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Because charge is conserved, it is not possible to create an antiparticle without either destroying another particle of the same charge (as is for instance the case when antiparticles are produced naturally via beta decay or the collision of cosmic rays with Earth's atmosphere), or by the simultaneous creation of both ... | Antiparticle | Wikipedia | 464 | 1327 | https://en.wikipedia.org/wiki/Antiparticle | Physical sciences | Antimatter | null |
Solutions of the Dirac equation contain negative energy quantum states. As a result, an electron could always radiate energy and fall into a negative energy state. Even worse, it could keep radiating infinite amounts of energy because there were infinitely many negative energy states available. To prevent this unphysic... | Antiparticle | Wikipedia | 509 | 1327 | https://en.wikipedia.org/wiki/Antiparticle | Physical sciences | Antimatter | null |
Composite antiparticles
Particle–antiparticle annihilation
If a particle and antiparticle are in the appropriate quantum states, then they can annihilate each other and produce other particles. Reactions such as + → (the two-photon annihilation of an electron-positron pair) are an example. The single-photon annih... | Antiparticle | Wikipedia | 503 | 1327 | https://en.wikipedia.org/wiki/Antiparticle | Physical sciences | Antimatter | null |
where we use the symbol k to denote the quantum numbers p and σ of the previous section and the sign of the energy, E(k), and ak denotes the corresponding annihilation operators. Of course, since we are dealing with fermions, we have to have the operators satisfy canonical anti-commutation relations. However, if one no... | Antiparticle | Wikipedia | 386 | 1327 | https://en.wikipedia.org/wiki/Antiparticle | Physical sciences | Antimatter | null |
By considering the propagation of the negative energy modes of the electron field backward in time, Ernst Stückelberg reached a pictorial understanding of the fact that the particle and antiparticle have equal mass m and spin J but opposite charges q. This allowed him to rewrite perturbation theory precisely in the for... | Antiparticle | Wikipedia | 199 | 1327 | https://en.wikipedia.org/wiki/Antiparticle | Physical sciences | Antimatter | null |
In mathematics, the associative property is a property of some binary operations that means that rearranging the parentheses in an expression will not change the result. In propositional logic, associativity is a valid rule of replacement for expressions in logical proofs.
Within an expression containing two or more o... | Associative property | Wikipedia | 489 | 1335 | https://en.wikipedia.org/wiki/Associative%20property | Mathematics | Algebra | null |
If a binary operation is associative, repeated application of the operation produces the same result regardless of how valid pairs of parentheses are inserted in the expression. This is called the generalized associative law.
The number of possible bracketings is just the Catalan number,
, for n operations on n+1 val... | Associative property | Wikipedia | 511 | 1335 | https://en.wikipedia.org/wiki/Associative%20property | Mathematics | Algebra | null |
Some non-associative operations are fundamental in mathematics. They appear often as the multiplication in structures called non-associative algebras, which have also an addition and a scalar multiplication. Examples are the octonions and Lie algebras. In Lie algebras, the multiplication satisfies Jacobi identity inste... | Associative property | Wikipedia | 445 | 1335 | https://en.wikipedia.org/wiki/Associative%20property | Mathematics | Algebra | null |
Right-associative operations include the following:
Exponentiation of real numbers in superscript notation
Exponentiation is commonly used with brackets or right-associatively because a repeated left-associative exponentiation operation is of little use. Repeated powers would mostly be rewritten with multiplication:
F... | Associative property | Wikipedia | 310 | 1335 | https://en.wikipedia.org/wiki/Associative%20property | Mathematics | Algebra | null |
Apatosaurus (; meaning "deceptive lizard") is a genus of herbivorous sauropod dinosaur that lived in North America during the Late Jurassic period. Othniel Charles Marsh described and named the first-known species, A. ajax, in 1877, and a second species, A. louisae, was discovered and named by William H. Holland in 191... | Apatosaurus | Wikipedia | 477 | 1346 | https://en.wikipedia.org/wiki/Apatosaurus | Biology and health sciences | Dinosaurs and prehistoric reptiles | null |
Apatosaurus is a genus in the family Diplodocidae. It is one of the more basal genera, with only Amphicoelias and possibly a new, unnamed genus more primitive. Although the subfamily Apatosaurinae was named in 1929, the group was not used validly until an extensive 2015 study. Only Brontosaurus is also in the subfamily... | Apatosaurus | Wikipedia | 382 | 1346 | https://en.wikipedia.org/wiki/Apatosaurus | Biology and health sciences | Dinosaurs and prehistoric reptiles | null |
The skull is small in relation to the size of the animal. The jaws are lined with spatulate (chisel-like) teeth suited to an herbivorous diet. The snout of Apatosaurus and similar diplodocoids is squared, with only Nigersaurus having a squarer skull. The braincase of Apatosaurus is well preserved in specimen BYU17096, ... | Apatosaurus | Wikipedia | 156 | 1346 | https://en.wikipedia.org/wiki/Apatosaurus | Biology and health sciences | Dinosaurs and prehistoric reptiles | null |
