Work of breathing When there is increased gas flow resistance, the optimal respiratory rate decreases. This work (generally during the inhalation phase) is stored as potential energy which is recovered during exhalation. A pressure difference is required to overcome the frictional resistance to gas flow due to viscosity, and to provide non-elastic components of movement of the airway tissues to accommodate pulmonary volume change. Total work done against non elastic forces is 35% of total. Work is defined as a force applied over a distance. The SI unit of work is the Joule, equivalent to a force of 1 Newton exerted along a
History of UNIT alien threats, and Sarah Jane is concerned that UNIT would treat her son Luke as a test subject with no regard for his human rights should they discover him. UNIT returned in the 2009 Easter special "Planet of the Dead" investigating the disappearance of the 200 bus. Captain Erisa Magambo makes a reappearance from her last in "Turn Left" as the commander of UNIT, aided by the new scientific adviser Malcolm Taylor. They appeared again during "Death of the Doctor" which introduced a UNIT Base at Mount Snowdon. In 2012, after a 3-year absence, UNIT returned to "Doctor Who" in