In 1D, a self-consistent treatment of core collapse supernovae with presently known input physics and computer simulations does not yet lead to successful explosions, while 2D models show promise. On the other hand there is a need to provide correct nucleosynthesis abundances for the quickly evolving field of galactic evolution and observations of low metallicity stars. The innermost ejecta are directly affected by the explosion mechanism, most strongly the yields of Fe-group nuclei for which an induced piston or thermal bomb treatment will not provide the correct yields because the neutrino interactions are not included. I will show how parametrized variations in the neutrino reaction cross sections can mimic effects of a multi-D convection treatment and cause explosions with an electron fraction Y_e>0.5 in the innermost zones. Nucleosynthesis predictions from these models show improved Fe group abundances and enhanced abundances of 45Sc, 49Ti, and 64Zn. In addition, I will present a new nucleosynthesis process, the $\nu p$-process. This process occurs in proton-rich ejecta which are subject to large neutrino fluxes (e.g. in core collapse supernovae and possibly in gamma-ray bursts). This process allows for the nucleosynthesis of nuclei with mass number $A>64$, making it a possible candidate for the origin of light p-nuclei abundances and to explain the large Sr abundance observed in hyper-metal-poor stars. Finally, I will focus on the metallicity dependence of the ejected element abundances of core collapse supernovae. The observational features in low metallicity stars will be summarized, the complementarity of type Ia and type II supernovae addressed, and a special emphasis will be put on the explanation of specific abundance features at very low metallicities.
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