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Nickel hydrazine nitrate (NHN) , (chemical formula: [Ni(N 2 H 4 ) 3 ](NO 3 ) 2 is an energetic material having explosive properties in between that of primary explosive and a secondary explosive. [ 2 ] [ 3 ] It is a salt of a coordination compound of nickel .
NHN can be synthesized by reacting nickel(II) nitrate hexahydrate with a dilute aqueous solution of hydrazine monohydrate at 65 C. [ 4 ]
To help speed the drying of the product after filtration from the hot water, it can be rinsed with alcohol. The product is a fluffy powder (density=0.9 g/cm 3 ). To increase its bulk density to (1.2 g/cm 3 ), dextrin in the amount of (1%) of the weight of the nickel(II) nitrate hexahydrate can be added. [ 5 ]
The sensitivity of NHN straddles the line between highly sensitive primaries and a sensitive secondary, so it can be considered a true non-primary explosive detonator (NPED).
Another benefit of NHN is that it will make the DDT ( deflagration to detonation transition ) in a cardboard shell, eliminating the danger of shrapnel from a metal shell.
NHN straddles the line between primary and secondary. Because of this it is a relatively safe explosive to work with having 80x less sensitivity to friction (16.0 N) than lead azide (0.1N) as shown in table 2.
Friction sensitivities of some traditional explosives (lead azide – 0.1N; lead styphnate – 1.5 N; mercury fulminate (white) – 5.0 N; tetrazene – 8.0 N; PETN – 60 N; RDX – 120 N; HMX – 120 N, show that NHN is not very sensitive, and is thereby not exceedingly hazardous in handling. [ 6 ]
Source: [ 2 ]
a Values in brackets are theoretical
a Experimental value, b literature value, and c theoretical value | https://en.wikipedia.org/wiki/Nickel_hydrazine_nitrate |
Nickel monosilicide is an intermetallic compound formed out of nickel and silicon . Like other nickel silicides , NiSi is of importance in the area of microelectronics .
Nickel monosilicide can be prepared by depositing a nickel layer on silicon and subsequent annealing . In the case of Ni films with thicknesses above 4 nm , the normal phase transition is given by Ni 2 Si at 250 °C followed by NiSi at 350 °C and NiSi 2 at approximately 800 °C. [ 4 ] For films with an initial Ni thickness below 4 nm a direct transition from orthorhombic Ni 2 Si to epitaxial NiSi 2−x , skipping the nickel monosilicide phase, is observed. [ 5 ]
Several properties make NiSi an important local contact material in the area of microelectronics, among them a reduced thermal budget , low resistivity of 13–14 μΩ·cm and a reduced Si consumption when compared to alternative compounds. [ 6 ]
This inorganic compound –related article is a stub . You can help Wikipedia by expanding it . | https://en.wikipedia.org/wiki/Nickel_monosilicide |
The nickel organic acid salts are organic acid salts of nickel . In many of these the ionised organic acid acts as a ligand .
Nickel acetate has the formula (CH 3 COO) 2 Ni·4H 2 O. It has monodentate acetate and hydrogen bonding. A dihydrate also exists. Nickel acetate is used to seal anodised aluminium . [ 1 ]
Nickel formate Ni(HCOO) 2.2 H 2 O decomposes when heated to yield carbon dioxide, carbon monoxide, hydrogen, water and finely divided porous nickel. [ 2 ] All the nickel atoms are six coordinated, but half have four water molecules and two formate oxygens close to the atom, and the other half are coordinated by six oxygens of formate groups. [ 3 ]
Aspergillus niger is able to dispose of otherwise toxic levels of nickel in its environment by forming nickel oxalate dihydrate crystals. [ 4 ] nickel oxalate can also be formed in to various nanorods and nanofibres by use of surfacants. [ 5 ] When heated nickel oxalate dihydrate dehydrates at 258° and decomposes to Ni metal [ 6 ] over 316 °C. [ 7 ] Double oxalate salts where oxalate is a ligand on the nickel atom may be called oxalatonickelates .
Other organic acid salts of nickel include nickel oleate, nickel propionate, nickel butyrate, nickel caprylate, nickel lactate, nickel benzoate, nickel bis(acetyl acetonate), nickel salicylate, nickel alkyl phenyl salicylate. Nickel stearate forms a green solution, however when precipitated with alcohol a gel is produced, that also contains a mixture of basic salts, and free stearic acid . [ 8 ]
Nickel malonate, and nickel hydrogen malonate both crystallise with two molecules of water. They decomposes when heated to yield gaseous water, carbon dioxide, carbon monoxide, ethanol, acetic acid , methyl formate and ethyl formate . Nickel acetate exists as an intermediate and the final result is that solid nickel, nickel oxide, Ni 3 C and carbon remain. [ 9 ] With malonate nickel can form a bis-malonato-nickelate anion, which can form double salts. [ 10 ] Nickel maleate can be made from maleic acid and nickel carbonate in boiling water. A dihydrate crystallises from the water solution. [ 11 ] Nickel fumarate prepared from fumaric acid and nickel carbonate is pale green as a tetrahydrate, and mustard coloured as an anhydride. It decomposes when heated to 300° to 340° in vacuum. Decomposition mostly produces nickel carbide, carbon dioxide, carbon monoxide and methane. But also produced were butanes , benzene, toluene , and organic acid. [ 12 ]
Nickel succinate can form metal organic framework compounds. [ 13 ]
Nickel citrate complexes are found in leaves of some nickel accumulating plant species in New Caledonia such as Pycnandra acuminata . [ 14 ] Citrate complexes include NiHcit, NiHcit 2 3− , Nicit − , Nicit 2 4− , and Ni 2 H 2 cit 2 4− . (ordered from low to high pH). Also there is Ni 4 H 4 cit 3 5− . Nickel citrate is important in nickel plating. [ 15 ] When precipitation of nickel citrate is attempted a gel forms. This apparently consists of tangled fibres of [(C 6 H 6 O 7 )Ni] n , which can be reduced to nickel metal fibres less than a micron thick, and meters long. [ 16 ] Double nickel citrates exist, including tetraanion citrate when pH is over 9.5. [ 17 ] An amorphous nickel iron citrate Ni 3 Fe 6 O 4 (C 6 H 6 O 7 ) 8 ·6H 2 O produces carbon monoxide, carbon dioxide and acetone when heated over 200 °C leaving Trevorite , NiFe 2 O 4 a nickel ferrite . [ 18 ] A green crystalline nickel citrate with formula Ni 3 (C 6 H 5 O 7 ) 2 ·10H 2 O melts at 529K and decomposition starts at 333K. [ 19 ]
Nickel glutarate in the form called Mil-77, [Ni 20 {(C 5 H 6 O 4 ) 20 (H 2 O) 8 }]⋅40H 2 O is pale green. It crystallises in a porous structure containing twenty member rings. The 40 water molecules "occluded" in the porous channels come out when it is heated to 150 °C retaining the crystal framework. At 240 °C the crystal form changes and over 255° the remaining water is lost. Between 330° and 360° the organic components burn and it is destroyed. [ 20 ]
Cyclopropane carboxylic acid forms two basic salts with nickel, a hydrate Ni 9 (OH) 2 (H 2 O) 6 (C 4 H 5 O 2 ) 8 • 2H 2 O with density 1.554 Mg/m 3 and an anhydrous form Ni 5 (OH) 2 (C 4 H 5 O 2 ) 8 with density 2.172 mg/m 3 . [ 21 ]
Nickel trifluoroacetate tetrahydrate exists, as well as two emerald green acid trifluoroacetates, a bridged trinuclear form [Ni 3 (CF 3 COO) 6 (CF 3 COOH) 6 ](CF 3 COOH) and a hydrated acid form [Ni 3 (CF 3 COO) 6 (CF 3 COOH) 2 (H 2 O) 4 ](CF 3 COOH) 2 both with triclinic crystal form. The first has density 2.205 and the second 2.124. They are made by dissolving the nickel trifluoroacetate tetrahydrate in trifluoroacetic acid either anhydrous or 1% hydrated. [ 22 ]
Nickel naphthenate is used as a fuel additive to suppress smoke, [ 23 ] as a rubber catalyst and as an oil additive .
When Nickel benzoate is heated in a vacuum, carbon dioxide, carbon monoxide, benzene , benzoic acid , phenol , biphenyl , nickel, nickel oxide, and nickel carbide are formed. [ 24 ] It can crystallise as anhydrous, a trihydrate or a tetrahydrate. [ 25 ]
Nickel terephthalate can be made by a double decomposition of sodium terephthalate and nickel nitrate. Nickel terephthalate precipitates. Its solubility is 0.38 g/100g water at 25 °C. In ammonium hydroxide a violet solution forms. Boiling acetic acid converts the nickel to nickel acetate. The terephthalate converts to a basic salt when boiled in water. Understating this compound is important when reducing coloured contaminants in polymers made from terephthalate. [ 26 ] | https://en.wikipedia.org/wiki/Nickel_organic_acid_salts |
Nickel oxide hydroxide is the inorganic compound with the chemical formula NiO(OH). It is a black solid that is insoluble in all solvents but attacked by base and acid. It is a component of the nickel–metal hydride battery and of the nickel–iron battery .
Nickel(III) oxides are often poorly characterized and are assumed to be nonstoichiometric compounds . Nickel(III) oxide (Ni 2 O 3 ) has not been verified crystallographically. For applications in organic chemistry, nickel oxides or peroxides are generated in situ and lack crystallographic characterization. For example, "nickel peroxide" ( CAS# 12035-36-8) is also closely related to or even identical with NiO(OH). [ 1 ]
Its layered structure resembles that of the brucite polymorph of nickel(II) hydroxide , but with half as many hydrogens. The oxidation state of nickel is +3. [ 2 ] It can be prepared by the reaction of nickel(II) hydroxide with aqueous potassium hydroxide and bromine as the oxidant: [ 3 ]
Nickel(III) oxides catalyze the oxidation of benzyl alcohol to benzoic acid using bleach: [ 4 ]
Similarly it catalyzes the double oxidation of 3-butenoic acid to fumaric acid :
This electrochemistry -related article is a stub . You can help Wikipedia by expanding it . | https://en.wikipedia.org/wiki/Nickel_oxide_hydroxide |
A nickel sulfide inclusion , also abbreviated to NiS, occurs during the process of manufacturing float glass (normal window glass).
In a batch of glass , contaminants that contain nickel might be present (e.g. stainless steel .)
These can combine with sulfur to form nickel sulfide inclusions. Furnaces produce hundreds of tons of glass every day, so it is difficult to eliminate all contaminants. This causes a problem later in the manufacturing process. [ 1 ]
While total elimination is difficult, specific controlled processes can significantly reduce the formation of NiS in the float glass. These are actions taken by US flat glass manufacturers supplying to the automotive industry in the early 1990s:
The process of tempering float glass can cause a NiS to change from its normal state (known as a low-temperature structure) to a different high-temperature, crystalline structure . When the glass is cooled quickly (as part of the process) the NiS particle is unable to change back to its original form.
Over a certain period of time NiS will slowly convert to the original low temperature structure. This means the NiS increases in size, and the mechanical stresses caused by this cause the tempered pane to shatter, for no apparent reason (hence spontaneous glass breakage ). [ 1 ] | https://en.wikipedia.org/wiki/Nickel_sulfide_inclusion |
Nickel titanium , also known as nitinol , is a metal alloy of nickel and titanium , where the two elements are present in roughly equal atomic percentages. Different alloys are named according to the weight percentage of nickel; e.g., nitinol 55 and nitinol 60 .
Nitinol alloys exhibit two closely related and unique properties: the shape memory effect and superelasticity (also called pseudoelasticity ). Shape memory is the ability of nitinol to undergo deformation at one temperature, stay in its deformed shape when the external force is removed, then recover its original, undeformed shape upon heating above its "transformation temperature." Superelasticity is the ability for the metal to undergo large deformations and immediately return to its undeformed shape upon removal of the external load. Nitinol can undergo elastic deformations 10 to 30 times larger than alternative metals. Whether nitinol behaves with shape memory effect or superelasticity depends on whether it is above its transformation temperature during the action. Nitinol behaves with the shape memory effect when it is colder than its transformation temperature, and superelastically when it is warmer than it.
The word "nitinol" is derived from its composition and its place of discovery, Nickel Titanium - Naval Ordnance Laboratory. William J. Buehler [ 1 ] along with Frederick E. Wang , [ 2 ] discovered its properties during research at the Naval Ordnance Laboratory in 1959. [ 3 ] [ 4 ] Buehler was attempting to make a better missile nose cone, which could resist fatigue , heat and the force of impact . Having found that a 1:1 alloy of nickel and titanium could do the job, in 1961 he presented a sample at a laboratory management meeting. The sample, folded up like an accordion , was passed around and flexed by the participants. One of them applied heat from his pipe lighter to the sample and, to everyone's surprise, the accordion-shaped strip contracted and took its previous shape. [ 5 ]
While potential applications for nitinol were realized immediately, practical efforts to commercialize the alloy did not take place until two decades later in the 1980s, largely due to the extraordinary difficulty of melting, processing and machining the alloy.
The discovery of the shape-memory effect in general dates back to 1932, when Swedish chemist Arne Ölander [ 6 ] first observed the property in gold–cadmium alloys. The same effect was observed in Cu-Zn ( brass ) in the early 1950s. [ 7 ]
Nitinol's unusual properties are derived from a reversible solid-state phase transformation known as a martensitic transformation , between two different martensite crystal phases, requiring 69–138 MPa (10,000–20,000 psi) of mechanical stress.
At high temperatures, nitinol assumes an interpenetrating simple cubic structure referred to as austenite (also known as the parent phase). At low temperatures, nitinol spontaneously transforms to a more complicated monoclinic crystal structure known as martensite (daughter phase). [ 8 ] There are four transition temperatures associated to the austenite-to-martensite and martensite-to-austenite transformations. Starting from full austenite, martensite begins to form as the alloy is cooled to the so-called martensite start temperature , or M s , and the temperature at which the transformation is complete is called the martensite finish temperature , or M f . When the alloy is fully martensite and is subjected to heating, austenite starts to form at the austenite start temperature , A s , and finishes at the austenite finish temperature , A f . [ 9 ]
The cooling/heating cycle shows thermal hysteresis . The hysteresis width depends on the precise nitinol composition and processing. Its typical value is a temperature range spanning about 20–50 °C (36–90 °F) but it can be reduced or amplified by alloying [ 10 ] and processing. [ 11 ]
Crucial to nitinol properties are two key aspects of this phase transformation. First is that the transformation is "reversible", meaning that heating above the transformation temperature will revert the crystal structure to the simpler austenite phase. The second key point is that the transformation in both directions is instantaneous.
Martensite's crystal structure (known as a monoclinic, or B19' structure) has the unique ability to undergo limited deformation in some ways without breaking atomic bonds. This type of deformation is known as twinning , which consists of the rearrangement of atomic planes without causing slip, or permanent deformation. It is able to undergo about 6–8% strain in this manner. When martensite is reverted to austenite by heating, the original austenitic structure is restored, regardless of whether the martensite phase was deformed. Thus the shape of the high temperature austenite phase is "remembered," even though the alloy is severely deformed at a lower temperature. [ 12 ]
A great deal of pressure can be produced by preventing the reversion of deformed martensite to austenite—from 240 MPa (35,000 psi) to, in many cases, more than 690 MPa (100,000 psi). One of the reasons that nitinol works so hard to return to its original shape is that it is not just an ordinary metal alloy, but what is known as an intermetallic compound . In an ordinary alloy, the constituents are randomly positioned in the crystal lattice; in an ordered intermetallic compound, the atoms (in this case, nickel and titanium) have very specific locations in the lattice. [ 13 ] The fact that nitinol is an intermetallic is largely responsible for the complexity in fabricating devices made from the alloy. [ why? ]
To fix the original "parent shape," the alloy must be held in position and heated to about 500 °C (930 °F). This process is usually called shape setting . [ 14 ] A second effect, called superelasticity or pseudoelasticity, is also observed in nitinol. This effect is the direct result of the fact that martensite can be formed by applying a stress as well as by cooling. Thus in a certain temperature range, one can apply a stress to austenite, causing martensite to form while at the same time changing shape. In this case, as soon as the stress is removed, the nitinol will spontaneously return to its original shape. In this mode of use, nitinol behaves like a super spring, possessing an elastic range 10 to 30 times greater than that of a normal spring material. There are, however, constraints: the effect is only observed up to about 40 °C (72 °F) above the A f temperature. This upper limit is referred to as M d , [ 15 ] which corresponds to the highest temperature in which it is still possible to stress-induce the formation of martensite. Below M d , martensite formation under load allows superelasticity due to twinning. Above M d , since martensite is no longer formed, the only response to stress is slip of the austenitic microstructure, and thus permanent deformation.
Nitinol is typically composed of approximately 50 to 51% nickel by atomic percent (55 to 56% weight percent). [ 13 ] [ 16 ] Making small changes in the composition can change the transition temperature of the alloy significantly. Transformation temperatures in nitinol can be controlled to some extent, where A f temperature ranges from about −20 to +110 °C (−4 to 230 °F). Thus, it is common practice to refer to a nitinol formulation as "superelastic" or "austenitic" if A f is lower than a reference temperature, while as "shape memory" or "martensitic" if higher. The reference temperature is usually defined as the room temperature or the human body temperature (37 °C or 99 °F).
One often-encountered effect regarding nitinol is the so-called R-phase . The R-phase is another martensitic phase that competes with the martensite phase mentioned above. Because it does not offer the large memory effects of the martensite phase, it is usually of no practical use.
Nitinol is exceedingly difficult to make, due to the exceptionally tight compositional control required, and the tremendous reactivity of titanium. Every atom of titanium that combines with oxygen or carbon is an atom that is robbed from the NiTi lattice, thus shifting the composition and making the transformation temperature lower.
There are two primary melting methods used today. Vacuum arc remelting (VAR) is done by striking an electrical arc between the raw material and a water-cooled copper strike plate. Melting is done in a high vacuum, and the mold itself is water-cooled copper. Vacuum induction melting (VIM) is done by using alternating magnetic fields to heat the raw materials in a crucible (generally carbon). This is also done in a high vacuum. While both methods have advantages, it has been demonstrated that an industrial state-of-the-art VIM melted material has smaller inclusions than an industrial state-of-the-art VAR one, leading to a higher fatigue resistance. [ 17 ] Other research report that VAR employing extreme high-purity raw materials may lead to a reduced number of inclusions and thus to an improved fatigue behavior. [ 18 ] Other methods are also used on a boutique scale, including plasma arc melting, induction skull melting, and e-beam melting. Physical vapour deposition is also used on a laboratory scale.
Heat treating nitinol is delicate and critical. It is a knowledge intensive process to fine-tune the transformation temperatures. Aging time and temperature controls the precipitation of various Ni-rich phases, and thus controls how much nickel resides in the NiTi lattice; by depleting the matrix of nickel, aging increases the transformation temperature. The combination of heat treatment and cold working is essential in controlling the properties of nitinol products. [ 19 ]
Fatigue failures of nitinol devices are a constant subject of discussion. Because it is the material of choice for applications requiring enormous flexibility and motion (e.g., peripheral stents , heart valves, smart thermomechanical actuators and electromechanical microactuators), it is necessarily exposed to much greater fatigue strains compared to other metals. While the strain-controlled fatigue performance of nitinol is superior to all other known metals, fatigue failures have been observed in the most demanding applications; with a great deal of effort underway to better understand and define the durability limits of nitinol.
Nitinol is half nickel, and thus there has been a great deal of concern in the medical industry regarding the release of nickel, a known allergen and possible carcinogen. [ 19 ] (Nickel is also present in substantial amounts in stainless steel and cobalt-chrome alloys also used in the medical industry.) When treated (via electropolishing or passivation ), nitinol forms a very stable protective TiO 2 layer that acts as an effective and self-healing barrier against ion exchange; repeatedly showing that nitinol releases nickel at a slower pace than stainless steel, for example. Early Nitinol medical devices were made without electropolishing, and corrosion was observed. [ citation needed ] Today's nitinol vascular self-expandable metallic stents show no evidence of corrosion or nickel release, and outcomes in patients with and without nickel allergies are indistinguishable. [ citation needed ]
There are constant and long-running discussions [ by whom? ] regarding inclusions in nitinol, both TiC and Ti 2 NiO x . As in all other metals and alloys, inclusions can be found in nitinol. The size, distribution and type of inclusions can be controlled to some extent. Theoretically, smaller, rounder, and fewer inclusions should lead to increased fatigue durability. In literature, some early works report to have failed to show measurable differences, [ 20 ] [ 21 ] while novel studies demonstrate a dependence of fatigue resistance on the typical inclusion size in an alloy. [ 17 ] [ 18 ] [ 22 ] [ 23 ] [ 24 ]
Nitinol is difficult to weld, both to itself and other materials. Laser welding nitinol to itself is a relatively routine process. Strong joints between NiTi wires and stainless steel wires have been made using nickel filler. [ 25 ] Laser and tungsten inert gas (TIG) welds have been made between NiTi tubes and stainless steel tubes. [ 26 ] [ 27 ] More research is ongoing into other processes and other metals to which nitinol can be welded.
Actuation frequency of nitinol is dependent on heat management, especially during the cooling phase. Numerous methods are used to increase the cooling performance, such as forced air, [ 28 ] flowing liquids, [ 29 ] thermoelectric modules (i.e. Peltier or semiconductor heat pumps), [ 30 ] heat sinks, [ 31 ] conductive materials [ 32 ] and higher surface-to-volume ratio [ 33 ] (improvements up to 3.3 Hz with very thin wires [ 34 ] and up to 100 Hz with thin films of nitinol [ 35 ] ). The fastest nitinol actuation recorded was carried by a high voltage capacitor discharge which heated an SMA wire in a manner of microseconds, and resulted in a complete phase transformation (and high velocities) in a few milliseconds. [ 36 ]
Recent advances have shown that processing of nitinol can expand thermomechanical capabilities, allowing for multiple shape memories to be embedded within a monolithic structure. [ 37 ] [ 38 ] Research on multi-memory technology is on-going and may deliver enhanced shape memory devices in the near future, [ 39 ] [ 40 ] and new materials and material structures, such as hybrid shape memory materials (SMMs) and shape memory composites (SMCs). [ 41 ]
There are four commonly used types of applications for nitinol:
Superelastic materials undergo stress-induced transformation and are commonly recognized for their "shape-memory" property. Due to its superelasticity, NiTi wires exhibit "elastocaloric" effect, which is stress-triggered heating/cooling. NiTi wires are currently under research as the most promising material for the technology. The process begins with tensile loading on the wire, which causes fluid (within the wire) to flow to HHEX (hot heat exchanger). Simultaneously, heat will be expelled, which can be used to heat the surrounding. In the reverse process, tensile unloading of the wire leads to fluid flowing to CHEX (cold heat exchanger), causing the NiTi wire to absorb heat from the surrounding. Therefore, the temperature of the surrounding can be decreased (cooled).
Elastocaloric devices are often compared with magnetocaloric devices as new methods of efficient heating/cooling. Elastocaloric device made with NiTi wires has an advantage over magnetocaloric device made with gadolinium due to its specific cooling power (at 2 Hz), which is 70X better (7 kWh/kg vs. 0.1 kWh/kg). However, elastocaloric device made with NiTi wires also have limitations, such as its short fatigue life and dependency on large tensile forces (energy consuming).
In 1989 a survey was conducted in the United States and Canada that involved seven organizations. The survey focused on predicting the future technology, market, and applications of SMAs. The companies predicted the following uses of nitinol in a decreasing order of importance: (1) Couplings, (2) Biomedical and medical, (3) Toys, demonstration, novelty items, (4) Actuators, (5) Heat Engines, (6) Sensors, (7) Cryogenically activated die and bubble memory sockets, and finally (8) lifting devices. [ 42 ]
A process of making parts and forms of Type 60 Nitinol having a shape memory effect, comprising: selecting a Type 60 Nitinol. Inventor G, Julien, CEO of Nitinol Technologies, Inc. (Washington State) | https://en.wikipedia.org/wiki/Nickel_titanium |
A nicking enzyme (or nicking endonuclease ) is an enzyme that cuts only one strand of a double-stranded DNA or RNA molecule [ 1 ] at a specific recognition nucleotide sequence known as the restriction site . Such enzymes hydrolyze (cut) only one strand of the DNA duplex, to produce DNA molecules that are “ nicked ”, rather than cleaved. [ 2 ] [ 3 ]
They can be used for strand-displacement amplification, [ 4 ] Nicking Enzyme Amplification Reaction , exonucleolytic degradation, the creation of small gaps, [ 5 ] or nick translation . [ 6 ] The latter process has been successfully used to incorporate both radioactively labelled nucleotides and fluorescent nucleotides allowing specific regions on a double stranded DNA to be studied. [ 6 ] [ 7 ] Over 200 nicking enzymes have been studied, and 13 of these are available commercially [ 8 ] and are routinely used for research and in commercial products. | https://en.wikipedia.org/wiki/Nicking_enzyme |
Nicking Enzyme Amplification Reaction (NEAR) is a method for in vitro DNA amplification like the polymerase chain reaction (PCR). NEAR is isothermal, replicating DNA at a constant temperature using a polymerase (and nicking enzyme ) to exponentially amplify the DNA at a temperature range of 55 °C to 59 °C.
One disadvantage of PCR is that it consumes time uncoiling the double-stranded DNA with heat into single strands (a process called denaturation ) . This leads to amplification times typically thirty minutes or more for significant production of amplified products. [ 1 ] [ circular reference ]
Potential advantages of NEAR over PCR are increased speed and lower energy requirements, characteristics that are shared with other isothermal amplification schemes. [ 2 ] A major disadvantage of NEAR relative to PCR is that production of nonspecific amplification products is a common issue with isothermal amplification reactions. [ 3 ]
The NEAR reaction uses naturally occurring or engineered endonucleases that introduce a strand break on only one strand of a double-stranded DNA cleavage site. The ability of several of these enzymes to catalyze isothermal DNA amplification was disclosed but not claimed in the patents issued for the enzymes themselves. [ 4 ] [ 5 ]
This biochemistry article is a stub . You can help Wikipedia by expanding it . | https://en.wikipedia.org/wiki/Nicking_enzyme_amplification_reaction |
A Nicol prism is a type of polarizer . It is an optical device made from calcite crystal used to convert ordinary light into plane polarized light . It is made in such a way that it eliminates one of the rays by total internal reflection , i.e. the ordinary ray is eliminated and only the extraordinary ray is transmitted through the prism .
It was the first type of polarizing prism, invented in 1828 by William Nicol (1770–1851) of Edinburgh .
The Nicol prism consists of a rhombohedral crystal of Iceland spar (a variety of calcite ) that has been cut at an angle of 68° with respect to the crystal axis , cut again diagonally, and then rejoined, using a layer of transparent Canada balsam as a glue. [ 1 ]
Unpolarized light ray enters through the side face of the crystal, and is split into two orthogonally polarized, differently directed rays by the birefringence property of calcite. The ordinary ray, or o -ray, experiences a refractive index of n o = 1.658 in the calcite and undergoes a total internal reflection at the calcite–glue interface because of its angle of incidence at the glue layer (refractive index n = 1.550) exceeds the critical angle for the interface. It passes out the top side of the upper half of the prism with some refraction . The extraordinary ray, or e -ray, experiences a lower refractive index ( n e = 1.486) in the calcite crystal and is not totally reflected at the interface because it strikes the interface at a sub-critical angle. The e -ray merely undergoes a slight refraction , or bending, as it passes through the interface into the lower half of the prism . It finally leaves the prism as a ray of plane-polarized light , undergoing another refraction, as it exits the opposite side of the prism. The two exiting rays have polarizations orthogonal (at right angles) to each other, but the lower, or e -ray, is the more commonly used for further experimentation because it is again traveling in the original horizontal direction, assuming that the calcite prism angles have been properly cut. The direction of the upper ray, or o -ray, is quite different from its original direction because it alone suffers total internal reflection at the glue interface, as well as a final refraction on exit from the upper side of the prism.
Nicol prisms were once widely used in mineralogical microscopy and polarimetry , and the term "using crossed Nicols" (abbreviated as XN ) is still used to refer to the observing of a sample placed between orthogonally oriented polarizers.
In most instruments, however, Nicol prisms have been replaced by other types of polarizers such as polaroid sheets and Glan–Thompson prisms . | https://en.wikipedia.org/wiki/Nicol_prism |
Nicolae Popescu ( Romanian: [nikoˈla.e poˈpesku] ; 22 September 1937 – 29 July 2010) was a Romanian mathematician and professor at the University of Bucharest . He also held a research position at the Institute of Mathematics of the Romanian Academy , and was elected corresponding Member of the Romanian Academy in 1997. [ 1 ]
He is best known for his contributions to algebra and the theory of abelian categories . From 1964 to 2007 he collaborated with Pierre Gabriel on the characterization of abelian categories; their best-known result is the Gabriel–Popescu theorem , published in 1964. [ 2 ] His areas of expertise were category theory , abelian categories with applications to rings and modules , adjoint functors , limits and colimits , the theory of sheaves, the theory of rings , fields and polynomials , and valuation theory . He also had interests and published in algebraic topology , algebraic geometry , commutative algebra , K-theory , class field theory , and algebraic function theory .
Popescu was born on September 22, 1937, in Strehaia-Comanda , Mehedinți County , Romania . In 1954 he graduated from the Carol I High School in Craiova and went on to study mathematics at the University of Iași . In his third year of studies he was expelled from the university, having been deemed "hostile to the regime" for remarking that "the achievements of American scientists are also worth of consideration." [ 3 ] [ 4 ] He then went back home to Strehaia, where he worked for a year in a collective farm, after which he was admitted in 1959 at the University of Bucharest , only to start anew as a freshman. Popescu earned his M.S. degree in mathematics in 1964, and his Ph.D. degree in mathematics in 1967, with thesis Krull–Remak–Schmidt Theorem and Theory of Decomposition written under the direction of Gheorghe Galbură [ ro ] . [ 5 ] He was awarded a D. Phil. degree (Doctor Docent) in 1972, also by the University of Bucharest.
While still a student, Popescu focused on category theory . He first approached the general theory, with its connections to homological algebra and algebraic topology, then shifted his focus on theory of Abelian categories , being one of the main promoters of this theory in Romania. [ 6 ] He carried out mathematics studies at the Institute of Mathematics of the Romanian Academy in the Algebra research group, [ 7 ] and also had international collaborations on three continents. He shared many moral, ethical, and religious values with Alexander Grothendieck , who visited the Faculty of Mathematics in Bucharest in 1968. Like Grothendieck, he had a long-standing interest in category theory and number theory , and supported promising young mathematicians in his fields of interest. He also promoted the early developments of category theory applications in relational biology and mathematical biophysics/ mathematical biology .
Popescu was appointed as a Lecturer at the University of Bucharest in 1968 where he taught graduate students until 1972. Starting in 1964 he also held a research appointment at the Institute of Mathematics of the Romanian Academy . [ 8 ] [ 6 ] The institute was closed in 1976 by order of Nicolae Ceaușescu (for reasons related to his daughter Zoia Ceaușescu , who had been hired at the institute two years before), but was reopened in 1990, after the Romanian Revolution .
Between 1962 and 2008 Popescu published more than 102 papers in peer-reviewed mathematics journals, several monographs on the theory of sheaves, and several books on abelian category theory and abstract algebra , including
In a Grothendieck -like, energetic style, he initiated and provided scientific leadership to several seminars on category theory, sheaves and abstract algebra which resulted in a continuous stream of high-quality mathematical publications in international, peer-reviewed mathematics journals by several members participating in his Seminar series.
Popescu died in Bucharest on July 29, 2010. [ 4 ] He is survived by his wife, Professor Dr. Elena Liliana Popescu [ ro ] (a mathematician, poet, literary translator and editor), and their three children, one of whom, Dan Cristian Popescu [ ro ] , is a politician. [ 3 ]
In 1971 Popescu received the Simion Stoilow Prize in Mathematics of the Romanian Academy. He was elected President of the Romanian Mathematical Society in 1990 [ 4 ] and corresponding Member of the Romanian Academy in 1997. On the 80th anniversary of his birthday, the Faculty of Mathematics and Informatics at the University of Bucharest and the Institute of Mathematics of the Romanian Academy organized a conference in his memory. [ 9 ] | https://en.wikipedia.org/wiki/Nicolae_Popescu |
The Nicolaou Taxol total synthesis , published by K. C. Nicolaou and his group in 1994 concerns the total synthesis of taxol . [ 1 ] Taxol is an important drug in the treatment of cancer but also expensive because the compound is harvested from a scarce resource, namely the pacific yew .
This synthetic route to taxol is one of several; other groups have presented their own solutions, notably the group of Holton with a linear synthesis starting from borneol , the Samuel Danishefsky group starting from the Wieland-Miescher ketone and the Wender group from pinene .
The Nicolaou synthesis is an example of convergent synthesis because the molecule is assembled from three pre-assembled synthons. Two major parts are cyclohexene rings A and C that are connected by two short bridges creating an 8 membered ring in the middle (ring B). The third pre-assembled part is an amide tail. Ring
D is an oxetane ring fused to ring C. Two key chemical transformations are the Shapiro reaction and the pinacol coupling reaction . [ 2 ] The overall synthesis was published in 1995 in a series of four papers. [ 3 ] [ 4 ] [ 5 ] [ 6 ]
As illustrated in Retrosynthetic Scheme I, Taxol was derived from diol 7.2 by an ester bond formation, according to the Ojima-Holton method. This diol comes from carbonate 6.3 by the addition of phenyllithium . The oxetane ring in compound 6.3 was obtained via an S N 2 reaction involving a mesylate derived from acetal 4.9. Ring B was closed via a McMurry reaction involving dialdehyde 4.8 which ultimately was derived from aldehyde 4.2 and hydrazone 3.6 using a Shapiro coupling reaction .
Retrosynthetic Scheme II indicates that both the aldehyde and the hydrazone used in the Shapiro coupling reaction were synthesized using Diels-Alder reactions .
As shown in Scheme 1 , the ring synthesis of ring C began with a Diels-Alder reaction between diene 1.3 and dienophile 1.1 in the presence of phenylboronic acid ( 1.2 ), which, after addition of 2,2-dimethyl-1,3-propanediol, gave five-membered lactone 1.8 in 62% yield. Boron served as a molecular tether and aligned both diene and dienophile for this endo Diels-Alder cycloaddition . After protection of the hydroxyl groups as tert -butyldimethylsilyl ethers , reduction of the ester with lithium aluminium hydride and selective deprotection of the secondary hydroxyl group gave lactone diol 1.11 . The unusual lactone hydrates 1.9 and 1.10 were isolated as synthetic intermediates in this process.
Lactone diol 2.1 , after selective protection, was reduced with lithium aluminium hydride to give triol 2.4 . This triol, after conversion to the acetonide , was selectively oxidized to the aldehyde using tetrapropylammonium perruthenate (TPAP) and N-methylmorpholine N-oxide . Aldehyde 2.6 served as a starting point for the construction of ring B ( Scheme 4 , compound 4.2 ).
The A ring synthesis ( Scheme 3 ) started with a Diels-Alder reaction of diene 3.1 with the commercially available dienophile 2-chloroacrylonitrile 3.2 to give cyclohexene 3.3 with complete regioselectivity . Hydrolysis of the cyanochloro group and simultaneous cleavage of the acetate group led to hydroxyketone 3.4 . The hydroxyl group was protected as a tert-butyldimethylsilyl ether ( 3.5 ). In preparation for a Shapiro reaction , this ketone was converted to hydrazone 3.6 .
The coupling of ring A and ring C created the 8 membered B ring. One connection was made via a nucleophilic addition of a vinyllithium compound to an aldehyde and the other connection through a pinacol coupling reaction of two aldehydes ( Scheme 4 ).
A Shapiro reaction of the vinyllithium compound derived from hydrazone 4.1 with aldehyde 4.2 makes the first connection that will become the B ring. The control of stereochemistry in 4.3 is thought to be derived from the relative hindrance of the Si face in the orientation shown on the right, due to the proximity of the axial methyl group. Epoxidation with vanadyl(acetylacetate) converted alkene 4.3 to epoxide 4.4 , which, upon reduction with lithium aluminium hydride , gave diol 4.5 . This diol was then protected as carbonate ester 4.6 . The carbonate group also served to create rigidity in the ring structure for the imminent pinacol coupling reaction . The two silyl ether groups were removed, and diol 4.7 was then oxidized to give dialdehyde 4.8 using N -methylmorpholine N -oxide in the presence of a catalytic amount of tetrapropylammonium perruthenate . In the final step of the formation of Ring B, a pinacol coupling using conditions developed by McMurry ( titanium(III) chloride and a zinc / copper alloy ) gave diol 4.9 .
At this point in the synthesis of Taxol, the material was a racemic mixture . To obtain the desired enantiomer , allylic alcohol 4.9 was acylated with (1S)-(−)-camphanic chloride and dimethylaminopyridine , giving two diastereomers . These were then separated using standard column chromatography . The desired enantiomer was then isolated when one of the separated disatereomers was treated with potassium bicarbonate in methanol .
The desired enantiomer from resolution, allylic alcohol 5.1 ( Scheme 5 ) was acetylated with acetic anhydride and 4-(dimethylamino)pyridine in methylene chloride to yield monoacetate 5.2 . It is noteworthy that this reaction was exclusive for the allylic alcohol, and the adjacent hydroxyl group was not acetylated . Alcohol 5.2 was oxidized with tetrapropylammonium perruthenate and N-methylmorpholine N-oxide to give ketone 5.3 . Alkene 5.3 underwent hydroboration in tetrahydrofuran . Oxidation with basic hydrogen peroxide and sodium bicarbonate gave alcohol 5.4 in 35% yield, with 15% yield of a regioisomer. The acetonide was removed, giving triol 5.5 . This alcohol was monoacetylated, to give acetate 5.6 . The benzyl group was removed and replaced with a triethylsilyl group. Diol 5.7 was selectively activated using methanesulfonyl chloride and 4-(dimethylamino)pyridine to give mesylate 5.8 , in 78% yield.
The acetyl group in 6.1 ( Scheme 6 ) was removed to give primary alcohol 6.2 . The Taxol ring (D) was added by an intramolecular nucleophilic substitution involving this hydroxyl group to give oxetane 6.3 . After acetylation, phenyllithium was used to open the carbonate ester ring to give alcohol 6.5 . Allylic oxidation with pyridinium chlorochromate , sodium acetate , and celite gave ketone 6.6 , which was subsequently reduced using sodium borohydride to give secondary alcohol 6.7 . This was the last compound before the addition of the amide tail.
As shown in Scheme 7 , Ojima lactam 7.1 reacted with alcohol 7.2 with sodium bis(trimethylsilyl)amide as a base. This alcohol is the triethylsilyl ether of the naturally occurring compound baccatin III. The related compound, 10-deacetylbaccatin III, is found in Taxus baccata , also known as the European Yew, in concentrations of 1 gram per kilogram leaves. Removal of the triethylsilyl protecting group gave Taxol.
The ethyl ester of propionic acid ( 1 ) was brominated and then converted to the Wittig reagent using triphenylphosphine . Aldehyde 6 was obtained from allyl alcohol ( 4 ) by protection as the tert-butyldiphenylsilyl ether ( 5 ) followed by ozonolysis . Wittig reagent 3 and aldehyde 6 reacted in a Wittig reaction to give unsaturated ester 7 , which was deprotected to give dienophile 8 (Scheme 1, compound 1).
Aldol condensation of acetone and ethyl acetoacetate gave β-keto-ester 3 . A Grignard reaction involving methylmagnesium bromide provided alcohol 4 , which was subjected to acid catalyzed elimination to give diene 5 . Reduction and acetylation gave diene 7 (Scheme 3, compound 1).
The synthesis makes use of various protecting groups as follows: | https://en.wikipedia.org/wiki/Nicolaou_Taxol_total_synthesis |
Nicolas Bourbaki ( French: [nikola buʁbaki] ) is the collective pseudonym of a group of mathematicians, predominantly French alumni of the École normale supérieure (ENS). Founded in 1934–1935, the Bourbaki group originally intended to prepare a new textbook in analysis . Over time the project became much more ambitious, growing into a large series of textbooks published under the Bourbaki name, meant to treat modern pure mathematics . The series is known collectively as the Éléments de mathématique ( Elements of Mathematics ), the group's central work. Topics treated in the series include set theory , abstract algebra , topology , analysis, Lie groups and Lie algebras .
Bourbaki was founded in response to the effects of the First World War which caused the death of a generation of French mathematicians; as a result, young university instructors were forced to use dated texts. While teaching at the University of Strasbourg , Henri Cartan complained to his colleague André Weil of the inadequacy of available course material, which prompted Weil to propose a meeting with others in Paris to collectively write a modern analysis textbook. The group's core founders were Cartan, Claude Chevalley , Jean Delsarte , Jean Dieudonné and Weil; others participated briefly during the group's early years, and membership has changed gradually over time. Although former members openly discuss their past involvement with the group, Bourbaki has a custom of keeping its current membership secret.
The group's name derives from the 19th century French general Charles-Denis Bourbaki , who had a career of successful military campaigns before suffering a dramatic loss in the Franco-Prussian War . [ 3 ] The name was therefore familiar to early 20th-century French students. Weil remembered an ENS student prank in which an upperclassman posed as a professor and presented a "theorem of Bourbaki"; the name was later adopted.
The Bourbaki group holds regular private conferences for the purpose of drafting and expanding the Éléments . Topics are assigned to subcommittees, drafts are debated, and unanimous agreement is required before a text is deemed fit for publication. Although slow and labor-intensive, the process results in a work which meets the group's standards for rigour and generality. The group is also associated with the Séminaire Bourbaki , a regular series of lectures presented by members and non-members of the group, also published and disseminated as written documents. Bourbaki maintains an office at the ENS. [ 4 ]
Nicolas Bourbaki was influential in 20th-century mathematics, particularly during the middle of the century when volumes of the Éléments appeared frequently. The group is noted among mathematicians for its rigorous presentation and for introducing the notion of a mathematical structure , an idea related to the broader, interdisciplinary concept of structuralism . [ 5 ] [ 6 ] [ 7 ] Bourbaki's work informed the New Math , a trend in elementary math education during the 1960s. Although the group remains active, its influence is considered to have declined due to infrequent publication of new volumes of the Éléments . However, since 2012 the group has published four new (or significantly revised) volumes, the most recent in 2023 (treating spectral theory ). Moreover, at least three further volumes are under preparation.
Charles-Denis Sauter Bourbaki was a successful general during the era of Napoleon III , serving in the Crimean War and other conflicts. During the Franco-Prussian war however, Charles-Denis Bourbaki suffered a major defeat in which the Armée de l'Est , under his command, retreated across the Swiss border and was disarmed. The general unsuccessfully attempted suicide. The dramatic story of his defeat was known in the French popular consciousness following his death. [ 8 ] [ 9 ]
In the early 20th century, the First World War affected Europeans of all professions and social classes, including mathematicians and male students who fought and died in the front. For example, the French mathematician Gaston Julia , a pioneer in the study of fractals , lost his nose during the war and wore a leather strap over the affected part of his face for the rest of his life. The deaths of ENS students resulted in a lost generation in the French mathematical community; [ 10 ] the estimated proportion of ENS mathematics students (and French students generally) who died in the war ranges from one-quarter to one-half, depending on the intervals of time (c. 1900–1918, especially 1910–1916) and populations considered. [ 11 ] [ 12 ] Furthermore, Bourbaki founder André Weil remarked in his memoir Apprenticeship of a Mathematician that France and Germany took different approaches with their intelligentsia during the war: while Germany protected its young students and scientists, France instead committed them to the front, owing to the French culture of egalitarianism . [ 12 ]
A succeeding generation of mathematics students attended the ENS during the 1920s, including Weil and others, the future founders of Bourbaki. During his time as a student, Weil recalled a prank in which an upperclassman, Raoul Husson [ fr ] , posed as a professor and gave a math lecture, ending with a prompt: "Theorem of Bourbaki: you are to prove the following...". Weil was also aware of a similar stunt around 1910 [ 3 ] in which a student claimed to be from the fictional, impoverished nation of "Poldevia" and solicited the public for donations. [ 13 ] [ 14 ] Weil had strong interests in languages and Indian culture , having learned Sanskrit and read the Bhagavad Gita . [ 15 ] [ 16 ] After graduating from the ENS and obtaining his doctorate, Weil took a teaching stint at the Aligarh Muslim University in India. While there, Weil met the mathematician Damodar Kosambi , who was engaged in a power struggle with one of his colleagues. Weil suggested that Kosambi write an article with material attributed to one "Bourbaki", in order to show off his knowledge to the colleague. [ 17 ] Kosambi took the suggestion, attributing the material discussed in the article to "the little-known Russian mathematician D. Bourbaki , who was poisoned during the Revolution." It was the first article in the mathematical literature with material attributed to the eponymous "Bourbaki". [ 18 ] [ 19 ] [ 20 ] Weil's stay in India was short-lived; he attempted to revamp the mathematics department at Aligarh, without success. [ 21 ] The university administration planned to fire Weil and promote his colleague Vijayaraghavan to the vacated position. However, Weil and Vijayaraghavan respected one another. Rather than play any role in the drama, Vijayaraghavan instead resigned, later informing Weil of the plan. [ 22 ] Weil returned to Europe to seek another teaching position. He ended up at the University of Strasbourg, joining his friend and colleague Henri Cartan. [ 23 ]
During their time together at Strasbourg, Weil and Cartan regularly complained to each other regarding the inadequacy of available course material for calculus instruction. In his memoir Apprenticeship , Weil described his solution in the following terms: "One winter day toward the end of 1934, I came upon a great idea that would put an end to these ceaseless interrogations by my comrade. 'We are five or six friends', I told him some time later, 'who are in charge of the same mathematics curriculum at various universities. Let us all come together and regulate these matters once and for all, and after this, I shall be delivered of these questions.' I was unaware of the fact that Bourbaki was born at that instant." [ 23 ] Cartan confirmed the account. [ 24 ]
The first, unofficial meeting of the Bourbaki collective took place at noon on Monday, 10 December 1934, at the Café Grill-Room A. Capoulade, Paris, in the Latin Quarter . [ 25 ] [ 26 ] [ 27 ] [ 28 ] [ b ] Six mathematicians were present: Henri Cartan , Claude Chevalley , Jean Delsarte , Jean Dieudonné , René de Possel , and André Weil . Most of the group were based outside Paris and were in town to attend the Julia Seminar, a conference prepared with the help of Gaston Julia at which several future Bourbaki members and associates presented. [ 30 ] [ 31 ] [ c ] The group resolved to collectively write a treatise on analysis, for the purpose of standardizing calculus instruction in French universities. The project was especially meant to supersede the text of Édouard Goursat , which the group found to be badly outdated, and to improve its treatment of Stokes' Theorem . [ 27 ] [ 35 ] [ 36 ] [ 37 ] The founders were also motivated by a desire to incorporate ideas from the Göttingen school, particularly from exponents Hilbert , Noether and B.L. van der Waerden . Further, in the aftermath of World War I, there was a certain nationalist impulse to save French mathematics from decline, especially in competition with Germany. As Dieudonné stated in an interview, "Without meaning to boast, I can say that it was Bourbaki that saved French mathematics from extinction." [ 38 ]
Jean Delsarte was particularly favorable to the collective aspect of the proposed project, observing that such a working style could insulate the group's work against potential later individual claims of copyright . [ 35 ] [ 39 ] [ d ] As various topics were discussed, Delsarte also suggested that the work begin in the most abstract, axiomatic terms possible, treating all of mathematics prerequisite to analysis from scratch. [ 41 ] [ 42 ] The group agreed to the idea, and this foundational area of the proposed work was referred to as the "Abstract Packet" (Paquet Abstrait). [ 43 ] [ 44 ] [ 45 ] Working titles were adopted: the group styled itself as the Committee for the Treatise on Analysis , and their proposed work was called the Treatise on Analysis ( Traité d'analyse ). [ 46 ] [ 47 ] In all, the collective held ten preliminary biweekly meetings at A. Capoulade before its first official, founding conference in July 1935. [ 47 ] [ 48 ] During this early period, Paul Dubreil , Jean Leray and Szolem Mandelbrojt joined and participated. Dubreil and Leray left the meetings before the following summer, and were respectively replaced by new participants Jean Coulomb and Charles Ehresmann . [ 46 ] [ 49 ]
The group's official founding conference was held in Besse-en-Chandesse , from 10 to 17 July 1935. [ 50 ] [ 51 ] At the time of the official founding, the membership consisted of the six attendees at the first lunch of 10 December 1934, together with Coulomb, Ehresmann and Mandelbrojt. On 16 July, the members took a walk to alleviate the boredom of unproductive proceedings. During the malaise, some decided to skinny-dip in the nearby Lac Pavin , repeatedly yelling "Bourbaki!" [ 52 ] At the close of the first official conference, the group renamed itself "Bourbaki", in reference to the general and prank as recalled by Weil and others. [ 45 ] [ e ] During 1935, the group also resolved to establish the mathematical personhood of their collective pseudonym by getting an article published under its name. [ 50 ] [ 54 ] A first name had to be decided; a full name was required for publication of any article. To this end, René de Possel's wife Eveline "baptized" the pseudonym with the first name of Nicolas, becoming Bourbaki's "godmother". [ 50 ] [ 55 ] [ 56 ] [ 57 ] This allowed for the publication of a second article with material attributed to Bourbaki, this time under "his" own name. [ 58 ] Henri Cartan's father Élie Cartan , also a mathematician and supportive of the group, presented the article to the publishers, who accepted it. [ 54 ]
At the time of Bourbaki's founding, René de Possel and his wife Eveline were in the process of divorcing. Eveline remarried to André Weil in 1937, and de Possel left the Bourbaki collective some time later. This sequence of events has caused speculation that de Possel left the group because of the remarriage, [ 59 ] however this suggestion has also been criticized as possibly historically inaccurate, since de Possel is supposed to have remained active in Bourbaki for years after André's marriage to Eveline. [ 60 ]
Bourbaki's work slowed significantly during the Second World War , though the group survived and later flourished. Some members of Bourbaki were Jewish and therefore forced to flee from certain parts of Europe at certain times. Weil, who was Jewish, spent the summer of 1939 in Finland with his wife Eveline, as guests of Lars Ahlfors . Due to their travel near the border, the couple were suspected as Soviet spies by Finnish authorities near the onset of the Winter War , and André was later arrested. [ 61 ] According to an anecdote, Weil was to have been executed but for the passing mention of his case to Rolf Nevanlinna , who asked that Weil's sentence be commuted. [ 62 ] However, the accuracy of this detail is dubious. [ 63 ] Weil reached the United States in 1941, later taking another teaching stint in São Paulo from 1945 to 1947 before settling at the University of Chicago from 1947 to 1958 and finally the Institute for Advanced Study in Princeton , where he spent the remainder of his career. Although Weil remained in touch with the Bourbaki collective and visited Europe and the group periodically following the war, his level of involvement with Bourbaki never returned to that at the time of founding.
Second-generation Bourbaki member Laurent Schwartz was also Jewish and found pickup work as a math teacher in rural Vichy France . Moving from village to village, Schwartz planned his movements in order to evade capture by the Nazis . [ 64 ] On one occasion Schwartz found himself trapped overnight in a certain village, as his expected transportation home was unavailable. There were two inns in town: a comfortable, well-appointed one, and a very poor one with no heating and bad beds. Schwartz's instinct told him to stay at the poor inn; overnight, the Nazis raided the good inn, leaving the poor inn unchecked. [ 65 ]
Meanwhile, Jean Delsarte, a Catholic, was mobilized in 1939 as the captain of an audio reconnaissance battery. He was forced to lead the unit's retreat from the northeastern part of France toward the south. While passing near the Swiss border, Delsarte overheard a soldier say "We are the army of Bourbaki"; [ 66 ] [ 67 ] the 19th-century general's retreat was known to the French. Delsarte had coincidentally led a retreat similar to that of the collective's namesake.
Following the war, Bourbaki had solidified the plan of its work and settled into a productive routine. Bourbaki regularly published volumes of the Éléments during the 1950s and 1960s, and enjoyed its greatest influence during this period. [ 68 ] [ 69 ] Over time the founding members gradually left the group, slowly being replaced with younger newcomers including Jean-Pierre Serre and Alexander Grothendieck . Serre, Grothendieck and Laurent Schwartz were awarded the Fields Medal during the postwar period, in 1954, 1966 and 1950 respectively. Later members Alain Connes and Jean-Christophe Yoccoz also received the Fields Medal, in 1982 and 1994 respectively. [ 70 ]
The later practice of accepting scientific awards contrasted with some of the founders' views. [ 71 ] During the 1930s, Weil and Delsarte petitioned against a French national scientific "medal system" proposed by the Nobel physics laureate Jean Perrin . Weil and Delsarte felt that the institution of such a system would increase unconstructive pettiness and jealousy in the scientific community. [ 72 ] Despite this, the Bourbaki group had previously successfully petitioned Perrin for a government grant to support its normal operations. [ 73 ] Like the founders, Grothendieck was also averse to awards, albeit for pacifist reasons. Although Grothendieck was awarded the Fields Medal in 1966, he declined to attend the ceremony in Moscow, in protest of the Soviet government. [ 74 ] In 1988, Grothendieck rejected the Crafoord Prize outright, citing no personal need to accept prize money, lack of recent relevant output, and general distrust of the scientific community. [ 75 ]
Born to Jewish anarchist parentage, Grothendieck survived the Holocaust and advanced rapidly in the French mathematical community, despite poor education during the war. [ 76 ] Grothendieck's teachers included Bourbaki's founders, and so he joined the group. During Grothendieck's membership, Bourbaki reached an impasse concerning its foundational approach. Grothendieck advocated for a reformulation of the group's work using category theory as its theoretical basis, as opposed to set theory. The proposal was ultimately rejected [ 77 ] [ 78 ] [ 79 ] in part because the group had already committed itself to a rigid track of sequential presentation, with multiple already-published volumes. Following this, Grothendieck left Bourbaki "in anger". [ 37 ] [ 64 ] [ 80 ] Biographers of the collective have described Bourbaki's unwillingness to start over in terms of category theory as a missed opportunity. [ 64 ] [ 81 ] [ 82 ] However, Bourbaki has in 2023 announced that a book on category theory is currently under preparation (see below the last paragraph of this section).
During the founding period, the group chose the Parisian publisher Hermann to issue installments of the Éléments . Hermann was led by Enrique Freymann, a friend of the founders willing to publish the group's project, despite financial risk. During the 1970s, Bourbaki entered a protracted legal battle with Hermann over matters of copyright and royalty payment . Although the Bourbaki group won the suit and retained collective copyright of the Éléments , the dispute slowed the group's productivity. [ 83 ] [ 84 ] Former member Pierre Cartier described the lawsuit as a pyrrhic victory , saying: "As usual in legal battles, both parties lost and the lawyer got rich." [ 64 ] Later editions of the Éléments were published by Masson , and modern editions are published by Springer . [ 85 ] From the 1980s through the 2000s, Bourbaki published very infrequently, with the result that in 1998 Le Monde pronounced the collective "dead". [ 86 ]
However, in 2012 Bourbaki resumed the publication of the Éléments with a revised chapter 8 of algebra, the first 4 chapters of a new book on algebraic topology , and two volumes on spectral theory (the first of which is an expanded and revised version of the edition of 1967 while the latter consist of three new chapters). Moreover, the text of the two latest volumes announces that books on category theory and modular forms are currently under preparation (in addition to the latter part of the book on algebraic topology). [ 87 ] [ 88 ]
Bourbaki holds periodic conferences for the purpose of expanding the Éléments ; these conferences are the central activity of the group's working life. Subcommittees are assigned to write drafts on specific material, and the drafts are later presented, vigorously debated, and re-drafted at the conferences. Unanimous agreement is required before any material is deemed acceptable for publication. [ 90 ] [ 91 ] [ 92 ] A given piece of material may require six or more drafts over a period of several years, and some drafts are never developed into completed work. [ 91 ] [ 93 ] Bourbaki's writing process has therefore been described as " Sisyphean ". [ 92 ] Although the method is slow, it yields a final product which satisfies the group's standards for mathematical rigour , one of Bourbaki's main priorities in the treatise. Bourbaki's emphasis on rigour was a reaction to the style of Henri Poincaré , who stressed the importance of free-flowing mathematical intuition at the cost of thorough presentation. [ f ] During the project's early years, Dieudonné served as the group's scribe, authoring several final drafts which were ultimately published. For this purpose, Dieudonné adopted an impersonal writing style which was not his own, but which was used to craft material acceptable to the entire group. [ 94 ] [ 95 ] Dieudonné reserved his personal style for his own work; like all members of Bourbaki, Dieudonné also published material under his own name, [ 96 ] including the nine-volume Éléments d'analyse , a work explicitly focused on analysis and of a piece with Bourbaki's initial intentions.
