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NB-Fi Protocol is an open LPWAN protocol, which operates in unlicensed ISM radio band . Using the NB-Fi Protocol in devices allows data transmission range of up to 10 km in dense urban conditions, and up to 30 km in rural areas with up to 10 years on battery power. [ 1 ]
NB-Fi Protocol is developed by WAVIoT. [ 2 ]
NB-Fi Protocol employs a Narrow Band technology that enables communication using the Industrial, Scientific and Medical ISM radio band (and in other parts of sub-GHz license-free spectrum as well).
NB-Fi devices could be manufactured using widespread electronic components which could easily be manufactured or purchased in every particular country. WAVIoT has developed an NB-Fi transceiver that encapsulates the NB-Fi protocol at a physical layer.
The NB-Fi transceiver [ 3 ] supports 430–500 MHz and 860–925 MHz frequency bands at 50 to 25,600 bit/s data rates.
The network is based on one-hop star topology and requires a SDR-technology base stations to operate. [ 4 ] The signal can also be used to easily cover large areas and to reach underground objects. [ 5 ]
NB-Fi Protocol stack is currently implemented on: | https://en.wikipedia.org/wiki/NB-Fi |
An NBC (nuclear, biological, chemical) suit , also called a chem suit , [ 1 ] or chemical suit [ 1 ] is a type of military personal protective equipment . NBC suits are designed to provide protection against direct contact with and contamination by radioactive , biological , or chemical substances, and provide protection from contamination with radioactive materials and all types of radiation. [ 1 ] They are generally designed to be worn for extended periods to allow the wearer to fight (or generally function) while under threat of or under actual nuclear, biological, or chemical attack. The civilian equivalent is the hazmat suit . The term NBC has been replaced by CBRN ( c hemical, b iological, r adiological, n uclear), with the addition of the new threat of radiological weapons .
NBC stands for nuclear , biological , and chemical . [ 1 ] It is a term used in the armed forces and in health and safety, mostly in the context of weapons of mass destruction (WMD) clean-up in overseas conflict or protection of emergency services during the response to terrorism , though there are civilian and common-use applications (such as recovery and clean up efforts after industrial accidents ).
In military operations, NBC suits are intended to be quickly donned over a soldier’s uniform and can continuously protect the user for up to several days. Most are made of impermeable material such as rubber, but some incorporate a filter, allowing air, sweat and condensation to slowly pass through. An example of this is the Canadian military NBC suit.
The older Soviet suit was impermeable rubber-coated canvas. Now known as the CBRN suit, the British Armed Forces suit is reinforced nylon with charcoal impregnated felt. It is more comfortable because of the breathability but has a shorter useful life, and must be replaced often. The British Armed Forces suit is known as a "Noddy suit" because some of them had a pointed hood like the hat worn by the fictional character Noddy . The Soviet style suit will protect the wearer at higher concentrations than the British suit but is less comfortable due to the build-up of moisture within it. A Soviet suit was known as a " Womble " because of its long faced respirator with round visor glasses. In Canadian terminology, an NBC suit or any kind of similar protective over-suit is also known as a " Bunnysuit ". | https://en.wikipedia.org/wiki/NBC_suit |
NBQX (2,3-dioxo-6-nitro-7-sulfamoyl-benzo[f]quinoxaline) is an antagonist of the AMPA receptor .
NBQX blocks AMPA receptors in micromolar concentrations (~10–20 μM) and also blocks kainate receptors . In experiments, it is used to counter glutamate excitotoxicity . [ 1 ] NBQX was found to have anticonvulsant activity in rodent seizure models. [ 2 ]
As the disodium salt, NBQX is soluble in water at high concentrations (at least up to 100 mM).
This biochemistry article is a stub . You can help Wikipedia by expanding it . | https://en.wikipedia.org/wiki/NBQX |
NBR2 is a gene best known for its location near the breast cancer associated gene BRCA1 . [ 1 ] Like BRCA1, NBR2 has been a subject of research, [ 2 ] but links to breast cancer are currently inconclusive.
NBR2 recently was identified as a glucose starvation-induced long non-coding RNA . NBR2 interacts with AMP-activated protein kinase ( AMPK ), a critical energy sensor in most eukaryotic cells, and promotes AMPK function to mediate energy stress response. Knockdown of NBR2 attenuates energy stress-induced AMPK activation, resulting in unchecked cell cycling, altered apoptosis / autophagy response, and increased tumour development in vivo. [ 3 ] [ 4 ] It is now appreciated that NBR2, a former junk gene, plays critical roles in tumor suppression. [ 5 ]
This biochemistry article is a stub . You can help Wikipedia by expanding it . | https://en.wikipedia.org/wiki/NBR2 |
Nitrogen tribromide is a chemical compound with the formula NBr 3 . It is extremely explosive in its pure form, even at −100 °C, and was not isolated until 1975. [ 2 ] It is a deep-red and volatile solid.
NBr 3 was first prepared by reaction of bistrimethylsilylbromamine ( bis(trimethylsilyl)amine bromide) with bromine monochloride (with trimethylsilyl chloride as byproduct) at −87 °C according to the following equation:
where "Me" is a methyl group .
NBr 3 can be produced by the reaction of bromine or hypobromite and ammonia in a dilute aqueous buffer solution. [ 3 ] It can also be prepared by the reaction of bromine and bromine azide . [ 4 ] Ammonia and bromine undergo glow discharge, and after treatment, red NBr 3 ·6NH 3 can be obtained. [ 5 ] Pure nitrogen NBr 3 was only produced in 1975. [ 6 ]
Nitrogen tribromide reacts instantly with ammonia in dichloromethane solution at −87 °C to yield NBrH 2 . [ 7 ]
It also reacts with iodine in dichloromethane solution at −87 °C to produce NBr 2 I, which is a red-brown solid that stable up to -20 °C. [ 7 ] | https://en.wikipedia.org/wiki/NBr3 |
The National Center for Atmospheric Research Land Surface Model (LSM) is a unidimensional computational model developed by Gordon Bonan that describes ecological processes joined in many ecosystem models , hydrological processes found in hydrological models and flow of surface common in surface models using atmospheric models.
In this way, the model examines interactions especially biogeophysics (sensible and latent heat, momentum, albedo , emission of long waves) and biogeochemistry (CO 2 ) of the land-atmosphere the effect of surface of the land in the climate and composition of the atmosphere .
This model has a simplified treatment of the surface flows that reproduce at the very least computational cost the essential characteristics of the important interactions of the land-atmosphere for climatic simulations.
As the types of surface vegetated for some species are several, have a standardization of types of covering being enclosed surfaces covered with water as lakes (amongst others); thus the model wheel for each point of independent form, with the same average of the atmospheric interactions. The model functions in a space grating that can vary of a point until global.
This computational science article is a stub . You can help Wikipedia by expanding it . | https://en.wikipedia.org/wiki/NCAR_LSM_1.0 |
NCBioImpact is a group of organizations in the U.S. state of North Carolina created to enhance the trained workforce for biotechnology and other life science employers by educating students and retraining incumbent workers. The partnership works to promote economic development in North Carolina while offering comprehensive biomanufacturing training and education programs located at two universities in the University of North Carolina System and the North Carolina Community College System .
In 2002, biomanufacturing executives in the Research Triangle region in North Carolina, working with NCBIO, asked the North Carolina Biotechnology Center to conduct a study of the workforce and training needs of the industry. "Window on the Workplace 2003" was published the following year. [ 1 ]
As a result of that study, a partnership among industry, government, academic leaders and nonprofits, such as the North Carolina Biotechnology Center and NCBIO, submitted a proposal to provide unique training to increase the number of workers to the Golden LEAF Foundation . Equipment and construction funds were provided for three initiatives, which now receive part of their operating funds from the North Carolina General Assembly , along with contracts, grants and training fees.
A 2010 Battelle report commissioned by the North Carolina Biotechnology Center found that almost 47,000 biotechnology-related (direct and indirect) jobs were added during the period of 2008-2010, bringing the total jobs in North Carolina to almost 227,000 and annual compensation and benefits increased nearly $3.3 Billion. [ 2 ] The president of the North Carolina Biosciences Organization (NCBIO), the trade association for North Carolina's life science community, stated "NCBioImpact makes it possible for companies growing or relocating to North Carolina to bring new facilities and new workers on-line in substantially shortened timelines with better quality outcomes and higher productivity." [ 3 ] As an example, two major companies, Novartis and Merck & Co. located facilities in North Carolina after considering all factors, including the hands-on training programs offered by the university and community college systems. [ 4 ] [ 5 ]
The program offers continuing education, workforce development, business services and outreach activities for startup companies. The seven BioNetwork centers are located throughout the state in order to provide specialized life science training where it is needed. BioNetwork offers training in the following centers:
The Golden LEAF Biomanufacturing Training and Education Center (BTEC) is located on the Centennial Campus at North Carolina State University . BTEC offers many programs, including graduate and undergraduate education, workforce training, and bioprocess and analytical services. It operates several pilot-scale bioprocessing laboratories that simulate the production of biological products according to Good Manufacturing Practice (cGMP) expectations.
The facility is home to the first cross-disciplinary Master's in Biomanufacturing program in the United States, which offers education in advanced biomanufacturing, business coursework taught by the Jenkins Graduate College of Management , and professional development courses. The center also offers an undergraduate minor for NC State students and a post-baccalaureate certificate for non-degree students. Professional development courses are offered to individuals or can be customized for industry partners.
BTEC has trained investigators from the Food and Drug Administration (FDA) in bioprocessing methods, analytical techniques, and aseptic manufacturing. BTEC has also trained influenza vaccine manufacturing employees from around the world as part of a contract with the Biomedical Advanced Research and Development Authority (BARDA) . The goal of the training is to increase influenza vaccine production capacity around the world and in developing countries. BTEC also offers analytical testing and development services for the biopharmaceutical industry, government and academia for preparation for preclinical trials and commercialization.
Located on the campus of North Carolina Central University , the Biomanufacturing Research Institute and Technology Enterprise (BRITE) prepares undergraduate and graduate students for scientific careers in the biomanufacturing and biopharmaceutical industries. BRITE's 52,000 sq. ft. research and teaching facility provides hands-on training in process and analytical technology, drug discovery and biomanufacturing. Students can pursue undergraduate and graduate degrees in the classroom and gain hands-on experience in laboratories.
BRITE also offers short courses for incumbent biotechnology workers and potential industry employees. The facility also includes a 350,000 compound library, which was provided by Biogen Idec . | https://en.wikipedia.org/wiki/NCBioImpact |
Cyanoacetylene is an organic compound with the formula C 3 H N or H−C≡C−C≡N . It is the simplest cyanopolyyne . Cyanoacetylene has been detected by spectroscopic methods in interstellar clouds , [ 2 ] in the coma of comet Hale–Bopp and in the atmosphere of Saturn 's moon Titan , [ 3 ] where it sometimes forms expansive fog-like clouds. [ 4 ]
Cyanoacetylene is one of the molecules that was produced in the Miller–Urey experiment . [ 5 ]
Nickel carbonyl catalyzes cyanoacetylene carboalkoxylation to cyanoacrylate esters. [ 6 ] | https://en.wikipedia.org/wiki/NCCCH |
The Pathway Interaction Database (PID) is a free biomedical database of human cellular signaling pathways. [ 1 ] The database contains information about the molecular interactions and reactions that take place in cells, with a particular focus on processes that might be relevant to cancer research and treatment. The database was established as collaboration between the U.S. National Cancer Institute , NIH and Nature Publishing Group in 2005 and was launched in November 2006. In September 2012, active curation was stopped and the PID data are now available in the Network Data Exchange, NDEx .
As of November 2007, the database contained 59 pathways (comprising 3309 molecular interactions) curated by the NCI-Nature editorial team. New pathways are added each month. The database also contains 254 pathways (comprising 3003 interactions) imported from the June 2004 edition of the BioCarta pathway database.
The NCI-Nature curated data is gathered from published research literature and reviewed by expert scientists before publication. Evidence codes are assigned to each molecular interaction, which allows users to evaluate the reliability of the interactions or to search for interactions identified by particular experimental techniques.
The database content can be viewed in self-contained, pre-defined pathways. The database can also dynamically generate interaction networks to visualize the results of database searches. Pathways and dynamically generated networks are displayed in GIF and SVG images and can be downloaded as XML (including the standard pathway interchange format, BioPAX ). The entire database is also available for download. | https://en.wikipedia.org/wiki/NCI-Nature_Pathway_Interaction_Database |
1T5Z
8031
27057
ENSG00000266412
ENSMUSG00000056234
Q13772
n/a
NM_005437 NM_001145260 NM_001145261 NM_001145262 NM_001145263
NM_001033988 NM_001284319 NM_019744
NP_001138732 NP_001138733 NP_001138734 NP_001138735 NP_005428
n/a
Nuclear receptor coactivator 4, also known as Androgen Receptor Activator (ARA70), is a protein that in humans is encoded by the NCOA4 gene . [ 5 ] [ 6 ] [ 7 ] It plays an important role in ferritinophagy, acting as a cargo receptor, binding to the ferritin heavy chain and latching on to ATG8 on the surface of the autophagosome.
NCOA4 has been shown to interact with:
This article incorporates text from the United States National Library of Medicine , which is in the public domain . | https://en.wikipedia.org/wiki/NCOA4 |
23054
56406
ENSG00000198646
ENSMUSG00000038369
Q14686
Q9JL19
NM_001242539 NM_014071 NM_001318240
NM_001242558 NM_019825
NP_001229468 NP_001305169 NP_054790
n/a
Nuclear receptor coactivator 6 is a protein that in humans is encoded by the NCOA6 gene . [ 5 ] [ 6 ] [ 7 ]
The protein encoded by this gene is a transcriptional coactivator that can interact with nuclear hormone receptors to enhance their transcriptional activator functions. The encoded protein has been shown to be involved in the hormone-dependent coactivation of several receptors, including prostanoid, retinoid, vitamin D 3 , thyroid hormone, and steroid receptors. The encoded protein may also act as a general coactivator since it has been shown to interact with some basal transcription factors, histone acetyltransferases , and methyltransferases . [ 7 ]
NCOA6 has been shown to interact with:
This article incorporates text from the United States National Library of Medicine , which is in the public domain . | https://en.wikipedia.org/wiki/NCOA6 |
135112
211329
ENSG00000111912
ENSMUSG00000039697
Q8NI08
Q6DFV7
NM_181782
NM_001111267 NM_172495 NM_001358841 NM_001358842
NP_861447
NP_001104737 NP_766083 NP_001345770 NP_001345771
Nuclear receptor coactivator 7 is a protein that in humans is encoded by the NCOA7 gene . [ 5 ] [ 6 ]
This article incorporates text from the United States National Library of Medicine , which is in the public domain .
This article on a gene on human chromosome 6 is a stub . You can help Wikipedia by expanding it . | https://en.wikipedia.org/wiki/NCOA7 |
Early research and development:
Merging the networks and creating the Internet:
Commercialization, privatization, broader access leads to the modern Internet:
Examples of Internet services:
NCSA Mosaic is a discontinued web browser . It was instrumental in popularizing the World Wide Web and the general Internet during the 1990s by integrating multimedia such as text and graphics. [ 3 ] [ 4 ] [ 5 ] Although not the first web browser (preceded by WorldWideWeb , Erwise , [ 6 ] and ViolaWWW ), it was the first browser to display images inline with text instead of a separate window. [ 7 ]
It supported various Internet protocols such as HTTP , FTP , NNTP , and Gopher . [ 8 ] Its interface, reliability, personal computer support, and simple installation contributed to Mosaic's initial popularity. [ 9 ]
Mosaic was developed at the National Center for Supercomputing Applications (NCSA) [ 7 ] at the University of Illinois at Urbana–Champaign beginning in late 1992, released in January 1993, [ 10 ] with official development and support until January 1997. [ 11 ] Mosaic lost market share to Netscape Navigator in late 1994, [ 12 ] and had only a tiny fraction of users left by 1997, when the project was discontinued. Microsoft licensed one of the derivative commercial products, Spyglass Mosaic, to create Internet Explorer in 1995.
In 1991, the High Performance Computing Act of 1991 was passed, which provided funding for new projects at the NCSA, where after trying ViolaWWW , David Thompson demonstrated it to the NCSA software design group. [ 13 ] This inspired Marc Andreessen and Eric Bina – two programmers working at NCSA – to create Mosaic. Andreessen and Bina began developing Mosaic in February 1991 for Unix's X Window System , calling it xmosaic . [ 7 ] [ 10 ] [ 13 ] [ 14 ] Marc Andreessen announced the project's first release, the "alpha/beta version 0.5," on January 23, 1993. [ 15 ] Version 1.0 was released on April 21, 1993. [ 16 ] Ports to Microsoft Windows and Macintosh were released in September. [ 13 ] A port of Mosaic to the Amiga was available by October 1993. NCSA Mosaic for Unix (X Window System) version 2.0 was released on November 10, 1993 [ 17 ] and was notable for adding support for forms , thus enabling the creation of the first dynamic web pages . From 1994 to 1997, the National Science Foundation supported the further development of Mosaic. [ 18 ]
Marc Andreessen, the leader of the team that developed Mosaic, left NCSA and, with James H. Clark , one of the founders of Silicon Graphics, Inc. (SGI), and four other former students and staff of the University of Illinois , started Mosaic Communications Corporation. Mosaic Communications eventually became Netscape Communications Corporation , producing Netscape Navigator . Mosaic's popularity as a separate browser began to decrease after the 1994 release of Netscape Navigator , the relevance of which was noted in The HTML Sourcebook: The Complete Guide to HTML : "Netscape Communications has designed an all-new WWW browser Netscape, that has significant enhancements over the original Mosaic program." [ 19 ] : 332
In 1994, SCO released Global Access, a modified version of SCO's Open Desktop Unix , which became the first commercial product to incorporate Mosaic. [ 20 ] However, by 1998, the Mosaic user base had almost completely evaporated as users moved to other web browsers.
The licensing terms for NCSA Mosaic were generous for a proprietary software program. In general, non-commercial use was free of charge for all versions (with certain limitations). Additionally, the X Window System/Unix version publicly provided source code (source code for the other versions was available after agreements were signed). Despite persistent rumors to the contrary, however, Mosaic was never released as open source software during its brief reign as a major browser; there were always constraints on permissible uses without payment.
As of 1993 [update] , license holders included these: [ 21 ]
Robert Reid notes that Andreessen's team hoped:
... to rectify many of the shortcomings of the very primitive prototypes then floating around the Internet. Most significantly, their work transformed the appeal of the Web from niche uses in the technical area to mass-market appeal. In particular, these University of Illinois students made two key changes to the Web browser, which hyper-boosted its appeal: they added graphics to what was otherwise boring text-based software, and, most importantly, they ported the software from so-called Unix computers that are popular only in technical and academic circles, to the [Microsoft] Windows operating system, which is used on more than 80 percent of the computers in the world, especially personal and commercial computers. [ 23 ] : xxv
Mosaic is based on the libwww library [ 24 ] [ 25 ] [ 26 ] and thus supported a wide variety of Internet protocols included in the library: Archie , FTP , gopher , HTTP , NNTP , telnet , WAIS . [ 10 ]
Mosaic is not the first web browser for Microsoft Windows; this is Thomas R. Bruce 's little-known Cello . The Unix version of Mosaic was already famous before the Microsoft Windows, Amiga, and Mac versions were released. Other than displaying images embedded in the text (rather than in a separate window), Mosaic's original feature set is similar to the browsers on which it was modeled, such as ViolaWWW. [ 7 ] But Mosaic was the first browser written and supported by a team of full-time programmers, was reliable and easy enough for novices to install, and the inline graphics proved immensely appealing. Mosaic is said to have made the Internet accessible to the ordinary person.
Mosaic was the first browser to explore the concept of collaborative annotation in 1993 [ 27 ] but never passed the test state. [ 28 ]
Mosaic was the first browser that could submit forms to a server. [ 29 ] [ 30 ]
Mosaic led to the Internet boom of the 1990s. [ 23 ] : xlii Other browsers existed during this period, such as Erwise , ViolaWWW , MidasWWW , and tkWWW , but did not have the same effect as Mosaic on public use of the Internet. [ 31 ]
In the October 1994 issue of Wired magazine, Gary Wolfe notes in the article titled "The (Second Phase of the) Revolution Has Begun: Don't look now, but Prodigy , AOL , and CompuServe are all suddenly obsolete – and Mosaic is well on its way to becoming the world's standard interface":
When it comes to smashing a paradigm, pleasure is not the most important thing. It is the only thing. If this sounds wrong, consider Mosaic. Mosaic is the celebrated graphical "browser" that allows users to travel through the world of electronic information using a point-and-click interface. Mosaic's charming appearance encourages users to load their own documents onto the Net, including color photos, sound bites, video clips, and hypertext "links" to other documents. By following the links – click, and the linked document appears – you can travel through the online world along paths of whim and intuition. Mosaic is not the most direct way to find online information. Nor is it the most powerful. It is merely the most pleasurable way, and in the 18 months since it was released, Mosaic has incited a rush of excitement and commercial energy unprecedented in the history of the Net. [ 21 ]
Reid also refers to Matthew K. Gray's website, Internet Statistics: Growth and Usage of the Web and the Internet , which indicates a dramatic leap in web use around the time of Mosaic's introduction. [ 23 ] : xxv
David Hudson concurs with Reid:
Marc Andreessen's realization of Mosaic, based on the work of Berners-Lee and the hypertext theorists before him, is generally recognized as the beginning of the web as it is now known. Mosaic, the first web browser to win over the Net masses, was released in 1993 and made freely accessible to the public. The adjective phenomenal, so often overused in this industry, is genuinely applicable to the... 'explosion' in the growth of the web after Mosaic appeared on the scene. Starting with next to nothing, the rates of the web growth (quoted in the press) hovering around tens of thousands of percent over ridiculously short periods of time were no real surprise. [ 32 ] : 42
Ultimately, web browsers such as Mosaic became the killer applications of the 1990s. Web browsers were the first to bring a graphical interface to search tools the Internet's burgeoning wealth of distributed information services. A mid-1994 guide lists Mosaic alongside the traditional, text-oriented information search tools of the time, Archie and Veronica , Gopher , and WAIS [ 33 ] but Mosaic quickly subsumed and displaced them all. Joseph Hardin, the director of the NCSA group within which Mosaic was developed, said downloads were up to 50,000 a month in mid-1994. [ 34 ]
In November 1992, there were twenty-six websites in the world [ 35 ] and each one attracted attention. In its release year of 1993, Mosaic had a What's New page, and about one new link was being added per day. This was a time when access to the Internet was expanding rapidly outside its previous domain of academia and large industrial research institutions. Yet it was the availability of Mosaic and Mosaic-derived graphical browsers themselves that drove the explosive growth of the Web to over 10,000 sites by August 1995 and millions by 1998. [ 36 ] Metcalfe expressed the pivotal role of Mosaic this way:
In the Web's first generation, Tim Berners-Lee launched the Uniform Resource Locator (URL), Hypertext Transfer Protocol (HTTP), and HTML standards with prototype Unix-based servers and browsers. A few people noticed that the Web might be better than Gopher.
In the second generation, Marc Andreessen and Eric Bina developed NCSA Mosaic at the University of Illinois. Several million then suddenly noticed that the Web might be better than sex.
In the third generation, Andreessen and Bina left NCSA to found Netscape...
Netscape Navigator was later developed by Netscape , which employed many of the original Mosaic authors; however, it intentionally shared no code with Mosaic. Netscape Navigator's code descendant is Mozilla Firefox . [ 39 ] [ page needed ]
Spyglass, Inc. licensed the technology and trademarks from NCSA for producing its own web browser but never used any of the NCSA Mosaic source code. [ 40 ] Microsoft licensed Spyglass Mosaic in 1995 for US$ 2 million, modified it, and renamed it Internet Explorer . [ 41 ] After a later auditing dispute, Microsoft paid Spyglass $8 million. [ 41 ] [ 42 ] The 1995 user guide The HTML Sourcebook: The Complete Guide to HTML , specifically states, in a section called Coming Attractions , that Internet Explorer "will be based on the Mosaic program". [ 19 ] : 331 Versions of Internet Explorer before version 7 stated "Based on NCSA Mosaic" in the About box. Internet Explorer 7 was audited by Microsoft to ensure that it contained no Spyglass Mosaic code, [ 43 ] and thus no longer credits Spyglass or Mosaic.
After NCSA stopped work on Mosaic, development of the NCSA Mosaic for the X Window System source code was continued by several independent groups. These independent development efforts include mMosaic (multicast Mosaic) [ 44 ] which ceased development in early 2004, and Mosaic-CK and VMS Mosaic.
VMS Mosaic , a version specifically targeting OpenVMS operating system, is one of the longest-lived efforts to maintain Mosaic. Using the VMS support already built-in in original version (Bjorn S. Nilsson ported Mosaic 1.2 to VMS in the summer of 1993), [ 45 ] developers incorporated a substantial part of the HTML engine from mMosaic, another defunct flavor of the browser. [ 46 ] As of the most recent version (4.2), released in 2007, VMS Mosaic supported HTML 4.0, OpenSSL , cookies , and various image formats including GIF , JPEG , PNG , BMP , TGA , TIFF and JPEG 2000 image formats. [ 47 ] The browser works on VAX , Alpha , and Itanium platforms. [ 48 ]
Another long-lived version, Mosaic-CK , developed by Cameron Kaiser, was last released (version 2.7ck9) on July 11, 2010; a maintenance release with minor compatibility fixes (version 2.7ck10) was released on January 9, 2015, followed by another one (2.7ck11) in October 2015. [ 49 ] The stated goal of the project is " Lynx with graphics" and runs on Mac OS X, Power MachTen , Linux and other compatible Unix-like OSs . [ 49 ]
The X, Windows, and Mac versions of Mosaic all had separate development teams and code bases. | https://en.wikipedia.org/wiki/NCSA_Mosaic |
The North Carolina Turnpike Authority was created in 2002 to speed the implementation of needed transportation improvements by funding some projects with tolls. Governed by a nine-member authority board, it is located within the Department of Transportation and under the direct supervision of the Secretary of Transportation. The authority has the power to study, plan, develop and undertake preliminary design work on up to eleven turnpike projects. At the conclusion of these actives, the authority is authorized to design, establish, purchase, construct, operate and maintain toll highways and bridges . The authority is also authorized to designate one or more lanes of any highway, or portion thereof, into a high-occupancy toll lanes (HOT lanes) or other type of managed lanes; provided that such designation does not reduce the number of existing non-toll general purpose lanes.
The nine-member Authority Board consist of eight appointees, from the General Assembly (four members) and Governor (four members), and the Secretary of Transportation. The General Assembly appoints four members, two by recommendation by the President pro tempore of the Senate and two by recommendation by the Speaker of the House of Representatives . Appointments to the board are four-year staggered terms. The Chair of the Authority is selected by the Authority Board. Members of the North Carolina Board of Transportation may serve as members of the Authority Board.
Upon end of term, all members of the Authority Board will remain in office until their successors are appointed and qualified. The original appointing authority may appoint a member to serve out the unexpired term of any member. Each member of the Authority Board serves at the pleasure of the appointing authority. The Chair of the Authority serves at the pleasure of the Authority Board. The appointed members of the Authority Board receives no salary for their services; however, are entitled to receive per diem and travel allowances.
An executive director, appointed by the Authority Board, serves as the Authority's chief administrative officer and is responsible for the daily administration of the toll roads and bridges constructed, maintained or operated. The Executive Director or his/her designee shall appoint, employ, dismiss and, within the limits approved by the Authority Board, fix the compensation of administrative employees as the executive director deems necessary. [ 2 ]
The North Carolina Turnpike Authority was established on October 3, 2002, by ratification of House Bill 644 (S.L. 2002-133) and signed by Governor Mike Easley . [ 1 ] In its original draft, the authority was independent and only able to establish the first three projects in the following conditions: one project located in whole or in part in a county with a population equal to or greater than 650,000 persons; one project located in a county or counties that each have a population of fewer that 650,000 persons; and one project shall be a bridge of more than two miles (3.2 km) in length going from the mainland to a peninsula bordering the state of Virginia. In 2005, Senate Bill 622 (S.L. 2005-276) added new language regarding establishing tollways on Federally funded highways designated as interstates; the purpose was so that the state can possibly add tolls along Interstate 95 (I-95), if approved by the Federal Highway Administration (FHWA) and all interested parties along the route. [ 3 ] [ 4 ] In 2006, Senate Bill 1381 (S.L. 2006-228) focused the project to the following:
The 2006 law also made an exception to the prohibition of converting any segment of the nontolled state highway system to toll by specifically identifying I-540 (under construction in 2006) in Wake and Durham counties and extending from I-40 southwest to North Carolina Highway 55 (NC 55). In addition, the law also mandates the North Carolina Department of Transportation (NCDOT) to maintain an existing, alternate, comparable non-toll route for each toll route constructed by the authority. [ 5 ] In December 2006, FHWA approved the tolling project on what was going to be I-540 along the Western Wake Freeway. [ 6 ]
In 2008, Senate Bill 1697 (S.L. 2008-225) established the enforcement of tolls on turnpike projects and clarified and revised several sections, including: removal of I-540 from project list, collection of tolls (via mail or transponder), payment system for tolls, civil penalties for not paying tolls and procedures for contesting liability for unpaid tolls. The Triangle Parkway was also renamed the Triangle Expressway, which incorporated segments also known as NC 147 (Triangle Parkway) and NC 540 (Western Wake Freeway), in Wake and Durham counties. [ 7 ]
In 2009, House Bill 1617 (S.L. 2009-343) transferred the functions and funds of the North Carolina Turnpike Authority to NCDOT to conserve expenditures and improve efficiency. [ 8 ] [ 9 ] In August, the groundbreaking ceremony took place on the first phase of the Triangle Expressway. [ 6 ] On May 4, 2010, the Authority signed a contract with TransCore to provide transponders. [ 10 ]
In December 2011, phase one of the Triangle Expressway was open to traffic; on January 3, 2012, toll collection began. On June 26, 2012, Senate Bill 895 (S.L. 2012-85) gave the authority the ability to enter into reciprocal toll enforcement agreements with other toll agencies. [ 11 ] In August, 2012, phase two of the Triangle Expressway was open to traffic and immediately began toll collection. In December 2012, phase three of the Triangle Expressway was opened to traffic; on January 3, 2013, toll collection began on the final section. [ 6 ]
In 2013, House Bill 817 (S.R. 2013-183) made sweeping changes to the authority, including: removal of several turnpike projects, including the Triangle Expressway Southeast Extension, Garden Parkway, Cape Fear Skyway and the Mid-Currituck Bridge. reestablishing the turnpike project limit to nine, with the existing Triangle Expressway counting as three and the Monroe Connector/Bypass as one. New turnpike projects must follow new conditions prior to the letting of a contract for project. A limit of up to three agreements with a private entity, with an agreement of no more than 50 years from the date of the beginning of operations on the toll facility. The designation of HOT and managed lanes. [ 12 ]
As of 2018 [update] , the Authority operates 37.5 miles (60.4 km) of tollways in four counties in North Carolina:
The authority currently has one set of HOT lanes in North Carolina:
Unlike the turnpike projects, the Authority is not limited to the number of managed lane projects it may construct and operate. The authority may also convert lanes that may previously have been designated as high-occupancy vehicle lane (HOV) or other type of managed lanes; provided that such designated does not reduce the number of existing non-toll general purpose lanes. In making such designations, the authority will specify the high-occupancy requirement or other conditions for use of such lanes, which may include restricting vehicle types, access controls, or the payment of tolls for vehicles that do not meet the high-occupancy requirements or conditions for use. [ 2 ]
As of 2023 [update] , two additional managed lane projects were fully funded and are either scheduled or are under construction:
As of 2018 [update] , one turnpike project is fully funded for construction:
Any other project proposed by the authority requires prior consultation with the Joint Legislative Commission on Governmental Operations. For a project to be considered a turnpike project, it must meet the following conditions prior to the letting of a contract for the project: 1) Two of the projects must be ranked in the top 35 based on total score on the department-produced list entitled "Mobility Fund Project Scores" dated June 6, 2012, and, in addition, may be subject to G.S. 136-18(39a). [ a ] 2) Of the projects not ranked as provided in (1), one may be subject to G.S. 136-18(39a). 3) The project shall be included in any applicable locally adopted comprehensive transportation plans. 4) The project shall be shown in the current State Transportation Improvement Program (STIP). [ 26 ] 5) Toll projects must be approved by all affected Metropolitan Planning Organizations and Rural Transportation Planning Organizations for tolling.
Stipulated in the 2013 law, proposed toll road and bridges must go through same process as other transportation projects, have an STIP score and rated with other criteria contained in the Strategic Mobility Formula. [ 12 ] NCDOT will circulate a draft of the STIP for public comment in December 2014. [ 27 ] NCDOT anticipates the Board of Transportation will adopt it in June 2015. Listed below are proposed projects, currently in review and subject to change:
The NC Quick Pass is a pre-paid account used for all electronic toll collection (ETC) facilities in North Carolina. Three types of transponders are available: transponder sticker (free version), E-ZPass (hard case) transponder and E-ZPass bumper-mounted transponder. [ 45 ] Personal (limited to five transponders/vehicles) and business accounts (unlimited) are available; a $1 fee is imposed per month if the account has been inactive for 12 months. [ 46 ]
While NC Quick Pass users receive a discounted toll rate, non-users will be invoiced at a higher toll rate through the bill by mail program. This is done when a vehicle passes through a toll gantry, where an overhead camera will take a video image of the license plate. The registered owner of the vehicle is identified through the Division of Motor Vehicles and a bill by mail is sent for payment.
If the bill is not paid within 30 days from the date of the bill, it may escalate to include fees, civil penalties, DMV registration holds, submission to a collection agency, or all of the above. [ 47 ]
NC Quick Pass is interoperable with the following ETC systems:
The toll collection equipment used in North Carolina, Florida, and Georgia are compatible, so that NC Quick Pass drivers may simply use any NC Quick Pass transponder in Florida and Georgia, and vice versa (SunPass and Peach Pass drivers may simply use their transponder in North Carolina).
The North Carolina Turnpike Authority and North Carolina Department of Transportation received criticism following the introduction of a law allowing toll highways and bridges in the state in 2002. Introduced to speed along the implementation of transportation improvements, many of the projects selected by the Authority were controversial, leading to delays. Originally planned to be an extension of I-540, the Triangle Expressway garnered criticism from both politicians and residents for tolling the Western Wake Freeway and for the organisers being unable to sell bonds to fund the project. [ 51 ] [ 52 ] Following its opening, criticism shifted onto its expansion with towns raising issues about its routing and environmental concerns . [ 53 ] [ 54 ] [ 55 ] [ 56 ] Other projects, such as the Garden Parkway and Monroe Connector/Bypass prompted fear of additional urban sprawl , the criticism of politicians who had land deals along the routes, and generated lawsuits stemming from the flawed environmental studies. [ 57 ] [ 58 ] [ 59 ] Both the Cape Fear Skyway and Mid-Currituck Bridge were criticized [ by whom? ] as expensive pork projects . In response to the criticism the North Carolina General Assembly removed the Garden Parkway, Cape Fear Skyway and Mid-Currituck Bridge from the authority's purview. [ 60 ] [ 61 ] [ 62 ]
A more recent contract between the authority and Cintra to build I-77 HOT lanes and operate them for 50 years provoked local groups to hire legal counsel and attempt to have it nullified. [ 63 ] Additional criticisms have stemmed from the irregular distribution of toll roads recommended by the authority throughout the state. [ 64 ] | https://en.wikipedia.org/wiki/NC_Quick_Pass |
Nitrogen trichloride , also known as trichloramine , is the chemical compound with the formula NCl 3 . This yellow, oily, and explosive liquid is most commonly encountered as a product of chemical reactions between ammonia -derivatives and chlorine (for example, in swimming pools ). Alongside monochloramine and dichloramine , trichloramine is responsible for the distinctive 'chlorine smell' associated with swimming pools, where the compound is readily formed as a product from hypochlorous acid reacting with ammonia and other nitrogenous substances in the water, such as urea from urine . [ 1 ]
The compound is generated by treatment of ammonium chloride with calcium hypochlorite . When prepared in an aqueous-dichloromethane mixture, the trichloramine is extracted into the nonaqueous phase. [ 2 ] Intermediates in this conversion include monochloramine and dichloramine , NH 2 Cl and NHCl 2 , respectively.
Nitrogen trichloride, trademarked as Agene , was at one time used to bleach flour , [ 3 ] but this practice was banned in the United States in 1949 due to safety concerns.
Like ammonia, NCl 3 is a pyramidal molecule . The N-Cl distances are 1.76 Å, and the Cl-N-Cl angles are 107°. [ 4 ]
Nitrogen trichloride can form in small amounts when public water supplies are disinfected with monochloramine , and in swimming pools by disinfecting chlorine reacting with urea in urine and sweat from bathers.
The chemistry of NCl 3 has been well explored. [ 5 ] It is moderately polar with a dipole moment of 0.6 D. The nitrogen center is basic but much less so than ammonia. It is hydrolyzed by hot water to release ammonia and hypochlorous acid .
Concentrated samples of NCl 3 can explode to give N 2 and chlorine gas . [ citation needed ]
In the presence of aluminium trichloride , NCl 3 react with some branch hydrocarbon to produce, after a hydrolysis step, amines . [ 2 ]
Nitrogen trichloride can irritate mucous membranes — it is a lachrymatory agent , but has never been used as such. [ 6 ] [ 7 ] The compound (rarely encountered) is a dangerous explosive, being sensitive to light, heat, even moderate shock, and organic compounds. Pierre Louis Dulong first prepared it in 1812, and lost several fingers and an eye in two explosions. [ 8 ] In 1813, an NCl 3 explosion blinded Sir Humphry Davy temporarily, inducing him to hire Michael Faraday as a co-worker. They were both injured in another NCl 3 explosion shortly thereafter. [ 9 ] | https://en.wikipedia.org/wiki/NCl3 |
Netzler & Dahlgren Co AB, or NDC for short, was a Swedish company founded in 1962 by Göran Netzler and Anders Dahlgren. The initial business idea was to build customized electronics equipment. Over the years, NDC evolved into a technology platform provider (navigation, hardware, software) for AGV ( automated guided vehicle ) builders. Danaher acquired NDC in 2001. [ 1 ]
NDC began producing specially built electronics equipment on a small scale for a variety of industries, for example, manufacturing and marine. The number of owners grew in the 1960s to include Ingvar Bergström, Arne Nilsson and Jan Jutander.
At the beginning of the 1970s, NDC had some 30 employees and started to attract big companies such as Getinge , Tetra Pak and Volvo . The first AGV project was for the Volvo Kalmar Assembly plant in 1972. NDC was involved in producing the AGV prototypes but was considered too small to take on the total project. They were, however, commissioned to deliver all the drives. At that time, the Volvo plant was a revolution in the automotive industry, introducing a totally new way of working.
In 1976, Tetra Pak installed twenty AGVs in their plant in Lund , Sweden. NDC provided the electronics, Tellus the mechanics and ErgoData the control system. The project was a success, and Tetra Pak began to introduce AGVs in their plants worldwide. NDC was involved in many AGV projects for Tetra Pak during the 1970s and 1980s, and saw its chance to expand the business into something more.
In the early 1980s, NDC made the strategically important decision to focus on creating a generic controls platform for AGV builders. Driven by the development of computer technology, it was now possible for NDC to offer the flexibility that AGV builders needed to create customized driverless vehicles. The new NDC business model was born: “Generic technology to be applied by others.”
The first partner was the French company Lamson Saunier Duval, and the number of partners quickly grew into two digits. NDC spent a lot of time educating partners on all the possibilities of generic technology.
The new business model paved the way for international expansion with NDC subsidiaries in Italy, the Czech Republic and the United States. The American NDC subsidiary, NDC Automation Inc., had its own subsidiary in Australia. NDC Automation Inc. went public on March 28, 1990, and subsequently changed its name to Transbotics in 2001.
Laser technology took off in many industrial applications in the 1980s, and NDC started to explore the potential. In 1991, NDC introduced laser technology as AGV navigation for a Tetra Pak factory in Singapore. Tetra Pak appreciated the ease-of-change to new working patterns with laser navigation and began a worldwide plant upgrade to laser navigation. NDC named their navigation technology Lazerway.
In the 1990s, AGVs increased in complexity. By focusing on being a technology platform provider (navigation, hardware, software), NDC could stay strong in an AGV industry that had split into new categories such as mobile robots .
After the Danaher acquisition in 2001, NDC was named Danaher Motion and later on transformed into the Kollmorgen brand. The NDC brand name was kept but is now the name of the technology platform: NDC Solutions.
As of July 2016, Kollmorgen is part of Fortive Corporation . | https://en.wikipedia.org/wiki/NDC_Netzler_&_Dahlgren_Co_AB |
NDMC Supercomputer ( Russian : НЦУО Суперкомпьютер) is a military supercomputer with a speed of 16 petaflops . [ 1 ] It is located in Moscow , Russia. The storage capacity is 236 petabytes . [ 2 ] The supercomputer is designed to predict the development of armed conflicts and is able to analyze the situation and draw conclusions based on the information about past military conflicts. [ 3 ] The database of the supercomputer contains data on the major armed conflicts of modernity for the efficient analysis of future threats. [ 4 ]
This computing article is a stub . You can help Wikipedia by expanding it . | https://en.wikipedia.org/wiki/NDMC_Supercomputer |
5'-guanosyl-methylene-triphosphate (GDPCP) and 5'-adenosyl-methylene-triphosphate (ADPCP) are analogues of guanosine 5'-triphosphate (GTP) and adenosine 5'-triphosphate (ATP), which store chemical energy from metabolism in the cell . Hydrolysis of nucleoside triphosphates (NTPs) such as ATP and GTP yields energy, inorganic phosphate (P i or PP i ), and either NDP or NMP. GDPCP and ADPCP are not subject to hydrolysis under the same conditions as NTPs; it is this property which makes them useful in experiments in biochemistry and molecular biology .
NTPs can be hydrolyzed at the phosphodiester bonds between phosphates , releasing energy and one or more of the three phosphate groups. Additionally, NTPs are inextricable components of some proteins , where their role may be structural and need not involve hydrolysis. In some cases, the presence of an NTP may be required for association of one protein with another, while hydrolysis is necessary for dissociation. GDPCP and ADPCP could be used in such a case, since association can still occur, but hydrolysis-dependent dissociation cannot.
GDPCP was used to examine the prokaryotic elongation factor EF-Tu . EF-Tu is required for the elongation phase of protein synthesis ( translation ). EF-Tu requires GTP in order for the ribosome to bind it, necessary for recruiting an aminoacyl-tRNA . The later dissociation of EF-Tu from the ribosome, however, requires that the GTP first be hydrolyzed to GDP and P i . GDPCP was used in place of GTP to differentiate between these two steps: the elongation factor could associate, but without hydrolysis, it was effectively stuck. [ 1 ] [ 2 ]
This molecular biology article is a stub . You can help Wikipedia by expanding it .
