All articles A–Z

Stereoselective olefin metathesis

Stereoselective olefin metathesis is the control of alkene E/Z geometry in metathesis reactions, achieved with Z-selective molybdenum MAP and ruthenium catalysts introduced from 2009, plus stereoretentive ruthenium dithiolate catalysts reported in 2013.

Stereoselective synthesis

Stereoselective synthesis is a chemical reaction or sequence in which new elements of chirality form and stereoisomeric products arise in unequal amounts, measured as enantiomeric excess.

Stereoselectivity

Stereoselectivity is the preferential formation of one stereoisomer over another in a chemical reaction, called enantioselectivity or diastereoselectivity depending on the products, and central to pharmaceutical and natural product synthesis.

Oct 22, 2026

Stereospecific cross-coupling

Stereospecific cross-coupling is a metal-catalyzed carbon–carbon bond-forming reaction in which an enantioenriched substrate's stereochemistry is transferred predictably to the product, typically with retention or inversion of configuration.

Stereospecificity

Stereospecificity is the property of a reaction mechanism by which reactants differing only in configuration are converted into stereoisomeric products, as in SN2 inversion; unlike stereoselectivity, it describes the mechanism itself.

Stereotactic biopsy

Stereotactic biopsy is a minimally invasive neurosurgical procedure that uses three-dimensional imaging coordinates to guide a needle to deep brain lesions, achieving diagnostic yields above 95%.

Stereotactic body radiation therapy

Stereotactic body radiation therapy (SBRT), also called stereotactic ablative body radiotherapy (SABR), delivers high ablative radiation doses to body tumors in 1 to 5 fractions with submillimeter accuracy.

Stereotactic surgery

Stereotactic surgery: 3D coordinate-guided minimally invasive brain surgery, also called stereotaxis. Frame-based or frameless targeting for biopsy, functional neurosurgery, and radiosurgery; pioneered by Horsley-Clarke (1908) and Spiegel-Wycis (1947).

Stereotaxis

Stereotaxis is the robotic magnetic navigation technology of Stereotaxis, Inc., a St. Louis, Missouri company whose systems steer magnetically tipped catheters inside the heart under remote physician control.

Stereotaxy

Stereotaxy is a neurosurgical technique that uses a three-dimensional coordinate system to reach targets inside the brain, used for biopsy, deep brain stimulation, and radiosurgery.

Stereotomy

Stereotomy is the art and science of cutting stones into precisely shaped pieces that assemble into walls, arches, and vaults, codified in Renaissance treatises from 1567.

Stereotype

Stereotype: an oversimplified belief associating traits with a social group, introduced by Walter Lippmann in Public Opinion (1922) from a printing term. Distinguished from prejudice (affect) and discrimination (behavior), studied as explicit and implicit cognition.

Stereotype threat

Stereotype threat, from Steele and Aronson (1995), is the risk of confirming a negative group stereotype in relevant situations, disrupting performance. Covers working-memory mechanisms, self-affirmation and belonging interventions, and meta-analytic evidence on effect sizes and publication bias.

Oct 21, 2026

Stereotyped movement disorder

Stereotyped movement disorder (SMD, motor stereotypies, ICD-11 6A06) is a neurodevelopmental disorder of repetitive, purposeless movements such as hand flapping or head banging, beginning before age 3, treated mainly with habit reversal training.

Stereotypes of African Americans

Stereotypes of African Americans: demeaning beliefs and caricatures (Sambo, Mammy, Jezebel, Black Buck) rooted in slavery and blackface minstrelsy, spread through advertising and film, persisting in news and screen media per Pew and Common Sense Media data.

Stereotypes of Americans

Stereotypes of Americans covers both national-character stereotypes of the typical American held worldwide (hardworking, greedy, inaccurate against measured personality) and internal U.S. racial, ethnic, and regional caricatures such as Mammy, model minority, and redneck.

Stereotypes of East Asians in the United States

Stereotypes of East Asians in the United States, also called perpetual foreigner, model minority, and yellow peril tropes, cast Chinese, Japanese, and Korean Americans as unassimilable foreigners and uniformly high achievers, driving discrimination and media underrepresentation.

Stereotypes of Hispanic and Latino Americans in the United States

Stereotypes of Hispanic and Latino Americans in U.S. media: the six classic Hollywood types (el bandido, harlot, buffoons, Latin lover, dark lady), criminality and immigration tropes in news and TV, and the underrepresentation data behind them.

Stereotypes of Jews

Stereotypes of Jews: false beliefs about Jewish greed, dual loyalty, and secret power, rooted in early Christian anti-Judaism and medieval tropes like the blood libel, measured today by the ADL Global 100 index.

Stereotypes of South Asians

Stereotypes of South Asians: oversimplified beliefs about South Asian people and the diaspora, including comic-relief media tropes (Apu, Raj), the perpetual foreigner and terrorist slurs, workplace and healthcare discrimination, and recent shifts in screen representation.

Stereotypes of white Americans

Stereotypes of white Americans: beliefs ascribed to white Americans by other groups, including high competence, racism, and entitlement; studied via minority attitudes, class-based stereotypes like "white trash," and competence downshift in speech.

Stereotypy

Stereotypy: repetitive, rhythmic, apparently purposeless movements, object use, or vocalizations (hand flapping, rocking, echolalia) with early-childhood onset; seen in autism, intellectual disability, and healthy children; basal ganglia-based, usually automatically reinforced.

Steric effect

A steric effect is any effect on a molecule's structure, reactivity, or properties arising from the size and spatial requirements of its atoms, causing steric hindrance.

Steric effects

Steric effects, also called steric interactions, arise when substituents with different spatial requirements change molecular structure, reaction rates, and equilibria, often slowing reactions involving bulky groups.

Steric stabilization

Steric stabilization is a way of keeping colloidal particles dispersed by attaching polymer chains to their surfaces; overlapping layers generate repulsion that offsets van der Waals attraction.

Steric strain

Steric strain, also called van der Waals strain, is the increase in a molecule's energy when unbonded atoms are forced closer than their van der Waals radii allow.

Sterigmatocystin

Sterigmatocystin (STC, CAS 10048-13-2) is a polyketide mycotoxin from Aspergillus fungi, a precursor of aflatoxin B1, an IARC Group 2B genotoxic carcinogen found in grains, cheese, coffee, spices, and beer.

Sterile flight deck rule

The sterile flight deck rule, also called the sterile cockpit rule, is a US aviation regulation barring crew distractions during taxi, takeoff, landing, and flight below 10,000 feet.