The interaction of a jet-like pulse with a wind from a stellar companion
  We present numerical simulations of the interaction between a collimated, bipolar ``pulse'' ejected from a star and a continuous wind ejected from a stellar companion. We explore the characteristics of the predicted H$\alpha$ intensity maps by varying selected input parameters. We find that the asymmetry (in size and strength) between the two lobes of the proto-planetary nebula OH 231.8+4.2 is reproduced in this scenario if the wind ejected by the companion star has a strong latitude dependence. 
A. Riera, A.C. Raga and J. Alcolea