Like those of other sauropods, the neck vertebrae are deeply bifurcated; they carried neural spines with a large trough in the middle, resulting in a wide, deep neck. The vertebral formula for the holotype of A.louisae is 15cervicals, 10dorsals, 5sacrals, and 82caudals. The caudal vertebra number may vary, even within ... | Apatosaurus | Wikipedia | 366 | 1346 | https://en.wikipedia.org/wiki/Apatosaurus | Biology and health sciences | Dinosaurs and prehistoric reptiles | null |
The limb bones are also very robust. Within Apatosaurinae, the scapula of Apatosaurus louisae is intermediate in morphology between those of A.ajax and Brontosaurus excelsus. The arm bones are stout, so the humerus of Apatosaurus resembles that of Camarasaurus, as well as Brontosaurus. However, the humeri of Brontosaur... | Apatosaurus | Wikipedia | 396 | 1346 | https://en.wikipedia.org/wiki/Apatosaurus | Biology and health sciences | Dinosaurs and prehistoric reptiles | null |
The first Apatosaurus fossils were discovered by Arthur Lakes, a local miner, and his friend Henry C. Beckwith in the spring of 1877 in Morrison, a town in the eastern foothills of the Rocky Mountains in Jefferson County, Colorado. Arthur Lakes wrote to Othniel Charles Marsh, Professor of Paleontology at Yale Universit... | Apatosaurus | Wikipedia | 331 | 1346 | https://en.wikipedia.org/wiki/Apatosaurus | Biology and health sciences | Dinosaurs and prehistoric reptiles | null |
During excavation and transportation, the bones of the holotype skeleton were mixed with those of another Apatosaurine individual originally described as Atlantosaurus immanis; as a consequence, some elements cannot be ascribed to either specimen with confidence. Marsh distinguished the new genus Apatosaurus from Atlan... | Apatosaurus | Wikipedia | 319 | 1346 | https://en.wikipedia.org/wiki/Apatosaurus | Biology and health sciences | Dinosaurs and prehistoric reptiles | null |
Second Dinosaur Rush and skull issue
After the end of the Bone Wars, many major institutions in the eastern United States were inspired by the depictions and finds by Marsh and Cope to assemble their own dinosaur fossil collections. The competition to mount the first sauropod skeleton specifically was the most intense... | Apatosaurus | Wikipedia | 399 | 1346 | https://en.wikipedia.org/wiki/Apatosaurus | Biology and health sciences | Dinosaurs and prehistoric reptiles | null |
In 1903, Elmer Riggs published a study that described a well-preserved skeleton of a diplodocid from the Grand River Valley near Fruita, Colorado, Field Museum of Natural History specimen P25112. Riggs thought that the deposits were similar in age to those of the Como Bluff in Wyoming from which Marsh had described Bro... | Apatosaurus | Wikipedia | 198 | 1346 | https://en.wikipedia.org/wiki/Apatosaurus | Biology and health sciences | Dinosaurs and prehistoric reptiles | null |
Despite Riggs' publication, Henry Fairfield Osborn, who was a strong opponent of Marsh and his taxa, labeled the Apatosaurus mount of the American Museum of Natural History Brontosaurus. Because of this decision the name Brontosaurus was commonly used outside of scientific literature for what Riggs considered Apatosaur... | Apatosaurus | Wikipedia | 433 | 1346 | https://en.wikipedia.org/wiki/Apatosaurus | Biology and health sciences | Dinosaurs and prehistoric reptiles | null |
No Apatosaurus skull was mentioned in literature until the 1970s when John Stanton McIntosh and David Berman redescribed the skulls of Diplodocus and Apatosaurus. They found that though he never published his opinion, Holland was almost certainly correct, that Apatosaurus had a Diplodocus-like skull. According to them,... | Apatosaurus | Wikipedia | 398 | 1346 | https://en.wikipedia.org/wiki/Apatosaurus | Biology and health sciences | Dinosaurs and prehistoric reptiles | null |
Almost all modern paleontologists agreed with Riggs that the two dinosaurs should be classified together in a single genus. According to the rules of the ICZN (which governs the scientific names of animals), the name Apatosaurus, having been published first, has priority as the official name; Brontosaurus was considere... | Apatosaurus | Wikipedia | 122 | 1346 | https://en.wikipedia.org/wiki/Apatosaurus | Biology and health sciences | Dinosaurs and prehistoric reptiles | null |
In 2015, Emanuel Tschopp, Octávio Mateus, and Roger Benson released a paper on diplodocoid systematics, and proposed that genera could be diagnosed by thirteen differing characters, and species separated based on six. The minimum number for generic separation was chosen based on the fact that A.ajax and A.louisae diffe... | Apatosaurus | Wikipedia | 452 | 1346 | https://en.wikipedia.org/wiki/Apatosaurus | Biology and health sciences | Dinosaurs and prehistoric reptiles | null |
Many species of Apatosaurus have been designated from scant material. Marsh named as many species as he could, which resulted in many being based upon fragmentary and indistinguishable remains. In 2005, Paul Upchurch and colleagues published a study that analyzed the species and specimen relationships of Apatosaurus. T... | Apatosaurus | Wikipedia | 149 | 1346 | https://en.wikipedia.org/wiki/Apatosaurus | Biology and health sciences | Dinosaurs and prehistoric reptiles | null |
Apatosaurus ajax was named by Marsh in 1877 after Ajax, a hero from Greek mythology. Marsh designated the incomplete, juvenile skeleton YPM1860 as its holotype. The species is less studied than Brontosaurus and A.louisae, especially because of the incomplete nature of the holotype. In 2005, many specimens in addition t... | Apatosaurus | Wikipedia | 434 | 1346 | https://en.wikipedia.org/wiki/Apatosaurus | Biology and health sciences | Dinosaurs and prehistoric reptiles | null |
