Browsing by Author "Assefa, Taye"

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    Production and Characterization of Custard Apple Seed Extract for its Possible Application as Bio-pesticide
    (Addis Ababa University, 2019-06) Assefa, Taye; Shegaw, Ahmed (PhD)
    The intensive use of synthetic pesticide has undeniably resulted in adverse and sometimes irreparable effects on the environment including human health. Therefore, alternative pest management strategies are desired. Natural pesticides have proven potential for pest management and they are being used throughout the world. To this effect, this thesis investigated the production and characterization of locally available custard apple seed extract for its possible application as natural pesticide using ethanol (97%) as a solvent. The raw seed moisture content, fat content, ash and organic matter content were determined properly. The extraction parameters were extraction time, temperature and ethanol to custard apple seed ratio. A maximum of 12.63 % total extraction yield of pesticide was achieved at the optimal conditions of 4h, 50 and 7:1 v/w of extraction time, temperature and ethanol to CAS ratio respectively. The individual and interaction effect of these parameters on the yield of oil was studied and optimum conditions were established by using RSM of Box-Behnken method of Design Expert 7.0.0 software. The characteristics of CAS extract were then evaluated using different analytical methods. Specific gravity, flash point, water solubility, pH value and TVOCs were analyzed with respective methods. The FT-IR analysis indicates presence of C=O group of the unsaturated lactone group. The GC-MS result shows that the presence of uvaricin, annonacin and squamocin. From the statistical analysis method, all the three factors had an impact on the yield directly and extraction time with temperature, extraction time with ethanol to CAS ratio, temperature with ethanol to CAS ratio had also a significant effect on the yield. Using model optimization of the factors were found the optimum points of extraction time (3.99hr), temperature (49.92 ) and ethanol to CAS ratio (7.04:1 v/w) with 12.63 % yield of product. Generally, the results found in this study showed that CAS extract seems to be a viable alternative option for the production of the natural pesticide.
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    Tewodros in Historical Fiction
    (Addis Ababa University, 1980-05) Assefa, Taye; Araaya, Hailu (PhD)
    Of all the national efforts of Ethiopi an emperors, those of Tewodros are the most highly uppreciuted by the present publ i c. This may be because he was the one who under difficult circumstances strove to reunite and rebuild the crumbling empire. It was he who for the first time seriously challenged the power of the nobility and the clergy and thus practically disproved the inviol ~bility of the old status quo. Those who were aspiring for radical changes in the semi - feudal regime of Emperor Haile Sellassie therefore easily identified themselves with Tewodros . In this r espec t, he alone has inspired some six of the major writers to produce plays and novels which tell the story of his exp loits. These works are: Ande Lennatu, Tayitu Bi~ul, Warrior King, Yetewodros Enba, and Tsegaye ' s and Girmachew ' s TewodroGo There being little or no systematic study of these fictional works so far , this study has been undertaken to provide such a literary appraisal . In this context then , it hJS been the objective of this thesis to f ind out vlhat Tewodros symbolizes for these writers and also to determine what the literary worth of these fictional works is. As the nature of the l-J'orks examined has been fictional and their contents historical, so the approaches employed h~ve been both literary and historicalo Moreover, in order to maintain the objectiveness of the thesis, the actual analysis 0 2 t ;,e literary texts hes been supplemented by an introductory historical sketch of Tewodros , interviews with three authors of the works examined , and a compilation of folk poetry related to Tel-lOdros and collected from already existing sources. After an examination of the six works and the folk poems, this study has arrived at the conclusion that while oral literature focuses on Tewodros ' personality, most written historica l fictions, however, pay more attention to his nationale efforts. Though both written and oral historical fiction see Tewodros ' violence as "ruthlessness to the enemy" and though both pOrtray Tewodros as a symbol of heroism , written fiction alone associates with Tewodros such symbolic values as nationa l unity, national independence ,and progress. Tayitu_?itu~ , however, identifies Tewodros only with tyranny.In spite of mos t of the "lritten historical fic tions ' preoccupation withTewodros ' ideals and national efforts, they are not successful in presenting these in their proper socio-historica l perspec tive. Most of the politicalal portrayals could not co~sistently see the traditional society as being divided into antagonist ic classes with irreco ncilab l e interests.. As a r esu lt, the ",orks attribute" the opposition to Tewodros to such subjective f actors as the l ack of coop~rat ion, understanding , tact and tolerance on one or the other side . Accordingly, social advanc e is seen not as the outcome of class conflicts, but as the making of individuals \.,ho effect reforms from above. ;\s U,e focus of all the portrayals has been on the members of the ruli ng class, the fact of the peasantry 's being the basic motive force of the traditional society has no t been forcefully established . hpart from these shortcomings most of the works also suffer from t echnical vJeaknesses whi ch tend to undermine their literary values 0 These weaknesses are the sl~vish adapta tion of the st;ndard history of Tewodros, the lack of organic unity in their plot schemes and smooth flo .in their narratives, the abstractness of their ch3racters, and their inartistic emp loyment of flashback s and foreshadowings. The only works which have be(~n able to overcome some of these weaknesses are Warrior King and Yetewodros Enba .In spite of these weaknesses, the concern the most of these .Iorks have shown for the most etlical events in the lives of the people indicates a positive trend in the development of Ethiopian historical fiction. Besides, some of these works like Yetewodros Enba do succeed in giving us Some insight into the nature cif the forces that were opposed to Tewodroe. In their technica aspects , too, some of the works like Yetewodros Enba do possess lite rary qualities such as the judicious selection of one representative situa tion in the course of who se development characters and events unfold their essentiali natures . The use of dreams in some of these works indicates that these i1rc potential devices that could be fully deve loped and exploited in future lritings . In comparison with each other, however ,Yetewodros Enba and or King come out as the best of these fictional works both in r egard t o the treatment of their themes and the employment of devices like flashback and descripti on . i'ihile the shortcomings in many of the works may teach futu re writers by negative examples, their literary qualities surely serve to enrich the tradition of creative writing.