Density and structural effects in the radiation tolerance of TiO2 polymorphs.

The radiation response of TiO2 has been studied using molecular dynamics. The simulations are motivated by experimental observations that the three low-pressure polymorphs, rutile, brookite and anatase, exhibit vastly different tolerances to amorphization under ion-beam irradiation. To understand the role of structure we perform large numbers of simulations using the small thermal spike method. We quantify to high statistical accuracy the number of defects created as a function of temperature and structure type, and reproduce all the main trends observed experimentally. To evaluate a hypothesis that volumetric strain relative to the amorphous phase is an important driving force for defect recovery, we perform spike simulations in which the crystalline density is varied over a wide range. Remarkably, the large differences between the polymorphs disappear once the density difference is taken into account. This finding demonstrates that density is an important factor which controls radiation tolerance in TiO2.

Feminism meets the "new" epidemiologies: toward an appraisal of antifeminist biases in epidemiological research on women's health.

This essay explores an alternative paradigm for epidemiology, one which is explicitly informed by a feminist perspective. We intend to expand upon recent critiques and debates within the emergent fields of "critical", "popular", and "alternative" epidemiology to examine how epidemiology's conceptual models--which are meant to contribute to the prevention of social inequalities in health, but may instead reinforce social hierarchies based on gender, race, and class--constrain our understanding of health and disease. Specifically, we examine persistent antifeminist biases in contemporary epidemiological research on women's health. Issues highlighted include: problem definition and knowledge production in women's health: biological essentialization of women as reproducers; and decontextualization and depoliticization of women's health risks. As part of this critique, we include suggestions for an emancipatory epidemiology that incorporates an alternative feminist framework.

Rethinking difference: a feminist reframing of gender/race/class for the improvement of women's health research.

In exploring the history of the social construction of gender/race/class in Western scientific discourse and examining the legacy of these persisting constructions in modern research on women's health, the authors join in a growing debate about sexism/racism/classism in women's health research--a debate being forwarded most forcefully by feminist epidemiologists. A major purpose of this article is to aid in the development of a new research paradigm for examining the relationship between gender, race, and class, one that considers the interdisciplinary theorizing of Third World feminists and European/American feminists of color. Following the examination of both historical and epistemological issues surrounding interlocking forms of oppression based on gender/race/class, the authors propose a feminist research agenda that not only is responsive to different women's health needs, but can potentially contribute to a process for understanding and answering the health needs of all persons.

Marine toxins.

Seafood products are important both nutritionally and economically. Within Europe, some 12 billion Pounds of fishery products are consumed annually and an enormous variety of species are available. Although seafood is rarely implicated in food poisoning, compared to other food sources, it does provide some specific human health hazards unique to this particular resource. Generally, these are toxins from toxic microscopic algae which accumulate through the food-chain. The toxins can cause various neurological and gastrointestinal illnesses and, potentially, consumers are exposed from seafood produced within Europe, from imported products, or from seafood eaten while travelling abroad. The symptoms of illness which may be encountered, the source and mode of action of the toxins, and some emerging problems are described. European legislation aims to ensure the quality and safety of seafood products by prohibiting sale of some toxic species, setting toxin limits, requiring monitoring and controlling imports.

Dental caries in 12-year-old children and the effectiveness of dental services in Salford, UK in 1960, 1988 and 1997.

OBJECTIVE: To investigate the dental health of 12-year-old children and the effectiveness of dental services in 1997 and compare the results with studies carried out in 1960 and 1988. BASIC RESEARCH DESIGN: Analytical survey using a one in five random sample of children in all seven secondary schools in Salford UK. Standard clinical criteria were used. SETTING: Clinical examinations were carried out in school. PARTICIPANTS: 65 boys and 49 girls were examined. OUTCOME MEASURES: Caries experience expressed as DMFT, Restorative Index and Care Index. RESULTS: The boys and girls both had a mean DMFT of 1.65. (95% confidence intervals were 1.18-2.12 for the boys and 1.16-2.14 for the girls.) This compared with means of 2.34 (1.85-2.83) for boys and 3.40 (2.63-4.17) for girls in 1988, and 6.04 (5.65-6.43) and 6.54 (6.09-7.00), respectively in 1960. The prevalence of caries fell least in first permanent molar teeth. The Care Index for the boys was 22.0 in 1960, 51.4 in 1988 and 31.5 in 1997. The pattern was similar for the girls for whom the values were 19.5, 48.6 and 32.2 respectively. The boys' Restorative Index scores (modified to include fissure sealants) were 25.7 in 1960, 58.5 in 1988 and 57.1 in 1997. The girls' scores were 23.9, 53.7 and 58.0. CONCLUSIONS: Caries has declined considerably in Salford since 1960. More of the total disease was concentrated in first permanent molar teeth in 1997. Indices, which measure the effectiveness of dental services, show that a greater proportion of overall disease was being treated in 1988 than in 1960 or 1997.

Household income in relation to dental health and dental health behaviours: the use of Super Profiles.

