Science terms starting with P

1,062 terms

polymery The phenomenon whereby a number of genes at different loci (which may be polygenes ) can act together to produce a single effect.
polymorphism (PAH-lee-MOR-fih-zum) A common variation or mutation in DNA.
Polymorphisms Variant forms of a particular gene that occur simultaneously in a population.
Polynucleotide A DNA polymer composed of multiple nucleotides. (See Nucleotide.)
Polypeptide A linear polymer composed of covalently linked amino acids. Each link is formed by a single peptide bond.
Polypeptide (protein) A polymer composed of multiple amino acid units linked by peptide bonds.
Polyploid A multiple of the haploid chromosome number that results from chromosome replication without nuclear division.
polysaccharide (PAH-lee-SA-kuh-ride) A large carbohydrate molecule. It contains many small sugar molecules that are joined chemically. Also called glycan.
polysaccharide capsule See: capsule.
polysome A multi-ribosomal structure representing a linear array of ribosomes held together by mRNA.
polyspermy The entry of several sperm nuclei into the egg during fertilization, although only one actually fuses with the egg nucleus.
Polystyrene (See Foam Insulation)
polytene chromosome Giant chromosomes produced by interphase replication without division, and consisting of many identical chromatid s arranged side by side.
polyunsaturates Oils in which some of the carbon-carbon bonds are not fully hydrogenated - i.e. of the form -CH=CH-, rather than -CH2-CH2-.
Polyvalent vaccine A recombinant organism into which has been cloned antigenic determinants from a number of different disease-causing organisms. (See Vaccine.)
Polyvinyl Chloride (PVC) A type of plastic used to make pipe and fittings for water distribution and irrigation.
polyvinylpyrrolidone (Abbreviation: PVP). An occasional constituent of plant tissue culture isolation media.
Pond A small lake. Water impounded by a diversion dam.
Pondage (1) The holding back of water for later release for power development above the dam of a hydroelectric plant to (a) equalize daily or weekly fluctuations…
Ponding In flat areas, runoff collects, or ponds in depression and cannot drain out. Flood waters must infiltrate slowly into the soil, evaporate, or be pumped…
Ponding (or flooding) A method for compacting soil using water added after the soil is in place until free water stands on the surface.
Pool A deep area of a stream between rapids or where the current is slow.
Pool Height The height of the water behind a dam. (Various datums may be used and various pool heights may be used, e.g., conservation pool, flood control pool, etc.)
POP Contraction of "Repopulation", often used as a shortened term for the re-spawn of monsters.
Popcorn Convection Slang for showers and thunderstorms that form on a scattered basis with little or no apparent organization, usually during the afternoon in response to…
POPS Probability of Precipitation
Population the totality of items or units of material under consideration.
Population at risk (PAR) The population potentially affected by flood waters as a result of large operational releases or dam failure.
Population density Number of cells or individuals per unit. The unit could be an area, or a volume of medium.
Population doublings The number of times cells growing in vitro have increased the total number of cells by a factor of 2 compared to the initial number of cells.
Population genetics The branch of genetics that deals with frequencies of alleles and genotypes in breeding populations.
porcine endogenous retrovirus (Abbreviation: PERV). The provirus of a porcine retrovirus. The possibility that PERVs could be activated after xenotransplantation of pig organs into…
Pore A small to minute opening or interstice in a rock or soil.
Pore Pressure The interstitial pressure of fluid (air or water) within a mass of soil, rock, or concrete.
Pore spaces The open areas, or spaces, in soil, sediments, and rocks that are filled by air or water.
Pore-water pressure Internal hydrostatic pressure in an embankment caused by the level of water in the reservoir acting through pressure-transmitting paths between soil…
Porosity The ratio of the volume of void space to the total volume of an undisturbed sample.
Porous Media A solid that contains pores; normally, it refers to interconnected pores that can transmit the flow of fluids.
Portal An opening into a tunnel.
Portfolio Standard The requirement that an electric power provider generate or purchase a specified percentage of the power it supplies/sells from renewable energy…
POS Positive
position effect The influence of the location of a gene (particularly a transgene ) on its expression and hence its effect on phenotype.
positional candidate gene A gene known to be located in the same region as a DNA marker that has been shown to be linked to a single-locus trait or to a QTL, and whose deduced…
positional cloning A strategy for gene cloning that relies on the identification of closely linked markers to the target trait, and then uses chromosome walking to identify…
Positive Area The area on a sounding representing the layer in which a lifted parcel would be warmer than the environment; thus, the area between the environmental…
Positive Cloud to Ground Lightning A CG flash that delivers positive charge to the ground, as opposed to the more common negative charge.
positive control system A mechanism in which a regulatory protein (s) is required to turn on gene expression.
Positive Energy Balance When producing a fuel takes less energy than the amount of energy the fuel provides.
positive feedback the process in which an initial change will bring about an additional change in the same direction.
Positive pressure Pressure within a pipe that is greater than atmospheric pressure.
positive selectable marker See: dominant selectable marker.
positive selection A method by which cells that carry a DNA insert integrated at a specific chromosomal location can be selected, since this integration confers a…
Positive Vorticity Advection (Abbrev. PVA) - Advection of higher values of vorticity into an area, which often is associated with upward motion (lifting) of the air.
