[en] In this paper, a new stage structured prey–predator model with Monod–Haldane functional response is proposed and the stages for predator have been considered. The proposed mathematical model consists of three nonlinear delay differential equations to describe the interaction among prey, immature predator and mature predator populations. Two time delays viz. feedback delay and gestation delay have been used as the bifurcation parameter. A rigorous mathematical analysis has been carried out by considering all possible cases for both the delays. Conditions for local stability and Hopf bifurcation have been investigated in all cases. Furthermore, by using normal form method, Riesz representing theory and central manifold theorem, formulae are derived for the direction of Hopf bifurcation and stability of bifurcating periodic solutions. Global stability analysis is carried out and the numerical simulation to validate the theory is also executed at the end.

[en] Divalent alkaline earth metal oxalates have been the subject of research for many of the researchers in the past as a result of which many binary oxides of Ca, Ba, Sr with uranium have been discovered. Alkaline earth elements Ca, Ba, Sr and their oxides also have an important role while deciding the reprocessing of irradiated fuels from the reactors. All these alkaline earth elements can be precipitated from the solution of their nitrates along with uranium, as oxalates. Thermal decomposition of these oxalate powders yield oxides of the metal. Thus, thermogravimetry has been used to study the mechanism of the reactions and the kinetics of the solid state reaction between the oxalates of Ca, Ba and Sr with uranyl oxalate at elevated temperatures. Reaction of calcium oxalate, strontium oxalate and barium oxalate with uranyl oxalate were studied by combined TG/DTA. Thermograms were also recorded for pure oxalates of calcium, strontium and barium as well as uranyl oxalate to predict the mechanisms for each step in the reactions