The solar system characteristic Lyapunov time is evaluated to be in the order of 10 000 000 years. The terms of negative and positive feedback (Table I) concern interactions that are respectively regulations and amplifications. An example of negative feedback is the regulation of heat in houses, through

interactions of heating apparatus and a thermostat. Biology created negative feedback long ago, and the domain of endocrinology is replete with such interactions. An example of positive feedback would be the Larsen effect, when a microphone is placed to close to a loud-speaker. Inhibitors,research,lifescience,medical In biology, positive feedbacks are operative, although seemingly less frequent, and they can convey a risk of amplification. Negative and positive feedback mechanisms are ubiquitous Inhibitors,research,lifescience,medical in living systems, in ecology, in daily life psychology, as well as in mathematics. A feedback does not greatly

influence a linear system, while it can induce major changes in a nonlinear system. Thus, feedback participates in the frontiers between order and chaos. The golden age of chaos theory Felgenbaum and the logistic map Mitchell Jay Feigenbaum proposed the scenario called period doubling to Quizartinib order describe the transition between a regular dynamics and chaos. His proposal was based on the Inhibitors,research,lifescience,medical logistic map introduced by the biologist Robert M. May in 1976.24,25 While so Inhibitors,research,lifescience,medical far there have been no equations this text, I will make an exception to the rule

of explaining physics without writing equations, and give here a rather simple example. The logistic map is a function of the segment [0,1] within itself defined by: xn+1=rxn(1-xn) where n = 0, 1, … describes the discrete time, the single dynamical variable, and 0≤r≤4 is a parameter. The dynamic Inhibitors,research,lifescience,medical of this function presents very different behaviors depending on the value of the parameter r: For 0≤r≤3, the system has a fixed point attractor that becomes unstable when r=3. Pour 3Mephenoxalone attractor. When over the value of r=4, the function goes out of the interval [0,1] (Figure 2). Figure 2. The horizontal axis shows the values of the parameter r while the vertical axis shows the possible long-term values of x. This function of a simple beauty, in the eyes of mathematicians I should add, has numerous applications, for example, for the calculation of populations taking into account only the initial number of subjects and their growth parameter r (as birth rate). When food is abundant, the population increases, but then the quantity of food for each individual decreases and the long-term situation cannot easily be predicted.