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Delta Scuti variable
A Delta Scuti variable, also called a dwarf cepheid, is a pulsating variable star of spectral type A0 to F5, named for the prototype Delta Scuti.
Delta Tauri
Delta Tauri is the Bayer designation for three stars in Taurus, all members of the Hyades cluster: δ¹ Tauri, a K-type giant, plus δ² and δ³ Tauri.
Delta Trianguli
Delta Trianguli (δ Trianguli), officially named Deltoton by the IAU in 2025, is a double-lined spectroscopic binary star about 35 light-years away in Triangulum, with a G-type primary orbiting a lower-mass companion every 10.02 days.
Delta-cadinene
Delta-cadinene is a bicyclic sesquiterpene hydrocarbon, C15H24, made in cotton as the first committed intermediate in gossypol biosynthesis, also found in tea, hops, and iris, and dehydrogenating to cadalene, a higher-plant biomarker.
Delta-matroid
A delta-matroid is a combinatorial structure that generalizes a matroid by replacing equicardinal bases with feasible sets of varying sizes, introduced independently in the mid-1980s by André Bouchet and others.
Delta3 Tauri
Delta3 Tauri, also designated 68 Tauri, is a naked-eye binary star in Taurus, a Hyades cluster member about 149 light-years away and a blue straggler.
Demagnetizing field
The demagnetizing field is the magnetic field generated inside a magnetized body by its own magnetization, opposing it. Described by a demagnetizing factor, it explains shape anisotropy and domain formation.
Demarcation problem
The demarcation problem, or problem of demarcation, is the philosophy of science problem of distinguishing science from pseudoscience and metaphysics; Karl Popper named it in 1933, proposing falsifiability as the criterion.
Demeclocycline
Demeclocycline, also known as demethylchlortetracycline and marketed as Declomycin, is a tetracycline antibiotic isolated from Streptomyces aureofaciens in 1957, used for infections and to raise serum sodium in SIADH hyponatremia.
Demecolcine
Demecolcine, also sold under the name Colcemid, is a colchicine alkaloid isolated from the autumn crocus in 1950 that arrests dividing cells in metaphase for chromosome analysis.
Demetri Psaltis
Demetri Psaltis is an optical scientist and electrical engineer known for holographic data storage, optofluidics, and optical neural networks, who taught at Caltech from 1980 before joining EPFL in Lausanne.
Demetrios Christodoulou
Demetrios Christodoulou, born in Athens in 1951, is a Greek mathematical physicist known for proving black-hole irreducible mass and the nonlinear stability of Minkowski spacetime.
Demetrios N. Christodoulides
Demetrios N. Christodoulides is an optical physicist known for discrete solitons, Airy beams, and parity-time symmetry in optics, holding an engineering chair at USC since 2022.
Demographic and Health Surveys
The Demographic and Health Surveys (DHS) are standardized, nationally representative household surveys collecting population, health, and nutrition data in over 90 low- and middle-income countries since 1984.
Demon core
The demon core was a 6.2 kg plutonium sphere at Los Alamos that killed physicists Harry Daghlian and Louis Slotin in criticality accidents in 1945 and 1946.
Demonstration (teaching)
A demonstration in teaching is an instructional method where a teacher performs an experiment or phenomenon for learners to observe, widely used in school and university science courses.
Dempo
Dempo (Gunung Dempo), active stratovolcano, 3,142 m, SE Sumatra, Indonesia, Sunda arc; frequent small phreatic eruptions from a crater lake since 1817; last eruption 2025; distinct rhyolitic magma.
Dempster–Shafer theory
Dempster–Shafer theory is a mathematical framework for reasoning under uncertainty that assigns degrees of belief to sets of propositions and combines evidence from independent sources.
DEN 0255 4700
DEN 0255-4700 (DENIS 0255-4700, DENIS-P J0255.0-4700) is a nearby isolated late-L brown dwarf about 16.2 light years away, near the L-T transition, with temperature ≤1400 K, mass 60-70 Jupiter masses, and rapid 40 km/s rotation.
DEN 1048 3956
DEN 1048-3956 is a faint M9 flare star about 13.2 light-years from the Sun in Antlia, one of the closest such objects, known for strong radio flares.
Denali Fault
The Denali Fault is a major right-lateral strike-slip fault system in Alaska and Yukon, about 2,100 km long, comparable in length to the San Andreas fault.
Denathonium benzoate
Denathonium benzoate (denatonium benzoate, Bitrex), CAS 3734-33-6, is an extremely bitter quaternary ammonium salt used as a taste repellent, denaturant, and animal repellent; EU-approved only for repellent uses, rat oral LD50 485-740 mg/kg.
Denatonium
Denatonium benzoate, sold as Bitrex, is a quaternary ammonium salt used as a bittering agent in denatured alcohol, detergents, and pesticides to discourage accidental ingestion.
Denatured alcohol
Denatured alcohol, also known as methylated spirits or Metho, is ethanol with denaturants added to make it undrinkable, so it can be sold tax-free as a solvent, fuel, and cosmetic ingredient.
Denbury
Denbury Inc. was an independent oil and gas company in Plano, Texas that specialized in CO2 enhanced oil recovery and carbon capture, and was acquired by ExxonMobil for $4.9 billion in 2023.
Dendrimer
A dendrimer, also known as an arborol or cascade molecule, is a highly branched macromolecule built from a central core in repeating layers called generations.
Dendrochronology
Dendrochronology, or tree-ring dating, is the science of dating annual growth rings in wood to their exact calendar year. It dates artifacts and reconstructs past climate and fire history.
Dendroclimatology
Dendroclimatology is the science of reconstructing past climate from the annual growth rings of trees, using ring width, wood density, and isotopes to estimate past temperature and precipitation.
Deneb
Deneb, also known as Alpha Cygni, is a blue-white supergiant in the constellation Cygnus, the 19th brightest star in the night sky and a vertex of the Summer Triangle.
Denebola
Denebola, also known as Beta Leonis, is the second-brightest star in Leo, a white A-type main-sequence star about 36 light-years from the Sun, known for its circumstellar dust.