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There is a close analogy between statistical thermodynamics and the evolution of allele frequencies under mutation, selection and random drift. Wright's formula for the stationary distribution of allele frequencies is analogous to the Boltzmann distribution in statistical physics. Population size, 2N, plays the role of the inverse temperature, 1/kT, and(More)
We present some analytic results for the steady states of the Penna model of senescence, generalized to allow genetically identical individuals to die at different ages via an arbitrary survival function. Modeling this with a Fermi function (of modest width) we obtain a clear mortality plateau late in life: something that has so far eluded explanation(More)
  • J B Coe, Y Mao
  • 2005
The Penna model is a model of evolutionary ageing through mutation accumulation where traditionally time and the age of an organism are treated as discrete variables and an organism's genome is represented by a binary bit string. We reformulate the asexual Penna model and show that a universal scale invariance emerges as we increase the number of discrete(More)
The Gaia hypothesis [Lovelock, J., Margulis, L., 1974. Atmospheric homeostasis: the Gaia hypothesis. Tellus 26, 1], that the earth functions as a self-regulating system, has never sat particularly comfortably with ideas in mainstream biology [Anon, 2002. In pursuit of arrogant simplicities. Nature 416, 247]. A lack of any clear role for evolution in the(More)
We build upon our previous analytical results for the Penna model of senescence to include positive mutations. We investigate whether a small but nonzero positive mutation rate gives qualitatively different results to the traditional Penna model in which no positive mutations are considered. We find that the high-lifespan tail of the distribution is(More)
  • J B Coe, Y Mao
  • 2003
In 1995 Penna introduced a simple model of biological aging. A modified Penna model has been demonstrated to exhibit behavior of real-life systems including catastrophic senescence in salmon and a mortality plateau at advanced ages. We present a general steady-state, analytic solution to the Penna model which is able to deal with arbitrary birth and(More)
  • J B Coe, Y Mao
  • 2004
We build upon the recent steady-state Penna model solution [J. B. Coe, Y. Mao, and M. E. Cates, Phys. Rev. Lett. 89, 288103 (2002)] to study the population dynamics within the Penna model. We show that any perturbation to the population can be broken into a collection of modes each of which decay exponentially with its respective time constant. The long(More)
STUDY DESIGN Descriptive, cross-sectional observational study. BACKGROUND In the physical therapist profession, the outcomes of specialty practice analyses are used to determine content areas for specialty board examinations and for American Physical Therapy Association (APTA)-accredited residency curricula. To maintain currency for specialty practices,(More)