Thesis (Ph.D.)--University of Texas at Arlington, 2008.

Thesis (Ph. D.)--University of Texas at Austin, 2001. / Vita. Includes bibliographical references. Available also from UMI/Dissertation Abstracts International.

Thesis (Ph. D.)--University of Texas at Austin, 2000. / Vita. Includes bibliographical references (leaves 178-187). Available also in a digital version from Dissertation Abstracts.

Thesis (Ph. D.)--Ohio State University, 2001. / Title from first page of PDF file. Document formatted into pages; contains xiii, 165 p.; also contains graphics (some col.). Includes abstract and vita. Advisor: Jonathan P. Pelz, Dept. of Physics. Includes bibliographical references (p. 160-165).

Thesis (Ph. D.)--University of Texas at Austin, 1999. / Vita. Includes bibliographical references (leaves 147-156). Available also in a digital version from Dissertation Abstracts.

Thesis (Ph. D.)--University of Texas at Austin, 2003. / Vita. Includes bibliographical references. Available also from UMI Company.

Thesis (Ph. D.)--University of Texas at Austin, 2002. / Vita. Includes bibliographical references. Available also from UMI Company.

Thesis (M.S.) in Physics--University of Maine, 2002. / Includes vita. Bibliography: leaves 74-77.

Iron plays an important role in the regulation of biological productivity and the carbon cycle of the Southern Ocean. Recently, synchrotron X-ray spectromicroscopy revealed that molar iron to silicon (Fe:Si) ratios in living diatom samples collected from surface waters and ice in the coastal Antarctic are significantly higher than reported dissolved Fe:Si ratios of Circumpolar Deep Water. Upwelling of Circumpolar Deep Water is a dominant source of iron and silicon to coastal Southern Ocean surface waters. Thus with higher Fe:Si ratios, diatom production preferentially depletes dissolved iron relative to silicon, potentially contributing to perennial iron limitation in this region. Combining diatom and water column dissolved iron and silicon datasets with a simple inverse box model we estimate the regional coupled iron and silicon budget. Upwelling of subsurface waters cannot supply enough iron to balance the loss due to diatom production, which indicates that the closed budget requires additional iron sources or additional methods of silicon removal. To evaluate the ecological and biogeochemical impacts of the high Fe:Si ratio, a three-dimensional ocean biogeochemistry and ecosystem model is used to simulate the sensitivity of ocean productivity and nutrient cycling to a wide range of Fe:Si ratios in modeled diatoms. The Fe:Si ratio of diatoms regulates the surface iron and macronutrient distribution in vast regions beyond the Southern Ocean. A globally higher Fe:Si ratio strongly decreases subpolar productivity and is partially compensated by the moderate increase in subtropical productivity. Our results indicate that the Fe:Si ratio of diatoms has a global impact controlling the distribution of both micro- and macro-nutrients and associated biological production.

Optics and photonics enable important technological solutions for critical areas such as health, communications, energy, and manufacturing. Novel nanofabrication techniques, on the other hand, have enabled the realization of ever shirking devices. On-chip photonic micro-resonators, the fabrication of which was made possible in the recent decade thanks to the progress in nanofabrication, provide a sensitive and scalable transduction mechanism that can be used for biochemical sensing applications. The recognition and quantification of biological molecules is of great interest for a wide range of applications from environmental monitoring and hazard detection to early diagnosis of diseases such as cancer and heart failure. A sensitive and scalable biosensor platform based on an optimized array of silicon nitride microring resonators is proposed for multiplexed, rapid, and label-free detection of biomolecules. The miniature dimension of the proposed sensor allows for the realization of handheld detection devices for limited-resource and point-of-care applications. To realize these sensors, the design, fabrication, stabilization, and integration challenges are addressed. Especially, the focus is placed on solving a major problem in using resonancebased integrated photonic sensors (i.e., the insufficiency of wavelength scan accuracy in typical tunable lasers available) by using an interferometric referencing technique for accurate resonance tracking. This technique can improve the limit of detection of the proposed sensor by more than one order of magnitude. The method does not require any temperature control or cooling, and the biosensor platform does not require narrow linewidths necessary for the biosensors based on ultrahigh quality factor resonators, thus enabling low-cost and reliable integration on the biosensor platform.