International Journal of Biomathematics

Asymptotic properties of a malaria model with partial immunity and two discrete time delays are investigated. The time delays represent latent period and partial immunity period in the human population. The results obtained show that the global dynamics are completely determined by the values of the reproductive number. Using a suitable Lyapunov function the endemic equilibrium is shown to be globally asymptotically stable under certain conditions. Moreover, we show that when the partially immune humans are assumed to be noninfectious, the disease is uniformly persistent if the corresponding reproductive number is greater than unity.

This paper deals with the problem of asymptotical stability in mean square for a class of impulsive stochastic high-order bi-directional associative memory (BAM) neural networks with mixed delays and Markovian jumping parameters. Based on Lyapunov stability theory, linear matrix inequality and mathematical induction, some sufficient conditions are derived for the asymptotical stability in mean square of the equilibrium point of the neural networks. The results obtained in this paper are new and complement previously known results.

The present communication considers Havrda and Charvat entropy measure to propose a generalized dynamic information measure. It is shown that the proposed measure determines the survival function uniquely. The residual lifetime distributions have been characterized. A bound for the dynamic entropy measure in terms of mean residual life function has been derived, and its monotonicity property is studied.

In this paper, we present a competition model of malignant tumor growth that includes the immune system response. The model considers two populations: immune system (effector cells) and population of tumor (tumor cells). Ordinary differential equations are used to model the system to take into account the delay of the immune response. The existence of positive solutions of the model (with/without delay) is showed. We analyze the stability of the possible steady states with respect to time delay and the existence of positive solutions of the model (with and without delay). We show theoretically and through numerical simulations that periodic oscillations may arise through Hopf bifurcation. An algorithm for determining the stability of bifurcating periodic solutions is proved.

In this paper, a mathematical model has been developed for studying blood flow through a porous vessel with a pair of stenoses under the action of an externally applied magnetic field. Blood flowing through the artery is considered to be Newtonian. This model is consistent with the principles of ferro-hydrodynamics and magnetohydrodynamics. Expressions for the velocity profile, volumetric flow rate, wall shear stress and pressure gradient have been derived analytically under the purview of the model. The above said quantities are computed for a specific set of values of the different parameters involved in the model analysis. This serves as an illustration of the validity of the mathematical model developed here. The results estimated on the basis of the computation are presented graphically. The obtained results for different values of the parameters involved in the problem under consideration, show that the flow is appreciably influenced by the presence of magnetic field and the rise in the hematocrit level.

In this paper, we study the global dynamics of an epidemic model with nonlinear incidence rate of saturated mass action which depends on the ratio of the number of infectives to that of the susceptibles. The model has set up a challenging issue regarding its dynamics at the R-axis since it is not well defined on it. By carrying out a global qualitative analysis of the model and studying the stabilities of the disease-free equilibrium and the endemic equilibrium, it is shown that either the number of infective individuals tends to zero as time evolves or the disease persists. Computer simulations are presented to illustrate the results.

In this paper, a two-dimensional finite element model has been developed to study thermal disturbances in elliptical shaped human limbs involving uniformly perfused tumor. The model incorporates the effect of important physiological parameters like blood mass flow rate, self-controlled metabolic activity and thermal conductivity in dermal regions. For tumor regions the uncontrolled rate of metabolic activity and abnormal rate of blood flow have been incorporated. The outer surface of the limb is exposed to the environment where heat loss takes place via the conduction, convection, radiation and evaporation. Appropriate boundary conditions have been framed. The model has been simulated using MATLAB 7.5 to obtain numerical results.