OBJECTIVE: To investigate the relationship between household income defined by Super Profiles, a socio-economic indicator, and dental health and dental health behaviours. BASIC RESEARCH DESIGN: Analytical survey involving a clinical examination and a questionnaire to parents. SETTING: Primary schools in Salford, UK. PARTICIPANTS: Two thousand five hundred and seventy eight 5-year-old children were examined; 1938 (75%) returned questionnaires. MAIN OUTCOME MEASURES: Mean caries experience and ages at first visit to dentist and when toothbrushing commenced. RESULTS: Children in the highest income group had a mean dmft of 1.83 compared with 2.56 in the middle group and 3.43 in the lowest income group. The proportions who had visited a dentist by their second birthday were 71%, 64% and 62% respectively. The corresponding proportions having their teeth brushed by their first birthday were 69%, 58% and 57%. CONCLUSIONS: The study showed a relationship between Super Profiles, and the dental health and dental health behaviours of 5-year-old children.

The Objective Structured Clinical Examination (OSCE) in the clinical clerkship: an overview.

The Objective Structured Clinical Examination (OSCE) for student assessment is well established, with an extensive body of research documenting that this is a valid means to assess clinical skills that are fundamental to the practice of medicine. The OSCE consists of a circuit of stations which tests a range of skills and learning to assess undergraduate medical students. A well-constructed OSCE provides important information about candidate performance and the quality of training. It is used at the University of South Dakota School of Medicine (USDSM) in assessment of third year medical students during their Obstetrics Clerkship, and as a teaching tool in the Pediatric Clerkship. On August 10, 1996, the USDSM administered an OSCE for the first time to third year medical students. The purpose of this article is to present state of the art information about setting up OSCE based on our recent experience and to provide practical examples of OSCE questions which can be addressed in the clinical setting. The narrative, references and examples give guidelines for the preparation of OSCE testing. The OSCE provided a standardized way of assessing clinical competence. Both students and faculty were very satisfied with the examination, and felt that the material tested was relevant and appropriate. The OSCE process does serve to identify areas of weakness in the curriculum and/or teaching methods, and thus can serve as a mechanism to improve educational effectiveness.

Five-year-old children: changes in their decay experience and dental health related behaviours over four years.

At the time of the 1989-90 survey of 5-year-old children, co-ordinated by the British Association for the Study of Community Dentistry, a questionnaire about dental health behaviour was sent home to 2,390 parents in Salford and 2,098 in Trafford. The response rates were 78 per cent and 81 per cent respectively. The questionnaire was repeated for the 5-year-old survey in 1993-94 with the aim of finding out if there had been any changes: 2,794 parents were contacted in Salford and 2,343 in Trafford. The response rates were 75 per cent and 73 per cent. The percentage of children who were having their teeth brushed before they were aged one and who had visited a dentist by their second birthday rose in both districts. Campaigns at regional and district levels are thought to have influenced these improvements. The percentage of children who had experienced toothache and the proportion who had received a general anaesthetic for tooth extraction were similar in both years.

Elevation of mercury in human blood from controlled chronic ingestion of methylmercury in fish.

The relationship between the intake of methylmercury in fish and mercury in blood has been investigated in man. The intakes of methylmercury were carefully controlled and lay in the range 40-230 micrograms/day, the Provisional Tolerable Weekly Intake is equivalent to about 30 micrograms/day. The results indicate that a daily intake of 1 microgram methylmercury would, at equilibrium, produce a blood mercury concentration of 0.8 micrograms/kg. There is a good close-to-linear correlation between methylmercury intake and blood mercury concentrations within the wide range of intakes employed.

Occurrence and fate of organic and inorganic contaminants in marine animals.

Most chemical contaminants occur in highest concentrations in coastal waters, often maximized in very localized areas. In general, this situation represents the exposure pattern for marine animals. However, the availability of contaminant to an organism depends not only on its concentration but also on its chemical nature, its physical state, and whether the source of exposure is the surrounding seawater or the diet. Depending on the type of exposure, uptake occurs across absorptive surfaces, such as those of the respiratory apparatus or gastrointestinal tract, where selectivity may occur, even among neighboring homologs. Deposition in tissues, accumulation, degradation, or depuration depends on tissue type, metabolic processes, detoxification mechanisms, and the adaptive status of a particular animal. This hypothesis is examined briefly for hydrocarbons, pesticides, other miscellaneous organic contaminants, heavy metals, and radionuclides. It is concluded that most data relate to occurrence and distribution. Considerably less information is available on the underlying biochemical processes.

The isolation and properties of delta-tocotrienol from Hevea latex.

1. delta-Tocotrienol (8-methyltocotrienol) was isolated from the latex of Hevea brasiliensis. This new member of the tocopherol family is a pale-yellow oil at room temperature. 2. The properties of delta-tocotrienol are very similar to those of delta-tocopherol and the small differences can be explained by the change in side chain. 3. The ultraviolet and infrared spectra of delta-tocotrienol were determined and a conversion factor for use with the Emmerie-Engel reaction was worked out. Details are given for the chromatography of delta-tocotrienol on thin layers (adsorption and partition) and reversed-phase paper, and the nitroso derivatives were formed. 4. An ethyl carbonate ester of delta-tocotrienol was prepared and compared with a similar ester of delta-tocopherol. 5. Hydroxymethylation of delta-tocotrienol followed by reduction gave beta-tocotrienol as a major product.