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Chloroplast DNA (cpDNA), also known as plastid DNA (ptDNA) is the DNA located in chloroplasts, which are photosynthetic organelles located within the cells of some eukaryotic organisms. Chloroplasts, like other types of plastid, contain a genome separate from that in the cell nucleus. The existence of chloroplast DNA w... | Chloroplast DNA | Wikipedia | 450 | 25777451 | https://en.wikipedia.org/wiki/Chloroplast%20DNA | Biology and health sciences | Plant cells | Biology |
The inverted repeats vary wildly in length, ranging from 4,000 to 25,000 base pairs long each. Inverted repeats in plants tend to be at the upper end of this range, each being 20,000–25,000 base pairs long.
The inverted repeat regions usually contain three ribosomal RNA and two tRNA genes, but they can be expanded or r... | Chloroplast DNA | Wikipedia | 460 | 25777451 | https://en.wikipedia.org/wiki/Chloroplast%20DNA | Biology and health sciences | Plant cells | Biology |
More than 5000 chloroplast genomes have been sequenced and are accessible via the NCBI organelle genome database. The first chloroplast genomes were sequenced in 1986, from tobacco (Nicotiana tabacum) and liverwort (Marchantia polymorpha). Comparison of the gene sequences of the cyanobacteria Synechocystis to those of ... | Chloroplast DNA | Wikipedia | 413 | 25777451 | https://en.wikipedia.org/wiki/Chloroplast%20DNA | Biology and health sciences | Plant cells | Biology |
Endosymbiotic gene transfer is how we know about the lost chloroplasts in many chromalveolate lineages. Even if a chloroplast is eventually lost, the genes it donated to the former host's nucleus persist, providing evidence for the lost chloroplast's existence. For example, while diatoms (a heterokontophyte) now have a... | Chloroplast DNA | Wikipedia | 460 | 25777451 | https://en.wikipedia.org/wiki/Chloroplast%20DNA | Biology and health sciences | Plant cells | Biology |
RNA editing in plastids
RNA editing is the insertion, deletion, and substitution of nucleotides in a mRNA transcript prior to translation to protein. The highly oxidative environment inside chloroplasts increases the rate of mutation so post-transcription repairs are needed to conserve functional sequences. The chlorop... | Chloroplast DNA | Wikipedia | 432 | 25777451 | https://en.wikipedia.org/wiki/Chloroplast%20DNA | Biology and health sciences | Plant cells | Biology |
In addition to the early microscopy experiments, this model is also supported by the amounts of deamination seen in cpDNA. Deamination occurs when an amino group is lost and is a mutation that often results in base changes. When adenine is deaminated, it becomes hypoxanthine (H). Hypoxanthine can bind to cytosine, and ... | Chloroplast DNA | Wikipedia | 475 | 25777451 | https://en.wikipedia.org/wiki/Chloroplast%20DNA | Biology and health sciences | Plant cells | Biology |
The movement of so many chloroplast genes to the nucleus means that many chloroplast proteins that were supposed to be translated in the chloroplast are now synthesized in the cytoplasm. This means that these proteins must be directed back to the chloroplast, and imported through at least two chloroplast membranes.
Cu... | Chloroplast DNA | Wikipedia | 349 | 25777451 | https://en.wikipedia.org/wiki/Chloroplast%20DNA | Biology and health sciences | Plant cells | Biology |
Polypeptides, the precursors of proteins, are chains of amino acids. The two ends of a polypeptide are called the N-terminus, or amino end, and the C-terminus, or carboxyl end. For many (but not all) chloroplast proteins encoded by nuclear genes, cleavable transit peptides are added to the N-termini of the polypeptides... | Chloroplast DNA | Wikipedia | 400 | 25777451 | https://en.wikipedia.org/wiki/Chloroplast%20DNA | Biology and health sciences | Plant cells | Biology |
After a chloroplast polypeptide is synthesized on a ribosome in the cytosol, ATP energy can be used to phosphorylate, or add a phosphate group to many (but not all) of them in their transit sequences. Serine and threonine (both very common in chloroplast transit sequences—making up 20–30% of the sequence) are often the... | Chloroplast DNA | Wikipedia | 498 | 25777451 | https://en.wikipedia.org/wiki/Chloroplast%20DNA | Biology and health sciences | Plant cells | Biology |
The first three proteins form a core complex that consists of one Toc159, four to five Toc34s, and four Toc75s that form four holes in a disk 13 nanometers across. The whole core complex weighs about 500 kilodaltons. The other two proteins, Toc64 and Toc12, are associated with the core complex but are not part of it.
