Asynchronous GeneratorA type of electric generator that produces alternating current that matches an existing power source.
At-rest earth pressureThe value of the earth pressure when the soil mass is in its natural state without having been permitted to yield or without having been compressed.
ataxia-telangiectasiaA rare, inherited, progressive, degenerative disease of childhood that causes loss of muscle control, a weakened immune system, and an increased risk of…
ATDTDCSAutomated Tone Dial Telephone Data Collection System - Data collection system where cooperative observers collect precipitation, stage, and temperature…
AtlatlA wood or bone shaft implement, held in one hand, and used to throw a spear. The tool functions as a lever, giving greater thrust and distance.
AtmosphereThe gaseous envelope surrounding the Earth, which consists almost entirely of nitrogen (78.1% volume mixing ratio) and oxygen (20.
Atmospheric absorptionAttenuation of sound during its passage through air, during which its sound energy is gradually converted into heat by a number of molecular processes in…
Atmospheric Boundary LayerSame as Boundary Layer - in general, a layer of air adjacent to a bounding surface.
Atmospheric circulationAtmospheric circulation System of atmospheric motions over the Earth on the scale of the whole globe (general atmospheric circulation), or over a certain…
Atmospheric Circulation ModelA mathematical model for quantitatively describing, simulating, and analyzing the structure of the circulation in the atmosphere and the underlying causes.
Atmospheric LifetimeThe lifetime of a greenhouse gas refers to the approximate amount of time it would take for the anthropogenic increment to an atmospheric pollutant…
atmospheric moistureThe moisture content of the air as indicated by several measurements including relative humidity, specific humidity, dewpoint, vapor pressure, water vapor…
Atmospheric phenomenonAtmospheric phenomenon (phenomena) As commonly used in weather observing practice, an observable occurrence of particular physical significance within the…
Atmospheric PressureThe pressure of the air at sea level; one standard atmosphere at zero degrees centigrade is equal to 14.695 pounds per square inch (1.
Atmospheric RadiationInfrared radiation (energy in the wavelength interval of 3- 80 micrometer) emitted by or being propagated through the atmosphere.
atmospheric temperatureThe temperature indicated by a thermometer exposed to the air in a place sheltered from direct solar radiation.
atmospheric turbulenceHigh frequency velocity fluctuations that lead to turbulent transport of momentum, heat, mositure, and passive scalars, and often expressed in terms of…
atmospheric windowA region of the electromagnetic spectrum, from 8 to 12 micrometers, where the atmosphere is transparent to radiation.
ATMPOn a buoy report, the air temperature (Celsius).
AtomA particle of matter indivisible by chemical means. It is the fundamental building block of elements.
Atomic numberThe number assigned to each element on the basis of the number of protons found in the element's nucleus.
Atomic weightThe average weight (or mass) of all the isotopes of an element, as determined from the proportions in which they are present in a given element, compared…
Atomic weight (atomic mass)Approximately the sum of the number of protons and neutrons found in the nucleus of an atom.
AtomsThe smallest unit of matter that possesses chemical properties. All atoms have the same basic structure: a nucleus containing positively charged protons…
ATPA substance present in all living cells that provides energy for many metabolic processes and is involved in making RNA.
ATP-aseAn enzyme that brings about the hydrolysis of adenosine triphosphate, by the cleavage of either one phosphate groups with the formation of ADP and…
AttainmentAn area considered to have air quality as good as or better than the National Ambient Air Quality Standards for a given pollutant.
Attainment areaA geographic region where the concentration of a specific air pollutant does not exceed federal standards.
attenuated vaccineA virulent organism that has been modified to produce a less virulent form, but nevertheless retains the ability to elicit antibodies against the virulent…
AttenuationA mechanism for controlling gene expression in prokaryotes that involves premature termination of transcription.
attenuatorA nucleotide sequence in the 5' region of a prokaryotic gene (or in its RNA ) that causes premature termination of transcription, possibly by forming a…
Atterberg limits (consistency limits)The boundaries (determined by laboratory tests) of moisture content in a soil between the liquid state and plastic state (known as liquid limit), between…
AtticThe usually unfinished space above a ceiling and below a roof.
Attic FanA fan mounted on an attic wall used to exhaust warm attic air to the outside.
Attic VentA passive or mechanical device used to ventilate an attic space, primarily to reduce heat buildup and moisture condensation.
Atypical(a-tip'ih-kul) irregular; not conformable to the type; an unusual type.
Audit (Energy)The process of determining energy consumption, by various techniques, of a building or facility.
AugerA rotating, screw-type device that moves material through a cylinder. In alcohol production, it is used to transfer grains from storage to the grinding…
Augmentation PlanA court-approved plan that allows a junior water user to divert water out of priority so long as adequate replacement is made to the affected stream…
Augmentation waterWater used for the replacement of out of priority depletions.
Augmented reportA meteorological report prepared by an automated surface weather observing system for transmission with certified observers signed on to the system to add…
aureofacinAn antifungal antibiotic produced by a strain of Streptomyces aureofaciens. A possible candidate for the transgenic control of plant fungal disease.
