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.
Lab #9: Muscle Physiology p.2 each sarcomere and, in turn, the length of the muscle (Fig. 9.4). Crossbridge cycling, and hence muscle contraction, can only occur under specific conditions. This is because normally troponin positions tropomyosin on top of myosin-binding sites on the actin molecule.