Before revision: The identifcation and separation of intrinsic variability from age-related phenomena has been the subject of a growing body of literature, supporting renewed interest in traditional analytic methodologies including use of the  von Foerster equation  for predicting population growth and cell age distributions.
After revision: The identifcation and separation of intrinsic variability from age-related phenomena : the fact that there is a nonuniform distribution of cells with different ages. This has led to a renewed interest in traditional analytic methodologies including use of the von Foerster equation for predicting population growth and cell age distributions.