Physiologically Based Liver Modeling and Risk Assessment

Because of the inherent complexity of biological systems, there is often a choice between a number of apparently equally applicable physiologically based models to describe uptake and metabolism processes in toxicology or risk assessment. These models may fit the particular data sets of interest equally well, but may give quite different parameter estimates or predictions under different (extrapolated) conditions. Such competing models can be discriminated by a number of methods, including potential refutation by means of strategic experiments, and their ability to suitably incorporate all relevant physiological processes. For illustration, three currently used models for steady-state hepatic elimination--the venous equilibration model, the parallel tube model, and the distributed sinusoidal perfusion model--are reviewed and compared with particular reference to their application in the area of risk assessment. The ability of each of the models to describe and incorporate such physiological processes as protein binding, precursor-metabolite relations and hepatic zones of elimination, capillary recruitment, capillary heterogeneity, and intrahepatic shunting is discussed. Differences between the models in hepatic parameter estimation, extrapolation to different conditions, and interspecies scaling are discussed, and criteria for choosing one model over the others are presented. In this case, the distributed model provides the most general framework for describing physiological processes taking place in the liver, and has so far not been experimentally refuted, as have the other two models. These simpler models may, however, provide useful bounds on parameter estimates and on extrapolations and risk assessments.     

Joint tests of non-nested models and general error specifications

This paper is concerned with joint tests of non-nested models and simultaneous departures from homoskedasticity, serial independence and normality of the disturbance terms. Locally equivalent alternative models are used to construct joint tests since they provide a convenient way to incorporate more than one type of departure from the classical conditions. The joint tests represent a simple asymptotic solution to the “pre-testing” problem in the context of non-nested linear regression models. Our simulation results indicate that the proposed tests have good finite sample properties.     

The availability of personal and external coping resources: Thier impact on job stress and employee attitudes during organizational restructuring

This study examines the relationships among personal coping resources, social support, external coping resources, job stressors and job strains in a sample of 110 American Telephone and Telegraph employees undergoing a major organizational restructuring. The study expanded on a model suggested by Ashford (1988) by defining another category of coping resources that employees may draw upon to deal with the stressors and strains which occur during major organizational changes. External coping resources were defined as those which provided employees with a sense of 'vicarious control' in stressful situations. Results indicated that personal coping resources, social support and external coping resources had a direct effect upon job stressor and strain levels. No 'buffering' effect of these coplng resources was found. Hierarchical regression analyses indicated that external coping resources added to the prediction of job stressors and strains even when pertonal coping resources and social support were entered first into the prediction questions.     

Accuracy of the College Majors Finder for Three Majors

The Self-Directed Search was administered to 68 university seniors who were majoring in Chemistry/Chemical Engineering, Elementary Education, and Office Administration. Their resulting three-letter summary codes were compared with three-letter college major codes obtained from the College Majors Finder. A high degree of agreement between the two sets of codes was found for each of the three majors. Effective methods for matching people to jobs have held the interest and occupied much time for career counselors and vocational theorists since the inception of the trait-factor approach to career counseling. More recently, Holland (1985a) broadened and clarified matching procedures through the development of his typological theory of vocational choice. Just as personality types and occupational environments have been organized using Holland's framework to foster an understanding of occupational choice, Holland's theory can also be used to explain other types of choices, such as choice of a college major.     

Abuse of children in day care centres: Characteristics and consequences

While day care sexual abuse cases share features in common with sexual abuse in other settings, many characteristics of abuse in day care settings merit special attention. These factors include the young age of the child victims, the involvement of multiple victims and multiple perpetrators, females as perpetrators, use of extreme threats, severity of the abuse, and in some instances ritualistic activities. Research findings support clinical impressions that children are negatively impacted by sexual abuse in day care. Consequences of abuse in day care include anxiety, excessive fearfulness, behavioural disturbances, sexual acting out and sleep disorders. Parents whose children are abused in day care centres also experience psychological distress with symptom profiles consistent with post-traumatic stress disorder. Abuse of children in day care settings warrants a specialized treatment approach. A major goal of treatment is to decrease symptomatology among all family members.