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During the twentieth century, a variant of the metric system was used in Russia and France in which the base unit of mass was the tonne. Instead of kilograms, this system used millitonnes (mt).
According to research, pregnant women tend to eat more if carrying a baby boy. Male fetuses may secrete a chemical that stimulates their mothers to step up her energy intake.
Vaccines prevent between 2.5 and 4 million deaths every year.
Acetaminophen (Tylenol) in overdose can seriously damage the liver. It should never be taken by people who use alcohol heavily; it can result in severe liver damage and even a condition requiring a liver transplant.
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.