Federal employees are compensated according to government-regulated pay scales. More than 70 percent of federal employees are paid according to the most common pay scale, the General Schedule (GS) , but there are a variety of alternative pay schedules as well.
Four heart valves control the flow of blood through the heart. They act as one-way doors, opening to let blood exit or enter a chamber, then closing to keep blood from flowing backward. 1  The tricuspid valve controls blood flow from the right atrium to the right ventricle.
Background. A heart valve acts as a check valve, opening and closing to control blood flow. This cycle occurs about 40 million times per year or two billion in an average lifetime. Natural valves can develop several problems, either the valve opening becomes narrow or may not close completely.