Typically, 4He and 14N are enhanced while `H, `2C, and 160 are depleted. The abundance changes that occur as a result of dredge-up are, for a given mass, greater in models with a lower Z or higher Y. The final size of the hydrogen-exhausted core that results after the dredge-up phase is, for a given initial mass, larger in models with a lower Z or higher Y. The magnitudes of both McRIT and Mup (defined as the minimum mass for nondegenerate carbon ignition) depend on the initial composition in ways that can be approximated analytically. The inward advance of the base of the convective envelope results in a reduction in the size of the hydrogen-exhausted core for stellar masses in a specific range: > MCRIT. A general description of the evolutionary behavior of our models from the start of the asymptotic giant branch to the first major thermal pulse is also presented. The effects produced by varying the overall rate of neutrino emission and by varying the size of the mixing length in convective regions are studied the role played by convective overshoot, semiconvection, and the energy cost of mixing across the hydrogen-helium discontinuity are discussed. Models investigated have masses in the range 3-11 M0. The asymptotic giant branch evolution of stars prior to the onset of thermal pulses is found to be highly sensitive to both initial composition and total stellar mass.

Stellar evolution dredge up