Science terms starting with U

164 terms

U Abbreviation for uracil.
U Burst In solar-terrestrial terms, a fast radio burst spectrum of a flare. It has a U-shaped appear- ance in an intensity-vs.-frequency plot
U-Value (see Coefficient of Heat Transmission) The reciprocal of R-Value. The lower the number, the greater the heat transfer resistance (insulating) characteristics of the material.
U.S. Army Corps of Engineers (USACE) As part of the Department of the Army, the Corps has responsibilities in civil and military areas.
U.S. Bureau of Reclamation (USBR) The Federal agency whose mandate was to reclaim the arid west of the United States.
U.S. Department of Agriculture The U.S. agency responsible for regulation of biotechnology products in plants and animals.
U.S. Environmental Protection Agency The independent federal agency, established in 1970, that regulates federal environmental matters and oversees the implementation of federal environmental…
U.S. Geological Survey (Abbrev. USGS)- The Federal Agency chartered in 1879 by congress to classify public lands, and to examine the geologic structure, mineral resources, and…
U.S. Geological Survey (USGS) The USGS serves the Nation by providing reliable scientific information to describe and understand the earth; minimize loss of life and property from…
ubiquitin A small protein, present in all eukaryotic cells, which plays an important role in tagging proteins destined for proteolytic cleavage (because they are…
UCP (Unit Control Position): The WSR-88D radar operator uses this to control the entire radar system.
UGC (Universal Geographic Code) - (e.g. ANZ300 for Western Long Island Sound) are used in many National Weather Service text products to provide geographical…
UKMET A medium-range (3 to 7 day) numerical weather prediction model operated by the U nited K ingdom MET eorological Agency.
ULJ Upper Level Jet
Ultimate Analysis A procedure for determining the primary elements in a substance (carbon, hydrogen, oxygen, nitrogen, sulfur, and ash).
Ultimate bearing capacity The load per unit of area required to produce failure by rupture of a supporting soil or rock mass.
Ultra High Frequency (UHF) Those radio frequencies exceeding 300 MHz
ultrasonication See: sonication.
Ultraviolet Electromagnetic radiation at wavelengths shorter than 400 nm.
Ultraviolet Index This index provides important information to help you plan your outdoor activities in ways that prevent overexposure to the sun's rays.
ultraviolet radiation (UL-truh-VY-oh-let RAY-dee-AY-shun) Invisible rays that are part of the energy that comes from the sun.
Ultraviolet Radiation (UV) The energy range just beyond the violet end of the visible spectrum. Although ultraviolet radiation constitutes only about 5 percent of the total energy…
Umbilical cord blood stem cells stem cells collected from the umbilical cord at birth that can produce all of the blood cells in the body (hematopoietic).
Umbilical cord stem cells Hematopoietic stem cells are present in the blood of the umbilical cord during and shortly after delivery.
Umbra In solar-terrestrial terms, the dark core or cores (umbrae) in a sunspot with penumbra, or a sunspot lacking penumbra.
UMP Abbreviation for the (ribo)nucleotide uridine 5'-monophosphate. See: uridylic acid.
Unbalanced head. See differential head.
Unbundling (functional unbundling) Electric service is traditionally provided on a bundled basis, meaning that generation, transmission, and distribution services are provided as a single…
Uncertainty Describes situations where potential outcomes cannot be estimated based on historical events.
Unclassified excavation Excavation paid for at a fixed price per yard, regardless of whether it is common or rock excavation.
Uncompacted backfill Material used in refilling an excavation without the material being compacted. See backfill.
Unconfined aquifer See Aquifer-unconfined
Unconformity A break or gap in the geologic record where rock layers were eroded or never deposited.
Unconsolidated (basin fill deposits) Loose sediment; lacking cohesion or cement.
Unconsolidated shore wetlands Includes all wetland habitats having three characteristics: (1) unconsolidated substrates with less than 75% areal cover of stones, boulders, or bedrock…
Unconventional natural gas A term applied to natural gas that is difficult and expensive to find and produce; if found, it often is bypassed in favor of more easily obtainable…
Undercurrent A current below the upper currents or surface of a fluid body.
Underflow The movement of groundwater through the soil or a subsurface stratum, or under a structure; specifically, the water flowing beneath the bed of a stream…
Underground Home A house built into the ground or slope of a hill, or which has most or all exterior surfaces covered with earth.
understock Host plant for a grafted scion, a branch or shoot from another plant; an understock may be a fully grown tree or a stump with a living root system.
Understory The trees and other woody species growing under a relatively continuous cover of branches and foliage formed by the overstory trees.
Undersun An optical effect seen by an observer above a cloud deck when looking toward the sun, as sunlight is reflected upwards off the faces of ice crystals in…
Undertaking Any project, activity, or program that could change the character or use of historic properties.
Undertow A relatively small-scale surf-zone current moving away from the beach. Rip currents form as waves disperse along the beach causing water to become trapped…
Undifferentiated A term used to describe cells or tissues that do not have specialized ("mature") structures or functions.
Undisturbed sample A soil sample that has been obtained by methods in which every precaution has been taken to minimize disturbance to the sample.
unencapsidated A virus not enclosed by a coat protein or capsid.
unequal crossing over Abnormal meiotic event, in which one chromatid contains a duplication and the other a deletion.
Unfaulted An area without faults.
Unfinished oils All oils requiring further refinery processing, except those requiring only mechanical blending.
Unglazed Solar Collector A solar thermal collector that has an absorber that does not have a glazed covering.
unicellular Tissues, organs or organisms consisting of a single cell.
unidentified flying object (UFO) Abbreviation for “unidentified flying object” which does not necessarily apply to extraterrestrial or secret governmental crafts, but can be anything…
Unified Soil Classification System A method of grouping and describing soils according to their engineering properties.