... | Chloroplast DNA | Wikipedia | 436 | 25777451 | https://en.wikipedia.org/wiki/Chloroplast%20DNA | Biology and health sciences | Plant cells | Biology |
Arabidopsis thaliana has two homologous proteins, AtToc33 and AtToc34 (The At stands for Arabidopsis thaliana), which are each about 60% identical in amino acid sequence to Toc34 in peas (called psToc34). AtToc33 is the most common in Arabidopsis, and it is the functional analogue of Toc34 because it can be turned off ... | Chloroplast DNA | Wikipedia | 426 | 25777451 | https://en.wikipedia.org/wiki/Chloroplast%20DNA | Biology and health sciences | Plant cells | Biology |
A family of Toc159 proteins, Toc159, Toc132, Toc120, and Toc90 have been found in Arabidopsis thaliana. They vary in the length of their A-domains, which is completely gone in Toc90. Toc132, Toc120, and Toc90 seem to have specialized functions in importing stuff like nonphotosynthetic preproteins, and can't replace Toc... | Chloroplast DNA | Wikipedia | 477 | 25777451 | https://en.wikipedia.org/wiki/Chloroplast%20DNA | Biology and health sciences | Plant cells | Biology |
Tic20 is an integral protein thought to have four transmembrane α-helices. It is found in the 1 million dalton TIC complex. Because it is similar to bacterial amino acid transporters and the mitochondrial import protein Tim17 (translocase on the inner mitochondrial membrane), it has been proposed to be part of the TIC ... | Chloroplast DNA | Wikipedia | 482 | 25777451 | https://en.wikipedia.org/wiki/Chloroplast%20DNA | Biology and health sciences | Plant cells | Biology |
Tic56
Tic56 is also a nuclear encoded protein. The preprotein its gene encodes is 527 amino acids long, weighing close to 62 thousand daltons; the mature form probably undergoes processing that trims it down to something that weighs 56 thousand daltons when it gets imported into the chloroplast. Tic56 is largely embedd... | Chloroplast DNA | Wikipedia | 116 | 25777451 | https://en.wikipedia.org/wiki/Chloroplast%20DNA | Biology and health sciences | Plant cells | Biology |
Graphene () is a carbon allotrope consisting of a single layer of atoms arranged in a honeycomb planar nanostructure. The name "graphene" is derived from "graphite" and the suffix -ene, indicating the presence of double bonds within the carbon structure.
Graphene is known for its exceptionally high tensile strength, ... | Graphene | Wikipedia | 413 | 911833 | https://en.wikipedia.org/wiki/Graphene | Physical sciences | Group 14 | Chemistry |
In 1859, Benjamin Brodie noted the highly lamellar structure of thermally reduced graphite oxide. Pioneers in X-ray crystallography attempted to determine the structure of graphite. The lack of large single crystal graphite specimens contributed to the independent development of X-ray powder diffraction by Peter Debye ... | Graphene | Wikipedia | 468 | 911833 | https://en.wikipedia.org/wiki/Graphene | Physical sciences | Group 14 | Chemistry |
In 1975, van Bommel et al. epitaxially grew a single layer of graphite on top of silicon carbide. Others grew single layers of carbon atoms on other materials. This "epitaxial graphene" consists of a single-atom-thick hexagonal lattice of sp2-bonded carbon atoms, as in free-standing graphene. However, there is signific... | Graphene | Wikipedia | 438 | 911833 | https://en.wikipedia.org/wiki/Graphene | Physical sciences | Group 14 | Chemistry |
Graphene was properly isolated and characterized in 2004 by Andre Geim and Konstantin Novoselov at the University of Manchester. They pulled graphene layers from graphite with a common adhesive tape in a process called micro-mechanical cleavage, colloquially referred to as the Scotch tape technique. The graphene flakes... | Graphene | Wikipedia | 510 | 911833 | https://en.wikipedia.org/wiki/Graphene | Physical sciences | Group 14 | Chemistry |
Three of the four outer-shell electrons of each atom in a graphene sheet occupy three sp2 hybrid orbitals – a combination of orbitals s, px and py — that are shared with the three nearest atoms, forming σ-bonds. The length of these bonds is about 0.142 nanometers.
The remaining outer-shell electron occupies a pz orbit... | Graphene | Wikipedia | 512 | 911833 | https://en.wikipedia.org/wiki/Graphene | Physical sciences | Group 14 | Chemistry |
Electronic properties
Graphene is a zero-gap semiconductor because its conduction and valence bands meet at the Dirac points. The Dirac points are six locations in momentum space on the edge of the Brillouin zone, divided into two non-equivalent sets of three points. These sets are labeled K and K'. These sets give g... | Graphene | Wikipedia | 472 | 911833 | https://en.wikipedia.org/wiki/Graphene | Physical sciences | Group 14 | Chemistry |
with the nearest-neighbor (π orbitals) hopping energy γ0 ≈ and the lattice constant . The conduction and valence bands correspond to the different signs. With one pz electron per atom in this model, the valence band is fully occupied, while the conduction band is vacant. The two bands touch at the zone corners (the K ... | Graphene | Wikipedia | 463 | 911833 | https://en.wikipedia.org/wiki/Graphene | Physical sciences | Group 14 | Chemistry |
Graphene exhibits high electron mobility at room temperature, with values reported in excess of . Hole and electron mobilities are nearly identical. The mobility is independent of temperature between and , showing minimal change even at room temperature (300 K), suggesting that the dominant scattering mechanism is def... | Graphene | Wikipedia | 435 | 911833 | https://en.wikipedia.org/wiki/Graphene | Physical sciences | Group 14 | Chemistry |
Electrical conductivity and charge transport
