A comparative study of Zinc (II) ions removal by a locally produced Granular activated carbon

Physiochemical properties of wastewater effluent from the plants of a brewery in Lagos, Nigeria were analyzed. The adsorption capacity of Granular activated carbon from animal horns when compared with the available commercial Granulated Activated Carbon (GAC) has been presented. Kinetics of adsorption was also investigated. The adsorption isotherms could be well defined with Freundlich model instead of Langmuir model for both GAC studied. The experimental data, when applied to the first and second-order kinetic models, followed the first-order with r² = 0.931 for GAC from animal horns while commercial GAC followed the second-order with r² = 0.936. The results illustrated how animal horns, a solid waste disposal menace from the abattoir at the Oshodi market in Lagos metropolis, was used as an effective biosorbent for the removal of Zn 2+ ions; offering a cheap option for primary treatment of the wastewater effluent

Stability of dynamic coherent states in intrinsic Josephson-junction stacks near internal cavity resonance

Stacks of intrinsic Josephson junctions in the resistive state can by efficiently synchronized by the internal cavity mode resonantly excited by the Josephson oscillations. We study the stability of dynamic coherent states near the resonance with respect to small perturbations. Three states are considered: the homogeneous and alternating-kink states in zero magnetic field and the homogeneous state in the magnetic field near the value corresponding to half flux quantum per junction. We found two possible instabilities related to the short-scale and long-scale perturbations. The homogeneous state in modulated junction is typically unstable with respect to the short-scale alternating phase deformations unless the Josephson current is completely suppressed in one half of the stack. The kink state is stable with respect to such deformations and homogeneous state in the magnetic field is only stable within a certain range of frequencies and fields. Stability with respect to the long-range deformations is controlled by resonance excitations of fast modes at finite wave vectors and typically leads to unstable range of the wave-vectors. This range shrinks with approaching the resonance and increasing the in-plane dissipation. As a consequence, in finite-height stacks the stability frequency range near the resonance increases with decreasing the height.Comment: 15 pages, 8 figures, to appear in Phys. Rev.

Role of the Relaxation of the Iron(ll1) Ion Spin States Equilibrium in the Kinetics of Ligand Binding to Methaemoglobin

Temperature-jump experiments of the reaction of the thiocyanate ion with human aquomethaemoglobin have been performed in the presence of a 10-fold excess of inositol hexakisphosphate (inositolP,). Two kinetic phases corresponding to the a and /3 subunits were observed. Kinetic parameters of the reaction were evaluated from the reciprocal relaxation times on the basis of a fast relaxation of the iron(iii) ion spin states equilibrium before binding of the ligand. The association, ki,, and dissociation, k-i,, rate constants determined were: k,, = 225 dm3 mol-' s-', k-aL = 1.52 s-', k,, = 2430 dm3 mol-' s-', k-pL = 6.51 s-' at 27"C, pH 6.44. There was good agreement between the equilibrium constant of the ligand binding step determined by static methods (Kequ = 204 & 11 dm3 mol-') and that evaluated from kinetic data [(KaLKpL)1'2 = 235 & 12 dm3 mol-'1. The value ksJkaL = 11 obtained ensured proper separation of the two kinetic phases. Analyses of the subunit relaxation amplitudes, a€,, , showed that inositolP, perturbed the absorption spectrum of the /3 subunits. This suggests that in the presence of the organic phosphate, methaemoglobin behaves as a protein with independent binding sites rather than as an allosteric molecule. The kinetic and relaxation amplitude spectral characteristics of the subunits, in the presence of inositolP, have demonstrated that the kinetic dynamics are effectively decoupled in a stable tetramer

Response of Lowland Rice Plants to Simulated Insect Defoliation in West Africa

Field experiments were conducted to investigate the impact of simulated insect-caused defoliation on irrigated rice. Defoliation levels tested were 0% (control), 25% defoliation at 21 days after transplanting (dat), 25% defoliation at 41 dat, 25% defoliation at 21 and 42 dat, 50% defoliation at 21 dat, 50% defoliation at 42 dat, 75% defoliation at 21 dat, 75% defoliation at 42 dat, 75% defoliation at 21 and 42 dat, 100% defoliation at 21 dat, and 100% defoliation at 21 and 42 dat. Tiller height, total number of tillers, percent panicle-bearing tillers, weight of 100 grains, and grain yields were recorded. The rice plant when defoliated just before tillering or in the tillering stage has the ability to compensate for defoliation damage. No yield losses occurred at 25% defoliation. Defoliation of 100% had a significant effect on the total number of tillers and on grain yield. Yield losses at 100% defoliation over the 3 years of the study averaged 40% in the 21 dat treatment and 55% in the 21 and 42 dat treatment. The implications of the development of cultural practices to manage lowland rice defoliating insects are discussed