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Puerto Rico has the highest rate of preterm birth in all of the states and territories of the United States, as well as extensive contamination of water sources. For these reasons, Puerto Rico has been selected as a test site by the Puerto Rico Testsite for Exploring Contamination Threats (PROTECT) Program. Groundwater and tap-water samples will be tested to determine the presence of specific threats. Environmental Protection Agency (EPA) methods were modified to extract and analyze the contaminants in environmental matrices. The process consists of performing a careful extraction process and analyzing the collected samples for the study area. These compounds include 10 chlorinated volatile organic compounds (CVOCs) and 3 phthalates. A gas chromatography/mass spectrometer (GC/MS) was used for the phthalates analysis, and a gas chromatography/electro capture detector (GC/ECD) was used for the CVOCs analysis. Different approaches were used to determine the detection and non-detection of the targeted compounds, depending on whether the samples had background or not. Phthalates have been found in most groundwater samples and in some of the tap water samples. These contaminants include di-n-butyl phthalate (DBP), di-ethyl phthalate (DEP), and di(2-ethyl hexyl) phthalate (DEHP). Also CVOCs have been found in some groundwater and tap-water samples. The CVOCs found were chloroform (TCM), carbon tetrachloride (CCl4), trichloroethylene (TCE), and tetrachloroethylene (PCE).
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ASSESSMENT OF WATER CONTAMINATION FOR HYDRO-EPIDEMIOLOGIC STUDIES OF PRETERM BIRTHNorma Torres Torres1, Ingrid Padilla1, José Cordero2, John Meeker3, Akram Alshawabkeh4.
University of Puerto Rico at Mayagüez, Mayagüez, PR, 2University of Puerto Rico School of Medicine, San Juan, PR, 1
University of Michigan, Ann Arbor, MI, 4Northeastern University, Boston, MA. 3
With a preterm birth rate of 17.7%, Puerto Rico has the highest preterm birth rate in the United States. As preliminary investigations indicate, the increase in preterm birth rates in Puerto Rico cannot be explained by known factors.
Chlorinated volatile organic compounds (CVOCs) and phthalates have been suggested as causes of adverse reproductive outcomes. Since the 1980s, extensive contamination in the karst groundwater system of Puerto Rico has been found. The Puerto Rico Testsite for Exploring Contamination Threats (PROTECT) is a multidisciplinary research project that attempts to assess the potential relationships between contaminants and preterm birth. The work involves collecting and analyzing historical and field water quality data from the karst aquifer of northern Puerto Rico to assess the spatial and temporal extent of groundwater contamination. The spatial extent is analyzed using geographic information system technologies. Also, pregnant women volunteers were recruited, in coordination with biomedical experts in the area of study, to be monitored during their entire pregnancy. Drinking water samples were collected from their houses to be analyzed for CVOCs and phthalates. Preliminary analysis shows a long-term, extensive level of groundwater contamination, and indicates complex fate and transport processes are affecting the mobility, storage, and release of legacy and emerging contaminants (including nitrates, trichloroethylene, and phthalates). Results suggest that water quality is also affected by hydrologic conditions in the study area. Comparison of detection results suggests that groundwater contamination is reaching drinking water sources and potentially exposing pregnant women.
312 GRADUATE POSTER ABSTRACTS
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ENVIRONMENTAL SURVIVAL OF FECAL INDICATOR BACTERIA ENTEROCOCCIAlejandra Ferrufino, Tao Yan.
University of Hawaii, Honolulu, HI.
The purpose of this experiment is to show the decay of fecal indicator bacteria in beach sand and beach waters with a lack of vegetation. In contrast, it also shows the survival and growth of Enterococci fecal indicator bacteria (ENT) in areas where vegetation is available. It is expected that the ENT bacteria collected from sand and beach water will grow exponentially with time when plant tissue powder (PTP) from surrounding areas is fed to it. However, if no PTP is given to bacteria, it is expected that the population will decrease with time and eventually die off. Therefore, the hypothesis of the experiment is that plant vegetation contributes to ENT in beach sand.
