Faculty of Natural Sciences

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Metamorphosis and Wing Formation in the Brown Plant Hopper, Nkparvafa lugens, After Topical Application of Precocene II
(J. Wiley -Liss Inc., 1996) Ayoade, Femi
In the present paper the effects of precocene on N. lugens strains obtained by successive selection for adults with specific wing form under highly crowded conditions over 70 generations are reported. When precocene II was applied, macropterous adults developed from presumptive brachypters. Our results also demonstrated the disruptive effects of precocene I1 on metamorphosis, and we report here the induction of precocious metamorphosis in N. lugens in details for the first time. The sensitive periods to precocene 11, affccting wing dimorphism and metamorphosis, differed between the two strains.
Induction of Macroptery, Precocious Metamorphosis, and Retarded Ovarian Growth by Topical Application of Precocene II, with Evidence for its Non-svstemic Allaticidal Effects in the Brown lugens
(Elsevier Science Ltd, 1996) Ayoade, Femi
Fermentation of Cashew Juice using the Wine Yeast Strain NCYC 125 and three other Isolated Yeast Strains
(Advance Food Science, 1999) Osho, Adeleke
Enhancement of short wing formation and ovarian growth in the genetically defined macropterous strain of the brown planthopper, Nilaparvata lugens
(Elsevier Science Ltd, 1999) Ayoade, Femi
When JH II, III or methoprene was applied in the nymphal stages to two different strains of the brown planthopper which were selected to produce long (macropterous) or short (brachypterous) wing forms, no effect was observed on the molting profile or metamorphosis. Brachypterization of a majority of the presumptive macropters was, however, observed by application of these chemicals, although there was no effect on wing form in the presumptive brachypters. The results show that the sensitive periods for the brachypterization of the presumptive macropters falls between early antepenultimate instar and within 1 or 2 days of the penultimate instar, and that the chemicals were effective, in the following order of potency: methoprene > JH III > JH II. Ovarian growth was greatly enhanced in the presumptive macropters when JH III or methoprene was applied twice, within 12 h of the 3rd or 4th nymphal instar and 6 h before adult emergence. JH II on the other hand had no effect on ovarian growth when applied to the presumptive macropters at any of the nymphal stages. None of the chemicals had any effect on ovarian growth in the presumptive brachypters.
Bacteriology of some Well Water Samples in Warri: A Comparative Study
(2001) Ogunlaja, Aemere
Seasonal Variations of Radio Refractivity Gradients in Nigeria
(2002) Willoughby, Alexander
Thermal Solid-State Isomerization Reactions in Re and Mo 'Piano Stool' Organometallic Complexes
(2002) Adeyemi, Olalere
The Solid-state Isomerization of cis and trans-(η5 -C5H4Me)Mo(CO)2(P(Oi Pr)3)I
(2002-06-16) Adeyemi, Olalere
The cis- and trans-(η5 -C5H4Me)Mo(CO)2(P(Oi Pr)3)I complexes undergo a bi-directional thermal ligand isomerization reaction to yield an equilibrium mixture of isomers (30/70 cis/trans ratio, 90 °C, < 80 min) in the solid state. The activation energy barrier for the cis-trans isomerization reaction (80–100 °C) was found to be 68 ± 10 kJ mol–1. In benzene (reflux, 2 h) this isomer ratio was found to be 70:30 cis/trans. DSC and powder XRD studies have revealed reactions that occur in the solid state entailing decomposition and isomerization. DSC experiments did not reveal the presence of the cis–trans isomerization reaction.
