Science terms starting with L

480 terms

1. L_dn 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…
2. L_eq 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…
3. La Niña La 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…
4. label The 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…
5. Labeling of foods The process of developing a list of ingredients contained in foods. Labels imply that the list of ingredients can be verified. The U.S.
6. labelling The process of attaching or inserting a label into a molecule. Most often in the context of nucleic acids or protein s.
7. lac repressor-lac promoter system See: IPTG.
8. Laccolith An 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…
9. lactose A type of sugar found in milk and milk products.
10. Lacunae The spaces occupied by cells (e.g., chondrocytes and osteocytes) of calcified tissues.
11. Lacustrine habitat Lake or reservoir wetland habitat.
12. Lacustrine wetland Wetlands that are generally larger than 20 acres and having less than 30% cover of vegetation such as trees, shrubs, or persistent emergent plants.
13. Lag Refers to slow game response times. The cause can be graphical based (weak graphics card), internet based (ping), system based (lack of memory, virtual…
14. 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…
15. Lag (Time) The time it takes a flood wave to move downstream.
16. Lag gravel Residual deposit of coarse material that has had the finer fraction removed by a transporting agent, usually wind or water.
17. Lag phase The initial growth phase, during which cell number remains relatively constant prior to rapid growth. See growth phase.
18. Lagging In tunneling, planking placed against the dirt or rock walls and ceiling, outside the ribs.
19. lagging strand The strand of DNA that is synthesized discontinuously during replication (because DNA synthesis can proceed only in the 5'?3' direction).
20. Lagomorphs The order of mammals including rabbits, hares, and pikas.
21. Lagoon In wastewater treatment or livestock facilities, a shallow pond used to store wastewater where sunlight and biological activity decompose the waste.
22. Lahar A 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.
23. Lake Breeze A 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…
24. Lake Effect Snow Snow 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.
25. Lake Effect Snow Advisory This 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…
26. Lake Effect Snow Squall A local, intense, narrow band of moderate to heavy snow squall that can extend long distances inland. It may persist for many hours.
27. Lake Effect Snow Warning This 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…
28. Lake Effect Storm A fall or winter storm that produces heavy but localized precipitation as a result of temperature differences between the air over snow-covered ground and…
29. Lakeshore Flood Advisory See Coastal/Lakeshore Flood Advisory.
30. Lakeshore Flood Watch See: COASTAL/LAKESHORE FLOOD WATCH
31. Lakeshore Flooding See COASTAL/LAKESHORE FLOODING
32. LALs (L)ightning (A)ctivity (L)evels. LAL 1 - No thunderstorms. LAL 2 - Few building cumulus with isolated thunderstorms.
33. lambda chain One of two classes of antibody light chains. The other is a kappa chain.
34. lambda phage A bacteriophage that infects E. coli, commonly used as a cloning vector. See: integration-excision region.
35. Lambda, Λ The cosmological constant, which measures the energy density of the vacuum.
36. lamella A structure, plate or vesicle that is formed by two membranes lying parallel to each other.
37. lamina Blade or expanded part of a leaf.
38. Laminar Smooth, 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.
39. laminar air-flow cabinet Cabinet designed for cell or tissue culture manipulations requiring a sterile environment.
40. Laminar Flow Flow in which the head loss is proportional to the first power of the velocity.
41. laminarin A storage polysaccharide of the brown algae.
42. LAMP A 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.
43. lampbrush chromosome Large diplotene chromosomes present in oocyte nuclei, and particularly conspicuous in amphibians.
44. Land area Includes dry land and land temporarily or partially covered by water, such as marshlands, swamps, and river flood plains; streams, sloughs, estuaries, and…
45. Land Breeze A coastal breeze at night blowing from land to sea, caused by the difference in the rates of cooling of their respective surfaces.
46. Land classification Reclamation's systematic placing of lands into classes based on their suitability for sustained irrigated farming.
47. Land Conservation and Development Commission (LCDC) In Oregon, a commission appointed to determine land use policy.
48. Land cover The physical coverage of land, usually expressed in terms of vegetation cover or lack of it.
49. Land disturbance Discrete event or process that alters soil and/or kills or damages vegetation. From an ecological and hierarchical perspective, disturbance is a change in…
50. Land disturbance in natural drainage systems Any movement (e.g., grading or excavation) of soil or sediment in a natural drainageway.
51. Land ownership Land held in title.
52. Land retirement Permanent removal of land from agricultural production.
53. Land sky Land sky The relatively dark appearance of the underside of a cloud layer when it is over land that is not snow covered.
54. Land subsidence The sinking or settling of land to a lower level in response to various natural and man-caused factors.
