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 collateralization is a clause in a purchase contract that secures a loan which serves as collateral for all other loans made with the borrower in the past, present, and future. This type of loan is usually found at credit unions, but can sometimes be found at your typical banks. Cross collateralization most commonly occurs with car loans. When you buy a vehicle from a bank or credit union you usually sign a security agreement that secures your car to the loan. This results in the lender holding the title to your car until you pay off the loan. If you default on the loan the bank or credit union can repossess your car.