Social and physical features of the neighborhood environment may influence obesity risk for the general public, as well as, for specific ethnic minority groups such as Latinos. According to the ethnic enclave perspective, minority communities contain protective resources such as social capital, which can promote the exchange of information and enhance trust among residents. In turn, these social resources can encourage healthful diets and physical activity, which then reduces the likelihood of health problems such as obesity. At the same time, according to the residential segregation perspective, minority communities also face structural disadvantages including the limited availability of health promoting resources such as parks. A lack of neighborhood parks can reduce opportunities for physical activity and increase obesity risk.

Accordingly, this dissertation investigated two features of Latino neighborhood environments in Los Angeles that may be related to obesity risk: social capital and park availability. First, I examined the relationship between Latino neighborhood composition and individual obesity risk among a sample of adults (n=2,919) using data from Wave 1 (2000-2001) of the Los Angeles Family and Neighborhood Survey (L.A. FANS). I used multilevel regression analysis to model the relationship between neighborhood percent Latino and Body Mass Index (BMI) controlling for individual age, race/ethnicity, gender, nativity status, family income and education. To test the hypothesis that social capital may help explain the relationship between neighborhood percent Latino and obesity, I used multilevel mediation analysis. My analyses showed that Latino-concentrated neighborhoods were associated with higher BMI, but I found no support for the mediating role of social capital (e.g., social cohesion or group participation) in the neighborhood-obesity pathway.

Second, I also examined differences in neighborhood-level park features using data from the Los Angeles County Location Management System (2010), a database of park location information for all Los Angeles County census tracts (n=2,258). I used zero-inflated negative binomial regression to model the number of park features as a function of Latino immigrant neighborhoods, controlling for percent black, percent Asian, percent living in poverty, total population, population density, land area, and attached housing. These data showed that there were fewer total park features available in Latino immigrant neighborhoods. Further, Latino immigrant neighborhoods had fewer natural park features such as campgrounds and hiking trails.

Findings from this dissertation contribute to the emerging body of literature that suggests Latino neighborhoods may have obesogenic features. I find some support for the residential segregation perspective--Latino neighborhoods were associated with higher BMI, and social capital does not appear to attenuate this relationship. In addition, Latino immigrant neighborhoods had few park features. These findings are noteworthy because differences in neighborhood resources may contribute to the disproportionately high prevalence of obesity among Latinos. More research is required to explicate what role, if any, the neighborhood social environment plays in the relationship between Latino neighborhoods and obesity. In addition, future work should consider the connections between disparities in the availability of neighborhood resources such as parks, and disparities in physical activity and obesity.

We offer a new tool to improve matchups between surname and ethnicity, illustrating the use of this method with data on Spanish surname matching drawn from the U.S. Census. We first show that there is no such thing as the proportion of bearers of a given name who are Hispanic. How Hispanic any given name will turn out to be is a function of the overall Hispanicity of the population, which will affect both the distribution of names and the conditional probability that the possessor of any given name will be Hispanic.  We then propose a simple approach, using only two common names -- one of which is far more likely to be Hispanic and one of which is far more likely to be non-Hispanic -- that allows us to generate, via Bayes Theorem, remarkably accurate estimates about the size of Hispanic populations in California cities from very limited data, here the ratio of those with the name ‘Garcia’ to those with the name ‘Anderson’.  

DNA encodes the genetic information required for function and is packed into the nucleus by wrapping DNA around a protein complex comprised of histone proteins. Packing of the DNA into these complexes termed nucleosomes posses problems because DNA that requires expression must be easily accessible, while regions whose expression will be deleterious must remain transcriptionally inactive. To address this problem the DNA is further organized into large functional domains of heterochromatin and euchromatin, where the

former is transcriptionally repressed and the latter is transcriptionally active. To achieve this organization the nucleosomes within these domains are differentially post-transcriptionally modified to define chromatin domains.

