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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 30 for “"PFG"”.
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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 ähnelt, …
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Nanopower Analog Frontends for Cyber-Physical Systems
… technology, the Piezoelectric-Floating-Gate (PFG) was employed. The PFG matches physics of Impact-</p><p>Ionized Hot-Electron Injection (IIHEI) in silicon metal-oxide field effect transistors with a piezoelectric transducer to drive nonvolatile data-logging measurements. The PFG implementation …
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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
… Spatially unresolved Pulsed Field Gradient NMR (PFG NMR) methods have been used to measure the self diffusion coefficient of liquid contained within catalyst support pellets. Mass transport in catalyst pellets is often characterized through the tortuosity parameter, which impacts the catalyst …
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Vapour-Liquid Equilibria within Nanoporous Media
… relaxation and pulsed field gradient (PFG) diffusion experiments were performed on each of the systems discussed in this report. Cyclohexane was initially studied inside a porous titania catalyst support at 188 °C and various pressures up to 13 bar. The adsorption and desorption …
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Taking Magnetic Resonance into Industrial Applications
… are described using pulsed field gradient (PFG) MR. A cumulant analysis of the PFG MR signal is first used to characterise the rheology of model power-law fluids, namely xanthan gum-in-water solutions, accurate to within 5% of conventional rheometry, the data being acquired in only 6% of the …
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Tuning polymeric chiral surfactants for enhanced enantiomeric recognition in micellar electrokinetic chromatography
… 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 was …
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Evaluation of short-term conservative treatment in patients with tennis elbow (lateral epicondylitis): A prospective randomised, assessor-blinded trial.
… questionnaire (PRTEE), pain-free grip strength (PFG) and patient preference were assessed twice at baseline, at 10 days, 6 weeks and 6 months and analysed as an intention to treat analysis. In the short term of 6 weeks injection was the most effective treatment demonstrating both statistically …
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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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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
… example of dimethylsulfone and simulated data. PFG-NMR is used to measure translational motion of liquids in different areas of application. In granular flow in a half filled rotating horizontal cylinder the influence of inertia effects of the particles on the velocity-depth profile is shown. 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
… on the application of a pulsed-field gradient (PFG) NMR emulsion detection technique to characterise hydrocarbon-in-water emulsions and study their droplet size distribution (DSD) inside porous media under operando conditions ($\geq$180 $\degree$ C and $\geq$36 bar). The initial study into …
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Cation and Anion Transport in a Dicationic Imidazolium-Based Plastic Crystal Ion Conductor
… 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 for the cation upon varying …
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Plants in urban brownfields: modeling the driving factors of site conditions and of plant functional group occurrence in a dynamic environment
… to their traits into plant functional groups (PFGs) and subsequent modeling, in the first part of the thesis, I identified relevant strategies for species survival. The results revealed that dispersal in space and in time as well as vegetative persistence on sites are most crucial factors for …
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NMR of geophysical drill cores with a mobile Halbach scanner
… the influence of the diffusion. Furthermore, PFG NMR technique was used to study restricted diffusion in the same kind of samples. Preliminary results are reported.
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Diffusionsuntersuchungen an (polymer-modifizierten) Mikroemulsionen mittels Feldgradientenimpuls-NMR-Spektroskopie
… unter Verwendung gepulster Feldgradienten (PFG) in Abhängigkeit des Zusatzes des Polykations Poly-(diallyl-dimethyl-ammoniumchlorid) (PDADMAC) untersucht. Der zentrale Gegenstand dieser Untersuchungen war die strukturelle und dynamische Charakterisierung der verwendeten Mikroemulsionen …
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Multiscale Transport and Dynamics in Ion-Dense Organic Electrolytes and Copolymer Micelles
… 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 organic ionic plastic crystal, a proton-exchange membrane, and a polymer-gel …
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