All articles starting with H

Hydraulic transformer

A hydraulic transformer is a fluid-power component that converts pressurized hydraulic fluid between different pressure and flow rates at nearly constant power, chiefly for Common Pressure Rail systems.

Hydraulically amplified self-healing electrostatic actuators

Hydraulically amplified self-healing electrostatic (HASEL) actuators are soft artificial muscles driven by voltage, introduced in 2018 at the University of Colorado Boulder and able to self-heal after dielectric breakdown.

Hydraulics

Hydraulics is the engineering science of liquid pressure and flow, covering fluid power systems, where confined liquid transmits force by Pascal's law, and water flow in open channels and pipelines.

Hydrazide

Hydrazide, also called acylhydrazine, is a compound derived from an oxoacid in which acidic hydroxy groups are replaced by hydrazine-derived groups; isoniazid is a well-known example.

Hydrazine

Hydrazine, also called diazane, is a toxic, fuming compound of nitrogen and hydrogen used as a rocket propellant and to make agricultural chemicals and blowing agents.

Hydrazine oxidation reaction

The hydrazine oxidation reaction is the electrochemical oxidation of hydrazine at an electrode, used in direct hydrazine fuel cells and as a low-voltage substitute for oxygen evolution in hydrogen production.

Hydrazino-Pictet–Spengler ligation

The hydrazino-Pictet–Spengler (HIPS) ligation is a bioconjugation reaction introduced in 2013 that couples aldehyde-tagged proteins to hydrazine-indole linkers, forming a stable carbon–carbon bond near neutral pH.

Hydrazoic acid

Hydrazoic acid, also called hydrogen azide or hydronitric acid, is the colorless, volatile, toxic and explosive liquid nitrogen hydride (HN₃) used to make heavy metal azides for shell detonators.

Hydreuma to epi tou Paneiou

Hydreuma to epi tou Paneiou (el-Kanais, الكنيس), a fortified Ptolemaic watering station and Pan/Min sanctuary (Paneion) in Egypt's Eastern Desert on the Edfu-Berenike road, 47.4 km from Edfu, beside Seti I's rock temple.

Hydride

Hydride is the anion of hydrogen, H−, and by extension the broad class of compounds hydrogen forms with other elements, grouped as ionic, covalent, and metallic hydrides.

Hydride generation

Hydride generation is a sample-introduction technique in atomic spectrometry that converts elements like arsenic, selenium, and tin in acidified solution to volatile hydrides for detection, first applied analytically in 1969.

Hydride superconductivity

Hydride superconductivity is superconductivity in hydrogen-rich compounds compressed to megabar pressures. It holds the highest known transition temperatures, with lanthanum decahydide superconducting at about 250 K near 170 GPa.

Hydrilla

Hydrilla (Hydrilla verticillata), or waterthyme, is an invasive submerged aquatic plant of Hydrocharitaceae with whorled serrated leaves, tubers, and turions; introduced via the aquarium trade, it infests 28 US states and is a Federal Noxious Weed.

Hydriotaphia, Urn Burial

Hydriotaphia, Urn Burial is a treatise by Sir Thomas Browne, published in London in 1658, that began as a report on burial urns found in Norfolk and ends as a meditation on mortality.

Oct 10, 2026

Hydro One

Hydro One is Ontario's largest electricity transmission and distribution utility, a publicly traded company formed from Ontario Hydro in 1999 that serves about 1.5 million mostly rural customers.

Hydro Tasmania

Hydro Tasmania is the trading name of the Hydro-Electric Corporation, the Tasmanian government business that generates and retails electricity and is Australia's largest generator of clean, renewable energy.

Hydro-Man

Hydro-Man (Morris 'Morrie' Bench), Marvel Comics Spider-Man villain whose body became living water after an undersea generator accident; first appearance The Amazing Spider-Man #212 (January 1981), by Denny O'Neil and John Romita Jr., Sandman's water-based counterpart and inspiration for Far From Home's water Elemental.

Hydro-Québec

Hydro-Québec is a government-owned Canadian utility, founded in 1944, that supplies nearly all electricity in Québec and is Canada's largest power utility and electricity distributor.

Oct 20, 2026

Hydroa vacciniforme

Hydroa vacciniforme (Bazin's hydroa vacciniforme) is a rare childhood photodermatosis causing vesicles on sun-exposed skin that heal with permanent varioliform scars; severe EBV-associated forms (HVLPD) can progress to lymphoma.

Hydroa vacciniforme-like lymphoma

Hydroa vacciniforme-like lymphoma (HVLL), now hydroa vacciniforme lymphoproliferative disorder, is a rare EBV-positive T/NK-cell lymphoproliferative disease of childhood, mainly in Asia and Latin America, with ulcerative skin lesions and risk of systemic lymphoma.

Sep 29, 2026

Hydroacylation

Hydroacylation is an organic reaction in which the formyl C–H bond of an aldehyde adds across an alkene or alkyne to give a ketone, typically catalyzed by transition-metal complexes such as rhodium.

Hydroalkylation

Hydroalkylation is a catalytic reaction in which hydrogen and an alkyl group add across an alkene's double bond, converting it directly into a substituted alkane.

Sep 29, 2026

Hydroamination

Hydroamination is the addition of an amine N–H bond across a carbon–carbon double or triple bond, forming a new C–N bond in one step with 100% theoretical atom economy.

Hydroaminoalkylation

Hydroaminoalkylation (HAA) is a catalytic reaction that inserts an inexpensive alkene directly into the C–H bond beside an amine's nitrogen, an atom-economic route to substituted amines found in pharmaceuticals.

Hydroarylation

Hydroarylation is the addition of an aryl group and hydrogen across a carbon-carbon double or triple bond, an atom-economical alternative to Friedel-Crafts alkylation that preferentially gives linear, anti-Markovnikov products.

Hydrobates

Hydrobates (Boie, 1822) is the genus of northern storm petrels, family Hydrobatidae; it absorbed Oceanodroma after genetic work showed paraphyly, and includes H. pelagicus, H. leucorhous, and H. castro.

Hydrobatidae

Hydrobatidae, the northern storm petrels (family Mathews, 1912, order Procellariiformes), small pelagic seabirds now placed in a single genus Hydrobates with about 18 species, split from the southern Oceanitidae.

Hydrobia

Hydrobia (W. Hartmann, 1821) is a genus of minute brackish-water hydrobiid mud snails of the northern Atlantic and Mediterranean; type species Hydrobia acuta, with former members like H. ulvae and H. ventrosa now split into Peringia and Ecrobia/Ventrosia.

Hydrobiidae

Hydrobiidae (mud snails, spring snails) is the largest family of freshwater gastropods, minute operculate Truncatelloidea snails of springs, subterranean, brackish and fresh waters; ~910–1200 species, ~180 genera, diversifying after the K–Pg boundary ~60 Ma.