Browsing by Author "Tesfaye, Melaku"
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Item Evaluation of In-Vitro Antibacterial and Antifungal Activities of Crude Extract and Solvent Fractions of the Leaves of Justicia Schimperianahochst. Ex Nees(Acanthaceae)(Addis Ababa University, 2017-05) Tesfaye, Melaku; Shibeshi, Workineh(PhD); Engidawork, Ephrem (PhD)Management of infectious diseases has been challenged due to antimicrobial resistance and slow rate of new antimicrobial discovery. Therefore, intensive search has to be conducted on the claimed traditional medicinal plants like Justicia schimperiana which have been used traditionally for wound healing, skin burn and other medicinal purposes. There is a report confirming antibacterial activity of leave extracts of Justicia schimpriana. Based on previousfindings, it was necessary to further investigate antimicrobial activity of the plant. In this study the leaves of Justicia schimperiana was extracted with 80% methanol by maceration. Then, the crude extract was fractionated with solvents of increasing polarity: ethyl acetate, n-butanol and water. The antimicrobial activity of the crude extract and solvent fractions was evaluated on eight bacterial (S. aureus, S. pneumoniae, S. pyogenes, S. typhi, K. pneumoniae, S. flexneri, P. aeruginosa and E. coli) and two fungal (C. albicans and T. mentagrophytes) species using agar well diffusion method with different concentrations (800 mg/ml, 400 mg/ml and 200 mg/ml). Minimum inhibitory concentrations were determined by broth micro-dilution method. Among the tested bacterial species S. pneumoniae was found to be the most susceptible species with MIC of 1.56 mg/ml. Among the solvent fractions, n-butanol fraction showed strong inhibition with mean zone of inhibition ranging from 16.33mm to 28mm for bacterial species and 18mm to 18.33mm for fungal species at concentration of 200mg/ml. In conclusion, all solvent fractions demonstrated antimicrobial activity and the n-butanol fraction was observed to be more active against the tested microorganisms. KEY WORDS: Justicia schimpriana, Antibacterial activity, antifungal activityItem Investigation of Alternative Design Forms of Precast Beam for Low Cost Buildings(Addis Ababa University, 2009-11) Tesfaye, Melaku; Taye, Shifferaw (PhD)It should not be puzzling to have 55% of the condominium house lottery winners did not show up interest to sign and receive ‘their’ houses, which is claimed to be low cost and affordable to lower and middle class society, this figure will be larger in country side towns. This still tells us the claiming low cost houses are still far beyond the affordable limit of the target group. In this study an endeavor is made to investigate structurally safe and economical forms of precast beam. Hence a new plane truss forms of precast beam is investigated and compared to the practicing space truss form of precast beam. The new model, though it has relatively shorter length of span for the similar sizes of bar, it is found reducing the cost by around 25% and mass (weight) of the beam by 33% for relatively similar span lengths.Item Retrival of Atmosph Eric Aerosol Optical and Microphysical Parameters from Ground Base Passive Remote Sensing Measurement over Addis Ababa(Addis Ababa University, 2009-03) Tesfaye, Melaku; Mengistu, Gizaw (PhD)Aerosol optical depth is determined from measurements of atmospheric effective spectral transmission, for clear-sky days on May 21, 2008 and May 23, 2008, at Addis Ababa (9° 1′ 48″ N, 38° 44′ 24″ E) carried out using pyrheliometer, which we constructed in department of physics at AAU. It has effective discrete optical channels in the range between 0.699mm and 0.753mm. With in framework of Mie theory and non-linear inversion method, column integrated effective optical and microphysical parameters are retrieved. The effective refractive index, temporal variation related to atmospheric particle size distribution, and modeling the effect of water vapor implies that, atmospheric aerosols have chemically distinct compositions due to their different sources and the hygroscopic growth is facilitated by chemical alterations. Removal processes of particles are more efficient when the aerosol size increases. Retrieved real part of effective refractive index ranges between 1.53 and 1.59 while computed single scattering albedo ( 0 w ) ranges between 0.98 and 0.99. This is indicating that dust is by far the dominant aerosol component in Addis AbabaItem Retrival of Atmosph Eric Aerosol Optical and Microphysical Parameters from Ground base Passive Remote Sensing Measurement Over Addis Ababa(Addis Ababa University, 2009-03) Tesfaye, Melaku; Mengistu, Gizaw (PhD)Aerosol optical depth is determined from measurements of atmospheric effective spectral transmission, for clear-sky days on May 21, 2008 and May 23, 2008, at Addis Ababa (9° 1′ 48″ N, 38° 44′ 24″ E) carried out using pyrheliometer, which we constructed in department of physics at AAU. It has effective discrete optical channels in the range between 0.699mm and 0.753mm. With in framework of Mie theory and non-linear inversion method, column integrated effective optical and microphysical parameters are retrieved. The effective refractive index, temporal variation related to atmospheric particle size distribution, and modeling the effect of water vapor implies that, atmospheric aerosols have chemically distinct compositions due to their different sources and the hygroscopic growth is facilitated by chemical alterations. Removal processes of particles are more efficient when the aerosol size increases. Retrieved real part of effective refractive index ranges between 1.53 and 1.59 while computed single scattering albedo ( 0 w ) ranges between 0.98 and 0.99. This is indicating that dust is by far the dominant aerosol component in Addis Ababa