This biochemistry article is a stub . You can help Wikipedia by expanding it . | https://en.wikipedia.org/wiki/NDPCP |
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NP_001078962
NADH:ubiquinone oxidoreductase complex assembly factor 6 is a protein that in humans is encoded by the NDUFAF6 gene . The protein is involved in the assembly of complex I in the mitochondrial electron transport chain . [ 4 ] Mutations in the NDUFAF6 gene have been shown to cause Complex I deficiency, Leigh syndrome , and Acadian variant Fanconi Syndrome . [ 5 ]
The NDUFAF6 gene is located on the q arm of chromosome 8 in position 22.1 and spans 222,728 base pairs. [ 4 ] The gene produces a 38.2 kDa protein composed of 333 amino acids . [ 6 ] [ 7 ] The protein contains a predicted phytoene synthase domain. [ 4 ]
The NDUFAF6 gene encodes a protein that localizes to mitochondria . The encoded protein plays an important role in the assembly of complex I ( NADH-ubiquinone oxidoreductase ) of the mitochondrial respiratory chain through regulation of subunit ND1 biogenesis. [ 4 ]
Mutations in the NDUFAF6 gene are associated with complex I enzymatic deficiency [ 4 ] and lead to Leigh syndrome , [ 8 ] which is characterized by lesions in the central nervous system and rapid deterioration of cognitive and motor functions. In Acadians , a non-coding mutation in NDUFAF6 has been shown to cause Acadian variant Fanconi Syndrome , symptoms of which include pulmonary interstitial fibrosis and proximal tubular dysfunction accompanied by slowly progressive kidney disease. Inheritance of mutations in the NDUFAF6 gene is autosomal recessive . [ 5 ]
The protein encoded by NDUFAF6 interacts with RHOXF2 , OTX1 , GUCD1, [ 9 ] and GALNT6 [ 10 ] proteins.
This article incorporates text from the United States National Library of Medicine , which is in the public domain . | https://en.wikipedia.org/wiki/NDUFAF6 |
The NE-Z8000 is a Brazilian homebuilt computer clone of the Sinclair ZX81 , introduced in late 1982 by Prológica's subsidiary, the monthly magazine Nova Eletrônica . [ 1 ] [ 2 ] [ 3 ] [ 4 ] [ 5 ] [ 6 ] [ 7 ]
The NE-Z8000 computer is based around a Z80A CPU clocked at 3.6 MHz with 1KB of RAM [ 8 ] (expandable to 16 KB [ 3 ] [ 1 ] [ 8 ] ). The 8KB ROM comes with a built-in Sinclair BASIC interpreter. [ 8 ]
The machine has four plugs on the back ( 9V DC , EAR , MIC and TV ), and an exposed part of the circuit board where you can connect extra equipment. [ 4 ] [ 1 ]
The video connector cable is about 120 cm long and connects the TV plug to a regular PAL-M television, outputting a monochrome image on VHF channel 2 or 3. [ 1 ] The EAR and MIC plugs allow to connect a cassette tape recorder for data storage, supporting a rate of 300 Baud . [ 1 ]
It has no switch; to turn it on, you simply plug it into the power supply. A power supply provides 9V DC power usable by the machine. [ 1 ] [ 8 ]
The NE-Z8000 is considered rare, [ 7 ] and in 2013 it could be auctioned by as much as R$ 1000. [ 9 ]
This computing article is a stub . You can help Wikipedia by expanding it .
This computer hardware article is a stub . You can help Wikipedia by expanding it . | https://en.wikipedia.org/wiki/NE-Z8000 |
The NEC V25 ( μPD70320 ) is the microcontroller version of the NEC V20 processor , manufactured by NEC Corporation . Features include:
[ 1 ]
[ 2 ] base address of which can be dynamically relocated with Internal Data area Base (IDB) Register. [ 3 ]
It was officially phased out by NEC in early 2003. [ 5 ]
This computing article is a stub . You can help Wikipedia by expanding it . | https://en.wikipedia.org/wiki/NEC_V25 |
NEKAAL is the Northeast Kansas Amateur Astronomers' League , a non-profit educational and scientific organization founded 1978 and based in Topeka, Kansas . NEKAAL and its members specialize in educational outreach to surrounding counties, and in discovering and refining orbits of solar system objects including comets and asteroids . [ 1 ] [ 2 ]
NEKAAL is a member of the International Dark-Sky Association and the Night Sky Network , and operates the Farpoint Observatory southwest of Topeka.
This astronomy -related article is a stub . You can help Wikipedia by expanding it .
This Kansas -related article is a stub . You can help Wikipedia by expanding it . | https://en.wikipedia.org/wiki/NEKAAL |
NEO Surveyor , formerly called Near-Earth Object Camera ( NEOCam ), then NEO Surveillance Mission , is a planned space-based infrared telescope designed to survey the Solar System for potentially hazardous asteroids . [ 3 ]
The NEO Surveyor spacecraft will survey from the Sun–Earth L 1 (inner) Lagrange point , allowing it to see objects inside Earth's orbit, and its mid-infrared detectors sensitive to thermal emission will detect asteroids independently of their reflected sunlight. [ 4 ] [ 5 ] [ 6 ] The NEO Surveyor mission will be a successor to the NEOWISE mission, and the two missions have the same principal investigator , Amy Mainzer at the University of Arizona . [ 7 ] [ 8 ]
Since first proposed in 2006, the concept repeatedly competed unsuccessfully for NASA funding against science missions unrelated to planetary defense , despite an unfunded 2005 US Congressional directive to NASA. [ 1 ] [ 7 ] In 2019, the Planetary Defense Coordination Office decided to fund this mission outside NASA's science budget due to its national security implications. [ 9 ] [ 10 ] On 11 June 2021, NASA authorized the NEO Surveyor mission to proceed to the preliminary design phase . [ 11 ] The Jet Propulsion Laboratory will lead development of the mission. [ 1 ]
As of December 2022, NEO Surveyor is expected to be launched no later than June 2028. [ 12 ] As of February 2025, it will be launched on a SpaceX Falcon 9 from Florida in September 2027. [ 13 ]
In 2005, the U.S. Congress mandated NASA to achieve by the year 2020 specific levels of search completeness for discovering, cataloging, and characterizing dangerous asteroids larger than 140 m (460 ft) (Act of 2005, H.R. 1022; 109th), [ 14 ] [ 3 ] but it never appropriated specific funds for this effort. [ 15 ] NASA did not prioritize this unfunded mandate , and directed the NEOCam project to compete against science missions for general funds unrelated to planetary defense and disaster mitigation planning. [ 16 ] [ 17 ]
Proposals for NEOCam were submitted to NASA's Discovery Program in 2006, 2010, 2015, 2016 and 2017, but each time were not selected for launch. [ 17 ] [ 18 ] The mission concept nonetheless received technology development funding in 2010 to design and test new infrared detectors optimized for asteroid and comet detection and sizing. [ 19 ] [ 20 ] The project received additional funding for further technological development in September 2015 (US$3 million), [ 21 ] [ 22 ] [ 23 ] and in January 2017. [ 24 ]
Following calls to fully fund the mission outside NASA's Planetary Science Division or directly from Congress itself, [ 25 ] [ 26 ] NASA's associate administrator for science announced on 23 September 2019 that instead of competing for funding, NEOCam will be implemented under the name NEO Surveillance Mission with budget from NASA's Planetary Defense Coordination Office , within the Planetary Science Division . [ 1 ] The near-miss of asteroid 2019 OK , which slipped past extant detection methods in July 2019, has been suggested to have helped prompt this decision. [ 18 ] [ 7 ] [ 27 ]
For funding and management purposes, the NEO Surveillance Mission is officially a new project, but it is the same space telescope, the same team, and the mission's goals remain unchanged. [ 1 ] [ 28 ]
On February 11, 2025 the mission passed its critical design review, moving the project towards construction and testing. [ 29 ]
The main objective of the mission is to discover most of the potentially hazardous asteroids larger than 140 m (460 ft) over the course of its mission and characterize their orbits. [ 1 ] [ 28 ] Its field of view and its sensitivity will be wide and deep enough to allow the mission to discover about 200,000 to 300,000 new NEOs with sizes as small as 10 m (33 ft) in diameter. [ 2 ] [ 31 ] Secondary science goals include detection and characterization of approximately one million asteroids in the asteroid belt and thousands of comets , as well as identification of potential NEO targets for human and robotic exploration. [ 32 ] [ 33 ]
The Jet Propulsion Laboratory (JPL) leads the development of the mission. The total cost of the mission is estimated to be between US$500 million and US$600 million. [ 1 ] [ 28 ] The mission has a development cost baseline of $1.2 billion. [ 34 ]
On the NEO Surveyor website the following mission requirements are stated: [ 35 ]
The NEO Surveyor spacecraft will have a total mass of no more than 1,300 kg (2,900 lb), allowing it to launch on a vehicle like a Falcon 9 Block 5 to the Sun–Earth L 1 Lagrange point . The mission should reach the 90% congressional goal within 10 years, with an anticipated mission lifetime of 12 years. [ 36 ]
Asteroids are dark, with albedos of at most 30% and as low as 5%. An optical telescope looks for the light they reflect and can therefore only see them when looking away from the Sun at the sunlit side of the asteroids, and not when looking towards the Sun at the unlit backside of the object. In addition, opposition surge makes asteroids even brighter when the Earth is close to the axis of sunlight, and the sky on Earth is much brighter in daytime. The combined effect is equivalent to the comparison of a Full moon at night to a New Moon in daytime, and the light of the Sun-lit asteroids has been called "full asteroid" similar to a "full moon". A telescope operating at thermal infrared wavelengths instead detects their surfaces that have been warmed by the Sun and is almost equally sensitive to their lit and unlit sides, but needs to operate in space to achieve good sensitivity over a wide field of view. [ 37 ]
The NEO Surveillance Mission will employ a 50 cm (20 in) infrared telescope operating wide-field cameras at two thermal infrared wavelength channels for a total wavelength range between 4 μm and 10 μm. [ 3 ] The camera will have two channels: NC1 has a wavelength range of 4–5.2 μm and NC2 spans 6–10 μm. NC1 is intended to detect background stars for astrometric registration and calibration, as well as the measurement of effective temperatures . NC2 is optimized to maximize sensitivity to typical NEO thermal emission at 200-300 K . [ 2 ] Its field of view is 11.56 square degrees . [ 38 ] It will use a version of the Astronomical Wide Area Infrared Imager (HAWAII) mercury–cadmium–telluride detector modified by Teledyne Imaging Sensors for optimal sensitivity in the NC1 and NC2 bands. [ 39 ] The mission prototype detector was successfully tested in April 2013. [ 40 ] [ 41 ] The detector array is 2,048 × 2,048 pixels and will produce 82 gigabits of data per day. [ 38 ] For good infrared performance without the use of cryogenic fluid refrigeration, [ 39 ] the detector will be passively cooled to 30 K (−243.2 °C; −405.7 °F) using techniques proven by the Spitzer Space Telescope . [ 38 ] Unlike its predecessor NEOWISE , it will therefore not suffer from a performance degradation due to running out of coolant (its mission duration will however still be limited, as the orbital station keeping needed to maintain its position at Sun–Earth L 1 uses propellant; also, cosmic radiation will slowly degrade the detectors over time).
The NEO Surveyor spacecraft will operate in a halo orbit around the Sun–Earth L 1 , and employ a sunshade . [ 38 ] This orbit will allow fast data downlink speeds to Earth, allowing full-frame images to be downloaded from the telescope. [ 42 ]
One advantage over NEOWISE is the wide field of regard . NEO Surveyor will be able to point anywhere from 45-120° in longitudinal distance from the sun and stopping at ±40° ecliptic latitude . The survey will be optimized to detect potentially hazardous objects and be performed continuously during the baseline mission (5 years). The survey will be halted each day for 2.25 hours to downlink the data. It will also be halted for calibration , station-keeping and momentum management maneuvers. NEO Surveyor will also be able to conduct targeted follow-up (TFO) to obtain more information for an object of special interest. [ 2 ]
It is planned that moving object tracklets are delivered to the Minor Planet Center 2 to 3 times a day, on average 72 hours after their discovery. Additionally deep co-added images are published every 12 months. [ 2 ] These deep co-added images most likely will like those of WISE be used by astronomers to study stars, brown dwarfs , and distant galaxies. It was also proposed that NEO Surveyor will include a transient alerting infrastructure , [ 43 ] but none are planned to this date (October 2023). [ 2 ]
In the first 30 days after the launch the in-orbit checkouts will be performed. After arriving at L 1 NEO Surveyor team will conduct a 6-month survey verification. In the nominal survey the telescope is expected to detect two-thirds of asteroids with a diameter larger than 140 meters in the first 5 years. The nominal mission will last for at least 12 years. After the survey end, the telescope will be decommissioned and put into a heliocentric orbit . [ 44 ]
old archived websites:
other official websites: | https://en.wikipedia.org/wiki/NEO_Surveyor |
Net-centric Enterprised Solutions for Interoperability ( NESI ) is a joint effort between the United States Navy ’s Program Executive Office for C4I & Space and the United States Air Force ’s Electronic Systems Center. It provides implementation guidance which facilitates the design, development, maintenance, evolution, and use of information systems for the Net-Centric Operations and Warfare ( NCOW ) environment. NESI has also been provided to other Department of Defense (DoD) services and agencies for potential adoption. [ 1 ]
NESI comprises six parts, each focusing on a specific area of guidance. NESI provides guidance, best practices, and examples for developing Net-Centric software. The overall goal is to provide common, cross-service guidance in basic terms for the program managers and developers of net-centric solutions. The objective is not to replace or repeat existing direction, but to help translate into concrete actions the plethora of mandated and sometimes contradictory guidance on the topic of net-centric compliance and standards. [ 1 ] [ 2 ]
NESI subsumes two now obsolete references; in particular, the Air Force C2 Enterprise Technical Reference Architecture (C2ERA) and the Navy Reusable Applications Integration and Development Standards (RAPIDS). Initial authority for NESI is per the Memorandum of Agreement between Space and Naval Warfare Systems Command (SPAWAR), Navy PEO C4I & Space and the United States Air Force Electronic Systems Center, dated 22 December 2003, Subject: Cooperation Agreement for Net-Centric Solutions for Interoperability (NESI). This guidance will continue to evolve as direction and understanding of the requirements of net-centricity evolve. NESI will be updated to reflect changes to the guiding documents and new regulations.
The NESI documentation, a six-part information set, is available as PDF files. These parts consist of:
In order to evaluate programs/projects, NESI has developed a technical checklist. The current version of the checklist should be used to analyze the current status of a program/project. The technical checklist is produced from the guidance details and provides public, published, consistent interpretation of NESI guidance. Overall, the checklist will provide a uniform interpretation for all of participating organizations. [ 3 ] | https://en.wikipedia.org/wiki/NESI |
NEST is a simulation software for spiking neural network models, including large-scale neuronal networks. NEST was initially developed by Markus Diesmann and Marc-Oliver Gewaltig and is now developed and maintained by the NEST Initiative.
A NEST simulation tries to follow the logic of an electrophysiological experiment that takes place inside a computer with the difference, that the neural system to be investigated must be defined by the experimenter.
The neural system is defined by a possibly large number of neurons and their connections . In a NEST network, different neuron and synapse models can coexist. Any two neurons can have multiple connections with different properties. Thus, the connectivity can in general not be described by a weight or connectivity matrix but rather as an adjacency list .
To manipulate or observe the network dynamics, the experimenter can define so-called devices which represent the various instruments (for measuring and stimulation) found in an experiment. These devices write their data either to memory or to file.
NEST is extensible and new models for neurons, synapses, and devices can be added.
The following example simulates spiking activity in a sparse random network with recurrent excitation and inhibition [ 1 ]
The figure shows the spiking activity of 50 neurons as a raster plot . Time increases along the horizontal axis, neuron id increases along the vertical axis. Each dot corresponds to a spike of the respective neuron at a given time. The lower part of the figure shows a histogram with the mean firing-rate of the neurons.
NEST development was started in 1993 by Markus Diesmann and Marc-Oliver Gewaltig at the Ruhr University Bochum , Bochum , Germany and the Weizmann Institute of Science in Rehovot , Israel . At this time, the simulator was called SYNOD and simulations were defined in a stack based simulation language, called SLI. [ 7 ]
In 2001, the software changed its name from SYNOD to NEST. Until 2004, NEST was exclusively developed and used by the founding members of the NEST Initiative. The first public release appeared in summer 2004. Since then, NEST was released regularly, about once or twice per year.
Since 2007, NEST supports hybrid parallelism, using POSIX threads and MPI . [ 5 ]
In 2008, the stack-based simulation language SLI was superseded by a modern Python interface, however, the old simulation language is still used internally. [ 8 ] At the same time, the simulator independent specification language PyNN was developed with support for NEST. [ 9 ] In 2012, the NEST Initiative changed the license from the proprietary NEST License to GNU GPL V2 or later. | https://en.wikipedia.org/wiki/NEST_(software) |
The tetrafluoroammonium cation (also known as perfluoroammonium ) is a positively charged polyatomic ion with chemical formula NF + 4 . It is equivalent to the ammonium ion where the hydrogen atoms surrounding the central nitrogen atom have been replaced by fluorine . [ 1 ] Tetrafluoroammonium ion is isoelectronic with tetrafluoromethane CF 4 , trifluoramine oxide ONF 3 , tetrafluoroborate BF − 4 anion and the tetrafluoroberyllate BeF 2− 4 anion.
The tetrafluoroammonium ion forms salts with a large variety of fluorine-bearing anions. These include the bifluoride anion ( HF − 2 ), tetrafluorobromate ( BrF − 4 ), metal pentafluorides ( MF − 5 where M is Ge , Sn , or Ti ), hexafluorides ( MF − 6 where M is P , As , Sb , Bi , or Pt ), heptafluorides ( MF − 7 where M is W , U , or Xe ), octafluorides ( XeF 2− 8 ), [ 2 ] various oxyfluorides ( MF 5 O − where M is W or U; FSO − 3 , BrF 4 O − ), and perchlorate ( ClO − 4 ). [ 3 ] Attempts to make the nitrate salt, NF 4 NO 3 , were unsuccessful because of quick fluorination: NF + 4 + NO − 3 → NF 3 + FONO 2 . [ 4 ]
The geometry of the tetrafluoroammonium ion is tetrahedral , with an estimated nitrogen-fluorine bond length of 124 pm . All fluorine atoms are in equivalent positions. [ 5 ]
Tetrafluoroammonium salts are prepared by oxidising nitrogen trifluoride with fluorine in the presence of a strong Lewis acid which acts as a fluoride ion acceptor. The original synthesis by Tolberg, Rewick, Stringham, and Hill in 1966 employs antimony pentafluoride as the Lewis acid: [ 5 ]
The hexafluoroarsenate salt was also prepared by a similar reaction with arsenic pentafluoride at 120 °C: [ 5 ]
The reaction of nitrogen trifluoride with fluorine and boron trifluoride at 800 °C yields the tetrafluoroborate salt: [ 6 ]
NF + 4 salts can also be prepared by fluorination of NF 3 with krypton difluoride ( KrF 2 ) and fluorides of the form MF n , where M is Sb, Nb, Pt, Ti, or B. For example, reaction of NF 3 with KrF 2 and TiF 4 yields [NF + 4 ] 2 TiF 2− 6 . [ 7 ]
Many tetrafluoroammonium salts can be prepared with metathesis reactions .
Tetrafluoroammonium salts are extremely hygroscopic . The NF + 4 ion, when dissolved in water, readily decomposes into NF 3 , H 2 F + , and oxygen gas. Some hydrogen peroxide ( H 2 O 2 ) is also formed during this process: [ 5 ]
Reaction of NF + 4 SbF − 6 with alkali metal nitrates yields fluorine nitrate , FONO 2 . [ 4 ]
Because NF + 4 salts are destroyed by water, water cannot be used as a solvent. Instead, bromine trifluoride , bromine pentafluoride , iodine pentafluoride , or anhydrous hydrogen fluoride can be used. [ 8 ]
Tetrafluoroammonium salts usually have no colour. However, some are coloured due to other elements in them. (NF + 4 ) 2 CrF 2− 6 , (NF + 4 ) 2 NiF 2− 6 and (NF + 4 ) 2 PtF 2− 6 have a red colour, while (NF + 4 ) 2 MnF 2− 6 , NF + 4 UF − 7 , NF + 4 UOF − 5 and NF + 4 XeF − 7 are yellow. [ 8 ]
NF + 4 salts are important for solid propellant NF 3 –F 2 gas generators. They are also used as reagents for electrophilic fluorination of aromatic compounds in organic chemistry . [ 5 ] As fluorinating agents, they are also strong enough to react with methane. [ 9 ] | https://en.wikipedia.org/wiki/NF4+ |
Nitrogen pentafluoride is a theoretical compound of nitrogen and fluorine with the chemical formula N F 5 . It is hypothesized to exist based on the existence of the pentafluorides of the atoms below nitrogen in the periodic table, such as phosphorus pentafluoride . Theoretical models of the nitrogen pentafluoride molecule are either a trigonal bipyramidal covalently bound molecule with symmetry group D 3h , or [NF 4 ] + F − (tetrafluoroammonium fluoride), which would be an ionic solid.
A variety of other tetrafluoroammonium salts are known ( [NF 4 ] + X − ), as are fluoride salts of other ammonium cations ( [NR 4 ] + F − ).
In 1966, W. E. Tolberg first synthesized a five-valent nitrogen compound of nitrogen and fluorine when tetrafluoroammonium compounds, tetrafluoroammonium hexafluoroantimonate(V) [NF 4 ] + [SbF 6 ] − and tetrafluoroammonium hexafluoroarsenate(V) [NF 4 ] + [AsF 6 ] − were made. [ 2 ] In 1971 C. T. Goetschel announced the preparation of [NF 4 ] + [BF 4 ] − and also produced a white solid assumed to be tetrafluoroammonium fluoride ( [NF 4 ] + F − ). This was made by treating nitrogen trifluoride and fluorine with 3 MeV electron radiation at 77 K. It decomposed above 143 K back into those ingredients. [ 2 ] Theoretical studies also show the ionic compound is very likely to decompose to nitrogen trifluoride and fluorine gas. [ 3 ]
Karl O. Christe synthesised bis(tetrafluoroammonium) hexafluoronickelate(IV) ([NF 4 ] + ) 2 [NiF 6 ] 2− . [ 4 ] He also prepared compounds with manganese, a fluorouranate, tetrafluoroammonium perchlorate [NF 4 ] + ClO − 4 , tetrafluoroammonium fluorosulfate [NF 4 ] + SO 3 F − and [N 2 F 3 ] + (trifluorodiazenium) salts. [ 5 ] Christe attempted to make [NF 4 ] + F − by metathesis of [NF 4 ] + [SbF 6 ] − with CsF in HF solvent at 20 °C. However, a variant, tetrafluoroammonium bifluoride hydrofluorates ( [NF 4 ] + [HF 2 ] − · n HF ), was produced. At room temperature it was a milky liquid, but when cooled, turned pasty. At −45 °C it had the form of a white solid. When reheated it frothed, giving off F 2 , HF and NF 3 as gases . [ 5 ] This has CAS number 71485-49-9. [ 6 ]
I. J. Solomon believed that nitrogen pentafluoride was produced by the thermal decomposition of [NF 4 ] + [AsF 6 ] − , but experimental results were not reproduced. [ 7 ]
Dominik Kurzydłowski and Patryk Zaleski-Ejgierd predict that a mixture of fluorine and nitrogen trifluoride under pressure between 10 and 33 GPa forms [NF 4 ] + F − with space group R3m . This is a high-pressure oxidation. Over 33 GPa it will form a stable ionic compound with formula ([NF 4 ] + ) 2 [NF 6 ] − F − (bis(tetrafluoroammonium) hexafluoronitrate(V) fluoride) with space group I4/m . Over 151 GPa this is predicted to transform to [NF 4 ] + [NF 6 ] − (tetrafluoroammonium hexafluoronitrate(V)) with space group P4/n . [ 8 ] A NF 5 molecular compound is not stable under any pressure conditions.
For a NF 5 molecule to form, five fluorine atoms have to be arranged around a nitrogen atom. There is insufficient space to do this at typical nitrogen–fluorine covalent-bond lengths, so at least some bonds are forced to be longer. Calculations show that fragmentation to form NF 4 and F radicals would have a transition state barrier of around 66–84 kJ/mol (15.8–20.0 kcal/mol) and that this process is thermodynamically favourable ( exothermic ) by 38 kJ/mol (9 kcal/mol). [ 9 ] Nitrogen pentafluoride also violates the octet rule in which compounds with eight outer shell electrons are particularly stable. [ 10 ] | https://en.wikipedia.org/wiki/NF5 |
The NFC Institute of Engineering and Fertilizer Research (NFC-IEFR) was incorporated in 1986 by National Fertilizer Corporation of Pakistan (NFC) and is located in Faisalabad , Punjab , Pakistan . The first Principal/Director was Dr. Anwar ul Haq from 1986 to 2006. Thereafter Dr.Javaid Rabbani Khan served as Director from 2006 until 2013. Dr Shahid Raza Khan and Dr Ashraf Dogar also remained Director’s in 2013 and 2018, respectively. Mr.Essa Khan was the first Administrator/Registrar at NFC-IEFR and present Registrar is Engr. Adeel Safdar since 2021. From 1986 until 2021, Institute remained under the administrative control of National Fertilizer Corporation of Pakistan Ministry of Industries & Production Government of Pakistan. In 2021, Ministry of Education Govt. of Pakistan took over the administrative control. It is affiliated with University of Engineering and Technology, Lahore for awarding of engineering degrees.
The university is spread over 25 acres. The main building of the institute has administration wing, central library, spectacular air-conditioned auditorium, seminar hall, conference room, IT and linguistic laboratories and research and development department. The academic block is composed of offices for faculty members, classrooms, laboratories and computational lab. For the extension of facilities in the IE&FR campus, a three-story multi purposes block has been constructed, which comprises a large number of multi-disciplined laboratories, classrooms and offices for faculty members. [ 2 ] [ 3 ] [ 4 ]
The disciplines and the degree programs offered by the institute have been tabulated below. The regular duration of BS and MS/M Phil degree programs is 4 and 2 years, respectively.
Following is a list of the officially constituted societies:
NFC Institute of Engineering and Technology, Multan | https://en.wikipedia.org/wiki/NFC_Institute_of_Engineering_and_Fertilizer_Research |
NGC 1240 is a double star which is located in the Aries constellation . [ 1 ] [ 2 ] It was recorded by British-German astronomer William Herschel on 12 September 1784. [ 3 ]
This binary or multiple star system–related article is a stub . You can help Wikipedia by expanding it . | https://en.wikipedia.org/wiki/NGC_1240 |
NGC 6863 is an asterism in the constellation Aquila . The celestial object was found on July 25, 1827, by the British astronomer John Herschel .
In 2009 an astronomical study by Bidin et al. concluded that whereas the small group of stars in Aquila had been classified as an OCR (Open Cluster Remnant i.e. the dispersed remains of a group of physically related stars) they were in fact an asterism, a group of unrelated stellar bodies. [ 2 ]
This constellation -related article is a stub . You can help Wikipedia by expanding it . | https://en.wikipedia.org/wiki/NGC_6863 |
NGLY1 deficiency is a very rare genetic disorder caused by biallelic pathogenic variants in NGLY1 . It is an autosomal recessive disorder. Errors in deglycosylation are responsible for the symptoms of this condition. [ 1 ] Clinically, most affected individuals display developmental delay, lack of tears , elevated liver transaminases and a movement disorder. [ 2 ] NGLY1 deficiency is difficult to diagnose, and most individuals have been identified by exome sequencing.
NGLY1 deficiency causes a dysfunction in the endoplasmic reticulum -associated degradation pathway. NGLY1 encodes an enzyme, N-glycanase 1 , that cleaves N-glycans . Without N-glycanase, N-glycosylated proteins that are misfolded in the endoplasmic reticulum cannot be degraded, and thus accumulate in the cytoplasm of cells. [ 3 ] [ 4 ]
Four common findings have been identified in a majority of patients: developmental delay or intellectual disability of varying degrees, lack of or greatly reduced tears , elevated liver transaminases, and a complex movement disorder. The elevated liver enzymes often resolve in childhood. In addition, approximately 50% of patients described with NGLY1 deficiency have seizures, which can vary in their difficulty to control. Other symptoms that have been reported in affected individuals include sleep apnea , constipation , scoliosis , oral motor defects, auditory neuropathy and peripheral neuropathy. [ 2 ]
NGLY1 deficiency can be suspected based on clinical findings, however confirmation of the diagnosis requires the identification of biallelic pathogenic variants in NGLY1 through genetic testing . Traditional screening tests utilized for congenital disorders of glycosylation , including carbohydrate deficient transferrin are not diagnostic in NGLY1 deficiency. To date all variants identified as being causative of NGLY1 deficiency have been sequence variants, rather than copy number variants. This spectrum may change as additional cases are identified. [ 2 ] A common nonsense variant (c.1201A>T (p.Arg401Ter)) accounts for approximately a third of pathogenic variants identified, and is associated with a more severe clinical course. [ 2 ]
There is also a biomarker for NGLY1 deficiency. [ 5 ] [ 6 ] When the NGLY1 protein is missing or not functioning correctly, a specific molecule called GlcNAc-Asn (GNA) accumulates. GNA is elevated in individuals with NGLY1 deficiency compared to individuals without the disease. [ 6 ] [ 5 ] Elevated GNA alone is not enough to confirm an NGLY1 deficiency diagnosis, but in combination with molecular genetic testing and clinical findings, it can provides additional support for NGLY1 deficiency.
There is no cure for NGLY1 deficiency. [ 7 ] Supportive care is indicated for each patient based on their specific symptoms, and can include eye drops to manage the alacrima , pharmaceutical management of seizures, feeding therapy and physical therapy. [ 2 ] Most potential treatment options for NGLY1 deficiency are in the pre-clinical stages. These include enzyme replacement therapy, as well as ENGase inhibitors. [ 2 ]
Forty-seven patients with confirmed NGLY1 deficiency have been reported in the medical literature. [ 8 ] The Grace Science Foundation, a patient advocacy group, has identified approximately 150 world-wide. Currently, the majority of individuals reported with NGLY1 deficiency are of northern European descent, however this likely reflects an ascertainment bias in these early stages of the disorder. Affected individuals with African and Hispanic backgrounds have been identified. [ 2 ]
The first cases of NGLY1 deficiency were described in 2012. [ 1 ] NGLY1 deficiency has received a large amount of attention, despite its rarity, due to the children of two media-savvy families being afflicted. [ 9 ] The Wilseys, descendants of Dede Wilsey , founded the Grace Science Foundation [ 10 ] in honor of their daughter, while Matt Might and his wife founded the Bertrand Might Research Fund. These foundations have contributed millions of dollars to research efforts. [ 9 ] [ 11 ] | https://en.wikipedia.org/wiki/NGLY1_deficiency |
NGSI-LD is an information model and API for publishing , querying and subscribing to context information . It is meant to facilitate the open exchange and sharing of structured information between different stakeholders. It is used across application domains such as smart cities , [ 1 ] [ 2 ] [ 3 ] smart industry , smart agriculture , [ 4 ] [ 5 ] and more generally for the Internet of things , [ 6 ] cyber-physical systems , systems of systems [ 7 ] and digital twins . [ 8 ]
NGSI-LD has been standardized by ETSI (European Telecommunications Standardization Institute) through the Context Information Management Industry Specification Group, following a request [ 9 ] from the European Commission . Its takeup and further development are spelled out in the EU's "Rolling plan for ICT standardization". [ 10 ] NGSI-LD builds upon a decades-old corpus of research in context management frameworks and context modelling. [ 11 ] The acronym NGSI stands for "Next Generation Service Interfaces", a suite of specifications originally issued by the OMA which included Context Interfaces. [ 12 ] These were taken up and evolved as NGSIv2 [ 13 ] by the European Future Internet Public-Private-Partnership (PPP), which spawned the FIWARE open source community.
The NGSI-LD information model represents Context Information as entities that have properties and relationships to other entities. It is derived from property graphs, [ 14 ] with semantics formally defined on the basis of RDF and the semantic web framework. It can be serialized using JSON-LD . Every entity and relationship is given a unique IRI reference as identifier, making the corresponding data exportable as linked data datasets. The -LD suffix denotes this affiliation to the linked data universe.
The NGSI-LD information model [ 15 ] can be considered as the first formal specification by a de jure standards organization of the property graph model, which has emerged since the early 2000s as an informal common denominator model for graph databases .
The core concepts are:
The NGSI-LD meta-model [ 15 ] formally defines these foundational concepts (Entities, Relationships, Properties) on the basis of RDF / RDFS / OWL , and partially on the basis of JSON-LD .
Complementing this metamodel, the NGSI-LD information model specification also provides a cross-domain ontology [ 15 ] that defines key constructs related to spatial, temporal or system-composition characteristics of entities.
The flexible information model allows the specification of any kind of entity. In order to allow interoperability between NGSI-LD users, standardized entities are collaboratively defined at Smart Data Models Program and made available at its repository with an open-source license.
The NGSI-LD specification consists of an information model and an API. The API provides functionalities to support the architectural roles described in the following.
The architectural roles allow the implementation of different deployment architectures. In a centralized architectures, there is a central Context Broker that stores the context information provided by Context Producers. In a distributed setting, all context information can be stored by Context Sources. In a federated architecture, Context Sources can again be Context Brokers that make aggregated information from a lower hierarchy level available. These architectures are not mutually exclusive, i.e. an actual deployment may combine them in different ways.
The NGSI-LD Context Information Management API [ 16 ] allows users to provide, consume and subscribe to context information in multiple scenarios and involving multiple stakeholders. It enables close to real-time access to information coming from many different sources (not only IoT data sources), named Context Sources, as well as publishing that information through interoperable data publication platforms.
It provides advanced geo-temporal queries, and it includes subscription mechanisms, in order for content consumers to be notified when content matching some constraints becomes available.
The API is designed to be agnostic to the architecture (central, distributed, federated or combinations thereof), so that applications which produce and consume information do not have to be tailored to the specifics of the system that distributes/brokers context information for them.
API operations comprise:
NGSI-LD was initiated by partners of the FIWARE programme , and is primarily used by the FIWARE open source community, [ 17 ] supported by the FIWARE Foundation [ 18 ] as well as a diverse range of other projects and users such as below:
NGSI-LD is the result of an evolution of Context Interfaces that started as part of the "Next Generation Service Interfaces" (NGSI) suite published by the Open Mobile Alliance (OMA) in 2012, which is also the source of the acronym NGSI. The NGSI suite included NGSI-9 as the Context Entity Discovery Interface and NGSI-10 as the Context Information Interface. [ 12 ] The NGSI standard from OMA and its intermediary evolutions relied on a classical Entity–attribute–value model and an XML-based representation. The NGSI Context Interfaces were adapted by the FI-WARE project, which developed the platform for the European Future Internet Public-Private-Partnership (PPP). The OMA NGSI Context Interfaces got an HTTP binding with a JSON representation, referred to as NGSIv1, which included both NGSI-9 and NGSI-10. In the course of FI-PPP the interfaces further evolved into NGSIv2, [ 13 ] which became the key interface of the FIWARE platform. After the end of the FI-PPP in 2016, the FIWARE platform became the core of the FIWARE Open Source Community managed by the FIWARE Foundation . In 2017, the ETSI Industry Specification Group on cross-cutting Context Information Management (ETSI ISG CIM) was created to evolve the Context Information Interface, which resulted in the creation of NGSI-LD. The limitations of the original information model led to the specification of a broader model which derives from property graphs, explicitly including relationships between entities, on a par with entities themselves. ETSI ISG CIM continues to evolve the NGSI-LD Information Model and API. It publishes new versions of the specification once or twice a year. | https://en.wikipedia.org/wiki/NGSI-LD |
NGSmethDB is a database of methylation data derived from next-generation sequencing data. [ 1 ]
This Biological database -related article is a stub . You can help Wikipedia by expanding it . | https://en.wikipedia.org/wiki/NGSmethDB |
Cadaverine is an organic compound with the formula (CH 2 ) 5 (NH 2 ) 2 . Classified as a diamine , it is a colorless liquid with an unpleasant odor. [ 3 ] It is present in small quantities in living organisms but is often associated with the putrefaction of animal tissue . Together with putrescine , it is largely responsible for the foul odor of putrefying flesh, but also contributes to other unpleasant odors.
Cadaverine is produced by decarboxylation of lysine . [ 4 ] It can be synthesized by many methods including the hydrogenation of glutaronitrile and the reactions of 1,5-dichloropentane. [ 3 ]
Putrescine [ 5 ] and cadaverine [ 6 ] were first described in 1885 by the Berlin physician Ludwig Brieger (1849–1919). [ 7 ] It was named from the English adjective cadaverous .
In zebrafish , the trace amine-associated receptor 13c (or TAAR13c) has been identified as a high-affinity receptor for cadaverine. [ 8 ] In humans, molecular modelling and docking experiments have shown that cadaverine fits into the binding pocket of the human TAAR6 and TAAR8 . [ 9 ]
Seminal plasma contains cadaverine as basic amines. [ 10 ] Elevated levels of cadaverine have been found in the urine of some patients with defects in lysine metabolism. The odor commonly associated with bacterial vaginosis has been linked to cadaverine and putrescine . [ 11 ]
Acute oral toxicity of cadaverine is 2,000 mg/kg body weight; its no-observed-adverse-effect level is 2,000 ppm (180 mg/kg body weight/day). [ 12 ] | https://en.wikipedia.org/wiki/NH2(CH2)5NH2 |
L -Tyrosine or tyrosine (symbol Tyr or Y ) [ 2 ] or 4-hydroxyphenylalanine is one of the 20 standard amino acids that are used by cells to synthesize proteins . It is a conditionally essential amino acid with a polar side group . The word "tyrosine" is from the Greek tyrós , meaning cheese , as it was first discovered in 1846 by German chemist Justus von Liebig in the protein casein from cheese. [ 3 ] [ 4 ] It is called tyrosyl when referred to as a functional group or side chain. While tyrosine is generally classified as a hydrophobic amino acid, it is more hydrophilic than phenylalanine . [ 5 ] It is encoded by the codons UAC and UAU in messenger RNA .
The one-letter symbol Y was assigned to tyrosine for being alphabetically nearest of those letters available. Note that T was assigned to the structurally simpler threonine, U was avoided for its similarity with V for valine, W was assigned to tryptophan, while X was reserved for undetermined or atypical amino acids. [ 6 ] The mnemonic t Y rosine was also proposed. [ 7 ]
Aside from being a proteinogenic amino acid , tyrosine has a special role by virtue of the phenol functionality. Its hydroxy group is able to form the ester linkage , with phosphate in particular. Phosphate groups are transferred to tyrosine residues by way of protein kinases . This is one of the post-translational modifications . Phosphorylated tyrosine occurs in proteins that are part of signal transduction processes.
Similar functionality is also presented in serine and threonine , whose side chains have a hydroxy group, but are alcohols . Phosphorylation of these three amino acids' moieties (including tyrosine) creates a negative charge on their ends, that is greater than the negative charge of the only negatively charged aspartic and glutamic acids. Phosphorylated proteins keep these same properties—which are useful for more reliable protein-protein interactions—by means of phosphotyrosine, phosphoserine and phosphothreonine. [ 8 ]
Binding sites for a signalling phosphoprotein may be diverse in their chemical structure. [ 9 ]
Phosphorylation of the hydroxyl group can change the activity of the target protein, or may form part of a signaling cascade via SH2 domain binding. [ 10 ]
A tyrosine residue also plays an important role in photosynthesis . In chloroplasts ( photosystem II ), it acts as an electron donor in the reduction of oxidized chlorophyll . In this process, it loses the hydrogen atom of its phenolic OH-group. This radical is subsequently reduced in the photosystem II by the four core manganese clusters . [ 11 ]
The Dietary Reference Intake for tyrosine is usually estimated together with phenylalanine . It varies depending on an estimate method, however the ideal proportion of these two amino acids is considered to be 60:40 (phenylalanine:tyrosine) as a human body has such composition. [ 12 ] Tyrosine, which can also be synthesized in the body from phenylalanine, is found in many high- protein food products such as meat , fish , cheese , cottage cheese , milk , yogurt , peanuts , almonds , pumpkin seeds , sesame seeds , soy protein and lima beans . [ 13 ] [ 14 ] For example, the white of an egg has about 250 mg per egg, [ 15 ] while beef, lamb, pork, tuna, salmon, chicken, and turkey contain about 500–1000 mg per 3 ounces (85 g) portion. [ 15 ] [ 16 ]
In plants and most microorganisms, tyrosine is produced via prephenate , an intermediate on the shikimate pathway . Prephenate is oxidatively decarboxylated with retention of the hydroxyl group to give p -hydroxyphenylpyruvate, which is transaminated using glutamate as the nitrogen source to give tyrosine and α-ketoglutarate .
Mammals synthesize tyrosine from the essential amino acid phenylalanine (Phe), which is derived from food. The conversion of Phe to Tyr is catalyzed by the enzyme phenylalanine hydroxylase , a monooxygenase. This enzyme catalyzes the reaction causing the addition of a hydroxyl group to the end of the 6-carbon aromatic ring of phenylalanine , such that it becomes tyrosine.
Some of the tyrosine residues can be tagged (at the hydroxyl group) with a phosphate group ( phosphorylated ) by protein kinases . In its phosphorylated form, tyrosine is called phosphotyrosine . Tyrosine phosphorylation is considered to be one of the key steps in signal transduction and regulation of enzymatic activity. Phosphotyrosine can be detected through specific antibodies . Tyrosine residues may also be modified by the addition of a sulfate group, a process known as tyrosine sulfation . [ 17 ] Tyrosine sulfation is catalyzed by tyrosylprotein sulfotransferase (TPST). Like the phosphotyrosine antibodies mentioned above, antibodies have recently been described that specifically detect sulfotyrosine. [ 18 ]
In dopaminergic cells in the brain , tyrosine is converted to L-DOPA by the enzyme tyrosine hydroxylase (TH). TH is the rate-limiting enzyme involved in the synthesis of the neurotransmitter dopamine . Dopamine can then be converted into other catecholamines , such as norepinephrine (noradrenaline) and epinephrine (adrenaline).
The thyroid hormones triiodothyronine (T 3 ) and thyroxine (T 4 ) in the colloid of the thyroid are also derived from tyrosine.
The latex of Papaver somniferum , the opium poppy, has been shown to convert tyrosine into the alkaloid morphine and the bio-synthetic pathway has been established from tyrosine to morphine by using Carbon-14 radio-labelled tyrosine to trace the in-vivo synthetic route. [ 22 ] Tyrosine ammonia lyase (TAL) is an enzyme in the natural phenols biosynthesis pathway. It transforms L -tyrosine into p -coumaric acid . Tyrosine is also the precursor to the pigment melanin . Tyrosine (or its precursor phenylalanine) is needed to synthesize the benzoquinone structure which forms part of coenzyme Q10 . [ 23 ] [ 24 ]
[ citation needed ]
The decomposition of L -tyrosine (syn. para -hydroxyphenylalanine) begins with an α-ketoglutarate dependent transamination through the tyrosine transaminase to para -hydroxyphenylpyruvate . The positional description para , abbreviated p , mean that the hydroxyl group and side chain on the phenyl ring are across from each other (see the illustration below).
The next oxidation step catalyzes by p -hydroxyphenylpyruvate dioxygenase and splitting off CO 2 homogentisate (2,5-dihydroxyphenyl-1-acetate). [ 25 ] In order to split the aromatic ring of homogentisate, a further dioxygenase, homogentisate 1,2-dioxygenase is required. Thereby, through the incorporation of a further O 2 molecule, maleylacetoacetate is created.
Fumarylacetoacetate is created by maleylacetoacetate cis - trans -isomerase through rotation of the carboxyl group created from the hydroxyl group via oxidation. This cis-trans -isomerase contains glutathione as a coenzyme . Fumarylacetoacetate is finally split by the enzyme fumarylacetoacetate hydrolase through the addition of a water molecule.
Thereby fumarate (also a metabolite of the citric acid cycle) and acetoacetate (3-ketobutyroate) are liberated. Acetoacetate is a ketone body , which is activated with succinyl-CoA, and thereafter it can be converted into acetyl-CoA , which in turn can be oxidized by the citric acid cycle or be used for fatty acid synthesis .
