kbpAbbreviation for kilobase pairs (of double-stranded DNA ).
kcatThe catalytic rate constant that characterizes an enzyme-catalysed reaction. The larger the kcat value, the faster the conversion of substrate into…
kcat/KmThe catalytic efficiency of an enzyme-catalysed reaction. The greater the value of kcat/Km, the more rapidly and efficiently the substrate is converted…
KdAbbreviation for dissociation constant. Describes the strength of binding (or affinity) between molecules and their ligands . See: avidity.
kDaAbbreviation for kiloDalton. A unit of molecular mass equal to 1000 Dalton.
KelvinOne Kelvin degree is equivalent to one Celsius degree. The difference between the two temperature scales: All motion within an atom ceases at zero Kelvin…
Kelvin Temperature ScaleAn absolute temperature scale in which a change of 1 Kelvin equals a change of 1 degree Celsius; 0°K is the lowest temperature on the Kelvin scale.
Kelvin WavesFluctuations in wind speed at the ocean surface at the Equator result in eastward propagating waves, known as Kelvin Waves.
Kelvin-Helmholtz WavesVertical waves in the air associated with wind shear across statically-stable regions.
Kelvin-Helmoltz wavesVertical waves in the air associated with wind shear across statically stable regions.
KeratinAn extremely tough protein substance found in hair, nails, skin, and cornea.
KeratinocytesCells that synthesize keratin and are found in the skin, hair, and nails. A fibrous protein is produced by keratinocytes and may be hard or soft.
KerogenSolid, waxy mixture of rock is heated to high temperatures, the kerogen is vaporized.
KeroseneA type of heating fuel derived by refining crude oil that has a boiling range at atmospheric pressure from 400 degrees to 550 degrees F.
Key observation point(s) (KOP)One or a series of points on a travel route or at a use area or a potential use area, where the view of a management activity would be most revealing.
killer T cellT cells that kill cells displaying recognized antigens.
Kilovolt-Ampere (kVa)A unit of apparent power, equal to 1,000 volt-amperes; the mathematical product of the volts and amperes in an electrical circuit.
KilowattA unit of electrical power equal to 1,000 watts (W).
Kilowatt (kW)(kW)A standard unit of electrical power equal to one thousand watts, or to the energy consumption at a rate of 1000 Joules per second.
Kilowatt hour (kWh)(kWh)A measure of energy equivalent to the expenditure of one kilowatt for one hour. For example, 1 kWh will light a 100-watt light bulb for 10 hours.
Kilowatt-hourA unit or measure of electricity supply or consumption of 1,000 Watts over the period of one hour; equivalent to 3,412 Btu.
Kilowatthour (kWh)(kWh)A measure of electricity defined as a unit of work or energy, measured as 1 kilowatt (1,000 watts) of power expended for 1 hour.
kinaseAn enzyme that catalyses the transfer of a phosphate group from a high energy state (as in ATP) to another molecule.
Kinetic EnergyEnergy available as a result of motion that varies directly in proportion to an object's mass and the square of its velocity.
kineticsDynamic processes involving motion. Often used as a suffix to indicate studies involving movement or rates of reactions.
kinetochoreStructure at the centromere of eukaryotic chromosomes. The kinetochore consists of inner and outer electron dense plates and a central zone containing…
kinetosomeGranular cytoplasmic structure which forms the base of a cilium or flagellum. Synonym: basal body.
kininA substance promoting cell division. In plant systems, the prefix cyto- has been added (cytokinin ) to distinguish it from kinin in animal systems.
KivaAn underground (or partially underground) ceremonial room or chamber used in ancient and modern Pueblo villages.
Klason ligninLignin obtained from wood after the non-lignin components of the wood have been removed with a prescribed sulfuric acid treatment.
Klenow fragmentA truncated form of DNA polymerase I from E. coli, used extensively for the production of synthetic DNA molecules as it retains polymerase and…
KlystronAn electron tube used as a low-power oscillator or a high-power amplifier at ultrahigh frequencies.
KmA dissociation constant that characterizes the binding of an enzyme to a substrate.
KneewallA wall usually about 3 to 4 feet high located that is placed in the attic of a home, anchored with plates between the attic floor joists and the roof…
Knock InReplacement of a gene by a mutant version of the same gene using homologous recombination.
Knock OutInactivation of a gene by homologous recombination following transfection with a suitable DNA construct.
Knock-out mouseA mouse that has had one or both copies of a specific gene deleted or inactivated.
knockoutA mutant individual, in which a single functional gene has been replaced by a non-functional form of the gene.
Knot(abbrev. Kt) Unit of speed used in navigation, equal to 1 nautical mile (the length of 1 minute latitude) per hour or about 1.
