Science terms starting with P

1,062 terms

p Denotes the shorter of the two chromosome arms, e.g. human 14p is the short arm of human chromosome 14.
P element A Drosophila transposon.
P N A semiconductor (photovoltaic) device structure in which the junction is formed between a p-type layer and an n-type layer.
P-I-N A semiconductor (photovoltaic) device structure that layers an intrinsic semiconductor between a p-type semiconductor and an n-type semiconductor; this…
P-site Abbreviation for peptidyl-tRNA binding site.
P-Type Semiconductor A semiconductor in which holes carry the current; produced by doping an intrinsic semiconductor with an electron acceptor impurity (e.g.
P.T Pipe thread.
P1, P2 Generational symbols for the two parents of a given individual.
P1-derived artificial chromosome (PAC) One type of vector used to clone DNA fragments (100- to 300-kb insert size; average, 150 kb) in Escherichia coli cells.
p53 A gene which normally regulates the cell cycle and protects the cell from damage to its genome.
p53 gene A tumor suppressor gene that normally inhibits the growth of tumors. This gene is altered in many types of cancer.
PAC Patent Assistance Center (prior), now the Inventors Assistance Center or IAC, call (toll-free) 1-800-786-9199 or 703-308-4357
pachynema A mid-prophase stage in the first meiotic division, between zygonema and diplonema. Chromosomes appear as long, paired threads.
pachytene (adj.) See: pachynema.
Pacific Decadal Oscillation (Abbrev. PDO) - a recently described pattern of climate variation similar to ENSO though on a timescale of decades and not seasons.
Pacific flyway An established air route of migratory birds along the west coast of the United States.
packaging cell line A cell line designed to produce viral particles that do not contain nucleic acid.
packed cell volume (Abbreviation: PCV). The proportion of a cell culture volume that is occupied by cells.
Packing Factor The ratio of solar collector array area to actual land area.
PAGE A single image of the equivalent of one piece of paper. One or several pages make up a Document.
pair-rule gene A gene that influences the formation of body segments in Drosophila.
pairing The pairing of homologous chromosomes during the prophase of the first meiotic division.
palaeontology The study of the fossil record of past geological periods and of the phylogenetic relationships between extinct and contemporary plant and animal species.
Paleo- Refers to the studies of the geolgic past.
paleoclimate past or ancient climates.
paleoclimatologist one who studies ancient (paleo-) climate.
paleoenvironmental proxy an environmental relict (pollen grains, tree rings, lake sediments, pack rat middens, ice cores, coral skeletons) that is used by scientists to infer past…
Paleoflood Paleoflood peak discharges are estimated using geology, fluvial, geomorphology, and stratigraphic records.
Paleoflood data Paleoflood data include two broad categories: fluvial geomorphic evidence and botanical evidence.
Paleoflood hydrology The study of past or ancient floods which occurred prior to the time of human observation or direct measurement by modern hydrologic procedures.
Paleontological resources Fossilized remains, imprints, and traces of plants and animals preserved in rocks and sediments since some past geologic time.
Paleontology The study of the fossil record of past geo- logical periods and of the phylogenetic relationships between ancient and contemporary plant and animal…
Paleozoic An era of geologic time, from the end of the Precambrian to the beginning of the Mesozoic, spanning the time between 542 and 251 million years ago.
Palindrome See Palindromic sequence.
Palindromic sequence A DNA locus whose 5'-to-3' sequence is identical on each DNA strand. The sequence is the same when one strand is read left to right and the other strand…
palisade parenchyma Elongated cells found just beneath the upper epidermis of leaves, typically rich in chloroplasts.
Palm oasis (1) A desert habitat with permanent water or a water table near the surface that supports a canopy of palm trees.
Palmer Drought Severity Index An index whereby excesses or deficiencies of precipitation are determined in relation to average climate values.
Palustrine habitat Marsh habitat.
Palustrine wetlands Shallow freshwater wetlands that often support plant communities of trees, shrubs, emergent plants, mosses, or lichens.
pAMP Ampicillin-resistant plasmid developed for this laboratory course. (See Plasmid.)
Pan evaporation A measurement that combines or integrates the effects of several climate elements: temperature, humidity, solar radiation, and wind.
Pan Pan A headline within National Weather Service high seas forecasts transmitted via the GMDSS to indicate that a hurricane or hurricane force winds are…
Pancake Ice Circular flat pieces of ice with a raised rim; the shape and rim are due to repeated collisions.
pancreas A glandular organ located in the abdomen. It makes pancreatic juices, which contain enzymes that aid in digestion, and it produces several hormones…
Pancreatic beta cells Cells of the pancreas (located in pancreatic islets, or islets of Langerhans) that produce insulin.
Pancreatic polypeptide An endocrine protein produced by islet cells of the pancreas.
Pane (Window) The area of glass that fits in the window frame.
Panel (Solar) A term generally applied to individual solar collectors, and typically to solar photovoltaic collectors or modules.
Panel Radiator A mainly flat surface for transmitting radiant energy.
Panemone A drag-type wind machine that can react to wind from any direction.
