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.
Cross Junction, Virginia. Cross Junction is an unincorporated community in northern Frederick County, Virginia, United States. Cross Junction is located on the North Frederick Pike (U.S. Highway 522) at its intersection with Collinsville Road. Cross Junction also encompasses the residential communities at Lake Holiday to the south.