42,772 articles
MCMC convergence diagnostics
MCMC convergence diagnostics are tools that check whether Markov chain Monte Carlo draws plausibly represent the target posterior distribution, such as R-hat and effective sample size.
McMurry reaction
The McMurry reaction, also called McMurry coupling, reductively couples two aldehydes or ketones to form an alkene using low-valent titanium, named for John E. McMurry.
McNemar's test
McNemar's test, also known as McNemar's chi-squared test, is a nonparametric statistical test for paired binary data, proposed by Quinn McNemar at Stanford in 1947.
MCNP
MCNP (Monte Carlo N-Particle) is a widely used Monte Carlo radiation transport code developed by Los Alamos National Laboratory, simulating neutrons, photons, electrons, and ions.
mCPBA
mCPBA, also written m-CPBA and called meta-chloroperbenzoic acid, is a peroxycarboxylic acid oxidant in organic synthesis, best known for converting alkenes to epoxides and ketones to esters.
MCSNR J0525-6938
MCSNR J0525-6938, commonly known as N132D, is a young, oxygen-rich supernova remnant in the Large Magellanic Cloud and its brightest X-ray source of its kind.
MD17
MD17 is a benchmark dataset of ab initio energies and atomic forces for small organic molecules, released in 2017 to train and compare machine-learned force fields.
MDABCO ammonium perovskite
MDABCO ammonium perovskite is a metal-free all-organic perovskite ferroelectric, reported in Science in 2018, with a polarization of 22 μC cm⁻² near that of barium titanate.
MDMA
MDMA (Ecstasy, Molly), 3,4-methylenedioxymethamphetamine, is a synthetic empathogen-stimulant releasing serotonin, dopamine, and norepinephrine; Schedule I in the US since 1985; FDA rejected MDMA-assisted PTSD therapy in 2024.
Meager
Meager (Mount Meager Volcanic Complex, Qw'elqw'elústen) is Canada's northernmost Cascade arc volcano in British Columbia; VEI 4 eruption about 2360 years BP, Canada's greatest-threat volcano, major 2010 landslide.
Mealy machine
A Mealy machine, or Mealy automaton, is a finite-state machine whose output depends on its current state and current input, named after George H. Mealy, who introduced it in 1955.
Mean absolute error
Mean absolute error (MAE) is a scale-dependent measure of prediction accuracy, the average of absolute differences between predicted and true values, minimized by forecasting the median.
Mean absolute percentage error
The mean absolute percentage error (MAPE), also called the mean absolute percentage deviation, is a unit-free measure of forecast accuracy, most widely used in businesses.
Mean anomaly
The mean anomaly is a Keplerian orbital element, an angle increasing steadily by 360 degrees each orbit that specifies a body's position along its elliptical orbit.
Mean centering
Mean centering is a statistical preprocessing step that subtracts a variable's mean from each observation, giving transformed values that average to zero; it is used in regression and PCA.
Mean curvature
Mean curvature is the average of the two principal curvatures of a surface at a point, one of the two standard curvature quantities in classical surface theory.
Mean curvature flow
Mean curvature flow is a geometric evolution process in which every point of a surface moves in the normal direction at a speed equal to the local mean curvature.
Mean field theory
Mean field theory is a physics method that replaces each particle's fluctuating interactions with their thermal average, widely used for magnetism, phase transitions, and spin glasses.
Mean first passage time
The mean first passage time, also called the mean hitting time, is the expected number of steps a Markov chain takes to reach a given state from another specified state.
Mean free path
The mean free path is the average distance a gas molecule travels between successive collisions, or a photon before absorption or scattering, central to kinetic theory.
Mean high water
Mean high water is a tidal datum, the average of all high water heights observed over the 19-year National Tidal Datum Epoch used by NOAA.
Mean higher high water
Mean higher high water (MHHW) is a tidal datum averaging the higher of each day's two high tides over a 19-year National Tidal Datum Epoch, used as the reference for coastal flooding.
Mean imputation
Mean imputation is a statistical method for handling missing data that replaces each missing value with the mean of that variable's observed values, keeping incomplete records in an analysis.
Mean low water
Mean low water is a tidal datum, the average of all low water heights observed over a 19-year period, used as a reference for charting and coastal legal boundaries.
Mean lower low water
Mean lower low water (MLLW) is the tidal datum, averaged over 19 years, that serves as the chart datum for depths on U.S. coastal nautical charts.
Mean opinion score
The mean opinion score (MOS) is the average rating a panel of human judges gives to speech, audio, or video quality on a scale from 1 (bad) to 5 (excellent).
Mean spherical approximation
The mean spherical approximation (MSA) is a linearized closure of the Ornstein–Zernike equations that keeps the hard-core exclusion exact, with analytic solutions for electrolytes, Yukawa fluids, and polar liquids.
Mean squared error
Mean squared error (MSE), also called mean squared deviation, is the expected squared difference between an estimator or prediction and the true value, decomposing into variance plus squared bias.
Mean time between failures
Mean time between failures (MTBF), also called mean time before failure, is a reliability metric: the expected time between successive failures of a repairable item that can be restored to service.
Mean value theorem
The mean value theorem, also called Lagrange's mean value theorem, is a calculus theorem guaranteeing a point where instantaneous rate of change equals average rate of change.