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When blood is exposed to air, it clots. Heparin allows the blood to come in direct contact with air without clotting.
Astigmatism is the most common vision problem. It may accompany nearsightedness or farsightedness. It is usually caused by an irregularly shaped cornea, but sometimes it is the result of an irregularly shaped lens. Either type can be corrected by eyeglasses, contact lenses, or refractive surgery.
There used to be a metric calendar, as well as metric clocks. The metric calendar, or "French Republican Calendar" divided the year into 12 months, but each month was divided into three 10-day weeks. Each day had 10 decimal hours. Each hour had 100 decimal minutes. Due to lack of popularity, the metric clocks and calendars were ended in 1795, three years after they had been first marketed.
In the United States, there is a birth every 8 seconds, according to the U.S. Census Bureau's Population Clock.
Aspirin is the most widely used drug in the world. It has even been recognized as such by the Guinness Book of World Records.