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period
period unit of time on the geologic timescale . Periods are shorter than an era and longer than an epoch. Periods are of variable length, generally lasting tens of millions of years, with characteristic fossils found preserved in the sediments deposited during the period. It is also used to... Read more |
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Carboniferous period
Carboniferous period , fifth period of the Paleozoic era of geologic time (see Geologic Timescale , table), from 350 to 290 million years ago. Historical Geology of the Period The Carboniferous period was marked by vast, coal-forming swamps (see also bog ) and a succession of changes in the... Read more |
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Latent Period
LATENT PERIOD A "latent period" is the lag time between exposure to a disease-causing agent and the onset of the disease the agent causes. In infectious diseases it is often identical to the incubation period, but not always. A disease may have incubated but remains latent, or dormant, within the... Read more |
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Incubation
INCUBATION PERIOD The time that elapses between the invasion of a susceptible host by an infectious agent and the onset of symptoms of the disease caused by that agent is called the incubation period. The term is also used to describe the comparable period in the life cycle of parasitic pathogens... Read more |
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Pennsylvanian Period
Pennsylvanian Period The Pennsylvanian Period lasted from 320 to 286 million years ago. During the Pennsylvanian Period, widespread swamps laid down the thick beds of dead plant material that today constitute most of the world's coal . The term Pennsylvanian is a U.S. coinage based on the... Read more |
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Menstruation disorders
Oligomenorrhea Definition Medical dictionaries define oligomenorrhea as infrequent or very light menstruation . But physicians typically apply a narrower definition, restricting the diagnosis of oligomenorrhea to women whose periods were regularly established before they developed problems with... Read more |
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Risorgimento
Risorgimento [Ital.,=resurgence], in 19th-century Italian history, period of cultural nationalism and of political activism, leading to unification of Italy. Roots of the Risorgimento The Risorgimento's roots lie in 18th-century Italian culture in the works of such people as Ludovico Antonio ... Read more |
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dry season
dry season A period each year during which there is little precipitation. In tropical climates (e.g. over much of India) the dry period is often in the winter season. In places in very low latitudes, two dry seasons may occur each year, between the northward and southward passage of the equatorial... Read more |
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Bicentennial
BICENTENNIAL BICENTENNIAL. The 200th anniversary of the signing of the Declaration of Independence was the country's most broadly celebrated anniversary. Like the 1876 centennial, it followed a period of social tension that created an ominous backdrop for the event. The bicentennial represented,... Read more |
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Mississippian Period
Mississippian Period Shallow, low-latitude seas and lush, terrestrial swamps covered the interior of the North American continent during the Mississippian Period of the Paleozoic Era , from about 360 to 320 million years ago. The Pennsylvanian and Mississippian Periods are uniquely American... Read more |
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