Search

HIV infection is one of the most serious causes of death throughout the world. CD4+ T cells which play an important role in immune protection, are the primary targets for HIV infection. The hallmark of HIV infection is the progressive loss in population of CD4+ T cells. However, the pathway causing this slow T cell decline is poorly understood [16]. This paper studies a discontinuous mathematical model for HIV-1 infection, to investigate the effect of pyroptosis on the disease. For this purpose, we use the theory of discontinuous dynamical systems. In this way, we can better analyze the dynamical behavior of the HIV-1 system. Especially, considering the dynamics of the system on its discontinuity boundary enables us to obtain more comprehensive results rather than the previous researches. A stability region for the system, corresponding to its equilibria on the discontinuity boundary, will be determined. In such a parametric region, the trajectories of the system will be trapped on the discontinuity manifold forever. It is also shown that in the obtained stability region, the disease can lead to a steady state in which the population of uninfected T cells and viruses will preserve at a constant level of cytokines. This means that the pyroptosis will be restricted and the disease cannot progress for a long time. Some numerical simulations based on clinical and experimental data are given which are in good agreement with our theoretical results. [ABSTRACT FROM AUTHOR]

This paper is devoted to analyze dynamical behavior of a four-dimensional nonlinear tourism-based social–ecological system by using the Hopf bifurcation theory. Our purpose is using a criterion based on the Routh–Hurwitz criterion for existence of a region for Hopf bifurcation. Because existence of Hopf bifurcation and therefore bifurcated periodic solutions helps us to show an interesting type of coexistence between mass-tourists and eco-tourists through a periodic pattern, although they have different effects on environmental quality. Furthermore, numerical simulations are carried out to support our theoretical results and show sustainability of tourism. In fact by simulation we indicate a coexistence between mass-tourists and eco-tourists, the existence of chaotic behavior and sustainability of tourism industry. Moreover another criterion, Bendixson's negative criterion, which is based on the connection between compound matrices and ordinary differential equations is applied to prove the nonexistence of periodic orbits and then nonexistence of Hopf bifurcation. [ABSTRACT FROM AUTHOR]

This work numerically examined effects of nanofluids flow on heat transfer in a C-shaped geometiy with the aim to evaluate potential advantages of using nanofluids in a chaotic flow. Numerical computations revealed that the combination of nanofluids and chaotic advection can be an effective way to improve thermal performance of laminar flows. The results indicated that addition of only 1-3% CuO or Al2O3 nanoparticles (volumetric concentration) to the chaotic flow improved heat transfer by 4-14% and 4-18%, respectively, with a marginal increase in the pressure drop. [ABSTRACT FROM AUTHOR]