Interpretation of some morphological aspects of survival curves

Proof of necessary relationships between some morphological aspects of survival curves and some characteristics of theoretical models offers obvious interest for the elaboration of these models, regarding their empirical value. The search for such relationships is all the more useful that specialized literature provides with numerous ambiguous or contradictory interpretations regarding such or such aspect of survival curves (shoulders, slope at the origin, asymptotic region, restoration curves, etc...). This is not a surprising situation as, in final outcome, all interpretation results from some theoretical presuppositions. To the extent that such presuppositions are note clearly explicited, there is no reason to presume that all investigators should have exactly the same ones. If this difficult situation is to be remedied, it is therefore indispensable to clearly explicit the underlying theoretical context corresponding to the various types of experiments that are fulfilled. This, of course, has to be done at a relatively general level so that a priori non-justified restrictive hypotheses are not introduced. If such hypotheses sometimes find their place in the elaboration of particular models, they must nevertheless be excluded at the level of a general theory whose essential purpose is to provide a framework for description and thought that is acceptable to all. Specific examples are given regarding the signification of shoulders, slopes at the origin, asymptotes, (either in continuous or fractionated irradiations), signs of concavities, shapes of restoration curves