Polymeric compositions are described comprising a biocompatible polymer including a biodegradable linkage to a visualization agent and a non-physiological pH solution; wherein the biocompatible polymer is soluble in the non-physiological pH solution and insoluble at a physiological pH. A list of keys identifying a plurality of locked records is created at a start of the backup operation. In addition, the method includes predistorting the waveform for input to the amplifier, based on the chain model, an ideal waveform, and target output power.