English for Science & Nature Glossary of Terms - U

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ultraviolet radiation - Radiation in the wavelength range between visible light and X-rays, divided into wavelength bands A, B, C. Much of the ultraviolet radiations in bands B and C are prevented from reaching the earth's surface by the ozone layer present in the atmosphere.

untreated wastewater - Wastewater discharged without any wastewater treatment.

upwelling - Upward movement of cool and nutrient-rich sub-surface waters towards the surface. There exist various types of upwelling. For fisheries, the most important type is the wind-induced coastal upwelling where the upward movement is a consequence of wind stress (along shore) and Eckman transport (offshore).

uranium - a heavy, radioactive metal (atomic number 92) used in the explosion of nuclear weapons (especially one isotope, U-235).

Urbanisation - the increase in the proportion of people living in towns and cities. Urbanisation occurs because people move from rural areas (countryside) to urban areas (towns and cities). This usually occurs when a country is still developing.

urban parks - parks in cities and areas of high population concentration.

urban planning - the science of managing and directing city growth.

utilities - companies (usually power distributors) permitted by a government agency to provide important public services (such as energy or water) to a region; as utilities are provided with a local monopoly, their prices are regulated by the permitting government agency.