Kippenhahn-like diagram of the diffusion coefficient for AM transport given by Eq. (29) for models AM100 (left) and MTS100 (right). The y axis is the Lagrangian mass coordinate. The x4 axis is the decimal logarithm of the time before the last computed model. We plot roughly from the end of the MS. As the two models are not computed up to exactly the same time, this axis is not directly comparable. The vertical dashed black line shows the time when oxygen burning ends, which is the same time as in the plots of Fig. 7. The blue lines correspond to the inner and outer limits of the oxygen shell, defined as X_O16 > 0.5, and the dot-dash black line corresponds to the evolution of M₄ Eq. (36).