Panhandle Hook Low pressure systems that originate in the panhandle region of Texas and Oklahoma which initially move east and then "hook" or recurve more northeast…
panicle An inflorescence, the main axis of which is branched; the branches bear loose racemose flower clusters.
panicle culture Aseptic culture of immature panicle explants to induce microspore germination and development.
panmictic population A population in which mating occurs at random.
panmixis Random mating in a population.
paper raft technique See: nurse culture.
PAR Performance and Accountability Report -- see Annual Reports for more
par gene One of a class of genes required for faithful plasmid segregation at cell division.
Parabolic Aluminized Reflector Lamp A type of lamp having a lens of heavy durable glass that focuses the light. They have longer lifetimes with less lumen depreciation than standard…
Parabolic Dish A solar energy conversion device that has a bowl shaped dish covered with a highly reflective surface that tracks the sun and concentrates sunlight on a…
Parabolic solar collector trough See Parabolic trough
Parabolic Trough A solar energy conversion device that uses a trough covered with a highly reflective surface to focus sunlight onto a linear absorber containing a working…
Parabolic trough system See Parabolic trough
paracentric inversion A chromosomal rearrangement in which a segment of chromosome, excluding the centromere, is rotated.
Paracrine factors Cytokines or hormones that act on cells or tissues within an extremely limited area.
Paradox gate Similar to a ring follower gate except the gate leaf is supported along either side by endless trains of rollers.
paraffin [wax] A translucent, white, solid hydrocarbon with a low melting point. One use is as an embedding medium to support tissue for sectioning for light microscopy…
Parafilmä A stretchable film based on paraffin wax; used to seal tubes and Petri dishes. Parafilmä is a proprietary name which is incorrectly applied colloquially…
parahormone A substance with hormone-like properties that is not a secretory product (e.g. ethylene; carbon dioxide).
Parallax A method of finding astronomical distances. One uses a super distant background of stars as a reference plane, and observes the difference in position of…
Parallel Transmission of all the bits (e.g. in a character) at the same time. If the character has eight bits, there are eight wires.
Parallel Connection A way of joining photovoltaic cells or modules by connecting positive leads together and negative leads together; such a configuration increases the…
parallel evolution The development of different organisms along similar evolutionary paths due to similar selection pressures acting on them.
Parallel path flow As defined by the North American Electric Reliability Council, this refers to the flow of electric power on an electric system's transmission facilities…
paralogous Homologous genes/gene products that have duplicated and evolved divergently within a species. e.g. beta- and gamma-globulin genes
parameter A value or measurement that varies with circumstances, and is used as a reference to quantify a situation or a process.
Parametric Data Data such as rating curves, unit hydrographs, and rainfall/runoff curves which define hydrologic variables in models.
Paranormal Literally, “above normal,” it refers to anything outside or beyond current scientific explanation.
Paranormal Pop Culture Term given to paranormal-themed movies, TV shows, comic books, video games, music and literature; also known as “entertainment of the unexplained.”
Paranormal Tourism The niche within the travel industry where tourists attend paranormal-themed conventions and festivals, investigate famously haunted locations (or camp…
Parapet Wall A solid wall built along the top of a dam (upstream and/or downstream edge) used for ornamentation, for safety of vehicles and pedestrians, or to prevent…
parasexual cycle A sexual cycle involving changes in chromosome number but differing in time and place from the usual sexual cycle; occurring in those fungi in which the…
parasexual hybridization See: somatic hybridization.
parasite An animal or plant that gets nutrients by living on or in an organism of another species.
Parasitism The closee association of two or more dissimilar organisms where the association is harmful to at least one. See Commensalism, Parasitism, Symbiosis.
parasporal crystal Tightly packaged insect pro-toxin molecules that are produced by strains of Bacillus thuringiensis during the formation of resting spores.
paratope Synonym for antibody binding site.
Parcel A volume of air small enough to contain uniform distribution of its meteorological properties and large enough to remain relatively self-contained and…
Pareidolia Also known as “matrixing,” it is the brain’s perception of a meaningful pattern within random sounds or images.
parenchyma (pah-REN-kih-ma) The essential or functional elements of an organ.
parenchymatous (adj.) See: parenchyma.
Parent A radionuclide that decays to another nuclide which may be either radioactive or stable.
Parhelion The scientific name for sun dogs. Either of two colored luminous spots that appear at roughly 22 degrees on both sides of the sun at the same elevation.
Parkinson disease (PAR-kin-sun dih-ZEEZ) A progressive disorder of the nervous system marked by muscle tremors, muscle rigidity, decreased mobility, stooped posture, slow…
Parkinson's disease A common progressive neurological disorder that results from degeneration of nerve cells in a region of the brain that controls movement.
Parsec A unit of distance, derived from a technique of finding distances to astronomical objects, called parallax. 3.1 x 1013 km or 3.26 light years.
Parshall Flume (Improved Venturi Flume) A flume with a specially shaped open-channel flow section that may be installed in a drainage lateral or ditch to measure the rate of flow of water.
parthenocarpy The development of fruit without fertilization.
Parthenogenesis Production of an embryo from an unfertilized egg.