Tympanic membrane retraction commercially available devices (e.g. Otovent and Ear Popper). A ventilation tube, also known as a tympanostomy tube or a grommet, may be placed through the eardrum to equalize middle ear pressure. Although this intervention may be effective, research has not yet shown whether it provides better results than simple observation. Further weakness or perforation of the eardrum may occur. These are intended to improve Eustachian tube function. Adenoidectomy can improve middle ear function and nasal steroid sprays can reduce adenoid size but it is not known whether these treatments alter tympanic membrane retraction. Enlargement of the Eustachian tube opening in
Membrane gas separation when the pores in the polymer membrane appear and disappear faster relative to the movement of the particles. In a typical membrane system the incoming feed stream is separated into two components: permeant and retentate. Permeant is the gas that travels across the membrane and the retentate is what is left of the feed. On both sides of the membrane, a gradient of chemical potential is maintained by a pressure difference which is the driving force for the gas molecules to pass through. The ease of transport of each species is quantified by the permeability, P. With the assumptions of