Physical Sciences and Mathematics Commons^™

Survival Analysis With Error-Prone Time-Varying Covariates: A Risk Set Calibration Approach, Xiaomei Liao, David M. Zucker, Yi Li, Donna Spiegelman

Harvard University Biostatistics Working Paper Series

No abstract provided.

A Comparison Of Frequentist And Bayesian Approaches To The Estimation Of Long-Stay Per-Diems, Jeff Hatcher, Jason M. Sutherland

Dartmouth Scholarship

Within many diagnosis related group (DRG) systems, there is recognition that a single cost weight per DRG is not suitable, and that cost weights should take into account extremely lengthy hospital stays. Long lengths of stay are considered to be due to factors largely beyond the control of the hospital, and a single weight per DRG would potentially place hospitals under financial risk.

Within Canada's acute-care, inpatient grouping methodology - Case Mix Groups (CMG+) - long-stay episodes represent approximately 4.5% of all discharges. Within a CMG (analogous to DRG), the cost weight assigned to long-stay cases consists of the typical …

Lot Quality Assurance Sampling (Lqas) And The Mozambique Malaria Indicator Surveys, Caitlin Biedron, Marcello Pagano, Bethany L. Hedt, Albert Kilian, Amy Ratcliffe, Samuel Mabunda, Joseph J. Valadez

Harvard University Biostatistics Working Paper Series

No abstract provided.

Analysis Of Subgroup Data In Clinical Trials, Kao-Tai Tsai, Karl E. Peace

Biostatistics Faculty Presentations

This conference abstract was published in the Proceedings of the Sixteenth Annual Biopharmaceutical Applied Statistics Symposium.

Agenda: World Energy Justice Conference And Appropriate Technology Arcade, University Of Colorado Boulder. Center For Energy & Environmental Security, University Of Colorado Boulder. School Of Law

World Energy Justice Conference (October 23-24)

The 2009 CEES Energy Justice Conference took place at the University of Colorado Law School on October 23rd and 24th, 2009. It featured 11 sessions, more than 40 speakers, and attracted over 200 attendees. The Conference brought together leading international and U.S. decision-makers in politics, engineering, public health, law, business, economics, and innovators in the sciences to explore how best to address the critical needs of the energy-oppressed poor (EOP) through long-term interdisciplinary action, information sharing, and deployment of appropriate sustainable energy technologies (ASETs).

The Colorado Journal of International Environmental Law & Policy (CJIELP) at the University of Colorado Law …

Causal Inference In Epidemiological Studies With Strong Confounding, Kelly L. Moore, Romain S. Neugebauer, Mark J. Van Der Laan, Ira B. Tager

U.C. Berkeley Division of Biostatistics Working Paper Series

One of the identifiabilty assumptions of causal effects defined by marginal structural model (MSM) parameters is the experimental treatment assignment (ETA) assumption. Practical violations of this assumption frequently occur in data analysis, when certain exposures are rarely observed within some strata of the population. The inverse probability of treatment weighted (IPTW) estimator is particularly sensitive to violations of this assumption, however, we demonstrate that this is a problem for all estimators of causal effects. This is due to the fact that the ETA assumption is about information (or lack thereof) in the data. A new class of causal models, causal …

Causal Inference For Nested Case-Control Studies Using Targeted Maximum Likelihood Estimation, Sherri Rose, Mark J. Van Der Laan

U.C. Berkeley Division of Biostatistics Working Paper Series

A nested case-control study is conducted within a well-defined cohort arising out of a population of interest. This design is often used in epidemiology to reduce the costs associated with collecting data on the full cohort; however, the case control sample within the cohort is a biased sample. Methods for analyzing case-control studies have largely focused on logistic regression models that provide conditional and not marginal causal estimates of the odds ratio. We previously developed a Case-Control Weighted Targeted Maximum Likelihood Estimation (TMLE) procedure for case-control study designs, which relies on the prevalence probability q0. We propose the use of …

Impact Of Ambient Air Pollution On Survival Of Renal Transplant Recipients, Rhonda Kristine Hwang

Loma Linda University Electronic Theses, Dissertations & Projects

There is increasing evidence that ambient air pollution is associated with coronary heart disease morbidity and mortality. This research has focused on the general public and less so on possible sensitive subgroups even though these may have even greater susceptibility to adverse effects of ambient air pollution. With highly prevalent traditional as well as nontraditional risk factors, renal transplant recipients may potentially be a sensitive subgroup. The purpose of this study was to evaluate the possible effect of between long-term exposure to air pollution on the risk of CHD mortality among renal transplant recipients. This cohort study includes 32,239 adult, …

