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.
Tip If you need to connect two hubs together and neither one has an uplink port, you can connect them together with a cross cable. A cross cable is a twisted-pair wire that has the transmit-and-receive pairs switched at one end; this provides the same functionality as an uplink port.