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  • About
  • The Global ETD Search service is a free service for researchers to find electronic theses and dissertations. This service is provided by the Networked Digital Library of Theses and Dissertations.
    Our metadata is collected from universities around the world. If you manage a university/consortium/country archive and want to be added, details can be found on the NDLTD website.
431

Dynamic NMR studies of molecular motions and order in calamitic and discotic liquid crystals

Zhang, Jing 14 September 2007 (has links)
This dissertation reports a study of three kinds of liquid crystals using modern solid state NMR techniques: chiral rod-like liquid crystals, bent-core mesogens and disc-like liquid crystals. The properties and structures of liquid crystals are first introduced in Chapter 1. To understand the principles of different NMR phenomena, quantum mechanical theory is adopted to study different nuclear spin interactions and NMR techniques in Chapter 2. In the next part of this dissertation (Chapter 3-6), deuterium NMR methods are used to investigate the dynamics and structures of some liquid crystal phases. This is first done using the spin relaxation study. The parameters obtained from the model simulation can describe the molecular motion and internal dynamics in the fast motion region. Secondly, we investigate the dynamic process of discotic mesophases and unwound smectic C* phase using the line shape simulation study. 2D deuterium NMR exchange experiments are then performed to study the jump process in TGBA* phase and SmC* phase. The above investigation has demonstrated some powerful NMR methods for the dynamic study of liquid crystals. The third part of the dissertation (Chapter 7-9) is concerned with C-13 NMR techniques. After we introduce the quantum theory of different pulse sequences, theoretical models are presented to fit observations such as chemical shifts and dipolar splittings. Moreover high resolution liquid C-13 NMR experiments are introduced to study some bent-core molecules. They are useful to assist the carbon peak assignments of these molecules. The structure and ordering information of liquid crystals can be determined in their mesophases. Finally, a brief summary of the dissertation is given in the last chapter.
432

Implementation of Wavelet Encoding Spectroscopic Imaging Technique on a 3 Tesla Whole Body MR Scanner

Fu, Yao 12 April 2010 (has links)
A 3D wavelet based encoding spectroscopic method (WE-SI) is investigated and implemented on a 3 Tesla Siemens Scanner. Compared to CSI, the proposed method is able to reduce acquisition time, and preserves the spatial metabolite distribution. As expected, a decrease in Signal to Noise Ratio (SNR) is noticed in WE-SI data compared to CSI. The dissertation explores important physical principles in MRI and spectroscopic imaging as a background, following by introduction of the wavelet encoding theory and comparison to Fourier encoding.
433

Solid-state NMR investigation of structure and dynamics of polyrotaxanes

Nagapudi, Karthik January 1997 (has links)
No description available.
434

Interactive computer simulation for instruction in magnetic resonance imaging

Rogers, Erika 12 1900 (has links)
No description available.
435

Magnetic resonance imaging based percent stenosis and pressure drop measurements in an aortic coarctation model

Larson, Blake E. 05 1900 (has links)
No description available.
436

Magnetic resonance imaging of flow through a stenosis : accuracy of angiography and phase velocity measurements

Siegel, John Mather, Jr. 12 1900 (has links)
No description available.
437

Use of magnetic resonance imaging to evaluate stenotic flows

Oshinski, John N. 05 1900 (has links)
No description available.
438

Magnetic resonance imaging of flow using phase velocity encoding : an in vitro study

Poiseau, Eric 08 1900 (has links)
No description available.
439

Evaluation of the accuracy of magnetic resonance phase velocity encoding in straight tubes and stenoses

Oshinski, John N. 05 1900 (has links)
No description available.
440

Magnetic resonance imaging of flow in simple arterial models

Biancheri, Catherine L. 12 1900 (has links)
No description available.

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