Study Of The Four Factor Theory Of Women’S Sexual Function, Julie M. Merrell

Loma Linda University Electronic Theses, Dissertations & Projects

Tiefer, Hall, and Tavris (2002) described factors comprising four categories of female sexual function. They suggested that unique factors need to be examined to understand sexual function in women. Socio-cultural, political, or economic factors, partner and relationship factors, psychological factors, and medical factors were described as aspects of women’s lives that can be the source of sexual dysfunction. In a previous study, Merrell (2007) utilized Tiefer et al’s (2002) four factor model of sexual functioning to examine female sexual functioning looking specifically at body shame, relationship satisfaction, positive and negative affect, sexual self-schema, and overall health. Based on the results …

The Effects Of Physical Activity And Nutrient Intake On The Risk Of Hip Fracture : Results From The Adventist Health Study-2, Wen-Ling Liao

Loma Linda University Electronic Theses, Dissertations & Projects

This is a two year of follow up study of Adventist Health Study-2 (AHS-2). We assessed the association between physical activity, nutrient intake and risk of hip fracture among peri- and post menopausal Caucasian women using unconditional logistic regression models. All subjects completed a lifestyle questionnaire which including information of physical activity and frequency and portion size of food intake at enrollment into the study (2002-2007). The “Bi-Annual Hospitalization History” questionnaire which included a question about hip fractures due to minor trauma/falls was sent to subjects approximately two years after enrollment, with a response rat of 82.84%. In this cohort, …

A Spatio-Temporal Approach For Estimating Chronic Effects Of Air Pollution, Sonja Greven, Francesca Dominici, Scott L. Zeger

Johns Hopkins University, Dept. of Biostatistics Working Papers

Estimating the health risks associated with air pollution exposure is of great importance in public health. In air pollution epidemiology, two study designs have been used mainly. Time series studies estimate acute risk associated with short-term exposure. They compare day-to-day variation of pollution concentrations and mortality rates, and have been criticized for potential confounding by time-varying covariates. Cohort studies estimate chronic effects associated with long-term exposure. They compare long-term average pollution concentrations and time-to-death across cities, and have been criticized for potential confounding by individual risk factors or city-level characteristics.

We propose a new study design and a statistical model, …

Spatial Cluster Detection For Repeatedly Measured Outcomes While Accounting For Residential History, Andrea J. Cook, Diane Gold, Yi Li

Harvard University Biostatistics Working Paper Series

No abstract provided.

Spatial Cluster Detection For Weighted Outcomes Using Cumulative Geographic Residuals, Andrea J. Cook, Yi Li, David Arterburn, Ram C. Tiwari

Harvard University Biostatistics Working Paper Series

No abstract provided.

Residential Modifications And Decline In Physical Function Among Community-Dwelling Older Ad, Sze Yan Liu, Kate L. Lapane

Department of Public Health Scholarship and Creative Works

Purpose: The purpose of this study is to quantify the effect of residential modification on decreasing the risk of physical function decline in 2 years.

Design: Cohort study using propensity scores method to control for baseline differences between individuals with residential modifications and those without residential modifications.

Participants: Participants (N = 9,447) were from the Second Longitudinal Study on Aging, a nationally representative sample of the civilian noninstitutionalized population, aged 70 years and older in the United States at the time of baseline interview in 1994-1995.

Methods: Participants self-reported residential modifications at baseline (e.g., railings, bathroom modifications). The decline in …

Modeling And Analysis Of The Spread Of Japanese Encephalitis With Environmental Effects, Ram Naresh, Surabhi Pandey

Applications and Applied Mathematics: An International Journal (AAM)

A nonlinear mathematical model for the spread of Japanese Encephalitis, caused by infected mosquito feeding on susceptible human population incorporating demographic and environmental factors is proposed and analyzed. In the modeling process, it is assumed that the growth rates of reservoir animal population and vector mosquito population are enhanced due to environmental discharges caused by human population related factors. The model is analyzed by stability theory of differential equations and computer simulation. Both the disease-free and the endemic equilibria are found and their stability is investigated. It is found that whenever the disease-free equilibrium is locally asymptotically stable, the endemic …

Anthropometric Parameters Of Under-Five Years Old Children With Different Dietary Habits In Ukambani Region : A Study In Eastern Rural Kenya, Hellen M. Ndiku

Loma Linda University Electronic Theses, Dissertations & Projects

The objective of this descriptive cross sectional study was to assess dietary intake and nutritional status of children under-five years in two rural sites of Eastern Kenya where the staple cereals may differ. A modified rapid, knowledge, practice and coverage (KPC) questionnaire and a 24-hr dietary recall form were used to collect the data. A total of 403 households were surveyed from four randomly selected divisions. This yielded 629 surrogate 24-hr dietary recalls of children < 5 years with 314 from Mwingi district and 315 from Makueni district (49 % boys and 51 % girls).