The work of this thesis focuses on two distinct topics in heterochromatin function: how heterochromatin-induced transcriptional silencing is mediated in a sequence independent manner and how transcriptional silencing is maintained within the boundaries of the heterochromatin domain.

Chapter two presents work that examines the effect of the heterochromatin machinery on the chromatin structure of domains designated as heterochromatin. We find, through the creation of nucleosome occupancy maps of silencing-defective mutants, that nucleosome-free regions (NFRs), which associate with transcriptional start sites and regulatory regions in heterochromatin, had been eliminated upon the formation of heterochromatin. Additionally, the required heterochromatin machinery needed to eliminate NFRs within heterochromatin differs based on the type of sequence that is encountered. Through this work we propose that sequence independent transcriptional silencing is a result of the silencing factors acting in a sequence specific manner to eliminate NFRs.

Chapter 3 explores how the cell maintains and defines the transition between euchromatin and heterochromatin to prevent the encroachment of transcriptional silencing or activation into the neighboring chromatin domain. DNA sequence elements called boundary elements have been defined in many metazoans to be required for this activity. To understand how boundary elements function, we describe the development and potential uses of a genetic reporter gene system that displays boundary activity in Schizosaccharomyces pombe. Using this reporter, we show that two parallel mechanisms prevent heterochromatin spread from escaping its chromatin domain. Additionally, we report a novel function for a silencing factor, Swi6, in preventing heterochromatin spread at boundary elements.

On a daily basis, black legislators, like all legislators, are faced with competing demands for their limited time and resources. They must decide which of their priorities are worth fighting for and how best to fight for them. It is through these daily decisions that members provide their constituents with representation. The primary purpose of this dissertation is to understand how black legislators make these choices. More broadly, this dissertation asks why black members of Congress engage in the legislative strategies they do. Are they distinct from the strategies used by non-black members? What influences which activities they engage in and when? And, what does this mean for the substantive representation of blacks in America?

Based upon analyses of an original dataset that looks at floor speeches and committee work of all legislators in the U.S. House of Representatives in four issue areas during select congresses over a 50-year span of time, I show that race impacts how members of Congress strategically invest their limited resources in the legislative process. More particularly, I argue that in comparison to their white counterparts, and all else equal, black legislators will exploit strategic opportunities to advocate for the interests of African American communities. How they exploit these opportunities, however, varies in response to the particular conditions they face. I show that shifts in black legislative strategies have occurred on two levels. First, as black legislators have become more institutionally incorporated they have shifted their strategies away from rhetorical floor advocacy (protest) to one focused on committee advocacy (policymaking). On another level, black legislative behavior is much more nuanced, responding to the continually changing congressional circumstances. More particularly, black legislative strategies shift in response to the changing (1) positions of black legislators in Congress, (2) the partisan control of the House and the position of key Congressional players, and (3) the issue being pursued.

The project holds major implications for evaluating the substantive benefits of descriptive representation by showing that there are inherent benefits to electing black legislators. However, the benefits they provide are not equally felt among all segments of the black community.

Explaining land use change in Mexico requires understanding the behavior of the local institutions involved. We develop two theories to explain deforestation in communities with and without forestry projects, where the former involves a process of side payments to non-members of the community and the latter of partial cooperation among community members. Data collected in 2002 combined with satellite imagery are used to test these theories. For the forestry villages, we establish a positive relationship between the distribution of profits as dividends instead of public goods and forest loss. For communities not engaged in forestry projects, deforestation is largely related to the ability of the community to induce the formation of a coalition of members that cooperates in not encroaching. This happens more easily in smaller communities with experienced leaders. A disturbing result of the analysis is that deforestation is higher when a community engages in forestry projects, even after properly accounting for self-selection into this activity. This suggests that forestry projects as they now exist in Mexico are not sustainable and contribute to the deforestation problem.

Grower Benefits from the Adoption of Genetically Modified Rice in California

The California Wine Industry: Entering a New Era?

Targeting Payments for Environmental Services: The Role of Risk