants …
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Vapour-Liquid Equilibria within Nanoporous Media
… materials using Nuclear Magnetic Resonance (NMR) techniques, with an aim to benefit catalysis research. Included in this report are studies of pure fluids and their mixtures, confined in titania and silica catalyst supports. These investigations are conducted at industrially-relevant, …
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MRI and NMR Investigations of Transport in Soft Materials and Explorations of Electron-Nuclear Interactions for Liquid-State Dynamic Nuclear Polarization
… 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 …
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NMR von rotatorischer und translatorischer Dynamik
… out of two-dimensional solid-state exchange NMR spectra, describing the rotational motion of the molecules. This analysis was performed for the example of dimethylsulfone and simulated data. PFG-NMR is used to measure translational motion of liquids in different areas of application. In …
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Transport and Structure in Fuel Cell Proton Exchange Membranes
… field gradient nuclear magnetic resonance (PFG NMR), which was used as a measure of the state of absorbed water in the membrane. Generally, transport properties decreased in the order Nafion > sulfonated poly(arylene ether sulfone) > sulfonated poly(imide). The water diffusion coefficients …
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Multiscale Tortuous Diffusion in Anion- and Cation-Exchange Membranes: Exploration of Counterions, Water Content, and Polymer Functionality
… in AEMs and CEMs using pulsed-field-gradient (PFG) NMR diffusometry. Water diffusion in both AEMs and CEMs exhibit specific trends as a function of water uptake (wt%), indicating morphological similarities across common chemical structures. Furthermore, restricted diffusion reveals micron-scale …
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NMR Studies of Emulsions in Porous Media and Applications to Fischer-Tropsch Synthesis
… this thesis employs nuclear magnetic resonance (NMR) and magnetic resonance imaging (MRI) to gain insight into and elucidate the multiphase behaviour and transport processes of Fischer-Tropsch Synthesis (FTS) reactants and products. In order to achieve this, the world’s first operando NMR …
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Cation and Anion Transport in a Dicationic Imidazolium-Based Plastic Crystal Ion Conductor
… by means of multi-nuclear solid-state (SS) NMR and pulsed-field-gradient (PFG) NMR. We quantify distinct cation and anion diffusion coefficients as well as the diffusion activation energies (Ea) in this dicationic imidazolium-based OIPC. Our studies suggest a change in transport mechanism …
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NMR of geophysical drill cores with a mobile Halbach scanner
This thesis is devoted to a mobile NMR with an improved Halbach scanner. This is a lightweight tube-shaped magnet with sensitive volume larger and a homogeneity of the magnetic field higher than the previous prototype version. The improved Halbach scanner is used for analysis of water-saturated …
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Multiscale Transport and Dynamics in Ion-Dense Organic Electrolytes and Copolymer Micelles
… capabilities via nuclear magnetic resonance (NMR) techniques. By employing variable temperature pulsed-field-gradient (PFG) NMR diffusometry, which can probe molecular transport over nm – μm length scales, I first explore transport and morphology on a series of ion-conducting materials: an …
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Fluid dynamics of single levitated drops by fast NMR techniques
… of the droplets. Nuclear magnetic resonance (NMR) velocity imaging can give quantitative information about drop shape and velocities and is able to distinguish between different chemical compounds that will become relevant for the direct investigation of mass transfer. The potential of pulsed …
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Diffusion and Relaxometry Studies in Mesoporous Systems using Nuclear Magnetic Resonance
… has been examined using Pulsed Field Gradient (PFG) NMR. This includes a diffusion study of binary mixtures consisting of *n*-dodecane and one of octane isomers. It has shown that linear octane diffuses distinctively faster than branched octane isomers, indicating physical restriction to …
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Magnetic Resonance Studies of the Diffusion Dynamics of Molecular Systems Relevant to Fischer-Tropsch Catalysis
… confined mixtures using Pulsed-Field Gradient (PFG) Nuclear Magnetic Resonance (NMR) techniques. An advancement on this calibration technique is used to show that the diffusion mechanism of these liquids, in addition to the activation energy and molecular free volume, changes significantly when …
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NMR studies of carbon dioxide sequestration in porous media
… 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 …
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Novel microemulsions with an anionic/non-ionic surfactant mixture
… untersucht. Mittels Leitfähigkeits-, SANS-, PFG-NMR-Messungen und elektronenmikroskopischen cryo-TEM Aufnahmen konnten die Nanostrukturen identifiziert werden. Während im unteren Einphasenkanal die Strukturen aus kleinen Öl-Tröpfchen in einer kontinuierlichen Wasserphase bestehen, welche mit …
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NMR Applications in Soft Materials Science: Correlation of Structure, Dynamics, and Transport
… using multiple Nuclear Magnetic Resonance (NMR) methodologies, including solid-state NMR (SSNMR), diffusometry, and imaging, and with the help of X-ray scattering. First, we report the investigation of structure and dynamics of three polymeric membranes: hydroxyalkyl-containing imidazolium …
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