Despite zero carrier density near the Dirac points, graphene exhibits a minimum conductivity on the order of . The origin of this minimum conductivity is still unclear. However, rippling of the graphene sheet or ionized impurities in the substrate may lead to local puddles... | Graphene | Wikipedia | 417 | 911833 | https://en.wikipedia.org/wiki/Graphene | Physical sciences | Group 14 | Chemistry |
Graphene shows the quantum Hall effect: the conductivity quantization is unusual in that the sequence of steps is shifted by 1/2 with respect to the standard sequence and with an additional factor of 4. Graphene's Hall conductivity is , where N is the Landau level and the double valley and double spin degeneracies give... | Graphene | Wikipedia | 467 | 911833 | https://en.wikipedia.org/wiki/Graphene | Physical sciences | Group 14 | Chemistry |
Graphene's unit cell has two identical carbon atoms and two zero-energy states: one where the electron resides on atom A, and the other on atom B. However, if the unit cell's two atoms are not identical, the situation changes. Research shows that placing hexagonal boron nitride (h-BN) in contact with graphene can alter... | Graphene | Wikipedia | 511 | 911833 | https://en.wikipedia.org/wiki/Graphene | Physical sciences | Group 14 | Chemistry |
Permittivity
Graphene's permittivity varies with frequency. Over a range from microwave to millimeter wave frequencies, it is approximately 3.3. This permittivity, combined with its ability to function as both a conductor and as an insulator, theoretically allows compact capacitors made of graphene to store large amo... | Graphene | Wikipedia | 468 | 911833 | https://en.wikipedia.org/wiki/Graphene | Physical sciences | Group 14 | Chemistry |
Tunable band gap and optical response
Graphene's band gap can be tuned from 0 to (about 5-micrometer wavelength) by applying a voltage to a dual-gate bilayer graphene field-effect transistor (FET) at room temperature. The optical response of graphene nanoribbons is tunable into the terahertz regime by an applied magn... | Graphene | Wikipedia | 411 | 911833 | https://en.wikipedia.org/wiki/Graphene | Physical sciences | Group 14 | Chemistry |
Excitonic properties
First-principle calculations incorporating quasiparticle corrections and many-body effects have been employed to study the electronic and optical properties of graphene-based materials. The approach was described as three stages. With GW calculation, the properties of graphene-based materials were... | Graphene | Wikipedia | 509 | 911833 | https://en.wikipedia.org/wiki/Graphene | Physical sciences | Group 14 | Chemistry |
Mechanical properties
The (two-dimensional) density of graphene is 0.763 mg per square meter.
Graphene is the strongest material ever tested, with an intrinsic tensile strength of (with representative engineering tensile strength ~50-60 GPa for stretching large-area freestanding graphene) and a Young's modulus (stif... | Graphene | Wikipedia | 299 | 911833 | https://en.wikipedia.org/wiki/Graphene | Physical sciences | Group 14 | Chemistry |
In two-dimensional structures like graphene, thermal and quantum fluctuations cause relative displacement, with fluctuations growing logarithmically with structure size as per the Mermin–Wagner theorem. This shows that the amplitude of long-wavelength fluctuations grows logarithmically with the scale of a 2D structure,... | Graphene | Wikipedia | 485 | 911833 | https://en.wikipedia.org/wiki/Graphene | Physical sciences | Group 14 | Chemistry |
Graphene grain boundaries typically contain heptagon-pentagon pairs. The arrangement of such defects depends on whether the GB is in a zig-zag or armchair direction. It further depends on the tilt-angle of the GB. In 2010, researchers from Brown University computationally predicted that as the tilt-angle increases, the... | Graphene | Wikipedia | 402 | 911833 | https://en.wikipedia.org/wiki/Graphene | Physical sciences | Group 14 | Chemistry |
Compared to the fairly well-understood nature of the effect that grain boundary and vacancies have on the mechanical properties of graphene, there is no clear consensus on the general effect that the average grain size has on the strength of polycrystalline graphene. In fact, three notable theoretical or computational ... | Graphene | Wikipedia | 484 | 911833 | https://en.wikipedia.org/wiki/Graphene | Physical sciences | Group 14 | Chemistry |
Such discrepancies show the complexity of the effects that grain size, arrangements of defects, and the nature of defects have on the mechanical properties of polycrystalline graphene | Graphene | Wikipedia | 37 | 911833 | https://en.wikipedia.org/wiki/Graphene | Physical sciences | Group 14 | Chemistry |
Other properties
Thermal conductivity
Thermal transport in graphene is a burgeoning area of research, particularly for its potential applications in thermal management. Most experimental measurements have posted large uncertainties in the results of thermal conductivity due to the limitations of the instruments used... | Graphene | Wikipedia | 418 | 911833 | https://en.wikipedia.org/wiki/Graphene | Physical sciences | Group 14 | Chemistry |
Graphite, a 3D counterpart to graphene, exhibits a basal plane thermal conductivity exceeding (similar to diamond), In graphite, the c-axis (out of plane) thermal conductivity is over a factor of ~100 smaller due to the weak binding forces between basal planes as well as the larger lattice spacing. In addition, the ba... | Graphene | Wikipedia | 503 | 911833 | https://en.wikipedia.org/wiki/Graphene | Physical sciences | Group 14 | Chemistry |
Graphene can self-repair holes in its sheets, when exposed to molecules containing carbon, such as hydrocarbons. Bombarded with pure carbon atoms, the atoms perfectly align into hexagons, filling the holes.
