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.
The carotid artery, which is located in the neck, supplies the brain with oxygenated blood. A carotid artery vascular clamp will likely be used during surgery to treat a brain aneurysm. A vascular clamp is a device surgeons use to prevent blood flowing into areas that are being operated on. They are also able to stem the flow of blood from severed or ruptured vessels. The vascular clamps are manufactured in a variety of shapes and materials, typically high-grade surgical stainless steel and durable plastics.