The Search for New/Unknown Signals

dc.contributor.advisor

Warren, Warren S

dc.contributor.author

Chen, Yuming Morris

dc.date.accessioned

2012-01-10T15:58:28Z

dc.date.available

2013-01-04T05:30:14Z

dc.date.issued

2011

dc.department

Chemistry

dc.description.abstract

This dissertation focuses on a very special topic in the field of Nuclear Magnetic Resonance (NMR) in solution: Intermolecular Multiple Quantum Coherences, or iMQCs, which can only be created by intermolecular dipolar couplings. Since the very beginnings of NMR, it has been known that dipolar couplings dominate the solid-state linewidth for spin-1/2 nuclei, but the effects are still not fully understood. The angular dependency (1-3cos2θij) and distant dependency (rij-3) of dipolar coupling led to an oversimplified conclusion that it can be ignored in an isotropic liquid. Thus, it was surprising when COSY Revamped by Asymmetric Z-gradient Echo Detection (CRAZED) was first introduced in the early `90s and showed strong iMQC signals. Since then, CRAZED has inspired a wide range of applications for iMQCs and led to two different but equivalent mathematical frameworks to describes these effects, which we call the conventional DDF theory.

However, several disagreements between the conventional DDF theory and experiments have grasped our attention recently. This dissertation will: first, demonstrate how conventional picture fails by two examples, Multi-axis CRAZED (MAXCRAZED) and Gradient-embedded COSY Experiment (GRACE); second, provide a corrected DDF theory; and, third, discuss what impact this correction will bring.

Intermolecular double quantum coherences (iDQCs) are very sensitive to the local anisotropy (10μm - 1mm) and can be used to create positive contrast highlighting superparamagnetic iron oxide nanoparticles (SPIONs). This dissertation will show the design and optimization of iDQC anisotropy by a series of phantom experiments. A set of numerical simulations will then be provided for a sub-voxel level explanation. We will also demonstrate how the newly corrected DDF theory can be quickly adapted to improve the iDQC anisotropy.

Finally, as a side product of this research, the mechanism of diacetyl hydration/dehydration as solved by NMR will be provided.

dc.identifier.uri

https://hdl.handle.net/10161/4987

dc.subject

Chemistry

dc.subject

Physical chemistry

dc.subject

Biomedical engineering

dc.subject

distant dipolar field

dc.subject

intermolecular multiple quantum coherences

dc.subject

magnetic resonance imaging

dc.subject

nuclear magnetic resonance

dc.title

The Search for New/Unknown Signals

dc.type

Dissertation

duke.embargo.months

12

Files

Original bundle

Now showing 1 - 1 of 1
Loading...
Thumbnail Image
Name:
Chen_duke_0066D_11142.pdf
Size:
56.72 MB
Format:
Adobe Portable Document Format

Collections