Solvent-Free Organometallic Migratory Insertion Reactions
(2003-03-10) Adeyemi, Olalere
Migratory insertion reactions of organometallic complexes have been shown to occur in the absence of solvent and, more significantly, between solid reagents. Reaction between (η5-C5H5)M(CO)3Me (M ) Mo, W) or (η5-C5H5)Fe(CO)2Me and PPh3 (no solvent) took place at temperatures between 40 and 90 °C and gave the products (η5-C5H5)M(CO)2(PPh3)COMe and (η5-C5H5)Fe(CO)(PPh3)COMe in moderate to good yield (60-99%). The Mo and W complexes reacted in the solid state when T < 80 °C. The decarbonylation of (η5-C5H5)- Mo(CO)2(PPh3)COMe to yield (η5-C5H5)Mo(CO)2(PPh3)Me also occurred in the solid state (120 °C). Reaction of (η5-C5H5)Mo(CO)3Me with a range of ligands, L (L ) PPh3, P(p MeOC6H4)3, PCy3, PEt3, AsPh3, POPh3, P(OEt)3; 1:1 reagent ratio, 90 °C, 15 min), in the absence of solvent gave (η5-C5H5)Mo(CO)2(L)COMe (7-100% yield) and, on extended reaction, (η5-C5H5)Mo(CO)2(L)Me in varying yields. A kinetic study of the solid-state reaction between (η5-C5H5)Mo(CO)3Me and PPh3 yielded rate constants, e.g. k ) 5.18 × 10-5 s-1 (Mo:P ) 1:10; 50 °C), which compares with the literature solution data in toluene (k ) (0.8-2.5) × 10-5 s-1, 50 °C) using similar metal to ligand ratios. The data are consistent with a pseudo-first order reaction in the presence of PPh3. Diffusional effects on the reaction rate are detected at low temperature and low PPh3 ratios
Adsorption of some heavy metal ions on sulfate- and phosphate-modified Kaolin
(Elsevier, 2004) Unuabonah, Emmanuel
Kaolin (bright white lumps) from Ubulu-Ukwu in Delta State of Nigeria was modified with 200 µg mL-1 of phosphate and sulphate anions to give phosphate- and sulfate-modified adsorbents, respectively. The adsorption of four metal ions (Pb2+, Cd2+, Zn2+, and Cu2+) was studied as a function of metal ions concentration. The metal ions showed stronger affinity for the phosphate-modified adsorbent with Pb2+, Cu2+, Zn2+, and Cd2+ giving an average of 93.28%, 80.94%, 68.99%, and 61.44% uptake capacity. The order of preference for the various adsorbents shown by the metal ions was as follows: Pb2+>Cu2+>Zn2+>Cd2+. Desorption studies showed that the phosphate-modified adsorbent had the highest affinity for the metal ions, followed by the sulfate-modified clay while the unmodified clay had the least affinity. The experimental data were fitted by both the Langmuir and Freundlich models
Solid-state Isomerisation Reactions of (g5 -C5H4R)M(CO)2(PR3 0 )I (M ¼ W, Mo; R ¼ t Bu, Me; R0 ¼ Ph, Oi Pr3
(2004-04-06) Adeyemi, Olalere
The cis and trans monosubstituted cyclopentadienyl tungsten and molybdenum complexes (g5-C5H4R)M(CO)2(L)I (1) (M¼ W, R ¼ Me, t Bu, L ¼ P(Oi Pr)3, PPh3; M ¼ Mo, R ¼ Me, L ¼ PPh3) have been synthesised and fully characterised by elemental analysis and IR and NMR spectroscopy. It was found that 1 underwent a thermal solid-state ligand isomerisation reaction and that the favoured direction of the isomerisation reaction is related to the melting points of the cis and trans isomers, i.e., with intermolecular forces in the solid state. No obvious relationship between the melting point and the metal, the ring-substituent or the ligand was observed. Crystal structure determinations of the cis and trans isomers of (g5-C5H4Me)W(CO)2(PPh3)I reveal that a limited amount of isomer conversion can be accommodated in the unit cell of the trans isomer, prior to crystal fragmentation. The rearrangement of the molecules within the unit cell, during isomerisation, also leads to disorder in the crystal
The solid-state isomerization of cis and trans-(η5 -C5H4Me)Mo(CO)2(P(Oi Pr)3)I
(2004-04-06) Adeyemi, Olalere
The cis and trans monosubstituted cyclopentadienyl tungsten and molybdenum complexes (g5-C5H4R)M(CO)2(L)I (1) (M¼ W, R ¼ Me, t Bu, L ¼ P(Oi Pr)3, PPh3; M ¼ Mo, R ¼ Me, L ¼ PPh3) have been synthesised and fully characterised by elemental analysis and IR and NMR spectroscopy. It was found that 1 underwent a thermal solid-state ligand isomerisation reaction and that the favoured direction of the isomerisation reaction is related to the melting points of the cis and trans isomers, i.e., with intermolecular forces in the solid state. No obvious relationship between the melting point and the metal, the ring-substituent or the ligand was observed. Crystal structure determinations of the cis and trans isomers of (g5-C5H4Me)W(CO)2(PPh3)I reveal that a limited amount of isomer conversion can be accommodated in the unit cell of the trans isomer, prior to crystal fragmentation. The rearrangement of the molecules within the unit cell, during isomerisation, also leads to disorder in the crystal.