Most of the final drafts of Bourbaki's Éléments carefully avoided using illustrations, favoring a formal presentation based only in text and formulas. An exception to this was the treatment of Lie groups and Lie algebras (especially in chapters 4–6), which did make use of diagrams and illustrations. The inclusion of illustration in this part of the work was due to Armand Borel . Borel was minority-Swiss in a majority-French collective, and self-deprecated as "the Swiss peasant", explaining that visual learning was important to the Swiss national character. [ 64 ] [ 97 ] When asked about the dearth of illustration in the work, former member Pierre Cartier replied:
The Bourbaki were Puritans , and Puritans are strongly opposed to pictorial representations of truths of their faith. The number of Protestants and Jews in the Bourbaki group was overwhelming. And you know that the French Protestants especially are very close to Jews in spirit.
The conferences have historically been held at quiet rural areas. [ 98 ] These locations contrast with the lively, sometimes heated debates which have occurred. Laurent Schwartz reported an episode in which Weil slapped Cartan on the head with a draft. The hotel's proprietor saw the incident and assumed that the group would split up, but according to Schwartz, "peace was restored within ten minutes." [ 99 ] The historical, confrontational style of debate within Bourbaki has been partly attributed to Weil, who believed that new ideas have a better chance of being born in confrontation than in an orderly discussion. [ 91 ] [ 99 ] Schwartz related another illustrative incident: Dieudonné was adamant that topological vector spaces must appear in the work before integration , and whenever anyone suggested that the order be reversed, he would loudly threaten his resignation. This became an in-joke among the group; Roger Godement's wife Sonia attended a conference, aware of the idea, and asked for proof. As Sonia arrived at a meeting, a member suggested that integration must appear before topological vector spaces, which triggered Dieudonné's usual reaction. [ 99 ]
Despite the historical culture of heated argument, Bourbaki thrived during the middle of the twentieth century. Bourbaki's ability to sustain such a collective, critical approach has been described as "something unusual", [ 100 ] surprising even its own members. In founder Henri Cartan's words, "That a final product can be obtained at all is a kind of miracle that none of us can explain." [ 101 ] [ 102 ] It has been suggested that the group survived because its members believed strongly in the importance of their collective project, despite personal differences. [ 91 ] [ 103 ] When the group overcame difficulties or developed an idea that they liked, they would sometimes say l'esprit a soufflé ("the spirit breathes"). [ 91 ] [ 104 ] Historian Liliane Beaulieu noted that the "spirit"—which might be an avatar , the group mentality in action, or Bourbaki "himself"—was part of an internal culture and mythology which the group used to form its identity and perform work. [ 105 ]
Humor has been an important aspect of the group's culture, beginning with Weil's memories of the student pranks involving "Bourbaki" and "Poldevia". For example, in 1939 the group released a wedding announcement for the marriage of "Betti Bourbaki" (daughter of Nicolas) to one " H. Pétard " (H. "Firecrackers" or "Hector Pétard"), a "lion hunter". [ 106 ] Hector Pétard was itself a pseudonym, but not one originally coined by the Bourbaki members. The Pétard moniker was originated by Ralph P. Boas , Frank Smithies and other Princeton mathematicians who were aware of the Bourbaki project; inspired by them, the Princeton mathematicians published an article on the "mathematics of lion hunting". After meeting Boas and Smithies, Weil composed the wedding announcement, which contained several mathematical puns. [ 107 ] Bourbaki's internal newsletter La Tribu has sometimes been issued with humorous subtitles to describe a given conference, such as "The Extraordinary Congress of Old Fogies" (where anyone older than 30 was considered a fogy) or "The Congress of the Motorization of the Trotting Ass" (an expression used to describe the routine unfolding of a mathematical proof, or process). [ 108 ] [ 109 ]
During the 1940s–1950s, [ 110 ] [ 111 ] the American Mathematical Society received applications for individual membership from Bourbaki. They were rebuffed by J.R. Kline who understood the entity to be a collective, inviting them to re-apply for institutional membership. In response, Bourbaki floated a rumor that Ralph Boas was not a real person, but a collective pseudonym of the editors of Mathematical Reviews with which Boas had been affiliated. The reason for targeting Boas was because he had known the group in its earlier days when they were less strict with secrecy, and he'd described them as a collective in an article for the Encyclopædia Britannica . [ 112 ] In November 1968, a mock obituary of Nicolas Bourbaki was released during one of the seminars. [ 113 ] [ 114 ]
The group developed some variants of the word "Bourbaki" for internal use. The noun "Bourbaki" might refer to the group proper or to an individual member, e.g. "André Weil was a Bourbaki." "Bourbakist" is sometimes used to refer to members [ 37 ] but also denotes associates, supporters, and enthusiasts. [ 115 ] [ 116 ] To "bourbakize" meant to take a poor existing text and to improve it through an editing process. [ 93 ]
Bourbaki's culture of humor has been described as an important factor in the group's social cohesion and capacity to survive, smoothing over tensions of heated debate. [ 117 ] As of 2025, a Twitter account registered to "Betty_Bourbaki" provides regular updates on the group's activity. [ 118 ]
Bourbaki's work includes a series of textbooks, a series of printed lecture notes, journal articles, and an internal newsletter. The textbook series Éléments de mathématique (Elements of mathematics) is the group's central work. The Séminaire Bourbaki is a lecture series held regularly under the group's auspices, and the talks given are also published as lecture notes. Journal articles have been published with authorship attributed to Bourbaki, and the group publishes an internal newsletter La Tribu ( The Tribe ) which is distributed to current and former members. [ 119 ] [ 120 ]
Like those before him, Bourbaki insisted on setting mathematics in a “formalized language” with crystal-clear deductions based on strict formal rules. When Bertrand Russell and Alfred North Whitehead applied this approach at the turn of the twentieth century, they famously filled over 700 pages with formal symbols before establishing the proposition usually abbreviated as 1+1=2 . Bourbaki's formalism would dwarf even this, requiring some 4.5 trillion symbols just to define the number 1 . [ 121 ]
The content of the Éléments is divided into books —major topics of discussion, volumes —individual, physical books, and chapters , together with certain summaries of results, historical notes, and other details. The volumes of the Éléments have had a complex publication history. Material has been revised for new editions, published chronologically out of order of its intended logical sequence, grouped together and partitioned differently in later volumes, and translated into English. For example, the second book on Algebra was originally released in eight French volumes: the first in 1942 being chapter 1 alone, and the last in 1980 being chapter 10 alone. This presentation was later condensed into five volumes with chapters 1–3 in the first volume, chapters 4–7 in the second, and chapters 8–10 each remaining the third through fifth volumes of that portion of the work. [ 119 ] The English edition of Bourbaki's Algebra consists of translations of the three volumes consisting of chapters 1–3, 4–7 and 8, with chapters 9 and 10 unavailable in English as of 2025.
When Bourbaki's founders began working on the Éléments , they originally conceived of it as a "treatise on analysis", the proposed work having a working title of the same name ( Traité d'analyse ). The opening part was to comprehensively deal with the foundations of mathematics prior to analysis, and was referred to as the "Abstract Packet". Over time, the members developed this proposed "opening section" of the work to the point that it would instead run for several volumes and comprise a major part of the work, covering set theory, abstract algebra, and topology. Once the project's scope expanded far beyond its original purpose, the working title Traité d'analyse was dropped in favor of Éléments de mathématique . [ 45 ] The unusual, singular "Mathematic" was meant to connote Bourbaki's belief in the unity of mathematics. [ 123 ] [ 124 ] [ 125 ] The first six books of the Éléments , representing the first half of the work, are numbered sequentially and ordered logically, with a given statement being established only on the basis of earlier results. [ 126 ] This first half of the work bore the subtitle Les structures fondamentales de l’analyse ( Fundamental Structures of Analysis ), [ 119 ] [ 127 ] [ 128 ] covering established mathematics (algebra, analysis) in the group's style. The second half of the work consists of unnumbered books treating modern areas of research (Lie groups, commutative algebra), each presupposing the first half as a shared foundation but without dependence on each other. This second half of the work, consisting of newer research topics, does not have a corresponding subtitle.
The volumes of the Éléments published by Hermann were indexed by chronology of publication and referred to as fascicules : installments in a large work. Some volumes did not consist of the normal definitions, proofs, and exercises in a math textbook, but contained only summaries of results for a given topic, stated without proof. These volumes were referred to as Fascicules de résultats , with the result that fascicule may refer to a volume of Hermann's edition, or to one of the "summary" sections of the work (e.g. Fascicules de résultats is translated as "Summary of Results" rather than "Installment of Results", referring to the content rather than a specific volume). [ g ] The first volume of Bourbaki's Éléments to be published was the Summary of Results in the Theory of Sets , in 1939. [ 64 ] [ 119 ] [ 131 ] Similarly one of the work's later books, Differential and Analytic Manifolds , consisted only of two volumes of summaries of results, with no chapters of content having been published.
Later installments of the Éléments appeared infrequently during the 1980s and 1990s. A volume of Commutative Algebra (chapters 8–9) was published in 1983, and no other volumes were issued until the appearance of the same book's tenth chapter in 1998. During the 2010s, Bourbaki increased its productivity. A re-written and expanded version of the eighth chapter of Algebra appeared in 2012, the first four chapters of a new book treating Algebraic Topology was published in 2016, and the first two chapters of a revised and expanded edition of Spectral Theory was issued in 2019 while the remaining three (completely new) chapters appeared in 2023.
The Séminaire Bourbaki has been held regularly since 1948, and lectures are presented by non-members and members of the collective. As of 2025 the Séminaire Bourbaki has run to over a thousand recorded lectures in its written incarnation, denoted chronologically by simple numbers. [ 140 ] At the time of a June 1999 lecture given by Jean-Pierre Serre on the topic of Lie groups, the total lectures given in the series numbered 864, corresponding to roughly 10,000 pages of printed material. [ 141 ]
Several journal articles have appeared in the mathematical literature with material or authorship attributed to Bourbaki; unlike the Éléments , they were typically written by individual members [ 119 ] and not crafted through the usual process of group consensus. Despite this, Jean Dieudonné's essay "The Architecture of Mathematics" has become known as Bourbaki's manifesto . [ 142 ] [ 143 ] Dieudonné addressed the issue of overspecialization in mathematics, to which he opposed the inherent unity of mathematic (as opposed to mathematics) and proposed mathematical structures as useful tools which can be applied to several subjects, showing their common features. [ 144 ] To illustrate the idea, Dieudonné described three different systems in arithmetic and geometry and showed that all could be described as examples of a group , a specific kind of ( algebraic ) structure. [ 145 ] Dieudonné described the axiomatic method as "the ' Taylor system ' for mathematics" in the sense that it could be used to solve problems efficiently. [ 146 ] [ i ] Such a procedure would entail identifying relevant structures and applying established knowledge about the given structure to the specific problem at hand. [ 146 ]
La Tribu is Bourbaki's internal newsletter, distributed to current and former members. The newsletter usually documents recent conferences and activity in a humorous, informal way, sometimes including poetry. [ 147 ] Member Pierre Samuel wrote the newsletter's narrative sections for several years. [ 148 ] Early editions of La Tribu and related documents have been made publicly available by Bourbaki. [ 33 ]
Historian Liliane Beaulieu examined La Tribu and Bourbaki's other writings, describing the group's humor and private language as an "art of memory" which is specific to the group and its chosen methods of operation. [ 149 ] Because of the group's secrecy and informal organization, individual memories are sometimes recorded in a fragmentary way, and may not have significance to other members. [ 150 ] On the other hand, the predominantly French, ENS background of the members, together with stories of the group's early period and successes, create a shared culture and mythology which is drawn upon for group identity. La Tribu usually lists the members present at a conference, together with any visitors, family members or other friends in attendance. Humorous descriptions of location or local "props" (cars, bicycles, binoculars, etc.) can also serve as mnemonic devices. [ 108 ]
As of 2000, Bourbaki has had "about forty" members. [ 151 ] Historically the group has numbered about ten [ 152 ] to twelve [ 64 ] members at any given point, although it was briefly (and officially) limited to nine members at the time of founding. [ 47 ] Bourbaki's membership has been described in terms of generations:
Bourbaki was always a very small group of mathematicians, typically numbering about twelve people. Its first generation was that of the founding fathers, those who created the group in 1934: Weil, Cartan, Chevalley, Delsarte, de Possel, and Dieudonné. Others joined the group, and others left its ranks, so that some years later there were about twelve members, and that number remained roughly constant. Laurent Schwartz was the only mathematician to join Bourbaki during the war, so his is considered an intermediate generation. After the war, a number of members joined: Jean-Pierre Serre , Pierre Samuel , Jean-Louis Koszul , Jacques Dixmier , Roger Godement , and Sammy Eilenberg . These people constituted the second generation of Bourbaki. In the 1950s, the third generation of mathematicians joined Bourbaki. These people included Alexandre Grothendieck , François Bruhat , Serge Lang , the American mathematician John Tate , Pierre Cartier , and the Swiss mathematician Armand Borel . [ 64 ] [ 153 ]
After the first three generations there were roughly twenty later members, not including current participants. Bourbaki has a custom of keeping its current membership secret, a practice meant to ensure that its output is presented as a collective, unified effort under the Bourbaki pseudonym, not attributable to any one author (e.g. for purposes of copyright or royalty payment). This secrecy is also intended to deter unwanted attention which could disrupt normal operations. However, former members freely discuss Bourbaki's internal practices upon departure. [ 64 ] [ 154 ]
Prospective members are invited to conferences and styled as guinea pigs , a process meant to vet the newcomer's mathematical ability. [ 64 ] [ 155 ] In the event of agreement between the group and the prospect, the prospect eventually becomes a full member. [ j ] The group is supposed to have an age limit: active members are expected to retire at (or about) 50 years of age. [ 64 ] [ 92 ] At a 1956 conference, Cartan read a letter from Weil which proposed a "gradual disappearance" of the founding members, forcing younger members to assume full responsibility for Bourbaki's operations. [ 37 ] [ 160 ] This rule is supposed to have resulted in a complete change of personnel by 1958. [ 55 ] However, historian Liliane Beaulieu has been critical of the claim. She reported never having found written affirmation of the rule, [ 161 ] and has indicated that there have been exceptions. [ 162 ] The age limit is thought to express the founders' intent that the project should continue indefinitely, operated by people at their best mathematical ability—in the mathematical community, there is a widespread belief that mathematicians produce their best work while young. [ 160 ] [ 163 ] Among full members there is no official hierarchy; all operate as equals, having the ability to interrupt conference proceedings at any point, or to challenge any material presented. However, André Weil has been described as "first among equals" during the founding period, and was given some deference. [ 164 ] On the other hand, the group has also poked fun at the idea that older members should be afforded greater respect. [ 165 ]
Bourbaki conferences have also been attended by members' family, friends, visiting mathematicians, and other non-members of the group. [ k ] Bourbaki is not known ever to have had any female members. [ 92 ] [ 152 ]
Bourbaki was influential in 20th century mathematics and had some interdisciplinary impact on the humanities and the arts, although the extent of the latter influence is a matter of dispute. The group has been praised and criticized for its method of presentation, its working style, and its choice of mathematical topics.
Bourbaki introduced several mathematical notations which have remained in use. Weil took the letter Ø of the Norwegian alphabet and used it to denote the empty set , ∅ . [ 175 ] This notation first appeared in the Summary of Results on the Theory of Sets , [ 176 ] and remains in use. The words injective , surjective and bijective were introduced to refer to functions which satisfy certain properties. [ 177 ] [ 178 ] Bourbaki used simple language for certain geometric objects, naming them pavés ( paving stones ) and boules ( balls ) as opposed to " parallelotopes " or " hyperspheroids ". [ 179 ] Similarly in its treatment of topological vector spaces, Bourbaki defined a barrel as a set which is convex , balanced , absorbing , and closed . [ 180 ] The group were proud of this definition, believing that the shape of a wine barrel typified the mathematical object's properties. [ 181 ] [ 182 ] Bourbaki also employed a " dangerous bend " symbol ☡ in the margins of its text to indicate an especially difficult piece of material. Bourbaki enjoyed its greatest influence during the 1950s and 1960s, when installments of the Éléments were published frequently.
Bourbaki had some interdisciplinary influence on other fields, including anthropology and psychology . This influence was in the context of structuralism , a school of thought in the humanities which stresses the relationships between objects over the objects themselves, pursued in various fields by other French intellectuals. In 1943, André Weil met the anthropologist Claude Lévi-Strauss in New York, where the two undertook a brief collaboration. At Lévi-Strauss' request, Weil wrote a brief appendix describing marriage rules for four classes of people within Aboriginal Australian society, using a mathematical model based on group theory . [ 5 ] [ 183 ] The result was published as an appendix in Lévi-Strauss' Elementary Structures of Kinship , a work examining family structures and the incest taboo in human cultures. [ 184 ] In 1952, Jean Dieudonné and Jean Piaget participated in an interdisciplinary conference on mathematical and mental structures. Dieudonné described mathematical "mother structures" in terms of Bourbaki's project: composition, neighborhood, and order. [ 185 ] Piaget then gave a talk on children's mental processes, and considered that the psychological concepts he had just described were very similar to the mathematical ones just described by Dieudonné. [ 186 ] [ 187 ] According to Piaget, the two were "impressed with each other". [ 188 ] The psychoanalyst Jacques Lacan liked Bourbaki's collaborative working style and proposed a similar collective group in psychology, an idea which did not materialize. [ 189 ]
Bourbaki was also cited by post-structuralist philosophers. In their joint work Anti-Oedipus , Gilles Deleuze and Félix Guattari presented a criticism of capitalism . The authors cited Bourbaki's use of the axiomatic method (with the purpose of establishing truth) as a distinct counter-example to management processes which instead seek economic efficiency . The authors said of Bourbaki's axiomatics that "they do not form a Taylor system", inverting the phrase used by Dieudonné in "The Architecture of Mathematics". [ 146 ] [ 190 ] In The Postmodern Condition , Jean-François Lyotard criticized the "legitimation of knowledge", the process by which statements become accepted as valid. As an example, Lyotard cited Bourbaki as a group which produces knowledge within a given system of rules. [ 191 ] [ 192 ] Lyotard contrasted Bourbaki's hierarchical, "structuralist" mathematics with the catastrophe theory of René Thom and the fractals of Benoit Mandelbrot , [ s ] expressing preference for the latter "postmodern science" which problematized mathematics with "fracta, catastrophes, and pragmatic paradoxes". [ 191 ] [ 192 ]
Although biographer Amir Aczel stressed Bourbaki's influence on other disciplines during the mid-20th century, Maurice Mashaal moderated the claims of Bourbaki's influence in the following terms:
While Bourbaki's structures were often mentioned in social science conferences and publications of the era, it seems that they didn't play a real role in the development of these disciplines. David Aubin, a science historian who analyzed Bourbaki's role in the structuralist movement in France, believes Bourbaki's role was that of a "cultural connector". [ 194 ] According to Aubin, while Bourbaki didn't have any mission outside of mathematics, the group represented a sort of link between the various cultural movements of the time. Bourbaki provided a simple and relatively precise definition of concepts and structures, which philosophers and social scientists believed was fundamental within their disciplines and in bridges among different areas of knowledge. Despite the superficial nature of these links, the various schools of structuralist thinking, including Bourbaki, were able to support each other. So, it is not a coincidence that these schools suffered a simultaneous decline in the late 1960s.
The impact of "structuralism" on mathematics itself was also criticized. The mathematical historian Leo Corry argued that Bourbaki's use of mathematical structures was unimportant within the Éléments , having been established in Theory of Sets and cited infrequently afterwards. [ 199 ] [ 200 ] [ 201 ] [ 202 ] Corry described the "structural" view of mathematics promoted by Bourbaki as an "image of knowledge"—a conception about a scientific discipline—as opposed to an item in the discipline's "body of knowledge", which refers to the actual scientific results in the discipline itself. [ 200 ]
Bourbaki also had some influence in the arts. The literary collective Oulipo was founded on 24 November 1960 under circumstances similar to Bourbaki's founding, with the members initially meeting in a restaurant. Although several members of Oulipo were mathematicians, the group's purpose was to create experimental literature by playing with language. Oulipo frequently employed mathematically-based constrained writing techniques, such as the S+7 method . Oulipo member Raymond Queneau attended a Bourbaki conference in 1962. [ 187 ] [ 203 ]
In 2016, an anonymous group of economists collaboratively wrote a note alleging academic misconduct by the authors and editor of a paper published in the American Economic Review . [ 204 ] [ 205 ] The note was published under the name Nicolas Bearbaki in homage to Nicolas Bourbaki. [ 206 ]
In 2018, the American musical duo Twenty One Pilots released a concept album named Trench . The album's conceptual framework was the mythical city of "Dema" ruled by nine "bishops"; one of the bishops was named "Nico", short for Nicolas Bourbaki. Another of the bishops was named Andre, which may refer to André Weil. Following the album's release, there was a spike in internet searches for "Nicolas Bourbaki". [ 37 ] [ v ]
Bourbaki's work has been praised by some mathematicians. In a book review, Emil Artin described the Éléments in broad, positive terms:
Our time is witnessing the creation of a monumental work: an exposition of the whole of present day mathematics. Moreover this exposition is done in such a way that the common bond between the various branches of mathematics become clearly visible, that the framework which supports the whole structure is not apt to become obsolete in a very short time, and that it can easily absorb new ideas.
Among the volumes of the Éléments , Bourbaki's work on Lie Groups and Lie Algebras has been identified as "excellent", [ 195 ] having become a standard reference on the topic. In particular, former member Armand Borel described the volume with chapters 4–6 as "one of the most successful books by Bourbaki". [ 208 ] The success of this part of the work has been attributed to the fact that the books were composed while leading experts on the topic were Bourbaki members. [ 64 ] [ 209 ]
Jean-Pierre Bourguignon expressed appreciation for the Séminaire Bourbaki, saying that he'd learned a large amount of material at its lectures, and referred to its printed lecture notes regularly. [ 210 ] He also praised the Éléments for containing "some superb and very clever proofs". [ 211 ]
Bourbaki has also been criticized by several mathematicians—including its own former members—for a variety of reasons. Criticisms have included the choice of presentation of certain topics within the Éléments at the expense of others, [ w ] dislike of the method of presentation for given topics, dislike of the group's working style, and a perceived elitist mentality around Bourbaki's project and its books, especially during the collective's most productive years in the 1950s and 1960s.
Bourbaki's deliberations on the Éléments resulted in the inclusion of some topics, while others were not treated. When asked in a 1997 interview about topics left out of the Éléments , former member Pierre Cartier replied:
There is essentially no analysis beyond the foundations: nothing about partial differential equations , nothing about probability . There is also nothing about combinatorics , nothing about algebraic topology , [ x ] nothing about concrete geometry . And Bourbaki never seriously considered logic . Dieudonné himself was very vocal against logic. Anything connected with mathematical physics is totally absent from Bourbaki's text.
Although Bourbaki had resolved to treat mathematics from its foundations, the group's eventual solution in terms of set theory was attended by several problems. Bourbaki's members were mathematicians as opposed to logicians , and therefore the collective had a limited interest in mathematical logic . [ 93 ] As Bourbaki's members themselves said of the book on set theory, it was written "with pain and without pleasure, but we had to do it." [ 214 ] Dieudonné personally remarked elsewhere that ninety-five percent of mathematicians "don't care a fig" for mathematical logic. [ 215 ] In response, logician Adrian Mathias harshly criticized Bourbaki's foundational framework, noting that it did not take Gödel 's results into account. [ 216 ] [ 217 ]
Bourbaki also influenced the New Math, a failed [ 218 ] reform in Western mathematics education at the elementary and secondary levels, which stressed abstraction over concrete examples. During the mid-20th century, reform in basic math education was spurred by a perceived need to create a mathematically literate workforce for the modern economy, and also to compete with the Soviet Union . In France, this led to the Lichnerowicz Commission of 1967, headed by André Lichnerowicz and including some (then-current and former) Bourbaki members. Although Bourbaki members had previously (and individually) reformed math instruction at the university level, they had less direct involvement with implementation of the New Math at the primary and secondary levels. New Math reforms resulted in instructional material which was incomprehensible to both students and teachers, failing to meet the cognitive needs of younger students. The attempted reform was harshly criticized by Dieudonné and also by brief founding Bourbaki participant Jean Leray. [ 219 ] Apart from French mathematicians, the French reforms also met with harsh criticism from Soviet-born mathematician Vladimir Arnold , who argued that in his time as a student and teacher in Moscow, the teaching of mathematics was firmly rooted in analysis and geometry, and interweaved with problems from classical mechanics; hence, the French reforms cannot be a legitimate attempt to emulate Soviet scientific education. In 1997, while speaking to a conference on mathematical teaching in Paris, he commented on Bourbaki by stating: "genuine mathematicians do not gang up, but the weak need gangs in order to survive." and suggested that Bourbaki's bonding over "super-abstractness" was similar to groups of mathematicians in the 19th century who had bonded over anti-Semitism. [ 220 ]
Dieudonné later regretted that Bourbaki's success had contributed to a snobbery for pure mathematics in France, at the expense of applied mathematics . In an interview, he said: "It is possible to say that there was no serious applied mathematics in France for forty years after Poincaré. There was even a snobbery for pure math. When one noticed a talented student, one would tell him 'You should do pure math.' On the other hand, one would advise a mediocre student to do applied math while thinking, "It's all that he can do! ... The truth is actually the reverse. You can't do good work in applied math until you can do good work in pure math." [ 221 ] Claude Chevalley confirmed an elitist culture within Bourbaki, describing it as "an absolute certainty of our superiority over other mathematicians." [ 93 ] Alexander Grothendieck also confirmed an elitist mentality within Bourbaki. [ 79 ] Some mathematicians, especially geometers and applied mathematicians, found Bourbaki's influence to be stifling. [ 222 ] Benoit Mandelbrot's decision to emigrate to the United States in 1958 was motivated in part by a desire to escape Bourbaki's influence in France. [ 223 ]
Several related criticisms of the Éléments have concerned its target audience and the intent of its presentation. Volumes of the Éléments begin with a note to the reader which says that the series "takes up mathematics at the beginning, and gives complete proofs" and that "the method of exposition we have chosen is axiomatic and abstract, and normally proceeds from the general to the particular." [ 224 ] Despite the opening language, Bourbaki's intended audience are not absolute beginners in mathematics, but rather undergraduates, graduate students, and professors who are familiar with mathematical concepts. [ 225 ] Claude Chevalley said that the Éléments are "useless for a beginner", [ 226 ] and Pierre Cartier clarified that "The misunderstanding was that it should be a textbook for everybody. That was the big disaster." [ 64 ]
The work is divided into two halves. While the first half—the Structures fondamentales de l’analyse —treats established subjects, the second half deals with modern research areas like commutative algebra and spectral theory. This divide in the work is related to a historical change in the intent of the treatise. The Éléments' content consists of theorems, proofs, exercises and related commentary, common material in math textbooks. Despite this presentation, the first half was not written as original research but rather as a reorganized presentation of established knowledge. In this sense, the Éléments' first half was more akin to an encyclopedia than a textbook series. As Cartier remarked, "The misunderstanding was that many people thought it should be taught the way it was written in the books. You can think of the first books of Bourbaki as an encyclopedia of mathematics... If you consider it as a textbook, it's a disaster." [ 64 ]
The strict, ordered presentation of material in the Éléments' first half was meant to form the basis for any further additions. However, developments in modern mathematical research have proven difficult to adapt in terms of Bourbaki's organizational scheme. This difficulty has been attributed to the fluid, dynamic nature of ongoing research which, being new, is not settled or fully understood. [ 195 ] [ 227 ] Bourbaki's style has been described as a particular scientific paradigm which has been superseded in a paradigm shift . For example, Ian Stewart cited Vaughan Jones' novel work in knot theory as an example of topology which was done without dependence on Bourbaki's system. [ 228 ] Bourbaki's influence has declined over time; [ 228 ] this decline has been partly attributed to the absence of certain modern topics—such as category theory—from the treatise. [ 81 ] [ 82 ]
Although multiple criticisms have pointed to shortcomings in the collective's project, one has also pointed to its strength: Bourbaki was a "victim of its own success" [ 195 ] in the sense that it accomplished what it set out to do, achieving its original goal of presenting a thorough treatise on modern mathematics. [ 229 ] [ 230 ] [ 231 ] These factors prompted biographer Maurice Mashaal to conclude his treatment of Bourbaki in the following terms:
Such an enterprise deserves admiration for its breadth, for its enthusiasm and selflessness, for its strongly collective character. Despite some mistakes, Bourbaki did add a little to 'the honor of the human spirit'. In an era when sports and money are such great idols of civilization, this is no small virtue.
Other collective mathematical pseudonyms | https://en.wikipedia.org/wiki/Nicolas_Bourbaki |
Nicolas Chuquet ( French: [ʃykɛ] ; born c. 1445 – c. 1455 ; died c. 1488 – c. 1500 ) was a French mathematician . He invented his own notation for algebraic concepts and exponentiation . He may have been the first mathematician to recognize zero and negative numbers as exponents. [ 1 ]
In 1475, Jehan Adam recorded the words "bymillion" and "trimillion" (for 10 12 and 10 18 ) and it is believed that these words or similar ones were in general use at that time.
In 1484, Chuquet wrote an article Triparty en la science des nombres , [ 2 ] [ 3 ] which was unpublished in his lifetime. Most of it, however, was copied without attribution by Estienne de La Roche in his 1520 textbook, l'Arismetique. In the 1870s, scholar Aristide Marre discovered Chuquet's manuscript and published it in 1880. The manuscript contained notes in de la Roche's handwriting. His article shows a huge number divided into groups of six digits, and in a short passage he states that the groups can be called:
In a second passage, he wrote:
In the extract from Chuquet's manuscript, the transcription and translation provided here all contain an original mistake: one too many zeros in the 804300 portion of the fully written out example: 745324'8043000 '700023'654321 ...
Chuquet was, however, the original author of the earliest work using of a systematic, extended series of names ending in -illion or -yllion. The system in which the names million, billion, trillion, etc. refer to powers of one million is sometimes referred to as the Chuquet system.
In 1514, Budaeus introduced the term Milliard or Milliart for 10 12 , which was widely publicised around 1550 by the influential Jacques Peletier du Mans . Milliard was reduced to 10 9 around the end of the 17th century, leaving the modern Long scale system. This system is sometimes referred to as the Chuquet-Peletier system.
Much later, in France and in the US, a different system, the short scale , became established where the term billion signifies 10 9 .
Last century, England and other English-speaking countries joined the US and some countries in using the short scale system; whereas, France rejoined Germany, much of Europe, and some other countries in the Chuquet-Peletier, or long scale , system. | https://en.wikipedia.org/wiki/Nicolas_Chuquet |
Nicolas Dauphas (born December 10, 1975) is a planetary scientist and isotope geochemist. He is a professor of geochemistry and cosmochemistry in the Department of the Geophysical Sciences and Enrico Fermi Institute at the University of Chicago . [ 1 ] Within cosmochemistry, his research focus is on isotope geochemistry . [ 1 ] He studies the origin and evolution of planets and other objects in the Solar System by analyzing the natural distributions of elements and their isotopes using mass spectrometers. [ 2 ] [ 3 ]
Born in Nantes in Brittany, France, [ 4 ] Dauphas received a B.Sc. degree from École Nationale Supérieure de Géologie in 1998. The same year, he obtained an M.Sc. from Centre de Recherches Pétrographiqueset Géochimiques , at the National Polytechnic Institute of Lorraine ( French : L'Institut National Polytechnique de Lorraine ; INPL). In 2002, also from INPL, he was awarded a Ph.D. in geochemistry and cosmochemistry, working with Bernard Marty and Laurie Reisberg. He then completed his postdoctoral research at the Enrico Fermi Institute of the University of Chicago and the Field Museum of Natural History from 2002 to 2004, before joining the faculty at the University of Chicago in 2004. [ 5 ] [ 6 ] [ 7 ]
In 2005, Dauphas was awarded Nier Prize of the Meteoritical Society which recognizes outstanding research in meteoritics and closely allied fields by young scientists. [ 8 ] In 2007, he was awarded the David and Lucile Packard Foundation Fellowship, given to the most promising early-career scientists and engineers, across the US. [ 9 ] He won the 2008 Houtermans Award , given by the European Association of Geochemistry for outstanding contributions to geochemistry. [ 10 ] He was awarded the James B. Macelwane Medal of the American Geophysical Union (AGU) for "significant contributions to the geophysical sciences", and was selected as an AGU Fellow in 2011. [ 11 ] In 2014, he became a Fellow of the Meteoritical Society . [ 12 ] He was one of the finalists in 2017 for the Blavatnik National Awards. [ 13 ] In 2016, Dauphas received a named professorship from the University of Chicago as the Louis Block professor, Physical Sciences Division. [ 14 ] [ 15 ] [ 16 ] In 2019, Dauphas was elected Geochemical Fellow of the Geochemical Society and the European Association of Geochemistry in recognition of his career contribution to the field of geochemistry. [ 17 ] [ 18 ]
On April 30, 2024, it was announced that Nicolas Dauphas had been elected to the National Academy of Sciences . [ 19 ] [ 4 ]
By analyzing the isotopic compositions of stable and radiogenic nuclides in meteorites, Dauphas investigates the timing and processes that lead to the formation of Solar System bodies and the establishment of habitable conditions on Earth and Mars. He used iron isotopes to study how the iron biogeochemical cycle of the Earth changed through time. [ 20 ] He established that Mars was formed rapidly, within the first 2~4 million years of the birth of the Solar System, which explains the much smaller size of Mars compared to Earth and Venus. [ 21 ] He first identified the mineralogical carrier of the 54 Cr isotopic anomalies in meteorites as Cr-rich nano-sized spinels from supernovae. [ 22 ] He constrained the nature of Earth's accreting materials through time, using a novel approach that relies on the different affinities of elements with Earth's core, and showed that the materials formed Earth are from an isotopically homogeneous reservoir. [ 23 ] [ 24 ]
Dauphas was part of the preliminary examination team for JAXA 's Hayabusa2 mission, [ 25 ] which returned a fragment of Ryugu carbonaceous asteroid to Earth for scientific research. He was selected as a member of the Mars Sample Return Campaign Science Group in 2022. [ 26 ] [ 16 ]
Nicolas Dauphas married a fellow planetary scientist, Reika Yokochi . The couple had two children. [ 4 ] In February 2024, Dauphas posted to his Twitter ( X ) account that Yokochi had died from EGFR-positive lung cancer. [ 27 ]
Dauphas states that he is of "French-American citizenship". [ 3 ] | https://en.wikipedia.org/wiki/Nicolas_Dauphas |
Nicolas Leblanc ( French pronunciation: [nikɔla ləblɑ̃] ; December 6, 1742 – January 16, 1806) was a French chemist and surgeon who discovered how to manufacture soda ash from common salt . [ 1 ]
Leblanc was born in Ivoy le Pré , Cher , France on 6 December 1742. [ 2 ] His father, a minor official at an iron works , died in 1751. Leblanc was sent to Bourges to live with Dr. Bien, a close family friend. Under the influence of his guardian, Leblanc developed an interest in medicine . When Bien died in 1759, Leblanc enrolled at the École de Chirurgie (College of Surgeons) in Paris to study medicine.
Graduating with a master's degree in surgery, Leblanc opened a medical practice. He married in 1776, and the couple's first child followed three years later. [ 2 ] Unable to provide adequately for his family on the medical fees he obtained from his patients, Leblanc in 1780 accepted a position as the private physician to the household of the Louis Philip II, Duke of Orléans .
In 1775, the French Academy of Sciences offered a prize for a process whereby soda ash could be produced from salt. The French Academy wanted to promote the production of much-needed sodium carbonate from inexpensive sodium chloride .
By 1791, Nicolas Leblanc had succeeded in producing sodium carbonate from salt by a 2-step process. In the first step, sodium chloride is mixed with concentrated sulfuric acid at temperatures of 800–900 ° C ; hydrogen chloride gas is evolved, leaving solid sodium sulfate. In the second step, the sodium sulfate is crushed, mixed with charcoal and limestone and again heated in a furnace .
The prize was awarded to Nicolas Leblanc for a process which used sea salt and sulfuric acid as the raw materials . Later a plant (of his own) was in operation producing 320 tons of soda ash per year. The process, however, is now obsolete and is superseded by the Solvay process .
Two years later the plant was confiscated by the French revolutionary government, which refused to pay him the prize money he had earned ten years earlier.
In 1802 Napoleon returned the plant (but not the prize) to him, but by then Leblanc could not afford to run it. He committed suicide by a gunshot to the head in 1806.
William Losh visited Paris to study Leblanc's process. In 1807, Losh, Wilson and Bell opened the first alkali works in England that used the Leblanc process, at Walker, Newcastle upon Tyne . [ 3 ] | https://en.wikipedia.org/wiki/Nicolas_Leblanc |
Nicole Marie Passonno Stott (born November 19, 1962) is an American engineer and a retired NASA astronaut . She served as a flight engineer on ISS Expedition 20 and Expedition 21 and was a mission specialist on STS-128 and STS-133 . [ 2 ] After 27 years of working at NASA, the space agency announced her retirement effective June 1, 2015. [ 3 ] She is married to Christopher Stott , a Manx -born American space entrepreneur.
Stott was born in Albany , New York and resides in St. Petersburg, Florida . She attended St. Petersburg College studying aviation administration, graduated with a B.S. degree in aeronautical engineering from Embry-Riddle Aeronautical University in 1987, and received her M.S. degree in Engineering Management from the University of Central Florida in 1992. Nicole Stott began her career in 1987 as a structural design engineer with Pratt & Whitney Government Engines in West Palm Beach , Florida . She spent a year with the Advanced Engines Group performing structural analyses of advanced jet engine component designs. Stott is an instrument rated private pilot.
In 1988, Stott joined NASA at the Kennedy Space Center (KSC), Florida as an Operations Engineer in the Orbiter Processing Facility (OPF). After six months, she was detailed to the Director of Shuttle Processing as part of a two-person team tasked with assessing the overall efficiency of Shuttle processing flows, and implementing tools for measuring the effectiveness of improvements. She was the NASA KSC Lead for a joint Ames/KSC software project to develop intelligent scheduling tools. The Ground Processing Scheduling System (GPSS) was developed as the technology demonstrator for this project. GPSS was a success at KSC, and also a commercial success that is part of the PeopleSoft suite of software products. During her time at KSC, Stott also held a variety of positions within NASA Shuttle Processing, including Vehicle Operations Engineer; NASA Convoy Commander; assistant to the Flow Director for Space Shuttle Endeavour ; and Orbiter Project Engineer for Columbia. During her last two years at KSC, she was a member of the Space Station Hardware Integration Office and relocated to Huntington Beach, California where she served as the NASA Project Lead for the ISS truss elements under construction at the Boeing Space Station facility. In 1998, she joined the Johnson Space Center (JSC) team in Houston, Texas as a member of the NASA Aircraft Operations Division, where she served as a Flight Simulation Engineer (FSE) on the Shuttle Training Aircraft (STA).
Selected as a mission specialist by NASA in July 2000, Stott reported for astronaut candidate training in August 2000. Following the completion of two years of training and evaluation, she was assigned technical duties in the Astronaut Office Station Operations Branch, where she performed crew evaluations of station payloads. She also worked as a support astronaut and CAPCOM for the ISS Expedition 10 crew. In April 2006, she was a crew member on the NEEMO 9 mission (NASA Extreme Environment Mission Operations) where she lived and worked with a six-person crew for 18 days on the Aquarius undersea research habitat . [ 4 ] Stott was previously assigned to Expedition 20 and Expedition 21 . She was launched to the International Space Station with the crew of STS-128 , participating in the first spacewalk of that mission, [ 5 ] and returned on STS-129 , thus becoming the last Expedition crew-member to return to Earth via the space shuttle. Stott completed her second spaceflight on STS-133 , the third to last (antepenultimate) flight of the space shuttle. [ 6 ] [ 7 ]
On October 21, 2009, Stott and her Expedition 21 crewmate Jeff Williams participated in the first NASA Tweetup from the station with members of the public gathered at NASA Headquarters in Washington, D.C. [ 8 ] This involved the first live Twitter connection for the astronauts. [ 9 ] Previously, astronauts on board the Space Shuttle or ISS had sent the messages they desired to send as tweets down to Mission Control which then posted them via the Internet to Twitter. [ 10 ]
Stott was featured in a Super Bowl LIV commercial promoting Girls Who Code . [ 11 ] Stott has also written Back To Earth, described as "What Life in Space Taught Me About Our Home Planet and Our Mission to Protect It". She is also an artist and brought a small watercolor kit on ISS Expedition 21 where she was the first person to paint with watercolor in space. Her current works often relate to astronomy including her Earth Observation collection and Spacecraft collection. [ 12 ] [ 13 ] In 2022, she is providing the narration to a piece being performed by the Schenectady Symphony Orchestra, Glen Cortese's "Voyager: A Journey to the Stars." [ 14 ]
This article incorporates public domain material from websites or documents of the National Aeronautics and Space Administration . | https://en.wikipedia.org/wiki/Nicole_Stott |
Nicolson pavement , alternatively spelled " Nicholson " and denominated wooden block pavement and wood block pavement , is a road surface material consisting of wooden blocks. Samuel Nicolson invented it in the mid-19th century. [ 1 ] Wooden block pavement has since become unfavored because of its poor surface quality and high cost of maintenance.
Wood block pavement may have originated in Russia in the 14th century, but it gained prominence in the 1820s and 1830s as a road building alternative to the irregularly surfaced cobblestone streets common during that era. [ 2 ] Wood block was also favored because stone was scarce and wood was abundant. [ 3 ] Additionally, horse traffic reportedly made less noise on wood-surfaced streets. [ 4 ] However, the drawbacks of Nicolson pavement include slippery surfaces when wet or icy, [ 4 ] [ 5 ] and the tendency of the blocks to rot, decay, and heave due to moisture seeping between the blocks. [ 6 ] For example, the 1910 Great Flood of Paris caused substantial damage to inundated streets when the wood blocks floated and became dislodged. [ 7 ] When treated with creosote , wood block pavement would last longer, but the creosoted pavement had a noticeable unpleasant smell. [ 2 ]
M. Gourieff introduced [to St. Petersburg] the hexagonal wooden pavement with which, in London, we are all acquainted. This, with continuous reparation, answers pretty well, taking into consideration that equality of surface seems utterly unattainable, that the knavish contractors supply blocks so rotten as to be worthless a few days after they are put down, and that the horses are continually slipping and frequently falling on the perilous highway. It is unpleasant, also, to be semi-asphyxiated each time you take your walks abroad, by the fumes of the infernal pitch-cauldrons, round which the moujik workmen gather, like witches.
Nicolson pavement was the focus of a Supreme Court case, City of Elizabeth v. American Nicholson Pavement Co. which held that while the public use of an invention more than one year prior to the inventor's application for a patent normally causes the inventor to lose his right to a patent, there is an exception to this rule for public uses for experimental purposes.
Remnants of Nicolson pavement still exist in several cities across the US. Touted as the only remaining wooden street in the US, Roslyn Place in Pittsburgh , Pennsylvania, is completely paved in wooden blocks. [ 4 ] [ 5 ] In addition, patches of creosoted wooden block pavement are still visible in an alley along 10th street between Olive and Locust Streets in St. Louis , Missouri, [ 6 ] and at least three other alleys in Chicago , Illinois, still retain the use of wood block pavement, though some are in states of disrepair. [ 8 ] The 200 block of Camac Street in Philadelphia , Pennsylvania, is also paved with wooden blocks, and it is regularly maintained, having been listed in the Philadelphia Register of Historic Places. [ 9 ] Hessler Court in Cleveland , Ohio, known for its Hessler Street Fair , likewise maintains its Nicolson Pavement for historic reasons. [ 10 ] In 2009, a series of wood block pavers were installed in Wall Street in New York City from Broadway to William Street. The locations of the pavers follow the exact path of the Dutch wooden defense wall that gave the street its name. [ 11 ] | https://en.wikipedia.org/wiki/Nicolson_pavement |
Nicolson–Ross–Weir method is a measurement technique for determination of complex permittivities and permeabilities of material samples for microwave frequencies. The method is based on insertion of a material sample with a known thickness inside a waveguide , such as a coaxial cable or a rectangular waveguide, after which the dispersion data is extracted from the resulting scattering parameters . The method is named after A. M. Nicolson and G. F. Ross, [ 1 ] and W. B. Weir, [ 2 ] who developed the approach in 1970 and 1974, respectively.
The technique is one of the most common procedures for material characterization in microwave engineering . [ 3 ]
The method uses scattering parameters of a material sample embedded in a waveguide, namely S 11 {\displaystyle S_{11}} and S 21 {\displaystyle S_{21}} , to calculate permittivity and permeability data. S 11 {\displaystyle S_{11}} and S 21 {\displaystyle S_{21}} correspond to the cumulative reflection and transmission coefficient of the sample that are referenced to the each sample end, respectively: these parameters account for the multiple internal reflections inside the sample, which is considered to have a thickness of d {\displaystyle d} . The reflection coefficient of the bulk sample is: [ 1 ] [ 2 ]
where
The sign of the root for the reflection coefficient is chosen appropriately to ensure its passivity ( | Γ | ≤ 1 {\displaystyle |\Gamma |\leq 1} ). Similarly, the transmission coefficient of the bulk sample can be written as:
Thus, the effective permeability ( μ ∗ {\displaystyle \mu ^{*}} ) and permittivity ( ε ∗ {\displaystyle \varepsilon ^{*}} ) of the material can be written as:
where
and
The constitutive relation for Λ {\displaystyle \Lambda } admits an infinite number of solutions due to the branches of the complex logarithm . The ambiguity regarding its result can be resolved by taking the group delay into account. [ 2 ]
In the case of low material loss, the Nicolson–Ross–Weir method is known to be unstable for sample thicknesses at integer multiples of one half wavelength due to resonance phenomenon. Improvements over the standard algorithm have been presented in engineering literature to alleviate this effect. [ 4 ] [ 5 ] [ 6 ] Furthermore, complete filling of a waveguide with sample material may pose a particular challenge: presence of gaps during the filling of the waveguide section would excite higher-order modes, which may yield errors in scattering parameter results. [ 7 ] In such cases, more advanced methods based on the rigorous modal analysis of partially-filled waveguides [ 8 ] [ 9 ] or optimization methods [ 10 ] can be used. A modification of the method for single-port measurements was also reported. [ 11 ]
In addition to homogenous materials, the extension of the method was developed to obtain constitutive parameters of isotropic and bianisotropic metamaterials . [ 12 ] [ 13 ] [ 14 ] | https://en.wikipedia.org/wiki/Nicolson–Ross–Weir_method |
In enzymology , nicotinamide-nucleotide adenylyltransferase ( NMNAT ) ( EC 2.7.7.1 ) are enzymes that catalyzes the chemical reaction
Thus, the two substrates of this enzyme are ATP and nicotinamide mononucleotide (NMN), whereas its two products are diphosphate and NAD + .
This enzyme participates in nicotinate and nicotinamide metabolism .
Humans have three protein isoforms : NMNAT1 (widespread), NMNAT2 (predominantly in brain), and NMNAT3 (highest in liver, heart, skeletal muscle, and erythrocytes ). [ 1 ] Mutations in the NMNAT1 gene lead to the LCA9 form of Leber congenital amaurosis . [ 1 ] Mutations in NMNAT2 or NMNAT3 genes are not known to cause any human disease. [ 1 ] NMNAT2 is critical for neurons: loss of NMNAT2 is associated with neurodegeneration . [ 1 ] All NMNAT isoforms reportedly decline with age. [ 2 ]
This enzyme belongs to the family of transferases , specifically those transferring phosphorus-containing nucleotide groups ( nucleotidyltransferases ). The systematic name of this enzyme class is ATP:nicotinamide-nucleotide adenylyltransferase . Other names in common use include NAD+ pyrophosphorylase , adenosine triphosphate-nicotinamide mononucleotide transadenylase , ATP:NMN adenylyltransferase , diphosphopyridine nucleotide pyrophosphorylase , nicotinamide adenine dinucleotide pyrophosphorylase , nicotinamide mononucleotide adenylyltransferase , and NMN adenylyltransferase . [ citation needed ]
As of late 2007, 11 structures have been solved for this class of enzymes, with PDB accession codes 1EJ2 , 1GZU , 1HYB , 1KKU , 1KQN , 1KQO , 1KR2 , 1M8F , 1M8G , 1M8J , and 1M8K .
The three protein isoforms have the following cellular localizations [ 3 ]
All three NMNATs compete for the NMN produced by NAMPT . [ 4 ]
Chronic inflammation due to obesity and other causes reduced NMNAT and NAD+ levels in many tissues. [ 5 ]
This EC 2.7 enzyme -related article is a stub . You can help Wikipedia by expanding it . | https://en.wikipedia.org/wiki/Nicotinamide-nucleotide_adenylyltransferase |
Nicotinamide adenine dinucleotide phosphate , abbreviated NADP [ 1 ] [ 2 ] or, in older notation, TPN (triphosphopyridine nucleotide), is a cofactor used in anabolic reactions , such as the Calvin cycle and lipid and nucleic acid syntheses, which require NADPH as a reducing agent ('hydrogen source'). NADPH is the reduced form, whereas NADP + is the oxidized form. NADP + is used by all forms of cellular life. NADP + is essential for life because it is needed for cellular respiration. [ 3 ]
NADP + differs from NAD + by the presence of an additional phosphate group on the 2' position of the ribose ring that carries the adenine moiety . This extra phosphate is added by NAD + kinase and removed by NADP + phosphatase. [ 4 ]
In general, NADP + is synthesized before NADPH is. Such a reaction usually starts with NAD + from either the de-novo or the salvage pathway, with NAD + kinase adding the extra phosphate group. ADP-ribosyl cyclase allows for synthesis from nicotinamide in the salvage pathway, and NADP + phosphatase can convert NADPH back to NADH to maintain a balance. [ 3 ] Some forms of the NAD + kinase, notably the one in mitochondria, can also accept NADH to turn it directly into NADPH. [ 5 ] [ 6 ] The prokaryotic pathway is less well understood, but with all the similar proteins the process should work in a similar way. [ 3 ]
NADPH is produced from NADP + . The major source of NADPH in animals and other non-photosynthetic organisms is the pentose phosphate pathway , by glucose-6-phosphate dehydrogenase (G6PDH) in the first step. The pentose phosphate pathway also produces pentose, another important part of NAD(P)H, from glucose. Some bacteria also use G6PDH for the Entner–Doudoroff pathway , but NADPH production remains the same. [ 3 ]
Ferredoxin–NADP + reductase , present in all domains of life, is a major source of NADPH in photosynthetic organisms including plants and cyanobacteria. It appears in the last step of the electron chain of the light reactions of photosynthesis . It is used as reducing power for the biosynthetic reactions in the Calvin cycle to assimilate carbon dioxide and help turn the carbon dioxide into glucose. It has functions in accepting electrons in other non-photosynthetic pathways as well: it is needed in the reduction of nitrate into ammonia for plant assimilation in nitrogen cycle and in the production of oils. [ 3 ]
There are several other lesser-known mechanisms of generating NADPH, all of which depend on the presence of mitochondria in eukaryotes. The key enzymes in these carbon-metabolism-related processes are NADP-linked isoforms of malic enzyme , isocitrate dehydrogenase (IDH), and glutamate dehydrogenase . In these reactions, NADP + acts like NAD + in other enzymes as an oxidizing agent. [ 7 ] The isocitrate dehydrogenase mechanism appears to be the major source of NADPH in fat and possibly also liver cells. [ 8 ] These processes are also found in bacteria. Bacteria can also use a NADP-dependent glyceraldehyde 3-phosphate dehydrogenase for the same purpose. Like the pentose phosphate pathway, these pathways are related to parts of glycolysis . [ 3 ] Another carbon metabolism-related pathway involved in the generation of NADPH is the mitochondrial folate cycle, which uses principally serine as a source of one-carbon units to sustain nucleotide synthesis and redox homeostasis in mitochondria. Mitochondrial folate cycle has been recently suggested as the principal contributor to NADPH generation in mitochondria of cancer cells. [ 9 ]
NADPH can also be generated through pathways unrelated to carbon metabolism. The ferredoxin reductase is such an example. Nicotinamide nucleotide transhydrogenase transfers the hydrogen between NAD(P)H and NAD(P) + , and is found in eukaryotic mitochondria and many bacteria. There are versions that depend on a proton gradient to work and ones that do not. Some anaerobic organisms use NADP + -linked hydrogenase , ripping a hydride from hydrogen gas to produce a proton and NADPH. [ 3 ]
Like NADH , NADPH is fluorescent . NADPH in aqueous solution excited at the nicotinamide absorbance of ~335 nm (near UV) has a fluorescence emission which peaks at 445-460 nm (violet to blue). NADP + has no appreciable fluorescence. [ 10 ]
NADPH provides the reducing agents, usually hydrogen atoms, for biosynthetic reactions and the oxidation-reduction involved in protecting against the toxicity of reactive oxygen species (ROS), allowing the regeneration of glutathione (GSH). [ 11 ] NADPH is also used for anabolic pathways, such as cholesterol synthesis , steroid synthesis, [ 12 ] ascorbic acid synthesis, [ 12 ] xylitol synthesis, [ 12 ] cytosolic fatty acid synthesis [ 12 ] and microsomal fatty acid chain elongation .
The NADPH system is also responsible for generating free radicals in immune cells by NADPH oxidase . These radicals are used to destroy pathogens in a process termed the respiratory burst . [ 13 ] It is the source of reducing equivalents for cytochrome P450 hydroxylation of aromatic compounds , steroids , alcohols , and drugs .
NADH and NADPH are very stable in basic solutions, but NAD + and NADP + are degraded in basic solutions into a fluorescent product that can be used conveniently for quantitation. Conversely, NADPH and NADH are degraded by acidic solutions while NAD + /NADP + are fairly stable to acid. [ 14 ] [ 15 ]
Many enzymes that bind NADP share a common super-secondary structure named named the "Rossmann fold". The initial beta-alpha-beta (βαβ) fold is the most conserved segment of the Rossmann folds. This segment is in contact with the ADP portion of NADP. Therefore, it is also called an "ADP-binding βαβ fold". [ 16 ]
In 2018 and 2019, the first two reports of enzymes that catalyze the removal of the 2' phosphate of NADP(H) in eukaryotes emerged. First the cytoplasmic protein MESH1 ( Q8N4P3 ), [ 19 ] then the mitochondrial protein nocturnin [ 20 ] were reported. Of note, the structures and NADPH binding of MESH1 ( 5VXA ) and nocturnin ( 6NF0 ) are not related. | https://en.wikipedia.org/wiki/Nicotinamide_adenine_dinucleotide_phosphate |
Nicotinamide cofactor analogues ( mNADs ), also called nicotinamide coenzyme biomimetics (NCBs), are artificial compounds that mimic the natural nicotinamide adenine dinucleotide cofactors in structure, to explore a mechanism or be used in biocatalysis or other applications. [ 1 ] These nicotinamide cofactor mimics generally retain the nicotinamide moiety with varying substituents.
An estimated 50% of oxidoreductases catalyze the transfer of a hydride using the nicotinamide adenine dinucleotide cofactor NAD(P). [ 2 ] Nicotinamide adenine dinucleotide phosphate (NADPH) is used in anabolic reactions while nicotinamide adenine dinucleotide (NAD) is used in catabolic reactions. [ 3 ] In the field of biocatalysis , NAD(P)-dependent oxidoreductases are widely used for the production of chiral alcohols, amines, and other valuable compounds. Yet the reduced forms of the cofactor, NADH and NADPH, needed for the catalysis, is too expensive to be used in stoichiometric amounts. Therefore a cofactor recycling system is usually employed.
Nicotinamide cofactor analogues have been synthesized with varying substituents on the dihydropyridine ring to tune their redox potential and stability, to replace NADH or NADPH in certain enzymatic reactions. These synthetic cofactors have been used as early as 1937 to better understand the mechanisms of enzymatic reactions, in particular of alcohol dehydrogenases. These cofactor analogues can serve as an alternative to traditional cofactor regeneration techniques and be used in orthogol pathways. [ 3 ] [ 4 ] | https://en.wikipedia.org/wiki/Nicotinamide_cofactor_analogues |
Nicotinamide mononucleotide (" NMN " and " β-NMN ") is a nucleotide derived from ribose , nicotinamide , nicotinamide riboside and niacin . [ 1 ] In humans, several enzymes use NMN to generate nicotinamide adenine dinucleotide (NADH). [ 1 ] In mice, it has been proposed that NMN is absorbed via the small intestine within 10 minutes of oral uptake and converted to nicotinamide adenine dinucleotide ( NAD+ ) [ 2 ] through the Slc12a8 transporter. [ 3 ] However, this observation has been challenged, [ 4 ] and the matter remains unsettled. [ 5 ]
Because NADH is a cofactor for processes inside mitochondria , for sirtuins and PARP , NMN has been studied in animal models as a potential neuroprotective and anti-aging agent. [ 6 ] [ 7 ] The alleged anti-aging effect at the cellular level by inhibiting mitochondrial decay in presence of increased levels of NAD+ makes it popular among anti-aging products. [ 8 ] Dietary supplement companies have aggressively marketed NMN products, claiming those benefits. [ 9 ] [ 10 ] However, no human studies to date have properly proven its anti-aging effects with proposed health benefits only suggested through research done in vitro or through animal models . [ 11 ] Single-dose administration of up to 500 mg was shown safe in men in a study at Keio University . [ 12 ] One 2021 clinical trial found that NMN improved muscular insulin sensitivity in prediabetic women, [ 13 ] while another found that it improved aerobic capacity in amateur runners. [ 14 ] A 2023 clinical trial showed that NMN improves performance on a six-minute walking test and a subjective general health assessment. [ 15 ]
NMN is vulnerable to extracellular degradation by CD38 enzyme, [ 16 ] which can be inhibited by compounds such as CD38-IN-78c . [ 17 ]
NMN is found in fruits and vegetables such as edamame , broccoli , cabbage , cucumber and avocado at a concentration of about 1 mg per 100g, [ 18 ] [ 19 ] [ 20 ] making these natural sources impractical to acquire the quantities needed to accomplish the dosing currently being investigated for NMN as a pharmaceutical.
