Production of the LiBeB isotopes with time-dependent GCR fluxes
  It is well known that no time-independent galactic cosmic ray (GCR) flux model can account for the observed linear relationship of Be and B abundances with metallicity. In this contribution we solve the time-dependent CR propagation equation using simple analytic time dependences for the CR spectrum at the source, the galactic CR escape-length and gas density evolution. The CR fluxes so obtained are used to study the early evolution of the LiBeB abundances in the Galaxy. 
Carlos Abia, Ute Lisenfeld, Jordi Isern