Ph.D.

Solar energy has come to the forefront as a scalable and largely underutilized renewable energy resource. The current cost of solar electricity, namely from photovoltaics, along with other logistics factors, has prevented the widespread adaptation of the technology. A key determinant of efficiency and cost for a solar cell is the current collector grid. This work presents the Collimated Aerosol Beam Direct Write (CAB-DW) system as a non-contact printing method that can achieve current collector grid finger widths of less than 10 μm which are amenable to decreasing both resistive and optical losses. The ability to produce high aspect ratio grid fingers, and deposit optimized grid structures on high efficiency SHJ solar cells using silver nanoparticle inks is also demonstrated. A decrease in shadowing and via profile modification of the grid fingers is presented, along with a study of aging and degradation of electrical properties within silver nanoparticle inks.

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A 42-year-old woman with idiopathic Raynaud's phenomenon developed localized necrosis of her fingertip after using an aerosol can of spray hair color. Laboratory measurements indicated that while such products did not achieve freezing temperatures, they did become cold enough to potentially produce vasospasm. Patients with Raynaud's phenomenon should be cautioned that use of some aerosol products may result in a cold induced injury.

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No description available.

This thesis concerns various aspects of the influence of atmospheric particulate matter on the terrestrial system. In Part I, the radiative influence of particulate matter on the production of crops is explored using the CERES crop model. It is known that the presence of aerosols in the atmosphere simultaneously reduces the amount of sunlight reaching the surface and increases the fraction of that light which is diffuse. Reduction of the total amount of sunlight tends to slow the rate of photosynthesis occurring in plants while increasing the fraction which is diffuse tends to increase the net rate of photosynthesis by more evenly distributing sunlight throughout all layers of a plant canopy. The CERES crop model was modified to estimate the influence of both a reduction in total sunlight and an increase in the diffuse fraction. Model simulations were performed for rice, maize and wheat at a variety of locations and found the likely influence of aerosols on crop production to be a 0-10% reduction in yield compared to the base case. In Part II, the concentration and size distribution of water-insoluble aerosols (WIA) is explored. It has been well-established that atmospheric particulate matter influences the planetary radiation budget both directly and indirectly. The magnitude of these influences is related to particle solubility. A new technique was developed to provide these measurements in real-time. This instrumentation was evaluated in a laboratory setting and implemented into several field studies. Results from these sampling campaigns indicate that in areas heavily influenced by motor vehicle traffic, the WIA concentration is dominated by particulate soot. Many episodes of high levels of crustal dust were also observed. At these times, the WIA size distribution shifted toward larger sizes in a characteristic manner. This suggests that this method is useful for detecting insoluble mineral aerosols as well as particulate soot and that examination of the WIA size-distribution may provide a basis to distinguish between the two.

The Earth’s atmosphere supports microorganisms and they include potential pathogens and microbial allergens. Whilst indoor environments have been well studied, relatively little is known of bio-aerosols in outdoor locations and their potential influence on human health, particularly with regard to urban development. Hong Kong provides an ideal model system for testing hypotheses related to the impact of urbanization on bio-aerosols, with a well-defined gradient of urbanization and large population. This thesis describes work to establish the biodiversity and spatio-temporal dynamics of outdoor bio-aerosols in Hong Kong. A comprehensive study of multi-domain microbial diversity and allergen levels in urban aerosols over a contiguous annual timescale and along a gradient of urbanization was carried out. A comprehensive suite of climatic and pollutant variables were also recorded during the sampling interval. Terminal restriction fragment length polymorphism (T-RFLP) was employed to investigate variations in bacterial and eukaryal assemblages, followed by phylogenetic assessment using high-throughput sequencing. The results revealed a strong seasonality in both bacterial and eukaryal assemblages, with Archaea forming a negligible part of the urban bio-aerosols. The most abundant bacteria were proteobacteria but community shifts were seen due to increases in algae in summer, and betaproteobacteria and cyanobacteria in winter. This was most parsimoniously explained by considering the backward trajectory analysis of air mass. A greater abundance of marine-associated phylotypes such as Bacillariophyta and Chlorophyta were identified when the dominant air mass arriving in Hong Kong in the summer originated from oceanic sources. In contrast, betaproteobacteria, which indicated soil sources were prevalent when the origin of air mass was from terrestrial sources. A trend in fungal phylotypes was also apparent, with summer samples dominated by basidiomycetous Agaricales, and winter samples by the ascomycete genus Cladosporium. This was likely due to favourable climatic conditions during wetter summer months enhancing release of fungal basidiospores. A range of airborne human pathogens was also detectable at low levels including pathogenic bacteria such as Acinetobacter baumannii, Clostridium perfringens, Escherichia coli O157:H7, and Ricinus communis, and the pathogenic fungus Aspergillus terreus. Microbial allergens including bacterial endotoxins and fungal glucans were also quantified with immunological assays. These generally followed variations in biomass, and during some months were recorded at levels that may impact human health upon chronic exposure. Carbon dioxide levels were the only climatic or pollutant variable that correlated with allergen levels. Conversely changes in microbial assemblages were strongly correlated to several climatic variables including temperature, rainfall, air pressure and relative humidity, but not with the degree of urbanization or airborne pollutants. This study highlights the importance of including microbial assessments in future bio-surveillance of urban aerosols. / published_or_final_version / Biological Sciences / Doctoral / Doctor of Philosophy

Thesis (Ph. D.)--University of California, Riverside, 2009. / Includes abstract. Includes bibliographical references. Issued in print and online. Available via ProQuest Digital Dissertations.

Thesis (Ph. D.)--University of California, Riverside, 2009. / Includes abstract. Available via ProQuest Digital Dissertations. Title from first page of PDF file (viewed March 10, 2010). Includes bibliographical references. Also issued in print.