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P. Walter, G.J. Mathews (Univ. Notre Dame)
Recently, it has been proposed that low-metallicity stars may experience a different paradigm for s-process nucleosynthesis. In particular, a single-episode of neutron exposure may occur during the initial onset of the thermally pulsing AGB. This seems marginally supported by the enhanced s-process abundances observed in two stars. A crucial ingridient of this hypothesis is that there should be a change in the characteristic s-process abundance curve for [Fe/H] < -2.5. In this talk we survey what evidence exists for such a transition from observed abundances of neutron-capture elements in metal-poor halo stars. We suggest that evidence indeed exists for such a transition at the right metallicity.