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Sperm cells are so tiny that 400 to 500 million (400,000,000–500,000,000) of them fit onto 1 tsp.
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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).
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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.
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Giardia is one of the most common intestinal parasites worldwide, and infects up to 20% of the world population, mostly in poorer countries with inadequate sanitation. Infections are most common in children, though chronic Giardia is more common in adults.
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For high blood pressure (hypertension), a new class of drug, called a vasopeptidase blocker (inhibitor), has been developed. It decreases blood pressure by simultaneously dilating the peripheral arteries and increasing the body's loss of salt.
Audiometry. The child in this photograph is undergoing a hearing test with an audiologist.
Current Positions of Known Dwarf Planets and SSSBs in the Outer Solar System
Testing hearing acuity using a tuning fork.
Number of positive, negative, and neutral images recalled by younger, middle-age, and older adults. ...
Response to Sound Waves
Sound intensity log question