Abstract: A cell in one example comprises an alkali metal and a coating of parylene on an interior surface of the cell. In one implementation, the alkali metal may be an optically pumped gaseous phase of an alkali metal. The parylene coating minimizes interaction of the excited state of the alkali metal, increases lifetime of the excited state, and minimizes interaction of nuclear spin states with the cell walls.

Abstract: A low drag fan assembly is provided which is adapted to be mounted within a ducting conduit of a ram air induction system of a vehicle for cooling a heat exchanger. The assembly includes a motor having an output drive; a motor bracketing system attached to the motor for suspending the motor within the ducting conduit; a fan hub attached to the output drive; and a plurality of foldable fan blades hingedly attached to an outer perimeter of the fan hub. When the motor is not activated, the plurality of fan blades are folded back in a non-deployed state which is generally longitudinally congruent to the airflow within the ducting conduit. When the motor is activated, the plurality of fan blades radially extend to a deployed state generally normal to and transverse to the airflow within the ducting conduit.