The current invention relates to a perylene-3,4-dicarboxylic anhydride, substituted in the 9-position, of the general formula IIIwherein Z is bromine or cyano, and processes for preparing 9-bromoperylene-3,4-dicarboxylic anhydride and 9-cyanoperylene-3,4-dicarboxylic anhydride. Using the disclosed methods, cell populations containing a high proportion of cells positive for tyrosine hydroxylase, a specific marker for dopaminergic neurons, have been isolated. A secure connection is established from an external source with a secure key repository securely maintaining the crypto key. A predetermined value will be transferred to and held at an output Q of a second circuit element triggered by the output Q of the first circuit element, and the predetermined value will be cleared from the output Q of the second circuit element a predetermined time period after being triggered.