No fasting is required prior to this test. The test evaluates how your body processes sugar. A high level in your blood may indicate your body is not processing sugar effectively (positive test). If the results of this screen are positive, the woman may have the Glucose Tolerance Test performed.
A valve is a mechanism that opens and closes to control the flow of fluids. In a scientific context, fluids include both liquids and gases â any substance that can flow freely â and valves may use either. Valves control fluid flow in motors, plumbing, irrigation, pneumatic and hydraulic systems.
The word is derived from the Latin valva, the moving part of a door, in turn from volvere, to turn, roll. The simplest, and very ancient, valve is simply a freely hinged flap which drops to obstruct fluid (gas or liquid) flow in one direction, but is pushed open by flow in the opposite direction. This is called a check valve, as it prevents or checks the flow in one direction.