Production of nicotinamide mononucleotide has been redacted since the latter half of 2022 by the FDA because it is under investigation as a pharmaceutical drug. [ 21 ] [ 22 ]
The synthesizing enzymes and consumption enzymes of NMN also exhibit tissue specificity: NMN is widely distributed in tissues and organs throughout the body and has been present in various cells since embryonic development. [ 22 ]
NMN is a precursor for NAD + biosynthesis, and NMN dietary supplementation has been demonstrated to increase NAD + concentration and thus has the potential to mitigate aging-related disorders such as oxidative stress , DNA damage , neurodegeneration and inflammatory responses . [ 23 ] The potential benefits and risks of NMN supplementation, as of 2023, are currently under investigation. [ 23 ]
Certain enzymes are sensitive to the intracellular NMN/ NAD + ratio, such as SARM1 , [ 24 ] a protein responsible for initiating cellular degeneration pathways such as MAP kinase and inducing axonal loss and neuronal death . [ 25 ] [ 26 ] NMNAT is an enzyme with neurorescuing properties that functions to deplete NMN and produce NAD + , attenuating SARM1 activity and aiding neuronal survival in vitro , [ 27 ] [ 28 ] an effect that is reversed by applying exogenous NMN which promptly resumed axon destruction. [ 25 ] The similar molecule nicotinic acid mononucleotide (NaMN) opposes the activating effect of NMN on SARM1 , and is a neuroprotector. [ 29 ] | https://en.wikipedia.org/wiki/Nicotinamide_mononucleotide |
Nicotinamide riboside ( NR , SR647 ) is a pyridine - nucleoside and a form of vitamin B 3 . It functions as a precursor to nicotinamide adenine dinucleotide , or NAD+ , [ 2 ] through a two-step and a three-step pathway. [ 3 ]
While the molecular weight of nicotinamide riboside is 255.25 g/mol, [ 4 ] that of its chloride salt is 290.70 g/mol. [ 5 ] [ 6 ] As such, 100 mg of nicotinamide riboside chloride provides 88 mg of nicotinamide riboside. [ citation needed ]
NRCl is susceptible to degradation through both thermal decomposition and base-catalyzed hydrolysis:
These properties emphasize the need for careful formulation strategies to ensure NRCl's stability during storage, processing, and delivery. [ citation needed ]
Nicotinamide riboside (NR) has been identified as an NAD precursor, involved in salvage NAD synthesis in both bacteria and eukaryotes . [ 7 ] In bacteria, it was first described in 1944 as a necessary growth factor for the culture of Haemophilus influenza , H. influenza was identified as requiring both X factor ( hemin ) and V factor (NAD) to grow. [ 8 ] V factor, purified from blood, was shown to exist in three forms: Nicotinamide adenine dinucleotide (NAD+), NMN and NR. NR was the compound that led to the most rapid growth of the H. influenza bacterium. [ 9 ] [ 7 ]
H. influenza cannot grow on nicotinic acid (NA), nicotinamide (NAM), or amino acids such as tryptophan (Trp) or aspartic acid (Asp), which were the previously known precursors of NAD+. [ 7 ] [ 10 ] H. influenza depends entirely on salvage of NAD precursors from other cells in its environment. [ 9 ]
The identification of Nicotinamide riboside (NR) as an NAD precursor in eukaryotes developed out of the study of pellagra . [ 11 ] Pellagra was the first disease to be associated with NAD+ deficiency. [ 12 ] It was linked to nutritional deficiency by Joseph Goldberger in 1914, and to deficiency of niacin ( vitamin B 3 ) by Conrad Elvehjem in 1937. NAD+ (then called coenzyme I) was shown to be extremely low in cases of pellagra, and NA and NAM were identified as molecular precursors in rebuilding NAD+ levels. Pellagra is now understood as a severe, chronic depletion of NAD+, which can be treated through diet. [ 11 ]
Subsequent studies of NAD+ metabolism have identified regulatory pathways used by cells and tissues to maintain NAD+ availability. NAD+ and its precursors nicotinic acid (NA) and nicotinamide (NAM) have been shown to be vital cofactors in cellular oxidation/reduction reactions and ATP synthesis. Classic NAD+ synthesis pathways characterized in eukaryotes include an eight-step de novo pathway from Trp and two pathways using the NAD+ precursors NA and NAM: a three-step NA-based pathway known as the Preiss-Handler pathway; and an NAM-based pathway involving the enzyme Nicotinamide phosphoribosyltransferase (NAMPT) and the formation of nicotinamide mononucleotide (NMN). [ 11 ] [ 13 ] [ 14 ]
In 2004, a previously unknown pathway was reported when nicotinamide riboside (NR) was identified as an additional NAD+ precursor in eukaryotes . [ 11 ] [ 13 ] [ 14 ] NR is now recognized as a form of vitamin B 3 [ 15 ] which can be found in both cow and human milk. [ 11 ] [ 16 ] Once internalized into a cell, NR is rapidly phosphorylated by the activity of nicotinamide riboside kinase enzymes (NRK1 and NRK2) to form nicotinamide mononucleotide (NMN), bypassing the previously known biosynthetic routes to NAD+ production. NMN is then converted to NAD+ by NMN-adenylyltransferase (NMNAT). [ 13 ]
Research in mammals indicates that NRK1 is a cytosolic protein, encoded by the Nmrk1 gene. It is found in most tissues but predominantly in the liver and kidney. The NRK2 protein may be related to muscle tissue including cardiac muscle. It is encoded by the Nmrk2 gene and appears to be more highly expressed in cases of metabolic stress or cellular damage. [ 11 ] [ 13 ] [ 14 ] Since different types of tissues display differing concentrations of NR and NRKs, it is likely that NR utilization will vary in different tissues. [ 3 ] [ 13 ]
Metabolic studies indicate that NAD+, once considered a stable molecule, is continuously turned over and used, requiring tight regulation to maintain metabolic homeostasis. NR utilization in mammals may involve both exogenous dietary sources and endogenous salvage processes that recycle intermediates. NR metabolism and the interactions of different NAD+ pathways continue to be studied. The NAM and NR pathways involve an amide group and are referred to as 'amidated' pathways. The pathways for de novo synthesis from tryptophan and from NA salvage are 'deamidated' pathways, which share a rate-limiting amidation enzyme NADsynthase1 (NADSYN). [ 13 ] [ 11 ] Disruptions or imbalances in NAD+ metabolism have been observed in many disease conditions, and the possibility of restoring NAD+ levels by administering NAD+ precursors is an area of interest for researchers. [ 11 ] [ 12 ] [ 13 ]
Nicotinamide riboside (NR) is now known to be an NAD+ precursor, involved in the biosynthetic pathways that convert B3 vitamins into NAD+. NAD+ is primarily synthesized in mammals de novo from tryptophan, through the Priess-Handler pathway from nicotinic acid (NA) or via a salvage pathway from nicotinamide (NAM). [ 17 ]
Nicotinamide riboside (NR) is utilized through an additional pathway involving phosphorylation by the nicotinamide riboside kinase enzymes (NRK1 and NRK2). [ 17 ] [ 13 ] In yeasts, NR has also been shown to be degraded by the nucleosidases Pnp1, Urh1 and Meu1, before being converted to NAD⁺ via the Preiss-Handler pathway and the action of the nicotinamidase Pnc1. [ 3 ] [ 10 ]
Niagen Bioscience, formerly ChromaDex licensed patents for nicotinamide riboside from Dartmouth College , Cornell University , and Washington University in St. Louis in July 2012. [ 18 ] [ 19 ] The company developed a commercial production process for nicotinamide riboside chloride under the trademark Niagen. [ 20 ] Following the acquisition, ChromaDex continued to expand the Tru Niagen brand globally while also supplying Niagen as an ingredient to other manufacturers. [ 21 ] [ 22 ]
ChromaDex has been in a patent dispute with Elysium Health over the rights to nicotinamide riboside supplements since 2016. [ 23 ] [ 24 ]
In 2016, the U.S. Food and Drug Administration (FDA) accepted nicotinamide riboside chloride (NRC, Niagen) as Generally recognized as safe (GRAS) as described in the dossier prepared by ChromaDex, Inc. [ 5 ] [ 25 ] [ 3 ]
The above regulatory acceptances were all in relation to the safety and manufacturing information provided by ChromaDex, Inc. for Niagen. [ 26 ] It was designated a new dietary ingredient (NDI) for use in dietary supplements by the U.S. Food and Drug Administration in 2015 and 2017. It was listed in Health Canada's Licensed Natural Health Products Database (LNHPD) in 2018. The European Union has granted NRC a "New dietary ingredient" designation as a novel food pursuant to Regulation (EU) 2015/2283, as of 2019. It was authorized for use in food supplements by the EU in 2020. The EFSA Panel on Nutrition, Novel Foods and Food Allergens (NDA) considered it as safe as pure nicotinamide for use in food for special medical purposes (FSMP) and total diet replacement for weight control (TDRWC) in adults as of 2021 but noted that further investigation would be required to establish safety for some other types of use. [ 27 ] The Australian government has given nicotinamide riboside chloride a positive listing under the compositional guidelines of its Therapeutic Goods Administration (TGA). [ 28 ]
ChromaDex holds several patents related to nicotinamide riboside, including manufacturing methods, compositions, and uses. As of 2025, ChromaDex's patent portfolio for nicotinamide riboside includes 50+granted patents and numerous pending patent applications worldwide. [ 29 ] | https://en.wikipedia.org/wiki/Nicotinamide_riboside |
[ 6 ]
Nicotine is a naturally produced alkaloid in the nightshade family of plants (most predominantly in tobacco and Duboisia hopwoodii ) [ 8 ] and is widely used recreationally as a stimulant and anxiolytic . As a pharmaceutical drug , it is used for smoking cessation to relieve withdrawal symptoms . [ 9 ] [ 6 ] [ 10 ] [ 11 ] Nicotine acts as a receptor agonist at most nicotinic acetylcholine receptors (nAChRs), [ 12 ] [ 13 ] [ 14 ] except at two nicotinic receptor subunits ( nAChRα9 and nAChRα10 ) where it acts as a receptor antagonist . [ 12 ]
Nicotine constitutes approximately 0.6–3.0% of the dry weight of tobacco. [ 15 ] Nicotine is also present at ppb concentrations in edible plants in the family Solanaceae , including potatoes , tomatoes , and eggplants , [ 16 ] though sources disagree on whether this has any biological significance to human consumers. [ 16 ] It functions as an antiherbivore toxin ; consequently, nicotine was widely used as an insecticide in the past, [ 17 ] [ 18 ] and neonicotinoids (structurally similar to nicotine), such as imidacloprid , are some of the most effective and widely used insecticides.
Nicotine is highly addictive . [ 19 ] [ 20 ] [ 21 ] Slow-release forms (gums and patches, when used correctly) can be less addictive and help in quitting. [ 22 ] [ 23 ] [ 24 ] [ 25 ] Animal research suggests that monoamine oxidase inhibitors present in tobacco smoke may enhance nicotine's addictive properties. [ 26 ] [ 27 ] An average cigarette yields about 2 mg of absorbed nicotine. [ 28 ] The estimated lower dose limit for fatal outcomes is 500–1,000 mg of ingested nicotine for an adult (6.5–13 mg/kg). [ 26 ] [ 28 ] Nicotine addiction involves drug-reinforced behavior, compulsive use, and relapse following abstinence. [ 29 ] Nicotine dependence involves tolerance , sensitization , [ 30 ] physical dependence , and psychological dependence , [ 31 ] which can cause distress. [ 32 ] [ 33 ] Nicotine withdrawal symptoms include depression , stress, anxiety, irritability , difficulty concentrating, and sleep disturbances. [ 2 ] Mild nicotine withdrawal symptoms are measurable in unrestricted smokers, who experience normal moods only as their blood nicotine levels peak, with each cigarette. [ 34 ] On quitting, withdrawal symptoms worsen sharply, then gradually improve to a normal state. [ 34 ]
Nicotine use as a tool for quitting smoking has a good safety history. [ 35 ] Animal studies suggest that nicotine may adversely affect cognitive development in adolescence, but the relevance of these findings to human brain development is disputed. [ 36 ] [ 26 ] At low amounts, it has a mild analgesic effect. [ 37 ] According to the International Agency for Research on Cancer , "nicotine is not generally considered to be a carcinogen". [ 38 ] [ 39 ] The Surgeon General of the United States indicates that evidence is inadequate to infer the presence or absence of a causal relationship between exposure to nicotine and risk for cancer. [ 40 ] Nicotine has been shown to produce birth defects in humans and is considered a teratogen . [ 41 ] [ 42 ] The median lethal dose of nicotine in humans is unknown. [ 43 ] High doses are known to cause nicotine poisoning , organ failure, and death through paralysis of respiratory muscles, [ 40 ] [ 44 ] though serious or fatal overdoses are rare. [ 45 ]
The primary therapeutic use of nicotine is treating nicotine dependence to eliminate smoking and the damage it does to health. Controlled levels of nicotine are given to patients through gums , dermal patches , lozenges, inhalers, or nasal sprays to wean them off their dependence. A 2018 Cochrane Collaboration review found high-quality evidence that all current forms of nicotine replacement therapy (gum, patch, lozenges, inhaler, and nasal spray) increase the chances of successfully quitting smoking by 50–60% , regardless of setting. [ 46 ]
Combining nicotine patch use with a faster acting nicotine replacement, like gum or spray, improves the odds of treatment success. [ 47 ]
In contrast to recreational nicotine products, which have been designed to maximize the likelihood of addiction, nicotine replacement products (NRTs) are designed to minimize addictiveness. [ 40 ] : 112 The more quickly a dose of nicotine is delivered and absorbed, the higher the addiction risk. [ 32 ]
Nicotine has been used as an insecticide since at least 1690, in the form of tobacco extracts or as pure nicotine sulphate [ 18 ] [ 48 ] [ 49 ] (although other components of tobacco also seem to have pesticide effects). [ 50 ] It acts on the nicotinic acetylcholine receptor , and gave the receptor its name. Nicotine is in IRAC group 4B. Nicotine insecticides have been banned in the US since 2014, [ 51 ] including use on organic crops, [ 52 ] and caution is recommended for small gardeners. [ 53 ] Nicotine pesticides have been banned in the EU since 2009. [ 54 ] Foods are imported from countries in which nicotine pesticides are allowed, such as China, but foods may not exceed maximum nicotine levels. [ 54 ] [ 55 ] Neonicotinoids , such as imidacloprid , which are derived from and structurally similar to nicotine, are widely used as agricultural and veterinary pesticides as of 2016. [ 56 ] [ 48 ]
Nicotine-containing products are sometimes used for the performance-enhancing effects of nicotine on cognition. [ 57 ] A 2010 meta-analysis of 41 double-blind , placebo -controlled studies concluded that nicotine or smoking had significant positive effects on aspects of fine motor abilities, alerting and orienting attention, and episodic and working memory. [ 58 ] A 2015 review noted that stimulation of the α4β2 nicotinic receptor is responsible for certain improvements in attentional performance; [ 59 ] among the nicotinic receptor subtypes, nicotine has the highest binding affinity at the α4β2 receptor (k i =1 nM ), which is also the biological target that mediates nicotine's addictive properties. [ 60 ] Nicotine has potential beneficial effects, but it also has paradoxical effects , which may be due to the inverted U-shape of the dose-response curve or pharmacokinetic features. [ 61 ]
Nicotine is used as a recreational drug . [ 62 ] It is widely used, highly addictive and hard to discontinue. [ 21 ] Nicotine is often used compulsively , [ 63 ] and dependence can develop within days. [ 63 ] [ 64 ] Recreational drug users commonly use nicotine for its mood-altering effects. [ 32 ] Recreational nicotine products include chewing tobacco , cigars , [ 65 ] cigarettes , [ 65 ] e-cigarettes , [ 66 ] snuff , pipe tobacco , [ 65 ] snus , and nicotine pouches .
Alcohol infused with nicotine is called nicotini . [ 67 ]
Nicotine use for tobacco cessation has few contraindications. [ 68 ]
It is not known whether nicotine replacement therapy is effective for smoking cessation in adolescents, as of 2014. [ 69 ] It is therefore not recommended to adolescents. [ 70 ] It is not safe to use nicotine during pregnancy or breastfeeding, although it is safer than smoking. The desirability of NRT use in pregnancy is therefore debated. [ 71 ] [ 72 ] [ 73 ]
Randomized trials and observational studies of nicotine replacement therapy in cardiovascular patients show no increase in adverse cardiovascular events compared to those treated with placebo. [ 74 ] Using nicotine products during cancer treatment may be contraindicated, as nicotine may promote tumour growth, but temporary use of NRTs to quit smoking may be advised for harm reduction . [ 75 ]
Nicotine gum is contraindicated in individuals with temporomandibular joint disease . [ 76 ] People with chronic nasal disorders and severe reactive airway disease require additional precautions when using nicotine nasal sprays. [ 70 ] Nicotine in any form is contraindicated in individuals with a known hypersensitivity to nicotine. [ 76 ] [ 70 ]
Nicotine is classified as a poison, [ 78 ] [ 79 ] and it is "extremely hazardous". [ 80 ] However, at doses typically used by consumers, it presents little if any hazard to the user. [ 81 ] [ 82 ] [ 83 ] A 2018 Cochrane Collaboration review lists nine main adverse events related to nicotine replacement therapy: headache , dizziness , lightheadedness , nausea , vomiting , gastrointestinal symptoms, insomnia , abnormal dreams , non- ischemic palpitations and chest pain, skin reactions, oral/nasal reactions, and hiccups . [ 84 ] Many of these were also common in the placebo group without nicotine. [ 84 ] Palpitations and chest pain were deemed "rare" and there was no evidence of an increased number of serious cardiac problems compared to the placebo group, even in people with established cardiac disease. [ 46 ] The common side effects from nicotine exposure are listed in the table below. Serious adverse events due to the use of nicotine replacement therapy are extremely rare. [ 46 ] At low amounts, it has a mild analgesic effect. [ 37 ] However, at sufficiently high doses, nicotine may result in nausea, vomiting, diarrhea , salivation , bradycardia , and possibly seizures , hypoventilation , and death. [ 85 ]
Nicotine reduces the amount of rapid eye movement (REM) sleep, slow-wave sleep (SWS), and total sleep time in healthy nonsmokers given nicotine via a transdermal patch , and the reduction is dose-dependent . [ 89 ] Acute nicotine intoxication has been found to significantly reduce total sleep time and increase REM latency, sleep onset latency , and non-rapid eye movement (NREM) stage 2 sleep time. [ 89 ] [ 90 ] Depressive non-smokers experience mood and sleep improvements under nicotine administration; however, subsequent nicotine withdrawal has a negative effect on both mood and sleep. [ 91 ]
Nicotine exerts several significant effects on the cardiovascular system . Primarily, it stimulates the sympathetic nervous system , leading to the release of catecholamines . This activation results in an increase in heart rate and blood pressure , as well as enhanced myocardial contractility , which raises the workload on the heart. Additionally, nicotine causes systemic vasoconstriction , including constriction of coronary arteries, which can reduce blood flow to the heart. Long-term exposure to nicotine may impair endothelial function, potentially contributing to atherosclerosis . Furthermore, nicotine has been associated with the development of cardiac arrhythmias , particularly in individuals who already have underlying heart disease. [ 92 ]
The effects of nicotine can be differentiated between short-term and long-term use. Short-term nicotine use, such as that associated with nicotine replacement therapy (NRT) for smoking cessation, appears to pose little cardiovascular risk, even for patients with known cardiovascular conditions. In contrast, longer-term nicotine use may not accelerate atherosclerosis but could contribute to acute cardiovascular events in those with pre-existing cardiovascular disease. Many severe cardiovascular effects traditionally associated with smoking may not be solely attributable to nicotine itself. Cigarette smoke contains numerous other potentially cardiotoxic substances, including carbon monoxide and oxidant gases. [ 92 ]
A 2016 review of the cardiovascular toxicity of nicotine concluded, "Based on current knowledge, we believe that the cardiovascular risks of nicotine from e-cigarette use in people without cardiovascular disease are quite low. We have concerns that nicotine from e-cigarettes could pose some risk for users with cardiovascular disease." [ 92 ]
A 2018 Cochrane review found that, in rare cases, nicotine replacement therapy can cause non- ischemic chest pain (i.e., chest pain that is unrelated to a heart attack ) and heart palpitations , but does not increase the incidence of serious cardiac adverse events (i.e., myocardial infarction, stroke , and cardiac death ) relative to controls. [ 46 ]
In the short term, nicotine causes a transient increase in blood pressure . Long term, epidemiological studies generally show increased blood pressure and hypertension among nicotine users. [ 92 ]
Nicotine is highly addictive but paradoxically has quite weak reinforcing property compared to other drugs of abuse in various animals. [ 20 ] [ 21 ] [ 95 ] [ 96 ] Its addictiveness depends on how it is administered and also depends upon form in which nicotine is used. [ 24 ] Animal research suggests that monoamine oxidase inhibitors , acetaldehyde [ 96 ] [ 97 ] and other constituents in tobacco smoke may enhance its addictiveness. [ 26 ] [ 27 ] Nicotine dependence involves aspects of both psychological dependence and physical dependence , since discontinuation of extended use has been shown to produce both affective (e.g., anxiety, irritability, craving, anhedonia ) and somatic (mild motor dysfunctions such as tremor ) withdrawal symptoms. [ 2 ] Withdrawal symptoms peak in one to three days [ 98 ] and can persist for several weeks. [ 99 ] Even though other drugs of dependence can have withdrawal states lasting 6 months or longer, this does not appear to occur with cigarette withdrawal. [ 100 ]
Normal between-cigarettes discontinuation, in unrestricted smokers, causes mild but measurable nicotine withdrawal symptoms. [ 34 ] These include mildly worse mood, stress, anxiety, cognition, and sleep, all of which briefly return to normal with the next cigarette. [ 34 ] Smokers have a worse mood than they typically would have if they were not nicotine-dependent; they experience normal moods only immediately after smoking. [ 34 ] Nicotine dependence is associated with poor sleep quality and shorter sleep duration among smokers. [ 101 ] [ 102 ]
In dependent smokers, withdrawal causes impairments in memory and attention, and smoking during withdrawal returns these cognitive abilities to pre-withdrawal levels. [ 103 ] The temporarily increased cognitive levels of smokers after inhaling smoke are offset by periods of cognitive decline during nicotine withdrawal. [ 34 ] Therefore, the overall daily cognitive levels of smokers and non-smokers are roughly similar. [ 34 ]
Nicotine activates the mesolimbic pathway and induces long-term ΔFosB expression (i.e., produces phosphorylated ΔFosB isoforms ) in the nucleus accumbens when inhaled or injected frequently or at high doses, but not necessarily when ingested. [ 104 ] [ 105 ] [ 106 ] Consequently, high daily exposure (possibly excluding oral route ) to nicotine can cause ΔFosB overexpression in the nucleus accumbens, resulting in nicotine addiction. [ 104 ] [ 105 ]
Contrary to popular belief , nicotine itself does not cause cancer in humans, [ 39 ] [ 107 ] although it is unclear whether it functions as a tumor promoter as of 2012 [update] . [ 108 ] A 2018 report by the US National Academies of Sciences, Engineering, and Medicine concludes, "[w]hile it is biologically plausible that nicotine can act as a tumor promoter, the existing body of evidence indicates this is unlikely to translate into increased risk of human cancer." [ 109 ]
Although nicotine is classified as a non-carcinogenic substance, it can still promote tumor growth and metastasis. It induces several processes that contribute to cancer progression, including cell cycle progression, epithelial-to-mesenchymal transition , migration , invasion, angiogenesis , and evasion of apoptosis . [ 110 ] These effects are primarily mediated through nicotinic acetylcholine receptors (nAChRs), particularly the α7 subtype , and to a lesser extent, β-adrenergic receptors (β-ARs). Activation of these receptors triggers several signaling cascades crucial in cancer biology, notably the MAPK/ERK pathway , PI3K/AKT pathway , and JAK-STAT signaling . [ 110 ]
Nicotine promotes lung cancer development by enhancing proliferation, angiogenesis, migration, invasion, and epithelial–mesenchymal transition (EMT) via nAChRs, which are present in lung cancer cells. [ 111 ] Additionally, nicotine-induced EMT contributes to drug resistance in cancer cells. [ 112 ]
Nicotine in tobacco can form carcinogenic tobacco-specific nitrosamines through a nitrosation reaction. This occurs mostly in the curing and processing of tobacco. However, nicotine in the mouth and stomach can react to form N-nitrosonornicotine , [ 113 ] a known type 1 carcinogen, [ 114 ] suggesting that consumption of non-tobacco forms of nicotine may still play a role in carcinogenesis. [ 115 ]
Nicotine causes DNA damage in several types of human cells as judged by assays for genotoxicity such as the comet assay , cytokinesis-block micronucleus test and chromosome aberrations test. In humans, this damage can happen in primary parotid gland cells, [ 116 ] lymphocytes , [ 117 ] and respiratory tract cells. [ 118 ]
Nicotine has been shown to produce birth defects in some animal species, but not others; [ 42 ] consequently, it is considered to be a possible teratogen in humans. [ 42 ] In animal studies that resulted in birth defects, researchers found that nicotine negatively affects fetal brain development and pregnancy outcomes; [ 42 ] [ 40 ] the negative effects on early brain development are associated with abnormalities in brain metabolism and neurotransmitter system function. [ 119 ] Nicotine crosses the placenta and is found in the breast milk of mothers who smoke as well as mothers who inhale passive smoke . [ 120 ]
Nicotine exposure in utero is responsible for several complications of pregnancy and birth: pregnant women who smoke are at greater risk for both miscarriage and stillbirth and infants exposed to nicotine in utero tend to have lower birth weights . [ 121 ] A McMaster University research group observed in 2010 that rats exposed to nicotine in the womb (via parenteral infusion) later in life had conditions including type 2 diabetes , obesity , hypertension , neurobehavioral defects, respiratory dysfunction, and infertility . [ 122 ]
It is unlikely that a person would overdose on nicotine through smoking alone. The US Food and Drug Administration (FDA) stated in 2013 that there are no significant safety concerns associated with the use of more than one form of over-the-counter (OTC) nicotine replacement therapy at the same time, or using OTC NRT at the same time as another nicotine-containing product, like cigarettes. [ 123 ] The median lethal dose of nicotine in humans is unknown. [ 43 ] [ 28 ] Nevertheless, nicotine has a relatively high toxicity in comparison to many other alkaloids such as caffeine , which has an LD 50 of 127 mg/kg when administered to mice. [ 124 ] At sufficiently high doses, it is associated with nicotine poisoning, [ 40 ] which, while common in children (in whom poisonous and lethal levels occur at lower doses per kilogram of body weight [ 37 ] ) rarely results in significant morbidity or death. [ 42 ] The estimated lower dose limit for fatal outcomes is 500–1,000 mg of ingested nicotine for an adult (6.5–13 mg/kg). [ 26 ] [ 28 ]
The initial symptoms of a nicotine overdose typically include nausea , vomiting, diarrhea, hypersalivation , abdominal pain, tachycardia (rapid heart rate), hypertension (high blood pressure), tachypnea (rapid breathing), headache, dizziness, pallor (pale skin), auditory or visual disturbances, and perspiration, followed shortly after by marked bradycardia (slow heart rate), bradypnea (slow breathing), and hypotension (low blood pressure). [ 42 ] An increased respiratory rate (i.e., tachypnea ) is one of the primary signs of nicotine poisoning. [ 42 ] At sufficiently high doses, somnolence (sleepiness or drowsiness), confusion , syncope (loss of consciousness from fainting), shortness of breath , marked weakness , seizures , and coma may occur. [ 7 ] [ 42 ] Lethal nicotine poisoning rapidly produces seizures, and death – which may occur within minutes – is believed to be due to respiratory paralysis . [ 42 ]
Today nicotine is less commonly used in agricultural insecticides , which was a main source of poisoning. More recent cases of poisoning typically appear to be in the form of Green Tobacco Sickness (GTS), [ 42 ] accidental ingestion of tobacco or tobacco products , or ingestion of nicotine-containing plants. [ 125 ] [ 126 ] [ 127 ] People who harvest or cultivate tobacco may experience GTS, a type of nicotine poisoning caused by dermal exposure to wet tobacco leaves. This occurs most commonly in young, inexperienced tobacco harvesters who do not consume tobacco. [ 125 ] [ 128 ] People can be exposed to nicotine in the workplace by breathing it in, skin absorption, swallowing it, or eye contact. The Occupational Safety and Health Administration (OSHA) has set the legal limit ( permissible exposure limit ) for nicotine exposure in the workplace as 0.5 mg/m 3 skin exposure over an 8-hour workday. The US National Institute for Occupational Safety and Health (NIOSH) has set a recommended exposure limit (REL) of 0.5 mg/m 3 skin exposure over an 8-hour workday. At environmental levels of 5 mg/m 3 , nicotine is immediately dangerous to life and health . [ 129 ]
Nicotine and cigarette smoke both induce the expression of liver enzymes (e.g., certain cytochrome P450 proteins) which metabolize drugs, leading to the potential for alterations in drug metabolism . [ 76 ]
Nicotine acts as a receptor agonist at most nicotinic acetylcholine receptors (nAChRs), [ 12 ] [ 13 ] except at two nicotinic receptor subunits ( nAChRα9 and nAChRα10 ) where it acts as a receptor antagonist . [ 12 ] Such antagonism results in mild analgesia .
By binding to nicotinic acetylcholine receptors in the brain, nicotine elicits its psychoactive effects and increases the levels of several neurotransmitters in various brain structures – acting as a sort of "volume control". [ 130 ] [ 131 ] Nicotine has a higher affinity for nicotinic receptors in the brain than those in skeletal muscle , though at toxic doses it can induce contractions and respiratory paralysis. [ 132 ] Nicotine's selectivity is thought to be due to a particular amino acid difference on these receptor subtypes. [ 133 ] Nicotine is unusual in comparison to most drugs, as its profile changes from stimulant to sedative with increasing dosages , a phenomenon known as "Nesbitt's paradox" after the doctor who first described it in 1969. [ 134 ] [ 135 ] At very high doses it dampens neuronal activity . [ 136 ] Nicotine induces both behavioral stimulation and anxiety in animals. [ 7 ] Research into nicotine's most predominant metabolite, cotinine , suggests that some of nicotine's psychoactive effects are mediated by cotinine. [ 137 ]
Nicotine activates nicotinic receptors (particularly α4β2 nicotinic receptors , but also α5 nAChRs ) on neurons that innervate the ventral tegmental area and within the mesolimbic pathway where it appears to cause the release of dopamine . [ 138 ] [ 139 ] This nicotine-induced dopamine release occurs at least partially through activation of the cholinergic–dopaminergic reward link in the ventral tegmental area . [ 139 ] [ 140 ] Nicotine can modulate the firing rate of the ventral tegmental area neurons. [ 140 ] These actions are largely responsible for the strongly reinforcing effects of nicotine, which often occur in the absence of euphoria ; [ 138 ] however, mild euphoria from nicotine use can occur in some individuals. [ 138 ] Chronic nicotine use inhibits class I and II histone deacetylases in the striatum , where this effect plays a role in nicotine addiction. [ 141 ] [ 142 ]
Nicotine also activates the sympathetic nervous system , [ 143 ] acting via splanchnic nerves to the adrenal medulla, stimulating the release of epinephrine. Acetylcholine released by preganglionic sympathetic fibers of these nerves acts on nicotinic acetylcholine receptors, causing the release of epinephrine (and norepinephrine) into the bloodstream .
By binding to ganglion type nicotinic receptors in the adrenal medulla, nicotine increases flow of adrenaline (epinephrine), a stimulating hormone and neurotransmitter. By binding to the receptors, it causes cell depolarization and an influx of calcium through voltage-gated calcium channels. Calcium triggers the exocytosis of chromaffin granules and thus the release of epinephrine (and norepinephrine) into the bloodstream . The release of epinephrine (adrenaline) causes an increase in heart rate , blood pressure and respiration , as well as higher blood glucose levels. [ 144 ]
As nicotine enters the body, it is distributed quickly through the bloodstream and crosses the blood–brain barrier reaching the brain within 10–20 seconds after inhalation. [ 146 ] The elimination half-life of nicotine in the body is around two hours. [ 147 ] [ 148 ] Nicotine is primarily excreted in urine and urinary concentrations vary depending upon urine flow rate and urine pH . [ 7 ]
The amount of nicotine absorbed by the body from smoking can depend on many factors, including the types of tobacco, whether the smoke is inhaled, and whether a filter is used. However, it has been found that the nicotine yield of individual products has only a small effect (4.4%) on the blood concentration of nicotine, [ 149 ] suggesting "the assumed health advantage of switching to lower-tar and lower-nicotine cigarettes may be largely offset by the tendency of smokers to compensate by increasing inhalation".
Nicotine has a half-life of 1–2 hours. Cotinine is an active metabolite of nicotine that remains in the blood with a half-life of 18–20 hours, making it easier to analyze. [ 150 ]
Nicotine is metabolized in the liver by cytochrome P450 enzymes (mostly CYP2A6 , and also by CYP2B6 ) and FMO3 , which selectively metabolizes ( S )-nicotine. A major metabolite is cotinine . Other primary metabolites include nicotine N -oxide, nornicotine , nicotine isomethonium ion, 2-hydroxynicotine and nicotine glucuronide. [ 151 ] Under some conditions, other substances may be formed such as myosmine . [ 152 ] [ 153 ]
Glucuronidation and oxidative metabolism of nicotine to cotinine are both inhibited by menthol , an additive to mentholated cigarettes , thus increasing the half-life of nicotine in vivo . [ 154 ]
Nicotine decreases hunger and as a consequence food consumption, alongside increasing energy expenditure . [ 155 ] [ 156 ] The majority of research shows that nicotine reduces body weight, but some researchers have found that nicotine may result in weight gain under specific types of eating habits in animal models. [ 156 ] Nicotine effect on weight appears to result from nicotine's stimulation of α3β4 nAChR receptors located in the POMC neurons in the arcuate nucleus and subsequently the melanocortin system , especially the melanocortin-4 receptors on second-order neurons in the paraventricular nucleus of the hypothalamus, thus modulating feeding inhibition. [ 140 ] [ 156 ] POMC neurons are a precursor of the melanocortin system, a critical regulator of body weight and peripheral tissue such as skin and hair. [ 156 ]
Nicotine is a hygroscopic , colorless [ 80 ] to yellow-brown, oily liquid, that is readily soluble in alcohol, ether or light petroleum. It is miscible with water in its neutral amine base form between 60 °C and 210 °C. It is a dibasic nitrogenous base , having K b1 =1×10 −6 , K b2 =1×10 −11 . [ 158 ] It readily forms ammonium salts with acids that are usually solid and water-soluble. Its flash point is 95 °C and its auto-ignition temperature is 244 °C. [ 159 ] Nicotine is readily volatile ( vapor pressure 5.5 Pa at 25 °C) [ 158 ] On exposure to ultraviolet light or various oxidizing agents, nicotine is converted to nicotine oxide, nicotinic acid (niacin, a B3 vitamer), and methylamine . [ 160 ]
Nicotine is chiral and hence optically active , having two enantiomeric forms. The naturally occurring form of nicotine is levorotatory with a specific rotation of [α] D =–166.4° ((−)-nicotine). The dextrorotatory form, (+)-nicotine is physiologically less active than (−)-nicotine. (−)-nicotine is more toxic than (+)-nicotine. [ 161 ] The salts of (−)-nicotine are usually dextrorotatory; this conversion between levorotatory and dextrorotatory upon protonation is common among alkaloids. [ 160 ] The hydrochloride and sulfate salts become optically inactive if heated in a closed vessel above 180 °C. [ 160 ] Anabasine is a structural isomer of nicotine, as both compounds have the molecular formula C 10 H 14 N 2 .
Nicotine that is found in natural tobacco is primarily (99%) the S-enantiomer. [ 162 ] Conversely, the most common chemistry synthetic methods for generating nicotine yields a product that is approximately equal proportions of the S- and R-enantiomers. [ 163 ] This suggests that tobacco-derived and synthetic nicotine can be determined by measuring the ratio of the two different enantiomers, although means exist for adjusting the relative levels of the enantiomers or performing a synthesis that only leads to the S-enantiomer. There is limited data on the relative physiological effects of these two enantiomers, especially in people. However, the studies to date indicate that (S)-nicotine is more potent than (R)-nicotine and (S)-nicotine causes stronger sensations or irritation than (R)-nicotine. Studies have not been adequate to determine the relative addictiveness of the two enantiomers in people.
Pod mod electronic cigarettes use nicotine in the form of a protonated nicotine , rather than free-base nicotine found in earlier generations. [ 164 ]
The first laboratory preparation of nicotine (as its racemate ) was described in 1904. [ 165 ] The starting material was an N-substituted pyrrole derivative, which was heated to convert it by a [1,5] sigmatropic shift to the isomer with a carbon bond between the pyrrole and pyridine rings, followed by methylation and selective reduction of the pyrrole ring using tin and hydrochloric acid. [ 165 ] [ 166 ] Many other syntheses of nicotine, in both racemic and chiral forms have since been published. [ 167 ]
The biosynthetic pathway of nicotine involves a coupling reaction between the two cyclic structures that comprise nicotine. Metabolic studies show that the pyridine ring of nicotine is derived from nicotinic acid the pyrrolidine is derived from N -methyl-Δ 1 -pyrrollidium cation. [ 168 ] [ 169 ] Biosynthesis of the two component structures proceeds via two independent syntheses, the NAD pathway for nicotinic acid and the tropane pathway for N -methyl-Δ 1 -pyrrollidium cation.
The NAD pathway in the genus Nicotiana begins with the oxidation of aspartic acid into α-amino succinate by aspartate oxidase (AO). This is followed by a condensation with glyceraldehyde-3-phosphate and a cyclization catalyzed by quinolinate synthase (QS) to give quinolinic acid . Quinolinic acid then reacts with phosphoribosyl pyrophosphate catalyzed by quinolinic acid phosphoribosyl transferase (QPT) to form nicotinic acid mononucleotide (NaMN). The reaction now proceeds via the NAD salvage cycle to produce nicotinic acid via the conversion of nicotinamide by the enzyme nicotinamidase . [ citation needed ]
The N -methyl-Δ 1 -pyrrollidium cation used in the synthesis of nicotine is an intermediate in the synthesis of tropane-derived alkaloids. Biosynthesis begins with decarboxylation of ornithine by ornithine decarboxylase (ODC) to produce putrescine . Putrescine is then converted into N -methyl putrescine via methylation by SAM catalyzed by putrescine N -methyltransferase (PMT). N -methyl putrescine then undergoes deamination into 4-methylaminobutanal by the N -methyl putrescine oxidase (MPO) enzyme, 4-methylaminobutanal then spontaneously cyclize into N -methyl-Δ 1 -pyrrollidium cation. [ citation needed ]
The final step in the synthesis of nicotine is the coupling between N -methyl-Δ 1 -pyrrollidium cation and nicotinic acid. Although studies conclude some form of coupling between the two component structures, the definite process and mechanism remains undetermined. The current agreed theory involves the conversion of nicotinic acid into 2,5-dihydropyridine through 3,6-dihydronicotinic acid. The 2,5-dihydropyridine intermediate would then react with N -methyl-Δ 1 -pyrrollidium cation to form enantiomerically pure (−)-nicotine. [ 170 ]
Nicotine can be quantified in blood, plasma, or urine to confirm a diagnosis of poisoning or to facilitate a medicolegal death investigation. Urinary or salivary cotinine concentrations are frequently measured for the purposes of pre-employment and health insurance medical screening programs. Careful interpretation of results is important, since passive exposure to cigarette smoke can result in significant accumulation of nicotine, followed by the appearance of its metabolites in various body fluids. [ 171 ] [ 172 ] Nicotine use is not regulated in competitive sports programs. [ 173 ]
Methods for measuring the two enantiomers are straightforward and include normal-phase liquid chromatography, [ 162 ] liquid chromatography with a chiral column. [ 174 ] However, since methods can be used to alter the two enantiomers, it may not be possible to distinguish tobacco-derived from synthetic nicotine simply by measuring the levels of the two enantiomers. A new approach uses hydrogen and deuterium nuclear magnetic resonance to distinguish tobacco-derived and synthetic nicotine based on differences the substrates used in the natural synthetic pathway performed in the tobacco plant and the substrates most used in synthesis. [ 175 ] Another approach measures the carbon-14 content which also differs between natural and laboratory-based tobacco. [ 176 ] These methods remain to be fully evaluated and validated using a wide range of samples.
Analogues and derivatives of nicotine are known. [ 177 ] [ 178 ] [ 179 ] [ 180 ] [ 181 ] Examples include altinicline , anabasine , anatabine , altinicline , arecoline , 6-chloronicotine , cotinine , cytisine , dianicline , epibatidine , levamisole , RJR-2429 , TC-1698 , UB-165 , and varenicline , among others. [ 182 ] [ 177 ]
Nicotine is a secondary metabolite produced in a variety of plants in the family Solanaceae , most notably in tobacco Nicotiana tabacum , where it can be found at high concentrations of 0.5 to 7.5%. [ 183 ] Nicotine is also found in the leaves of other tobacco species, such as Nicotiana rustica (in amounts of 2–14%). Nicotine production is strongly induced in response to wounding as part of a jasmonate -dependent reaction. [ 184 ] Specialist insects on tobacco, such as the tobacco hornworm ( Manduca sexta ), have a number of adaptations to the detoxification and even adaptive re-purposing of nicotine. [ 185 ] Nicotine is also found at low concentrations in the nectar of tobacco plants, where it may promote outcrossing by affecting the behavior of hummingbird pollinators. [ 186 ]
Nicotine occurs in smaller amounts (varying from 2–7 μg / kg , or 20–70 millionths of a percent wet weight [ 16 ] ) in other Solanaceaeous plants, including some crop species such as potatoes , tomatoes , eggplant , and peppers , [ 16 ] [ 187 ] as well as non-crop species such as Duboisia hopwoodii . [ 158 ] The amounts of nicotine in tomatoes lowers substantially as the fruit ripens. [ 16 ] A 1999 report found "In some papers it is suggested that the contribution of dietary nicotine intake is significant when compared with exposure to ETS [environmental tobacco smoke] or by active smoking of small numbers of cigarettes. Others consider the dietary intake to be negligible unless inordinately large amounts of specific vegetables are consumed." [ 16 ] The amount of nicotine eaten per day is roughly around 1.4 and 2.25 μg /day at the 95th percentile. [ 16 ] These numbers may be low due to insufficient food intake data. [ 16 ] The concentrations of nicotine in vegetables are difficult to measure accurately, since they are very low (parts per billion range). [ 188 ] Pure nicotine tastes "terrible". [ 80 ]
Nicotine was originally isolated from the tobacco plant in 1828 by chemists Wilhelm Heinrich Posselt and Karl Ludwig Reimann from Germany , who believed it was a poison. [ 189 ] [ 190 ] Its chemical empirical formula was described by Melsens in 1843, [ 191 ] its structure was discovered by Adolf Pinner and Richard Wolffenstein in 1893, [ 192 ] [ 193 ] [ 194 ] [ clarification needed ] and it was first synthesized by Amé Pictet and A. Rotschy in 1904. [ 165 ] [ 195 ]
Nicotine is named after the tobacco plant Nicotiana tabacum , which in turn is named after the French ambassador in Portugal , Jean Nicot de Villemain , who sent tobacco and seeds to Paris in 1560, presented to the French King, [ 196 ] and who promoted their medicinal use. Smoking was believed to protect against illness, particularly the plague. [ 196 ]
Tobacco was introduced to Europe in 1559, and by the late 17th century, it was used not only for smoking but also as an insecticide . After World War II , over 2,500 tons of nicotine insecticide were used worldwide, but by the 1980s the use of nicotine insecticide had declined below 200 tons. This was due to the availability of other insecticides that are cheaper and less harmful to mammals . [ 18 ]
The nicotine content of popular American-brand cigarettes has increased over time, and one study found that there was an average increase of 1.78% per year between the years of 1998 and 2005. [ 197 ]
Although methods of production of synthetic nicotine have existed for decades, [ 198 ] it was believed that the cost of making nicotine by laboratory synthesis was cost prohibitive compared to extracting nicotine from tobacco. [ 199 ] However, recently synthetic nicotine started to be found in different brands of e-cigarettes and oral pouches and marketed as "tobacco-free." [ 200 ]
The US FDA is tasked with reviewing tobacco products such as e-cigarettes and determining which can be authorized for sale. In response to the likelihood that FDA would not authorize many e-cigarettes to be marketed, e-cigarette companies began marketing products that they claimed to contain nicotine that were not made or derived from tobacco, but contained synthetic nicotine instead, and thus, would be outside FDA's tobacco regulatory authority. [ 201 ] Similarly, nicotine pouches that claimed to contain non-tobacco (synthetic) nicotine were also introduced. The cost of synthetic nicotine has decreased as the market for the product increased. In March 2022, the U.S. Congress passed a law (the Consolidated Appropriations Act, 2022 ) that expanded FDA's tobacco regulatory authority to include tobacco products containing nicotine from any source, thereby including products made with synthetic nicotine.
In the United States, nicotine products and nicotine replacement therapy products like Nicotrol are only available to people 18 and above; proof of age is required; not for sale in vending machine or from any source where proof of age cannot be verified. As of 2019, the minimum age to purchase tobacco in the US is 21 at the federal level. [ 202 ]
In the European Union, the minimum age to purchase nicotine products is 18. However, there is no minimum age requirement to use tobacco or nicotine products. [ 203 ]
In the United Kingdom, the Tobacco and Related Products Regulations 2016 implemented the European directive 2014/40/EU, amended by Tobacco Products and Nicotine Inhaling Products (Amendment etc.) (EU Exit) Regulations 2019 and the Tobacco Products and Nicotine Inhaling Products (Amendment) (EU Exit) Regulations 2020. Additionally other regulations limit advertising, sale and display of tobacco products and other products containing nicotine for human consumption. The Sunak government proposed banning disposable vapes to limit their appeal and affordability for children and to reduce the amount of waste generated.
In some anti-smoking literature, the harm that tobacco smoking and nicotine addiction does is personified as Nick O'Teen , represented as a humanoid with some aspect of a cigarette or cigarette butt about him or his clothes and hat. [ 204 ] Nick O'Teen was a villain that was created for the Health Education Council . The character was featured in three animated anti-smoking public service announcements in which he tries to get kids addicted to cigarettes before being foiled by the DC Comics character Superman . [ 204 ]
Nicotine was often compared to caffeine in advertisements in the 1980s by the tobacco industry, and later in the 2010s by the electronic cigarettes industry, in an effort to reduce the stigmatization and the public perception of the risks associated with nicotine use. [ 205 ]
While acute/initial nicotine intake causes activation of neuronal nicotinic receptors, chronic low doses of nicotine use leads to desensitization of those receptors (due to the development of tolerance) and results in an antidepressant effect, with early research showing low dose nicotine patches could be an effective treatment of major depressive disorder in non-smokers. [ 206 ]
Though tobacco smoking is associated with an increased risk of Alzheimer's disease , [ 207 ] there is evidence that nicotine itself has the potential to prevent and treat Alzheimer's disease. [ 208 ]
Smoking is associated with a decreased risk of Parkinson's disease ; however, it is unknown whether this is due to people with healthier brain dopaminergic reward centers (the area of the brain affected by Parkinson's) being more likely to enjoy smoking and thus pick up the habit, nicotine directly acting as a neuroprotective agent , or other compounds in cigarette smoke acting as neuroprotective agents. [ 209 ]
Nicotine may partly attenuate sensory gating and attentional deficits associated with schizophrenia . Short-term use of transdermal nicotine was found to improve subjects’ reaction time and alertness in given tasks. Nicotine was not found to improve negative , positive , or other cognitive symptoms of schizophrenia. [ 210 ]
Immune cells of both the innate immune system and adaptive immune systems frequently express the α 2 , α 5 , α 6 , α 7 , α 9 , and α 10 subunits of nicotinic acetylcholine receptors . [ 211 ] Evidence suggests that nicotinic receptors which contain these subunits are involved in the regulation of immune function . [ 211 ]
A photoactivatable form of nicotine, which releases nicotine when exposed to ultraviolet light with certain conditions, has been developed for studying nicotinic acetylcholine receptors in brain tissue. [ 212 ]
Several in vitro studies have investigated the potential effects of nicotine on a range of oral cells. A recent systematic review concluded that nicotine was unlikely to be cytotoxic to oral cells in vitro in most physiological conditions but further research is needed. [ 213 ] Understanding the potential role of nicotine in oral health has become increasingly important given the recent introduction of novel nicotine products and their potential role in helping smokers quit. [ 214 ] | https://en.wikipedia.org/wiki/Nicotine |
Niello / n iː ˈ ɛ l oʊ / [ 1 ] [ 2 ] is a black mixture, usually of sulphur , copper , silver , and lead , [ 3 ] used as an inlay on engraved or etched metal, especially silver. It is added as a powder or paste, then fired until it melts or at least softens, and flows or is pushed into engraved lines in the metal. It hardens and blackens when cool, and the niello on the flat surface is polished off to show the filled lines in black, contrasting with the polished metal around it. [ 4 ] It may also be used with other metalworking techniques to cover larger areas, as seen in the sky in the diptych illustrated here. The metal where niello is to be placed is often roughened to provide a key . In many cases, especially in objects that have been buried underground, where the niello is now lost, the roughened surface indicates that it was once there.
Niello was used on a variety of objects including sword hilts, chalices, plates, horns, adornment for horses, jewellery such as bracelets, rings, pendants, and small fittings such as strap-ends, purse-bars, buttons, belt buckles and the like. [ 5 ] It was also used to fill in the letters in inscriptions engraved on metal. Periods when engraving filled in with niello has been used to make full images with figures have been relatively few, but the practice has produced some significant achievements. In ornament, niello came to have competition from enamel , with far wider colour possibilities, which eventually displaced it in most of Europe.
The name derives from the Latin nigellum for the substance, [ 6 ] or from nigello or neelo , the medieval Latin word for "black". [ 7 ] Though historically most common in Europe, niello has also been produced in many parts of Asia and the Near East . [ 8 ]
There are a number of claimed uses of niello from the Mediterranean Bronze Age , all of which have been the subjects of disputes as to the actual composition of the materials used, that have not been conclusively settled, despite some decades of debate. The earliest claimed use of niello appears in late Bronze Age Byblos in Syria, around 1800 BC, in inscriptions in hieroglyphs on scimitars . [ 9 ] In Ancient Egypt it appears a little later, in the tomb of Queen Ahhotep II , who lived about 1550 BC, on a dagger decorated with a lion chasing a calf in a rocky landscape in a style that shows Greek influence, or at least similarity to the roughly contemporary daggers from Mycenae , and perhaps other objects in the tomb. [ 10 ]
At about the same time of c.1550 BC it appears on several bronze daggers from shaft grave royal tombs at Mycenae (in Grave Circle A and Grave Circle B ), especially in long thin scenes running along the centre of the blade. These show the violence typical of the art of Mycenaean Greece , as well as a sophistication in both technique and figurative imagery that is startlingly original in a Greek context. There are a number of scenes of lions hunting and being hunted, attacking men and being attacked; most are now in the National Archaeological Museum, Athens . [ 11 ]
These are in a mixed-media technique often called metalmalerei (German: "painting in metal"), which involves using gold and silver inlays or applied foils with black niello and the bronze, which would originally have been brightly polished. As well as providing a black colour, the niello was also used as the adhesive to hold the thin gold and silver foils in place. [ 12 ]
Byblos in Syria, where niello first appears, was something of an Egyptian outpost on the Levant , and many scholars think that it was highly-skilled metalworkers from Syria who introduced the technique to both Egypt and Mycenaean Greece. The iconography can most easily be explained by some combination of influence from the broader traditions of Mesopotamian art where somewhat comparable imagery had been produced for over a thousand years in cylinder seals and the like, and some (such as the physique of the figures) from Minoan art , although no early niello has been found on Crete . [ 13 ]
A decorated metal cup, the " Enkomi Cup" from Cyprus has also been claimed to use niello decoration. However, controversy has continued since the 1960s as to whether the material used on all these pieces actually is niello, and a succession of increasingly sophisticated scientific tests have failed to provide evidence of the presence of the sulphurous compounds which define niello. [ 14 ] It has been suggested that these artefacts, or at least the daggers, use in fact a technique of patinated metal that may be the same as the Corinthian bronze known from ancient literature, and is similar to the Japanese Shakudō . [ 15 ]
The Sassanid Persians enjoyed dining and drinking together, a social event that is visible through ceramic, glass, and silver vessels. Elite circles handled silver cups, plates, and bowls on which artisans hammered and chased intricate designs. [ 16 ]
Sasanian niello is a decorative technique used in metalworking during the Sasanian Empire (224-651 AD). This technique was particularly popular in Sasanian silverwork, adorning objects such as plates, bowls, ewers, and jewelry. The designs often featured scenes of hunting, courtly life, animals, and mythical creatures. [ 17 ]
Sasanian niello is notable for its fine craftsmanship and the skillful use of negative space to create detailed imagery. But in general, Niello was rarely used in Sasanian metalwork , which could use it inventively. The Metropolitan Museum of Art has Sasanian shallow bowls or dishes where in one case it forms the stripes on a tiger, [ 18 ] and in another the horns and hoofs of goats in relief, as well as parts of the king's weapons. This relief use of niello seems to be paralleled from this period in only one piece of Byzantine silver. [ 19 ]
A silver oval bowl decorated with tigers and grapevines, attributed to the Sasanian period of Iran (3rd-7th centuries CE) and held in the Metropolitan Museum of Art's Department of Ancient Near Eastern Art, was examined using non-invasive analytical techniques to identify the composition of the silver alloy and the niello inlay used in its decoration. The study revealed that the bowl is made of a silver-copper alloy containing approximately 3 wt.% copper. The niello inlays were found to consist solely of silver sulfide ( acanthite ). This composition closely resembles that of early Roman niello inlays, suggesting a possible technological link between Roman and Sasanian metalworkers during this period. [ 20 ]
Niello is then hardly found until the Roman period; or perhaps it first appears around this point. [ 21 ] Pliny the Elder (AD 23–79) describes the technique as Egyptian, and remarks the oddness of decorating silver in this way. [ 22 ] Some of the earliest uses, from 1–300 AD, seem to be small statuettes and brooches of big cats, where niello is used for the stripes of tigers and the spots on panthers ; these were very common in Roman art, as creatures of Bacchus . The animal repertoire of Roman Britain was somewhat different, and provides brooches with niello stripes on a hare and a cat. [ 23 ] From about the 4th century, it was used for ornamental details such as borders and for inscriptions in late Roman silver, such as a dish and bowl in the Mildenhall Treasure and pieces in the Hoxne Hoard , including Christian church plate. It was often used on spoons, which were often inscribed with the owner's name, or later crosses. This type of use continued in Byzantine metalwork, from where it passed to Russia.
It is very common in Anglo-Saxon metalwork, with examples including the Tassilo Chalice , Strickland Brooch , and the Fuller Brooch , [ 8 ] generally forming the background for motifs carried in the metal, but also used for rather crude geometric decoration of spots, triangles and stripes on small relatively everyday fittings such as strap-ends in base metal. There is similar use in Celtic , Viking, and other types of Early Medieval jewellery and metalwork, especially in northern Europe. [ 24 ] Similar uses continued in the traditional styles of jewellery of the Middle East until at least the 20th century. The Late Roman buckle from Gaul illustrated here shows a relatively high quality early example of this sort of decoration.
In Romanesque art colourful champlevé enamel largely replaced it, although it continued to be used for small highlights of ornament, and some high quality Mosan art began to use it for small figurative images as part of large pieces, very often applied as plaques. These began to exploit the possibilities of niello for carrying a precise graphic style. The back of the Ottonian Imperial Cross (1020s) has outline engravings of figures filled with niello, the black lines forming the figures on a gold background. Later Romanesque pieces began to use a more densely engraved style, where the figures are mostly carried by the polished metal, against a black background. Romanesque champlevé enamel was applied to a cheap copper or copper alloy form, which was a great advantage, but for some pieces the prestige of precious metal was desired, and a small number of nielloed silver pieces from c. 1175–1200 adopt the ornamental vocabulary developed in Limoges enamel . [ 25 ]
A group of high-quality pieces apparently originating in the Rhineland , which use both niello and enamel, include what may be the earliest reliquary with scenes of the murder and burial of Thomas Becket , probably from a few years after his death in 1170 ( The Cloisters ). Eight large nielloed plaques decorate the sides and roof, six with figures seen close-up at less than half-length, in a very different style from the cruder full-length figures in the many Limoges enamel equivalent reliquaries. [ 26 ]
Gothic art from the 13th century continued to develop this pictorial use of niello, which reached its high point in the Renaissance. [ 8 ] Niello continued to be widely used for simple ornament on small pieces, though at the top end goldsmiths were more likely to use black enamel to fill inscriptions on rings and the like. Niello was also used on plate armour , in this case over etched steel, as well as weapons.