Biological properties
Despite the promising results in different cell studies and proof of concept studies, th... | Graphene | Wikipedia | 449 | 911833 | https://en.wikipedia.org/wiki/Graphene | Physical sciences | Group 14 | Chemistry |
In 2013 a group of Polish scientists presented a production unit that allows the manufacture of continuous monolayer sheets. The process is based on graphene growth on a liquid metal matrix. The product of this process was called High Strength Metallurgical Graphene. In a new study published in Nature, the researchers ... | Graphene | Wikipedia | 466 | 911833 | https://en.wikipedia.org/wiki/Graphene | Physical sciences | Group 14 | Chemistry |
Periodically stacked graphene and its insulating isomorph provide a fascinating structural element in implementing highly functional superlattices at the atomic scale, which offers possibilities for designing nanoelectronic and photonic devices. Various types of superlattices can be obtained by stacking graphene and it... | Graphene | Wikipedia | 462 | 911833 | https://en.wikipedia.org/wiki/Graphene | Physical sciences | Group 14 | Chemistry |
Graphene oxide is usually produced through chemical exfoliation of graphite. A particularly popular technique is the improved Hummers' method. Using paper-making techniques on dispersed, oxidized and chemically processed graphite in water, the monolayer flakes form a single sheet and create strong bonds. These sheets, ... | Graphene | Wikipedia | 471 | 911833 | https://en.wikipedia.org/wiki/Graphene | Physical sciences | Group 14 | Chemistry |
Refluxing single-layer graphene oxide (SLGO) in solvents leads to size reduction and folding of individual sheets as well as loss of carboxylic group functionality, by up to 20%, indicating thermal instabilities of SLGO sheets dependent on their preparation methodology. When using thionyl chloride, acyl chloride groups... | Graphene | Wikipedia | 512 | 911833 | https://en.wikipedia.org/wiki/Graphene | Physical sciences | Group 14 | Chemistry |
Graphene fiber
In 2011, researchers reported a novel yet simple approach to fabricating graphene fibers from chemical vapor deposition-grown graphene films. The method was scalable and controllable, delivering tunable morphology and pore structure by controlling the evaporation of solvents with suitable surface tensio... | Graphene | Wikipedia | 454 | 911833 | https://en.wikipedia.org/wiki/Graphene | Physical sciences | Group 14 | Chemistry |
Box-shaped graphene (BSG) nanostructure appearing after mechanical cleavage of pyrolytic graphite was reported in 2016. The discovered nanostructure is a multilayer system of parallel hollow nanochannels located along the surface and having quadrangular cross-section. The thickness of the channel walls is approximately... | Graphene | Wikipedia | 464 | 911833 | https://en.wikipedia.org/wiki/Graphene | Physical sciences | Group 14 | Chemistry |
In 2015, researchers from the University of Illinois at Urbana-Champaign (UIUC) developed a new approach for forming 3D shapes from flat, 2D sheets of graphene. A film of graphene that had been soaked in solvent to make it swell and become malleable was overlaid on an underlying substrate "former". The solvent evaporat... | Graphene | Wikipedia | 484 | 911833 | https://en.wikipedia.org/wiki/Graphene | Physical sciences | Group 14 | Chemistry |
A solenoid made with such a coil behaves as a quantum conductor whose current distribution between the core and exterior varies with applied voltage, resulting in nonlinear inductance.
Crumpled graphene
In 2016, Brown University introduced a method for "crumpling" graphene, adding wrinkles to the material on a nanos... | Graphene | Wikipedia | 465 | 911833 | https://en.wikipedia.org/wiki/Graphene | Physical sciences | Group 14 | Chemistry |
As of 2014, exfoliation produced graphene with the lowest number of defects and highest electron mobility. Alternatively, a sharp single-crystal diamond wedge can penetrate onto the graphite source to cleave layers. In the same year, defect-free, unoxidized graphene-containing liquids were made from graphite using mixe... | Graphene | Wikipedia | 460 | 911833 | https://en.wikipedia.org/wiki/Graphene | Physical sciences | Group 14 | Chemistry |
Exfoliation with supercritical carbon dioxide
Liquid-phase exfoliation can also be done by a less-known process of intercalating supercritical carbon dioxide (scCO2) into the interstitial spaces in the graphite lattice, followed by rapid depressurization. The scCO2 intercalates easily inside the graphite lattice at a ... | Graphene | Wikipedia | 432 | 911833 | https://en.wikipedia.org/wiki/Graphene | Physical sciences | Group 14 | Chemistry |
A dispersed reduced graphene oxide suspension was synthesized in water by a hydrothermal dehydration method without using any surfactant. The approach is facile, industrially applicable, environmentally friendly, and cost-effective. Viscosity measurements confirmed that the graphene colloidal suspension (graphene nanof... | Graphene | Wikipedia | 504 | 911833 | https://en.wikipedia.org/wiki/Graphene | Physical sciences | Group 14 | Chemistry |
Epitaxy
Epitaxial graphene growth on silicon carbide is a wafer-scale technique to produce graphene. Epitaxial graphene may be coupled to surfaces weakly enough (by the active valence electrons that create Van der Waals forces) to retain the two-dimensional electronic band structure of isolated graphene.
A normal sil... | Graphene | Wikipedia | 386 | 911833 | https://en.wikipedia.org/wiki/Graphene | Physical sciences | Group 14 | Chemistry |
As reported by a group led by D. H. Adamson, graphene can be produced from natural graphite while preserving the integrity of the sheets using the solvent interface trapping method (SITM). SITM uses a high-energy interface, such as oil and water, to exfoliate graphite to graphene. Stacked graphite delaminates, or sprea... | Graphene | Wikipedia | 475 | 911833 | https://en.wikipedia.org/wiki/Graphene | Physical sciences | Group 14 | Chemistry |
Accelerating carbon ions inside an electrical field into a semiconductor made of thin nickel films on a substrate of SiO2/Si, creates a wafer-scale () wrinkle/tear/residue-free graphene layer at a relatively low temperature of 500 °C.
