Genetic association analyses have successfully identified thousands of genetic variants contributing to complex disease susceptibility. However, these discoveries do not explain the full heritability of many diseases, due to the limited statistical power to detect loci with smal…
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The atopic dermatitis, an inflammatory disease affecting skin, is known to play an important role in allergen sensitization via the damaged skin barrier. This sensitization can lead to allergic diseases such as allergic rhinitis and allergic asthma. The inflammatory reactions le…
Choline and betaine are important methyl donors that contribute to protein and phospholipid synthesis and DNA methylation. They can either be obtained through diet or synthesized de novo. Evidence from human and animal research indicates that choline metabolic pathways may be ac…
Maximizing data quality may be especially difficult in trauma-related clinical research. Strategies are needed to improve data quality and assess the impact of data quality on clinical predictive models. This study had two objectives. The first was to compare missing data betwee…
The performance of several widely-known methods for analyzing data utilizing nonlinear mixed effects models are evaluated via simulation in two settings. Each setting is a hierarchical mixed effects model in which repeated observations on a subject are modeled by subject-specifi…
The genetics of obesity has been studied extensively in white populations, but very few studies have involved black populations. The genetic inheritance of obesity was examined in two samples of families of African origin. We used segregation analysis to study the transmission o…
When evaluating the protective effect of a vaccine against infection, or vaccine efficacy (VE), it is important to consider whether the protection conferred on vaccinated individuals wanes with time. We consider the case that data are available on time to infection for both vacc…
Data from mercury poisoning episodes in Japan and Iraq have been used to derive threshold levels for health effects in humans, and the U.S. Environmental Protection Agency (EPA) has established a reference dose (RfD) for methylmercury of 0.30 μg/kg/day. It is desirable, therefor…
This study presents an analysis of demographic, socio-economic and environmental characteristics that may influence the quantum and timing of first, second and third births among Iranian women. This study focuses on the role that these variables played in influencing the fertili…
SRN-39 is a recently released sorghum cultivar in Sudan. Understanding the nitrogen (N) and growth patterns are crucial in its adaptation to a N deficient environment of the intensively cultivated regions of Sudan. However, study of N to conserve soil fertility must be coupled w…
Estimates of total fecundability and total fetal loss are confounded by an inability to detect pregnancies very early in gestation. A cycle in which no pregnancy is observed results from either no conception or a conception followed by an unrecognized fetal loss. This research e…
The hypothesis of common childhood exposure for Hodgkin's Disease (HD) as suggested by previous studies was tested in this study by evaluating school clusters. The cases consisting of Los Angeles County residents, diagnosed with HD within 1968-1997, ascertained from the Universi…
Data in the form of proportions arise in toxicology (Weil, 1970; Williams, 1975) and other similar fields (Crowder, 1978; Otake and Prentice, 1984). These proportions often exhibit variation greater than predicted by a simple binomial model. Several parametric models such as the…
This dissertation is composed of three papers which address the problem of variable selection for models with missing data. In the first paper, we consider variable selection for generalized linear models with missing data, including missing covariate and/or response data. The s…
Matched cohort study designs appear often in medical research. These designs match nt exposed study subjects to nc unexposed subjects on one or more characteristics. The purpose of matching is to control measured and unmeasured confounding effects and to increase estimation prec…
An early warning system for dengue disease in the province of Yogyakarta, Indonesia was developed. Using Poisson general linear models, accurate predictions of the number of recorded dengue cases between June 1999 and August 2004 were obtained up to four months in advance based …
Consisting of four articles, this thesis focuses on using time series analyses and theoretical modeling approaches to understand cholera dynamics and evolution in endemic regions. The first article develops a nonlinear statistical model with two related objectives: the reconstru…
Background. Group A Beta-hemolytic Streptococcal (GAS) pharyngitis is the precipitating cause of rheumatic fever (RF) and rheumatic heart disease (RHD). Primary prevention of RF/RHD is accomplished via identification of and subsequent treatment of the organism that causes GAS, S…
The Laboratory Information Systems Applications (LISA) is a LIMS system designed for the management and analysis of genetic data from large scale investigations of human identification. The validation study evaluated the pedigree construction and analytical tools of the Kinship …