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To specify an AI system's purpose, AI designers typically provide an objective function, examples, or feedback to the system. But designers are often unable to completely specify all important values and constraints, so they resort to easy-to-specify proxy goals such as maximizing the approval of human overseers, who a... | AI alignment | Wikipedia | 417 | 50785023 | https://en.wikipedia.org/wiki/AI%20alignment | Technology | Artificial intelligence concepts | null |
Explaining such side effects, Berkeley computer scientist Stuart Russell noted that the omission of implicit constraints can cause harm: "A system ... will often set ... unconstrained variables to extreme values; if one of those unconstrained variables is actually something we care about, the solution found may be high... | AI alignment | Wikipedia | 413 | 50785023 | https://en.wikipedia.org/wiki/AI%20alignment | Technology | Artificial intelligence concepts | null |
Development of advanced AI
Many AI companies, such as OpenAI, Meta and DeepMind, have stated their aim to develop artificial general intelligence (AGI), a hypothesized AI system that matches or outperforms humans at a broad range of cognitive tasks. Researchers who scale modern neural networks observe that they indeed... | AI alignment | Wikipedia | 490 | 50785023 | https://en.wikipedia.org/wiki/AI%20alignment | Technology | Artificial intelligence concepts | null |
According to some researchers, humans owe their dominance over other species to their greater cognitive abilities. Accordingly, researchers argue that one or many misaligned AI systems could disempower humanity or lead to human extinction if they outperform humans on most cognitive tasks.
In 2023, world-leading AI res... | AI alignment | Wikipedia | 464 | 50785023 | https://en.wikipedia.org/wiki/AI%20alignment | Technology | Artificial intelligence concepts | null |
Because it is difficult for AI designers to explicitly specify an objective function, they often train AI systems to imitate human examples and demonstrations of desired behavior. Inverse reinforcement learning (IRL) extends this by inferring the human's objective from the human's demonstrations. Cooperative IRL (CIRL)... | AI alignment | Wikipedia | 508 | 50785023 | https://en.wikipedia.org/wiki/AI%20alignment | Technology | Artificial intelligence concepts | null |
Machine ethics supplements preference learning by directly instilling AI systems with moral values such as well-being, equality, and impartiality, as well as not intending harm, avoiding falsehoods, and honoring promises. While other approaches try to teach AI systems human preferences for a specific task, machine ethi... | AI alignment | Wikipedia | 426 | 50785023 | https://en.wikipedia.org/wiki/AI%20alignment | Technology | Artificial intelligence concepts | null |
Some AI systems have discovered that they can gain positive feedback more easily by taking actions that falsely convince the human supervisor that the AI has achieved the intended objective. An example is given in the video above, where a simulated robotic arm learned to create the false impression that it had grabbed ... | AI alignment | Wikipedia | 385 | 50785023 | https://en.wikipedia.org/wiki/AI%20alignment | Technology | Artificial intelligence concepts | null |
Honest AI
A area of research focuses on ensuring that AI is honest and truthful.
Language models such as GPT-3 can repeat falsehoods from their training data, and even confabulate new falsehoods. Such models are trained to imitate human writing as found in millions of books' worth of text from the Internet. But this ... | AI alignment | Wikipedia | 478 | 50785023 | https://en.wikipedia.org/wiki/AI%20alignment | Technology | Artificial intelligence concepts | null |
Power-seeking and instrumental strategies
Since the 1950s, AI researchers have striven to build advanced AI systems that can achieve large-scale goals by predicting the results of their actions and making long-term plans. As of 2023, AI companies and researchers increasingly invest in creating these systems. Some AI r... | AI alignment | Wikipedia | 441 | 50785023 | https://en.wikipedia.org/wiki/AI%20alignment | Technology | Artificial intelligence concepts | null |
One aim of alignment is "corrigibility": systems that allow themselves to be turned off or modified. An unsolved challenge is specification gaming: if researchers penalize an AI system when they detect it seeking power, the system is thereby incentivized to seek power in ways that are hard to detect, or hidden during t... | AI alignment | Wikipedia | 494 | 50785023 | https://en.wikipedia.org/wiki/AI%20alignment | Technology | Artificial intelligence concepts | null |
Emergent goals
One challenge in aligning AI systems is the potential for unanticipated goal-directed behavior to emerge. As AI systems scale up, they may acquire new and unexpected capabilities, including learning from examples on the fly and adaptively pursuing goals. This raises concerns about the safety of the goal... | AI alignment | Wikipedia | 348 | 50785023 | https://en.wikipedia.org/wiki/AI%20alignment | Technology | Artificial intelligence concepts | null |
Goal misgeneralization has been observed in some language models, navigation agents, and game-playing agents. It is sometimes analogized to biological evolution. Evolution can be seen as a kind of optimization process similar to the optimization algorithms used to train machine learning systems. In the ancestral enviro... | AI alignment | Wikipedia | 480 | 50785023 | https://en.wikipedia.org/wiki/AI%20alignment | Technology | Artificial intelligence concepts | null |
For example, even if the scalable oversight problem is solved, an agent that could gain access to the computer it is running on may have an incentive to tamper with its reward function in order to get much more reward than its human supervisors give it. A list of examples of specification gaming from DeepMind researche... | AI alignment | Wikipedia | 410 | 50785023 | https://en.wikipedia.org/wiki/AI%20alignment | Technology | Artificial intelligence concepts | null |
Pessimism, in the sense of assuming the worst within reason, has been formally shown to produce conservatism, in the sense of reluctance to cause novelties, including unprecedented catastrophes. Pessimism and worst-case analysis have been found to help mitigate confident mistakes in the setting of distributional shift,... | AI alignment | Wikipedia | 441 | 50785023 | https://en.wikipedia.org/wiki/AI%20alignment | Technology | Artificial intelligence concepts | null |
AI alignment is often perceived as a fixed objective, but some researchers argue it would be more appropriate to view alignment as an evolving process. One view is that AI technologies advance and human values and preferences change, alignment solutions must also adapt dynamically. Another is that alignment solutions n... | AI alignment | Wikipedia | 241 | 50785023 | https://en.wikipedia.org/wiki/AI%20alignment | Technology | Artificial intelligence concepts | null |
Vertical pressure variation is the variation in pressure as a function of elevation. Depending on the fluid in question and the context being referred to, it may also vary significantly in dimensions perpendicular to elevation as well, and these variations have relevance in the context of pressure gradient force and it... | Vertical pressure variation | Wikipedia | 492 | 33914934 | https://en.wikipedia.org/wiki/Vertical%20pressure%20variation | Physical sciences | Fluid mechanics | Physics |
The barometric formula depends only on the height of the fluid chamber, and not on its width or length. Given a large enough height, any pressure may be attained. This feature of hydrostatics has been called the hydrostatic paradox. As expressed by W. H. Besant,
Any quantity of liquid, however small, may be made to s... | Vertical pressure variation | Wikipedia | 509 | 33914934 | https://en.wikipedia.org/wiki/Vertical%20pressure%20variation | Physical sciences | Fluid mechanics | Physics |
Therefore, instead of pressure being a linear function of height as one might expect from the more simple formula given in the "basic formula" section, it is more accurately represented as an exponential function of height.
