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.
Definition of clamp. 1  transitive verb. 2  1 : to fasten with or as if with a clamp clamp two boards together. 3  2a : to place by decree : impose âoften used with on clamped on a curfew after the riotsb : to hold tightly.