so bates Fe MICROCURIE: A one-miilionth part of a curie. MILLIREM: A one-thousandth part of a rem. MILLIROENTGEN: A one-thousandth part of a roentgen. OVERPRESSURE: The transient pressure, usually expressed in pounds per square inch, exceeding the ambient pressure, manifested in the shock (or blast) wave from an explosion. PICOCURIE: One millionth of a millionth of a curie. RAD: A unit of absorbed dose of radiation; it represents the absorption of 100 ergs of nuclear (or ionizing) radiation per gram of the absorbing material or tissue. RBE (OR RELATIVE BIOLOGICAL EFFECTIVENESS): The ratio of the number of rads of gamma (or X-) radiation of a certain energy which will produce a specified biological effect to the number of rads of another radia- tion required to produce the sameeffect is the RBE of this latter radiation. REM: A unit of bioiogical dose of radiation; the name is derived from the initial letters of the term “roentgen equivalent man (or mammal).” The number of rems of radiation is equal to the number of rads absorbed multiplied by the RBE ofthe given radiation (for a specified effect), REP: A unit of absorbed dose of radiation now being replaced by the rad; the name rep is derived from the initial letters of the term “roentgen equivalent physical.” Basically, the rep was intended to express the amountof energy absorbed per gram of soft tissue as a result of exposure to 1 roentgen of gamma (or X-) radiation. RESIDENCE HALF-TIME: As applied to delayed fallout, it is the time required for the amount of weapon debris deposited in a particular part of the atmosphere, e.g., stratosphere or troposphere, to decrease to half of its initial value. ROENTGEN: A unit of exposure dose of gamma (or X-) radiation. It is de- fined precisely as the quantity of gamma (or X-) radiation such that the asso- ciated corpuscular emission per 0.001293 gram of air produces, in air, ions carrying one electrostatic unit quantity of electricity of either sign. STRATOSPHERE: A relatively stable layer of the atmosphere between the tropopause and a height of about 30 miles in which the temperature changes very little (in polar and temperate zones) or increases (in the tropics) with increasing altitudes. In the stratosphere clouds of water never form and there is practically no convection. TNT EQUIVALENT: A measure of the energy released in the detonation of a nuciear (or atomic) weapon, or in the explosion of a given quantityof fissionable material, expressed in terms of the weight of TNT which would release the same amount of energy when exploded. The TNT equivalent is usually stated in kilotons or megatons. TRITIUM: A radioactive isotope of hydrogen, having a mass of 3 units; it is produced in nuclear reactors by the action of neutrons on lithium nuclei. TROPOPAUSE: The imaginary boundary layer dividing the stratosphere from the lower part of the atmosphere, the troposphere. The tropopause normally occurs at an altitude of about 25.000 to 45,000 feet in polar and temperate zones, and at 55,000 feet in the tropics. TROPOSPHERE: The region of the atmosphere immediately above the earth’s surface and up to the tropopause in which the temperaturefalls fairly regu- larly with increasing altitude, clouds form, convection is active, and mixing is continuous and more or less complete. WEAPON DEBRIS: The highly radioactive material, consisting of fission products, various products of neutron capture, and uranium and plutonium that have escaped fission, remaining after the explosion. 51