Note that in this simplification, the temperature is treated as constant, even though temperatu... | Vertical pressure variation | Wikipedia | 166 | 33914934 | https://en.wikipedia.org/wiki/Vertical%20pressure%20variation | Physical sciences | Fluid mechanics | Physics |
The dark web is the World Wide Web content that exists on darknets (overlay networks) that use the Internet but require specific software, configurations, or authorization to access. Through the dark web, private computer networks can communicate and conduct business anonymously without divulging identifying informatio... | Dark web | Wikipedia | 430 | 40712897 | https://en.wikipedia.org/wiki/Dark%20web | Technology | Internet | null |
Identities and locations of darknet users stay anonymous and cannot be tracked due to the layered encryption system. The darknet encryption technology routes users' data through a large number of intermediate servers, which protects the users' identity and guarantees anonymity. The transmitted information can be decryp... | Dark web | Wikipedia | 444 | 40712897 | https://en.wikipedia.org/wiki/Dark%20web | Technology | Internet | null |
Commercial darknet markets mediate transactions for illegal goods and typically use Bitcoin as payment. These markets have attracted significant media coverage, starting with the popularity of Silk Road and Diabolus Market and its subsequent seizure by legal authorities. Silk Road was one of the first dark web marketpl... | Dark web | Wikipedia | 487 | 40712897 | https://en.wikipedia.org/wiki/Dark%20web | Technology | Internet | null |
Due to its relevance in the digital world, bitcoin has become a popular product for users to scam companies with. Cybercriminal groups such as DDOS"4" have led to over 140 cyberattacks on companies since the emergence of bitcoins in 2014. These attacks have led to the formation of other cybercriminal groups as well as ... | Dark web | Wikipedia | 438 | 40712897 | https://en.wikipedia.org/wiki/Dark%20web | Technology | Internet | null |
Illegal pornography
The type of content that has the most popularity on the dark web is illegal pornography—more specifically, child pornography. About 80% of its web traffic is related to accessing child pornography despite it being difficult to find even on the dark web. A website called Lolita City, which has since... | Dark web | Wikipedia | 432 | 40712897 | https://en.wikipedia.org/wiki/Dark%20web | Technology | Internet | null |
There are at least some real and fraudulent websites claiming to be used by ISIL (ISIS), including a fake one seized in Operation Onymous. With the increase of technology, it has allowed cyber terrorists to flourish by attacking the weaknesses of the technology. In the wake of the November 2015 Paris attacks, an actual... | Dark web | Wikipedia | 437 | 40712897 | https://en.wikipedia.org/wiki/Dark%20web | Technology | Internet | null |
Policing the dark web
There have been arguments that the dark web promotes civil liberties, like "free speech, privacy, anonymity". Some prosecutors and government agencies are concerned that it is a haven for criminal activity. The deep and dark web are applications of integral internet features to provide privacy an... | Dark web | Wikipedia | 412 | 40712897 | https://en.wikipedia.org/wiki/Dark%20web | Technology | Internet | null |
Journalism
Many journalists, alternative news organizations, educators, and researchers are influential in their writing and speaking of the darknet, and making its use clear to the general public. Media coverage typically reports on the dark web in two ways; detailing the power and freedom of speech the dark web allo... | Dark web | Wikipedia | 229 | 40712897 | https://en.wikipedia.org/wiki/Dark%20web | Technology | Internet | null |
Fission, in biology, is the division of a single entity into two or more parts and the regeneration of those parts to separate entities resembling the original. The object experiencing fission is usually a cell, but the term may also refer to how organisms, bodies, populations, or species split into discrete parts. The... | Fission (biology) | Wikipedia | 433 | 30064130 | https://en.wikipedia.org/wiki/Fission%20%28biology%29 | Biology and health sciences | Cellular division | null |
More specifically, the following steps occur:
The bacterium before binary fission is when the DNA is tightly coiled.
The DNA of the bacterium has uncoiled and duplicated.
The DNA is pulled to the separate poles of the bacterium as it increases the size to prepare for splitting.
