Understanding Community Resilience from a PRA Perspective Using Binary Decision Diagrams

Probabilistic risk assessment (PRA) is a useful tool to assess complex interconnected systems. This article leverages the capabilities of PRA tools developed for industrial and nuclear risk analysis in community resilience evaluations by modeling the food security of a community in terms of its built environment as an integrated system. To this end, we model the performance of Gilroy, CA, a moderate‐size town, with regard to disruptions in its food supply caused by a severe earthquake. The food retailers of Gilroy, along with the electrical power network, water network elements, and bridges are considered as components of a system. Fault and event trees are constructed to model the requirements for continuous food supply to community residents and are analyzed efficiently using binary decision diagrams (BDDs). The study also identifies shortcomings in approximate classical system analysis methods in assessing community resilience. Importance factors are utilized to rank the importance of various factors to the overall risk of food insecurity. Finally, the study considers the impact of various sources of uncertainties in the hazard modeling and performance of infrastructure on food security measures. The methodology can be applicable for any existing critical infrastructure system and has potential extensions to other hazards.     

Stakeholder value disclosures: anchoring on primacy and importance of financial and nonfinancial performance measures

In the growing debate about stakeholder values, there has been little discussion about information overload or whether the requested disclosures can be effectively used. Stakeholder advocates call for complicated and massive environmental and related social disclosures while not considering how information overload might affect the discourse about corporate performance. Stakeholders, including shareholders, plead for more transparency in financial statements, management discussion and analysis (MDA), and other corporate disclosures. As we know, shareholders and boards of directors are most concerned with the ‘Holy Trinity’ of earnings per share, dividends and market value changes. We believe that managers and stakeholders involved in performance evaluations have multiple interests that extend beyond traditional shareholder value measures. We note that the Balanced Scorecard (BSC) was developed as one tool to reflect and communicate these multiple measures. We test how managers use (or ignore) multiple performance measures and we posit that stakeholders will face many of the same constraints when using and processing multiple disclosures including Corporate Social Reports (CSR), environmental, or similar disclosures. While we do not directly test a wide variety of stakeholder disclosures, we examine eight (four for a single subject) shareholder values (financial measures) and four stakeholder values (nonfinancial measures). The eight measures included in our research instruments serve as proxies for the multiple concerns that might be of interest to many stakeholders. Note that stakeholders are likely to be extremely interested in nonfinancial performance measures, while many shareholders will likely concentrate on financial performance measures. Field research has reported managers tend to favor financial measures while discounting or ignoring nonfinancial measures when evaluating subordinates, making it difficult to align performance evaluations and incentives with corporate strategies (Ittner et al. Account Rev 78:725–758, 2003). In this study, we find the relative weights managers place on financial and nonfinancial performance measures are influenced by both (1) presentation order and (2) the relative importance of specific measures. When financial measures are presented first, the manager who performs better on financial measures is rated higher than the manager who performs better on nonfinancial measures. However, when nonfinancial measures are presented first, managers who excel on nonfinancial measures are rated higher. Reports that include financial measures that are relatively more (less) important also produce higher (lower) ratings for the manager who excels on financial measures. Thus, the relative weights that superiors place on financial and nonfinancial measures in evaluating corporate managers’ performance are substantially anchored both by the order in which measures are presented as well as by the importance of the specific performance measures employed. Other stakeholder disclosures are likely to be similarly anchored, perhaps biased, by primacy and a priori importance rankings.     

Risk Management in a Polio-Free World

Inherent in the decision to launch the Global Polio Eradication Initiative in 1988 was the expectation for many people that immunization against poliomyelitis would eventually simply stop, as had been the case with smallpox following its eradication in 1977. However, the strategies for managing the risks associated with a "polio-free" world must be continuously refined to reflect new developments, particularly in our understanding of the live polioviruses in the oral poliovirus vaccine (OPV) and in the international approach to managing potential biohazards. The most important of these developments has been the confirmation in 2000 that vaccine-derived polioviruses (VDPVs) can circulate and cause polio outbreaks, making the use of OPV after interruption of wild poliovirus transmission incompatible with a polio-free world. A comprehensive strategy has been developed to minimize the risks associated with eventual OPV cessation, centered on appropriate long-term biocontainment of poliovirus stocks (whether for vaccine production, diagnosis, or research), the controlled reintroduction of any live poliovirus vaccine (i.e., from an OPV stockpile), and appropriate use of the inactivated poliovirus vaccine (IPV). Although some aspects of this risk management strategy are still debated, there is wide agreement that no strategy would entirely eliminate the potential risks to a polio-free world. The current strategy for risk management in a polio-free world will continue to evolve with better characterization of these risks and the development of more effective approaches both to reduce those risks and to limit their consequences should they occur.     