CMOS-compatible graphene
Integration of graphene in the widely employed CMOS fabri... | Graphene | Wikipedia | 470 | 911833 | https://en.wikipedia.org/wiki/Graphene | Physical sciences | Group 14 | Chemistry |
Graphene analogs (also referred to as "artificial graphene") are two-dimensional systems which exhibit similar properties to graphene. Graphene analogs have been studied intensively since the discovery of graphene in 2004. People try to develop systems in which the physics is easier to observe and manipulate than in gr... | Graphene | Wikipedia | 488 | 911833 | https://en.wikipedia.org/wiki/Graphene | Physical sciences | Group 14 | Chemistry |
The potential of epitaxial graphene on SiC for metrology has been shown since 2010, displaying quantum Hall resistance quantization accuracy of three parts per billion in monolayer epitaxial graphene. Over the years precisions of parts-per-trillion in the Hall resistance quantization and giant quantum Hall plateaus hav... | Graphene | Wikipedia | 395 | 911833 | https://en.wikipedia.org/wiki/Graphene | Physical sciences | Group 14 | Chemistry |
In 2014, research at Stony Brook University showed that graphene nanoribbons, graphene nanoplatelets, and graphene nano–onions are non-toxic at concentrations up to 50 μg/ml. These nanoparticles do not alter the differentiation of human bone marrow stem cells towards osteoblasts (bone) or adipocytes (fat), suggesting t... | Graphene | Wikipedia | 162 | 911833 | https://en.wikipedia.org/wiki/Graphene | Physical sciences | Group 14 | Chemistry |
A turbidite is the geologic deposit of a turbidity current, which is a type of amalgamation of fluidal and sediment gravity flow responsible for distributing vast amounts of clastic sediment into the deep ocean.
Sequencing
Turbidites were first properly described by Arnold H. Bouma (1962), who studied deepwater sedim... | Turbidite | Wikipedia | 499 | 911953 | https://en.wikipedia.org/wiki/Turbidite | Physical sciences | Sedimentary rocks | Earth science |
The distinction is that, in a normal river or stream bed, particles of rock are carried along by frictional drag of water on the particle (known as tractional flow). The water must be travelling at a certain velocity in order to suspend the particle in the water and push it along. The greater the size or density of the... | Turbidite | Wikipedia | 445 | 911953 | https://en.wikipedia.org/wiki/Turbidite | Physical sciences | Sedimentary rocks | Earth science |
Submarine fan models
Submarine fan models are often based on source-to-sink [S2S] concepts linking sediment source areas, and sediment routing systems to the eventual depositional environments of turbidite deposits. They are aimed at providing insights into the relationships between different geologic processes and tur... | Turbidite | Wikipedia | 449 | 911953 | https://en.wikipedia.org/wiki/Turbidite | Physical sciences | Sedimentary rocks | Earth science |
Economic importance
Turbidite sequences are classic hosts for lode gold deposits, the prime example being Bendigo and Ballarat in Victoria, Australia, where more than 2,600 tons of gold have been extracted from saddle-reef deposits hosted in shale sequences from a thick succession of Cambrian-Ordovician turbidites. Pro... | Turbidite | Wikipedia | 142 | 911953 | https://en.wikipedia.org/wiki/Turbidite | Physical sciences | Sedimentary rocks | Earth science |
Ovis dalli, also known as the Dall sheep or thinhorn sheep, is a species of wild sheep native to northwestern North America. Ovis dalli contains two subspecies: Ovis dalli dalli and Ovis dalli stonei. O. dalli live in mountainous alpine habitats distributed across northwestern British Columbia, the Yukon, Northwest Ter... | Dall sheep | Wikipedia | 466 | 913362 | https://en.wikipedia.org/wiki/Dall%20sheep | Biology and health sciences | Bovidae | Animals |
Description
O. dalli stand about at the shoulder. They are off-white in color, and their coat consists of a fine wool undercoat and stiff, long, and hollow guard hairs. Their winter coats can be over thick. O. dalli can live to be 12 to 16 years of age.
