Graduation date: 2004

On August 31, 1992, Quality Printing Circuits, a circuit board manufacturing plant in Phoenix, Arizona, burned to the ground. The fire lasted approximately eight hours, creating a thick, black smoke that blew into the surrounding community. Emergency evacuation was erratic and since no air samples were taken during the fire, community exposure levels were unknown. Immediately afterwards, residents reported health problems but government studies on the community were unable to link reported health problems and the fire. Eight months after the fire, a local advocacy group performed a health study on the community. The 690 people surveyed reported symptoms such as asthma, blurred vision, vomiting, hair loss, rashes, and extremity numbness. The survey was never analyzed and the case was closed. Community members continued to report health problems and five years after the fire, the US Environmental Protection Agency reopened the case. They performed two sampling studies but results found that chemical levels were below allowable exposure levels. This thesis contains three chapters that investigate the political, health, and scientific issues related to the QPC fire. The scientific chapter uses the EPA's ISCST3 dispersion model and a mixed-box model, to approximate community exposure concentrations and compare them to allowable human exposure levels. Results of the ISCST3 model show that four (hydrogen chloride, polycyclic aromatic hydrocarbons, Acrolein, and naphthalene) of the twenty chemicals modeled were above government allowable concentrations. Inhalation exposure to these chemicals causes similar symptoms as those reported by residents. The health-focused chapter characterized health symptoms reported in the 1993 health survey. Results found that symptoms experienced by residents were similar to those documented in other studies of exposure to chemical smoke. The study also found that residents living closest to QPC reported a greater number of symptoms than residents living further away. The political chapter analyzed the debate as to whether QPC officials and government agencies took the steps needed to protect the exposed community during and after the QPC fire. What became evident was that a significant conflict existed between the interests of residents involved in the QPC fire and the government agencies responsible for protecting them. / Graduation date: 2004

In the United States, falls are the leading cause of unintentional death with one of every three people 65 years and older falling each year. Falls account for approximately 95% of hip fractures among older adults and falls to the side predominate hip fracture related falls in this population. However, risk factors for side and frequent falls are poorly understood. Furthermore, few data exist to explain differences in bone mineral density among older postmenopausal women. In particular, data regarding the timing of hormone replacement therapy (HRT) among older women is scarce. In the first aim of this dissertation, we examined changes in mobility and balance-related risk factors for side falls as well as differences in these risk factors according to fall status in a population of 107 independent, elderly women (>70 yrs), who were followed over 2 years. We found hip abduction strength decreased (p<.001) in all subjects, with side-fallers exhibiting weaker hip abduction strength (p=.008), greater sway velocity (p=.027), and slower performances on the tandem walk (p=.039) and Get Up and Go (p<.001) compared to non-fallers. For the second study, in the same population, we examined 2-year changes in balance self-efficacy (BSE) and the relationship of BSE to side fall risk factors and falls incidence. Results showed BSE at baseline was predictive of Get Up and Go, hip abduction strength and tandem walk at follow-up (p<.008), but that BSE decreased only among the non-fallers (p=.013). In the third study, we examined 3-yr hip bone mineral density (BMD) changes in women with distinct hormone replacement therapy (HRT) profiles: 1) no hormone replacement therapy (N0HRT), 2) HRT continually since menopause (Continual), 3) HRT begun 10 years after menopause (Late), 4) HRT initiated within 5 years (New), and compared the change in BMD of the hip across HRT groups. Only the NoHRT group lost bone over the 3 years (p=.014). We also assessed BMD of the lateral spine across levels of estrogen use in a sub-sample of participants and found long-term HRT users had significantly higher lateral spine BMD (p=.041) compared to women who had never been on HRT. / Graduation date: 2003

