A process for producing cured rubber is disclosed wherein the process comprises:A) mixing rubber, carbon black, and azodicarbonamide without other curative ingredients;B) adding the remaining curative ingredients in one or more subsequent mixing steps; and thenC) curing the rubber;whereby a cured rubber having improved hysteresis is obtained. The present invention also relates to a method for protecting a subject from radiation damage, a method of cancer radiotherapy and use as an antimicrobial or radioprotective agent of the compound of formula defined above. An impedance circuit includes a feedback controller that adjusts an effective impedance associated with the second electrode based on a difference signal, a common mode signal, a phase-shifted signal, and an impedance associated with the first electrode.