The growth of a new cell wall begins ... | Fission (biology) | Wikipedia | 444 | 30064130 | https://en.wikipedia.org/wiki/Fission%20%28biology%29 | Biology and health sciences | Cellular division | null |
Fission of organelles
Some organelles in eukaryotic cells reproduce using binary fission. Mitochondrial fission occurs frequently within the cell, even when the cell is not actively undergoing mitosis, and is necessary to regulate the cell's metabolism. All chloroplasts and some mitochondria (not in animals), both orga... | Fission (biology) | Wikipedia | 495 | 30064130 | https://en.wikipedia.org/wiki/Fission%20%28biology%29 | Biology and health sciences | Cellular division | null |
Fission of green algae
Green algae can divide into more than two daughter cells. The exact number of daughter cells depends on the species of algae and is an effect of temperature and light.
Multiple fission of bacteria
Most species of bacteria primarily undergo binary reproduction. Some species and groups of bacteria... | Fission (biology) | Wikipedia | 330 | 30064130 | https://en.wikipedia.org/wiki/Fission%20%28biology%29 | Biology and health sciences | Cellular division | null |
A sediment gravity flow is one of several types of sediment transport mechanisms, of which most geologists recognize four principal processes. These flows are differentiated by their dominant sediment support mechanisms, which can be difficult to distinguish as flows can be in transition from one type to the next as th... | Sediment gravity flow | Wikipedia | 81 | 33926405 | https://en.wikipedia.org/wiki/Sediment%20gravity%20flow | Physical sciences | Sedimentology | Earth science |
Grain flow – Grains in the flow are kept in suspension by grain-to-grain interactions, with the fluid acting only as a lubricant. As such, the grain-to-grain collisions generate a dispersive pressure that helps prevent grains from settling out of suspension. Although common in terrestrial environments on the slip faces... | Sediment gravity flow | Wikipedia | 406 | 33926405 | https://en.wikipedia.org/wiki/Sediment%20gravity%20flow | Physical sciences | Sedimentology | Earth science |
Turbidity current – Grains are suspended by fluid turbulence within the flow. Because the behavior of turbidity currents is largely predictable, they exhibit newtonian behavior, in contrast to flows with cohesive strength (i.e., mudflows and debris flows). The behavior of turbidity currents in subaqueous settings is st... | Sediment gravity flow | Wikipedia | 173 | 33926405 | https://en.wikipedia.org/wiki/Sediment%20gravity%20flow | Physical sciences | Sedimentology | Earth science |
Resulting deposits
Description
Although the deposits of all four types of sediment support mechanisms are found in nature, pure grain flows are largely restricted to aeolian settings, whereas subaqueous environments are characterized by a spectrum of flow types with debris flows and mud flows on one end of the spectru... | Sediment gravity flow | Wikipedia | 181 | 33926405 | https://en.wikipedia.org/wiki/Sediment%20gravity%20flow | Physical sciences | Sedimentology | Earth science |
Grain flow deposits are characterized by a coarsening-upward distribution of grain sizes (inverse grading) within the bed. This results from smaller grains within the flow falling down in between larger grains during grain-to-grain collisions, and thereby depositing preferentially at the base of flow. Although present ... | Sediment gravity flow | Wikipedia | 471 | 33926405 | https://en.wikipedia.org/wiki/Sediment%20gravity%20flow | Physical sciences | Sedimentology | Earth science |
Hybrid event beds (HEB) transitional between mud flows and turbidity currents are characterized by features indicative of both cohesionless (turbulence-supported) and cohesive (mud-supported) flow with no separating bed boundary between the two. In most cases, they are represented by grain-supported textures that grade... | Sediment gravity flow | Wikipedia | 114 | 33926405 | https://en.wikipedia.org/wiki/Sediment%20gravity%20flow | Physical sciences | Sedimentology | Earth science |
Modern and ancient examples
Modern and ancient (outcrop) examples of deposits resulting from different types of sediment gravity flows.