Positive-tilt Trough An upper level system which is tilted to the east with increasing latitude (i.e., from southwest to northeast).
Positron The antiparticle of the electron, carry a charge that is opposite to an electron.
Possession The state where an entity inhabits and exerts a level of control over a living thing or object.
Post-aeration The introduction of oxygen into waste water to further reduce BOD and COD after secondary or advanced treatment.
Post-Flare Loops In solar-terrestrial terms, a loop prominence system often seen after a major two-ribbon flare, which bridges the ribbons.
Post-implantation embryo Implanted embryos in the early stages of development until the establishment of the body plan of a developed organism with identifiable tissues and organs.
post-replication repair A recombination-dependent mechanism for repairing damaged DNA.
Post-storm Report A report issued by a local National Weather Service office summarizing the impact of a tropical cyclone on it's forecast area.
post-translational modification The addition of specific chemical residues to a protein after it has been translated.
Post-tropical Cyclone A former tropical cyclone. This generic term describes a cyclone that no longer possesses sufficient tropical characteristics to be considered a tropical…
Posted operating instructions Operations and maintenance instructions taken from the Standing Operating Procedures (SOP) that pertain to the mechanical features in the immediate area…
Potable water Water that is suitable for drinking, as defined by local health officials.
Potential dam safety deficiency A condition that currently does not significantly affect the safety of the dam, but is capable of becoming a dam safety deficiency; for example…
Potential Energy Energy available due to position.
Potential evapotranspiration Rate at which water, if available, would be removed from soil and plant surfaces.
Potential Fossil Yield Classification (PFYC) Initially developed by the U.S. Forest Service and the Region 2 Paleo Initiative in May 1996, the PFYC system provides baseline guidance for assessing the…
Potential spill An accident or other circumstances which threatens to result in discharge of oil or other hazardous substances.
Potential Temperature The temperature a parcel of dry air would have if brought adiabatically (i.e., without transfer of heat or mass) to a standard pressure level of 1000 mb.
Potential Vorticity This plays an important role in the generation of vorticity in cyclogenesis, especially along the polar front.
Potentially Active Fault See Fault, potentially active
potentiometric See: enzyme electrode.
Pound Pound mass (sometimes abbreviated lb(m)). A unit of mass equal to 0.454 kilograms.
Pound force (sometimes abbreviated lb(f)) A force which will accelerate one pound mass at a rate of 32.2 ft/second(2).
Pound of Steam One pound of water in vapor phase; is NOT steam pressure, which is expressed as pounds per square inch (psi).
Pound Per Square Inch Absolute (psia) A unit of pressure [hydraulic (liquid) or pneumatic (gas)] that does not include atmospheric pressure.
Pounds per square inch (psi or lb/in2) A pressure designation for pounds per square inch. May be pounds per square inch gage (psig) or absolute (psia).
Powder factor (explosives factor) A term expressing the amount of explosives used to break a quantity of rock. Normal units for the powder factor are lb/yd3 or kg/m3; however, lb/ton and…
Powder Snow Dry, loose, unconsolidated snow.
Power Authority to do. One has the power to do something if he is of legal age. Also, used as "powers," the term refers to authority granted by one person to…
Power (Output) Curve A plot of a wind energy conversion device's power output versus wind speed.
Power (Solar) Tower A term used to describe solar thermal, central receiver, power systems, where an array of reflectors focus sunlight onto a central receiver and absorber…
Power block Portion of the facility at which electrical power is generated.
Power Coefficient The ratio of power produced by a wind energy conversion device to the power in a reference area of the free windstream.
Power Conditioning The process of modifying the characteristics of electrical power (for e.g., inverting dc to ac).
Power conditioning system (PCS) In solar energy facilities, the collection of electrical equipment that converts direct current (DC) from a photovoltaic array to alternating current (AC)…
Power demand Rate at which electric energy is required and delivered to or by a system over any designated period of time.
Power Density The amount of power per unit area of a free windstream.
Power factor The ratio of real to total power. In alternating-current power transmission and distribution, the cosine of the phase angle between the voltage and…
Power Factor (PF) The ratio of actual power being used in a circuit, expressed in watts or kilowatts, to the power that is apparently being drawn from a power source…
Power Generation Mix The proportion of electricity distributed by a power provider that is generated from available sources such as coal, natural gas, petroleum, nuclear…
Power marketer A business entity engaged in buying and selling electricity. Power marketers do not usually own generating or transmission facilities.
Power pool Two or more interconnected electric systems which operate as a single system to supply power to meet combined load requirements.
Power production capacity The amount of power that a facility can produce under ideal operating conditions. See also Battery capacity
Power Provider A company or other organizational unit that sells and distributes electrical power (e.g.
Power purchase agreement Guarantees a market for power produced by an independent power producer and the price at which it is sold to a purchaser.
Power tower A type of CSP technology composed of many large, sun-tracking mirrors (heliostats) that focus sunlight on a receiver at the top of a centrally located…
Power tower system See Power tower