O. dalli are sexually dimorphic, which means rams and ewes look... | Dall sheep | Wikipedia | 460 | 913362 | https://en.wikipedia.org/wiki/Dall%20sheep | Biology and health sciences | Bovidae | Animals |
Rams and ewes are rarely found in the same groups outside of the mating season, or rut, which occurs from mid-November through mid-December. For most of the year, rams feed in the best foraging areas to enhance their reproductive fitness. During spring and summer, ewes are more likely to select areas such as steep, roc... | Dall sheep | Wikipedia | 405 | 913362 | https://en.wikipedia.org/wiki/Dall%20sheep | Biology and health sciences | Bovidae | Animals |
The Inupiat people have a long history of hunting O. dalli that dates back to at least the 16th century. Sheep are valued for their skin, which is used for warm clothing, and their meat, especially in times when caribou are not available. Historically, the sheep were hunted in summer by foot and in winter by dog sled t... | Dall sheep | Wikipedia | 507 | 913362 | https://en.wikipedia.org/wiki/Dall%20sheep | Biology and health sciences | Bovidae | Animals |
Omega Centauri (ω Cen, NGC 5139, or Caldwell 80) is a globular cluster in the constellation of Centaurus that was first identified as a non-stellar object by Edmond Halley in 1677. Located at a distance of , it is the largest known globular cluster in the Milky Way at a diameter of roughly 150 light-years. It is estima... | Omega Centauri | Wikipedia | 498 | 914432 | https://en.wikipedia.org/wiki/Omega%20Centauri | Physical sciences | Other notable objects | null |
The stars in the core of Omega Centauri are so crowded that they are estimated to average only 0.1 light-year away from each other. The internal dynamics have been analyzed using measurements of the radial velocities of 469 stars. The members of this cluster are orbiting the center of mass with a peak velocity dispersi... | Omega Centauri | Wikipedia | 473 | 914432 | https://en.wikipedia.org/wiki/Omega%20Centauri | Physical sciences | Other notable objects | null |
Disrupted dwarf galaxy
It has been speculated that Omega Centauri is the core of a dwarf galaxy that was disrupted and absorbed by the Milky Way. Indeed, Kapteyn's Star, which is currently only 13 light-years away from Earth, is thought to originate from Omega Centauri. Omega Centauri's chemistry and motion in the Milk... | Omega Centauri | Wikipedia | 262 | 914432 | https://en.wikipedia.org/wiki/Omega%20Centauri | Physical sciences | Other notable objects | null |
The Turing test, originally called the imitation game by Alan Turing in 1949, is a test of a machine's ability to exhibit intelligent behaviour equivalent to that of a human. In the test, a human evaluator judges a text transcript of a natural-language conversation between a human and a machine. The evaluator tries to ... | Turing test | Wikipedia | 476 | 21391751 | https://en.wikipedia.org/wiki/Turing%20test | Technology | Artificial intelligence concepts | null |
In 1966, Joseph Weizenbaum created a program called ELIZA, which mimicked a Rogerian psychotherapist. The program would search the user's sentence for keywords before repeating them back to the user, providing the impression of a program listening and paying attention. Weizenbaum thus succeeded by designing a context w... | Turing test | Wikipedia | 457 | 21391751 | https://en.wikipedia.org/wiki/Turing%20test | Technology | Artificial intelligence concepts | null |
Philosophical background
The question of whether it is possible for machines to think has a long history, which is firmly entrenched in the distinction between dualist and materialist views of the mind. René Descartes prefigures aspects of the Turing test in his 1637 Discourse on the Method when he writes:
Here Desca... | Turing test | Wikipedia | 472 | 21391751 | https://en.wikipedia.org/wiki/Turing%20test | Technology | Artificial intelligence concepts | null |
Cultural background
A rudimentary idea of the Turing test appears in the 1726 novel Gulliver's Travels by Jonathan Swift. When Gulliver is brought before the king of Brobdingnag, the king thinks at first that Gulliver might be a "a piece of clock-work (which is in that country arrived to a very great perfection) contr... | Turing test | Wikipedia | 409 | 21391751 | https://en.wikipedia.org/wiki/Turing%20test | Technology | Artificial intelligence concepts | null |
Turing, in particular, had been running the notion of machine intelligence since at least 1941 and one of the earliest-known mentions of "computer intelligence" was made by him in 1947. In Turing's report, "Intelligent Machinery," he investigated "the question of whether or not it is possible for machinery to show inte... | Turing test | Wikipedia | 478 | 21391751 | https://en.wikipedia.org/wiki/Turing%20test | Technology | Artificial intelligence concepts | null |
We now ask the question, "What will happen when a machine takes the part of A in this game?" Will the interrogator decide wrongly as often when the game is played like this as he does when the game is played between a man and a woman? These questions replace our original, "Can machines think?"
Later in the paper, Turi... | Turing test | Wikipedia | 491 | 21391751 | https://en.wikipedia.org/wiki/Turing%20test | Technology | Artificial intelligence concepts | null |
The first Loebner Prize competition in 1991 led to a renewed discussion of the viability of the Turing test and the value of pursuing it, in both the popular press and academia. The first contest was won by a mindless program with no identifiable intelligence that managed to fool naïve interrogators into making the wro... | Turing test | Wikipedia | 505 | 21391751 | https://en.wikipedia.org/wiki/Turing%20test | Technology | Artificial intelligence concepts | null |
The reCaptcha is a CAPTCHA system owned by Google. The reCaptcha v1 and v2 both used to operate by asking the user to match distorted pictures or identify distorted letters and numbers. The reCaptcha v3 is designed to not interrupt users and run automatically when pages are loaded or buttons are clicked. This "invisibl... | Turing test | Wikipedia | 505 | 21391751 | https://en.wikipedia.org/wiki/Turing%20test | Technology | Artificial intelligence concepts | null |
In this version, both player A (the computer) and player B are trying to trick the interrogator into making an incorrect decision.
The standard interpretation is not included in the original paper, but is both accepted and debated.
