shotgun sequencingAn approach used to decode an organism's genome by shredding it into smaller fragments of DNA which can be sequenced individually.
Shoulder (shell)The upstream and downstream parts of the cross section of an embankment dam on each side of the core or core wall.
Showalter Index(Abbrev. SWI) - a stability index used to determine thunderstorm potential. The SWI is calculated by lifting an air parcel adiabatically from 850 mb to…
ShowerA descriptor, SH, used to qualify precipitation characterized by the suddenness with which they start and stop, by the rapid changes of intensity, and…
Shrink-swell potentialThe extent to which soil shrinks or swells with changes in soil moisture content.
ShrinkageLoss of bulk of soil when compacted in a fill.
Shrinkage index (SI)The numerical difference between the plastic and shrinkage limits.
Shrinkage limit (SL)The maximum water content at which a reduction in water content will not cause a decrease in volume of the soil mass.
Shrinkage ratio (R)The ratio of a given volume change, expressed as a percentage of the dry volume, to the corresponding change in moisture content above the shrinkage…
SHRTWVShortwave - a disturbance in the mid or upper part of the atmosphere which induces upward motion ahead of it.
ShrubA plant with persistent woody stems and relatively low growth form; usually produces several basal shoots as opposed to a single bole; differs from a tree…
Shrub-steppeHabitat primarily composed of various shrubs and grasses.
Shrubsteppe obligateA species that is dependent on shrubsteppe habitats to provide food and/or habitat necessary for its survival.
Shunt LoadAn electrical load used to safely use excess generated power when not needed for its primary uses.
ShutterAn interior or exterior movable panel that operates on hinges or slides into place, used to protect windows or provide privacy.
shuttle vectorA plasmid capable of replicating in two different host organisms because it carries two different origins of replication and can therefore be used to…
sib-matingThe deliberate crossing of siblings. Generally done where self-incompatibility prevents the production of self-fertilized progeny.
Siberian HighSiberian High An area of high pressure which forms over Siberia in winter, and which is particularly apparent on mean charts of sea-level pressure.
sickle cell disease(SIH-kul sel dih-ZEEZ) An inherited disease in which the red blood cells have an abnormal crescent shape, block small blood vessels, and do not last as…
Side Channel SpillwayA spillway whose crest is roughly parallel to the channel immediately downstream of the spillway.
Side population (SP) stem cellTwo examples of multipotent stem cell populations found in bone marrow and skeletal muscle. SPs are not yet fully characterized.
SidelobeA secondary energy maximum located outside the main radar beam. Typically, it contains a small percentage of energy compared to the main lobe, but it may…
siderophoreA low molecular weight entity that binds very tightly to iron. Siderophores are synthesized by a variety of soil micro-organisms to ensure that the…
SidingA construction element applied to the outermost surface of an exterior wall.
sieve cellA long and slender sieve element in vascular plants, characterized by relatively unspecialized sieve areas and tapering end walls that lack sieve plates.
sieve elementThe phloem cell concerned with longitudinal conduction of food materials.
sieve platePerforated wall area in a sieve tube element, through which strands connecting sieve tube protoplasts can pass.
sieve tubeA tube within the phloem tissue of a plant, composed of joined sieve elements.
sievert (Sv)A unit for expressing the equivalent magnitude of an absorbed dose which has been adjusted by a factor that expresses the relative tissue damage potential…
sigma factorThe sub-unit of prokaryotic RNA polymerases responsible for the initiation of transcription at specific initiation sequences.
Sigma HeatThe sum of sensible heat and latent heat in a substance above a base temperature, typically 32 degrees Fahrenheit.
signal sequenceA stretch of 15-30 amino acid residues at the N terminus of a protein, which is thought to enable the protein to be secreted (pass through a cell…
signal transduction(SIG-nul trans-DUK-shun) The process by which a cell responds to substances in its environment.
Signal-to-Noise RatioA specifically produced response (signal) compared to the response level (noise) when no specific stimulus (activity) is present.
SignalsInternal and external factors that control changes in cell structure and function.
Significant hazardA downstream hazard classification for dams in which 1-6 lives are in jeopardy and appreciable economic loss (rural area with notable agriculture…
Significant Wave HeightThe average height of the one-third highest waves of a given wave group.