Statistical analysis was done using SPSS and SAS. Comparison of means was done using t- test and chi square was used for proportions. The 24-hr …

A Machine-Learning Algorithm For Estimating And Ranking The Impact Of Environmental Risk Factors In Exploratory Epidemiological Studies, Jessica G. Young, Alan E. Hubbard, B Eskenazi, Nicholas P. Jewell

U.C. Berkeley Division of Biostatistics Working Paper Series

No abstract provided.

La Calidad Del Agua Potable En Arica, Con Respecto A La Salud, Emily Lubell

Independent Study Project (ISP) Collection

Water is essential to sustain life, and the availability of safe drinking water is a concern throughout the world. This study examines the potential negative health effects related to drinking the potable water in Arica, Chile. It also looks at who has access to purified water. This study was implemented over a span of four weeks in which information was collected from different local resources including, the potable water distributor, private water vendors, professors, and public health service workers. In comparison with 2001, 2009 levels of boron, total hardness and total dissolved solids are higher in concentration. In both 2001 …

The Importance Of Scale For Spatial-Confounding Bias And Precision Of Spatial Regression Estimators, Christopher J. Paciorek

Harvard University Biostatistics Working Paper Series

Increasingly, regression models are used when residuals are spatially correlated. Prominent examples include studies in environmental epidemiology to understand the chronic health effects of pollutants. I consider the effects of residual spatial structure on the bias and precision of regression coefficients, developing a simple framework in which to understand the key issues and derive informative analytic results. When the spatial residual is induced by an unmeasured confounder, regression models with spatial random effects and closely-related models such as kriging and penalized splines are biased, even when the residual variance components are known. Analytic and simulation results show how the bias …

Smoking Enhances Risk For New External Genital Warts In Men, Dorothy J. Wiley, David Elashoff, Emmanuel V. Masongsong, Diane M. Harper

Dartmouth Scholarship

Repeat episodes of HPV-related external genital warts reflect recurring or new infections. No study before has been sufficiently powered to delineate how tobacco use, prior history of EGWs and HIV infection affect the risk for new EGWs. Behavioral, laboratory and examination data for 2,835 Multicenter AIDS Cohort Study participants examined at 21,519 semi-annual visits were evaluated. Fourteen percent (391/2835) of men reported or were diagnosed with EGWs at 3% (675/21,519) of study visits. Multivariate analyses showed smoking, prior episodes of EGWs, HIV infection and CD4+ T-lymphocyte count among the infected, each differentially influenced the risk for new EGWs.

Analysis Of Randomized Comparative Clinical Trial Data For Personalized Treatment Selections, Tianxi Cai, Lu Tian, Peggy H. Wong, L. J. Wei

Harvard University Biostatistics Working Paper Series

No abstract provided.

The Prevalence And Determinants Of Health Risk Behaviors Among High School Students In Mexico, Nellie León

Loma Linda University Electronic Theses, Dissertations & Projects

The Centers for Disease Control and Prevention report that despite health promotion efforts, adolescents continue to engage in behaviors that put them at risk for morbidity and mortality. Alcohol consumption, illicit drug use, smoking, and risky sexual behaviors are among the behaviors that contribute to leading causes of morbidity and mortality in youth; these four behaviors were explored in this study. An observational cross-sectional design was utilized. The Youth Risk Behavior Survey from the Centers for Disease Control and Prevention was utilized to assess the prevalence of the four risk behaviors among high school students in Jalisco, Mexico. Items constructed …

Approaches To Estimation Of Haplotype Frequencies And Haplotype-Trait Associations, Xiaohong Li

Doctoral Dissertations 1896 - February 2014

Characterizing the genetic contributors to complex disease traits will inevitably require consideration of haplotypic phase, the specific alignment of alleles on a single homologous chromosome. In population based studies, however, phase is generally unobservable as standard genotyping techniques provide investigators only with data on unphased genotypes. Several statistical methods have been described for estimating haplotype frequencies and their association with a trait in the context of phase ambiguity. These methods are limited, however, to diploid populations in which individuals have exactly two homologous chromosomes each and are thus not suitable for more general infectious disease settings. Specifically, in the context …

The Environment And Climate Change: Is International Migration Part Of The Problem Or Part Of The Solution?, Howard F. Chang

All Faculty Scholarship

No abstract provided.

