42,772 articles
Heavy Ion Medical Accelerator in Chiba
The Heavy Ion Medical Accelerator in Chiba (HIMAC) is a heavy-ion accelerator at the National Institute of Radiological Sciences in Chiba, Japan, the world's first dedicated to medical use.
Heavy metals
Heavy metals is a loosely defined term, considered deprecated by IUPAC, grouping metals linked with pollution and toxicity; lead, mercury, cadmium, and arsenic raise the main health concerns.
Heavy neutral lepton
A heavy neutral lepton, or HNL, is a hypothetical electrically neutral fermion heavier than the known neutrinos, proposed to explain neutrino masses, dark matter, and the matter-antimatter asymmetry.
Heavy quark effective theory
Heavy quark effective theory (HQET) is an effective field theory of quantum chromodynamics describing hadrons containing one heavy quark, treating it as a nearly static color source.
Heavy seed scenario
The heavy seed scenario is a model in which the first supermassive black holes, 10^4 to 10^5 solar masses, form directly from collapsing primordial gas clouds, without stars.
Heavy water
Heavy water, or deuterium oxide (D2O), is water in which deuterium replaces ordinary hydrogen. It is best known as the moderator and coolant of Canadian CANDU reactors.
Heavy-fermion superconductivity in CeRh2As2
CeRh2As2 is a cerium-based heavy-fermion compound that superconducts near 0.26 K, known since 2021 for two superconducting phases of different parity switched by a magnetic field along its c axis.
Heavy-fermion superconductor
A heavy-fermion superconductor is an intermetallic compound, usually cerium or uranium based, where electrons with masses 50 to 1000 times normal pair magnetically rather than by phonons.
Heavy-ion fusion
Heavy-ion fusion is a proposed inertial confinement fusion approach in which particle accelerators fire heavy-ion beams, rather than lasers, at fuel targets; it has been studied since the 1970s.
Heavy-tailed distribution
A heavy-tailed distribution is a probability distribution whose tail decays more slowly than any exponential, so extreme values occur far more often than in Gaussian or exponential models.
Heber Cinco Ley
Heber Cinco Ley is a Mexican petroleum reservoir engineer known for pressure transient analysis of fractured reservoirs, who led the Instituto Mexicano del Petróleo from 2007 to 2010.
Heber Doust Curtis
Heber Doust Curtis (1872–1942) was an American astronomer who spent eighteen years at the Lick Observatory and argued in the 1920 Shapley–Curtis Debate that spiral nebulae are separate galaxies.
HEC-HMS
HEC-HMS (Hydrologic Modeling System) is a free hydrology program from the US Army Corps of Engineers' Hydrologic Engineering Center that converts precipitation into streamflow hydrographs, replacing HEC-1.
HEC-RAS
HEC-RAS, the Hydrologic Engineering Center's River Analysis System, is free hydraulic modeling software from the U.S. Army Corps of Engineers, first released in July 1995 and used for floodplain and dam safety studies.
Heck reaction
The Heck reaction, also called the Mizoroki–Heck reaction, is a palladium-catalyzed coupling of an aryl or alkenyl halide with an alkene, forming a substituted alkene.
Hecke algebra
A Hecke algebra is a commutative algebra of operators acting on modular forms, generated by the Hecke operators T_n, which encode averaging over sublattices of a lattice.
Hecke operator
A Hecke operator is a linear operator on spaces of modular forms, introduced by Erich Hecke in 1937, whose commuting eigenvalues decompose them into eigenforms.
Hecla Mining
Hecla Mining Company is an American mining company based in Coeur d'Alene, Idaho. Founded in 1891, it is the largest silver producer in the United States and Canada.
Hectare
The hectare, equal to one square hectometre or 10,000 square meters, is a metric unit accepted for use with the SI and standard for land area.
Héctor D. Abruña
Héctor D. Abruña, also written Hector D. Abruna, is a Puerto Rico-born electrochemist and Émile M. Chamot Professor at Cornell University who received the 2024 Enrico Fermi Presidential Award.
Hector Munro Macdonald
Hector Munro Macdonald (1865–1935) was a Scottish mathematician and Fellow of the Royal Society, professor of mathematics at Aberdeen from 1904, known for Macdonald's theorem on zeros of analytic functions.
Hecuba-gap asteroid
A Hecuba-gap asteroid is an asteroid in the 2:1 mean-motion resonance with Jupiter near 3.27 au, one of the largest Kirkwood gaps, home to a few hundred known asteroids.
Hedonic regression
Hedonic regression is an econometric method that regresses the price of a good on its attributes, such as a house's size, age, and location, to estimate each attribute's implicit price.
Hee Cheul Choi
Hee Cheul Choi (최희철) is a South Korean materials chemist who holds a chaired professorship at POSTECH, known for carbon nanotube etching of silicon oxide and vapor-grown nanostructures.
Heegaard Floer homology
Heegaard Floer homology is a collection of invariants of oriented 3-manifolds and of knots and links, introduced by Peter Ozsváth and Zoltán Szabó in the early 2000s.
Heegaard splitting
A Heegaard splitting decomposes a closed 3-manifold into two handlebodies glued along a common Heegaard surface, and every closed orientable 3-manifold admits one; diagrams from splittings underlie Heegaard Floer homology.
Heegner number
A Heegner number is a squarefree positive integer for which the imaginary quadratic field Q(√−n) has class number one; there are exactly nine: 1, 2, 3, 7, 11, 19, 43, 67, and 163.
Heejun Yang
Heejun Yang (양희준) is a South Korean condensed matter physicist, professor at KAIST since 2024, known for the graphene barristor in Science in 2012 and MoTe2 homojunction contacts.
Heidelberg Ion-Beam Therapy Center
The Heidelberg Ion-Beam Therapy Center is a particle therapy facility at Heidelberg University Hospital, Germany, opened in 2009 as Europe's first hospital-based combined proton and heavy-ion center.
Heidi B. Hammel
Heidi B. Hammel is an American planetary astronomer known for her studies of Uranus and Neptune and for leading the Hubble team observing Comet Shoemaker–Levy 9's 1994 impacts on Jupiter.