Apatosaurus grandis was named in 1877 by Marsh in the article that described A.ajax. It was briefly described, figured, and diagnosed. Marsh later mentioned it was only provisionally assigned to Apatosaurus when he reassigned it to his new genus Morosaurus in 1878. Since Morosaurus has been considered a synonym of Cama... | Apatosaurus | Wikipedia | 505 | 1346 | https://en.wikipedia.org/wiki/Apatosaurus | Biology and health sciences | Dinosaurs and prehistoric reptiles | null |
Apatosaurus yahnahpin was named by James Filla and Patrick Redman in 1994. Bakker made A.yahnahpin the type species of a new genus, Eobrontosaurus in 1998, and Tschopp reclassified it as Brontosaurus yahnahpin in 2015. | Apatosaurus | Wikipedia | 63 | 1346 | https://en.wikipedia.org/wiki/Apatosaurus | Biology and health sciences | Dinosaurs and prehistoric reptiles | null |
Classification
Apatosaurus is a member of the family Diplodocidae, a clade of gigantic sauropod dinosaurs. The family includes some of the longest creatures ever to walk the earth, including Diplodocus, Supersaurus, and Barosaurus. Apatosaurus is sometimes classified in the subfamily Apatosaurinae, which may also incl... | Apatosaurus | Wikipedia | 435 | 1346 | https://en.wikipedia.org/wiki/Apatosaurus | Biology and health sciences | Dinosaurs and prehistoric reptiles | null |
A 2015 study of the necks of Apatosaurus and Brontosaurus found many differences between them and other diplodocids, and that these variations may have shown that the necks of Apatosaurus and Brontosaurus were used for intraspecific combat. Various uses for the single claw on the forelimb of sauropods have been propose... | Apatosaurus | Wikipedia | 439 | 1346 | https://en.wikipedia.org/wiki/Apatosaurus | Biology and health sciences | Dinosaurs and prehistoric reptiles | null |
Matthew Cobley et al. (2013) dispute this, finding that large muscles and cartilage would have limited movement of the neck. They state the feeding ranges for sauropods like Diplodocus were smaller than previously believed, and the animals may have had to move their whole bodies around to better access areas where they... | Apatosaurus | Wikipedia | 435 | 1346 | https://en.wikipedia.org/wiki/Apatosaurus | Biology and health sciences | Dinosaurs and prehistoric reptiles | null |
James Spotila et al. (1991) concludes that the large body size of sauropods would have made them unable to maintain high metabolic rates because they would not have been able to release enough heat. They assumed sauropods had a reptilian respiratory system. Wedel says that an avian system would have allowed it to dump ... | Apatosaurus | Wikipedia | 426 | 1346 | https://en.wikipedia.org/wiki/Apatosaurus | Biology and health sciences | Dinosaurs and prehistoric reptiles | null |
Long-bone histology enables researchers to estimate the age that a specific individual reached. A study by Eva Griebeler etal. (2013) examined long-bone histological data and concluded the Apatosaurus sp.SMA0014 weighed , reached sexual maturity at 21years, and died aged 28. The same growth model indicated Apatosaurus ... | Apatosaurus | Wikipedia | 345 | 1346 | https://en.wikipedia.org/wiki/Apatosaurus | Biology and health sciences | Dinosaurs and prehistoric reptiles | null |
A pathology has been identified on the tail of Apatosaurus, caused by a growth defect. Two caudal vertebrae are seamlessly fused along the entire articulating surface of the bone, including the arches of the neural spines. This defect might have been caused by the lack or inhibition of the substance that forms interver... | Apatosaurus | Wikipedia | 434 | 1346 | https://en.wikipedia.org/wiki/Apatosaurus | Biology and health sciences | Dinosaurs and prehistoric reptiles | null |
Apatosaurus was the second most common sauropod in the Morrison Formation ecosystem, after Camarasaurus. Apatosaurus may have been more solitary than other Morrison Formation dinosaurs. Fossils of the genus have only been found in the upper levels of the formation. Those of Apatosaurus ajax are known exclusively from t... | Apatosaurus | Wikipedia | 150 | 1346 | https://en.wikipedia.org/wiki/Apatosaurus | Biology and health sciences | Dinosaurs and prehistoric reptiles | null |
The Morrison Formation records a time when the local environment was dominated by gigantic sauropod dinosaurs. Dinosaurs known from the Morrison Formation include the theropods Allosaurus, Ceratosaurus, Ornitholestes, and Torvosaurus; the sauropods Brontosaurus, Brachiosaurus, Camarasaurus, and Diplodocus; and the orni... | Apatosaurus | Wikipedia | 364 | 1346 | https://en.wikipedia.org/wiki/Apatosaurus | Biology and health sciences | Dinosaurs and prehistoric reptiles | null |
Allosaurus () is an extinct genus of large carnosaurian theropod dinosaur that lived 155 to 145 million years ago during the Late Jurassic period (Kimmeridgian to late Tithonian ages). The name "Allosaurus" means "different lizard", alluding to its unique (at the time of its discovery) concave vertebrae. It is derived ... | Allosaurus | Wikipedia | 491 | 1347 | https://en.wikipedia.org/wiki/Allosaurus | Biology and health sciences | Dinosaurs and prehistoric reptiles | null |
The discovery and early study of Allosaurus is complicated by the multiplicity of names coined during the Bone Wars of the late 19th century. The first described fossil in this history was a bone obtained secondhand by Ferdinand Vandeveer Hayden in 1869. It came from Middle Park, near Granby, Colorado, probably from Mo... | Allosaurus | Wikipedia | 375 | 1347 | https://en.wikipedia.org/wiki/Allosaurus | Biology and health sciences | Dinosaurs and prehistoric reptiles | null |
