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synthetic elements

(Encyclopedia)synthetic elements, in chemistry, radioactive elements that were not discovered occurring in nature but as artificially produced isotopes. They are technetium (at. no. 43), which was the first element...

Precambrian

(Encyclopedia)Precambrian, name of a major division of geologic time (see Geologic Timescale, tablegeologic timescale, table), from c.5 billion to 570 million years ago. It is now usually divided into the Archean a...

Iran

(Encyclopedia)CE5 Iran ēränˈ, ĭrănˈ [key], officially Islamic Republic of Iran, republic (2015 est. pop. 79,360,000), 636,290 sq mi (1,648,000 sq km), SW Asia. The country's name was changed from Persia to...

Great Basin

(Encyclopedia)Great Basin, semiarid, N section of the Basin and Range province, the intermontane plateau region of W United States and N Mexico. Lying mostly in Nevada and extending into California, Oregon, Idaho, ...

atomic bomb

(Encyclopedia)atomic bomb or A-bomb, weapon deriving its explosive force from the release of nuclear energy through the fission (splitting) of heavy atomic nuclei. The first atomic bomb was produced at the Los Alam...

nucleosynthesis

(Encyclopedia)nucleosynthesis or nucleogenesis, in astronomy, production of all the chemical elements from the simplest element, hydrogen, by thermonuclear reactions within stars, supernovas, and in the big bang at...

lung cancer

(Encyclopedia)lung cancer, cancer that originates in the tissues of the lungs. Lung cancer is the leading cause of cancer death in the United States in both men and women. Like other cancers, lung cancer occurs aft...

calcium

(Encyclopedia)calcium kălˈsēəm [key] [Lat.,=lime], metallic chemical element; symbol Ca; at. no. 20; at. wt. 40.078; m.p. about 839℃; b.p. 1,484℃; sp. gr. 1.55 at 20℃; valence +2. Calcium is a malleable, ...

Portsmouth, cities, United States

(Encyclopedia)Portsmouth. 1 City (1990 pop. 25,925), Rockingham co., SE N.H., a port of entry with a good harbor and a state-owned port terminal at the mouth of the Piscataqua River opposite Kittery, Maine; inc. 16...

Gabon

(Encyclopedia)CE5 Gabon gäbôNˈ [key], officially Gabonese Republic, republic (2015 est. pop. 1,930,000), 103,346 sq mi (267,667 sq km), W central Africa. It borders on the Atlantic Ocean in the west, on Equat...