SURVIVAL CURVES SUBJECTED TO OCCASIONAL INSULTS

We describe a parametric family of survival curves which can be used t o model time to event data in systems subjected to occasional insults or shocks. Parameters control the location, magnitude, and duration of the effect for each insult. We use these models to describe the survi val history of a large cohort of Drosophila that were transferred to n ew vials on a weekly basis as their nutrient medium deteriorated. A pe riodic model with fewer parameters exhibits a good fit to the data.