Uniform Building Code (UBC) A building code published by the International Conference of Building Officials, adopted and amended by Oregon Department of Commerce.
Uniform flow Open channel flow where the depth and discharge remain constant with respect to space. Also, the velocity at a given depth is the same everywhere.
Uniform Mechanical Code (UMC) A code sponsored by the International Association of Plumbing and Mechanical Officials and the International Conference of Building Officials, adopted and…
Unimodal A distribution having only one localized maximum, i.e., only one peak.
uniparental inheritance The inheritance of genes exclusively from one parent, e.g. chloroplast DNA is inherited either maternally (many angiosperms) or paternally (most…
Unipotent Refers to a cell that can only develop in a specific way to produce a certain end result.
Unipotent stem cells Stem cells that self-renew as well as give rise to a single mature cell type; e.g., spermatogenic stem cells.
unisexual Higher organisms (animals or plants) possessing either male or female reproductive organs, but not both.
Unit (fuel or pulp) A bulk measure of hog fuel or pulp chips containing 200 cubic feet. A unit contains varying amounts of solid material depending on the amount of…
Unit (timber) A timber harvest area with defined boundaries. The area is managed as a unit for harvest and subsequent management activities.
Unit Control Position The WSR-88D radar operator uses this to control the entire radar system. One of the main things that the radar operator will do at the UCP is change…
Unit Hydrograph The direct runoff hydrograph resulting from a unit depth of excess rainfall produced by a storm of uniform intensity and specified duration.
Unit Hydrograph (or Unitgraph) The discharge hydrograph from one inch of surface runoff distributed uniformly over the entire basin for a given time period.
Unit Hydrograph Duration The time over which one inch of surface runoff is distributed for unit hydrograph theory.
Unit Hydrograph Theory Unit Hydrograph Theory states that surface runoff hydrographs for storm events of the same duration will have the same shape, and the ordinates of the…
Unit weight Weight per unit volume. See density, dry unit weight, maximum unit weight, saturated unit weight, unit weight of water, wet unit weight.
Unit weight of water The weight per unit volume of water. See unit weight.
Unitary Air Conditioner An air conditioner consisting of one or more assemblies that move, clean, cool, and dehumidify air.
United Nations Framework Convention on Climate Change (UNFCC) The international treaty unveiled at the United Nations Conference on Environment and Development (UNCED) in June 1992.
United Nations Framework Convention on Climate Change (UNFCCC) The Convention on Climate Change sets an overall framework for intergovernmental efforts to tackle the challenge posed by climate change.
United States Includes the several States, the District of Columbia, the Commonwealth of Puerto Rico, the Virgin Islands of the United States, American Samoa, Guam, and…
United States Army Corps of Engineers (USACE, Corps) The United States Army Corps of Engineers provides quality, responsive engineering services to the nation which includes planning, designing, building and…
United States Code (USC) A compilation of the general and permanent federal laws of the United States. It is divided into 51 titles that represent broad areas subject to federal…
univalent An unpaired chromosome at the first division of meiosis.
universal donor cell Cells that, after introduction into a recipient, will not induce an immune response that leads to their rejection.
Universal Geographic Code (UGC) - UGC's, (e.g. ANZ300 for Western Long Island Sound) are used in many National Weather Service text products to provide geographical information.
Universal Time (UT) By international agreement, the local time at the prime meridian, which passes through Greenwich, England.
Universal Type Weighting and Recording Gage A gage which collects precipitation and then converts the weight onto an inked pen movement which traces on graph paper fixed to a clock driven drum.
universality Referring to the genetic code, the triplet codon s are translated to the same amino acid, with minor exceptions, in virtually all species.
Universe In the world of investments, the word universe refers to a specific group or category of investments that share certain characteristics.
Unlisted items Line item used in an appraisal estimate for design changes and to estimate pay items that have little influence on the total cost.
Unload-reload cycle A loading sequence resulting in rebound and recompression.
Unmanned Aerospace Vehicle (UAV) Program A U.S. Department of Energy program that uses an unmanned aerospace vehicle and occupied aircraft to make key climate measurements that cannot be made my…
Unmerchantable wood Material which is unsuitable for conversion to wood products due to poor size, form, or quality.
unorganized growth In vitro formation of tissues with few differentiated cell types and no recognizable structure; typical structure of calli formed in tissue culture.
Unpaid Federal investment A year-end amount owned to the Treasury which remains to be repaid and is synonymous to "balance to be repaid."
Unrest (episode) Usually non-eruptive volcanic activity (e.g., ground deformation, steam plumes, degassing) that may be interpreted as a precursor to an eruption.
Unsaturated zone The subsurface zone, usually starting at the land surface and ending at the water table, that includes both water and air in spaces between rocks.
UNSBL Unseasonable
Unsettled In meteorological use: A colloquial term used to describe a condition in the atmosphere conducive to precipitation.
Unstable Air Air that is able to rise easily, and has the potential to produce clouds, rain, and thunderstorms.
Unstable slopes Slopes considered unstable due to their incline (or critical angle of repose), applied to slopes made of unconsolidated material.
UNSTBL Unstable
Unsteady flow The velocity at a point varies with time.
Unsuitable areas Areas not appropriate for timber harvest due to fragile or shallow soils, scenic values, special wildlife habitat areas, and riparian or wetland values…
Unsuitable material Those soils that cannot be compacted in embankment or backfill or where excavated to finished grade result in unstable material.