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.
BULLDOG Clamps. The bulldog clamp is a surgical tool used to clamp off or close blood vessels. Made of stainless steel or titanium, the most common bulldog clamp is a spring-loaded crossover clamp. It has serrated blades that when pressed together become an effective tool to cut off blood supply.