A generalised life-expectancy model for a population

In a recent paper, it was shown that the life-expectancy behaviour for homogeneous and non-homogeneous population differs markedly for moderately high and low ages. One therefore has two curves for each of these regions and the problem is how to construct a single life-expectancy curve which blends these two curves together in a satisfactory way. This note offers a simple mathematical and analytical model which is useful in estimating an acceptable life expectancy under all severities of life situation. A simple numerical example is given to illustrate the application of the method.     

An Improvement to Kamerud's Mortality-risk and Life-expectancy Model

Every life faces a certain age-specific mortality risk. Changing this mortality risk for a life aged A by a small quantity R, say, would change the life expectancy by R x K, where K is some constant. Kamerud has proposed a model for K which is independent of R. This note offers an improvement to Kamerud's model which depends on both A and R.     

Kinetics and Equilibrium Models for Sorption of Cu(II) onto a Novel Manganese Nano-adsorbent

The studies of kinetics and equilibrium sorption of Cu(II) were undertaken using nanoscale zerovalent manganese (nZVMn) synthesized by chemical reduction in a single pot system. nZVMn was characterized using scanning electron microscopy, energy dispersive x-ray, and surface area determined by Brunauer–Emmett–Teller. The effect of pH, contact time, adsorbent dose, agitation speed, initial Cu(II) concentrations, temperature, and ionic strength on the sorption of Cu(II) onto nZVMn were investigated in a batch system. The kinetic data followed pseudo-second-order. The mechanism was governed by pore diffusion. The equilibrium sorption data were tested by Freundlich, Langmuir, Temkin, Dubinin–Kaganer–Raduskevich, and Halsey isotherm models. The Langmuir monolayer adsorption capacity (Q_max = 181.818 mg/g) is much greater compared to other nano-adsorbents used in sorption of Cu(II). The thermodynamic parameters (ΔH⁰, ΔS⁰, ΔG⁰) revealed a feasible, spontaneous, and endothermic adsorption process. nZVMn has a great potential for effective removal of copper (II) in aqueous solution.     

Equilibrium sorption of hexavalent chromium from aqueous solution using synthetic hematite

Hematite sample prepared by transformation of ferrihydrite was used to remove Cr(VI) from aqueous solution. Effects of initial concentration, contact time, pH, ionic strength, and temperature were investigated. The data were fitted to Langmuir, Freundlich, Dubinin-Kaganer-Radushkevich and Temkin models of adsorption. The results showed the best fit to the Langmuir isotherm. The increase of pH as well as that of increasing ionic strength resulted in the decrease of adsoiption of Cr(VI). Two kinetic models namely pseudo-first order and pseudo-second order were used to fit the experimental data. The thermodynamic parameters were found, and the results indicated spontaneous and exothermic nature of the process.