Coupler-based amplifiers provide a measure of load mismatch based on the difference between the two output signal amplitudes from the amplifiers. It concerns novel introns and compositions comprising such introns as well as a method to improve expression of polypeptides from nucleic acids such as cloned genes with heterologous introns, especially genes encoding antibodies and antibody derived fragments, and the production of various polypeptides in eukaryotic host cells using said novel intron sequences as heterologous introns. A compression piston is received within a compression cylinder and operatively connected to the crankshaft such that the compression piston reciprocates through an intake stroke and a compression stroke in a single rotation of the crankshaft. The lens may, for example, provide a macro lens option in a camera lens arrangement. When the light emitting element of the first light guide plate is lit, different color lights are produced, such that a light transmission effect of single-color light or mixed multiple-color light occurs at the surface of the keypad corresponding to the first light guide plate. A first relay node having received an up-link ACK packet transmitted by the terminal station transmits to an second relay node the up-link ACK packet including a source terminal station ID and a relay source node ID representing its own node ID.