In some embodiments, a string of nonvolatile memory cells may be erased by driving their control gates with erase voltages that may have different levels for different cells. Compositions comprising such compounds; and methods for treating conditions and disorders using such compounds and compositions are also described. In the present invention, a metal-semiconductor alloy layer is formed on an anode material by contacting a portion of the anode material with a displacement solution. A second elastic member 31 is provided to operate in parallel with first elastic member 30 to realize a low rigidity on the negative side of the torsional characteristics.