Physical world and mathematics

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.

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.

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.

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.

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.

Oxybenzone

Oxybenzone, also known as benzophenone-3, is an organic compound used as a UV filter in sunscreens; it is widely used but banned in Hawaii since 2021 over coral toxicity.

Oxychalcogenide thermoelectrics

Oxychalcogenide thermoelectrics are layered mixed-anion compounds containing oxide and chalcogenide anions, developed for heat-to-electricity conversion; the leading material, BiCuSeO, reported in 2010, offers low thermal conductivity, non-toxic elements, and a figure of merit of about 1.5.

Oxyfuel combustion

Oxyfuel combustion, also written oxy-fuel combustion, burns fuel in nearly pure oxygen with recycled flue gas, yielding a CO2-rich exhaust for carbon capture and storage.

Oxygen

Oxygen is the chemical element with atomic number 8, a colorless, odorless diatomic gas making up 21% of Earth's atmosphere, isolated by Joseph Priestley in 1774.

Oxygen cycle

The oxygen cycle is the biogeochemical cycle through which oxygen moves among the atmosphere, ocean, biosphere, and rocks, produced mainly by photosynthesis and consumed by respiration and weathering.

Oxygen deletion of furans and benzofurans

Oxygen deletion of furans and benzofurans is a class of skeletal-editing reactions that removes the ring oxygen atom from these aromatic heterocycles, typically forming a new carbon–carbon bond.

Oxygen electrocatalysis

Oxygen electrocatalysis is the branch of electrocatalysis concerned with the oxygen reduction and oxygen evolution reactions, whose sluggish four-electron kinetics bottleneck fuel cells, water electrolyzers, and metal–air batteries.

Oxygen insertion into aryl rings

Oxygen insertion into aryl rings is a skeletal-editing reaction that inserts a single oxygen atom into an arene's carbon framework, yielding lactones or aryl ethers valued in drug discovery.

Sep 29, 2026

Oxygen isotope analysis

Oxygen isotope analysis measures the relative abundance of stable oxygen isotopes in rocks, waters, ice, and biogenic minerals, using those ratios to reconstruct past temperatures and water-cycle history.

Oxygen minimum zone

An oxygen minimum zone (OMZ) is a persistent ocean layer, about 100 to 1,500 m deep, where dissolved oxygen falls far above and below levels of nearby waters, and zones are expanding as the ocean warms.

Oxygen potential

Oxygen potential is the chemical potential of oxygen in a system, expressed as the free energy of oxide formation or as an equilibrium oxygen partial pressure.

Sep 29, 2026

Oxygen radical absorbance capacity

Oxygen radical absorbance capacity (ORAC) is a chemical assay measuring antioxidant capacity of foods and biological samples in Trolox equivalents; the USDA removed its ORAC database in 2012.

Oxygen reduction reaction

The oxygen reduction reaction (ORR) is the critical cathode reaction in fuel cells and metal-air batteries. It is known for its kinetic sluggishness and reliance on expensive platinum group catalysts.

Oxygen saturation

Oxygen saturation (SaO2) is the percentage of hemoglobin binding sites in blood occupied by oxygen, normally 96 to 98%, and routinely estimated non-invasively by pulse oximetry.

Oxygen sensor

An oxygen sensor, also called an O2 sensor or lambda probe, measures the oxygen concentration in a gas or liquid and converts it into an electrical or optical signal.

Oxygen-18

Oxygen-18, a stable isotope making up about 0.205 percent of natural oxygen, serves as a paleoclimate tracer in ice cores and as enriched water feedstock for producing fluorine-18 in PET imaging.

Oxygen-evolving complex mimics

Oxygen-evolving complex mimics are synthetic manganese-based catalysts modeled on photosystem II's Mn4CaO5 cluster, designed to study water oxidation and build efficient catalysts for artificial photosynthesis.

OXZEO

OXZEO, short for oxide–zeolite composite, is a catalyst design concept introduced in 2016 at the Dalian Institute of Chemical Physics that converts syngas or CO₂ directly into light olefins.

OY Carinae

OY Carinae is an eclipsing SU Ursae Majoris-type dwarf nova in the southern constellation Carina, discovered in 1963, whose white dwarf, accretion disc, and hotspot are all eclipsed.

Oct 10, 2026

Øystein Ore

Øystein Ore (1899–1968) was a Norwegian-born mathematician who spent his career at Yale, working in algebra, lattice theory, graph theory, and the history of mathematics.