All articles starting with O
9,097 articles
Oxime ester N–O bond activation
Oxime ester N–O bond activation is the deliberate cleavage of an oxime ester's weak nitrogen–oxygen bond, generating iminyl radicals used to build N-heterocycles and functionalize C–H bonds.
Oximetry
Oximetry, or pulse oximetry (SpO2), is the non-invasive optical measurement of blood oxygen saturation, invented by Takuo Aoyagi in 1972-1974; accuracy is under 2% bias at SaO2 ≥90% but reduced by dark skin pigmentation and poor perfusion.
Oxindole
Oxindole, also called 2-oxindole or indolin-2-one, is a bicyclic aromatic organic compound first synthesized by Adolf von Baeyer in 1878 whose derivatives are widely used in medicinal chemistry, especially as kinase inhibitors for cancer treatment.
Oxine copper
Oxine copper (copper oxinate, copper 8-quinolinolate, bis(8-hydroxyquinolato)copper(II), C18H12CuN2O2) is a chelated organic copper fungicide and wood preservative with multi-site FRAC M01 action, not EU-approved as a crop pesticide.
Oxiracetam
Oxiracetam is a synthetic racetam-family nootropic drug tested in clinical trials for dementia, post-stroke cognitive impairment, and cognitive impairment after traumatic brain injury, with favorable safety but mixed results.
Oxisols
Oxisols, known as Ferralsols in the World Reference Base, are the most highly weathered of the twelve USDA soil orders, forming in hot, humid tropics with low natural fertility.
Oxkintok
Oxkintok (Tzat Tun Tzat), a major Maya site in Maxcanú, Yucatán, on the Puuc Route; occupied 300 BC to about AD 1200, known for the three-level Satunsat labyrinth and 475 AD inscriptions.
Oxlade
Oxlade is a Nigerian Afrobeats singer and songwriter, born Ikuforiji Olaitan Abdulrahman in Lagos, best known for the 2022 global hit "Ku Lo Sa" and the 2024 debut album Oxlade From Africa.
Oxmo Puccino
Oxmo Puccino is the stage name of Abdoulaye Diarra, a French rapper born in Mali in 1974 and raised in Paris, active in French hip-hop since the mid-1990s.
Oxnard, California
Oxnard, California: largest city in Ventura County on the Oxnard Plain, incorporated 1903 around the Oxnard brothers' sugar beet factory; about 200,000 residents, 77.1% Hispanic or Latino, gateway to Channel Islands National Park.
Oxo (crater)
Oxo is a small, bright impact crater on the dwarf planet Ceres, about 10 km wide, and the site of the first spectroscopically detected surface water ice.
Oxo alcohol
Oxo alcohols are industrial alcohols made by hydroformylation of olefins with syngas and hydrogenation, ranging from C4 to C18 and used in solvents, plasticizers, and detergents.
Oxo-Diels–Alder reaction
The oxo-Diels–Alder reaction, also called the oxa-Diels–Alder reaction, is a hetero-Diels–Alder reaction in which a carbonyl compound acts as heterodienophile or heterodiene, typically yielding dihydropyranones useful for natural product synthesis.
Oxocarbon
An oxocarbon (carbon oxide) is a compound made only of carbon and oxygen, ranging from carbon monoxide and carbon dioxide to cyclic acids like squaric and croconic acid.
Oxoglutarate dehydrogenase complex
Oxoglutarate dehydrogenase complex (OGDHc, KGDHC, α-ketoglutarate dehydrogenase complex): mitochondrial E1/E2/E3 multienzyme complex converting 2-oxoglutarate to succinyl-CoA, CO2 and NADH; rate-limiting TCA-cycle step, not phosphorylation-regulated.
Oxoglutaric aciduria
Oxoglutaric aciduria, or alpha-ketoglutarate dehydrogenase deficiency (OMIM 203740), is a very rare autosomal recessive TCA cycle disorder caused by OGDH variants on 7p13, presenting neonatally with hypotonia, seizures, lactic acidemia, and elevated urinary alpha-ketoglutaric acid, distinct from 2-hydroxyglutaric acidurias and glutaric aciduria type I.
Oxolamine
Oxolamine (CAS 959-14-8), a non-narcotic 1,2,4-oxadiazole antitussive with mainly peripheral action, used for non-productive cough in Latin America, Turkey, and Taiwan; not US-approved.
Oxomemazine
Oxomemazine (oxomémazine), also known by brands like Toplexil, is a sedative phenothiazine H1 antihistamine (ATC R06AD08) used as an antitussive for dry cough in adults and children over 2, despite lacking RCT evidence of efficacy.
Oxomoco Tholus
Oxomoco Tholus is a 140-km-wide volcanic dome (tholus) on Venus at 32.28S, 218.99E, named by the IAU on May 5, 2023 for the Aztec moon and night goddess.
Oxone
Oxone is the trademarked name, held by LANXESS, for a white granular triple salt of potassium peroxymonosulfate used as a stable oxidant in organic synthesis, water treatment, and non-chlorine pool shock.
Oxonium
Oxonium is the positively charged ion with a trivalent oxygen atom, whose parent member H3O+, the hydronium ion, forms in all acidic aqueous solutions.
Oxotremorine
Oxotremorine is a synthetic muscarinic acetylcholine receptor agonist, identified in 1961 as the active metabolite of tremorine and used to induce tremor in Parkinson's disease research.
Oxpoconazole
Oxpoconazole (okspokonazol, окспоконазол) is a Ube Industries azole fungicide, CAS 134074-64-9, C19H24ClN3O2, introduced in Japan in 2000 as the fumarate salt AL-SHINE; an ergosterol-biosynthesis inhibitor (FRAC 3) used against Botrytis cinerea and rice blast, not approved in the EU.
Oxprenolol
Oxprenolol, marketed as Trasicor, is a nonselective beta blocker with partial agonist activity (ISA) used to treat hypertension, angina pectoris, arrhythmias, and anxiety; it was never sold in the United States.
OXT
OXT (oxytocin/neurophysin I prepropeptide), HGNC:8528, is the human chromosome 20p13 gene encoding the oxytocin precursor; adjacent paralog of AVP, 3 exons, ~12 kb apart.
Oxtail
Oxtail, or cow tail (queue de bœuf, rabo de toro), is a collagen-rich beef variety meat sold in cross-sections, braised 3–5 hours into gelatinous stews such as Jamaican oxtail, kare-kare, and sokkoritang.
Oxtankah
Oxtankah, a pre-Hispanic Maya port city on Chetumal Bay, Quintana Roo, Mexico, named in 1937 by Alberto Escalona Ramos; largest city of the bay, apogee 250–600 AD, abandoned before the Spanish arrived.
Oxus Treasure
The Oxus Treasure is a hoard of about 180 gold and silver objects from Achaemenid Persia, found near the River Oxus around 1877–1880 and held mostly in the British Museum.
Oxy-fuel combustion process
Oxy-fuel combustion, also called oxy-combustion, burns fuel in nearly pure oxygen instead of air so the carbon dioxide can be captured by cooling and compression.
Oxy-fuel welding and cutting
Oxy-fuel welding and cutting, also known as oxyacetylene welding or flame cutting, burns a fuel gas such as acetylene with pure oxygen to weld or cut steel.