Aerospace Industry, Fabrication processes and materials

Fabrication involves the manufacture of individual components that make up larger assemblies or end products. This activity encompasses the working of metals and the incorporation of electrical and electronic devices into processors, circuit boards, and subassemblies for the components of navigation, communication, and control systems. Most of the basic

Managua

City, capital of Nicaragua, lying amid small crater lakes on the southern shore of Lake Managua. One of Central America's warmest capitals, the city is only 163 feet (50 m) above sea level. Throughout the Spanish colonial period, Managua was recognized only as an Indian town, outranked by the relatively nearby Spanish cities of León and Granada. Its choice as a permanent capital

Digestive System, Vertebrate, Vitamin D

Vitamin D is essentially a hormone and is available from two sources. First, under the influence of photosynthesis made possible by ultraviolet rays from the Sun, a sterol compound from the liver (dehydrocholesterol) is converted to vitamin D3. This supplies enough vitamin D3 for human needs. In the absence of contact between sunlight and skin, dietary supplements

Arts, Central Asian, Ghaznavids and Ghurids

Alp Tigin, a slave of Turkic origin at the Samanid court, escaped in AD 962 to Kabul, where he rapidly gained control of the town. He transferred his headquarters to Ghazna in central Afghanistan and established his dynasty there. Few Ghaznavid works of art have survived, but the admirably proportioned and decorated mortuary towers at Ghazna are architectural achievements

Howland Island

Sighted in 1842 by American whalers and named for one of the first

Lens

In optics, piece of glass or other transparent substance that is used to form an image of an object by focusing rays of light from the object. A lens is a piece of transparent material, usually circular in shape, with two polished surfaces, either or both of which is curved and may be either convex (bulging) or concave (depressed). The curves are almost always spherical, i.e.,

China, Relations with other peoples

Simultaneously with the rise of the Ch'in and Han empires, some of the nomadic peoples of Central Asia, known as the Hsiung-nu, succeeded in achieving a measure of unity under a single leader. As a result, while the Chinese were consolidating their government, the lands lying to the north of the empire, and the northern provinces themselves, became subject to incursion

Bilberry

The dark blue berries, ripening in

United States, “Black Codes”

Given little guidance from Washington, Southern whites turned to the traditional political leaders of their section for guidance in reorganizing their governments; and the new regimes in the South were suspiciously like those of the antebellum period. To be sure, slavery was abolished; but each reconstructed Southern state government proceeded to adopt a “Black Code,” regulating the rights and privileges of freedmen. Varying from state to state, these codes in general treated blacks as inferiors, relegated to a secondary and subordinate position in society. Their right to own land was restricted, they could not bear arms, and they might be bound out in servitude for vagrancy and other offenses. The conduct of white Southerners indicated that they were not prepared to guarantee even minimal protection of Negro rights. In riots in Memphis (May 1866) and New Orleans (July 1866), black persons were brutally assaulted and promiscuously killed.

Charadriiform, Molt

Most Charadriiformes have two molts between breeding periods, which are on an annual cycle in all except some populations of the sooty tern (Sterna fuscata). A partial body molt generally precedes breeding, and a complete molt follows breeding. In some species flight feathers of the wing and tail are molted before the fall migration; in others they are retained through