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The modern decimal position system was the invention of the Hindus (around 800 AD), involving the placing of numerals to indicate their value (units, tens, hundreds, and so on).
When blood is exposed to air, it clots. Heparin allows the blood to come in direct contact with air without clotting.
Illicit drug use costs the United States approximately $181 billion every year.
The familiar sounds of your heart are made by the heart's valves as they open and close.
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.