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abstract
New grids of models of thermally pulsing asymptotic giant branch (AGB) stars are calculated using the method of Renzini and Voli (1981) to follow the surface abundances of $^{1}$H, $^{4}$He, $^{12}$C, $^{13}$C, $^{14}$N, and $^{16}$O over time. We use a new relation for the luminosity, based on the recent AGB models (Blocker and Schonberner (1991); Boothroyd and Sackmann (1988, 1992); Boothroyd, Sackmann and Ahern (1993); Lattanzio (1992); and Vassilidias and Wood (1993)). The mass loss from the AGB is parameterized using the relations given by Vassiliadis and Wood (1993). The predicted abundance ratios of He/H are compared to those observed in planetary nebulae. The yield of $^{4}$He from 1-8$M_{\odot}$ stars is discussed.
