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The Romans did not use numerals to indicate fractions but instead used words to indicate parts of a whole.

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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.

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The horizontal fraction bar was introduced by the Arabs.

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The term bacteria was devised in the 19th century by German biologist Ferdinand Cohn. He based it on the Greek word "bakterion" meaning a small rod or staff. Cohn is considered to be the father of modern bacteriology.

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Malaria mortality rates are falling. Increased malaria prevention and control measures have greatly improved these rates. Since 2000, malaria mortality rates have fallen globally by 60% among all age groups, and by 65% among children under age 5.

Possible symbiotic or endosymbiotic relationships that gave rise to the first eukaryotic cells Possible symbiotic or endosymbiotic relationships that gave rise to the first eukaryotic cells
Brain cells of a laboratory mouse are shown glowing with multicolor fluorescent proteins Brain cells of a laboratory mouse are shown glowing with multicolor fluorescent proteins
Photograph of the flea that transmits Yersinia pestis to cause bubonic plague, called the oriental r Photograph of the flea that transmits Yersinia pestis to cause bubonic plague, called the oriental r
A Littoral Cell—Sediment transfer A Littoral Cell—Sediment transfer
Stages in the establishment of a cell culture. Stages in the establishment of a cell culture.
When the exhaust is rich, the PCM applies a negative current into the pump cell. When the exhaust is rich, the PCM applies a negative current into the pump cell.
Video: Retina

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