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.
a device for compressing a part or structure. beam clamp. a scissors-like instrument originally used to pick up large blocks of ice. Consists of two inward pointing, sharp pointed hooks, pivoting around a pin at their middle, like scissors, and connected to each other at their blunt ends by a short chain.