A gas-liquid contacting plate of the present invention in which a treatment liquid flows from an upper side to a lower side direction of a substrate and a part of gas being in contact with the treatment liquid is absorbed into the treatment liquid, includes a downward protruding saw teeth-shaped portion in which a lower end side of the substrate has pitches at predetermined gaps. The arc tube includes an auxiliary mirror that reflects the light radiated from the arc tube toward the region being illuminated into a direction of the ellipsoidal reflector. The apparatus and method have the benefit that the peaks of the signal to be transmitted will be consistent over a wide range of TX power values. A vertically-adjustable lumbar mechanism is adjustably supported on the back support structure and operably engages the flexible sheet for flexing a lumbar area of the flexible sheet forwardly to provide an optimal ergonomic horizontal and vertical convex shape for postural lumbar support. The valve may be mechanically fastened to the adapter to prevent thread disengagement.