America's Mayors: Who Serves and How Mayors Shape Policy

This dissertation asks three fundamental questions about representation in American cities. Who serves as mayor? How do voters select mayors? And, do mayors shape policy? Responsible for funding and providing essential services, municipal governments have a huge impact on the public's safety and quality of life. As chief elected officials, mayors are unquestionably important but also understudied political actors. A number of rich and detailed case studies provide valuable insights on individual mayors and their influence, but quantitative cross-city studies have yielded mixed findings on mayors' abilities to affect outcomes. To date, efforts to comprehensively and systematically study mayors have been hampered by a lack of data. To overcome these data limitations, I amassed an original dataset that includes detailed background information on more than 3,200 mayoral candidates, covering nearly 300 U.S. cities over the last 60 years. My data reveal that mayors, like politicians at higher levels of government, are not very representative of their constituents---they are much more likely to be white and male, with prior political experience and white-collar careers. Business owners and executives are especially well represented in American city halls, accounting for about 32% candidates and mayors. This study provides compelling new evidence that mayors can and do influence policy outcomes. Using a regression discontinuity design, I find that business executive mayors shape spending priorities, leading to significantly lower levels of spending on redistributive programs and greater investment in infrastructure. Perhaps counterintuitively, electing a business executive mayor appears to have little effect on the overall size of government. However, suggestive evidence indicates that they may increase local revenue, but in the form of fees and charges rather than taxes. My findings suggest that business executives preside over policy changes with implications for the distribution of both costs and benefits of local government. In another component of the dissertation, I employ a conjoint survey experiment to investigate why voters so often elect business executives. The experimental results suggest that a candidate's experience as a business owner or executive is likely to influence voters preferences and evaluations. These findings are consistent with longstanding claims that voters rely on candidate characteristics, such as race, ethnicity, or incumbency, as information shortcuts in the absence of party cues. Notably, the cues they use may vary with party identification. In nonpartisan contests, political experience has an even stronger influence on the preferences of Democratic respondents, while Republicans give more weight to occupation. Overall, my experimental results suggest that electoral institutions may interact with voters' preferences to shape descriptive representation. At the same time, my analyses of new observational data on mayoral candidates document striking deficits of descriptive representation in America's cities and suggest that who serves in office has meaningful policy consequences

Simulation of attempts to influence crowd dynamics, A

Includes bibliographical references.An understanding of how to alter crowd dynamics would have a significant impact in a number of scenarios, e.g., during riots or evacuations. The social force model, where individuals are self-driven particles interacting through social and physical forces, is one approach that has been used to describe crowd dynamics. This work uses the framework of the social force model to study the effects of introducing autonomous robots into crowds. Two simple pedestrian flow problems are used as illustrative examples, namely flow in varying width hallways and lane formation in bidirectional pedestrian flow. Preliminary results indicate that robots capable of inducing an attractive social force are effective at improving pedestrian flow in both of these scenarios.This work was supported by the Non-lethal Technology Innovation Center, University of New Hampshire

Totally Nonnegative (0, 1)-Matrices

We investigate (0, 1)-matrices which are totally nonnegative and therefore which have all of their eigenvalues equal to nonnegative real numbers. Such matrices are characterized by four forbidden submatrices (of orders 2 and 3). We show that the maximum number of 0s in an irreducible (0, 1)-matrix of order n is (n − 1)2 and characterize those matrices with this number of 0s. We also show that the minimum Perron value of an irreducible, totally nonnegative (0, 1)-matrix of order n equals 2 + 2 cos (2∏/n+2) and characterize those matrices with this Perron value

Federal and State Remedies to Clean Up Hazardous Waste Sites

Over fifty-seven million metric tons of hazardous waste are produced as a by-product of manufacturing in the United States each year. Only ten percent of this waste is disposed of in an environmentally sound manner. The improper disposal of hazardous waste has given rise to crisis areas of national notoriety such as Love Canal and Valley of the Drums. Although the danger to public health and the environment cannot be precisely calculated, the disposal of hazardous waste presents a problem that can no longer be ignored. Virginia\u27s own experience with kepone contamination in the James River exemplifies the dangers and costs associated with this disposal problem

Enhanced Ex Vivo expansion of human hematopoietic progenitors on native and spin coated acellular matrices prepared from bone marrow stromal cells

The extracellular microenvironment in bone marrow (BM) is known to regulate the growth and differentiation of hematopoietic stem and progenitor cells (HSPC). We have developed cell-free matrices from a BM stromal cell line (HS-5), which can be used as substrates either in native form or as tissue engineered coatings, for the enhanced ex vivo expansion of umbilical cord blood (UCB) derived HSPC. The physicochemical properties (surface roughness, thickness, and uniformity) of native and spin coated acellular matrices (ACM) were studied using scanning and atomic force microscopy (SEM and AFM). Lineage-specific expansion of HSPC, grown on these substrates, was evaluated by immunophenotypic (flow cytometry) and functional (colony forming) assays. Our results show that the most efficient expansion of lineage-specific HSPC occurred on spin coated ACM. Our method provides an improved protocol for ex vivo HSPC expansion and it offers a system to study the in vivo roles of specific molecules in the hematopoietic niche that influence HSPC expansion

Essentially Negative News About Positive Systems

In this paper the discretisation of switched and non-switched linear positive systems using Padé approximations is considered. Padé approximations to the matrix exponential are sometimes used by control engineers for discretising continuous time systems and for control system design. We observe that this method of approximation is not suited for the discretisation of positive dynamic systems, for two key reasons. First, certain types of Lyapunov stability are not, in general, preserved. Secondly, and more seriously, positivity need not be preserved, even when stability is. Finally we present an alternative approximation to the matrix exponential which preserves positivity, and linear and quadratic stability