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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.
Not getting enough sleep can greatly weaken the immune system. Lack of sleep makes you more likely to catch a cold, or more difficult to fight off an infection.
Drug abusers experience the following scenario: The pleasure given by their drug (or drugs) of choice is so strong that it is difficult to eradicate even after years of staying away from the substances involved. Certain triggers may cause a drug abuser to relapse. Research shows that long-term drug abuse results in significant changes in brain function that persist long after an individual stops using drugs. It is most important to realize that the same is true of not just illegal substances but alcohol and tobacco as well.
The longest a person has survived after a heart transplant is 24 years.
The Babylonians wrote numbers in a system that used 60 as the base value rather than the number 10. They did not have a symbol for "zero."