Some Renaissance goldsmiths in Europe, such as Maso Finiguerra and Antonio del Pollaiuolo in Florence, decorated their works, usually in silver, by engraving the metal with a burin , after which they filled up the hollows produced by the burin with a black enamel-like compound made of silver, lead and sulphur. The resulting design, called a niello, was of much higher contrast and thus much more visible. Sometimes niello decoration was incidental to the objects, but some pieces such as paxes were effectively pictures in niello. A range of religious objects such as crucifixes and reliquaries might be decorated in this way, as well as secular objects such as knife handles, rings and other jewellery, and fittings such as buckles. It appears that niello-work was probably a specialist activity of some goldsmiths, not practiced by others, and most work came from Florence or Bologna . [ 27 ]
Niellists were important in the history of art because they had developed skills and techniques that transferred easily to engraving plates for printmaking on paper, and nearly all the earliest engravers were trained as goldsmiths, enabling the new art medium to develop very quickly. At least in Italy, some of the very earliest engraved prints were in fact made by treating a silver object intended for niello as a printing plate with ink, before the niello was added. These are known as "niello prints", or in the cautious words of modern curators, "printed from a plate engraved in the niello manner"; [ 28 ] in later centuries, after a collector's market grew up, many were forgeries. The genuine Renaissance prints were probably made mainly as a record of his work by the goldsmith, and perhaps as independent art objects. [ 29 ]
By the late 16th century relatively little use was made of niello, especially to create pictures, and a different type of mastic that could be used in much the same way for contrasts in decoration was devised, so European pictorial use was largely restricted to Russia, except for some watches, guns, instruments and the like. [ 8 ] Niello has continued to be used sometimes by Western jewellers.
During the 10th to 13th century AD, Kievan Rus craftsmen possessed a high degree of skill in jewellery making . John Tsetses , a 12th-century Byzantine writer, praised the work of Kievan Rus artisans and likened their work to the creations of Daedalus , the highly skilled craftsman of Greek mythology .
The Kievan Rus technique for niello application was first shaping silver or gold by repoussé work, embossing, and casting. They would raise objects in high relief and fill the background with niello using a mixture of red copper, lead, silver, potash, borax, sulphur which was liquefied and poured into concave surfaces before being fired in a furnace. The heat of the furnace would blacken the niello and make the other ornamentation stand out more vividly.
Nielloed items were mass-produced using moulds that still survive today and were traded with Greeks , the Byzantine Empire , and other peoples that traded along the trade route from the Varangians to the Greeks .
During the Mongol invasion from 1237 to 1240 AD, nearly all of Kievan Rus was overrun. Settlements and workshops were burned and razed and most of the craftsmen and artisans were killed. Afterwards, skill in niello and cloisonné enamel diminished greatly. The Ukrainian Museum of Historic Treasures, located in Kiev , has a large collection of nielloed items mostly recovered from tombs found throughout Ukraine . [ 30 ]
Later, Veliky Ustyug in North Russia, Tula and Moscow produced high quality pictorial niello pieces such as snuff boxes in contemporary styles such as Rococo and Neoclassicism in the late 18th and early 19th centuries; by then Russia was virtually the only part of Europe regularly using niello in fashionable styles.
In the early Islamic world silver, though continuing in use for vessels at the courts of princes, was much less widely used by the merely wealthy. Instead, vessels of the copper alloys bronze and brass included inlays of silver and gold in their often elaborate decoration, leaving less of a place for niello. Other black fillings were also used, and museum descriptions are often vague about the actual substances involved.
The famous " Baptistère de Saint Louis ", c. 1300, a Mamluk basin of engraved brass with gold, silver and niello inlay, which has been in France since at least 1440 ( Louis XIII of France and perhaps other kings were baptized in it; now Louvre ), is one example where niello is used. Here niello is the background to the figures and the arabesque ornament around them, and used to fill the lines in both.
It is used on the locking bars of some ivory boxes and caskets, and perhaps continued more widely in use on weapons, where it is certainly found in later centuries from which more material survives. It is common in the decoration of the scabbards and hilts of the large daggers called khanjali and qama traditionally carried by all males in the Caucasus region (whether Muslim or Christian). It was also used to decorate handguns when they came into use. Until modern times relatively simple niello was common on the jewellery of the Levant, used in much the same way as in medieval Europe.
Nielloware jewellery [ 31 ] and related items from Thailand were popular gifts from American soldiers taking "R&R" in Thailand to their girlfriends/wives back home from the 1930s to the 1970s. Most of it was completely handmade jewellery. [ citation needed ]
The technique is as follows: the artisan would carve a design into the silver, leaving the figure raised by carving out the "background". He would then use the niello inlay to fill in the "background". After being baked in an open fire, the alloy would harden. It would then be sanded smooth and buffed. Finally, a silver artisan would add minute details by hand. Filigree was often used for additional ornamentation. Nielloware is classified as only being black and silver coloured. Other coloured jewellery originating during this time uses a different technique and is not considered niello. [ citation needed ]
Many of the characters shown in nielloware are characters originally found in the Hindu legend Ramayana . The Thai version is called Ramakien. Important Thai cultural symbols were also frequently used. [ citation needed ]
Various slightly different recipes are found by modern scientific analysis, and historic accounts. In early periods, niello seems to have been made with a single sulphide, that of the main metal of the piece, even if it was gold (which would be difficult to handle). Copper sulphide niello has only been found on Roman pieces, and silver sulphide is used on silver. [ 32 ] Later a mixture of metals was used; Pliny gives a mixed sulphide recipe with silver and copper, but seems to have been some centuries ahead of his time, as such mixtures have not been identified by analysis on pre-medieval pieces. Most Byzantine and early medieval pieces analysed are silver-copper, while silver-copper-lead pieces appear from about the 11th century onwards. [ 33 ]
The Mappae clavicula of about the 9th century, Theophilus Presbyter (1070–1125) and Benvenuto Cellini (1500–1571) give detailed accounts, using silver-copper-lead mixtures with slightly different ratios of ingredients, Cellini using more lead. [ 34 ] Typical ingredients have been described as: "sulfur with several metallic ingredients and borax "; [ 6 ] "copper, silver, and lead, to which had been added sulphur while the metal was in fluid form ... [the design] was then brushed over with a solution of borax..." [ 35 ]
While some recipes talk of using furnaces and muffles to melt the niello, others just seem to use an open fire. The necessary temperatures vary with the mixture; overall silver-copper-lead mixtures are easier to use. All mixtures have the same black appearance after work is completed. [ 36 ] | https://en.wikipedia.org/wiki/Niello |
Niels Fabian Helge von Koch (25 January 1870 – 11 March 1924) was a Swedish mathematician who gave his name to the famous fractal known as the Koch snowflake , one of the earliest fractal curves to be described.
He was born to Swedish nobility . His grandfather, Nils Samuel von Koch (1801–1881), was the Chancellor of Justice . His father, Richert Vogt von Koch (1838–1913) was a Lieutenant-Colonel in the Life Guards of Horse of the Swedish Army . He was enrolled at the newly created Stockholm University College in 1887 (studying under Gösta Mittag-Leffler ), and at Uppsala University in 1888, where he also received his bachelor's degree ( filosofie kandidat ) since the non-governmental college in Stockholm had not yet received the rights to issue degrees. He received his PhD in Uppsala in 1892. He was appointed professor of mathematics at the Royal Institute of Technology in Stockholm in 1905, succeeding Ivar Bendixson , and became professor of pure mathematics at Stockholm University College in 1911.
Von Koch wrote several papers on number theory . One of his results was a 1901 theorem proving that the Riemann hypothesis implies what is now known to be the strongest possible form of the prime number theorem . [ 1 ]
He described the Koch curve in a 1904 paper entitled Sur une courbe continue sans tangente, obtenue par une construction géométrique élémentaire ("On a continuous curve without tangents constructible from elementary geometry"). [ 2 ]
He was an invited speaker at the International Congress of Mathematicians in 1900 in Paris with talk Sur la distribution des nombres premiers ("On the distribution of prime numbers") [ 3 ] and in 1912 in Cambridge , England, with talk On regular and irregular solutions of some infinite systems of linear equations . [ 4 ] | https://en.wikipedia.org/wiki/Niels_Fabian_Helge_von_Koch |
Nielsen's theorem is a result in quantum information concerning transformations between bipartite states due to Michael Nielsen . [ 1 ] It makes use of majorization .
A bipartite state | ψ ⟩ {\displaystyle |\psi \rangle } transforms to another | ϕ ⟩ {\displaystyle |\phi \rangle } using local operations and classical communication if and only if λ ψ {\displaystyle \lambda _{\psi }} is majorized by λ ϕ {\displaystyle \lambda _{\phi }} where the λ i {\displaystyle \lambda _{i}} are the Schmidt coefficients of the respective state.
This can be written more concisely as
| ψ ⟩ → | ϕ ⟩ {\displaystyle |\psi \rangle \rightarrow |\phi \rangle } iff λ ψ ≺ λ ϕ {\displaystyle \lambda _{\psi }\prec \lambda _{\phi }} .
The proof is detailed in the paper and will be added here at a later date. | https://en.wikipedia.org/wiki/Nielsen's_theorem |
The Nielsen realization problem is a question asked by Jakob Nielsen ( 1932 , pp. 147–148) about whether finite subgroups of mapping class groups can act on surfaces, that was answered positively by Steven Kerckhoff ( 1980 , 1983 ).
Given an oriented surface, we can divide the group Diff( S ), the group of diffeomorphisms of the surface to itself, into isotopy classes to get the mapping class group π 0 (Diff( S )). The conjecture asks whether a finite subgroup of the mapping class group of a surface can be realized as the isometry group of a hyperbolic metric on the surface.
The mapping class group acts on Teichmüller space . An equivalent way of stating the question asks whether every finite subgroup of the mapping class group fixes some point of Teichmüller space.
Jakob Nielsen ( 1932 , pp. 147–148) asked whether finite subgroups of mapping class groups can act on surfaces. Kravetz (1959) claimed to solve the Nielsen realization problem but his proof depended on trying to show that Teichmüller space (with the Teichmüller metric ) is negatively curved. Linch (1971) pointed out a gap in the argument, and Masur (1975) showed that Teichmüller space is not negatively curved. Steven Kerckhoff ( 1980 , 1983 ) gave a correct proof that finite subgroups of mapping class groups can act on surfaces using left earthquakes . | https://en.wikipedia.org/wiki/Nielsen_realization_problem |
Nielsen theory is a branch of mathematical research with its origins in topological fixed-point theory . Its central ideas were developed by Danish mathematician Jakob Nielsen , and bear his name.
The theory developed in the study of the so-called minimal number of a map f from a compact space to itself, denoted MF [ f ]. This is defined as:
where ~ indicates homotopy of mappings, and #Fix( g ) indicates the number of fixed points of g . The minimal number was very difficult to compute in Nielsen's time, and remains so today. Nielsen 's approach is to group the fixed-point set into classes, which are judged "essential" or "nonessential" according to whether or not they can be "removed" by a homotopy.
Nielsen 's original formulation is equivalent to the following:
We define an equivalence relation on the set of fixed points of a self-map f on a space X . We say that x is equivalent to y if and only if there exists a path c from x to y with f ( c ) homotopic to c as paths. The equivalence classes with respect to this relation are called the Nielsen classes of f , and the Nielsen number N ( f ) is defined as the number of Nielsen classes having non-zero fixed-point index sum.
Nielsen proved that
making his invariant a good tool for estimating the much more difficult MF [ f ]. This leads immediately to what is now known as the Nielsen fixed-point theorem: Any map f has at least N(f) fixed points.
Because of its definition in terms of the fixed-point index , the Nielsen number is closely related to the Lefschetz number . Indeed, shortly after Nielsen 's initial work, the two invariants were combined into a single "generalized Lefschetz number" (more recently called the Reidemeister trace ) by Wecken and Reidemeister . | https://en.wikipedia.org/wiki/Nielsen_theory |
In group theory , a branch of mathematics, the Nielsen–Schreier theorem states that every subgroup of a free group is itself free. [ 1 ] [ 2 ] [ 3 ] It is named after Jakob Nielsen and Otto Schreier .
A free group may be defined from a group presentation consisting of a set of generators with no relations. That is, every element is a product of some sequence of generators and their inverses, but these elements do not obey any equations except those trivially following from gg −1 = 1. The elements of a free group may be described as all possible reduced words , those strings of generators and their inverses in which no generator is adjacent to its own inverse. Two reduced words may be multiplied by concatenating them and then removing any generator-inverse pairs that result from the concatenation.
The Nielsen–Schreier theorem states that if H is a subgroup of a free group G , then H is itself isomorphic to a free group. That is, there exists a set S of elements which generate H , with no nontrivial relations among the elements of S .
The Nielsen–Schreier formula , or Schreier index formula , quantifies the result in the case where the subgroup has finite index: if G is a free group of rank n (free on n generators), and H is a subgroup of finite index [ G : H ] = e , then H is free of rank 1 + e ( n − 1 ) {\displaystyle 1+e(n{-}1)} . [ 4 ]
Let G be the free group with two generators a , b {\displaystyle a,b} , and let H be the subgroup consisting of all reduced words of even length (products of an even number of letters a , b , a − 1 , b − 1 {\displaystyle a,b,a^{-1},b^{-1}} ). Then H is generated by its six elements p = a a , q = a b , r = b a , s = b b , t = a b − 1 , u = a − 1 b . {\displaystyle p=aa,\ q=ab,\ r=ba,\ s=bb,\ t=ab^{-1},\ u=a^{-1}b.} A factorization of any reduced word in H into these generators and their inverses may be constructed simply by taking consecutive pairs of letters in the reduced word. However, this is not a free presentation of H because the last three generators can be written in terms of the first three as s = r p − 1 q , t = p r − 1 , u = p − 1 q {\displaystyle s=rp^{-1}q,\ t=pr^{-1},\ u=p^{-1}q} . Rather, H is generated as a free group by the three elements p = a a , q = a b , r = b a , {\displaystyle p=aa,\ q=ab,\ r=ba,} which have no relations among them; or instead by several other triples of the six generators. [ 5 ] Further, G is free on n = 2 generators, H has index e = [ G : H ] = 2 in G , and H is free on 1 + e ( n –1) = 3 generators. The Nielsen–Schreier theorem states that like H , every subgroup of a free group can be generated as a free group, and if the index of H is finite, its rank is given by the index formula.
A short proof of the Nielsen–Schreier theorem uses the algebraic topology of fundamental groups and covering spaces . [ 1 ] A free group G on a set of generators is the fundamental group of a bouquet of circles , a topological graph X with a single vertex and with a loop-edge for each generator. [ 6 ] Any subgroup H of the fundamental group is itself the fundamental group of a connected covering space Y → X. The space Y is a (possibly infinite) topological graph, the Schreier coset graph having one vertex for each coset in G/H . [ 7 ] In any connected topological graph, it is possible to shrink the edges of a spanning tree of the graph, producing a bouquet of circles that has the same fundamental group H . Since H is the fundamental group of a bouquet of circles, it is itself free. [ 6 ]
The rank of H can be computed using two properties of Euler characteristic that follow immediately from its definition. The first property is that the Euler characteristic of a bouquet of s circles is 1 - s . The second property is multiplicativity in covering spaces : If Y is a degree- d cover of X , then
χ ( Y ) = d ⋅ χ ( X ) {\displaystyle \chi (Y)=d\cdot \chi (X)} .
Now suppose H is a subgroup of the free group G , with index [G:H] = e . The previous part of the proof shows that H is a free group; let r denote the rank of H . Applying the two properties of Euler characteristic for the covering graph Y corresponding to H gives the following:
χ ( Y ) = 1 − r {\displaystyle \chi (Y)=1-r}
and
χ ( Y ) = e ⋅ χ ( X ) = e ( 1 − n ) . {\displaystyle \chi (Y)=e\cdot \chi (X)=e(1-n).}
Combining these equations, we obtain r = 1 − e ( 1 − n ) = 1 + e ( n − 1 ) . {\displaystyle r=1-e(1-n)=1+e(n-1).}
This proof appears in May's Concise Course . [ 8 ] An equivalent proof using homology and the first Betti number of Y is due to Reinhold Baer and Friedrich Levi ( 1936 ).
The original proof by Schreier forms the Schreier graph in a different way as a quotient of the Cayley graph of G modulo the action of H . [ 9 ]
According to Schreier's subgroup lemma , a set of generators for a free presentation of H may be constructed from cycles in the covering graph formed by concatenating a spanning tree path from a base point (the coset of the identity) to one of the cosets, a single non-tree edge, and an inverse spanning tree path from the other endpoint of the edge back to the base point. [ 10 ] [ 9 ]
Although several different proofs of the Nielsen–Schreier theorem are known, they all depend on the axiom of choice . In the proof based on fundamental groups of bouquets, for instance, the axiom of choice appears in the guise of the statement that every connected graph has a spanning tree. The use of this axiom is necessary, as there exist models of Zermelo–Fraenkel set theory in which the axiom of choice and the Nielsen–Schreier theorem are both false. The Nielsen–Schreier theorem in turn implies a weaker version of the axiom of choice, for finite sets. [ 11 ] [ 12 ]
The Nielsen–Schreier theorem is a non-abelian analogue of an older result of Richard Dedekind , that every subgroup of a free abelian group is free abelian . [ 3 ]
Jakob Nielsen ( 1921 ) originally proved a restricted form of the theorem, stating that any finitely-generated subgroup of a free group is free. His proof involves performing a sequence of Nielsen transformations on the subgroup's generating set that reduce their length (as reduced words in the free group from which they are drawn). [ 1 ] [ 13 ] Otto Schreier proved the Nielsen–Schreier theorem in its full generality in his 1926 habilitation thesis , Die Untergruppen der freien Gruppe , also published in 1927 in Abh. math. Sem. Hamburg. Univ. [ 14 ] [ 15 ]
The topological proof based on fundamental groups of bouquets of circles is due to Reinhold Baer and Friedrich Levi ( 1936 ). Another topological proof, based on the Bass–Serre theory of group actions on trees , was published by Jean-Pierre Serre ( 1970 ). [ 16 ] | https://en.wikipedia.org/wiki/Nielsen–Schreier_theorem |
In mathematics , Thurston's classification theorem characterizes homeomorphisms of a compact orientable surface . William Thurston 's theorem completes the work initiated by Jakob Nielsen ( 1944 ).
Given a homeomorphism f : S → S , there is a map g isotopic to f such that at least one of the following holds:
The case where S is a torus (i.e., a surface whose genus is one) is handled separately (see torus bundle ) and was known before Thurston's work. If the genus of S is two or greater, then S is naturally hyperbolic , and the tools of Teichmüller theory become useful. In what follows, we assume S has genus at least two, as this is the case Thurston considered. (Note, however, that the cases where S has boundary or is not orientable are definitely still of interest.)
The three types in this classification are not mutually exclusive, though a pseudo-Anosov homeomorphism is never periodic or reducible . A reducible homeomorphism g can be further analyzed by cutting the surface along the preserved union of simple closed curves Γ . Each of the resulting compact surfaces with boundary is acted upon by some power (i.e. iterated composition ) of g , and the classification can again be applied to this homeomorphism.
Thurston's classification applies to homeomorphisms of orientable surfaces of genus ≥ 2, but the type of a homeomorphism only depends on its associated element of the mapping class group Mod(S) . In fact, the proof of the classification theorem leads to a canonical representative of each mapping class with good geometric properties. For example:
Thurston's original motivation for developing this classification was to find geometric structures on mapping tori of the type predicted by the Geometrization conjecture . The mapping torus M g of a homeomorphism g of a surface S is the 3-manifold obtained from S × [0,1] by gluing S × {0} to S × {1} using g . If S has genus at least two, the geometric structure of M g is related to the type of g in the classification as follows:
The first two cases are comparatively easy, while the existence of a hyperbolic structure on the mapping torus of a pseudo-Anosov homeomorphism is a deep and difficult theorem (also due to Thurston ). The hyperbolic 3-manifolds that arise in this way are called fibered because they are surface bundles over the circle , and these manifolds are treated separately in the proof of Thurston's geometrization theorem for Haken manifolds . Fibered hyperbolic 3-manifolds have a number of interesting and pathological properties; for example, Cannon and Thurston showed that the surface subgroup of the arising Kleinian group has limit set which is a sphere-filling curve .
The three types of surface homeomorphisms are also related to the dynamics of the mapping class group Mod( S ) on the Teichmüller space T ( S ). Thurston introduced a compactification of T ( S ) that is homeomorphic to a closed ball, and to which the action of Mod( S ) extends naturally. The type of an element g of the mapping class group in the Thurston classification is related to its fixed points when acting on the compactification of T ( S ):
This is reminiscent of the classification of hyperbolic isometries into elliptic , parabolic , and hyperbolic types (which have fixed point structures similar to the periodic , reducible , and pseudo-Anosov types listed above). | https://en.wikipedia.org/wiki/Nielsen–Thurston_classification |
The Niementowski quinazoline synthesis is the chemical reaction of anthranilic acids with amides to form 4-oxo-3,4-dihydro quinazolines (3 H -quinazolin-4-ones). [1] [2] [3]
Research has demonstrated that the Niementowski quinazoline synthesis could be employed for the creation of potential EGFR-inhibiting molecules. Hensbergen et al . [4] have shown a synthetic route to a new class of privileged tri- and tetra-cyclic quinazolines containing a medium-sized ring.
A nucleophilic aromatic substitution is combined with the Niementowski reaction and a BOP -mediated ring closure to afford several analogues. | https://en.wikipedia.org/wiki/Niementowski_quinazoline_synthesis |
The Niementowski quinoline synthesis is the chemical reaction of anthranilic acids and ketones (or aldehydes ) to form γ-hydroxyquinoline derivatives. [ 1 ] [ 2 ] [ 3 ] [ 4 ]
In 1894, Niementowski reported that 2-phenyl-4-hydroxyquinoline was formed when anthranilic acid and acetophenone were heated to 120–130 °C. He later found that at higher heat, 200 °C, anthranilic acid and heptaldehyde formed minimal yields of 4-hydroxy-3-pentaquinoline. [ 5 ] Several reviews have been published. [ 6 ] [ 7 ]
The temperatures required for this reaction make it less popular than other quinoline synthetic procedures. However, variations have been proposed to make this a more pragmatic and useful reaction. Adding phosphorus oxychloride to the reaction mixture mediates a condensation to make both isomers of an important precursor to an important α 1 -adrenoreceptor antagonist. [ 8 ] When the 3 position of an arylketone is substituted, it has been shown that a Niementowski-type reaction with propionic acid can produce a 4-hydroxyquinoline with 2-thiomethyl substitute. [ 9 ] The method has also been altered to occur with a catalytic amount of base, [ 10 ] or in the presence of polyphosphoric acid. [ 11 ]
Because of the similarity of these to the reagents in the Friedlander quinolone synthesis , a benzaldehyde with an aldehyde or ketone , the Niementowski quinoline synthesis mechanism is minimally different from that of the Friedländer synthesis. While studied in depth, two reaction pathways are possible and both have significant support. [ 5 ] The reaction is thought to begin with the formation of a Schiff base, and then proceed via an intra-molecular condensation to make an imine intermediate (see below). There is then a loss of water that leads to a ring closing and formation of the quinoline derivative. Most evidence supports this as the mechanism in normal conditions of 120–130 °C. Alternatively, the reaction begins with an intermolecular condensation and subsequent formation of the imine intermediate. [ 12 ] The latter has been shown to be more common under acidic or basic conditions. A similar pathway has been proposed for the Niementowski quinazoline synthesis . [ 13 ] | https://en.wikipedia.org/wiki/Niementowski_quinoline_synthesis |
The Nier Prize is named after Alfred O. C. Nier . It is awarded annually by the Meteoritical Society and recognizes outstanding research in meteoritics and closely allied fields by young scientists.
Recipients must be under 35 years old at the end of the calendar year in which they are selected. [ 1 ] The Leonard Medal Committee recommends to the Council candidates for the Nier Prize. | https://en.wikipedia.org/wiki/Nier_Prize |
The Nierenstein reaction is an organic reaction describing the conversion of an acid chloride into a haloketone with diazomethane . [ 1 ] [ 2 ] It is an insertion reaction in that the methylene group from the diazomethane is inserted into the carbon-chlorine bond of the acid chloride.
The reaction proceeds through a diazonium salt intermediate formed by displacement of the chloride with diazomethyl anion.
If excess diazomethane is present during the reaction, it can act as a base, abstracting a hydrogen from the diazonium-salt intermediate. The result is a neutral diazoketone, which does not react with the chloride. Instead, the byproduct, diazonium-methyl from the other diazomethane molecule, can be attacked by the chloride to produce chloromethane . The unreactive diazoketone can be re-activated and reacted by treatment with hydrogen chloride to give the normal Nierenstein product.
In some cases, even limiting the amount of diazomethane gives a reaction process that stalls via the neutral diazoketone pathway, requiring the addition of HCl gas to rescue it. [ 3 ]
One original 1924 Nierenstein reaction: [ 4 ]
and a reaction starting from benzoyl bromide going haywire with formation of the dioxane dimer: [ 5 ] | https://en.wikipedia.org/wiki/Nierenstein_reaction |
Nigel Boston (July 20, 1961 – March 31, 2024) was a British-American mathematician, who made notable contributions to algebraic number theory , group theory , and arithmetic geometry .
Boston attended Harvard University , earning his doctorate in 1987, under supervision of Barry Mazur . [ 1 ] He was a Professor Emeritus at the University of Wisconsin–Madison . In 2012, he became a fellow of the American Mathematical Society . [ 2 ]
Boston died on March 31, 2024, at the age of 62. [ 3 ]
This article about an American mathematician is a stub . You can help Wikipedia by expanding it . | https://en.wikipedia.org/wiki/Nigel_Boston |
Nigel Shaun Scrutton (born 2 April 1964) FRS FRSB FRSC is a British biochemist and biotechnology innovator known for his work on enzyme catalysis , biophysics and synthetic biology . [ 2 ] He is Director of the UK Future Biomanufacturing Research Hub, Director of the Fine and Speciality Chemicals Synthetic Biology Research Centre (SYNBIOCHEM), and Co-founder, Director and Chief Scientific Officer of the 'fuels-from-biology' company C3 Biotechnologies Ltd. He is Professor of Enzymology and Biophysical Chemistry in the Department of Chemistry at the University of Manchester . [ 2 ] He is former Director of the Manchester Institute of Biotechnology (MIB) (2010 to 2020). [ 3 ]
Scrutton was born in Batley , West Riding of Yorkshire and was brought up in Cleckheaton where he went to Whitcliffe Mount School . Scrutton graduated from King's College London with a first class Bachelor of Science degree in Biochemistry in 1985. He was a Benefactors' Scholar at St John's College, Cambridge where he completed his doctoral research ( PhD ) in 1988 supervised by Richard Perham . [ 4 ] [ 5 ] He was a Research Fellow of St John's College , Cambridge (1989–92) and a Fellow / Director of Studies at Churchill College , Cambridge (1992–95). He was awarded a Doctor of Science (ScD) degree in 2003 by the University of Cambridge .
Following his PhD, Scrutton was appointed as Lecturer (1995), then Reader (1997) and Professor (1999) at the University of Leicester before being appointed Professor at the University of Manchester in 2005. He has held successive research fellowships over 29 years from the Royal Commission for the Exhibition of 1851 ( 1851 Research Fellowship ), St John's College, Cambridge , the Royal Society ( Royal Society University Research Fellow and Royal Society Wolfson Research Merit Award ), the Lister Institute of Preventive Medicine , the Biotechnology and Biological Sciences Research Council (BBSRC) and the Engineering and Physical Sciences Research Council (EPSRC) . He has been Visiting Professor at Tsinghua University (Beijing, China) and Cardiff University (UK), and adjunct professor at VISTEC ( Thailand ) and Beijing University of Chemical Technology (China).
He has made major contributions to the study of enzyme catalysis , the mechanisms and structures of enzymes and the photochemistry of photoreceptor proteins . His group has pioneered investigations that have led to both deep understanding and recognition of the general importance of quantum tunnelling and protein dynamics in enzyme H-transfer and conformational ensemble sampling in electron transfer reactions. This has involved the development of new biophysical approaches for reaction kinetics analysis including kinetic isotope effect studies, their integration into structural and computational programmes, and extension of theory. He has also made important contributions to enzyme kinetics , coenzyme chemistry, protein engineering , directed evolution , synthetic biology , biological engineering , biocatalysis and metabolic engineering , [ 3 ] [ 6 ] [ 7 ] [ 8 ] [ 9 ] including the first rational redesign of the coenzyme specificity of an enzyme, [ 6 ] the establishment of automated microorganism bioengineering platforms for the production of chemicals (e.g. fuels, materials, active pharmaceutical ingredients) and the discovery of new riboflavin cofactors.
His research has been funded by the Engineering and Physical Sciences Research Council , the Biotechnology and Biological Sciences Research Council . [ 10 ] the Defence Science and Technology Laboratory , the Office of Naval Research Global, the European Union ( Framework Programmes for Research and Technological Development ) and other industry / charity funders. He has supervised about 70 students for the degree of Doctor of Philosophy , [ 11 ] [ 12 ] [ 13 ] [ 14 ] [ 15 ] [ 16 ] [ 17 ] about 60 postdoctoral research workers. He has published over 500 research papers and several patents.
In 2015 Scrutton co-founded the company C3 Biotechnologies Ltd to commercialise technologies for chemicals, fuels and materials production.
He was founding Director of the Manchester Synthetic Biology Research Centre SYNBIOCHEM, which he established in 2014 following major investment by the UK government in synthetic biology . In 2019, he established and became Director of the UK Future Biomanufacturing Research Hub, which is developing new technologies to accelerate bio-based manufacturing in the UK in three key sectors – pharmaceuticals, chemicals and engineering materials. He has served on several national committees, including research council / funding committees ( BBSRC , EPSRC , Royal Society ) and strategic advisory boards / scientific steering groups (e.g. Science and Technology Facilities Council ). He is a former member of BBSRC Council (2021-24).
Under his leadership as Director, the enterprising vision of MIB was recognised by the award of the Queen's Anniversary Prize for Higher and Further Education (2018–20) as 'a leader in the UK’s strategic development of biotechnology and bio-manufacturing, through innovative technologies in partnerships with industry'.
Scrutton was awarded the Colworth Medal in 1999 [ 1 ] from the Biochemical Society ; the Enzyme Chemistry Award (Charmian Medal) from the Royal Society of Chemistry in 2002; the Rita and John Cornforth Award from the Royal Society of Chemistry in 2009; the Interdisciplinary Prize from the Royal Society of Chemistry in 2019.
Scrutton was elected a Fellow of the Royal Society (FRS) in 2020; Fellow of the Royal Society of Chemistry (FRSC) in 1996; a Fellow of the Royal Society of Biology (FRSB) in 2009; a Member of the Lister Institute in 2004.
He is recipient of a number of academic awards including: Sambrooke Exhibition Prize ( King's College London , University of London , 1983); William Robson Prize ( King's College London , University of London , 1985); Benefactors' Scholarship ( St John's College , University of Cambridge , 1985); Henry Humphreys Research Prize / Research Fellowship ( St John's College , University of Cambridge , 1989).
Scrutton married Nia Francis Roberts in 1989 with whom he has two sons and one daughter. | https://en.wikipedia.org/wiki/Nigel_Scrutton |
The Nigerian Society of Chemical Engineers (NSChE) is an organization for chemical engineers in Nigeria . NSChE was officially inaugurated on 12 March 1969 at a meeting at BP House in Lagos attended by twenty four Chemical Engineers, all trained abroad. [ 1 ] In 1999 it became a Division of the Nigerian Society of Engineers. [ 2 ] The Society publishes the Nigerian Society of Chemical Engineering Journal . [ 2 ]
The following Chapters have been granted Charter status by the Council.
The following student chapters have also been granted Charter Status by the Council:
Umudike Abia state
This article about an organization in Nigeria is a stub . You can help Wikipedia by expanding it .
This article about a chemistry organization is a stub . You can help Wikipedia by expanding it . | https://en.wikipedia.org/wiki/Nigerian_Society_of_Chemical_Engineers |
Night Sky is a discontinued American bimonthly magazine for entry-level stargazers . It was published between May/June 2004 and March/April 2007 by Sky Publishing, which also produces Sky & Telescope ( S&T ). [ 1 ] [ 2 ]
Night Sky was intended to be a less technical than S&T . The target audience was recreational naked-eye and low-power instrument observers. The magazine was discontinued because of low sales, and subscriptions were converted to an equal number of issues of S&T . [ 3 ]
This astronomy -related article is a stub . You can help Wikipedia by expanding it .
This science and technology magazine–related article is a stub . You can help Wikipedia by expanding it .
See tips for writing articles about magazines . Further suggestions might be found on the article's talk page . | https://en.wikipedia.org/wiki/Night_Sky_(magazine) |
Night Sky Network is an educational effort sponsored by NASA to help educate the public through astronomy clubs across the United States , as part of NASA's Science Activation program. [ 1 ] [ 2 ]
This astronomy -related article is a stub . You can help Wikipedia by expanding it . | https://en.wikipedia.org/wiki/Night_Sky_Network |
Operation Night Train was part of a series of chemical and biological warfare tests overseen by the Deseret Test Center as part of Project 112 . The test was conducted near Fort Greely , Alaska from November 1963 to January 1964. The primary purpose of Night Train was to study the penetration of an arctic inversion by a biological aerosol cloud . The test's first purpose was to study the downwind travel and diffusion of this cloud when disseminated into different arctic meteorological regimes. [ 1 ] All documents about Night Train were considered classified by the US military until 2002, when the Department of Defense (DOD) released medically relevant information of all the chemical and biological warfare agent tests conducted under Project 112. [ 2 ]
A total of 18 biological trials were conducted for Night Train. The trials, meant to study the spread and behavior of biological warfare agents in arctic conditions, were conducted in a temperature range of -39.3 to 3.3 °C. In all of these trials, Bacillus subtitles var. niger (also referred to as Bacillus globigii ) was released as a biological warfare simulant, along with fluorescent particles of zinc cadmium sulfide as a tracer material. The trials tested both dry simulant and simulant released from a liquid biological spray tank in order to better investigate the behavior of the simulant in an arctic climate, as the behavior of wet versus dry agents varies based on humidity and other climatic conditions. [ 3 ] [ 4 ]
Of the 18, a series of 4 surface trials were conducted with dry B. globigii released from the back of a moving and tracked vehicle, accompanied by the release from contractor-flown aircraft of yellow and green fluorescent particles of zinc cadmium sulfide. [ 3 ]
The remaining 14 trials involved the aerial release of B. globigii from the A/B45Y-1 liquid biological spray tank, an ejectable and aerodynamic store meant to disseminate and spray a liquid biological agent. [ 3 ] [ 5 ] The tank was carried on F-105 or F-100 aircraft, and was also accompanied by the release of fluorescent tracer particles. [ 3 ]
The declassification of documents pertaining to Night Train and other Project 112 tests began in response to claims that veterans who were exposed to biological agents as a part of Project 112 were falling ill. [ 6 ] Although Night Train used only a biological warfare simulant, which is considered harmless to healthy individuals, it has been acknowledged that B. globigii is an organism that can cause illness in those who are immunocompromised . [ 1 ] [ 6 ]
In order to address health claims, the VA contracted with the National Academy of Sciences to conduct an independent epidemiological study of participants in these tests as compared to veterans who did not participate. [ 6 ] However, the VA sponsored study found no evidence that the health of veterans in exposure groups was significantly different from that of veterans who did not participate in the tests. [ 7 ]
Approximately 5,500 servicemembers were unknowingly involved in Project 112 tests. [ 6 ] Due to pressure from the Department of Veterans Affairs (VA), the DOD began to declassify medically relevant information regarding Night Train and other Project 112 tests that involved the exposure of military personnel to either biological or chemical simulants or active agents, though most of the information remains classified. [ 6 ] | https://en.wikipedia.org/wiki/Night_Train_(test) |
A night safari is a nocturnal visit to a zoo or wildlife-spotting natural area. The term was first used by the Night Safari, Singapore , which opened in 1994. [ 1 ]
While the term generally applies to zoos or facilities that allow visitors to view animals within enclosures or fenced areas, the term is expanding to include viewing of wildlife in national parks and other natural areas, such as in Laos. | https://en.wikipedia.org/wiki/Night_safari |
Night soil is a historical euphemism for human excreta collected from cesspools , privies, pail closets , pit latrines , privy middens , septic tanks , etc. This material was removed from the immediate area, usually at night, by workers employed in this trade. Sometimes it could be transported out of towns and sold on as a fertilizer .
Another definition is "untreated excreta transported without water (e.g. via containers or buckets)". [ 1 ] Night soil was produced as a result of a sanitation system in areas without sewer systems or septic tanks . In this system of waste management, human feces are collected without dilution in water.
Night soil is largely an outdated term used in historical contexts, while fecal sludge management remains an ongoing challenge, particularly in developing countries . [ 2 ]
Feces were excreted into a container such as a chamber pot , and sometimes collected in the container with urine and other waste ("slops", hence slopping out ). The excrement in the pail was often covered with ashes or earth (soil), which may have contributed to the term "night soil". Often the deposition or excretion occurred within the residence, such as in a shophouse . [ clarification needed ] This system may still be used in isolated rural areas or in urban slums in developing countries. The material was collected for temporary storage and disposed of depending on local custom.
Disposal has varied through time. In urban areas, before deep drainage, a night soil collector usually arrived during the night, hence its name. The vehicle used for collection has been called a night-cart , and its operator a night-man or night-cart man . [ 3 ]
In isolated rural areas such as in farms, the householders usually disposed of the night soil themselves.
Human excreta may be attractive as fertilizer because of the high demand for fertilizer and the relative availability of the material to create night soil. In areas where native soil is of poor quality, the local population may weigh the risk of using night soil.
The use of unprocessed human feces as fertilizer is a risky practice as it may contain disease-causing pathogens . Nevertheless, in some developing nations it is still widespread. Common parasitic worm infections, such as ascariasis , in these countries are linked to night soil use in agriculture, because the helminth eggs are in feces and can thus be transmitted from one infected person to another person ( fecal-oral transmission of disease).
These risks are reduced by proper fecal sludge management , e.g. via composting . The safe reduction of human excreta into compost is possible. Some municipalities create compost from the sewage sludge , but then recommend that it be used only on flower beds — not vegetable gardens.
The use of sewage as fertilizer was common in ancient Attica . The sewage system of ancient Athens collected the sewage of the city in a large reservoir and then channelled it to the Cephissus river valley for use as fertilizer. [ 4 ]
The term is known, or even infamous, among the generations that were born in parts of China or Chinatowns (depending on the development of the infrastructure) before 1960. Post- World War II Chinatown, Singapore , before the independence of Singapore , utilized night-soil collection as a primary means of waste disposal, especially as much of the infrastructure was damaged and took a long time to rebuild following the Battle of Singapore and subsequent Japanese occupation . Following the development of the economy and the standard of living after independence, the night soil system in Singapore is now an anecdote from the time of colonial rule when new systems developed.
The collection method is generally very manual and heavily relies on close human contact with the waste. During the Nationalist era when the Kuomintang ruled mainland China , as well as Chinatown in Singapore, the night soil collector usually arrived with spare and relatively empty honey buckets to exchange for the full honey buckets. The method of transporting the honey buckets from individual households to collection centers was very similar to delivering water supplies by an unskilled laborer, with the exception that the item being transported was not at all potable and it was being delivered from the household, rather than to the household. The collector would hang full honey buckets onto each end of a pole he carried on his shoulder and then proceeded to carry it through the streets until he reached the collection point.
Chinese has a similar euphemism for night soil collection, 倒夜香 dou2 je6 hoeng1 , which literally means "emptying nocturnal fragrance".
The reuse of feces as fertilizer was common in Japan. In the city of Edo , compost merchants gathered feces to sell to farmers. That was good additional income for apartment owners. Human excreta of rich people were sold at higher prices because their diet was better; presumably, more nutrients remained in their excreta. Various historic documents dating from the 9th century detail the disposal procedures for toilet waste. [ 5 ]
Selling human waste products as fertilizers became much less common after World War II , both for sanitary reasons and because of the proliferation of chemical fertilizers, and less than 1% is used for night soil fertilization. [ clarification needed ] The presence of the United States occupying force , by whom the use of human waste as fertilizer was seen as unhygienic and suspect, was also a contributing factor: "the Occupationaires condemned the practice, and tried to prevent their compatriots from eating vegetables and fruit from the local markets". [ 6 ]
Various Mesoamerican civilizations used human feces to fertilize their crops. The Aztecs, in particular, are well known for their famous chinampas , artificial islands made of mud and human waste used to grow crops that could be harvested up to seven times a year. Current research has placed the origins of chinampas in an Aztec town of Culhuacan in the year 1100 C.E. [ 7 ] They were constructed by first fencing an area between 30 m x 2.5 m and 91 m x 9 m, using wattle. [ 8 ] [ 9 ] Then filled in with mud, sediment, feces and decaying vegetation. To stabilize the chinampas, trees were often planted on the corners, primarily āhuexōtl ( Salix bonplandiana ) or āhuēhuētl ( Taxodium mucronatum ). [ 10 ] Chinampas were very common before Spanish conquest and are still found in Mexico today.
In Britain during the Medieval period, it was not uncommon for human feces to be spread on farms for use as fertilizer . [ 11 ]
A gong farmer was the term used in Tudor England for a person employed to remove human excrement from privies and cesspits. Gong farmers were only allowed to work at night and the waste they collected had to be taken outside the city or town boundaries.
The rapid industrialisation of England during the 19th century led to mass urbanisation, over-crowding, and epidemics. One response was the development of the "Rochdale system", in which the town council arranged for the collection of night soil from outhouses attached to each dwelling or group of dwellings [ 12 ] (see pail closet ). A later response was the passage of the Public Health Act 1875 , which led to the creation of byelaws regarding housing , mandating one outhouse per house. These were "earth closets" (not water closets i.e. WCs) and depended on "night soil men" or "nightmen".
Before reticulated sewerage systems replaced them, major cities in Australia had a nightsoil collection system, with its own special terms. "Nightsoil" was collected from " dunnies " (outhouses/water closets) at the rear of dwellings, often accessed by "dunny lanes" (narrow laneways) by a "dunny man" (a nightsoil collector). Most inner-city areas were connected to the sewer in the early 1900s, but it was not until the 1970s that all suburban areas were sewered. [see Sheppard v Smith [2021] NSWSC 1207 at paragraphs 22 and 29]. [ citation needed ]
People responsible for the disposal of night soil were also in India. The tradition widely persists as the law is difficult to enforce. This " manual scavenging " is now illegal in all Indian states.
The Indian government's Union Ministry for Social Justice and Empowerment stated in 2003 that 676,000 people were employed in the manual collection of human waste in India. Social organizations have estimated that up to 1.3 million Indians collect such waste. Further, workers in the collection of human waste were confined to marriage amongst themselves, thereby leading to a waste-collecting caste, which passes its profession on from generation to generation.
Employment of Manual Scavengers and Creation of Dry Latrines (Prohibition) Act 1993 has made manual scavenging illegal. [ 13 ]
Modern Japan still has areas with ongoing night soil collection and disposal. The Japanese name for the "outhouse within the house" style toilet, where night soil is collected for disposal, is kumitori benjo (汲み取り便所). The proper disposal or recycling of sewage remains an important research area that is highly political. | https://en.wikipedia.org/wiki/Night_soil |
In Jain cosmology , the Nigoda is a realm existing in which the lowest forms of invisible life reside in endless numbers, and without any hope of release by self-effort. Jain scriptures describe nigodas which are microorganisms [ 1 ] living in large clusters, having only one sense, [ 2 ] having a very short life and are said to pervade each and every part of universe, even in tissues of plants and flesh of animals. [ 3 ] The Nigoda exists in contrast to the Supreme Abode, also located at the Siddhashila (top of the universe) where liberated souls exist in omnisciencent and eternal bliss. According to Jain tradition, it is said that when a human being achieves liberation ( Moksha ) or if a human would be born as a Nigoda due to karma , another from the Nigoda is given the potential of self-effort and hope. [ 2 ] Nigoda belongs in the lowest class of Jiva (soul).
The life in Nigoda is that of a sub-microscopic organism possessing only one sense, i.e., of touch. [ 3 ]
This article about Jain philosophy is a stub . You can help Wikipedia by expanding it .
This cosmology -related article is a stub . You can help Wikipedia by expanding it . | https://en.wikipedia.org/wiki/Nigoda |
In alchemy , nigredo , or blackness, means putrefaction or decomposition . Many alchemists believed that as a first step in the pathway to the philosopher's stone , all alchemical ingredients had to be cleansed and cooked extensively to a uniform black matter. [ 1 ]
In analytical psychology , the term became a metaphor for "the dark night of the soul , when an individual confronts the shadow within." [ 2 ]
For Carl Jung , "the rediscovery of the principles of alchemy came to be an important part of my work as a pioneer of psychology ". [ 3 ] As a student of alchemy, he (and his followers) "compared the 'black work' of the alchemists (the nigredo) with the often highly critical involvement experienced by the ego, until it accepts the new equilibrium brought about by the creation of the self." [ 4 ] Jungians interpreted nigredo in two main psychological senses.
The first sense represented a subject's initial state of undifferentiated unawareness, "the first nigredo, that of the unio naturalis , is an objective state, visible from the outside only ... an unconscious state of non-differentiation between self and object, consciousness and the unconscious." [ 5 ] Here the subject is unaware of the unconscious; i.e. the connection with the instincts. [ 6 ]
In the second sense, "the nigredo of the process of individuation on the other hand is a subjectively experienced process brought about by the subject's painful, growing awareness of his shadow aspects." [ 7 ] It could be described as a moment of maximum despair, that is a prerequisite to personal development. [ 8 ] As individuation unfolds, so "confrontation with the shadow produces at first a dead balance, a standstill that hampers moral decisions and makes convictions ineffective or even impossible ... nigredo , tenebrositas , chaos, melancholia." [ 9 ] Here is "the darkest time, the time of despair, disillusionment, envious attacks; the time when Eros and Superego are at daggers drawn, and there seems no way forward ... nigredo , the blackening." [ 10 ]
Only subsequently would come "an enantiodromia ; the nigredo gives way to the albedo ... the ever deepening descent into the unconscious suddenly becomes illumination from above." [ 11 ]
Further steps of the alchemical opus include such images as albedo (whiteness), citrinitas (yellowness), and rubedo (redness). Jung also found psychological equivalents for many other alchemical concepts, with "the characterization of analytic work as an opus ; the reference to the analytic relationship as a vas , vessel or container; the goal of the analytic process as the coniunctio , or union of conflicting opposites." [ 12 ] | https://en.wikipedia.org/wiki/Nigredo |
The nik operon is an operon required for uptake of nickel ions into the cell. It is present in many bacteria, but has been extensively studied in Helicobacter pylori . Nickel is an essential nutrient for many microorganisms, where it participates in a variety of cellular processes. However, excessive levels of nickel ions in cell can be fatal to the cell. Nickel ion concentration in the cell is regulated through the nik operon.
The nik operon consists of six genes. The first five genes nikABCDE encode components of a typical ABC transport system and the last gene nikR encodes a DNA-binding protein that represses transcription of nikABCDE when sufficient Ni 2+ is present. The nikR gene is located 5 bp downstream of the end of nikE , transcribed in the same direction as nikABCDE . The following table summarizes the structure of the nik operon:
Regulation of expression of the nikR gene is achieved by two promoters . The first is through the FNR regulon . The FNR controlled regulation of nikABCDE–nikR occurs at a FNR box located upstream of nikA at a putative NikR binding site. [ 1 ] The second promoter element regulating nikR expression occurs 51 bp upstream of the nikR transcription start site and results in low-level constitutive expression. There is also evidence that nikR expression is partially autoregulated. [ 2 ]
Ni 2+ is taken up into prokaryotic cells by one of two types of high-affinity transport systems. [ 3 ] The first method involves ABC-type transporters (discussed in this article) and the second mechanism makes use of transition-metal permeases (such as HoxN of Ralstonia eutropha ). The ABC-type transporter system consists of five proteins, NikA–E, that carry out the ATP-dependent transport of Ni 2+ . [ 1 ] NikA is a soluble, periplasmic, Ni-binding protein; NikB and NikC form a transmembrane pore for passage of Ni; and NikD and NikE hydrolyze ATP and couple this energy to Ni 2+ -transport. When Ni 2+ is available in excess, NikR protein represses transcription of nikABCDE . [ 2 ]
Using profile-based sequence database searches, NikR was shown to be a member of the ribbon-helix-helix (RHH) family of transcription factors. [ 4 ] It has been demonstrated that the N-terminal domain of NikR is responsible for binding to DNA and that it only binds in presence of Ni 2+ . NikR has two sites for binding to Ni 2+ ions. Binding of Ni 2+ at concentrations that allow full occupancy of only the high-affinity sites is sufficient for operator binding, but the affinity for the operator is increased 1000-fold and the operator footprints are larger when both nickel-binding sites are occupied. [ 5 ] These results, combined with estimates of intracellular Ni 2+ and NikR concentrations, lead to the conclusion that NikR is able to sense Ni 2+ and regulate the nik operon expression over a range of intracellular Ni 2+ concentrations from as low as one to as high as 10,000 molecules per cell. | https://en.wikipedia.org/wiki/Nik_operon |
In mathematics, Nikiel's conjecture in general topology was a conjectural characterization of the continuous image of a compact total order . The conjecture was first formulated by Jacek Nikiel [ pl ] in 1986. [ 1 ] The conjecture was proven by Mary Ellen Rudin in 1999. [ 2 ]
The conjecture states that a compact topological space is the continuous image of a total order if and only if it is a monotonically normal space .
This topology-related article is a stub . You can help Wikipedia by expanding it . | https://en.wikipedia.org/wiki/Nikiel's_conjecture |
Nikolaev Institute of Inorganic Chemistry of the Siberian Branch of the RAS ( Russian : Институт неорганической химии имени А. В. Николаева СО РАН ) is a research institute in Akademgorodok , Novosibirsk, Russia. It was founded in 1957.
Its field includes the chemistry of inorganic compounds, chemical thermodynamics of inorganic systems, crystal chemistry and electronic structure of inorganic substances. [ 1 ]
This article about a chemistry organization is a stub . You can help Wikipedia by expanding it . | https://en.wikipedia.org/wiki/Nikolaev_Institute_of_Inorganic_Chemistry |
Nikolai Ivanovich Ivanov ( Russian : Никола́й Ива́нович Ивано́в ; April 8, 1836 – February 13, 1906) was a Russian businessman operating out of Tashkent , Russian Turkestan . He was known as the largest and most successful entrepreneur and commerce advisor in Tashkent, owning multiple distilleries and breweries in Tashkent and other Central Asian cities.
Born the son of a small merchant from Orenburg , Ivanov began his career in business at the age of fifteen as an errand boy. Thanks to his abilities, Ivanov rose up the ranks without graduating from school. He worked at the Yenisei gold mines, and was working independently by 1865, performing government contracts in Turkestan. [ 1 ]
Ivanov was interested in chemical enterprises. He owned plants in Tashkent that produced artificial ice and mineral water, as well as distilleries of vodka. In 1874, Ivanov was the first person in Tashkent to set up production of beer. The reputation of his "sixth brewery" was high until the end of the 20th century owing to the high quality of his products.
Having bought the Degress estate near Tashkent, Ivanov organized winemaking events there and began to produce vintage wines. Pre-Russian Revolution wine tasters enjoyed Ivanov's wines, particularly the brand of Semilion, Sultani, Muscat and Siabchashma. Ivanov's various factories operated out of many cities in Turkestan.
Ivanov owned a company that mined "Dragomirovsky Coal", and between the years of 1882 and 1895, before the construction of the Tashkent Railway, he controlled the Tashkent postal station, Terekli Station (1.4 thousand kilometers long), the only transport station connecting Turkestan with the Russian heartland. [ 2 ]
Ivanov was known as the largest producer of high-quality vodka in Turkestan. His factories carried out full production cycles. In 1882, Ivanov was approached by German chemist Wilhelm Pfaff with a proposal to organize santonin production in Shymkent, as the city was near the Arys river valley, where santonin could be extracted naturally from plants. Ivanov built the Savinkov-Ivanov Chemical-Pharmaceutical Plant, and heavy equipment was carried from Altona, Hamburg to Shymkent through Orenburg on camel-drawn wagons with specially designed wheels and axels. The plant started production in 1882. [ 3 ] [ 4 ] It is now known as Chimfarm JSC, a prominent pharmaceutical company in Kazakhstan . As the santonin was shipped to Japan, India, Germany and England, the plant became known around the world.
In Ivanov's Turkestan enterprises, owned by his firm, 2700 workers were employed. In 1881, Ivanov established the Central Asian Commercial Bank. For many decades, Ivanov was looked up to as an elder by businesspeople in Tashkent, receiving the honorary title of Commerce Advisor . He was given several awards for his success. Ivanov was also known for the fact that he donated much money to the Russian Orthodox Church for the construction and arrangement of churches, charity houses, shelters and other structures. [ 5 ]
Ivanov was married to Alexandra Petrovna Ivanova (December 14, 1845 - August 13, 1913, Tashkent). He had 3 sons - Ivan, Vasily, and Alexander, as well as a daughter, Olga Nikolaevna Ivanova. These children were the owners of the firm Heirs of Commerce Advisor N. I. Ivanov , having inherited their father's enterprises. Olga (later married to Orenburg merchant Nikifor Prokofievich Savinkov) (died October 27, 1915) was the co-owner of the santonin factory in Shymkent and the first female chemical engineer and pharmacist in Russian Turkestan. [ 6 ]
Ivanov's summer residence near Tashkent was transformed into a Russian Orthodox cemetery after his death. The cemetery is now known as the Botkin Cemetery for the street it is located on. It is the largest memorial, cultural and historical complex in Tashkent. Near the Temple to Alexander Nevsky on the territory of the Botkin Cemetery is Ivanov's grave. [ 7 ] | https://en.wikipedia.org/wiki/Nikolai_Ivanov_(entrepreneur) |
Nikolai V. Ivanov ( Russian : Николай Владимирович Иванов , born 1954) is a Russian mathematician who works on topology , geometry and group theory (particularly, modular Teichmüller groups ). [ 1 ] He is a professor at Michigan State University . [ 2 ]
He obtained his Ph.D. under the guidance of Vladimir Abramovich Rokhlin in 1980 at the Steklov Mathematical Institute . [ 3 ]
According to Google Scholar , on 15 March 2024, Ivanov's works had received 3,006 citations and his h-index was 25. [ 2 ]
He is a fellow of the American Mathematical Society since 2012. [ 4 ]
He is the author of the 1992 book Subgroups of Teichmüller Modular Groups . [ 5 ]
Among his contributions to mathematics are his classification of subgroups of surface mapping class groups , [ 6 ] and the establishment that surface mapping class groups satisfy the Tits alternative . [ 7 ] | https://en.wikipedia.org/wiki/Nikolai_Ivanov_(mathematician) |
Nikos Kyrpides (Greek: Νίκος Κυρπίδης) is a Greek-American bioscientist who has worked on the origins of life , information processing, bioinformatics , microbiology , metagenomics and microbiome data science . [ 1 ] [ 2 ] [ 3 ] He is a senior staff scientist at the Berkeley National Laboratory , [ 4 ] head of the Prokaryote Super Program [ 5 ] and leads the Microbiome Data Science program [ 6 ] at the US Department of Energy Joint Genome Institute . [ 7 ]
Kyrpides was born in Serres , Greece , where he studied biology at the Aristotle University of Thessaloniki and received his PhD in molecular biology and biotechnology from the University of Crete . He pursued postdoctoral studies in microbiology with Carl Woese at the University of Illinois at Urbana-Champaign and in bioinformatics with Ross Overbeek at the Argonne National Laboratory . From 1999 to 2004 Kyrpides worked in the biotech industry in Chicago , where he led the development of genome analysis and bioinformatics. He joined the United States Department of Energy Joint Genome Institute (JGI) in 2004 to lead the Genome Biology Program and develop the data management and comparative analysis platforms for microbial genomes and metagenomes. Kyrpides became the Metagenomics Program head in 2010 and founded the Prokaryotic Super Program in 2011, which he still leads with the Microbiome Data Science Group.
