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Three-way calling
Three-way calling is a telephone service feature that adds a third party to an existing two-party call, forming a small conference on landline, mobile, and VoIP systems.
Three-way catalyst
A three-way catalyst (TWC) is the catalytic converter on gasoline engines that oxidizes carbon monoxide and hydrocarbons and reduces nitrogen oxides at once, using platinum, palladium, and rhodium.
Three-wheeler
A three-wheeler is a motor vehicle with three wheels, in delta or tadpole configurations, ranging from auto rickshaws to the Piaggio Ape, and classified in Europe's L category.
Three-winding transformer
A three-winding transformer is a power transformer with primary, secondary, and tertiary windings per phase, connecting three voltage levels or supplying station auxiliaries and voltage control.
Three-year examination cycle
The Three-year examination cycle (三年一贡举) was a Song dynasty policy, issued under Emperor Yingzong in the Zhiping era, fixing the civil service examinations at one session every three years.
Three-Year Plan (North Korea)
The Three-Year Plan, formally the Plan for Postwar Reconstruction and Development, was North Korea's first postwar economic plan, running from 1954 to 1956 to restore prewar production levels.
Three: Going Home
Three: Going Home (三更之回家) is Peter Chan's 2002 Hong Kong segment of the pan-Asian horror anthology Three, in which Leon Lai's herbalist preserves his dead wife's body for three years; it won Golden Horse Best Actor and HKFA Best New Performer.
Three's Company
Three's Company is the ABC sitcom (1977–84, 169–172 episodes) adapted from the British ITV comedy Man About the House, starring John Ritter as Jack Tripper, who pretends to be gay to share an apartment with Janet and Chrissy.
Threefold repetition
Threefold repetition, or draw by repetition, is a chess rule letting a player claim a draw when the identical position, including castling rights, occurs three times.
Threepence (British coin)
British pre-decimal coin worth 3d, a quarter shilling (1.25p decimal), also called the thruppenny bit; silver from 1551, twelve-sided nickel-brass from 1937; demonetised 31 August 1971, surviving in Maundy money.
Threesome
Threesome: sexual interaction among three people, at least one active with both others; distinct from group sex (4+). Surveyed lifetime rates 10-18% US adults; motives, safer sex, CNM context, and outcomes covered.
Threesome (Swedish TV series)
Threesome is a Swedish drama series created, written and directed by Lisa Linnertorp, premiering on Viaplay 29 August 2021. It stars Matilda Källström and Simon Lööf as London couple Siri and David, whose relationship is tested by a threesome with French art student Camille (Alma Jodorowsky); SVT acquired both seasons in 2024.
Threnody
Threnody is a song of lamentation for the dead, from the Greek thrēnos, the formal funeral lament sung by mourners at ancient Greek funerals and used as a literary genre.
Threonine
Threonine (symbol Thr or T) is a polar, proteinogenic amino acid with a hydroxyl-bearing side chain, and one of the nine essential amino acids humans must obtain from food.
Threonine ammonia-lyase
Threonine ammonia-lyase (threonine deaminase, threonine dehydratase, EC 4.3.1.19, ilvA) is a PLP-dependent enzyme converting L-threonine to 2-oxobutanoate; the biosynthetic form starts isoleucine synthesis and is the classic example of isoleucine feedback inhibition, reversed by valine.
Threonine catabolism
Threonine catabolism: degradation of the essential amino acid L-threonine via threonine dehydrogenase, dehydratase, and aldolase to glycine, acetyl-CoA, pyruvate, or propionyl-CoA; humans lack functional TDH, so the dehydratase route dominates.
Threonine proteases
Threonine proteases (EC 3.4.25) are proteases using an N-terminal threonine hydroxyl as catalytic nucleophile, discovered 1995 in the proteasome; examples include the 20S/26S proteasome and bacterial HslVU.
Threonine Synthase
Threonine synthase (thrC, EC 4.2.3.1) is a PLP-dependent, fold-type II enzyme converting O-phospho-L-homoserine to L-threonine, the last step of threonine biosynthesis in bacteria, yeasts, and plants; plant TS is allosterically activated by SAM.
Threonine synthase-like
Threonine synthase-like (InterPro IPR004450) is a PLP-dependent enzyme family; canonical threonine synthase (EC 4.2.3.1) makes L-threonine from O-phosphohomoserine, while animal THNSL2 members degrade O-phospho-threonine instead.
Threonine/serine transporter TdcC
TdcC (tdcC, b3116, P0AAD8) is an E. coli K-12 inner-membrane H+/threonine-serine symporter of the HAAAP family, 443 aa, Km 6 μM for L-threonine, induced anaerobically in rich medium, Na+ independent, part of the tdc catabolic operon.
Thresher shark
Thresher sharks (Alopias vulpinus, A. pelagicus, A. superciliosus) are pelagic sharks with an upper tail lobe nearly body-length, used in tail-slap strikes up to 35 m/s to stun schooling fish; all three are IUCN Vulnerable.
Threshing
Threshing is the post-harvest operation that separates edible grain from the ears, stalks, and husks of harvested crops, done by flail, animals, or threshing machines such as Andrew Meikle's 1786 design.
Threshing machine
A threshing machine is a farm machine that separates grain from the stalks and ears of harvested cereal crops; the first successful design was built by Andrew Meikle in 1786.
Threshold (band)
Threshold are an English progressive metal band formed in Surrey in the late 1980s, centered on Karl Groom and Richard West, known for Wounded Land (1993), Hypothetical, Legends of the Shires, and rotating vocalists.
Threshold autoregressive model
The threshold autoregressive (TAR) model is a nonlinear time series model in which autoregressive coefficients switch between regimes according to whether a lagged value exceeds a threshold.
Threshold braking
Threshold braking is a braking technique, also called maximum braking, that holds brake pressure at the edge of wheel lock to achieve the shortest possible stopping distance.
Threshold energy
Threshold energy is the minimum kinetic energy an incoming particle must bring to a collision or reaction for a specified outcome, such as producing a new particle, to be possible.
Threshold function (graph theory)
A threshold function in random graph theory is a function p0(n) marking where a graph property switches from almost surely absent to almost surely present in G(n,p).
Threshold graph
A threshold graph is a graph whose independent sets are exactly the vertex sets with total weight at most some threshold, defined by Chvátal and Hammer in 1977.
Threshold model
The threshold model is a statistical model in which the relationship between variables changes when an observed variable crosses a threshold, creating two or more linear regimes.