Removal of Lead from Aqueous Solution by Palm Kernel Fibre
(SABINET, 2005) Unuabonah, Emmanuel
The sorption of lead on palm kernel fibre, an agricultural waste product, has been studied. The sorption process was studied as a function of initial lead concentration and initial solution pH. The percentage lead removal was found to increase with increasing initial solution pH up to pH 5 and then to decrease as pH was increased to 6. The pseudo-second order kinetic rate model was employed in the analysis of the kinetics of lead uptake onto the palm kernel fibre. The results show that the pseudo-second order model fits the experimental data with high coefficients of determination (r2). The equilibrium sorption capacity was found to be 33.33 mg g–1 when 1.0 g of fibre was contacted with 90 mg dm–3 of lead solution at pH 5. Mathematical expressions were derived to relate the pseudo-second order rate constant, k, and the change in solution pH with initial lead concentration.
Quantification of steric interactions in phosphine ligands from single crystal X-ray diffraction data. Crystal structures of (g5 -C5H4Me)Mo(CO)2(PR3)I (R3 = PhMe2, PhEt2, Et3)
(2005-12-05) Adeyemi, Olalere
Distorted square pyramidal complexes of molybdenum (g5 -C5H4Me)Mo(CO)2(PR3)I (R3 = PhMe2 (2a); PhEt2 (3a) and Et3 (4a)) have been synthesized and the structures of the lateral (cis) isomers have been determined by X-ray diffraction. The cone (H) and solid (X) angles as well as the angular profiles of the phosphine ligands in the complexes have been computed using the program STERIC. Values for the crystallographic cone and solid angles calculated for 2a, 3a and 4a are H (129 , 135 and 139 ) and X (2.73, 2.99 and 2.93 sr), respectively. A search of the Cambridge Structural Database (CSD) was made for piano stool, 5- and 6-coordinate complexes containing the title phosphine ligands. Results from this study show a wide range of sizes for each of the ligands and even the seemingly simple PPhMe2 ligand exhibited a wide range of values for the cone (113–137 ) and solid (2.49–3.07 sr) angles. These observations have been rationalized and related to the possible group conformations from the crystallographic data
The Effect of some Operating Variables in the Adsorption of Lead and Cadmium ions unto Modified Kaolin Clay
(Elsevier: Journal of Hazardous Materials, 2005-12-15) Unuabonah, Emmanuel
Modification of kaolinite clay mineral with orthophosphate (p-modified sample) enhanced adsorption of Pb and Cd ions from aqueous solutions of the metal ions. Increasing pH of solutions of metal ions, increasing adsorbent dose and increasing concentration of metal ion, increased the adsorption of metal ions. Adsorption of both metal ions simultaneously on both unmodified and p-modified samples indicates that adsorption of one metal ion is suppressed to some degree by the other. The presence of electrolyte and their increasing concentration reduced the adsorption capacities of both unmodified and p-modified samples for the metal ions. Ca-electrolytes had more negative effect on the adsorption capacities of the adsorbents than Na-electrolytes. Ca-electrolytes reduced adsorption capacities of the adsorbents for Pb and Cd ions. From Langmuir plots it was observed that these electrolytes increased the binding energy constant of the metal ions unto the adsorbents especially on the p-modified samples. The rate of adsorption of Pb and Cd ions on p-modified adsorbent were increased and equilibrium of metal ion solution were more quickly reached (8 min for Pb ions and 12 min for Cd ions) with p-modified adsorbent as against 20 min for adsorption of both metal ions on unmodified adsorbent when 200 mg/L of metal ion solutions were used during the kinetic studies. When adsorption data were fitted against Langmuir, Freundlich, Toth and Langmuir–Freundlich isotherms, satisfactory fits were found with the Freundlich isotherm. However, at low concentration of metal ions, data also showed satisfactory fits to Langmuir isotherm.
