Traditionally, hydrogen sulfide (H2S) has been regarded as toxic. It can affect the various human systems and even cause death. However, research in the 1990s has shown that H2S can be endogenously generated by many cells and tissues in mammalian bodies, and that H2S also may play physiological roles such as those of neuromodulator and vasorelaxant in the biological system. As such, the precise measurement of the amount of H2S in a mammalian body has generated researchers strong interest. The ultimate goal of such a measurement should be conducted in-vivo and in real time.<p>The existing methods for H2S measurement require both a large quantity of tissue samples and a complex procedure, so they are not highly practicable for the purpose of achieving the aforementioned goal. In this dissertation, a new method that uses carbon nanotube as an absorbent or transducer and laser-based microscopy techniques (Raman and confocal laser scanning microscopy) as signal excitation and acquisition is proposed and developed. Experimental studies are described of using this new method for analysis of both distilled water samples and serum samples in which a group of proteins are present. <p>The study concludes that the new method (1) can measure H2S in water solutions down to a low level of concentration of 10 µM, (2) can measure H2S in sera down to a low concentration of approximately 20 µM), and (3) has a high feasibility for being used in the clinical context. Regarding (3), this is confirmed by presenting a control system that allows the laser microscopy to track carbon nanotube in a solution that has Brownian motion.<p>While not having reached the ultimate goal as mentioned above, this work advances the state-of-the-art of the measurement of low concentration and nano-quantity of H2S in water and serum samples, in particular providing a promise toward a real-time and in-vivo H2S measurement.

Thesis (Ph. D.)--University of Texas at Austin, 2001. / Vita. Includes bibliographical references (leaves 337-351). Available also in a digital version from Dissertation Abstracts.

The finite-difference time-domain method is used to simulate the propagation of focused beams used for stimulated emission depletion (STED) microscopy as they scatter through layers of biological cells. Depletion beams that facilitate axial and lateral confinement of the fluorescence emission are modeled, and the effective point spread function of the system as a function of focal depth is assessed under one- and two-photon excitation. Results show that the lateral depletion beam retains a well-defined minimum up to the maximum simulation depth of 42 µm. In addition, the relative spatial shift between excitation and de-excitation beam foci is less than 44 nm for all simulated depths. PSF calculations suggest that sub-diffraction imaging is possible beyond the maximum simulated depth, as long as the fluorescence emission is detectable. However, strong attenuation of the fluorescence emission by the axial confinement beam may make this beam unsuitable for sub-diffraction imaging in scattering samples. / text

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Thesis (Ph.D.)--University of Melbourne, Dept. of Physics, 2005. / Typescript. Includes bibliographical references (leaves 205-223).

Thesis (M.S.) in Electrical Engineering--University of Maine, 2007. / Includes vita. Includes bibliographical references (leaf 75).

Thesis (Ph. D.)--University of Hong Kong, 1991.

Thesis (M.S. in Physics)--United States Naval Postgraduate School, California. / Includes bibliographical references (p. 23). 9

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