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The heart is located in the center of the chest, with part of it tipped slightly so that it taps against the left side of the chest.
The lipid bilayer is made of phospholipids. They are arranged in a double layer because one of their ends is attracted to water while the other is repelled by water.
The immune system needs 9.5 hours of sleep in total darkness to recharge completely.
Signs of depression include feeling sad most of the time for 2 weeks or longer; loss of interest in things normally enjoyed; lack of energy; sleep and appetite disturbances; weight changes; feelings of hopelessness, helplessness, or worthlessness; an inability to make decisions; and thoughts of death and suicide.
Malaria was not eliminated in the United States until 1951. The term eliminated means that no new cases arise in a country for 3 years.