In a resonance converter for driving variable loads at first an input signal provided by a switch controlled by control means is converted to an output signal by a transformer. Further disclosed are methods of synthesis of the isatin analogues, and uses of the analogues, including inhibition of caspase-3 and caspase-7, and in vivo imaging of apoptosis by Positron emission tomography or Single Photon Emission Computed Tomography. Also disclosed is a method of filtering particles from a particle laden fluid. The corrective action includes refining the incremental calculations to obtain additional precision andor aborting the incremental calculations when the resulting numbers are sufficient. During the discharging period the transformer discharges to power the load and a current flowing through the secondary winding decreases. In one embodiment of the invention, first and second inflators are employed.