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We conduct numerical analysis of the 2-dimensional discrete-time gene expression model originally introduced by Andrecut and Kauffman (Phys. Lett. A 367: 281-287, 2007). In contrast to the previous studies, we analyze the dynamics with different reaction rates $\alpha_1$ and $\alpha_2$ for each of the two genes under consideration. We explore bifurcation diagrams for the system with $\alpha_1$ varying in a wide range and $\alpha_2$ fixed. We detect chaotic dynamics by means of a positive maximum Lyapunov exponent and we scan through selected parameters to detect those combinations for which chaotic dynamics can be found in the system. Moreover, we find bistability in the model, that is, the existence of two disjoint attractors. Both situations are interesting from the point of view of applications, as they imply unpredictability of the system. Finally, we show some specific values of parameters of the model in which the two attractors are of different kind (a periodic orbit and a chaotic attractor) or of the same kind (two periodic orbits or two chaotic attractors)., Comment: 17 pages, 11 figures

The accuracy of description of measured nuclear masses by presently used nuclear-mass models is studied. Twelve models of various kinds are considered, eleven of the global character and one local model specially adapted to description of heavy nuclei. To decrease the number of nuclei over which the accuracy is averaged, the global region (Z,N >= 8) is divided into four subregions, in which the accuracy is studied separately. Still, to reach the best precision, the accuracy is finally investigated without any averaging, for each nucleus separately. The results are presented in a form of colored maps, large enough to be easily and accurately read. Besides the accuracy of the studied models, also their predictive power is considered. It is found that the accuracy of description of mass strongly depends on a nuclear-mass model and on the region of nuclei to which the model is applied. The best accuracy is obtained by the recent two Chinese models WS3+ and WS4+. Generally, no clear, strong correlation between the accuracy of description of already known masses by a given model and its predictive power for new masses is observed. Still, such correlation is found for separate models and in separate regions of nuclei. More often for the macroscopic-microscopic models than for the other approaches., Comment: 70 pages