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Defective pixel
A defective pixel, also called a dead pixel, is a pixel in an electronic display that does not work correctly, such as one stuck bright or dark.
Defects per million opportunities
Defects per million opportunities (DPMO) is a Six Sigma measure: defects divided by opportunities for defects, multiplied by one million, standardized at Motorola in 1986.
Deferasirox
Deferasirox is an oral, once-daily iron chelator sold as Exjade and Jadenu that removes excess iron in patients with transfusion-related iron overload, first FDA approved in 2005.
Deferent and epicycle
The deferent and epicycle are two linked circles of the geocentric model: a planet moves on a small epicycle whose center travels a larger deferent around Earth.
Deferiprone
Deferiprone (Ferriprox) is an oral iron chelator developed in the United Kingdom in 1981, used to remove excess iron in transfusion-dependent anemias such as thalassemia and sickle cell disease.
Deferoxamine
Deferoxamine, also known as desferrioxamine and sold as Desferal, is an injectable iron-chelating drug, produced by the bacterium Streptomyces pilosus, used for iron overload and acute iron poisoning.
Definable set
A definable set is a subset of a structure's universe picked out exactly by a first-order formula, and is a basic object of study in model theory.
Definite matrix
A definite matrix is a Hermitian (in the real case, symmetric) matrix whose quadratic form takes values of only one sign, classified as positive, negative, semidefinite, or indefinite.
Definition
A definition is a statement that fixes the meaning, extension, or essence of a term, concept, or thing; varieties include real, nominal, and operational definitions used in science.
Definition of planet
The definition of planet, also called the IAU definition of planet, is the 2006 International Astronomical Union resolution requiring a body to orbit the Sun, be nearly round, and clear its orbital neighborhood.
Deflection (engineering)
In structural and mechanical engineering, deflection is the displacement of a structural element such as a beam or column under load, calculated with Euler-Bernoulli beam theory and capped by building codes as a fraction of span.
Deflection of light by the Sun
The deflection of light by the Sun is the bending of starlight by the Sun's gravity, predicted at 1.75 arcseconds at the solar limb and first measured in 1919.
Defluorinative functionalization
Defluorinative functionalization is a set of organic chemistry methods in which a carbon–fluorine bond is selectively cleaved and replaced by a new C–C or C–X bond.
Defluorinative functionalization of polyfluoroarenes
Defluorinative functionalization of polyfluoroarenes is a set of synthetic methods that selectively cleaves carbon–fluorine bonds in polyfluoroarenes and replaces them with alkyl, aryl, amino, or boryl groups.
Deformable mirror
A deformable mirror is an adaptive optic whose reflective surface is reshaped by an array of actuators to correct wavefront errors, used in astronomy, high-power lasers, and retinal imaging.
Deformation (engineering)
Deformation in engineering is the change in a solid body's size or shape produced by forces or other loads; it is elastic if it disappears when the load is removed, and plastic if it remains.
Deformation (physics)
Deformation in physics is a change in the shape or size of an object caused by applied force. Elastic deformation recovers; plastic deformation does not.
Deformation gradient
The deformation gradient F is a second-order tensor describing how a material deforms locally, defined as the gradient of the motion from reference to current configuration.
Deformation quantization
Deformation quantization is a mathematical technique for constructing quantum theories by deforming the algebra of functions on a classical phase space into a noncommutative star product.
Deformed doubly magic 100Zr
Zirconium-100, also written 100Zr, is a neutron-rich, even-even zirconium isotope discovered in 1970, sitting at the center of an abrupt nuclear shape transition in which its ground state becomes strongly deformed.
Degassing (chemistry)
Degassing in chemistry is the removal of dissolved gases, most often oxygen, from a solvent, done by freeze-pump-thaw cycling, sparging, or vacuum to protect sensitive reactions and measurements.
Degaussing
Degaussing is reducing an object's magnetization to a very low level: first used from 1939 to protect ships from German magnetic mines, later to erase magnetic tapes and hard drives and to correct color CRT screens. Named after the gauss unit.
Degenerate energy levels
Degenerate energy levels, known as quantum degeneracy, occur when two or more quantum states share the same energy; fields split these levels, as in the Zeeman and Stark effects.
Degenerate four-wave mixing
Degenerate four-wave mixing is a third-order nonlinear optical process in which four light waves of the same frequency interact in a material to generate a phase-conjugate wave.
Degenerate matter
Degenerate matter, also called a degenerate Fermi gas, is matter so compressed that degeneracy pressure from the Pauli exclusion principle resists collapse, supporting white dwarfs and neutron stars.
Degenerate perturbation theory
Degenerate perturbation theory extends Rayleigh–Schrödinger perturbation theory to quantum systems where several unperturbed eigenstates share the same energy, central to the Stark and Zeeman effects.
Degree
In mathematics, degree is a numerical measure of size or complexity, most familiarly a polynomial's highest total exponent, also naming the angle unit of 1/360 of a rotation.
Degree (angle)
The degree, also known as the degree of arc, is a unit of angular measure in which a full rotation is 360 degrees; one degree equals π/180 radians.
Degree (graph theory)
Degree (also vertex degree) is a graph theory measure of how many edges meet at a vertex; it underlies the handshaking lemma and degree centrality in networks.
Degree day
A degree day measures how cold or warm a location is, comparing daily mean temperature to a base of 65°F; heating, cooling, and growing degree days track energy use and crops.