All articles A–Z

Strongylocentrotus purpuratus

Strongylocentrotus purpuratus, the purple or California purple sea urchin, is a Pacific coast echinoid from Alaska to Mexico, a 150-year developmental biology model with an 814-Mb, ~23,300-gene genome sequenced in 2006.

Strongyloides stercoralis

Strongyloides stercoralis, the threadworm, is a soil-transmitted nematode causing strongyloidiasis in an estimated 300–600 million people; its autoinfective life cycle permits lifelong infection and fatal hyperinfection under corticosteroid immunosuppression.

Strongyloidiasis

Strongyloidiasis, a soil-transmitted helminth infection caused by Strongyloides stercoralis (rarely S. fuelleborni), infects 300–600 million people; its autoinfection cycle allows lifelong infection and fatal hyperinfection in immunosuppressed patients; treated with ivermectin.

Strongylus vulgaris

Strongylus vulgaris, the horse bloodworm, is the most pathogenic equine GI helminth; larvae migrate in the cranial mesenteric artery causing verminous arteritis and intestinal infarction, and it is reemerging in Denmark and Sweden under prescription-only anthelmintic rules.

Stronnictwo Ludowe

Stronnictwo Ludowe (People's Party) was a Polish agrarian party founded in Warsaw in 1931 from a merger of three peasant parties, the main legal opposition to the Sanacja regime.

Strontianite

Strontianite is a strontium carbonate mineral (SrCO3) of the aragonite group, named in 1791 after Strontian, Scotland, its type locality. Though the richer strontium ore, it is mined less than celestite.

Strontium

Strontium, also known as Element 38, is a soft, silvery alkaline earth metal of Group 2, named after Strontian in Scotland and best known for the red its salts give fireworks.

Strontium barium niobate

Strontium barium niobate (SBN) is a lead-free ferroelectric solid solution with formula SrxBa1−xNb2O6 and a tetragonal tungsten bronze structure, valued for its exceptionally large electro-optic coefficients.

Strontium ferrite

Strontium ferrite (SrFe₁₂O₁₉) is a magnetically hard ceramic permanent-magnet material, developed by Philips in the 1950s and used in motors, loudspeakers, and other inexpensive magnets.

Strontium iridate

Strontium iridate (Sr₂IrO₄) is a layered transition-metal oxide and spin-orbit-coupled Mott insulator, antiferromagnetic below 17 K and the closest non-cuprate analog of the cuprate superconductors.

Strontium oxide

Strontium oxide, also called strontia or strontium monoxide, is the strongly basic oxide of strontium, a grayish-white ionic solid used chiefly as a glass modifier and fluxing agent.

Strontium ruthenate

Strontium ruthenate (Sr2RuO4) is a layered perovskite that becomes superconducting below about 1.5 K, discovered in 1994 and studied for three decades as an unconventional superconductor.

Strontium titanate

Strontium titanate (SrTiO3, abbreviated STO) is a lead-free perovskite oxide of strontium and titanium, a model quantum material showing quantum paraelectricity and, when doped, superconductivity.

Strontium-87 optical lattice clock

A strontium-87 optical lattice clock is an atomic clock using thousands of laser-cooled strontium-87 atoms trapped in an optical lattice, accurate to parts in 10^18.

Strontium-89

Strontium-89 (⁸⁹Sr) is a radioactive isotope of strontium with a 50.5-day half-life that decays by beta emission and is used, as strontium-89 chloride, to relieve pain from bone metastases.

Strontium-90

Strontium-90, or Sr-90, is a radioactive isotope of strontium with a 29.1-year half-life, made in nuclear fission and infamous as a bone-seeking component of fallout.

Stroop effect

Stroop effect: delayed ink-color naming when a word names an incongruent color, first reported by J. Ridley Stroop in 1935; the classic measure of selective attention, response inhibition, and frontal lobe function.

Sep 29, 2026

Stroop test

The Stroop test is a cognitive psychology task in which naming the ink color of a mismatched word, like red printed in blue, slows responses and raises errors.

Stroopwafel

Stroopwafel (syrup waffle): Dutch cookie of two thin waffle discs with syrup filling, invented in Gouda around 1810, credited to baker Gerard Kamphuisen; oldest recipe 1840, warmed on coffee.

Strophanthin

Strophanthin is a family of steroidal cardiac glycosides extracted from Strophanthus vine seeds, historically used as injectable drugs for heart failure and including ouabain, still used in the laboratory to inhibit the sodium pump.

Oct 21, 2026

Strophanthus

Strophanthus DC. (Apocynaceae), a genus of about 38-39 liana and shrub species from Africa to Malesia, source of cardiac glycosides such as ouabain, used as arrow poison and in heart medicine.

Oct 21, 2026

Strophanthus kombe

Strophanthus kombe (kombe arrow poison) is an East and southern African Apocynaceae liana whose glycoside-rich seeds served as arrow poison and yielded the heart medicine strophanthin-K, distinct from S. gratus (ouabain).

Oct 21, 2026

Strophomena

Strophomena is an extinct Ordovician (Caradoc–Ashgill) strophomenid brachiopod genus, type species Leptaena planumbona, a stationary epifaunal suspension feeder with a semicircular, resupinate shell, distinct from the mollusk Strophomenia.

Strossmayer Gallery of Old Masters

Strossmayer Gallery of Old Masters (Strossmayerova galerija starih majstora HAZU), Zagreb art museum founded by Bishop Josip Juraj Strossmayer, opened 9 November 1884 with 256 donated Old Master paintings in the HAZU Academy Palace; closed since the 2020 earthquake.

Stroszek

Stroszek (1977) is Werner Herzog's West German drama starring Bruno S., Eva Mattes, and Clemens Scheitz; a Berlin busker, a prostitute, and an eccentric emigrate to Wisconsin and find the American dream hollow. Written in four days for Bruno S., it won the German Film Critics' Award.