In general, this disclosure describes techniques for moving a graphical selector. The present invention provides a method and apparatus for writing servo information on a magnetic disk through a magnetic head by driving an actuator of a hard disk drive directly without employing a servo writer using control of a laser. Methods of releasing additives into coolant compositions are also provided. The invention may be practiced at the microscale. The processor provides the second signal having a first state to reset the trigger circuit and a second state to enable the trigger circuit. Methods for selecting integral gain and reference model are also presented.