In their haste, Cope and Marsh did not always follow up on their discoveries (or, more commonly, those made by their subordinates). For example, after the discovery by Benjamin Mudge of the type specimen of Allosaurus in Colorado, Marsh elected to concentrate work in Wyoming. When work resumed at Garden Park in 1883, M... | Allosaurus | Wikipedia | 504 | 1347 | https://en.wikipedia.org/wiki/Allosaurus | Biology and health sciences | Dinosaurs and prehistoric reptiles | null |
Although sporadic work at what became known as the Cleveland-Lloyd Dinosaur Quarry in Emery County, Utah, had taken place as early as 1927 and the fossil site itself described by William L. Stokes in 1945, major operations did not begin there until 1960. Under a cooperative effort involving nearly 40 institutions, thou... | Allosaurus | Wikipedia | 471 | 1347 | https://en.wikipedia.org/wiki/Allosaurus | Biology and health sciences | Dinosaurs and prehistoric reptiles | null |
In 1991, "Big Al" (MOR 693), a 95% complete, partially articulated specimen of Allosaurus was discovered, measuring about long. MOR 693 was excavated near Shell, Wyoming, by a joint Museum of the Rockies and University of Wyoming Geological Museum team. This skeleton was discovered by a Swiss team, led by Kirby Siber.... | Allosaurus | Wikipedia | 358 | 1347 | https://en.wikipedia.org/wiki/Allosaurus | Biology and health sciences | Dinosaurs and prehistoric reptiles | null |
In 1988, during construction works of a warehouse, a skeleton of a large theropod was discovered near the village of Andrés, Leiria District, Portugal. The Andrés quarry is included in the Bombarral Formation ("Grés Superiores"). The lower part of this formation is diachronic with the Alcobaça Formation in the northen ... | Allosaurus | Wikipedia | 497 | 1347 | https://en.wikipedia.org/wiki/Allosaurus | Biology and health sciences | Dinosaurs and prehistoric reptiles | null |
In 2005, the Andrés quarry was reactivated for further prospection, which yielded remains of a diverse vertebrate fauna and new Allosaurus remains. These new remains (such as a partial right frontal, MNHNUL/AND.001/062), along with further preparation of the original Andrés specimen, allowed for a more detailed compari... | Allosaurus | Wikipedia | 254 | 1347 | https://en.wikipedia.org/wiki/Allosaurus | Biology and health sciences | Dinosaurs and prehistoric reptiles | null |
A detailed description of the remains of the Andrés specimen was published on the doctoral thesis of Elisabete Malafaia. The remains were collected between 1988 and 2010, and include cranial elements (such as the maxilla, nasal, lacrimals, prefrontal, postorbitals, frontals, palatines, quadrate, quadratojugal, squamosa... | Allosaurus | Wikipedia | 430 | 1347 | https://en.wikipedia.org/wiki/Allosaurus | Biology and health sciences | Dinosaurs and prehistoric reptiles | null |
Seven species of Allosaurus have been named: A. anax, A. amplus, A. atrox, A. europaeus, the type species A. fragilis, A. jimmadseni and A. lucasi. Among these (excluding A. anax, which was named in 2024), Daniel Chure and Mark Loewen in 2020 only recognized the species A. fragilis, A. europaeus, and the newly-named A.... | Allosaurus | Wikipedia | 408 | 1347 | https://en.wikipedia.org/wiki/Allosaurus | Biology and health sciences | Dinosaurs and prehistoric reptiles | null |
A. fragilis, A. jimmadseni, A. anax, A. amplus, and A. lucasi are all known from remains discovered in the Kimmeridgian–Tithonian Upper Jurassic-age Morrison Formation of the United States, spread across Colorado, Montana, New Mexico, Oklahoma, South Dakota, Utah and Wyoming. A. fragilis is regarded as the most common,... | Allosaurus | Wikipedia | 386 | 1347 | https://en.wikipedia.org/wiki/Allosaurus | Biology and health sciences | Dinosaurs and prehistoric reptiles | null |
The Allosaurus material from Portugal has a controversial taxonomic research history. The Andrés Allosaurus specimens, consisting of very complete cranial and post-cranial remains, have been attributed to A. fragilis, A. sp, A. europaeus and A. cf. europaeus. The Vale Frades Allosaurus, consisting of a partial skull an... | Allosaurus | Wikipedia | 507 | 1347 | https://en.wikipedia.org/wiki/Allosaurus | Biology and health sciences | Dinosaurs and prehistoric reptiles | null |
In his 1988 book, Predatory Dinosaurs of the World, the freelance artist & author Gregory S. Paul proposed that A. fragilis had tall pointed horns and a slender build compared to a postulated second species A. atrox, as well as not being a different sex due to rarity. Allosaurus atrox was originally named by Marsh in 1... | Allosaurus | Wikipedia | 486 | 1347 | https://en.wikipedia.org/wiki/Allosaurus | Biology and health sciences | Dinosaurs and prehistoric reptiles | null |
"Wyomingraptor" was informally coined by Bakker for allosaurid remains from the Morrison Formation of the Late Jurassic. The remains unearthed are labeled as Allosaurus and are housed in the Tate Geological Museum. However, there has been no official description of the remains and "Wyomingraptor" has been dismissed as ... | Allosaurus | Wikipedia | 440 | 1347 | https://en.wikipedia.org/wiki/Allosaurus | Biology and health sciences | Dinosaurs and prehistoric reptiles | null |
Allosaurus sibiricus was described in 1914 by A. N. Riabinin on the basis of a bone, later identified as a partial fourth metatarsal, from the Early Cretaceous of Buryatia, Russia. It was transferred to Chilantaisaurus in 1990, but is now considered a nomen dubium indeterminate beyond Theropoda.
