Design optimality for models defined by a system of ordinary differential equations.

Many scientific processes, specially in pharmacokinetics (PK) and pharmacodynamics (PD) studies, are defined by a system of ordinary differential equations (ODE). If there are unknown parameters that need to be estimated, the optimal experimental design approach offers quality estimators for the different objectives of the practitioners. When computing optimal designs the standard procedure uses the linearization of the analytical expression of the ODE solution, which is not feasible when this analytical form does not exist. In this work some methods to solve this problem are described and discussed. Optimal designs for two well-known example models, Iodine and Michaelis-Menten, have been computed using the proposed methods. A thorough study has been done for a specific two-parameter PK model, the biokinetic model of ciprofloxacin and ofloxacin, computing the best designs for different optimality criteria and numbers of points. The designs have been compared according to their efficiency, and the goodness of the designs for the estimation of each parameter has been checked. Although the objectives of the paper are focused on the optimal design field, the methodology can be used as well for a sensitivity analysis of ordinary differential equation systems.

The relationship between attribution of blame and the perception of resistance in relation to victims of sexual violence.

Several studies have examined victim blaming in rape scenarios. However, there is limited research on the analysis of the perception of blame when two or more perpetrators are involved. The present article explores the perception of blame in cases involving rape based on the level of resistance shown by the victim and the presence of one or more perpetrators. A study was carried out involving 351 university students who responded to a survey after reading a hypothetical assault scenario. Six situations were established where the victim showed either low or high resistance, depending on whether the resistance was verbal or physical and verbal, and in the presence of one or two male perpetrators. It is expected that perpetrators are more culpable when acting in groups and that less resistance from the victim leads to greater attribution of blame. The results confirm that more blame is attributed to the perpetrators when they act in groups than when they act alone. Likewise, women consider the victim generally exerts greater resistance and this variable influences the attribution of greater blame.

Bioassays in workers exposed to long time random intakes.

Workers who are occupationally exposed to radioactive aerosols are usually subjected to periodic controls of internal contamination by performing bioassays (whole body or partial body monitoring and measurement of excreta samples). The intakes are also estimated by using Static Air Samples (SAS). These measurements are used to estimate the radioactive intakes of the workers. A typical assumption is the workers are chronically (constant) exposed for long periods of time. However, the intakes are random and there are also periods without any exposure (weekends, holidays, etc.). The method presented here considers both facts. Simulations help to choose the most appropriate method of evaluation to minimize the statistical uncertainties in the intake. It has been applied to evaluate workers exposed to UO2 aerosols for a long time (30 years or more for most of them) in the same working area (sintering). Results of measurements of uranium in urine and daily intakes (from SAS) of these workers have been used. For this evaluation, the new Occupational Intakes of Radionuclides (OIR) biokinetic models of the International Commission on Radiological Protection (ICRP) for uranium have been solved. For some workers the evaluation gives a significative deviation between the intake estimated from urine samples and the intake estimated using the SAS values, supporting the idea that the physiological standard parameters of the reference worker are not always applicable. The computations have been implemented in the BIOKMOD code.