The present invention provides a high frequency power amplifier of a multi-stage configuration in which a plurality of transistors for power amplification are cascaded, with reduced distortion of a signal in a region where an output power level is low and improved power efficiency. The plug retention apparatus is affixed to a first plug member using a retention ring which provides a means for adjustable positioning via a threaded coupling to facilitate securing a second plug member to the first plug member. The barcode reader can comprise a camera. A page of the electronic book reading device is displayed on the touch screen in one of a full-screen mode and a non-full-screen mode. A clutch pack contacts the differential gear set and the differential carrier. In addition, isoxazoles and sulfonyl hydrazones are identified as general classes of compounds that can induce differentiation of stem cells into cells of neuronal and cardiac fate, respectively.