Cryogenics Cryogenics In physics, cryogenics is the production and behaviour of materials at very low temperatures. A person who studies elements that have been subjected to extremely cold temperatures is called a "cryogenicist". It is not well-defined at what point on the temperature scale refrigeration ends and cryogenics begins, but scientists assume a gas to be cryogenic if it can be liquefied at or below . The U.S. National Institute of Standards and Technology has chosen to consider the field of cryogenics as that involving temperatures below . This is a logical dividing line, since the normal boiling points of the
Ship prefix in 1970. A United States Navy ship that is not in active commission does not hold the title of United States Ship with simply the name without prefix used before and after commissioned service. Vessels, such as yard and harbor craft that are not commissioned and "in service" are officially referred to by name or hull number without prefix. Military Sealift Command (MSC) civilian manned ships "in service" are given the prefix United States Naval Ship (USNS). Prior to commissioning, ships may be described as a pre-commissioning unit or PCU; for example, the uncommissioned has been described as the "pre-commissioning