The effects of nest temperature on hatchling emergence in the loggerhead sea turtle Caretta caretta

A system for timing the maximum lengths of inspiration and expiration phases of the respiration cycles of a positive pressure breathing apparatus, the rate control system including a timing cylinder with a movable piston therein forming two mutually adjustable timing chambers, two conduits receiving equal flows of gas through an adjustable needle valve and operable alternately to charge the respective chambers, and pressure-responsive actuators pressurized through the respective chambers and each operable upon attainment of a selected actuating pressure level in the associated chamber to produce a pressure signal for terminating one phase and initiating the next. The chambers are activated alternately by a controller which vents one chamber while sealing the other.