The invention relates to a gas exchange detection method and device particularly, but not exclusively, for rapid detection of the presence of micro-organisms, the effect of an additional substance upon a micro-organism andor the rate at which oxygen is consumed, in solutions, aqueous emulsions andor suspensions. To lock the WTL to an ITU grid line, a portion of the output beam from the WTL is routed through the etalon to split the beam into a transmission line for detection by an etalon fringe detector. A cutting edge of each blade includes an outer cutting edge, an inner cutting edge, and a stepped cutting edge. In another embodiment, a single immersive video mapping an environment greater than 360 is played in a standard display software program. Pharmaceutical compositions containing said compounds as well as methods of treating various disease states responding to inhibition of matrix metalloproteinase are also claimed herein. After receipt, the print data and the packet-based control data are extracted from the one or more data streams for control of at least the plurality of printhead controllers.