A stable topical alcohol-free aerosol foam containing one or more keratolytic agents is provided. The retaining device is adapted for holding a container or other items; the retaining device being adapted to affix the container by way of the retaining device to a person or a personal item so ready access is provided for the held containeritem. Preferably, the salt is an iron salt of a carboxylic acid having the general formula CnH2nO2 in which n is from 2 to 5. The method provides for ablating cardiac tissue of a patient utilizing a sub-xyphoid approach and identifying cardiac tissue prior to ablation. The second processing chamber may include one or a combination of a first electrode and a second electrode comprising a plasma cavity formed therein. The computing device creates a new cluster center for the first image.