Kyrpides's early work focused on the origins and evolution of the genetic code . In collaboration with Christos Ouzounis , he developed a series of hypotheses for the transfer of information from proteins to nucleic acids known as reverse interpretation. [ 8 ] [ 9 ] [ 10 ] With the advent of genomics , Kyrpides turned his interest to the study and understanding of the last universal common ancestor . With Ouzounis he coined the acronym "LUCA" at a conference organized by Patrick Forterre at Les Treilles, France, and performed some of the first comparative genome analysis to predict the gene content of the LUCA. [ 11 ] [ 12 ] Kyrpides's work on the information processing systems revealed several previously-unsuspected relationships, suggesting new models for the evolution of those processes. He identified previously-undetected relationships between the eukaryotic and bacterial translation machinery, suggesting that the rudiments of translation initiation would have been present at the universal-ancestor stage. [ 13 ] [ 14 ] Kyrpides's work on the evolution of transcription helped change the understanding of the nature and organization of archaeal transcription machinery, which (at the time) was that transcription in Archaea was strictly similar to that in eukaryotes. Kyrpides and Ouzounis demonstrated the parallel existence of a large number of bacterial-type transcription factors in archaeal genomes. [ 15 ] [ 16 ] [ 17 ]
He led the development of several pioneering data-management systems in microbial genomics and metagenomics, which are widely used in the scientific community (with several thousand users worldwide). [ 18 ] These include systems for data management and curation of genome projects and their associated metadata, such as the Genomes OnLine Database (GOLD), [ 19 ] and comparative-genomics systems such as ERGO [ 20 ] and the Integrated Microbial Genomes (IMG). [ 21 ] [ 22 ]
Kyrpides's current research focuses on microbiome research, with an emphasis on microbiome data science. This includes the understanding of structure and function of various microorganisms and microbial communities and the elucidation of the evolutionary dynamics shaping the microbial genomes. To accomplish that, his group is developing novel computational methods for enabling large-scale comparative analysis and mining and visualizing big data . He proposed and published the first study on the use of standard benchmarking data for the evaluation of method accuracy in metagenomics. [ 23 ] This approach has become the standard in the field. [ 24 ] Some of Kyrpides's recent research in microbiome data science include the exploration of Earth’s virome , [ 25 ] [ 26 ] the identification of new bacterial phyla [ 27 ] the prediction of novel folds using metagenomic sequences, [ 28 ] and the discovery and characterization of new protein families from microbiome data. [ 29 ]
Kyrpides began the MikroBioKosmos (MBK) initiative in Greece in 2007, with the goal of exploring and commercially using microbial national resources. MikroBioKosmos became a scientific society, with Kyrpides its first president. He is a founding member of two bioinformatics societies in Greece: the Hellenic Society of Computational Biology and Bioinformatics (HSCBB) in 2010 and Hellenic Bioinformatics in 2016. Kyrpides is also a board member [ 30 ] of the international Genomic Standards Consortium (GSC), [ 31 ] which aims to enable genomic data integration, discovery and comparison with international, community-driven standards.
He began the Genomic Encyclopedia of Bacteria and Archaea (GEBA) project at the JGI and the Microbial Earth Project with Hans-Peter Klenk, Philip Hugenholtz and Jonathan Eisen in 2007, [ 32 ] with the goal of improving the genome characterization of phylogenetically-diverse cultured microbes. [ 33 ] The latter project evolved into an international effort to sequence all the type strains of bacteria and archaea, [ 34 ] through a series of GEBA 1,000-genome projects. [ 35 ] [ 36 ] [ 37 ] [ 38 ] The rapid growth of microbial genome sequences at the end of 2010, without a parallel venue for describing those projects in a standardized manner, led to the need for a new scientific forum which would be a clearinghouse for capturing and presenting this information to the community. This idea led Kyrpides, George Garrity and Dawn Field to launch a new scientific journal: Standards in Genomic Sciences (SIGS), which became part of BioMed Central . [ 39 ] [ 40 ]
Kyrpides proposed the development of a Microbial Environmental Genomics Administration in 2009, analogous to NASA , for the study and exploration of the most abundant life on the planet. [ 41 ] In 2016, following the enormous growth of microbiome data, he outlined the need for a common infrastructure for microbiome data analysis and proposed the development of a National Microbiome Data Center (NMDC), later renamed to National Microbiome Data Collaborative. [ 42 ] [ 43 ] With Emiley Eloe-Fadrosh, Kyrpides organized the first NMDC workshop to launch this initiative at the Joint Genome Institute. This was followed by additional workshops in 2017 hosted by the American Society for Microbiology to promote the initiative. [ 44 ]
Kyrpides has received several awards, including the 2022 Exceptional Scientific Achievement Award from the Director of Lawrence Berkeley National Laboratory, the 2018 USFCC/J. Roger Porter Award from the American Society for Microbiology , [ 45 ] the 2014 van Niel International Prize for Studies in Bacterial Systematics from the International Union of Microbiological Societies (IUMS), [ 46 ] a 2007 outstanding-performance award from the Lawrence Berkeley National Laboratory , and the 2012 Academic Excellence Prize from the Empirikion Foundation. He is an elected fellow of the American Academy of Microbiology (AAM) (2014), [ 47 ] and has been on the Thomson Reuters list of the world’s most frequently-cited scientists since 2014. [ 48 ] [ 49 ] A bacterial genus ( Kyrpidia ) was named after Kyrpides in 2011. [ 50 ] In 2017, he received an honorary doctorate from the Aristotle University of Thessaloniki . [ 51 ] | https://en.wikipedia.org/wiki/Nikos_Kyrpides |
In mathematics , a nilmanifold is a differentiable manifold which has a transitive nilpotent group of diffeomorphisms acting on it. As such, a nilmanifold is an example of a homogeneous space and is diffeomorphic to the quotient space N / H {\displaystyle N/H} , the quotient of a nilpotent Lie group N modulo a closed subgroup H . This notion was introduced by Anatoly Mal'cev in 1949. [ 1 ]
In the Riemannian category, there is also a good notion of a nilmanifold. A Riemannian manifold is called a homogeneous nilmanifold if there exist a nilpotent group of isometries acting transitively on it. The requirement that the transitive nilpotent group acts by isometries leads to the following rigid characterization: every homogeneous nilmanifold is isometric to a nilpotent Lie group with left-invariant metric (see Wilson [ 2 ] ).
Nilmanifolds are important geometric objects and often arise as concrete examples with interesting properties; in Riemannian geometry these spaces always have mixed curvature, [ 3 ] almost flat spaces arise as quotients of nilmanifolds, [ 4 ] and compact nilmanifolds have been used to construct elementary examples of collapse of Riemannian metrics under the Ricci flow . [ 5 ]
In addition to their role in geometry, nilmanifolds are increasingly being seen as having a role in arithmetic combinatorics (see Green–Tao [ 6 ] ) and ergodic theory (see, e.g., Host–Kra [ 7 ] ).
A compact nilmanifold is a nilmanifold which is compact. One way to construct such spaces is to start with a simply connected nilpotent Lie group N and a discrete subgroup Γ {\displaystyle \Gamma } . If the subgroup Γ {\displaystyle \Gamma } acts cocompactly (via right multiplication) on N , then the quotient manifold N / Γ {\displaystyle N/\Gamma } will be a compact nilmanifold. As Mal'cev has shown, every compact
nilmanifold is obtained this way. [ 1 ]
Such a subgroup Γ {\displaystyle \Gamma } as above is called a lattice in N . It is well known that a nilpotent Lie group admits a lattice if and only if its Lie algebra admits a basis with rational structure constants : this is Mal'cev's criterion . Not all nilpotent Lie groups admit lattices; for more details, see also M. S. Raghunathan . [ 8 ]
A compact Riemannian nilmanifold is a compact Riemannian manifold which is locally isometric to a nilpotent Lie group with left-invariant metric. These spaces are constructed as follows. Let Γ {\displaystyle \Gamma } be a lattice in a simply connected nilpotent Lie group N , as above. Endow N with a left-invariant (Riemannian) metric. Then the subgroup Γ {\displaystyle \Gamma } acts by isometries on N via left-multiplication. Thus the quotient Γ ∖ N {\displaystyle \Gamma \backslash N} is a compact space locally isometric to N . Note: this space is naturally diffeomorphic to N / Γ {\displaystyle N/\Gamma } .
Compact nilmanifolds also arise as principal bundles . For example, consider a 2-step nilpotent Lie group N which admits a lattice (see above). Let Z = [ N , N ] {\displaystyle Z=[N,N]} be the commutator subgroup of N . Denote by p the dimension of Z and by q the codimension of Z ; i.e. the dimension of N is p+q. It is known (see Raghunathan) that Z ∩ Γ {\displaystyle Z\cap \Gamma } is a lattice in Z . Hence, G = Z / ( Z ∩ Γ ) {\displaystyle G=Z/(Z\cap \Gamma )} is a p -dimensional compact torus. Since Z is central in N , the group G acts on the compact nilmanifold P = N / Γ {\displaystyle P=N/\Gamma } with quotient space M = P / G {\displaystyle M=P/G} . This base manifold M is a q -dimensional compact torus. It has been shown that every principal torus bundle over a torus is of this form, see. [ 9 ] More generally, a compact nilmanifold is a torus bundle, over a torus bundle, over...over a torus.
As mentioned above, almost flat manifolds are intimately compact nilmanifolds. See that article for more information.
Historically, a complex nilmanifold meant a quotient of a complex nilpotent Lie group over a cocompact lattice . An example of such a nilmanifold is an Iwasawa manifold . From the 1980s, another (more general) notion of a complex nilmanifold gradually replaced this one.
An almost complex structure on a real Lie algebra g is an endomorphism I : g → g {\displaystyle I:\;g\rightarrow g} which squares to
−Id g . This operator is called a complex structure if its eigenspaces, corresponding to eigenvalues ± − 1 {\displaystyle \pm {\sqrt {-1}}} , are subalgebras in g ⊗ C {\displaystyle g\otimes {\mathbb {C} }} . In this case, I defines a left-invariant complex structure on the corresponding Lie group. Such a manifold ( G , I ) is called a complex group manifold .
It is easy to see that every connected complex homogeneous manifold equipped with a free, transitive, holomorphic action by a real Lie group is obtained this way.
Let G be a real, nilpotent Lie group. A complex nilmanifold is a quotient of a complex group manifold ( G , I ), equipped with a left-invariant complex structure, by a discrete, cocompact lattice, acting from the right.
Complex nilmanifolds are usually not homogeneous, as complex varieties.
In complex dimension 2, the only complex nilmanifolds are a complex torus and a Kodaira surface . [ 10 ]
Compact nilmanifolds (except a torus) are never homotopy formal . [ 11 ] This implies immediately that compact nilmanifolds (except a torus) cannot
admit a Kähler structure (see also [ 12 ] ).
Topologically, all nilmanifolds can be obtained
as iterated torus bundles over a torus. This is easily seen from a filtration by ascending central series . [ 13 ]
From the above definition of homogeneous nilmanifolds, it is clear that any nilpotent Lie group with left-invariant metric is a homogeneous nilmanifold. The most familiar nilpotent Lie groups are matrix groups whose diagonal entries are 1 and whose lower diagonal entries are all zeros.
For example, the Heisenberg group is a 2-step nilpotent Lie group. This nilpotent Lie group is also special in that it admits a compact quotient. The group Γ {\displaystyle \Gamma } would be the upper triangular matrices with integral coefficients. The resulting nilmanifold is 3-dimensional. One possible fundamental domain is (isomorphic to) [0,1] 3 with the faces identified in a suitable way. This is because an element ( 1 x z 1 y 1 ) Γ {\displaystyle {\begin{pmatrix}1&x&z\\&1&y\\&&1\end{pmatrix}}\Gamma } of the nilmanifold can be represented by the element ( 1 { x } { z − x ⌊ y ⌋ } 1 { y } 1 ) {\displaystyle {\begin{pmatrix}1&\{x\}&\{z-x\lfloor y\rfloor \}\\&1&\{y\}\\&&1\end{pmatrix}}} in the fundamental domain. Here ⌊ x ⌋ {\displaystyle \lfloor x\rfloor } denotes the floor function of x , and { x } {\displaystyle \{x\}} the fractional part . The appearance of the floor function here is a clue to the relevance of nilmanifolds to additive combinatorics: the so-called bracket polynomials, or generalised polynomials, seem to be important in the development of higher-order Fourier analysis. [ 6 ]
A simpler example would be any abelian Lie group. This is because any such group is a nilpotent Lie group. For example, one can take the group of real numbers under addition, and the discrete, cocompact subgroup consisting of the integers. The resulting 1-step nilmanifold is the familiar circle R / Z {\displaystyle \mathbb {R} /\mathbb {Z} } . Another familiar example might be the compact 2-torus or Euclidean space under addition.
A parallel construction based on solvable Lie groups produces a class of spaces called solvmanifolds . An important example of a solvmanifolds are Inoue surfaces , known in complex geometry . | https://en.wikipedia.org/wiki/Nilmanifold |
A nilometer is a structure for measuring the Nile River's clarity and water level during the annual flood season in Egypt. [ 1 ] There were three main types of nilometers, calibrated in Egyptian cubits : (1) a vertical column, (2) a corridor stairway of steps leading down to the Nile, and (3) a deep well with a culvert . [ 1 ] If the water level was low, the fertility of the floodplain would suffer. If it was too high, the flooding would be destructive. There was a specific mark that indicated how high the flood should be if the fields were to get good soil. [ 1 ] [ 2 ]
Nilometers originated in pharaonic times, were also built in Roman times, and were highly prevalent in Islamic Egypt in Rashidun , Ummayad , Abbasid , Tulunid , Mamluk , Alawiyya and Republican periods, until the Aswan Dam rendered them obsolete in the 1960s.
Between July and November, the reaches of the Nile running through Egypt would burst their banks and cover the adjacent floodplain . When the waters receded, around September or October, they left behind a rich alluvial deposit of exceptionally fertile black silt over the croplands. The akhet , or Season of the Inundation , was one of the three seasons into which the ancient Egyptians divided their year.
The annual flood was of great importance to Egyptian civilization. A moderate inundation was a vital part of the agricultural cycle; however, a lighter inundation than normal would cause famine , and too much flood water would be equally disastrous, washing away much of the infrastructure built on the flood plain. Records from AD 622–999 indicate that, on average, 28% of the years saw an inundation that fell short of expectations. [ 2 ]
Across Egypt various nilometers could be found that recorded readings of the Nile's annual levels. A fragment of a recovered Egyptian stele "Royal Annals of the Old Kingdom" known as the "Palermo stone" deemed to be from the times of the First Dynasty around 3,000 B.C.E. [ 3 ] The Palermo Stone reports systems of measurements utilizing units such as cubits, palms, and fingers. [ 4 ]
The ability to predict the volume of the coming inundation was part of the mystique of the ancient Egyptian priesthood. The same skill also played a political and administrative role, since the quality of the year's flood was used to determine the levels of tax to be paid. This is where the nilometer came into play, with priests monitoring the day-to-day level of the river and announcing the awaited arrival of the summer flood.
Religious attributes related to the Nile intertwined with the ideology or belief in Ma'at (a system of natural balance). Nilometers were accessible to only members of the city's priests and nobles. [ 5 ] The restriction on who may access these structures ensured both accountability in proper readings and political control for the religious communities and ruling classes. [ 5 ]
The simplest nilometer design is a vertical column submerged in the waters of the river, with marked intervals indicating the depth of the water. [ 1 ] One that follows this simple design, albeit housed in an elaborate and ornate stone structure, can still be seen on the island of Roda in central Cairo [ 1 ] [ 2 ] ( 30°00′25″N 31°13′30″E / 30.0069°N 31.2250°E / 30.0069; 31.2250 ( Rhoda Island nilometer ) ). This nilometer visible today dates as far back as AD 861, when the Abbasid caliph al-Mutawakkil ordered its construction, [ 6 ] overseen by the astronomer al-Farghani . Another nilometer had been ordered in 715 by Usāma b. Zayd b. ʿAdī, who was in charge of collecting the land tax ( kharaj ) in Egypt for the Umayyad caliph Sulaymān ibn ʿAbd al-Malik . [ 2 ] [ 7 ]
The second nilometer design comprises a flight of stairs leading down into the water, with depth markings along the walls. [ 1 ] The best known example of this kind can be seen on Elephantine in Aswan , [ 1 ] where a stairway of 52 steps leads down to a doorway at the Nile. [ 8 ] This location was also particularly important, since for much of Egyptian history, Elephantine marked Egypt's southern border and was therefore the first place where the onset of the annual flood was detected.
The most elaborate design involved a canal or culvert that led from the riverbank – often running for a considerable distance – and then fed a well, tank, or cistern . [ 1 ] These nilometer wells were most frequently located within the confines of temples , where only the priests and rulers were allowed access. A particularly fine example, with a deep, cylindrical well and a culvert opening in the surrounding wall, can be seen at the Temple of Kom Ombo , to the north of Aswan.
While nilometers originated in Pharaonic times, they continued to be used by the later civilizations that held sway in Egypt. [ 1 ] Some were constructed in Roman times. [ 1 ] In the 20th century, the Nile's annual inundation was first greatly reduced, and then eliminated entirely, with the construction of the Aswan Dams . While the Aswan High Dam 's impact on Egypt and its agriculture has been controversial for other, more complex reasons, it has also had the additional effect of rendering the nilometer obsolete.
The first nilometer on Roda Island was constructed by Usama bin Zayd bin Adl before Jumada II , 96 AH (February 715), during the reign of the Umayyad caliph al-Walid . The 14th-century Arabic historian Maqrīzī claims that the construction cost 24,000 dirhams . During the reign of Sulayman ibn Abd al-Malik , Usama wrote to the caliph informing him of the dilapidated state of the nilometer. He received a reply ordering him to construct a new one, which he did in 97 AH (5 September 715—24 August 716). [ 9 ] : 296 Yaqut al-Hamawi , writing in the 12th–13th centuries, claims that in the beginning of year 247 AH (March 861), during Yazid ibn Abd Allah al-Turki's governorship of Egypt, the Abbasid caliph al-Mutawakkil had the 'new' nilometer constructed and ordered that the privilege of measuring the river 'be taken away from the Christians.' The governor then appointed a man from Basra named Abu'r-Raddad who had emigrated to Egypt and taught hadith . He died in 266 AH (879/80), with Yaqut claiming 'the supervision of the Nilometer has remained in the hands of his descendants until the present day' (which would have been around 1225 for the author). [ 9 ] : 297 Ibn Khallikan , a 13th-century historian, gives a different account of this nilometer, recounting that a 'pious' muezzin in the old Mosque of Amr wished to carve inscriptions in various places of the nilometer. After consulting with Yazid ibn Abd Allah, Sulayman ibn Wahb and Hasan al-Khadim, the muezzin proposed to inscribe various Qu'ranic passages in the name of al-Mutawakkil. Sulayman ibn Wahb then wrote to the caliph, who replied in writing to choose verses of the Qu'ran 'most appropriate' to the nilometer and to inscribe the caliph's name. [ 9 ] : 297–298
Ibn Khallikan writes that the architect of the nilometer was Ahmad ibn Muhammad al-Hasib. Abu Ja'far al-Katib and Ibn Abi Usaybi'a mention that Ahmad ibn Kathir al-Farghani was sent to Fustat by al-Mutawakkil to supervise the construction. Abu al-Mahasin Yusuf (d. 1604) makes the same statement but calls him Muhammad ibn Kathir al-Farghani (full name: Abu'l-Abbas Ahmad ibn Muhammad ibn Kathir al-Farghani). For this reason, Gaston Wiet and Creswell argue that the al-Farghani and al-Hasib are the same person. [ 9 ] : 303
In 872–3 (259 AH), Ahmad ibn Tulun , the autonomous ruler of Egypt, would also have the nilometer restored. Al-Mutawakkil's name was removed from the Kufic inscription of the nilometer. [ 10 ] K. A. C. Creswell states that the main inscription of the nilometer was probably tampered with by Ibn Tulun, saying "there can be little doubt that it was he who removed the name of the Abbasid Khalif ." Ibn Tulun would however refrain from substituting his own name, with Creswell claiming as he did not feel sufficiently secure to do so. The first Tulunid Emir during 872-873 would spend 1,000 dinars on works carried out on the nilometer. [ 9 ] : 298–299 Consequently, according to Abdul Rofik Bruno, the Nile's irrigation would be enhanced, and agricultural output increased. [ 11 ]
Amr ibn al-As after the conquest of Egypt reported to the Caliph Umar that when the Nile rose to 14 cubits there was a sufficient harvest, 16 an abundant harvest, 17 being the most advantageous height of all, and that at 18, one-fourth of Egypt would be inundated and usually be followed by plague. The Baghdad doctor, Abd al-Latif al-Baghdadi who traveled Egypt between 1192-1201 would also relate similar measurements. In the exceedingly low water levels of 1201 and 1202, the nilometer remained dry. In 1201, the year commenced with a rise in 2 cubits before rising an average 15¹⁶⁄₂₄ cubits. In 1202, the year began with 1½ cubits before rising to 15²³⁄₂₄ cubits. [ 12 ] : 31–32 During the Abbasid Period , the nilometer was used to measure the river level and hence determine the rates of tax in Egypt. [ 13 ]
In 1937, efforts to drain and excavate the nilometer were begun by Kamil Bey Ghalib, the Under-Secretary of State for Public Works, employing a new method used by Rothpletz and Lienhard. In this method, the mud could be removed completely and the structure examined. [ 9 ] : 304 | https://en.wikipedia.org/wiki/Nilometer |
In mathematics , the nilpotent cone N {\displaystyle {\mathcal {N}}} of a finite-dimensional semisimple Lie algebra g {\displaystyle {\mathfrak {g}}} is the set of elements that act nilpotently in all representations of g . {\displaystyle {\mathfrak {g}}.} In other words,
The nilpotent cone is an irreducible subvariety of g {\displaystyle {\mathfrak {g}}} (considered as a vector space ).
The nilpotent cone of sl 2 {\displaystyle \operatorname {sl} _{2}} , the Lie algebra of 2×2 matrices with vanishing trace , is the variety of all 2×2 traceless matrices with rank less than or equal to 1. {\displaystyle 1.}
This article incorporates material from Nilpotent cone on PlanetMath , which is licensed under the Creative Commons Attribution/Share-Alike License .
This algebra -related article is a stub . You can help Wikipedia by expanding it . | https://en.wikipedia.org/wiki/Nilpotent_cone |
The Nilsson model is a nuclear shell model treating the atomic nucleus as a deformed sphere. In 1953, the first experimental examples were found of rotational bands in nuclei, with their energy levels following the same J(J+1) pattern of energies as in rotating molecules. Quantum mechanically, it is impossible to have a collective rotation of a sphere, so this implied that the shape of these nuclei was nonspherical. In principle, these rotational states could have been described as coherent superpositions of particle-hole excitations in the basis consisting of single-particle states of the spherical potential. But in reality, the description of these states in this manner is intractable, due to the large number of valence particles—and this intractability was even greater in the 1950s, when computing power was extremely rudimentary. For these reasons, Aage Bohr , Ben Mottelson , and Sven Gösta Nilsson constructed models in which the potential was deformed into an ellipsoidal shape. The first successful model of this type is the one now known as the Nilsson model. It is essentially a nuclear shell model using a harmonic oscillator potential, but with anisotropy added, so that the oscillator frequencies along the three Cartesian axes are not all the same. Typically the shape is a prolate ellipsoid, with the axis of symmetry taken to be z.
For an axially symmetric shape with the axis of symmetry being the z axis, the Hamiltonian is
H = 1 2 m ω z 2 z 2 + 1 2 m ω ⊥ 2 ( x 2 + y 2 ) − c 1 ℓ ⋅ s − c 2 ( ℓ 2 − ⟨ ℓ 2 ⟩ N ) . {\displaystyle H={\frac {1}{2}}m\omega _{z}^{2}z^{2}+{\frac {1}{2}}m\omega _{\perp }^{2}(x^{2}+y^{2})-c_{1}\ell \cdot s-c_{2}(\ell ^{2}-\langle \ell ^{2}\rangle _{N}).}
Here m is the mass of the nucleon , N is the total number of harmonic oscillator quanta in the spherical basis, ℓ {\displaystyle \ell } is the orbital angular momentum operator, ℓ 2 {\displaystyle \ell ^{2}} is its square (with eigenvalues ℓ ( ℓ + 1 ) {\displaystyle \ell (\ell +1)} ), ⟨ ℓ 2 ⟩ N = ( 1 / 2 ) N ( N + 3 ) {\displaystyle \langle \ell ^{2}\rangle _{N}=(1/2)N(N+3)} is the average value of ℓ 2 {\displaystyle \ell ^{2}} over the N shell, and s is the intrinsic spin.
The anisotropy of the potential is such that the length of an equipotential along the z is greater than the length on the transverse axes in the ratio ω ⊥ / ω z {\displaystyle \omega _{\perp }/\omega _{z}} . This is conventionally expressed in terms of a deformation parameter δ so that the harmonic oscillator part of the potential can be written as the sum of a spherically symmetric harmonic oscillator and a term proportional to δ. Positive values of δ indicate prolate deformations, like an American football. Most nuclei in their ground states have equilibrium shapes such that δ ranges from 0 to 0.2, while superdeformed states have δ ≈ 0.5 {\displaystyle \delta \approx 0.5} (a 2-to-1 axis ratio).
The mathematical details of the deformation parameters are as follows. Considering the success of the nuclear liquid drop model , in which the nucleus is taken to be an incompressible fluid, the harmonic oscillator frequencies are constrained so that ω z ω ⊥ 2 = ω 0 3 {\displaystyle \omega _{z}\omega _{\perp }^{2}=\omega _{0}^{3}} remains constant with deformation, preserving the volume of equipotential surfaces. Reproducing the observed density of nuclear matter requires ℏ ω 0 ≈ ( 42 MeV ) A − 1 / 3 {\displaystyle \hbar \omega _{0}\approx (42\ {\text{MeV}})A^{-1/3}} , where A is the mass number. The relation between δ and the anisotropy is ( ω ⊥ / ω z ) 2 = ( 1 + 2 3 δ ) / ( 1 − 4 3 δ ) {\displaystyle (\omega _{\perp }/\omega _{z})^{2}=(1+{\frac {2}{3}}\delta )/(1-{\frac {4}{3}}\delta )} , while the relation between δ and the axis ratio R = ω ⊥ / ω z {\displaystyle R=\omega _{\perp }/\omega _{z}} is δ = ( 3 / 2 ) ( R 2 − 1 ) / ( 2 R 2 + 1 ) {\displaystyle \delta =(3/2)(R^{2}-1)/(2R^{2}+1)} .
The remaining two terms in the Hamiltonian do not relate to deformation and are present in the spherical shell model as well. The spin-orbit term represents the spin-orbit dependence of the strong nuclear force ; it is much larger than, and has the opposite sign compared to, the special-relativistic spin-orbit splitting. The purpose of the ℓ 2 {\displaystyle \ell ^{2}} term is to mock up the flat profile of the nuclear potential as a function of radius. For nuclear wavefunctions (unlike atomic wavefunctions) states with high angular momentum have their probability density concentrated at greater radii. The term − ⟨ ℓ 2 ⟩ N {\displaystyle -\langle \ell ^{2}\rangle _{N}} prevents this from shifting a major shell up or down as a whole. The two adjustable constants are conventionally parametrized as c 1 = 2 κ ℏ ω 0 {\displaystyle c_{1}=2\kappa \hbar \omega _{0}} and c 2 = μ κ ℏ ω 0 {\displaystyle c_{2}=\mu \kappa \hbar \omega _{0}} . Typical values of κ and μ for heavy nuclei are 0.06 and 0.5. With this parametrization, ℏ ω 0 {\displaystyle \hbar \omega _{0}} occurs as a simple scaling factor throughout all the calculations.
For ease of computation using the computational resources of the 1950s, Nilsson used a basis consisting of eigenstates of the spherical hamiltonian. The Nilsson quantum numbers are { N , ℓ , m ℓ , m s } {\displaystyle \{N,\ell ,m_{\ell },m_{s}\}} . The difference between the spherical and deformed Hamiltonian is proportional to r 2 Y 20 δ {\displaystyle r^{2}Y_{20}\delta } , and this has matrix elements that are easy to calculate in this basis. They couple the different N shells. Eigenstates of the deformed Hamiltonian have good parity (corresponding to even or odd N) and Ω, the projection of the total angular momentum along the symmetry axis. In the absence of a cranking term (see below), time-reversal symmetry causes states with opposite signs of Ω to be degenerate, so that in the calculations only positive values of Ω need to be considered.
In an odd, well-deformed nucleus, the single-particle levels are filled up to the Fermi level, and the odd particle's Ω and parity give the spin and parity of the ground state.
Because the potential is not spherically symmetric, the single-particle states are not states of good angular momentum J. However, a Lagrange multiplier − ω ⋅ J {\displaystyle -\omega \cdot J} , known as a "cranking" term, can be added to the Hamiltonian. Usually the angular frequency vector ω is taken to be perpendicular to the symmetry axis, although tilted-axis cranking can also be considered. Filling the single-particle states up to the Fermi level then produces states whose expected angular momentum along the cranking axis ⟨ J x ⟩ {\displaystyle \langle J_{x}\rangle } has the desired value set by the Lagrange multiplier.
Often one wants to calculate a total energy as a function of deformation. Minima of this function are predicted equilibrium shapes. Adding the single-particle energies does not work for this purpose, partly because kinetic and potential terms are out of proportion by a factor of two, and partly because small errors in the energies accumulate in the sum. For this reason, such sums are usually renormalized using a procedure introduced by Strutinsky.
Single-particle levels can be shown in a "spaghetti plot," as functions of the deformation. A large gap between energy levels at zero deformation indicates a particle number at which there is a shell closure: the traditional " magic numbers ." Any such gap, at a zero or nonzero deformation, indicates that when the Fermi level is at that height, the nucleus will be stable relative to the liquid drop model. | https://en.wikipedia.org/wiki/Nilsson_model |
Niludipine is a calcium channel blocker of the dihydropyridine class. It is a vasodilator that acts upon the coronary arteries of the heart-lung. It was found to produce a calcium antagonistic effect on the smooth muscle of hearts of canines and guinea pigs inhibiting myocardial oxidative metabolism. [ 1 ]
This biochemistry article is a stub . You can help Wikipedia by expanding it . | https://en.wikipedia.org/wiki/Niludipine |
Nim is a mathematical combinatorial game in which two players take turns removing (or "nimming") objects from distinct heaps or piles. On each turn, a player must remove at least one object, and may remove any number of objects provided they all come from the same heap or pile. Depending on the version being played, the goal of the game is either to avoid taking the last object or to take the last object.
Nim is fundamental to the Sprague–Grundy theorem , which essentially says that every impartial game is equivalent to a nim game with a single pile.
Variants of nim have been played since ancient times. [ 1 ] The game is said to have originated in China —it closely resembles the Chinese game of jiǎn-shízǐ ( 捡石子 ), or "picking stones" [ 2 ] —but the origin is uncertain; the earliest European references to nim are from the beginning of the 16th century. Its current name was coined by Charles L. Bouton of Harvard University , who also developed the complete theory of the game in 1901, [ 3 ] but the origins of the name were never fully explained. The Oxford English Dictionary derives the name from the German verb nimm , meaning "take".
At the 1939 New York World's Fair , Westinghouse displayed a machine, the Nimatron , that played nim. [ 4 ] From May 11 to October 27, 1940, only a few people were able to beat the machine in that six-month period; if they did, they were presented with a coin that said "Nim Champ". [ 5 ] It was also one of the first-ever electronic computerized games. Ferranti built a nim-playing computer which was displayed at the Festival of Britain in 1951. In 1952, Herbert Koppel, Eugene Grant and Howard Baller, engineers from the W. L. Maxson Corporation, developed a machine weighing 23 kilograms (50 lb) which played nim against a human opponent and regularly won. [ 6 ] A nim playing machine has been described made from tinkertoys . [ 7 ]
The game of nim was the subject of Martin Gardner 's February 1958 Mathematical Games column in Scientific American . A version of nim is played—and has symbolic importance—in the French New Wave film Last Year at Marienbad (1961). [ 8 ]
Nim is typically played as a misère game , in which the player to take the last object loses. Nim can also be played as a "normal play" game whereby the player taking the last object wins. In either normal play or a misère game, when there is exactly one heap with at least two objects, the player who takes next can easily win. If this removes either all or all but one objects from the heap that has two or more, then no heaps will have more than one object, so the players are forced to alternate removing exactly one object until the game ends. If the player leaves an even number of non-zero heaps (as the player would do in normal play), the player takes last; if the player leaves an odd number of heaps (as the player would do in misère play), then the other player takes last.
The normal game is between two players and is played with three heaps of any number of objects. The two players alternate taking any number of objects from any one of the heaps. The goal is to be the last to take an object. In misère play, the goal is instead to ensure that the opponent is forced to take the last remaining object.
The following example of a normal game is played between fictional players Bob and Alice , who start with heaps of three, four and five objects.
The practical strategy to win at the game of nim is for a player to get the other into one of the following positions, and every successive turn afterwards they should be able to make one of the smaller positions. Only the last move changes between misère and normal play.
For the generalisations, n and m can be any value > 0, and they may be the same.
Normal-play nim (or more precisely the system of nimbers ) is fundamental to the Sprague–Grundy theorem , which essentially says that in normal play every impartial game is equivalent to a nim heap that yields the same outcome when played in parallel with other normal play impartial games (see disjunctive sum ).
While all normal-play impartial games can be assigned a nim value, that is not the case under the misère convention. Only tame games can be played using the same strategy as misère nim.
Nim is a special case of a poset game where the poset consists of disjoint chains (the heaps).
The evolution graph of the game of nim with three heaps is the same as three branches of the evolution graph of the Ulam–Warburton automaton . [ 9 ]
Nim has been mathematically solved for any number of initial heaps and objects, and there is an easily calculated way to determine which player will win and which winning moves are open to that player.
The key to the theory of the game is the binary digital sum of the heap sizes, i.e., the sum (in binary), neglecting all carries from one digit to another. This operation is also known as " bitwise xor " or "vector addition over GF (2) " (bitwise addition modulo 2). Within combinatorial game theory it is usually called the nim-sum , as it will be called here. The nim-sum of x and y is written x ⊕ y to distinguish it from the ordinary sum, x + y . An example of the calculation with heaps of size 3, 4, and 5 is as follows:
An equivalent procedure, which is often easier to perform mentally, is to express the heap sizes as sums of distinct powers of 2, cancel pairs of equal powers, and then add what is left:
In normal play, the winning strategy is to finish every move with a nim-sum of 0. This is always possible if the nim-sum is not zero before the move. If the nim-sum is zero, then the next player will lose if the other player does not make a mistake. To find out which move to make, let X be the nim-sum of all the heap sizes. Find a heap where the nim-sum of X and heap-size is less than the heap-size; the winning strategy is to play in such a heap, reducing that heap to the nim-sum of its original size with X. In the example above, taking the nim-sum of the sizes is X = 3 ⊕ 4 ⊕ 5 = 2 . The nim-sums of the heap sizes A=3, B=4, and C=5 with X=2 are
The only heap that is reduced is heap A, so the winning move is to reduce the size of heap A to 1 (by removing two objects).
As a particular simple case, if there are only two heaps left, the strategy is to reduce the number of objects in the bigger heap to make the heaps equal. After that, no matter what move the opponent makes, the player can make the same move on the other heap, guaranteeing that they take the last object.
When played as a misère game, nim strategy is different only when the normal play move would leave only heaps of size one. In that case, the correct move is to leave an odd number of heaps of size one (in normal play, the correct move would be to leave an even number of such heaps).
These strategies for normal play and a misère game are the same until the number of heaps with at least two objects is exactly equal to one. At that point, the next player removes either all objects (or all but one) from the heap that has two or more, so no heaps will have more than one object (in other words, so all remaining heaps have exactly one object each), so the players are forced to alternate removing exactly one object until the game ends. In normal play, the player leaves an even number of non-zero heaps, so the same player takes last; in misère play, the player leaves an odd number of non-zero heaps, so the other player takes last.
In a misère game with heaps of sizes three, four and five, the strategy would be applied like this:
The soundness of the optimal strategy described above was demonstrated by C. Bouton.
Theorem . In a normal nim game, the player making the first move has a winning strategy if and only if the nim-sum of the sizes of the heaps is not zero. Otherwise, the second player has a winning strategy.
Proof: Notice that the nim-sum (⊕) obeys the usual associative and commutative laws of addition (+) and also satisfies an additional property, x ⊕ x = 0.
Let x 1 , ..., x n be the sizes of the heaps before a move, and y 1 , ..., y n the corresponding sizes after a move. Let s = x 1 ⊕ ... ⊕ x n and t = y 1 ⊕ ... ⊕ y n . If the move was in heap k , we have x i = y i for all i ≠ k , and x k > y k . By the properties of ⊕ mentioned above, we have
t = 0 ⊕ t = s ⊕ s ⊕ t = s ⊕ ( x 1 ⊕ ⋯ ⊕ x n ) ⊕ ( y 1 ⊕ ⋯ ⊕ y n ) = s ⊕ ( x 1 ⊕ y 1 ) ⊕ ⋯ ⊕ ( x n ⊕ y n ) = s ⊕ 0 ⊕ ⋯ ⊕ 0 ⊕ ( x k ⊕ y k ) ⊕ 0 ⊕ ⋯ ⊕ 0 = s ⊕ x k ⊕ y k ( ∗ ) t = s ⊕ x k ⊕ y k {\displaystyle {\begin{aligned}t&=0\oplus t\\&=s\oplus s\oplus t\\&=s\oplus (x_{1}\oplus \cdots \oplus x_{n})\oplus (y_{1}\oplus \cdots \oplus y_{n})\\&=s\oplus (x_{1}\oplus y_{1})\oplus \cdots \oplus (x_{n}\oplus y_{n})\\&=s\oplus 0\oplus \cdots \oplus 0\oplus (x_{k}\oplus y_{k})\oplus 0\oplus \cdots \oplus 0\\&=s\oplus x_{k}\oplus y_{k}\\[10pt](*)\quad t&=s\oplus x_{k}\oplus y_{k}\end{aligned}}}
That is, to update the total nim sum s {\displaystyle s} after updating the x k {\displaystyle x_{k}} heap, we need to cancel it from s {\displaystyle s} by nim summing with x k {\displaystyle x_{k}} , and then nim sum in y k {\displaystyle y_{k}} .
The theorem follows by induction on the length of the game from these two lemmas.
Lemma 1 . If s = 0, then t ≠ 0 no matter what move is made.
Proof: If there is no possible move, then the lemma is vacuously true (and the first player loses the normal play game by definition). Otherwise, any move in heap k will produce t = x k ⊕ y k from (*). This number is nonzero, since x k ≠ y k .
Lemma 2 . If s ≠ 0, it is possible to make a move so that t = 0.
Proof: Let d be the position of the leftmost (most significant) nonzero bit in the binary representation of s , and choose k such that the d th bit of x k is also nonzero. (Such a k must exist, since otherwise the d th bit of s would be 0.)
Then letting y k = s ⊕ x k , we claim that y k < x k : all bits to the left of d are the same in x k and y k , bit d decreases from 1 to 0 (decreasing the value by 2 d ), and any change in the remaining bits will amount to at most 2 d −1. The first player can thus make a move by taking x k − y k objects from heap k , then
The modification for misère play is demonstrated by noting that the modification first arises in a position that has only one heap of size 2 or more. Notice that in such a position s ≠ 0, and therefore this situation has to arise when it is the turn of the player following the winning strategy. The normal play strategy is for the player to reduce this to size 0 or 1, leaving an even number of heaps with size 1, and the misère strategy is to do the opposite. From that point on, all moves are forced.
In another game which is commonly known as nim (but is better called the subtraction game ), an upper bound is imposed on the number of objects that can be removed in a turn. Instead of removing arbitrarily many objects, a player can only remove 1 or 2 or ... or k at a time. This game is commonly played in practice with only one heap.
Bouton's analysis carries over easily to the general multiple-heap version of this game. The only difference is that as a first step, before computing the nim-sums we must reduce the sizes of the heaps modulo k + 1. If this makes all the heaps of size zero (in misère play), the winning move is to take k objects from one of the heaps. In particular, in ideal play from a single heap of n objects, the second player can win if and only if
This follows from calculating the nim-sequence of S (1, 2, ..., k ),
0.123 … k 0123 … k 0123 … = 0 ˙ .123 … k ˙ , {\displaystyle 0.123\ldots k0123\ldots k0123\ldots ={\dot {0}}.123\ldots {\dot {k}},}
from which the strategy above follows by the Sprague–Grundy theorem .
The game "21" is played as a misère game with any number of players who take turns saying a number. The first player says "1" and each player in turn increases the number by 1, 2, or 3, but may not exceed 21; the player forced to say "21" loses. This can be modeled as a subtraction game with a heap of 21 − n objects. The winning strategy for the two-player version of this game is to always say a multiple of 4; it is then guaranteed that the other player will ultimately have to say 21; so in the standard version, wherein the first player opens with "1", they start with a losing move.
The 21 game can also be played with different numbers, e.g., "Add at most 5; lose on 34".
A sample game of 21 in which the second player follows the winning strategy:
A similar version is the "100 game": Two players start from 0 and alternately add a number from 1 to 10 to the sum. The player who reaches 100 wins. The winning strategy is to reach a number in which the digits are subsequent (e.g., 01, 12, 23, 34,...) and control the game by jumping through all the numbers of this sequence. Once a player reaches 89, the opponent can only choose numbers from 90 to 99, and the next answer can in any case be 100.
In another variation of nim, besides removing any number of objects from a single heap, one is permitted to remove the same number of objects from each heap.
Yet another variation of nim is "circular nim", wherein any number of objects are placed in a circle and two players alternately remove one, two or three adjacent objects. For example, starting with a circle of ten objects,
three objects are taken in the first move
then another three
then one
but then three objects cannot be taken out in one move.
In Grundy's game , another variation of nim, a number of objects are placed in an initial heap and two players alternately divide a heap into two nonempty heaps of different sizes. Thus, six objects may be divided into piles of 5+1 or 4+2, but not 3+3. Grundy's game can be played as either misère or normal play.
Greedy nim is a variation wherein the players are restricted to choosing stones from only the largest pile. [ 10 ] It is a finite impartial game . Greedy nim misère has the same rules as greedy nim, but the last player able to make a move loses.
Let the largest number of stones in a pile be m and the second largest number of stones in a pile be n . Let p m be the number of piles having m stones and p n be the number of piles having n stones. Then there is a theorem that game positions with p m even are P positions. [ 11 ] This theorem can be shown by considering the positions where p m is odd. If p m is larger than 1, all stones may be removed from this pile to reduce p m by 1 and the new p m will be even. If p m = 1 (i.e. the largest heap is unique), there are two cases:
Thus, there exists a move to a state where p m is even. Conversely, if p m is even, if any move is possible ( p m ≠ 0), then it must take the game to a state where p m is odd. The final position of the game is even ( p m = 0). Hence, each position of the game with p m even must be a P position.
A generalization of multi-heap nim was called "nim k {\displaystyle {}_{k}} " or "index- k " nim by E. H. Moore , [ 12 ] who analyzed it in 1910. In index- k nim, instead of removing objects from only one heap, players can remove objects from at least one but up to k different heaps. The number of elements that may be removed from each heap may be either arbitrary or limited to at most r elements, like in the "subtraction game" above.
The winning strategy is as follows: Like in ordinary multi-heap nim, one considers the binary representation of the heap sizes (or heap sizes modulo r + 1). In ordinary nim one forms the XOR-sum (or sum modulo 2) of each binary digit, and the winning strategy is to make each XOR sum zero. In the generalization to index- k nim, one forms the sum of each binary digit modulo k + 1.
Again, the winning strategy is to move such that this sum is zero for every digit. Indeed, the value thus computed is zero for the final position, and given a configuration of heaps for which this value is zero, any change of at most k heaps will make the value non-zero. Conversely, given a configuration with non-zero value, one can always take from at most k heaps, carefully chosen, so that the value will become zero.
Building nim is a variant of nim wherein the two players first construct the game of nim. Given n stones and s empty piles, the players, alternating turns, place exactly one stone into a pile of their choice. [ 13 ] Once all the stones are placed, a game of Nim begins, starting with the next player that would move. This game is denoted BN(n,s) .
n -d nim is played on a k 1 × ⋯ × k n {\displaystyle k_{1}\times \dots \times k_{n}} board, whereon any number of continuous pieces can be removed from any hyper-row. The starting position is usually the full board, but other options are allowed. [ 14 ]
The starting board is a disconnected graph, and players take turns to remove adjacent vertices. [ 15 ]
Candy nim is a version of normal-play nim in which players try to achieve two goals at the same time: taking the last object (in this case, candy) and taking the maximum number of candies by the end of the game. [ 16 ] | https://en.wikipedia.org/wiki/Nim |
Nima is a portable food sensor designed to enable individuals with food allergies and sensitivities to test their food for specific proteins. Nima created and leads the category of consumer food testers.
The first product, a gluten sensor, was released in for general availability in February 2017. The second product, a peanut sensor, was released for general availability in September 2018. Nima caters to people who have food sensitivities and food allergies, and require additional data before making a decision at mealtime.
The founders of Nima met at the Massachusetts Institute of Technology (MIT) and have severe food sensitivities and family members with extreme food allergies. They were personally motivated to find a solution to help improve the chances of staying healthy and social when eating outside of the home for themselves, their families and the millions of people who are actively avoiding certain foods to stay healthy. Nima was born out of MIT in 2013. [ 1 ]
Nima was acquired by Medline Industries in 2020. [ 2 ] Whether by decision or Covid19 impact, testing capsules for the testing units were immediately unavailable for purchase on Amazon after the acquisition announcement; however, became available a few months after the acquisition. Medline spun out Nima and re-branded the company to Nima Partners. The gluten products are still available for purchase on the Nima Partners website. [ 3 ]
A food sample is placed in a one-time-use capsule, which is inserted into the Nima sensor. Once the test begins, the food is mixed with proprietary antibodies and analyzed by the sensor in under 5 minutes. Nima delivers a binary result for the sample tested for gluten and peanut. The gluten sensor is tuned to 20 parts per million for gluten and 10 parts per million for peanut. If the sample contains 20 ppm or more of gluten, Nima is designed to deliver a gluten found indication, to indicate gluten was found. If the sample contained 10 ppm or more of peanut, Nima is designed to deliver a peanut found for the sample. If there is no detectable gluten or peanut, Nima will display a smiley face to indicate that there was no detectable target protein in the sampled food. The device has not been approved by the FDA, and the developers contest that such approval is not necessary because they "are not using it to diagnose or manage disease." [ 4 ]
Nima has also developed a companion application for iOS and Android , connected through Bluetooth , that allows users to connect with other Nima owners and find allergen information for specific restaurants and packaged foods. [ 5 ] The company plans to eventually expand its technology to detect other allergens, such as dairy and tree nuts. They are also exploring detection methods for additives, GMOs , preservatives and possible causes of food poisoning. [ 6 ]
Nima uses antibody based chemistry to detect proteins in food at the parts per million level for both gluten and peanut. The Nima science has been third-party validated and published in peer reviewed journals. Nima reports accuracy as the ability to detect gluten in samples of food at 20ppm and above, and to detect peanut in samples of food at 10ppm and above. Nima reports above 97% accuracy when comparing the performance of gluten and peanut detection to the leading food diagnostic lab ELISA tests for traces of gluten at the range of 20ppm and above in food samples and peanut at the range of 10ppm and above. [ 7 ] Dr. Stephen Taylor, founder and director of the Food Allergy Research and Resource program, [ 8 ] concludes on behalf of the validation study for Nima gluten, "We conclude that the portable, handheld Nima gluten sensor functions reliably detect gluten residues at appropriate levels in a range of different foods. The foods were deliberately chosen to represent the wide range of products that might be available as gluten-free options. In our opinion, use of the Nima device will protect the health of gluten-sensitive consumers, if properly used on foods with reasonably uniform gluten distribution." [ 9 ] Nima also has published third-party validation for the Nima peanut sensor. [ 10 ]
In addition to the third-party validation, Nima's validation studies have been published in peer-reviewed journals, including Food Chemistry [ 11 ] and The Journal of Food Protection . [ 9 ] Studies of Nima's food testing data have also been published in the American Journal of Gastroenterology . [ 12 ] A clinical study by researchers and clinicians at the Columbia University Celiac Disease Center found that Nima improved the quality of life of adult celiacs. [ 13 ]
Nima Labs, Inc, the company behind Nima, communicates that Nima is a supplement and extra data point to what users are already doing to try to avoid gluten and peanut when eating out. As quoted on the Nima packaging, "Nima test results are only representative of the sample and are not a guarantee of the entire dish. Use of this product should not replace education, medical advice, compliance with food labeling and adherence to avoidance strategies. Failure to use this product in accordance with the instruction could result in serious injury or death. Neither the Nima device or individual capsules are designed to be ingested or eaten."
While Nima works on most food types, Nima's sensing technology has a few limitations, including detection of proteins in hydrolyzed and fermented foods for gluten. This is most challenging for gluten detection in the case of soy sauce and alcohol - Nima cannot detect gluten in soy sauce or alcohol. The peanut sensor also has limitations for some high concentrations of ingredients. The full list of limitations are published and linked on the Nima FAQs website. [ 14 ]
The majority of Nima users use Nima when eating out at restaurants and testing samples of food that may be higher risk for cross-contamination, such as shared fryers, gluten-free pizzas cooked in pizza ovens with non-gluten items, sauces, and marinades. When testing at home, Nima users typically test packaged foods with unclear ingredients or no gluten or peanut ingredients, which are not labelled gluten-free or peanut-free. Nima users can share their test results on the Nima app and see what other people are testing. A study by the Columbia Celiac Disease Center analyzed thousands of Nima user test results and found that gluten was present in one out of three gluten-free labelled dishes in restaurants. [ 12 ]
Generally, Nima has been positively received in the marketplace, with recognition by top publications, including Time magazine 's Best Inventions [ 15 ] and Popular Science ' s 12 Most Important Health Innovations of the Year. [ 16 ] An investigative reporter as part of the Rossen Reports put the Nima peanut sensor to the test on the Today Show , [ 17 ] with positive results. | https://en.wikipedia.org/wiki/Nima_(device) |
In numerical analysis , given a square grid in two dimensions, the nine-point stencil of a point in the grid is a stencil made up of the point itself together with its eight "neighbors". It is used to write finite difference approximations to derivatives at grid points. It is an example for numerical differentiation . This stencil is often used to approximate the Laplacian of a function of two variables.
If we discretize the 2D Laplacian by using central-difference methods , we obtain the commonly used five-point stencil , represented by the following convolution kernel:
D C D = [ 0 1 0 1 − 4 1 0 1 0 ] {\displaystyle D_{CD}={\begin{bmatrix}0&1&0\\1&-4&1\\0&1&0\end{bmatrix}}}
Even though it is simple to obtain and computationally lighter, the central difference kernel possess an undesired intrinsic anisotropic property, since it doesn't take into account the diagonal neighbours. This intrinsic anisotropy poses a problem when applied on certain numerical simulations or when more accuracy is required, by propagating the Laplacian effect faster in the coordinate axes directions and slower in the other directions, thus distorting the final result. [ 1 ]
This drawback calls for finding better methods for discretizing the Laplacian, reducing or eliminating the anisotropy.
The two most commonly used isotropic nine-point stencils are displayed below, in their convolution kernel forms. They can be obtained by the following formula: [ 2 ] [ 3 ]
D = ( 1 − γ ) [ 0 1 0 1 − 4 1 0 1 0 ] + γ [ 1 / 2 0 1 / 2 0 − 2 0 1 / 2 0 1 / 2 ] {\displaystyle D=(1-\gamma ){\begin{bmatrix}0&1&0\\1&-4&1\\0&1&0\end{bmatrix}}+\gamma {\begin{bmatrix}1/2&0&1/2\\0&-2&0\\1/2&0&1/2\end{bmatrix}}}
The first one is known by Oono-Puri, [ 4 ] [ 5 ] [ 6 ] [ 7 ] [ 8 ] and it is obtained when γ=1/2. [ 2 ]
D O P = [ 1 / 4 2 / 4 1 / 4 2 / 4 − 12 / 4 2 / 4 1 / 4 2 / 4 1 / 4 ] = [ 0.25 0.5 0.25 0.5 − 3 0.5 0.25 0.5 0.25 ] {\displaystyle D_{OP}={\begin{bmatrix}1/4&2/4&1/4\\2/4&-12/4&2/4\\1/4&2/4&1/4\end{bmatrix}}={\begin{bmatrix}0.25&0.5&0.25\\0.5&-3&0.5\\0.25&0.5&0.25\end{bmatrix}}}
The second one is known by Patra-Karttunen or Mehrstellen, [ 1 ] [ 7 ] [ 8 ] [ 9 ] [ 10 ] and it is obtained when γ=1/3. [ 2 ]
D P K = [ 1 / 6 4 / 6 1 / 6 4 / 6 − 20 / 6 4 / 6 1 / 6 4 / 6 1 / 6 ] = [ 0.16 0.66 0.16 0.66 − 3.33 0.66 0.16 0.66 0.16 ] {\displaystyle D_{PK}={\begin{bmatrix}1/6&4/6&1/6\\4/6&-20/6&4/6\\1/6&4/6&1/6\end{bmatrix}}={\begin{bmatrix}0.16&0.66&0.16\\0.66&-3.33&0.66\\0.16&0.66&0.16\end{bmatrix}}}
Both are isotropic forms of discrete Laplacian , [ 8 ] and in the limit of small Δx, they all become equivalent, [ 11 ] as Oono-Puri being described as the optimally isotropic form of discretization, [ 8 ] displaying reduced overall error, [ 2 ] and Patra-Karttunen having been systematically derived by imposing conditions of rotational invariance, [ 9 ] displaying smallest error around the origin. [ 2 ]
On the other hand, if controlled anisotropic effects are a desired feature, when solving anisotropic diffusion problems for example, it is also possible to use the 9-point stencil combined with tensors to generate them.
Consider the laplacian in the following form:
c ∇ 2 A = c D O P ∗ A {\displaystyle c\nabla ^{2}A=cD_{OP}*A}
Where c is just a constant coefficient. Now if we replace c by the 2nd rank tensor C:
C = [ c 1 0 0 c 2 ] {\displaystyle C={\begin{bmatrix}c_{1}&0\\0&c_{2}\end{bmatrix}}}
Where c1 is the constant coefficient for the principal direction in x axis, and c2 is the constant coefficient for the secondary direction in y axis. In order to generate anisotropic effects, c1 and c2 must be different.
By multiplying it by the rotation matrix Q, we obtain C', allowing anisotropic propagations in arbitrary directions other than the coordinate axes . [ 12 ] [ 13 ]
Q = [ cos θ sin θ − sin θ cos θ ] {\displaystyle Q={\begin{bmatrix}\cos \theta &\sin \theta \\-\sin \theta &\cos \theta \end{bmatrix}}}
C ′ = Q C Q T {\displaystyle C'=QCQ^{\operatorname {T} }}
C ′ = [ c x x c x y c x y c y y ] = [ c 1 cos 2 θ + c 2 sin 2 θ ( c 2 − c 1 ) cos θ sin θ ( c 2 − c 1 ) cos θ sin θ c 2 cos 2 θ + c 1 sin 2 θ ] {\displaystyle C'={\begin{bmatrix}c_{xx}&c_{xy}\\c_{xy}&c_{yy}\end{bmatrix}}={\begin{bmatrix}c_{1}\cos ^{2}\theta +c_{2}\sin ^{2}\theta &(c_{2}-c_{1})\cos \theta \sin \theta \\(c_{2}-c_{1})\cos \theta \sin \theta &c_{2}\cos ^{2}\theta +c_{1}\sin ^{2}\theta \end{bmatrix}}}
Which is very similar to the Cauchy stress tensor in 2 dimensions. The angle θ {\displaystyle \theta } can be obtained by generating a vector field V = V x i + V y j {\displaystyle \mathbf {V} =V_{x}{\mathbf {i} }+V_{y}{\mathbf {j} }} in order to orientate the pattern as desired. [ 13 ] Then:
θ = arctan ( V y / V x ) {\displaystyle \theta =\arctan(V_{y}/V_{x})}
Or, for different anisotropic effects using the same vector field [ 14 ]
θ = arctan ( V y / − V x ) {\displaystyle \theta =\arctan(V_{y}/-V_{x})}
It is important to note that, regardless of the values of θ {\displaystyle \theta } , the anisotropic propagation will occur parallel to the secondary direction c2 and perpendicular to the principal direction c1:. [ 15 ] The resulting convolution kernel is as follows [ 13 ]
D A n i s o = [ − c x y 2 c y y c x y 2 c x x − 2 ( c x x + c y y ) c x x c x y 2 c y y − c x y 2 ] {\displaystyle D_{Aniso}={\begin{bmatrix}{\frac {-c_{xy}}{2}}&c_{yy}&{\frac {c_{xy}}{2}}\\c_{xx}&-2(c_{xx}+c_{yy})&c_{xx}\\{\frac {c_{xy}}{2}}&c_{yy}&{\frac {-c_{xy}}{2}}\end{bmatrix}}}
If, for example, c1=c2=1, the cxy component will vanish, resulting in the simple five-point stencil , rendering no controlled anisotropy.
