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More than 2,500 barbiturates have been synthesized. At the height of their popularity, about 50 were marketed for human use.
When blood is exposed to air, it clots. Heparin allows the blood to come in direct contact with air without clotting.
Blood in the urine can be a sign of a kidney stone, glomerulonephritis, or other kidney problems.
Approximately one in three babies in the United States is now delivered by cesarean section. The number of cesarean sections in the United States has risen 46% since 1996.
Though the United States has largely rejected the metric system, it is used for currency, as in 100 pennies = 1 dollar. Previously, the British currency system was used, with measurements such as 12 pence to the shilling, and 20 shillings to the pound.