African Journal of Science and Technology最新文献

{"title":"Evaluation of the feeding value of two tropical cereal straws, maize stover, rice straw and their botanical fractions by nylon and mobile bag technique","authors":"D. M. Mgheni, E. Ndemanisho, T. Hvelplund, Weisbjerg","doi":"10.4314/AJST.V2I1.44642","DOIUrl":"https://doi.org/10.4314/AJST.V2I1.44642","url":null,"abstract":"Degradability characteristics of dry matter (DM), protein free DM (PFDM) and nitrogen (N) were estimated in maize stover, rice straw and their botanical fractions using the nylon bag technique. True intestinal digestibility of the intact feed protein (TID) was also estimated using the mobile bag technique. The results indicated that cereal straws and their botanical fractions have substantial variation in the extent and rate at which DM, PFDM and N were degraded in the rumen. The protein values of Total amino acid absorbed from the small intestine (AAT) , Protein balance in the rumen (PB) and TID ranged from 49 to 81 g kg-1DM, in PBV from –89 to – 61 g kg-1 DM and TID of 34 to 69 percent DM in both straws and their botanical fractions. The predicted dry matter intake (DMI) value for whole maize stover was slightly higher (5.2 kg DM d-1) than whole rice straw (4.9 kg DM d-1). High variations (4.5 to 6.1 kg DM d-1 for maize stover and 4.5 to 5.7 kg DM d-1 for rice straw) were observed within the two cereal straw botanical fractions. It was concluded that the two cereal straws are of very low feeding value and to increase their production potential improvement method strategies like chemical treatment and/or supplementation are inevitable.","PeriodicalId":7641,"journal":{"name":"African Journal of Science and Technology","volume":"74 1","pages":""},"PeriodicalIF":0.0,"publicationDate":"2009-07-28","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"83202433","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}

{"title":"Non-square quantum well growth for reduced threshold current in tensilely strained lasers operating at 1.52m","authors":"K. Kaduki","doi":"10.4314/AJST.V2I1.44630","DOIUrl":"https://doi.org/10.4314/AJST.V2I1.44630","url":null,"abstract":"This paper presents calculations demonstrating that non-square quantum well growth (well shaping) can result in reduced threshold current for tensilely strained quantum well bipolar diode lasers operating at 1.52im m. Calculations of subband structure, optical matrix elements and laser gain are performed for arbitrarily shaped quantum wells based on a 4-band (electron/heavyhole/ light-hole/split off-hole) Hamiltonian. For long wavelength (1.3im m to 1.55im) lasers, Auger recombination dominates the threshold current. Compared to a 1.52 mm optimal square well just below critical thickness, an InGaAs-InGaAsP (on InP) well incorporating potential ‘spikes’ and having the same wavelength can be much wider. The wider well, possible with well shaping, results in a lower value for three-dimensional (3D) carrier density at a given value of modal gain. For low loss lasers, this implies a reduction in Auger (and hence total) threshold current to a value below the best obtainable in a laser based on a square quantum well.","PeriodicalId":7641,"journal":{"name":"African Journal of Science and Technology","volume":"33 1","pages":""},"PeriodicalIF":0.0,"publicationDate":"2009-07-28","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"82038514","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}

{"title":"THIN- LAYER DRYING OF DICED CASSAVA ROOTS","authors":"S. Kajuna, V. Silayo, A. Mkenda, P. Makungu","doi":"10.4314/AJST.V2I2.44677","DOIUrl":"https://doi.org/10.4314/AJST.V2I2.44677","url":null,"abstract":"Fresh cassava (Manihot spp) roots were obtained from a farm and used in this study. They were peeled and diced using a special dicing machine into cubes of side 0.5 cm. The cubes were dried in thin layers (one to three layers) in a drier that was specifically designed and fabricated in the Department of Agricultural Engineering and Land Planning, Morogoro, Tanzania for the purpose. The drier had a motor driven fan, a heater and a tray chamber, with thermometers for determining entry and exit temperature (dry and wet bulb) conditions of the air. The input variables were: depth of thin layer (0.5, 1.0 and 1.5 cm), drying temperature of the air (55 and 65 oC) and drying time (from 0 min until the sample attained equilibrium, at intervals of 25 min). The response variable was the moisture content of the cassava cubes. Weather conditions during the experiments were also monitored. A parallel sun drying experiment was carried out to compare thin layer drying on the sun and thin layer drying in the fabricated dryer. For the fresh cassava that was used in the experiments, a duplicate sample was placed in an oven at 75 oC for 7 hours to determine the initial moisture content. The results indicated that the average moisture content of fresh cassava roots was about 75.4 %(w.b.). Both temperature and depth of layers were found to affect the drying characteristics of cassava cubes, with single layer and higher drying temperature giving faster approaches to equilibrium moisture content. Comparing sun drying of one layer at an average temperature of 25 oC with artificial drying at the above named temperatures, it was found that sun drying took 2 to 3 days to reduce the moisture content to Equilibrium Moisture Content (EMC), while this was achieved within 150 min and 125 min with artificial drying at 55 oC and 65 oC respectively. The generally accepted thin layer drying equations were fitted to the drying data of cassava cubes, and the Page model was found to agree with the drying data of one, two and three layers with high accuracy for artifial drying, but not for sundrying. The exponential model only agreed accurately with drying of one layer.","PeriodicalId":7641,"journal":{"name":"African Journal of Science and Technology","volume":"96 1","pages":""},"PeriodicalIF":0.0,"publicationDate":"2009-07-28","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"80018255","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}

