A polish head for Chemical Mechanical Polishing includes a backing film of silicone on a rigid support element, preferably, of amorphous ceramic. The second processing unit is selectively inactivated and activated under control of the first processing unit to reduce power consumption in the second processing unit. When the oxidized compound is para-xylene and the product from the oxidation reaction is crude terephthalic acid, such CTA product can be purified and separated by more economical techniques than could be employed if the CTA were formed by a conventional high-temperature oxidation process. The seismic data may be P-P, P-S, or S-S data. Also disclosed herein is a process for dyeing human keratin fibers, for example, the hair, comprising applying such a composition to the keratin fibers. In a first aspect of the invention, the sensor or one of the first sensors is calibrated in such a way that the radiation power of a spectral range which is located within the first spectral sensitivity range can be determined from its output signal.