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1.
To explain higher-level heritability, we propose a dynamical systems approach, based on simulations of the high-dimensional replicator equation with mutation dynamics. We assume that all variants are generated from within the groups of variants through mutations. Simulating the equation with a random interaction matrix and possible variants, we report that this system tends to have many attractors, of fixed point, chaotic and quasiperiodic type. In a chaotic attractor, special gene-like variants appear to control the heritability ofthe system, in the sense that removal of the variants would easily enable the system to depart from the attractor. Those variants do not predominate in thepopulation size, but have the lowest net reproduction and mutation rates on average. Because their rate of growth is small, they are named neutral phenotypes. Additionally, combinatorial effects of these neutral variants to the entire system are reported. 相似文献
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B. Gasser M. Toussaint R. Luthringer J. P. Macher R. Cerf 《Journal of biological physics》1996,22(4):209-225
Attempts to demonstrate low-dimensional attractor behaviour in the analysis of electroencephalographic (EEG) signals meet with difficulties that in part stem from a departure from single-system dynamics. In order to address this problem, the -waves can be extracted by digital filtering or by wave separation; these two techniques are compared in order to specify the conditions in which finite impulse response (FIR) bandpass filters can be used. The comparison was made using 18 EEG records of 3 min duration under resting conditions (6 subjects, 3 records per subject: prior to apomorphine administration, then 90 min and 150 min post-treatment). No presence of low-dimensional dynamic episodes in -signals was observed without digital processing. Sixty 5 s sections showing attractor behaviour were found after filtering and twenty five 5 s sections after wave separation. The mean correlation dimension was calculated for each experimental condition and for 4 subjects, in order to observe the temporal profile of the drug. When attractors were found after wave separation, bandpass filtering then also showed attractor behaviour, with the same temporal profile. However, the reverse is not true: attractors were found after bandpass filtering that were not present after wave separation; in this case the results deserve confirmation, although the temporal profiles for all cases in which attractors were found after filtering remained comparable. 相似文献
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R. Cerf M. Ould Hénoune M. L. Ben Matti E. H. El Ousdad A. Daoudi 《Journal of biological physics》1993,19(3):223-233
A departure from single-system dynamics, that may arise in characterizing self-organized dynamics of complex systems, is dealt with by using the Karhunen-Loève expansion of the trajectory matrix to decompose an experimental signal in a sum of spectral features. For an electroencephalographic -signal, a separation of waves and extraction of additive sub-signals are achieved, each sub-signal covering a well-bounded and physiologically meaningful frequency range. From the subsignals, an attractor that vanishes on phase-randomizing the data is characterized, under conditions where none was found for the recorded signal. 相似文献
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The effects of periodic pulsatile stimulation on a simple mathematical model of biological oscillations, called the radial isochron clock (RIC), are investigated as a function of stimulus frequency and amplitude. This system can be reduced to a two parameter, one-dimensional circle map. Numerical and topological methods are used to give a very detailed picture of the observed bifurcations over the complete range of parameters. The bifurcations are generic for a class of models which generalize the RIC. 相似文献
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文[1]提出了单种生长的连续性文广义Logistic dx/dt=γx({K-x}/(K+px))其中γ>ο为种群的内禀生长率,K>0为环境容纳量,ν>-1表示种群对环境(包括营 相似文献
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蛋白质序列特性的研究对于蛋白质的结构及功能具有重要意义。该文为了研究蛋白质序列是否具有混沌行为,先将蛋白质序列通过氨基酸电子离子相互作用势(electron interaction potential,EIIP)转化为时间序列,再根据混沌理论对其进行相空间重构,利用去偏自相关系数,经典G-P算法确定系统的时间延迟t和嵌入维数m,系统的最大Lyapunov指数则用改进的最大Lyapunov指数计算方法计算,其结果绝大多数为正,从而确认了蛋白质时间序列的混沌行为,并对特例进行了说明。 相似文献
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We examined the diel vertical migration (DVM) of zooplankton in three lakes of western New York; Lakes Conesus, Lime, and McCargo. In all three lakes, the dipteran predator Chaoborus was a more dramatic migrator than any of the cladocerans or copepods. In contrast, another invertebrate predator, Leptodora, seemed to have the least vertical dispersal. In Conesus Lake, following the evening ascent and upper-water night-positioning of Chaoborus flavicans, Daphnia pulicaria expanded its own vertical range of dispersal thereby decreasing its degree of overlap with Chaoborus. The vertical distribution of Diaptomus sicilis was mostly below that of Daphnia pulicaria, thus reducing possible competition for food resources. Poor oxygen conditions in the lower waters of Lakes Lime and McCargo restricted all zooplankton (except Chaoborus) to an epilimnetic zone where the regions of niche overlap and predation were narrowed. Such annually-induced restrictions on vertical dispersal are probably common features of numerous stratified lakes with hypolimnetic reducing conditions. No fixed pattern of vertical dispersal or migration is likely in lakes where stratification and non-stratification follow each other seasonally. Vertical migration does provide some flexibility in niche separation, but the potential for chaotic behavior in interacting predators and prey may confound simple explanations of DVM. 相似文献