Phloretic acid is also a urinary metabolite of tyrosine in rats. [ 26 ]
Three structural isomers of L -tyrosine are known. In addition to the common amino acid L -tyrosine, which is the para isomer ( para -tyr, p -tyr or 4-hydroxyphenylalanine), there are two additional regioisomers, namely meta -tyrosine (also known as 3-hydroxyphenylalanine , L- m -tyrosine , and m -tyr) and ortho -tyrosine ( o -tyr or 2-hydroxyphenylalanine), that occur in nature. The m -tyr and o -tyr isomers, which are rare, arise through non-enzymatic free-radical hydroxylation of phenylalanine under conditions of oxidative stress . [ 27 ] [ 28 ]
Tyrosine is a precursor to neurotransmitters and increases plasma neurotransmitter levels (particularly dopamine and norepinephrine), [ 29 ] but has little if any effect on mood in normal subjects. [ 30 ] [ 31 ] [ 32 ]
A 2015 systematic review found that "tyrosine loading acutely counteracts decrements in working memory and information processing that are induced by demanding situational conditions such as extreme weather or cognitive load " and therefore "tyrosine may benefit healthy individuals exposed to demanding situational conditions". [ 33 ]
L -Tyrosine is used in pharmaceuticals , dietary supplements , and food additives . Two methods were formerly used to manufacture L -tyrosine. The first involves the extraction of the desired amino acid from protein hydrolysates using a chemical approach. The second utilizes enzymatic synthesis from phenolics, pyruvate, and ammonia through the use of tyrosine phenol-lyase . [ 34 ] Advances in genetic engineering and the advent of industrial fermentation have shifted the synthesis of L-tyrosine to the use of engineered strains of E. coli . [ 35 ] [ 34 ] | https://en.wikipedia.org/wiki/NH2CH(CH2C6H4OH)COOH |
14.11 g/L at 25 °C 21.87 g/L at 50 °C 37.08 g/L at 75 °C 68.9 g/L at 100 °C
Phenylalanine (symbol Phe or F ) [ 3 ] is an essential α- amino acid with the formula C 9 H 11 NO 2 . It can be viewed as a benzyl group substituted for the methyl group of alanine , or a phenyl group in place of a terminal hydrogen of alanine. This essential amino acid is classified as neutral, and nonpolar because of the inert and hydrophobic nature of the benzyl side chain. The L -isomer is used to biochemically form proteins coded for by DNA . Phenylalanine is a precursor for tyrosine , the monoamine neurotransmitters dopamine , norepinephrine (noradrenaline), and epinephrine (adrenaline), and the biological pigment melanin . It is encoded by the messenger RNA codons UUU and UUC.
Phenylalanine is found naturally in the milk of mammals . It is used in the manufacture of food and drink products and sold as a nutritional supplement as it is a direct precursor to the neuromodulator phenethylamine . As an essential amino acid, phenylalanine is not synthesized de novo in humans and other animals, who must ingest phenylalanine or phenylalanine-containing proteins.
The one-letter symbol F was assigned to phenylalanine for its phonetic similarity. [ 4 ]
The first description of phenylalanine was made in 1879, when Schulze and Barbieri identified a compound with the empirical formula , C 9 H 11 NO 2 , in yellow lupine ( Lupinus luteus ) seedlings. In 1882, Erlenmeyer and Lipp first synthesized phenylalanine from phenylacetaldehyde , hydrogen cyanide , and ammonia . [ 5 ] [ 6 ]
The genetic codon for phenylalanine was first discovered by J. Heinrich Matthaei and Marshall W. Nirenberg in 1961. They showed that by using mRNA to insert multiple uracil repeats into the genome of the bacterium E. coli , they could cause the bacterium to produce a polypeptide consisting solely of repeated phenylalanine amino acids. This discovery helped to establish the nature of the coding relationship that links information stored in genomic nucleic acid with protein expression in the living cell.
Good sources of phenylalanine are eggs, chicken, liver, beef, milk, and soybeans. [ 7 ] Another common source of phenylalanine is anything sweetened with the artificial sweetener aspartame , such as diet drinks , diet foods and medication; the metabolism of aspartame produces phenylalanine as one of the compound's metabolites . [ 8 ]
The Food and Nutrition Board (FNB) of the U.S. Institute of Medicine set Recommended Dietary Allowances (RDAs) for essential amino acids in 2002. For phenylalanine plus tyrosine, for adults 19 years and older, 33 mg/kg body weight/day. [ 9 ] In 2005 the DRI is set to 27 mg/kg per day (with no tyrosine), the FAO / WHO / UNU recommendation of 2007 is 25 mg/kg per day (with no tyrosine). [ 10 ]
L -Phenylalanine is biologically converted into L - tyrosine , another one of the DNA-encoded amino acids. L -tyrosine in turn is converted into L -DOPA , which is further converted into dopamine , norepinephrine (noradrenaline), and epinephrine (adrenaline). The latter three are known as the catecholamines .
Phenylalanine uses the same active transport channel as tryptophan to cross the blood–brain barrier . In excessive quantities, supplementation can interfere with the production of serotonin and other aromatic amino acids [ 11 ] as well as nitric oxide due to the overuse (eventually, limited availability) of the associated cofactors, iron or tetrahydrobiopterin . [ citation needed ] The corresponding enzymes for those compounds are the aromatic amino acid hydroxylase family and nitric oxide synthase .
Phenylalanine is the starting compound used in the synthesis of flavonoids . Lignan is derived from phenylalanine and from tyrosine . Phenylalanine is converted to cinnamic acid by the enzyme phenylalanine ammonia-lyase . [ 15 ]
Phenylalanine is biosynthesized via the shikimate pathway .
The genetic disorder phenylketonuria (PKU) is the inability to metabolize phenylalanine because of a lack of the enzyme phenylalanine hydroxylase . Individuals with this disorder are known as "phenylketonurics" and must regulate their intake of phenylalanine. Phenylketonurics often use blood tests to monitor the amount of phenylalanine in their blood. Lab results may report phenylalanine levels using either mg/dL and μmol/L. One mg/dL of phenylalanine is approximately equivalent to 60 μmol/L.
A (rare) "variant form" of phenylketonuria called hyperphenylalaninemia is caused by the inability to synthesize a cofactor called tetrahydrobiopterin , which can be supplemented. Pregnant women with hyperphenylalaninemia may show similar symptoms of the disorder (high levels of phenylalanine in blood), but these indicators will usually disappear at the end of gestation. Pregnant women with PKU must control their blood phenylalanine levels even if the fetus is heterozygous for the defective gene because the fetus could be adversely affected due to hepatic immaturity. [ medical citation needed ]
A non-food source of phenylalanine is the artificial sweetener aspartame . This compound is metabolized by the body into several chemical byproducts including phenylalanine. The breakdown problems phenylketonurics have with the buildup of phenylalanine in the body also occurs with the ingestion of aspartame, although to a lesser degree. Accordingly, all products in Australia, the U.S. and Canada that contain aspartame must be labeled: "Phenylketonurics: Contains phenylalanine." In the UK, foods containing aspartame must carry ingredient panels that refer to the presence of "aspartame or E951" [ 16 ] and they must be labeled with a warning "Contains a source of phenylalanine." In Brazil, the label "Contém Fenilalanina" (Portuguese for "Contains Phenylalanine") is also mandatory in products which contain it. These warnings are placed to help individuals avoid such foods.
The stereoisomer D -phenylalanine (DPA) can be produced by conventional organic synthesis , either as a single enantiomer or as a component of the racemic mixture. It does not participate in protein biosynthesis although it is found in proteins in small amounts - particularly aged proteins and food proteins that have been processed . The biological functions of D -amino acids remain unclear, although D -phenylalanine has pharmacological activity at niacin receptor 2 . [ 17 ]
DL -Phenylalanine (DLPA) is marketed as a nutritional supplement for its purported analgesic and antidepressant activities, which have been supported by clinical trials. [ 18 ] [ 19 ] [ 20 ] DL -Phenylalanine is a mixture of D -phenylalanine and L -phenylalanine. The reputed analgesic activity of DL -phenylalanine may be explained by the possible blockage by D -phenylalanine of enkephalin degradation by the enzyme carboxypeptidase A . [ 21 ] [ 22 ] Enkephalins act as agonists of the mu and delta opioid receptors , and agonists of these receptors are known to produce antidepressant effects. [ 23 ] The mechanism of DL -phenylalanine's supposed antidepressant activity may also be accounted for in part by the precursor role of L -phenylalanine in the synthesis of the neurotransmitters norepinephrine and dopamine , though clinical trials have not found an antidepressant effect from L -phenylalanine alone. [ 18 ] Elevated brain levels of norepinephrine and dopamine are thought to have an antidepressant effect. D -Phenylalanine is absorbed from the small intestine and transported to the liver via the portal circulation . A small amount of D -phenylalanine appears to be converted to L -phenylalanine. D -Phenylalanine is distributed to the various tissues of the body via the systemic circulation . It appears to cross the blood–brain barrier less efficiently than L -phenylalanine, and so a small amount of an ingested dose of D -phenylalanine is excreted in the urine without penetrating the central nervous system. [ 24 ]
L -Phenylalanine is an antagonist at α 2 δ Ca 2+ calcium channels with a K i of 980 nM. [ 25 ]
In the brain, L -phenylalanine is a competitive antagonist at the glycine binding site of NMDA receptor [ 26 ] and at the glutamate binding site of AMPA receptor . [ 27 ] At the glycine binding site of NMDA receptor L -phenylalanine has an apparent equilibrium dissociation constant (K B ) of 573 μM estimated by Schild regression [ 28 ] which is considerably lower than brain L -phenylalanine concentration observed in untreated human phenylketonuria . [ 29 ] L -Phenylalanine also inhibits neurotransmitter release at glutamatergic synapses in hippocampus and cortex with IC 50 of 980 μM, a brain concentration seen in classical phenylketonuria , whereas D -phenylalanine has a significantly smaller effect. [ 27 ]
L -Phenylalanine is produced for medical, feed, and nutritional applications, such as aspartame , in large quantities by utilizing the bacterium Escherichia coli , which naturally produces aromatic amino acids like phenylalanine. The quantity of L -phenylalanine produced commercially has been increased by genetically engineering E. coli , such as by altering the regulatory promoters or amplifying the number of genes controlling enzymes responsible for the synthesis of the amino acid. [ 30 ]
Boronophenylalanine (BPA) is a dihydroxyboryl derivative of phenylalanine, used in neutron capture therapy .
4-Azido- L -phenylalanine is a protein-incorporated unnatural amino acid used as a tool for bioconjugation in the field of chemical biology . | https://en.wikipedia.org/wiki/NH2CH(CH2C6H5)COOH |
Glutamine (symbol Gln or Q ) [ 3 ] is an α-amino acid that is used in the biosynthesis of proteins . Its side chain is similar to that of glutamic acid , except the carboxylic acid group is replaced by an amide . It is classified as a charge-neutral, polar amino acid. It is non-essential and conditionally essential in humans, meaning the body can usually synthesize sufficient amounts of it, but in some instances of stress, the body's demand for glutamine increases, and glutamine must be obtained from the diet. [ 4 ] [ 5 ] It is encoded by the codons CAA and CAG. It is named after glutamic acid, which in turn is named after its discovery in cereal proteins, gluten . [ 6 ]
In human blood , glutamine is the most abundant free amino acid . [ 7 ]
The dietary sources of glutamine include especially the protein-rich foods like beef , chicken , fish , dairy products , eggs , vegetables like beans , beets , cabbage , spinach , carrots , parsley , vegetable juices and also in wheat , papaya , Brussels sprouts , celery , kale and fermented foods like miso .
The one-letter symbol Q for glutamine was assigned in alphabetical sequence to N for asparagine , being larger by merely one methylene –CH2– group. Note that P was used for proline, and O was avoided due to similarity with D. The mnemonic Q lutamine was also proposed. [ 6 ]
Glutamine plays a role in a variety of biochemical functions:
Glutamine maintains redox balance by participating in glutathione synthesis and contributing to anabolic processes such as lipid synthesis by reductive carboxylation. [ 14 ]
Glutamine provides a source of carbon and nitrogen for use in other metabolic processes. Glutamine is present in serum at higher concentrations than other amino acids [ 15 ] and is essential for many cellular functions. Examples include the synthesis of nucleotides and non-essential amino acids . [ 16 ] One of the most important functions of glutamine is its ability to be converted into α-KG, which helps to maintain the flow of the tricarboxylic acid cycle, generating ATP via the electron carriers NADH and FADH 2 . [ 17 ] The highest consumption of glutamine occurs in the cells of the intestines, [ 7 ] kidney cells (where it is used for acid-base balance), activated immune cells, [ 18 ] and many cancer cells. [ 8 ] [ 11 ] [ 19 ]
Glutamine is produced industrially using mutants of Brevibacterium flavum , which gives ca. 40 g/L in 2 days using glucose as a carbon source. [ 20 ]
Glutamine synthesis from glutamate and ammonia is catalyzed by the enzyme glutamine synthetase . The majority of glutamine production occurs in muscle tissue, accounting for about 90% of all glutamine synthesized. Glutamine is also released, in small amounts, by the lungs and brain. [ 21 ] Although the liver is capable of glutamine synthesis, its role in glutamine metabolism is more regulatory than productive, as the liver takes up glutamine derived from the gut via the hepatic portal system . [ 7 ]
Glutamine is the most abundant naturally occurring, nonessential amino acid in the human body, and one of the few amino acids that can directly cross the blood–brain barrier . [ 7 ] Humans obtain glutamine through catabolism of proteins in foods they eat. [ 22 ] In states where tissue is being built or repaired, like growth of babies, or healing from wounds or severe illness, glutamine becomes conditionally essential . [ 22 ]
In 2017, the U.S. Food and Drug Administration (FDA) approved L -glutamine oral powder, marketed as Endari , to reduce severe complications of sickle cell disease in people aged five years and older with the disorder. [ 1 ]
The safety and efficacy of L-glutamine oral powder were studied in a randomized trial of subjects ages five to 58 years old with sickle cell disease who had two or more painful crises within the 12 months prior to enrollment in the trial. [ 1 ] Subjects were assigned randomly to treatment with L-glutamine oral powder or placebo, and the effect of treatment was evaluated over 48 weeks. [ 1 ] Subjects who were treated with L-glutamine oral powder experienced fewer hospital visits for pain treated with a parenterally administered narcotic or ketorolac (sickle cell crises), on average, compared to subjects who received a placebo (median 3 vs. median 4), fewer hospitalizations for sickle cell pain (median 2 vs. median 3), and fewer days in the hospital (median 6.5 days vs. median 11 days). [ 1 ] Subjects who received L-glutamine oral powder also had fewer occurrences of acute chest syndrome (a life-threatening complication of sickle cell disease) compared with patients who received a placebo (8.6 percent vs. 23.1 percent). [ 1 ]
Common side effects of L-glutamine oral powder include constipation, nausea, headache, abdominal pain, cough, pain in the extremities, back pain and chest pain. [ 1 ]
L-glutamine oral powder received orphan drug designation. [ 1 ] The FDA granted the approval of Endari to Emmaus Medical Inc. [ 1 ]
Glutamine is marketed as medical food and is prescribed when a medical professional believes a person in their care needs supplementary glutamine due to metabolic demands beyond what can be met by endogenous synthesis or diet. [ 23 ]
Glutamine is safe in adults and in preterm infants. [ 24 ] Although glutamine is metabolized to glutamate and ammonia, both of which have neurological effects, their concentrations are not increased much, and no adverse neurological effects were detected. [ 24 ] The observed safe level for supplemental L -glutamine in normal healthy adults is 14 g/day. [ 25 ]
Adverse effects of glutamine have been described for people receiving home parenteral nutrition and those with liver-function abnormalities. [ 26 ] Although glutamine has no effect on the proliferation of tumor cells, it is still possible that glutamine supplementation may be detrimental in some cancer types. [ 27 ]
Ceasing glutamine supplementation in people adapted to very high consumption may initiate a withdrawal effect, raising the risk of health problems such as infections or impaired integrity of the intestine. [ 27 ]
Glutamine can exist in either of two enantiomeric forms, L -glutamine and D -glutamine. The L -form is found in nature. Glutamine contains an α-amino group which is in the protonated −NH 3 + form under biological conditions and a carboxylic acid group which is in the deprotonated −COO − form, known as carboxylate, under physiological conditions.
Glutamine supplementation was investigated for its possible effects in critically ill people or after abdominal surgery, but the low quality of research prevented conclusions about any effect. [ 29 ] Supplementation does not appear to have an effect in infants with significant stomach or intestinal disorders. [ 30 ] | https://en.wikipedia.org/wiki/NH2CH(CH2CH2CONH2)COOH |
Glutamic acid (symbol Glu or E ; [ 4 ] known as glutamate in its anionic form) is an α- amino acid that is used by almost all living beings in the biosynthesis of proteins . It is a non-essential nutrient for humans, meaning that the human body can synthesize enough for its use. It is also the most abundant excitatory neurotransmitter in the vertebrate nervous system . It serves as the precursor for the synthesis of the inhibitory gamma-aminobutyric acid (GABA) in GABAergic neurons.
Its molecular formula is C 5 H 9 NO 4 . Glutamic acid exists in two optically isomeric forms; the dextrorotatory L -form is usually obtained by hydrolysis of gluten or from the waste waters of beet -sugar manufacture or by fermentation. [ 5 ] [ full citation needed ] Its molecular structure could be idealized as HOOC−CH( NH 2 )−( CH 2 ) 2 −COOH, with two carboxyl groups −COOH and one amino group − NH 2 . However, in the solid state and mildly acidic water solutions, the molecule assumes an electrically neutral zwitterion structure − OOC−CH( NH + 3 )−( CH 2 ) 2 −COOH. It is encoded by the codons GAA or GAG.
The acid can lose one proton from its second carboxyl group to form the conjugate base , the singly-negative anion glutamate − OOC−CH( NH + 3 )−( CH 2 ) 2 −COO − . This form of the compound is prevalent in neutral solutions. The glutamate neurotransmitter plays the principal role in neural activation . [ 6 ] This anion creates the savory umami flavor of foods and is found in glutamate flavorings such as monosodium glutamate (MSG). In Europe, it is classified as food additive E620 . In highly alkaline solutions the doubly negative anion − OOC−CH( NH 2 )−( CH 2 ) 2 −COO − prevails. The radical corresponding to glutamate is called glutamyl .
The one-letter symbol E for glutamate was assigned as the letter following D for aspartate , as glutamate is larger by one methylene –CH 2 – group. [ 7 ]
When glutamic acid is dissolved in water, the amino group (− NH 2 ) may gain a proton ( H + ), and/or the carboxyl groups may lose protons, depending on the acidity of the medium.
In sufficiently acidic environments, both carboxyl groups are protonated and the molecule becomes a cation with a single positive charge, HOOC−CH( NH + 3 )−( CH 2 ) 2 −COOH. [ 8 ]
At pH values between about 2.5 and 4.1, [ 8 ] the carboxylic acid closer to the amine generally loses a proton, and the acid becomes the neutral zwitterion − OOC−CH( NH + 3 )−( CH 2 ) 2 −COOH. This is also the form of the compound in the crystalline solid state. [ 9 ] [ 10 ] The change in protonation state is gradual; the two forms are in equal concentrations at pH 2.10. [ 11 ]
At even higher pH, the other carboxylic acid group loses its proton and the acid exists almost entirely as the glutamate anion − OOC−CH( NH + 3 )−( CH 2 ) 2 −COO − , with a single negative charge overall. The change in protonation state occurs at pH 4.07. [ 11 ] This form with both carboxylates lacking protons is dominant in the physiological pH range (7.35–7.45).
At even higher pH, the amino group loses the extra proton, and the prevalent species is the doubly-negative anion − OOC−CH( NH 2 )−( CH 2 ) 2 −COO − . The change in protonation state occurs at pH 9.47. [ 11 ]
Glutamic acid is chiral ; two mirror-image enantiomers exist: d (−), and l (+). The l form is more widely occurring in nature, but the d form occurs in some special contexts, such as the bacterial capsule and cell walls of the bacteria (which produce it from the l form with the enzyme glutamate racemase ) and the liver of mammals . [ 12 ] [ 13 ]
Although they occur naturally in many foods, the flavor contributions made by glutamic acid and other amino acids were only scientifically identified early in the 20th century. The substance was discovered and identified in the year 1866 by the German chemist Karl Heinrich Ritthausen , who treated wheat gluten (for which it was named) with sulfuric acid . [ 14 ] In 1908, Japanese researcher Kikunae Ikeda of the Tokyo Imperial University identified brown crystals left behind after the evaporation of a large amount of kombu broth as glutamic acid. These crystals, when tasted, reproduced the novel flavor he detected in many foods, most especially in seaweed. Professor Ikeda termed this flavor umami . He then patented a method of mass-producing a crystalline salt of glutamic acid, monosodium glutamate. [ 15 ] [ 16 ]
Glutamic acid is produced on the largest scale of any amino acid, with an estimated annual production of about 1.5 million tons in 2006. [ 18 ] Chemical synthesis was supplanted by the aerobic fermentation of sugars and ammonia in the 1950s, with the organism Corynebacterium glutamicum (also known as Brevibacterium flavum ) being the most widely used for production. [ 19 ] Isolation and purification can be achieved by concentration and crystallization ; it is also widely available as its hydrochloride salt. [ 20 ]
Glutamate is a key compound in cellular metabolism . In humans, dietary proteins are broken down by digestion into amino acids , which serve as metabolic fuel for other functional roles in the body. A key process in amino acid degradation is transamination , in which the amino group of an amino acid is transferred to an α- ketoacid , typically catalysed by a transaminase . The reaction can be generalised as such:
A very common α-keto acid is α-ketoglutarate , an intermediate in the citric acid cycle . Transamination of α-ketoglutarate gives glutamate. The resulting α-ketoacid product is often a useful one as well, which can contribute as fuel or as a substrate for further metabolism processes. Examples are as follows:
Both pyruvate and oxaloacetate are key components of cellular metabolism, contributing as substrates or intermediates in fundamental processes such as glycolysis , gluconeogenesis , and the citric acid cycle .
Glutamate also plays an important role in the body's disposal of excess or waste nitrogen . Glutamate undergoes deamination , an oxidative reaction catalysed by glutamate dehydrogenase , [ 17 ] as follows:
Ammonia (as ammonium ) is then excreted predominantly as urea , synthesised in the liver . Transamination can thus be linked to deamination, effectively allowing nitrogen from the amine groups of amino acids to be removed, via glutamate as an intermediate, and finally excreted from the body in the form of urea.
Glutamate is also a neurotransmitter (see below), which makes it one of the most abundant molecules in the brain. Malignant brain tumors known as glioma or glioblastoma exploit this phenomenon by using glutamate as an energy source, especially when these tumors become more dependent on glutamate due to mutations in the gene IDH1 . [ 21 ] [ 22 ]
Glutamate is the most abundant excitatory neurotransmitter in the vertebrate nervous system . [ 23 ] At chemical synapses , glutamate is stored in vesicles . Nerve impulses trigger the release of glutamate from the presynaptic cell. Glutamate acts on ionotropic and metabotropic ( G-protein coupled ) receptors. [ 23 ] In the opposing postsynaptic cell, glutamate receptors , such as the NMDA receptor or the AMPA receptor , bind glutamate and are activated. Because of its role in synaptic plasticity , glutamate is involved in cognitive functions such as learning and memory in the brain. [ 24 ] The form of plasticity known as long-term potentiation takes place at glutamatergic synapses in the hippocampus , neocortex , and other parts of the brain. Glutamate works not only as a point-to-point transmitter, but also through spill-over synaptic crosstalk between synapses in which summation of glutamate released from a neighboring synapse creates extrasynaptic signaling/ volume transmission . [ 25 ] In addition, glutamate plays important roles in the regulation of growth cones and synaptogenesis during brain development as originally described by Mark Mattson .
Extracellular glutamate in Drosophila brains has been found to regulate postsynaptic glutamate receptor clustering, via a process involving receptor desensitization. [ 26 ] A gene expressed in glial cells actively transports glutamate into the extracellular space , [ 26 ] while, in the nucleus accumbens -stimulating group II metabotropic glutamate receptors , this gene was found to reduce extracellular glutamate levels. [ 27 ] This raises the possibility that this extracellular glutamate plays an "endocrine-like" role as part of a larger homeostatic system.
Glutamate also serves as the precursor for the synthesis of the inhibitory gamma-aminobutyric acid (GABA) in GABA-ergic neurons. This reaction is catalyzed by glutamate decarboxylase (GAD). [ 28 ] GABA-ergic neurons are identified (for research purposes) by revealing its activity (with the autoradiography and immunohistochemistry methods) [ 29 ] which is most abundant in the cerebellum and pancreas . [ 30 ]
Stiff person syndrome is a neurologic disorder caused by anti-GAD antibodies, leading to a decrease in GABA synthesis and, therefore, impaired motor function such as muscle stiffness and spasm. Since the pancreas has abundant GAD, a direct immunological destruction occurs in the pancreas and the patients will have diabetes mellitus . [ 31 ]
Glutamic acid, being a constituent of protein, is present in foods that contain protein, but it can only be tasted when it is present in an unbound form. Significant amounts of free glutamic acid are present in a wide variety of foods, including cheeses and soy sauce , and glutamic acid is responsible for umami , one of the five basic tastes of the human sense of taste . Glutamic acid often is used as a food additive and flavor enhancer in the form of its sodium salt , known as monosodium glutamate (MSG).
All meats, poultry, fish, eggs, dairy products, and kombu are excellent sources of glutamic acid. Some protein-rich plant foods also serve as sources. 30% to 35% of gluten (much of the protein in wheat) is glutamic acid. Ninety-five percent of the dietary glutamate is metabolized by intestinal cells in a first pass. [ 32 ]
Auxigro is a plant growth preparation that contains 30% glutamic acid.
In recent years, [ when? ] there has been much research into the use of residual dipolar coupling (RDC) in nuclear magnetic resonance spectroscopy (NMR). A glutamic acid derivative, poly-γ-benzyl-L-glutamate (PBLG), is often used as an alignment medium to control the scale of the dipolar interactions observed. [ 33 ]
Brain glutamate levels tend to decline with age, and may be a useful as a marker of age-related diseases of the brain. [ 34 ]
The drug phencyclidine (more commonly known as PCP or 'Angel Dust') antagonizes glutamic acid non-competitively at the NMDA receptor . For the same reasons, dextromethorphan and ketamine also have strong dissociative and hallucinogenic effects. Acute infusion of the drug eglumetad (also known as eglumegad or LY354740), an agonist of the metabotropic glutamate receptors 2 and 3 ) resulted in a marked diminution of yohimbine -induced stress response in bonnet macaques ( Macaca radiata ); chronic oral administration of eglumetad in those animals led to markedly reduced baseline cortisol levels (approximately 50 percent) in comparison to untreated control subjects. [ 35 ] Eglumetad has also been demonstrated to act on the metabotropic glutamate receptor 3 (GRM3) of human adrenocortical cells , downregulating aldosterone synthase , CYP11B1 , and the production of adrenal steroids (i.e. aldosterone and cortisol ). [ 36 ] Glutamate does not easily pass the blood brain barrier , but, instead, is transported by a high-affinity transport system. [ 37 ] [ 38 ] It can also be converted into glutamine .
Glutamate toxicity can be reduced by antioxidants , and the psychoactive principle of cannabis , tetrahydrocannabinol (THC), and the non psychoactive principle cannabidiol (CBD), and other cannabinoids , is found to block glutamate neurotoxicity with a similar potency, and thereby potent antioxidants. [ 39 ] [ 40 ] | https://en.wikipedia.org/wiki/NH2CH(CH2CH2COOH)COOH |
Methionine (symbol Met or M ) [ 3 ] ( / m ɪ ˈ θ aɪ ə n iː n / ) [ 4 ] is an essential amino acid in humans.
As the precursor of other non-essential amino acids such as cysteine and taurine , versatile compounds such as SAM-e , and the important antioxidant glutathione , methionine plays a critical role in the metabolism and health of many species, including humans. Methionine is also involved in angiogenesis and various processes related to DNA transcription, epigenetic expression, and gene regulation.
Methionine was first isolated in 1921 by John Howard Mueller . [ 5 ] It is encoded by the codon AUG. It was named by Satoru Odake in 1925, as an abbreviation of its structural description 2-amino-4-( meth ylt hio )butanoic acid. [ 6 ]
Methionine (abbreviated as Met or M ; encoded by the codon AUG) is an α- amino acid that is used in the biosynthesis of proteins . It contains a carboxyl group (which is in the deprotonated −COO − form under biological pH conditions), an amino group (which is in the protonated −NH + 3 form under biological pH conditions) located in α-position with respect to the carboxyl group, and an S -methyl thioether side chain, classifying it as a nonpolar , aliphatic amino acid. [ citation needed ]
In nuclear genes of eukaryotes and in Archaea , methionine is coded for by the start codon , meaning it indicates the start of the coding region and is the first amino acid produced in a nascent polypeptide during mRNA translation . [ 7 ]
Cysteine and methionine are the two sulfur -containing proteinogenic amino acids . Excluding the few exceptions where methionine may act as a redox sensor (e.g., methionine sulfoxide [ 8 ] ), methionine residues do not have a catalytic role. [ 9 ] This is in contrast to cysteine residues, where the thiol group has a catalytic role in many proteins. [ 9 ] The thioether within methionine does however have a minor structural role due to the stability effect of S/π interactions between the side chain sulfur atom and aromatic amino acids in one-third of all known protein structures. [ 9 ] This lack of a strong role is reflected in experiments where little effect is seen in proteins where methionine is replaced by norleucine , a straight hydrocarbon sidechain amino acid which lacks the thioether. [ 10 ] It has been conjectured that norleucine was present in early versions of the genetic code, but methionine intruded into the final version of the genetic code due to the fact it is used in the cofactor S -adenosylmethionine (SAM-e). [ 11 ] This situation is not unique and may have occurred with ornithine and arginine . [ 12 ]
Methionine is one of only two amino acids encoded by a single codon (AUG) in the standard genetic code ( tryptophan , encoded by UGG, is the other). In reflection to the evolutionary origin of its codon, the other AUN codons encode isoleucine , which is also a hydrophobic amino acid. In the mitochondrial genome of several organisms, including metazoa and yeast , the codon AUA also encodes for methionine. In the standard genetic code AUA codes for isoleucine and the respective tRNA ( ileX in Escherichia coli ) uses the unusual base lysidine (bacteria) or agmatidine (archaea) to discriminate against AUG. [ 13 ] [ 14 ]
The methionine codon AUG is also the most common start codon. A "Start" codon is message for a ribosome that signals the initiation of protein translation from mRNA when the AUG codon is in a Kozak consensus sequence . As a consequence, methionine is often incorporated into the N -terminal position of proteins in eukaryotes and archaea during translation, although it can be removed by post-translational modification . In bacteria , the derivative N -formylmethionine is used as the initial amino acid. [ citation needed ]
The methionine-derivative S -adenosylmethionine (SAM-e) is a cofactor that serves mainly as a methyl donor. SAM-e is composed of an adenosyl molecule (via 5′ carbon) attached to the sulfur of methionine, therefore making it a sulfonium cation (i.e., three substituents and positive charge). The sulfur acts as a soft Lewis acid (i.e., donor/electrophile) which allows the S -methyl group to be transferred to an oxygen, nitrogen, or aromatic system, often with the aid of other cofactors such as cobalamin (vitamin B 12 in humans). Some enzymes use SAM-e to initiate a radical reaction; these are called radical SAM-e enzymes.
As a result of the transfer of the methyl group, S -adenosylhomocysteine is obtained. In bacteria, this is either regenerated by methylation or is salvaged by removing the adenine and the homocysteine, leaving the compound dihydroxypentandione to spontaneously convert into autoinducer-2 , which is excreted as a waste product or quorum signal. [ citation needed ]
As an essential amino acid, methionine is not synthesized de novo in humans and other animals, which must ingest methionine or methionine-containing proteins. In plants and microorganisms, methionine biosynthesis belongs to the aspartate family, along with threonine and lysine (via diaminopimelate , but not via α-aminoadipate ). The main backbone is derived from aspartic acid , while the sulfur may come from cysteine , methanethiol , or hydrogen sulfide . [ 9 ]
The pathway using cysteine is called the " transsulfuration pathway ", while the pathway using hydrogen sulfide (or methanethiol) is called "direct-sulfurylation pathway".
Cysteine is similarly produced, namely it can be made from an activated serine and either from homocysteine ("reverse transsulfurylation route") or from hydrogen sulfide ("direct sulfurylation route"); the activated serine is generally O -acetylserine (via CysK or CysM in E. coli ), but in Aeropyrum pernix and some other archaea O -phosphoserine is used. [ 15 ] CysK and CysM are homologues, but belong to the PLP fold type III clade. [ citation needed ]
Enzymes involved in the E. coli transsulfurylation route of methionine biosynthesis: [ citation needed ]
Although mammals cannot synthesize methionine, they can still use it in a variety of biochemical pathways:
Methionine is converted to S -adenosylmethionine (SAM-e) by (1) methionine adenosyltransferase . [ citation needed ]
SAM-e serves as a methyl donor in many (2) methyltransferase reactions, and is converted to S -adenosylhomocysteine (SAH). [ citation needed ]
(3) Adenosylhomocysteinase cysteine.
Methionine can be regenerated from homocysteine via (4) methionine synthase in a reaction that requires vitamin B 12 as a cofactor . [ citation needed ]
Homocysteine can also be remethylated using glycine betaine ( N , N , N -trimethylglycine, TMG) to methionine via the enzyme betaine-homocysteine methyltransferase (E.C.2.1.1.5, BHMT). BHMT makes up to 1.5% of all the soluble protein of the liver, and recent evidence suggests that it may have a greater influence on methionine and homocysteine homeostasis than methionine synthase. [ citation needed ]
Homocysteine can be converted to cysteine.
This amino acid is also used by plants for synthesis of ethylene . The process is known as the Yang cycle or the methionine cycle.
The degradation of methionine is impaired in the following metabolic diseases : [ citation needed ]
The industrial synthesis combines acrolein , methanethiol , and cyanide, which affords the hydantoin . [ 16 ] Racemic methionine can also be synthesized from diethyl sodium phthalimidomalonate by alkylation with chloroethylmethylsulfide (ClCH 2 CH 2 SCH 3 ) followed by hydrolysis and decarboxylation. Also see Methanol. [ 17 ]
There is inconclusive clinical evidence on methionine supplementation. [ 18 ] Dietary restriction of methionine can lead to bone-related disorders. [ 18 ]
Methionine supplementation may benefit those suffering from copper poisoning . [ 19 ]
Overconsumption of methionine, the methyl group donor in DNA methylation , is related to cancer growth in a number of studies. [ 20 ] [ 21 ]
The Food and Nutrition Board of the U.S. Institute of Medicine set Recommended Dietary Allowances (RDAs) for essential amino acids in 2002. For methionine combined with cysteine, for adults 19 years and older, 19 mg/kg body weight/day. [ 22 ]
This translates to about 1.33 grams per day for a 70 kilogram individual. [ citation needed ]
High levels of methionine can be found in eggs, meat, and fish; sesame seeds, Brazil nuts, and some other plant seeds; and cereal grains. Most fruits and vegetables contain very little. Most legumes , though protein dense, are low in methionine. Proteins without adequate methionine are not considered to be complete proteins . [ 23 ] For that reason, racemic methionine is sometimes added as an ingredient to pet foods . [ 24 ]
Loss of methionine has been linked to senile greying of hair. Its lack leads to a buildup of hydrogen peroxide in hair follicles , a reduction in tyrosinase effectiveness, and a gradual loss of hair color. [ 25 ] Methionine raises the intracellular concentration of glutathione , thereby promoting antioxidant-mediated cell defense and redox regulation. It also protects cells against dopamine induced nigral cell loss by binding oxidative metabolites. [ 26 ]
Methionine is an intermediate in the biosynthesis of cysteine , carnitine , taurine , lecithin , phosphatidylcholine , and other phospholipids . Improper conversion of methionine can lead to atherosclerosis [ 27 ] due to accumulation of homocysteine .
DL -Methionine is sometimes given as a supplement to dogs; It helps reduce the chances of kidney stones in dogs. Methionine is also known to increase the urinary excretion of quinidine by acidifying the urine. Aminoglycoside antibiotics used to treat urinary tract infections work best in alkaline conditions, and urinary acidification from using methionine can reduce its effectiveness. If a dog is on a diet that acidifies the urine, methionine should not be used. [ 28 ]
Methionine is allowed as a supplement to organic poultry feed under the US certified organic program. [ 29 ]
Methionine can be used as a nontoxic pesticide option against giant swallowtail caterpillars, which are a serious pest to orange crops. [ 30 ] | https://en.wikipedia.org/wiki/NH2CH(CH2CH2SCH3)COOH |
Asparagine (symbol Asn or N [ 2 ] ) is an α- amino acid that is used in the biosynthesis of proteins . It contains an α-amino group (which is in the protonated −NH + 3 form under biological conditions), an α-carboxylic acid group (which is in the deprotonated −COO − form under biological conditions), and a side chain carboxamide , classifying it as a polar (at physiological pH), aliphatic amino acid. It is non-essential in humans, meaning the body can synthesize it. It is encoded by the codons AAU and AAC.
The one-letter symbol N for asparagine was assigned arbitrarily, [ 3 ] with the proposed mnemonic asparagi N e; [ 4 ]
Asparagine was first isolated in 1806 in a crystalline form by French chemists Louis Nicolas Vauquelin and Pierre Jean Robiquet (then a young assistant). It was isolated from asparagus juice, [ 5 ] [ 6 ] in which it is abundant, hence the chosen name. It was the first amino acid to be isolated. [ 7 ]
Three years later, in 1809, Pierre Jean Robiquet identified a substance from liquorice root with properties which he qualified as very similar to those of asparagine, [ 8 ] and which Plisson identified in 1828 as asparagine itself. [ 9 ] [ 10 ]
The determination of asparagine's structure required decades of research. The empirical formula for asparagine was first determined in 1833 by the French chemists Antoine François Boutron Charlard and Théophile-Jules Pelouze ; in the same year, the German chemist Justus Liebig provided a more accurate formula. [ 11 ] [ 12 ] In 1846 the Italian chemist Raffaele Piria treated asparagine with nitrous acid , which removed the molecule's amine (–NH 2 ) groups and transformed asparagine into malic acid . [ 13 ] This revealed the molecule's fundamental structure: a chain of four carbon atoms. Piria thought that asparagine was a diamide of malic acid; [ 14 ] however, in 1862 the German chemist Hermann Kolbe showed that this surmise was wrong; instead, Kolbe concluded that asparagine was an amide of an amine of succinic acid . [ 15 ] In 1886, the Italian chemist Arnaldo Piutti (1857–1928) discovered a mirror image or " enantiomer " of the natural form of asparagine, which shared many of asparagine's properties, but which also differed from it. [ 16 ] Since the structure of asparagine was still not fully known – the location of the amine group within the molecule was still not settled [ 17 ] – Piutti synthesized asparagine and thus published its true structure in 1888. [ 18 ]
Since the asparagine side-chain can form hydrogen bond interactions with the peptide backbone, asparagine residues are often found near the beginning of alpha-helices as asx turns and asx motifs , and in similar turn motifs, or as amide rings , in beta sheets . Its role can be thought as "capping" the hydrogen bond interactions that would otherwise be satisfied by the polypeptide backbone. [ citation needed ]
Asparagine also provides key sites for N-linked glycosylation , modification of the protein chain with the addition of carbohydrate chains. Typically, a carbohydrate tree can solely be added to an asparagine residue if the latter is flanked on the C side by X- serine or X- threonine , where X is any amino acid with the exception of proline . [ 19 ]
Asparagine can be hydroxylated in the HIF1 hypoxia-inducible transcription factor . This modification inhibits HIF1-mediated gene activation. [ 20 ]
Asparagine is not essential for humans, which means that it can be synthesized from central metabolic pathway intermediates and is not required in the diet. [ citation needed ]
Asparagine is found in:
The precursor to asparagine is oxaloacetate , which a transaminase enzyme converts to aspartate . The enzyme transfers the amino group from glutamate to oxaloacetate producing α-ketoglutarate and aspartate. The enzyme asparagine synthetase produces asparagine, AMP , glutamate, and pyrophosphate from aspartate, glutamine , and ATP . Asparagine synthetase uses ATP to activate aspartate, forming β-aspartyl-AMP. Glutamine donates an ammonium group, which reacts with β-aspartyl-AMP to form asparagine and free AMP. [ 21 ]
In reaction that is the reverse of its biosynthesis, asparagine is hydrolyzed to aspartate by asparaginase . Aspartate then undergoes transamination to form glutamate and oxaloacetate from alpha-ketoglutarate. Oxaloacetate, which enters the citric acid cycle (Krebs cycle). [ 21 ]
Heating a mixture of asparagine and reducing sugars or other source of carbonyls produces acrylamide in food. These products occur in baked goods such as French fries, potato chips, and toasted bread. Acrylamide is converted in the liver to glycidamide , which is a possible carcinogen. [ 22 ]
Asparagine synthetase is required for normal development of the brain. [ 23 ] Asparagine is also involved in protein synthesis during replication of poxviruses . [ 24 ]
The addition of N -acetylglucosamine to asparagine is performed by oligosaccharyltransferase enzymes in the endoplasmic reticulum . [ 25 ] This glycosylation is involved in protein structure [ 26 ] and function. [ 27 ] | https://en.wikipedia.org/wiki/NH2CH(CH2CONH2)COOH |
Aspartic acid (symbol Asp or D ; [ 4 ] the ionic form is known as aspartate ), is an α- amino acid that is used in the biosynthesis of proteins. [ 5 ] The L -isomer of aspartic acid is one of the 22 proteinogenic amino acids , i.e., the building blocks of proteins . D -aspartic acid is one of two D -amino acids commonly found in mammals. [ 6 ] [ 7 ] Apart from a few rare exceptions, D -aspartic acid is not used for protein synthesis but is incorporated into some peptides and plays a role as a neurotransmitter / neuromodulator . [ 6 ]
Like all other amino acids, aspartic acid contains an amino group and a carboxylic acid. Its α-amino group is in the protonated –NH + 3 form under physiological conditions, while its α-carboxylic acid group is deprotonated −COO − under physiological conditions. Aspartic acid has an acidic side chain (CH 2 COOH) which reacts with other amino acids, enzymes and proteins in the body. [ 5 ] Under physiological conditions (pH 7.4) in proteins the side chain usually occurs as the negatively charged aspartate form, −COO − . [ 5 ] It is a non- essential amino acid in humans, meaning the body can synthesize it as needed. It is encoded by the codons GAU and GAC.
In proteins aspartate sidechains are often hydrogen bonded to form asx turns or asx motifs , which frequently occur at the N-termini of alpha helices .
Aspartic acid, like glutamic acid , is classified as an acidic amino acid, with a pK a of 3.9; however, in a peptide this is highly dependent on the local environment, and could be as high as 14.