Significance
Sediment gravity flows, primarily turbidity currents, but to a lesser extent debris flows and mud flows, are thought to be the primary processes responsible for depositin... | Sediment gravity flow | Wikipedia | 156 | 33926405 | https://en.wikipedia.org/wiki/Sediment%20gravity%20flow | Physical sciences | Sedimentology | Earth science |
Lepas anatifera, commonly known as the pelagic gooseneck barnacle or smooth gooseneck barnacle, is a species of barnacle in the family Lepadidae. These barnacles are found, often in large numbers, attached by their flexible stalks to floating timber, the hulls of ships, piers, pilings, seaweed, and various sorts of flo... | Lepas anatifera | Wikipedia | 386 | 33936518 | https://en.wikipedia.org/wiki/Lepas%20anatifera | Biology and health sciences | Crustaceans | Animals |
Lepas anatifera has long been known to grow on sea turtles, but in 2008, some small specimens were found attached to an American crocodile (Crocodylus acutus) on the Pacific coast of Mexico. That crocodile species mostly inhabits mangrove swamps and river estuaries, but it is salt tolerant, and sometimes is found in ma... | Lepas anatifera | Wikipedia | 325 | 33936518 | https://en.wikipedia.org/wiki/Lepas%20anatifera | Biology and health sciences | Crustaceans | Animals |
In Earth science, a geochemical cycle is the pathway that chemical elements undergo to be able to interact with the reservoirs of chemicals in the surface and crust of the Earth. The term "geochemical" tells us that geological and chemical factors are all included. The migration of heated and compressed chemical elemen... | Geochemical cycle | Wikipedia | 504 | 40723560 | https://en.wikipedia.org/wiki/Geochemical%20cycle | Physical sciences | Geochemistry | Earth science |
Volcanism is the process that takes place at divergent boundaries by which one tectonic plate separates from another creating a rift in which molten rock (magma) erupts onto the surface of the Earth. This molten rock magma then cools and crystallizes, forming igneous rocks. If crystallization occurs at the Earth's surf... | Geochemical cycle | Wikipedia | 127 | 40723560 | https://en.wikipedia.org/wiki/Geochemical%20cycle | Physical sciences | Geochemistry | Earth science |
The BOSS Great Wall is a supercluster complex that was identified, using the Baryon Oscillation Spectroscopic Survey (BOSS) of the Sloan Digital Sky Survey (SDSS), in early 2016. It was discovered by a research team from several institutions, consisting of: Heidi Lietzen, Elmo Tempel, Lauri Juhan Liivamägi, Antonio Mon... | BOSS Great Wall | Wikipedia | 292 | 49717050 | https://en.wikipedia.org/wiki/BOSS%20Great%20Wall | Physical sciences | Notable patches of universe | Astronomy |
The superstructure is roughly 1 billion light years in diameter, and has a total mass approximately 10,000 times the Milky Way galaxy. It contains at least 830 visible galaxies (represented in the figure within their respective superclusters), as well as many others that are not visible (dark galaxies). The researchers... | BOSS Great Wall | Wikipedia | 299 | 49717050 | https://en.wikipedia.org/wiki/BOSS%20Great%20Wall | Physical sciences | Notable patches of universe | Astronomy |
Helium is the smallest and the lightest noble gas and one of the most unreactive elements, so it was commonly considered that helium compounds cannot exist at all, or at least under normal conditions. Helium's first ionization energy of 24.57 eV is the highest of any element. Helium has a complete shell of electrons, a... | Helium compounds | Wikipedia | 509 | 45452439 | https://en.wikipedia.org/wiki/Helium%20compounds | Physical sciences | Noble gas compounds | Chemistry |
Disodium helide (Na2He) is a compound of helium and sodium that is stable at high pressures above . Disodium helide was first predicted using USPEX code and was first synthesised in 2016. It was predicted to be thermodynamically stable over 160 GPa and dynamically stable over 100 GPa. Na2He has a cubic crystal structur... | Helium compounds | Wikipedia | 432 | 45452439 | https://en.wikipedia.org/wiki/Helium%20compounds | Physical sciences | Noble gas compounds | Chemistry |
Chibaite, another natural silica clathrate has its structure penetrated by helium under pressures higher than 2.5 GPa. The presence of guest hydrocarbons does not prevent this happening. Neon requires a higher pressure, 4.5 GPa to penetrate, and unlike helium shows hysteresis. Linde-type A zeolites are also rendered le... | Helium compounds | Wikipedia | 450 | 45452439 | https://en.wikipedia.org/wiki/Helium%20compounds | Physical sciences | Noble gas compounds | Chemistry |
Small molecule
is a van der Waals compound with hexagonal crystals. At 10 GPa the unit cell of 22 nitrogen atoms has a unit cell volume of 558 Å3, and about 512 Å3 at 15 GPa. These sizes are around 10 Å3 smaller than the equivalent amount of solid δ-N2 nitrogen at these pressures. The substance is made by compressing ... | Helium compounds | Wikipedia | 397 | 45452439 | https://en.wikipedia.org/wiki/Helium%20compounds | Physical sciences | Noble gas compounds | Chemistry |
Fullerites
Helium can form intercalation compounds with the fullerites, including buckminsterfullerene C60 and C70. In solid C60 there are spaces between the C60 balls, either tetrahedral or octahedral in shape. Helium can diffuse into the solid fullerite even at one atmosphere pressure. Helium enters the lattice in tw... | Helium compounds | Wikipedia | 443 | 45452439 | https://en.wikipedia.org/wiki/Helium%20compounds | Physical sciences | Noble gas compounds | Chemistry |
Impurity helium condensates
Impurity helium condensates (IHCs) (or impurity helium gels) are deposited as a snow-like gel in liquid helium when various atoms or molecules are absorbed on the surface of superfluid helium. Atoms can include H, N, Na, Ne, Ar, Kr, Xe, alkalis or alkaline earths. The impurities form nanopar... | Helium compounds | Wikipedia | 492 | 45452439 | https://en.wikipedia.org/wiki/Helium%20compounds | Physical sciences | Noble gas compounds | Chemistry |
[Kr]/[He] contains 40–60 helium atoms per krypton atom and is stable up to 20 K.
[Xe]/[He] contains 40–60 helium atoms per xenon atom.
