Ingestion exposure estimates typically use a default bioavailability of 100%, thereby assuming that the entirety of an ingested dose is absorbed into systemic circulation. However, the actual bioavailability of ingested contaminants is oftentimes lower than 100%. The research described herein investigates the use of the Simulator of the Human Intestinal Microbial Ecosystem (SHIME) for the calculation of <i>in vitro</i> bioaccessibility (IVBA), a conservative predictor of bioavailability, of mercury (Hg) from traditional northern foods and arsenic (As) from soils. The primary objective of the research described herein is to address data-gaps which have hindered attempts to incorporate IVBA into risk assessment on more than a case-by-case basis. The hypotheses of this thesis are that (1) the bioaccessibility of contaminants is dependent upon concentration due to kinetic limitations on dissolution, (2) gastrointestinal (GI) microbes in the ileum and colon alter contaminant bioaccessibility and/or speciation, (3) the GI microbial effect on bioaccessibility is toxicologically relevant, and (4) metal bioaccessibility is predictable according to dissolution kinetics.<p> Mercury bioaccessibility from country food samples was independent of total Hg concentration (F=0.5726, P=0.578) whereas As bioaccessibility was inversely related to total As concentration for Nova Scotia mine tailings, synthesized ferrihydrite with adsorbed AsV, and synthesized amorphous scorodite (P=2 x 10-10). Isotherm analysis indicated that, at high soil As concentrations, saturation of simulated GI fluids limited As bioaccessibility under gastric conditions whereas kinetic limitations constrained As bioaccessibility under intestinal conditions. Additionally, we demonstrated that GI microbes may affect Hg bioaccessibility, either increasing or decreasing bioaccessibility depending upon the type of food. For example, the bioaccessibility of HgT decreased in the presence of GI microbial activity for caribou kidney, caribou tongue, seal blood, seal brain, seal liver, and walrus flesh. In contrast, HgT bioaccessibility from Arctic char and seal intestine increased in the presence of GI microbial activity. Similarly, colon microbial activity increased (Fishers Protected LSD, P<0.05) As bioaccessibility from synthesized amorphous scorodite (56 110%), Nova Scotia mine tailings (140 300%), an agricultural soil (53%) and an ironstone soil (350%) containing elevated arsenic concentrations. However, under small intestinal conditions, this microbial effect was transient and demonstrated a small effect size. The toxicological relevance of microbial effects upon As bioaccessibility was assessed using a juvenile swine model with co-administration of oral antibiotics (neomycin and metronidazole). This study research indicated that microbial effects on As bioaccessibility are not reflected in the juvenile swine model. For example, the microbial communities present in the pigs proximal colon clustered according to antibiotic treatment (e.g. microbial communities of antibiotic treated pigs differed from non-treated pigs). Despite this, the urinary arsenic excretion (and hence arsenic bioavailability) of antibiotic-treated juvenile swine orally exposed to soil-borne arsenic was equivalent (Holm-Sidak, P=0.930) to the urinary arsenic excretion of juvenile swine not treated with antibiotics. Therefore, in vitro GI models may not need to include a microbially active intestinal stage when measuring As IVBA.<p> Metal bioaccessibility from soils appears predictable according to fundamental chemical properties of the metal-of-concern. Specifically, metal bioaccessibility of 7 of the 13 metals (V, Ni, Zn, Cu, U, Cd, & Ba but not Tl, Pb, As, Se, Cr, and Hg) regulated according to Canadian Council of Ministers of the Environment Soil Quality Guidelines (CCME SQG) were strongly dependent (R2 = 0.7) on water exchange rate constants of metal cations (kH20) indicating that desorption kinetics may serve as the foundation of a predictive model of metal bioaccessibility.

