Background: Free radicals have harmful effects on cells and tissues and are thought to be responsible for the pathogenesis of many diseases including bronchial asthma. Selenium (Se), Zinc (Zn), copper (Cu), and magnesium (Mg) are trace elements required for the antioxidant enzymes and hence the optimal functions of the immune system. Changes in the levels of these elements may lead to a reduction in antioxidant activities in asthma.Objective: This study was conducted to determine serum levels of the trace elements Se, Zn, Cu, and Mg in asthmatic patients in order to evaluate the associations of these nutrients with asthma in adults Subjects and Methods: Serum Se, Zn, Cu, and Mg concentrations were measured in 100 asthmatic adult patients and 170 healthy control subjects matched for age and sex. The patients were recruited from asthma casualties, referred clinics and wards of Elshaab and Omdurman Teaching Hospital, Khartoum Sudan. Socio-demographic data and clinical history of all subjects were collected in questionnaires. Results: Serum Se and Cu levels were found to be significantly decreased in asthmatic patients compared to controls. Mean serum Se and Cu for patients were 65.8 ± 5.5Ig/l (mean ±SD) and 0.711± 0.37g/l respectively while that for controls were 78.2± 7.5 Ig/l and 0.939± 0.322g/l respectively (P value was < 0.001). On the other hand the mean serum Zn level was significantly higher in patients compared to controls (1.2 ± 0.51g/l and 0.94± 0.254g/l respectively) (P value was <0.001). No significant difference was found in the mean serum Mg level between patients and controls (16.4 ± 4.2 g/l and 16.3 ± 2.89g/l) (P value was 0.825). Conclusions:The observed changes in the levels of the trace elements which were a decrease in serum copper and selenium and an increase in zinc may affect the antioxidant enzymes' functions, and decrease the antioxidant capacity in asthma.
Test results obtained on the effect of specimen size and aggregate size on concrete compressive strength and modulus of elasticity are presented. The concrete was prepared using 4.75, 9.5, 19.0, 37.5, and 75-mm nominal maximum size aggregate. Over 600 cylinders were cast and tested for concrete compressive strength and modulus of elasticity. Four different sizes of plastic cylinder molds were used: 150 by 300 mm, 100 by 200 mm, 75 by 150 mm, and 50 by 100 mm. The testing was carried out in accordance with ASTM standards for concrete compressive strength (ASTM 39) and modulus of elasticity (ASTM C 469). The test results were presented in terms of the concrete modulus of elasticity-to-compressive strength ratio (E/f′c) versus cylinder diameter, maximum aggregate size, age at testing, among other factors. The results revealed that a size effect exists. The strength ratio was higher for the larger nominal maximum aggregate size concrete at each testing date. Hence, as the nominal maximum aggregate size decreased, the strength ratio decreased. The strength ratio followed a dished trend with respect to specimen size. For each cylinder size, as the nominal maximum aggregate size increased, the coefficient of variation increased. It was also found that for the same nominal maximum aggregate size specimens, the coefficient of variation increased as the cylinder size decreased.
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