This study was designed to investigate the relationship between retinol intake, bone mineral density, and falls in 101 elderly women aged 72 to 90 years (78.6 yrs. �� 4.3 yrs.). Bone mineral density (BMD) (g/cm��) of the left hip, anterior-posterior lumbar spine (L3), and lateral spine (L3) was measured using dual-energy x-ray absorptiometry. Dietary intake and physical activity were assessed by validated questionnaires (the 100-item Block Food Frequency Questionnaire and the Physical Activity Scale for the Elderly, respectively). Isometric hip abduction strength of the right and left legs was assessed using a hand-held dynamometer. Fall surveillance was collected using a "postcard" system at three-month intervals over a two-year period. Multiple regression analyses were used to show the predictability of retinol, vitamin D, calcium, years past menopause, years on hormone replacement therapy, and physical activity on BMD variables. Together, these variables explained 14% of the variance in total hip BMD at follow-up (R��=0.14, SEE=0.12, p=0.020), 26% of the variance in the anterior-posterior spine BMD at follow-up BMD (R��=0.26, SEE=0.17, p=0.051), and 33% of the variance in lateral spine BMD at follow-up (R��=0.33, SEE=0.10, p=0.009). Two-year changes in hip BMD were poorly predicted using the model with only 5% of total hip BMD variance being explained by the six independent variables (R��=0.05, SEE=0.03, p=0.558). Logistic regression was used to determine whether the likelihood of being a faller vs. a non-faller could be predicted from a model using retinol, vitamin D, average hip strength, and physical activity. It was shown that 11.5% of the variability in fall status could be explained by the model (Cox & Snell's R��=0.115). Using an ROC curve analysis, the model correctly classified 69% of the individuals into the correct "fall category". We conclude that retinol, although not an independent predictor of BMD or fall status, is an important component in the prediction of both BMD and falls. Further interventional research is needed to determine the effects of retinol on BMD and falling. / Graduation date: 2004

The goal of the project was to develop a functional prototype of an environmental risk assessment parameter database on the World-Wide Web. The ability to develop a consolidated environmental database has become possible due to the phenomenal growth of the Internet and the World-Wide Web over the past few years. A large number of environmental resources do currently exist; however, with the large volume of information available, access, management, reliability, and retrievability have become increasingly difficult. To illustrate the prototype database, a practical environmental concern and the tools necessary to evaluate and characterize that concern were needed. Uranium (�������U) daughters leaching from abandoned mill tailing piles at three abandoned uranium mines in southwestern Colorado were chosen to demonstrate the database concept. The RESRAD environmental pathway modeling code served as the evaluation and characterization tool. Due to the size and complexity of RESRAD, a single radionuclide release rate equation was isolated as a controllable component of the code. The equation was a small part of the water pathway factor and examined the rate at which radionuclides absorbed in soil were leached by infiltrating water. This serves as the source term for groundwater contamination and directly applies to the �������U progeny leaching from mill tailing piles scenario. Parameters selected from the equation dealt with the background data that directly influenced the mobility of contaminates in the environment. Environmental data for the three Colorado sites were gathered and interpreted. Probability Density Functions (PDFs) were developed for input parameters and the results were then incorporated into the web site. / Graduation date: 1998

An approach for developing a computer-based aid to assist in monitoring and assessing nuclear power plant status during situations requiring emergency response has been developed. It is based on the representation of regulatory requirements and plant-specific systems and instrumentation in the form of hierarchical rules. Making use of inferencing techniques from the field of artificial intelligence, the rules are combined with dynamic state data to determine appropriate emergency response actions. In a joint project with Portland General Electric Company, a prototype system, called EM-CLASS, was been created to demonstrate the knowledge-based approach for use at the Trojan Nuclear Power Plant. The knowledge domain selected for implementation addresses the emergency classification process chat is used to communicate the severity of the emergency and the extent of response actions required. EM-CLASS was developed using Personal Consultant Plus (PCPlus), a knowledge-based system development shell from Texas Instruments which runs on IBM-PC compatible computers. The knowledge base in EM-CLASS contains over 200 rules. The regulatory basis, as defined in 10 CFR 50, calls for categorization of emergencies into four emergency action level classes: (1) notification of unusual event, (2) alert, (3) site area emergency, and (4) general emergency. Each class is broadly defined by expected frequency and the potential for release of radioactive materials to the environment. In a functional sense, however, each class must be ultimately defined by a complex combination of in- plant conditions, plant instrumentation and sensors, and radiation monitoring information from stations located both on- and off-site. The complexity of this classification process and the importance of accurate and timely classification in emergency response make this particular application amenable to an automated, knowledge-based approach. EM-CLASS has been tested with a simulation of a 1988 Trojan Nuclear Power Plant emergency exercise and was found to produce accurate classification of the emergency using manual entry of the data into the program. / Graduation date: 1997

Graduation date: 1993

Traditional inventory models focus on risk-neutral decision makers, i.e., characterizing replenishment strategies that maximize expected total profit, or equivalently, minimize expected total cost over a planning horizon. In this paper, we propose a framework for incorporating risk aversion in multi-period inventory models as well as multi-period models that coordinate inventory and pricing strategies. In each case, we characterize the optimal policy for various measures of risk that have been commonly used in the finance literature. In particular, we show that the structure of the optimal policy for a decision maker with exponential utility functions is almost identical to the structure of the optimal risk-neutral inventory (and pricing) policies. Computational results demonstrate the importance of this approach not only to risk-averse decision makers, but also to risk-neutral decision makers with limited information on the demand distribution. / Singapore-MIT Alliance (SMA)

Thesis (M.Sc.)--Memorial University of Newfoundland, 2005. / Bibliography: leaves 115-122.