Use of Markov Chain Monte Carlo Analysis with a Physiologically-Based Pharmacokinetic Model of Methylmercury to Estimate Exposures in U.S. Women of Childbearing Age

A Bayesian approach, implemented using Markov Chain Monte Carlo (MCMC) analysis, was applied with a physiologically‐based pharmacokinetic (PBPK) model of methylmercury (MeHg) to evaluate the variability of MeHg exposure in women of childbearing age in the U.S. population. The analysis made use of the newly available National Health and Nutrition Survey (NHANES) blood and hair mercury concentration data for women of age 16–49 years (sample size, 1,582). Bayesian analysis was performed to estimate the population variability in MeHg exposure (daily ingestion rate) implied by the variation in blood and hair concentrations of mercury in the NHANES database. The measured variability in the NHANES blood and hair data represents the result of a process that includes interindividual variation in exposure to MeHg and interindividual variation in the pharmacokinetics (distribution, clearance) of MeHg. The PBPK model includes a number of pharmacokinetic parameters (e.g., tissue volumes, partition coefficients, rate constants for metabolism and elimination) that can vary from individual to individual within the subpopulation of interest. Using MCMC analysis, it was possible to combine prior distributions of the PBPK model parameters with the NHANES blood and hair data, as well as with kinetic data from controlled human exposures to MeHg, to derive posterior distributions that refine the estimates of both the population exposure distribution and the pharmacokinetic parameters. In general, based on the populations surveyed by NHANES, the results of the MCMC analysis indicate that a small fraction, less than 1%, of the U.S. population of women of childbearing age may have mercury exposures greater than the EPA RfD for MeHg of 0.1 μg/kgg/day, and that there are few, if any, exposures greater than the ATSDR MRL of 0.3 μgg/kgg/day. The analysis also indicates that typical exposures may be greater than previously estimated from food consumption surveys, but that the variability in exposure within the population of U.S. women of childbearing age may be less than previously assumed.     

Absorptive and transformative capacities in nanotechnology innovation systems

We identify managerial challenges offered by an emergent nanotechnology innovation system in which knowledge is dispersed, asymmetric and contested. We argue the proposed models of knowledge absorption and transformation enhance existing theories of knowledge and emergent technology by recognizing how and why knowledge flows among the actors in emergent technology innovation system. We base our argument on combined research evidence from a Delphi study concerning the future of European manufacturing, from which a selected statement has been analyzed, and from analysis of the NanoManufacturing Institute at Leeds University, UK; specifically its work in building ties between different actors associated with nanotechnology. We conclude our paper with suggestions for future research.     

Exposure of medical students to body fluids

Three hundred forty-two students at 3 Florida medical schools were surveyed concerning occupational exposures to blood and body fluids during their 3rd-year clerkship. The 16-item questionnaire was anonymously returned by 150 students, and differences among groups were assessed at p < .05. Most of the students complied with universal precautions guidelines (UVPG); 62 reported 101 exposures, including 9 with HIV-positive blood and body fluids. Most of the exposed students knew about the guidelines but regarded the incidents as irrelevant to their safety or supervision training. Noncompliant students reported significantly more exposures than compliant students. Time constraints, inconvenience of using gloves during procedures, and belief that patients were at low HIV risk discouraged adherence to the guidelines. Common practices following exposure were "no action" or "washed area only" without medical follow-up. Medical students' UVPG adherence should be increased by workload modification, user-friendly safety products, and supervised practice training in clinical exposure settings.     

Chaos: A Challenge to Refine Systems Theory

Chaos theory may have relevance to marital and family therapy. Some connections are tentatively explored.