Is neutrino decay really ruled out as a solution to the atmospheric neutrino problem from Super-Kamiokande data?

We analyse ASCA satellite X-ray data and Whipple Observatory TeV y-ray data from the Blazars Mkn421 and Mkn501 for short limescale variability using the excess pair fraelion method. We discuss the method and the data as well as EPF sensitivity to these data. We find that in these data sets. we can rule out an amplitude of variability greater than 10% on timescales less than l0 min from both sources and at both wavelengths at aconfidence level of >99.7%. We discuss briefly the implications of low amplitudes of variability on short timescales for the beamed jet of relativistic particles probably producing these radiations and, we derive limits from the data on the local percentage change in both the lepton density and the magnetic field strength in these Blazar jets.