The one-letter code D for aspartate was assigned arbitrarily, [ 8 ] with the proposed mnemonic aspar D ic acid. [ 9 ]
Aspartic acid was first discovered in 1827 by Auguste-Arthur Plisson and Étienne-Ossian Henry [ 10 ] [ 11 ] by hydrolysis of asparagine , which had been isolated from asparagus juice in 1806. [ 12 ] Their original method used lead hydroxide , but various other acids or bases are now more commonly used instead. [ citation needed ]
There are two forms or enantiomers of aspartic acid. The name "aspartic acid" can refer to either enantiomer or a mixture of two. [ 13 ] Of these two forms, only one, " L -aspartic acid", is directly incorporated into proteins. The biological roles of its counterpart, " D -aspartic acid" are more limited. Where enzymatic synthesis will produce one or the other, most chemical syntheses will produce both forms, " DL -aspartic acid", known as a racemic mixture . [ citation needed ]
In the human body, aspartate is most frequently synthesized through the transamination of oxaloacetate . The biosynthesis of aspartate is facilitated by an aminotransferase enzyme: the transfer of an amine group from another molecule such as alanine or glutamine yields aspartate and an alpha-keto acid. [ 5 ]
Industrially, aspartate is produced by amination of fumarate catalyzed by L- aspartate ammonia-lyase . [ 14 ]
Racemic aspartic acid can be synthesized from diethyl sodium phthalimidomalonate,
(C 6 H 4 (CO) 2 NC(CO 2 Et) 2 ). [ 15 ]
In plants and microorganisms , aspartate is the precursor to several amino acids, including four that are essential for humans: methionine , threonine , isoleucine , and lysine . The conversion of aspartate to these other amino acids begins with reduction of aspartate to its "semialdehyde", O 2 CCH(NH 2 )CH 2 CHO. [ 16 ] Asparagine is derived from aspartate via transamidation:
(where G C(O)NH 2 and G C(O)OH are glutamine and glutamic acid , respectively)
Aspartate has many other biochemical roles. It is a metabolite in the urea cycle [ 17 ] and participates in gluconeogenesis . It carries reducing equivalents in the malate-aspartate shuttle , which utilizes the ready interconversion of aspartate and oxaloacetate , which is the oxidized (dehydrogenated) derivative of malic acid . Aspartate donates one nitrogen atom in the biosynthesis of inosine , the precursor to the purine bases. In addition, aspartic acid acts as a hydrogen acceptor in a chain of ATP synthase. Dietary L-aspartic acid has been shown to act as an inhibitor of Beta-glucuronidase , which serves to regulate enterohepatic circulation of bilirubin and bile acids. [ 18 ]
Click on genes, proteins and metabolites below to link to respective articles. [ § 1 ]
Aspartate (the conjugate base of aspartic acid) stimulates NMDA receptors , though not as strongly as the amino acid neurotransmitter L-glutamate does. [ 19 ] Aspartate is the "A" in NMDA (N-methyl-D- aspartate receptor).
In 2014, the global market for aspartic acid was 39.3 thousand short tons (35.7 thousand tonnes ) [ 20 ] or about $117 million annually. [ 21 ] The three largest market segments include the U.S., Western Europe, and China. Current applications include biodegradable polymers ( polyaspartic acid ), low calorie sweeteners ( aspartame ), scale and corrosion inhibitors, and resins. [ citation needed ]
One area of aspartic acid market growth is biodegradable superabsorbent polymers (SAP), and hydrogels. [ 22 ] Around 75% of superabsorbent polymers are used in disposable diapers and an additional 20% is used for adult incontinence and feminine hygiene products. Polyaspartic acid , the polymerization product of aspartic acid, is a biodegradable substitute to polyacrylate . [ 22 ] [ 23 ] [ 24 ]
In addition to SAP, aspartic acid has applications in the fertilizer industry , where polyaspartate improves water retention and nitrogen uptake. [ 25 ]
Aspartic acid is not an essential amino acid , which means that it can be synthesized from central metabolic pathway intermediates in humans, and does not need to be present in the diet. In eukaryotic cells, roughly 1 in 20 amino acids incorporated into a protein is an aspartic acid, [ 26 ] and accordingly almost any source of dietary protein will include aspartic acid. Additionally, aspartic acid is found in: | https://en.wikipedia.org/wiki/NH2CH(CH2COOH)COOH |
Serine /ˈsɪəriːn/ (symbol Ser or S ) [ 3 ] [ 4 ] is an α- amino acid that is used in the biosynthesis of proteins. It contains an α- amino group (which is in the protonated − NH + 3 form under biological conditions), a carboxyl group (which is in the deprotonated − COO − form under biological conditions), and a side chain consisting of a hydroxymethyl group, classifying it as a polar amino acid. It can be synthesized in the human body under normal physiological circumstances, making it a nonessential amino acid. It is encoded by the codons UCU, UCC, UCA, UCG, AGU and AGC.
This compound is one of the proteinogenic amino acids . Only the L - stereoisomer appears naturally in proteins. It is not essential to the human diet, since it is synthesized in the body from other metabolites , including glycine . Serine was first obtained from silk protein, a particularly rich source, in 1865 by Emil Cramer. [ 5 ] Its name is derived from the Latin for silk, sericum . Serine's structure was established in 1902. [ 6 ] [ 7 ]
The biosynthesis of serine starts with the oxidation of 3-phosphoglycerate (an intermediate from glycolysis ) to 3-phosphohydroxypyruvate and NADH by phosphoglycerate dehydrogenase ( EC 1.1.1.95 ). Reductive amination (transamination) of this ketone by phosphoserine transaminase ( EC 2.6.1.52 ) yields 3-phosphoserine ( O -phosphoserine) which is hydrolyzed to serine by phosphoserine phosphatase ( EC 3.1.3.3 ). [ 8 ] [ 9 ]
In bacteria such as E. coli these enzymes are encoded by the genes serA (EC 1.1.1.95), serC (EC 2.6.1.52), and serB (EC 3.1.3.3). [ 10 ]
Serine hydroxymethyltransferase (SMHT) also catalyzes the biosynthesis of glycine (retro-aldol cleavage) from serine, transferring the resulting formalddehyde synthon to 5,6,7,8-tetrahydrofolate . However, that reaction is reversible, and will convert excess glycine to serine. [ 11 ] SHMT is a pyridoxal phosphate (PLP) dependent enzyme. [ 8 ]
Industrially, L -serine is produced from glycine and methanol catalyzed by hydroxymethyltransferase . [ 12 ]
Racemic serine can be prepared in the laboratory from methyl acrylate in several steps: [ 13 ]
Hydrogenation of serine gives the diol serinol :
Serine is important in metabolism in that it participates in the biosynthesis of purines and pyrimidines . It is the precursor to several amino acids including glycine and cysteine , as well as tryptophan in bacteria. It is also the precursor to numerous other metabolites, including sphingolipids and folate , which is the principal donor of one-carbon fragments in biosynthesis. [ citation needed ]
D -Serine, synthesized in neurons by serine racemase from L -serine (its enantiomer ), serves as a neuromodulator by coactivating NMDA receptors , making them able to open if they then also bind glutamate . D -serine is a potent agonist at the glycine site (NR1) of canonical diheteromeric NMDA receptors . For the receptor to open, glutamate and either glycine or D -serine must bind to it; in addition a pore blocker must not be bound (e.g. Mg 2+ or Zn 2+ ). [ 14 ] Some research has shown that D -serine is a more potent agonist at the NMDAR glycine site than glycine itself. [ 15 ] [ 16 ] However, D-serine has been shown to work as an antagonist/inverse co-agonist of t -NMDA receptors through the glycine binding site on the GluN3 subunit. [ 17 ] [ 18 ]
D -serine was thought to exist only in bacteria until relatively recently; it was the second D amino acid discovered to naturally exist in humans, present as a signaling molecule in the brain, soon after the discovery of D -aspartate . Had D amino acids been discovered in humans sooner, the glycine site on the NMDA receptor might instead be named the D -serine site. [ 19 ] Apart from central nervous system, D -serine plays a signaling role in peripheral tissues and organs such as cartilage, [ 20 ] kidney, [ 21 ] and corpus cavernosum. [ 22 ]
Pure D -serine is an off-white crystalline powder with a very faint musty aroma. D -Serine is sweet with an additional minor sour taste at medium and high concentrations. [ 23 ]
Serine deficiency disorders are rare defects in the biosynthesis of the amino acid L -serine. At present three disorders have been reported:
These enzyme defects lead to severe neurological symptoms such as congenital microcephaly and severe psychomotor retardation and in addition, in patients with 3-phosphoglycerate dehydrogenase deficiency to intractable seizures. These symptoms respond to a variable degree to treatment with L -serine, sometimes combined with glycine. [ 24 ] [ 25 ] Response to treatment is variable and the long-term and functional outcome is unknown. To provide a basis for improving the understanding of the epidemiology, genotype/phenotype correlation and outcome of these diseases their impact on the quality of life of patients, as well as for evaluating diagnostic and therapeutic strategies a patient registry was established by the noncommercial International Working Group on Neurotransmitter Related Disorders (iNTD). [ 26 ]
Besides disruption of serine biosynthesis, its transport may also become disrupted. One example is spastic tetraplegia, thin corpus callosum, and progressive microcephaly , a disease caused by mutations that affect the function of the neutral amino acid transporter A .
The classification of L -serine as a non-essential amino acid has come to be considered as conditional, since vertebrates such as humans cannot always synthesize optimal quantities over entire lifespans. [ 27 ] Safety of L -serine has been demonstrated in an FDA-approved human phase I clinical trial with Amyotrophic Lateral Sclerosis, ALS , patients (ClinicalTrials.gov identifier: NCT01835782), [ 28 ] [ 29 ] but treatment of ALS symptoms has yet to be shown. A 2011 meta-analysis found adjunctive sarcosine to have a medium effect size for negative and total symptoms of schizophrenia. [ 30 ] There also is evidence that L ‐serine could acquire a therapeutic role in diabetes. [ 31 ]
D -Serine is being studied in rodents as a potential treatment for schizophrenia. [ 32 ] D -Serine also has been described as a potential biomarker for early Alzheimer's disease (AD) diagnosis, due to a relatively high concentration of it in the cerebrospinal fluid of probable AD patients. [ 33 ] D-serine, which is made in the brain, has been shown to work as an antagonist/inverse co-agonist of t -NMDA receptors mitigating neuron loss in an animal model of temporal lobe epilepsy . [ 34 ]
D -Serine has been theorized as a potential treatment for sensorineural hearing disorders such as hearing loss and tinnitus . [ 35 ] | https://en.wikipedia.org/wiki/NH2CH(CH2OH)COOH |
Cysteine ( / ˈ s ɪ s t ɪ iː n / ; [ 5 ] symbol Cys or C [ 6 ] ) is a semiessential [ 7 ] proteinogenic amino acid with the formula HS−CH 2 −CH(NH 2 )−COOH . The thiol side chain in cysteine enables the formation of disulfide bonds , and often participates in enzymatic reactions as a nucleophile . Cysteine is chiral, but both D and L -cysteine are found in nature. L ‑Cysteine is a protein monomer in all biota, and D -cysteine acts as a signaling molecule in mammalian nervous systems. [ 8 ] Cysteine is named after its discovery in urine, which comes from the urinary bladder or cyst, from Greek κύστις kýstis , "bladder". [ 9 ]
The thiol is susceptible to oxidation to give the disulfide derivative cystine , which serves an important structural role in many proteins . In this case, the symbol Cyx is sometimes used. [ 10 ] [ 11 ] The deprotonated form can generally be described by the symbol Cym as well. [ 11 ] [ 10 ]
When used as a food additive, cysteine has the E number E920.
Cysteine is encoded by the codons UGU and UGC.
Like other amino acids (not as a residue of a protein), cysteine exists as a zwitterion . Cysteine has l chirality in the older d / l notation based on homology to d - and l -glyceraldehyde. In the newer R / S system of designating chirality, based on the atomic numbers of atoms near the asymmetric carbon, cysteine (and selenocysteine) have R chirality, because of the presence of sulfur (or selenium) as a second neighbor to the asymmetric carbon atom. The remaining chiral amino acids, having lighter atoms in that position, have S chirality. Replacing sulfur with selenium gives selenocysteine .
Cysteinyl is a residue in high- protein foods. Some foods considered rich in cysteine include poultry, eggs, beef, and whole grains. In high-protein diets, cysteine may be partially responsible for reduced blood pressure and stroke risk. [ 12 ] Although classified as a non essential amino acid , [ 13 ] in rare cases, cysteine may be essential for infants, the elderly, and individuals with certain metabolic diseases or who suffer from malabsorption syndromes . Cysteine can usually be synthesized by the human body under normal physiological conditions if a sufficient quantity of methionine is available.
The majority of l -cysteine is obtained industrially by hydrolysis of animal materials, such as poultry feathers or hog hair. Despite widespread rumor, [ 14 ] human hair is rarely a source material. [ 15 ] Indeed, food additive or cosmetic product manufactures may not legally source from human hair in the European Union. [ 16 ] [ 17 ]
Some animal-originating sources of l -cysteine as a food additive contravene kosher, halal, vegan, or vegetarian diets. [ 14 ] To avoid this problem, synthetic l -cysteine, compliant with Jewish kosher and Muslim halal laws, is also available, albeit at a higher price. [ 18 ] The typical synthetic route involves fermentation with an artificial E. coli strain. [ 19 ]
Alternatively, Evonik (formerly Degussa) introduced a route from substituted thiazolines . [ 20 ] Pseudomonas thiazolinophilum hydrolyzes racemic 2‑amino-Δ 2 ‑thiazoline-4‑carboxylic acid to l ‑cysteine. [ 19 ]
In animals, biosynthesis begins with the amino acid serine . The sulfur is derived from methionine , which is converted to homocysteine through the intermediate S -adenosylmethionine . Cystathionine beta-synthase then combines homocysteine and serine to form the asymmetrical thioether cystathionine . The enzyme cystathionine gamma-lyase converts the cystathionine into cysteine and alpha-ketobutyrate . In plants and bacteria , cysteine biosynthesis also starts from serine, which is converted to O -acetylserine by the enzyme serine transacetylase . The enzyme cysteine synthase , using sulfide sources, converts this ester into cysteine, releasing acetate. [ 21 ]
The cysteine sulfhydryl group is nucleophilic and easily oxidized. The reactivity is enhanced when the thiol is ionized, and cysteine residues in proteins have pK a values close to neutrality, so are often in their reactive thiolate form in the cell. [ 22 ] Because of its high reactivity, the sulfhydryl group of cysteine has numerous biological functions.
Due to the ability of thiols to undergo redox reactions, cysteine and cysteinyl residues have antioxidant properties. Its antioxidant properties are typically expressed in the tripeptide glutathione , which occurs in humans and other organisms. The systemic availability of oral glutathione (GSH) is negligible; so it must be biosynthesized from its constituent amino acids, cysteine, glycine , and glutamic acid . While glutamic acid is usually sufficient because amino acid nitrogen is recycled through glutamate as an intermediary, dietary cysteine and glycine supplementation can improve synthesis of glutathione. [ 23 ]
Cysteine is an important source of sulfide in human metabolism . The sulfide in iron-sulfur clusters and in nitrogenase is extracted from cysteine, which is converted to alanine in the process. [ 24 ]
Beyond the iron-sulfur proteins, many other metal cofactors in enzymes are bound to the thiolate substituent of cysteinyl residues. Examples include zinc in zinc fingers and alcohol dehydrogenase , copper in the blue copper proteins , iron in cytochrome P450 , and nickel in the [NiFe]- hydrogenases . [ 25 ] The sulfhydryl group also has a high affinity for heavy metals , so that proteins containing cysteine, such as metallothionein , will bind metals such as mercury, lead, and cadmium tightly. [ 26 ]
In the translation of messenger RNA molecules to produce polypeptides, cysteine is coded for by the UGU and UGC codons .
Cysteine has traditionally been considered to be a hydrophilic amino acid, based largely on the chemical parallel between its sulfhydryl group and the hydroxyl groups in the side chains of other polar amino acids. However, the cysteine side chain has been shown to stabilize hydrophobic interactions in micelles to a greater degree than the side chain in the nonpolar amino acid glycine and the polar amino acid serine. [ 27 ] In a statistical analysis of the frequency with which amino acids appear in various proteins, cysteine residues were found to associate with hydrophobic regions of proteins. Their hydrophobic tendency was equivalent to that of known nonpolar amino acids such as methionine and tyrosine (tyrosine is polar aromatic but also hydrophobic [ 28 ] ), those of which were much greater than that of known polar amino acids such as serine and threonine . [ 29 ] Hydrophobicity scales , which rank amino acids from most hydrophobic to most hydrophilic, consistently place cysteine towards the hydrophobic end of the spectrum, even when they are based on methods that are not influenced by the tendency of cysteines to form disulfide bonds in proteins. Therefore, cysteine is now often grouped among the hydrophobic amino acids, [ 30 ] [ 31 ] though it is sometimes also classified as slightly polar, [ 32 ] or polar. [ 7 ]
Most cysteine residues are covalently bonded to other cysteine residues to form disulfide bonds , which play an important role in the folding and stability of some proteins, usually proteins secreted to the extracellular medium. [ 33 ] Since most cellular compartments are reducing environments , disulfide bonds are generally unstable in the cytosol with some exceptions as noted below.
Disulfide bonds in proteins are formed by oxidation of the sulfhydryl group of cysteine residues. The other sulfur-containing amino acid, methionine, cannot form disulfide bonds. More aggressive oxidants convert cysteine to the corresponding sulfinic acid and sulfonic acid . Cysteine residues play a valuable role by crosslinking proteins, which increases the rigidity of proteins and also functions to confer proteolytic resistance (since protein export is a costly process, minimizing its necessity is advantageous). Inside the cell, disulfide bridges between cysteine residues within a polypeptide support the protein's tertiary structure. Insulin is an example of a protein with cystine crosslinking, wherein two separate peptide chains are connected by a pair of disulfide bonds.
Protein disulfide isomerases catalyze the proper formation of disulfide bonds ; the cell transfers dehydroascorbic acid to the endoplasmic reticulum , which oxidizes the environment. In this environment, cysteines are, in general, oxidized to cystine and are no longer functional as a nucleophiles.
Aside from its oxidation to cystine, cysteine participates in numerous post-translational modifications . The nucleophilic sulfhydryl group allows cysteine to conjugate to other groups, e.g., in prenylation . Ubiquitin ligases transfer ubiquitin to its pendant, proteins, and caspases , which engage in proteolysis in the apoptotic cycle. Inteins often function with the help of a catalytic cysteine. These roles are typically limited to the intracellular milieu, where the environment is reducing, and cysteine is not oxidized to cystine.
Cysteine is considered a "newcomer" amino acid, being the 17th amino acid incorporated into the genetic code . [ 34 ] [ 35 ] Similar to other later-added amino acids such as methionine , tyrosine , and tryptophan , cysteine exhibits strong nucleophilic and redox-active properties. [ 36 ] [ 37 ] These properties contribute to the depletion of cysteine from respiratory chain complexes, such as Complexes I and IV , [ 38 ] since reactive oxygen species ( ROS ) produced by the respiratory chain can react with the cysteine residues in these complexes, leading to dysfunctional proteins and potentially contributing to aging. The primary response of a protein to ROS is the oxidation of cysteine and the loss of free thiol groups, [ 39 ] resulting in increased thiyl radicals and associated protein cross-linking. [ 40 ] [ 41 ] In contrast, another sulfur-containing, redox-active amino acid, methionine, does not exhibit these biochemical properties and its content is relatively upregulated in mitochondrially encoded proteins. [ 42 ]
Cysteine, mainly the l - enantiomer , is a precursor in the food, pharmaceutical, and personal-care industries. One of the largest applications is the production of flavors. For example, the reaction of cysteine with sugars in a Maillard reaction yields meat flavors. [ 43 ] l -Cysteine is also used as a processing aid for baking. [ 44 ]
In the field of personal care, cysteine is used for permanent-wave applications, predominantly in Asia. Again, the cysteine is used for breaking up the disulfide bonds in the hair 's keratin .
Cysteine is a very popular target for site-directed labeling experiments to investigate biomolecular structure and dynamics. Maleimides selectively attach to cysteine using a covalent Michael addition . Site-directed spin labeling for EPR or paramagnetic relaxation-enhanced NMR also uses cysteine extensively.
Cysteine has been proposed as a preventive or antidote for some of the negative effects of alcohol, including liver damage and hangover . It counteracts the poisonous effects of acetaldehyde . [ 45 ] It binds to acetaldehyde to form the low-toxicity heterocycle methyl thioproline . [ 46 ]
In a rat study, test animals received an LD 90 dose of acetaldehyde. Those that received cysteine had an 80% survival rate; when both cysteine and thiamine were administered, all animals survived. The control group had a 10% survival rate. [ 47 ]
In 2020 an article was published that suggests L-cysteine might also work in humans. [ 48 ]
N -Acetyl- l -cysteine is a derivative of cysteine wherein an acetyl group is attached to the nitrogen atom. This compound is sold as a dietary supplement, and used as an antidote in cases of acetaminophen overdose. [ 49 ]
Cysteine is required by sheep to produce wool. It is an essential amino acid that is taken in from their feed. As a consequence, during drought conditions, sheep produce less wool; however, transgenic sheep that can make their own cysteine have been developed. [ 50 ]
Being multifunctional, cysteine undergoes a variety of reactions. Much attention has focused on protecting the sulfhydryl group. [ 51 ] Methylation of cysteine gives S-methylcysteine . Treatment with formaldehyde gives the thiazolidine thioproline . With phosgene and related carbonylating agents, cysteine gives procysteine .
Cysteine forms a variety of coordination complexes upon treatment with metal ions. [ 52 ] This coordination behavior is seen in many metal-cysteine metalloenzymes.
Relative to most other amino acids, cysteine is much more toxic. [ 53 ]
In 1884 German chemist Eugen Baumann found that reduction of cystine with zinc gave monomer , which he named "cysteïne". [ 54 ] The easy redox interconversion of cysteine and cystine has "provided more puzzles to protein chemists than any of the other amino acids. [ 55 ] | https://en.wikipedia.org/wiki/NH2CH(CH2SH)COOH |
Alanine (symbol Ala or A ), [ 4 ] or α-alanine , is an α- amino acid that is used in the biosynthesis of proteins . It contains an amine group and a carboxylic acid group , both attached to the central carbon atom which also carries a methyl group side chain. Consequently it is classified as a non-polar , aliphatic α-amino acid. Under biological conditions, it exists in its zwitterionic form with its amine group protonated (as −NH + 3 ) and its carboxyl group deprotonated (as −CO − 2 ). It is non-essential to humans as it can be synthesized metabolically and does not need to be present in the diet. It is encoded by all codons starting with G C (GC U , GCC, GC A , and GCG).
The L - isomer of alanine ( left-handed ) is the one that is incorporated into proteins. L -alanine is second only to L -leucine in rate of occurrence, accounting for 7.8% of the primary structure in a sample of 1,150 proteins . [ 5 ] The right-handed form, D -alanine, occurs in peptides in some bacterial cell walls [ 6 ] : 131 (in peptidoglycan ) and in some peptide antibiotics , and occurs in the tissues of many crustaceans and molluscs as an osmolyte . [ 7 ]
Alanine was first synthesized in 1850 when Adolph Strecker combined acetaldehyde and ammonia with hydrogen cyanide . [ 8 ] [ 9 ] [ 10 ] The amino acid was named Alanin in German, in reference to aldehyde , with the interfix -an- for ease of pronunciation, [ 11 ] the German ending -in used in chemical compounds being analogous to English -ine .
Alanine is an aliphatic amino acid, because the side-chain connected to the α-carbon atom is a methyl group (-CH 3 ). Alanine is the simplest α-amino acid after glycine . The methyl side-chain of alanine is non-reactive and is therefore hardly ever directly involved in protein function. [ 12 ] Alanine is a nonessential amino acid , meaning it can be manufactured by the human body, and does not need to be obtained through the diet. Alanine is found in a wide variety of foods, but is particularly concentrated in meats.
Alanine can be synthesized from pyruvate and branched chain amino acids such as valine , leucine , and isoleucine .
Alanine is produced by reductive amination of pyruvate , a two-step process. In the first step, α-ketoglutarate , ammonia and NADH are converted by glutamate dehydrogenase to glutamate , NAD + and water. In the second step, the amino group of the newly formed glutamate is transferred to pyruvate by an aminotransferase enzyme, regenerating the α-ketoglutarate, and converting the pyruvate to alanine. The net result is that pyruvate and ammonia are converted to alanine, consuming one reducing equivalent . [ 6 ] : 721 Because transamination reactions are readily reversible and pyruvate is present in all cells, alanine can be easily formed and thus has close links to metabolic pathways such as glycolysis , gluconeogenesis , and the citric acid cycle . [ 13 ]
L -Alanine is produced industrially by decarboxylation of L -aspartate by the action of aspartate 4-decarboxylase . Fermentation routes to L -alanine are complicated by alanine racemase . [ 14 ]
Racemic alanine can be prepared by the condensation of acetaldehyde with ammonium chloride in the presence of sodium cyanide by the Strecker reaction , [ 15 ]
or by the ammonolysis of 2-bromopropanoic acid . [ 16 ]
Alanine is broken down by oxidative deamination , the inverse reaction of the reductive amination reaction described above, catalyzed by the same enzymes. The direction of the process is largely controlled by the relative concentration of the substrates and products of the reactions involved. [ 6 ] : 721
Alanine is one of the twenty canonical α-amino acids used as building blocks (monomers) for the ribosome-mediated biosynthesis of proteins. Alanine is believed to be one of the earliest amino acids to be included in the genetic code standard repertoire. [ 17 ] [ 18 ] [ 19 ] [ 20 ] On the basis of this fact the "alanine world" hypothesis was proposed. [ 21 ] This hypothesis explains the evolutionary choice of amino acids in the repertoire of the genetic code from a chemical point of view. In this model the selection of monomers (i.e. amino acids) for ribosomal protein synthesis is rather limited to those alanine derivatives that are suitable for building α-helix or β-sheet secondary structural elements. Dominant secondary structures in life as we know it are α-helices and β-sheets and most canonical amino acids can be regarded as chemical derivatives of alanine. Therefore, most canonical amino acids in proteins can be exchanged with alanine by point mutations while the secondary structure remains intact. The fact that alanine mimics the secondary structure preferences of the majority of the encoded amino acids is practically exploited in alanine scanning mutagenesis. In addition, classical X-ray crystallography often employs the polyalanine-backbone model [ 22 ] to determine three-dimensional structures of proteins using molecular replacement —a model-based phasing method.
In mammals, alanine plays a key role in glucose–alanine cycle between tissues and liver. In muscle and other tissues that degrade amino acids for fuel, amino groups are collected in the form of glutamate by transamination . Glutamate can then transfer its amino group to pyruvate , a product of muscle glycolysis , through the action of alanine aminotransferase , forming alanine and α-ketoglutarate . The alanine enters the bloodstream, and is transported to the liver. The alanine aminotransferase reaction takes place in reverse in the liver, where the regenerated pyruvate is used in gluconeogenesis , forming glucose which returns to the muscles through the circulation system. Glutamate in the liver enters mitochondria and is broken down by glutamate dehydrogenase into α-ketoglutarate and ammonium , which in turn participates in the urea cycle to form urea which is excreted through the kidneys. [ 23 ]
The glucose–alanine cycle enables pyruvate and glutamate to be removed from muscle and safely transported to the liver. Once there, pyruvate is used to regenerate glucose, after which the glucose returns to muscle to be metabolized for energy: this moves the energetic burden of gluconeogenesis to the liver instead of the muscle, and all available ATP in the muscle can be devoted to muscle contraction. [ 23 ] It is a catabolic pathway, and relies upon protein breakdown in the muscle tissue. Whether and to what extent it occurs in non-mammals is unclear. [ 24 ] [ 25 ]
Alterations in the alanine cycle that increase the levels of serum alanine aminotransferase (ALT) are linked to the development of type II diabetes. [ 26 ]
Alanine is useful in loss of function experiments with respect to phosphorylation . Some techniques involve creating a library of genes, each of which has a point mutation at a different position in the area of interest, sometimes even every position in the whole gene: this is called "scanning mutagenesis". The simplest method, and the first to have been used, is so-called alanine scanning , where every position in turn is mutated to alanine. [ 27 ]
Hydrogenation of alanine gives the amino alcohol alaninol , which is a useful chiral building block.
The deamination of an alanine molecule produces the free radical CH 3 C • HCO 2 − . Deamination can be induced in solid or aqueous alanine by radiation that causes homolytic cleavage of the carbon–nitrogen bond. [ 28 ]
This property of alanine is used in dosimetric measurements in radiotherapy . When normal alanine is irradiated, the radiation causes certain alanine molecules to become free radicals, and, as these radicals are stable, the free radical content can later be measured by electron paramagnetic resonance in order to find out how much radiation the alanine was exposed to. [ 29 ] This is considered to be a biologically relevant measure of the amount of radiation damage that living tissue would suffer under the same radiation exposure. [ 29 ] Radiotherapy treatment plans can be delivered in test mode to alanine pellets, which can then be measured to check that the intended pattern of radiation dose is correctly delivered by the treatment system. [ 30 ] | https://en.wikipedia.org/wiki/NH2CH(CH3)COOH |
Glycine (symbol Gly or G ; [ 6 ] / ˈ ɡ l aɪ s iː n / ⓘ ) [ 7 ] is an amino acid that has a single hydrogen atom as its side chain . It is the simplest stable amino acid. Glycine is one of the proteinogenic amino acids . It is encoded by all the codons starting with GG (GGU, GGC, GGA, GGG). [ 8 ] Glycine disrupts the formation of alpha-helices in secondary protein structure . Its small side chain causes it to favor random coils instead. [ 9 ] Glycine is also an inhibitory neurotransmitter [ 10 ] – interference with its release within the spinal cord (such as during a Clostridium tetani infection) can cause spastic paralysis due to uninhibited muscle contraction. [ 11 ]
It is the only achiral proteinogenic amino acid . [ 12 ] It can fit into both hydrophilic and hydrophobic environments, due to its minimal side chain of only one hydrogen atom. [ 13 ]
Glycine was discovered in 1820 by French chemist Henri Braconnot when he hydrolyzed gelatin by boiling it with sulfuric acid . [ 14 ] He originally called it "sugar of gelatin", [ 15 ] [ 16 ] but French chemist Jean-Baptiste Boussingault showed in 1838 that it contained nitrogen. [ 17 ] In 1847 American scientist Eben Norton Horsford , then a student of the German chemist Justus von Liebig , proposed the name "glycocoll"; [ 18 ] [ 19 ] however, the Swedish chemist Berzelius suggested the simpler current name a year later. [ 20 ] [ 21 ] The name comes from the Greek word γλυκύς "sweet tasting" [ 22 ] (which is also related to the prefixes glyco- and gluco- , as in glycoprotein and glucose ). In 1858, the French chemist Auguste Cahours determined that glycine was an amine of acetic acid . [ 23 ]
Although glycine can be isolated from hydrolyzed proteins , this route is not used for industrial production, as it can be manufactured more conveniently by chemical synthesis. [ 24 ] The two main processes are amination of chloroacetic acid with ammonia , giving glycine and hydrochloric acid , [ 25 ] and the Strecker amino acid synthesis , [ 26 ] which is the main synthetic method in the United States and Japan. [ 27 ] About 15 thousand tonnes are produced annually in this way. [ 28 ]
Glycine is also co-generated as an impurity in the synthesis of EDTA , arising from reactions of the ammonia co-product. [ 29 ]
Its acid–base properties are most important. In aqueous solution, glycine is amphoteric : below pH = 2.4, it converts to the ammonium cation called glycinium. Above about pH 9.6, it converts to glycinate.
Glycine functions as a bidentate ligand for many metal ions, forming amino acid complexes . [ 30 ] A typical complex is Cu(glycinate) 2 , i.e. Cu(H 2 NCH 2 CO 2 ) 2 , which exists both in cis and trans isomers. [ 31 ] [ 32 ]
With acid chlorides, glycine converts to the amidocarboxylic acid, such as hippuric acid [ 33 ] and acetylglycine . [ 34 ] With nitrous acid , one obtains glycolic acid ( van Slyke determination ). With methyl iodide , the amine becomes quaternized to give trimethylglycine , a natural product:
Glycine condenses with itself to give peptides, beginning with the formation of glycylglycine : [ 35 ]
Pyrolysis of glycine or glycylglycine gives 2,5-diketopiperazine , the cyclic diamide. [ 36 ]
Glycine forms esters with alcohols . They are often isolated as their hydrochloride , such as glycine methyl ester hydrochloride . Otherwise, the free ester tends to convert to diketopiperazine .
As a bifunctional molecule, glycine reacts with many reagents. These can be classified into N-centered and carboxylate-center reactions.
Glycine is not essential to the human diet , as it is biosynthesized in the body from the amino acid serine , which is in turn derived from 3-phosphoglycerate . In most organisms, the enzyme serine hydroxymethyltransferase catalyses this transformation via the cofactor pyridoxal phosphate : [ 37 ]
In E. coli , antibiotics that target folate depletes the supply of active tetrahydrofolates, halting glycine biosynthesis as a consequence. [ 38 ]
In the liver of vertebrates , glycine synthesis is catalyzed by glycine synthase (also called glycine cleavage enzyme). This conversion is readily reversible : [ 37 ]
In addition to being synthesized from serine, glycine can also be derived from threonine , choline or hydroxyproline via inter-organ metabolism of the liver and kidneys. [ 39 ]
Glycine is degraded via three pathways. The predominant pathway in animals and plants is the reverse of the glycine synthase pathway mentioned above. In this context, the enzyme system involved is usually called the glycine cleavage system : [ 37 ]
In the second pathway, glycine is degraded in two steps. The first step is the reverse of glycine biosynthesis from serine with serine hydroxymethyl transferase. Serine is then converted to pyruvate by serine dehydratase . [ 37 ]
In the third pathway of its degradation, glycine is converted to glyoxylate by D-amino acid oxidase . Glyoxylate is then oxidized by hepatic lactate dehydrogenase to oxalate in an NAD + -dependent reaction. [ 37 ]
The half-life of glycine and its elimination from the body varies significantly based on dose. [ 40 ] In one study, the half-life varied between 0.5 and 4.0 hours. [ 40 ]
The principal function of glycine is it acts as a precursor to proteins . Most proteins incorporate only small quantities of glycine, a notable exception being collagen , which contains about 35% glycine due to its periodically repeated role in the formation of collagen's helix structure in conjunction with hydroxyproline . [ 37 ] [ 41 ] In the genetic code , glycine is coded by all codons starting with GG, namely GGU, GGC, GGA and GGG. [ 8 ]
In higher eukaryotes , δ-aminolevulinic acid , the key precursor to porphyrins , is biosynthesized from glycine and succinyl-CoA by the enzyme ALA synthase . Glycine provides the central C 2 N subunit of all purines . [ 37 ]
Glycine is an inhibitory neurotransmitter in the central nervous system , especially in the spinal cord , brainstem , and retina . When glycine receptors are activated, chloride enters the neuron via ionotropic receptors, causing an inhibitory postsynaptic potential (IPSP). Strychnine is a strong antagonist at ionotropic glycine receptors, whereas bicuculline is a weak one. Glycine is a required co-agonist along with glutamate for NMDA receptors . In contrast to the inhibitory role of glycine in the spinal cord, this behaviour is facilitated at the ( NMDA ) glutamatergic receptors which are excitatory. [ 42 ] The LD 50 of glycine is 7930 mg/kg in rats (oral), [ 43 ] and it usually causes death by hyperexcitability. [ citation needed ]
Glycine conjugation pathway has not been fully investigated. [ 44 ] Glycine is thought to be a hepatic detoxifier of a number endogenous and xenobiotic organic acids. [ 45 ] Bile acids are normally conjugated to glycine in order to increase their solubility in water. [ 46 ]
The human body rapidly clears sodium benzoate by combining it with glycine to form hippuric acid which is then excreted. [ 47 ] The metabolic pathway for this begins with the conversion of benzoate by butyrate-CoA ligase into an intermediate product, benzoyl-CoA , [ 48 ] which is then metabolized by glycine N -acyltransferase into hippuric acid. [ 49 ]
In the US, glycine is typically sold in two grades: United States Pharmacopeia ("USP"), and technical grade. USP grade sales account for approximately 80 to 85 percent of the U.S. market for glycine. If purity greater than the USP standard is needed, for example for intravenous injections, a more expensive pharmaceutical grade glycine can be used. Technical grade glycine, which may or may not meet USP grade standards, is sold at a lower price for use in industrial applications, e.g., as an agent in metal complexing and finishing. [ 50 ]
Glycine is not widely used in foods for its nutritional value, except in infusions. Instead, glycine's role in food chemistry is as a flavorant. It is mildly sweet, and it counters the aftertaste of saccharine . It also has preservative properties, perhaps owing to its complexation to metal ions. Metal glycinate complexes, e.g. copper(II) glycinate are used as supplements for animal feeds. [ 28 ]
As of 1971 [update] , the U.S. Food and Drug Administration "no longer regards glycine and its salts as generally recognized as safe for use in human food", [ 52 ] and only permits food uses of glycine under certain conditions. [ 53 ]
Glycine has been researched for its potential to extend life . [ 54 ] [ 55 ] The proposed mechanisms of this effect are its ability to clear methionine from the body, and activating autophagy . [ 54 ]
Glycine is an intermediate in the synthesis of a variety of chemical products. It is used in the manufacture of the herbicides glyphosate , [ 56 ] iprodione , glyphosine, imiprothrin , and eglinazine. [ 28 ] It is used as an intermediate of antibiotics such as thiamphenicol . [ citation needed ]
Glycine is a significant component of some solutions used in the SDS-PAGE method of protein analysis. It serves as a buffering agent, maintaining pH and preventing sample damage during electrophoresis. [ 57 ] Glycine is also used to remove protein-labeling antibodies from Western blot membranes to enable the probing of numerous proteins of interest from SDS-PAGE gel. This allows more data to be drawn from the same specimen, increasing the reliability of the data, reducing the amount of sample processing, and number of samples required. [ 58 ] This process is known as stripping.
The presence of glycine outside the Earth was confirmed in 2009, based on the analysis of samples that had been taken in 2004 by the NASA spacecraft Stardust from comet Wild 2 and subsequently returned to Earth. Glycine had previously been identified in the Murchison meteorite in 1970. [ 59 ] The discovery of glycine in outer space bolstered the hypothesis of so-called soft-panspermia , which claims that the "building blocks" of life are widespread throughout the universe. [ 60 ] In 2016, detection of glycine within Comet 67P/Churyumov–Gerasimenko by the Rosetta spacecraft was announced. [ 61 ]
The detection of glycine outside the Solar System in the interstellar medium has been debated. [ 62 ]
Glycine is proposed to be defined by early genetic codes. [ 63 ] [ 64 ] [ 65 ] [ 66 ] For example, low complexity regions (in proteins), that may resemble the proto-peptides of the early genetic code are highly enriched in glycine. [ 66 ] | https://en.wikipedia.org/wiki/NH2CH2COOH |
Alanine (symbol Ala or A ), [ 4 ] or α-alanine , is an α- amino acid that is used in the biosynthesis of proteins . It contains an amine group and a carboxylic acid group , both attached to the central carbon atom which also carries a methyl group side chain. Consequently it is classified as a non-polar , aliphatic α-amino acid. Under biological conditions, it exists in its zwitterionic form with its amine group protonated (as −NH + 3 ) and its carboxyl group deprotonated (as −CO − 2 ). It is non-essential to humans as it can be synthesized metabolically and does not need to be present in the diet. It is encoded by all codons starting with G C (GC U , GCC, GC A , and GCG).
The L - isomer of alanine ( left-handed ) is the one that is incorporated into proteins. L -alanine is second only to L -leucine in rate of occurrence, accounting for 7.8% of the primary structure in a sample of 1,150 proteins . [ 5 ] The right-handed form, D -alanine, occurs in peptides in some bacterial cell walls [ 6 ] : 131 (in peptidoglycan ) and in some peptide antibiotics , and occurs in the tissues of many crustaceans and molluscs as an osmolyte . [ 7 ]
Alanine was first synthesized in 1850 when Adolph Strecker combined acetaldehyde and ammonia with hydrogen cyanide . [ 8 ] [ 9 ] [ 10 ] The amino acid was named Alanin in German, in reference to aldehyde , with the interfix -an- for ease of pronunciation, [ 11 ] the German ending -in used in chemical compounds being analogous to English -ine .
Alanine is an aliphatic amino acid, because the side-chain connected to the α-carbon atom is a methyl group (-CH 3 ). Alanine is the simplest α-amino acid after glycine . The methyl side-chain of alanine is non-reactive and is therefore hardly ever directly involved in protein function. [ 12 ] Alanine is a nonessential amino acid , meaning it can be manufactured by the human body, and does not need to be obtained through the diet. Alanine is found in a wide variety of foods, but is particularly concentrated in meats.
Alanine can be synthesized from pyruvate and branched chain amino acids such as valine , leucine , and isoleucine .
Alanine is produced by reductive amination of pyruvate , a two-step process. In the first step, α-ketoglutarate , ammonia and NADH are converted by glutamate dehydrogenase to glutamate , NAD + and water. In the second step, the amino group of the newly formed glutamate is transferred to pyruvate by an aminotransferase enzyme, regenerating the α-ketoglutarate, and converting the pyruvate to alanine. The net result is that pyruvate and ammonia are converted to alanine, consuming one reducing equivalent . [ 6 ] : 721 Because transamination reactions are readily reversible and pyruvate is present in all cells, alanine can be easily formed and thus has close links to metabolic pathways such as glycolysis , gluconeogenesis , and the citric acid cycle . [ 13 ]
L -Alanine is produced industrially by decarboxylation of L -aspartate by the action of aspartate 4-decarboxylase . Fermentation routes to L -alanine are complicated by alanine racemase . [ 14 ]
Racemic alanine can be prepared by the condensation of acetaldehyde with ammonium chloride in the presence of sodium cyanide by the Strecker reaction , [ 15 ]
or by the ammonolysis of 2-bromopropanoic acid . [ 16 ]
Alanine is broken down by oxidative deamination , the inverse reaction of the reductive amination reaction described above, catalyzed by the same enzymes. The direction of the process is largely controlled by the relative concentration of the substrates and products of the reactions involved. [ 6 ] : 721
Alanine is one of the twenty canonical α-amino acids used as building blocks (monomers) for the ribosome-mediated biosynthesis of proteins. Alanine is believed to be one of the earliest amino acids to be included in the genetic code standard repertoire. [ 17 ] [ 18 ] [ 19 ] [ 20 ] On the basis of this fact the "alanine world" hypothesis was proposed. [ 21 ] This hypothesis explains the evolutionary choice of amino acids in the repertoire of the genetic code from a chemical point of view. In this model the selection of monomers (i.e. amino acids) for ribosomal protein synthesis is rather limited to those alanine derivatives that are suitable for building α-helix or β-sheet secondary structural elements. Dominant secondary structures in life as we know it are α-helices and β-sheets and most canonical amino acids can be regarded as chemical derivatives of alanine. Therefore, most canonical amino acids in proteins can be exchanged with alanine by point mutations while the secondary structure remains intact. The fact that alanine mimics the secondary structure preferences of the majority of the encoded amino acids is practically exploited in alanine scanning mutagenesis. In addition, classical X-ray crystallography often employs the polyalanine-backbone model [ 22 ] to determine three-dimensional structures of proteins using molecular replacement —a model-based phasing method.
In mammals, alanine plays a key role in glucose–alanine cycle between tissues and liver. In muscle and other tissues that degrade amino acids for fuel, amino groups are collected in the form of glutamate by transamination . Glutamate can then transfer its amino group to pyruvate , a product of muscle glycolysis , through the action of alanine aminotransferase , forming alanine and α-ketoglutarate . The alanine enters the bloodstream, and is transported to the liver. The alanine aminotransferase reaction takes place in reverse in the liver, where the regenerated pyruvate is used in gluconeogenesis , forming glucose which returns to the muscles through the circulation system. Glutamate in the liver enters mitochondria and is broken down by glutamate dehydrogenase into α-ketoglutarate and ammonium , which in turn participates in the urea cycle to form urea which is excreted through the kidneys. [ 23 ]
The glucose–alanine cycle enables pyruvate and glutamate to be removed from muscle and safely transported to the liver. Once there, pyruvate is used to regenerate glucose, after which the glucose returns to muscle to be metabolized for energy: this moves the energetic burden of gluconeogenesis to the liver instead of the muscle, and all available ATP in the muscle can be devoted to muscle contraction. [ 23 ] It is a catabolic pathway, and relies upon protein breakdown in the muscle tissue. Whether and to what extent it occurs in non-mammals is unclear. [ 24 ] [ 25 ]
Alterations in the alanine cycle that increase the levels of serum alanine aminotransferase (ALT) are linked to the development of type II diabetes. [ 26 ]
Alanine is useful in loss of function experiments with respect to phosphorylation . Some techniques involve creating a library of genes, each of which has a point mutation at a different position in the area of interest, sometimes even every position in the whole gene: this is called "scanning mutagenesis". The simplest method, and the first to have been used, is so-called alanine scanning , where every position in turn is mutated to alanine. [ 27 ]
Hydrogenation of alanine gives the amino alcohol alaninol , which is a useful chiral building block.