The current method of determining component failure rates for probabilistic risk assessment (PRA) in the nuclear industry is to take the total number of failures divided by the time over which the failures occurred. The method proposed in this study is the reliability growth method and involves taking into account the fact that the amount of failures per additional year of operation generally decreases yearly because the operational staff becomes familiar with the equipment. The reliability growth method will result in lower component failure rates which when used in PRA studies could result in a lower core melt frequency value. The component failure rate would be expected to be higher in the early stages and should gradually decrease as time goes on. This study will compare the final core melt frequency of the Trojan Nuclear Power Plant using both methods. The Nuclear Power Reactor Data System (NPRDS) data base from the Institute of Nuclear Power Operations (INPO) was used in this study. The components which were examined for the reliability growth method are motor operated valves, service water pump/motors and emergency diesel generator air chargers. These data were screened to ensure that only true failures were reported. A comparison was made of the overall core melt frequency between the conventional failure rate method and reliability growth method for the motor operated valves. The overall core melt frequency was decreased by 1.8 % when using the reliability growth method compared to the conventional method. / Graduation date: 1993

The aim of this study was to compare online child pornography offenders and contact offenders along the predictive items of the Static-2002 actuarial risk assessment tool, as well as, several other items and scales predictive of recidivism. In addition, the study wished to determine if the Static-2002 was a well-equipped to assess online offenders. 120 subjects were assessed in this study, 53 online child pornography offenders, 53 child molesters, and 7 offenders who committed both a contact and online offense. The research identified a number of similarities between the two groups of offenders, including a finding that the two groups did not significantly differ in age. The most pronounced differences were found on the several measures of criminality used in the study where contact offenders scored significantly higher. The Static-2002 was found to not be well suited for use with online offenders as the tool had difficulty assessing their sexual deviancy.

