Browsing by Author "Tefera, Nahom"

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    The association between dietary fluoride and calcium intake of school-age children to the level of dental and skeletal fluorosis in Halaba, Southern Ethiopia
    (Addis Ababa University, 2019-09) Tefera, Nahom; Baye, Kaleab (PhD)
    Fluorosis, which is the toxic effect of excess fluoride ~ntake, is a major public health problem in Ethiopian Rift Valleys. This study is aimed to investigate the relationships between dietary fluoride and calcium intakes of school age (6-13 years) children to the levels of dental and skeletal fluorosis, in Halaba, Southern Ethiopia. A study designed in environment assessment and crosssectional analysis was undertaken in which 127 children were selected using cluster and simple random sampling techniques. The dietary calcium andfluoride intake data were collected by using 24 hour andfoodfrequency questionnaire methods. Dental and skeletal fluorosis assessment was conducted by a qualified dentist and physiotherapist respectively. The average diet diversity score was 3.13 from seven food groups. The mean dietary calcium and • fluoride intakes were 520 mg/day and 70 mg/day respectively. At all age categories, the average calcium intake was too low compared to the RDA for calcium and the fluoride intake was very high compared to the tolerable upper intake level of fluoride. Among 127 children 70.9% were prevalent to dental fluorOSiS (from very mild to severe symptoms), whereas 27.6- 44.9% were prevalent to skeletal fluorosis. The calcium andfluoride intakes were significantly ajsociated with dental and skeletal fluorOSiS levels (P < 0.05). Improving the consumption of calcium-rich foods like dailY products, Ethiopian kale, millet, and enset are recommended. Key words: Calcium intake, Fluoride intake, Dental fluorosis, Skeletal fluorosis, Rift Valley, Ethiopia
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    Iron based Superconductors
    (Addis Ababa University, 2012-06) Tefera, Nahom
    This project is well organized review of new class of high-Tc superconductors i.e iron-based layered compounds such as ReOFeAs (Re is a rare-earth element), AFe2As2 (A = Ba, Sr, Ca), and LiFeAs, all of which are becoming superconducting with the current maximum Tc up to 55 K. The crystal and electronic structure, and magnatic properties all these compounds were discussed. In this paper, the superconducting properties of such systems are reviewed in detail, including the dependence of Tc on the doping level, and external pressure. In this project we discussed about the pairing symmetry and possible mechanism of superconductivity of iron based superconductors. we also discussed the progress and potential application of iron based superconductors