247 research outputs found

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    Asymptotic analysis of the Navier-Stokes equations in a curved domain with a non-characteristic boundary

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    We consider the Navier-Stokes equations of an incompressible fluid in a three dimensional curved domain with permeable walls in the limit of small viscosity. Using a curvilinear coordinate system, adapted to the boundary, we construct a corrector function at order εj\varepsilon^{j}, j=0,1j = 0, 1, where ε\varepsilon is the (small) viscosity parameter. This allows us to obtain an asymptotic expansion of the Navier-Stokes solution at order εj\varepsilon^{j}, j=0,1j = 0, 1, for ε\varepsilon small . Using the asymptotic expansion, we prove that the Navier-Stokes solutions converge, as the viscosity parameter tends to zero, to the corresponding Euler solution in the natural energy norm. This work generalizes earlier results in [14] or [26], which discussed the case of a channel domain, while here the domain is curved

    Missed opportunities in the diagnosis of pulmonary tuberculosis in children

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    In 52% of children with confirmed and probable tuberculosis the diagnosis could have been made earlier than it was. The main clinical clues which should have led to suspicion of tuberculosis were close adult contacts and previous recurrent respiratory tract infections

    The use of a geographical information system (GIS) to evaluate the distribution of tuberculosis in a high-incidence community

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    CITATION: Beyers, N. et al. 1996. The use of a geographical information system (GIS) to evaluate the distribution of tuberculosis in a high-incidence community. South African Medical Journal, 86(1):40-44.The original publication is available at http://www.samj.org.zaObjective. To determine the geographical distribution of tuberculosis in the two Western Cape suburbs with the highest reported incidence of tuberculosis. Design. Descriptive illustrative study. Setting. Two adjacent Western Cape suburbs covering 2.42 km2 with a population of 34 294 and a reported tuberculosis incidence of > 1 000/100 000. Subjects. All patients notified as having tuberculosis over a 10-year period (1985-1994). Interventions. None. Outcome measure. The geographical distribution of the cases was determined using a geographical information system (GIS) and the National Population Census (1991). Results. One thousand eight hundred and thirty-five of the 5 345 dwelling units (34.3%) housed at least 1 case of tuberculosis during the past decade and in 483 houses 3 or more cases occurred. These cases were distributed unevenly through the community, with the tuberculosis incidence per enumerator subdistrict (ESD) varying from 78 to 3 150/100 000 population. Conclusion. In a small area with a high incidence of tuberculosis, the cases are spread unevenly through the community and there are certain houses where tuberculosis occurs repeatedly. This information should be used to direct health services to concentrate on certain high-risk areas.Publisher’s versio

    Cross-sectional study of 24-hour urinary electrolyte excretion and associated health outcomes in a convenience sample of Australian primary schoolchildren: the salt and other nutrients in children (SONIC) study protocol

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    BACKGROUND: Dietary sodium and potassium are involved in the pathogenesis of cardiovascular disease. Data exploring the cardiovascular outcomes associated with these electrolytes within Australian children is sparse. Furthermore, an objective measure of sodium and potassium intake within this group is lacking. OBJECTIVE: The primary aim of the Salt and Other Nutrient Intakes in Children ("SONIC") study was to measure sodium and potassium intakes in a sample of primary schoolchildren located in Victoria, Australia, using 24-hour urine collections. Secondary aims were to identify the dietary sources of sodium and potassium, examine the association between these electrolytes and cardiovascular risk factors, and assess children\u27s taste preferences and saltiness perception of manufactured foods. METHODS: A cross-sectional study was conducted in a convenience sample of schoolchildren attending primary schools in Victoria, Australia. Participants completed one 24-hour urine collection, which was analyzed for sodium, potassium, and creatinine. Completeness of collections was assessed using collection time, total volume, and urinary creatinine. One 24-hour dietary recall was completed to assess dietary intake. Other data collected included blood pressure, body weight, height, waist and hip circumference. Children were also presented with high and low sodium variants of food products and asked to discriminate salt level and choose their preferred variant. Parents provided demographic information and information on use of discretionary salt. Descriptive statistics will be used to describe sodium and potassium intakes. Linear and logistic regression models with clustered robust standard errors will be used to assess the association between electrolyte intake and health outcomes (blood pressure and body mass index/BMI z-score and waist circumference) and to assess differences in taste preference and discrimination between high and low sodium foods, and correlations between preference, sodium intake, and covariates. RESULTS: A total of 780 children across 43 schools participated. The results from this study are expected at the end of 2015. CONCLUSIONS: This study will provide the first objective measure of sodium and potassium intake in Australian schoolchildren and improve our understanding of the relationship of these electrolytes to cardiovascular risk factors. Furthermore, this study will provide insight into child taste preferences and explore related factors. Given the cardiovascular implications of consuming too much sodium and too little potassium, monitoring of these nutrients during childhood is an important public health initiative

    The Inviscid Limit and Boundary Layers for Navier-Stokes Flows

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    The validity of the vanishing viscosity limit, that is, whether solutions of the Navier-Stokes equations modeling viscous incompressible flows converge to solutions of the Euler equations modeling inviscid incompressible flows as viscosity approaches zero, is one of the most fundamental issues in mathematical fluid mechanics. The problem is classified into two categories: the case when the physical boundary is absent, and the case when the physical boundary is present and the effect of the boundary layer becomes significant. The aim of this article is to review recent progress on the mathematical analysis of this problem in each category.Comment: To appear in "Handbook of Mathematical Analysis in Mechanics of Viscous Fluids", Y. Giga and A. Novotn\'y Ed., Springer. The final publication is available at http://www.springerlink.co

    Guideline for the management of acute asthma in children: 2013 update

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    Background. Acute asthma exacerbations remain a common cause of hospitalisation and healthcare utilisation in South African children. Aim. To update the South African paediatric acute asthma guidelines according to current evidence, and produce separate recommendations for children above and below 2 years of age. Methods. A working group of the South African Childhood Asthma Group was established to review the published literature on acute asthma in children from 2000 to 2012, and to revise the South African guidelines accordingly. Recommendations. Short-acting inhaled bronchodilators remain the first-line treatment of acute asthma. A metered-dose inhaler with spacer is preferable to nebulisation for bronchodilator therapy to treat mild to moderate asthma. Two to four puffs of a short-acting bronchodilator given every 20 - 30 minutes, depending on clinical response, should be given for mild attacks; up to 10 puffs may be needed for more severe asthma. Children with severe asthma or oxygen saturation (SpO2
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