The deamination of an alanine molecule produces the free radical CH 3 C • HCO 2 − . Deamination can be induced in solid or aqueous alanine by radiation that causes homolytic cleavage of the carbon–nitrogen bond. [ 28 ]
This property of alanine is used in dosimetric measurements in radiotherapy . When normal alanine is irradiated, the radiation causes certain alanine molecules to become free radicals, and, as these radicals are stable, the free radical content can later be measured by electron paramagnetic resonance in order to find out how much radiation the alanine was exposed to. [ 29 ] This is considered to be a biologically relevant measure of the amount of radiation damage that living tissue would suffer under the same radiation exposure. [ 29 ] Radiotherapy treatment plans can be delivered in test mode to alanine pellets, which can then be measured to check that the intended pattern of radiation dose is correctly delivered by the treatment system. [ 30 ] | https://en.wikipedia.org/wiki/NH2CHCH3COOH |
Formamide is an amide derived from formic acid . It is a colorless liquid which is miscible with water and has an ammonia -like odor. It is chemical feedstock for the manufacture of sulfa drugs and other pharmaceuticals , herbicides and pesticides , and in the manufacture of hydrocyanic acid . It has been used as a softener for paper and fiber. It is a solvent for many ionic compounds . It has also been used as a solvent for resins and plasticizers . [ 4 ] Some astrobiologists suggest that it may be an alternative to water as the main solvent in other forms of life. [ 5 ]
Formamides are compounds of the type RR′NCHO. One important formamide is dimethylformamide , (CH 3 ) 2 NCHO.
In the past, formamide was produced by treating formic acid with ammonia , which produces ammonium formate , which in turn yields formamide upon heating: [ 6 ]
Formamide is also generated by aminolysis of ethyl formate : [ 7 ]
The current industrial process for the manufacture of formamide involves the carbonylation of ammonia: [ 4 ]
An alternative two-stage process involves the ammonolysis of methyl formate , which is formed from carbon monoxide and methanol :
Formamide is used in the industrial production of hydrogen cyanide . It is also used as a solvent for processing various polymers such as polyacrylonitrile . [ 8 ]
Formamide decomposes into carbon monoxide and ammonia when heated above 100 °C.
The reaction is slow below 160 °C, but accelerates thereafter. At very high temperatures, the reaction products shift to hydrogen cyanide (HCN) and water instead:
The same effect occurs in the presence of solid acid catalysts. [ 8 ]
Formamide is a constituent of cryoprotectant vitrification mixtures used for cryopreservation of tissues and organs .
Formamide is also used as an RNA stabiliser in gel electrophoresis by deionizing RNA. In capillary electrophoresis, it is used for stabilizing (single) strands of denatured DNA.
Another use is to add it in sol-gel solutions in order to avoid cracking during sintering .
Formamide, in its pure state, has been used as an alternative solvent for the electrostatic self-assembly of polymer nanofilms. [ 9 ]
Formamide is used to prepare primary amines directly from ketones via their N-formyl derivatives, using the Leuckart reaction .
Formamides are intermediates in the methanogenesis cycle.
Formamide has been proposed as an alternative solvent to water, perhaps with the ability to support life with alternative biochemistries to that currently found on Earth. It forms by the hydrolysis of hydrogen cyanide. With a large dipole moment, its solvation properties are similar to those of water. [ 11 ]
Formamide has been shown to convert to traces of guanine upon heating in the presence of ultraviolet light. [ 12 ]
Several prebiotic chemical reactions producing amino acid derivatives have been shown to take place in formamide. [ 13 ]
Contact with skin and eyes is not recommended. With an LD50 of grams per kg, formamide is of low acute toxicity. It also has low mutagenicity. [ 8 ]
Formamide is classified as toxic to reproductive health. [ 14 ] | https://en.wikipedia.org/wiki/NH2CHO |
50 g/L ethanol ~4 g/L acetonitrile [ 4 ]
Urea , also called carbamide (because it is a diamide of carbonic acid ), is an organic compound with chemical formula CO(NH 2 ) 2 . This amide has two amino groups (– NH 2 ) joined by a carbonyl functional group (–C(=O)–). It is thus the simplest amide of carbamic acid . [ 6 ]
Urea serves an important role in the cellular metabolism of nitrogen -containing compounds by animals and is the main nitrogen-containing substance in the urine of mammals . Urea is Neo-Latin , from French urée , from Ancient Greek οὖρον ( oûron ) ' urine ' , itself from Proto-Indo-European *h₂worsom .
It is a colorless, odorless solid, highly soluble in water, and practically non-toxic ( LD 50 is 15 g/kg for rats). [ 7 ] Dissolved in water, it is neither acidic nor alkaline . The body uses it in many processes, most notably nitrogen excretion . The liver forms it by combining two ammonia molecules ( NH 3 ) with a carbon dioxide ( CO 2 ) molecule in the urea cycle . Urea is widely used in fertilizers as a source of nitrogen (N) and is an important raw material for the chemical industry .
In 1828, Friedrich Wöhler discovered that urea can be produced from inorganic starting materials, which was an important conceptual milestone in chemistry. This showed for the first time that a substance previously known only as a byproduct of life could be synthesized in the laboratory without biological starting materials, thereby contradicting the widely held doctrine of vitalism , which stated that only living organisms could produce the chemicals of life.
The structure of the molecule of urea is O=C(−NH 2 ) 2 . The urea molecule is planar when in a solid crystal because of sp 2 hybridization of the N orbitals. [ 8 ] [ 9 ] It is non-planar with C 2 symmetry when in the gas phase [ 10 ] or in aqueous solution, [ 9 ] with C–N–H and H–N–H bond angles that are intermediate between the trigonal planar angle of 120° and the tetrahedral angle of 109.5°. In solid urea, the oxygen center is engaged in two N–H–O hydrogen bonds . The resulting hydrogen-bond network is probably established at the cost of efficient molecular packing: The structure is quite open, the ribbons forming tunnels with square cross-section. The carbon in urea is described as sp 2 hybridized, the C-N bonds have significant double bond character, and the carbonyl oxygen is relatively basic. Urea's high aqueous solubility reflects its ability to engage in extensive hydrogen bonding with water.
By virtue of its tendency to form porous frameworks, urea has the ability to trap many organic compounds. In these so-called clathrates , the organic "guest" molecules are held in channels formed by interpenetrating helices composed of hydrogen-bonded urea molecules. In this way, urea-clathrates have been well investigated for separations. [ 11 ]
Urea is a weak base, with a p K b of 13.9. [ 5 ] When combined with strong acids, it undergoes protonation at oxygen to form uronium salts. [ 13 ] [ 14 ] It is also a Lewis base , forming metal complexes of the type [M(urea) 6 ] n + . [ 15 ]
Urea reacts with malonic esters to make barbituric acids .
Molten urea decomposes into ammonium cyanate at about 152 °C, and into ammonia and isocyanic acid above 160 °C: [ 16 ]
Heating above 160 °C yields biuret NH 2 CONHCONH 2 and triuret NH 2 CONHCONHCONH 2 via reaction with isocyanic acid: [ 17 ] [ 16 ]
At higher temperatures it converts to a range of condensation products , including cyanuric acid (CNOH) 3 , guanidine HNC(NH 2 ) 2 , and melamine . [ 17 ] [ 16 ]
In aqueous solution, urea slowly equilibrates with ammonium cyanate. This elimination reaction [ 18 ] cogenerates isocyanic acid , which can carbamylate proteins, in particular the N-terminal amino group, the side chain amino of lysine , and to a lesser extent the side chains of arginine and cysteine . [ 19 ] [ 20 ] Each carbamylation event adds 43 daltons to the mass of the protein, which can be observed in protein mass spectrometry . [ 20 ] For this reason, pure urea solutions should be freshly prepared and used, as aged solutions may develop a significant concentration of cyanate (20 mM in 8 M urea). [ 20 ] Dissolving urea in ultrapure water followed by removing ions (i.e. cyanate) with a mixed-bed ion-exchange resin and storing that solution at 4 °C is a recommended preparation procedure. [ 21 ] However, cyanate will build back up to significant levels within a few days. [ 20 ] Alternatively, adding 25–50 mM ammonium chloride to a concentrated urea solution decreases formation of cyanate because of the common ion effect . [ 20 ] [ 22 ]
Urea is readily quantified by a number of different methods, such as the diacetyl monoxime colorimetric method, and the Berthelot reaction (after initial conversion of urea to ammonia via urease). These methods are amenable to high throughput instrumentation, such as automated flow injection analyzers [ 23 ] and 96-well micro-plate spectrophotometers. [ 24 ]
Ureas describes a class of chemical compounds that share the same functional group, a carbonyl group attached to two organic amine residues: R 1 R 2 N−C(=O)−NR 3 R 4 , where R 1 , R 2 , R 3 and R 4 groups are hydrogen (–H), organyl or other groups. Examples include carbamide peroxide , allantoin , and hydantoin . Ureas are closely related to biurets and related in structure to amides , carbamates , carbodiimides , and thiocarbamides .
More than 90% of world industrial production of urea is destined for use as a nitrogen-release fertilizer . [ 17 ] Urea has the highest nitrogen content of all solid nitrogenous fertilizers in common use. Therefore, it has a low transportation cost per unit of nitrogen nutrient . The most common impurity of synthetic urea is biuret , which impairs plant growth. Urea breaks down in the soil to give ammonium ions ( NH + 4 ). The ammonium is taken up by the plant through its roots. In some soils, the ammonium is oxidized by bacteria to give nitrate ( NO − 3 ), which is also a nitrogen-rich plant nutrient. The loss of nitrogenous compounds to the atmosphere and runoff is wasteful and environmentally damaging so urea is sometimes modified to enhance the efficiency of its agricultural use. Techniques to make controlled-release fertilizers that slow the release of nitrogen include the encapsulation of urea in an inert sealant, and conversion of urea into derivatives such as urea-formaldehyde compounds, which degrade into ammonia at a pace matching plants' nutritional requirements.
Urea is a raw material for the manufacture of formaldehyde based resins , such as UF, MUF, and MUPF, used mainly in wood-based panels, for instance, particleboard , fiberboard , OSB, and plywood . [ 25 ]
Urea can be used in a reaction with nitric acid to make urea nitrate , a high explosive that is used industrially and as part of some improvised explosive devices .
Urea is used in Selective Non-Catalytic Reduction (SNCR) and Selective Catalytic Reduction (SCR) reactions to reduce the NO x pollutants in exhaust gases from combustion from diesel , dual fuel, and lean-burn natural gas engines. The BlueTec system, for example, injects a water-based urea solution into the exhaust system. Ammonia ( NH 3 ) produced by the hydrolysis of urea reacts with nitrogen oxides ( NO x ) and is converted into nitrogen gas ( N 2 ) and water within the catalytic converter. The conversion of noxious NO x to innocuous N 2 is described by the following simplified global equation: [ 26 ]
When urea is used, a pre-reaction (hydrolysis) occurs to first convert it to ammonia:
Being a solid highly soluble in water (545 g/L at 25 °C), [ 2 ] urea is much easier and safer to handle and store than the more irritant , caustic and hazardous ammonia ( NH 3 ), so it is the reactant of choice. Trucks and cars using these catalytic converters need to carry a supply of diesel exhaust fluid , also sold as AdBlue , a solution of urea in water.
Urea in concentrations up to 10 M is a powerful protein denaturant as it disrupts the noncovalent bonds in the proteins. This property can be exploited to increase the solubility of some proteins. A mixture of urea and choline chloride is used as a deep eutectic solvent (DES), a substance similar to ionic liquid . When used in a deep eutectic solvent, urea gradually denatures the proteins that are solubilized. [ 27 ]
Urea in concentrations up to 8 M can be used to make fixed brain tissue transparent to visible light while still preserving fluorescent signals from labeled cells. This allows for much deeper imaging of neuronal processes than previously obtainable using conventional one photon or two photon confocal microscopes. [ 28 ]
Urea-containing creams are used as topical dermatological products to promote rehydration of the skin . Urea 40% is indicated for psoriasis , xerosis , onychomycosis , ichthyosis , eczema , keratosis , keratoderma , corns, and calluses . If covered by an occlusive dressing , 40% urea preparations may also be used for nonsurgical debridement of nails . Urea 40% "dissolves the intercellular matrix" [ 29 ] [ 30 ] of the nail plate. Only diseased or dystrophic nails are removed, as there is no effect on healthy portions of the nail. [ 31 ] This drug (as carbamide peroxide ) is also used as an earwax removal aid. [ 32 ]
Urea has also been studied as a diuretic . It was first used by Dr. W. Friedrich in 1892. [ 33 ] In a 2010 study of ICU patients, urea was used to treat euvolemic hyponatremia and was found safe, inexpensive, and simple. [ 34 ]
Like saline , urea has been injected into the uterus to induce abortion , although this method is no longer in widespread use. [ 35 ]
The blood urea nitrogen (BUN) test is a measure of the amount of nitrogen in the blood that comes from urea. It is used as a marker of renal function , though it is inferior to other markers such as creatinine because blood urea levels are influenced by other factors such as diet, dehydration, [ 36 ] and liver function.
Urea has also been studied as an excipient in drug-coated balloon (DCB) coating formulations to enhance local drug delivery to stenotic blood vessels. [ 37 ] [ 38 ] Urea, when used as an excipient in small doses (~3 μg/mm 2 ) to coat DCB surface was found to form crystals that increase drug transfer without adverse toxic effects on vascular endothelial cells . [ 39 ]
Urea labeled with carbon-14 or carbon-13 is used in the urea breath test , which is used to detect the presence of the bacterium Helicobacter pylori ( H. pylori ) in the stomach and duodenum of humans, associated with peptic ulcers . The test detects the characteristic enzyme urease , produced by H. pylori , by a reaction that produces ammonia from urea. This increases the pH (reduces the acidity) of the stomach environment around the bacteria. Similar bacteria species to H. pylori can be identified by the same test in animals such as apes , dogs , and cats (including big cats ).
Amino acids from ingested food (or produced from catabolism of muscle protein) that are used for the synthesis of proteins and other biological substances can be oxidized by the body as an alternative source of energy, yielding urea and carbon dioxide . [ 47 ] The oxidation pathway starts with the removal of the amino group by a transaminase ; the amino group is then fed into the urea cycle . The first step in the conversion of amino acids into metabolic waste in the liver is removal of the alpha-amino nitrogen, which produces ammonia . Because ammonia is toxic, it is excreted immediately by fish, converted into uric acid by birds, and converted into urea by mammals. [ 48 ]
Ammonia ( NH 3 ) is a common byproduct of the metabolism of nitrogenous compounds. Ammonia is smaller, more volatile, and more mobile than urea. If allowed to accumulate, ammonia would raise the pH in cells to toxic levels. Therefore, many organisms convert ammonia to urea, even though this synthesis has a net energy cost. Being practically neutral and highly soluble in water, urea is a safe vehicle for the body to transport and excrete excess nitrogen.
Urea is synthesized in the body of many organisms as part of the urea cycle , either from the oxidation of amino acids or from ammonia . In this cycle, amino groups donated by ammonia and L - aspartate are converted to urea, while L - ornithine , citrulline , L - argininosuccinate , and L - arginine act as intermediates. Urea production occurs in the liver and is regulated by N -acetylglutamate . Urea is then dissolved into the blood (in the reference range of 2.5 to 6.7 mmol/L) and further transported and excreted by the kidney as a component of urine . In addition, a small amount of urea is excreted (along with sodium chloride and water) in sweat .
In water, the amine groups undergo slow displacement by water molecules, producing ammonia, ammonium ions , and bicarbonate ions . For this reason, old, stale urine has a stronger odor than fresh urine.
The cycling of and excretion of urea by the kidneys is a vital part of mammalian metabolism. Besides its role as carrier of waste nitrogen, urea also plays a role in the countercurrent exchange system of the nephrons , that allows for reabsorption of water and critical ions from the excreted urine . Urea is reabsorbed in the inner medullary collecting ducts of the nephrons, [ 49 ] thus raising the osmolarity in the medullary interstitium surrounding the thin descending limb of the loop of Henle , which makes the water reabsorb.
By action of the urea transporter 2 , some of this reabsorbed urea eventually flows back into the thin descending limb of the tubule, [ 50 ] through the collecting ducts, and into the excreted urine. The body uses this mechanism, which is controlled by the antidiuretic hormone , to create hyperosmotic urine — i.e., urine with a higher concentration of dissolved substances than the blood plasma . This mechanism is important to prevent the loss of water, maintain blood pressure , and maintain a suitable concentration of sodium ions in the blood plasma.
The equivalent nitrogen content (in grams ) of urea (in mmol ) can be estimated by the conversion factor 0.028 g/mmol. [ 51 ] Furthermore, 1 gram of nitrogen is roughly equivalent to 6.25 grams of protein , and 1 gram of protein is roughly equivalent to 5 grams of muscle tissue. In situations such as muscle wasting , 1 mmol of excessive urea in the urine (as measured by urine volume in litres multiplied by urea concentration in mmol/L) roughly corresponds to a muscle loss of 0.67 gram.
In aquatic organisms the most common form of nitrogen waste is ammonia, whereas land-dwelling organisms convert the toxic ammonia to either urea or uric acid . Urea is found in the urine of mammals and amphibians , as well as some fish. Birds and saurian reptiles have a different form of nitrogen metabolism that requires less water, and leads to nitrogen excretion in the form of uric acid. Tadpoles excrete ammonia, but shift to urea production during metamorphosis . Despite the generalization above, the urea pathway has been documented not only in mammals and amphibians, but in many other organisms as well, including birds, invertebrates , insects, plants, yeast , fungi , and even microorganisms . [ 52 ]
Urea can be irritating to skin, eyes, and the respiratory tract. Repeated or prolonged contact with urea in fertilizer form on the skin may cause dermatitis . [ 53 ]
High concentrations in the blood can be damaging. Ingestion of low concentrations of urea, such as are found in typical human urine , are not dangerous with additional water ingestion within a reasonable time-frame. Many animals (e.g. camels , rodents or dogs) have a much more concentrated urine which may contain a higher urea amount than normal human urine.
Urea can cause algal blooms to produce toxins, and its presence in the runoff from fertilized land may play a role in the increase of toxic blooms. [ 54 ]
The substance decomposes on heating above melting point, producing toxic gases, and reacts violently with strong oxidants, nitrites, inorganic chlorides, chlorites and perchlorates, causing fire and explosion. [ 55 ]
Urea was first discovered in urine in 1727 by the Dutch scientist Herman Boerhaave , [ 56 ] although this discovery is often attributed to the French chemist Hilaire Rouelle as well as William Cruickshank . [ 57 ]
Boerhaave used the following steps to isolate urea: [ 58 ] [ 59 ]
In 1828, the German chemist Friedrich Wöhler obtained urea artificially by treating silver cyanate with ammonium chloride . [ 60 ] [ 61 ] [ 62 ]
This was the first time an organic compound was artificially synthesized from inorganic starting materials, without the involvement of living organisms. The results of this experiment implicitly discredited vitalism , the theory that the chemicals of living organisms are fundamentally different from those of inanimate matter. This insight was important for the development of organic chemistry . His discovery prompted Wöhler to write triumphantly to Jöns Jakob Berzelius :
I must tell you that I can make urea without the use of kidneys, either man or dog. Ammonium cyanate is urea.
In fact, his second sentence was incorrect. Ammonium cyanate [NH 4 ] + [OCN] − and urea CO(NH 2 ) 2 are two different chemicals with the same empirical formula CON 2 H 4 , which are in chemical equilibrium heavily favoring urea under standard conditions . [ 63 ] Regardless, with his discovery, Wöhler secured a place among the pioneers of organic chemistry.
Uremic frost was first described in 1865 by Harald Hirschsprung , the first Danish pediatrician in 1870 who also described the disease that carries his name in 1886. Uremic frost has become rare since the advent of dialysis . It is the classical pre-dialysis era description of crystallized urea deposits over the skin of patients with prolonged kidney failure and severe uremia. [ 64 ]
Urea was first noticed by Herman Boerhaave in the early 18th century from evaporates of urine. In 1773, Hilaire Rouelle obtained crystals containing urea from human urine by evaporating it and treating it with alcohol in successive filtrations. [ 65 ] This method was aided by Carl Wilhelm Scheele 's discovery that urine treated by concentrated nitric acid precipitated crystals. Antoine François, comte de Fourcroy and Louis Nicolas Vauquelin discovered in 1799 that the nitrated crystals were identical to Rouelle's substance and invented the term "urea." [ 66 ] [ 67 ] Berzelius made further improvements to its purification [ 68 ] and finally William Prout , in 1817, succeeded in obtaining and determining the chemical composition of the pure substance. [ 69 ] In the evolved procedure, urea was precipitated as urea nitrate by adding strong nitric acid to urine. To purify the resulting crystals, they were dissolved in boiling water with charcoal and filtered. After cooling, pure crystals of urea nitrate form. To reconstitute the urea from the nitrate, the crystals are dissolved in warm water, and barium carbonate added. The water is then evaporated and anhydrous alcohol added to extract the urea. This solution is drained off and evaporated, leaving pure urea.
Ureas in the more general sense can be accessed in the laboratory by reaction of phosgene with primary or secondary amines :
These reactions proceed through an isocyanate intermediate. Non-symmetric ureas can be accessed by the reaction of primary or secondary amines with an isocyanate.
Urea can also be produced by heating ammonium cyanate to 60 °C.
In 2020, worldwide production capacity was approximately 180 million tonnes. [ 70 ]
For use in industry, urea is produced from synthetic ammonia and carbon dioxide . As large quantities of carbon dioxide are produced during the ammonia manufacturing process as a byproduct of burning hydrocarbons to generate heat (predominantly natural gas, and less often petroleum derivatives or coal), urea production plants are almost always located adjacent to the site where the ammonia is manufactured.
The basic process, patented in 1922, is called the Bosch–Meiser urea process after its discoverers Carl Bosch and Wilhelm Meiser. [ 71 ] The process consists of two main equilibrium reactions , with incomplete conversion of the reactants. The first is carbamate formation : the fast exothermic reaction of liquid ammonia with gaseous carbon dioxide ( CO 2 ) at high temperature and pressure to form ammonium carbamate ( [NH 4 ] + [NH 2 COO] − ): [ 17 ]
The second is urea conversion : the slower endothermic decomposition of ammonium carbamate into urea and water:
The overall conversion of NH 3 and CO 2 to urea is exothermic, with the reaction heat from the first reaction driving the second. The conditions that favor urea formation (high temperature) have an unfavorable effect on the carbamate formation equilibrium. The process conditions are a compromise: the ill-effect on the first reaction of the high temperature (around 190 °C) needed for the second is compensated for by conducting the process under high pressure (140–175 bar), which favors the first reaction. Although it is necessary to compress gaseous carbon dioxide to this pressure, the ammonia is available from the ammonia production plant in liquid form, which can be pumped into the system much more economically. To allow the slow urea formation reaction time to reach equilibrium, a large reaction space is needed, so the synthesis reactor in a large urea plant tends to be a massive pressure vessel.
Because the urea conversion is incomplete, the urea must be separated from the unconverted reactants, including the ammonium carbamate. Various commercial urea processes are characterized by the conditions under which urea forms and the way that unconverted reactants are further processed.
In early "straight-through" urea plants, reactant recovery (the first step in "recycling") was done by letting down the system pressure to atmospheric to let the carbamate decompose back to ammonia and carbon dioxide. Originally, because it was not economic to recompress the ammonia and carbon dioxide for recycle, the ammonia at least would be used for the manufacture of other products such as ammonium nitrate or ammonium sulfate , and the carbon dioxide was usually wasted. Later process schemes made recycling unused ammonia and carbon dioxide practical. This was accomplished by the "total recycle process", developed in the 1940s to 1960s and now called the "conventional recycle process". It proceeds by depressurizing the reaction solution in stages (first to 18–25 bar and then to 2–5 bar) and passing it at each stage through a steam-heated carbamate decomposer , then recombining the resulting carbon dioxide and ammonia in a falling-film carbamate condenser and pumping the carbamate solution back into the urea reaction vessel. [ 17 ]
The "conventional recycle process" for recovering and reusing the reactants has largely been supplanted by a stripping process, developed in the early 1960s by Stamicarbon in The Netherlands, that operates at or near the full pressure of the reaction vessel. It reduces the complexity of the multi-stage recycle scheme, and it reduces the amount of water recycled in the carbamate solution, which has an adverse effect on the equilibrium in the urea conversion reaction and thus on overall plant efficiency. Effectively all new urea plants use the stripper, and many total recycle urea plants have converted to a stripping process. [ 17 ] [ 73 ]
In the conventional recycle processes, carbamate decomposition is promoted by reducing the overall pressure, which reduces the partial pressure of both ammonia and carbon dioxide, allowing these gasses to be separated from the urea product solution. The stripping process achieves a similar effect without lowering the overall pressure, by suppressing the partial pressure of just one of the reactants in order to promote carbamate decomposition. Instead of feeding carbon dioxide gas directly to the urea synthesis reactor with the ammonia, as in the conventional process, the stripping process first routes the carbon dioxide through the stripper. The stripper is a carbamate decomposer that provides a large amount of gas-liquid contact. This flushes out free ammonia, reducing its partial pressure over the liquid surface and carrying it directly to a carbamate condenser (also under full system pressure). From there, reconstituted ammonium carbamate liquor is passed to the urea production reactor. That eliminates the medium-pressure stage of the conventional recycle process. [ 17 ] [ 73 ]
The three main side reactions that produce impurities have in common that they decompose urea.
Urea hydrolyzes back to ammonium carbamate in the hottest stages of the synthesis plant, especially in the stripper, so residence times in these stages are designed to be short. [ 17 ]
Biuret is formed when two molecules of urea combine with the loss of a molecule of ammonia.
Normally this reaction is suppressed in the synthesis reactor by maintaining an excess of ammonia, but after the stripper, it occurs until the temperature is reduced. [ 17 ] Biuret is undesirable in urea fertilizer because it is toxic to crop plants to varying degrees, [ 74 ] but it is sometimes desirable as a nitrogen source when used in animal feed. [ 75 ]
Isocyanic acid HNCO and ammonia NH 3 results from the thermal decomposition of ammonium cyanate [NH 4 ] + [OCN] − , which is in chemical equilibrium with urea:
This decomposition is at its worst when the urea solution is heated at low pressure, which happens when the solution is concentrated for prilling or granulation (see below). The reaction products mostly volatilize into the overhead vapours, and recombine when these condense to form urea again, which contaminates the process condensate. [ 17 ]
Ammonium carbamate solutions are highly corrosive to metallic construction materials – even to resistant forms of stainless steel – especially in the hottest parts of the synthesis plant such as the stripper. Historically corrosion has been minimized (although not eliminated) by continuous injection of a small amount of oxygen (as air) into the plant to establish and maintain a passive oxide layer on exposed stainless steel surfaces. Highly corrosion resistant materials have been introduced to reduce the need for passivation oxygen, such as specialized duplex stainless steels in the 1990s, and zirconium or zirconium-clad titanium tubing in the 2000s. [ 17 ]
Urea can be produced in solid forms ( prills , granules , pellets or crystals) or as solutions.
For its main use as a fertilizer urea is mostly marketed in solid form, either as prills or granules. Prills are solidified droplets, whose production predates satisfactory urea granulation processes. Prills can be produced more cheaply than granules, but the limited size of prills (up to about 2.1 mm in diameter), their low crushing strength, and the caking or crushing of prills during bulk storage and handling make them inferior to granules. Granules are produced by acretion onto urea seed particles by spraying liquid urea in a succession of layers. Formaldehyde is added during the production of both prills and granules in order to increase crushing strength and suppress caking. Other shaping techniques such as pastillization (depositing uniform-sized liquid droplets onto a cooling conveyor belt) are also used. [ 17 ]
Solutions of urea and ammonium nitrate in water (UAN) are commonly used as a liquid fertilizer. In admixture, the combined solubility of ammonium nitrate and urea is so much higher than that of either component alone that it gives a stable solution with a total nitrogen content (32%) approaching that of solid ammonium nitrate (33.5%), though not, of course, that of urea itself (46%). UAN allows use of ammonium nitrate without the explosion hazard. [ 17 ] UAN accounts for 80% of the liquid fertilizers in the US. [ 76 ] | https://en.wikipedia.org/wiki/NH2CONH2 |
Carbamic acid , which might also be called aminoformic acid or aminocarboxylic acid , [ 2 ] is the chemical compound with the formula H 2 NCOOH . It can be obtained by the reaction of ammonia NH 3 and carbon dioxide CO 2 at very low temperatures, which also yields ammonium carbamate [NH 4 ] + [NH 2 CO 2 ] − . The compound is stable only up to about 250 K (−23 °C); at higher temperatures it decomposes into those two gases. [ 3 ] The solid apparently consists of dimers , with the two molecules connected by hydrogen bonds between the two carboxyl groups –COOH. [ 4 ]
Carbamic acid could be seen as both an amine and carboxylic acid , and therefore an amino acid ; [ 3 ] however, the attachment of the carboxyl group –COOH directly to the nitrogen atom (without any intermediate carbon chain) makes it behave very differently from the amino acids with intermediate carbon chain. ( Glycine NH 2 CH 2 COOH is generally considered to be the simplest amino acid.) The hydroxyl group –OH attached to the carbon also excludes it from the amide class.
The term "carbamic acid" is also used generically for any compounds of the form RR′NCOOH, where R and R′ are organic groups or hydrogen. [ 5 ]
Deprotonation of a carbamic acid yields a carbamate anion RR′NCOO − , the salts of which can be relatively stable. Carbamate is also a term used for esters of carbamic acids, such as methyl carbamate H 2 N−C(=O)−OCH 3 . The carbamoyl functional group RR′N–C(=O)– (often denoted by Cbm ) is the carbamic acid molecule minus the OH part of the carboxyl.
Carbamic acid is a planar molecule. [ 3 ]
The H 2 N− group of carbamic acid, unlike that of most amines, cannot be protonated to an ammonium group H 3 N + − . The zwitterionic form H 3 N + −COO − is very unstable and promptly decomposes into ammonia and carbon dioxide, [ 6 ] yet there is a report of its detection in ices irradiated with high-energy protons . [ 3 ]
Carbamic acid is formally the parent compound of several important families of organic compounds:
Many substituted carbamic acids (RHNCOOH or RR′NCOOH), can be readily synthesized by bubbling carbon dioxide through solutions of the corresponding amine ( RNH 2 or RR′NH, respectively) in an appropriate solvent, such as DMSO or supercritical carbon dioxide. [ 5 ] These carbamic acids are generally unstable at room temperature, reverting to the parent amine and carbon dioxide. [ 7 ]
Unlike carbamic acids, carbamate esters are generally stable at room temperature as a higher state. They are prepared by reaction of carbamoyl chlorides with alcohols, the addition of alcohols to isocyanates , and the reaction of carbonate esters with ammonia. [ 8 ] Methyl carbamate and ethyl carbamate are among the simplest examples and have historically been used in the textile industry, both are now suspected carcinogens. Benzyl carbamate is also known.
The enzyme class carbamate kinase , involved in several metabolic pathways of living organisms, catalyzes the formation of carbamoyl phosphate H 2 N−C(=O)−O−PO 2− 3 :
An important example of an enzyme with this activity is carbamoyl phosphate synthetase , e.g. carbamoyl phosphate synthetase I carrying out the first step of the urea cycle in order to dispose of waste ammonia.
One hemoglobin molecule can carry four molecules of carbon dioxide to the lungs as carbamate groups formed by reaction of CO 2 with four terminal amine groups of the deoxy form . The resulting compound is called carbaminohaemoglobin .
Carbamic acid is an intermediate in the industrial production of urea , which involves the reaction of carbon dioxide and ammonia. [ 9 ]
Some carbamate esters have use as muscle relaxants , including Emylcamate , Phenprobamate , Styramate and other members of ATC code M03BA . These bind to the barbiturate site of the GABA A receptor. [ 10 ]
Several carbamic acid based insecticides have been developed; for example aldicarb , carbaryl , carbofuran . [ 11 ]
An amine functional group −NH 2 can be protected from unwanted reactions by being formed as carbamate ester residue –NHC(=O)–OR. Hydrolysis of the ester bond then produces a carbamic acid –NHC(=O)OH, which then loses carbon dioxide yielding the desired amine. | https://en.wikipedia.org/wiki/NH2COOH |
Hydrazine is an inorganic compound with the chemical formula N 2 H 4 . It is a simple pnictogen hydride , and is a colourless flammable liquid with an ammonia -like odour. Hydrazine is highly hazardous unless handled in solution as, for example, hydrazine hydrate ( N 2 H 4 · x H 2 O ).
Hydrazine is mainly used as a foaming agent in preparing polymer foams , but applications also include its uses as a precursor to pharmaceuticals and agrochemicals , as well as a long-term storable propellant for in- space spacecraft propulsion. Additionally, hydrazine is used in various rocket fuels and to prepare the gas precursors used in airbags . Hydrazine is used within both nuclear and conventional electrical power plant steam cycles as an oxygen scavenger to control concentrations of dissolved oxygen in an effort to reduce corrosion. [ 8 ] As of 2000 [update] , approximately 120,000 tons of hydrazine hydrate (corresponding to a 64% solution of hydrazine in water by weight) were manufactured worldwide per year. [ 9 ]
Hydrazines are a class of organic substances derived by replacing one or more hydrogen atoms in hydrazine by an organic group. [ 9 ]
The name "hydrazine" was coined by Emil Fischer in 1875; he was trying to produce organic compounds that consisted of mono-substituted hydrazine. [ 10 ] By 1887, Theodor Curtius had produced hydrazine sulfate by treating organic diazides with dilute sulfuric acid; however, he was unable to obtain pure hydrazine, despite repeated efforts. [ 11 ] [ 12 ] [ 13 ] Pure anhydrous hydrazine was first prepared by the Dutch chemist Lobry de Bruyn in 1895. [ 14 ] [ 15 ] [ 16 ]
The nomenclature is a bi-valent form, with prefix hydr- used to indicate the presence of hydrogen atoms and suffix beginning with -az- , from azote , the French word for nitrogen .
The largest use of hydrazine is as a precursor to blowing agents . Specific compounds include azodicarbonamide and azobisisobutyronitrile , which produce 100–200 mL of gas per gram of precursor. In a related application, sodium azide , the gas-forming agent in airbags , is produced from hydrazine by reaction with sodium nitrite . [ 9 ]
Hydrazine is also used as a long-term storable propellant on board space vehicles, such as the Dawn mission to Ceres and Vesta, and to both reduce the concentration of dissolved oxygen in and control pH of water used in large industrial boilers. The F-16 fighter jet, [ 17 ] Space Shuttle , and U-2 spy plane use hydrazine to fuel their Emergency Start System in the event of an engine stall. [ 18 ]
Hydrazine is a precursor to several pharmaceuticals and pesticides. Often these applications involve conversion of hydrazine to heterocyclic rings such as pyrazoles and pyridazines . Examples of commercialized bioactive hydrazine derivatives include cefazolin , rizatriptan , anastrozole , fluconazole , metazachlor, metamitron, metribuzin , paclobutrazol , diclobutrazole, propiconazole , hydrazine sulfate , [ 19 ] diimide , triadimefon , [ 9 ] and the diacylhydrazine insecticides.
Hydrazine compounds can be effective as active ingredients in insecticides, miticides, nematicides , fungicides, antiviral agents, attractants, herbicides, or plant growth regulators. [ 20 ]
The Italian catalyst manufacturer Acta (chemical company) has proposed using hydrazine as an alternative to hydrogen in fuel cells . The chief benefit of using hydrazine is that it can produce over 200 m W /cm 2 more than a similar hydrogen cell without requiring (expensive) platinum catalysts. [ 21 ] Because the fuel is liquid at room temperature, it can be handled and stored more easily than hydrogen. By storing the hydrazine in a tank full of a double-bonded carbon - oxygen carbonyl , the fuel reacts and forms a safe solid called hydrazone . By then flushing the tank with warm water, the liquid hydrazine hydrate is released. Hydrazine has a higher electromotive force of 1.56 V compared to 1.23 V for hydrogen. Hydrazine breaks down in the cell to form nitrogen and hydrogen which bonds with oxygen, releasing water. [ 21 ] Hydrazine was used in fuel cells manufactured by Allis-Chalmers Corp. , including some that provided electric power in space satellites in the 1960s.
A mixture of 63% hydrazine, 32% hydrazine nitrate and 5% water is a standard propellant for experimental bulk-loaded liquid propellant artillery . The propellant mixture above is one of the most predictable and stable, with a flat pressure profile during firing. Misfires are usually caused by inadequate ignition. The movement of the shell after a mis-ignition causes a large bubble with a larger ignition surface area, and the greater rate of gas production causes very high pressure, sometimes including catastrophic tube failures (i.e. explosions). [ 22 ] From January–June 1991, the U.S. Army Research Laboratory conducted a review of early bulk-loaded liquid propellant gun programs for possible relevance to the electrothermal chemical propulsion program. [ 22 ]
The United States Air Force (USAF) regularly uses H-70, a 70% hydrazine 30% water mixture, in operations employing the General Dynamics F-16 Fighting Falcon fighter aircraft and the Lockheed U-2 "Dragon Lady" reconnaissance aircraft. The single jet engine F-16 utilizes hydrazine to power its Emergency Power Unit (EPU), which provides emergency electrical and hydraulic power in the event of an engine flame out. The EPU activates automatically, or manually by pilot control, in the event of loss of hydraulic pressure or electrical power in order to provide emergency flight controls. The single jet engine U-2 utilizes hydrazine to power its Emergency Starting System (ESS), which provides a highly reliable method to restart the engine in flight in the event of a stall. [ 23 ]
Hydrazine was first used as a component in rocket fuels during World War II . A 30% mix by weight with 57% methanol (named M-Stoff in the German Luftwaffe ) and 13% water was called C-Stoff by the Germans. [ 24 ] The mixture was used to power the Messerschmitt Me 163B rocket-powered fighter plane, in which the German high test peroxide T-Stoff was used as an oxidizer. Unmixed hydrazine was referred to as B-Stoff by the Germans, a designation also used later for the ethanol/water fuel for the V-2 missile . [ 25 ]
Hydrazine is used as a low-power monopropellant for the maneuvering (RCS/Reaction control system) thrusters of spacecraft, and was used to power the Space Shuttle 's auxiliary power units (APUs). In addition, mono-propellant hydrazine-fueled rocket engines are often used in terminal descent of spacecraft. Such engines were used on the Viking program landers in the 1970s as well as the Mars landers Phoenix (May 2008), Curiosity (August 2012), and Perseverance (February 2021).
During the Soviet space program , unsymmetrical dimethylhydrazine (also discovered by Fischer in 1875) was used instead of hydrazine. Together with nitric oxidizers it became known as " devil's venom " due to its highly dangerous nature. [ 26 ]
In all hydrazine mono-propellant engines, the hydrazine is passed over a catalyst such as iridium metal supported by high-surface-area alumina (aluminium oxide), which causes it to decompose into ammonia ( NH 3 ), nitrogen gas ( N 2 ), and hydrogen ( H 2 ) gas according to the three following reactions: [ 27 ]
The first two reactions are extremely exothermic (the catalyst chamber can reach 800 °C in a matter of milliseconds, [ 28 ] ) and they produce large volumes of hot gas from a small volume of liquid, [ 29 ] making hydrazine a fairly efficient thruster propellant with a vacuum specific impulse of about 220 seconds. [ 30 ] Reaction 2 is the most exothermic, but produces a smaller number of molecules than that of reaction 1. Reaction 3 is endothermic and reverts the effect of reaction 2 back to the same effect as reaction 1 alone (lower temperature, greater number of molecules). The catalyst structure affects the proportion of the NH 3 that is dissociated in reaction 3; a higher temperature is desirable for rocket thrusters, while more molecules are desirable when the reactions are intended to produce greater quantities of gas. [ 31 ]
Since hydrazine is a solid below 2 °C, it is not suitable as a general purpose rocket propellant for military applications. Other variants of hydrazine that are used as rocket fuel are monomethylhydrazine , CH 3 NHNH 2 , also known as MMH (melting point −52 °C), and unsymmetrical dimethylhydrazine , (CH 3 ) 2 NNH 2 , also known as UDMH (melting point −57 °C). These derivatives are used in two-component rocket fuels, often together with dinitrogen tetroxide , N 2 O 4 . A 50:50 mixture by weight of hydrazine and UDMH was used in the engine of the service propulsion system of the Apollo command and service module , both the ascent and descent engines of the Apollo Lunar Module and Titan II ICBMs and is known as Aerozine 50 . [ 24 ] These reactions are extremely exothermic, and the burning is also hypergolic (it starts burning without any external ignition). [ 32 ]
There are ongoing efforts in the aerospace industry to find a replacement for hydrazine, given its potential ban across the European Union. [ 33 ] [ 34 ] [ 35 ] Promising alternatives include nitrous oxide -based propellant combinations, with development being led by commercial companies Dawn Aerospace , Impulse Space , [ 36 ] and Launcher . [ 37 ] The first nitrous oxide-based system ever flown in space was by D-Orbit onboard their ION Satellite Carrier in 2021, using six Dawn Aerospace B20 thrusters. [ 38 ] [ 39 ] Another alternative is more safe blends of hydrazine with much lower vapor pressure , hence reduced inhalation hazard. Aerojet Rocketdyne has developed HPB-G28 blend that have 150 times lower vapor pressure, same specific impulse, and 35% higher density specific impulse than neat hydrazine. HPB-G28 can be used with same thrusters and catalysts as hydrazine, but has freezing point of -55°C, making propellant line heating unnecessary. It contains 65% (by mol) hydrazine, 27% hydroxyethylhydrazinuim nitrate (HEHN) and 8% hydrazinium nitrate . [ 40 ]
Potential routes of hydrazine exposure include dermal, ocular, inhalation and ingestion. [ 41 ]
Hydrazine exposure can cause skin irritation/contact dermatitis and burning, irritation to the eyes/nose/throat, nausea/vomiting, shortness of breath, pulmonary edema, headache, dizziness, central nervous system depression, lethargy, temporary blindness, seizures and coma. Exposure can also cause organ damage to the liver, kidneys and central nervous system. [ 41 ] [ 42 ] Hydrazine is documented as a strong skin sensitizer with potential for cross-sensitization to hydrazine derivatives following initial exposure. [ 43 ] In addition to occupational uses reviewed above, exposure to hydrazine is also possible in small amounts from tobacco smoke. [ 42 ]
The official U.S. guidance on hydrazine as a carcinogen is mixed but generally there is recognition of potential cancer-causing effects. The National Institute for Occupational Safety and Health (NIOSH) lists it as a "potential occupational carcinogen". The National Toxicology Program (NTP) finds it is "reasonably anticipated to be a human carcinogen". The American Conference of Governmental Industrial Hygienists (ACGIH) grades hydrazine as "A3—confirmed animal carcinogen with unknown relevance to humans". The U.S. Environmental Protection Agency (EPA) grades it as "B2—a probable human carcinogen based on animal study evidence". [ 44 ]
The International Agency for Research on Cancer (IARC) rates hydrazine as "2A—probably carcinogenic to humans" with a positive association observed between hydrazine exposure and lung cancer. [ 45 ] Based on cohort and cross-sectional studies of occupational hydrazine exposure, a committee from the National Academies of Sciences , Engineering and Medicine concluded that there is suggestive evidence of an association between hydrazine exposure and lung cancer, with insufficient evidence of association with cancer at other sites. [ 46 ] The European Commission 's Scientific Committee on Occupational Exposure Limits (SCOEL) places hydrazine in carcinogen "group B—a genotoxic carcinogen". The genotoxic mechanism the committee cited references hydrazine's reaction with endogenous formaldehyde and formation of a DNA-methylating agent. [ 47 ]
In the event of a hydrazine exposure-related emergency, NIOSH recommends removing contaminated clothing immediately, washing skin with soap and water, and for eye exposure removing contact lenses and flushing eyes with water for at least 15 minutes. NIOSH also recommends anyone with potential hydrazine exposure to seek medical attention as soon as possible. [ 41 ] There are no specific post-exposure laboratory or medical imaging recommendations, and the medical work-up may depend on the type and severity of symptoms. The World Health Organization (WHO) recommends potential exposures be treated symptomatically with special attention given to potential lung and liver damage. Past cases of hydrazine exposure have documented success with pyridoxine ( vitamin B6 ) treatment. [ 43 ]
The odor threshold for hydrazine is 3.7 ppm, thus if a worker is able to smell an ammonia-like odor then they are likely over the exposure limit. However, this odor threshold varies greatly and should not be used to determine potentially hazardous exposures. [ 48 ]
For aerospace personnel, the United States Air Force uses an emergency exposure guideline, developed by the National Academy of Sciences Committee on Toxicology, which is utilized for non-routine exposures of the general public and is called the Short-Term Public Emergency Exposure Guideline (SPEGL). The SPEGL, which does not apply to occupational exposures, is defined as the acceptable peak concentration for unpredicted, single, short-term emergency exposures of the general public and represents rare exposures in a worker's lifetime. For hydrazine the 1-hour SPEGL is 2 ppm, with a 24-hour SPEGL of 0.08 ppm. [ 49 ]
A complete surveillance programme for hydrazine should include systematic analysis of biologic monitoring, medical screening and morbidity/mortality information. The CDC recommends surveillance summaries and education be provided for supervisors and workers. Pre-placement and periodic medical screening should be conducted with specific focus on potential effects of hydrazine upon functioning of the eyes, skin, liver, kidneys, hematopoietic, nervous and respiratory systems. [ 41 ]
Common controls used for hydrazine include process enclosure, local exhaust ventilation and personal protective equipment (PPE). [ 41 ] Guidelines for hydrazine PPE include non-permeable gloves and clothing, indirect-vent splash resistant goggles, face shield and in some cases a respirator. [ 48 ] The use of respirators for the handling of hydrazine should be the last resort as a method of controlling worker exposure. In cases where respirators are needed, proper respirator selection and a complete respiratory protection program consistent with OSHA guidelines should be implemented. [ 41 ]
For USAF personnel, Air Force Occupational Safety and Health (AFOSH) Standard 48-8, Attachment 8 reviews the considerations for occupational exposure to hydrazine in missile, aircraft and spacecraft systems. Specific guidance for exposure response includes mandatory emergency shower and eyewash stations and a process for decontaminating protective clothing. The guidance also assigns responsibilities and requirements for proper PPE, employee training, medical surveillance and emergency response. [ 49 ] USAF bases requiring the use of hydrazine generally have specific base regulations governing local requirements for safe hydrazine use and emergency response.