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HYBRID ANALYTICAL APPROACH FOR EMERGENCY MEDICAL SERVICE TIME RESPONSE IMPROVEMENTCarlos Escobar Sr., Hansuk Sohn.
New Mexico State University, Las Cruces, NM.
Doña Ana County, New Mexico, has contracted with American Medical Response (AMR) as the community’s exclusive 911 and non-emergency ambulance provider since July 2007. In this research, we present a hybrid analytical approach where a linear regression forecasting model and a computer simulation model are combined to analyze the quality of the AMR’s Emergency Medical Service (EMS). First, statistical tests of homogeneity were conducted to break down 24-hour periods into several equal-length periods of time such that the time-dependent travel time (speed) and arrival rate can be reasonably viewed as stationary. The forecasting model was used to determine the expected number of calls per shift. According to this volume, the minimum number of ambulances required per shift with 90% reliability were computed. Also a categorical variable is included to predict call locations based on zip code.
At the end of the statistical analysis, the number of ambulances per shift was input in the simulations model. Using the hybrid approach, we are able to identify the optimal ambulance location, which enables the AMR not only to reduce response time, but also to increase the reliability of the service. According to our simulation experiment, there are several candidate ambulance locations that provide superior response performance. Our hybrid analytical approach is a valuable tool in determining optimal location in the EMS.
MATHEMATICS & STATISTICS
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STEADY STATES AND THEIR TRANSIENTS FOR A FAMILY OF FINITE DYNAMICAL SYSTEMSXavier Teran Batista, Dorothy Bollman.
University of Puerto Rico at Mayagüez, Mayagüez, PR.
Finite dynamical systems have many applications in engineering and the sciences, including biology, computer science, and social science. In all of these applications, it is important to know what states reach a steady state and, if so, how long they take to reach the steady state, i.e., the transient. In this ongoing work we consider a family of Boolean monomial dynamical systems (BMDS) whose dependency graph is primitive. It has been shown that such a BMDS is a fixed-point system: every state eventually attains a steady-state, fixed point. Furthermore, the transient of such a BMDS is equal to the exponent of the dependency graph. In this work, we characterize transients explicitly in terms of the cycle lengths of the dependency graph, and we show a way to compute transients using programs.
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EXPLICIT SOLUTIONS TO THE HALF-LINE KORTEWEG-DE VRIES EQUATIONSarah Gauntt, Tuncay Aktosun.
University of Texas at Arlington, Arlington, TX.
The half-line Korteweg-de Vries (KdV) equation is an integrable, nonlinear partial differential equation used to describe propagation of surface water waves in shallow, narrow canals and propagation of acoustic waves in ionized gases. A formula is presented for certain explicit solutions to the half-line KdV equation in terms of three constant matrices A, B, and C with sizes n x n, n x 1, and 1 x n respectively, for any positive integer n. Such solutions include all solitary wave solutions called n-soliton solutions. In addition to their physical importance, such explicit solutions can be used to test the accuracy of numerical methods developed for solving nonlinear partial differential equations. The solution formula is generalized to the case when the matrix size n becomes infinite. This is done by writing the solution formula in terms of a determinant and by interpreting that determinant as a Fredholm determinant as the matrix size n becomes infinite. Thus, explicit solutions are obtained for the half-line KdV equation containing infinitely many solitons.
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MODELING AND COMPUTATION OF TISSUE GROWTH DRIVEN BY STEM-CELL NICHESSeth Figueroa, Jeremy Ovadia, Qing Nie.
University of California, Irvine, Irvine, CA.
