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Implementing variable energy positron lifetime spectroscopy based on secondary electron timing from thin carbon foil in transmission geometryNg, Cheuk-kwong, 吳卓光 January 2014 (has links)
abstract / Physics / Doctoral / Doctor of Philosophy
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Measuring physical properties of pre-main sequence stars using high resolution infrared spectroscopyDoppmann, Gregory William 28 August 2008 (has links)
Not available / text
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Low temperature single molecule spectroscopy of MEH-PPV conjugated polymer moleculesKim, Doo Young 28 August 2008 (has links)
Not available / text
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Construction of a low temperature nuclear magnetic resonance force microscopeLee, Yong J. 28 August 2008 (has links)
Not available / text
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Combined intravascular ultrasound and photoacoustic imagingSethuraman, Shriram 28 August 2008 (has links)
The primary focus of the work was to evaluate the capability of intravascular photoacoustic (IVPA) imaging in combination with intravascular ultrasound (IVUS) to detect and differentiate atherosclerotic plaques. The composition rather than structural narrowing of the arteries is a major indicator of the propensity of a vascular lesion to rupture. Consequently, intravascular imaging of these high-risk plaques is required to exactly determine the vulnerable plaque constituents for appropriate follow-up therapy. Our multi-modality imaging approach aims to utilize the high resolution structural assessment abilities of IVUS and the optical contrast of IVPA imaging and is capable of differentiating the lipid, fibrous and fibro-cellular components of an inflammatory lesion. To test the hypothesis, we developed an IVUS catheter based laboratory prototype of a combined IVUS/IVPA imaging system. The performance of the synergistic combination of IVUS and IVPA imaging was evaluated through tissue mimicking phantom studies. Further, to test the ability of the combined imaging to detect plaques, excised samples of an aorta were utilized from a specifically designed animal model of atherosclerosis. Ex-vivo IVPA imaging studies were performed using a 532 nm laser excitation to detect the lipids in the plaque. In addition, multi-wavelength spectroscopic IVPA imaging studies were evaluated to differentiate plaques. Finally, an ultrasound based temperature estimation method was utilized to demonstrate and confirm safety of IVPA imaging for clinical intravascular applications. Upon analysis of the results of our investigation, we believe that IVPA imaging offer numerous potential advantages when integrated with clinical IVUS imaging. The IVUS imaging system with integrated IVPA imaging capability could play a major role in interventional cardiology. / text
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Extension of the linear dynamic range for high resolution continuum source atomic absorption spectrometry and its application in the analysis of biological samples. / The linear dynamic range for high resolution continuum source atomic absorption spectrometryHlongwane, Mokgadi Miranda. January 2013 (has links)
M. Tech. Chemistry / Recently, traditional electro-thermal atomic absorption spectrometry has lost its popularity to other multi-element spectrometric techniques. Limited linear determination range, which is usually two orders of magnitude, is one of the reasons for the loss. As a result, tens of calibration standards and diluted samples have become an indispensable part of the electro-thermal atomic absorption spectrometric analysis, particularly if numerous samples containing a broad concentration range of analytes are to be analysed. The objective of this work was to establish the mechanism of absorption signals for high concentrations of analyte atoms in the absorption volume. Secondly, to employ the findings for HR-CS ET-AAS data quantification, within a broad range of analyte concentrations. It was expected that the sought algorithm would permit the use of the most sensitive analytical lines or those less prone to interferences, independent of the concentration of the respective analyte in the sample.
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Extracting Surface Structural Information from Vibrational Spectra with Linear ProgrammingHung, Kuo Kai 21 August 2015 (has links)
Vibrational spectra techniques such as IR, Raman and SFG all carry molecular orientation
information. Extracting the orientation information from the vibrational spectra often
involves creating model spectra with known orientation details to match the experimental
spectra. The running time for the exhaustive approach is O(n!). With the help of linear
programming, the running time is pseudo O(n). The linear programming approach is
with out a doubt far more superior than exhaustive approach in terms of running time.
We verify the accuracy of the answer of the linear programming approach by creating
mock experimental data with known molecular orientation distribution information of
alanine, isoleucine, methionine, lysine, valine and threonine. Linear programming returns
the correct orientation distribution information when the mock experimental spectrum
consisted of different amino acids. As soon as the mock experimental spectrum consisted
of same amino acids, different conformer with different orientation distribution, linear
programming fails to give the correct answer albeit the species population is roughly
correct. / Graduate
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Spectro-electrochemical studies of [conjugated] polymer single-molecules, nanoparticles, and thin filmsChang, Ya-Lan, 1980- 07 January 2011 (has links)
Conjugated polymers are widely used and rapidly developed in practical polymer-based light-emitting electronic devices. Understanding the electrochemical reaction of conjugated polymer has become essential in the design and operation of devices such as electrochemical light-emitting diodes. In particular, we have studied the dynamics and kinetics of oxidation/reduction behavior of conjugated polymer single-molecules and nanoparticles in order to obtain the molecular level properties of deeply trapped holes in organic semiconductor devices. Theoretical calculations suggest the penetration of ions and solvent molecules effectively stabilizes the injected charges, which allows homogeneous charge distribution and further hole injection. The formation and decay of deep traps have been explored by changing the charging rate and duration. We found that the laser excitation significantly promotes the untrapping of deep holes. Electrogenerated chemiluminescence of single nanoparticles has been investigated to unravel the effects due to particle heterogeneity, which are masked in bulk electrochemical studies of nanoparticles. Bigger particles showed more intense light and longer duration time than smaller ones. Co-reactant, tripropylamine can facilitate the formation of electrogenerated chemiluminescence as well as alleviate the polymer oxidation and following irreversible electrochemical reaction. Electrochemically generated light waves from the conjugated polymer thin films have been visualized to obtain microscopic level understanding on the complex reaction mechanism. Electrochemical reaction occurs at local defects and propagates isotropically over macroscopic distances with a sharp wave front. The initially injected holes (oxidized polymers) drag counter-ions into the film, thereby induce a phase-transition-like swelling that enhances transport of ions and solvent and move forward the double layer and corresponding propagation of the wave. / text
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Single molecule spectroscopy of conjugated polymersYu, Ji 10 May 2011 (has links)
Not available / text
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Discontinuity survey using laser scanning technology葉社榮, Yip, Sair-wing. January 2003 (has links)
published_or_final_version / abstract / toc / Applied Geosciences / Master / Master of Science
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