Backup Energy SystemA reserve appliance; for example, a stand-by generator for a home or commercial building.
Backup rateA utility charge for providing occasional electricity service to replace on-site generation.
BackwaterShallow area of a river that is sometimes isolated, often being located behind a sand bar or other obstruction in the river.
Backwater CurveThe longitudinal profile of the surface of a liquid in a non-uniform flow in an open channel, when the water surface is not parallel to the invert owing…
Backwater EffectThe effect which a dam or other obstruction or construction has in raising the surface of the water upstream from it.
Backwater FloodingUpstream flooding caused by downstream conditions such as channel restriction and/ or high flow in a downstream confluence stream.
bacterial toxin(bak-TEER-ee-ul TOK-sin) A toxic substance, made by bacteria, that can be modified to kill specific tumor cells without harming normal cells.
BacteriocideA class of antibiotics that kills bacterial cells.
bacteriocinA protein produced by bacteria of one strain and active against those of a closely related strain.
Bacteriophage(Abbreviation: phage). A virus that infects bacteria. Altered forms are used as cloning vectors. See: lambda phage, M13.
BaffleA device, such as a steel plate, used to check, retard, or divert a flow of a material.
Baffle block (dentate)One of a series of upright obstructions designed to dissipate energy as in the case of a stilling basin or drop structure.
Baffle chamberIn incinerator design, a chamber designed to settle fly ash and coarse particulate matter by changing the direction and reducing the velocity of the…
BagasseThe fibrous material remaining after the extraction of juice from sugarcane; often burned by sugar mills as a source of energy.
BaghouseAn air pollution control device used to filter particulates from waste combustion gases; a chamber containing a bag filter.
BailerA 10- to 20-foot-long pipe equipped with a valve at the lower end. A bailer is used to remove slurry from the bottom or the side of a well as it is being…
BajadaA broad sloping deposit caused by the joining together of alluvial fans. These occur on the lower slopes of mountains and are often characterized by loose…
Balance PointAn outdoor temperature, usually 20 to 45 degrees Fahrenheit, at which a heat pump's output equals the heating demand.
Balance-of-SystemIn a renewable energy system, refers to all components other than the mechanism used to harvest the resource (such as photovoltaic panels or a wind…
Balanced head conditionThe condition in which the water pressure on the upstream and downstream sides of an object are equal (such as an emergency or regulating gate).
balanced lethal systemA system for maintaining a recessive lethal allele at each of two loci on the same pair of chromosomes.
balanced polymorphismTwo or more phenotypes maintained in the same breeding population.
BalancingThe requirement imposed by electricity grids or natural gas pipelines that supply and demand be equal over a certain time period.
Bald and Golden Eagle Protection ActThis Act was originally enacted in 1940 as the Bald Eagle Protection Act to protect bald eagles and later amended to include golden eagles.
BalingA means of reducing the volume of a material by compaction into a bale.
Ball-millingThe repeated churning action of cobbles, gravel, and sand caused by the force of water in a stilling basin or other structure by which severe concrete…
BallastA device used to control the voltage in a fluorescent lamp.
Ballast Efficacy FactorThe measure of the efficiency of fluorescent lamp ballasts. It is the relative light output divided by the power input.
Ballast FactorThe ratio of light output of a fluorescent lamp operated on a ballast to the light output of a lamp operated on a standard or reference ballast.
Band GapIn a semiconductor, the energy difference between the highest valence band and the lowest conduction band.
Band Gap EnergyThe amount of energy (in electron volts) required to free an outer shell electron from its orbit about the nucleus to a free state, and thus promote it…
BANDPASS FILTERA filter whose frequencies are between given upper and lower cutoff values, while substantially attenuating all frequencies outside these values (this…
BandwidthThe amount of information or data that can be sent over a network connection in a given period of time.
BankAmerica has a "dual banking system" which means that both states and the federal government issue bank charters for the need and convenience of their…
Bank fullAn established river stage at a given location along a river which is intended to represent the maximum safe water level that will not overflow the river…
Bank StorageWater that has inflitrated from a reservoir into the surrounding land where it remains in storage until water level in the reservoir is lowered.
BankfullThe water level, or stage, at which a stream, river or lake is at the top of its banks and any further rise would result in water moving into the flood…
Bankfull StageAn established river stage at a certain point along a river which is intended to represent the maximum safe water level which will not overflow the river…
Bankfull Stage/ElevationAn established river stage/water surface elevation at a given location along a river which is intended to represent the maximum water level that will not…
Banner CloudA cloud plume often observed to extend downwind behind isolated mountain peaks, even on otherwise cloud-free days.
BAPSUBay Area Public Service Unit. Public Service section of the San Francisco Bay Area Weather Service Forecast Office.
Bar1. Historically, the partition separating the general public from the space occupied by the judges, lawyers and other participants in a trial. 2.
