In a recent paper (LAUTERBORN, REFSDAL, WEIGERT, 1971) the central He burning phase of 5 M⊙ stars was investigated. It was shown that the structure of such stars is very sensitive to the chemical profile in and above the hydrogen burning shell. The loops in the H-R diagram which such stars often make were for instance found to be very sensitive to changes in this profile. It was also shown that an assumed mass loss of about 10% in the red giant region will suppress a loop completely.

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