Novel compounds of formula I, with the exception of. The method includes the steps of taking a period measurement of an internal temperature of the product to be cooled and of the temperature of the ambient air in a chamber; and using the temperature measurements to determine a set value for the temperature of the ambient air inside the chamber. The tissue material of the patient is disposed between the upper and lower housing elements such that the light energy emitted by the source passes through the tissue material to the detector. The statistics server aggregates the statistical data from the plurality of servers in an optimized staggered manner during a recurring interval.