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-link. tr.v. cross-linked, cross-linkÂ·ing, cross-links. To join (adjacent chains of a polymer or protein) by creating covalent bonds. n. A chemical bond or link created by cross-linking. or cross-linkage.