42,772 articles
Isobar (nuclide)
Isobars are nuclides of different chemical elements that have the same mass number but different atomic numbers; beta decay connects them, and examples include argon-40, potassium-40, and calcium-40.
Isobaric process
An isobaric process is a thermodynamic process in which pressure stays constant while volume and temperature change, often shown as a gas expanding in a piston.
Isobutane
Isobutane, also known as I-butane and formally named 2-methylpropane, is the branched isomer of butane, a highly flammable gas used in petroleum refining, refrigeration as R-600a, and aerosol propellants.
Isobutanol
Isobutanol (isobutyl alcohol, 2-methylpropan-1-ol) is a four-carbon branched primary alcohol that is a clear, flammable liquid, used mainly as a solvent, chemical intermediate, and gasoline-blending biofuel.
Isobutene
Isobutene (2-methylpropene) is a gaseous C4 hydrocarbon alkene produced on a scale above 10 million metric tons per year, used chiefly to make fuel ethers, isooctane, and butyl rubber.
Isobutylene
Isobutylene, also called isobutene or 2-methylpropene, is a colorless, flammable four-carbon hydrocarbon gas produced mainly in petroleum refining and used to make butyl rubber and the gasoline octane enhancers MTBE and ETBE.
Isobutyraldehyde
Isobutyraldehyde, also called 2-methylpropanal, is a branched four-carbon aldehyde with the formula C₄H₈O, made from propylene hydroformylation and consumed mainly as an intermediate for isobutanol and neopentyl glycol.
Isobutyronitrile
Isobutyronitrile, also called 2-methylpropanenitrile or isopropyl cyanide, is a branched four-carbon nitrile, a colorless liquid with an almond-like odor, detected in interstellar space in 2014.
Isochoric heating
Isochoric heating is the rapid heating of a solid-density sample at constant volume, depositing energy faster than the material can expand, a standard route to warm dense matter.
Isochoric process
An isochoric process, also called a constant-volume or isovolumetric process, is a thermodynamic process in which volume stays constant, so no work is done and heat equals internal-energy change.
Isochron dating
Isochron dating determines the age of cogenetic rock samples by fitting a line to parent and daughter isotope ratios, giving both an age and the initial daughter composition.
Isochronous cyclotron
An isochronous cyclotron is a particle accelerator whose magnetic field increases with radius, keeping ions in phase with fixed radiofrequency voltage and delivering a continuous beam.
Isocitric acid
Isocitric acid is a tricarboxylic acid and isomer of citric acid that acts as an intermediate in the citric acid cycle, formed from citrate by aconitase.
Isocratic elution
Isocratic elution is a chromatography mode in which the mobile phase composition stays constant during the run, contrasting with gradient elution, which raises elution strength.
Isocurvature perturbations
Isocurvature perturbations, also called entropy perturbations, are primordial fluctuations in the relative amounts of dark matter, baryons, photons, or neutrinos that produce no net curvature.
Isocyanate
An isocyanate, also known as an isocyanate group, is an organic compound containing the highly reactive N=C=O group, making it the reactive half of nearly all polyurethane chemistry.
Isocyanide
An isocyanide, also called an isonitrile or carbylamine, is an organic functional group R–N≡C, isomeric with nitriles but far more reactive, serving in multicomponent reactions and metal coordination.
Isoelectric focusing
Isoelectric focusing (IEF) is an electrophoresis technique that separates proteins and other ampholytic molecules along a pH gradient by their isoelectric points, concentrating each into a sharp band.
Isoelectric point
The isoelectric point (pI) is the pH at which a molecule or particle carries zero net electric charge, existing as a neutral zwitterion. It is measured by isoelectric focusing and used to separate and purify proteins.
Isoeugenol
Isoeugenol is a plant-derived phenylpropene with a sweet, spicy, floral scent, found in ylang-ylang oil and wood smoke, used in perfumes and foods, and classified by IARC as possibly carcinogenic.
Isoflavone
Isoflavone is a plant-derived flavonoid, a 3-phenylchromen-4-one compound found chiefly in soybeans, known as a phytoestrogen that binds estrogen receptors weakly and has been studied for the health effects of soy.
Isoglutamine (α-glutamine)
Isoglutamine, also called α-glutamine, is the amino acid amide of glutamic acid formed at the α-carboxyl group rather than the side chain, making it an isomer of glutamine.
Isograd
An isograd is a map line marking the first appearance of a metamorphic index mineral, such as garnet or biotite, meaning rocks of the same grade.
Isoindole
Isoindole is a bicyclic aromatic heterocycle, a benzene ring fused to a pyrrole and the regioisomer of indole; the unstable parent compound yields stable derivatives like phthalimide.
Isoindoline
Isoindoline, also known as 2,3-dihydro-1H-isoindole, is a bicyclic organic compound with a benzene ring fused to a saturated nitrogen-containing ring, found in drugs like thalidomide and lenalidomide.
Isolated binary evolution channel
The isolated binary evolution channel is a way merging black hole or neutron star pairs form, when massive stars born together evolve without other objects' help.
Isolated black hole
An isolated black hole is a stellar-mass black hole not bound in a binary or cluster, detectable mainly by microlensing; the first confirmed case was found in 2022.
Isolated horizon
An isolated horizon is a quasi-local null boundary of a black hole in equilibrium, defined using only quantities intrinsic to the horizon, introduced by Abhay Ashtekar in 1998.
Isolated point
An isolated point is a point of a subset of a topological space that has a neighborhood containing no other point of the subset; a space of only isolated points is discrete.
Isolated singularity
An isolated singularity of a complex function is a point where the function fails to be analytic yet stays analytic on a punctured neighborhood around it.