The invention provides a padlock with a quickly changeable shackle, comprising a locking core, a locking member, blocking balls, a lock body on which two limb receiving chambers and a passage are disposed, and a shackle which takes U-shape defined by a longer and a shorter parallel limbs respectively received in the limb receiving chambers to lock the padlock. The SAR is used to iteratively trim the oscillator output clock frequency based on a difference between a reference clock frequency and the oscillator output clock frequency. Thus, the movement of the downhole device is governed by the detent mechanism, rather than by variable factors such as pressure changes. Methods of using such a data structure are also provided. Pharmaceutical compositions comprising the isotopes-enriched compounds, and methods of using such compounds are also provided.