All articles starting with S
44,216 articles
Stern tube bearing
A stern tube bearing is a plain journal bearing in a ship's stern tube that supports the propeller shaft and transfers radial propeller forces to the hull.
Stern v. Marshall
Stern v. Marshall, 564 U.S. 462 (2011), Supreme Court case holding bankruptcy judges lack Article III authority to enter final judgment on certain state-law counterclaims, despite statutory core-proceeding authority; Anna Nicole Smith estate dispute.
Stern–Gerlach experiment
The Stern–Gerlach experiment, also known as the Stern–Gerlach effect, is a 1922 experiment that split a beam of silver atoms in two, first showing atomic angular momentum is quantized.
Sternal cleft
Sternal cleft (bifid sternum, sternum bifidum) is a rare congenital chest wall malformation in which the sternal halves fail to fuse, leaving a complete or partial gap; usually asymptomatic at birth and treated by surgical closure, ideally neonatal.
Sternberg item recognition task
The Sternberg item recognition task is a working memory paradigm, introduced by Saul Sternberg in 1966, that measures how fast people retrieve items from short-term memory.
Sternenkinder
Sternenkinder (star children) is a 2005 children's dice game by Monika Mulzer-Adam, published by Beleduc, for 2-4 players aged 4+, on the Kinderspiel des Jahres 2005 recommended list; the name also denotes a 1946 Asscher-Pinkhof novel and a 2006 Tatort episode.
Sternfeld (lunar crater)
Sternfeld is a 109.80-km-diameter lunar crater at 19.75°S, 142.27°W, formerly designated Lodygin G, named in 1991 by the IAU for Ari Abramovich Sternfeld, a Soviet space scientist (1905–1980).
Sterno
Sterno, also known as Sterno Canned Heat, is an American brand of jellied alcohol cooking fuel in steel cans, used to keep food warm under chafing dishes.
Sternocleidomastoid muscle
Sternocleidomastoid (SCM), sternomastoid: paired superficial neck muscle from sternum and clavicle to mastoid process; rotates and flexes the head, innervated by CN XI, divides neck into triangles.
Sternotherus
Sternotherus, American musk turtles (Kinosternidae), Gray 1825, small North American aquatic turtles to 17.6 cm; traditionally four species, expanded by a 2017 RAD-locus study that described S. intermedius and elevated two subspecies.
Sternula
Sternula (Boie, 1822) is a genus of small terns in Laridae, type species the Little Tern S. albifrons; seven species including the Least Tern, Fairy Tern, and Peruvian Tern, separated from Sterna on molecular grounds.
Sternum
Sternum (breastbone): flat midline chest bone of manubrium, body, and xiphoid process; protects the mediastinum, anchors ribs 1-7 via costal cartilage, and marks the sternal angle at the 2nd rib.
Sternwheeler
A sternwheeler is a steam-powered riverboat driven by a single paddle wheel at the stern, whose shallow draft made it the standard freight and passenger carrier on western North American rivers.
Steroid
Steroid: organic compounds on the four-fused-ring cyclopenta[a]phenanthrene (sterane) skeleton, spanning cholesterol, steroid hormones, bile acids, sterols, and vitamin D derivatives; parent hydrocarbons estrane through cholestane (C18–C27), all biosynthesized from cholesterol.
Steroid hormone
Steroid hormone: cholesterol-derived lipophilic signaling molecule (corticosteroids, sex steroids) acting via intracellular nuclear receptors on gene transcription, plus rapid membrane-initiated non-genomic signaling; purified mainly 1929–1954.
Steroid-induced osteoporosis
Steroid-induced osteoporosis, or glucocorticoid-induced osteoporosis (GIOP), is iatrogenic bone loss from steroid therapy, the most common secondary osteoporosis, causing rapid dose-dependent fracture risk and treated with bisphosphonates or teriparatide.
Steroid-responsive encephalopathy associated with autoimmune thyroiditis
SREAT, or Hashimoto encephalopathy, is a rare steroid-responsive encephalopathy with elevated antithyroid antibodies, diagnosed after excluding other causes; seizures, confusion, and cognitive decline are common, and corticosteroids help most patients.
Steroidal alkaloid biosynthesis
Steroidal alkaloid biosynthesis is the plant pathway that converts cholesterol into nitrogen-containing steroidal alkaloids, best studied in tomato and potato, which make α-tomatine and α-solanine.
Steroidogenic acute regulatory protein
StAR (STARD1) is a mitochondrial protein that transports cholesterol across mitochondrial membranes for pregnenolone synthesis, the rate-limiting step of steroidogenesis; mutations cause congenital lipoid adrenal hyperplasia.
Sterol
A sterol is an amphiphilic steroid alcohol built on a four-ring nucleus that stabilizes eukaryotic cell membranes: cholesterol in animals, ergosterol in fungi and yeast, and phytosterols in plants.
Sterol 14-demethylase
Sterol 14-demethylase (CYP51, EC 1.14.14.154) is a cytochrome P450 removing the 14α-methyl group of sterols in all kingdoms of life; it is the target of azole antifungals, agricultural fungicides, and antitrypanosomal drug development.
Sterol 22-desaturase
Sterol 22-desaturase (C22DES, ERG5/CYP61 in fungi, CYP710 in plants) is a cytochrome P450 enzyme adding a C22(23) double bond to sterols, making ergosterol and stigmasterol; absent in humans, azole-sensitive, an antifungal target.
Sterol C-14 reductase (14-sterol reductase step)
Sterol C-14 reductase (EC 1.3.1.70, ERG24/TM7SF2/LBR/FK) is an NADPH-dependent membrane enzyme reducing the C14(15) double bond in sterol biosynthesis; LBR mutations cause Greenberg dysplasia and Pelger-Huët anomaly.
Sterol C-24 methyltransferase
Sterol C-24 methyltransferase (SMT) is a membrane-bound enzyme that adds a methyl group to sterol side chains in fungi and plants, making ergosterol and phytosterols.
Sterol C-24 reductase in plants (FACKEL/DWARF1)
Sterol C-24 reductase in plants, encoded in Arabidopsis by the DWARF1 (DIMINUTO) gene, is an FAD-containing enzyme that reduces the C-24 double bond of phytosterol intermediates, producing campesterol and sitosterol.
Sterol C-4 demethylation complex
The sterol C-4 demethylation complex is a three-enzyme assembly of the endoplasmic reticulum that removes the methyl groups at carbon 4 of sterols during ergosterol and cholesterol biosynthesis.
Sterol esterase
Sterol esterase (EC 3.1.1.13, CAS 9026-00-0) hydrolyzes sterol esters; a Trichoderma reesei-produced preparation from Melanocarpus albomyces is FDA GRAS (GRN 981) for baked goods at up to 10 mg TOS/kg flour.
Sterol regulatory element-binding protein
SREBPs (SREBP-1a, SREBP-1c, SREBP-2) are membrane-bound bHLH-Zip transcription factors regulating cholesterol, fatty acid, and triglyceride synthesis, activated by SCAP-mediated Golgi cleavage and retained by Insig when sterols are high.
Stertor
Stertor is a low-pitched, snoring-like breathing sound from soft-tissue vibration above the larynx (nose, nasopharynx, oropharynx), ICD-11 MD11.80; distinct from high-pitched stridor, seen in sleep, coma, congestion, and adenotonsillar hypertrophy.
Stesichorus
Stesichorus (Στησίχορος), traditionally named Teisias, was a Greek lyric poet from Himera in Sicily, active c. 600–550 BC, who retold Trojan and Heraclean myths on an epic scale.