A Physiologically Based Model for Gastrointestinal Absorption and Excretion of Chemicals Carried by Lipids

Pharmacokinetic models which incorporate independently measured anatomical characteristics and physiological flows have been widely used to predict the pharmacokinetic behavior of drugs, anesthetics, and other chemicals. Models appearing in the literature have included as many as 18,⁽¹⁾ or as few as 5 tissue compartments.⁽²⁾ With the exception of the multiple-compartment delay trains used by Bischoff⁽³⁾ to model the delays inherent to the appearance of drug metabolites in bile and segments of the intestinal lumen, very little effort has been made to incorporate the available information on gastrointestinal anatomy and physiology into more accurate gastrointestinal absorption/enterohepatic recirculation submodels. Since several authors have shown that the lymphatic system is the most significant route of absorption for highly lipophilic chemicals, we have constructed a model of gastrointestinal absorption that emphasizes chylomicron production and transport as the most significant route of absorption for nonvolatile, lipophilic chemicals. The absorption and distribution of hexachlorobenzene after intravenous vs. oral dosing are used to demonstrate features of this model.     

ESTIMATION OF LLUCH'S EXTENDED LINEAR EXPENDITURE SYSTEM FROM CROSS-SECTIONAL DATA1

Complete sets of demand relations may be fitted using varying types of sample information and varying a priori specifications. In this paper the identification and estimation of Lluch's extended linear expenditure system (ELES) from cross-sectional data alone is investigated. Under the most favourable conditions of data availability, all of the parameters of the ELES model are identified, and are estimable by the method of reduced form least squares. This is the case where observations on permanent income are available for the consuming units of the cross section and where, in addition, prices are recorded (even though they do not vary from one consuming unit to the next). Under the least favourable conditions only the marginal budget shares are identified. This corresponds to the case where no data on permanent income, or on savings, are available. The conventional ordinary least squares estimators of the marginal budget shares are, under these conditions, biased and inconsistent. Expressions are developed for the large-sample biases.     

Personal Influence Networks and Voluntary Association Affiliation*

Individuals ordinarily have considerable information about voluntary associations even before they seriously think about joining a group. In becoming affiliated, members usually rely on personal networks and often several persons are consulted. When mass media sources are utilized in the affiliation process, they serve as a stimulus or catalyst (not one respondent in the sample joined an organization solely on the basis of mass media sources of information). Those with an extensive network of friends and relatives often become members through informal leaders. Moreover, they are sought out and encouraged to join. Individuals who have fewer primary-group resources frequently become members through formal leaders and themselves initiate the contact which results in membership. Finally, personal influence networks are more likely to play an important role for those joining expressive rather than instrumental voluntary associations.     

The empirical basis of risk assessment in child welfare: the accuracy of risk assessment and clinical judgment

The importance of risk assessment is juxtaposed with the lack of empirical support regarding the validity of risk inventories. This study compared risk ratings of one risk assessment tool to decisions made by case managers. The researchers sampled 450 children and compared predictive utility of risk assessment to child protection decisions. Risk assessment was consistent with clinical judgment in 74% to 81% of cases, more than previously reported in studies of risk assessment validity. Further analyses identified discriminate functions at the instrument's category and individual-item levels. The results have implications for the validity of the instrument and its utility in child welfare.     

Binge drinking during the first semester of college: continuation and desistance from high school patterns

Students' first semester on campus may set the stage for their alcohol use/misuse throughout college. The authors surveyed 274 randomly sampled first-semester freshmen at a large southwestern university on their past 2 weeks' binge drinking, their high school binge drinking, and psychosocial factors possibly associated with drinking. They conducted separate analyses among high school nonbinge drinkers (testing for predictors of college binge onset vs continued nonbinge drinking) and high school binge drinkers (testing for predictors of continued binge drinking in college vs desistance from drinking). In both analyses, the variables that predicted college binge drinking largely revolved around gregarious socializing (e.g, partying, having a social network of individuals who drank relatively heavily). Gender was predictive only among high school nonbinge drinkers; women had a higher probability than did men of adopting binge drinking in college.     

A Monte Carlo Analysis of Health Risks from PCB-Contaminated Mineral Oil Transformer Fires

The objective of this study is the estimation of health hazards due to the inhalation of combustion products from accidental mineral oil transformer fires. Calculations of production, dispersion, and subsequent human intake of polychlorinated dibenzofurans (PCDFs) provide us with exposure estimates. PCDFs are believed to be the principal toxic products of the pyrolysis of polychlorinated biphenyls (PCBs) sometimes found as contaminants in transformer mineral oil. Cancer burdens and birth defect hazard indices are estimated from population data and exposure statistics. Monte Carlo-derived variational factors emphasize the statistics of uncertainty in the estimates of risk parameters. Community health issues are addressed and risks are found to be insignificant.     

The structural organization and micropolitics of everyday secret telling interactions

The interactions that typically precede and follow explicit secrets display a structural organization of sequentially ordered items that form the vehicle for micropolitical processes of reality construction, selectivity and coalition making. Our data showed a preference for secret receivers to accept the frame, construction, political formulation, bonding, and coalitions of explicit secrets. The teller can define information as exclusive, select the secret recipient, specify the exclusivity rules, and infuse the information with political vectors. After the secret is told the power shifts to the receiver who can then sanction the teller for divulging a confidence, and/or choose to break the explicit and implicit rules and alliance of the preference system that organizes secret telling.