AuroraA display of colored light in the atmosphere, caused by collisions between charged particles from a planet’s magnetosphere and atmospheric gases near…
Aurora AustralisSame as Aurora Borealis, but in the Southern Hemisphere. Also known as the southern lights; the luminous, radiant emission from the upper atmosphere over…
Aurora BorealisAlso known as the northern lights; the luminous, radiant emission from the upper atmosphere over middle and high latitudes, and centred around the earth's…
Auroral OvalThe ring-shaped belts of auroral activity around the north and south magnetic poles.
Auroral SubstormsThey are caused by streams of charged particles in the magnetotail that are accelerated to high energies and collide with atoms in the upper atmosphere…
authentic proteinA recombinant protein that has all the properties - including any post-translational modifications - of its naturally occurring counterpart.
Author's signatureThis is the signature of the person or persons with primary responsibility for writing the document.
AuthorizationThe issuance of approval, by a credit card issuer, merchant, or other affiliate, to complete a credit card transaction.
Authorized Reclamation projectA congressionally approved Bureau of Reclamation project that has been authorized for specific purposes.
auto-immune diseaseDisorder in which the immune systems of affected individuals produce antibodies against molecules that are normally produced by those individuals (called…
auto-immunityA disorder in the body's defence mechanism in which an immune response is elicited against its own (self) tissues.
AutoantibodyAn antibody that reacts with antigens found on the cells and tissues of an individual's ownbody. Autoantibodies can cause autoimmune diseases.
autocatalysisCatalysis in which one of the products of the reaction is a catalyst for the reaction.
autoclave(AW-toh-KLAYV) A device that uses steam under high pressure to sterilize medical and laboratory supplies and equipment.
autogenous controlThe action of a gene product to inhibit (negative autogenous control) or enhance (positive autogenous control) the expression of the gene that codes for…
Autoignition TemperatureThe lowest temperature at which a flammable gas vapor will ignite spontaneously, without a source of ignition, after several minutes of exposure to…
Autoimmune disease(AW-toh-ih-MYOON...) A condition in which the body recognizes its own tissues as foreign and directs an immune response against them.
Autologous(aw-TAH-luh-gus) Taken from an individual's own tissues, cells, or DNA.
autologous cellsCells taken from an individual, cultured (or stored), and, possibly, genetically manipulated before being transferred back into the original donor.
Autologous Stem Cell TransplantA transplant involving the infusion of a patient's own bone marrow or stem cells to produce new, healthy marrow.
Autologous transplantCell, tissue or organ transplants from one individual back to the same individual. Such transplants do not induce an immune response and are not rejected.
autolysisThe process of self destruction of a cell, cell organelle, or tissue, through the action of lysosomic enzymes.
Automated Event Reporting Gage(see Tipping Bucket Rain Gage); for river stage gages, IFLOWS pressure transducer type gages can be programmed to report if water surface rises or falls…
Automated mitigation procedureA procedure under which the bids of individual suppliers are capped under certain predetermined conditions.
Automated ReportA meteorological report prepared by an automated surface weather observing system for transmission, and with no certified weather observers signed on to…
Automated Surface Observing SystemThe ASOS program is a joint effort of the National Weather Service (NWS), the Federal Aviation Administration (FAA), and the Department of Defense (DOD).
Automatic (or Remote) Meter Reading SystemA system that records the consumption of electricity, gas, water, etc, and sends the data to a central data accumulation device.
Automatic DamperA device that cuts off the flow of hot or cold air to or from a room as controlled by a thermostat.
AUTOMATIC GAIN CONTROLAny method of automatically controlling the gain of a receiver, particularly one that holds the output level constant regardless of the input level.
Automatic generation controlThe automatic regulation of the power output of electric generators within a prescribed range in response to a change in system frequency, or tie-line…
Automatic generation control (AGC)Computerized power system regulation to maintain scheduled generation within a prescribed area in response to changes in transmission system operational…
autonomousA term applied to any biological unit that can function on its own, i.e. without the help of another unit, such as a transposable element that encodes an…
autopolyploidA polyploid whose constituent genomes are derived from the same or nearly the same progenitor.
autoradiographA technique for visualizing the presence, location and intensity of radioactivity in histological preparations, paper chromatograms or electrophoretic gel…
AutoradiographyA technique that uses X-ray film to visualize radioactively labeled molecules or fragments of molecules; used in analyzing length and number of DNA…
Autosomal dominantA pattern of Mendelian inheritance whereby an affected individual possesses one copy of a mutant allele and one normal allele.
AutosomeA chromosome that is not involved in sex determination.
autotrophOrganism capable of self-nourishment utilizing carbon dioxide or carbonates as the sole source of carbon and obtaining energy from radiant energy or from…
AutumnThe season of the year that is the transition period from summer to winter, occurring as the sun approaches the winter solstice.
Autumnal EquinoxThe equinox at which the sun approaches the Southern Hemisphere, marking the start of astronomical autumn in the Northern Hemisphere.
Auxiliary Energy or SystemEnergy required to operate mechanical components of an energy system, or a source of energy or energy supply system to back-up another.
Auxiliary equipmentAccessory equipment necessary for the operation of a generating station.