Formation and sustenance of a stem cell niche in stratified epithelia is key in controlling the tissue’s growth, morphology, and regenerative capabilities. Often, stratified epithelia develop advantageous finger-like structures, such as rete ridges (or rete pegs) in the epidermis and the palisades of Vogt in the limbal, corneal epithelium, along which the stem-cell niche forms. These structures provide the basal layer of the epithelia with better protection and allow the tissue a more efficient wound response. However, how these undulating structures are formed and the role of the spatial aspects of the niche on its local environment are not fully understood. Interesting questions arising from this include how do extracellular cues and the tissue’s underlying genetic system affect niche formation and tissue morphology; how does the tissue’s morphology, in return, affect the dynamics of the cell lineage and the stem cell system’s regenerative capabilities? Here we present a 2-dimensional multiscale model of stratified epithelial growth. The tissue growth model consists of stem cells, cell lineages, and regulatory diffusive molecules. We have shown that stem cell niche development triggers distorted epithelial morphologies similar to rete ridges with stem cells accumulating along the tips, agreeing with experimental observations. Furthermore, we explore factors affecting niche formation and size as well as potential biochemical regulations that can prompt formation and stabilization of advantageous tissue architecture.
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A GENERALIZED APPROACH TO DARBOUX TRANSFORMATIONS FOR DIFFERENTIAL EQUATIONSMehmet Unlu, Tuncay Aktosun.
University of Texas at Arlington, Arlington, TX.
A Darboux transformation is a mathematical procedure used to produce a solution to a differential equation when the solution to a related differential equation is known. The basic idea behind a Darboux transformation is to change the discrete spectrum of a linear differential operator in a controlled way without changing its continuous spectrum. For example, by using a Darboux transformation, one can describe the change in a quantum mechanical system when some its quantum levels are removed or some extra quantum levels are added. Darboux transformation formulas
314 GRADUATE POSTER ABSTRACTS
for various differential equations have been developed, but such formulas seem to be specific to those particular equations without much connection among them. In our method, we develop a generalized and unified approach for Darboux transformations that is applicable to a large class of differential equations. This approach uses the solution to a linear integral equation where the kernel and nonhomogeneous terms coincide. We apply our unified approach to some specific differential equations such as the Schrodinger equation, the Korteweg-de Vries equation, and the nonlinear Schrodinger equation, and compare our formulas with the existing Darboux transformation formulas for those specific equations.
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STABILIZING GENE REGULATORY NETWORKS THROUGH FEEDFORWARD LOOPSClaus Kadelka, Reinhard Laubenbacher.
Virginia Bioinformatics Institute, Virginia Polytechnic Institute and State University, Blacksburg, VA.
The concept of canalization in gene regulation was developed as a possible solution to the question of why the outcome of embryonal development leads to predictable phenotypes in the face of widely varying environmental conditions. The key step of gene expression is fundamentally a stochastic process, which makes the stability of genetic regulation programs all the more surprising. An entirely novel gene regulatory mechanism, discovered and studied during the last decade, which is believed to play an important role in cancer, is shedding some light on how canalization may in fact take place as part of a cell’s gene regulatory program. Short segments of single-stranded RNA, so-called microRNAs, which are embedded in several different types of feedforward loops, help smooth out noise and generate canalizing effects in gene regulation by overriding the effect of certain genes on others. In a computational study, we used the modeling framework of generalized Boolean networks to explore the role that microRNA-mediated feedforward loops play in stabilizing the global dynamics of various gene regulatory networks.
We compared the degree of stochasticity of a basic gene network and an extended network in which various numbers of microRNAs have been introduced in a biologically inspired way and were able to exactly quantify the stabilizing effect for any gene regulatory network. Thus, this research contributed to an answer for the question as to what extent microRNAs stabilize gene regulatory programs.
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A COMPUTATIONAL FRAMEWORK FOR PENALIZED DISCONTINUOUS GALERKIN METHODS APPLIED TO
TIME-HARMONIC MAXWELL’S EQUATIONS IN 3DArlin Alvarado Hernandez Sr., Paul Castillo.
University of Puerto Rico at Mayagüez, Mayagüez, PR.