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.
Myosin pulls the thin filaments towards the middle on each side, thus shortening the sarcomere and causing contraction. Cross-Bridge Cycling. In the context of muscular contraction, a cross-bridge refers to the attachment of myosin with actin within the muscle cell. All muscle types - whether we're talking about skeletal, cardiac, or smooth - contract by cross-bridge cycling - that is, repeated attachment of actin and myosin within the cell.