Science terms starting with O

286 terms

One-Axis Tracking A system capable of rotating about one axis.
Ongoing Visual Inspection (OVI) The Ongoing Visual Inspection Checklist identifies specific visual inspection items that should regularly receive special attention.
Onroad mobile source (emissions) Any mobile source of air pollution such as cars, trucks, motorcycles, and buses that travels on roads and highways.
Onshore Breeze A wind that blows from a body of water towards the land. Also known as a seabreeze
Onshore Flow Occurs when air moves from sea to land, and is usually associated wtih increased moisture.
Onsite Coordinator (OSC) For Reclamation-operated facilities, the OSC is any employee discovering hazardous or suspected hazardous waste on Reclamation lands.
ontogeny Developmental life history of an organism.
Oocyte The egg mother cell; it undergoes two meiotic divisions (oogenesis ) to form the egg cell.
Oocytes Egg cells.
oogenesis The formation and growth of the egg in an animal ovary.
oogonium 1. A germ cell of the female animal, that gives rise to oocytes by mitotic division. 2. The female sex organ of algae and fungi.
oosphere The non-motile female gamete in plants and some algae.
oospore A spore developing from a zygote of certain algae and fungi, following the fusion of heterogametes.
Opacity The degree to which smoke or particles emitted into the air reduce the transmission of light and obscure the view of an object in the background.
opal stop codon See: stop codon.
Opaque A condition where a material, such as a cloud, blocks the passage of radiant energy, especially light.
Opaque to Radiation A condition when radiation is absorbed or scattered many times. For the first 400,000 years the universe was so hot that the matter was ionized and…
OPC Ocean Prediction Center (Formally the Marine Prediction Center. An NCEP center which produces marine forecasts north of 30oN.
Open Access The ability to send or wheel electric power to a customer over a transmission and distribution system that is not owned by the power generator (seller).
Open access same-time information system (OASIS) An electronic information system that allows users to instantly receive data on the current operating status and transmission capacity of a transmission…
open continuous culture A continuous culture system, in which inflow of fresh medium is balanced by outflow of a corresponding volume of spent medium plus cells.
Open Lakes Forecast (GLF) - A National Weather Service marine forecast product for the U.S. waters within a Great Lake not including the waters covered by an existing…
Open outcry When exchange-based commodities traders shout out their buy and sell orders or use a combination of words and hand signals to negotiate an order, it's…
Open pollination Pollination by wind, insects, or other natural mechanisms.
Open reading frame A long DNA sequence that is unin- terrupted by a stop codon and encodes part or all of a protein. (See Reading frame.)
Open reading frame (ORF) The sequence of DNA or RNA located between the start-code sequence (initiation codon) and the stop-code sequence (termination codon).
Open Space Used to describe undeveloped land or land that is used for recreation. Farmland as well as all natural habitats (forests, fields, wetlands etc.
Open Space Residential Design (OSRD) A form of residential subdivision that maximizes resource protection and conservation of natural areas through the use of design strategies that result in…
Open transmission access Enables all participants in the wholesale market equal access to transmission service, as long as capacity is available, with the objective of creating a…
Open Universe , Ω A universe where the geometry of space is curved like an infinite saddle-shaped surface.
Open-Circuit Voltage The maximum possible voltage across a photovoltaic cell; the voltage across the cell in sunlight when no current is flowing.
Open-cut A method of excavation in which the working area is kept open to the sky. Used to distinguish from cut-and-cover and underground work.
Open-Loop Geothermal Heat Pump System Open-loop (also known as "direct") systems circulate water drawn from a ground or surface water source.
Open-work materials Poorly-graded (uniform or gap-graded gradation) gravels, cobbles and boulders with few fines in the matrix, resulting in a deposit containing a large…
Operating basis earthquake (OBE) The earthquake that the structure must safely withstand with no damage. All systems and components necessary to the uninterrupted functioning of the…
Operating Cycle The processes that a work input/output system undergoes and in which the initial and final states are identical.
Operating log. See logbook.
Operating reserve Generation capacity dedicated to maintaining adequate and reliable system operation during sudden reduction in system capacity.
Operating reserves That capability above firm system demand required to provide for regulation, load forecasting error, equipment forced and scheduled outages, and local…
operational definition An operation or procedure that can be carried out to define or delimit something.
Operational losses Losses of water resulting from evaporation, seepage, and spills.
Operational Products A product that has been fully tested and evaluated and is produced on a regular and ongoing basis.
Operational waste Water that is lost or otherwise discarded from an irrigation system after having been diverted into it as part of normal operations.
Operations and Maintenance (O&M) Operations and maintenance (O&M) activities protect the integrity of the selected cleanup plan for a Superfund site.
Operations and maintenance costs The ongoing, repetitive costs of operating and maintaining a water system.
operator A prokaryotic regulatory element that interacts with a repressor to control the transcription of adjacent structural genes.