[N2]/[He] contains 12—17 He atoms per N2 molecule. It is stable up to 13 K
[N]/[Ne]/[He] Formed from a gas beam generated from a radio-frequency electric discharge in mixtures of neo... | Helium compounds | Wikipedia | 469 | 45452439 | https://en.wikipedia.org/wiki/Helium%20compounds | Physical sciences | Noble gas compounds | Chemistry |
Impurity solid helium
Introducing impurities into solid helium yields a blue solid that melts at a higher temperature than pure He. For cesium the absorption has a peak at 750 nm, and for rubidium, maximal absorption is at 640 nm. These are due to metal clusters with diameters of 10 nm or so. However the low concentrat... | Helium compounds | Wikipedia | 403 | 45452439 | https://en.wikipedia.org/wiki/Helium%20compounds | Physical sciences | Noble gas compounds | Chemistry |
Nanowires
Gold, copper, rubidium, caesium, or barium atoms evaporated into liquid helium form spiderweb-like structures. Rhenium produces nano flakes. Molybdenum, tungsten, and niobium produce thin nanowires with diameters of 20, 25 and 40 Å. When platinum, molybdenum or tungsten is evaporated into liquid helium, nanoc... | Helium compounds | Wikipedia | 508 | 45452439 | https://en.wikipedia.org/wiki/Helium%20compounds | Physical sciences | Noble gas compounds | Chemistry |
Known ions
Helium has the highest ionisation energy, so a He+ ion will strip electrons off any other neutral atom or molecule. However it can also then bind to the ion produced. The He+ ion can be studied in gas, or in liquid helium. Its chemistry is not completely trivial. For example, He+ can react with SF6 to yield ... | Helium compounds | Wikipedia | 489 | 45452439 | https://en.wikipedia.org/wiki/Helium%20compounds | Physical sciences | Noble gas compounds | Chemistry |
Many different HenKr+ exist with n between 1 and 17, with higher values possible. HenKr and HenKr also exist for many values of n. He12Kr and He12Kr ions are common. These singly charged cluster ions can be made from krypton in helium nanodroplets subject to vacuum ultraviolet radiation.
The Ar+ argon ion can form man... | Helium compounds | Wikipedia | 385 | 45452439 | https://en.wikipedia.org/wiki/Helium%20compounds | Physical sciences | Noble gas compounds | Chemistry |
When there are many helium atoms around, alkali metal ions can attract shells of helium atoms. Clusters can be formed from absorbing metal into helium droplets. The doped droplets are ionised with high speed electrons. For sodium clusters appear with the formula Na+Hen with n from 1 to 26. Na+He is the most common, but... | Helium compounds | Wikipedia | 492 | 45452439 | https://en.wikipedia.org/wiki/Helium%20compounds | Physical sciences | Noble gas compounds | Chemistry |
When tritium substituted methane (CH3T) decays, CH3He+ is produced in a very small amount.
The helium formyl cation, HeHCO+ is a linear molecule. It has a vibrational frequency red shifted 12.4 cm−1 compared to HCO+. It can be considered as a deenergized protonation reaction intermediate for the HeH+ + CO → HCO+ + He.... | Helium compounds | Wikipedia | 511 | 45452439 | https://en.wikipedia.org/wiki/Helium%20compounds | Physical sciences | Noble gas compounds | Chemistry |
Helium is predicted to be included under pressure in ionic compounds of the form A2B or AB2. These compounds could include Na2OHe, MgF2He (over 107 GPa) and CaF2He (30-110 GPa). Stabilisation occurs by the helium atom positioning itself between the two like charged ions, and partially shielding them from each other.
H... | Helium compounds | Wikipedia | 463 | 45452439 | https://en.wikipedia.org/wiki/Helium%20compounds | Physical sciences | Noble gas compounds | Chemistry |
Calculation for binary van der Waals helium molecules include HeNe,
Li4He binding energy 0.008 cm−1, the Li3He is not stable.
Na4He binding energy 0.03 cm−1, the Na3He is not stable.
Cu3He binding energy 0.90 cm−1,
O4He binding energy 5.83 cm−1,
S4He binding energy 6.34 cm−1,
Se4He binding energy 6.50 cm−1,
F4He bindin... | Helium compounds | Wikipedia | 391 | 45452439 | https://en.wikipedia.org/wiki/Helium%20compounds | Physical sciences | Noble gas compounds | Chemistry |
Many ions have been investigated theoretically to see if they could exist. Just about every diatomic cation with helium has been studied. For the diatomic dications, for stability the second ionisation level of the partner atom has to be below the first ionisation level of helium, 24.6 eV. For Li, F, and Ne the ground ... | Helium compounds | Wikipedia | 472 | 45452439 | https://en.wikipedia.org/wiki/Helium%20compounds | Physical sciences | Noble gas compounds | Chemistry |
For negative ions the adduct is very weakly bound. Those studied include HeCl−, HeBr−, HeF−, HeO− and HeS−.
FHeS−
FHeSe−
C7H6He2+
C7H6HeHe2+
FHeCC−
HHeOH
HHeBF+
HeNC+
HeNN+
HHeNN+ H-He 0.765 Å He-N bond length 2.077 Å. Decomposition barrier of 2.3 kJ/mol.