Allosaurus meriani was... | Allosaurus | Wikipedia | 394 | 1347 | https://en.wikipedia.org/wiki/Allosaurus | Biology and health sciences | Dinosaurs and prehistoric reptiles | null |
A. maximus was a new combination by David K. Smith for Chure's Saurophaganax maximus, a taxon created by Chure in 1995 for giant allosaurid remains from the Morrison of Oklahoma. These remains had been known as Saurophagus, but that name was already in use, leading Chure to propose a substitute. Smith, in his 1998 ana... | Allosaurus | Wikipedia | 497 | 1347 | https://en.wikipedia.org/wiki/Allosaurus | Biology and health sciences | Dinosaurs and prehistoric reptiles | null |
Kurzanov and colleagues in 2003 designated six teeth from Siberia as Allosaurus sp. (meaning the authors found the specimens to be most like those of Allosaurus, but did not or could not assign a species to them). They were reclassified as an indeterminate theropod. Also, reports of Allosaurus in Shanxi, China go back ... | Allosaurus | Wikipedia | 289 | 1347 | https://en.wikipedia.org/wiki/Allosaurus | Biology and health sciences | Dinosaurs and prehistoric reptiles | null |
Allosaurus was a typical large theropod, having a massive skull on a short neck, a long, slightly sloping tail, and reduced forelimbs. Allosaurus fragilis, the best-known species, had an average length of and mass of , with the largest definitive Allosaurus specimen (AMNH 680) estimated at long, with an estimated wei... | Allosaurus | Wikipedia | 478 | 1347 | https://en.wikipedia.org/wiki/Allosaurus | Biology and health sciences | Dinosaurs and prehistoric reptiles | null |
David K. Smith, examining Allosaurus fossils by quarry, found that the Cleveland-Lloyd Dinosaur Quarry (Utah) specimens are generally smaller than those from Como Bluff (Wyoming) or Brigham Young University's Dry Mesa Quarry (Colorado), but the shapes of the bones themselves did not vary between the sites. A later stud... | Allosaurus | Wikipedia | 437 | 1347 | https://en.wikipedia.org/wiki/Allosaurus | Biology and health sciences | Dinosaurs and prehistoric reptiles | null |
The skull had a pair of horns above and in front of the eyes. These horns were composed of extensions of the lacrimal bones, and varied in shape and size. There were also lower paired ridges running along the top edges of the nasal bones that led into the horns. The horns were probably covered in a keratin sheath and m... | Allosaurus | Wikipedia | 289 | 1347 | https://en.wikipedia.org/wiki/Allosaurus | Biology and health sciences | Dinosaurs and prehistoric reptiles | null |
Allosaurus had nine vertebrae in the neck, 14 in the back, and five in the sacrum supporting the hips. The number of tail vertebrae is unknown and varied with individual size; James Madsen estimated about 50, while Gregory S. Paul considered that to be too many and suggested 45 or less. There were hollow spaces in the ... | Allosaurus | Wikipedia | 316 | 1347 | https://en.wikipedia.org/wiki/Allosaurus | Biology and health sciences | Dinosaurs and prehistoric reptiles | null |
The forelimbs of Allosaurus were short in comparison to the hindlimbs (only about 35% the length of the hindlimbs in adults) and had three fingers per hand, tipped with large, strongly curved and pointed claws. The arms were powerful, and the forearm was somewhat shorter than the upper arm (1:1.2 ulna/humerus ratio). T... | Allosaurus | Wikipedia | 497 | 1347 | https://en.wikipedia.org/wiki/Allosaurus | Biology and health sciences | Dinosaurs and prehistoric reptiles | null |
Allosaurus was an allosaurid, a member of a family of large theropods within the larger group Carnosauria. The family name Allosauridae was created for this genus in 1878 by Othniel Charles Marsh, but the term was largely unused until the 1970s in favor of Megalosauridae, another family of large theropods that eventual... | Allosaurus | Wikipedia | 371 | 1347 | https://en.wikipedia.org/wiki/Allosaurus | Biology and health sciences | Dinosaurs and prehistoric reptiles | null |
Allosauridae is one of four families in Allosauroidea; the other three are Neovenatoridae, Carcharodontosauridae and Sinraptoridae. Allosauridae has at times been proposed as ancestral to the Tyrannosauridae (which would make it paraphyletic), one example being Gregory S. Paul's Predatory Dinosaurs of the World, but th... | Allosaurus | Wikipedia | 486 | 1347 | https://en.wikipedia.org/wiki/Allosaurus | Biology and health sciences | Dinosaurs and prehistoric reptiles | null |
Medullary bone tissue (endosteally derived, ephemeral, mineralization located inside the medulla of the long bones in gravid female birds) has been reported in at least one Allosaurus specimen, a shin bone from the Cleveland-Lloyd Quarry. Today, this bone tissue is only formed in female birds that are laying eggs, as i... | Allosaurus | Wikipedia | 353 | 1347 | https://en.wikipedia.org/wiki/Allosaurus | Biology and health sciences | Dinosaurs and prehistoric reptiles | null |
Most paleontologists accept Allosaurus as an active predator of large animals. There is dramatic evidence for allosaur attacks on Stegosaurus, including an Allosaurus tail vertebra with a partially healed puncture wound that fits a Stegosaurus tail spike, and a Stegosaurus neck plate with a U-shaped wound that correlat... | Allosaurus | Wikipedia | 352 | 1347 | https://en.wikipedia.org/wiki/Allosaurus | Biology and health sciences | Dinosaurs and prehistoric reptiles | null |
Similar conclusions were drawn by another study using finite element analysis on an Allosaurus skull. According to their biomechanical analysis, the skull was very strong but had a relatively small bite force. By using jaw muscles only, it could produce a bite force of 805 to 8,724 N, but the skull could withstand near... | Allosaurus | Wikipedia | 483 | 1347 | https://en.wikipedia.org/wiki/Allosaurus | Biology and health sciences | Dinosaurs and prehistoric reptiles | null |
When compared with Tyrannosaurus and the therizinosaurid Erlikosaurus in the same study, it was found that Allosaurus had a wider gape than either; the animal was capable of opening its jaws to a 92-degree angle at maximum. The findings also indicate that large carnivorous dinosaurs, like modern carnivores, had wider j... | Allosaurus | Wikipedia | 79 | 1347 | https://en.wikipedia.org/wiki/Allosaurus | Biology and health sciences | Dinosaurs and prehistoric reptiles | null |
A biomechanical study published in 2013 by Eric Snively and colleagues found that Allosaurus had an unusually low attachment point on the skull for the longissimus capitis superficialis neck muscle compared to other theropods such as Tyrannosaurus. This would have allowed the animal to make rapid and forceful vertical ... | Allosaurus | Wikipedia | 402 | 1347 | https://en.wikipedia.org/wiki/Allosaurus | Biology and health sciences | Dinosaurs and prehistoric reptiles | null |
Sauropod carrion may also have been important to large theropods in the Morrison Formation. Forensic techniques indicate that sauropod carcasses were targeted by Allosaurus at all stages of decomposition, indicating that late-stage decay pathogens were not a significant deterrent. A survey of sauropod bones from the Mo... | Allosaurus | Wikipedia | 430 | 1347 | https://en.wikipedia.org/wiki/Allosaurus | Biology and health sciences | Dinosaurs and prehistoric reptiles | null |
It has been speculated since the 1970s that Allosaurus preyed on sauropods and other large dinosaurs by hunting in groups.
