Abstract: A liquid coating composition that is useful to form retro-reflective marks that actuate photoscanner sensing devices and that comprises a liquid vehicle and retro-reflective elements uniformly dispersed in the vehicle. The vehicle includes a high proportion of volatile solvent and a gel agent that gels the vehicle so that the retro-reflective elements are suspended in the vehicle. The gel agent comprises at least a large proportion of the non-volatile portion of the vehicle.

Abstract: A printed circuit card retainer formed of a unitary elongated ring element having an inwardly projecting tongue at one end and a pair of outwardly projecting hooked tines at the opposite end. Whereby in use the tongue is hooked over the edge of a printed circuit card while the tines are passed around a connector mounting bar onto which they are hooked.

Abstract: A simple, reliable, and fast-acting means for releasing a control element and allowing it to be inserted rapidly into the core region of a nuclear reactor for scram purposes. A latch mechanism grips a coupling head on a nuclear control element to connect the control element to the control drive assembly. The latch mechanism is closed by tensioning a cable or rod with an actuator. The control element is released by de-energizing the actuator, providing fail-safe, rapid release of the control element to effect reactor shutdown. A sensing rod provides indication that the control element is properly positioned in the latch. Two embodiments are illustrated, one involving a collet-type latch mechanism, the other a pliers-type latch mechanism with the actuator located inside the reactor vessel.