HHeNH is predicted to have a C3v symmetry and a H-He ... | Helium compounds | Wikipedia | 507 | 45452439 | https://en.wikipedia.org/wiki/Helium%20compounds | Physical sciences | Noble gas compounds | Chemistry |
Boomer claimed the discovery of tungsten helide WHe2 as a black solid. It is formed by way of an electric discharge in helium with a heated tungsten filament. When dissolved in nitric acid or potassium hydroxide, tungstic acid forms and helium escapes in bubbles. The electric discharge had a current of 5 mA and 1,000 V... | Helium compounds | Wikipedia | 229 | 45452439 | https://en.wikipedia.org/wiki/Helium%20compounds | Physical sciences | Noble gas compounds | Chemistry |
Aluminium triacetate, formally named aluminium acetate, is a chemical compound with composition . Under standard conditions it appears as a white, water-soluble solid that decomposes on heating at around 200 °C. The triacetate hydrolyses to a mixture of basic hydroxide / acetate salts, and multiple species co-exist i... | Aluminium triacetate | Wikipedia | 285 | 52275513 | https://en.wikipedia.org/wiki/Aluminium%20triacetate | Physical sciences | Acetates | Chemistry |
Nomenclature
According to the formal rules for naming inorganic compounds, the name for is aluminium acetate, though more formal names like aluminium(III) acetate and aluminium ethanoate are acceptable. The use of the "tri" multiplying prefix in the name aluminium triacetate, while not technically required, is regul... | Aluminium triacetate | Wikipedia | 508 | 52275513 | https://en.wikipedia.org/wiki/Aluminium%20triacetate | Physical sciences | Acetates | Chemistry |
NMR investigations of the aqueous aluminium(III) / acetate system show the presence of aluminium as a hexaaqua complex, , as well as mononuclear species with different substitutions. In addition, the investigations demonstrate that a significant solution-phase species is an tridecamer, a moiety reported in conflicting... | Aluminium triacetate | Wikipedia | 511 | 52275513 | https://en.wikipedia.org/wiki/Aluminium%20triacetate | Physical sciences | Acetates | Chemistry |
+ 3 → 2 + 3
+ 2 → + 2
Decomposition
On heating, aluminium triacetate decomposes above 200 °C in a process similar to that of aluminium formate. The process begins with loss of acetic anhydride () between 120 and 140 °C to form the a mixture of the basic oxide acetates such as and , whic... | Aluminium triacetate | Wikipedia | 501 | 52275513 | https://en.wikipedia.org/wiki/Aluminium%20triacetate | Physical sciences | Acetates | Chemistry |
A mordant is a substance used to set dyes on fabrics or tissue sections by forming a coordination complex with the dye, which subsequently attaches to the fabric or tissue. A mordant often contains a polyvalent metal ion, commonly aluminium or iron, as is the case with mixtures of aluminium triacetate with aluminium s... | Aluminium triacetate | Wikipedia | 480 | 52275513 | https://en.wikipedia.org/wiki/Aluminium%20triacetate | Physical sciences | Acetates | Chemistry |
Monazite geochronology is a dating technique to study geological history using the mineral monazite. It is a powerful tool in studying the complex history of metamorphic rocks particularly, as well as igneous, sedimentary and hydrothermal rocks. The dating uses the radioactive processes in monazite as a clock.
The uni... | Monazite geochronology | Wikipedia | 485 | 52282223 | https://en.wikipedia.org/wiki/Monazite%20geochronology | Physical sciences | Geochronology | Earth science |
Monazite geochronology studies the ratio of parent isotopes to daughter isotopes (isotopic ratio), and calculates how much time has passed since daughter isotopes start accumulating.
Radiometric age and geological age
Radiometric age represents the time when the decay process starts. Geological age represents the time... | Monazite geochronology | Wikipedia | 410 | 52282223 | https://en.wikipedia.org/wiki/Monazite%20geochronology | Physical sciences | Geochronology | Earth science |
The rate of diffusion increases with temperature as atoms are moving faster. However, as the mineral cools and the crystal structure becomes more complete, the diffusions of parent and daughter isotopes slow down and finally become insignificant at a certain temperature. This closure temperature (Tc) depends on the cry... | Monazite geochronology | Wikipedia | 440 | 52282223 | https://en.wikipedia.org/wiki/Monazite%20geochronology | Physical sciences | Geochronology | Earth science |
There are basically two factors which can cause the reaction to cease. (A) Reaction ceases due to the recrystallisation of precipitating phase, removing all the fluid infiltration paths. This results in fluid inclusions in monazite. (B) Reaction ceases due to a change in the system such as the composition of fluid and ... | Monazite geochronology | Wikipedia | 480 | 52282223 | https://en.wikipedia.org/wiki/Monazite%20geochronology | Physical sciences | Geochronology | Earth science |
Zonation is a characteristic of monazite. A single monazite grain can contain domains of distinctively different compositions and ages. These domains are widely accepted to represent episodes in geological history with monazite growth or recrystallisation. The key to monazite geochronology is to find out what geologica... | Monazite geochronology | Wikipedia | 498 | 52282223 | https://en.wikipedia.org/wiki/Monazite%20geochronology | Physical sciences | Geochronology | Earth science |
Other zoning patterns
Mottled and patchy zoning patterns are more complex zonations. The interpretations are usually not simple.
Dating approaches
Isotopic dating and chemical dating are the two typical methods used in monazite geochronology. Both methods make use of the radioactive nature of Th and U in monazite.
I... | Monazite geochronology | Wikipedia | 409 | 52282223 | https://en.wikipedia.org/wiki/Monazite%20geochronology | Physical sciences | Geochronology | Earth science |
The first assumption tends to be true since monazite is very unlikely to incorporate Pb during its growth. The non-radiogenic Pb content in many laboratory tests was found to be very low, nearly always less than 1 ppm. The most common error arising from this assumption is contamination with lead during sample preparati... | Monazite geochronology | Wikipedia | 392 | 52282223 | https://en.wikipedia.org/wiki/Monazite%20geochronology | Physical sciences | Geochronology | Earth science |
For the above reasons, the demand for in-situ analysis is increasing. In-situ means analyzing monazite grains in their original host rocks without separation (refer to in situ) such that the texture and zonation pattern are kept intact in order to reveal a more comprehensive geological history of the host rock. Direct ... | Monazite geochronology | Wikipedia | 482 | 52282223 | https://en.wikipedia.org/wiki/Monazite%20geochronology | Physical sciences | Geochronology | Earth science |
A number of spots within an age domain are selected and further dated accurately with the measurement tools by isotopic dating method. The results are then analysed statistically to give an accurate age of each age domain.