Such a depiction is common in semitechnical and popular dinosaur literature. Robert T. Bakker has extended social behavior to parental care, and has interpreted shed allosaur teeth and chewed bones... | Allosaurus | Wikipedia | 192 | 1347 | https://en.wikipedia.org/wiki/Allosaurus | Biology and health sciences | Dinosaurs and prehistoric reptiles | null |
Although Allosaurus may have hunted in packs, it has been argued that Allosaurus and other theropods had largely aggressive interactions instead of cooperative interactions with other members of their own species. The study in question noted that cooperative hunting of prey much larger than an individual predator, as i... | Allosaurus | Wikipedia | 458 | 1347 | https://en.wikipedia.org/wiki/Allosaurus | Biology and health sciences | Dinosaurs and prehistoric reptiles | null |
In 2001, Bruce Rothschild and others published a study examining evidence for stress fractures and tendon avulsions in theropod dinosaurs and the implications for their behavior. Since stress fractures are caused by repeated trauma rather than singular events they are more likely to be caused by the behavior of the ani... | Allosaurus | Wikipedia | 406 | 1347 | https://en.wikipedia.org/wiki/Allosaurus | Biology and health sciences | Dinosaurs and prehistoric reptiles | null |
The left scapula and fibula of an Allosaurus fragilis specimen cataloged as USNM 4734 are both pathological, both probably due to healed fractures. The specimen USNM 8367 preserved several pathological gastralia which preserve evidence of healed fractures near their middle. Some of the fractures were poorly healed and ... | Allosaurus | Wikipedia | 313 | 1347 | https://en.wikipedia.org/wiki/Allosaurus | Biology and health sciences | Dinosaurs and prehistoric reptiles | null |
Other pathologies reported in Allosaurus include:
Willow breaks in two ribs
Healed fractures in the humerus and radius
Distortion of joint surfaces in the foot, possibly due to osteoarthritis or developmental issues
Osteopetrosis along the endosteal surface of a tibia.
Distortions of the joint surfaces of the tail... | Allosaurus | Wikipedia | 363 | 1347 | https://en.wikipedia.org/wiki/Allosaurus | Biology and health sciences | Dinosaurs and prehistoric reptiles | null |
The Morrison Formation has been a rich fossil hunting ground. The flora of the period has been revealed by fossils of green algae, fungi, mosses, horsetails, ferns, cycads, ginkgoes, and several families of conifers. Animal fossils discovered include bivalves, snails, ray-finned fishes, frogs, salamanders, turtles, sph... | Allosaurus | Wikipedia | 358 | 1347 | https://en.wikipedia.org/wiki/Allosaurus | Biology and health sciences | Dinosaurs and prehistoric reptiles | null |
Allosaurus coexisted with fellow large theropods Ceratosaurus and Torvosaurus in both the United States and Portugal. The three appear to have had different ecological niches, based on anatomy and the location of fossils. Ceratosaurus and Torvosaurus may have preferred to be active around waterways, and had lower, thin... | Allosaurus | Wikipedia | 390 | 1347 | https://en.wikipedia.org/wiki/Allosaurus | Biology and health sciences | Dinosaurs and prehistoric reptiles | null |
The AK-47, officially known as the Avtomat Kalashnikova (; also known as the Kalashnikov or just AK), is an assault rifle that is chambered for the 7.62×39mm cartridge. Developed in the Soviet Union by Russian small-arms designer Mikhail Kalashnikov, it is the originating firearm of the Kalashnikov (or "AK") family of ... | AK-47 | Wikipedia | 463 | 1348 | https://en.wikipedia.org/wiki/AK-47 | Technology | Specific firearms | null |
The Soviets soon developed the 7.62×39mm M43 cartridge, used in the semi-automatic SKS carbine and the RPD light machine gun. Shortly after World War II, the Soviets developed the AK-47 rifle, which quickly replaced the SKS in Soviet service. Introduced in 1959, the AKM is a lighter stamped steel version and the most u... | AK-47 | Wikipedia | 455 | 1348 | https://en.wikipedia.org/wiki/AK-47 | Technology | Specific firearms | null |
Early designs
Kalashnikov started work on a submachine gun design in 1942 and a light machine gun design in 1943. Early in 1944, Kalashnikov was given some 7.62×39mm M43 cartridges and informed that other designers were working on weapons for this new Soviet small-arms cartridge. It was suggested that a new weapon migh... | AK-47 | Wikipedia | 410 | 1348 | https://en.wikipedia.org/wiki/AK-47 | Technology | Specific firearms | null |
In November 1947, the new prototypes (AK-47s) were completed. The rifle used a long-stroke gas piston above the barrel. The upper and lower receivers were combined into a single receiver. The selector and safety were combined into a single control lever/dust cover on the right side of the rifle and the bolt handle was ... | AK-47 | Wikipedia | 507 | 1348 | https://en.wikipedia.org/wiki/AK-47 | Technology | Specific firearms | null |
Most licensed and unlicensed productions of the Kalashnikov assault rifle abroad were of the AKM variant, partially due to the much easier production of the stamped receiver. This model is the most commonly encountered, having been produced in much greater quantities. All rifles based on the Kalashnikov design are ofte... | AK-47 | Wikipedia | 342 | 1348 | https://en.wikipedia.org/wiki/AK-47 | Technology | Specific firearms | null |
The AK fires the 7.62×39mm cartridge with a muzzle velocity of .
