Browsing by Author "Hailemariam, Solomon"

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    Extraction and Characterization of Essential Oil from Rosemary Leaves
    (Addis Ababa University, 2016-10) Hailemariam, Solomon; Worku, Teshome (Ass.Professor)
    Rosemary (Rosmarinus officinalis L.) extracts enriched in phenolic compounds are effective antioxidants due to their phenolic hydroxyl groups and they also possess innumerable applications starting from markers for plant identifications to bases for semi-synthesis of highly complex molecules. Therefore, the aim of this research is extraction and characterization of rosemary essential oil (Rosmarinus officinalis) using steam distillation method. In this research, rosemary leaves were collected from Sebeta region (town and separate wereda in central Ethiopia). An integrated procedure for steam distillation extraction followed by volatiles sampling and characterization from the leaves of the rosemary was implored. The effect of different process parameters, such as pre-distillation drying conditions and extraction time on the extraction yield was investigated. The parameters taken up for the study like the pre-distillation drying conditions and extraction time were found to significantly affect the extraction yield and quality of the essential oil. Increase in yield was observed when increase the extraction time and pre-distillation drying conditions. The essential oil yield was found to vary from 0.378 to 1.137% under different method of drying and extraction time. Maximum yield was observed from sun dried rosemary leaves at 120 min of extraction time. The volatiles rosemary essential oil in vapour form released from the leaves were condensed and characterized their physical and chemical properties and found within the recommended range. The components of rosemary essential oil was determined using Gas Chromatography-Mass Spectroscopy, and eight major components were identified. Monoterpene hydrocarbons were found to be predominant. The major components were α-pinene (12.08 %), camphor (9.14 %), camphene (2.14 %), bornyl acetate (6.79 %), borneol (5.07%), and α‐terpineol (3.08%). Therefore, pre-distillation drying and extraction time have greater effect on the quality and quantity of rosemary essential oils. Key words: Rosmarinus officinalis L; rosemary; essential oil composition; extraction; steam distillation.
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    Mechanisms for Formations of Photoluminescience from Silicon and Germanium Nanostructures and Formulating Models
    (Addis Ababa University, 2011-06) Hailemariam, Solomon; Bedassa, Tesgera (PhD)
    Bulk silicon (Si) and germanium (Ge) have an indirect band gap transitions however when they are miniaturized to nanometer scale, the energy gap between the highest occupied molecular orbital (HOMO) and the lowest unoccupied molecular orbital (LUMO) increases, and hence the transition changes to direct due to confinement. The HOMO-LUMO gap determines the excitation of electrons so that the nanostructures will emit light. In this work,quantum confinement effects for Si and Ge,some methods to calculate band structures and formation mechanisms of photoluminescence from Si and Ge nanostructures are presented. We presented the parameters that influence the photoluminescence intensity of Si and Ge nanostructures. Finally we developed a model that could explain experimental results of Si nanocrystal photoluminescence versus size and wavelength by using Matlab program
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    Transforming State Broadcasting into Public Service Broadcasting in Ethiopia: Challenges and Prospects
    (Addis Ababa University, 2005-12) Hailemariam, Solomon; Skjerdal, Terje (Assistant Professor); Tefera, Negussie (PhD)
    The existence of freedom of_ expression in general and media freedom in particular is one of the most important indicators of the presence of democracy in a given country. Article 29 of the 1995 Constitution of the Federal Democratic Republic of Ethiopia has laid the legal structure for the existence of freedom of _expression in Ethiopia. Accordingly, all the subsidiary laws advocate the flourishing of media freedom in Ethiopia. The legal framework for transforming state broadcasting into public service broadcasting (PSB) is encouraging. However, what is happening in practice is questionable. This thesis looks at the state of affairs of State Broadcasting in Ethiopia, using content analysis as a quantitative data-gathering instrument. Key informant interviews and legal documents have been used to collect data as a qualitative means. The study has selected 131 news items from 15 days of Ethiopian Radio Amharic prime time news bulletin. The data collected via content analysis has been supplemented by the data gathered through qualitative means. In this study, the practice of state broadcasting has been tested against the principles and practices of public service broadcasting. One of the findings of the study is that there is a very tight form of political control in the activities of journalists working in state broadcasting in general, and in Ethiopian Radio in particular. Government officials, predominantly from the Ministry of Information, directly and indirectly interfere in the editorial independence of journalists working on Ethiopian Radio. In order to protect state broadcasting from political interference, and to maintain editorial independence, the study suggests a new law should be drafted by the Ethiopian Parliament. This would facilitate a smooth transformation from state broadcasting to public service broadcasting. Article 29, sub Article 2 of the 1995 Constitution of the Federal Democratic Republic of Ethiopia explicitly supports the enactment of a law that promotes media independence in the country. [ iii 10 Public service broadcasting must be guaranteed protection from political and/or commercial interference. This will be closer to reality when the appointment and accountability of PSB officials, their duties and responsibilities are clearly supported by a law according to the accepted principles of PSB. Public service broadcasting demands that editorial independence be respected. Moreover, the programming should serve the public interest and, in particular, should be balanced and impartial. At the very least, PSB should be editorially independent as an institution, and should serve the public fairly, helping to empower people so as to enable them make to decisions and to play a role towards the establishment and continuity of a democracy.