While a memory section is in standby mode, a power supplyinterruption circuit supplies electric power to a memory section only during periods in which a refresh operation is performed in synchronization with a timing of the refresh operation generated by the clock circuit, and interrupts power supply to the memory section during periods in which the refresh operation is not performed. The invention also provides methods for polymerizing olefins, as well as copolymers having polar monomers incorporated therein. The first cover forms two first locking members and the second cover forms two restriction members.