Degut als impactes ecològics i socioeconòmics causats per les invasions biològiques, la seva gestió s’ha convertit en un repte important i una prioritat pels gestors mediambientals. A Espanya, la informació sobre la gestió de les plantes exòtiques està força dispersa i, en general, no hi ha gaire flux d’informació entre el món acadèmic i el món de la gestió. Per aquests motius, el principal objectiu d’aquesta tesi ha estat aprofundir en les mesures de gestió de plantes exòtiques a Espanya, identificant les seves principals limitacions. Conèixer aquestes limitacions ens ha dut a plantejar‐nos els següents objectius específics: 1) Identificar les principals plantes exòtiques problemàtiques a Espanya i avaluar els criteris utilitzats a l’hora de prioritzar la seva gestió; 2) Identificar i classificar les espècies potencialment invasores per Espanya; 3) A nivell global, quantificar mitjançant un metaanalisi els impactes de les plantes invasores i les conseqüències de la seva eliminació en les comunitats natives; i 4) Com a cas d’estudi, avaluar l’eficàcia de l’eliminació manual de Carpobrotus sp. a la costa d’Andalusia, i la recuperació de la vegetació nativa. Tenint en compte que les mesures de control i eradicació d’espècies exòtiques són extremadament costoses és molt important prevenir l’entrada i l’establiment d’espècies potencialment invasores, així com garantir l'eficàcia de les mesures de gestió aplicades. Aquesta tesi omple una mica el buit d’informació entre el món acadèmic i el de la gestió, proporcionant informació als gestors ambientals per tal de millorar l’eficàcia de les mesures de gestió aplicades. Les principals conclusions són: I. Les invasions biològiques són considerades pels gestors ambientals un problema de prioritat mitjana i un total de 109 plantes exòtiques problemàtiques han estat gestionades. II. La gestió de les plantes exòtiques s'ha centrat principalment en l'aplicació de mesures de control mecànic o químic a escala local i dissenyades, normalment, amb objectius a curt termini. Existeix, per tant, una manca de mesures de prevenció, mesures de seguiment a llarg termini i de pautes per a la priorització de la gestió d’espècies exòtiques. III. Mitjançant l'ús d'esquemes d'avaluació de riscos, s'ha elaborat una llista preliminar de 80 espècies potencialment invasores per Espanya, sent la jardineria la principal via d’entrada d’aquestes espècies. Les espècies amb les puntuacions més altes han resultat ser principalment plantes aquàtiques, i s’hauria de prohibir la seva entrada i comerç. Chromolaena odorata (Asteraceae) és l’espècie amb les puntuacions més altes i, per tant, podria ser considerada l'espècie amb major risc d'esdevenir invasora a Espanya, en cas que s'introduís al medi natural. IV. Aquesta tesi presenta un marc conceptual que compara llocs envaïts, llocs de referència no envaïts i llocs on una determinada espècie invasora ha estat eliminada. Aquestes comparacions permeten quantificar el impacte de l’espècie invasora en qüestió i supervisar la recuperació de les plantes natives després de la seva eliminació. En estudis científics, aquestes comparacions no solen ser utilitzades de manera combinada, i els llocs de referència són poc emprats per avaluar la recuperació d'espècies natives després de l'eliminació. Creiem que l’ús d’aquest enfocament comparatiu hauria de ser més emprat per supervisar l’eficàcia de les mesures de gestió, perquè a més, permet avaluar els possibles efectes secundaris de les tècniques d'eliminació, així com la necessitat de dur a terme mesures de restauració específiques a posteriori. V. La revisió bibliogràfica global demostra que les plantes invasores són responsables d'una disminució local en la riquesa i abundància d'espècies natives. Això, ha estat corroborat pel cas d’estudi sobre l’eliminació de Carpobrotus, on aquesta espècie també redueix significativament la riquesa d'espècies natives en les comunitats que envaeix. VI. En general, després de l'eliminació de les plantes invasores, la vegetació nativa té el potencial de recuperar‐se fins arribar als nivells desitjats previs a la invasió. / Now that the increasing impacts and costs of invasive species are being recognized, management of alien species has become an important challenge and a high priority for environmental managers. However, in Spain, management information on alien plants is quite scattered and, in general, there is a lack of communication between managers and scientists. The general aim of this thesis has been to investigate the management measures on alien plants carried out in Spain and to identify the main limitations of these measures. Once knowing these limitations the following specific objectives have been addressed: 1) To identify the most problematic invasive plant species in Spain and to assess the main criteria used to prioritize their management; 2) To identify and rank potentially invasive species in Spain, not present in the wild yet; 3) To quantify at a global scale, by means of a meta‐analysis, the impacts of invasive plants as well as the consequences of their removal over native communities, and 4) To evaluate, as a case study, the efficacy of the manual removal of Carpobrotus sp. in the coast of Andalucía, and the recovery of the native vegetation after the alien plant removal. Given that management measures are extremely costly in terms of human, technical and economic resources, it is really important to prevent potential invasive species as well as to guarantee management effectiveness in those cases where prevention is no longer a solution. This thesis have provided clear direction for bridging the current gap between the availability in information on alien plant species and the need for environmental managers to successfully prevent and control invasive species. Specifically, the main conclusions are: 1) Biological invasions are considered by Spanish environmental managers a medium priority problem and a total of 109 noxious alien species are being managed. 2) Management of alien plants in Spain has mainly focused, so far, in the application of either mechanical or chemical control measures at a local scale and mostly with short‐term goals in mind. Thus, there is a lack of preventive measures, absence of long‐term monitoring of control actions and few guidelines for prioritization. 3) By using risk assessment schemes, we have identified a preliminary list of 80 potential invasive species, being gardening the most common pathway of introduction. The species with the highest scores, were mainly aquatic plants, and should be prohibited or kept out of trade. Chromolaena odorata (Asteraceae) obtained the highest scores and therefore it might be the species with the highest risk to become invasive in Spain if introduced. 4) We have presented a conceptual framework that compares invaded, non‐invaded and removal sites to quantify invaders’ impacts and to monitor native plant recovery after their removal. In scientific studies, these comparisons are rarely used in concert, and reference sites are scarcely employed to assess native species recovery after removal. Thus, we believe that this comparative approach should be more frequently used to evaluate management effectiveness because it may also be useful to determine possible side‐effects of removal techniques and whether further restoration measures are necessary. 5) Our global literature review has demonstrated that invasion by alien plants is responsible for a local decline in native species richness and abundance. This has been corroborated by monitoring Carpobrotus invaded sites in coastal dunes of Andalucía, where this species has significantly decreased species richness in the communities it invades. 6) Our global literature review has also indicated that, in general, after alien plant removal, the native vegetation has the potential to recover to a pre‐invasion state. The same trend has been found in the case study of Carpobrotus.

