Science terms starting with P

1,062 terms

  1. Partial Beam Filling A limitation of the rainfall estimation techniques used by NEXRAD. At far ranges from the radar, a storm may occupy only a portion of the radar beam…
  2. Partial cut A harvest method in which portions of a stand of timber are cut during a number of entries over time. Compare precommercial thinning.
  3. partial digest Incomplete reaction of a restriction enzyme with DNA, such that only a proportion of the target sites are cleaved.
  4. Partial-Duration Flood Series A list of all flood peaks that exceed a chosen base stage or discharge, regardless of the number of peaks occurring in a year.
  5. Particle acceleration The time rate of change of particle velocity.
  6. Particle Accelerators A machine used to accelerate particles to high speeds, and thus, high energy compared to their rest-mass energy.
  7. Particle displacement The difference between the initial position of a soil particle and any later temporary position during shaking.
  8. particle number concentration The number of particles present in any given volume of air.
  9. Particle Physics The study of fundamental particles (such as quarks and leptons) and the fundamental interactions (four forces).
  10. particle radiation High energy nuclear emissions, used as physical agents of mutagenesis. Three major types typically used: alpha (☐) (positively charged), beta (☐)…
  11. Particle size Diameter of the various particles comprising a particular soil.
  12. particle size distribution The number of particles present in any given volume of air within a specified size range.
  13. Particle Trajectory Model A computer sub-model that tracks the trajectories of multiple particles that are released into an atmospheric flow model.
  14. Particle velocity The time rate of change of particle displacement.
  15. Particulate A small, discrete mass of solid or liquid matter that remains individually dispersed in gas or liquid emissions.
  16. Particulate emissions Fine liquid or solid particles discharged with exhaust gases. Usually measured as grains per cubic foot or pounds per million Btu input.
  17. Particulate matter Fine solid or liquid particles such as dust, smoke, mist, fumes, or smog, found in air or emissions.
  18. Particulate Matter (PM) Very small pieces of solid or liquid matter such as particles of soot, dust, fumes, mists or aerosols.
  19. Particulates The fine liquid or solid particles contained in combustion gases. The quantity and size of particulates emitted by cars, power and industrial plants, wood…
  20. Partly Cloudy Between 3/8 and 5/8 of the sky is covered by clouds.
  21. Partly Sunny Between 3/8 and 5/8 of the sky is covered by clouds. The term "Partly Sunny" is used only during daylight hours.
  22. Parts per billion (ppb) A measurement of concentration on a weight or volume basis. Equivalent to micrograms per liter.
  23. parts per million (Abbreviation: ppm). Unit of concentration: 1ppm = 1mg dissolved matter per litre of solution.
  24. Parts per million (ppm) A measurement of concentration on a weight or volume basis. Equivalent to milligrams per liter (mg/l).
  25. parturition The process of giving birth.
  26. Pascal The unit of pressure produced when one newton acts on one square meter (1 N/m2). It is abbreviated Pa.
  27. Pascal (Pa) The pressure or stress of one newton per square meter. 1 psi = 6895 Pa.
  28. PASS A working trip or passage of an excavating, grading, or compaction machine. See compaction.
  29. Passage The transfer or transplantation of cells from one culture medium to another.
  30. passage number The number of times cells in culture have been sub-cultured.
  31. passage time Time interval between successive sub-cultures.
  32. Passenger-Miles per Gallon Pmpg is the vehicle miles per gallon multiplied by the number of passengers traveling in the vehicle.
  33. Passerine Birds of the order Passeriformes, which includes perching birds and songbirds such as the jays, blackbirds, finches, warblers, and sparrows.
  34. Passivation A chemical reaction that eliminates the detrimental effect of electrically reactive atoms on a photovoltaic cell's surface.
  35. Passive earth pressure The maximum value of earth pressure. This condition exists when a soil mass is compressed sufficiently to cause its internal shearing resistance along a…
  36. passive immunity 1. Natural acquisition of antibodies by the foetus or neonate (newborn) from the mother. 2.
  37. Passive Solar (Building) Design A building design that uses structural elements of a building to heat and cool a building, without the use of mechanical equipment, which requires careful…
  38. Passive solar energy system Solar heating or cooling that uses natural energy flows to transfer heat.
  39. Passive Solar Heater A solar water or space-heating system in which solar energy is collected, and/or moved by natural convection without using pumps or fans.
  40. Passive Solar Home A house built using passive solar design techniques.
  41. Passive/Natural Cooling To allow or augment the natural movement of cooler air from exterior, shaded areas of a building through or around a building.
  42. Past weather Past weather Predominant characteristic of the weather which had existed at an observing station during a given period of time (during the preceding hour…
  43. PAT In blackjack, an unbusted hand worth at least 17 points. In draw poker, a hand that does not need any more hands.
  44. pat gene A gene obtained from Streptomyces sp. encoding resistance to glufosinate-ammonium containing herbicides. (These inhibit plant synthesis of glutamine).
  45. patent A grant to an inventor of the right to exclude others, for a limited time, from making, using, or selling his invention in the United States.
  46. paternal Pertaining to the father.
  47. Pathogen Bacteria, viruses, parasites or fungi can cause disease.
  48. pathogen-free Uncontaminated with pathogen.
