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Distance redshift relation
The distance redshift relation links an object's redshift, the stretching of its light by cosmic expansion, to its distance; measured with supernovae, it revealed the accelerating expansion driven by dark energy.
Distance sampling
Distance sampling is a suite of survey methods, built on line and point transects, that estimates animal or plant density and abundance from measured distances to detected individuals.
Distance-regular graph
A distance-regular graph is a connected graph where, for any two vertices at a given distance, the counts of neighbors at each distance depend only on that distance.
Distorted-wave Born approximation
The distorted-wave Born approximation (DWBA) is a perturbative method in scattering theory treating strong refraction and reflection exactly, developed by George Vineyard in 1982 for grazing-incidence X-ray and neutron scattering.
Distortion (optics)
Distortion, also called lens distortion or image distortion, is an optical aberration in which magnification varies across the field, rendering straight lines as barrel- or pincushion-shaped curves.
Distributary channel
A distributary channel is a stream branch carrying water and sediment away from a main channel rather than adding to it as a tributary does, forming river deltas.
Distributed acoustic sensing
Distributed acoustic sensing, or DAS, also called distributed vibration sensing, is a fiber-optic technique that turns standard optical fiber into a dense array of vibration sensors.
Distributed algorithm
A distributed algorithm is a concurrent algorithm executed by multiple processors that lack shared memory and a common clock, coordinating only by message passing across a network.
Distributed Bragg reflector
A distributed Bragg reflector, or Bragg mirror, is a mirror of alternating dielectric layers, each a quarter wavelength thick, whose reflections add constructively at a design wavelength.
Distributed fiber optic sensing
Distributed fiber optic sensing is a measurement technique that turns an ordinary optical fiber into thousands of sensors, measuring temperature, strain, or vibration along up to 100 km.
Distributed lag model
A distributed lag model is a time series regression that estimates a predictor's effect on an outcome as spread over several past values, with coefficients called lag weights.
Distributed lag non-linear model
The distributed lag non-linear model (DLNM) is a regression framework estimating non-linear exposure–outcome relationships and how they unfold over time lags, developed for environmental epidemiology.
Distributed temperature sensing
Distributed temperature sensing (DTS) is a measurement technique that uses optical fiber as a continuous temperature sensor, reading temperature at every point along cables up to 30 km long.
Distribution (mathematics)
In mathematics, a distribution, also known as a Schwartz distribution or generalized function, is an object that extends the notion of function, making differentiation possible for every element.
Distribution fitting
Distribution fitting is the statistical method of selecting a candidate probability distribution family, estimating its parameters from data, and assessing how well the fitted distribution reproduces the data.
Distributional regression
Distributional regression is a class of statistical models that estimates the full conditional distribution of a response given explanatory variables, capturing variance, skewness, and tails.
Distributive lattice
Distributive lattice: a lattice whose meet and join satisfy the distributive laws; examples include power sets and products of chains. Characterized by forbidden sublattices N5 and M3, and finite ones are lattices of order ideals of a poset (Birkhoff).
Distributive property
The distributive property, also called the distributive law, is the arithmetic rule that a factor times a sum equals the sum of the factor times each addend, written a(b + c) = ab + ac.
Disulfide
A disulfide is a chemical compound containing a covalent sulfur–sulfur single bond, R–S–S–R′, formed by oxidation of thiols; in proteins, disulfide bonds between cysteine residues stabilize secreted proteins.
Dither
Dither, also known as dithering, is low-level noise deliberately added to a signal before quantization, replacing signal-dependent distortion with a benign noise floor when audio bit depth is reduced.
Dithiane
Dithiane is a saturated six-membered heterocycle with two sulfur atoms and four carbon atoms; 1,3-dithiane, a cyclic thioacetal of formaldehyde, acts as a masked carbonyl group in umpolung synthesis.
Dithiocarbamate
A dithiocarbamate is a monoanionic sulfur-containing ligand, R₂N–C(S)–S⁻, formed from a primary or secondary amine and carbon disulfide, used in metal coordination, fungicides, rubber vulcanization, and mineral flotation.
Dithioesters
Dithioesters are organosulfur compounds of formula R–C(=S)–S–R′, the sulfur analogs of carboxylate esters with both oxygens replaced by sulfur, best known as RAFT chain-transfer agents for living radical polymerization.
Dithiol (analytical reagent)
Dithiol (toluene-3,4-dithiol, C₇H₈S₂) is a colorimetric reagent described in 1936 by W. H. Mills and R. E. D. Clark that forms colored complexes with tin, molybdenum, and tungsten.
Dithionite
Dithionite is the sulfur oxoanion S₂O₄²⁻, a strong reducing agent whose sodium salt, sodium dithionite, is used at industrial scale in vat dyeing, pulp bleaching, and groundwater remediation.
Dithiothreitol
Dithiothreitol (DTT), also called Cleland's reagent, is a dithiol reducing agent introduced by W. W. Cleland in 1964 to reduce disulfide bonds and keep thiol groups reduced.
Dithizone
Dithizone, or diphenylthiocarbazone, is an intensely dark-green chelating reagent that forms brightly colored, water-insoluble complexes with heavy metals, long used for extracting and measuring trace metals such as lead and mercury.
Diuron
Diuron is a phenylurea herbicide and algicide that blocks photosynthesis in weeds and algae, used on crops like sugarcane and cotton and as a paint preservative.
Divacancy in silicon carbide
The divacancy in silicon carbide is a point defect of neighboring missing silicon and carbon atoms whose spin-1 state serves as a qubit and quantum sensor with near-infrared emission.
Divergence
Divergence, or divergence operator, is a vector calculus operator measuring a vector field's net outflow per unit volume, positive at sources and negative at sinks.