42,772 articles
Claus process
Claus process: industrial method, patented by Carl Friedrich Claus in 1883, converting hydrogen sulfide from natural gas and refinery acid gas into elemental sulfur via a thermal step (one-third H2S burned to SO2) followed by catalytic H2S-SO2 reaction stages, recovering 92-99.9% of sulfur.
Claus Ropers
Claus Ropers, born 1977 in Stade, is a German physicist known for ultrafast electron microscopy, a professor at Göttingen and director at the Max Planck Institute for Multidisciplinary Sciences.
Clausius theorem
The Clausius theorem, also called the Clausius inequality, states that the cyclic integral of heat divided by absolute temperature cannot be positive for any cycle.
Clausius–Clapeyron relation
The Clausius–Clapeyron relation, also called Clapeyron's equation, is a thermodynamic equation giving the slope of a phase boundary, equating it to entropy change divided by volume change.
Clay
Clay is a fine-grained earthy material made of layered hydrous silicate minerals, also defined by particle size below 2 micrometers; it forms by weathering near the Earth's surface.
Clay Mathematics Institute
The Clay Mathematics Institute, founded in 1998 by Landon T. Clay, is a private foundation in Cambridge, Massachusetts, best known for its seven $1 million Millennium Prize Problems.
Clays and Clay Minerals
Clays and Clay Minerals is a peer-reviewed journal and official publication of The Clay Minerals Society, covering research on clays and other fine-grained minerals since 1956.
Clayton Heathcock
Clayton Heathcock (Clayton H. Heathcock, born 1936) is an American synthetic organic chemist and professor emeritus at UC Berkeley, known for aldol stereocontrol and biomimetic total synthesis.
Clean Development Mechanism
The Clean Development Mechanism (CDM) is a Kyoto Protocol carbon offset mechanism that lets developing-country projects earn credits industrialized countries use toward their emission targets.
Clean Monday
Clean Monday (Kathara Deftera), also called Pure Monday, Ash Monday, or Green Monday in Cyprus, opens Great Lent in Eastern Orthodox and Eastern Catholic churches, falling seven weeks before Pascha.
Clean Power Plan
The Clean Power Plan was a 2015 EPA rule establishing state guidelines to cut carbon dioxide emissions from existing power plants; it was stayed, repealed, and never took effect.
Clearing the neighbourhood
Clearing the neighborhood, also called dynamical dominance, is the third criterion in the IAU's 2006 planet definition, distinguishing the eight planets from dwarf planets such as Pluto.
Clearwater Formation
Clearwater Formation: Lower Cretaceous (Albian) Mannville Group unit in Alberta; Wabiskaw Member at base; cap rock for Athabasca oil sands, Cold Lake bitumen reservoir, and fast-growing multilateral heavy oil play.
Cleavage (crystal)
Cleavage, or mineral cleavage, is the tendency of a crystal to break along flat planes where atomic bonds are weakest, a key property for identifying minerals.
Clebsch–Gordan coefficients
Clebsch–Gordan coefficients (CG coefficients) are the amplitudes that express combined states of two quantum angular momenta as combinations of product states in the coupled basis.
Clémence Corminbœuf
Clémence Corminboeuf, born 1977, is a Swiss computational and theoretical chemist who heads the Computational Molecular Design Laboratory at EPFL and develops electronic-structure methods for catalysis and organic electronics.
Clemens Bechinger
Clemens Bechinger is a physicist and full professor at the University of Konstanz, leading a soft condensed matter group; his 2008 Nature paper directly measured critical Casimir forces.
Clemens Roothaan
Clemens Roothaan (Clemens C. J. Roothaan) was a Dutch-American physicist and quantum chemist at the University of Chicago whose Roothaan equations made molecular calculations practical.
Clemens Schöpf
Clemens Schöpf (Clemens Josef Schöpf, 1899–1970) was a German organic chemist, professor at TH Darmstadt from 1929, whose Robinson–Schöpf reaction synthesizes tropinone and related alkaloids under physiological conditions.
Clement D. Child
Clement D. Child, also known as Clement Dexter Child, was an American physicist born in 1868 who derived the 1911 space-charge law, now called the Child–Langmuir law.
Clément Sánchez
Clément Sanchez, born in Paris in 1949, is a French materials chemist who pioneered hybrid organic–inorganic materials and soft chemistry at CNRS and the Collège de France.
Clemmensen reduction
The Clemmensen reduction is an organic reaction that converts the carbonyl group of an aldehyde or ketone into a methylene group using zinc amalgam and concentrated hydrochloric acid.
Clenbuterol
Clenbuterol, sold as Planipart, is a long-acting beta-2 agonist bronchodilator used in veterinary medicine and never approved by the FDA for humans; it is widely known as a doping substance.
Cleo (mathematician)
Cleo was a pseudonymous Mathematics Stack Exchange user who posted 39 unproven answers to hard integrals from 2013 to 2015, identified in 2025 as Vladimir Reshetnikov.
CLEO detector
CLEO was a particle physics detector at Cornell's CESR collider that operated from 1979 to 2008 and published 530 papers on bottom, charm, and tau physics.
Clepsydra of the Oropos Amphiareion
Clepsydra of the Oropos Amphiareion, a monumental 4th-century BC built water clock at the sanctuary of Amphiaraus, Oropos, Greece; outflow tank with calibrated bronze aperture, twin of the Athenian Agora clock, possibly for medical timekeeping.
Cleve Moler
Cleve Moler (1939–2026) was an American numerical analyst and computer scientist who created MATLAB, coauthored the LINPACK and EISPACK libraries, and cofounded MathWorks, serving as its chief mathematician and chairman.
Cleveland Abbe
Cleveland Abbe (1838–1916) was an American meteorologist and astronomer who built the first US daily weather forecasts from telegraph reports and campaigned for standard time zones.
Clevenger apparatus
The Clevenger apparatus is a glass distillation device, designed by J. F. Clevenger in 1928, that measures the essential oil content of plant materials by hydrodistillation.
Click chemistry
Click chemistry, also called the click reaction, is a class of high-yielding chemical reactions for joining molecules under mild conditions, coined by K. Barry Sharpless in 2001.