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.
Iron ring/clamp. An iron ring/clamp that holds glassware such as a funnels or other objects, like the a wire gauze or clay triangle for heating with a Bunsen burner. Often, the iron ring/clamp will be attached to an iron stand. Iron stand. A metal rod attached to a heavy metal base.