If c2>c1 and θ {\displaystyle \theta } =0, the anisotropic effects will be more pronounced in the vertical axis.
If c2>c1 and θ {\displaystyle \theta } =45 degrees, the anisotropic effects will be more pronounced in the upper-right / lower-left diagonal. | https://en.wikipedia.org/wiki/Nine-point_stencil |
Nines are an informal logarithmic notation for proportions very near to one or, equivalently, percentages very near 100%. Put simply, "nines" are the number of consecutive nines in a percentage such as 99% (two nines) [ 1 ] or a decimal fraction such as 0.999 (three nines). Their common uses include grading the purity of materials – especially precious metals and industrial gases – or measuring the availability of a service.
The nines are a count of the leftmost digits 9 that appear in a proportion. For example, 90% would be described as "one nine"; 99% as "two nines"; 99.9% as "three nines"; and so forth.
However, there are different conventions for representing inexact multiples of 9. For example, a percentage of 99.5% could be expressed as "two nines five" (2N5, or N2.5) [ 2 ] or as 2.3 nines, [ citation needed ] following from the logarithm definition.
A percentage of 100% would, in theory, have an infinite number of nines – though, in the context of purity of materials, 100% is virtually unachievable. [ 3 ]
The number of nines of a proportion x is: [ 4 ]
n i n e s = − log 10 ( 1 − x ) {\displaystyle \mathrm {nines} =-\log _{10}(1-x)}
The exact purity of very fine precious metals such as platinum , gold and silver can be of great interest. Based on the system of millesimal fineness , a metal is said to be one nine or one nine fine if it is 900 fine, or 90% pure. A metal that is 990 fine is then described as two nines fine and one that is 999 fine is described as three nines fine . Thus, nines are a logarithmic scale of purity for very fine precious metals. Similarly, percentages ending in a 5 have conventional names, traditionally the number of nines, then "five", so 999.5 fine (99.95% pure) is "three nines five", abbreviated 3N5.
Canada's Big Maple Leaf , a coin made of gold at 5N (99.999%) purity, stands as the purest gold coin ever minted, anywhere. [ 5 ] The purest gold ever achieved was reportedly produced at the Perth Mint in 1957, at "almost six nines" (99.9999%) purity, as measured by the Worshipful Company of Goldsmiths of London. [ 6 ]
The nines scale is also used in other contexts, such as describing the purity of gases . The purity of a gas is an indication of the ratio of it to other gases in its mixture , as measured by volume. Thus, a high purity refers to a low amount of other gases, or impurities. Gases of higher purity are in many contexts considered to be of better quality and are usually more expensive.
The purity of a gas is generally expressed as a grade prefixed with the letter N (rather than postfixed), indicating the "number of nines" in the percentage or decimal fraction . For example, a N2.0 gas is 99% (two nines) pure and 1% impurities by volume; a N6.0 gas is 99.9999% (six nines) pure, with 1 part per million (1 ppm or 1 vpm, volume per million) impurities. [ 7 ]
Intermediate values indicate the digit following the last nine. For example, N4.6 estimates a purity level of 99.996% (four nines followed by a six). [ 7 ] An alternative representation uses the common logarithm : for example, a gas which is 99.97% pure would be described as N3.5, since log 10 (0.03%) = −3.523. [ citation needed ]
Nines are used in a similar manner to describe computer system availability . In this context, a "one nine" (90%) uptime indicates a system that is available 90% of the time or, as is more commonly described, unavailable 10% of the time – about 72 hours per month. [ 8 ] A "five nines" (99.999%) uptime describes a system that is unavailable for at most 26 seconds per month. [ 8 ] | https://en.wikipedia.org/wiki/Nines_(notation) |
The Ninetology Vox (C1240) is a dual-band GSM 900/1800 color mobile phone manufactured by Ninetology with dual SIM capabilities. It was announced in November 2012 via a campaign called VOX G.O.L.D Fund that aimed to raise donations funds for Yayasan Maha Karuna . [ 1 ]
The Ninetology Vox (C1240) has an MT 6250 single core (260 MHz) processor. Its dimensions are 115.6 mm (H) x 49.6 mm (W) x 14.5 mm (T) and weighs 88 grams.
It possesses a 2.4-inch IPS display screen with a 240 x 320 resolution and is capable of producing up to 65K colors. It is also equipped with a 1.3 MP rear-facing camera.
The battery has a capacity of Li-Ion 1200 mAh, and additional storage is available via a MicroSD card socket, which is certified to support up to 8 GB of additional storage.
The VOX G.O.L.D Fund campaign organized by Ninetology aims to raise donations funds for Yayasan Maha Karuna. Ninetology does this by donating a large percentage of its accumulated sales from its Vox model to the organization. [ 2 ] | https://en.wikipedia.org/wiki/Ninetology_Vox |
Ninhydrin (2,2-dihydroxyindane-1,3-dione) is an organic compound with the formula C 6 H 4 (CO) 2 C(OH) 2 . It is used to detect ammonia and amines . Upon reaction with these amines, ninhydrin gets converted into deep blue or purple derivatives, which are called Ruhemann's purple. Ninhydrin is most commonly used to detect fingerprints in forensic cases, as the terminal amines of lysine residues in peptides and proteins sloughed off in fingerprints react with ninhydrin. [ 2 ] [ 3 ]
Ninhydrin is a white solid that is soluble in ethanol and acetone . [ 1 ] Ninhydrin can be considered as the hydrate of indane-1,2,3-trione .
Ninhydrin was discovered in 1910 by the German-English chemist Siegfried Ruhemann (1859–1943). [ 4 ] [ 5 ] In the same year, Ruhemann observed ninhydrin's reaction with amino acids . [ 6 ] In 1954, Swedish investigators Oden and von Hofsten proposed that ninhydrin could be used to develop latent fingerprints. [ 7 ] [ 8 ]
Ninhydrin can be used in Kaiser test to monitor deprotection in solid phase peptide synthesis . [ 9 ] The chain is linked via its C-terminus to the solid support, with the N-terminus extending off it. When that nitrogen is deprotected, a ninhydrin test yields blue. Amino-acid residues are attached with their N-terminus protected, so if the next residue has been successfully coupled onto the chain, the test gives a colorless or yellow result.
Ninhydrin is also used in qualitative analysis of proteins. Most of the amino acids, except proline , are hydrolyzed and react with ninhydrin. Also, certain amino acid chains are degraded. Therefore, separate analysis is required for identifying such amino acids that either react differently or do not react with ninhydrin at all. The rest of the amino acids are then quantified colorimetrically after separation by chromatography .
A solution suspected of containing the ammonium ion can be tested by ninhydrin by dotting it onto a solid support (such as silica gel ); treatment with ninhydrin should result in a dramatic purple color if the solution contains this species. In the analysis of a chemical reaction by thin layer chromatography (TLC), the reagent can also be used (usually 0.2% solution in either n-butanol or in ethanol). It will detect, on the TLC plate, virtually all amines , carbamates and also, after vigorous heating, amides .
Upon reaction with ninhydrin, amino acids undergo decarboxylation . The released CO 2 originates from the carboxyl carbon of the amino acid. This reaction has been used to release the carboxyl carbons of bone collagen from ancient bones [ 10 ] for stable isotope analysis in order to help reconstruct the palaeodiet of cave bears . [ 11 ] Release of the carboxyl carbon (via ninhydrin) from amino acids recovered from soil that has been treated with a labeled substrate demonstrates assimilation of that substrate into microbial protein. [ 12 ] This approach was successfully used to reveal that some ammonium oxidizing bacteria, also called nitrifying bacteria use urea as a carbon source in soil. [ 13 ]
A ninhydrin solution is commonly used by forensic investigators in the analysis of latent fingerprints on porous surfaces such as paper. The amino acids present in the minute sweat secretions that gather on the finger's unique ridges transfer to surfaces that are touched. Exposure of the surface to ninhydrin converts the amino acids into visibly colored products and thus reveals the print. [ 14 ] The test solutions suffer from poor long-term stability, especially if not kept cold. [ 15 ]
To further enhance the ability of ninhydrin, a solution of 1,2-indandione and zinc chloride (IND-Zn) can be used prior to ninhydrin. This sequence leads to greater overall reaction of the amino acids, possibly by IND-Zn helping to release them from the surface for the subsequent ninhydrin reaction. [ 16 ]
Ninhydrin exists in equilibrium with the triketone indane-1,2,3-trione , which reacts readily with nucleophiles (including water). Whereas for most carbonyl compounds, a carbonyl form is more stable than a product of water addition (hydrate), ninhydrin forms a stable hydrate of the central carbon because of the destabilizing effect of the adjacent carbonyl groups.
To generate the ninhydrin chromophore [2-(1,3-dioxoindan-2-yl)iminoindane-1,3-dione], the amine must condense to give a Schiff base . The reaction of ninhydrin with secondary amines gives an iminium salt, which is also coloured, generally being yellow–orange.
Ninhydrin may cause allergic, IgE-mediated rhinitis and asthma. [ 17 ] A case has been described in which a 41 year old forensic laboratory worker working with Ninhydrin developed rhinitis and respiratory difficulty. Her specific IgE levels were found almost doubled. [ 17 ] | https://en.wikipedia.org/wiki/Ninhydrin |
The Nininger Meteorite Award awarded by the Center for Meteorite Studies recognizes outstanding student achievement in the "Science of Meteoritics " as embodied by an original research paper. [ 1 ] In 1965, Dr. Harvey H. Nininger and Mrs. Addie D. Nininger endowed the Nininger Science of Meteoritics Fund to the Center for Meteorite Studies at Arizona State University in order to promote interest in meteorite-related topics among young scientists. A number of prominent planetary scientists and meteoriticists have won this award including William K. Hartmann , Hap McSween , and Dante Lauretta .
Source: Nininger Past Recipients | https://en.wikipedia.org/wiki/Nininger_Meteorite_Award |
Nintendo European Research & Development ( NERD ) is a French subsidiary for Nintendo , located in Paris, which develops software technologies and middleware for Nintendo platforms. [ 1 ] This includes retro console emulators , patented video codecs , and digital rights management technology.
The organization originated as Mobiclip and Actimagine ( / ˈ ɑː k t ɪ m ə dʒ iː n / ) with notable customers including Nintendo , Sony Pictures Digital , and Fisher-Price . Nintendo licensed Mobiclip compression technology for the Game Boy Advance and Nintendo DS video game consoles, used by popular games such as Square Enix 's Final Fantasy III and Konami 's Contra 4 . Fisher-Price used them for its Pixter Multi-Media educational toy. Sony Pictures Digital and The Carphone Warehouse used Mobiclip software to deliver TV-like full-length movies on MicroSD memory cards for smart phones . Nintendo purchased the company, to create NERD.
Actimagine was established in March 2003 by a team of engineers (Eric Bécourt, Alexandre Delattre, Laurent Hiriart, Jérôme Larrieu, Sylvain Quendez) and a businessman (André Pagnac). [ 2 ] Actimagine started out with mobile gaming consoles. The video compression technology offered by Mobiclip was an optimized response to the battery life and video quality requirements of Nintendo video gaming platforms: Game Boy Advance, Nintendo DS, Wii, and Nintendo 3DS.
The Mobiclip codec provides high video quality with low battery consumption and has been selected by major studios, such as Sony Pictures Digital, Paramount , Fox and Gaumont Columbia TriStar Films , and by leading handset manufacturers, such as Nokia or Sony Ericsson, to deliver video on memory cards for mobile phones. [ citation needed ] [ promotion? ]
In April 2006, Actimagine raised €3 million in equity financing from US venture capital firm GRP Partners . This first round of institutional fund raising enabled Actimagine to accelerate its business development in the US and Japan.
The same year, Adobe acquired Actimagine's Flash rendering engine optimized for mobile devices. [ 3 ]
In 2008, Mobiclip launched the first application delivering live TV on the iPhone, a year before Apple. [ 4 ] [ 5 ]
In October 2011, Mobiclip [ 6 ] was bought by Nintendo and is now a subsidiary of the latter. Since then it is now known as "Nintendo European Research & Development" or "NERD".
In 2017, the United States branch was merged with Nintendo Technology Development. [ 7 ]
Mobiclip was developed with a completely different algorithm from the one used for other video codecs on the market, based on minimal use of the processor resources, allowing battery life to be increased considerably and the cost of the hardware to be reduced.
Nintendo selected Mobiclip as its main provider of video codec technologies on the Game Boy Advance, Nintendo DS, Nintendo Wii and Nintendo 3DS.
Major software titles used it for in-game cinematics, including: | https://en.wikipedia.org/wiki/Nintendo_European_Research_&_Development |
Niobium(III) chloride also known as niobium trichloride is a compound of niobium and chlorine . The binary phase NbCl 3 is not well characterized but many adducts are known.
Nb 3 Cl 8 is produced by reduction of niobium(V) chloride with hydrogen , or just by heating.
Salt-free reduction of dimethoxyethane solution of NbCl 5 with 1,4-disilyl-cyclohexadiene in the presence of 3-hexyne produces the coordination complex NbCl 3 (dimethoxyethane)(3-hexyne):
An impure dimethoxyethane (dme) adduct of niobium trichloride was produced by reduction of a dme solution of niobium pentachloride with tributyltin hydride : [ 3 ]
Nb 3 Cl 8 has a hexagonal close packed array of chloride ions. Triangles of niobium occur in octahedral spaces in the chloride array. The compositions with higher chloride have some niobium atoms missing from the structure, creating vacancies and giving rise to nonstoichiometric compounds . NbCl 4 has this pattern of vacancies stretched until the niobium atoms are in pairs rather than triangles. So NbCl 3 can be considered as a solid solution of Nb 3 Cl 8 and Nb 2 Cl 8 . [ 4 ]
The colour of niobium trichloride varies depending on the niobium:chloride ratio. NbCl 2.67 is green, while NbCl 3.13 is brown. [ 1 ]
When heated to over 600 °C niobium trichloride disproportionates to niobium metal and niobium pentachloride.
NbCl 3 (dimethoxyethane) has received significant attention as a reagent for reductive coupling of carbonyls and imines. [ 6 ] It is sold as a 1,2-dimethoxyethane complex. Nb(III) adducts are also known for 1,4-dioxane and diethyl ether .
Niobium(III) chloride forms a series of compounds with the formula Nb 2 Cl 6 L x with Nb=Nb double bond . With tertiary phosphines and arsines, the complexes are edge-share bioctahedra, e.g., Nb 2 Cl 6 (PPhMe 2 ) 4 . [ 7 ] Thioethers form adducts with one bridging thioether (R 2 S). These face-sharing bioctahedra have the formula Nb 2 X 6 (R 2 S) 3 (X = Cl, Br). | https://en.wikipedia.org/wiki/Niobium(III)_chloride |
Niobium dioxide , is the chemical compound with the formula NbO 2 . It is a bluish-black non-stoichiometric solid with a composition range of NbO 1.94 -NbO 2.09 . [ 1 ] It can be prepared by reducing Nb 2 O 5 with H 2 at 800–1350 °C. [ 1 ] An alternative method is reaction of Nb 2 O 5 with Nb powder at 1100 °C. [ 2 ]
The room temperature form of NbO 2 has a tetragonal , rutile -like structure with short Nb-Nb distances, indicating Nb-Nb bonding. [ 3 ] The high temperature form also has a rutile -like structure with short Nb-Nb distances. [ 4 ] Two high-pressure phases have been reported: one with a rutile-like structure (again, with short Nb-Nb distances); and a higher pressure with baddeleyite -related structure. [ 5 ]
NbO 2 is insoluble in water and is a powerful reducing agent, reducing carbon dioxide to carbon and sulfur dioxide to sulfur. [ 1 ] In an industrial process for the production of niobium metal, NbO 2 is produced as an intermediate, by the hydrogen reduction of Nb 2 O 5 . [ 6 ] The NbO 2 is subsequently reacted with magnesium vapor to produce niobium metal. [ 7 ] | https://en.wikipedia.org/wiki/Niobium_dioxide |
Niobium nitride is a compound of niobium and nitrogen ( nitride ) with the chemical formula NbN. At low temperatures (about 16 K) NbN becomes a superconductor , and is used in detectors for infrared light . [ 1 ] [ 2 ] [ 3 ] | https://en.wikipedia.org/wiki/Niobium_nitride |
Niobium-germanium ( Nb 3 Ge ) is an intermetallic chemical compound of niobium (Nb) and germanium (Ge). It has A15 phase structure.
It is a superconductor with a critical temperature of 23.2 K .
Sputtered films have been reported to have an upper critical field of 37 teslas at 4.2 K. [ 1 ]
Nb 3 Ge was discovered to be a superconductor in 1973 [ 2 ] and for 13 years (until the discovery in 1986 of the cuprate superconductors ) it held the record as having the highest critical temperature. [ 3 ]
It has not been as widely used for superconductive applications as niobium–tin or niobium–titanium .
Niobium-germanium-aluminium has an upper critical field of about 10 teslas. [ 4 ] | https://en.wikipedia.org/wiki/Niobium–germanium |
Niobium–tin is an intermetallic compound of niobium (Nb) and tin (Sn), used industrially as a type-II superconductor . This intermetallic compound has a simple structure: A3B . It is more expensive than niobium–titanium (NbTi), but remains superconducting up to a magnetic flux density of 30 teslas [T] (300,000 G), [ 1 ] compared to a limit of roughly 15 T for NbTi.
Nb 3 Sn was discovered to be a superconductor in 1954. The material's ability to support high currents and magnetic fields was discovered in 1961 and started the era of large-scale applications of superconductivity.
The critical temperature is 18.3 kelvins (−254.8 °C; −426.7 °F). Application temperatures are commonly around 4.2 K (−268.95 °C; −452.11 °F), the boiling point of liquid helium at atmospheric pressure.
In April 2008 a record non-copper current density was claimed of 2,643 A mm −2 at 12 T and 4.2 K. [ 2 ]
Nb 3 Sn was discovered to be a superconductor in 1954, one year after the discovery of V 3 Si , the first example of an A 3 B superconductor. [ 3 ] In 1961 it was discovered that niobium–tin still exhibits superconductivity at large currents and strong magnetic fields, thus becoming the first known material to support the high currents and fields necessary for making useful high-power magnets and electric power machinery . [ 4 ] [ 5 ]
The central solenoid and toroidal field superconducting magnets for the planned experimental ITER fusion reactor use niobium–tin as a superconductor. [ 6 ] The central solenoid coil will produce a field of 13.5 teslas (135,000 G). The toroidal field coils will operate at a maximum field of 11.8 T. Estimated use is 600 metric tons (590 long tons) of Nb 3 Sn strands and 250 metric tonnes of NbTi strands. [ 7 ] [ 8 ]
At the Large Hadron Collider at CERN , extra-strong quadrupole magnets (for focussing beams) made with niobium–tin are being installed in key points of the accelerator between late 2018 and early 2020. [ 9 ] Niobium tin had been proposed in 1986 as an alternative to niobium–titanium , since it allowed coolants less complex than superfluid helium , [ clarification needed ] [ citation needed ] but this was not pursued in order to avoid delays while competing with the then-planned US-led Superconducting Super Collider .
Mechanically, Nb 3 Sn is extremely brittle and thus cannot be easily drawn into a wire, which is necessary for winding superconducting magnets . To overcome this, wire manufacturers typically draw down composite wires containing ductile precursors. The "internal tin" process includes separate alloys of Nb, Cu and Sn. The "bronze" process contains Nb in a copper –tin bronze matrix. With both processes the strand is typically drawn to final size and coiled into a solenoid or cable before heat treatment. It is only during heat treatment that the Sn reacts with the Nb to form the brittle, superconducting niobium–tin compound. [ 10 ] The powder-in-tube process is also used. [ 2 ] [ 11 ]
The high field section of modern NMR magnets are composed of niobium–tin wire.
Inside a magnet the wires are subjected to high Lorentz forces as well as thermal stresses during cooling. Any strain in the niobium tin causes a decrease in the superconducting performance of the material, and can cause the brittle material to fracture. Because of this, the wires need to be as stiff as possible. The Young's modulus of niobium tin is around 140 GPa ( gigapascals ) at room temperature. However, the stiffness drops to as low as 50 GPa when the material is cooled below 50 K (−223.2 °C; −369.7 °F). [ 12 ] Engineers must therefore find ways of improving the strength of the material. Strengthening fibers are often incorporated in the composite niobium tin wires to increase their stiffness. Common strengthening materials include Inconel , stainless steel , molybdenum , and tantalum because of their high stiffness at cryogenic temperatures. [ 13 ] Since the thermal expansion coefficients of the matrix, fiber, and niobium tin are all different, significant amounts of strain can be generated after the wire is annealed and cooled all the way down to operating temperatures. This strain is referred to as the pre-strain in the wire. Since any strain in the niobium tin generally decreases the superconducting performance of the material, a proper combination of materials must be used to minimize this value. The pre-strain in a composite wire can be calculated by the formula
where ε m is the pre-strain, ΔL/L c and ΔL/L f are changes in length due to thermal expansion of the niobium tin conduit and strengthening fiber respectively; V c , V f , V cu , and V bz are the volume fractions of conduit, fiber, copper, and bronze; σ cu,y , and σ bz,y are the yield stresses of copper and bronze; and E c , and E f are the Young's modulus of the conduit and the fiber. [ 14 ] Since the copper and bronze matrix deforms plastically during cooldown, they apply a constant stress equal to their yield stress. The conduit and fiber, however, deform elastically by design. Commercial superconductors manufactured by the bronze process generally have a pre-strain value around 0.2% to 0.4%. The so-called strain effect causes a reduction in the superconducting properties of many materials including niobium tin. The critical strain, the maximum allowable strain over which superconductivity is lost, is given by the formula
where ε c is the critical strain, ε co is a material dependent parameter equal to 1.5% in tension (−1.8% in compression) for niobium tin, B is the applied magnetic field, and B c2m is the maximum upper critical field of the material. [ 15 ] Strain in the niobium tin causes tetragonal distortions in the crystal lattice, which changes the electron-phonon interaction spectrum. This is equivalent to an increase in disorder in the A15 crystal structure. [ 16 ] At high enough strain, around 1%, the niobium tin conduit will develop fractures and the current carrying capability of the wire will be irreversibly damaged. In most circumstances, except for high field conditions, the niobium tin conduit will fracture before the critical strain is reached.
Hafnium or zirconium added to niobium–tin increases the maximum current density in a magnetic field. This may allow it to be used at 16 tesla for CERN's planned Future Circular Collider . [ 17 ] | https://en.wikipedia.org/wiki/Niobium–tin |
Niobium–titanium ( Nb-Ti ) is a ductile alloy of niobium and titanium , used industrially as a type II superconductor wire for superconducting magnets , normally as Nb-Ti fibres in an aluminium or copper matrix.
Its critical temperature is about 10 kelvins . [ 1 ]
The high critical magnetic field and high critical supercurrent density of Nb-Ti was discovered in 1962 at Atomics International by T. G. Berlincourt and R. R. Hake. [ 2 ] [ 3 ] Nb-Ti alloys are notable for their easy workability and affordability, distinguishing them from other superconducting materials.
Nb-Ti alloys have a maximal critical magnetic field of about 15 teslas and, thus, are suitable for fabricating supermagnets capable of generating magnetic fields of up to about 10 teslas. For stronger magnetic fields, higher performance superconductors, such as niobium–tin , are commonly used, but these are more difficult to fabricate and more expensive to produce.
The global superconductivity market was valued at around five billion euros in 2014. [ 4 ] Magnet resonance imaging (MRI) systems, most of which use Nb-Ti, accounted for about 80% of the total market value.
A bubble chamber at Argonne National Laboratory has a 4.8-meter-diameter Nb-Ti magnet, which produces a magnetic field of 1.8 tesla. [ 5 ]
About 1,000 Nb-Ti SC magnets were used in the 4-mile-long main ring of the Tevatron accelerator at Fermilab . [ 6 ] The magnets were wound with 50 tons of copper cables, containing 17 tons of Nb-Ti filaments. [ 7 ] They operate at 4.5 K and generate fields of up to 4.5 T.
1999: The Relativistic Heavy Ion Collider uses 1,740 Nb-Ti SC 3.45 T magnets to bend beams in its 3.8 km double storage ring. [ 8 ]
In the Large Hadron Collider particle accelerator , the magnets contain 1,200 tonnes of Nb-Ti cable, [ 9 ] of which 470 tons are Nb-Ti [ 10 ] and the rest copper, and they are cooled to 1.9 K to allow the safe operation of fields of up to 8.3 T.
Niobium–titanium superconducting magnet coils (liquid-helium-cooled) were built to be used in the Alpha Magnetic Spectrometer mission at the International Space Station . They were later replaced by non-superconducting magnets.
The experimental fusion reactor ITER uses niobium–titanium for its poloidal field coils. In 2008, a test coil achieved stable operation at 52 kA and 6.4 T. [ 11 ]
The Wendelstein 7-X stellarator uses Nb-Ti for its magnets, which are cooled to 4 K to create a 3 T field.
The SCMaglev uses Nb-Ti for the magnets onboard trains. A train using the technology currently holds the train speed world record of 603 km/h. It will be deployed for the Chūō Shinkansen , providing passenger service between Tokyo , Nagoya , and Osaka at a planned maximum operating speed of 505 km/h. Construction is underway for the Tokyo–Nagoya segment, with a planned opening date of 2027. [ 12 ] | https://en.wikipedia.org/wiki/Niobium–titanium |
Nion was a manufacturer of scanning transmission electron microscopes (STEMs) based in Kirkland , Washington State, USA . It was acquired by Bruker Corp. in 2024.
Nion Co. was founded in 1997 in Washington State, USA, by Ondrej Krivanek [ 2 ] and Niklas Dellby, with a mission to design and build advanced instruments for electron microscopy. Prior to founding Nion, Krivanek and Dellby built a working proof-of-principle aberration corrector for a STEM, in Cambridge UK. Following this success, Philip Batson of IBM TJ Watson Research Center asked them to build an aberration corrector for his STEM. Krivanek was a research professor at University of Washington at the time, and he and Dellby decided to start Nion Co. and build a redesigned corrector. The new corrector was delivered to IBM in June 2020, and demonstrated direct sub-Å resolution. Nion went on to supply the scientific community with correctors for 100 and 300 kV dedicated STEMs made by Vacuum Generators. Nion's 2004 Science article [ 3 ] demonstrated 0.78 Å resolution and led to wide acceptance of aberration correction as the best way to achieve high spatial resolution in electron microscopy.
It soon became clear that a new, higher stability electron microscope was needed, built from the ground up so that resolutions of 0.5 Ångstroms and below could be reached. [ 4 ] Nion developed such an instrument as its next project: a 100 kV aberration corrected, high-stability electron microscope called UltraSTEM, [ 5 ] with resolution capability well below one Angstrom. [ 6 ] [ 7 ] The first deliveries of this instrument took place in 2008, to Cornell University and the SuperSTEM Daresbury Laboratory . [ 8 ] A 200 kV version of this microscope was delivered to the Orsay STEM laboratory near Paris in 2010 and many other labs since. It is able to reach 0.5 Å resolution.
Nion went on to develop a monochromated STEM, with the first delivery to Arizona State University in 2013 and subsequent deliveries to Rutgers University, Daresbury SuperSTEM, [ 9 ] and many other laboratories in the USA, Canada, Europe and China. In 2014, the ASU and Rutgers monochromatic STEMs showed that phonons could be detected with high spatial resolution in an electron microscope by ultra-high energy resolution electron energy loss spectroscopy (EELS). [ 10 ] In 2018, Nion introduced a new EELS spectrometer, which improved the EELS resolution to 3 meV, and allowed the vibrations of single atoms to be studied. [ 11 ]
Other innovations introduced by Nion and the ongoing operation under the Bruker umbrella include X-ray spectroscopy with single-atom sensitivity, [ 12 ] imaging samples in a contamination-free ultra-high vacuum (UHV) environment, atomic resolution secondary electron imaging (SEI) of surfaces of samples held in UHV, and stable imaging at temperatures <10 K.
In 2020, co-founder of Nion, Ondrej Krivanek, shared the Kavli Prize for Nanoscience for work creating the first aberration-corrected scanning transmission electron microscope with resolution below one ångstrom (0.1 nanometers). [ 13 ] [ 14 ] [ 6 ]
In January 2024, Nion was acquired by Bruker , which moved Bruker into the manufacture of electron microscopes . [ 15 ] | https://en.wikipedia.org/wiki/Nion_(company) |
In plumbing and piping , a nipple is a fitting, consisting of a short piece of pipe , usually provided with a male pipe thread at each end, for connecting two other fittings.
The length of the nipple is usually specified by the overall length with thread. It may have a hexagonal section in the center for a wrench to grasp (sometimes referred to as a "hex nipple"), or it may simply be made from a short piece of pipe (sometimes referred to as a "barrel nipple" or "pipe nipple"). A "close nipple" has no unthreaded area; when screwed tightly between two female fittings, very little of the nipple remains exposed. A close nipple can only be unscrewed by gripping one threaded end with a pipe wrench which will damage the threads and necessitate replacing the nipple, or by using a specialty tool known as a nipple wrench (or known as an internal pipe wrench) which grips the inside of the pipe, leaving the threads undamaged. When the ends are of two different sizes it is called a reducer or unequal nipple.
Threads used on nipples are BSP , BSPT , NPT , NPSM and Metric .
A chase nipple is a short pipe fitting, which creates a path for wires between two electrical boxes . A chase nipple has male threads on one end only. The other end is a hexagon. The chase nipple passes through the knockouts of two boxes, and is secured by an internally threaded ring called a lock nut. [ 1 ] [ 2 ]
Chase-Shawmut Company, of Boston , is the company which first produced chase nipples. [ 3 ] | https://en.wikipedia.org/wiki/Nipple_(plumbing) |
NIRA Dynamics AB is a Swedish company focusing on research and development of signal processing and control systems for the automotive industry . It supplies automotive original equipment manufacturers (OEMs) and suppliers in Europe, North America, Latin America, and Asia with its products and systems. In 2021, the number of vehicles equipped with NIRA's main product, TPI, exceeded the benchmark of 75,000,000. [ 1 ]
NIRA was founded in 2001 and is located at Mjärdevi Science Park in Linköping , Sweden.
During the early period, NIRA Dynamics developed the first two of its products: the anti-spin system NSC and a positioning system MAP .
NSC received the Volvo Technology Award and until 2004 was featured in the Volvo S40 and V40 models under the name DSA (Dynamic Stability Assistance). [ 2 ] Since 2007, NSC is in series production and featured in a line of motorcycles from one of the world leading motorcycle manufacturers.
In 2008, NIRA was presented the European Automotive Chassis Product of the Year Award by Frost & Sullivan for its product TPI.
Since 2014, NIRA has broadened its product portfolio with RSI (Road Surface Information), TGI (Tire Grip Indicator), LWI (Loose Wheel Indicator).
Since 2017, NIRA has started working in the road maintenance space, where they provide their products Winter Road Insights and Road Health to cities, authorities, road operators and road contractors.
Since 2020, NIRA has been collecting road surface information data from regular passenger vehicles. The data is used to improve road safety, by either supporting drivers, assisting vehicles or providing the data to the road maintenance industry. In 2020, NIRA launched Road Surface Alerts with the Volkswagen Group, providing slipperiness warnings to drivers.
NIRA Dynamics holds an ISO 9001:2000 certificate stating that it has efficient and structured processes and tools to manage collaborative development projects in international environments.
NIRA Dynamics' core product is its Tire Pressure Indicator ( TPI ), an indirect tire-pressure monitoring system (TPMS) capable of detecting underinflation simultaneously in up to four tires . At the moment, TPI is installed in several Audi models (the A1 , A3 , A4 , A5 , A6 , A7 , A8 , Q3 , Q5 , Q7 , TT and many more); several Volkswagen models ( Polo , Golf , Jetta , Beetle , Scirocco , Passat , Tiguan , Touran , Sharan and many more); several SEAT and Skoda models; as well as the Chery Arrizo 7 and the MG 3 . It is also fitted to many Volvo, Fiat and Renault vehicles. The system meets the American FMVSS 138 and the European ECE R-64 regulations on tire pressure monitoring systems. [ 3 ] TPI is a software component that uses both relative rolling radius information as well as wheel oscillation measurement. It estimates tire pressure mainly from the signals of the wheel speed sensors that are part of the anti-lock braking system (ABS) and electronic stability control system (ESC). It gets active shortly after a reset which triggers a self-learning process. A reset needs to be initiated by the driver when the tires have been changed or the pressure adjusted. TPI does not require any in-wheel pressure sensors and RF ( radio frequency ) components. The Audi TT series was the first to be equipped with TPI, in 2006. The Audi A4 and A5 models followed the next year. [ 4 ] TPI can be fit into different electronic stability control hardware hosts, including those of Continental AG , Robert Bosch GmbH , and TRW Automotive .
NIRA Dynamics is developing sensor fusion based systems for different vehicle applications. Sensor fusion or sensor data fusion is the use of information from several different physical sensors to compute new virtual sensor signals. The virtual sensors can be of two different types: improved versions of physical sensor signals, or soft sensors that have no direct physical counterpart among the sensors used.
TPI ABS is a TPI version for vehicles with built-in anti-lock braking system (which is standard in most cars) but no electronic stability control system (which is not standard, particularly in emerging markets).
Loose Wheel Indicator ( LWI ) detects when the wheel bolts/nuts have come loose on at least one wheel position and the wheel starts to separate from the hub. It warns the driver who then can bring the vehicle to a safe halt before the wheel falls off. As TPI and all other NIRA products, this software-based function does not require any additional sensors.
Tire Grip Indicator ( TGI ) constantly estimates the available friction between the road and the tires. Unlike comparable functions, it does not need any additional sensors like tire-mounted sensors or cameras. This makes TGI very cost effective.
Road Surface Information ( RSI ) includes the friction estimation function of TGI , but goes one step further by completing this with road roughness information and detecting irregular events like potholes, speedbumps etc. This information can either be used directly in the car, for example to adapt the chassis, or be distributed via cloud services to other vehicles, road authorities etc.
In the winter 2015/2016, NIRA started a field study in Sweden where a fleet of taxi vehicles has been equipped with RSI delivering for example an online, real-time friction map of the roads of Gothenburg, Sweden.
In 2020 the product was taken to market full-scale and was in 2021 installed in over one million passenger vehicles, collecting road surface data.
Road Surface Alerts ( RSA ) - Based on world-leading friction estimation technology, Road Surface Alerts is the next generation local hazard warning system providing the most precise slipperiness warnings ever.
Road Surface Conditions ( RSC ) - Designed to make cars smarter and roads safer, Road Surface Conditions combines and assesses data from connected vehicles, RWIS, radar/satellite images, and weather prognoses to provide a real-time picture of the road status – with unmatched data coverage. This, in turn, helps enable SAE Level 2 and 3 vehicle functions in all kinds of weather and road conditions. | https://en.wikipedia.org/wiki/Nira_Dynamics_AB |
The nirayana system is a traditional Indian system of calendrical computations in which the phenomenon of precession of equinoxes is not taken into consideration. [ 1 ] In Indian astronomy, the precession of equinoxes is called ayana-calana which literally means shifting of the solstices and so nirayana is nir- + ayana meaning without ayana . [ 2 ] Ayanacalana refers to the continuous backward movement of the point of intersection of the ecliptic (which is a fixed circle) and the celestial equator (which keeps on moving backward). In contrast, the Indian systems of calendrical computations which take into consideration the effects of precession of equinoxes are called sayana systems.
The nirayana year is the sidereal year , that is, is the actual time required for the Earth to revolve once around the Sun with respect to a fixed point on the ecliptic, and its duration is approximately 365.256363 days (365 days 6 hours 9 minutes 10 seconds). In the nirayana system, this fixed point is taken as that point 180° from the bright star Citrā (Spica). The starting point of the nirayana year coincided with the March equinox in the year 285 CE. Since the stars are fixed with respect to the ecliptic, the starting point remains unchanged, hence the name nirayana . [ 3 ] [ 4 ]
vaiśākha
jyaiṣṭha
āṣāḍha
śrāvaṇa
bhādrapada
āśvina
kārttika
mārgaśīrṣa
pauṣa
māgha
phalguna
caitra
In the calendars that follow the nirayana system, a month is an artificial unit of time. In the nirayana system, the ecliptic is divided into 12 parts of 30° and each part is called a rāśi . The first rāśi starts from the same point as that of the start the nirayana year. The beginning of a nirayana month is the moment at which the Sun enter into a rāśi . The length of a nirayana month is the duration of time taken by the Sun to travel completely in a rāśi , that is, to travel 30° of its elliptical orbit. [ 4 ] Since the speed at which the Sun is traversing its elliptical orbit around the sun is not constant, the durations of the sidereal months are also not constant. The mean length of a nirayana month is about 30.4369 days, but its actual length can vary from 29.45 days to 31.45 days. Calendar makers of different regions of India follow different computational systems, so, the duration of a nirayana month may vary from region to region. [ 6 ]
Since the nirayana months are defined artificially, there are no astronomical phenomena associated with the beginning of a nirayana month. The exact moment at which a new nirayana month begins can occur at any time of day, early morning, evening or night. To facilitate dating of days, the first day of a month has to be properly defined in terms of saṃkrānti , the time at which the Sun enters a new rāśi . Unfortunately, there is no consensus among calendar-makers, and tradition varies from region to region. A few of these are: [ 4 ]
The most important deficiency of the nirayana calendar is that the predictions of the dates of the onsets of the various seasons as per the nirayana system do not correspond to the actual dates on which they occur. This is because the seasons depend on the position of the sun on the ecliptic relative to the celestial equator . In particular, they depend on the positions of the equinoxes. Since, the positions of the equinoxes are slowly moving, the predictions of the seasons which ignore this movement of the equinoxes will be definitely erroneous.
To be more specific, the winter season begins on the winter solstice day which date is marked by sun's entry into Makara constellation. This event occurs on the 22nd December. But in the nirayana system , this happens not on the 22nd December but on the 14th January and the winter season is also supposed to begin on that date. Similar is the case with other seasons also. The result is that there is a clear difference of 23 days in the reckoning of seasons. [ 1 ] | https://en.wikipedia.org/wiki/Nirayana_system |
Nissan ben Avraham Deliatitz ( Hebrew : ניסן בן אברהם דעליאטיץ ) was a 19th-century Russian rabbi and mathematician .
He wrote Keneh Ḥokhmah , a manual of algebra in five parts, published in Vilna and Grodno in 1829. [ 1 ] The work received approbations from Rabbi David, the av beit din of Novhardok , and Rabbi Avraham Abele ben Avraham Shlomo Poswoler, an eminent scholar who headed the Vilna beit din . [ 2 ]
This article about a Russian mathematician is a stub . You can help Wikipedia by expanding it . | https://en.wikipedia.org/wiki/Nissan_Deliatitz |
NAPS ( Nissan Anti Pollution System ) [ 1 ] is a moniker used in Japan to identify vehicles built with emission control technology. The technology was installed so that their vehicles would be in compliance with Japanese Government emission regulations passed in 1968. The term was first introduced in Japan, with an externally mounted badge on the trunk of vehicles equipped. Nissan's implementation began with the Y44E V8 engine installed in the Nissan President along with all vehicles installed with the Nissan L engine and the Nissan A engine in 1975. The initial introduction of Nissan's technology was the installation of an exhaust gas recirculation valve, followed with the addition of a catalytic converter and an air pump that added oxygen into the exhaust to promote higher temperatures in the catalytic converter, thus cleaning the exhaust further.
The NAPS-Z technology, introduced in 1978, was developed with assistance from Hitachi . [ 2 ] It uses a novel implementation of two spark plugs per cylinder, called dual ignition together with electronically controlled fuel injection, installed on the Nissan Z engine . This terminology is often confused with the engine installed in the Nissan 280Z , which used the "L" engine. However, the NAPS technology was installed in the Fairlady/Z and sold internationally.
Another version of the twin spark plug method was introduced on the Nissan Stanza with the CA engine , called NAPS-X, which eventually replaced the NAPS-Z approach. The CA engine implemented a hemispherical cylinder head, an approach used by several auto makers.
This article about an automotive technology is a stub . You can help Wikipedia by expanding it . | https://en.wikipedia.org/wiki/Nissan_NAPS |
NiTiNOL 60 , or 60 NiTiNOL, is a Nickel Titanium alloy (nominally Ni-40wt% Ti) discovered in the late 1950s by the U. S. Naval Ordnance Laboratory (hence the "NOL" portion of the name NiTiNOL). [ 1 ] Depending upon the heat treat history, 60 NiTiNOL has the ability to exhibit either superelastic properties in the hardened state or shape memory characteristics in the softened state. [ 2 ]
Producing the material in any meaningful quantities, however, proved quite difficult by conventional methods and the material was largely forgotten.
The composition and processing parameters have recently been revived by Summit Materials , LLC under the trademarked name SM-100. SM-100 maintains 60 NiTiNOL's combination of superb corrosion resistance [NASA terms it "Corrosion Proof" [ 3 ] ] and equally impressive wear and erosion properties. [ 4 ]
In bearing lifting tests conducted by NASA , SM-100 has been shown to have over twice the life of 440C stainless steel and over ten times the life of conventional titanium alloys with a significantly lower coefficient of friction. [ 5 ] The superelastic nature of the material gives it the ability to withstand compression loading of well over 350 ksi (2,400 MPa) with no permanent yielding. [ citation needed ]
Common applications for Nitinol 60 include:
The following table compares 60 NiTiNOL against commonly used bearing materials. [ 3 ] | https://en.wikipedia.org/wiki/Nitinol_60 |
Nitinol biocompatibility is an important factor in biomedical applications. Nitinol (NiTi), which is formed by alloying nickel and titanium (~ 50% Ni), is a shape-memory alloy with superelastic properties more similar to that of bone, [ clarification needed ] when compared to stainless steel , another commonly used biomaterial . Biomedical applications that utilize nitinol include stents , heart valve tools, bone anchors, staples, septal defect devices and implants. It is a commonly used biomaterial especially in the development of stent technology.
Metal implants containing a combination of biocompatible metals or used in conjunction with other biomaterials are often considered the standard for many implant types. Passivation is a process that removes corrosive implant elements from the implant-body interface and creates an oxide layer on the surface of the implant. The process is important for making biomaterials more biocompatible.
When materials are introduced to the body it is important not only that the material does not damage the body, but also that the environment of the body does not damage the implant. [ 1 ] One method that prevents the negative effects resulting from this interaction is called passivation . [ citation needed ]
In general, passivation is considered to be a process that creates a non-reactive layer at the surface of materials, such that the material may be protected from damage caused by the environment. Passivation can be accomplished through many mechanisms. Passive layers can be made through the assembly of monolayers through polymer grafting. Often, for corrosion protection, passive layers are created through the formation of oxide or nitride layers at the surface. [ citation needed ]
Passivation often occurs naturally in some metals like titanium, a metal that often forms an oxide layer mostly composed of TiO 2 . This process occurs spontaneously as the enthalpy of formation of TiO 2 is negative. In alloys, such as nitinol, the formation of an oxide layer not only protects against corrosion, but also removes Ni atoms from the surface of the material. Removing certain elements from the surface of materials is another form of passivation. In nitinol, the removal of Ni is important, because Ni is toxic if leached into the body. [ 2 ] Stainless steel is commonly passivated by the removal of iron from the surface through the use of acids and heat. Nitric acid is commonly used as a mild oxidant to create the thin oxide film on the surface of materials that protects against corrosion. [ 3 ]
Another mode of passivation involves polishing. Mechanical polishing removes many surface impurities and crystal structure breaks that may promote corrosion. Electropolishing is even more effective, because it doesn’t leave the scratches that mechanical polishing will. Electropolishing is accomplished by creating electrochemical cells where the material of interest is used as the anode . The surface will have jagged qualities where certain points are higher than others. In this cell the current density will be higher at the higher points and cause those points dissolve at a higher rate than the lower points, thus smoothing the surface. Crystal lattice point impurities will also be removed as the current will force these high-energy impurities to dissolve from the surface. [ 4 ]
Another commonly used method of passivation is accomplished through coating the material with polymer layers. Layers composed of polyurethane have been used to improve biocompatibility, but have seen limited success. Coating materials with biologically similar molecules has seen much better success. For example, phosphorylcholine surface modified stents have exhibited reduced thrombogenic activity. Passivation is an extremely important area of research for biomedical applications, as the body is a harsh environment for materials and materials can damage the body through leaching and corrosion. All of the above passivation methods have been used in the development of nitinol biomaterials to produce the most biocompatible implants. [ 5 ]
Surface passivation techniques can greatly increase the corrosion resistance of nitinol. In order for nitinol to have the desired superelastic and shape memory properties, heat treatment is required. After heat treatment, the surface oxide layer contains a larger concentration of nickel in the form of NiO 2 and NiO. This increase in nickel has been attributed to the diffusion of nickel out of the bulk material and into the surface layer during elevated temperature treatments. Surface characterization methods have shown that some surface passivation treatments decrease the concentration of NiO 2 and NiO within the surface layer, leaving a higher concentration of the more stable TiO 2 than in raw, heat-treated nitinol. [ 6 ]
The decrease in nickel concentration in the surface layer of nitinol is correlated with a greater corrosion resistance. A potentiodynamic test is commonly employed to measure a material’s resistance to corrosion. This test determines the electrical potential at which a material begins to corrode. The measurement is called the pitting or breakdown potential. After passivation in a nitric acid solution, nitinol stent components showed significantly higher breakdown potentials than those that were unpassivated. [ 6 ] In fact, there are many surface treatments that can greatly enhance the breakdown potentials of nitinol. These treatments include mechanical polishing, electropolishing, and chemical treatments such as, Nitric Oxide submersion, etching of the raw surface oxide layer, and pickling to break down bulk material near the surface. [ citation needed ]
Thrombogenicity , a material’s tendency to induce clot formation, is an important factor that determines the biocompatibility of any biomaterial that comes into contact with the bloodstream. There are two proteins, fibrinogen and albumin , that first adsorb to the surface of a foreign object in contact with blood. It has been suggested that fibrinogen may cause platelet activation due to a breakdown of the protein structure as it interacts with high energy grain boundaries on certain surfaces. Albumin on the other hand, inhibits platelet activation. This implies that there are two mechanisms which can help lower thrombogenicity, an amorphous surface layer where there will be no grain boundary interactions with fibrinogen, and a surface with a higher affinity to albumin than fibrinogen. [ citation needed ]
Just as thrombogenicity is important in determining suitability of other biomaterials, it is equally important with nitinol as a stent material. Currently, when stents are implanted, the patient receives antiaggregant therapy for a year or more in order to prevent the formation of a clot near the stent. By the time the drug therapy has ceased, ideally, a layer of endothelial cells , which line the inside of blood vessels would coat the outside of the stent. The stent is effectively integrated into the surrounding tissue and no longer in direct contact with the blood. There have been many attempts made using surface treatments to create stents that are more biocompatible and less thrombogenic, in an attempt to reduce the need for extensive antiplatelet therapy. Surface layers that are higher in nickel concentration cause less clotting due to albumin’s affinity to nickel. This is opposite of the surface layer characteristics that increase corrosion resistance. In vitro tests use indicators of thrombosis, such as platelet, Tyrosine aminotransferase , and β-TG levels. Surface treatments that have to some extent, lowered thrombogenicity in vitro are:
Another area of research involves binding various pharmaceutical agents such as heparin to the surface of the stent. These drug-eluting stents show promise in further reducing thrombogenicity while not compromising corrosion resistance.
New advances with micro laser welding have vastly improved the quality of medical devices made with nitinol. [ citation needed ]
Nitinol is an important alloy for use in medical devices, due to its exceptional biocompatibility, especially in the areas of corrosion resistance and thrombogenicity. Corrosion resistance is enhanced through methods that produce a uniform titanium dioxide layer on the surface with very few defects and impurities. Thrombogenicity is lowered on nitinol surfaces that contain nickel, so processes that retain nickel oxides in the surface layer are beneficial. The use of coatings has also been shown to greatly improve biocompatibility.
Because implanted devices contact the surface of the material, surface science plays an integral role in research aimed at enhancing biocompatibility, and in the development of new biomaterials. The development and improvement of nitinol as an implant material, from characterizing and improving the oxide layer to developing coatings, has been based largely on surface science.
Research is underway to produce better, more biocompatible, coatings. This research involves producing a coating that is very much like biologic material in order to further lessen the foreign body reaction. Biocomposite coatings containing cells or protein coatings are being explored for use with nitinol as well as many other biomaterials. [ 8 ] | https://en.wikipedia.org/wiki/Nitinol_biocompatibility |
Nitramex and Nitramon Explosives are compositions of various chemical compounds . They are explosives based on ammonium nitrate , with other ingredients such as paraffin wax , aluminum and dinitrotoluene . The inclusion of these additional ingredients creates a more stable explosive. Nitramex and Nitramon have in modern times been replaced by more advanced high explosives based on ammonium nitrate, such as ANFO .
A typical nitramon formula contains approximately 92 percent ammonium nitrate, 4 percent dinitrotoluene and 4 percent paraffin wax. [ citation needed ]
Nitramon is insensitive to shock, friction, flame and impact. It can't be detonated by blasting cap and requires booster to set it off. Different grades of Nitramon were produced, including S and WW for seismic exploration and HH for blasting in high temperature environments, like coal-seam fires . [ 1 ]
Nitramex has much the same formula as nitramon but with the addition of trinitrotoluene (TNT). It has higher density and explosive strength than Nitramon. Nitramex was developed for blasting hard rock. [ 2 ]
This explosive was used in the removal of Ripple Rock . Large quantities of Nitramex 2H (over a thousand tonnes) were packed into tunnels. The explosion, in 1958, was one of the largest non-nuclear explosions in history. [ citation needed ]
This explosives -related article is a stub . You can help Wikipedia by expanding it . | https://en.wikipedia.org/wiki/Nitramex_and_Nitramon_Explosives |
Nitrate is a polyatomic ion with the chemical formula NO − 3 . Salts containing this ion are called nitrates . Nitrates are common components of fertilizers and explosives. [ 1 ] Almost all inorganic nitrates are soluble in water . An example of an insoluble nitrate is bismuth oxynitrate .
The nitrate anion is the conjugate base of nitric acid , consisting of one central nitrogen atom surrounded by three identically bonded oxygen atoms in a trigonal planar arrangement. The nitrate ion carries a formal charge of −1. [ citation needed ] This charge results from a combination formal charge in which each of the three oxygens carries a − 2 ⁄ 3 charge, [ citation needed ] whereas the nitrogen carries a +1 charge, all these adding up to formal charge of the polyatomic nitrate ion. [ citation needed ] This arrangement is commonly used as an example of resonance . Like the isoelectronic carbonate ion, the nitrate ion can be represented by three resonance structures:
In the NO − 3 anion, the oxidation state of the central nitrogen atom is V (+5). This corresponds to the highest possible oxidation number of nitrogen. Nitrate is a potentially powerful oxidizer as evidenced by its explosive behaviour at high temperature when it is detonated in ammonium nitrate ( NH 4 NO 3 ), or black powder , ignited by the shock wave of a primary explosive . In contrast to red fuming nitric acid ( HNO 3 /N 2 O 4 ), or concentrated nitric acid ( HNO 3 ), nitrate in aqueous solution at neutral or high pH is only a weak oxidizing agent in redox reactions in which the reductant does not produce hydrogen ions (such as mercury going to calomel ). However it is still a strong oxidizer when the reductant does produce hydrogen ions, such as in the oxidation of hydrogen itself. Nitrate is stable in the absence of microorganisms or reductants such as organic matter. In fact, nitrogen gas is thermodynamically stable in the presence of 1 atm of oxygen only in very acidic conditions, and otherwise should combine with the oxygen to form nitrate. This is shown by subtracting the two oxidation reactions: [ 2 ]
giving:
Dividing by 0.0118 and rearranging gives the equilibrium relation:
However, in reality, nitrogen, oxygen, and water do not combine directly to form nitrate. Rather, a reductant such as hydrogen reacts with nitrogen to produce "fixed nitrogen" such as ammonia , which is then oxidized, eventually becoming nitrate. Nitrate does not accumulate to high levels in nature because it reacts with reductants in the process called denitrification (see Nitrogen cycle ).
Nitrate is used as a powerful terminal electron acceptor by denitrifying bacteria to deliver the energy they need to thrive. Under anaerobic conditions , nitrate is the strongest electron acceptor used by prokaryote microorganisms ( bacteria and archaea ) to respirate. The redox couple NO − 3 / N 2 is at the top of the redox scale for the anaerobic respiration , just below the couple oxygen ( O 2 / H 2 O ), but above the couples Mn(IV)/Mn(II), Fe(III)/Fe(II), SO 2− 4 / HS − , CO 2 / CH 4 . In natural waters, inevitably contaminated by microorganisms, nitrate is a quite unstable and labile dissolved chemical species because it is metabolised by denitrifying bacteria. Water samples for nitrate/nitrite analyses need to be kept at 4 °C in a refrigerated room and analysed as quick as possible to limit the loss of nitrate.
In the first step of the denitrification process, dissolved nitrate ( NO − 3 ) is catalytically reduced into nitrite ( NO − 2 ) by the enzymatic activity of bacteria. In aqueous solution, dissolved nitrite, N(III), is a more powerful oxidizer that nitrate, N(V), because it has to accept less electrons and its reduction is less kinetically hindered than that of nitrate.
During the biological denitrification process, further nitrite reduction also gives rise to another powerful oxidizing agent: nitric oxide (NO). NO can fix on myoglobin , accentuating its red coloration. NO is an important biological signaling molecule and intervenes in the vasodilation process. Still, it can also produce free radicals in biological tissues , accelerating their degradation and aging process. The reactive oxygen species (ROS) generated by NO contribute to the oxidative stress , a condition involved in vascular dysfunction and atherogenesis . [ 3 ]
The nitrate anion is commonly analysed in water by ion chromatography (IC) along with other anions also present in the solution. The main advantage of IC is its ease and the simultaneous analysis of all the anions present in the aqueous sample. Since the emergence of IC instruments in the 1980s, this separation technique, coupled with many detectors, has become commonplace in the chemical analysis laboratory and is the preferred and most widely used method for nitrate and nitrite analyses. [ 4 ]
Previously, nitrate determination relied on spectrophotometric and colorimetric measurements after a specific reagent is added to the solution to reveal a characteristic color (often red because it absorbs visible light in the blue). Because of interferences with the brown color of dissolved organic matter (DOM: humic and fulvic acids ) often present in soil pore water, artefacts can easily affect the absorbance values. In case of weak interference, a blank measurement with only a naturally brown-colored water sample can be sufficient to subtract the undesired background from the measured sample absorbance. If the DOM brown color is too intense, the water samples must be pretreated, and inorganic nitrogen species must be separated before measurement. Meanwhile, for clear water samples, colorimetric instruments retain the advantage of being less expensive and sometimes portable, making them an affordable option for fast routine controls or field measurements.
Colorimetric methods for the specific detection of nitrate ( NO − 3 ) often rely on its conversion to nitrite ( NO − 2 ) followed by nitrite-specific tests. The reduction of nitrate to nitrite can be effected by a copper - cadmium alloy , metallic zinc , [ 5 ] or hydrazine . The most popular of these assays is the Griess test , whereby nitrite is converted to a deeply red colored azo dye suited for UV–vis spectrophotometry analysis. The method exploits the reactivity of nitrous acid ( HNO 2 ) derived from the acidification of nitrite. Nitrous acid selectively reacts with aromatic amines to give diazonium salts , which in turn couple with a second reagent to give the azo dye . The detection limit is 0.02 to 2 μM. [ 6 ] Such methods have been highly adapted to biological samples [ 7 ] and soil samples. [ 8 ] [ 9 ]
In the dimethylphenol method, 1 mL of concentrated sulfuric acid ( H 2 SO 4 ) is added to 200 μL of the solution being tested for nitrate. Under strongly acidic conditions, nitrate ions react with 2,6-dimethylphenol, forming a yellow compound, 4-nitro-2,6-dimethylphenol . This occurs through electrophilic aromatic substitution where the intermediate nitronium ( + NO 2 ) ions attack the aromatic ring of dimethylphenol. The resulting product ( ortho- or para-nitro-dimethylphenol ) is analyzed using UV-vis spectrophotometry at 345 nm according to the Lambert-Beer law . [ 10 ] [ 11 ]
Another colorimetric method based on the chromotropic acid (dihydroxynaphthalene-disulfonic acid) was also developed by West and Lyles in 1960 for the direct spectrophotometric determination of nitrate anions . [ 12 ]
If formic acid is added to a mixture of brucine (an alkaloid related to strychnine ) and potassium nitrate ( KNO 3 ), its color instantly turns red. This reaction has been used for the direct colorimetric detection of nitrates. [ 13 ]
For direct online chemical analysis using a flow-through system, the water sample is introduced by a peristaltic pump in a flow injection analyzer , and the nitrate or resulting nitrite-containing effluent is then combined with a reagent for its colorimetric detection.
Nitrate salts are found naturally on earth in arid environments as large deposits, particularly of nitratine , a major source of sodium nitrate .
Nitrates are produced by a number of species of nitrifying bacteria in the natural environment using ammonia or urea as a source of nitrogen and source of free energy. Nitrate compounds for gunpowder were historically produced, in the absence of mineral nitrate sources, by means of various fermentation processes using urine and dung.