{"title":"REACTIONS OF O-AMINO-N-(1,1-DIMETHYLPROP-2-YNYL)-BENZAMIDE","authors":"C. Usifoh, L. Okunrobo","doi":"10.4314/AJST.V2I1.44638","DOIUrl":"https://doi.org/10.4314/AJST.V2I1.44638","url":null,"abstract":"Carbonylation of o-amino-N-(1,1-dimethylprop-2-ynyl)-benzamide 3 with ethyl chloroformate gave 2-carbethoxyamino-N-(1,1-dimethylprop- 2-ynyl)-benzamide 6. Attempted cyclization of 6 under basic conditions did not give the quinazoline 8 but an oxazole 7. When 3 was also refluxed in triethylorthoformate-acetic anhydride mixture, 2-acetylamino-N-(1,1-dimethylprop- 2-ynyl)-benza-mide 4 was formed as the major compound with negligible amount of 3-(1,1- dimethylprop-2-ynyl)-quinazolin-4-(3H)-one 5.","PeriodicalId":7641,"journal":{"name":"African Journal of Science and Technology","volume":"92 1","pages":""},"PeriodicalIF":0.0,"publicationDate":"2009-07-28","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"75319640","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}

{"title":"Lathe stability charts via acoustic emission monitoring","authors":"J. Keraita, Hj Oyango, G. K. Misoi","doi":"10.4314/AJST.V2I2.44675","DOIUrl":"https://doi.org/10.4314/AJST.V2I2.44675","url":null,"abstract":"Signal parameters characterizing acoustic emission (AE) detected during metal cutting have been theoretically correlated in a simple manner, to the work material properties, cutting conditions, and tool geometry. During chatter, the cutting conditions and the tool geometry change considerably. Self-exited chatter, an instability of the cutting process in combination with the machine structure, is a basic performance limitation of machine tools. In the research findings presented in this paper, changes occurring to AE signal parameters have been used to detect the onset of chatter and hence plot stability charts, during a turning operation. Apart from showing the borderlines of stability, such charts can be used to identify the necessary changes required to eliminate chatter at minimum or no loss of production. The signal parameters investigated include AE mean intensity level, the skew and kurtosis of the power spectrum; as well as the count rate of the emissions.","PeriodicalId":7641,"journal":{"name":"African Journal of Science and Technology","volume":"5 1","pages":""},"PeriodicalIF":0.0,"publicationDate":"2009-07-28","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"73599409","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}

{"title":"Elements de precision sur la systematique d’especes adventices dugenre corchorus l. (tiliaceae) au Senegal","authors":"Mbaye, K. Noba, R. Sarr, A. Kane, Jm Sambou, B. Tidiane","doi":"10.4314/AJST.V2I1.44639","DOIUrl":"https://doi.org/10.4314/AJST.V2I1.44639","url":null,"abstract":"Corchorus L is a genus includes nearly 40 species widelydistributed throughout the tropics and is represented in Senegal by 5 species according to Berhaut : C. aestuans L.; C. fascicularis Lam., C. olitorius L. with 2 varieties C. olitorius var olitorius L. and C. olitorius var incisifolius Asch. & Schw; C. tridens L. and C. trilocularis L.. Interest for these species is both economic and systematic. Indeed, beyond their weed statute and because of their ethnobotanical properties some species are cultivated. Besides, in the botanical point of view they belong to a genus which is a transition group between two tribes ; Tiliae and Grewiae. Even works done on the genus, identification of these species is still difficult. In fact, the more discriminant characters put ahead concern those of the fruit, an organ which appears late in the plant life cycle. Investigations on vegetative and reproductive organs on adult plant showed that, the presence or absence of basal hair on the limb, the dentate or lacerate leaves, the ovary 3 or 5-celled, the circular or hexagonal or pentagonal or trigonal secttion of the fruit, the seeds contiguous or separate inside the fruit are additional characters which could better help to identify these species.","PeriodicalId":7641,"journal":{"name":"African Journal of Science and Technology","volume":"9 1","pages":""},"PeriodicalIF":0.0,"publicationDate":"2009-07-28","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"84189492","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}

