Wiktionary
n. (context chemistry English) a technique whereby a solution is forced through a semipermeable membrane under pressure; used to generate drinkable water from sea water, or to separate chemical compounds
Wikipedia
Reverse Osmosis is a seventeen-person co-ed a cappella group at the University of Southern California founded in January 2001. Reverse Osmosis (RO) routinely performs on the USC campus, but has also toured the East and West Coast, performing in Times Square in NYC and Ghirardelli Square on San Francisco Bay. RO is a perennial competitor in the annual International Championship of Collegiate A Cappella competition.
In the 2005-2006 ICCA competition, RO took first place overall in the Quarterfinal round held at USC's Bovard Auditorium. They also received special awards that night for best soloist (Jordan Koppelman for "Fix You") best arrangement (David Stal for "Fix You") best vocal percussion (Baraka May for "Fix You") and best choreography (Joey Payo and Melissa Joseph).
At the West Seminfal round, held at Stanford University on March 18, 2006, RO placed 2nd overall. Due to a timing error, however, the judges missed a significant portion of Reverse Osmosis' performance. RO was then invited to the final round so that they could have a fair chance to perform their set in full for the ICCA judges, thus becoming the first group from USC to reach the ICCA Finals.
On April 29, 2006, RO performed their award-winning set at Lincoln Center's Alice Tully Hall in New York City. Once again, they were awarded best vocal percussion (Baraka May for "Fix You").
A documentary, Rock and R.O., was filmed about the group and has been screened at the Newport Beach and Westwood Film Festival in Southern California. The feature-length movie was shown most recently at Florida's Delray Beach Film Festival, where it was named Official Selection and won the Audience Choice Award for Best Documentary. On May 20, 2009, Reverse Osmosis opened for Ben Folds at the Hollywood Palladium in Los Angeles.
Reverse osmosis (RO) is a water purification technology that uses a semipermeable membrane to remove ions, molecules, and larger particles from drinking water. In reverse osmosis, an applied pressure is used to overcome osmotic pressure, a colligative property, that is driven by chemical potential differences of the solvent, a thermodynamic parameter. Reverse osmosis can remove many types of dissolved and suspended species from water, including bacteria, and is used in both industrial processes and the production of potable water. The result is that the solute is retained on the pressurized side of the membrane and the pure solvent is allowed to pass to the other side. To be "selective", this membrane should not allow large molecules or ions through the pores (holes), but should allow smaller components of the solution (such as solvent molecules) to pass freely.
In the normal osmosis process, the solvent naturally moves from an area of low solute concentration (high water potential), through a membrane, to an area of high solute concentration (low water potential). The driving force for the movement of the solvent is the reduction in the free energy of the system when the difference in solvent concentration on either side of a membrane is reduced, generating osmotic pressure due to the solvent moving into the more concentrated solution. Applying an external pressure to reverse the natural flow of pure solvent, thus, is reverse osmosis. The process is similar to other membrane technology applications. However, key differences are found between reverse osmosis and filtration. The predominant removal mechanism in membrane filtration is straining, or size exclusion, so the process can theoretically achieve perfect efficiency regardless of parameters such as the solution's pressure and concentration. Reverse osmosis also involves diffusion, making the process dependent on pressure, flow rate, and other conditions. Reverse osmosis is most commonly known for its use in drinking water purification from seawater, removing the salt and other effluent materials from the water molecules.