Lightning strikes in earth's nitrogen- and oxygen-rich atmosphere produce a mixture of oxides of nitrogen, which form nitrous ions and nitrate ions, which are washed from the atmosphere by rain or in occult deposition .
Nitrates are produced industrially from nitric acid . [ 1 ]
Nitrate is a chemical compound that serves as a primary form of nitrogen for many plants. This essential nutrient is used by plants to synthesize proteins, nucleic acids, and other vital organic molecules. [ 14 ] The transformation of atmospheric nitrogen into nitrate is facilitated by certain bacteria and lightning in the nitrogen cycle, which exemplifies nature's ability to convert a relatively inert molecule into a form that is crucial for biological productivity. [ 15 ]
Nitrates are used as fertilizers in agriculture because of their high solubility and biodegradability. The main nitrate fertilizers are ammonium , sodium , potassium , calcium , and magnesium salts. Several billion kilograms are produced annually for this purpose. [ 1 ] The significance of nitrate extends beyond its role as a nutrient since it acts as a signaling molecule in plants, regulating processes such as root growth, flowering, and leaf development. [ 16 ]
While nitrate is beneficial for agriculture since it enhances soil fertility and crop yields, its excessive use can lead to nutrient runoff, water pollution, and the proliferation of aquatic dead zones. [ 17 ] Therefore, sustainable agricultural practices that balance productivity with environmental stewardship are necessary. Nitrate's importance in ecosystems is evident since it supports the growth and development of plants, contributing to biodiversity and ecological balance. [ 18 ]
Nitrates are used as oxidizing agents , most notably in explosives , where the rapid oxidation of carbon compounds liberates large volumes of gases (see gunpowder as an example).
Sodium nitrate is used to remove air bubbles from molten glass and some ceramics . Mixtures of molten salts are used to harden the surface of some metals. [ 1 ]
Nitrate was also used as a film stock through nitrocellulose . Due to its high combustibility, the film making studios swapped to cellulose acetate safety film in 1950.
In the medical field, nitrate-derived organic esters , such as glyceryl trinitrate , isosorbide dinitrate , and isosorbide mononitrate , are used in the prophylaxis and management of acute coronary syndrome , myocardial infarction , acute pulmonary oedema . [ 19 ] This class of drug, to which amyl nitrite also belongs, is known as nitrovasodilators .
The two areas of concerns about the toxicity of nitrate are the following:
One of the most common cause of methemoglobinemia in infants is due to the ingestion of nitrates and nitrites through well water or foods.
In fact, nitrates ( NO − 3 ), often present at too high concentration in drinkwater, are only the precursor chemical species of nitrites ( NO − 2 ), the real culprits of methemoglobinemia. Nitrites produced by the microbial reduction of nitrate (directly in the drinkwater, or after ingestion by the infant, in his digestive system) are more powerful oxidizers than nitrates and are the chemical agent really responsible for the oxidation of Fe 2+ into Fe 3+ in the tetrapyrrole heme of hemoglobin . Indeed, nitrate anions are too weak oxidizers in aqueous solution to be able to directly, or at least sufficiently rapidly, oxidize Fe 2+ into Fe 3+ , because of kinetics limitations.
Infants younger than 4 months are at greater risk given that they drink more water per body weight, they have a lower NADH - cytochrome b5 reductase activity, and they have a higher level of fetal hemoglobin which converts more easily to methemoglobin . Additionally, infants are at an increased risk after an episode of gastroenteritis due to the production of nitrites by bacteria . [ 22 ]
However, other causes than nitrates can also affect infants and pregnant women. [ 23 ] [ 24 ] Indeed, the blue baby syndrome can also be caused by a number of other factors such as the cyanotic heart disease , a congenital heart defect resulting in low levels of oxygen in the blood, [ 25 ] or by gastric upset, such as diarrheal infection, protein intolerance, heavy metal toxicity, etc. [ 26 ]
Through the Safe Drinking Water Act , the United States Environmental Protection Agency has set a maximum contaminant level of 10 mg/L or 10 ppm of nitrate in drinking water. [ 27 ]
An acceptable daily intake (ADI) for nitrate ions was established in the range of 0–3.7 mg (kg body weight) −1 day −1 by the Joint FAO/WHO Expert Committee on Food Additives (JEFCA). [ 28 ]
In freshwater or estuarine systems close to land, nitrate can reach concentrations that are lethal to fish. While nitrate is much less toxic than ammonia, [ 29 ] levels over 30 ppm of nitrate can inhibit growth, impair the immune system and cause stress in some aquatic species. [ 30 ] Nitrate toxicity remains a subject of debate. [ 31 ]
In most cases of excess nitrate concentrations in aquatic systems, the primary sources are wastewater discharges, as well as surface runoff from agricultural or landscaped areas that have received excess nitrate fertilizer. The resulting eutrophication and algae blooms result in anoxia and dead zones . As a consequence, as nitrate forms a component of total dissolved solids , they are widely used as an indicator of water quality .
Nitrate deposition into ecosystems has markedly increased due to anthropogenic activities, notably from the widespread application of nitrogen-rich fertilizers in agriculture and the emissions from fossil fuel combustion. [ 32 ] Annually, about 195 million metric tons of synthetic nitrogen fertilizers are used worldwide, with nitrates constituting a significant portion of this amount. [ 33 ] In regions with intensive agriculture, such as parts of the U.S., China, and India, the use of nitrogen fertilizers can exceed 200 kilograms per hectare. [ 33 ]
The impact of increased nitrate deposition extends beyond plant communities to affect soil microbial populations . [ 34 ] The change in soil chemistry and nutrient dynamics can disrupt the natural processes of nitrogen fixation , nitrification , and denitrification , leading to altered microbial community structures and functions. This disruption can further impact the nutrient cycling and overall ecosystem health. [ 35 ]
A source of nitrate in the human diets arises from the consumption of leafy green foods, such as spinach and arugula . NO − 3 can be present in beetroot juice. Drinking water represents also a primary nitrate intake source. [ 36 ]
Nitrate ingestion rapidly increases the plasma nitrate concentration by a factor of 2 to 3, and this elevated nitrate concentration can be maintained for more than 2 weeks. Increased plasma nitrate enhances the production of nitric oxide , NO. Nitric oxide is a physiological signaling molecule which intervenes in, among other things, regulation of muscle blood flow and mitochondrial respiration. [ 37 ]
Nitrite ( NO − 2 ) consumption is primarily determined by the amount of processed meats eaten, and the concentration of nitrates ( NO − 3 ) added to these meats ( bacon , sausages …) for their curing. Although nitrites are the nitrogen species chiefly used in meat curing , nitrates are used as well and can be transformed into nitrite by microorganisms, or in the digestion process, starting by their dissolution in saliva and their contact with the microbiota of the mouth. Nitrites lead to the formation of carcinogenic nitrosamines . [ 38 ] The production of nitrosamines may be inhibited by the use of the antioxidants vitamin C and the alpha-tocopherol form of vitamin E during curing. [ 39 ]
Many meat processors claim their meats (e.g. bacon) is "uncured" – which is a marketing claim with no factual basis: there is no such thing as "uncured" bacon (as that would be, essentially, raw sliced pork belly). [ 40 ] [ better source needed ] "Uncured" meat is in fact actually cured with nitrites with virtually no distinction in process – the only difference being the USDA labeling requirement between nitrite of vegetable origin (such as from celery) vs. "synthetic" sodium nitrite. An analogy would be purified " sea salt " vs. sodium chloride – both being exactly the same chemical with the only essential difference being the origin.
Anti-hypertensive diets, such as the DASH diet , typically contain high levels of nitrates, which are first reduced to nitrite in the saliva , as detected in saliva testing , prior to forming nitric oxide (NO). [ 36 ]
Symptoms of nitrate poisoning in domestic animals include increased heart rate and respiration; in advanced cases blood and tissue may turn a blue or brown color. Feed can be tested for nitrate; treatment consists of supplementing or substituting existing supplies with lower nitrate material. Safe levels of nitrate for various types of livestock are as follows: [ 41 ]
The values above are on a dry (moisture-free) basis.
Nitrate formation with elements of the periodic table: | https://en.wikipedia.org/wiki/Nitrate |
In organic chemistry , a nitrate ester is an organic functional group with the formula R−ONO 2 , where R stands for any organyl group. They are the esters of nitric acid and alcohols . A well-known example is nitroglycerin , which is not a nitro compound, despite its name.
Nitrate esters are typically prepared by condensation of nitric acid and the alcohol: [ 1 ] [ 2 ] For example, the simplest nitrate ester, methyl nitrate , is formed by reaction of methanol and nitric acid in the presence of sulfuric acid : [ 3 ]
Formation of a nitrate ester is called a nitrooxylation (less commonly, nitroxylation).
Most commonly, "mixed acid" (nitric and sulfuric acids) are used, but in the 1980s production of the nitrocellulose with magnesium nitrate as a dehydrating agent was started in the US. [ 4 ] In laboratory, phosphoric acid and phosphorus pentoxide or acetic acid and its anhydride may be used for the same purpose, or the nitroxylation can be conducted in anhydrous conditions (such as dichloromethane or chloroform ). [ 5 ]
The thermal decomposition of nitrate esters mainly yields the gases molecular nitrogen (N 2 ) and carbon dioxide. The considerable chemical energy of the detonation is due to the high strength of the bond in molecular nitrogen. This stoichiometry is illustrated by the equation for the detonation of nitroglycerin.
Illustrative of the highly sensitive nature of some organic nitrates is Si(CH 2 ONO 2 ) 4 . [ 6 ] [ 7 ] A single crystal of this compound detonates even upon contact with a teflon spatula and in fact made full characterization impossible. Another contributor to its exothermic decomposition (inferred from much safer in silico experimentation) is the ability of silicon in its crystal phase to coordinate to two oxygen nitrito groups in addition to regular coordination to the four carbon atoms. This additional coordination would make formation of silicon dioxide (one of the decomposition products) more facile.
The nitrate esters isosorbide dinitrate (Isordil) and isosorbide mononitrate (Imdur, Ismo, Monoket, Mononitron) are converted in the body to nitric oxide , a potent natural vasodilator. In medicine , these esters are used as a medicine for angina pectoris ( ischemic heart disease ).
Acetyl nitrate is a nitrate anhydride, being derived from the condensation of nitric and acetic acids. | https://en.wikipedia.org/wiki/Nitrate_ester |
Nitrogen trioxide or nitrate radical is an oxide of nitrogen with formula NO 3 , consisting of three oxygen atoms covalently bound to a nitrogen atom. This highly unstable blue compound has not been isolated in pure form, but can be generated and observed as a short-lived component of gas, liquid, or solid systems. [ 1 ]
Like nitrogen dioxide NO 2 , it is a radical (a molecule with an unpaired valence electron ), which makes it paramagnetic . It is the uncharged counterpart of the nitrate anion NO − 3 and an isomer of the peroxynitrite radical OONO . [ 1 ]
Nitrogen trioxide is an important intermediate in reactions between atmospheric components, including the destruction of ozone . [ 1 ] [ 2 ]
The existence of the NO 3 radical was postulated in 1881-1882 by Hautefeuille and Chappuis to explain the absorption spectrum of air subjected to a silent electrical discharge. [ 1 ]
The neutral NO 3 molecule appears to be planar, with three-fold rotational symmetry (symmetry group D 3 h ); or possibly a resonance between three Y-shaped molecules. [ 1 ]
The NO 3 radical does not react directly with water, and is relatively unreactive towards closed-shell molecules, as opposed to isolated atoms and other radicals. It is decomposed by light of certain wavelengths into nitric oxide NO and oxygen O 2 . [ 1 ]
The absorption spectrum of NO 3 has a broad band for light with wavelengths from about 500 to 680 nm , with three salient peaks in the visible at 590, 662, and 623 nm. Absorption in the range 640–680 nm does not lead to dissociation but to fluorescence : specifically, from about 605 to 800 nm following excitation at 604.4 nm, and from about 662 to 800 nm following excitation at 661.8 nm. [ 1 ] In water solution, another absorption band appears at about 330 nm ( ultraviolet ). An excited state NO * 3 can be achieved by photons of wavelength less than 595 nm. [ 1 ]
Nitrogen trioxide can be prepared in the gas phase by mixing nitrogen dioxide and ozone: [ 1 ]
This reaction can be performed also in the solid phase or water solutions, by irradiating frozen gas mixtures, flash photolysis and radiolysis of nitrate salts and nitric acid, and several other methods. [ 1 ]
Nitrogen trioxide is a product of the photolysis of dinitrogen pentoxide N 2 O 5 , chlorine nitrate ClONO 2 , and peroxynitric acid HO 2 NO 2 and its salts. [ 1 ] | https://en.wikipedia.org/wiki/Nitrate_radical |
A nitrate test is a chemical test used to determine the presence of nitrate ion in solution. Testing for the presence of nitrate via wet chemistry is generally difficult compared with testing for other anions, as almost all nitrates are soluble in water. In contrast, many common ions give insoluble salts, e.g. halides precipitate with silver, and sulfate precipitate with barium.
The nitrate anion is an oxidizer, and many tests for the nitrate anion are based on this property. However, other oxidants present in the analyte may interfere and give erroneous results.
Nitrate can also be detected by first reducing it to the more reactive nitrite ion and using one of many nitrite tests . [ 1 ]
A common nitrate test, known as the brown ring test [ 2 ] can be performed by adding iron(II) sulfate to a solution of a nitrate, then slowly adding concentrated sulfuric acid such that the acid forms a layer below the aqueous solution. A brown ring will form at the junction of the two layers, indicating the presence of the nitrate ion. [ 3 ] Note that the presence of nitrite ions will interfere with this test. [ 4 ]
The overall reaction is the reduction of the nitrate ion to nitric oxide by iron(II), which is oxidised to iron(III), followed by the formation of nitrosyl ferrous sulfate between the nitric oxide and the remaining iron(II), where nitric oxide is reduced to NO − . [ 5 ]
This test is sensitive up to 2.5 micrograms and a concentration of 1 in 25,000 parts. [ citation needed ] [ 6 ]
Devarda's alloy (Copper/Aluminium/Zinc) is a reducing agent . When reacted with nitrate in sodium hydroxide solution, ammonia is liberated. The ammonia formed may be detected by its characteristic odor, and by damp red litmus paper's turning blue, signalling that it is an alkali — very few gases other than ammonia evolved from wet chemistry are alkaline.
Aluminium is the reducing agent in this reaction that will occur.
Diphenylamine may be used as a wet chemical test for the presence of the nitrate ion. In this test, a solution of diphenylamine and ammonium chloride in sulfuric acid is used. In the presence of nitrates, diphenylamine is oxidized, giving a blue coloration. This reaction has been used to test for organic nitrates as well, [ 7 ] and has found use in gunshot residue kits detecting nitroglycerine and nitrocellulose . [ 8 ]
The nitrate ion can easily be identified by heating copper turnings along with concentrated sulfuric acid. Effervescence of a brown, pungent gas is observed which turns moist blue litmus paper red.
Here sulfuric acid reacts with the nitrate ion to form nitric acid. Nitric acid then reacts with the copper turnings to form nitric oxide. Nitric oxide is thus oxidised to nitrogen dioxide. | https://en.wikipedia.org/wiki/Nitrate_test |
Nitrazine or phenaphthazine is a pH indicator dye often used in medicine . More sensitive than litmus , nitrazine indicates pH in the range of 4.5 to 7.5. Nitrazine is usually used as the disodium salt.
This test, however, can produce false positives. If blood gets in the sample or if there is an infection present, the pH of the vaginal fluid may be higher than normal. Semen also has a higher pH, so recent vaginal intercourse can produce a false reading. | https://en.wikipedia.org/wiki/Nitrazine |
In chemistry , a nitrene or imene ( R−:Ṅ· ) is the nitrogen analogue of a carbene . The nitrogen atom is uncharged and monovalent , [ 1 ] so it has only 6 electrons in its valence level—two covalent bonded and four non-bonded electrons. It is therefore considered an electrophile due to the unsatisfied octet . A nitrene is a reactive intermediate and is involved in many chemical reactions . [ 2 ] [ 3 ] The simplest nitrene, HN, is called imidogen , and that term is sometimes used as a synonym for the nitrene class. [ 4 ]
In the simplest case, the linear N–H molecule (imidogen) has its nitrogen atom sp hybridized , with two of its four non-bonded electrons as a lone pair in an sp orbital and the other two occupying a degenerate pair of p orbitals . The electron configuration is consistent with Hund's rule : the low energy form is a triplet with one electron in each of the p orbitals and the high energy form is the singlet with an electron pair filling one p orbital and the other p orbital vacant. [ 5 ]
As with carbenes, a strong correlation exists between the spin density on the nitrogen atom which can be calculated in silico and the zero-field splitting parameter D which can be derived experimentally from electron spin resonance . [ 6 ] Small nitrenes such as NH or CF 3 N have D values around 1.8 cm −1 with spin densities close to a maximum value of 2. At the lower end of the scale are molecules with low D (< 0.4) values and spin density of 1.2 to 1.4 such as 9-anthrylnitrene and 9-phenanthrylnitrene.
Because nitrenes are so reactive, they are rarely isolated. Instead, they are formed as reactive intermediates during a reaction. There are two common ways to generate nitrenes:
Since formation of the nitrene typically starts from a diamagnetic precursor, the direct chemical product is a singlet nitrene, which then relaxes to its ground state triplet state. As has been shown for phenylazide as a model system, the direct photoproduct of photochemical-induced N 2 loss can either be the singlet or triplet nitrene. [ 7 ] [ 8 ] [ 9 ] By using a triplet sensitizer, the triplet nitrene can also be formed without initial formation of the singlet nitrene. [ 10 ]
Although highly reactive, some nitrenes could be isolated and characterized recently.
In 2019, a triplet nitrene was isolated by Betley and Lancaster, stabilized by coordination to a copper center in a bulky ligand. [ 11 ] Later on, Schneider and coworkers characterized Pd and Pt triplet metallonitrenes, where the organic residue is replaced by a metal. [ 12 ] [ 13 ] [ 14 ] In 2024, the groups of Beckmann, Ye and Tan reported the isolation and characterization of organic triplet nitrenes, which are protected from chemical reactivity by an extremely bulky ligand. [ 15 ] [ 16 ]
Nitrene reactions include:
For several compounds containing both a nitrene group and a free radical group an ESR high-spin quartet has been recorded (matrix, cryogenic temperatures). One of these has an amine oxide radical group incorporated, [ 29 ] another system has a carbon radical group. [ 30 ]
In this system one of the nitrogen unpaired electrons is delocalized in the aromatic ring making the compound a σ–σ–π triradical. A carbene nitrogen radical (imidyl radical) resonance structure makes a contribution to the total electronic picture. | https://en.wikipedia.org/wiki/Nitrene |
Dinitrogen tetroxide Dinitrogen trioxide Nitrogen dioxide Nitrous oxide Nitroxyl (reduced form) Hydroxylamine (hydrogenated form)
Nitric oxide ( nitrogen oxide or nitrogen monoxide [ 1 ] ) is a colorless gas with the formula NO . It is one of the principal oxides of nitrogen . Nitric oxide is a free radical : it has an unpaired electron , which is sometimes denoted by a dot in its chemical formula ( • N=O or • NO). Nitric oxide is also a heteronuclear diatomic molecule , a class of molecules whose study spawned early modern theories of chemical bonding . [ 6 ]
An important intermediate in industrial chemistry , nitric oxide forms in combustion systems and can be generated by lightning in thunderstorms. In mammals, including humans, nitric oxide is a signaling molecule in many physiological and pathological processes. [ 7 ] It was proclaimed the " Molecule of the Year " in 1992. [ 8 ] The 1998 Nobel Prize in Physiology or Medicine was awarded for discovering nitric oxide's role as a cardiovascular signalling molecule. [ 9 ] Its impact extends beyond biology, with applications in medicine, such as the development of sildenafil (Viagra), and in industry, including semiconductor manufacturing. [ 10 ] [ 11 ]
Nitric oxide should not be confused with nitrogen dioxide (NO 2 ), a brown gas and major air pollutant , or with nitrous oxide (N 2 O), an anesthetic gas. [ 6 ]
Nitric oxide (NO) was first identified by Joseph Priestley in the late 18th century, originally seen as merely a toxic byproduct of combustion and an environmental pollutant. [ 12 ] Its biological significance was later uncovered in the 1980s when researchers Robert F. Furchgott , Louis J. Ignarro , and Ferid Murad discovered its critical role as a vasodilator in the cardiovascular system, a breakthrough that earned them the 1998 Nobel Prize in Physiology or Medicine. [ 13 ]
The ground state electronic configuration of NO is, in united atom notation: [ 14 ]
( 1 σ ) 2 ( 2 σ ) 2 ( 3 σ ) 2 ( 4 σ ∗ ) 2 ( 5 σ ) 2 ( 1 π ) 4 ( 2 π ∗ ) 1 {\displaystyle (1\sigma )^{2}(2\sigma )^{2}(3\sigma )^{2}(4\sigma ^{*})^{2}(5\sigma )^{2}(1\pi )^{4}(2\pi ^{*})^{1}}
The first two orbitals are actually pure atomic 1 s O and 1 s N from oxygen and nitrogen respectively and therefore are usually not noted in the united atom notation. Orbitals noted with an asterisk are antibonding. The ordering of 5σ and 1π according to their binding energies is subject to discussion. Removal of a 1π electron leads to 6 states whose energies span over a range starting at a lower level than a 5σ electron an extending to a higher level. This is due to the different orbital momentum couplings between a 1π and a 2π electron.
The lone electron in the 2π orbital makes NO a doublet (X ²Π) in its ground state whose degeneracy is split in the fine structure from spin-orbit coupling with a total momentum J = 3 ⁄ 2 or J = 1 ⁄ 2 .
The dipole of NO has been measured experimentally to 0.15740 D and is oriented from O to N (⁻NO⁺) due to the transfer of negative electronic charge from oxygen to nitrogen. [ 15 ]
Upon condensing to a neat liquid, nitric oxide dimerizes to colorless dinitrogen dioxide (O=N–N=O), but the association is weak and reversible. The N–N distance in crystalline NO is 218 pm, nearly twice the N–O distance. Condensation in a highly polar environment instead gives the red alternant isomer O=N–O + =N − . [ 6 ]
Since the heat of formation of • NO is endothermic , NO can be decomposed to the elements. Catalytic converters in cars exploit this reaction:
When exposed to oxygen , nitric oxide converts into nitrogen dioxide :
This reaction is thought to occur via the intermediates ONOO • and the red compound ONOONO. [ 16 ]
In water, nitric oxide reacts with oxygen to form nitrous acid (HNO 2 ). The reaction is thought to proceed via the following stoichiometry :
Nitric oxide reacts with fluorine , chlorine , and bromine to form the nitrosyl halides, such as nitrosyl chloride :
With NO 2 , also a radical, NO combines to form the intensely blue dinitrogen trioxide : [ 6 ]
Nitric oxide rarely sees organic chemistry use. Most reactions with it produce complex mixtures of salts, separable only through careful recrystallization . [ 17 ]
The addition of a nitric oxide moiety to another molecule is often referred to as nitrosylation . The Traube reaction is the addition of a two equivalents of nitric oxide onto an enolate , giving a diazeniumdiolate (also called a nitrosohydroxylamine ). [ 18 ] The product can undergo a subsequent retro- aldol reaction , giving an overall process similar to the haloform reaction . For example, nitric oxide reacts with acetone and an alkoxide to form a diazeniumdiolate on each α position , with subsequent loss of methyl acetate as a by-product : [ 19 ]
This reaction, which was discovered around 1898, remains of interest in nitric oxide prodrug research. Nitric oxide can also react directly with sodium methoxide , ultimately forming sodium formate and nitrous oxide by way of an N -methoxydiazeniumdiolate. [ 20 ]
Sufficiently basic secondary amines undergo a Traube-like reaction to give NONOates . [ 21 ] However, very few nucleophiles undergo the Traube reaction, either failing to adduce NO or immediately decomposing with nitrous oxide release. [ 17 ]
Nitric oxide reacts with transition metals to give complexes called metal nitrosyls . The most common bonding mode of nitric oxide is the terminal linear type (M−NO). [ 6 ] Alternatively, nitric oxide can serve as a one-electron pseudohalide. In such complexes, the M−N−O group is characterized by an angle between 120° and 140°. The NO group can also bridge between metal centers through the nitrogen atom in a variety of geometries.
In commercial settings, nitric oxide is produced by the oxidation of ammonia at 750–900 °C (normally at 850 °C) with platinum as catalyst in the Ostwald process :
The uncatalyzed endothermic reaction of oxygen (O 2 ) and nitrogen (N 2 ), which is effected at high temperature (>2000 °C) by lightning has not been developed into a practical commercial synthesis (see Birkeland–Eyde process ):
In the laboratory, nitric oxide is conveniently generated by reduction of dilute nitric acid with copper :
An alternative route involves the reduction of nitrous acid in the form of sodium nitrite or potassium nitrite :
The iron(II) sulfate route is simple and has been used in undergraduate laboratory experiments.
So-called NONOate compounds are also used for nitric oxide generation, especially in biological laboratories. However, other Traube adducts may decompose to instead give nitrous oxide . [ 22 ]
Nitric oxide concentration can be determined using a chemiluminescent reaction involving ozone . [ 23 ] A sample containing nitric oxide is mixed with a large quantity of ozone. The nitric oxide reacts with the ozone to produce oxygen and nitrogen dioxide , accompanied with emission of light ( chemiluminescence ):
which can be measured with a photodetector . The amount of light produced is proportional to the amount of nitric oxide in the sample.
Other methods of testing include electroanalysis (amperometric approach), where ·NO reacts with an electrode to induce a current or voltage change. The detection of NO radicals in biological tissues is particularly difficult due to the short lifetime and concentration of these radicals in tissues. One of the few practical methods is spin trapping of nitric oxide with iron- dithiocarbamate complexes and subsequent detection of the mono-nitrosyl-iron complex with electron paramagnetic resonance (EPR). [ 24 ] [ 25 ]
A group of fluorescent dye indicators that are also available in acetylated form for intracellular measurements exist. The most common compound is 4,5-diaminofluorescein (DAF-2). [ 26 ]
Nitric oxide reacts with the hydroperoxyl radical ( HO • 2 ) to form nitrogen dioxide (NO 2 ), which then can react with a hydroxyl radical (HO • ) to produce nitric acid (HNO 3 ):
Nitric acid, along with sulfuric acid , contributes to acid rain deposition.
• NO participates in ozone layer depletion . Nitric oxide reacts with stratospheric ozone to form O 2 and nitrogen dioxide:
This reaction is also utilized to measure concentrations of • NO in control volumes.
As seen in the acid deposition section, nitric oxide can transform into nitrogen dioxide (this can happen with the hydroperoxy radical, HO • 2 , or diatomic oxygen, O 2 ). Symptoms of short-term nitrogen dioxide exposure include nausea, dyspnea and headache. Long-term effects could include impaired immune and respiratory function. [ 27 ]
NO is a gaseous signaling molecule . [ 28 ] It is a key vertebrate biological messenger , playing a role in a variety of biological processes. [ 29 ] It is a bioproduct in almost all types of organisms, including bacteria, plants, fungi, and animal cells. [ 30 ]
Nitric oxide, an endothelium-derived relaxing factor (EDRF), is biosynthesized endogenously from L -arginine , oxygen , and NADPH by various nitric oxide synthase (NOS) enzymes . [ 31 ] Reduction of inorganic nitrate may also make nitric oxide. [ 32 ] One of the main enzymatic targets of nitric oxide is guanylyl cyclase . [ 33 ] The binding of nitric oxide to the heme region of the enzyme leads to activation, in the presence of iron. [ 33 ] Nitric oxide is highly reactive (having a lifetime of a few seconds), yet diffuses freely across membranes. These attributes make nitric oxide ideal for a transient paracrine (between adjacent cells) and autocrine (within a single cell) signaling molecule. [ 32 ] Once nitric oxide is converted to nitrates and nitrites by oxygen and water, cell signaling is deactivated. [ 33 ]
The endothelium (inner lining) of blood vessels uses nitric oxide to signal the surrounding smooth muscle to relax, resulting in vasodilation and increasing blood flow. [ 32 ] Sildenafil (Viagra) is a drug that uses the nitric oxide pathway. Sildenafil does not produce nitric oxide, but enhances the signals that are downstream of the nitric oxide pathway by protecting cyclic guanosine monophosphate (cGMP) from degradation by cGMP-specific phosphodiesterase type 5 (PDE5) in the corpus cavernosum , allowing for the signal to be enhanced, and thus vasodilation . [ 31 ] Another endogenous gaseous transmitter, hydrogen sulfide (H 2 S) works with NO to induce vasodilation and angiogenesis in a cooperative manner. [ 34 ] [ 35 ]
Nasal breathing produces nitric oxide within the body, while oral breathing does not. [ 36 ] [ 37 ]
In the U.S., the Occupational Safety and Health Administration (OSHA) has set the legal limit ( permissible exposure limit ) for nitric oxide exposure in the workplace as 25 ppm (30 mg/m 3 ) over an 8-hour workday. The National Institute for Occupational Safety and Health (NIOSH) has set a recommended exposure limit (REL) of 25 ppm (30 mg/m 3 ) over an 8-hour workday. At levels of 100 ppm, nitric oxide is immediately dangerous to life and health . [ 38 ]
Liquid nitrogen oxide is very sensitive to detonation even in the absence of fuel, and can be initiated as readily as nitroglycerin. Detonation of the endothermic liquid oxide close to its boiling point (−152 °C or −241.6 °F or 121.1 K) generated a 100 kbar pulse and fragmented the test equipment. It is the simplest molecule that is capable of detonation in all three phases. The liquid oxide is sensitive and may explode during distillation, and this has been the cause of industrial accidents. [ 39 ] Gaseous nitric oxide detonates at about 2,300 metres per second (8,300 km/h; 5,100 mph), but as a solid it can reach a detonation velocity of 6,100 metres per second (22,000 km/h; 13,600 mph). [ 40 ]
Notes | https://en.wikipedia.org/wiki/Nitric_oxide |
Nitrification is the biological oxidation of ammonia to nitrate via the intermediary nitrite . Nitrification is an important step in the nitrogen cycle in soil . The process of complete nitrification may occur through separate organisms [ 1 ] or entirely within one organism, as in comammox bacteria. The transformation of ammonia to nitrite is usually the rate limiting step of nitrification. Nitrification is an aerobic process performed by small groups of autotrophic bacteria and archaea .
The process of nitrification begins with the first stage of ammonia oxidation, where ammonia (NH 3 ) or ammonium (NH 4 + ) get converted into nitrite (NO 2 − ). This first stage is sometimes known as nitritation. It is performed by two groups of organisms, ammonia-oxidizing bacteria ( AOB ) and ammonia-oxidizing archaea ( AOA [ 2 ] ).
Ammonia-Oxidizing Bacteria (AOB) are typically Gram-negative bacteria and belong to Betaproteobacteria and Gammaproteobacteria [ 3 ] including the commonly studied genera Nitrosomonas and Nitrococcus . They are known for their ability to utilize ammonia as an energy source and are prevalent in a wide range of environments, such as soils, aquatic systems, and wastewater treatment plants.
AOB possess enzymes called ammonia monooxygenases (AMOs), which are responsible for catalyzing the conversion of ammonia to hydroxylamine (NH 2 OH), a crucial intermediate in the process of nitrification. [ 4 ] This enzymatic activity is sensitive to environmental factors, such as pH, temperature, and oxygen availability.
AOB play a vital role in soil nitrification, making them key players in nutrient cycling . They contribute to the transformation of ammonia derived from organic matter decomposition or fertilizers into nitrite, which subsequently serves as a substrate for nitrite-oxidizing bacteria (NOB).
Prior to the discovery of archaea capable of ammonia oxidation, ammonia-oxidizing bacteria (AOB) were considered the only organisms capable of ammonia oxidation. Since their discovery in 2005, [ 5 ] two isolates of AOAs have been cultivated: Nitrosopumilus maritimus [ 6 ] and Nitrososphaera viennensis . [ 7 ] When comparing AOB and AOA, AOA dominate in both soils and marine environments, [ 2 ] [ 8 ] [ 6 ] [ 9 ] [ 10 ] [ 11 ] suggesting that Nitrososphaerota (formerly Thaumarchaeota ) may be greater contributors to ammonia oxidation in these environments. [ 2 ]
Crenarchaeol , which is generally thought to be produced exclusively by AOA (specifically Nitrososphaerota), has been proposed as a biomarker for AOA and ammonia oxidation. Crenarchaeol abundance has been found to track with seasonal blooms of AOA, suggesting that it may be appropriate to use crenarchaeol abundances as a proxy for AOA populations [ 12 ] and thus ammonia oxidation more broadly. However the discovery of Nitrososphaerota that are not obligate ammonia-oxidizers [ 13 ] complicates this conclusion, [ 14 ] as does one study that suggests that crenarchaeol may be produced by Marine Group II Euryarchaeota. [ 15 ]
The second step of nitrification is the oxidation of nitrite into nitrate. This process is sometimes known as nitratation. Nitrite oxidation is conducted by nitrite-oxidizing bacteria ( NOB ) from the taxa Nitrospirota , [ 16 ] Nitrospinota , [ 17 ] Pseudomonadota [ 18 ] and Chloroflexota . [ 19 ] NOB are typically present in soil, geothermal springs, freshwater and marine ecosystems.
Ammonia oxidation to nitrate in a single step within one organism was predicted in 2006 [ 20 ] and discovered in 2015 in the species Nitrospira inopinata . A pure culture of the organism was obtained in 2017, [ 21 ] representing a revolution in our understanding of the nitrification process.
The idea that oxidation of ammonia to nitrate is in fact a biological process was first given by Louis Pasteur in 1862. [ 22 ] Later in 1875, Alexander Müller , while conducting a quality assessment of water from wells in Berlin , noted that ammonium was stable in sterilized solutions but nitrified in natural waters. A. Müller put forward, that nitrification is thus performed by microorganisms. [ 23 ] In 1877, Jean-Jacques Schloesing and Achille Müntz , two French agricultural chemists working in Paris , proved that nitrification is indeed microbially mediated process by the experiments with liquid sewage and artificial soil matrix (sterilized sand with powdered chalk). [ 24 ] Their findings were confirmed soon (in 1878) by Robert Warington who was investigating nitrification ability of garden soil at the Rothamsted experimental station in Harpenden in England. [ 25 ] R. Warington made also the first observation that nitrification is a two-step process in 1879 [ 26 ] which was confirmed by John Munro in 1886. [ 27 ] Although at that time, it was believed that two-step nitrification is separated into distinct life phases or character traits of a single microorganism.
The first pure nitrifier (ammonia-oxidizing) was most probably isolated in 1890 by Percy Frankland and Grace Frankland , two English scientists from Scotland. [ 28 ] Before that, Warington , [ 25 ] Sergei Winogradsky [ 29 ] and the Franklands were only able to enrich cultures of nitrifiers. Frankland and Frankland succeeded with a system of serial dilutions with very low inoculum and long cultivation times counting in years. Sergei Winogradsky claimed pure culture isolation in the same year (1890), [ 29 ] but his culture was still co-culture of ammonia- and nitrite-oxidizing bacteria. [ 30 ] S. Winogradsky succeeded just one year later in 1891. [ 31 ]
In fact, during the serial dilutions ammonia-oxidizers and nitrite-oxidizers were unknowingly separated resulting in pure culture with ammonia-oxidation ability only. Thus Frankland and Frankland observed that these pure cultures lose ability to perform both steps. Loss of nitrite oxidation ability was observed already by R. Warington . [ 26 ] Cultivation of pure nitrite oxidizer happened later during 20th century, however it is not possible to be certain which cultures were without contaminants as all theoretically pure strains share same trait (nitrite consumption, nitrate production). [ 30 ]
Both steps are producing energy to be coupled to ATP synthesis. Nitrifying organisms are chemoautotrophs , and use carbon dioxide as their carbon source for growth. Some AOB possess the enzyme, urease , which catalyzes the conversion of the urea molecule to two ammonia molecules and one carbon dioxide molecule. Nitrosomonas europaea , as well as populations of soil-dwelling AOB, have been shown to assimilate the carbon dioxide released by the reaction to make biomass via the Calvin Cycle , and harvest energy by oxidizing ammonia (the other product of urease) to nitrite. This feature may explain enhanced growth of AOB in the presence of urea in acidic environments. [ 32 ]
In most environments, organisms are present that will complete both steps of the process, yielding nitrate as the final product. However, it is possible to design systems in which nitrite is formed (the Sharon process ).
Nitrification is important in agricultural systems, where fertilizer is often applied as ammonia. Conversion of this ammonia to nitrate increases nitrogen leaching because nitrate is more water-soluble than ammonia.
Nitrification also plays an important role in the removal of nitrogen from municipal wastewater . The conventional removal is nitrification, followed by denitrification . The cost of this process resides mainly in aeration (bringing oxygen in the reactor) and the addition of an external carbon source (e.g., methanol ) for the denitrification.
Nitrification can also occur in drinking water. In distribution systems where chloramines are used as the secondary disinfectant, the presence of free ammonia can act as a substrate for ammonia-oxidizing microorganisms. The associated reactions can lead to the depletion of the disinfectant residual in the system. [ 33 ] The addition of chlorite ion to chloramine-treated water has been shown to control nitrification. [ 34 ] [ 35 ]
Together with ammonification , nitrification forms a mineralization process that refers to the complete decomposition of organic material, with the release of available nitrogen compounds. This replenishes the nitrogen cycle .
In the marine environment , nitrogen is often the limiting nutrient , so the nitrogen cycle in the ocean is of particular interest. [ 36 ] [ 37 ] The nitrification step of the cycle is of particular interest in the ocean because it creates nitrate , the primary form of nitrogen responsible for "new" production . Furthermore, as the ocean becomes enriched in anthropogenic CO 2 , the resulting decrease in pH could lead to decreasing rates of nitrification. Nitrification could potentially become a "bottleneck" in the nitrogen cycle. [ 38 ]
Nitrification, as stated above, is formally a two-step process; in the first step ammonia is oxidized to nitrite , and in the second step nitrite is oxidized to nitrate. Diverse microbes are responsible for each step in the marine environment. Several groups of ammonia-oxidizing bacteria (AOB) are known in the marine environment, including Nitrosomonas , Nitrospira , and Nitrosococcus . All contain the functional gene ammonia monooxygenase ( AMO ) which, as its name implies, is responsible for the oxidation of ammonia. [ 2 ] [ 37 ] Subsequent metagenomic studies and cultivation approaches have revealed that some Thermoproteota (formerly Crenarchaeota) possess AMO. Thermoproteota are abundant in the ocean and some species have a 200 times greater affinity for ammonia than AOB, contrasting with the previous belief that AOB are primarily responsible for nitrification in the ocean. [ 39 ] [ 36 ] Furthermore, though nitrification is classically thought to be vertically separated from primary production because the oxidation of nitrate by bacteria is inhibited by light, nitrification by AOA does not appear to be light inhibited, meaning that nitrification is occurring throughout the water column , challenging the classical definitions of "new" and "recycled" production . [ 36 ]
In the second step, nitrite is oxidized to nitrate. In the oceans, this step is not as well understood as the first, but the bacteria Nitrospina [ 17 ] [ 40 ] and Nitrobacter are known to carry out this step in the ocean. [ 36 ]
Nitrification is a process of nitrogen compound oxidation (effectively, loss of electrons from the nitrogen atom to the oxygen atoms), and is catalyzed step-wise by a series of enzymes.
OR
In Nitrosomonas europaea , the first step of oxidation (ammonia to hydroxylamine ) is carried out by the enzyme ammonia monooxygenase (AMO).
The second step (hydroxylamine to nitrite) is catalyzed by two enzymes. Hydroxylamine oxidoreductase (HAO), converts hydroxylamine to nitric oxide. [ 41 ]
Another currently unknown enzyme converts nitric oxide to nitrite.
The third step (nitrite to nitrate) is completed in a distinct organism.
Due to its inherent microbial nature, nitrification in soils is greatly susceptible to soil conditions. In general, soil nitrification will proceed at optimal rates if the conditions for the microbial communities foster healthy microbial growth and activity. Soil conditions that have an effect on nitrification rates include:
Nitrification inhibitors are chemical compounds that slow the nitrification of ammonia , ammonium-containing, or urea-containing fertilizers , which are applied to soil as fertilizers. These inhibitors can help reduce losses of nitrogen in soil that would otherwise be used by crops. Nitrification inhibitors are used widely, being added to approximately 50% of the fall-applied anhydrous ammonia in states in the U.S., like Illinois. [ 42 ] They are usually effective in increasing recovery of nitrogen fertilizer in row crops, but the level of effectiveness depends on external conditions and their benefits are most likely to be seen at less than optimal nitrogen rates. [ 43 ]
The environmental concerns of nitrification also contribute to interest in the use of nitrification inhibitors: the primary product, nitrate , leaches into groundwater, producing toxicity in both humans [ 44 ] and some species of wildlife and contributing to the eutrophication of standing water. Some inhibitors of nitrification also inhibit the production of methane , a greenhouse gas.
The inhibition of the nitrification process is primarily facilitated by the selection and inhibition/destruction of the bacteria that oxidize ammonia compounds. A multitude of compounds inhibit nitrification, which can be divided into the following areas: the active site of ammonia monooxygenase (AMO), mechanistic inhibitors, and the process of N- heterocyclic compounds . The process for the latter of the three is not yet widely understood, but is prominent. The presence of AMO has been confirmed on many substrates that are nitrogen inhibitors such as dicyandiamide , ammonium thiosulfate , and nitrapyrin .
The conversion of ammonia to hydroxylamine is the first step in nitrification, where AH 2 represents a range of potential electron donors.
This reaction is catalyzed by AMO. Inhibitors of this reaction bind to the active site on AMO and prevent or delay the process. The process of oxidation of ammonia by AMO is regarded with importance due to the fact that other processes require the co-oxidation of NH 3 for a supply of reducing equivalents. This is usually supplied by the compound hydroxylamine oxidoreductase (HAO) which catalyzes the reaction:
The mechanism of inhibition is complicated by this requirement. Kinetic analysis of the inhibition of NH 3 oxidation has shown that the substrates of AMO have shown kinetics ranging from competitive to noncompetitive . The binding and oxidation can occur on two sites on AMO: in competitive substrates, binding and oxidation occurs at the NH 3 site, while in noncompetitive substrates it occurs at another site.
Mechanism based inhibitors can be defined as compounds that interrupt the normal reaction catalyzed by an enzyme. This method occurs by the inactivation of the enzyme via covalent modification of the product, which ultimately inhibits nitrification. Through the process, AMO is deactivated and one or more proteins is covalently bonded to the final product. This is found to be most prominent in a broad range of sulfur or acetylenic compounds .
Sulfur-containing compounds, including ammonium thiosulfate (a popular inhibitor) are found to operate by producing volatile compounds with strong inhibitory effects such as carbon disulfide and thiourea .
In particular, thiophosphoryl triamide has been a notable addition where it has the dual purpose of inhibiting both the production of urease and nitrification. [ 45 ] In a study of inhibitory effects of oxidation by the bacteria Nitrosomonas europaea , the use of thioethers resulted in the oxidation of these compounds to sulfoxides , where the S atom is the primary site of oxidation by AMO. This is most strongly correlated to the field of competitive inhibition.
N-heterocyclic compounds are also highly effective nitrification inhibitors and are often classified by their ring structure. The mode of action for these compounds is not well understood: while nitrapyrin, a widely used inhibitor and substrate of AMO, is a weak mechanism-based inhibitor of said enzyme, the effects of said mechanism are unable to correlate directly with the compound's ability to inhibit nitrification. It is suggested that nitrapyrin acts against the monooxygenase enzyme within the bacteria, preventing growth and CH 4 /NH 4 oxidation. [ 46 ] Compounds containing two or three adjacent ring N atoms ( pyridazine , pyrazole , indazole ) tend to have a significantly higher inhibition effect than compounds containing non-adjacent N atoms or singular ring N atoms ( pyridine , pyrrole ). [ 47 ] This suggests that the presence of ring N atoms is directly correlated with the inhibition effect of this class of compounds.
Some enzymatic nitrification inhibitors, such as nitrapyrin, can also inhibit the oxidation of methane in methanotrophic bacteria. [ 48 ] AMO shows similar kinetic turnover rates to methane monooxygenase (MMO) found in methanotrophs, indicating that MMO is a similar catalyst to AMO for the purpose of methane oxidation. Furthermore, methanotrophic bacteria share many similarities to NH 3 oxidizers such as Nitrosomonas . [ 49 ] The inhibitor profile of particulate forms of MMO (pMMO) shows similarity to the profile of AMO, leading to similarity in properties between MMO in methanotrophs and AMO in autotrophs .
Nitrification inhibitors are also of interest from an environmental standpoint because of the production of nitrates and nitrous oxide from the nitrification process. Nitrous oxide (N 2 O), although its atmospheric concentration is much lower than that of CO 2, has a global warming potential of about 300 times greater than carbon dioxide and contributes 6% of planetary warming due to greenhouse gases. This compound is also notable for catalyzing the breakup of ozone in the stratosphere . [ 50 ] Nitrates, a toxic compound for wildlife and livestock and a product of nitrification, are also of concern.
Soil, consisting of polyanionic clays and silicates , generally has a net anionic charge. Consequently, ammonium (NH 4 + ) binds tightly to the soil, but nitrate ions (NO 3 − ) do not. Because nitrate is more mobile, it leaches into groundwater supplies through agricultural runoff . Nitrates in groundwater can affect surface water concentrations through direct groundwater-surface water interactions (e.g., gaining stream reaches, springs) or from when it is extracted for surface use. For example, much of the drinking water in the United States comes from groundwater, but most wastewater treatment plants discharge to surface water.
Among wildlife, amphibians (tadpoles) and freshwater fish eggs are most sensitive to elevated nitrate levels and experience growth and developmental damage at levels commonly found in U.S. freshwater bodies (<20 mg/l). In contrast, freshwater invertebrates are more tolerant (~90+mg/l), and adult freshwater fish can tolerate very high levels (800 mg+/l). [ 51 ] Nitrate levels also contribute to eutrophication , a process in which large algal blooms reduce oxygen levels in bodies of water and lead to death in oxygen-consuming creatures due to anoxia. Nitrification is also thought to contribute to the formation of photochemical smog, ground-level ozone, acid rain , changes in species diversity , and other undesirable processes. In addition, nitrification inhibitors have also been shown to suppress the oxidation of methane (CH 4 ), a potent greenhouse gas , to CO 2 . Both nitrapyrin and acetylene are shown to be potent suppressors of both processes, although the modes of action distinguishing them are unclear. | https://en.wikipedia.org/wiki/Nitrification |
Nitrifying bacteria are chemolithotrophic organisms that include species of genera such as Nitrosomonas , Nitrosococcus , Nitrobacter , Nitrospina , Nitrospira and Nitrococcus . These bacteria get their energy from the oxidation of inorganic nitrogen compounds . [ 1 ] Types include ammonia-oxidizing bacteria ( AOB ) and nitrite-oxidizing bacteria ( NOB ). Many species of nitrifying bacteria have complex internal membrane systems that are the location for key enzymes in nitrification : ammonia monooxygenase (which oxidizes ammonia to hydroxylamine ), hydroxylamine oxidoreductase (which oxidizes hydroxylamine to nitric oxide - which is further oxidized to nitrite by a currently unidentified enzyme), and nitrite oxidoreductase (which oxidizes nitrite to nitrate ). [ 2 ]
Nitrifying bacteria are present in distinct taxonomical groups and are found in highest numbers where considerable amounts of ammonia are present (such as areas with extensive protein decomposition, and sewage treatment plants). [ 3 ] Nitrifying bacteria thrive in lakes, streams, and rivers with high inputs and outputs of sewage, wastewater and freshwater because of the high ammonia content.
Nitrification in nature is a two-step oxidation process of ammonium ( NH + 4 ) or ammonia ( NH 3 ) to nitrite ( NO − 2 ) and then to nitrate ( NO − 3 ) catalyzed by two ubiquitous bacterial groups growing together. The first reaction is oxidation of ammonium to nitrite by ammonia oxidizing bacteria (AOB) represented by members of Betaproteobacteria and Gammaproteobacteria . Further organisms able to oxidize ammonia are Archaea ( AOA ). [ 4 ]
The second reaction is oxidation of nitrite ( NO − 2 ) to nitrate by nitrite-oxidizing bacteria (NOB), represented by the members of Nitrospinota , Nitrospirota , Pseudomonadota , and Chloroflexota . [ 5 ] [ 6 ]
This two-step process was described already in 1890 by the Ukrainian microbiologist Sergei Winogradsky .
Ammonia can be also oxidized completely to nitrate by one comammox bacterium.
Ammonia oxidation in autotrophic nitrification is a complex process that requires several enzymes as well as oxygen as a reactant. The key enzymes necessary for releasing energy during oxidation of ammonia to nitrite are ammonia monooxygenase (AMO) and hydroxylamine oxidoreductase (HAO). The first is a transmembrane copper protein which catalyzes the oxidation of ammonia to hydroxylamine ( 1.1 ) taking two electrons directly from the quinone pool. This reaction requires O 2 .
The second step of this process has recently fallen into question. [ 7 ] For the past few decades, the common view was that a trimeric multiheme c-type HAO converts hydroxylamine into nitrite in the periplasm with production of four electrons ( 1.2 ). The stream of four electrons is channeled through cytochrome c 554 to a membrane-bound cytochrome c 552 . Two of the electrons are routed back to AMO, where they are used for the oxidation of ammonia (quinol pool). The remaining two electrons are used to generate a proton motive force and reduce NAD(P) through reverse electron transport. [ 8 ]
Recent results, however, show that HAO does not produce nitrite as a direct product of catalysis. This enzyme instead produces nitric oxide and three electrons. Nitric oxide can then be oxidized by other enzymes (or oxygen) to nitrite. In this paradigm, the electron balance for overall metabolism needs to be reconsidered. [ 7 ]
Nitrite produced in the first step of autotrophic nitrification is oxidized to nitrate by nitrite oxidoreductase (NXR) ( 2 ). It is a membrane-associated iron-sulfur molybdo protein and is part of an electron transfer chain which channels electrons from nitrite to molecular oxygen. [ citation needed ] The enzymatic mechanisms involved in nitrite-oxidizing bacteria are less described than that of ammonium oxidation. Recent research (e.g. Woźnica A. et al., 2013) [ 9 ] proposes a new hypothetical model of NOB electron transport chain and NXR mechanisms. Here, in contrast to earlier models, [ 10 ] the NXR would act on the outside of the plasma membrane and directly contribute to a mechanism of proton gradient generation as postulated by Spieck [ 11 ] and coworkers. Nevertheless, the molecular mechanism of nitrite oxidation is an open question.
The two-step conversion of ammonia to nitrate observed in ammonia-oxidizing bacteria, ammonia-oxidizing archaea and nitrite-oxidizing bacteria (such as Nitrobacter ) is puzzling to researchers. [ 12 ] [ 13 ] Complete nitrification, the conversion of ammonia to nitrate in a single step known as comammox , has an energy yield (∆G°′) of −349 kJ mol −1 NH 3 , while the energy yields for the ammonia-oxidation and nitrite-oxidation steps of the observed two-step reaction are −275 kJ mol −1 NH 3 , and −74 kJ mol −1 NO 2 − , respectively. [ 12 ] These values indicate that it would be energetically favourable for an organism to carry out complete nitrification from ammonia to nitrate ( comammox ), rather than conduct only one of the two steps. The evolutionary motivation for a decoupled, two-step nitrification reaction is an area of ongoing research. In 2015, it was discovered that the species Nitrospira inopinata possesses all the enzymes required for carrying out complete nitrification in one step, suggesting that this reaction does occur. [ 12 ] [ 13 ] | https://en.wikipedia.org/wiki/Nitrifying_bacteria |
In organic chemistry , a nitrile is any organic compound that has a − C ≡ N functional group . The name of the compound is composed of a base, which includes the carbon of the −C≡N , suffixed with "nitrile", so for example CH 3 CH 2 C≡N is called " propionitrile " (or propanenitrile). [ 1 ] The prefix cyano - is used interchangeably with the term nitrile in industrial literature. Nitriles are found in many useful compounds, including methyl cyanoacrylate , used in super glue , and nitrile rubber , a nitrile-containing polymer used in latex-free laboratory and medical gloves . Nitrile rubber is also widely used as automotive and other seals since it is resistant to fuels and oils. Organic compounds containing multiple nitrile groups are known as cyanocarbons .
Inorganic compounds containing the −C≡N group are not called nitriles, but cyanides instead. [ 2 ] Though both nitriles and cyanides can be derived from cyanide salts, most nitriles are not nearly as toxic.
The N−C−C geometry is linear in nitriles, reflecting the sp hybridization of the triply bonded carbon. The C−N distance is short at 1.16 Å , consistent with a triple bond . [ 3 ] Nitriles are polar, as indicated by high dipole moments. As liquids, they have high relative permittivities , often in the 30s.
The first compound of the homolog row of nitriles, the nitrile of formic acid , hydrogen cyanide was first synthesized by C. W. Scheele in 1782. [ 4 ] [ 5 ] In 1811 J. L. Gay-Lussac was able to prepare the very toxic and volatile pure acid. [ 6 ] Around 1832 benzonitrile , the nitrile of benzoic acid , was prepared by Friedrich Wöhler and Justus von Liebig , but due to minimal yield of the synthesis neither physical nor chemical properties were determined nor a structure suggested. In 1834 Théophile-Jules Pelouze synthesized propionitrile , suggesting it to be an ether of propionic alcohol and hydrocyanic acid. [ 7 ] The synthesis of benzonitrile by Hermann Fehling in 1844 by heating ammonium benzoate was the first method yielding enough of the substance for chemical research.
Fehling determined the structure by comparing his results to the already known synthesis of hydrogen cyanide by heating ammonium formate . He coined the name "nitrile" for the newfound substance, which became the name for this group of compounds. [ 8 ]
Industrially, the main methods for producing nitriles are ammoxidation and hydrocyanation . Both routes are green in the sense that they do not generate stoichiometric amounts of salts.
In ammoxidation , a hydrocarbon is partially oxidized in the presence of ammonia . This conversion is practiced on a large scale for acrylonitrile : [ 9 ]
In the production of acrylonitrile, a side product is acetonitrile . On an industrial scale, several derivatives of benzonitrile , phthalonitrile , as well as Isobutyronitrile are prepared by ammoxidation. The process is catalysed by metal oxides and is assumed to proceed via the imine.
Hydrocyanation is an industrial method for producing nitriles from hydrogen cyanide and alkenes. The process requires homogeneous catalysts . An example of hydrocyanation is the production of adiponitrile , a precursor to nylon-6,6 from 1,3-butadiene :
Two salt metathesis reactions are popular for laboratory scale reactions. In the Kolbe nitrile synthesis , alkyl halides undergo nucleophilic aliphatic substitution with alkali metal cyanides . Aryl nitriles are prepared in the Rosenmund-von Braun synthesis .
In general, metal cyanides combine with alkyl halides to give a mixture of the nitrile and the isonitrile , although appropriate choice of counterion and temperature can minimize the latter. An alkyl sulfate obviates the problem entirely, particularly in nonaqueous conditions (the Pelouze synthesis). [ 5 ]
The cyanohydrins are a special class of nitriles. Classically they result from the addition of alkali metal cyanides to aldehydes in the cyanohydrin reaction . Because of the polarity of the organic carbonyl, this reaction requires no catalyst, unlike the hydrocyanation of alkenes. O-Silyl cyanohydrins are generated by the addition trimethylsilyl cyanide in the presence of a catalyst (silylcyanation). Cyanohydrins are also prepared by transcyanohydrin reactions starting, for example, with acetone cyanohydrin as a source of HCN. [ 10 ]
Nitriles can be prepared by the dehydration of primary amides . Common reagents for this include phosphorus pentoxide ( P 2 O 5 ) [ 11 ] and thionyl chloride ( SOCl 2 ). [ 12 ] In a related dehydration, secondary amides give nitriles by the von Braun amide degradation . In this case, one C-N bond is cleaved.
Numerous traditional methods exist for nitrile preparation by amine oxidation. [ 13 ] Common methods include the use of potassium persulfate , [ 14 ] Trichloroisocyanuric acid , [ 15 ] or anodic electrosynthesis . [ 16 ] In addition, several selective methods have been developed in the last decades for electrochemical processes. [ 17 ]
The conversion of aldehydes to nitriles via aldoximes is a popular laboratory route. Aldehydes react readily with hydroxylamine salts, sometimes at temperatures as low as ambient, to give aldoximes. These can be dehydrated to nitriles by simple heating, [ 18 ] although a wide range of reagents may assist with this, including triethylamine / sulfur dioxide , zeolites , or sulfuryl chloride . The related hydroxylamine-O-sulfonic acid reacts similarly. [ 19 ]
In specialised cases the Van Leusen reaction can be used. Biocatalysts such as aliphatic aldoxime dehydratase are also effective.