Quantitative microbial risk assessment (QMRA) is being increasingly used to support decision-making for food safety issues. Decision-makers need to know whether these QMRA results can be trusted, especially when urgent and important decisions have to be made. This can be achieved by setting up a quality assurance (QA) framework for QMRA. A Belgian risk assessment project (the METZOON project) aiming to assess the risk of human salmonellosis due to the consumption of fresh minced pork meat was used as a case study to develop and implement QA methods for the evaluation of the quality of input data, expert opinion, model assumptions, and the quality of the QMRA model (the METZOON model). The first part of this thesis consists of a literature review of available QA methods of interest in QMRA (chapter 2). In the next experimental part, different QA methods were applied to the METZOON model. A structured expert elicitation study (chapter 4) was set up to fill in missing parameters for the METZOON model. Judgements of experts were used to derive subjective probability density functions (PDFs) to quantify the uncertainty on the model input parameters. The elicitation was based on Cookes classical model (Cooke, 1991) which aims to achieve a rational consensus about the elicitation protocol and allowed comparing different weighting schemes for the aggregation of the experts PDFs. Unique to this method was the fact that the performance of experts as probability assessors was measured by the experts ability to correctly and precisely provide estimates for a set of seed variables (=variables from the experts area of expertise for which the true values were known to the analyst). The weighting scheme using the experts performance on a set of calibration variables was chosen to obtain the combined uncertainty distributions of lacking parameters for the METZOON model. A novel method for the assessment of data quality, known as the NUSAP (Numeral Unit Spread Assessment Pedigree) system (chapter 5) was tested to screen the quality of the METZOON input parameters. First, an inventory with the essential characteristics of parameters including the source of information, the sampling methodology and distributional characteristics was established. Subsequently the quality of these parameters was evaluated and scored by experts using objective criteria (proxy, empirical basis, methodological rigour and validation). The NUSAP method allowed to debate on the quality of the parameters within the members of the risk assessment team using a structured format. The quality evaluation was supported by graphical representations which facilitated decisions on the inclusion or exclusion of inputs into the model. It is well known that assumptions and subjective choices can have a large impact on the output of a risk assessment. To assess the value-ladenness (degree of subjectivity) of assumptions in the METZOON model a structured approach based on the protocol by Kloprogge et al. (2005) was chosen (chapter 6). The key assumptions for the METZOON model were first identified and then evaluated by experts in a workshop using four criteria: the influence of situational limitations, the plausibility, the choice space and the agreement among peers. The quality of the assumptions was graphically represented (using kite diagrams, pedigree charts and diagnostic diagrams) and allowed to identify assumptions characterised by high degree of subjectivity and high expected influence on the model results, which can be considered as weak links in the model. The quality assessment of the assumptions was taken into account to modify parts of the METZOON model, and allows to increase the transparency in the QMRA process. In a last application of a QA method, a quality audit checklist (Paisley, 2007) was used to critically review and score the quality of the METZOON model and to identify its strengths and weaknesses (chapter 7). A high total score (87%) was obtained by reviewing the METZOON model with the Paisley-checklist. A higher score would have been obtained if the model was subjected to external peer review, if a sensitivity analysis, validation of the model with recent data, updating/replacing expert judgement data with empirical data was carried out. It would also be advisable to repeat the NUSAP/Pedigree on the input data and assumptions of the final model. The checklist can be used in its current form to evaluate QMRA models and to support model improvements from the early phases of development up to the finalised model for internal as well as for external peer review of QMRAs. The applied QA methods were found useful to improve the transparency in the QMRA process and to open the debate about the relevance (fitness for purpose) of a QMRA. A pragmatic approach by combining several QA methods is recommendable, as the application of one QA method often facilitates the application of another method. Many QA methods (NUSAP, structured expert judgement, checklists) are however not yet or insufficiently described in QMRA related guidelines (at EFSA and WHO level). Another limiting factor is the time and resources which need to be taken into account as well. To understand the degree of quality required from a QMRA a clear communication with the risk managers is required. It is therefore necessary to strengthen the training in QA methods and in the communication of its results. Understanding the usefulness of these QA methods could improve among the risk analysis actors when they will be tested in large number of QMRAs.