Investigation of important odorants of palm wine (Elaeis guineensis)

Palm wine (Elaeis guineensis) was sensorially evaluated and the key odorants were investigated by means of high resolution gas chromatography–olfactometry and mass spectrometry of solvent extracts as well as headspace samples. A total of 41 compounds were identified, 32 of them previously unknown in palm wine. From these, a total of 13 compounds were quantified by means of stable isotope dilution assays. Quantitation and calculation of the odour-activity values (OAVs) of the 13 key odorants revealed that the earthy-smelling 3-isobutyl-2-methoxypyrazine, the buttery-smelling acetoin, the fruity compounds ethyl hexanoate, 3-methylbutyl acetate and the popcorn-like-smelling 2-acetyl-1-pyrroline are likely to be important odorants of palm wine, with 3-isobutyl-2-methoxypyrazine, acetoin, and 2-acetyl-1-pyrroline being reported here for the first time as aroma constituents of palm wine.     

The relative utility of regression and artificial neural networks models for rapidly predicting the capacity of water supply reservoirs

Rapid prediction tools for reservoir over-year and within-year capacities that dispense with the sequential analysis of time-series runoff data are developed using multiple linear regression and multi-layer perceptron, artificial neural networks (MLP-ANNs). Linear regression was used to model the total (i.e. within-year + over-year) capacity using the over-year capacity as one of the inputs, while the ANNs were used to simultaneously model directly the over-year and total capacities. The inputs used for the ANNs were basic runoff and systems variables such as the coefficient of variation (Cv) of annual and monthly runoff, minimum monthly runoff, the demand ratio and reservoir reliability. The results showed that all the models performed well during their development and when they were tested with independent data sets. Both models offer faster prediction tools for reservoir capacity at gauged sites when compared with behaviour simulation. Additionally, when the predictor variables can be evaluated at un-gauged sites using e.g. catchment characteristics, they make capacity estimation at such un-gauged sites a feasible proposition.     

Effect of common water contaminants on the corrosion of aluminium alloys in ethylene glycol-water solution

The effects of common water contaminants of chloride (Cl⁻), cupric (Cu²⁺) and ferric (Fe³⁺) ions, in four different mixture combination of Fe³⁺ + Cu²⁺, Cl⁻ + Fe³⁺, Cl⁻ + Cu²⁺ and Cl⁻ + Fe³⁺ + Cu²⁺, were examined on the corrosion behaviour of aluminium alloys in ethylene glycol-water solution, using mass loss technique. The highest material losses were recorded for the two alloys in ethylene glycol solution containing the combination of the chloride and the two heavy metal ions. The corrosivity of the solution in the presence of the combination of ions was in the order of Cl⁻ + Fe³⁺ + Cu²⁺ > Cl⁻ + Cu²⁺ > Cl⁻ + Fe³⁺ > Fe³⁺ + Cu²⁺. The results gave first-order kinetics with respect to aluminium in ethylene glycol solution-ion systems. Alloy 3SR exhibits maximum corrosion in all the solutions. It is concluded that the two commercial alloys in the solution polluted with all the three ions would not be able to survive for reasonable period of time without corrosion inhibitor.     

Fundamental and Derived Properties of Yam (Dioscorea Spp.) Starch Powders and Implications in Tablet and Capsule Formulation

A comparative investigation of the fundamental and derived properties of starches from some species of yam (Dioscorea spp.) was conducted with a view to establishing their suitability as excipients in tablet and capsule formulations. Variations were observed in the mean granular diameter of the starches obtained from the different Dioscorea species. Granular diameter ranged from 5.4 µm (Chinese yam) to 34.5 µm (Round leaf yellow yam). Chinese yam and Bitter yam had the highest specific surface area (625.91 m²/kg and 258.76 m²/kg, respectively) while Round leaf yellow yam and Negro yam had the lowest (117.4 m²/kg and 154.34 m²/kg, respectively). Chinese yam had the lowest granular volume (6.00 µm³), surface area (5.67 µm²) and granule surface‐mean diameter (6.74 µm), while Round leaf yellow yam had the largest mean granular diameter, highest granular volume (35.2 µm³), surface area (34.8 µm²) and granule surface mean diameter (35.88 µm). Particle size distribution plots of Chinese yam, Round leaf yellow yam and Negro yam displayed a Gaussian size distribution pattern while Bitter yam displayed a negatively skewed distribution. The variations observed in the granular size and shape may influence the observed derived properties of the starches.     

Application of a hybrid model of mushy zone to macrosegregation in alloy solidification

Solidification of an aqueous ammonium chloride (NH₄Cl-H₂O) solution inside a two-dimensional cavity is numerically investigated using a continuum mixture mathematical model. The mushy region where solid and liquid phases co-exist is considered a non-Newtonian fluid below a critical solid fraction, and a porous medium thereafter. This critical solid fraction is chosen as that corresponding to the coherency point, where a solid skeleton begins to form. The numerical results show that the solidification of a hypereutectic NH₄Cl-H₂O solution is mainly characterized by the rejection of solute at the mushy region and double diffusive convection induced by the opposing solutal and thermal buoyancy forces. The mathematical model agrees satisfactorily with the available experimental and numerical data.     

