This dissertation is comprised of three independent essays. Across each essay, I examine the impact of public policies on low-income households and individuals using administrative and survey data in conjunction with quasi-experimental econometric techniques. In Chapter 1, I study the impact of Source of income (SOI) housing policies which prohibit discrimination against prospective renters on the basis of the source of income they report on rental applications. Using county- and housing agency-level data, I exploit time-variation in the implementation of SOI policies across jurisdictions to identify the effects of these policies on renters using housing choice vouchers and the local housing agencies that administer the voucher program. I find that such policies are associated with reductions in average wait times prior to moving into rental units for voucher recipients. Additionally, I provide evidence that SOI policies increase the fraction of vouchers under lease for housing agencies with lower average utilization rates. In Chapter 2, I study the impact of notifications that water systems in California provide to consumers when they detect elevated levels of contaminants in the drinking water they supply. I find little evidence that home prices are affected by public notifications in general. However, public notifications regarding nitrates, a contaminant which is especially relevant to California, and which has received substantial media attention in the state, do appear to negatively affect home prices. Focusing on a sample of community water systems which experienced at least one nitrate notification over the sample period, notifications regarding nitrates are associated with statistically significant declines in home prices of approximately 5 percent in the two years following a notification. In Chapter 3, my co-authors and I examine the impact of state-level policies that give unauthorized immigrants the ability to legally obtain driver’s licenses, known as Unauthorized Immigrant License Policy (UILP). We exploit variation in the timing and location of the implementation of these policies to assess how UILPs affect driving behavior and insurance claims. We find that UILPs are associated with a 1 percent increase in insurance coverage, suggesting that newly licensed unauthorized immigrants do opt to purchase auto insurance. However, we also document a disproportionate increase in insurance claims, and we document a positive relationship between California’s UILP and the number of collisions.

This work deals with local governments and fiscal stress. In the first chapter, I analyze the response of individual housing sales prices to negative information or “news” about local public debt levels and their underlying impact on the provision of public goods and services. In particular, I use the announcement that rising levels of unfunded pension liabilities for the San Diego City Employees’ Retirement System (SDCERS) were higher than previously perceived. In the second chapter, I analyze the effect of fiscal stress on local government fiscal structures. For this analysis, I focus on the sudden investment losses of nearly $1.7 billion in 1994 that led to Orange County’s default on debt obligations and bankruptcy. In the third chapter, I analyze how local governments underfund their public pensions over the business cycle—where unfunded pension liabilities serve as an effective way to borrow from the public workforce. I look at changing levels of unfunded pension liabilities and the local government characteristics over the 2001 and 2008 recessions.

The recognition that cells can sense physical cues has inspired numerous investigations into the roles that mechanical forces play in both healthy and diseased cells. This rapidly growing area of research, often called cellular mechanobiology, has shown that physical interactions between cells and the surrounding extracellular matrix can regulate a number of fundamental cell behaviors. This insight has prompted the development of new methods to systematically engineer the mechanical properties of extracellular matrices (e.g., rigidity and geometry), both as a way to study the mechanisms behind cellular mechanosensing and as a way to directly control cell behavior in tissue engineering applications. In contrast, an equally powerful approach for manipulating cell-matrix interactions could be to directly engineer the mechanical properties of the cells themselves by modifying the intracellular signaling pathways that regulate how cells sense and respond to physical cues. This type of "inside-out" strategy would be useful for controlling cell behavior independently from extracellular matrix properties and would allow investigation into how changes in cellular mechanics such as cell shape, stiffness, and contractility can directly alter cell behavior.

In these dissertation studies, a genetic strategy was developed to precisely control the mechanical properties and motility of cells by manipulating the activity of cytoskeletal signaling proteins. Genetic mutants of the signaling proteins RhoA GTPase, Rac1 GTPase, or myosin light chain kinase (MLCK) were introduced into human glioblastoma cells under the control of conditional promoters, thereby enabling graded and dynamic control over their expression through addition and withdrawal of the transcriptional inducers. Increasing the activity of RhoA or MLCK by inducibly expressing constitutively active (CA) mutants increased both the stiffness and the contractility of cells in a graded manner, which had an inhibitory effect on cell migration. Interestingly, decreasing RhoA activity through expression of a dominant negative (DN) mutant also produced a graded decrease in cell migration speed, indicating that cell motility varies biphasically with RhoA activity levels. A similar biphasic dependence was discovered upon varying the activity of Rac1. These results demonstrate the importance of using quantitative methods to reveal potentially nonlinear relationships between protein activity and cell behavior.