{"title":"A CUTTING- PLANE APPROACH FOR SEMI- INFINITE MATHEMATICAL PROGRAMMING","authors":"M. Luhandjula, M. Ouanes","doi":"10.4314/AJST.V2I1.44628","DOIUrl":"https://doi.org/10.4314/AJST.V2I1.44628","url":null,"abstract":"Many situations ranging from industrial to social via economic and environmental problems may be cast into a Semi-infinite mathematical program. In this paper, the cutting-plane approach which lends itself better for standard non-linear programs is exploited with good reasons for grappling with linear, convex and geometric Semi-infinite programs. For each case, computational aspects are discussed and convergence statements established. Simple numerical examples are also provided for the sake of illustration. The paper ends by briefly comparing the cutting-plane approach discussed here with other existing approaches and by stressing the necessity of pushing forward a Decision Support System effectively capable for helping someone faced with a problem that can be formulated as a Semi-infinite mathematical program.","PeriodicalId":7641,"journal":{"name":"African Journal of Science and Technology","volume":"55 1","pages":""},"PeriodicalIF":0.0,"publicationDate":"2009-07-28","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"82732924","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}

{"title":"EFFETS DE L'EXTRAIT AU CYCLOHEXANE DE BIDENS PILOSA L. (ASTERACEAE) SUR LA MOTRICITE INTESTINALE DE RAT","authors":"D. Thiophile, A. Rakotonirina, R. Kamgang, Tr Tankwa, K. Wanda, G. Magloire","doi":"10.4314/AJST.V2I1.44632","DOIUrl":"https://doi.org/10.4314/AJST.V2I1.44632","url":null,"abstract":"Effects of cyclohexane extract of Bidens pilosa L. on rat intestinal motility. – In vitro, we have studied the effects of the cyclohexane extract of Bidens pilosa leaves (B.p.) on the rat ileum smooth muscle motility. B.p. has showed dose-dependent stimulators effects on both tonicity and amplitude of the spontaneous contractions. With 160 ig/mL of extract maximal stimulation was obtained. With that dose, the rate of variation was 1027 %. Atropine reduced by 77 % the spasmogenic effects of B.p. and by 94 % the acetylcholine effects. In Ca2+ free solution, stimulation contraction by 160 ig/mL of the extract was reduced to 400 %, while Nifedipine completely inhibited the spasmogenic effects of the extract. These results suggest that the cyclohexane extract of B.p. could stimulate ileal smooth muscle contractions through muscarinic receptors which increase Ca2+ mobilization from both extra- and intracellular milieu.","PeriodicalId":7641,"journal":{"name":"African Journal of Science and Technology","volume":"1 1","pages":""},"PeriodicalIF":0.0,"publicationDate":"2009-07-28","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"89671267","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}

{"title":"MACROPHYTES ET GROUPEMENTS VÉGÉTAUX AQUATIQUES ET AMPHIBIES DE LA BASSE VALLÉE DU FERLO (SÉNÉGAL)","authors":"A. Sarr, A. Thiam, A. Bâ","doi":"10.4314/AJST.V2I1.44651","DOIUrl":"https://doi.org/10.4314/AJST.V2I1.44651","url":null,"abstract":"The reflooding of the Ferlo Valley since 1988 after 32 years of drying up has caused progressive growth of aquatic plants. 103 woody and herbaceous plants falling into 81 genera and 38 families were identified in the Valley. Analysis of the vegetation using the transect technique and the Braun Blanquet method helped to establish the floristic composition of 7 aquatic and semi aquatic plants groups. Typha domingensis and Pistia stratiotes are dominant in the aquatic miieu whereas Tamarix senegalensis plant groups were frequently found in the flood plain, indicating that the tidal range is important and soil salinity was still high.","PeriodicalId":7641,"journal":{"name":"African Journal of Science and Technology","volume":"128 1","pages":""},"PeriodicalIF":0.0,"publicationDate":"2009-07-28","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"87976104","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}

{"title":"EU/Th AND 14 C isotope dating of lake sediments from sacred lake and lake Nkunga, Kenya","authors":"D. Olago, F. Street-Perrott, R. Perrott, M. Ivanovich, D. Harkness","doi":"10.4314/AJST.V2I1.44633","DOIUrl":"https://doi.org/10.4314/AJST.V2I1.44633","url":null,"abstract":"In the tropical regions, lake and swamp sediment core chronologies have traditionally been established solely by radiocarbon dating. In several instances, however, the radiocarbon sampling resolution has been coarse, entailing extrapolations over time periods where there may have been considerable change in sedimentation rates related, for example, to significant, albeit abrupt, palaeoclimatic and palaeoenvironmental change. Moreover, some cores may age-wise exceed the radiocarbon dating limit of ca.40,000 yr, thus entailing tenuous extrapolations of radiocarbon dates obtained in the younger sections of the core in order to obtain a whole core chronology. In this paper, the chronology of lake sediment cores retrieved from Sacred Lake and Lake Nkunga on the north-eastern flank of Mount Kenya is established using a combination of highresolution radiocarbon dating and experimental U/Th dating to circumvent the drawbacks mentioned above. The derived chronosequences, which show that these sediment records span almost the whole of the late Quaternary period, demonstrate the efficacy and synergism of these dating techniques.","PeriodicalId":7641,"journal":{"name":"African Journal of Science and Technology","volume":"34 1","pages":""},"PeriodicalIF":0.0,"publicationDate":"2009-07-28","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"82016514","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}