Operon A functionally integrated genetic unit for the control of gene expression in bacteria.
OPINE The condensation product of an amino acid with either a keto-acid or a sugar, produced by the plant host as a result of Agrobacterium infection, and used…
optical depth A measure of how much light airborne particles, whether aersols, cloud droplets, or ice particles, prevent from passing through a column of atmosphere.
Optimum moisture content, or Optimum water content The one water content (percent of dry weight of the total material) of a given soil and a given compactive effort that will result in a maximum dry…
Option value Value associated with people who know they can visit an area in the future if they so desire.
OPU Abbreviation for ovum pickup.
ORB An often translucent, circular anomaly (or “ball of light”) seen in photography -- and sometimes with the naked eye -- that may be, depending on your…
orbital cycles variations in the Earth's orbit around the sun with periods of 23,000 (precession of the equinoxes), 41,000 (obliquity), and 100,000 years (eccentricity).
Ore Rock or earth containing workable quantities of a mineral or minerals of commercial value.
ORF Abbreviation for open reading frame.
organ A part of the body that performs a specific function. For example, the heart is an organ.
organ culture The aseptic culture of complete living organs of animals and plants outside the body in a suitable culture medium.
organellar gene Genes located on organelles outside the nucleus.
organelle (OR-guh-NEL) A small structure in a cell that is surrounded by a membrane and has a specific function.
Organic Derived from living organisms.
Organic agriculture A concept and practice of agricultural production that focuses on production without the use of synthetic pesticides.
organic complex A chemically undefined compound added to nutrient media to stimulate growth, e.g. coconut milk; malt extract; yeast extract; casein hydrolysate.
Organic compound An organic compound contains carbon chemically bound to hydrogen. Organic compounds often contain other elements (particularly O, N, halogens, or S).
Organic compounds Chemical compounds based on carbon chains or rings and also containing hydrogen, with or without oxygen, nitrogen, and other elements.
organic evolution See: evolution.
Organic fertilizer Organic material such as manure or compost, applied to cropland as a source of plant nutrients.
Organic level The amount of organic matter prescribed to be left after logging.
organism A living thing, such as an animal, a plant, a bacterium, or a fungus.
organized growth The development under tissue culture conditions of organized explants (meristem tips or shoot tips, floral buds or organ primordia).
organized tissue Composed of normally differentiated cells.
organogenesis The initiation of adventitious or de novo shoots or roots from callus, meristem or suspension cultures. See: micropropagation; regeneration.
organoid An organ-like structure produced in culture.
organoleptic Having an effect on one of the organs of sense, such as taste or smell.
Orientation The alignment of a building along a given axis to face a specific geographical direction.
Orifice An opening with a closed perimeter and a regular form through which water flows.
ORIG Original
Origin of replication The nucleotide sequence at which DNA synthesis is initiated.
Original ground (surface) The surface of the earth as it exists in an unaltered state (i.e. prior to any earthwork). See existing ground.
Orographic Related to, or caused by, physical geography (such as mountains or sloping terrain).
Orographic Lifting Same as Upslope Flow; occurs when air is forced to rise and cool due to terrain features such as hills or mountains.
Orographic Precipitation Precipitation which is caused by hills or mountain ranges deflecting the moisture-laden air masses upward, causing them to cool and precipitate their…
Orographic Uplift Same as Orographic Lifting; occurs when air is forced to rise and cool due to terrain features such as hills or mountains.
Orographic Waves A wavelike airflow produced over and in the lee of a mountain barrier.
Orphan Anvil Slang for an anvil from a dissipated thunderstorm, below which no other clouds remain.
orphan gene A gene or DNA sequence whose function is not known.
orphan receptor A receptor for which a cellular function or ligand has yet to be identified.
ortet The plant from which a clone is obtained. Synonym: donor plant.
orthologous Homologous genes/gene products that have evolved divergently between species; many rice genes have orthologues in other cereal genomes, because of the…
Oscillation A shift in position of various high and low pressure systems that in climate terms is usually defined as an index (i.e.
OSHA See Occupational Safety and Health Administration.
osmosis Diffusion of water across a semi-permeable membrane from zones of low solute concentration to zones of higher solute concentration.
osmotic potential Change in the energy state of solvent brought about by dissolving a substance in the solvent - water in the biological sciences.
osmoticum A chemical agent (e.g. polyethylene glycol, mannitol, glucose or sucrose) employed to maintain the osmotic potential of a nutrient medium equivalent to…
Osteocalcin (OC) A cytokine produced by osteoblasts that promotes bone formation.
Osteoclast A giant multi-nuclear cell formed in the bone marrow of growing bones.
Osteocyte A cell from the bone tissue.
Osteogenesis imperfecta A large and miscellaneous group of conditions of abnormal fragility and plasticity of bone, with recurring fractures on trivial trauma.
Osteoprogenitor A cell-type that differentiates into a mature osteocyte.
ostracod a small crustacean that lives in either the ocean or in freshwater.