The invention describes methods and agents for improving cosmetic appearance, for promoting, improving or restoring health of cells and tissues, preferably skin, and more preferably, for restoring aged or damaged skin to a healthy appearance. The intakeexhaust valve member is axially movable within the combustion chamber, and operatively cooperates with wall structure of the combustion chamber. When the ignition switch is in the on position andor the cap is removed, a solenoid opens a valve and permits a timed or otherwise measured amount of additive to flow into the tank while the cap is off. The memory controller includes demand invalidation circuitry that, responsive to a data request for a requested data granule in the home system memory, reads an associated entry in the memory directory and issues an invalidating command to at least one remote node holding a cache line corresponding to the requested data granule. Chains extend along the side edges of the belt, and are driven by the sprockets.