There is adopted a constitution of arranging a spacer 53 at a shaft center portion and arranging a retainer 52 and a roller 51 at two sides thereof in order to prevent the roller from being rolled at the center portion in an axial direction of the shaft maximizing an amount of bending the shaft. In some examples, the methods and systems analyze motion data associated with the sequential frames of a video stream, and reject those frames where the detected camera movement exceeds a predetermined threshold. The piezoelectric transducer is for generating megasonic energy. This ensures that the part of the tag number which specifically identifies the particular product is kept private. The method also includes converting the acoustic energy sensed at the first and second locations into first and second electrical signals and processing the first and second electrical signals to digitally remove interfering acoustic energy present in the second signal to provide an electrical signal representative of the acoustic signal that is being monitored. The compounds synthesized by the processes of the invention are HIV reverse transcriptase inhibitors useful for inhibiting reverse transcriptase, HIV replication and the treatment of human immunodeficiency virus infection in humans.