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Density matrix renormalization group
The density matrix renormalization group (DMRG) is a numerical algorithm introduced by Steven R. White in 1992 for computing ground states of quantum many-body systems.
Density modification
Density modification is a family of crystallographic methods for improving initial phase estimates by modifying an electron-density map through solvent flattening, histogram matching, and non-crystallographic symmetry averaging.
Density of air
Density of air, or air density, is the mass of Earth's atmosphere in a unit volume, about 1.225 kg/m³ at sea level, falling with altitude, temperature, and humidity.
Density of states
The density of states (DOS) is a function giving the number of available quantum states per unit energy interval, central to solid-state physics, semiconductors, and materials science.
Density parameter
The density parameter, written Ω (Omega), is the ratio of the actual mean density of the universe or a component to the critical density, and the components sum to 1.
Density wave theory
Density wave theory, proposed by C. C. Lin and Frank Shu in 1964, explains spiral arms in galaxies as waves of enhanced density that stars and gas pass through.
Denudation
Denudation, from the Latin denudare meaning "to lay bare," is the total lowering of the land surface by weathering and erosion acting together, and is broader than erosion alone.
Denver–Julesburg Basin
The Denver–Julesburg Basin, shortened to DJ Basin and also called the Denver Basin, is a Laramide-age petroleum basin underlying eastern Colorado, Wyoming, Nebraska, and Kansas.
Denys Makarov
Denys Makarov is a Ukrainian-born materials scientist working on curvilinear magnetism and flexible magnetoelectronics, head of the Intelligent Materials and Systems department at the Helmholtz-Zentrum Dresden-Rossendorf since 2019.
Denys Wilkinson
Sir Denys Haigh Wilkinson (1922–2016) was a British experimental nuclear physicist who tested isospin rules, invented the Wilkinson analog-to-digital converter, and later served as Vice-Chancellor of Sussex.
Deontic logic
Deontic logic, or deontic modal logic, is the branch of logic studying obligation, permission, and prohibition, with roots in ethics and law and modern uses in computer science.
Deoxycorticosterone
Deoxycorticosterone (DOC), also called 11-deoxycorticosterone or cortexone, is a steroid hormone synthesized by the adrenal gland, a precursor of corticosterone and aldosterone with mineralocorticoid activity.
Deoxycytidine
Deoxycytidine (2′-deoxycytidine, dC) is a pyrimidine deoxyribonucleoside, one of the four nucleoside components of DNA, and the metabolic starting point for anticancer drugs such as gemcitabine and cytarabine.
Deoxydehydration
Deoxydehydration (DODH) is a catalytic reaction that removes two adjacent hydroxyl groups from a vicinal diol to form an alkene, studied for converting biomass polyols to olefins.
Deoxyfluorination
Deoxyfluorination is a chemical reaction that replaces oxygen-containing groups with fluorine, converting alcohols into alkyl fluorides and carbonyls into geminal difluorides; it is the most widely used method for installing aliphatic C–F bonds.
Deoxygenative alkylation
Deoxygenative alkylation is a set of synthetic organic reactions in which an alcohol's hydroxyl group is replaced by an alkyl group, usually via radical intermediates under photoredox or metal catalysis.
Deoxyguanosine
Deoxyguanosine (2′-deoxyguanosine, abbreviated dGuo or dG) is one of the four deoxynucleoside building blocks of DNA, consisting of the nucleobase guanine attached to a deoxyribose sugar.
Deoxyhypusine
Deoxyhypusine is a non-proteinogenic L-lysine derivative, Nε-(4-aminobutyl)-lysine, formed by deoxyhypusine synthase on eIF5A as the intermediate in hypusine biosynthesis, which activates eIF5A in eukaryotic and archaeal cells.
Deoxynojirimycin
Deoxynojirimycin (1-DNJ, DNJ), also known as moranoline, is a naturally occurring iminosugar from mulberry that potently inhibits α-glucosidase; its derivatives miglitol, miglustat, and migalastat are approved medicines.
Deoxypyridinoline
Deoxypyridinoline (DPD), also called lysyl pyridinoline, is a collagen crosslink found almost exclusively in bone and dentin whose urinary excretion serves as a marker of bone resorption.
Dependent (NIP) theories
Dependent (NIP) theories, meaning theories without the independence property, are first-order theories in which no formula encodes the random bipartite graph; introduced by Shelah, they include the real field and p-adic numbers.
Dependent and independent variables
The dependent variable is the outcome a study measures, and the independent variable, or predictor, is the factor that is manipulated or treated as the explanation for changes in that outcome.
Dependent Dirichlet process
The dependent Dirichlet process is a collection of random probability measures indexed by a covariate or time, each marginally Dirichlet-process distributed, introduced by MacEachern in 1999 to model how a distribution changes with inputs.
Dependent random choice
Dependent random choice is a probabilistic technique in combinatorics that extracts a large vertex subset with many common neighbors from a dense graph, enabling greedy embedding of sparse bipartite graphs.
Dependent type
Dependent typing is the defining feature of dependent type theories: a family of types indexed by a value, so each value may yield a distinct type.
Dephasing
Dephasing is the loss of phase coherence in a quantum state when relative phases become unpredictable, the main limit on how long a qubit holds a superposition.
Depleted uranium
Depleted uranium (DU), also known as Q-metal or Depletalloy, is uranium with its uranium-235 content reduced to about 0.2%, produced as a by-product of enrichment and used in tank armor and armor-piercing munitions.
Depletion force
The depletion force is an attractive effective force between colloids when smaller, non-adsorbing solutes like polymers are expelled from the gap, proposed by Asakura and Oosawa in 1954.
Depletion region
A depletion region, also called a space charge region or depletion layer, is the zone at a semiconductor junction stripped of mobile carriers, forming the nonconducting core of every diode.
Depolarizing channel
The depolarizing channel is the standard symmetric noise model in quantum information theory, applying bit flips, phase flips, and combined flips with equal probability, analogous to the binary symmetric channel.