A method and apparatus for estimating a frequency response of a channel. The active compounds of the present invention are useful in the therapeutic andor prophylactic treatment of e. A driving transistor is connected to the differential amplifying circuit and the outputting transistor. Such detection triggers the secondary stage in which the sample particles are tested for viability via processing through a dye with fluorescent properties affected when bonded with an entity universally found in all biological substances and a UV light source.