ventricular assist device: see under heart, artificial.

intrauterine device (IUD), variously shaped birth control device, usually of plastic, which is inserted into the uterus by a physician. The IUD may contain copper or levonorgestrel, a progestin (a hormone with progesteronelike effects; see progesterone). Apparently the IUD creates a hostile environment for the fertilized egg.

Electronic device that operates on the basis of the electric, magnetic, or optical properties of a solid material, especially one that uses a solid crystal in which an orderly three-dimensional arrangement of atoms, ions, or molecules is repeated throughout the entire crystal. Synthetic crystals of elements such as silicon, gallium arsenide, and germanium are used in transistors, rectifiers, and integrated circuits. The first solid-state device was the “cat's whisker” (1906), in which a fine wire was moved across a solid crystal to detect a radio signal. Seealso semiconductor.

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Any of various tools and instruments that generate and use compressed air. Examples include rock drills, pavement breakers, riveters, forging presses, paint sprayers, blast cleaners, and atomizers. Compressed-air power is flexible, economical, and safe. In general, pneumatic systems have relatively few moving parts, contributing to high reliability and low maintenance costs.

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