Devices useful in liquid transfer applications and in particular, devices for controlling the free surface of a source liquid in acoustic liquid ejection systems are disclosed. If a content is recorded in case it has been set that the content has to be checked out, the content having been recorded in the content data base is checked out to the portable device. An agent may provide information relating to fixed wireless reference points, and may control underlying operating systems for the reference points based on policies defined by a manager. Capturing the in vitro actuation data may include sorting the data based on in vitro age groups. The cavitated disk is positioned a pre-selected distance from the manifold so as to permit the cavitated disk to rotate on an air cushion between the cavitated disk and manifold which reduces friction and energy losses and permits the device to translate a wide range of rotary motion of a motor into linear cyclical motion of a piston.