42,772 articles
Hexane-2,5-dione
Hexane-2,5-dione, also called acetonyl acetone or 2,5-hexanedione, is a 1,4-diketone that is both the standard substrate for the Paal-Knorr pyrrole synthesis and the neurotoxic metabolite of n-hexane, whose urinary levels serve as the biomarker of exposure.
Hexanitrodiphenylamine
Hexanitrodiphenylamine, also known as dipicrylamine or Hexyl, is a powerful yellow crystalline explosive with a detonation velocity of 7200 m/s, used by Germany and Japan in the World Wars.
Hexavalent chromium
Hexavalent chromium, also called chromium-6 or Cr(VI), is chromium in the +6 oxidation state and a known human carcinogen used in electroplating, welding, and stainless steel production.
Hexylamine
Hexylamine, also known as hexan-1-amine, is a colorless six-carbon primary amine with a fishy odor, used in corrosion inhibitors, surfactants, rubber chemicals, and agrochemical synthesis.
Heyting algebra
A Heyting algebra, also called a pseudo-Boolean algebra, is a bounded lattice with an implication operation, serving as the algebraic semantics of intuitionistic logic as Boolean algebras do for classical logic.
HFLS3
HFLS3 is a starbursting galaxy group at redshift 6.34, seen about 880 million years after the Big Bang and found in 2013 with the Herschel space observatory.
HfO2 superlattice ferroelectrics
HfO2 superlattice ferroelectrics are artificial layered structures in which nanometer-scale HfO2 films alternate with ZrO2 layers, stabilizing hafnia's metastable polar phase for ferroelectric memory and logic devices.
HgTe colloidal quantum dots
HgTe colloidal quantum dots are solution-processed mercury telluride nanocrystals whose size tunes their optical response across the entire infrared range, the only colloidal material covering 0.7 to 100 µm.
HH 211
HH 211, also written HH211, is a Herbig-Haro object and protostellar outflow in the Perseus Molecular Cloud about 1,000 light-years away, driven by a very young protostar.
HH 212
HH 212 is a Herbig-Haro object in Orion, a bright symmetric bipolar jet from a very young protostar near the Horsehead nebula, first imaged in 1998.
HH 34
HH 34 (Herbig-Haro 34) is a Herbig-Haro object in Orion about 1,350 light-years away, a glowing knot of shock-heated gas ejected in a jet from a young star.
HH 46/47
HH 46/47 (HH-47) is a complex of Herbig-Haro objects in the constellation Vela, driven by a protostar inside a Bok globule and imaged by Spitzer, Hubble, and Webb.
HHL algorithm
The HHL algorithm, also called the Harrow-Hassidim-Lloyd algorithm, is a 2009 quantum algorithm that solves sparse linear systems exponentially faster than classical methods, outputting a quantum state.
HI intensity mapping
HI intensity mapping is a radio astronomy technique that maps the large-scale distribution of matter by measuring integrated redshifted 21-cm emission from neutral hydrogen, without resolving individual galaxies.
Hidden camera
A hidden camera, also known as a spy camera, is a camera concealed from the people it records, used for espionage, law enforcement, and surveillance.
Hidden Markov model
A hidden Markov model (HMM), also called a hidden Markov chain, is a statistical model for sequential data where hidden states follow a Markov chain and each emits observations.
Hidden Matching Problem
The Hidden Matching Problem is a communication complexity problem in which Alice holds an n-bit string and Bob holds a perfect matching, defined by Bar-Yossef, Jayram, and Kerenidis in 2004 with the first exponential quantum-classical separation.
Hidden order
Hidden order is the unidentified ordered electronic phase in the heavy-fermion compound URu2Si2, which appears below a sharp phase transition at 17.5 K and has resisted explanation since 1985.
Hidden semi-Markov model
A hidden semi-Markov model (HSMM), also called an explicit duration HMM, is a statistical model extending the hidden Markov model by letting hidden states persist for explicitly modeled random durations.
Hidden shift problem
The hidden shift problem is a computational problem where two functions differ by an unknown shift, and the task is to find it, introduced by van Dam, Hallgren, and Ip.
Hidden spin polarization
Hidden spin polarization, introduced in 2014 by Zhang, Liu, Luo, Freeman, and Zunger, is spin polarization of individual crystal sectors that cancels globally in centrosymmetric materials.
Hidden valley (physics)
A hidden valley in physics is a beyond-the-Standard-Model scenario where a hidden sector of particles couples weakly to the Standard Model, proposed by Strassler and Zurek in 2006.
Hidden-subgroup approach to graph isomorphism
The hidden-subgroup approach to graph isomorphism recasts the graph isomorphism problem as a hidden subgroup problem over the symmetric group, solvable in principle on a quantum computer.
Hidden-variable theory
A hidden-variable theory supplements the quantum state with variables that fix each measurement's outcome, beginning with Einstein's 1935 incompleteness argument and realized in Bohm's 1952 theory.
Hidehiko Yamabe
Hidehiko Yamabe (山辺英彦, 1923–1960) was a Japanese mathematician who worked on Hilbert's fifth problem and Riemannian geometry; his 1960 claimed proof of the Yamabe problem contained an error, and it was fully solved in 1984.
Hideki Shirakawa
Hideki Shirakawa (白川英樹) was a Japanese polymer chemist at the University of Tsukuba who shared the 2000 Nobel Prize in Chemistry for discovering electrically conductive polymers.
Hideki Yukawa
Hideki Yukawa (湯川秀樹, 1907–1981) was a Japanese theoretical physicist at Kyoto University who predicted the meson in 1934, winning the 1949 Nobel Prize in Physics.
Hidenori Takagi
Hidenori Takagi (高木英典, born 1961 in Tokyo) is a Japanese condensed matter physicist known for cuprate superconductivity, spin-orbit Mott physics, and Kitaev quantum spin liquids.
Hideo Aoki
Hideo Aoki (青木 秀夫) is a Japanese condensed-matter theorist and emeritus professor at the University of Tokyo, known for predicting the Floquet topological insulator in graphene in 2009.
Hideo Hosono
Hideo Hosono (細野秀雄, born 1953) is a Japanese materials scientist at Tokyo Institute of Technology known for discovering iron-based superconductors and inventing the IGZO semiconductor used in flat-panel displays.