When the most “pertinent” document should not be retrieved—An analysis of the Swets model

Most automated information retrieval systems operate by relating a document to a request by means of a measure of pertinance, and then retrieving the most pertinent documents for their patrons. In this paper the consistency of this operating procedure with the well known Swets Model is examined. It is shown that accepting the assumptions made by Swets would result in the possible rejection of the most pertinent documents in favor of those that are less pertinent. This conclusion is a consequence of the normality assumptions of the model, while other distributions, such as the Poisson distribution, is consistent with the standard procedure. In the course of the development, the fundamentals of decision theory and signal detection theory are reviewed.     

δ-ALA levels in serum and urine—A diagnostic tool for possible lead poisoning

We present 2 cases of lead poisoning, the first of a child playing with painted toys and the second of an adult on local medicine. The former presented with acute abdomen and the latter with peripheral muscle weakness. We propose that raised serum δ-amino leavulinic acid (δ-ALA) levels strongly point towards the possibility of lead poisoning.     

Design,implementation and evaluation of school-based sexual health education in sub-Saharan Africa: a qualitative study of researchers’ perspectives

This study investigated facilitators and challenges to designing, implementing and evaluating school-based sexual health education in sub-Saharan Africa, using interviews with intervention designers and researchers. At the pre-planning and planning stages, participants reported that facilitating factors included addressing the reproductive health needs of participants, contextual (culture, religion, economic and social) considerations and the adoption of holistic approach to sexuality education. Lack of open communication about sexual health matters between young people and adults; concerns that sexual health education could encourage sexual activity; and inadequate funding, were key barriers. Implementation was facilitated by the involvement of relevant stakeholders, the training of facilitators and adopting strategies to overcome resistance to sexual health education. The provision of structured, detailed lessons plans and monitoring with supportive supervision optimised fidelity of delivery. Barriers to implementation included facilitators’ resistance to teaching safe sex promotion and logistical challenges in school environments. Participants also reported that the validity of self-reported adolescent sexual behaviour (as part of evaluation) may be improved by complementing well-designed self-report surveys with computerised audio devices for data collection, qualitative interviews and participant observation. Study findings generate recommendations to improve future forms of school-based sexual health education in sub-Saharan Africa.