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Asymmetric digital subscriber line
Asymmetric digital subscriber line (ADSL) is a broadband technology that sends high-speed data over existing copper telephone wires, offering faster download than upload speeds; it was standardized in 1999.
Asymmetric electrocatalysis
Asymmetric electrocatalysis is a branch of organic electrosynthesis that merges asymmetric catalysis with electrode-driven redox chemistry, converting prochiral substrates into enantioenriched chiral products using electricity rather than stoichiometric oxidants or reductants.
Asymmetric ester hydrolysis with pig-liver esterase
Asymmetric ester hydrolysis with pig-liver esterase (PLE) is a biocatalytic method, used since the 1970s, in which the enzyme selectively cleaves one ester group of a meso or prochiral diester to give an enantiomerically enriched product.
Asymmetric flow field-flow fractionation
Asymmetric flow field-flow fractionation (AF4) is a liquid-phase separation technique that fractionates macromolecules, nanoparticles, and colloids by size using a cross-flow perpendicular to the channel flow.
Asymmetric hydroalkylation
Asymmetric hydroalkylation is the enantioselective addition of hydrogen and an alkyl group across an alkene's C=C bond, usually via nickel hydride catalysis, to build saturated stereogenic centers.
Asymmetric hydroboration
Asymmetric hydroboration is the addition of a boron-hydrogen bond across an unsaturated bond to create a stereocenter, typically using a chiral catalyst or chiral borane reagent.
Asymmetric hydrogenation
Asymmetric hydrogenation is a catalytic reaction in which a chiral catalyst adds hydrogen across a prochiral double bond, forming one enantiomer in excess; it is widely used in pharmaceutical synthesis.
Asymmetric induction
Asymmetric induction, also known as chiral induction or stereoinduction, is the preferential formation of one enantiomer or diastereoisomer in a reaction, driven by a chiral feature in the substrate, reagent, or catalyst.
Asymmetric Laplace distribution
The asymmetric Laplace distribution (ALD) is a skewed continuous probability distribution, introduced by Kozubowski and Podgórski, whose maximum likelihood reproduces quantile regression, making it standard in Bayesian quantile regression.
Asymmetric organocatalysis
Asymmetric organocatalysis is the use of small, metal-free organic molecules as catalysts to convert prochiral substrates into enantioenriched products, recognized by the 2021 Nobel Prize in Chemistry.
Asymmetric photoredox catalysis via chiral copper complexes
Asymmetric photoredox catalysis via chiral copper complexes is a synthesis strategy in which photocatalysis generates radicals by single-electron transfer and chiral copper complexes, typically bis(oxazoline)-ligated, control bond formation to give enantioenriched products.
Asymmetric radical catalysis
Asymmetric radical catalysis is the branch of asymmetric catalysis in which a chiral catalyst controls stereocenter formation in reactions that pass through free-radical intermediates, first achieved in 1996.
Asymmetric radical hydroamination
Asymmetric radical hydroamination is a radical-pathway addition of an amine N–H bond across alkenes or alkynes that builds chiral carbon–nitrogen bonds, enabling atom-economical synthesis of chiral amines.
Asymmetric reduction
Asymmetric reduction converts a prochiral carbonyl, imine, or alkene into a single-enantiomer product using a chiral metal catalyst, an enzyme, or a stoichiometric chiral reagent.
Asymmetric reductive Heck reaction
The asymmetric reductive Heck reaction is an enantioselective palladium- or nickel-catalyzed hydroarylation of alkenes, where hydride trapping replaces β-hydride elimination to give chiral saturated products.
Asymmetric simple exclusion process
The asymmetric simple exclusion process (ASEP) is a stochastic interacting-particle model in which particles hop with directional bias on a one-dimensional lattice, one particle per site.
Asymmetric top molecule
An asymmetric top molecule is a rotating molecule whose three principal moments of inertia are all different, so its energy levels have no closed form and must be computed numerically.
Asymmetric warfare
Asymmetric warfare: conflict between belligerents of unequal power or status who fight by deliberately different methods; also called irregular or guerrilla warfare. Weaker actors use ambushes, IEDs, terrorism, and protracted conflict; strong states use their own asymmetric advantages.
Asymmetrical intrauterine growth restriction
Asymmetrical intrauterine growth restriction (asymmetric IUGR/FGR): fetal growth restriction with reduced abdominal circumference relative to head circumference, classically from placental insufficiency with brain-sparing blood redistribution, monitored by Doppler.
Asymptomatic
Asymptomatic: having no symptoms, either from a symptomless condition (early hypertension, glaucoma) or after recovery. Distinct from pre-symptomatic; central to screening, whose benefits vary by disease (hepatitis C yes, thyroid screening no).
Asymptomatic carrier
Asymptomatic carrier: a person harboring an infectious agent without symptoms who can transmit it. Covers carrier types, Typhoid Mary, and SARS-CoV-2 evidence showing lower but real carrier transmission.
Asymptote
An asymptote is a straight line whose distance from a point on a curve tends to zero as the point moves to infinity; a term dating to Apollonius of Perga.
Asymptotic analysis
Asymptotic analysis, also known as asymptotics, is the branch of mathematics that studies the limiting behavior of functions and derives approximations, associated with Henri Poincaré's 1886 work.
Asymptotic expansion
An asymptotic expansion, or Poincaré expansion, is a series approximation of a function whose truncation error matches the first omitted term, even when the series diverges.
Asymptotic flatness
Asymptotic flatness is a general relativity property of spacetimes whose geometry approaches flat Minkowski space at large distances, introduced through Roger Penrose's 1963 conformal treatment of infinity.
Asymptotic freedom
Asymptotic freedom is the property of the strong interaction that quarks interact more weakly at shorter distances, discovered in 1973 and honored with the 2004 Nobel Prize in Physics.
Asymptotic giant branch
The asymptotic giant branch (AGB) is the final nuclear-burning stage of low- and intermediate-mass stars, 0.5 to 8 solar masses, which alternate hydrogen and helium shell burning and end as white dwarfs.
Asymptotic safety
Asymptotic safety is a proposal in quantum gravity that gravity becomes nonperturbatively renormalizable via an interacting ultraviolet fixed point, proposed by Steven Weinberg in 1976.
Asymptotic safety with matter
Asymptotic safety with matter asks whether gravity's ultraviolet fixed point survives when Standard Model quantum fields are coupled to it, with gauge fields favoring and scalars disfavoring it.
Asymptotic security proof techniques in quantum key distribution
Asymptotic security proof techniques in quantum key distribution (QKD) establish that a key can be made arbitrarily close to random and independent of an eavesdropper.