Aromatic nitriles are often prepared in the laboratory from the aniline via diazonium compounds . This is the Sandmeyer reaction . It requires transition metal cyanides. [ 20 ]
Nitrile groups in organic compounds can undergo a variety of reactions depending on the reactants or conditions. A nitrile group can be hydrolyzed, reduced, or ejected from a molecule as a cyanide ion.
The hydrolysis of nitriles RCN proceeds in the distinct steps under acid or base treatment to first give carboxamides RC(O)NH 2 and then carboxylic acids RC(O)OH . The hydrolysis of nitriles to carboxylic acids is efficient. In acid or base, the balanced equations are as follows:
Strictly speaking, these reactions are mediated (as opposed to catalyzed ) by acid or base, since one equivalent of the acid or base is consumed to form the ammonium or carboxylate salt, respectively.
Kinetic studies show that the second-order rate constant for hydroxide-ion catalyzed hydrolysis of acetonitrile to acetamide is 1.6 × 10 −6 M −1 s −1 , which is slower than the hydrolysis of the amide to the carboxylate (7.4 × 10 −5 M −1 s −1 ). Thus, the base hydrolysis route will afford the carboxylate (or the amide contaminated with the carboxylate). On the other hand, the acid catalyzed reactions requires a careful control of the temperature and of the ratio of reagents in order to avoid the formation of polymers, which is promoted by the exothermic character of the hydrolysis. [ 28 ] The classical procedure to convert a nitrile to the corresponding primary amide calls for adding the nitrile to cold concentrated sulfuric acid . [ 29 ] The further conversion to the carboxylic acid is disfavored by the low temperature and low concentration of water.
Two families of enzymes catalyze the hydrolysis of nitriles. Nitrilases hydrolyze nitriles to carboxylic acids:
Nitrile hydratases are metalloenzymes that hydrolyze nitriles to amides.
These enzymes are used commercially to produce acrylamide .
The "anhydrous hydration" of nitriles to amides has been demonstrated using an oxime as water source: [ 30 ]
Nitriles are susceptible to hydrogenation over diverse metal catalysts. The reaction can afford either the primary amine ( RCH 2 NH 2 ) or the tertiary amine ( (RCH 2 ) 3 N ), depending on conditions. [ 31 ] In conventional organic reductions , nitrile is reduced by treatment with lithium aluminium hydride to the amine. Reduction to the imine followed by hydrolysis to the aldehyde takes place in the Stephen aldehyde synthesis , which uses stannous chloride in acid.
Alkyl nitriles are sufficiently acidic to undergo deprotonation of the C-H bond adjacent to the C≡N group. [ 32 ] [ 33 ] Strong bases are required, such as lithium diisopropylamide and butyl lithium . The product is referred to as a nitrile anion . These carbanions alkylate a wide variety of electrophiles. Key to the exceptional nucleophilicity is the small steric demand of the C≡N unit combined with its inductive stabilization. These features make nitriles ideal for creating new carbon-carbon bonds in sterically demanding environments.
The carbon center of a nitrile is electrophilic , hence it is susceptible to nucleophilic addition reactions:
Nitriles are precursors to transition metal nitrile complexes , which are reagents and catalysts. Examples include tetrakis(acetonitrile)copper(I) hexafluorophosphate ( [Cu(MeCN) 4 ] + ) and bis(benzonitrile)palladium dichloride ( PdCl 2 (PhCN) 2 ). [ 40 ]
Cyanamides are N -cyano compounds with general structure R 1 R 2 N−C≡N and related to the parent cyanamide . [ 41 ]
Nitrile oxides have the chemical formula RCNO . Their general structure is R−C≡N + −O − . The R stands for any group (typically organyl , e.g., acetonitrile oxide CH 3 −C≡N + −O − , hydrogen in the case of fulminic acid H−C≡N + −O − , or halogen (e.g., chlorine fulminate Cl−C≡N + −O − ). [ 42 ] : 1187–1192
Nitrile oxides are quite different from nitriles: they are highly reactive 1,3-dipoles , and cannot be synthesized from the direct oxidation of nitriles. [ 43 ] Instead, they can be synthesised by nitroalkane dehydration, oxime dehydrogenation, [ 44 ] : 934–936 or halooxime elimination in base. [ 45 ] They are used in 1,3-dipolar cycloadditions , [ 42 ] : 1187–1192 such as to isoxazoles . [ 44 ] : 1201–1202 They undergo type 1 dyotropic rearrangement to isocyanates . [ 42 ] : 1700
The heavier nitrile sulfides are extremely reactive and rare, but temporarily form during the thermolysis of oxathiazolones . They react similarly to nitrile oxides. [ 46 ]
Nitriles occur naturally in a diverse set of plant and animal sources. Over 120 naturally occurring nitriles have been isolated from terrestrial and marine sources. Nitriles are commonly encountered in fruit pits, especially almonds, and during cooking of Brassica crops (such as cabbage, Brussels sprouts, and cauliflower), which release nitriles through hydrolysis. Mandelonitrile , a cyanohydrin produced by ingesting almonds or some fruit pits, releases hydrogen cyanide and is responsible for the toxicity of cyanogenic glycosides. [ 47 ]
Over 30 nitrile-containing pharmaceuticals are currently marketed for a diverse variety of medicinal indications with more than 20 additional nitrile-containing leads in clinical development. The types of pharmaceuticals containing nitriles are diverse, from vildagliptin , an antidiabetic drug, to anastrozole , which is the gold standard in treating breast cancer. In many instances the nitrile mimics functionality present in substrates for enzymes, whereas in other cases the nitrile increases water solubility or decreases susceptibility to oxidative metabolism in the liver. [ 48 ] The nitrile functional group is found in several drugs. | https://en.wikipedia.org/wiki/Nitrile |
Nitrile ylides also known as nitrilium ylides or nitrilium methylides , are generally reactive intermediates [ 1 ] formally consisting of a carbanion of an alkyl or similar group bonded to the nitrogen atom of a cyanide unit. With a few exceptions, they cannot be isolated. However, a structure has been determined on a particularly stable nitrile ylide by X-ray crystallography . [ 2 ] Another nitrile ylide has been captured under cryogenic conditions. [ 3 ]
As ylides , they possess a negative charge and a positive charge on adjacent atoms. However, they also have resonance , including 1,3-dipole contributing structures:
The most appropriate resonance structure is dependent upon the substituent pattern (the identity of the R and R′ groups). The 3-dimensional structure of the nitrilium ylide itself may also provide a clue as to the most appropriate resonance structure, with a linear R–C≡N–C unit supportive of the charge distribution indicated for resonance structures 1a & 1b and also consistent with the nomenclature nitril ium yl ide . As resonance structures 1c and 1d become more important the nitrilium ylide distorts its geometry from linear in favor of a different valence tautomer 2 that is distinctly bent:
Nitrile ylides are isoelectronic with nitrile oxides : R − C ≡ N ⊕ − O ⊖ {\displaystyle {\ce {R-C#}}{\overset {\oplus }{\ce {N}}}{\ce {-O^{\ominus }}}}
Nitrile ylides can be obtained by the addition of electrophilic carbenes to nitriles , by the photochemical ring opening of azirines and by dehydrochlorination of imidoyl chlorides . The latter is the most reliable method.
The synthetically most useful reaction of the nitrile ylides is the 1,3-dipolar cycloaddition to dipolarophiles: with electron-deficient alkenes, good yields of pyrrolines are obtained. Alkynes , carbonyl compounds, imines and azirines can also act as dipolarophile.
Nitrile ylides react with weak acids like methanol by protonation finally leading to a methoxyimine. | https://en.wikipedia.org/wiki/Nitrile_ylide |
Nitrilimines or nitrile amides are a class of organic compounds sharing a common functional group with the general structure R−CN−NR corresponding to the conjugate base of an amine bonded to the N-terminus of a nitrile . The dominant structure for the parent compound nitrilimine is that of the propargyl -like 1 in scheme 1 with a C–N triple bond and with a formal positive charge on nitrogen and two lone pairs and a formal negative charge on the terminal nitrogen. Other structures such as hypervalent 2 , allene -like 3 , allylic 4 and carbene 5 are of lesser relevance.
Nitrilimines were first observed in the thermal decomposition of 2- tetrazoles releasing nitrogen: [ 1 ]
Nitrilimines are linear 1,3-dipoles represented by structures 1 and 3 . A major use is in heterocyclic synthesis. E.g. with alkynes they generate pyrazoles in a 1,3-dipolar cycloaddition . Due to their high energy, they are usually generated in situ as a reactive intermediate. | https://en.wikipedia.org/wiki/Nitrilimine |
A nitrite test is a chemical test used to determine the presence of nitrite ion in solution.
A simple nitrite test can be performed by adding 4 M sulfuric acid to the sample until acidic, and then adding 0.1 M iron(II) sulfate to the solution. A positive test for nitrite is indicated by a dark brown solution, arising from the iron-nitric oxide complex ion. This test is related to the brown ring test for the nitrate ion, which forms the same complex in a ring. In contrast, nitrites turn the whole solution brown and therefore interfere with that test. [ 1 ]
A common method of quantitative nitrite detection is the Griess test, which relies on the reaction of nitrite with the two components of a Griess reagent to form a red azo dye . This allows the concentration of nitrite to be determined by UV-vis spectroscopy . [ 2 ]
A nitrite test is a standard component of a urinary test strip . A positive test for nitrites in the urine is called nitrituria .
This test is commonly used in diagnosing urinary tract infections (UTIs). A positive nitrite test indicates that the cause of the UTI is a Gram-negative organism, most commonly Escherichia coli . The reason for nitrites' existence in the presence of a UTI is due to a bacterial conversion of endogenous nitrates to nitrites. This may be a sign of infection. However, other parameters, such as leukocyte esterase , urine white blood cell count, and symptoms such as dysuria , urinary urgency , fevers, and chills must be correlated to diagnose an infection. [ 3 ]
False-negative nitrite tests in urinary tract infections occur in cases with a low colony forming unit (CFU) count, or in recently voided or dilute urine. [ 4 ] In addition, a nitrite test does not detect organisms unable to reduce nitrate to nitrite, such as enterococci , staphylococci ( Staphylococcus saprophyticus ), Acinetobacter , or adenovirus . [ 4 ]
This article about analytical chemistry is a stub . You can help Wikipedia by expanding it . | https://en.wikipedia.org/wiki/Nitrite_test |
The nitro-Mannich reaction (or aza-Henry reaction ) is the nucleophilic addition of a nitroalkane (or the corresponding nitronate anion) to an imine , resulting in the formation of a beta-nitroamine. [ 1 ] With the reaction involving the addition of an acidic carbon nucleophile to a carbon-heteroatom double bond , the nitro-Mannich reaction is related to some of the most fundamental carbon-carbon bond forming reactions in organic chemistry , including the aldol reaction , [ 2 ] Henry reaction (nitro-aldol reaction) [ 3 ] and Mannich reaction . [ 4 ]
Although extensive research has been conducted into the aforementioned reactions, the nitro-Mannich reaction has been studied to a far lesser extent even though it has been known for well over 100 years. [ 5 ] Significant attention only started to develop after the report of Anderson and co-workers at the turn of the century, [ 6 ] and has since resulted in a wide range of novel methodologies. The interest into the nitro-Mannich reaction stems from the synthetic utility of the beta-nitroamine products. They can be further manipulated by various methods, including reductive removal of the nitro group allowing access to monoamines , reduction of the nitro group affords 1,2-diamines and conversion of the nitro group into a carbonyl functionality furnishes beta-aminocarbonyl compounds .
The first nitro-Mannich reaction was reported by Henry in 1896. [ 5 ] In this report, Henry described the addition of nitroalkanes to an imine derived from hemiaminal . Elimination of water forms in-situ an imine , which then reacts with the nitro group (as a nitronate ion) to form a beta-nitroamine that can subsequently react further forming one of the two adducts. Although this is the first report of the nitro-Mannich reaction, no yields of the products were given.
After Henry’s seminal report, Mousset [ 7 ] and Duden [ 8 ] made contributions to the field by studying the addition of branched nitroalkanes to hemiaminals using the same procedures reported by Henry. An example of nitro group reduction to an amine using SnCl 2 and HCl was also disclosed by Duden and co-workers, thus representing the first use of the nitro-Mannich reaction to prepare polyamines . The next report did not appear until 1931, [ 9 ] when Cerf de Mauny conducted a thorough study of Henry’s original work using hemiaminals. The scope of the reaction was extended to higher order nitroalkanes affording a beta-nitroamine in excellent yields.
The next contributions appeared in 1946, when Senkus and Johnson independently reported their studies into the nitro-Mannich reaction. Senkus and co-workers [ 10 ] illustrated that nitroalkanes may react with methanal (formaldehyde) and substituted primary amines in the presence of sodium sulfate ( Na 2 SO 4 ) to afford a variety of substituted beta-nitroamines in moderate to good yields. When using primary nitroalkane substrates, double addition of the nitroalkane to the imine was observed, but this could be avoided by employing secondary nitroalkanes. The study reported by Johnson and co-workers [ 11 ] also employed formaldehyde, but this was used in conjunction with a selection of secondary amines, furnishing the corresponding beta-nitroamines in moderate to good yields. Both authors also reduced the nitro group to an amine functionality using Raney Nickel.
Up until this point, all of the nitro-Mannich methodologies reported had used imines that were formed in situ from an aldehyde and an amine. In 1950, Hurd and Strong reported [ 12 ] the first nitro-Mannich reaction using a preformed imine. Exposing an imine to a nitroalkane afforded a substituted beta-nitroamines in moderate yields. The moderate yields obtained when using the preformed imine could possibly be attributed to a competing decomposition pathway of the imine or the product.
These early nitro-Mannich methodologies have been used by a number of groups for the synthesis of a variety of heterocyclic products, conjugated nitroalkenes (via elimination of the amino group) [ 13 ] [ 14 ] and dinitroamines. [ 15 ]
Although the nitro-Mannich reaction enables access to synthetically useful beta-nitroamine motifs, the lack of selectivity in their synthesis remained a significant problem. Interest in the field started to increase considerably after Anderson and co-workers reported the first diastereoselective acyclic nitro-Mannich reaction. [ 6 ] A nitroalkane and n -butyllithium (nBuLi) were combined at -78 °C to give the corresponding nitronate ions. A selection of N -PMB imines were then added to the reaction mixture and after quenching with acetic acid , the beta-nitroamine products were afforded in good yields with moderate to good diastereoselectivities.
The authors then converted the beta-nitroamines into unprotected 1,2-diamines via a two step procedure. Firstly, the nitro group was reduced to amines using samarium iodide , followed by PMB removal in the presence of ceric ammonium nitrate (CAN). The same group later reported improvements to this methodology and expanded these preliminary results in further publications. [ 16 ] [ 17 ]
In 2000, Anderson and co-workers reported the racemic nitro-Mannich reaction of TMS -protected nitronate with N -PMB or N -PMP imines catalysed by Sc(OTf) 3 . [ 18 ] The authors first attempted the nitro-Mannich reaction using lithium-nitronates, however no product was formed using these conditions. As a result, the TMS-protected nitronate was used in conjunction with Scandium(III) trifluoromethanesulfonate [Sc(OTf) 3 ] (4 mol%) to afford the beta-nitroamine products in moderate to excellent yields for a range of alkyl and aryl N -PMB and N -PMP protected imines.
Following Anderson’s report, Qian and co-workers described the ytterbium(III) isopropylate [Yb(OiPr) 3 ] catalysed nitro-Mannich reaction of N -sulfonyl imines and nitromethane. [ 19 ] Using mild reactions conditions, the β-nitroamines bearing electron-rich and electron-poor aryl substituents were furnished in excellent yields after short reaction times.
The first enantioselective metal catalysed nitro-Mannich reaction was reported by Shibasaki and co-workers in 1999. [ 20 ] The authors used a binaphthol ligated Yb/K heterobimetallic complex ( Shibasaki catalyst ) to induce enantiocontrol in the reaction, furnishing β-nitroamines in moderate to good yields with good enantioselectivities. However, nitromethane was the only nitroalkane that could be used with the heterobimetallic complex and the reactions were very slow (2.5–7 days) even when using a relatively high catalyst loading of 20 mol%.
Building on the work of Shibasaki, Jørgensen and co-workers reported the asymmetric nitro-Mannich reaction of nitroalkanes and a N-PMP-α-iminoesters. [ 21 ] Catalysed by Cu(II)-BOX 52 and triethylamine (Et 3 N), the reaction afforded β-nitro-α-aminoesters in good yields with excellent enantiocontrol (up to 99% ee). The reaction tolerates a selection of nitroalkanes but is limited exclusively to N-PMP-α-iminoesters. The authors propose that the reaction proceeds via the chair-like transition structure, where both the N-PMP-α-iminoester and the nitronate anion bind to the Cu(II)-BOX complex.
In 2007, Feng and co-workers reported that CuOTf used in conjunction with the shown chiral N -oxide ligand and DIPEA is an efficient catalytic system for the enantioselective nitro-Mannich reaction of nitromethane with N-sulfonyl imines. [ 22 ] Combining all of the reagents in THF at –40 °C resulted in the formation of β-nitroamines in excellent yields (up to 99%) and good enantioselectivities for a variety of substituted aryls groups. The postulated intermediate complex is similar to the transition structure proposed by Jørgensen and co-workers, where the ligated copper species binds to the N-sulfonyl imine. A hydrogen bonding interaction is proposed to exist between the amide NH and the nitronate species.
Around the same time as the report of Feng, Shibasaki and co-workers reported one of the most successful enantioselective nitro-Mannich reactions, catalysed by the shown Cu/Sm heterobimetallic complex. [ 23 ] Combining N-Boc protected imines and nitroalkanes resulted in moderate to excellent yields and good to excellent enantioselectivities of the products. Interestingly, the nitro-Mannich reaction catalysed by complex affords syn-β-nitroamines, whereas most other enantioselective methodologies favour anti-β-nitroamines. The authors later reported an improved version of the protocol and proposed a mechanistic rational to account for the observed syn diastereoselectivity. [ 24 ]
Since the inception of organocatalysis, numerous accounts of organocatalysed enantioselective nitro-Mannich reactions have been reported. [ 1 ] These include examples using Brønsted base catalysts, Brønsted acid catalysts, bifunctional Brønsted base/H-bond donor catalysts and phase-transfer catalysts.
Small chiral molecule H-bond donors can be used as a powerful tool for enantioselective synthesis. [ 25 ] These low molecular weight entities containing structural frameworks with distinct H-bond donor motifs can catalyse a wide range of carbon-carbon and carbon-heteroatom bond-forming reactions, occurring via H-bond donor activation of the reaction partners as well as through organisation of their spatial arrangement. This area of organic chemistry received limited attention until the seminal work of Jacobsen and Sigman [ 26 ] in which they reported a highly enantioselective Strecker reaction using a H-bond donor organocatalyst :
Building on the work of Jacobsen, it was recognised that H-bond donor motifs can be linked via a chiral scaffold to Brønsted basic moieties , creating a new class of bifunctional organocatalysts (see concept figure below). The incorporation of these two functionalities allows the simultaneous activation of the nucleophile (via deprotonation by the Brønsted base) and electrophile (via H-bond donation), thus allowing the development of novel enantioselective reactions through new activation modes.
Based on this concept, Takemoto and co-workers reported the first bifunctional Brønsted base/H-bond donor thiourea organocatalyst 62 (see below) in 2003. [ 27 ] This organocatalyst, based on the 1,2-trans-cyclohexanediamine scaffold, imparts high levels of enantiocontrol in the Michael addition of dimethylmalonate to a variety of nitrostyrenes. After this seminal report, numerous other bifunctional organocatalysts were developed derived from the readily available cinchona alkaloid scaffold. The quinidine-derived bifunctional organocatalyst 63 (first reported by Deng and co-workers) acts as a proficient catalyst for Michael addition reactions. [ 28 ] In this organocatalytic system, the H-bonding interaction arising from the quinoline alcohol is thought to be crucial for achieving high enantioselectivities.
Also the bifunctional thioureas 64 and 65 , again derived from the cinchona alkaloids, are very effective catalysts in Michael addition reactions. [ 29 ] [ 30 ] [ 31 ] [ 32 ] The bifunctional thiourea 66 is able to impart high levels of enantiocontrol in the nitro-aldol (Henry) reaction. [ 33 ] Bifunctional thiourea 66 differs structurally from bifunctional thioureas 64 and 65 , as the thiourea moiety is attached to the quinoline ring of the cinchona scaffold instead of the central stereocentre . Also numerous other bifunctional organocatalyst systems are described, which further expand the range of reactions that can be conducted using bifunctional (thio)urea organocatalysis. [ 25 ]
This article incorporates text by David Michael Barber available under the CC BY 2.5 license. | https://en.wikipedia.org/wiki/Nitro-Mannich_reaction |
Nitro blue tetrazolium is a chemical compound composed of two tetrazole moieties . It is used in immunology for sensitive detection of alkaline phosphatase (with BCIP ). NBT serves as the oxidant and BCIP is the AP- substrate (and gives also dark blue dye).
In immunohistochemistry the alkaline phosphatase is often used as a marker, conjugated to an antibody . The colored product can either be of the NBT/BCIP reaction reveals where the antibody is bound, or can be used in immunofluorescence . [ 1 ]
The NBT/BCIP reaction is also used for colorimetric/ spectrophotometric activity assays of oxidoreductases . One application is in activity stains in gel electrophoresis , such as with the mitochondrial electron transport chain complexes. [ 2 ]
Nitro blue tetrazolium is used in a diagnostic test, [ 3 ] particularly for chronic granulomatous disease and other diseases of phagocyte function. When there is an NADPH oxidase defect, the phagocyte is unable to make reactive oxygen species or radicals required for bacterial killing. As a result, bacteria may thrive within the phagocyte. The higher the blue score, the better the cell is at producing reactive oxygen species. [ 4 ] | https://en.wikipedia.org/wiki/Nitro_blue_tetrazolium_chloride |
In organic chemistry , nitro compounds are organic compounds that contain one or more nitro functional groups ( −NO 2 ). The nitro group is one of the most common explosophores (functional group that makes a compound explosive) used globally. The nitro group is also strongly electron-withdrawing . Because of this property, C−H bonds alpha (adjacent) to the nitro group can be acidic. For similar reasons, the presence of nitro groups in aromatic compounds retards electrophilic aromatic substitution but facilitates nucleophilic aromatic substitution . Nitro groups are rarely found in nature. They are almost invariably produced by nitration reactions starting with nitric acid . [ 1 ]
Aromatic nitro compounds are typically synthesized by nitration. Nitration is achieved using a mixture of nitric acid and sulfuric acid , which produce the nitronium ion ( NO + 2 ), which is the electrophile:
The nitration product produced on the largest scale, by far, is nitrobenzene . Many explosives are produced by nitration including trinitrophenol (picric acid), trinitrotoluene (TNT), and trinitroresorcinol (styphnic acid). [ 3 ] Another but more specialized method for making aryl–NO 2 group starts from halogenated phenols, is the Zinke nitration .
Aliphatic nitro compounds can be synthesized by various methods; notable examples include:
In nucleophilic aliphatic substitution , sodium nitrite (NaNO 2 ) replaces an alkyl halide . In the so-called Ter Meer reaction (1876) named after Edmund ter Meer , [ 14 ] the reactant is a 1,1-halonitroalkane:
The reaction mechanism is proposed in which in the first slow step a proton is abstracted from nitroalkane 1 to a carbanion 2 followed by protonation to an aci-nitro 3 and finally nucleophilic displacement of chlorine based on an experimentally observed hydrogen kinetic isotope effect of 3.3. [ 15 ] When the same reactant is reacted with potassium hydroxide the reaction product is the 1,2-dinitro dimer. [ 16 ]
Chloramphenicol is a rare example of a naturally occurring nitro compound. At least some naturally occurring nitro groups arose by the oxidation of amino groups. [ 17 ] 2-Nitrophenol is an aggregation pheromone of ticks .
Examples of nitro compounds are rare in nature. 3-Nitropropionic acid found in fungi and plants ( Indigofera ). Nitropentadecene is a defense compound found in termites . Aristolochic acids are found in the flowering plant family Aristolochiaceae . Nitrophenylethane is found in Aniba canelilla . [ 18 ] Nitrophenylethane is also found in members of the Annonaceae , Lauraceae and Papaveraceae . [ 19 ]
Despite the occasional use in pharmaceuticals, the nitro group is associated with mutagenicity and genotoxicity and therefore is often regarded as a liability in the drug discovery process. [ 20 ]
Nitro compounds participate in several organic reactions , the most important being reduction of nitro compounds to the corresponding amines:
Virtually all aromatic amines (e.g. aniline ) are derived from nitroaromatics through such catalytic hydrogenation . A variation is formation of a dimethylaminoarene with palladium on carbon and formaldehyde : [ 21 ]
The α-carbon of nitroalkanes is somewhat acidic. The p K a values of nitromethane and 2-nitropropane are respectively 17.2 and 16.9 in dimethyl sulfoxide (DMSO) solution, suggesting an aqueous p K a of around 11. [ 22 ] In other words, these carbon acids can be deprotonated in aqueous solution. The conjugate base is called a nitronate , and behaves similar to an enolate . In the nitroaldol reaction , it adds directly to aldehydes , and, with enones , can serve as a Michael donor . Conversely, a nitroalkene reacts with enols as a Michael acceptor. [ 23 ] [ 24 ] Nitrosating a nitronate gives a nitrolic acid . [ 25 ]
Nitronates are also key intermediates in the Nef reaction : when exposed to acids or oxidants, a nitronate hydrolyzes to a carbonyl and azanone . [ 26 ]
Grignard reagents combine with nitro compounds to give a nitrone ; but a Grignard reagent with an α hydrogen will then add again to the nitrone to give a hydroxylamine salt. [ 27 ]
The Leimgruber–Batcho , Bartoli and Baeyer–Emmerling indole syntheses begin with aromatic nitro compounds. Indigo can be synthesized in a condensation reaction from ortho -nitrobenzaldehyde and acetone in strongly basic conditions in a reaction known as the Baeyer–Drewson indigo synthesis .
Many flavin -dependent enzymes are capable of oxidizing aliphatic nitro compounds to less-toxic aldehydes and ketones. Nitroalkane oxidase and 3-nitropropionate oxidase oxidize aliphatic nitro compounds exclusively, whereas other enzymes such as glucose oxidase have other physiological substrates. [ 28 ]
Explosive decomposition of organo nitro compounds are redox reactions, wherein both the oxidant (nitro group) and the fuel (hydrocarbon substituent) are bound within the same molecule. The explosion process generates heat by forming highly stable products including molecular nitrogen (N 2 ), carbon dioxide, and water. The explosive power of this redox reaction is enhanced because these stable products are gases at mild temperatures. Many contact explosives contain the nitro group. | https://en.wikipedia.org/wiki/Nitro_compound |
A nitro engine generally refers to an engine powered with a fuel that contains some portion (usually between 10% and 40%) of nitromethane mixed with methanol . Nitromethane is a highly combustible substance that is generally only used in very specifically designed engines found in Top Fuel drag racing and in miniature internal combustion engines in radio control , control line and free flight model aircraft.
The term "nitro" has come into use in the last few decades [ when? ] to describe these engines and has its origins in marketing hype in the model car market. For the fifty or so years prior to this term since the engines were first developed, they were simply referred to as "glow engines", but the term "nitro" has more impact in ad copy. These engines are actually fueled by methanol, but the fuel is often doped with nitromethane as a performance additive. The ignition system consists of a glow plug – hence the older term "glow" engine which has a coil of platinum-containing wire alloy, usually platinum – iridium . The glow plug is heated with electric current for starting, after which power is disconnected and the combination of residual heat and catalytic action of the platinum alloy with methanol ignites the fuel mixture.
Nitro engines for models can turn in excess of 50,000 RPM. Typical operating rpm for sport model aircraft engines is 10,000–14,000 RPM. For radio control (RC) boats and ducted fan aircraft engines, 20,000–25,000 is the usual range, and for cars RPM in the range of 25,000–37,000 is common. With this much movement, a lot of frictional heat is generated and the fuel used for these engines usually contains between 12 and 30% oil content depending on the nitromethane and methanol percentage, the engine type and application. Most engines in RC cars today are two-stroke engines , which means that it takes two strokes of the piston (one revolution) to complete the engine cycle. On the first stroke as the piston travels upward, a mixture of fuel and air is sucked into the crankcase, from the carburettor . When the piston travels downward the new fuel air mixture travels into the induction port and finally into the combustion chamber. As the piston travels upward the mixture is compressed which causes the fuel/air mixture to ignite, producing hot gas under pressure to force the piston down. As the piston travels downward the spent exhaust gases escape out of the combustion chamber through the exhaust port, and the cycle starts over by the fuel mixture being again pushed into the induction port.
When starting, the glow plug is electrically preheated by electric current. The glow plug is not to be confused with a spark plug – there is no spark in the glow plug. Catalysis from methanol vapor on the heated platinum element keeps it red-hot even after voltage has been removed, which ignites the fuel and keeps the engine running. Whereas spark plugs are constantly used to ignite the fuel/air mix every time the piston comes up, as seen in the petrol engine where the spark plug is used, the fuel cannot be ignited with compression alone. It is the plug's temperature, still red-hot from previous ignition and from catalysis with the new compressed mixture, that ignites the fuel.
Nitro engines typically use a carburetor to mix the fuel and air together, although for some applications where throttling is not required they have a simple venturi with a spraybar and needle valve . The carburetor can either be sliding or rotary. On a rotary carburetor, the slide is opened as the arm is turned by the servo . On a slide carburetor the slide is opened by sliding the arm out by the servo. Both are held open slightly by an idle screw which allows the engine to receive a very small amount of fuel to keep the engine running when the vehicle is at a stop. The carburetors usually feature two needles used to tune the mixture. A high speed needle tunes how much fuel is allowed into the carburetor at mid to high RPM, and a low speed needle determines how much fuel is allowed into the carburetor at low to mid range RPM. Turning either needle in a clockwise motion will thin the fuel mixture . Lean describes the amount of fuel in the fuel / air mixture. To a point this will make the engine run faster with better performance, but once too lean the engine will overheat, and wear out prematurely due to not receiving enough lubrication. Turning either needle counterclockwise will enrich the fuel mixture (unless the low speed needle is an air bleed in which case the opposite is true). Rich is the opposite of lean, it means more oil (fuel mixture) is entering the engine. If the engine is too rich, it will run poorly, and fuel that has not yet been burnt may start to spit out of the exhaust. The engine will run very slowly and seem to have no power and possibly cut out from being flooded with fuel. Although, being too rich is better than being too lean, because being too rich just means the engine is getting too much oil which is perfectly fine, although performance may not be as good as if the engine were lean. An excessively lean mixture can damage an engine in a short time, as it will run above its design temperature. A properly tuned engine will last a long time with good performance throughout its life.
There are different types of R/C engines. There are on-road, off-road, aircraft, marine, and monster truck engines.
On-road engines are designed to come into their power band from mid to high RPM. These engines can be used in off-road vehicles but are normally used in on-road sedans where very high RPM and high speed is required. Off-road engines have a less abrupt power curve compared to on-road engines. Off-road engines have a power band that extends through most of the RPM range. Off-road engines do not rev as high as on-road engines, but they do have more torque that can easily propel the vehicle it is in to impressive speeds. Off-road engines are usually used in 1/8 scale buggies where high speeds and bad accelerations are less important.
Monster truck engines are generally very large compared to on-road and off-road engines. Where an off-road engine may be 0.21 cubic inches (3.4 cm 3 ) in size, a monster truck engine may be as much as 0.46 cubic inches (7.5 cm 3 ). Monster truck engines generate much of their torque and horsepower at low to mid range RPM. They are usually used in large and heavy trucks where all that power is needed to get good performance out of the vehicle.
Aircraft engines are manufactured to be able to sustain high RPM. The biggest difference between all other nitro engines and aircraft engines is the ability to sustain RPM. Other nitro engines tend to break if run at full throttle for a full tank of fuel.
Marine engines are cooled with water rather than air like other nitro engines.
Members of the full scale drag racing industry use much higher concentrations of nitromethane: they are limited by the rules to 90% (at least in the NHRA, the main sanctioning body). Historically, racers used higher percentages which frequently caused massive explosions. Modern engines are estimated to generate around 8000 horsepower. The cars can accelerate from 0 to 100 mph in 0.8 seconds and 0 to 335 mph in 4.5 seconds. | https://en.wikipedia.org/wiki/Nitro_engine |
A nitroalkene , or nitro olefin, is a functional group combining the functionality of its constituent parts, an alkene and nitro group , while displaying its own chemical properties through alkene activation , making the functional group useful in specialty reactions such as the Michael reaction or Diels-Alder additions. [ 1 ]
Nitroalkenes are synthesized by various means, notable examples include:
Nitroalkenes are useful intermediates for various chemical functionalities.
The related nitroalkynes are rather unstable, easily losing nitrogen dioxide radicals, rearranging to nitriles over −40 °C, or adding nucleophiles . Fewer than 20 had been synthesized before 2014. Nitration of metalloalkynes requires nearly-bare nitronium , i.e. nitronium tetrafluoroborate or nitric anhydride . In contrast, Tilden's reagent suffices to nitrosylate metalloalkynes; the products then oxidize to nitroalkenes in peroxyacids . Protected nitroalkene dehydroiodination occurs delicately in the gas phase. [ 16 ] | https://en.wikipedia.org/wiki/Nitroalkene |
In organic and inorganic chemistry , nitroamines or nitramides are chemical compounds with the general chemical structure R 1 R 2 N−NO 2 . They consist of a nitro group ( −NO 2 ) bonded to the nitrogen of an amine . [ 1 ] [ 2 ] The R groups can be any group, typically hydrogen (e.g., methylnitroamine CH 3 −NH−NO 2 ) and organyl (e.g., diethylnitroamine (CH 3 CH 2 −) 2 N−NO 2 ). An example of inorganic nitroamine is chloronitroamine , Cl−NH−NO 2 . [ 3 ] The parent inorganic compound , where both R substituents are hydrogen, is nitramide or nitroamine, H 2 N−NO 2 .
N -Nitroaniline rearranges in the presence of acid to give 2-nitroaniline . [ 4 ]
This organic chemistry article is a stub . You can help Wikipedia by expanding it . | https://en.wikipedia.org/wiki/Nitroamine |
( C 6 H 8 (NO 2 ) 2 O 5 ) n (dinitrocellulose) ( C 6 H 7 (NO 2 ) 3 O 5 ) n (trinitrocellulose, pictured in structures above)
Nitrocellulose (also known as cellulose nitrate , flash paper , flash cotton , guncotton , pyroxylin and flash string , depending on form) is a highly flammable compound formed by nitrating cellulose through exposure to a mixture of nitric acid and sulfuric acid . One of its first major uses was as guncotton, a replacement for gunpowder as propellant in firearms. It was also used to replace gunpowder as a low-order explosive in mining and other applications. In the form of collodion it was also a critical component in an early photographic emulsion, the use of which revolutionized photography in the 1860s. In the 20th century it was adapted to automobile lacquer and adhesives .
The process uses a mixture of nitric acid and sulfuric acid to convert cellulose into nitrocellulose. [ 2 ] The quality of the cellulose is important. Hemicellulose , lignin , pentosans , and mineral salts give inferior nitrocelluloses. In organic chemistry, nitrocellulose is a nitrate ester , not a nitro compound . The glucose repeat unit (anhydroglucose) within the cellulose chain has three OH groups, each of which can form a nitrate ester. Thus, nitrocellulose can denote mononitrocellulose , dinitrocellulose , and trinitrocellulose , or a mixture thereof. With fewer OH groups than the parent cellulose, nitrocelluloses do not aggregate by hydrogen bonding . The overarching consequence is that the nitrocellulose is soluble in organic solvents such as acetone and esters; e.g., ethyl acetate , methyl acetate , ethyl carbonate . [ 3 ] Most lacquers are prepared from the dinitrate, whereas explosives are mainly the trinitrate. [ 4 ] [ 5 ]
The chemical equation for the formation of the trinitrate is 3 HNO 3 + C 6 H 7 (OH) 3 O 2 H 2 SO 4 → C 6 H 7 (ONO 2 ) 3 O 2 + 3 H 2 O .
The yields are about 85%, with losses attributed to complete oxidation of the cellulose to oxalic acid .
The principal uses of cellulose nitrate is for the production of lacquers and coatings, explosives, and celluloid . [ 6 ]
In terms of lacquers and coatings, nitrocellulose dissolves readily in organic solvents, which upon evaporation leave a colorless, transparent, flexible film. [ 4 ] Nitrocellulose lacquers have been used as a finish on furniture and musical instruments. [ 7 ]
Guncotton, dissolved at about 25% in acetone , forms a lacquer used in preliminary stages of wood finishing to develop a hard finish with a deep lustre. [ 8 ] It is normally the first coat applied, then it is sanded and followed by other coatings that bond to it.
Nail polish contains nitrocellulose, as it is inexpensive, dries quickly to a hard film, and does not damage skin. [ 9 ]
The explosive applications are diverse and nitrate content is typically higher for propellant applications than for coatings. [ 6 ] For space flight, nitrocellulose was used by Copenhagen Suborbitals on several missions as a means of jettisoning components of the rocket/space capsule and deploying recovery systems. However, after several missions and flights, it proved not to have the desired explosive properties in a near vacuum environment. [ 10 ] In 2014, the Philae comet lander failed to deploy its harpoons because its 0.3 grams of nitrocellulose propulsion charges failed to fire during the landing. [ 11 ]
Collodion, a solution of nitrocellulose, is used today in topical skin applications, such as liquid skin and in the application of salicylic acid , the active ingredient in Compound W wart remover. [ 12 ] [ 13 ] [ citation needed ]
In 1832 Henri Braconnot discovered that nitric acid, when combined with starch or wood fibers, would produce a lightweight combustible explosive material, which he named xyloïdine . [ 20 ] A few years later in 1838, another French chemist, Théophile-Jules Pelouze (teacher of Ascanio Sobrero and Alfred Nobel ), treated paper and cardboard in the same way. [ 21 ] Jean-Baptiste Dumas obtained a similar material, which he called nitramidine . [ 22 ]
Around 1846 Christian Friedrich Schönbein , a German-Swiss chemist, discovered a more practical formulation. [ 23 ] As he was working in the kitchen of his home in Basel , he spilled a mixture of nitric acid (HNO 3 ) and sulfuric acid (H 2 SO 4 ) on the kitchen table. He reached for the nearest cloth, a cotton apron, and wiped it up. He hung the apron on the stove door to dry, and as soon as it was dry, a flash occurred as the apron ignited. His preparation method was the first to be widely used. The method was to immerse one part of fine cotton in 15 parts of an equal blend of sulfuric acid and nitric acid. After two minutes, the cotton was removed and washed in cold water to set the esterification level and to remove all acid residue. The cotton was then slowly dried at a temperature below 40 °C (104 °F). Schönbein collaborated with the Frankfurt professor Rudolf Christian Böttger , who had discovered the process independently in the same year.
By coincidence, a third chemist, the Brunswick professor F. J. Otto had also produced guncotton in 1846 and was the first to publish the process, much to the disappointment of Schönbein and Böttger. [ 24 ] [ full citation needed ]
The patent rights for the manufacture of guncotton were obtained by John Hall & Son in 1846, and industrial manufacture of the explosive began at a purpose-built factory at Marsh Works in Faversham, Kent , a year later. The manufacturing process was not properly understood and few safety measures were put in place. A serious explosion in July that killed almost two dozen workers resulted in the immediate closure of the plant. Guncotton manufacture ceased for over 15 years until a safer procedure could be developed. [ 25 ]
The British chemist Frederick Augustus Abel developed the first safe process for guncotton manufacture, which he patented in 1865. The washing and drying times of the nitrocellulose were both extended to 48 hours and repeated eight times over. The acid mixture was changed to two parts sulfuric acid to one part nitric. Nitration can be controlled by adjusting acid concentrations and reaction temperature. Nitrocellulose is soluble in a mixture of ethanol and ether until nitrogen concentration exceeds 12%. Soluble nitrocellulose, or a solution thereof, is sometimes called collodion . [ 26 ]
Guncotton containing more than 13% nitrogen (sometimes called insoluble nitrocellulose) was prepared by prolonged exposure to hot, concentrated acids [ 26 ] for limited use as a blasting explosive or for warheads of underwater weapons such as naval mines and torpedoes . [ 27 ] Safe and sustained production of guncotton began at the Waltham Abbey Royal Gunpowder Mills in the 1860s, and the material rapidly became the dominant explosive, becoming the standard for military warheads, although it remained too potent to be used as a propellant. More-stable and slower-burning collodion mixtures were eventually prepared using less concentrated acids at lower temperatures for smokeless powder in firearms . The first practical smokeless powder made from nitrocellulose, for firearms and artillery ammunition, was invented by French chemist Paul Vieille in 1884.
Jules Verne viewed the development of guncotton with optimism. He referred to the substance several times in his novels. His adventurers carried firearms employing this substance. In his From the Earth to the Moon , guncotton was used to launch a projectile into space.
Because of their fluffy and nearly white appearance, nitrocellulose products are often referred to as cottons, e.g. lacquer cotton, celluloid cotton, and gun cotton. [ 4 ]
Guncotton was originally made from cotton (as the source of cellulose) but contemporary methods use highly processed cellulose from wood pulp . While guncotton is dangerous to store, the hazards it presents can be minimized by storing it dampened with various liquids, such as alcohol. For this reason, accounts of guncotton usage dating from the early 20th century refer to "wet guncotton."
The power of guncotton made it suitable for blasting. As a projectile driver, it had around six times the gas generation of an equal volume of black powder and produced less smoke and less heating.
Artillery shells filled with gun cotton were widely used during the American Civil War , and its use was one of the reasons the conflict was seen as the "first modern war." [ 28 ] Fired from breech-loading artillery , such high explosive shells could cause greater damage than previous solid round shot .
During the first World War , British authorities were slow to introduce new grenades , with soldiers at the front improvising by filling ration tin cans with gun cotton , scrap and a basic fuse. [ 29 ]
Further research indicated the importance of washing the acidified cotton. Unwashed nitrocellulose (sometimes called pyrocellulose) may spontaneously ignite and explode at room temperature , as the evaporation of water results in the concentration of unreacted acid. [ 27 ]
In 1855, the first human-made plastic , nitrocellulose (branded Parkesine , patented in 1862), was created by Alexander Parkes from cellulose treated with nitric acid and a solvent. In 1868, American inventor John Wesley Hyatt developed a plastic material he named Celluloid , improving on Parkes' invention by plasticizing the nitrocellulose with camphor so that it could be processed into a photographic film . This was used commercially as "celluloid", a highly flammable plastic that until the mid-20th century formed the basis for lacquers and photographic film. [ 8 ]
On May 2, 1887, Hannibal Goodwin filed a patent for "a photographic pellicle and process of producing same ... especially in connection with roller cameras", but the patent was not granted until September 13, 1898. [ 30 ] In the meantime, George Eastman had already started production of roll-film using his own process.
Nitrocellulose was used as the first flexible film base , beginning with Eastman Kodak products in August 1889. Camphor is used as a plasticizer for nitrocellulose film, often called nitrate film. Goodwin's patent was sold to Ansco , which successfully sued Eastman Kodak for infringement of the patent and was awarded $5,000,000 in 1914 to Goodwin Film. [ 31 ]
Disastrous fires related to celluloid or "nitrate film" became regular occurrences in the motion picture industry throughout the silent era and for many years after the arrival of sound film . [ 32 ] Projector fires and spontaneous combustion of nitrate footage stored in studio vaults and in other structures were often blamed during the early to mid 20th century for destroying or heavily damaging cinemas, inflicting many serious injuries and deaths, and for reducing to ashes the master negatives and original prints of tens of thousands of screen titles, [ 33 ] turning many of them into lost films . Even when nitrate stock did not start the blaze, flames from other sources spread to large nearby film collections, producing intense and highly destructive fires.
In 1914—the same year that Goodwin Film was awarded $5,000,000 from Kodak for patent infringement—nitrate film fires incinerated a significant portion of the United States' early cinematic history. In that year alone, five very destructive fires occurred at four major studios and a film-processing plant. Millions of feet of film burned on March 19 at the Eclair Moving Picture Company in Fort Lee, New Jersey . [ 34 ] Later that same month, many more reels and film cans of negatives and prints also burned at Edison Studios in New York City, in the Bronx. On May 13, a fire at Universal Pictures ' Colonial Hall "film factory" in Manhattan consumed another extensive collection. [ 35 ] [ 36 ] Yet again, on June 13 in Philadelphia, a fire and a series of explosions ignited inside the 186-square-meter (2,000-square-foot) film vault of the Lubin Manufacturing Company and quickly wiped out virtually all of that studio's pre-1914 catalogue. [ 37 ] Then a second fire hit the Edison Company at another location on December 9, at its film-processing complex in West Orange, New Jersey . That catastrophic fire started inside a film-inspection building and caused over $7,000,000 in property damages ($220,000,000 today). [ 38 ] Even after film technology changed, archives of older films remained vulnerable; the 1965 MGM vault fire burned many films that were decades old.
The use of volatile nitrocellulose film for motion pictures led many cinemas to fireproof their projection rooms with wall coverings made of asbestos . Those additions intended to prevent or at least delay the migration of flames beyond the projection areas. A training film for projectionists included footage of a controlled ignition of a reel of nitrate film, which continued to burn even when fully submerged in water. [ 39 ] Once burning, it is extremely difficult to extinguish. Unlike most other flammable materials, nitrocellulose does not need a source of air to continue burning, since it contains sufficient oxygen within its molecular structure to sustain a flame. For this reason, immersing burning film in water may not extinguish it, and could actually increase the amount of smoke produced. [ 40 ] Owing to public safety precautions, the United Kingdom 's Health and Safety Executive to this day forbids transportation of nitrate film by post or public transit, or disposal with household refuse. [ 41 ]
Cinema fires caused by the ignition of nitrocellulose film stock commonly occurred as well. In Ireland in 1926, it was blamed for the Dromcolliher cinema tragedy in County Limerick in which 48 people died. Then in 1929 at the Glen Cinema in Paisley, Scotland , a film-related fire killed 69 children. Today, nitrate film projection is rare and normally highly regulated and requires extensive precautions, including extra health-and-safety training for projectionists. A special projector certified to run nitrate films has many modifications, among them the chambering of the feed and takeup reels in thick metal covers with small slits to allow the film to run through them. The projector is additionally modified to accommodate several fire extinguishers with nozzles aimed at the film gate. The extinguishers automatically trigger if a piece of film near the gate starts to burn. While this triggering would likely damage or destroy a significant portion of the projector's components, it would contain a fire and prevent far greater damage. Projection rooms may also be required to have automatic metal covers for the projection windows, preventing the spread of fire to the auditorium . Today, the Dryden Theatre at the George Eastman Museum is one of a few theaters in the world that is capable of safely projecting nitrate films and regularly screens them to the public. [ 42 ] [ 43 ] The BFI Southbank in London is the only cinema in the United Kingdom licensed to show Nitrate Film. [ 44 ]
The use of nitrate film and its fiery potential were certainly not issues limited to the realm of motion pictures or to commercial still photography. The film was also used for many years in medicine, where its hazardous nature was most acute, especially in its application to X-ray photography. [ 8 ] In 1929, several tons of stored X-ray film were ignited by steam from a broken heating pipe at the Cleveland Clinic in Ohio . That tragedy claimed 123 lives during the fire and additional fatalities several days later, when hospitalized victims died due to inhaling excessive amounts of smoke from the burning film, which was laced with toxic gases such as sulfur dioxide and hydrogen cyanide . [ 45 ] [ 46 ] Related fires in other medical facilities prompted the growing disuse of nitrocellulose stock for X-rays by 1933, nearly two decades before its use was discontinued for motion-picture films in favour of cellulose acetate film , more commonly known as "safety film".
Nitrocellulose was found to gradually decompose, releasing nitric acid and further catalyzing the decomposition (eventually into a flammable powder). Decades later, storage at low temperatures was discovered as a means of delaying these reactions indefinitely. Many films produced during the early 20th century were lost through this accelerating, self-catalyzed disintegration or through studio warehouse fires, and many others were deliberately destroyed specifically to avoid the fire risk. Salvaging old films is a major problem for film archivists (see film preservation ).
Nitrocellulose film base manufactured by Kodak can be identified by the presence of the word "nitrate" in dark letters along one edge; the word only in clear letters on a dark background indicates derivation from a nitrate base original negative or projection print, but the film in hand itself may be a later print or copy negative, made on safety film. Acetate film manufactured during the era when nitrate films were still in use was marked "Safety" or "Safety Film" along one edge in dark letters. 8 , 9.5 , and 16 mm film stocks, intended for amateur and other nontheatrical use, were never manufactured with a nitrate base in the west, but rumors exist of 16 mm nitrate film having been produced in the former Soviet Union and China. [ 47 ]
Nitrate dominated the market for professional-use 35 mm motion picture film from the industry's origins to the early 1950s. While cellulose acetate-based safety film, notably cellulose diacetate and cellulose acetate propionate, was produced in the gauge for small-scale use in niche applications (such as printing advertisements and other short films to enable them to be sent through the mails without the need for fire safety precautions), the early generations of safety film base had two major disadvantages relative to nitrate: it was much more expensive to manufacture, and considerably less durable in repeated projection. The cost of the safety precautions associated with the use of nitrate was significantly lower than the cost of using any of the safety bases available before 1948. These drawbacks were eventually overcome with the launch of cellulose triacetate base film by Eastman Kodak in 1948. [ 48 ] Cellulose triacetate superseded nitrate as the film industry's mainstay base very quickly. While Kodak had discontinued some nitrate film stocks earlier, it stopped producing various nitrate roll films in 1950 and ceased production of nitrate 35 mm motion picture film in 1951. [ 49 ]
The crucial advantage cellulose triacetate had over nitrate was that it was no more of a fire risk than paper (the stock is often referred to as "non-flam": this is true—but it is combustible, just not in as volatile or as dangerous a way as nitrate), while it almost matched the cost and durability of nitrate. It remained in almost exclusive use in all film gauges until the 1980s, when polyester / PET film began to supersede it for intermediate and release printing. [ 50 ]
Polyester is much more resistant to polymer degradation than either nitrate or triacetate. Although triacetate does not decompose in as dangerous a way as nitrate does, it is still subject to a process known as deacetylation, often nicknamed "vinegar syndrome" (due to the acetic acid smell of decomposing film) by archivists, which causes the film to shrink, deform, become brittle and eventually unusable. [ 51 ] PET, like cellulose mononitrate, is less prone to stretching than other available plastics. [ 50 ] By the late 1990s, polyester had almost entirely superseded triacetate for the production of intermediate elements and release prints.
Triacetate remains in use for most camera negative stocks because it can be "invisibly" spliced using solvents during negative assembly, while polyester film is usually spliced using adhesive tape patches, which leave visible marks in the frame area. However, ultrasonic splicing in the frame line area can be invisible. Also, polyester film is so strong, it will not break under tension and may cause serious damage to expensive camera or projector mechanisms in the event of a film jam, whereas triacetate film breaks easily, reducing the risk of damage. Many were opposed to the use of polyester for release prints for this reason, and because ultrasonic splicers are very expensive, beyond the budgets of many smaller theaters. In practice, though, this has not proved to be as much of a problem as was feared. Rather, with the increased use of automated long-play systems in cinemas, the greater strength of polyester has been a significant advantage in lessening the risk of a film performance being interrupted by a film break. [ citation needed ]
Despite its self-oxidizing hazards, nitrate is still regarded highly as the stock is more transparent than replacement stocks, and older films used denser silver in the emulsion. The combination results in a notably more luminous image with a high contrast ratio. [ 52 ]
The solubility of nitrocellulose was the basis for the first " artificial silk " by Georges Audemars in 1855, which he called " Rayon ". [ citation needed ] . However, Hilaire de Chardonnet was the first to patent a nitrocellulose fiber marketed as "artificial silk" at the Paris Exhibition of 1889 . [ 53 ] Commercial production started in 1891, but the result was flammable and more expensive than cellulose acetate or cuprammonium rayon. Because of this predicament, production ceased early in the 1900s. Nitrocellulose was briefly known as "mother-in-law silk". [ 54 ]
Frank Hastings Griffin invented the double-godet, a special stretch-spinning process that changed artificial silk to rayon, rendering it usable in many industrial products such as tire cords and clothing. [ 55 ] Nathan Rosenstein invented the "spunize process" by which he turned rayon from a hard fiber to a fabric. This allowed rayon to become a popular raw material in textiles.
Nitrocellulose lacquer manufactured by (among others) DuPont , was the primary material for painting automobiles for many years. Durability of finish, complexities of "multiple stage" modern finishes, and other factors including environmental regulation led manufacturers to choose newer technologies. It remained the favorite of hobbyists for both historical reasons and for the ease with which a professional finish can be obtained. Most automobile "touch up" paints are still made from lacquer because of its fast drying, easy application, and superior adhesion properties – regardless of the material used for the original finish. Guitars sometimes shared color codes with current automobiles. It fell out of favor for mass production use for a number of reasons including environmental regulation and the cost of application vs. polyurethane finishes. However, Gibson still use nitrocellulose lacquers on all of their guitars, as well as Fender when reproducing historically accurate guitars. The nitrocellulose lacquer yellows and cracks over time, and custom shops will reproduce this aging to make instruments appear vintage. Guitars made by smaller shops (luthiers) also often use "nitro" as it has an almost mythical status among guitarists.
Because of its explosive nature, not all applications of nitrocellulose were successful. In 1869, with elephants having been poached to near extinction, the billiards industry offered a US$ 10,000 prize to whoever came up with the best replacement for ivory billiard balls . John Wesley Hyatt created the winning replacement, which he created with a new material he invented, called camphored nitrocellulose—the first thermoplastic , better known as celluloid . The invention enjoyed a brief popularity, but the Hyatt balls were extremely flammable, and sometimes portions of the outer shell would explode upon impact. An owner of a billiard saloon in Colorado wrote to Hyatt about the explosive tendencies, saying that he did not mind very much personally but for the fact that every man in his saloon immediately pulled a gun at the sound. [ 56 ] [ 57 ] The process used by Hyatt to manufacture the billiard balls, patented in 1881, [ 58 ] involved placing the mass of nitrocellulose in a rubber bag, which was then placed in a cylinder of liquid and heated. Pressure was applied to the liquid in the cylinder, which resulted in a uniform compression on the nitrocellulose mass, compressing it into a uniform sphere as the heat vaporized the solvents. The ball was then cooled and turned to make a uniform sphere. In light of the explosive results, this process was called the "Hyatt gun method". [ 59 ]
An overheated container of dry nitrocellulose is believed to be the initial cause of the 2015 Tianjin explosions . [ 60 ] | https://en.wikipedia.org/wiki/Nitrocellulose |
A nitrocellulose slide (or nitrocellulose film slide ) is a glass microscope slide that is coated with nitrocellulose that is used to bind biological material, often protein , for colorimetric and fluorescence detection assays. For this purpose, a nitrocellulose slide is generally considered to be superior to glass, because it binds a great deal more protein, and protects the tertiary structure of the protein (and other biological material, i.e.: cells). Typically, nitrocellulose slides have a thin, opaque film of nitrocellulose on a standard 25mm × 75 mm glass microscope slide . The film is extremely sensitive to contact, and to foreign material; contact causes deformation and deposition of material, especially liquids. [ citation needed ]
A nitrocellulose slide is different from a nitrocellulose membrane, which usually filters protein from solution (i.e.: physician's office pregnancy tests ), but that it serves a similar goal: to detect the presence and/or concentration level of certain biological material.
Nitrocellulose slides are used mainly in proteomics to do protein microarrays with automated systems that print the slides and record results. Microarrays of cell analytes, arrays of cell lysate , antibody microarrays, tissue printing, [ 1 ] [ 2 ] immunoarrays, etc. are also possible with the slide.
Due to their high surface roughness, conventional white nitrocellulose films scatter and reflect large amounts of excitation and emission light during the fluorescence detection in the microarray scanner. In addition, nitrocellulose exhibits a natural autofluorescence at the detection wavelengths commonly used. [ 3 ] Both these factors lead to a high background fluorescent signal from these membrane slides. To overcome this problem, a new process has been developed to generate black membranes that absorb the scattered light, significantly reducing the background auto-fluorescence and thus offering a very low and homogenous auto-fluorescence to achieve a significantly improved dynamic range. [ 4 ] These slides are commercially available through Schott AG . [ 5 ] [ self-published source? ] Nevertheless, conventional white nitrocellulose films continue to be the dominant surface for many protein microarray applications because the claims above have not proved relevant to end user requirements. Regardless, nitrocellulose slide manufacturers like Grace Bio-Labs continue to develop new nitrocellulose surfaces to further optimize their use in protein microarrays.
A method for protein quantitation on nitrocellulose coated glass slides uses near-IR fluorescent detection with quantum dots . Traditional porous nitrocellulose signal to noise is limited by auto-fluorescence of the nitrocellulose at the respective required wavelengths of excitation and emission for standard organic fluorescent detection probes. Near IR detection probes are excited and read at emission wavelengths outside the range of nitrocellulose fluorescence. [ 6 ] [ self-published source? ] | https://en.wikipedia.org/wiki/Nitrocellulose_slide |
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