In this study, a model is developed to assess risk to a municipal water supply system under the influence of population growth and climate change. To incorporate the uncertainly in water use, a model which combines time series Monte Carlo simulations and a deterministic artificial neural network (ANN) is developed to simulate the daily water demand under climate variability. The model is then expanded in two directions. One direction is to estimate the effects of demand management programs and system expansion on the reliability, resiliency, and vulnerability of the water supply system. Another direction is to capture the possible impacts of climate change on the risk of a water supply system. Twenty-six scenarios generated from different combinations of demand management programs, system expansions and Global Climate Model (GCM) scenarios were set to illustrate the risk indices: reliability, resiliency, and vulnerability. To illustrate the effects of a change of precipitation frequency and a higher population growth, twenty-five additional scenarios were evaluated.

Airports are fast-growing dynamic infrastructure assets. For example, the Canadian airport industry is growing by 5% annually and generates about $8 billion yearly. Since the 9/11 tragedy, airport security has been of paramount importance both in Canada and worldwide. Consequently, in 2002, in the wake of the attacks, the International Civil Aviation Organization (ICAO) put into force revised aviation security standards and recommended practices, and began a Universal Security Audit Program (USAP), in order to insure the worldwide safeguarding of civil aviation in general, and of airports in particular, against unlawful interference. To improve aviation security at both the national level and for individual airport, airport authorities in North America have initiated extensive programs to help quantify, detect, deter, and mitigate security risk. At the research level, a number of studies have examined scenarios involving threats to airports, the factors that contribute to airport vulnerability, and decision support systems for security management. However, more work is still required in the area of developing decision support tools that can assist airport officials in meeting the challenges associated with decision about upgrades; determining the status of their security systems and efficiently allocating financial resources to improve them to the level required. To help airport authorities make cost-effective decisions about airport security upgrades, this research has developed a risk-based optimization framework. The framework assists airport officials in quantitatively assessing the status of threats to their airports, the vulnerability to their security systems, and the consequences of security breaches. A key element of this framework is a new quantitative security metric ; the aim of which is to assist airport authorities self-assess the condition of their security systems, and to produce security risk indices that decision makers can use as prioritizing criteria and constraints when meeting decisions about security upgrades. These indices have been utilized to formulate an automated decision support system for upgrading security systems in airports. Because they represent one of the most important security systems in an airport, the research focuses on passenger and cabin baggage screening systems. Based on an analysis of the related threats, vulnerabilities and consequences throughout the flow of passengers, cabin baggage, and checked-in luggage, the proposed framework incorporates an optimization model for determining the most cost-effective countermeasures that can minimize security risks. For this purpose, the framework first calculates the level of possible improvement in security using a new risk metric. Among the important features of the framework is the fact that it allows airport officials to perform multiple “what-if” scenarios, to consider the limitations of security upgrade budgets, and to incorporate airport-specific requirements. Based on the received positive feedback from two actual airports, the framework can be extended to include other facets of security in airports, and to form a comprehensive asset management system for upgrading security at both single and multiple airports. From a broader perspective, this research contributes to the improvement of security in a major transportation sector that has an enormous impact on economic growth and on the welfare of regional, national and international societies.