Common understanding has it that the purpose of the Turing test is not specifically to ... | Turing test | Wikipedia | 252 | 21391751 | https://en.wikipedia.org/wiki/Turing%20test | Technology | Artificial intelligence concepts | null |
Controversy has arisen over which of the alternative formulations of the test Turing intended. Sterrett argues that two distinct tests can be extracted from his 1950 paper and that, pace Turing's remark, they are not equivalent. The test that employs the party game and compares frequencies of success is referred to as ... | Turing test | Wikipedia | 442 | 21391751 | https://en.wikipedia.org/wiki/Turing%20test | Technology | Artificial intelligence concepts | null |
Some writers argue that the imitation game is best understood by its social aspects. In his 1948 paper, Turing refers to intelligence as an "emotional concept," and notes that The extent to which we regard something as behaving in an intelligent manner is determined as much by our own state of mind and training as by t... | Turing test | Wikipedia | 506 | 21391751 | https://en.wikipedia.org/wiki/Turing%20test | Technology | Artificial intelligence concepts | null |
Should the interrogator know about the computer?
A crucial piece of any laboratory test is that there should be a control. Turing never makes clear whether the interrogator in his tests is aware that one of the participants is a computer. He states only that player A is to be replaced with a machine, not that player ... | Turing test | Wikipedia | 493 | 21391751 | https://en.wikipedia.org/wiki/Turing%20test | Technology | Artificial intelligence concepts | null |
The Feigenbaum test is designed to take advantage of the broad range of topics available to a Turing test. It is a limited form of Turing's question-answer game which compares the machine against the abilities of experts in specific fields such as literature or chemistry.
Emphasis on emotional and aesthetic intelligen... | Turing test | Wikipedia | 402 | 21391751 | https://en.wikipedia.org/wiki/Turing%20test | Technology | Artificial intelligence concepts | null |
Turing thus once again demonstrates his interest in empathy and aesthetic sensitivity as components of an artificial intelligence; and in light of an increasing awareness of the threat from an AI run amok, it has been suggested that this focus perhaps represents a critical intuition on Turing's part, i.e., that emotion... | Turing test | Wikipedia | 496 | 21391751 | https://en.wikipedia.org/wiki/Turing%20test | Technology | Artificial intelligence concepts | null |
Chatterbot programs such as ELIZA have repeatedly fooled unsuspecting people into believing that they are communicating with human beings. In these cases, the "interrogators" are not even aware of the possibility that they are interacting with computers. To successfully appear human, there is no need for the machine to... | Turing test | Wikipedia | 512 | 21391751 | https://en.wikipedia.org/wiki/Turing%20test | Technology | Artificial intelligence concepts | null |
Some intelligent behaviour is inhuman The Turing test does not test for highly intelligent behaviours, such as the ability to solve difficult problems or come up with original insights. In fact, it specifically requires deception on the part of the machine: if the machine is more intelligent than a human being it must ... | Turing test | Wikipedia | 428 | 21391751 | https://en.wikipedia.org/wiki/Turing%20test | Technology | Artificial intelligence concepts | null |
First, there are easier ways to test their programs. Most current research in AI-related fields is aimed at modest and specific goals, such as object recognition or logistics. To test the intelligence of the programs that solve these problems, AI researchers simply give them the task directly. Stuart Russell and Peter ... | Turing test | Wikipedia | 511 | 21391751 | https://en.wikipedia.org/wiki/Turing%20test | Technology | Artificial intelligence concepts | null |
The Turing Trap
By focusing on imitating humans, rather than augmenting or extending human capabilities, the Turing Test risks directing research and implementation toward technologies that substitute for humans and thereby drive down wages and income for workers. As they lose economic power, these workers may also lo... | Turing test | Wikipedia | 466 | 21391751 | https://en.wikipedia.org/wiki/Turing%20test | Technology | Artificial intelligence concepts | null |
Software that could reverse CAPTCHA with some accuracy by analysing patterns in the generating engine started being developed soon after the creation of CAPTCHA.
In 2013, researchers at Vicarious announced that they had developed a system to solve CAPTCHA challenges from Google, Yahoo!, and PayPal up to 90% of the time... | Turing test | Wikipedia | 448 | 21391751 | https://en.wikipedia.org/wiki/Turing%20test | Technology | Artificial intelligence concepts | null |
The "Total Turing test" variation of the Turing test, proposed by cognitive scientist Stevan Harnad, adds two further requirements to the traditional Turing test. The interrogator can also test the perceptual abilities of the subject (requiring computer vision) and the subject's ability to manipulate objects (requiring... | Turing test | Wikipedia | 502 | 21391751 | https://en.wikipedia.org/wiki/Turing%20test | Technology | Artificial intelligence concepts | null |
A related approach to Hutter's prize which appeared much earlier in the late 1990s is the inclusion of compression problems in an extended Turing test. or by tests which are completely derived from Kolmogorov complexity.
Other related tests in this line are presented by Hernandez-Orallo and Dowe.
Algorithmic IQ, or AI... | Turing test | Wikipedia | 444 | 21391751 | https://en.wikipedia.org/wiki/Turing%20test | Technology | Artificial intelligence concepts | null |
In parallel to the 2008 Loebner Prize held at the University of Reading,
the Society for the Study of Artificial Intelligence and the Simulation of Behaviour (AISB), hosted a one-day symposium to discuss the Turing test, organised by John Barnden, Mark Bishop, Huma Shah and Kevin Warwick.