Remote Method Invocation and Mobil Agent: A Comparative Analysis
(Issues in Informing Science and Information Technology, 2006) Oguntunde, Bosede
This paper presents a comparative analysis of Remote Method Invocation (RMI) and Mobile Agent (MA) paradigm used to implement the information storage and retrieval system in a distributed computing environment. Simulation program was developed to measure the performance of MA and RMI using object oriented programming language (the following parameters: search time, fault tolerance and invocation cost. We used search time, fault tolerance and invocation cost as performance parameters in this research work. Experimental results showed that Mobile Agent paradigm offers a superior performance compared to RMI paradigm, offers fast computational speed; procure lower invocation cost by making local invocations instead of remote invocations over the network, thereby reducing network bandwidth. Finally MA has a better fault tolerance than the RMI. With a probability of failure pr = 0.1, mobile agent degrades gracefully.
On the Comparison of Run Orders of Unreplicated 2 k–p Designs in the Presence of a Time-Trend
(2006) Adekeye, Kayode
The response from a factorial experiment carried out in a time sequence may be affected by uncontrollable variables that are highly correlated with the time in which they occur. In such a situation, one possibility is to randomize the run order of the experiment. Another possibility is to use a systematic run order that is robust against time trends. Since randomized run orders make the time trend part of the error, it can be hoped that systematic run orders will be more effective to identify truly active factors. In this paper, a simulation study is used to compare the performances of the randomized and the systematic run orders. The response from an experiment where we have observed a strong time trend is used to demonstrate the influence of a realistic time trend on the run orders under consideration. The performance of the run orders is then measured by taking the probabilities of false rejection and the probabilities of detection of active contrasts. Our results show that the randomized run order managed to keep the nominal level, while the systematic did not. Additionally, when there were active factors, then the systematic run orders did not achieve more power than did the randomized run order.
Building Data-Driven Decision Support System for Pragmatic Leadership.
(EDUCERE - Journal of Educational research, 2006) Oguntunde, Bosede
Decision Support System (DSS) is an interactive software-based system that assists leaders (decision makers) compile, analyze and manipulate information from raw-data documents, knowlede frameworks and/or business models to identify and solve problems and make decisions. In general, DSS's design and implementations are classified as data-driven, model-driven, knowledge-driven, document-driven and communication driven. Taxonomically, DSS could be passive, active, cooperative. A passive DSS is a system that aids the process of decision making, but that cannot bring out decision, suggestion or solutions. an active DSS can bring out such. A cooperative DSS allows the decision maker modify, complete, or refine the decision suggestions provided by the system, before sending them back to the system for validation. This paper focused on cooperative Data Driven DSS. Data-Drive DSS emphasizes access to and manipulation of time-series of internal organizatinal data and at times external data using Database Queries and On-Line Analytical Processing (OLAP0 tools.Thus, help managers (leaders) make prompt decision from the available data and models easily. The methodology forthe research is IDEFIX approach, nomally referred to as BOTTOM_UP approach to project work. The DSS is to speed-up data analysis for prompt decision-making through data model of relational Database Management System (RDBMS). the implementation optimizes the use of Mathematical Relational Algebra model for various report generation. it is implementable at any level, for practical, reality and pragmatic leadership qualities.
