An apparatus for recording and reproducing digital information uses a disk recording medium in which data recording area is divided into plural zones in the radial direction, and defect information is managed for each zone. The pump beam is directed at a slight angle through a first end of the medium, reflects off the inner surface of the second, opposite end, and then reflected by an external or integrated mirror back through the first end and off the inner surface of the opposite end again. The cooling jacket includes no portion located radially outward from a bottom of the groove unit between a first end portion of the groove unit located on the axial rear side of the main body and the first end face of the main body. The methods, apparatus, media and signals described herein may provide improvements to DC to AC maximum power point tracking in an energy conversion system such as a photovoltaic power generation system. This invention relates to the maize variety X95A921, the seed, the plant produced from the seed, and variants, mutants, and minor modifications of maize variety X95A921. The slot pair has a first slot and a second slot provided so that a slot length direction is oblique to a line direction of the waveguide line.