The present invention relates to compounds being esters of 5-aminolevulinic acids or pharmaceutically acceptable salts thereof, including compounds of formula R22N\u2014CH2COCH2\u2014CH2CO\u2014OR1, and their use in diagnosis and photochemotherapy of disorders or abnormalities of external or internal surfaces of the body, and products and kits for performing the invention. In one embodiment, the leadframe includes a rectangular frame. Also disclosed is an adaptive voltage positioning circuit and method for early detection of a transient event by sensing voltage changes at the load and adjusting the target voltage with pre-determined current values prior to the time that ATR event changes in the current at the load are detected. When the bypass sleeve is in the first position air that enters in the inlet is directed by the blocking sleeve into the bypass cylinder and when it is in the second position air that enters the inlet is allowed to enter an outer passage between the bypass cylinder and the outer housing. The compactness of the easel enables an art piece being worked on to be left mounted to the easel for drying or viewing, and the door can still be opened and closed normally with the easel mounted to it. The reliability of the system is improved because the internal electronic components are protected from moisture, dust, and other liquid or particle contaminants, all while maintaining an internal temperature that is lower than a maximum permissible operating temperature.