Small Q-D neutrino masses from a generic lepton mass hierarchy
  Exponential lepton mass ratios are studied in a low energy phenomenology. In view of the known data, the mass patterns of the charged leptons and widely discussed quasi-degenerate neutrinos are related to one another by two different traits - opposite mass ratios with large versus small exponents, and probably conformable mass-degeneracy-deviation hierarchies. The solar-atmospheric hierarchy parameter should have a special physical meaning in the Q-D neutrino scenario. A general generic hierarchy equation with two opposite solutions respectively for the charged lepton and neutrino mass ratios is considered. It determines a small upper bound on the Q-D neutrino mass scale, with estimations: m = 0.30 eV at 90% C.L., and m = 0.18 eV at best-fit mass-squared differences. 
E. M. Lipmanov