The current study used a probabilistic Quantitative Microbial Risk Assessment (QMRA) framework to describe the change of E. coli O157:H7 concentration in lettuce through a foodborne pathway, to develop a predictive model for risk estimation for E. coli O157:H7 infection associated with lettuce. The model consisted of a series of pathogen-associated events including initial contamination, growth during cooling, cold storage and distribution, disinfection (chlorine, gaseous chlorine dioxide and gamma irradiation), and dose response after consumption. A modified Baranyi growth model was proposed which described the initial physiological state of E. coli O157:H7 as a function of the initial temperature. The modified Baranyi growth model was used to predict E. coli O157:H7 growth under realistic time-temperature profiles, accounting for the time dynamics of temperature fluctuation. The risk assessment model was constructed in an Excel spreadsheet and Monte Carlo uncertainty analysis was simulated using Crystal Ball. The results in the current study showed that temperature control was the key measure for minimizing the risk of E. coli O157:H7 infection associated with lettuce. Disinfecting contaminated lettuce using the hypothetical methods examined in the study had limited effectiveness in risk reduction. Temperature abuse occurring before or after the hypothetical disinfections significantly diminished the disinfection effect and contributed to increased risk. Of all simulated scenarios, the lowest risk was associated with adequate temperature control and irradiation (44 infections per 1000 consumptions [95%: 94 infection per 1,000 consumption; 5%: 5 infections per 1,000 consumption]). The model can be used to explore the public health impact of other potential strategies that can be adopted to minimize the risk of E. coli O157:H7, while taking into account the possible amplification of pathogen through the food chain.

No description available.

In this study, a model is developed to assess risk to a municipal water supply system under the influence of population growth and climate change. To incorporate the uncertainly in water use, a model which combines time series Monte Carlo simulations and a deterministic artificial neural network (ANN) is developed to simulate the daily water demand under climate variability. The model is then expanded in two directions. One direction is to estimate the effects of demand management programs and system expansion on the reliability, resiliency, and vulnerability of the water supply system. Another direction is to capture the possible impacts of climate change on the risk of a water supply system. Twenty-six scenarios generated from different combinations of demand management programs, system expansions and Global Climate Model (GCM) scenarios were set to illustrate the risk indices: reliability, resiliency, and vulnerability. To illustrate the effects of a change of precipitation frequency and a higher population growth, twenty-five additional scenarios were evaluated.

Airports are fast-growing dynamic infrastructure assets. For example, the Canadian airport industry is growing by 5% annually and generates about $8 billion yearly. Since the 9/11 tragedy, airport security has been of paramount importance both in Canada and worldwide. Consequently, in 2002, in the wake of the attacks, the International Civil Aviation Organization (ICAO) put into force revised aviation security standards and recommended practices, and began a Universal Security Audit Program (USAP), in order to insure the worldwide safeguarding of civil aviation in general, and of airports in particular, against unlawful interference. To improve aviation security at both the national level and for individual airport, airport authorities in North America have initiated extensive programs to help quantify, detect, deter, and mitigate security risk. At the research level, a number of studies have examined scenarios involving threats to airports, the factors that contribute to airport vulnerability, and decision support systems for security management. However, more work is still required in the area of developing decision support tools that can assist airport officials in meeting the challenges associated with decision about upgrades; determining the status of their security systems and efficiently allocating financial resources to improve them to the level required. To help airport authorities make cost-effective decisions about airport security upgrades, this research has developed a risk-based optimization framework. The framework assists airport officials in quantitatively assessing the status of threats to their airports, the vulnerability to their security systems, and the consequences of security breaches. A key element of this framework is a new quantitative security metric ; the aim of which is to assist airport authorities self-assess the condition of their security systems, and to produce security risk indices that decision makers can use as prioritizing criteria and constraints when meeting decisions about security upgrades. These indices have been utilized to formulate an automated decision support system for upgrading security systems in airports. Because they represent one of the most important security systems in an airport, the research focuses on passenger and cabin baggage screening systems. Based on an analysis of the related threats, vulnerabilities and consequences throughout the flow of passengers, cabin baggage, and checked-in luggage, the proposed framework incorporates an optimization model for determining the most cost-effective countermeasures that can minimize security risks. For this purpose, the framework first calculates the level of possible improvement in security using a new risk metric. Among the important features of the framework is the fact that it allows airport officials to perform multiple “what-if” scenarios, to consider the limitations of security upgrade budgets, and to incorporate airport-specific requirements. Based on the received positive feedback from two actual airports, the framework can be extended to include other facets of security in airports, and to form a comprehensive asset management system for upgrading security at both single and multiple airports. From a broader perspective, this research contributes to the improvement of security in a major transportation sector that has an enormous impact on economic growth and on the welfare of regional, national and international societies.