Measurement techniques
The choice of various conventional or in-situ analysis techniques affects... | Monazite geochronology | Wikipedia | 466 | 52282223 | https://en.wikipedia.org/wiki/Monazite%20geochronology | Physical sciences | Geochronology | Earth science |
The tracer solution is a solution with a known amount of U and Pb tracer isotopes. Due to elemental fractionation, both elements cannot be measured simultaneously by TIMS. The tracer solution is therefore used to measure ratios of sample isotope to tracer isotopes. The ratios are converted to moles of sample isotopes f... | Monazite geochronology | Wikipedia | 464 | 52282223 | https://en.wikipedia.org/wiki/Monazite%20geochronology | Physical sciences | Geochronology | Earth science |
EMPA is employed in monazite geochronology especially for in-situ chemical dating (total-Pb dating). The high content of U, Th and Pb in monazite match with the requirement arising from the relatively higher lower detection limit. Therefore, EMPA is a high-resolution (approximately 1 μm), rapid and inexpensive method i... | Monazite geochronology | Wikipedia | 391 | 52282223 | https://en.wikipedia.org/wiki/Monazite%20geochronology | Physical sciences | Geochronology | Earth science |
The simplest monazite zonation showing successive crystallisation of melts is concentric zonation, in which new monazite layers are crystallized rim-by-rim around the pre-existing core. The rims often show compositional variations due to the preferential incorporation of certain elements in the crystal lattice. For exa... | Monazite geochronology | Wikipedia | 477 | 52282223 | https://en.wikipedia.org/wiki/Monazite%20geochronology | Physical sciences | Geochronology | Earth science |
Monazite geochronology is generally regarded as a powerful tool to reveal metamorphic history. Metamorphism is the mineralogical and textural changes in preexisting rocks in response to a change in environment to different temperatures and pressures. It occurs at a temperature above diagenesis (~200 °C) and below melti... | Monazite geochronology | Wikipedia | 432 | 52282223 | https://en.wikipedia.org/wiki/Monazite%20geochronology | Physical sciences | Geochronology | Earth science |
For example, a metamorphic rock in the Neil Bay area of northern Saskatchewan underwent high grade (high P/T) metamorphism followed by exhumation (uplift). The porphyroblast of garnet was formed during high grade metamorphism while the porphyroblast of cordierite was formed during subsequent exhumation. Both porphyrobl... | Monazite geochronology | Wikipedia | 435 | 52282223 | https://en.wikipedia.org/wiki/Monazite%20geochronology | Physical sciences | Geochronology | Earth science |
The mostly studied system is yttrium (Y) fractionation between the phosphate monazite and the silicates garnet and xenotime. All three minerals preferentially fractionate Y, yet they form and break down at different stages of metamorphism. Xenotime has the highest fractionating power, then garnet and then monazite. In ... | Monazite geochronology | Wikipedia | 479 | 52282223 | https://en.wikipedia.org/wiki/Monazite%20geochronology | Physical sciences | Geochronology | Earth science |
Deformation metamorphic reactions
Deformation events may trigger metamorphic reactions which produce monazite. For example, a metamorphic reaction associated with the movement in the Legs Lake shear zone partly replaced garnet with cordierite. This reaction also generated new monazite with high content of Y, and dated ... | Monazite geochronology | Wikipedia | 465 | 52282223 | https://en.wikipedia.org/wiki/Monazite%20geochronology | Physical sciences | Geochronology | Earth science |
Detrital monazite grains are produced by the weathering and erosion of pre-existing rocks and then transported into sedimentary basins. The detrital monazite contains zonation patterns which preserve the geological history of the source region. Investigating detrital monazite in the basin not only helps in reconstructi... | Monazite geochronology | Wikipedia | 260 | 52282223 | https://en.wikipedia.org/wiki/Monazite%20geochronology | Physical sciences | Geochronology | Earth science |
The Danyang–Kunshan Grand Bridge () is a viaduct on the Beijing–Shanghai High-Speed Railway. It is the longest bridge in the world.
Bridge
The bridge is located on the rail line between Shanghai and Nanjing in Jiangsu province. It is in the Yangtze River Delta, where the geography is characterized by lowland rice pa... | Danyang–Kunshan Grand Bridge | Wikipedia | 265 | 32359456 | https://en.wikipedia.org/wiki/Danyang%E2%80%93Kunshan%20Grand%20Bridge | Technology | Bridges | null |
A drug class is a group of medications and other compounds that share similar chemical structures, act through the same mechanism of action (i.e., binding to the same biological target), have similar modes of action, and/or are used to treat similar diseases. The FDA has long worked to classify and license new medicati... | Drug class | Wikipedia | 509 | 48471223 | https://en.wikipedia.org/wiki/Drug%20class | Biology and health sciences | General concepts_2 | Health |
5-alpha-reductase inhibitor
ACE inhibitor
Alpha-adrenergic agonist
Angiotensin II receptor antagonist
Beta blocker
Cholinergic
Dopaminergic
GABAergic
Incretin mimetic
Nonsteroidal anti-inflammatory drug − cyclooxygenase inhibitor
Proton-pump inhibitor
Renin inhibitor
Selective glucocorticoid receptor modula... | Drug class | Wikipedia | 299 | 48471223 | https://en.wikipedia.org/wiki/Drug%20class | Biology and health sciences | General concepts_2 | Health |
Amalgamated classes
Some drug classes have been amalgamated from these three principles to meet practical needs. The class of nonsteroidal anti-inflammatory drugs (NSAIDs) is one such example. Strictly speaking, and also historically, the wider class of anti-inflammatory drugs also comprises steroidal anti-inflammatory... | Drug class | Wikipedia | 381 | 48471223 | https://en.wikipedia.org/wiki/Drug%20class | Biology and health sciences | General concepts_2 | Health |
Agricultural expansion describes the growth of agricultural land (arable land, pastures, etc.) especially in the 20th and 21st centuries.
