Science terms starting with N

411 terms

  1. Nonmarket value Most environmental goods and services, such as clean air and water, and healthy fish and wildlife populations, are not traded in markets, meaning that…
  2. Nonpoint light source A light source that is sufficiently large in size and close enough to the viewer to appear as an illuminated surface rather than a star-like point of…
  3. Nonpoint source A contributing factor to water pollution that cannot be traced to a specific spot.
  4. Nonpoint sources Diffuse pollution sources (i.e., without a single point of origin or not introduced into a receiving stream from a specific outlet).
  5. Nonpreference customer A customer excluded by law from preference in the purchase of federally produced electrical energy.
  6. Nonrenewable Fuels Fuels that cannot be easily made or "renewed," such as oil, natural gas, and coal.
  7. Nonroad mobile sources (emissions) Sources such as farm and construction equipment, gasoline-powered lawn and garden equipment, and power boats and outdoor motors that emit pollutants.
  8. nonsense mutation A mutation which converts an amino-acid-specifying codon into a stop codon, e.g.
  9. Nontarget organism An organism which is affected by an interaction for which it was not the intended recipient.
  10. Nonterritorial communities Networks of associations around shared goals, values, and norms, such as the agricultural, environmental, or recreational community; also known as…
  11. Nonutility power producer A corporation, person, agency, authority, or other legal entity or instrumentality that owns electric generating capacity and is not an electric utility.
  12. NOR Abbreviation for nucleolar organizer region.
  13. Nor\'easter A strong low pressure system that affects the Mid Atlantic and New England States. It can form over land or over the coastal waters.
  14. Normal The long-term average value of a meteorological paramater (i.e., temperature, humidity, etc.) for a certain area.
  15. Normal depth The depth of flow that would exist for a steady-uniform flow condition.
  16. Normal loading conditions Loading conditions that occur or are anticipated to occur with some degree of regularity or frequency, as constrasted to unusual loading conditions such…
  17. Normal Recovery Capacity A characteristic applied to domestic water heaters that is the amount of gallons raised 100 degrees Fahrenheit per hour (or minute) under a specified…
  18. Normal Water Level (Normal Pool Level) For a reservoir with a fixed overflow, the lowest crest level of that overflow.
  19. Normal water surface The highest elevation at which water is normally stored, or that elevation which the reservoir should be operated for conservation purposes.
  20. Normal Water Surface Elevation In hydrologic terms, the lowest crest level of overflow on a reservoir with a fixed overflow level (spillway crest elevation).
  21. Normal Water Surface Elevation (Normal Pool Level) The lowest crest level of overflow on a reservoir with a fixed overflow level (spillway crest elevation).
  22. Normal Year A year during which the precipitation or stream flow approximates the average for a long period of record.
  23. North American Electric Reliability Council (NERC) A council formed in 1968 by the electric utility industry to promote the reliability and adequacy of bulk power supply in the electric utility systems of…
  24. North American High North American High The relatively weak general area of high pressure which, as shown on mean charts of sea-level pressure, covers most of North America…
  25. North Atlantic Oscillation (Abbrev. NAO) - the NAO is a large-scale fluctuation in atmospheric pressure between the subtropical high pressure system located near the Azores in the…
  26. North Pacific High A semi-permanent, subtropical area of high pressure in the North Pacific Ocean.
  27. North Slope of Alaska (NSA) site The third ARM research site, the NSA locale has is located in Barrow, Alaska. Its polar regions are predicted to undergo the largest warming in response…
  28. North Wall The north side boundary of the Gulf Stream generally extending northeast from Cape Hatteras where the Gulf Stream turns northeast.
  29. Northern blot A technique analogous to Southern blotting, but involving the transfer of RNA from an to a membrane, prior to probing.
