42,772 articles
Derived category
A derived category is a mathematical construction that replaces an abelian category by a category of chain complexes, invented by Grothendieck and Verdier in the early 1960s.
Derived functor
A derived functor, in left and right variants, is a homological algebra construction measuring how far a functor fails to be exact, computed by applying it to a projective or injective resolution and taking homology.
Dermatan sulfate
Dermatan sulfate, formerly called chondroitin sulfate B or β-heparin, is a glycosaminoglycan found mostly in skin, distinguished by iduronic acid, that contributes to wound healing, extracellular matrix assembly, and anticoagulation.
Dermot O’Hare
Dermot O'Hare, born in Newry, County Down, is Professor of Organometallic and Materials Chemistry at the University of Oxford, known for layered double hydroxide nanomaterials and CO2 capture research.
Derrick Henry Lehmer
Derrick Henry Lehmer (1905–1991) was an American number theorist who proved the Lucas-Lehmer primality test for Mersenne numbers in 1930 and built mechanical number sieves.
Deryn Fogg
Deryn E. Fogg is a Canadian chemist at the University of Ottawa known for designing ruthenium olefin-metathesis catalysts and for mechanistic studies of how those catalysts decompose.
Descartes' rule of signs
Descartes' rule of signs, also called Descartes' sign rule, is an algebra theorem stating that a polynomial's positive real roots number at most its coefficient sign changes.
Descent theory
Descent theory is a set of techniques in algebraic geometry and category theory for recovering an object from its pullback along a covering morphism, presented in general form by Alexander Grothendieck in 1960.
Descriptive complexity theory
Descriptive complexity theory is a branch of finite model theory that characterizes complexity classes by the logic needed to define problems, notably NP via Fagin's 1974 theorem.
Descriptive geometry
Descriptive geometry is a field of geometry and technical drawing, created by Gaspard Monge around 1765, that represents 3D objects on 2D paper so true lengths and angles can be found.
Descriptive research
Descriptive research is research that systematically characterizes a phenomenon, answering who, what, where, when, and to what extent without manipulating variables; it can show patterns and prevalence, but not causation.
Descriptive set theory
Descriptive set theory is the branch of mathematical logic that studies definable sets of real numbers and Polish spaces, including Borel, analytic, and coanalytic sets.
Descriptive statistics
Descriptive statistics is the branch of statistics that summarizes observed data set values using measures like the mean, median, standard deviation, histograms, and box plots.
Descriptor (chemistry)
In chemistry, a stereodescriptor is a rule-based affix such as R, S, E, or Z added to a chemical name to specify the configuration or conformation of a molecule.
Desert climate
A desert climate, also called an arid climate, is one where potential evapotranspiration exceeds annual precipitation, divided by the Köppen-Geiger system into hot desert (BWh) and cold desert (BWk).
Desert pavement
A desert pavement is a natural surface covering of closely packed, interlocking rock fragments over fine-grained sediment in arid regions, formed largely as wind-blown dust accumulates beneath the stones.
Desertification
Desertification, or desertization, is land degradation in arid, semi-arid, and dry sub-humid areas driven by climate change and human activities like overgrazing and deforestation, formalized in the 1994 UNCCD.
Desertification in the Sahel
Desertification in the Sahel is land degradation in the semi-arid belt south of the Sahara, the world's emblematic desertification case after the droughts and famines of the 1970s and 1980s.
DESI Legacy Surveys
The DESI Legacy Surveys are three public optical imaging surveys, combined with WISE infrared data, that produced the target catalogs for the Dark Energy Spectroscopic Instrument.
DESI survey
The DESI survey is a five-year spectroscopic redshift survey of tens of millions of galaxies and quasars, run by the Dark Energy Spectroscopic Instrument at Kitt Peak.
Desiccant
A desiccant is a hygroscopic substance that removes water vapor from air, gases, or liquids, such as silica gel, activated alumina, molecular sieve, clay, and calcium chloride.
Desiccation
Desiccation is the removal of water from a solid, liquid, or gas; in the laboratory it covers drying samples to constant weight and keeping dried materials dry with desiccators and drying agents.
Desiccator
A desiccator is a sealed laboratory container, typically of glass, that keeps samples dry with a drying agent such as silica gel, optionally under vacuum; dried samples cool in it before weighing.
Design effect
The design effect (deff or DEFF) is a survey sampling measure comparing a complex design's variance to that of simple random sampling, coined by Leslie Kish in 1965.
Design matrix
A design matrix is the matrix of independent-variable values used to fit a statistical model, with one row per observation and one column per model term.
Design of experiments
Design of experiments (DOE) is a statistical discipline for planning experiments so the data yield valid conclusions, built on Fisher's principles of randomization, replication, and blocking.
Design science research
Design science research (DSR) is a research methodology, used chiefly in information systems, that creates and evaluates novel artifacts such as systems, models, or methods to solve practical problems.
Design space
A design space, in pharmaceutical manufacturing, is the combination of input variables and process parameters demonstrated to provide assurance of quality, codified in the ICH Q8 guideline of 2005.
Design-based inference
Design-based inference is a framework for statistical inference in which uncertainty is quantified through the randomization used to select samples, not through assumed models, tracing to Jerzy Neyman's 1934 paper.
Design-based research
Design-based research (DBR), a methodology from the learning sciences, studies learning in real classrooms through iterative cycles of design, enactment, analysis, and redesign, aiming to improve practice and build theory.