The cartridge weight is , and the projectile weight is . The original Soviet M43 bullets are 123-grain boat-tail bullets with a copper-plated steel jacket, a large steel core, and some lead between the core and the jacket. The AK has excellent penetration... | AK-47 | Wikipedia | 321 | 1348 | https://en.wikipedia.org/wiki/AK-47 | Technology | Specific firearms | null |
To fire, the operator inserts a loaded magazine, pulls back and releases the charging handle, and then pulls the trigger. In semi-automatic, the firearm fires only once, requiring the trigger to be released and depressed again for the next shot. In fully automatic, the rifle continues to fire automatically cycling fres... | AK-47 | Wikipedia | 478 | 1348 | https://en.wikipedia.org/wiki/AK-47 | Technology | Specific firearms | null |
The fire selector is a large lever located on the right side of the rifle; it acts as a dust cover and prevents the charging handle from being pulled fully to the rear when it is on safe. It is operated by the shooter's right fore-fingers and has three settings: safe (up), full-auto (center), and semi-auto (down). The ... | AK-47 | Wikipedia | 496 | 1348 | https://en.wikipedia.org/wiki/AK-47 | Technology | Specific firearms | null |
Furniture
The AK-47 was originally equipped with a buttstock, handguard, and an upper heat guard made from solid wood. With the introduction of the Type 3 receiver the buttstock, lower handguard, and upper heat guard were manufactured from birch plywood laminates. Such engineered woods are stronger and resist warping ... | AK-47 | Wikipedia | 321 | 1348 | https://en.wikipedia.org/wiki/AK-47 | Technology | Specific firearms | null |
The early slab-sided steel AK-47 30-round detachable box magazines had sheet-metal bodies and weighed empty. The later steel AKM 30-round magazines had lighter sheet-metal bodies with prominent reinforcing ribs weighing empty. To further reduce weight, a lightweight magazine with an aluminum body with a prominent re... | AK-47 | Wikipedia | 477 | 1348 | https://en.wikipedia.org/wiki/AK-47 | Technology | Specific firearms | null |
Most Yugoslavian and some East German AK magazines were made with cartridge followers that hold the bolt open when empty; however, most AK magazine followers allow the bolt to close when the magazine is empty.
Accessories
Accessories supplied with the rifle include a long 6H3 bayonet featuring a long spear point b... | AK-47 | Wikipedia | 484 | 1348 | https://en.wikipedia.org/wiki/AK-47 | Technology | Specific firearms | null |
The AK-47 has small parts and springs that need to be replaced every few thousand rounds. However, "Every time it is disassembled beyond the field stripping stage, it will take some time for some parts to regain their fit, and some parts may tend to shake loose and fall out when firing the weapon. Some parts of the AK-... | AK-47 | Wikipedia | 502 | 1348 | https://en.wikipedia.org/wiki/AK-47 | Technology | Specific firearms | null |
A private company Kalashnikov Concern (formerly Izhmash) from Russia has repeatedly claimed that the majority of foreign manufacturers are producing AK-type rifles without proper licensing.
Accuracy potential
US military method
The AK-47's accuracy is generally sufficient to hit an adult male torso out to about , tho... | AK-47 | Wikipedia | 482 | 1348 | https://en.wikipedia.org/wiki/AK-47 | Technology | Specific firearms | null |
− Type 56 variant.
− EKAM: The counter-terrorist unit of the Hellenic Police
− Type 58 variant
– Locally made as well as being in service with the Army
− Used by Thahan Phran
Non-state current
ELN
FARC di... | AK-47 | Wikipedia | 508 | 1348 | https://en.wikipedia.org/wiki/AK-47 | Technology | Specific firearms | null |
The AK-47 has been used in the following conflicts:
1940s
Malayan Emergency (1948−1960)
1950s
Hungarian Revolution (1956)
Vietnam War (1955–1975)
Laotian Civil War (1959–1975)
1960s
Congo Crisis (1960–1965)
Portuguese Colonial War (1961–1974)
Rhodesian Bush War (1964–1979)
The Troubles (late 1960s–1998)
Com... | AK-47 | Wikipedia | 483 | 1348 | https://en.wikipedia.org/wiki/AK-47 | Technology | Specific firearms | null |
During the Cold War, the Soviet Union and the People's Republic of China, as well as United States and other NATO nations supplied arms and technical knowledge to numerous countries and rebel forces around the world. During this time the Western countries used relatively expensive automatic rifles, such as the FN FAL, ... | AK-47 | Wikipedia | 369 | 1348 | https://en.wikipedia.org/wiki/AK-47 | Technology | Specific firearms | null |
The Kalashnikov Museum (also called the AK-47 museum) opened on 4 November 2004 in Izhevsk, Udmurt Republic. This city is in the Ural Region of Russia. The museum chronicles the biography of General Kalashnikov and documents the invention of the AK-47. The museum complex of Kalashnikov's small arms, a series of halls, ... | AK-47 | Wikipedia | 469 | 1348 | https://en.wikipedia.org/wiki/AK-47 | Technology | Specific firearms | null |
The AK-47 made an appearance in U.S. popular culture as a recurring focus in the Nicolas Cage film Lord of War (2005). Numerous monologues in the movie focus on the weapon, and its effects on global conflict and the gun running market.