  30. Northern blotting See Northern hybridization.
  31. Northern hybridization (Northern blotting). A procedure in which RNA fragments are transferred from an agarose gel to a nitrocellulose filter, where the RNA is then hybridized…
  32. Northern Lights Common name for Aurora Borealis; the luminous, radiant emission from the upper atmosphere over middle and high latitudes, and centred around the earth's…
  33. Notification The third of five Early Warning System components consisting of communicating alerts and warnings about an emergency condition at a dam to appropriate…
  34. Notochord Forms the axial skeleton in embryos of all chordates. In vertebrates, it is replaced partially or completely by vertebrae.
  35. Nought Usually referring to the first value in a range, and denoted by a subscript, "0".
  36. Nowcast A short-term weather forecast, generally out to six hours or less. This is also called a Short Term Forecast.
  37. NOx Budget Trading Program (NBP) An ozone season cap-and-trade program intended to help states meet their NOx state implementation plan (SIP) required reductions.
  38. NOx State Implementation Plan (SIP) Building upon analyses done by the Ozone Transport Assessment Group (OTAG), this rule was finalized by the Environmental Protection Agency (EPA) in 1998.
  39. Noxious weeds Those plants regulated by law or those that are so difficult to control that early detection is important.
  40. npt-II Abbreviation for neomycin phosphotransferase II.
  41. NR Near
  42. NREL The National Renewable Energy Laboratory.
  43. NRN Northern
  44. NRW Narrow
  45. NS Nimbostratus- A cloud of the class characterized by a formless layer that is almost uniformly dark gray; a rain cloud of the layer type, of low altitude…
  46. NSF Lotus Notes Format Database File (i.e. database.nsf) Can be either an email database or the traditional type of fielded database.
  47. NSSFC National Severe Storm Forecast Center
  48. NSSL National Severe Storms Laboratory - this is one of NOAA's internationally known Environmental Research Laboratories, leading the way in investigations of…
  49. nucellar embryo An embryo which has developed vegetatively from somatic tissue surrounding the embryo sac, rather than by fertilization of the egg cell.
  50. nucellus Tissue forming the major part of the young ovule in which the embryo sac develops; Also known as megasporangium.
  51. Nuclear electric power Electricity generated by an electric power plant whose turbines are driven by steam generated in a reactor by heat from the fissioning of nuclear fuel.
  52. Nuclear Energy Energy that comes from splitting atoms of radioactive materials, such as uranium, and which produces radioactive wastes.
  53. Nuclear reactor A device in which a fission chain reaction can be initiated, maintained, and controlled.
  54. Nuclear reprogramming Restoration of the correct embryonic pattern of gene expression in a nucleus derived from a somatic cell and introduced into an oocyte.
  55. Nuclear transfer A technology by which novel animals are generated by cloning a single diploid somatic cell.
  56. Nuclear transfer (NT) The generation of a new animal nearly identical to another one by injection of the nucleus from a cell of the donor animal into an enucleated oocyte of…
  57. Nuclease A class of enzymes that degrades DNA and/or RNA molecules by cleaving the phosphodiester bonds that link adjacent nucleotides.
  58. Nucleic acid A macromolecule consisting of polymerized nucleotides . Two forms are found, DNA and RNA.
  59. nucleic acid probe See: DNA probe.
  60. Nucleic acids The two nucleic acids, deoxyribonucleic acid (DNA) and ribonucleic acid (RNA), are made up of long chains of molecules called nucleotides.
  61. Nuclein The term used by Friedrich Miescher to describe the nuclear material he discovered in 1869, which today is known as DNA.
  62. nucleo-cytoplasmic ratio In a cell, the ratio of nuclear to cytoplasmic volume. This ratio is high in meristematic cells and low in differentiated cells.
  63. nucleolar organizer (Abbreviation: NO). See: nucleolar organizer region.