55. Land Trusts Nonprofit organizations interested in the protection of natural resources and historic areas.
56. Land Use The manner in which a parcel of land is used or occupied.
57. Land Use Board of Appeals (LUBA) In Oregon, a seven-member board appointed to adjudicate land use disputes.
58. Land Use Plan A set of decisions that establish management direction for land within an administrative area, as prescribed under the planning provisions of FLPMA; an…
59. Land withdrawal Withdrawals are governed by regulations issued under FLPMA, contained in 43 CFR Part 2300.
60. Landfall The intersection of the surface center of a tropical cyclone with a coastline. Because the strongest winds in a tropical cyclone are not located precisely…
61. Landfill An open area where trash is buried. Facility in which solid waste from municipal and/or industrial sources is disposed; sanitary landfills are those that…
62. Landfill Gas Methane gas that forms in landfills from the decay of organic materials. The gas can be collected and used for power generation.
63. Landform Any feature of the Earth's surface having a distinct shape and origin. Landforms include major features (such as continents, ocean basins, plains…
64. Landholder A landholder is an individual or legal entity owning or leasing land subject to the acreage limitation provisions.
65. Landing A cleared working area on or near a timber harvest site at which processing steps are carried out.
66. Landmark Type of reference point external to the observer. Usually a simply defined physical object.
67. landrace In plant genetic resources, an early, cultivated form of a crop species, evolved from a wild population, and generally composed of a heterogeneous mixture…
68. Landscape A region consisting of interacting ecosystems determined by geology, soils, climate, biota, and human influences.
69. Landscape character The arrangement of a particular landscape as formed by the variety and intensity of the landscape features and the four basic elements of form, line…
70. Landscaping Features and vegetation on the outside of or surrounding a building for aesthetics and energy conservation.
71. Landslide The failure of a sloped bank of soil or rock in which the movement of the mass takes place along a surface of sliding.
72. Landspout [Slang], a tornado that does not arise from organized storm-scale rotation and therefore is not associated with a wall cloud (visually) or a mesocyclone…
73. Langley A unit or measure of solar radiation; 1 calorie per square centimeter or 3.69 Btu per square foot.
74. Lapse Rate The rate of change of an atmospheric variable, usually temperature, with height.
75. LARC (Limited Automatic Report Collector) An electronic device that interfaces a river or precipitation gage with a telephone line making it possible for remote computers to call a gaging site and…
76. Large Marine Ecosystems Regions of ocean space encompassing coastal areas from the river basins and estuaries out to the seaward boundary and continental shelves and to the…
77. Large Scale (Synoptic Scale) Size scale referring generally to weather systems with horizontal dimensions of several hundred miles or more.
78. Large Scale Structure Galaxies, galaxy clusters, and galaxy superclusters.
79. Large woody debris Dead woody material greater than 20" in diameter on the ground or in a stream or river. It may consist of logs, trees, or parts of trees.
80. Large-scale atmospheric processes Large-scale atmospheric processes (circulation) Atmospheric processes with a representative scale (large-scale) of 10 000 km.
81. Larval fish An immature stage that develops from the fertilized egg before assuming the characteristics of the adult.
82. Last Scattering Surface The farthest back in the history of the universe that photons could travel freely.
83. Last Update The time and date in which the forecast was issued or updated. The forecast may be updated at any time as weather conditions warrant.
84. Lasting For purposes of national system natural heritage and cultural heritage MPAs, the site's authority must clearly state its intent to provide permanent…
85. LAT Latitude- The location north or south in reference to the equator, which is designated at zero (0) degrees.
86. Late Archaic The period 3,000 to 1,500 years B.P.
87. Late seral species Shade tolerant species, primarily vine maple shrubs and western red cedar and western hemlock trees.
88. Late seral treatment A treatment in which late seral species will be established after thinning.
89. Late-successional forest Forest seral stages which include mature and old- growth age classes.
90. Late-successional reserve An area of forest where the management objective is to protect and enhance conditions of late successional and old-growth forest ecosystems.
91. latent agent A pathogen, usually a virus, present in a host organism without producing any symptoms.
92. latent bud An inactive bud not held back by rest or dormant period, but which may start growth if stimulated.
93. Latent Cooling Load The load created by moisture in the air, including from outside air infiltration and that from indoor sources such as occupants, plants, cooking…
94. Latent Heat The change in heat content that occurs with a change in phase and without change in temperature.
95. Latent Heat Flux The flux of heat from the earth's surface to the atmosphere that is associated with evaporation or condensation of water vapor at the surface; a component…
96. Latent Heat of Vaporization The quantity of heat produced to change a unit weight of a liquid to vapor with no change in temperature.
97. latent phase See: lag phase.
98. Lateral A channel that conveys water from a canal to a farm, municipality, etc.
99. lateral bud See: axillary bud.
100. lateral meristem A meristem giving rise to secondary plant tissues, such as the vascular and cork cambia.