The agricultural expansion is often explained as a direct consequence of the global increase in food and energy requirements due to continuing population growth (both which in turn ... | Agricultural expansion | Wikipedia | 396 | 56630559 | https://en.wikipedia.org/wiki/Agricultural%20expansion | Technology | Agriculture and ecology | null |
The human digestive system consists of the gastrointestinal tract plus the accessory organs of digestion (the tongue, salivary glands, pancreas, liver, and gallbladder). Digestion involves the breakdown of food into smaller and smaller components, until they can be absorbed and assimilated into the body. The process of... | Human digestive system | Wikipedia | 498 | 42193218 | https://en.wikipedia.org/wiki/Human%20digestive%20system | Biology and health sciences | Human anatomy | Health |
There are several organs and other components involved in the digestion of food. The organs known as the accessory digestive organs are the liver, gall bladder and pancreas. Other components include the mouth, salivary glands, tongue, teeth and epiglottis.
The largest structure of the digestive system is the gastroint... | Human digestive system | Wikipedia | 246 | 42193218 | https://en.wikipedia.org/wiki/Human%20digestive%20system | Biology and health sciences | Human anatomy | Health |
The mouth is the first part of the upper gastrointestinal tract and is equipped with several structures that begin the first processes of digestion. These include salivary glands, teeth and the tongue. The mouth consists of two regions; the vestibule and the oral cavity proper. The vestibule is the area between the tee... | Human digestive system | Wikipedia | 488 | 42193218 | https://en.wikipedia.org/wiki/Human%20digestive%20system | Biology and health sciences | Human anatomy | Health |
There are three pairs of main salivary glands and between 800 and 1,000 minor salivary glands, all of which mainly serve the digestive process, and also play an important role in the maintenance of dental health and general mouth lubrication, without which speech would be impossible. The main glands are all exocrine gl... | Human digestive system | Wikipedia | 417 | 42193218 | https://en.wikipedia.org/wiki/Human%20digestive%20system | Biology and health sciences | Human anatomy | Health |
Saliva moistens and softens food, and along with the chewing action of the teeth, transforms the food into a smooth bolus. The bolus is further helped by the lubrication provided by the saliva in its passage from the mouth into the esophagus. Also of importance is the presence in saliva of the digestive enzymes amylase... | Human digestive system | Wikipedia | 500 | 42193218 | https://en.wikipedia.org/wiki/Human%20digestive%20system | Biology and health sciences | Human anatomy | Health |
The tongue is attached to the floor of the mouth by a ligamentous band called the frenum and this gives it great mobility for the manipulation of food (and speech); the range of manipulation is optimally controlled by the action of several muscles and limited in its external range by the stretch of the frenum. The tong... | Human digestive system | Wikipedia | 467 | 42193218 | https://en.wikipedia.org/wiki/Human%20digestive%20system | Biology and health sciences | Human anatomy | Health |
Teeth are complex structures made of materials specific to them. They are made of a bone-like material called dentin, which is covered by the hardest tissue in the body—enamel. Teeth have different shapes to deal with different aspects of mastication employed in tearing and chewing pieces of food into smaller and small... | Human digestive system | Wikipedia | 437 | 42193218 | https://en.wikipedia.org/wiki/Human%20digestive%20system | Biology and health sciences | Human anatomy | Health |
The pharynx is a part of the conducting zone of the respiratory system and also a part of the digestive system. It is the part of the throat immediately behind the nasal cavity at the back of the mouth and above the esophagus and larynx. The pharynx is made up of three parts. The lower two parts—the oropharynx and the ... | Human digestive system | Wikipedia | 374 | 42193218 | https://en.wikipedia.org/wiki/Human%20digestive%20system | Biology and health sciences | Human anatomy | Health |
At rest the esophagus is closed at both ends, by the upper and lower esophageal sphincters. The opening of the upper sphincter is triggered by the swallowing reflex so that food is allowed through. The sphincter also serves to prevent back flow from the esophagus into the pharynx. The esophagus has a mucous membrane an... | Human digestive system | Wikipedia | 462 | 42193218 | https://en.wikipedia.org/wiki/Human%20digestive%20system | Biology and health sciences | Human anatomy | Health |
The stomach is a major organ of the gastrointestinal tract and digestive system. It is a consistently J-shaped organ joined to the esophagus at its upper end and to the duodenum at its lower end.
Gastric acid (informally gastric juice), produced in the stomach plays a vital role in the digestive process, and mainly con... | Human digestive system | Wikipedia | 428 | 42193218 | https://en.wikipedia.org/wiki/Human%20digestive%20system | Biology and health sciences | Human anatomy | Health |
The parietal cells in the fundus of the stomach, produce a glycoprotein called intrinsic factor which is essential for the absorption of vitamin B12. Vitamin B12 (cobalamin), is carried to, and through the stomach, bound to a glycoprotein secreted by the salivary glands – transcobalamin I also called haptocorrin, which... | Human digestive system | Wikipedia | 329 | 42193218 | https://en.wikipedia.org/wiki/Human%20digestive%20system | Biology and health sciences | Human anatomy | Health |
The liver is the second largest organ (after the skin) and is an accessory digestive gland which plays a role in the body's metabolism. The liver has many functions some of which are important to digestion. The liver can detoxify various metabolites; synthesise proteins and produce biochemicals needed for digestion. It... | Human digestive system | Wikipedia | 504 | 42193218 | https://en.wikipedia.org/wiki/Human%20digestive%20system | Biology and health sciences | Human anatomy | Health |
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