Bar screenA screen made of parallel bars set 3/4" to 2" apart used to filter out large objects.
Barber Pole[Slang], a thunderstorm updraft with a visual appearance including cloud striations that are curved in a manner similar to the stripes of a barber pole.
barkThe outer protective layer of a tree including the inner bark and the outer bark.
barnaseA bacterial ribonuclease, which, when transformed into plants and expressed in the anthers, generates a male sterile phenotype.
Baroclinic leaf shieldA cloud pattern on satellite images - frequently noted in advance of formation of a low pressure center.
Baroclinic ZoneA region in which a temperature gradient exists on a constant pressure surface.
BaroclinityA measure of the state of stratification in a fluid in which surfaces of constant pressure (isobaric) intersect surfaces of constant density (isosteric).
BarogramAn analog record of pressure produced by a barograph
BarographA barometer that records its observations continuously.
BarometerAn instrument that measures atmospheric pressure.
Barometric PressureThe pressure of the atmosphere as indicated by a barometer.
Barotropic SystemA weather system in which temperature and pressure surfaces are coincident, i.e.
BarotropyThe state of a fluid in which surfaces of constant density (or temperature) are coincident with surfaces of constant pressure; it is the state of zero…
Barr bodyA condensed mass of chromatin found in the nuclei of female mammals. It is a late-replicating, inactive X-chromosome. See: dosage compensation, sex linkage
BarrageAny artificial obstruction placed in water to increase water level or divert it. Usually the idea is to control peak flow for later release.
Barrage (gate-structure dam)A barrier built across a river, comprising a series of gates which when fully open allow the flood to pass without appreciably increasing the flood level…
BarrelA volumetric unit of measure for crude oil and petroleum products equivalent to 42 U.S. gallons.
barrel (of oil)A liquid measure equal to 42 U.S. gallons, or typically about 306 lb of oil. One barrel equals 5.6 ft3; for crude oil, one barrel contains about 5.
Barrel (petroleum)42 U.S. gallons (306 pounds of oil, or 5.78 million Btu).
Barrel of oil equivalentA unit of energy equal to the amount of energy contained in a barrel of crude oil. Approximately 5.78 million Btu or 1,700 kWh.
Barrier JetA jet-like wind current that forms when a stably-stratified low-level airflow approaches a mountain barrier and turns to the left to blow parallel to the…
Bartel's Rotation NumberThe serial number assigned to 27-day rotation periods of solar and geophysical parameters.
BaryonSubatomic particles comprised of three quarks. Protons (comprised of two up quarks and one down quark) and neutrons (made up of two down quarks and one up…
Baryonic MatterOrdinary matter, which is made up largely of baryons.
basal1. Located at the base of a plant or a plant organ. 2. A fundamental formulation of a tissue culture medium containing nutrients but no growth promoting…
Basal MetabolismThe amount of heat given off by a person at rest in a comfortable environment; approximately 50 Btu per hour (Btu/h).
BasaltVolcanic rock (or lava), characteristically dark in color and containing 45 to 54% silica and generally rich in iron and magnesium (mafic composition).
baseOne of the components of nucleosides, nucleotides and nucleic acids . Four different bases are found in naturally occurring DNA - the purines A (adenine )…
base analogueA non-natural purine or pyrimidine base that differs slightly in structure from the normal bases, but can be incorporated into nucleic acids .
Base campA site occupied by several families or more on either a year round or a seasonal basis.
Base courseA layer of specified or selected material of planned thickness constructed on the subgrade or subbase for the purpose of serving one or more functions…
BASE DATAThose digital fields of reflectivity, mean radial velocity, and spectrum width data in spherical coordinates provided at the finest resolution available…
Base exchangeThe physicochemical process whereby one species of ions adsorbed on soil particles is replaced by another species.
Base FloodThe flood having a 1% chance of being equaled or exceeded in any given year.
Base flood plainThe flood plain innundated by the 100-year flood.
Base flowGround water inflow to the river. Portion of stream discharge that is derived from natural storage.
base paircombination of 2 nucleotides (A and T or G and C) held together by weak hydrogen bonds; the DNA double helix is formed when a base pair of nucleotides in…
Base pair (bp)A pair of complementary nitrogenous bases in a DNA molecule--adenine-thymine and guanine-cytosine. Also, the unit of measurement for DNA sequences.
Base PowerPower generated by a power generator that operates at a very high capacity factor.
BASE PRODUCTSThose products that present some representation of the base data. This representation may not necessarily be either in full resolution or depict the full…
Base ReflectivityOne of the three fundamental quantities (along with base [radial] velocity and spectrum width) that a Doppler radar measures.
Base safety condition (BSC)The level of loading above which a dam failure does not contribute an incremental loss of life.
Base sequenceThe order of nucleotide bases in a DNA molecule; determines structure of proteins encoded by that DNA.