Policies to influence the spatial distribution of physicians: a conceptual review of selected programs and empirical evidence

To increase the usefulness of existing physician location literature for policy evaluation, literature is grouped into intraurban and urban-rural studies. A conceptual overview of physician location literature is presented. Consensus results, if any, are discussed. A list of hypotheses suggested by the literature is then utilized in a discussion of economic social, prior exposure, and professional development incentives embodied in selected public and private sector programs. Programs are evaluated by type of incentive mechanism and geographic target area to determine if present program structures are based on a solid empirical foundation. This assessment indicates that, in general, use of prevalent location incentive mechanisms is not justified by a consensus of empirical evidence.     

Studies on the development of Theileria annulata Dschunskowsky and Luhs, 1904 in the tick--Hyalomma anatolicum anatolicum Koch, 1844

The endogenous development of Theileria annulata in the vector tick--Hyalomma anatolicum anatolicum has been described. Parasites within and outside the erythrocytes were seen in the gut contents of larvae and nymphs immediately after their removal from the infected cattle but not after 24 hours. Two bodies resembling the intra-erythrocytic stage of the parasite, lying close to each other were seen near the gut epithelium of a larva on the 4th day of its dropping off the infected host. Neither multiplication nor union of the parasite resulting in zygote formation in the gut of the tick, was noticed. Next stage of the parasite was seen in the salivary glands of nymphs and adults. The pre-infective stage characterized by indistinct chromatin dots (nuclei) surrounded with cytoplasm was seen in alveolar cells of the salivary glands of nymphs and adult ticks from the first to the third day of their feeding of the host. This stage progressed to the infective stage consisting of distinct chromatin particles (the infective particles) surrounded with cytoplasm in the salivary glands of nymphs and adult ticks after the second and first day, respectively of feeding on the host. The infective particles were also seen within ducts of the salivary glands.     

Follow-up study of patients treated by x-ray epilation for tinea capitis. Estimation of the dose to the thyroid and pituitary glands and other structures of the head and neck

This study is a further investigation of radiation dose to various head structures in the children given X-ray therapy for tinea capitis (ringworm of the scalp). In this work, estimates of the dose to the thyroid and pituitary gland were obtained with lithium fluoride thermoluminescent dosemeters using a child's head phantom. Doses were also measured for the parotid gland and several skin sites where skin tumours developed in the irradiated cases. In a previous study, brain and scalp doses of 140 and 500-800 rad had been estimated for the treated group using this same head phantom. In this work dosemeters were also placed in the same brain locations so that comparisons could be obtained between the two studies. The thyroid dose was estimated to be 6 +/- 2 rad and the pituitary dose was 49 +/- 6 rad for the conventional tinea capitis treatment. The dose to the parotid gland was 39 rad and the dose to skin sites on the face and neck where tumours occurred ranged from 20 to 40 rad. The data for the thyroid adenoma response from this and other studies involving irradiation of children suggests a linear dose-response relationship within the first 30-40 years after exposure with a risk of about 0-04% per rad.     

Baseline immunity of the population and impact of insecticide-treated curtains on malaria infection

The aim of this study was to investigate the relationship between dietary fish consumption and self-reported respiratory symptoms among young adults. A random sample of 4,300 subjects, aged 20-44 yrs, living in Bergen, Norway, received a postal questionnaire on respiratory symptoms, of whom 80% responded. Mean fish consumption was assessed in a food-frequency questionnaire by asking how often the subject consumed units of fish (150 g) during the last year. Average fish consumption was 1.8 units x week(-1). Fish intake of <1 unit x week(-1) was reported by 24%, 41% reported consumption of 1 unit x week(-1) and 35% intake of >1 unit x week(-1). A high fish intake was significantly associated with increasing age after adjusting for smoking. Adjusted for smoking habits, the prevalence of "cough at night" and "chest tightness" showed a decreasing trend with increasing fish consumption (p<0.05), while such a trend for "wheeze" was demonstrated only in smokers (p=0.008 for interaction). In logistic regression models (adjusting for age, sex, body mass, smoking habits and occupational exposure) fish consumption (three categories) was not significantly associated with "wheeze", "chest tightness", "breathless at night" or "asthma attack", although the odds ratios (OR) were consistently less than 1 (except for "asthma attack"). Fish consumption was of borderline significance as a protective factor of "cough at night", OR = 0.86 (95% confidence interval: 0.76-0.97) but in stratified analyses only in smokers. Subjects reporting very high levels of fish consumption (>14 units x week(-1)) did not have lower prevalences of respiratory symptoms. In conclusion, among young Norwegian adults, with a relatively low prevalence of asthma and an overall high fish intake, fish consumption was not a significant predictor of four out of five respiratory symptoms.     

HOW TO MAKE THE HILL CIPHER SECURE

ABSTRACT

This paper presents a symmetric cipher that is actually a variation of the Hill cipher. The new scheme makes use of “random” permutations of columns and rows of a matrix to form a “different” key for each data encryption. The cipher has matrix products and permutations as the only operations which may be performed “efficiently” by primitive operators, when the system parameters are carefully chosen.     

Microbiological Aspects of Water Quality and Health

Historically, typhoid and cholera are well-recognized waterborne infections. Advances in laboratory techniques over the past 20 years have enabled a wide range of other faccally-excreted bacteria, viruses and protozoa to be identified as causing gastrointestinal infections. Record outbreaks are referred to where some of these micro-organisms have been spread by the contamination of drinking water, either at source or during distribution. This has usually happened when the water was untreated, or where there have been failures of the disinfection process or breaches in the integrity of the distribution system. Recent waterborne outbreaks of cryptosporidiosis have underlined the importance of adequate filtration in the prevention of waterborne transmission of this protozoon, the oocysts of which are completely resistant to the levels of chlorine that can be attained in water treatment practice. An outline is given of the current processes by which pathogenic micro-organisms are excluded from drinking-water supplies; their potential deficiencies for dealing with some of the 'newer' waterborne pathogens are also discussed.