Hydrazine, H 2 N−NH 2 , contains two amine groups NH 2 connected by a single bond between the two nitrogen atoms. Each N−NH 2 subunit is pyramidal. The structure of the free molecules was determined by gas electron diffraction and microwave spectroscopy . The N–N single bond length is 1.447(2) Å (144.7(2) pm ), the N-H distance is 1.015(2) Å , the N-N-H angles are 106(2)° and 112(2)°, the H-N-H angle is 107°. [ 50 ] The molecule adopts a gauche conformation with a torsion angle of 91(2)° (dihedral angle between the planes containing the N-N bond and the bisectors of the H-N-H angles). The rotational barrier is twice that of ethane . These structural properties resemble those of gaseous hydrogen peroxide , which adopts a "skewed" anticlinal conformation, and also experiences a strong rotational barrier.
The structure of solid hydrazine was determined by X-ray diffraction. In this phase the N-N bond has a length of 1.46 Å and the nearest non-bonded distances are 3.19, 3.25 and 3.30 Å . [ 51 ]
Diverse synthetic pathways for hydrazine production have been developed. [ 9 ] The key step is the creation of the N –N single bond. The many routes can be divided into those that use chlorine oxidants (and generate salt) and those that do not.
Hydrazine can be synthesized from ammonia and hydrogen peroxide with a ketone catalyst, in a procedure called the Peroxide process (sometimes called Pechiney-Ugine-Kuhlmann process, the Atofina–PCUK cycle, or ketazine process). [ 9 ] The net reaction is: [ 52 ]
In this route, the ketone and ammonia first condense to give the imine , which is oxidised by hydrogen peroxide to the oxaziridine , a three-membered ring containing carbon, oxygen, and nitrogen. Next, the oxaziridine gives the hydrazone by treatment with ammonia , which process creates the nitrogen-nitrogen single bond. This hydrazone condenses with one more equivalent of ketone.
The resulting azine is hydrolyzed to give hydrazine and regenerate the ketone, methyl ethyl ketone :
Unlike most other processes, this approach does not produce a salt as a by-product. [ 53 ]
The Olin Raschig process , first announced in 1907, produces hydrazine from sodium hypochlorite (the active ingredient in many bleaches ) and ammonia without the use of a ketone catalyst. This method relies on the reaction of monochloramine with ammonia to create the N –N single bond as well as a hydrogen chloride byproduct: [ 19 ]
Related to the Raschig process, urea can be oxidized instead of ammonia. Again sodium hypochlorite serves as the oxidant. The net reaction is shown: [ 54 ]
The process generates significant by-products and is mainly practised in Asia. [ 9 ]
The Bayer Ketazine Process is the predecessor to the peroxide process. It employs sodium hypochlorite as oxidant instead of hydrogen peroxide. Like all hypochlorite-based routes, this method produces an equivalent of salt for each equivalent of hydrazine. [ 9 ]
Hydrazine forms a monohydrate N 2 H 4 ·H 2 O that is denser (1.032 g/cm 3 ) than the anhydrous form N 2 H 4 (1.021 g/cm 3 ). Hydrazine has basic ( alkali ) chemical properties comparable to those of ammonia : [ 55 ]
(for ammonia K b = 1.78 × 10 −5 )
It is difficult to diprotonate: [ 56 ]
Exposure to extremely strong bases or alkali metals generates deprotonated hydrazide salts. Most explode on exposure to air or moisture. [ 57 ]
Ideally, the combustion of hydrazine in oxygen produces nitrogen and water:
An excess of oxygen gives oxides of nitrogen, including nitrogen monoxide and nitrogen dioxide :
The heat of combustion of hydrazine in oxygen (air) is 19.41 MJ/kg (8345 BTU/lb). [ 58 ]
Hydrazine is a convenient reductant because the by-products are typically nitrogen gas and water. This property makes it useful as an antioxidant , an oxygen scavenger , and a corrosion inhibitor in water boilers and heating systems. It also directly reduces salts of less active metals (e.g., bismuth, arsenic, copper, mercury, silver, lead, platinum, and palladium) to the element. [ 59 ] That property has commercial application in electroless nickel plating and plutonium extraction from nuclear reactor waste . Some colour photographic processes also use a weak solution of hydrazine as a stabilising wash, as it scavenges dye coupler and unreacted silver halides. Hydrazine is the most common and effective reducing agent used to convert graphene oxide (GO) to reduced graphene oxide (rGO) via hydrothermal treatment. [ 60 ]
Hydrazine can be protonated to form various solid salts of the hydrazinium cation [N 2 H 5 ] + , by treatment with mineral acids. A common salt is hydrazinium hydrogensulfate , [N 2 H 5 ] + [HSO 4 ] − . [ 61 ] Hydrazinium hydrogensulfate was investigated as a treatment of cancer-induced cachexia , but proved ineffective. [ 62 ]
Double protonation gives the hydrazinium dication or hydrazinediium, [N 2 H 6 ] 2+ , of which various salts are known. [ 63 ]
Hydrazines are part of many organic syntheses , often those of practical significance in pharmaceuticals (see applications section), as well as in textile dyes and in photography. [ 9 ]
Hydrazine is used in the Wolff–Kishner reduction , a reaction that transforms the carbonyl group of a ketone into a methylene bridge (or an aldehyde into a methyl group ) via a hydrazone intermediate. Upon the catalysis with transition-metals, the hydrazones are used as organometallic reagent equivalents (HOME chemistry) for C-C bond formations. [ 64 ] The production of the highly stable dinitrogen from the hydrazine derivative helps to drive the reaction.
Being bifunctional, with two amines, hydrazine is a key building block for the preparation of many heterocyclic compounds via condensation with a range of difunctional electrophiles . With 2,4-pentanedione , it condenses to give the 3,5-dimethylpyrazole . [ 65 ] In the Einhorn-Brunner reaction hydrazines react with imides to give triazoles .
Being a good nucleophile, N 2 H 4 can attack sulfonyl halides and acyl halides. [ 66 ] The tosylhydrazine also forms hydrazones upon treatment with carbonyls.
Hydrazine is used to cleave N -alkylated phthalimide derivatives. This scission reaction allows phthalimide anion to be used as amine precursor in the Gabriel synthesis . [ 67 ]
Illustrative of the condensation of hydrazine with a simple carbonyl is its reaction with acetone to give the acetone azine . The latter reacts further with hydrazine to yield acetone hydrazone : [ 68 ]
The propanone azine is an intermediate in the Atofina- PCUK process . Direct alkylation of hydrazines with alkyl halides in the presence of base yields alkyl-substituted hydrazines, but the reaction is typically inefficient due to poor control on level of substitution (same as in ordinary amines ). The reduction of hydrazones to hydrazines present a clean way to produce 1,1-dialkylated hydrazines.
In a related reaction, 2-cyanopyridines react with hydrazine to form amide hydrazides, which can be converted using 1,2-diketones into triazines .
Hydrazine is the intermediate in the anaerobic oxidation of ammonia ( anammox ) process. [ 69 ] It is produced by some yeasts and the open ocean bacterium anammox ( Brocadia anammoxidans ). [ 70 ]
The false morel produces the poison gyromitrin which is an organic derivative of hydrazine that is converted to monomethylhydrazine by metabolic processes. Even the most popular edible "button" mushroom Agaricus bisporus produces organic hydrazine derivatives, including agaritine , a hydrazine derivative of an amino acid, and gyromitrin . [ 71 ] [ 72 ]
In the novel The Martian (which was adapted into a feature film ) the main character uses an iridium catalyst to separate hydrogen gas from surplus hydrazine fuel, which he then burns to generate water for survival. | https://en.wikipedia.org/wiki/NH2NH2 |
Ammonia is an inorganic chemical compound of nitrogen and hydrogen with the formula N H 3 . A stable binary hydride and the simplest pnictogen hydride , ammonia is a colourless gas with a distinctive pungent smell. Biologically, it is a common nitrogenous waste , and it contributes significantly to the nutritional needs of terrestrial organisms by serving as a precursor to fertilisers . [ 13 ] Around 70% of ammonia produced industrially is used to make fertilisers [ 14 ] in various forms and composition, such as urea and diammonium phosphate . Ammonia in pure form is also applied directly into the soil.
Ammonia, either directly or indirectly, is also a building block for the synthesis of many chemicals.
Ammonia occurs in nature and has been detected in the interstellar medium. In many countries, it is classified as an extremely hazardous substance . [ 15 ]
Ammonia is toxic, causing damage to cells and tissues. For this reason it is excreted by most animals in the urine, in the form of dissolved urea.
Ammonia is produced biologically in a process called nitrogen fixation , but even more is generated industrially by the Haber process . The process helped revolutionize agriculture by providing cheap fertilizers. The global industrial production of ammonia in 2021 was 235 million tonnes. [ 16 ] [ 17 ] Industrial ammonia is transported by road in tankers , by rail in tank wagons , by sea in gas carriers , or in cylinders . [ 18 ]
Ammonia boils at −33.34 °C (−28.012 °F) at a pressure of one atmosphere , but the liquid can often be handled in the laboratory without external cooling. Household ammonia or ammonium hydroxide is a solution of ammonia in water.
Pliny , in Book XXXI of his Natural History , refers to a salt named hammoniacum , so called because of the proximity of its source to the Temple of Jupiter Amun ( Greek Ἄμμων Ammon ) in the Roman province of Cyrenaica . [ 19 ] However, the description Pliny gives of the salt does not conform to the properties of ammonium chloride . According to Herbert Hoover 's commentary in his English translation of Georgius Agricola 's De re metallica , it is likely to have been common sea salt. [ 20 ] In any case, that salt ultimately gave ammonia and ammonium compounds their name.
Traces of ammonia/ammonium are found in rainwater. Ammonium chloride ( sal ammoniac ), and ammonium sulfate are found in volcanic districts. Crystals of ammonium bicarbonate have been found in Patagonia guano . [ 21 ]
Ammonia is found throughout the Solar System on Mars , Jupiter , Saturn , Uranus , Neptune , and Pluto , among other places: on smaller, icy bodies such as Pluto, ammonia can act as a geologically important antifreeze, as a mixture of water and ammonia can have a melting point as low as −100 °C (−148 °F; 173 K) if the ammonia concentration is high enough and thus allow such bodies to retain internal oceans and active geology at a far lower temperature than would be possible with water alone. [ 22 ] [ 23 ] Substances containing ammonia, or those that are similar to it, are called ammoniacal . [ 24 ]
Ammonia is a colourless gas with a characteristically pungent smell . It is lighter than air , its density being 0.589 times that of air . It is easily liquefied due to the strong hydrogen bonding between molecules. Gaseous ammonia turns to a colourless liquid , which boils at −33.1 °C (−27.58 °F), and freezes to colourless crystals [ 21 ] at −77.7 °C (−107.86 °F). Little data is available at very high temperatures and pressures, but the liquid-vapor critical point occurs at 405 K and 11.35 MPa. [ 25 ]
The crystal symmetry is cubic, Pearson symbol cP16, space group P2 1 3 No.198, lattice constant 0.5125 nm . [ 26 ]
Liquid ammonia possesses strong ionising powers reflecting its high ε of 22 at −35 °C (−31 °F). [ 27 ] Liquid ammonia has a very high standard enthalpy change of vapourization (23.5 kJ/mol ; [ 28 ] for comparison, water 's is 40.65 kJ/mol, methane 8.19 kJ/mol and phosphine 14.6 kJ/mol) and can be transported in pressurized or refrigerated vessels; however, at standard temperature and pressure liquid anhydrous ammonia will vaporize. [ 29 ]
Ammonia readily dissolves in water. In an aqueous solution, it can be expelled by boiling. The aqueous solution of ammonia is basic , and may be described as aqueous ammonia or ammonium hydroxide . [ 30 ] The maximum concentration of ammonia in water (a saturated solution ) has a specific gravity of 0.880 and is often known as '.880 ammonia'. [ 31 ]
Liquid ammonia is a widely studied nonaqueous ionising solvent. Its most conspicuous property is its ability to dissolve alkali metals to form highly coloured, electrically conductive solutions containing solvated electrons . Apart from these remarkable solutions, much of the chemistry in liquid ammonia can be classified by analogy with related reactions in aqueous solutions . Comparison of the physical properties of NH 3 with those of water shows NH 3 has the lower melting point, boiling point, density, viscosity , dielectric constant and electrical conductivity . These differences are attributed at least in part to the weaker hydrogen bonding in NH 3 . The ionic self- dissociation constant of liquid NH 3 at −50 °C is about 10 −33 .
Liquid ammonia is an ionising solvent, although less so than water, and dissolves a range of ionic compounds, including many nitrates , nitrites , cyanides , thiocyanates , metal cyclopentadienyl complexes and metal bis(trimethylsilyl)amides . [ 32 ] Most ammonium salts are soluble and act as acids in liquid ammonia solutions. The solubility of halide salts increases from fluoride to iodide . A saturated solution of ammonium nitrate ( Divers' solution , named after Edward Divers ) contains 0.83 mol solute per mole of ammonia and has a vapour pressure of less than 1 bar even at 25 °C (77 °F). However, few oxyanion salts with other cations dissolve. [ 34 ]
Liquid ammonia will dissolve all of the alkali metals and other electropositive metals such as Ca , [ 35 ] Sr , Ba , Eu and Yb (also Mg using an electrolytic process [ 33 ] ). At low concentrations (<0.06 mol/L), deep blue solutions are formed: these contain metal cations and solvated electrons , free electrons that are surrounded by a cage of ammonia molecules.
These solutions are strong reducing agents. At higher concentrations, the solutions are metallic in appearance and in electrical conductivity. At low temperatures, the two types of solution can coexist as immiscible phases.
The range of thermodynamic stability of liquid ammonia solutions is very narrow, as the potential for oxidation to dinitrogen, E ° ( N 2 + 6 [NH 4 ] + + 6 e − ⇌ 8 NH 3 ), is only +0.04 V. In practice, both oxidation to dinitrogen and reduction to dihydrogen are slow. This is particularly true of reducing solutions: the solutions of the alkali metals mentioned above are stable for several days, slowly decomposing to the metal amide and dihydrogen. Most studies involving liquid ammonia solutions are done in reducing conditions; although oxidation of liquid ammonia is usually slow, there is still a risk of explosion, particularly if transition metal ions are present as possible catalysts.
The ammonia molecule has a trigonal pyramidal shape, as predicted by the valence shell electron pair repulsion theory (VSEPR theory) with an experimentally determined bond angle of 106.7°. [ 36 ] The central nitrogen atom has five outer electrons with an additional electron from each hydrogen atom. This gives a total of eight electrons, or four electron pairs that are arranged tetrahedrally . Three of these electron pairs are used as bond pairs, which leaves one lone pair of electrons. The lone pair repels more strongly than bond pairs; therefore, the bond angle is not 109.5°, as expected for a regular tetrahedral arrangement, but 106.7°. [ 36 ] This shape gives the molecule a dipole moment and makes it polar . The molecule's polarity, and especially its ability to form hydrogen bonds , makes ammonia highly miscible with water. The lone pair makes ammonia a base , a proton acceptor. Ammonia is moderately basic; a 1.0 M aqueous solution has a pH of 11.6, and if a strong acid is added to such a solution until the solution is neutral ( pH = 7 ), 99.4% of the ammonia molecules are protonated . Temperature and salinity also affect the proportion of ammonium [NH 4 ] + . The latter has the shape of a regular tetrahedron and is isoelectronic with methane .
The ammonia molecule readily undergoes nitrogen inversion at room temperature; a useful analogy is an umbrella turning itself inside out in a strong wind. The energy barrier to this inversion is 24.7 kJ/mol, and the resonance frequency is 23.79 GHz , corresponding to microwave radiation of a wavelength of 1.260 cm. The absorption at this frequency was the first microwave spectrum to be observed [ 37 ] and was used in the first maser .
One of the most characteristic properties of ammonia is its basicity . Ammonia is considered to be a weak base. It combines with acids to form ammonium salts ; thus, with hydrochloric acid it forms ammonium chloride (sal ammoniac); with nitric acid , ammonium nitrate , etc. Perfectly dry ammonia gas will not combine with perfectly dry hydrogen chloride gas; moisture is necessary to bring about the reaction. [ 38 ] [ 39 ]
As a demonstration experiment under air with ambient moisture, opened bottles of concentrated ammonia and hydrochloric acid solutions produce a cloud of ammonium chloride , which seems to appear 'out of nothing' as the salt aerosol forms where the two diffusing clouds of reagents meet between the two bottles.
The salts produced by the action of ammonia on acids are known as the ammonium salts and all contain the ammonium ion ( [NH 4 ] + ). [ 38 ]
Although ammonia is well known as a weak base, it can also act as an extremely weak acid. It is a protic substance and is capable of formation of amides (which contain the NH − 2 ion). For example, lithium dissolves in liquid ammonia to give a blue solution ( solvated electron ) of lithium amide :
Like water, liquid ammonia undergoes molecular autoionisation to form its acid and base conjugates :
Ammonia often functions as a weak base , so it has some buffering ability. Shifts in pH will cause more or fewer ammonium cations ( NH + 4 ) and amide anions ( NH − 2 ) to be present in solution . At standard pressure and temperature,
Ammonia does not burn readily or sustain combustion , except under narrow fuel-to-air mixtures of 15–28% ammonia by volume in air. [ 40 ] When mixed with oxygen , it burns with a pale yellowish-green flame. Ignition occurs when chlorine is passed into ammonia, forming nitrogen and hydrogen chloride ; if chlorine is present in excess, then the highly explosive nitrogen trichloride ( NCl 3 ) is also formed.
The combustion of ammonia to form nitrogen and water is exothermic :
The standard enthalpy change of combustion , Δ H ° c , expressed per mole of ammonia and with condensation of the water formed, is −382.81 kJ/mol. Dinitrogen is the thermodynamic product of combustion : all nitrogen oxides are unstable with respect to N 2 and O 2 , which is the principle behind the catalytic converter . Nitrogen oxides can be formed as kinetic products in the presence of appropriate catalysts , a reaction of great industrial importance in the production of nitric acid :
A subsequent reaction leads to NO 2 :
The combustion of ammonia in air is very difficult in the absence of a catalyst (such as platinum gauze or warm chromium(III) oxide ), due to the relatively low heat of combustion , a lower laminar burning velocity, high auto-ignition temperature , high heat of vapourization , and a narrow flammability range . However, recent studies have shown that efficient and stable combustion of ammonia can be achieved using swirl combustors, thereby rekindling research interest in ammonia as a fuel for thermal power production. [ 41 ] The flammable range of ammonia in dry air is 15.15–27.35% and in 100% relative humidity air is 15.95–26.55%. [ 42 ] [ clarification needed ] For studying the kinetics of ammonia combustion, knowledge of a detailed reliable reaction mechanism is required, but this has been challenging to obtain. [ 43 ]
Ammonia is a direct or indirect precursor to most manufactured nitrogen-containing compounds . It is the precursor to nitric acid, which is the source for most N-substituted aromatic compounds.
Amines can be formed by the reaction of ammonia with alkyl halides or, more commonly, with alcohols :
Its ring-opening reaction with ethylene oxide give ethanolamine , diethanolamine , and triethanolamine .
Amides can be prepared by the reaction of ammonia with carboxylic acid and their derivatives. For example, ammonia reacts with formic acid (HCOOH) to yield formamide ( HCONH 2 ) when heated. Acyl chlorides are the most reactive, but the ammonia must be present in at least a twofold excess to neutralise the hydrogen chloride formed. Esters and anhydrides also react with ammonia to form amides. Ammonium salts of carboxylic acids can be dehydrated to amides by heating to 150–200 °C as long as no thermally sensitive groups are present.
Other organonitrogen compounds include alprazolam , ethanolamine , ethyl carbamate and hexamethylenetetramine .
Nitric acid is generated via the Ostwald process by oxidation of ammonia with air over a platinum catalyst at 700–850 °C (1,292–1,562 °F), ≈9 atm. Nitric oxide and nitrogen dioxide are intermediate in this conversion: [ 44 ]
Nitric acid is used for the production of fertilisers , explosives , and many organonitrogen compounds.
The hydrogen in ammonia is susceptible to replacement by a myriad substituents.
Ammonia gas reacts with metallic sodium to give sodamide , NaNH 2 . [ 38 ]
With chlorine, monochloramine is formed.
Pentavalent ammonia is known as λ 5 -amine, nitrogen pentahydride decomposes spontaneously into trivalent ammonia (λ 3 -amine) and hydrogen gas at normal conditions. This substance was once investigated as a possible solid rocket fuel in 1966. [ 45 ]
Ammonia is also used to make the following compounds:
Ammonia is a ligand forming metal ammine complexes . For historical reasons, ammonia is named ammine in the nomenclature of coordination compounds . One notable ammine complex is cisplatin ( Pt(NH 3 ) 2 Cl 2 , a widely used anticancer drug. Ammine complexes of chromium (III) formed the basis of Alfred Werner 's revolutionary theory on the structure of coordination compounds. Werner noted only two isomers ( fac - and mer -) of the complex [CrCl 3 (NH 3 ) 3 ] could be formed, and concluded the ligands must be arranged around the metal ion at the vertices of an octahedron .
Ammonia forms 1:1 adducts with a variety of Lewis acids such as I 2 , phenol , and Al(CH 3 ) 3 . Ammonia is a hard base (HSAB theory) and its E & C parameters are E B = 2.31 and C B = 2.04. Its relative donor strength toward a series of acids, versus other Lewis bases, can be illustrated by C-B plots .
Ammonia and ammonium salts can be readily detected, in very minute traces, by the addition of Nessler's solution , which gives a distinct yellow colouration in the presence of the slightest trace of ammonia or ammonium salts. The amount of ammonia in ammonium salts can be estimated quantitatively by distillation of the salts with sodium (NaOH) or potassium hydroxide (KOH), the ammonia evolved being absorbed in a known volume of standard sulfuric acid and the excess of acid then determined volumetrically ; or the ammonia may be absorbed in hydrochloric acid and the ammonium chloride so formed precipitated as ammonium hexachloroplatinate , [NH 4 ] 2 [PtCl 6 ] . [ 46 ]
Sulfur sticks are burnt to detect small leaks in industrial ammonia refrigeration systems. Larger quantities can be detected by warming the salts with a caustic alkali or with quicklime , when the characteristic smell of ammonia will be at once apparent. [ 46 ] Ammonia is an irritant and irritation increases with concentration; the permissible exposure limit is 25 ppm , and lethal above 500 ppm by volume. [ 47 ] Higher concentrations are hardly detected by conventional detectors, the type of detector is chosen according to the sensitivity required (e.g. semiconductor, catalytic, electrochemical). Holographic sensors have been proposed for detecting concentrations up to 12.5% in volume. [ 48 ]
In a laboratorial setting, gaseous ammonia can be detected by using concentrated hydrochloric acid or gaseous hydrogen chloride. A dense white fume (which is ammonium chloride vapor) arises from the reaction between ammonia and HCl(g). [ 49 ]
Ammoniacal nitrogen (NH 3 –N) is a measure commonly used for testing the quantity of ammonium ions, derived naturally from ammonia, and returned to ammonia via organic processes, in water or waste liquids. It is a measure used mainly for quantifying values in waste treatment and water purification systems, as well as a measure of the health of natural and man-made water reserves. It is measured in units of mg/L ( milligram per litre ).
The ancient Greek historian Herodotus mentioned that there were outcrops of salt in an area of Libya that was inhabited by a people called the 'Ammonians' (now the Siwa oasis in northwestern Egypt, where salt lakes still exist). [ 50 ] [ 51 ] The Greek geographer Strabo also mentioned the salt from this region. However, the ancient authors Dioscorides , Apicius , Arrian , Synesius , and Aëtius of Amida described this salt as forming clear crystals that could be used for cooking and that were essentially rock salt . [ 52 ] Hammoniacus sal appears in the writings of Pliny , [ 53 ] although it is not known whether the term is equivalent to the more modern sal ammoniac (ammonium chloride). [ 21 ] [ 54 ] [ 55 ]
The fermentation of urine by bacteria produces a solution of ammonia ; hence fermented urine was used in Classical Antiquity to wash cloth and clothing, to remove hair from hides in preparation for tanning, to serve as a mordant in dyeing cloth, and to remove rust from iron. [ 56 ] It was also used by ancient dentists to wash teeth. [ 57 ] [ 58 ] [ 59 ]
In the form of sal ammoniac (نشادر, nushadir ), ammonia was important to the Muslim alchemists . It was mentioned in the Book of Stones , likely written in the 9th century and attributed to Jābir ibn Hayyān . [ 60 ] It was also important to the European alchemists of the 13th century, being mentioned by Albertus Magnus . [ 21 ] It was also used by dyers in the Middle Ages in the form of fermented urine to alter the colour of vegetable dyes. In the 15th century, Basilius Valentinus showed that ammonia could be obtained by the action of alkalis on sal ammoniac. [ 61 ] At a later period, when sal ammoniac was obtained by distilling the hooves and horns of oxen and neutralizing the resulting carbonate with hydrochloric acid , the name 'spirit of hartshorn' was applied to ammonia. [ 21 ] [ 62 ]
Gaseous ammonia was first isolated by Joseph Black in 1756 by reacting sal ammoniac ( ammonium chloride ) with calcined magnesia ( magnesium oxide ). [ 63 ] [ 64 ] It was isolated again by Peter Woulfe in 1767, [ 65 ] [ 66 ] by Carl Wilhelm Scheele in 1770 [ 67 ] and by Joseph Priestley in 1773 and was termed by him 'alkaline air'. [ 21 ] [ 68 ] Eleven years later in 1785, Claude Louis Berthollet ascertained its composition. [ 69 ] [ 21 ]
The production of ammonia from nitrogen in the air (and hydrogen) was invented by Fritz Haber and Robert LeRossignol. The patent was sent in 1909 (USPTO Nr 1,202,995) and awarded in 1916. Later, Carl Bosch developed the industrial method for ammonia production ( Haber–Bosch process ). It was first used on an industrial scale in Germany during World War I , [ 70 ] following the allied blockade that cut off the supply of nitrates from Chile . The ammonia was used to produce explosives to sustain war efforts. [ 71 ] The Nobel Prize in Chemistry 1918 was awarded to Fritz Haber "for the synthesis of ammonia from its elements".
Before the availability of natural gas, hydrogen as a precursor to ammonia production was produced via the electrolysis of water or using the chloralkali process .
With the advent of the steel industry in the 20th century, ammonia became a byproduct of the production of coking coal.
In the US as of 2019 [update] , approximately 88% of ammonia was used as fertilisers either as its salts, solutions or anhydrously . [ 72 ] When applied to soil, it helps provide increased yields of crops such as maize and wheat . [ 73 ] 30% of agricultural nitrogen applied in the US is in the form of anhydrous ammonia, and worldwide, 110 million tonnes are applied each year. [ 74 ] Solutions of ammonia ranging from 16% to 25% are used in the fermentation industry as a source of nitrogen for microorganisms and to adjust pH during fermentation. [ 75 ]
Because of ammonia's vapourization properties, it is a useful refrigerant . [ 70 ] It was commonly used before the popularisation of chlorofluorocarbons (Freons). Anhydrous ammonia is widely used in industrial refrigeration applications and hockey rinks because of its high energy efficiency and low cost. It suffers from the disadvantage of toxicity, and requiring corrosion resistant components, which restricts its domestic and small-scale use. Along with its use in modern vapour-compression refrigeration it is used in a mixture along with hydrogen and water in absorption refrigerators . The Kalina cycle , which is of growing importance to geothermal power plants, depends on the wide boiling range of the ammonia–water mixture.
Ammonia coolant is also used in the radiators aboard the International Space Station in loops that are used to regulate the internal temperature and enable temperature-dependent experiments. [ 76 ] [ 77 ] The ammonia is under sufficient pressure to remain liquid throughout the process. Single-phase ammonia cooling systems also serve the power electronics in each pair of solar arrays.
The potential importance of ammonia as a refrigerant has increased with the discovery that vented CFCs and HFCs are potent and stable greenhouse gases. [ 78 ]
As early as in 1895, it was known that ammonia was 'strongly antiseptic ; it requires 1.4 grams per litre to preserve beef tea (broth).' [ 79 ] In one study, anhydrous ammonia destroyed 99.999% of zoonotic bacteria in three types of animal feed , but not silage . [ 80 ] [ 81 ] Anhydrous ammonia is currently used commercially to reduce or eliminate microbial contamination of beef . [ 82 ] [ 83 ] Lean finely textured beef (popularly known as ' pink slime ') in the beef industry is made from fatty beef trimmings (c. 50–70% fat) by removing the fat using heat and centrifugation , then treating it with ammonia to kill E. coli . The process was deemed effective and safe by the US Department of Agriculture based on a study that found that the treatment reduces E. coli to undetectable levels. [ 84 ] There have been safety concerns about the process as well as consumer complaints about the taste and smell of ammonia-treated beef. [ 85 ]
Ammonia has been used as fuel, and is a proposed alternative to fossil fuels and hydrogen. Being liquid at ambient temperature under its own vapour pressure and having high volumetric and gravimetric energy density, ammonia is considered a suitable carrier for hydrogen, [ 86 ] and may be cheaper than direct transport of liquid hydrogen. [ 87 ]
Compared to hydrogen, ammonia is easier to store. Compared to hydrogen as a fuel , ammonia is much more energy efficient, and could be produced, stored and delivered at a much lower cost than hydrogen, which must be kept compressed or as a cryogenic liquid. [ 88 ] [ 89 ] The raw energy density of liquid ammonia is 11.5 MJ/L, [ 88 ] which is about a third that of diesel .
Ammonia can be converted back to hydrogen to be used to power hydrogen fuel cells, or it may be used directly within high-temperature solid oxide direct ammonia fuel cells to provide efficient power sources that do not emit greenhouse gases . [ 90 ] [ 91 ] Ammonia to hydrogen conversion can be achieved through the sodium amide process [ 92 ] or the catalytic decomposition of ammonia using solid catalysts. [ 93 ]
Ammonia engines or ammonia motors, using ammonia as a working fluid , have been proposed and occasionally used. [ 94 ] The principle is similar to that used in a fireless locomotive , but with ammonia as the working fluid, instead of steam or compressed air. Ammonia engines were used experimentally in the 19th century by Goldsworthy Gurney in the UK and the St. Charles Streetcar Line in New Orleans in the 1870s and 1880s, [ 95 ] and during World War II ammonia was used to power buses in Belgium . [ 96 ]
Ammonia is sometimes proposed as a practical alternative to fossil fuel for internal combustion engines . [ 96 ] [ 97 ] [ 98 ] [ 99 ] However, ammonia cannot be easily used in existing Otto cycle engines because of its very narrow flammability range . Despite this, several tests have been run. [ 100 ] [ 101 ] [ 102 ] Its high octane rating of 120 [ 103 ] and low flame temperature [ 104 ] allows the use of high compression ratios without a penalty of high NO x production. Since ammonia contains no carbon, its combustion cannot produce carbon dioxide , carbon monoxide , hydrocarbons , or soot .
Ammonia production currently creates 1.8% of global CO 2 emissions. 'Green ammonia' is ammonia produced by using green hydrogen (hydrogen produced by electrolysis with electricity from renewable energy), whereas 'blue ammonia' is ammonia produced using blue hydrogen (hydrogen produced by steam methane reforming) where the carbon dioxide has been captured and stored. [ 105 ]
Rocket engines have also been fueled by ammonia. The Reaction Motors XLR99 rocket engine that powered the X-15 hypersonic research aircraft used liquid ammonia. Although not as powerful as other fuels, it left no soot in the reusable rocket engine, and its density approximately matches the density of the oxidiser, liquid oxygen , which simplified the aircraft's design.
In 2020, Saudi Arabia shipped 40 metric tons of liquid 'blue ammonia' to Japan for use as a fuel. [ 106 ] It was produced as a by-product by petrochemical industries, and can be burned without giving off greenhouse gases . Its energy density by volume is nearly double that of liquid hydrogen. If the process of creating it can be scaled up via purely renewable resources, producing green ammonia, it could make a major difference in avoiding climate change . [ 107 ] The company ACWA Power and the city of Neom have announced the construction of a green hydrogen and ammonia plant in 2020. [ 108 ]
Green ammonia is considered as a potential fuel for future container ships. In 2020, the companies DSME and MAN Energy Solutions announced the construction of an ammonia-based ship, DSME plans to commercialize it by 2025. [ 109 ] The use of ammonia as a potential alternative fuel for aircraft jet engines is also being explored. [ 110 ]
Japan intends to implement a plan to develop ammonia co-firing technology that can increase the use of ammonia in power generation, as part of efforts to assist domestic and other Asian utilities to accelerate their transition to carbon neutrality . [ 111 ] In October 2021, the first International Conference on Fuel Ammonia (ICFA2021) was held. [ 112 ] [ 113 ]
In June 2022, IHI Corporation succeeded in reducing greenhouse gases by over 99% during combustion of liquid ammonia in a 2,000-kilowatt-class gas turbine achieving truly CO 2 -free power generation. [ 114 ] In July 2022, Quad nations of Japan, the U.S., Australia and India agreed to promote technological development for clean-burning hydrogen and ammonia as fuels at the security grouping's first energy meeting. [ 115 ] As of 2022 [update] , however, significant amounts of NO x are produced. [ 116 ] Nitrous oxide may also be a problem as it is a " greenhouse gas that is known to possess up to 300 times the Global Warming Potential (GWP) of carbon dioxide ". [ 117 ]
The IEA forecasts that ammonia will meet approximately 45% of shipping fuel demands by 2050. [ 118 ]
At high temperature and in the presence of a suitable catalyst ammonia decomposes into its constituent elements. [ 119 ] Decomposition of ammonia is a slightly endothermic process requiring 23 kJ/mol (5.5 kcal/mol ) of ammonia, and yields hydrogen and nitrogen gas.
Ammonia is used to scrub SO 2 from the burning of fossil fuels, and the resulting product is converted to ammonium sulfate for use as fertiliser. Ammonia neutralises the nitrogen oxide ( NO x ) pollutants emitted by diesel engines. This technology, called SCR ( selective catalytic reduction ), relies on a vanadia -based catalyst. [ 120 ]
Ammonia may be used to mitigate gaseous spills of phosgene . [ 121 ]
Ammonia, as the vapour released by smelling salts , has found significant use as a respiratory stimulant. Ammonia is commonly used in the illegal manufacture of methamphetamine through a Birch reduction . [ 123 ] The Birch method of making methamphetamine is dangerous because the alkali metal and liquid ammonia are both extremely reactive, and the temperature of liquid ammonia makes it susceptible to explosive boiling when reactants are added. [ 124 ]
Liquid ammonia is used for treatment of cotton materials, giving properties like mercerisation , using alkalis. In particular, it is used for prewashing of wool. [ 125 ]
At standard temperature and pressure, ammonia is less dense than atmosphere and has approximately 45–48% of the lifting power of hydrogen or helium . Ammonia has sometimes been used to fill balloons as a lifting gas . Because of its relatively high boiling point (compared to helium and hydrogen), ammonia could potentially be refrigerated and liquefied aboard an airship to reduce lift and add ballast (and returned to a gas to add lift and reduce ballast). [ 126 ]
Ammonia has been used to darken quartersawn white oak in Arts & Crafts and Mission-style furniture. Ammonia fumes react with the natural tannins in the wood and cause it to change colour. [ 127 ]
The US Occupational Safety and Health Administration (OSHA) has set a 15-minute exposure limit for gaseous ammonia of 35 ppm by volume in the environmental air and an 8-hour exposure limit of 25 ppm by volume. [ 129 ] The National Institute for Occupational Safety and Health (NIOSH) recently reduced the IDLH (Immediately Dangerous to Life or Health, the level to which a healthy worker can be exposed for 30 minutes without suffering irreversible health effects) from 500 to 300 ppm based on recent more conservative interpretations of original research in 1943. Other organisations have varying exposure levels. US Navy Standards [U.S. Bureau of Ships 1962] maximum allowable concentrations (MACs): for continuous exposure (60 days) is 25 ppm; for exposure of 1 hour is 400 ppm. [ 130 ]
Ammonia vapour has a sharp, irritating, pungent odor that acts as a warning of potentially dangerous exposure. The average odor threshold is 5 ppm, well below any danger or damage. Exposure to very high concentrations of gaseous ammonia can result in lung damage and death. [ 129 ] Ammonia is regulated in the US as a non-flammable gas, but it meets the definition of a material that is toxic by inhalation and requires a hazardous safety permit when transported in quantities greater than 3,500 US gallons (13,000 L; 2,900 imp gal). [ 131 ]
Liquid ammonia is dangerous because it is hygroscopic and because it can cause caustic burns . See Gas carrier § Health effects of specific cargoes carried on gas carriers for more information.
The toxicity of ammonia solutions does not usually cause problems for humans and other mammals, as a specific mechanism exists to prevent its build-up in the bloodstream. Ammonia is converted to carbamoyl phosphate by the enzyme carbamoyl phosphate synthetase , and then enters the urea cycle to be either incorporated into amino acids or excreted in the urine. [ 132 ] Fish and amphibians lack this mechanism, as they can usually eliminate ammonia from their bodies by direct excretion. Ammonia even at dilute concentrations is highly toxic to aquatic animals, and for this reason it is classified as "dangerous for the environment" . Atmospheric ammonia plays a key role in the formation of fine particulate matter . [ 133 ]
Ammonia is a constituent of tobacco smoke . [ 134 ]
Ammonia is present in coking wastewater streams, as a liquid by-product of the production of coke from coal . [ 135 ] In some cases, the ammonia is discharged to the marine environment where it acts as a pollutant. The Whyalla Steelworks in South Australia is one example of a coke-producing facility that discharges ammonia into marine waters. [ 136 ]
Ammonia toxicity is believed to be a cause of otherwise unexplained losses in fish hatcheries . Excess ammonia may accumulate and cause alteration of metabolism or increases in the body pH of the exposed organism. Tolerance varies among fish species. [ 137 ] At lower concentrations, around 0.05 mg/L, un-ionised ammonia is harmful to fish species and can result in poor growth and feed conversion rates, reduced fecundity and fertility and increase stress and susceptibility to bacterial infections and diseases. [ 138 ] Exposed to excess ammonia, fish may suffer loss of equilibrium, hyper-excitability, increased respiratory activity and oxygen uptake and increased heart rate. [ 137 ] At concentrations exceeding 2.0 mg/L, ammonia causes gill and tissue damage, extreme lethargy, convulsions, coma, and death. [ 137 ] [ 139 ] Experiments have shown that the lethal concentration for a variety of fish species ranges from 0.2 to 2.0 mg/L. [ 139 ]
During winter, when reduced feeds are administered to aquaculture stock, ammonia levels can be higher. Lower ambient temperatures reduce the rate of algal photosynthesis so less ammonia is removed by any algae present. Within an aquaculture environment, especially at large scale, there is no fast-acting remedy to elevated ammonia levels. Prevention rather than correction is recommended to reduce harm to farmed fish [ 139 ] and in open water systems, the surrounding environment.
Similar to propane , anhydrous ammonia boils below room temperature when at atmospheric pressure. A storage vessel capable of 250 psi (1.7 MPa ) is suitable to contain the liquid. [ 140 ] Ammonia is used in numerous different industrial applications requiring carbon or stainless steel storage vessels. Ammonia with at least 0.2% by weight water content is not corrosive to carbon steel. NH 3 carbon steel construction storage tanks with 0.2% by weight or more of water could last more than 50 years in service. [ 141 ] Experts warn that ammonium compounds not be allowed to come in contact with bases (unless in an intended and contained reaction), as dangerous quantities of ammonia gas could be released.
The hazards of ammonia solutions depend on the concentration: 'dilute' ammonia solutions are usually 5–10% by weight (< 5.62 mol/L); 'concentrated' solutions are usually prepared at >25% by weight. A 25% (by weight) solution has a density of 0.907 g/cm 3 , and a solution that has a lower density will be more concentrated. The European Union classification of ammonia solutions is given in the table.
The ammonia vapour from concentrated ammonia solutions is severely irritating to the eyes and the respiratory tract , and experts warn that these solutions only be handled in a fume hood . Saturated ('0.880'–see § Properties ) solutions can develop a significant pressure inside a closed bottle in warm weather, and experts also warn that the bottle be opened with care. This is not usually a problem for 25% ('0.900') solutions.
Experts warn that ammonia solutions not be mixed with halogens , as toxic and/or explosive products are formed. Experts also warn that prolonged contact of ammonia solutions with silver , mercury or iodide salts can also lead to explosive products: such mixtures are often formed in qualitative inorganic analysis , and that it needs to be lightly acidified but not concentrated (<6% w/v) before disposal once the test is completed.
