Carbocations are species bearing a formal + charge on carbon. The have sp2 hybridization and trigonal planar geometry, with an empty p orbital on carbon, perpendicular to the plane containing the substituents (see diagrams shown to the right).
Aortic cross-clamp. An aortic cross-clamp is a surgical instrument used in cardiac surgery to clamp the aorta and separate the systemic circulation from the outflow of the heart. An aortic cross-clamping procedure serves, for example, in the repairing of coarctation of the aorta.
clamp, root rubber dam, n a clamp with jaws designed to fit on the root surfaces of a tooth; usually used for the retention of a rubber dam. n a device made of spring metal and used to retain a rubber dam in place or improve the operating field by isolating it from the oral environment.