Doctor of Philosophy

dissertationShape analysis is a well-established tool for processing surfaces. It is often a first step in performing tasks such as segmentation, symmetry detection, and finding correspondences between shapes. Shape analysis is traditionally employed on well-sampled surfaces where the geometry and topology is precisely known. When the form of the surface is that of a point cloud containing nonuniform sampling, noise, and incomplete measurements, traditional shape analysis methods perform poorly. Although one may first perform reconstruction on such a point cloud prior to performing shape analysis, if the geometry and topology is far from the true surface, then this can have an adverse impact on the subsequent analysis. Furthermore, for triangulated surfaces containing noise, thin sheets, and poorly shaped triangles, existing shape analysis methods can be highly unstable. This thesis explores methods of shape analysis applied directly to such defect-laden shapes. We first study the problem of surface reconstruction, in order to obtain a better understanding of the types of point clouds for which reconstruction methods contain difficulties. To this end, we have devised a benchmark for surface reconstruction, establishing a standard for measuring error in reconstruction. We then develop a new method for consistently orienting normals of such challenging point clouds by using a collection of harmonic functions, intrinsically defined on the point cloud. Next, we develop a new shape analysis tool which is tolerant to imperfections, by constructing distances directly on the point cloud defined as the likelihood of two points belonging to a mutually common medial ball, and apply this for segmentation and reconstruction. We extend this distance measure to define a diffusion process on the point cloud, tolerant to missing data, which is used for the purposes of matching incomplete shapes undergoing a nonrigid deformation. Lastly, we have developed an intrinsic method for multiresolution remeshing of a poor-quality triangulated surface via spectral bisection

Interactions between Euwallacea Ambrosia Beetles, Their Fungal Symbionts and the Native Trees They Attack in the Eastern United States

In a globalized world, wood products are constantly being shipped from one location to another, along with tiny hitchhikers in the form of insects and microorganisms. Euwallacea validus is a fungus-farming ambrosia beetle native to East Asia that likely made its way to the United States in wood packaging materials in the latter half of the twentieth century. E. validus cultivates two fungal symbionts in the U.S., an unnamed Fusarium sp. (AF-4) and Raffaelea subfusca. Fusarium symbionts of Euwallacea ambrosia beetles as well as Raffaelea symbionts of closely related ambrosia beetles have incited widespread disease on more than one-hundred hosts worldwide. To resolve host range of Fusarium and Raffaelea symbionts from E. validus, inoculation studies, which mimicked natural infestation by creating numerous beetle-size holes along single stems, were conducted on twelve tree species native to the eastern United States known to be natural hosts for this beetle species. Four months post-inoculation, trees were destructively sampled to examine and measure symptoms associated with inoculation. Results of this study showed significant differences in canker incidence and mean streaking associated with inoculation sites, although neither Fusarium sp. AF-4 nor Raffealea symbionts caused significant disease on any host tested and do not appear to pose serious risks to the known hosts within the invaded range of this beetle. Nonetheless several other Euwallacea-Fusarium consortia have been introduced into the U.S. recently which do pose serious risks to avocado production and forest health. PCR multiplexes were recently developed to discriminate closely related AFC symbionts present in the U.S. to monitor their spread and have opened the door for widespread molecular surveillance. This includes testing whether fusaria differ between the native / invaded ranges of these beetles and if symbiont swapping is occurring between beetles whose ranges currently overlap in the U.S. Results of this study confirmed fidelity between certain Euwallacea sp. and their fungal partners such as E. validus and its symbiont, Fusarium sp. AF-4 in both South Korea and the U.S. with no evidence of additional AFC members despite uncovering other FSSC members within mycangial communities. No other Euwallacea spp. examined exhibited obvious fidelity between native and invaded ranges. Surprisingly, a number of known AFC lineages already existing in the U.S. were uncovered from the mycangia of other Euwallacea spp. within the geographic origin of beetles in East Asia. In addition to AFC members, other FSSC isolates were associated with galleries of all five Euwallacea spp. studied, indicating frequent interactions between symbiotic and asymbiotic FSSC members. These results uncovered widespread fungal infidelity among closely related Euwallacea beetles. Such novel beetle-fungus combinations could incite disease across a number of orchard, landscape, and forest trees

Implementing a United Nations Security Council Resolution: The President\u27s Power to Use Force without the Authorization of Congress

In light of the history of the United States Constitution and the continued expansion of Presidential power, the author urges the Congress, the press, and the American public to examine carefully every new assertion of Presidential power. This Note specifically focuses on the recent Persian Gulf conflict and President Bush\u27s justifications for the use of military force without congressional approval. The Note presents three distinct arguments: First, President Bush never had the constitutional power to use military force to implement a Security Council resolution without congressional authorization; second, the Persian Gulf conflict was a war within the meaning of the Constitution, and as such, only Congress, not the President, had the power to authorize it; third, Congress, during the Persian Gulf conflict did not delegate its war making power to the President. The author concludes that the United Nations growing role may lead to increased opportunities for the President to abuse the congressional war making power

Measures of neighborhood walkability and their association with diabetes and depressive symptoms in black women

Using data from the prospective Black Women's Health Study (BWHS; n=18,525), the impact of neighborhood walkability on incident diabetes and depressive symptomology was assessed. Neighborhood walkability was assessed for BWHS participants residing in Chicago, IL, Los Angeles, CA or New York, New York in 1995, 1997 or 1999 by factor-analyzing 14 components (e.g., sidewalk coverage, number/type of intersections, population/housing density) into a single continuous measure ("neighborhood walkability"), divided into four categories (least walkable, 2nd least walkable, 2nd most walkable, most walkable). Compared to women living in a most walkable neighborhood in 1995, women living in a least walkable neighborhood had a modestly higher hazard of incident diabetes over 16 years of follow-up (IRR=1.06; 95% CI=0.90-1.24) and a higher risk of depressive symptomology, using 1999 and 2005 Center for Epidemiologic Studies (CES-D) scores (CES-D≥16: RR=1.02, 95% CI=0.94-1.11; CES-D≥25: RR=1.18, 95% CI=1.02-1.37). Associations with incident diabetes were strongest among women who resided in a higher SES neighborhood, among the healthiest women (lowest body mass index, most frequent vigorous exercise), and when follow-up was lagged four or 10 years, while associations with depressive symptomology were strongest among women who resided in Los Angeles, who engaged in no vigorous activity at baseline, or who averaged less than one per hour travelling in a car or bus. Neighborhood walkability and neighborhood socioeconomic status (SES) were strongly inversely related; disentangling these two aspects is a methodological challenge to assessing the health impact of the built environment. In a subset of 3,000 addresses, neighborhood walkability in 1999 was highly positively correlated (r=0.70) with WalkScore® (a free, publicly-available measure relying upon walking distances to specified amenities) in 2012-13. Neighborhood walkability and WalkScore® were both valid measures of neighborhood walkability, best gauged using total length of bus routes, number of intersections, and total sidewalk length. WalkScore® has the potential to serve as a "standard" neighborhood walkability measure, allowing easier comparison of the health impact of the built environment across many studies