The Kano–Kazaure highway,north central Nigeria: the significance of the engineering geology in construction

Kano–Kazaure highway traverses granitic rock with minor occurrences of metasediments and fine sandy deposits. The soil profiles were studied to determine their suitability in the proposed dualization of the highway route as part of the Trans-Sahara international highway construction project. The soils derived from the granitic rocks are well graded, with a high maximum dry density and low optimum moisture content. The soils derived from the schistose and quartzite zone are also suitable for road base and sub-base but the transported loose silty fine sand/sandy silty soils of the Chad Formation are only limited suitability.     

Modeling mean flow and turbulence characteristics in gas-agitated bath with top layer

A numerical study is presented of the flow characteristics in a gas-agitated water bath in the presence of a top layer of dissimilar fluid. Two systems are considered, comprised separately of silicon and normal pentane as the top layer, to simulate slag cover in a real steelmaking process. The mathematical model involves solution of transport equations for the variables of each phase, with allowance for interphase transfer of momentum. Turbulence is assumed to be a property of the carrier (liquid) phase and represented through solution of additional transport equations for the turbulence kinetic energy, k, and its rate of dissipation, ɛ. The model also accounts for turbulence modulation by the bubbles through enhancement of the source terms in the equations for k and ɛ. The predicted mean and fluctuating velocities, stresses, and turbulence production are generally in the consensus of the experimental data. Both mean flow and turbulence characteristics are found to be suppressed in the water/silicon system of smaller density ratio, indicating enhanced re-entrainment of the top layer, than the water/normal pentane system.     

Chemical vapor generation of arsane in the presence of L-cysteine. Mechanistic studies and their analytical feedback

The complex reactivity of the system As-AH-RSH-THB (As=As(III), As(V); AH=HCl, HClO4, CH3COOH; RSH=L-cysteine (Cys); THB=NaBH4) was investigated using continuous flow (CF) hydride generation (HG) coupled either with atomic absorption (AAS) or atomic fluorescence spectrometry (AFS). AsH3 generation was examined in the presence of Cys by varying acidity and the type of acid, the mixing sequence, and the reaction time of reagents. The strong depression of arsane generation, which is typically observed in the range of acidity of 0.2-2 M HCl, can be addressed to the low reaction rate of thiol-borane, hydroboron complexes, or both toward those As(III) substrates that are formed in the same reaction environment. The simultaneous presence of Cys-borane and As(III)-Cys species is at the origin of the gap of the arsane generation efficiency in the 0.2-2 M HCl acidity range. The selective formation of Cys-borane complexes, which are formed faster than As(III)-thiol complexes, can be achieved by a careful choice of the mixing sequence of the reagents. The simultaneous mixing of sample, Cys, and THB is able to reduce substantially the gap of the arsane generation efficiency in the 0.2-2 M HCl acidity range. These properties were employed to implement a simple method for selective determination of As(III) in samples containing inorganic arsenic: (i) Total inorganic arsenic is determined by sample treatment with 0.2 M Cys for 30 min, acidity 0.1 M HCl, followed by CF-HG-AFS; (ii) As(III) is selectively determined in 0.005 M CH3COOH in the presence of Cys using a chemifold setup allowing the simultaneous mixing of sample, 0.2 M Cys and 0.1 M THB. The selectivity, measured from the ratio between the slopes of calibration graphs As(III)/As(V), is 220. The interference effects of Cu(II), Fe(III), Ni(II), Co(II), Ag(I), Pd(II), and Pt(IV) can be kept under control using the simultaneous mixing of all the reagents. The tolerance toward the interferences was almost the same as that obtained by allowing the formation of As(III)-Cys complexes (offline sample pretreatment with Cys for 30 min). The method was tested with the application to the natural waters and mineral well waters analysis employing CF-HG-AFS.     

Electrochemical Performance of Anthocleista djalonensis on Steel-Reinforcement Corrosion in Concrete Immersed in Saline/Marine Simulating-Environment

In this paper, electrochemical techniques were employed to study performance of different concentrations of Anthocleista djalonensis leaf-extract admixtures on the corrosion of steel-reinforcement in concrete immersed in 3.5 % NaCl, for simulating saline/marine environment. Analysed test-results showed that the corrosion rate correlated directly with admixture concentration and inversely with cube of the ratio of standard deviations of corrosion potential and corrosion current. The 0.4167 % A. djalonensis (per weight of cement) exhibited optimal inhibition efficiency, η = 97.43 ± 1.20 %, from analysed experimental data, or 94.80 ± 3.39 %, from predicted correlation model, on steel-reinforcement corrosion in the medium. The other admixture concentrations also exhibited high efficiencies at inhibiting steel-reinforcement corrosion in the chloride contaminated environment. Isotherm fittings of the experimental and predicted performance suggest that they both obeyed the Langmuir adsorption model. Evaluated parameters from the isotherm model indicated favourable adsorption and predominant chemisorption mechanism by this environmentally-friendly inhibitor of steel-reinforcement corrosion in the saline/marine simulating-environment.