Expanding upon this strategy, two orthogonal promoter systems were combined to provide simultaneous control over the activity of two proteins in the same cell. RhoA and Rac1 are known to suppress each other through crosstalk between their signaling pathways, suggesting that cells can normally have high activity of only one protein or the other. To investigate the effects of forcing high activation of both proteins, CA RhoA and CA Rac1 were introduced into the same cells under different conditional promoters (either doxycycline-inducible or cumate-inducible). Expression of CA RhoA did not alter Rac1 activity and vice versa, demonstrating that the activity levels of RhoA and Rac1 can be independently varied with this strategy. Notably, expressing both CA mutants had a greater inhibitory effect on cell migration than either mutant alone, indicating that the effects of these mutants were additive rather than suppressive.

Finally, these orthogonal promoters were used to dynamically control the motility of multiple cell populations in a three-dimensional matrix, providing a new way to spatially pattern cells. When cells were cultured as multicellular spheroids within a collagen matrix, CA Rac1 expression stimulated cell migration, while DN Rac1 expression strongly inhibited it. Thus the ability to switch these two phenotypes on and off by adding and withdrawing the transcriptional inducers provided a way to control both the timing and the extent of cell migration. To exploit this as a patterning method, cells expressing DN Rac1 from either the doxycycline-inducible promoter or the cumate-inducible promoter were mixed together as multicellular spheroids and then subjected to alternating administration of the two inducers. When the inducer was switched (e.g., doxycycline removed and replaced with cumate), one population was stimulated to migrate while the other was inhibited, and this created radially symmetric patterns of cells over time.

The strategies developed in these dissertation studies represent a novel method for tuning cellular mechanical properties and behaviors, which we expect will be useful in a number of tissue engineering applications. In addition, by enabling graded control over the activity of multiple proteins, these methods provide a unique opportunity to investigate the quantitative relationships describing how protein activity levels influence cell behavior. Given that cell and tissue mechanics have been discovered to play critical roles in a number of human diseases, a better understanding of these relationships may lead to new therapeutic targets for disease treatments.

Methyl tert-butyl ether (MTBE) is a contaminant of concern to groundwater resources due to its persistence in subsurface environments. MTBE appears to be degraded readily in the presence of oxygen but is recalcitrant under the anaerobic conditions prevalent in the subsurface, and can be converted into the more toxic compound tert-butanol (TBA). As ethanol is being promoted as a renewable fuel and a replacement for MTBE in gasoline formulations, its potential impact on the biodegradation of preexisting contaminants and on other components of petroleum must be examined. The purpose of this study is to investigate the effect of ethanol release on existing MTBE plumes and the fate of TBA under sulfate-reducing conditions. Our results suggest that TBA, MTBE and ethanol-induced methane concentrations are strong determinants of the composition of the indigenous microbial community that develops during MTBE transformation. Some of the changes in microbial communities induced by ethanol may be long lasting, thus potentially altering the natural attenuation capacity of the impacted aquifer.

In six experiments, this dissertation investigated duration judgments for verbal stimuli, testing predictions of information-processing models of time perception. Experiments 1, 2, and 3 explored the effects of low-valence, high-arousal taboo words on the perception of time. The results revealed that durations of taboo words were underestimated compared to neutral words in prospective timing tasks, including the temporal bisection task in Experiment 1 and the ordinality comparison procedure in Experiment 2. In both of these experiments, memory was better for taboo than neutral words in surprise free recall tasks. These results supported the predictions of the attentional gate model, which suggests that duration judgments are shorter when attention is directed away from time. In Experiments 1 and 2, emotion-linked memory encoding processes associated with taboo words may have been prioritized over the timing tasks, directing attention away from time and reducing duration judgments, as well as improving memory for taboo words. In Experiment 3, durations of taboo words were overestimated compared to neutral words in a retrospective duration reproduction task. This supported the predictions of the memory storage model, which suggests that retrospective duration judgments are longer for intervals in which greater quantities of non-temporal information are encoded. Experiments 4, 5, and 6 examined the effects of words displayed in novel combinations of fonts, sizes, and colors on the perception of time. Results from prospective temporal bisection tasks revealed that durations of words displayed in novel text styles were underestimated compared to words displayed in standard text styles. Similar results were found in Experiment 4, in which half of the words were displayed in novel text styles, and in Experiment 5, in which only one twelfth of the words were displayed in novel text styles. The similar effects of taboo words and novel text styles on duration judgments suggest that these effects are driven by attentional mechanisms. In Experiment 6, durations of novel shapes were judged to be longer than durations of novel words in the oddball task, providing tentative support for the hypothesis that words affect timing judgments differently than simple visual stimuli.