Adsorption of Lead and Cadmium Ions from Aqueous Solutions by Tripolyphosphate-Impregnated Kaolinite Clay
(Elsevier, 2006-06) Unuabonah, Emmanuel
The pretreatment of Kaolinite clay with tripolyphosphate (TPP) increased the cation exchange capacity (CEC) of Kaolinite clay from 13.45 meq/100 g to 128.7 meq/100 g. The equilibrium adsorption capacity of TPP–Kaolinite clay for Pb2+ and Cd2+ was 126.58 mg/g and 113.64 mg/g, respectively. The presence of Na- and Ca-electrolytes and with increase in their concentrations reduced the selectivity of TPP–Kaolinite clay for Pb2+ than Cd2+. TPP–Kaolinite clay showed higher selectivity for Pb2+ in the presence of these electrolytes and at all concentrations of these electrolytes used for the study. Binary mixtures of Pb2+ and Cd2+ in various concentrations caused a decrease in the adsorption capacity of TPP–Kaolinite for either metal ion. However, this may have caused the adsorption of Cd2+ onto high energy sites on the surface of the TPP–Kaolinite clay. Non-linear Chi-square model analysis of adsorption data using Langmuir, Langmuir–Freudlich, Freudlich, Toth and Temkin isotherms reveals that the adsorption of Pb2+ and Cd2+ by TPP–Kaolinite clay were best described by the Toth and Freudlich isotherms, respectively. At low concentrations (≤500 mg/L) the adsorption of these metal ions showed better fits to the five models with Langmuir–Freudlich and Freudlich isotherms giving the best fits for Pb2+ and Cd2+, respectively.
Kinetic and Thermodynamic Aspects of the Adsorption of Pb2+ and Cd2+ Ions on Tripolyphosphate-Modified Kaolinite Clay.
(Elsevier: Chemical Engineering Journal, 2007) Unuabonah, Emmanuel
Kaolinite clay obtained from Ubulu-Ukwu, Delta state in Nigeria was modified with tripolyphosphate reagent to obtain TPP-modified Kaolinite clay. The kinetics and thermodynamics of the adsorption of Pb2+ and Cd2+ by TPP-Kaolinite clay were studied. Increasing temperature and initial metal ion concentration increased the sorption capacity of the adsorbent. The rates of adsorption of both Pb2+ and Cd2+ increased with increasing temperature but decreased with increasing initial metal ion concentration and time. The pseudo-second-order initial sorption rates for the sorption of Pb2+ were found to be higher than those of Cd2+. Pseudo-first-order model was found to only describe well, the data obtained in the first 8 min of the adsorption process. The sorption of both metal ions was endothermic and spontaneous with H◦ values of +13.94 kJ mol−1 and +24.93 kJ mol−1 for Pb2+ and Cd2+, respectively. Activation energy values obtained were between +8 kJ mol−1 and +22 kJ mol−1. These values suggest that the rate-controlling step in the adsorption of Pb2+ and Cd2+ by TPP-Kaolinite clay was diffusion-controlled. The sorption of metal ions from binary solutions of both metal ions at different initial metal ion concentrations reduced the initial sorption rates of the adsorption of Pb2+ by TPP-Kaolinite clay and increased that for Cd2+. The adsorption capacity of TPP-Kaolinite clay for both metal ions was also decreased by simultaneous presence of both metal ions.

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