Anhydrous ammonia is classified as toxic ( T ) and dangerous for the environment ( N ). The gas is flammable ( autoignition temperature : 651 °C) and can form explosive mixtures with air (16–25%). The permissible exposure limit (PEL) in the United States is 50 ppm (35 mg/m 3 ), while the IDLH concentration is estimated at 300 ppm. Repeated exposure to ammonia lowers the sensitivity to the smell of the gas: normally the odour is detectable at concentrations of less than 50 ppm, but desensitised individuals may not detect it even at concentrations of 100 ppm. Anhydrous ammonia corrodes copper - and zinc -containing alloys , which makes brass fittings not appropriate for handling the gas. Liquid ammonia can also attack rubber and certain plastics.
Ammonia reacts violently with the halogens . Nitrogen triiodide , a primary high explosive , is formed when ammonia comes in contact with iodine . Ammonia causes the explosive polymerisation of ethylene oxide . It also forms explosive fulminating compounds with compounds of gold , silver , mercury , germanium or tellurium , and with stibine . Violent reactions have also been reported with acetaldehyde , hypochlorite solutions, potassium ferricyanide and peroxides .
Ammonia has one of the highest rates of production of any inorganic chemical. Production is sometimes expressed in terms of 'fixed nitrogen'. Global production was estimated as being 160 million tonnes in 2020 (147 tons of fixed nitrogen). [ 143 ] China accounted for 26.5% of that, followed by Russia at 11.0%, the United States at 9.5%, and India at 8.3%. [ 143 ]
Before the start of World War I , most ammonia was obtained by the dry distillation [ 144 ] of nitrogenous vegetable and animal waste products, including camel dung , where it was distilled by the reduction of nitrous acid and nitrites with hydrogen; in addition, it was produced by the distillation of coal , and also by the decomposition of ammonium salts by alkaline hydroxides [ 145 ] such as quicklime : [ 21 ]
For small scale laboratory synthesis, one can heat urea and calcium hydroxide or sodium hydroxide :
The Haber process , [ 146 ] also called the Haber–Bosch process, is the main industrial procedure for the production of ammonia . [ 147 ] [ 148 ] It converts atmospheric nitrogen (N 2 ) to ammonia (NH 3 ) by a reaction with hydrogen (H 2 ) using finely divided iron metal as a catalyst:
N 2 + 3 H 2 ↽ − − ⇀ 2 NH 3 Δ H 298 K ∘ = − 92.28 kJ per mole of N 2 {\displaystyle {\ce {N2 + 3H2 <=> 2NH3}}\qquad {\Delta H_{\mathrm {298~K} }^{\circ }=-92.28~{\text{kJ per mole of }}{\ce {N2}}}}
This reaction is exothermic but disfavored in terms of entropy because four equivalents of reactant gases are converted into two equivalents of product gas. As a result, high pressures and temperatures that are not too high are needed to drive the reaction forward .
The German chemists Fritz Haber and Carl Bosch developed the process in the first decade of the 20th century, and its improved efficiency over existing methods such as the Birkeland-Eyde and Frank-Caro processes was a major advancement in the industrial production of ammonia. [ 149 ] [ 150 ] [ 151 ]
The electrochemical synthesis of ammonia involves the reductive formation of lithium nitride , which can be protonated to ammonia, given a proton source. The first use of this chemistry was reported in 1930, where lithium solutions in ethanol were used to produce ammonia at pressures of up to 1000 bar, with ethanol acting as the proton source. [ 152 ] Beyond simply mediating proton transfer to the nitrogen reduction reaction, ethanol has been found to play a multifaceted role, influencing electrolyte transformations and contributing to the formation of the solid electrolyte interphase, which enhances overall reaction efficiency. [ 153 ] [ 154 ]
In 1994, Tsuneto et al. used lithium electrodeposition in tetrahydrofuran to synthesize ammonia at more moderate pressures with reasonable Faradaic efficiency . [ 155 ] Subsequent studies have further explored the ethanol–tetrahydrofuran system for electrochemical ammonia synthesis. [ 154 ] [ 156 ]
In 2020, a solvent-agnostic gas diffusion electrode was shown to improve nitrogen transport to the reactive lithium. NH 3 production rates of up to 30 ± 5 nmol/(s⋅cm 2 ) and Faradaic efficiencies of up to 47.5 ± 4% at ambient temperature and 1 bar pressure were achieved. [ 157 ]
In 2021, it was demonstrated that ethanol could be replaced with a tetraalkyl phosphonium salt . [ 158 ] The study observed NH 3 production rates of 53 ± 1 nmol/(s⋅cm 2 ) at 69 ± 1% Faradaic efficiency experiments under 0.5 bar hydrogen and 19.5 bar nitrogen partial pressure at ambient temperature. [ 158 ] Technology based on this electrochemistry is being developed for commercial fertiliser and fuel production. [ 159 ] [ 160 ]
In 2022, ammonia was produced via the lithium mediated process in a continuous-flow electrolyzer also demonstrating the hydrogen gas as proton source. The study synthesized ammonia at 61 ± 1% Faradaic efficiency at a current density of −6 mA/cm 2 at 1 bar and room temperature. [ 161 ]
Ammonia is essential for life. [ 163 ] For example, it is required for the formation of amino acids and nucleic acids , fundamental building blocks of life. Ammonia is however quite toxic. Nature thus uses carriers for ammonia. Within a cell, glutamate serves this role. In the bloodstream, glutamine is a source of ammonia. [ 164 ]
Ethanolamine, required for cell membranes, is the substrate for ethanolamine ammonia-lyase , which produces ammonia: [ 165 ]
Ammonia is both a metabolic waste and a metabolic input throughout the biosphere . It is an important source of nitrogen for living systems. Although atmospheric nitrogen abounds (more than 75%), few living creatures are capable of using atmospheric nitrogen in its diatomic form, N 2 gas. Therefore, nitrogen fixation is required for the synthesis of amino acids, which are the building blocks of protein . Some plants rely on ammonia and other nitrogenous wastes incorporated into the soil by decaying matter. Others, such as nitrogen-fixing legumes , benefit from symbiotic relationships with rhizobia bacteria that create ammonia from atmospheric nitrogen. [ 166 ]
In humans, inhaling ammonia in high concentrations can be fatal. Exposure to ammonia can cause headaches , edema , impaired memory, seizures and coma as it is neurotoxic in nature. [ 167 ]
In certain organisms, ammonia is produced from atmospheric nitrogen by enzymes called nitrogenases . The overall process is called nitrogen fixation . Intense effort has been directed toward understanding the mechanism of biological nitrogen fixation. The scientific interest in this problem is motivated by the unusual structure of the active site of the enzyme, which consists of an Fe 7 MoS 9 ensemble. [ 168 ]
Ammonia is also a metabolic product of amino acid deamination catalyzed by enzymes such as glutamate dehydrogenase 1 . Ammonia excretion is common in aquatic animals. In humans, it is quickly converted to urea (by liver ), which is much less toxic, particularly less basic . This urea is a major component of the dry weight of urine . Most reptiles, birds, insects, and snails excrete uric acid solely as nitrogenous waste.
Ammonia plays a role in both normal and abnormal animal physiology . It is biosynthesised through normal amino acid metabolism and is toxic in high concentrations. The liver converts ammonia to urea through a series of reactions known as the urea cycle . Liver dysfunction, such as that seen in cirrhosis , may lead to elevated amounts of ammonia in the blood ( hyperammonemia ). Likewise, defects in the enzymes responsible for the urea cycle, such as ornithine transcarbamylase , lead to hyperammonemia . Hyperammonemia contributes to the confusion and coma of hepatic encephalopathy , as well as the neurological disease common in people with urea cycle defects and organic acidurias . [ 169 ]
Ammonia is important for normal animal acid/base balance. After formation of ammonium from glutamine , α-ketoglutarate may be degraded to produce two bicarbonate ions, which are then available as buffers for dietary acids. Ammonium is excreted in the urine, resulting in net acid loss. Ammonia may itself diffuse across the renal tubules , combine with a hydrogen ion, and thus allow for further acid excretion . [ 170 ]
Ammonium ions are a toxic waste product of metabolism in animals . In fish and aquatic invertebrates, it is excreted directly into the water. In mammals, sharks, and amphibians, it is converted in the urea cycle to urea , which is less toxic and can be stored more efficiently. In birds, reptiles, and terrestrial snails, metabolic ammonium is converted into uric acid , which is solid and can therefore be excreted with minimal water loss. [ 171 ]
Ammonia has been detected in the atmospheres of the giant planets Jupiter , Saturn , Uranus and Neptune , along with other gases such as methane , hydrogen , and helium . The interior of Saturn may include frozen ammonia crystals. [ 172 ] It is found on Deimos and Phobos –the two moons of Mars . [ citation needed ]
Ammonia was first detected in interstellar space in 1968, based on microwave emissions from the direction of the galactic core . [ 173 ] This was the first polyatomic molecule to be so detected. The sensitivity of the molecule to a broad range of excitations and the ease with which it can be observed in a number of regions has made ammonia one of the most important molecules for studies of molecular clouds . [ 174 ] The relative intensity of the ammonia lines can be used to measure the temperature of the emitting medium.
The following isotopic species of ammonia have been detected: NH 3 , 15 NH 3 , NH 2 D , NHD 2 , and ND 3 . The detection of triply deuterated ammonia was considered a surprise as deuterium is relatively scarce. It is thought that the low-temperature conditions allow this molecule to survive and accumulate. [ 175 ]
Since its interstellar discovery, NH 3 has proved to be an invaluable spectroscopic tool in the study of the interstellar medium. With a large number of transitions sensitive to a wide range of excitation conditions, NH 3 has been widely astronomically detected–its detection has been reported in hundreds of journal articles. Listed below is a sample of journal articles that highlights the range of detectors that have been used to identify ammonia.
The study of interstellar ammonia has been important to a number of areas of research in the last few decades. Some of these are delineated below and primarily involve using ammonia as an interstellar thermometer.
The interstellar abundance for ammonia has been measured for a variety of environments. The [ NH 3 ]/[ H 2 ] ratio has been estimated to range from 10 −7 in small dark clouds [ 176 ] up to 10 −5 in the dense core of the Orion molecular cloud complex . [ 177 ] Although a total of 18 total production routes have been proposed, [ 178 ] the principal formation mechanism for interstellar NH 3 is the reaction:
The rate constant, k , of this reaction depends on the temperature of the environment, with a value of 5.2 × 10 − 6 {\displaystyle 5.2\times 10^{-6}} at 10 K. [ 179 ] The rate constant was calculated from the formula k = a ( T / 300 ) B {\displaystyle k=a(T/300)^{B}} . For the primary formation reaction, a = 1.05 × 10 −6 and B = −0.47 . Assuming an NH + 4 abundance of 3 × 10 − 7 {\displaystyle 3\times 10^{-7}} and an electron abundance of 10 −7 typical of molecular clouds, the formation will proceed at a rate of 1.6 × 10 −9 cm −3 s −1 in a molecular cloud of total density 10 5 cm −3 . [ 180 ]
All other proposed formation reactions have rate constants of between two and 13 orders of magnitude smaller, making their contribution to the abundance of ammonia relatively insignificant. [ 181 ] As an example of the minor contribution other formation reactions play, the reaction:
has a rate constant of 2.2 × 10 −15 . Assuming H 2 densities of 10 5 and [ NH 2 ]/[ H 2 ] ratio of 10 −7 , this reaction proceeds at a rate of 2.2 × 10 −12 , more than three orders of magnitude slower than the primary reaction above.
Some of the other possible formation reactions are:
There are 113 total proposed reactions leading to the destruction of NH 3 . Of these, 39 were tabulated in extensive tables of the chemistry among C, N and O compounds. [ 182 ] A review of interstellar ammonia cites the following reactions as the principal dissociation mechanisms: [ 174 ]
with rate constants of 4.39×10 −9 [ 183 ] and 2.2×10 −9 , [ 184 ] respectively. The above equations ( 1 , 2 ) run at a rate of 8.8×10 −9 and 4.4×10 −13 , respectively. These calculations assumed the given rate constants and abundances of [ NH 3 ]/[ H 2 ] = 10 −5 , [ [H 3 ] + ]/[ H 2 ] = 2×10 −5 , [ HCO + ]/[ H 2 ] = 2×10 −9 , and total densities of n = 10 5 , typical of cold, dense, molecular clouds. [ 185 ] Clearly, between these two primary reactions, equation ( 1 ) is the dominant destruction reaction, with a rate ≈10,000 times faster than equation ( 2 ). This is due to the relatively high abundance of [H 3 ] + .
Radio observations of NH 3 from the Effelsberg 100-m Radio Telescope reveal that the ammonia line is separated into two components–a background ridge and an unresolved core. The background corresponds well with the locations previously detected CO. [ 186 ] The 25 m Chilbolton telescope in England detected radio signatures of ammonia in H II regions , HNH 2 O masers , H–H objects, and other objects associated with star formation. A comparison of emission line widths indicates that turbulent or systematic velocities do not increase in the central cores of molecular clouds. [ 187 ]
Microwave radiation from ammonia was observed in several galactic objects including W3(OH), Orion A , W43 , W51 , and five sources in the galactic centre. The high detection rate indicates that this is a common molecule in the interstellar medium and that high-density regions are common in the galaxy. [ 188 ]
VLA observations of NH 3 in seven regions with high-velocity gaseous outflows revealed condensations of less than 0.1 pc in L1551, S140, and Cepheus A . Three individual condensations were detected in Cepheus A, one of them with a highly elongated shape. They may play an important role in creating the bipolar outflow in the region. [ 189 ]
Extragalactic ammonia was imaged using the VLA in IC 342 . The hot gas has temperatures above 70 K, which was inferred from ammonia line ratios and appears to be closely associated with the innermost portions of the nuclear bar seen in CO. [ 190 ] NH 3 was also monitored by VLA toward a sample of four galactic ultracompact HII regions: G9.62+0.19, G10.47+0.03, G29.96−0.02, and G31.41+0.31. Based upon temperature and density diagnostics, it is concluded that in general such clumps are probably the sites of massive star formation in an early evolutionary phase prior to the development of an ultracompact HII region. [ 191 ]
Absorption at 2.97 micrometres due to solid ammonia was recorded from interstellar grains in the Becklin–Neugebauer Object and probably in NGC 2264-IR as well. This detection helped explain the physical shape of previously poorly understood and related ice absorption lines. [ 192 ]
A spectrum of the disk of Jupiter was obtained from the Kuiper Airborne Observatory , covering the 100 to 300 cm −1 spectral range. Analysis of the spectrum provides information on global mean properties of ammonia gas and an ammonia ice haze. [ 193 ]
A total of 149 dark cloud positions were surveyed for evidence of 'dense cores' by using the (J,K) = (1,1) rotating inversion line of NH 3 . In general, the cores are not spherically shaped, with aspect ratios ranging from 1.1 to 4.4. It is also found that cores with stars have broader lines than cores without stars. [ 194 ]
Ammonia has been detected in the Draco Nebula and in one or possibly two molecular clouds, which are associated with the high-latitude galactic infrared cirrus . The finding is significant because they may represent the birthplaces for the Population I metallicity B-type stars in the galactic halo that could have been borne in the galactic disk. [ 195 ]
By balancing and stimulated emission with spontaneous emission, it is possible to construct a relation between excitation temperature and density. Moreover, since the transitional levels of ammonia can be approximated by a 2-level system at low temperatures, this calculation is fairly simple. This premise can be applied to dark clouds, regions suspected of having extremely low temperatures and possible sites for future star formation. Detections of ammonia in dark clouds show very narrow lines – indicative not only of low temperatures, but also of a low level of inner-cloud turbulence. Line ratio calculations provide a measurement of cloud temperature that is independent of previous CO observations. The ammonia observations were consistent with CO measurements of rotation temperatures of ≈10 K. With this, densities can be determined, and have been calculated to range between 10 4 and 10 5 cm −3 in dark clouds. Mapping of NH 3 gives typical clouds sizes of 0.1 pc and masses near 1 solar mass. These cold, dense cores are the sites of future star formation.
Ultra-compact HII regions are among the best tracers of high-mass star formation. The dense material surrounding UCHII regions is likely primarily molecular. Since a complete study of massive star formation necessarily involves the cloud from which the star formed, ammonia is an invaluable tool in understanding this surrounding molecular material. Since this molecular material can be spatially resolved, it is possible to constrain the heating/ionising sources, temperatures, masses, and sizes of the regions. Doppler-shifted velocity components allow for the separation of distinct regions of molecular gas that can trace outflows and hot cores originating from forming stars.
Ammonia has been detected in external galaxies, [ 196 ] [ 197 ] and by simultaneously measuring several lines, it is possible to directly measure the gas temperature in these galaxies. Line ratios imply that gas temperatures are warm (≈50 K), originating from dense clouds with sizes of tens of parsecs. This picture is consistent with the picture within our Milky Way galaxy – hot dense molecular cores form around newly forming stars embedded in larger clouds of molecular material on the scale of several hundred parsecs (giant molecular clouds; GMCs). | https://en.wikipedia.org/wiki/NH3 |
Carbamic acid , which might also be called aminoformic acid or aminocarboxylic acid , [ 2 ] is the chemical compound with the formula H 2 NCOOH . It can be obtained by the reaction of ammonia NH 3 and carbon dioxide CO 2 at very low temperatures, which also yields ammonium carbamate [NH 4 ] + [NH 2 CO 2 ] − . The compound is stable only up to about 250 K (−23 °C); at higher temperatures it decomposes into those two gases. [ 3 ] The solid apparently consists of dimers , with the two molecules connected by hydrogen bonds between the two carboxyl groups –COOH. [ 4 ]
Carbamic acid could be seen as both an amine and carboxylic acid , and therefore an amino acid ; [ 3 ] however, the attachment of the carboxyl group –COOH directly to the nitrogen atom (without any intermediate carbon chain) makes it behave very differently from the amino acids with intermediate carbon chain. ( Glycine NH 2 CH 2 COOH is generally considered to be the simplest amino acid.) The hydroxyl group –OH attached to the carbon also excludes it from the amide class.
The term "carbamic acid" is also used generically for any compounds of the form RR′NCOOH, where R and R′ are organic groups or hydrogen. [ 5 ]
Deprotonation of a carbamic acid yields a carbamate anion RR′NCOO − , the salts of which can be relatively stable. Carbamate is also a term used for esters of carbamic acids, such as methyl carbamate H 2 N−C(=O)−OCH 3 . The carbamoyl functional group RR′N–C(=O)– (often denoted by Cbm ) is the carbamic acid molecule minus the OH part of the carboxyl.
Carbamic acid is a planar molecule. [ 3 ]
The H 2 N− group of carbamic acid, unlike that of most amines, cannot be protonated to an ammonium group H 3 N + − . The zwitterionic form H 3 N + −COO − is very unstable and promptly decomposes into ammonia and carbon dioxide, [ 6 ] yet there is a report of its detection in ices irradiated with high-energy protons . [ 3 ]
Carbamic acid is formally the parent compound of several important families of organic compounds:
Many substituted carbamic acids (RHNCOOH or RR′NCOOH), can be readily synthesized by bubbling carbon dioxide through solutions of the corresponding amine ( RNH 2 or RR′NH, respectively) in an appropriate solvent, such as DMSO or supercritical carbon dioxide. [ 5 ] These carbamic acids are generally unstable at room temperature, reverting to the parent amine and carbon dioxide. [ 7 ]
Unlike carbamic acids, carbamate esters are generally stable at room temperature as a higher state. They are prepared by reaction of carbamoyl chlorides with alcohols, the addition of alcohols to isocyanates , and the reaction of carbonate esters with ammonia. [ 8 ] Methyl carbamate and ethyl carbamate are among the simplest examples and have historically been used in the textile industry, both are now suspected carcinogens. Benzyl carbamate is also known.
The enzyme class carbamate kinase , involved in several metabolic pathways of living organisms, catalyzes the formation of carbamoyl phosphate H 2 N−C(=O)−O−PO 2− 3 :
An important example of an enzyme with this activity is carbamoyl phosphate synthetase , e.g. carbamoyl phosphate synthetase I carrying out the first step of the urea cycle in order to dispose of waste ammonia.
One hemoglobin molecule can carry four molecules of carbon dioxide to the lungs as carbamate groups formed by reaction of CO 2 with four terminal amine groups of the deoxy form . The resulting compound is called carbaminohaemoglobin .
Carbamic acid is an intermediate in the industrial production of urea , which involves the reaction of carbon dioxide and ammonia. [ 9 ]
Some carbamate esters have use as muscle relaxants , including Emylcamate , Phenprobamate , Styramate and other members of ATC code M03BA . These bind to the barbiturate site of the GABA A receptor. [ 10 ]
Several carbamic acid based insecticides have been developed; for example aldicarb , carbaryl , carbofuran . [ 11 ]
An amine functional group −NH 2 can be protected from unwanted reactions by being formed as carbamate ester residue –NHC(=O)–OR. Hydrolysis of the ester bond then produces a carbamic acid –NHC(=O)OH, which then loses carbon dioxide yielding the desired amine. | https://en.wikipedia.org/wiki/NH3CO2 |
Hydroxylamine (also known as hydroxyammonia ) is an inorganic compound with the chemical formula N H 2 O H . The compound exists as hygroscopic colorless crystals . [ 4 ] Hydroxylamine is almost always provided and used as an aqueous solution or more often as one of its salts such as hydroxylammonium sulfate , a water-soluble solid.
Hydroxylamine and its salts are consumed almost exclusively to produce Nylon-6 . The oxidation of NH 3 to hydroxylamine is a step in biological nitrification . [ 5 ]
Hydroxylamine was first prepared as hydroxylammonium chloride in 1865 by the German chemist Wilhelm Clemens Lossen (1838-1906); he reacted tin and hydrochloric acid in the presence of ethyl nitrate . [ 6 ] It was first prepared in pure form in 1891 by the Dutch chemist Lobry de Bruyn and by the French chemist Léon Maurice Crismer (1858-1944). [ 7 ] [ 8 ] The coordination complex ZnCl 2 (NH 2 OH) 2 (zinc dichloride di(hydroxylamine)), known as Crismer's salt, releases hydroxylamine upon heating. [ 9 ]
Hydroxylamine and its N -substituted derivatives are pyramidal at nitrogen, with bond angles very similar to those of amines. The conformation of hydroxylamine places the NOH anti to the lone pair on nitrogen, seeming to minimize lone pair-lone pair interactions. [ 10 ]
Hydroxylamine or its salts (salts containing hydroxylammonium cations [NH 3 OH] + ) can be produced via several routes but only two are commercially viable. It is also produced naturally as discussed in a section on biochemistry .
NH 2 OH is mainly produced as its sulfuric acid salt , hydroxylammonium sulfate ( [NH 3 OH][SO 4 ] ), by the hydrogenation of nitric oxide over platinum catalysts in the presence of sulfuric acid. [ 11 ]
Another route to NH 2 OH is the Raschig process : aqueous ammonium nitrite is reduced by HSO − 3 and SO 2 at 0 °C to yield a hydroxylamido- N , N -disulfonate anion :
This ammonium hydroxylamine disulfonate anion is then hydrolyzed to give hydroxylammonium sulfate :
Julius Tafel discovered that hydroxylamine hydrochloride or sulfate salts can be produced by electrolytic reduction of nitric acid with HCl or H 2 SO 4 respectively: [ 12 ] [ 13 ]
Hydroxylamine can also be produced by the reduction of nitrous acid or potassium nitrite with bisulfite :
Hydrochloric acid disproportionates nitromethane to hydroxylamine hydrochloride and carbon monoxide via the hydroxamic acid . [ citation needed ]
A direct lab synthesis of hydroxylamine from molecular nitrogen in water plasma was demonstrated in 2024. [ 14 ]
Solid NH 2 OH can be collected by treatment with liquid ammonia . Ammonium sulfate , [NH 4 ] 2 SO 4 , a side-product insoluble in liquid ammonia, is removed by filtration; the liquid ammonia is evaporated to give the desired product. [ 4 ] The net reaction is:
Base, such as sodium butoxide, can be used to free the hydroxylamine from hydroxylammonium chloride : [ 4 ]
Hydroxylamine is a base with a pKa of 6.03:
Hydroxylamine reacts with alkylating agents usually at the nitrogen atom:
The reaction of NH 2 OH with an aldehyde or ketone produces an oxime .
This reaction can be useful in the purification of ketones and aldehydes: if hydroxylamine is added to an aldehyde or ketone in solution, an oxime forms, which generally precipitates from solution; heating the precipitate with aqueous acid then restores the original aldehyde or ketone. [ 15 ]
NH 2 OH reacts with chlorosulfonic acid to give hydroxylamine- O -sulfonic acid : [ 16 ]
It isomerizes to the amine oxide H 3 N + −O − . [ 17 ]
Hydroxylamine derivatives substituted in place of the hydroxyl or amine hydrogen are (respectively) called O - or N ‑hydroxylamines. In general N ‑hydroxylamines are more common. Examples are N ‑ tert ‑butylhydroxylamine or the glycosidic bond in calicheamicin . N , O ‑Dimethylhydroxylamine is a precursor to Weinreb amides .
Similarly to amines, one can distinguish hydroxylamines by their degree of substitution: primary, secondary and tertiary. When stored exposed to air for weeks, secondary hydroxylamines degrade to nitrones . [ 18 ]
N ‑organylhydroxylamines, R−NH−OH , where R is an organyl group, can be reduced to amines R−NH 2 : [ 19 ]
Oximes such as dimethylglyoxime are also employed as ligands .
The hydrolysis of N-substituted oximes, hydroxamic acids, and nitrones easily provides hydroxylamines.
Alkylating of hydroxylamine or N-alkylhydroxylamines proceeds usually at nitrogen. One challenge is dialkylation when only monoalkylation is desired.
For O-alkylation of hydroxylamines, strong base such as sodium hydride is required to first deprotonate the OH group: [ 20 ]
Amine oxidation with benzoyl peroxide is a common method to synthesize hydroxylamines. Care must be taken to prevent over-oxidation to a nitrone . Other methods include:
Approximately 95% of hydroxylamine is used in the synthesis of cyclohexanone oxime , a precursor to Nylon 6 . [ 11 ] The treatment of this oxime with acid induces the Beckmann rearrangement to give caprolactam . [ 21 ] The latter can then undergo a ring-opening polymerization to yield Nylon 6. [ 22 ]
Hydroxylamine and its salts are commonly used as reducing agents in myriad organic and inorganic reactions. They can also act as antioxidants for fatty acids.
High concentrations of hydroxylamine are used by biologists to introduce mutations by acting as a DNA nucleobase amine-hydroxylating agent. [ 23 ] In is thought to mainly act via hydroxylation of cytidine to hydroxyaminocytidine, which is misread as thymidine, thereby inducing C:G to T:A transition mutations. [ 24 ] But high concentrations or over-reaction of hydroxylamine in vitro are seemingly able to modify other regions of the DNA & lead to other types of mutations. [ 24 ] This may be due to the ability of hydroxylamine to undergo uncontrolled free radical chemistry in the presence of trace metals and oxygen, in fact in the absence of its free radical affects Ernst Freese noted hydroxylamine was unable to induce reversion mutations of its C:G to T:A transition effect and even considered hydroxylamine to be the most specific mutagen known. [ 25 ] Practically, it has been largely surpassed by more potent mutagens such as EMS , ENU , or nitrosoguanidine , but being a very small mutagenic compound with high specificity, it found some specialized uses such as mutation of DNA packed within bacteriophage capsids, [ 26 ] and mutation of purified DNA in vitro . [ 27 ]
An alternative industrial synthesis of paracetamol developed by Hoechst – Celanese involves the conversion of ketone to a ketoxime with hydroxylamine.
Some non-chemical uses include removal of hair from animal hides and photographic developing solutions. [ 2 ] In the semiconductor industry, hydroxylamine is often a component in the "resist stripper", which removes photoresist after lithography.
Hydroxylamine can also be used to better characterize the nature of a post-translational modification onto proteins. For example, poly(ADP-Ribose) chains are sensitive to hydroxylamine when attached to glutamic or aspartic acids but not sensitive when attached to serines. [ 28 ] Similarly, Ubiquitin molecules bound to serines or threonines residues are sensitive to hydroxylamine, but those bound to lysine (isopeptide bond) are resistant. [ 29 ]
In biological nitrification, the oxidation of NH 3 to hydroxylamine is mediated by the ammonia monooxygenase (AMO). [ 5 ] Hydroxylamine oxidoreductase (HAO) further oxidizes hydroxylamine to nitrite. [ 30 ]
Cytochrome P460, an enzyme found in the ammonia-oxidizing bacteria Nitrosomonas europea , can convert hydroxylamine to nitrous oxide , a potent greenhouse gas . [ 31 ]
Hydroxylamine can also be used to highly selectively cleave asparaginyl - glycine peptide bonds in peptides and proteins. [ 32 ] It also bonds to and permanently disables (poisons) heme-containing enzymes . It is used as an irreversible inhibitor of the oxygen-evolving complex of photosynthesis on account of its similar structure to water.
Hydroxylamine is a skin irritant but is of low toxicity.
A detonator can easily explode aqueous solutions concentrated above 80% by weight, and even 50% solution might prove detonable if tested in bulk. [ 33 ] [ 34 ] In air, the combustion is rapid and complete:
Absent air, pure hydroxylamine requires stronger heating and the detonation does not complete combustion:
At least two factories dealing in hydroxylamine have been destroyed since 1999 with loss of life. [ 35 ] It is known, however, that ferrous and ferric iron salts accelerate the decomposition of 50% NH 2 OH solutions. [ 36 ] Hydroxylamine and its derivatives are more safely handled in the form of salts .
It is an irritant to the respiratory tract , skin, eyes, and other mucous membranes . It may be absorbed through the skin, is harmful if swallowed, and is a possible mutagen . [ 37 ] | https://en.wikipedia.org/wiki/NH3O |
Ammonium is a modified form of ammonia that has an extra hydrogen atom. It is a positively charged ( cationic ) molecular ion with the chemical formula NH + 4 or [NH 4 ] + . It is formed by the addition of a proton (a hydrogen nucleus) to ammonia ( NH 3 ). Ammonium is also a general name for positively charged (protonated) substituted amines and quaternary ammonium cations ( [NR 4 ] + ), where one or more hydrogen atoms are replaced by organic or other groups (indicated by R). Not only is ammonium a source of nitrogen and a key metabolite for many living organisms, but it is an integral part of the global nitrogen cycle . [ 2 ] As such, human impact in recent years could have an effect on the biological communities that depend on it.
The ammonium ion is generated when ammonia, a weak base, reacts with Brønsted acids ( proton donors):
The ammonium ion is mildly acidic, reacting with Brønsted bases to return to the uncharged ammonia molecule:
Thus, the treatment of concentrated solutions of ammonium salts with a strong base gives ammonia. When ammonia is dissolved in water, a tiny amount of it converts to ammonium ions:
The degree to which ammonia forms the ammonium ion depends on the pH of the solution. If the pH is low, the equilibrium shifts to the right: more ammonia molecules are converted into ammonium ions. If the pH is high (the concentration of hydrogen ions is low and hydroxide ions is high), the equilibrium shifts to the left: the hydroxide ion abstracts a proton from the ammonium ion, generating ammonia.
Formation of ammonium compounds can also occur in the vapor phase; for example, when ammonia vapor comes in contact with hydrogen chloride vapor, a white cloud of ammonium chloride forms, which eventually settles out as a solid in a thin white layer on surfaces.
Ammonium cation is found in a variety of salts such as ammonium carbonate , ammonium chloride , and ammonium nitrate . Most simple ammonium salts are very soluble in water. An exception is ammonium hexachloroplatinate , the formation of which was once used as a test for ammonium. The ammonium salts of nitrate and especially perchlorate are highly explosive, in these cases, ammonium is the reducing agent.
In an unusual process, ammonium ions form an amalgam . Such species are prepared by the addition of sodium amalgam to a solution of ammonium chloride. [ 3 ] This amalgam eventually decomposes to release ammonia and hydrogen. [ 4 ]
To find whether the ammonium ion is present in the salt, first, the salt is heated in presence of alkali hydroxide releasing a gas with a characteristic smell, which is ammonia .
To further confirm ammonia, it is passed through a glass rod dipped in an HCl solution ( hydrochloric acid ), creating white dense fumes of ammonium chloride .
Ammonia, when passed through CuSO 4 ( copper(II) sulfate ) solution, changes its color from blue to deep blue, forming Schweizer's reagent .
Ammonia or ammonium ion when added to Nessler's reagent gives a brown color precipitate known as the iodide of Million's base in basic medium.
Ammonium ion when added to chloroplatinic acid gives a yellow precipitate of ammonium hexachloroplatinate(IV) .
Ammonium ion when added to sodium cobaltinitrite gives a yellow precipitate of ammonium cobaltinitrite.
Ammonium ion gives a white precipitate of ammonium bitartrate when added to potassium bitartrate .
The lone electron pair on the nitrogen atom (N) in ammonia, represented as a line above the N, forms a coordinate bond with a proton ( H + ). After that, all four N−H bonds are equivalent, being polar covalent bonds . The ion has a tetrahedral structure and is isoelectronic with methane and the borohydride anion. In terms of size, the ammonium cation ( r ionic = 175 pm) [ citation needed ] resembles the caesium cation ( r ionic = 183 pm). [ citation needed ]
The hydrogen atoms in the ammonium ion can be substituted with an alkyl group or some other organic group to form a substituted ammonium ion ( IUPAC nomenclature: aminium ion ). Depending on the number of organic groups, the ammonium cation is called a primary , secondary , tertiary , or quaternary . Except the quaternary ammonium cations, the organic ammonium cations are weak acids.
An example of a reaction forming an ammonium ion is that between dimethylamine , (CH 3 ) 2 NH , and an acid to give the dimethylammonium cation, [(CH 3 ) 2 NH 2 ] + :
Quaternary ammonium cations have four organic groups attached to the nitrogen atom, they lack a hydrogen atom bonded to the nitrogen atom. These cations, such as the tetra- n -butylammonium cation, are sometimes used to replace sodium or potassium ions to increase the solubility of the associated anion in organic solvents . Primary, secondary, and tertiary ammonium salts serve the same function but are less lipophilic . They are also used as phase-transfer catalysts and surfactants .
An unusual class of organic ammonium salts is derivatives of amine radical cations, [•NR 3 ] + such as tris(4-bromophenyl)ammoniumyl hexachloroantimonate .
Because nitrogen often limits net primary production due to its use in enzymes that mediate the biochemical reactions that are necessary for life, ammonium is utilized by some microbes and plants. [ 5 ] For example, energy is released by the oxidation of ammonium in a process known as nitrification , which produces nitrate and nitrite . [ 6 ] This process is a form of autotrophy that is common amongst Nitrosomonas , Nitrobacter , Nitrosolobus , and Nitrosospira , amongst others. [ 6 ]
The amount of ammonium in soil that is available for nitrification by microbes varies depending on environmental conditions. [ 7 ] [ 8 ] For example, ammonium is deposited as a waste product from some animals, although it is converted into urea in mammals, sharks, and amphibians, and into uric acid in birds, reptiles, and terrestrial snails. [ 9 ] Its availability in soils is also influenced by mineralization , which makes more ammonium available from organic nitrogen sources, and immobilization , which sequesters ammonium into organic nitrogen sources, both of which are mitigated by biological factors. [ 6 ]
Conversely, nitrate and nitrite can be reduced to ammonium as a way for living organisms to access nitrogen for growth in a process known as assimilatory nitrate reduction. [ 10 ] Once assimilated, it can be incorporated into proteins and DNA . [ 11 ]
Ammonium can accumulate in soils where nitrification is slow or inhibited, which is common in hypoxic soils. [ 12 ] For example, ammonium mobilization is one of the key factors for the symbiotic association between plants and fungi, called mycorrhizae . [ 13 ] However, plants that consistently utilize ammonium as a nitrogen source often must invest into more extensive root systems due to ammonium's limited mobility in soils compared to other nitrogen sources. [ 14 ] [ 15 ]
Ammonium deposition from the atmosphere has increased in recent years due to volatilization from livestock waste and increased fertilizer use. [ 16 ] Because net primary production is often limited by nitrogen , increased ammonium levels could impact the biological communities that rely on it. For example, increasing nitrogen content has been shown to increase plant growth, but aggravate soil phosphorus levels, which can impact microbial communities. [ 17 ]
The ammonium cation has very similar properties to the heavier alkali metal cations and is often considered a close equivalent. [ 18 ] [ 19 ] [ 20 ] Ammonium is expected to behave as a metal ( [NH 4 ] + ions in a sea of electrons ) at very high pressures, such as inside giant planets such as Uranus and Neptune . [ 19 ] [ 20 ]
Under normal conditions, ammonium does not exist as a pure metal but does as an amalgam (alloy with mercury ). [ 21 ] | https://en.wikipedia.org/wiki/NH4+ |
Ammonium chloride is an inorganic chemical compound with the chemical formula N H 4 Cl , also written as [NH 4 ]Cl . It is an ammonium salt of hydrogen chloride . It consists of ammonium cations [NH 4 ] + and chloride anions Cl − . It is a white crystalline salt that is highly soluble in water. Solutions of ammonium chloride are mildly acidic. In its naturally occurring mineralogic form, it is known as salammoniac . The mineral is commonly formed on burning coal dumps from condensation of coal-derived gases. It is also found around some types of volcanic vents. It is mainly used as fertilizer and a flavouring agent in some types of liquorice . It is a product of the reaction of hydrochloric acid and ammonia .
It is a product of the Solvay process used to produce sodium carbonate : [ 3 ]
Not only is that method the principal one for the manufacture of ammonium chloride, but also it is used to minimize ammonia release in some industrial operations.
Ammonium chloride is prepared commercially by combining ammonia (NH 3 ) with either hydrogen chloride (gas) or hydrochloric acid (water solution): [ 3 ]
Ammonium chloride occurs naturally in volcanic regions, forming on volcanic rocks near fume-releasing vents ( fumaroles ). The crystals deposit directly from the gaseous state and tend to be short-lived, as they dissolve easily in water. [ 11 ]
Ammonium chloride appears to sublime upon heating but actually reversibly decomposes into ammonia and hydrogen chloride gas: [ 3 ]
Ammonium chloride reacts with a strong base, like sodium hydroxide , to release ammonia gas:
Similarly, ammonium chloride also reacts with alkali-metal carbonates at elevated temperatures, giving ammonia and alkali-metal chloride:
A solution of 5% by mass of ammonium chloride in water has a pH in the range 4.6 to 6.0. [ 12 ]
Some reactions of ammonium chloride with other chemicals are endothermic , such as its reaction with barium hydroxide and its dissolving in water.
The dominant application of ammonium chloride is as a nitrogen source in fertilizers (corresponding to 90% of the world production of ammonium chloride) such as chloroammonium phosphate. [ 13 ] The main crops fertilized this way are rice and wheat in Asia . [ 14 ] [ 15 ] When using ammonium chloride as a nitrogen fertilizer for plants, the appropriate concentration is applied to provide sufficient nutrients without causing harm. [ 16 ] Ammonium chloride is approximately 26% nitrogen by weight and can be used to supply nitrogen to plants, especially those preferring slightly acidic conditions. [ 17 ] The concentration for nitrogen fertilization in solution is between 50 and 100 milligrams of nitrogen per liter of water (mg N/L), which is equivalent to 50–100 parts per million (ppm) nitrogen, which translates to approximately 0.2 to 0.4 grams of ammonium chloride per liter of water. [ 18 ] Ammonium chloride can acidify the soil over time, so soil pH is regularly monitored, especially when growing plants sensitive to acidic conditions. [ 19 ] Some plants are sensitive to chloride ions (e.g., avocados, beans, grapes), so applying ammonium chloride to such plants should be done with extra caution to prevent chloride toxicity. [ 20 ] While ammonium chloride can be beneficial as a nitrogen source, improper use can harm plants and the environment. [ 21 ]
Ammonium chloride solutions are generally stable and can be stored for a certain period if kept under appropriate conditions, [ 22 ] that is in airtight containers (to prevent contamination, evaporation and hydrolysis), away from light (to prevent photodegradation ) and heat sources (to reduce microbial growth and chemical degradation), and if contamination is prevented. [ 22 ] In agricultural applications the solution is used shortly after preparation, [ 23 ] for the following reasons:
Ammonium chloride was used in pyrotechnics in the 18th century but was superseded by safer and less hygroscopic chemicals. Its purpose was to provide a chlorine donor to enhance the green and blue colours from copper ions in the flame.
It had a secondary use to provide white smoke, but its ready double decomposition reaction with potassium chlorate producing the highly unstable ammonium chlorate made its use very dangerous. [ 28 ] [ 29 ] [ 30 ]
Ammonium chloride is used as a flux in preparing metals to be tin coated, galvanized or soldered. It works as a flux by cleaning the surface of workpieces by reacting with the metal oxides at the surface to form a volatile metal chloride. For that purpose, it is sold in blocks at hardware stores for use in cleaning the tip of a soldering iron, and it can also be included in solder as flux.
Ammonium chloride is used as an expectorant in cough medicine. Its expectorant action is caused by irritative action on the bronchial mucosa, which causes the production of excess respiratory tract fluid, which presumably is easier to cough up. Ammonium salts are an irritant to the gastric mucosa and may induce nausea and vomiting.
Ammonium chloride is used as a systemic acidifying agent in treatment of severe metabolic alkalosis , in oral acid loading test to diagnose distal renal tubular acidosis, to maintain the urine at an acid pH in the treatment of some urinary-tract disorders. [ citation needed ]
Ammonium chloride, under the name sal ammoniac or salmiak is used as food additive under the E number E510, working as a yeast nutrient in breadmaking and as an acidifier. [ 31 ] It is a feed supplement for cattle and an ingredient in nutritive media for yeasts and many microorganisms.
Ammonium chloride is used in baking to give cookies a very crisp texture, to spice up dark sweets called salty liquorice (popular in the Nordic countries, Benelux and northern Germany), [ 32 ] and in the liquor Salmiakki Koskenkorva for flavouring. In Turkey, Iran, Tajikistan, India, Pakistan and Arab countries it is called "noshader" and is used to improve the crispness of snacks such as samosas and jalebi .
Ammonium chloride has been used historically to produce low temperatures in cooling baths . [ 33 ]
Ammonium chloride solutions with ammonia are used as buffer solutions including ACK (Ammonium-Chloride-Potassium) lysis buffer . [ 34 ]
In paleontology , ammonium chloride vapor is deposited on fossils , where the substance forms a brilliant white, easily removed and fairly harmless and inert layer of tiny crystals that covers up any coloration the fossil may have, and if lighted at an angle highly enhances contrast in photographic documentation of three-dimensional specimens. [ 35 ] The same technique is applied in archaeology to eliminate reflection on glass and similar specimens for photography. [ 36 ]
In organic synthesis saturated NH 4 Cl solution is typically used to quench reaction mixtures. [ 37 ]
It has a lambda transition at 242.8 K and zero pressure. [ 38 ]
Giant squid and some other large squid species maintain neutral buoyancy in seawater through an ammonium chloride solution which is found throughout their bodies and is less dense than seawater. [ 39 ] This differs from the method of flotation used by most fish, which involves a gas-filled swim bladder .
Around the turn of the 20th century, ammonium chloride was used in aqueous solution as the electrolyte in Leclanché cells that found a commercial use as the "local battery" in subscribers' telephone installations. Those cells later evolved into zinc–carbon batteries still using ammonium chloride as electrolyte.
Ammonium chloride is known to be an aggressive cleaning agent.
A penetrating and intense reddish brown color is stained into concrete surfaces with a mixture of ammonium chloride and ferric chloride . [ 40 ] Pre-treatment with acid is unnecessary.