  64. nucleolar organizer region (Abbreviation: NOR). A chromosomal segment containing a large array of genes that encode ribosomal RNA; located at the secondary constriction of specific…
  65. Nucleolar organizing region A part of the chromosome containing rRNA genes.
  66. nucleolus An RNA -rich nuclear organelle in the nucleus of eukaryotic cells, produced by a nucleolar organizer.
  67. Nucleon Proton or neutron, part of atomic nucleus.
  68. Nucleonics The science, technology, and application of nuclear energy.
  69. nucleoplasm The non-staining or slightly chromophilic, liquid or semi-liquid, ground substance of the interphase nucleus and which fills the nuclear space around the…
  70. nucleoprotein Conjugated protein composed of nucleic acid and protein; the material of which the chromosomes are made.
  71. Nucleoside A building block of DNA and RNA, consisting of a nitrogenous base linked to a five carbon sugar. (See Nucleoside analog.)
  72. Nucleoside analog A synthetic molecule that resembles a naturally occuring nucleoside, but that lacks a bond site needed to link it to an adjacent nucleotide.
  73. nucleoside analogue A synthetic molecule that resembles a naturally occurring nucleoside.
  74. nucleosome Spherical sub-units of eukaryotic chromatin that are composed of a core particle consisting of an octamer of histones (two molecules each of histones H2a…
  75. Nucleosynthesis The process by which atoms are formed by the coming together of subatomic particles and other smaller atoms.
  76. Nucleotide (NOO-klee-oh-TIDE) A building block for nucleic acids (the molecules inside cells that carry genetic information).
  77. nucleotide sequence See: sequence.
  78. Nucleus (NOO-klee-us) In biology, the structure in a cell that contains the chromosomes.
  79. Nucleus/Nuclei (plural- nuclei; adjective- nuclear ) The center of an atom. Nearly 100% percent of the mass of an atom is contained in the nucleus.
  80. Nuclide Any species of atom that exists for a measurable length of time. A nuclide can be distinguished by its atomic weight, atomic number, and energy state.
  81. null allele An allele which produces no functional gene product.
  82. Null hypothesis The assumption that any observed difference between two samples of a statistical population is purely accidental and not due to systematic causes.
  83. null mutation See: amorph.
  84. nullisomic (Adj.) See: nullisomy.
  85. nullisomy An otherwise diploid cell or organism lacking both members of a homologous chromosome pair.
  86. Numerical Forecasting A computer forecast or prediction based on equations governing the motions and the forces affecting motion of fluids.
  87. Numerical Weather Prediction Same as Numerical Forecasting; a computer forecast or prediction based on equations governing the motions and the forces affecting motion of fluids.
  88. Numerous A National Weather Service convective precipitation descriptor for a 60 or 70 percent chance of measurable precipitation (0.01 inch).
  89. nurse culture Culturing cells from a suspension culture on a raft of filter paper above a callus tissue piece (nurse tissue).
  90. Nurse plants Mature plants that create favorable conditions for seeds to germinate and for seedlings to survive and grow.
  91. nutriceutical A conventional food product that has been modified (potentially by genetic engineering) to have improved nutritional characteristics and/or pharmaceutical…
  92. nutrient cycle The passage of a nutrient or element through an ecosystem, including its assimilation and release by various organisms and its transformation into various…
  93. nutrient deficiency Absence or insufficiency of an essential factor for normal growth and development.
  94. nutrient film technique (Abbreviation: NFT). A hydroponic technique used to grow plants. NFT delivers a thin film of water or nutrient solution either continuously or through…
  95. nutrient gradient A diffusion gradient of nutrients and gases that develops in tissues where only a portion of the tissue is in contact with the medium.
  96. nutrient medium (pl.: nutrient media) A solid, semi-solid or liquid formulation for in vitro cell or tissue growth.
  97. Nutrients Animal, vegetable, or mineral substance which sustains individual organisms and ecosystems.
  98. NVA Negative Vorticity Advection - the advection of lower values of vorticity into an area.
  99. NW Northwest
  100. NWD Northward