FACULTY OF SCIENCE
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Item Impact of the total solar eclipse of 29 March 2006 on the surface energy fluxes at Ibadan,Nigeria(2012) Nymphas,E.F.; Otunla,T.A.; Adeniyi,M.O.; Oladiran, E.O.This paper document the impact of the total solar eclipse (97.4%) of 29 March 2006 on the surface energy fluxes at Ibadan, Nigeria (longitude4.561E, latitude7.551N), a tropical location. The surface energy (determined by the BREB method) was found to be grossly affected by the eclipse. The latent heat and net radiation (Rn) lagged the sensible heat by 11 min in totality. The sensible heat lagged the latent heat and Rn by 6 min before it start to increase after the totality phase of the eclipse while global radiation (Rg) lagged Rn by 7 min. The sensible heat reversed sign reaching a value of _1.02 Wm_2 during the total phase of the eclipse while the latent heat dropped by 89.7%. All the radiation fluxes (global radiation, Rg, net radiation Rn, temperature and soil heat flux) measured during the eclipse event were significantly affected by the sudden ‘cutoff’of the solar irradiation.There was a 95% decrease in Rg, while Rn dropped from 354.3Wm_2 to _11.7 Wm_2.Item TLC phytochemical screening in some Nigerian loranthaceae(Academic Journals, 2010-07) Wahab, O. M.; Ayodele, A. E.; Moody, J. O.The phytochemical screening of specimens of the family Loranthaceae collected from the field was carried out with a view to ascertaining chemical constituents present and determining their importance in the taxonomic delimitation of the taxa. Thirty field collections from various localities were screened for secondary metabolites such as alkaloids, anthraquinones, terpenoids and ketones using thin layer chromatography (TLC). Most of the samples tested slightly positive for alkaloids, anthraquinone-related compounds, terpenoids and terpenoidrelated compounds but ketonic compounds were of rare occurrence in all the samples. The chemical profile was useful in separating the collections of Phragmanthera from the other two genera while the collections of Globimetula were found embedded in Tapinanthus. The secondary metabolites obtained however showed the relative affinity of the Nigerian species of Tapinanthus. It is concluded that chemical characters may only be used as supporting evidence in the identification and delimitation of the taxa.Item Fractional integration and structural breaks in bank share prices in Nigeria(Elsevier, 2015) Gil-Alana, L. A.; Yaya, O.S.; Adepoju, A. A.The paper employs both fractional integration and structural break techniques in studying the daily share prices structure of the banking sector in Nigeria. Our data span between 2001 and 2012, covers periods before and after the global financial crisis. The results obtained using both parametric and semi parametric methods indicate little evidence of mean reversion since most of the orders of integration are equal to or higher than1. Long memory is found in the absolute and squared return series. The possibility of structural breaks is also taken into account and the results show a different number of breaks depending on the bank examined. In general, an increase in the degree of dependence across time is noticed, and the most common break took place in December 2008, probably being related with the world financial crisis affecting also the banking system in NigeriaItem Comparative analysis of rainfall prediction using statistical neural network and classical linear regression model(Medwell Journals, 2011) Udomboso, C. G.; Amahia., G. N.Different types of models have been used in modeling rainfall. Since 1990s however, interest has shifted from traditional models to ANN in rainfall modeling. Many researchers found out that the ANN performed better than such traditional models. In this study, we compared a traditional linear model and ANN in the modeling of rainfall in Ibadan, Nigeria. Ibadan is a city in West Africa, located in the tropical rainforest zone, using the data obtained from the Nigeria Meteorological (NIMET) station. Three variables were considered in this study rainfall, temperature and humidity. In selecting between the two models, we concentrated on the choice of adjusted R2 (R-2 ), Akaike Information Criterion (AIC) and Schwarz Information Criterion (SIC). Though, the MSE and R2 were also used, it was concluded from results that MSE is not a good choice for model selection. This is due to the nature of the rainfall data (which has wide variations). It was found that the Statistical Neural Network (SNN), generally performed better than the traditional (OLS).Item Alternative goodness-of-fit test in logistic regression models(Medwell Journals, 2011) Nja, M. E.; Enang, E. I.; Chukwu, A. U.; Udomboso, C. G.The Deviance and the Pearson chi-square are two traditional goodness-of-fit tests in generalized linear models for which the logistic model is a special case. The effort involved in the computation of either the Deviance or Pearson chi-square statistic is enormous and this provides a reason for prospecting an alternative goodness-of-fit test in logistic regression models with discrete predictor variables. The Deviance is based on the log likelihood function while the Pearson chi-square derives from the discrepancies between observed and predicted counts. Replacing observed and predicted counts with observed proportions and predicted probabilities, respectively in a cross-classification data arrangement, the standard error of estimate is proposed as an alternative goodness-of-fit test in logistic regression models. The illustrative example returns favourable comparisons with Deviance and the Pearson chi-square statistics.