Investigation of Aerosol Properties Using Environmental Atomic Force Microscopy

Atmospheric aerosols affect both global and regional climate by altering the radiative balance of the atmosphere and acting as cloud condensation nuclei. Despite an increased focus on the research of atmospheric aerosols due to concerns about global climate change, current methods to observe the morphology of aerosols and to measure their hygroscopic properties are limited in various ways by experimental procedure. The primary objectives of this thesis were to use atomic force microscopy to determine the morphology of atmospherically relevant aerosols and to investigate theutility of environmental atomic force microscopy for imaging aerosols as they respond to changes in relative humidity. Traditional aerosol generation and collection techniques were used in conjunction with atomic force microscopy to image commonorganic and inorganic aerosols. In addition, environmental AFM was used to image aerosols at a variety of relative humidity values. The results of this research demonstrated the utility of atomic force microscopy for measuring the morphology of aerosols. In addition, the utility of environmental AFM for measuring the hygroscopic properties of aerosols was demonstrated. Further research in this area will lead to an increased understanding of the role oforganic and inorganic aerosols in the atmosphere, allowing for the effects of anthropogenic aerosol emissions to be quantified and for more accurate climate models to be developed.

Backward Extensions of Recursively Generated Weighted Shifts and Quadratic Hyponormality

Given the weight sequence for a subnormal recursively generated weighted shift on Hilbert space, one approach to the study of classes of operators weaker than subnormal has been to form a backward extension of the shift by prefixing weights to the sequence. We characterize positive quadratic hyponormality and revisit quadratic hyponormality of certain such backward extensions of arbitrary length, generalizing earlier results, and also show that a function apparently introduced as a matter of convenience for quadratic hyponormality actually captures considerable information about positive quadratic hyponormality.