Browsing by Subject "Droplets"
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Item Biomedical photoacoustics beyond thermal expansion : photoacoustic nanoDroplets(2012-05) Wilson, Katheryne Elizabeth; Emelianov, Stanislav Y.; Fowlkes, Brian; Hamilton, Mark; Sokolov, Konstantin; Williams, RobertThe recent increase in survival rates of most cancers is due to early detection greatly aided by medical imaging modalities. Combined ultrasound and photoacoustic imaging provide both morphological and functional/molecular information which can help to detect and diagnose cancer in its earliest stages. However, both modalities can benefit from the use of contrast agents. The objective of this thesis was to design, synthesize, and test a nano-sized, dual contrast agent for combined ultrasound and photoacoustic imaging named Photoacoustic nanoDroplets. This agent consists of liquid perfluorocarbon nanodroplets with encapsulated plasmonic nanoparticles. These dual contrast agents utilize optically triggered vaporization for photoacoustic signal generation, providing significantly higher signal amplitude than that from the traditionally used mechanism, thermal expansion. Upon pulsed laser irradiation, liquid perfluorocarbon undergoes a liquid-to-gas phase transition generating giant photoacoustic transients from these dwarf nanoparticles. Once triggered, the gaseous phase provides ultrasound contrast enhancement. Demonstrated in this work are the design, synthesis, characterization, and testing of Photoacoustic nanoDroplets in phantom and animal studies, and preliminary work into adapting these agents into targeted, drug delivery vehicles for simultaneous detection, diagnosis, and treatment of diseases.Item Isolation of ambient aerosols of known critical supersaturation: the differential critical supersaturation separator (DSCS)(Texas A&M University, 2007-09-17) Osborn, Robert JohnA field-deployable instrument has been developed that isolates from an ambient aerosol population only those particles that have critical supersaturations, Sc, within a narrow, user-specified, range. This Differential Critical Supersaturation Separator (DScS) is designed to supply one or more particle size and/or composition analyzers to permit the direct examination of the factors that influence the activation properties of ambient aerosols. The DScS consists of two coupled parallel plate continuous flow thermal gradient diffusion cloud chambers housed within a single enclosure. Descriptions of instrument operation, construction and calibration data collected, when pure ammonium sulfate aerosols were injected into the DScS for operation at 0.15%< Sc<0.175%, 0.30%< Sc<0.35%, and 0.60% < Sc<0.70%, are included. Following instrument development, the DScS was deployed during March 2006 for the Megacities Impact on Regional And Global Environment (MIRAGE) field campaign in Mexico City, Mexico. Throughout the MIRAGE field campaign a Differential Mobility Analyzer/Tandem Differential Mobility Analyzer (DMA/TDMA) system measured aerosol size distributions and size-resolved hygroscopicity of DScS separated aerosol. The dry diameter (Dp*) of particles sampled in the TDMA system as well as the known Sc prescribed in the DScS were combined in a modified version of K????hler Theory to make predictions of particle hygroscopicity. These predictions frequently overestimated the measurements. Further analysis of DScS separated aerosols compares the known particle Sc to a predicted particle Sc, providing insight into particle activation efficiency. Overall, the sampled aerosol exhibited properties that indicate they were more efficient at activation than K????hler Theory would predict.