In Iraq and Afghanistan, private military company contractors from the U.K. and oth... | AK-47 | Wikipedia | 211 | 1348 | https://en.wikipedia.org/wiki/AK-47 | Technology | Specific firearms | null |
The Atanasoff–Berry computer (ABC) was the first automatic electronic digital computer. The device was limited by the technology of the day. The ABC's priority is debated among historians of computer technology, because it was neither programmable, nor Turing-complete. Conventionally, the ABC would be considered the fi... | Atanasoff–Berry computer | Wikipedia | 481 | 1349 | https://en.wikipedia.org/wiki/Atanasoff%E2%80%93Berry%20computer | Technology | Early computers | null |
According to Atanasoff's account, several key principles of the Atanasoff–Berry computer were conceived in a sudden insight after a long nighttime drive to Rock Island, Illinois, during the winter of 1937–38. The ABC innovations included electronic computation, binary arithmetic, parallel processing, regenerative capac... | Atanasoff–Berry computer | Wikipedia | 438 | 1349 | https://en.wikipedia.org/wiki/Atanasoff%E2%80%93Berry%20computer | Technology | Early computers | null |
The memory of the Atanasoff–Berry computer was a system called regenerative capacitor memory, which consisted of a pair of drums, each containing 1600 capacitors that rotated on a common shaft once per second. The capacitors on each drum were organized into 32 "bands" of 50 (30 active bands and two spares in case a cap... | Atanasoff–Berry computer | Wikipedia | 470 | 1349 | https://en.wikipedia.org/wiki/Atanasoff%E2%80%93Berry%20computer | Technology | Early computers | null |
Intermediate results were binary, written onto paper sheets by electrostatically modifying the resistance at 1500 locations to represent 30 of the 50-bit numbers (one equation). Each sheet could be written or read in one second. The reliability of the system was limited to about 1 error in 100,000 calculations by these... | Atanasoff–Berry computer | Wikipedia | 495 | 1349 | https://en.wikipedia.org/wiki/Atanasoff%E2%80%93Berry%20computer | Technology | Early computers | null |
The case was legally resolved on October 19, 1973, when U.S. District Judge Earl R. Larson held the ENIAC patent invalid, ruling that the ENIAC derived many basic ideas from the Atanasoff–Berry computer. Judge Larson explicitly stated:
Herman Goldstine, one of the original developers of ENIAC wrote:
Replica
The origi... | Atanasoff–Berry computer | Wikipedia | 190 | 1349 | https://en.wikipedia.org/wiki/Atanasoff%E2%80%93Berry%20computer | Technology | Early computers | null |
An anchor is a device, normally made of metal, used to secure a vessel to the bed of a body of water to prevent the craft from drifting due to wind or current. The word derives from Latin , which itself comes from the Greek ().
Anchors can either be temporary or permanent. Permanent anchors are used in the creation o... | Anchor | Wikipedia | 361 | 1358 | https://en.wikipedia.org/wiki/Anchor | Technology | Naval transport | null |
Holding ground is the area of sea floor that holds an anchor, and thus the attached ship or boat. Different types of anchor are designed to hold in different types of holding ground. Some bottom materials hold better than others; for instance, hard sand holds well, shell holds poorly. Holding ground may be fouled with ... | Anchor | Wikipedia | 380 | 1358 | https://en.wikipedia.org/wiki/Anchor | Technology | Naval transport | null |
Using an anchor weight, kellet or sentinel
Lowering a concentrated, heavy weight down the anchor line – rope or chain – directly in front of the bow to the seabed behaves like a heavy chain rode and lowers the angle of pull on the anchor. If the weight is suspended off the seabed it acts as a spring or shock absorber ... | Anchor | Wikipedia | 482 | 1358 | https://en.wikipedia.org/wiki/Anchor | Technology | Naval transport | null |
Bahamian moor
Similar to the above, a Bahamian moor is used to sharply limit the swing range of a vessel, but allows it to swing to a current. One of the primary characteristics of this technique is the use of a swivel as follows: the first anchor is set normally, and the vessel drops back to the limit of anchor cable... | Anchor | Wikipedia | 495 | 1358 | https://en.wikipedia.org/wiki/Anchor | Technology | Naval transport | null |
Club hauling
Club hauling is an archaic technique. When a vessel is in a narrow channel or on a lee shore so that there is no room to tack the vessel in a conventional manner, an anchor attached to the lee quarter may be dropped from the lee bow. This is deployed when the vessel is head to wind and has lost headway. ... | Anchor | Wikipedia | 503 | 1358 | https://en.wikipedia.org/wiki/Anchor | Technology | Naval transport | null |
The earliest anchors were probably rocks, and many rock anchors have been found dating from at least the Bronze Age. Pre-European Māori waka (canoes) used one or more hollowed stones, tied with flax ropes, as anchors. Many modern moorings still rely on a large rock as the primary element of their design. However, usin... | Anchor | Wikipedia | 449 | 1358 | https://en.wikipedia.org/wiki/Anchor | Technology | Naval transport | null |
The Admiralty Anchor is an entirely independent reinvention of a classical design, as seen in one of the Nemi ship anchors. This basic design remained unchanged for centuries, with the most significant changes being to the overall proportions, and a move from stocks made of wood to iron stocks in the late 1830s and ear... | Anchor | Wikipedia | 500 | 1358 | https://en.wikipedia.org/wiki/Anchor | Technology | Naval transport | null |
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