A cutting tool comprising a cutting tool holder and a cutting insert adapted to be mounted thereon. Attenuation of acoustic energy that has entirely propagated within the wall of the conduit is measured and evaluated in order to derive parameters relating to the fluid or fluids flowing in the conduit. Whenever any MPEG frame arrives, the MPEG frame is processed to extract MAC packets. Methods and apparatus for collecting liquid carbon dioxide in a collecting tank are also provided. Further, during the active state the drawn air is expelled from the housing through channels of the fan at an angle of between about 20 degrees to about 75 degrees relative to the central axis of the housing. The zoom optical system comprises, in order from an object side thereof, a first lens group G1 of negative refracting power, an aperture stop S, a second lens group G2 of positive refracting power, a third lens group G3 of negative refracting power and a fourth lens group G4 of positive refracting power, and satisfies the following condition.