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.     

Naked reverse: unexpected plays for exceptional results

Following the herd is easy when it comes to business ventures. But if you really want to start something new, you must first carefully think it through. Learn some ways to do that before you set out on a new path.     

Was tun Lektoren?

What is the work of editors? Counselling of a ?service in background“The work of editors as employees in publishing houses or as free lancers is a ?service in background“ and hence it is less well-known in comparison with other media professionals. Nevertheless, editors have an important role as intermediary between authors and the reading public. The author delineates the profession of editors and the technical aspects of their work and explains some typical conflicts which may be relevant to a coaching of editors.     

AN IMPROVED HEURISTIC FOR STAFFING TELEPHONE CALL CENTERS WITH LIMITED OPERATING HOURS

Many telephone call centers that experience cyclic and random customer demand adjust their staffing over the day in an attempt to provide a consistent target level of customer service. The standard and widely used staffing method, which we call the stationary independent period by period (SIPP) approach, divides the workday into planning periods and uses a series of stationary independent Erlang‐c queuing models—one for each planning period—to estimate minimum staffing needs. Our research evaluates and improves upon this commonly used heuristic for those telephone call centers with limited hours of operation during the workday. We show that the SIPP approach often suggests staffing that is substantially too low to achieve the targeted customer service levels (probability of customer delay) during critical periods. The major reasons for SIPP‘ s shortfall are as follows: (1) SIPP's failure to account for the time lag between the peak in customer demand and when system congestion actually peaks; and (2) SIPP’ s use of the planning period average arrival rate, thereby assuming that the arrival rate is constant during the period. We identify specific domains for which SIPP tends to suggest inadequate staffing. Based on an analysis of the factors that influence the magnitude of the lag in infinite server systems that start empty and idle, we propose and test two simple “lagged” SIPP modifications that, in most situations, consistently achieve the service target with only modest increases in staffing.     

PIECING TOGETHER SERVICE QUALITY: A FRAMEWORK FOR ROBUST SERVICE*

This paper addresses the issue of service design, specifically that of designing the service encounter for improved quality. We introduce a framework based on the three T's of task, treatment, and tangibles as a means of organizing the application of the diverse and growing body of service quality literature to encounter design. The framework is consistent with how successful service managers disaggregate the design problem. More importantly, we show that mutually supportive interrelationships between the three T's produce an opportunity for designing in a robustness to service failure. The framework is supported by case based evidence.     

The Co-pay in Dutch Health Care: Policy and Effectiveness

This article describes the results of an empirical study into the design and effectiveness of the co-pay in Dutch Health care. With a reconstruction of the policy theory and the application of "the instrument theory" of Bressers and Klok, we are able to predict that the co-pay would not be effective. A process evaluation and an effect evaluation show that this is indeed the case. Not surprisingly, the second Kok administration determined that the instrument would be terminated.