Provided are compounds and pharmaceutically acceptable salts thereof, their pharmaceutical compositions, their methods of preparation, and their use for treating viral infections mediated by a member of the retrovirus family of viruses such as the Human Immunodeficiency Virus. A light emitting element outputs a light beam of a predetermined emission spectrum to the liquid fuel of the fuel tank. In another aspect, the milldrill is rotated with a rotary steerable system and in another aspect, the milldrill is rotated with a downhole motor or a drill stem. More specifically, the body-bias generator sets the body bias of the transistor so as to trade off performance and power consumption of the transistor.