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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.
On average, someone in the United States has a stroke about every 40 seconds. This is about 795,000 people per year.
A cataract is a clouding of the eyes' natural lens. As we age, some clouding of the lens may occur. The first sign of a cataract is usually blurry vision. Although glasses and other visual aids may at first help a person with cataracts, surgery may become inevitable. Cataract surgery is very successful in restoring vision, and it is the most frequently performed surgery in the United States.
Illicit drug use costs the United States approximately $181 billion every year.
The Romans did not use numerals to indicate fractions but instead used words to indicate parts of a whole.