Significant Weather OutlookA narrative statement produced by the National Weather Service, frequently issued on a routine basis, to provide information regarding the potential of…
SilencerA device used for reducing noise within air and gas flow systems.
silencingLoss of gene expression either through an alteration in the of a structural gene, or its regulatory region; or because of interactions between its…
Silicic volcanismVolcanism characterized by the eruption of magma that is rich in lighter elements such as silicon, oxygen, aluminum, sodium, and potassium.
SiliconA chemical element, of atomic number 14, that is semi-metallic, and an excellent semiconductor material used in solar photovoltaic devices; commonly found…
Sill1.The lower horizontal part of a window frame or window opening; also the accessory member which extends as a weather barrier from frame to outside face…
SiltA rock or mineral fragment of any composition that has a diameter ranging from 0.002 to 0.05 millimeter.
Silt (rock flour)The fine-grained portion of soil that is nonplastic or very slightly plastic and that exhibits little or no strength when air dry.
SiltationProcess by which loose soil is transferred and builds up in streams, rivers, and lakes, causing changes in stream channels and in depth.
SiltingFilling with soil or mud deposited by water.
SiltstoneA sedimentary rock made mostly of silt-sized grains.
SilvicultureThe theory and practice of forest stand establishment and management.
Simple CS (Caulk and Seal)A technique for insulating and sealing exterior walls that reduces vapor diffusion through air leakage points by installing pre-cut blocks of rigid foam…
Sine WaveThe type of alternative current generated by alternating current generators, rotary inverters, and solid-state inverters.
Single Cell ThunderstormThis type of thunderstorm develops in weak vertical wind shear environments. On a hodograph, this would appear as a closely grouped set of random dots…
single copyA gene or DNA sequence which occurs only once per (haploid ) genome. Many structural genes are single copy.
Single Glaze or PaneOne layer of glass in a window frame. It has very little insulating value (R-1) and provides only a thin barrier to the outside and can account for…
single node cultureCulture of separate lateral bud s, each carrying a piece of stem tissue.
single nucleotide polymorphism(... NOO-klee-oh-TIDE PAH-lee-MOR-fih-zum) The most common type of change in DNA (molecules inside cells that carry genetic information).
Single nucleotide polymorphism (SNP)DNA sequence variations that occur when a single nucleotide (A, T, C, or G) in the genome sequence is altered.
single primer amplification reaction(Abbreviation: SPAR). A PCR-based genotyping technique in which genomic template is amplified with a single primer.
Single-cell clonedA procedure pertaining to cells in vitro in which the descendants of a single cell are physically isolated from other cells growing in a dish, and then…
single-cell protein(Abbreviation: SCP). Protein produced by micro-organisms, particularly yeast. Used as either a feed or a food additive.
single-column modeling (SCM)An approach to the development and testing of cloud formation and parameterizations.
Single-Crystal MaterialIn reference to solar photovoltaic devices, a material that is composed of a single crystal or a few large crystals.
Single-gene disorderHereditary disorder caused by a mutant allele of a single gene (e.g., Duchenne muscular dystrophy, retinoblastoma, sickle cell disease).
Single-Package SystemA year 'round heating and air conditioning system that has all the components completely encased in one unit outside the home.
Single-PhaseA generator with a single armature coil, which may have many turns and the alternating current output consists of a succession of cycles.
single-strand DNA binding proteinA protein that coats single-stranded DNA, preventing renaturation and so maintaining the DNA in an extended state.
single-stranded DNA(Abbreviation: ssDNA). DNA molecules separated from their complementary strand, either by its absence or following denaturation.
single-stranded nucleic acidNucleic acid molecules consisting of only one polynucleotide chain. The genomes of many viruses are single-stranded DNA molecules, as are most…
SinkAny process, activity, or mechanism which removes a greenhouse gas, an aerosol, or a precursor of a greenhouse gas or aerosol from the atmosphere.
SinkholeA steep-sided depression formed when removal of subsurface embankment or foundation material causes overlying material to collapse into the resulting void.
SinuosityThe ratio of the length of a river's thalweg to the length of the valley proper. A measure of a river's meandering. Rivers with a sinuosity less than 1.
SiphonA pipe connecting two canals. A tube or pipe through which water flows over a high point by gravity.
Siphon SpillwayA spillway with one or more siphons built at crest level. This type of spillway is sometimes used for providing automatic surface-level regulation within…
Siphon tubeRelatively short, light-weight, curved tube used to convey water over ditch banks to irrigate furrows or borders.
SiphonageA partial vacuum created by the flow of liquids in pipes.