The present invention relates to allocating data regions in an orthogonal frequency division multiplexing access system. The method includes providing a mechanism to effect opening of the valve, verifying that the valve opened as a result of employing the mechanism to effect opening of the valve and after verifying the valve opened, signaling the valve to close after a first period of time has elapsed. The present invention further provides nucleic acids useful for encoding polypeptides capable of modulating a cell’s function andor activity. The bias transistor is coupled between the substrate and a bias voltage terminal.