  49. pathogenesis related protein (Abbreviation: PR protein ). One of a group of proteins that are characteristically highly expressed as part of a plant's response to pathogen attack.
  50. pathotoxin Substance secreted by certain pathogens, in order to attack the host tissue. Some pathotoxins are also toxic to non-hosts, especially animals or humans.
  51. pathovar Strain of a plant-attacking bacterium or fungus that can be differentiated from others by their interaction with specific s.
  52. Pattern cracking Fine cracks in the form of a pattern on a concrete surface.
  53. Patterned-body anthropomorphs Object or drawing having a human shape with a pattern or design. See also Anthropomorphic; Anthropomorphism
  54. Pay formation A layer or deposit of soil or rock whose value is sufficient to justify excavation.
  55. Payback Period The amount of time required before the savings resulting from your system equal the system cost.
  56. Payline Lines of excavation, backfill, compacted backfill or embankment which are described in the specifications or shown on the drawings which describe or show…
  57. PBL Probable
  58. PBR Abbreviation for plant breeders' rights.
  59. pBR322 A derivation of ColE1, one of the first plasmid vectors widely used. (See Plasmid.)
  60. PC-GRIDDS PC-Gridded Interactive Display and Diagnostic System - Allows the forecaster to view fields of gridded model output in contour or vector format.
  61. PCB´s Polychlorinated biphenyls. A group of organic compounds. PCB´s are highly toxic to aquatic life.
  62. PCPN Precipitation
  63. PCR A laboratory method used to make many copies of a specific DNA sequence. Also called polymerase chain reaction.
  64. PCR-RFLP AlteRNA tive term for cleaved amplified polymorphic sequence.
  65. PCT Patent Cooperation Treaty (more) provides a mechanism by which an applicant can file a single application that, when certain requirements have been…
  66. PCV Abbreviation for packed cell volume.
  67. PD Period
  68. PDI Palmer Drought Index
  69. PDMT Predominant
  70. PDO Pacific Decadal Oscillation - a recently described pattern of climate variation similar to ENSO though on a timescale of decades and not seasons.
  71. PDS Particularly Dangerous Situation (PDS) wording is used in rare situations when long-lived, strong and violent tornadoes are possible.
  72. PDS Watch The Particularly Dangerous Situation (PDS) wording is used in rare situations when long-lived, strong and violent tornadoes are possible.
  73. PDSI Palmer Drought Severity Index - an index used to gage the severity of drought conditions by using a water balance equation to track water supply and…
  74. PDT Pacific Daylight Time
  75. Pea gravel A uniformly graded gravel with a particle size of approximately 3/16".
  76. Peak Clipping/Shaving The process of implementing measures to reduce peak power demands on a system.
  77. Peak demand Maximum electrical demand occurring within a specified period of time. Maximum power used in a specific time period. See energy.
  78. Peak Demand/Load The maximum energy demand or load in a specified time period.
  79. Peak Discharge Highest rate of discharge of a volume of water passing a given location during a given period of time (during the year, or a flood event, etc..).
  80. Peak flow The highest flow of water attained during a particular flood for a given stream or river.
  81. Peak ground acceleration (PGA) That acceleration representing the peak acceleration of ground motion.
  82. Peak Gust The highest instantaneous wind speed observed or recorded.
  83. Peak horizontal acceleration See Acceleration
  84. Peak load The maximum power load in a stated period of time.
  85. Peak load plant Powerplant that normally is operated to provide power during maximum load periods.
  86. Peak load, peak demand These two terms are used interchangeably to denote the maximum power requirement of a system at a given time, or the amount of power required to supply…
  87. Peak Power Power generated that operates at a very low capacity factor; generally used to meet short-lived and variable high demand periods.
  88. Peak Pulse The amount of power transmitted by a radar during a given pulse. Note that because these pulses are widely spaced, the average power will be much smaller.
  89. Peak Shifting The process of moving existing loads to off-peak periods.
  90. Peak Sun Hours The equivalent number of hours per day when solar irradiance averages 1 kW/m2. For example, six peak sun hours means that the energy received during total…
  91. Peak Watt A unit used to rate the performance of a solar photovoltaic (PV) cells, modules, or arrays; the maximum nominal output of a PV device, in Watts (Wp) under…
  92. Peak Wind Speed The maximum instantaneous wind speed (or velocity) that occurs within a specific period of time or interval.
  93. Peaking capacity Power generation equipment or system capacity to meet peak power demands.
  94. Peaking Hydropower A hydropower plant that is operated at maximum allowable capacity for part of the day and is either shut down for the remainder of the time or operated at…
  95. Peaking power Powerplant capacity typically used to meet the highest levels of demand in a utility's load or demand profile.
  96. Peakshaving LNG facility A liquefied natural gas plant that supplies a gas pipeline system during peak-use periods. During slack periods the liquefied gas is stored.
  97. Peanut-body anthropomorphs Object or drawing having a human-like shape resembling that of a peanut. See also Anthropomorphic; Anthropomorphism
  98. Peat A fibrous mass of organic matter in various stages of decomposition, generally dark brown to black in color and of spongy consistency.
  99. pectin A group of naturally occurring complex polysaccharides, containing galacturonic acid, found in plant cell wall s, where their function is to cement cells…
  100. pectinase Enzyme catalysing the hydrolysis of pectin. Used in conjunction with cellulase to solubilize plant cell walls.