Damped-oscillator model of adaptive response and its consequences

Many experimental, ecological, and epidemiological studies have shown that low doses of ionising radiation may be beneficial to human health by causing an adaptive response, a process called 'hormesis'. The dual effect of radiation has been summarised by the qualitative dual-probability model, which estimates the resulting biological effect of the radiation by taking into account both (a) dose- and time-dependent damage and (b) dose- and timedependent beneficial health effects (adaptive protection). We report here further development of the dual-probability model into a quantitative phenomenological model. Our main objective is to model the time-evolution response to radiation as a time-evolution of a damped oscillator in the critical damping regime. The model predicts that an organism's resistance to radiation stress can be considerably improved by 'radiation training'. If the model is verified by future experiments, it may prove valuable; for example, it could considerably improve the efficacy of radiation therapy by increasing therapeutic doses.