Known Geothermal Area (KGA)(KGA)A region identified by the U.S. Geological Survey as containing geothermal resources.
KnucklesSlang for lumpy protrusions on the edges, and sometimes the underside, of a thunderstorm anvil.
Knutson-Vandenberg Act (KV)(KV)Federal law that allows the U.S. Forest Service to collect money from a timber sale for resource enhancement, protection, and improvement work in the…
Kp IndexA 3-hourly planetary geomagnetic index of activity generated in Gottingen, Germany, based on the K Index from 12 or 13 stations distributed around the…
kraft processChemical pulping process in which lignin is dissolved by a solution of sodium hydroxide and sodium sulfide.
KT(Knot)- Unit of speed used in navigation, equal to 1 nautical mile (the length of 1 minute latitude) per hour or about 1.15 statue miles per hour, or 0.
Kyoto ProtocolThis is an international agreement struck by 159 nations attending the Third Conference of Parties (COP) to the United Nations Framework Convention on…
L<sub>dn</sub>The day-night average sound level. It is the average A-weighted sound level over a 24-hour period that gives additional weight to noise that occurs during…
L<sub>eq</sub>Equivalent/continuous sound level. Leq is the steady sound level that would contain the same total sound energy as the time-varying sound over a given…
La NiñaLa Niña, a phase of ENSO, is a periodic cooling of surface ocean waters in the eastern tropical Pacific along with a shift in convection in the western…
labelThe FDA approved label is the official description of a drug product which includes indication (what the drug is used for); who should take it; adverse…
Labeling of foodsThe process of developing a list of ingredients contained in foods. Labels imply that the list of ingredients can be verified. The U.S.
labellingThe process of attaching or inserting a label into a molecule. Most often in the context of nucleic acids or protein s.
LaccolithAn igneous intrusion that has been forced between two layered rock units. The top of the intrusion is arched upwards and the bottom of the intrusion is…
lactoseA type of sugar found in milk and milk products.
LacunaeThe spaces occupied by cells (e.g., chondrocytes and osteocytes) of calcified tissues.
Lacustrine wetlandWetlands that are generally larger than 20 acres and having less than 30% cover of vegetation such as trees, shrubs, or persistent emergent plants.
LagRefers to slow game response times. The cause can be graphical based (weak graphics card), internet based (ping), system based (lack of memory, virtual…
Lag (of a basin)The measure of the time between the center of mass of precipitation to the center of mass of runoff (on the hydrograph); basin lag is a function of not…
Lag (Time)The time it takes a flood wave to move downstream.
Lag gravelResidual deposit of coarse material that has had the finer fraction removed by a transporting agent, usually wind or water.
Lag phaseThe initial growth phase, during which cell number remains relatively constant prior to rapid growth. See growth phase.
LaggingIn tunneling, planking placed against the dirt or rock walls and ceiling, outside the ribs.
lagging strandThe strand of DNA that is synthesized discontinuously during replication (because DNA synthesis can proceed only in the 5'?3' direction).
LagomorphsThe order of mammals including rabbits, hares, and pikas.
LagoonIn wastewater treatment or livestock facilities, a shallow pond used to store wastewater where sunlight and biological activity decompose the waste.
LaharA mudflow composed of water and volcanic ash. Lahars can be triggered by the flash melting of the snow cap of a volcanic mountain or from heavy rain.
Lake BreezeA thermally produced wind blowing during the day from the surface of a large lake to the shore, caused by the difference in the rates of heating of the…
Lake Effect SnowSnow showers that are created when cold, dry air passes over a large warmer lake, such as one of the Great Lakes, and picks up moisture and heat.
Lake Effect Snow AdvisoryThis product is issued by the National Weather Service when pure lake effect snow (this is where the snow is a direct result of lake effect snow and not…
Lake Effect Snow SquallA local, intense, narrow band of moderate to heavy snow squall that can extend long distances inland. It may persist for many hours.
Lake Effect Snow WarningThis product is issued by the National Weather Service when pure lake effect snow (this is where the snow is a direct result of lake effect snow and not…
Lake Effect StormA fall or winter storm that produces heavy but localized precipitation as a result of temperature differences between the air over snow-covered ground and…
LaminarSmooth, non-turbulent. Often used to describe cloud formations which appear to be shaped by a smooth flow of air traveling in parallel layers or sheets.
laminar air-flow cabinetCabinet designed for cell or tissue culture manipulations requiring a sterile environment.
Laminar FlowFlow in which the head loss is proportional to the first power of the velocity.
laminarinA storage polysaccharide of the brown algae.
LAMPA light source composed of a metal base, a glass tube filled with an inert gas or a vapor, and base pins to attach to a fixture.