The speakers included the Roya... | Turing test | Wikipedia | 121 | 21391751 | https://en.wikipedia.org/wiki/Turing%20test | Technology | Artificial intelligence concepts | null |
In computability theory, the halting problem is the problem of determining, from a description of an arbitrary computer program and an input, whether the program will finish running, or continue to run forever. The halting problem is undecidable, meaning that no general algorithm exists that solves the halting problem ... | Halting problem | Wikipedia | 402 | 21391870 | https://en.wikipedia.org/wiki/Halting%20problem | Mathematics | Computability theory | null |
While deciding whether these programs halt is simple, more complex programs prove problematic. One approach to the problem might be to run the program for some number of steps and check if it halts. However, as long as the program is running, it is unknown whether it will eventually halt or run forever. Turing proved n... | Halting problem | Wikipedia | 473 | 21391870 | https://en.wikipedia.org/wiki/Halting%20problem | Mathematics | Computability theory | null |
The halting problem is theoretically decidable for linear bounded automata (LBAs) or deterministic machines with finite memory. A machine with finite memory has a finite number of configurations, and thus any deterministic program on it must eventually either halt or repeat a previous configuration:
However, a compute... | Halting problem | Wikipedia | 407 | 21391870 | https://en.wikipedia.org/wiki/Halting%20problem | Mathematics | Computability theory | null |
The halting problem is Turing equivalent to both Davis's printing problem ("does a Turing machine starting from a given state ever print a given symbol?") and to the printing problem considered in Turing's 1936 paper ("does a Turing machine starting from a blank tape ever print a given symbol?"). However, Turing equiva... | Halting problem | Wikipedia | 496 | 21391870 | https://en.wikipedia.org/wiki/Halting%20problem | Mathematics | Computability theory | null |
Christopher Strachey outlined a proof by contradiction that the halting problem is not solvable. The proof proceeds as follows: Suppose that there exists a total computable function halts(f) that returns true if the subroutine f halts (when run with no inputs) and returns false otherwise. Now consider the following sub... | Halting problem | Wikipedia | 473 | 21391870 | https://en.wikipedia.org/wiki/Halting%20problem | Mathematics | Computability theory | null |
The verification that g is computable relies on the following constructs (or their equivalents):
computable subprograms (the program that computes f is a subprogram in program e),
duplication of values (program e computes the inputs i,i for f from the input i for g),
conditional branching (program e selects between ... | Halting problem | Wikipedia | 360 | 21391870 | https://en.wikipedia.org/wiki/Halting%20problem | Mathematics | Computability theory | null |
This proof is analogous to Cantor's diagonal argument. One may visualize a two-dimensional array with one column and one row for each natural number, as indicated in the table above. The value of f(i,j) is placed at column i, row j. Because f is assumed to be a total computable function, any element of the array can be... | Halting problem | Wikipedia | 419 | 21391870 | https://en.wikipedia.org/wiki/Halting%20problem | Mathematics | Computability theory | null |
Rice's theorem generalizes the theorem that the halting problem is unsolvable. It states that for any non-trivial property, there is no general decision procedure that, for all programs, decides whether the partial function implemented by the input program has that property. (A partial function is a function which may ... | Halting problem | Wikipedia | 356 | 21391870 | https://en.wikipedia.org/wiki/Halting%20problem | Mathematics | Computability theory | null |
Since the negative answer to the halting problem shows that there are problems that cannot be solved by a Turing machine, the Church–Turing thesis limits what can be accomplished by any machine that implements effective methods. However, not all machines conceivable to human imagination are subject to the Church–Turing... | Halting problem | Wikipedia | 319 | 21391870 | https://en.wikipedia.org/wiki/Halting%20problem | Mathematics | Computability theory | null |
Some results have been established on the theoretical performance of halting problem heuristics, in particular the fraction of programs of a given size that may be correctly classified by a recursive algorithm. These results do not give precise numbers because the fractions are uncomputable and also highly dependent on... | Halting problem | Wikipedia | 508 | 21391870 | https://en.wikipedia.org/wiki/Halting%20problem | Mathematics | Computability theory | null |
We consider partial computable functions (algorithms) . For each we consider the fraction of errors among all programs of size metric at most , counting each program for which fails to terminate, produces a "don't know" answer, or produces a wrong answer, i.e. halts and outputs DOES_NOT_HALT, or does not halt an... | Halting problem | Wikipedia | 497 | 21391870 | https://en.wikipedia.org/wiki/Halting%20problem | Mathematics | Computability theory | null |
The universal halting problem, also known (in recursion theory) as totality, is the problem of determining whether a given computer program will halt for every input (the name totality comes from the equivalent question of whether the computed function is total).
This problem is not only undecidable, as the halting pro... | Halting problem | Wikipedia | 413 | 21391870 | https://en.wikipedia.org/wiki/Halting%20problem | Mathematics | Computability theory | null |
The anglerfish are fish of the teleost order Lophiiformes (). They are bony fish named for their characteristic mode of predation, in which a modified luminescent fin ray (the esca or illicium) acts as a lure for other fish. The luminescence comes from symbiotic bacteria, which are thought to be acquired from seawater,... | Anglerfish | Wikipedia | 333 | 21392941 | https://en.wikipedia.org/wiki/Anglerfish | Biology and health sciences | Fishes | null |
A 2010 mitochondrial genome phylogenetic study suggested the anglerfishes diversified in a short period of the early to mid-Cretaceous, between 130 and 100 million years ago. A more recent preprint reduces this time to the Late Cretaceous, between 92 to 61 million years ago. Other studies indicate that anglerfish only ... | Anglerfish | Wikipedia | 222 | 21392941 | https://en.wikipedia.org/wiki/Anglerfish | Biology and health sciences | Fishes | null |
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