E-85 Vs. Regular Gasoline: Effects On Engine Performance, Fuel Efficiency, And Exhaust Emissions, Jordan W. Steinhaus, Donald M. Johnson, George W. Wardlow

Discovery, The Student Journal of Dale Bumpers College of Agricultural, Food and Life Sciences

This study compared the performance, fuel efficiency, and exhaust emissions of a 2.61 kW engine fueled with regular unleaded gasoline (87 octane) and an 85% ethanol blend (E85) under two load conditions. Four 1-h tests were conducted with each fuel at both governor’s maximum (3400 rpm) and peak torque (2800 rpm) conditions for a total of 16 tests. At governor’s maximum engine speed, there were no significant differences (p>0.05) between fuels for engine torque, power, specific carbon dioxide (sCO2 ), specific carbon monoxide (sCO), specific hydrocarbons (sHC), or specific oxides of nitrogen (sNOX) emissions. However, there was a significant …

An Examination Of The Persistence Of The Residual Child Welfare System In The United States: Addressing Charges Of Radical Theoretical Myopia With Implications For Social Work Practice, Peter Cabrera

Elián P. Cabrera-Nguyen

The United States follows what has been termed a residual approach to its public child welfare system. This article describes the residual model and contrasts it with the policies of other industrialized nations. It also explores the causes and persistence of the residual model in the United States through the lens of structural-functionalist theory. By doing so, this article attempts to respond to critics of structural social work who maintain that it is overly reliant on conflict theory and has nothing to offer in terms of distinct practice methods. Suggestions for a structurally informed social work practice are made.

Health Literacy In The Mathematics Classroom: The Iowa Core Curriculum As An Opportunity To Deepen Students’ Understanding Of Mathematics, Elana Joram, Susan Dobie-Roberts, Nadene Davidson

Faculty Publications

By 2012, all high schools in Iowa will be required to incorporate the new Iowa Core Curriculum, followed by elementary and middle schools in 2014 (Iowa Department of Education, 2009). The Iowa Core Curriculum addresses the question: "How is Iowa's educational system preparing our youth for successful lives in the 21st-century global environment?" (Davidson, 2009). It consists of core content standards, and identifies essential concepts and skills for content areas. The Iowa Core Curriculum also includes the ―21st Century Skills‖ of ―health, financial, technology, and civic literacy, and employability skills. These skills are to be infused into existing subject matter …

Complete Identification Of Permissible Sampling Rates For First-Order Sampling Of Multi-Band Bandpass Signals, Yan Wu, Daniel F. Linder

Biostatistics Faculty Publications

The first-order sampling of multi-band bandpass signals with arbitrary band positions is considered in this paper. Gaps between the spectral sub-bands are utilized to achieve lower sampling rates than the Nyquist. The lowest possible sampling rate along with other permissible sampling rates is identified via a unique partition of the frequency axis. With the complete identification of all the permissible sampling rates, a necessary and sufficient sampling theorem for multi-band bandpass signals is presented in terms of a series of csinc-interpolators.

Measurement Of Transient Smoke Emissions From Diesel And Biodiesel Fuel Blends In An Agricultural Tractor, Kristin M. Pennington, Sonia R. Munoz, Donald M. Johnson, George Wardlow

Discovery, The Student Journal of Dale Bumpers College of Agricultural, Food and Life Sciences

Transient smoke emissions pose potential hazards to human health and the environment. With the increased popularity of biodiesel, there is a need to determine if these fuels produce different levels of particulate matter in exhaust emissions. This study examined the transient smoke emissions of three fuels: No. 2 petroleum diesel fuel (D2, ASTM D 975), a blend of 20% biodiesel and 80% petroleum diesel (B20, ASTM 6751), and a 100% pure biodiesel derived from animal fats (B100, ASTM D 6751). Measurements of smoke emissions were taken using the SAE J1677 snap acceleration test procedure on a John Deere 3203 compact …

When To Spray: A Time-Scale Calculus Approach To Controlling The Impact Of West Nile Virus, Diana Thomas, Marion Weedermann, Lora Billings, Joan Hoffacker, Robert Washington-Allen

Department of Mathematics Facuty Scholarship and Creative Works

West Nile Virus (WNV) made its initial appearance in the New York City (NYC) metropolitan area in 1999 and was implicated in cases of human encephalitis and the extensive mortality in crows (Corvus sp.) and other avian species. Mosquitoes were found to be the primary vectors and NYC’s current policy on control strategies involved an eradication program that depends on the synchronicity of the summer mosquito population’s increases with the occurrence of cases in humans. The purpose of this paper is to investigate whether this is the most effective control strategy because past mathematical models assumed discrete behavior that …