In this paper, it is studied that two species predator-prey Lotka-Volterra type dispersal system with delay and Holling type II response function, in which the prey species can disperse among n patches, while the density-independent predator species is confined to one of the patches and cannot disperse. Sufficient conditions of integrable form for the boundedness, permanence, extinction and the existence of positive periodic solution are established, respectively. 相似文献
The bifurcation methods of differential equations are employed to investigate traveling waves of the oceanic currents motion equations. The sufficient conditions to guarantee the existence of different kinds of bounded traveling wave solutions are rigorously determined. Further, due to the existence of a singular line in the corresponding traveling wave system, the smooth periodic traveling wave solutions gradually lose their smoothness and evolve to periodic cusp waves. The results of numerical simulation accord with theoretical analysis. 相似文献
In this paper, on the basis of the theories and methods of ecology and ordinary differential equation, a food web system with impulsive perturbations and distributed time delay is established. By using the theories of impulsive equation, small amplitude perturbation skills and comparison technique, we get the condition which guarantees the global asymptotical stability of the prey and intermediate predator eradication periodic solution. On this basis, we get that the food web system is permanent if some parameters are satisfied with certain conditions. In order to show that these conditions are effective, the influences of impulsive perturbations on the inherent oscillation and distributed time delay are studied numerically; these show rich dynamics, such as period-halving bifurcation, chaotic band, narrow or wide periodic window, chaotic crises. Moreover, the computation of the largest Lyapunov exponent shows the chaotic dynamic behavior of the model. Meanwhile, we investigate the qualitative nature of strange attractor by using Fourier spectra. All of these results may be useful in the study of the dynamic complexity of ecosystems. 相似文献
We describe a method for the preparation of water-soluble gold nanoclusters (Au-NCs) from chloroauric acid using denatured-casein as both a reducing and stabilizing agent. The resulting Au-NCs were characterized by photoluminescence, UV–vis absorption, and X-ray photoelectron spectroscopies, and by transmission electron microscopy. The Au-NCs have an average diameter of 1.7 ± 0.2 nm and exhibit orange-red fluorescence emission peaking at 600 nm (with a Stokes’ shift as large as 237 nm), a quantum yield of 4.3 %, and good stability over the physiologically relevant range of pH values and ionic strength. Cytotoxicity studies showed the Au-NCs to display negligible effects in terms of altering cell proliferation or triggering apoptosis. Fluorescence imaging of HeLa cancer cells was accomplished by loading such cells with the Au-NCs. The fluorescence of the Au-NCs is found to be strongly quenched by Hg(II) ions, and thus the Au-NCs can be used for detecting and, possibly, imaging of Hg(II). An assay was worked out for the determination of Hg(II), and its limit of detection is 1.83 nM, which is 5.5 times lower than the maximum allowed concentration of Hg(II) in drinking water as defined by the US EPA.
In this paper, we study the boundary value problem of a fractional q-difference system with nonlocal integral boundary conditions involving the fractional q-derivatives of the Riemann–Liouville type. Using the properties of the Green function, and monotone iterative method, the extremal solutions were obtained. Finally, an example is presented to illustrate our main results. 相似文献