Ammonium chloride can also be used in the process of making albumen silver prints, commonly known as albumen prints . In traditional photographic printing processes of the 19th century, ammonium chloride served as a key component in preparing the albumen solution used to coat the photographic paper. Albumen printing was the dominant photographic printing technique from the 1850s through the 1890s, prized for its fine detail and rich tonal rendition. The incorporation of ammonium chloride in the albumen solution was a significant factor in the quality and popularity of this photographic process. [ 41 ] The process involves mixing egg whites (albumen) with ammonium chloride to create a viscous solution. This mixture is then applied as a thin layer onto paper, which, after drying, forms a smooth and glossy surface. [ 42 ] Ammonium chloride acts as a salting agent, contributing chloride ions that are essential for forming light-sensitive silver chloride when the coated paper is subsequently sensitized with a solution of silver nitrate. Upon exposure to light, the silver chloride reduces to metallic silver, creating a visible image. [ 43 ] The use of ammonium chloride, as opposed to sodium chloride (common salt), can influence the contrast and tonal range of the final print, often yielding warmer tones and greater image clarity. [ 44 ]
Ammonium chloride is used in a ~5% aqueous solution to work on oil wells with clay swelling problems. Other uses include in hair shampoo, in the glue that bonds plywood, and in cleaning products. In hair shampoo, it is used as a thickening agent in ammonium-based surfactant systems such as ammonium lauryl sulfate . Ammonium chloride is used in the textile and leather industry, in dyeing, tanning, textile printing and cotton clustering. In woodworking, a solution of ammonium chloride and water, when applied to unfinished wood, will burn when subjected to a heat gun resulting in a branding iron mark without use of a branding iron. The solution can be painted onto the wood or applied with a common rubber stamp. [ 45 ]
Pliny , in Book XXXI of his Natural History , refers to a salt produced in the Roman province of Cyrenaica named hammoniacum , so called because of its proximity to the nearby Temple of Jupiter Amun ( Greek Ἄμμων Ammon ). [ 46 ] [ 47 ] However, the description Pliny gives of the salt does not conform to the properties of ammonium chloride. According to Herbert Hoover's commentary in his English translation of Georgius Agricola's De re metallica , it is likely to have been common sea salt. [ 48 ] Nevertheless, that salt ultimately gave ammonia and ammonium compounds their name.
The earliest mention of ammonium chloride was in 554 in China. [ 49 ] At that time, ammonium chloride came from two sources: (1) the vents of underground coal fires in Central Asia, specifically, in the Tian Shan mountains (which extend from Xinjiang province of northwestern China through Kyrgyzstan ) as well as in the Alay (or Alai) mountains of southwestern Kyrgyzstan, and (2) the fumaroles of the volcano Mount Taftan in southeastern Iran . [ 50 ] [ 51 ] [ 52 ] (Indeed, the word for ammonium chloride in several Asian languages derives from the Iranian phrase anosh adur (immortal fire), a reference to the underground fires.) [ 53 ] Ammonium chloride was then transported along the Silk Road eastwards to China and westwards to the Muslim lands and Europe.
Around 800 A.D. the Arabian chemist Jabir ibn Hayyan discovered ammonium chloride in the soot that resulted from burning camel dung, and this source became an alternative to those in Central Asia. [ 54 ] [ 55 ]
The Jabirian alchemists were the authors of the Jabirian corpus , tentatively dated to c. 850 – c. 950 . [ 56 ] The word for ammonium chloride in the Jabirian corpus was nošāder , Arabian in origin. Whereas Greek alchemical texts had been almost exclusively focused on the use of mineral substances, Jabirian alchemy pioneered the use of vegetable and animal substances, and so represented an innovative shift towards ' organic chemistry '. [ 57 ] In the Jabirian corpus, the production of ammonium chloride from organic substances (such as plants, blood, and hair) is described. These are the oldest known instructions for deriving an inorganic compound from organic substances by chemical means. [ 58 ]
One of the innovations in Jabirian alchemy was the addition of ammonium chloride to the category of chemical substances known as ' spirits ' (i.e., strongly volatile substances). This included both naturally occurring sal ammoniac and synthetic ammonium chloride produced from organic substances. The addition of sal ammoniac to the list of 'spirits' can perhaps also be seen as a product of this new focus on organic chemistry.
The first attested reference to sal ammoniac as ammonium chloride is in the Pseudo-Geber work De inventione veritatis , where a preparation of sal ammoniac is given in the chapter De Salis ammoniaci præparatione , sal ammoniacus (genitive: salis ammoniaci) being a common name in Latin of the Middle Ages for sal ammoniac. [ 59 ] | https://en.wikipedia.org/wiki/NH4+Cl- |
Ammonium bromide , NH 4 Br, is the ammonium salt of hydrobromic acid . The chemical crystallizes in colorless prisms, possessing a saline taste; it sublimes on heating and is easily soluble in water. On exposure to air it gradually assumes a yellow color because of the oxidation of bromide (Br − ) to bromine (Br 2 ).
Ammonium bromide can be prepared by the direct action of hydrogen bromide on ammonia .
It can also be prepared by the reaction of ammonia with iron(II) bromide or iron(III) bromide , which may be obtained by passing aqueous bromine solution over iron filings.
Ammonium bromide is a weak acid with a p K a of approximately 9 in water. It is an acid salt because the ammonium ion hydrolyzes slightly in water.
Ammonium bromide is a strong electrolyte when put in water:
Ammonium bromide decomposes to ammonia and hydrogen bromide when heated at elevated temperatures:
Ammonium bromide is used for photography in films , plates and papers ; in fireproofing of wood; in lithography and process engraving; in corrosion inhibitors; and in pharmaceutical preparations. [ 2 ] | https://en.wikipedia.org/wiki/NH4Br |
Ammonium acetate , also known as spirit of Mindererus in aqueous solution, is a chemical compound with the formula NH 4 CH 3 CO 2 . It is a white, hygroscopic solid and can be derived from the reaction of ammonia and acetic acid . It is available commercially. [ 5 ]
The synonym Spirit of Mindererus is named after R. Minderer, a physician from Augsburg . [ 6 ]
It is the main precursor to acetamide : [ 7 ]
It is also used as a diuretic. [ 5 ]
As the salt of a weak acid and a weak base, ammonium acetate is often used with acetic acid to create a buffer solution . Ammonium acetate is volatile at low pressures. Because of this, it has been used to replace cell buffers that contain non-volatile salts in preparing samples for mass spectrometry. [ 8 ] It is also popular as a buffer for mobile phases for HPLC with ELSD and CAD -based detection for this reason. Other volatile salts that have been used for this include ammonium formate .
When dissolving ammonium acetate in pure water, the resulting solution typically has a pH of 7, because the equal amounts of acetate and ammonium neutralize each other. However, ammonium acetate is a dual component buffer system, which buffers around pH 4.75 ± 1 (acetate) and pH 9.25 ± 1 (ammonium), but it has no significant buffer capacity at pH 7, contrary to common misconception. [ 9 ]
Ammonium acetate is also used as a food additive as an acidity regulator; INS number 264. It is approved for usage in Australia and New Zealand. [ 10 ]
Ammonium acetate is produced by the neutralization of acetic acid with ammonium carbonate or by saturating glacial acetic acid with ammonia . [ 11 ] Obtaining crystalline ammonium acetate is difficult on account of its hygroscopic nature. | https://en.wikipedia.org/wiki/NH4C2H3O2 |
Ammonium cyanide is an unstable inorganic compound with the chemical formula N H 4 C N . It is the ammonium salt of hydrogen cyanide . It consists of ammonium cations NH + 4 and cyanide anions CN − . Its structural formula is [NH 4 ] + [C≡N] − .
Ammonium cyanide is generally used in organic synthesis . [ citation needed ] Being unstable, it is not shipped or sold commercially.
Ammonium cyanide is prepared by combining solutions of hydrogen cyanide and ammonia : [ citation needed ]
It may be prepared by the reaction of calcium cyanide and ammonium carbonate : [ citation needed ]
In dry state, ammonium cyanide is made by heating a mixture of potassium cyanide or potassium ferrocyanide with ammonium chloride and condensing the vapours into ammonium cyanide crystals: [ citation needed ]
Ammonium cyanide decomposes to ammonia and hydrogen cyanide, often forming a black polymer of hydrogen cyanide: [ 1 ]
It undergoes salt metathesis reaction in solution with a number of metal salts to form metal–cyanide complexes .
Reaction with ketones and aldehydes yield aminonitriles , as in the first step of the Strecker amino acid synthesis :
Ammonium cyanide is highly toxic. | https://en.wikipedia.org/wiki/NH4CN |
Ammonium chloride is an inorganic chemical compound with the chemical formula N H 4 Cl , also written as [NH 4 ]Cl . It is an ammonium salt of hydrogen chloride . It consists of ammonium cations [NH 4 ] + and chloride anions Cl − . It is a white crystalline salt that is highly soluble in water. Solutions of ammonium chloride are mildly acidic. In its naturally occurring mineralogic form, it is known as salammoniac . The mineral is commonly formed on burning coal dumps from condensation of coal-derived gases. It is also found around some types of volcanic vents. It is mainly used as fertilizer and a flavouring agent in some types of liquorice . It is a product of the reaction of hydrochloric acid and ammonia .
It is a product of the Solvay process used to produce sodium carbonate : [ 3 ]
Not only is that method the principal one for the manufacture of ammonium chloride, but also it is used to minimize ammonia release in some industrial operations.
Ammonium chloride is prepared commercially by combining ammonia (NH 3 ) with either hydrogen chloride (gas) or hydrochloric acid (water solution): [ 3 ]
Ammonium chloride occurs naturally in volcanic regions, forming on volcanic rocks near fume-releasing vents ( fumaroles ). The crystals deposit directly from the gaseous state and tend to be short-lived, as they dissolve easily in water. [ 11 ]
Ammonium chloride appears to sublime upon heating but actually reversibly decomposes into ammonia and hydrogen chloride gas: [ 3 ]
Ammonium chloride reacts with a strong base, like sodium hydroxide , to release ammonia gas:
Similarly, ammonium chloride also reacts with alkali-metal carbonates at elevated temperatures, giving ammonia and alkali-metal chloride:
A solution of 5% by mass of ammonium chloride in water has a pH in the range 4.6 to 6.0. [ 12 ]
Some reactions of ammonium chloride with other chemicals are endothermic , such as its reaction with barium hydroxide and its dissolving in water.
The dominant application of ammonium chloride is as a nitrogen source in fertilizers (corresponding to 90% of the world production of ammonium chloride) such as chloroammonium phosphate. [ 13 ] The main crops fertilized this way are rice and wheat in Asia . [ 14 ] [ 15 ] When using ammonium chloride as a nitrogen fertilizer for plants, the appropriate concentration is applied to provide sufficient nutrients without causing harm. [ 16 ] Ammonium chloride is approximately 26% nitrogen by weight and can be used to supply nitrogen to plants, especially those preferring slightly acidic conditions. [ 17 ] The concentration for nitrogen fertilization in solution is between 50 and 100 milligrams of nitrogen per liter of water (mg N/L), which is equivalent to 50–100 parts per million (ppm) nitrogen, which translates to approximately 0.2 to 0.4 grams of ammonium chloride per liter of water. [ 18 ] Ammonium chloride can acidify the soil over time, so soil pH is regularly monitored, especially when growing plants sensitive to acidic conditions. [ 19 ] Some plants are sensitive to chloride ions (e.g., avocados, beans, grapes), so applying ammonium chloride to such plants should be done with extra caution to prevent chloride toxicity. [ 20 ] While ammonium chloride can be beneficial as a nitrogen source, improper use can harm plants and the environment. [ 21 ]
Ammonium chloride solutions are generally stable and can be stored for a certain period if kept under appropriate conditions, [ 22 ] that is in airtight containers (to prevent contamination, evaporation and hydrolysis), away from light (to prevent photodegradation ) and heat sources (to reduce microbial growth and chemical degradation), and if contamination is prevented. [ 22 ] In agricultural applications the solution is used shortly after preparation, [ 23 ] for the following reasons:
Ammonium chloride was used in pyrotechnics in the 18th century but was superseded by safer and less hygroscopic chemicals. Its purpose was to provide a chlorine donor to enhance the green and blue colours from copper ions in the flame.
It had a secondary use to provide white smoke, but its ready double decomposition reaction with potassium chlorate producing the highly unstable ammonium chlorate made its use very dangerous. [ 28 ] [ 29 ] [ 30 ]
Ammonium chloride is used as a flux in preparing metals to be tin coated, galvanized or soldered. It works as a flux by cleaning the surface of workpieces by reacting with the metal oxides at the surface to form a volatile metal chloride. For that purpose, it is sold in blocks at hardware stores for use in cleaning the tip of a soldering iron, and it can also be included in solder as flux.
Ammonium chloride is used as an expectorant in cough medicine. Its expectorant action is caused by irritative action on the bronchial mucosa, which causes the production of excess respiratory tract fluid, which presumably is easier to cough up. Ammonium salts are an irritant to the gastric mucosa and may induce nausea and vomiting.
Ammonium chloride is used as a systemic acidifying agent in treatment of severe metabolic alkalosis , in oral acid loading test to diagnose distal renal tubular acidosis, to maintain the urine at an acid pH in the treatment of some urinary-tract disorders. [ citation needed ]
Ammonium chloride, under the name sal ammoniac or salmiak is used as food additive under the E number E510, working as a yeast nutrient in breadmaking and as an acidifier. [ 31 ] It is a feed supplement for cattle and an ingredient in nutritive media for yeasts and many microorganisms.
Ammonium chloride is used in baking to give cookies a very crisp texture, to spice up dark sweets called salty liquorice (popular in the Nordic countries, Benelux and northern Germany), [ 32 ] and in the liquor Salmiakki Koskenkorva for flavouring. In Turkey, Iran, Tajikistan, India, Pakistan and Arab countries it is called "noshader" and is used to improve the crispness of snacks such as samosas and jalebi .
Ammonium chloride has been used historically to produce low temperatures in cooling baths . [ 33 ]
Ammonium chloride solutions with ammonia are used as buffer solutions including ACK (Ammonium-Chloride-Potassium) lysis buffer . [ 34 ]
In paleontology , ammonium chloride vapor is deposited on fossils , where the substance forms a brilliant white, easily removed and fairly harmless and inert layer of tiny crystals that covers up any coloration the fossil may have, and if lighted at an angle highly enhances contrast in photographic documentation of three-dimensional specimens. [ 35 ] The same technique is applied in archaeology to eliminate reflection on glass and similar specimens for photography. [ 36 ]
In organic synthesis saturated NH 4 Cl solution is typically used to quench reaction mixtures. [ 37 ]
It has a lambda transition at 242.8 K and zero pressure. [ 38 ]
Giant squid and some other large squid species maintain neutral buoyancy in seawater through an ammonium chloride solution which is found throughout their bodies and is less dense than seawater. [ 39 ] This differs from the method of flotation used by most fish, which involves a gas-filled swim bladder .
Around the turn of the 20th century, ammonium chloride was used in aqueous solution as the electrolyte in Leclanché cells that found a commercial use as the "local battery" in subscribers' telephone installations. Those cells later evolved into zinc–carbon batteries still using ammonium chloride as electrolyte.
Ammonium chloride is known to be an aggressive cleaning agent.
A penetrating and intense reddish brown color is stained into concrete surfaces with a mixture of ammonium chloride and ferric chloride . [ 40 ] Pre-treatment with acid is unnecessary.
Ammonium chloride can also be used in the process of making albumen silver prints, commonly known as albumen prints . In traditional photographic printing processes of the 19th century, ammonium chloride served as a key component in preparing the albumen solution used to coat the photographic paper. Albumen printing was the dominant photographic printing technique from the 1850s through the 1890s, prized for its fine detail and rich tonal rendition. The incorporation of ammonium chloride in the albumen solution was a significant factor in the quality and popularity of this photographic process. [ 41 ] The process involves mixing egg whites (albumen) with ammonium chloride to create a viscous solution. This mixture is then applied as a thin layer onto paper, which, after drying, forms a smooth and glossy surface. [ 42 ] Ammonium chloride acts as a salting agent, contributing chloride ions that are essential for forming light-sensitive silver chloride when the coated paper is subsequently sensitized with a solution of silver nitrate. Upon exposure to light, the silver chloride reduces to metallic silver, creating a visible image. [ 43 ] The use of ammonium chloride, as opposed to sodium chloride (common salt), can influence the contrast and tonal range of the final print, often yielding warmer tones and greater image clarity. [ 44 ]
Ammonium chloride is used in a ~5% aqueous solution to work on oil wells with clay swelling problems. Other uses include in hair shampoo, in the glue that bonds plywood, and in cleaning products. In hair shampoo, it is used as a thickening agent in ammonium-based surfactant systems such as ammonium lauryl sulfate . Ammonium chloride is used in the textile and leather industry, in dyeing, tanning, textile printing and cotton clustering. In woodworking, a solution of ammonium chloride and water, when applied to unfinished wood, will burn when subjected to a heat gun resulting in a branding iron mark without use of a branding iron. The solution can be painted onto the wood or applied with a common rubber stamp. [ 45 ]
Pliny , in Book XXXI of his Natural History , refers to a salt produced in the Roman province of Cyrenaica named hammoniacum , so called because of its proximity to the nearby Temple of Jupiter Amun ( Greek Ἄμμων Ammon ). [ 46 ] [ 47 ] However, the description Pliny gives of the salt does not conform to the properties of ammonium chloride. According to Herbert Hoover's commentary in his English translation of Georgius Agricola's De re metallica , it is likely to have been common sea salt. [ 48 ] Nevertheless, that salt ultimately gave ammonia and ammonium compounds their name.
The earliest mention of ammonium chloride was in 554 in China. [ 49 ] At that time, ammonium chloride came from two sources: (1) the vents of underground coal fires in Central Asia, specifically, in the Tian Shan mountains (which extend from Xinjiang province of northwestern China through Kyrgyzstan ) as well as in the Alay (or Alai) mountains of southwestern Kyrgyzstan, and (2) the fumaroles of the volcano Mount Taftan in southeastern Iran . [ 50 ] [ 51 ] [ 52 ] (Indeed, the word for ammonium chloride in several Asian languages derives from the Iranian phrase anosh adur (immortal fire), a reference to the underground fires.) [ 53 ] Ammonium chloride was then transported along the Silk Road eastwards to China and westwards to the Muslim lands and Europe.
Around 800 A.D. the Arabian chemist Jabir ibn Hayyan discovered ammonium chloride in the soot that resulted from burning camel dung, and this source became an alternative to those in Central Asia. [ 54 ] [ 55 ]
The Jabirian alchemists were the authors of the Jabirian corpus , tentatively dated to c. 850 – c. 950 . [ 56 ] The word for ammonium chloride in the Jabirian corpus was nošāder , Arabian in origin. Whereas Greek alchemical texts had been almost exclusively focused on the use of mineral substances, Jabirian alchemy pioneered the use of vegetable and animal substances, and so represented an innovative shift towards ' organic chemistry '. [ 57 ] In the Jabirian corpus, the production of ammonium chloride from organic substances (such as plants, blood, and hair) is described. These are the oldest known instructions for deriving an inorganic compound from organic substances by chemical means. [ 58 ]
One of the innovations in Jabirian alchemy was the addition of ammonium chloride to the category of chemical substances known as ' spirits ' (i.e., strongly volatile substances). This included both naturally occurring sal ammoniac and synthetic ammonium chloride produced from organic substances. The addition of sal ammoniac to the list of 'spirits' can perhaps also be seen as a product of this new focus on organic chemistry.
The first attested reference to sal ammoniac as ammonium chloride is in the Pseudo-Geber work De inventione veritatis , where a preparation of sal ammoniac is given in the chapter De Salis ammoniaci præparatione , sal ammoniacus (genitive: salis ammoniaci) being a common name in Latin of the Middle Ages for sal ammoniac. [ 59 ] | https://en.wikipedia.org/wiki/NH4Cl |
Ammonium chlorate is an inorganic compound with the formula NH 4 ClO 3 .
It is obtained by neutralizing chloric acid with either ammonia or ammonium carbonate , or by precipitating barium , strontium or calcium chlorates with ammonium carbonate or ammonium sulfate, producing the respective carbonate or sulfate precipitate and an ammonium chlorate solution. Ammonium chlorate crystallizes in small needles, readily soluble in water.
The bitartrate method is a candidate for production and can be used if exotic chlorates are currently inaccessible or need to be synthesized. Warm solutions of potassium chlorate and ammonium bitartrate are needed. The latter can be synthesized by adding aqueous ammonia to an excess of tartaric acid. Then, a double displacement reaction will result in precipitation of ammonium chlorate.
On heating, ammonium chlorate decomposes at about 102 °C, with liberation of nitrogen, chlorine and oxygen. It is soluble in dilute aqueous alcohol, but insoluble in strong alcohol. This compound is a powerful oxidizer and should never be stored with flammable materials, as it can easily form sensitive explosive compositions.
Ammonium chlorate is a very unstable oxidizer and will decompose independently, sometimes violently, at room temperature. [ 1 ] This results from the mixture of the reducing ammonium cation and the oxidizing chlorate anion. Even solutions are known to be unstable. Because of the dangerous nature of this salt it should only be kept in solution when needed, and never be allowed to crystallize.
Ammonium chlorate can be made by mixing stoichiometric solutions of ammonium nitrate and sodium chlorate or ammonium sulfate and barium chlorate. [ 2 ]
This inorganic compound –related article is a stub . You can help Wikipedia by expanding it . | https://en.wikipedia.org/wiki/NH4ClO3 |
Ammonium perchlorate ("AP") is an inorganic compound with the formula NH 4 ClO 4 . It is a colorless or white solid that is soluble in water. It is a powerful oxidizer . Combined with a fuel, it can be used as a rocket propellant called ammonium perchlorate composite propellant . Its instability has involved it in accidents such as the PEPCON disaster .
Ammonium perchlorate (AP) is produced by reaction between ammonia and perchloric acid . This process is the main outlet for the industrial production of perchloric acid . The salt also can be produced by salt metathesis reaction of ammonium salts with sodium perchlorate . This process exploits the relatively low solubility of NH 4 ClO 4 , which is about 10% of that for sodium perchlorate. [ 6 ]
AP crystallises as colorless rhombohedra .
Like most ammonium salts, ammonium perchlorate decomposes before melting . Mild heating results in production of hydrogen chloride , nitrogen , oxygen , and water.
The combustion of AP is quite complex and is widely studied. AP crystals decompose before melting, even though a thin liquid layer has been observed on crystal surfaces during high-pressure combustion processes. [ 7 ] Strong heating may lead to explosions . Complete reactions leave no residue. Pure crystals cannot sustain a flame below the pressure of 2 MPa .
AP is a Class 4 oxidizer (can undergo an explosive reaction) for particle sizes over 15 micrometres [ 8 ] and is classified as an explosive for particle sizes less than 15 micrometres. [ 9 ] [ 10 ]
During World War I England and France used mixtures featuring ammonium perchlorate (such as "balstine") as a substitute high explosive.
The primary use of ammonium perchlorate is in making solid rocket propellants. [ 11 ] When AP is mixed with a fuel (like a powdered aluminium and/or with an elastomeric binder ), it can generate self-sustained combustion at pressures far below atmospheric pressure. It is an important oxidizer with a decades-long history of use in solid rocket propellants – space launch (including the Space Shuttle Solid Rocket Booster ), military, amateur , and hobby high-power rockets , as well as in some fireworks.
Some "breakable" epoxy adhesives contain suspensions of AP. Upon heating to 300°C, the AP degrades the organic adhesive, breaking the cemented joint.
Perchlorate itself confers little acute toxicity. For example, sodium perchlorate has an LD 50 of 2–4g/kg and is eliminated rapidly after ingestion. [ 6 ] However, chronic exposure to perchlorates, even in low concentrations, has been shown to cause various thyroid problems, as it is taken up in place of iodine. | https://en.wikipedia.org/wiki/NH4ClO4 |
Ammonium fluoride is the inorganic compound with the formula NH 4 F. It crystallizes as small colourless prisms, having a sharp saline taste, and is highly soluble in water. Like all fluoride salts, it is moderately toxic in both acute and chronic overdose. [ citation needed ]
Ammonium fluoride adopts the wurtzite crystal structure, in which both the ammonium cations and the fluoride anions are stacked in ABABAB... layers, each being tetrahedrally surrounded by four of the other. There are N−H···F hydrogen bonds between the anions and cations. [ 3 ] This structure is very similar to ice , and ammonium fluoride is the only substance which can form mixed crystals with water. [ 4 ]
On passing hydrogen fluoride gas (in excess) through the salt, ammonium fluoride absorbs the gas to form the addition compound ammonium bifluoride . The reaction occurring is:
Ammonium fluoride sublimes when heated—a property common among ammonium salts. In the sublimation, the salt decomposes to ammonia and hydrogen fluoride; the two gases can still recombine, i.e. the reaction is reversible:
This substance is commonly called "commercial ammonium fluoride". The word "neutral" is sometimes added to "ammonium fluoride" to represent the neutral salt [NH 4 ]F as opposed to the "acid salt" ( NH 4 HF 2 ). The acid salt is usually used in preference to the neutral salt in the etching of glass and related silicates . This property is shared among all soluble fluorides. For this reason it cannot be handled in glass test tubes or apparatus during laboratory work.
Ammonium fluoride is a critical component of buffered oxide etch (BOE), a wet etchant used in microfabrication . It acts as the buffering agent in a solution of concentrated HF , creating an etchant with a more controllable rate of etching (than that of simple concentrated HF solutions). [ 5 ]
It is also used for preserving wood, as a mothproofing agent, in printing and dyeing textiles , and as an antiseptic in breweries . [ 6 ] | https://en.wikipedia.org/wiki/NH4F |
Ammonium dihydrogen phosphate ( ADP ), also known as monoammonium phosphate ( MAP ) [ 5 ] is a chemical compound with the chemical formula (NH 4 )(H 2 PO 4 ). ADP is a major ingredient of agricultural fertilizers [ 6 ] and dry chemical fire extinguishers . It also has significant uses in optics [ 7 ] and electronics . [ 8 ]
Monoammonium phosphate is soluble in water and crystallizes from it as the anhydrous salt in the tetragonal system, as elongated prisms or needles. [ 7 ] It is practically insoluble in ethanol . [ 2 ]
Solid monoammonium phosphate can be considered stable in practice for temperatures up to 200 °C, when it decomposes into gaseous ammonia NH 3 and molten phosphoric acid H 3 PO 4 . [ 9 ] At 125 °C the partial pressure of ammonia is 0.05 mm Hg. [ 10 ]
A solution of stoichometric monoammonium phosphate is acidic ( pH 4.7 at 0.1% concentration, 4.2 at 5%). [ 11 ]
Monoammonium phosphate is industrially prepared by the exothermic reaction of phosphoric acid and ammonia in the correct proportions: [ 12 ]
Crystalline MAP then precipitates.
The largest use of monoammonium phosphate by weight is in agriculture, as an ingredient of fertilizers. It supplies soil with the elements nitrogen and phosphorus in a form usable by plants. Its NPK label is 12-61-0 (12-27-0), meaning that it contains 12% by weight of elemental nitrogen and (nominally) 61% of phosphorus pentoxide P 2 O 5 , or 27% of elemental phosphorus.
The compound is also a component of the ABC powder in some dry chemical fire extinguishers .
Monoammonium phosphate is a widely used crystal in the field of optics due to its birefringence properties. As a result of its tetragonal crystal structure, this material has negative uniaxial optical symmetry with typical refractive indices n o = 1.522 and n e = 1.478 at optical wavelengths. [ 7 ]
Monoammonium phosphate crystals are piezoelectric , a property required in some active sonar transducers (the alternative being transducers that use magnetostriction ). In the 1950s ADP crystals largely replaced the quartz and Rochelle salt crystals in transducers because they are easier to work than quartz and, unlike Rochelle salt, are not deliquescent . [ 8 ]
Being relatively non-toxic [ citation needed ] , MAP is also a popular substance for recreational crystal growing, being sold as toy kits mixed with dyes of various colors.
The compound appears in nature as the rare mineral biphosphammite. It is formed in guano deposits. [ 13 ] [ 14 ] A related compound, that is the monohydrogen counterpart, is the even more scarce phosphammite. [ 15 ] [ 16 ] | https://en.wikipedia.org/wiki/NH4H2PO4 |
Ammonium bicarbonate is an inorganic compound with formula (NH 4 )HCO 3 . The compound has many names, reflecting its long history. Chemically speaking, it is the bicarbonate salt of the ammonium ion. It is a colourless solid that degrades readily to carbon dioxide, water and ammonia.
Ammonium bicarbonate is produced by combining carbon dioxide and ammonia:
Since ammonium bicarbonate is thermally unstable, the reaction solution is kept cold, which allows the precipitation of the product as white solid. About 100,000 tons were produced in this way in 1997. [ 3 ]
Ammonia gas passed into a strong aqueous solution of the sesquicarbonate (a 2:1:1 mixture of (NH 4 )HCO 3 , (NH 4 ) 2 CO 3 , and H 2 O) converts it into normal ammonium carbonate ((NH 4 ) 2 CO 3 ), which can be obtained in the crystalline condition from a solution prepared at about 30 °C. This compound on exposure to air gives off ammonia and reverts to ammonium bicarbonate.
Compositions containing ammonium carbonate have long been known. They were once produced commercially, formerly known as sal volatile or salt of hartshorn . It was obtained by the dry distillation of nitrogenous organic matter such as hair, horn, leather. In addition to ammonium bicarbonate, this material contains ammonium carbamate (NH 4 CO 2 NH 2 ), and ammonium carbonate ((NH 4 ) 2 CO 3 ). It is sometimes called ammonium sesquicarbonate. It possesses a strong ammoniacal smell, and on digestion with alcohol, the carbamate is dissolved leaving a residue of ammonium bicarbonate. [ 3 ]
A similar decomposition takes place when the sesquicarbonate is exposed to air.
Ammonium bicarbonate is used in the food industry as a leavening agent for flat baked goods, such as cookies and crackers. It was commonly used in the home before modern-day baking powder was made available. Many baking cookbooks, especially from Scandinavian countries, may still refer to it as hartshorn or hornsalt, [ 4 ] [ 5 ] while it is known as "hirvensarvisuola" in Finnish, "hjortetakksalt" or "hornsalt" in Norwegian, "hjortetakssalt" in Danish, "hjorthornssalt" in Swedish, and "Hirschhornsalz" in German (lit., "salt of hart's horn"). Although there is a slight smell of ammonia during baking, this quickly dissipates, leaving no taste. It is used in, for example, Swedish "drömmar" biscuits and Danish "klejner" Christmas biscuits, and German Lebkuchen. In many cases it may be replaced with baking soda or baking powder, or a combination of both, depending on the recipe composition and leavening requirements. [ 6 ] Compared to baking soda or potash , hartshorn has the advantage of producing more gas for the same amount of agent, and of not leaving any salty or soapy taste in the finished product, as it completely decomposes into water and gaseous products that evaporate during baking. It cannot be used for moist, bulky baked goods however, such as normal bread or cakes, since some ammonia will be trapped inside and will cause an unpleasant taste. It has been assigned E number E503 for use as a food additive in the European Union .
It is commonly used as an inexpensive nitrogen fertilizer in China, but is now being phased out in favor of urea for quality and stability. This compound is used as a component in the production of fire-extinguishing compounds, pharmaceuticals, dyes , pigments, and it is also a basic fertilizer, being a source of ammonia. Ammonium bicarbonate is still widely used in the plastics and rubber industry, in the manufacture of ceramics , in chrome leather tanning , and for the synthesis of catalysts . [ citation needed ]
It is also used for buffering solutions to make them slightly alkaline during chemical purification, such as high-performance liquid chromatography . Because it entirely decomposes to volatile compounds, this allows rapid recovery of the compound of interest by freeze-drying . Relatedly it is also useful as an alkaline buffering agent for analytical LC–MS as its volatility allows it to be rapidly removed automatically from the sample stream in the low pressure spray chambers used by many standard mass spectrometry detectors found at the end of typical LC-MS systems, such as electrospray ionization detectors. This is critical as most mass spectrometry detectors become signal saturated or even damaged with more than a trace amount of ions entering the detector proper at any one time. This issue limits buffering agents and other additives in LC-MS buffers to either extremely trace concentrations or to fairly volatile compounds. In pH ranges from about 7 to 9, ammonium bicarbonate is one of the only options available as the primary buffering agent for most LC-MS buffers.
Ammonium bicarbonate is also a key component of the expectorant cough syrup " Senega and Ammonia".
It's also used as an attractant for catching insect such as walnut husk fly ( Rhagoletis completa ).
It dissolves in water to give a mildly alkaline solution. It is insoluble in acetone and alcohols .
Ammonium bicarbonate decomposes above about 36 °C into ammonia , carbon dioxide , and water in an endothermic process and so causes a drop in the temperature of the water:
When treated with acids , ammonium salts are also produced:
Reaction with base produces ammonia.
It reacts with sulfates of alkaline-earth metals precipitating their carbonates:
It also reacts with alkali metal halides, giving alkali metal bicarbonate and ammonium halide:
The compound occurs in nature as an exceedingly rare mineral teschemacherite . [ 7 ] [ 8 ] It can also be obtained from deer antlers. [ 9 ]
Ammonium bicarbonate is an irritant to the skin , eyes and respiratory system . Short-term health effects may occur immediately or shortly after exposure to ammonium bicarbonate. Breathing ammonium bicarbonate can irritate the nose, throat and lungs causing coughing, wheezing and/or shortness of breath. Repeated exposure may cause bronchitis to develop with cough, and/or shortness of breath. Health effects can occur some time after exposure to ammonium bicarbonate and can last for months or years.
Where possible, operations should be enclosed and the use of local exhaust ventilation at the site of chemical release is recommended. If local exhaust ventilation or enclosure is not used, respirators are necessary. Wear protective work clothing and change clothes and wash thoroughly immediately after exposure to ammonium bicarbonate. [ 10 ]
Ammonium bicarbonate from China used to make cookies was found to be contaminated with melamine , and imports were banned in Malaysia following the 2008 Chinese milk scandal . [ 11 ] | https://en.wikipedia.org/wiki/NH4HCO3 |
Ammonium bifluoride is an inorganic compound with the formula [NH 4 ][HF 2 ] or [NH 4 ]F·HF . It is produced from ammonia and hydrogen fluoride . This colourless salt is a glass- etchant and an intermediate in a once-contemplated route to hydrofluoric acid .
Ammonium bifluoride, as its name indicates, contains an ammonium cation ( [NH 4 ] + ), and a bifluoride (or hydrogen difluoride) anion ( [HF 2 ] − ). The triatomic bifluoride anion features a strong three-center four-electron bond (specifically, a symmetrical hydrogen bond ) with a bond energy greater than 155 kJ/mol, [ 2 ] and an H-F length of 114 pm. [ 3 ]
In solid form ( [NH 4 ][HF 2 ] ), ammonium biflouride is similar to other fluoride salts. [ 4 ] Its crystal system is considered orthorhombic , [ 5 ] with each cation coordinated with four anions in a tetrahedron (and vice versa). Hydrogen atoms in the ammonium ion form hydrogen bonds with the fluorine atoms, and in the resulting structure, N-H-F are roughly colinear. [ 6 ] [ 7 ] As a result of these hydrogen bonds, this crystal structure varies from those of other bifluoride salts, such as potassium bifluoride and rubidium bifluoride . [ 5 ] Its crystals are unstable, and decompose rapidly when exposed to air. [ 6 ]
Ammonium bifluoride is a component of some etchants. It attacks silica component of glass:
Potassium bifluoride is a related more commonly used etchant.
Ammonium bifluoride has been considered as an intermediate in the production of hydrofluoric acid from hexafluorosilicic acid . Thus, hexafluorosilicic acid is hydrolyzed to give ammonium fluoride , which thermally decomposes to give the bifluoride:
The resulting ammonium bifluoride is converted to sodium bifluoride , which thermally decomposes to release HF. [ 8 ]
Ammonium bifluoride is also used as an additive in tin-nickel plating processes as the fluoride ion acts as a complexing agent with the tin, allowing for greater control over the resulting composition and finish.
Ammonium bifluoride is toxic to consume and a skin corrosion agent. Upon exposure to skin, rinsing with water followed by a treatment of calcium gluconate is required. [ 1 ] In water, ammonium bifluoride exists in chemical equilibrium with hydrofluoric acid and heating releases hydrogen fluoride gas. [ 9 ] Consequently, there is an equivalent toxicological risk as is present with hydrofluoric acid, and the same safety precautions apply. [ 10 ] [ 9 ]
Ammonium bifluoride is used in some automotive wheel cleaning products. Many injuries have resulted in users not being aware of the risks posed by the products. [ 11 ] Ammonium bifluoride based products are often considered a safer alternative to hydrofluoric acid, yet still pose clear risks to the handler. [ 10 ] Ammonium bifluoride, ammonium fluoride, and hydrofluoric acid have been described as "too dangerous for any use in a car wash environment" by Professional Car Washing and Detailing magazine, [ 12 ] advice that accords with a 2015 report from the U.S. Centers for Disease Control and Prevention . [ 13 ] | https://en.wikipedia.org/wiki/NH4HF2 |
Ammonium hydrosulfide is the chemical compound with the formula [NH 4 ]SH .
It is the salt derived from the ammonium cation and the hydrosulfide anion . The salt exists as colourless, water-soluble, micaceous crystals. On Earth the compound is encountered mainly as a solution, not as the solid, but [NH 4 ]SH ice is believed to be a substantial component of the cloud decks of the gas-giant planets Jupiter and Saturn , with sulfur produced by its photolysis responsible for the color of some of those planets' clouds. It can be generated by mixing hydrogen sulfide and ammonia .
Solutions of ammonium hydrosulfide can be prepared by passing hydrogen sulfide gas through concentrated ammonia solution. [ 4 ] According to a detailed 1895 report, hydrogen sulfide reacts with concentrated aqueous ammonia solution at room temperature to give [NH 4 ] 2 S·2[NH 4 ]SH . When this species is cooled to 0 °C and treated with additional hydrogen sulfide, one obtains [NH 4 ] 2 S·12[NH 4 ]SH . [ 5 ] An ice-cold solution of this substance kept at 0 °C and having hydrogen sulfide continually passed through it gives the hydrosulfide.
The common " stink bomb " consists of an aqueous solution of ammonium sulfide. The mixture easily converts to ammonia and hydrogen sulfide gases. This conversion illustrates the ease of the following equilibrium:
Ammonia and hydrogen sulfide each possesses a powerful stench.
Solid ammonium hydrosulfide can be produced by reacting an equimolar mixture of ammonia and hydrogen sulfide under -18 °C: [ 6 ]
Aqueous solutions of ammonium sulfide (CAS registry number 12135-76-1 ), also known as diammonium sulfide are commercially available, although the composition of these solutions is uncertain as they could consist of a mixture of ammonia and [NH 4 ]SH . Ammonium sulfide solutions are used occasionally in photographic developing , to apply patina to bronze , and in textile manufacturing. It can be used as a selective reducing agent (cf. 2,4-dinitrochlorobenzene ); where there are two nitro groups, only one of them is selectively reduced.
The 1990–91 CRC Handbook of Chemistry and Physics gives information for anhydrous ammonium monosulfide ( [NH 4 ] 2 S ) and ammonium pentasulfide ( [NH 4 ] 2 S 5 ) as separate from anhydrous ammonium hydrosulfide ( [NH 4 ]SH ), describing the former two both as yellow crystalline substances that are soluble in cold water and alcohol, and which both decompose in hot water or at high temperature in general (115 °C for the pentasulfide), but the latter as a white crystalline solid (which also decomposes in hot water). [ 1 ] Thus, it seems that solid ammonium sulfide can be distinct from solid ammonium hydrosulfide, even if this is not true in aqueous solution. | https://en.wikipedia.org/wiki/NH4HS |
Ammonium iodide is the inorganic compound with the formula NH 4 I. A white solid. It is an ionic compound , although impure samples appear yellow. This salt consists of ammonium cation and an iodide anion. [ 1 ] It can be prepared by the action of hydroiodic acid on ammonia . It is easily soluble in water , from which it crystallizes in cubes. It is also soluble in ethanol . Ammonium iodide in aqueous solutions are observed as acidic and display elevated vapor pressures at high temperatures [ 2 ]
Ammonium iodide can be made in lab by treating ammonia with hydroiodic acid:
Ammonium iodide is used as dietary supplement to treat iodine deficiency . [ 3 ]
Ammonium iodide has recently been used in many research studies and experiments.
Vinyl sulfones have been prepared using ammonium iodide,. [ 4 ]
Organic reactions are not synthesized with organic solvents due to their increasing detrimental effects on the human body and ecosystem. [ 5 ] Many chemists have altered organic reactions to exclude solvents in order to have successful sustainable syntheses. A report was presented on an organic synthesis for the iodination of ketones and aromatic compounds using ammonium iodide and H 2 O 2 (hydrogen peroxide). [ 5 ] This resulted in the products' high yields, which were gathered more efficiently, in a shorter duration compared to the use of the abrasive compound: molecular iodine [ 5 ] | https://en.wikipedia.org/wiki/NH4I |
Ammonium triiodide [ 1 ] [ 2 ] (NH 4 I 3 ) is the salt of the ammonium cation with the triiodide anion.
Sometimes the name ammonium triiodide is mistakenly used to refer to a different compound, nitrogen triiodide (NI 3 ), or more precisely, the slightly more stable ammine , NI 3 · NH 3 .
This inorganic compound –related article is a stub . You can help Wikipedia by expanding it . | https://en.wikipedia.org/wiki/NH4I3 |
Ammonium nitrite is a chemical compound with the chemical formula [NH 4 ]NO 2 . It is the ammonium salt of nitrous acid . It is composed of ammonium cations [NH 4 ] + and nitrite anions NO − 2 . It is not used in pure isolated form since it is highly unstable and decomposes into water and nitrogen , even at room temperature.
Ammonium nitrite forms naturally in the air and can be prepared by the absorption of equal parts nitrogen dioxide and nitric oxide in aqueous ammonia . [ 1 ]
It can also be synthesized by oxidizing ammonia with ozone or hydrogen peroxide , or in a precipitation reaction of barium or lead nitrite with ammonium sulfate , or silver nitrite with ammonium chloride , or ammonium perchlorate with potassium nitrite . The precipitate is filtered off and the solution concentrated. It forms colorless crystals which are soluble in water.
Ammonium nitrite may explode at a temperature of 60–70 °C, [ 1 ] and will decompose quicker when dissolved in a concentrated aqueous solution, than in the form of a dry crystal. Even in room temperature the compound slowly decomposes into water and nitrogen:
It decomposes when heated or in the presence of acid into water and nitrogen. [ 2 ] Ammonium nitrite solution is stable at higher pH and lower temperature. If there is any decrease in pH lower than 7.0, it may lead to an explosion, since the nitrite can react to it. A safe pH can be maintained by adding an ammonia solution. The mole ratio of ammonium nitrite to ammonia must be above 10%. | https://en.wikipedia.org/wiki/NH4NO2 |
Ammonium nitrate is a chemical compound with the formula NH 4 NO 3 . It is a white crystalline salt consisting of ions of ammonium and nitrate . It is highly soluble in water and hygroscopic as a solid, but does not form hydrates . It is predominantly used in agriculture as a high-nitrogen fertilizer . [ 5 ]
Its other major use is as a component of explosive mixtures used in mining, quarrying, and civil construction. It is the major constituent of ANFO , an industrial explosive which accounts for 80% of explosives used in North America; similar formulations have been used in improvised explosive devices .
Many countries are phasing out its use in consumer applications due to concerns over its potential for misuse. [ 6 ] Accidental ammonium nitrate explosions have killed thousands of people since the early 20th century. [ 6 ] [ 7 ] Global production was estimated at 21.6 million tonnes in 2017. [ 8 ] By 2021, global production of ammonium nitrate was down to 16.7 million tonnes. [ 7 ]
Ammonium nitrate is found as the natural mineral gwihabaite (formerly known as nitrammite) [ 9 ] – the ammonium analogue of saltpetre (mineralogical name: niter) [ 10 ] [ 11 ] – in the driest regions of the Atacama Desert in Chile , often as a crust on the ground or in conjunction with other nitrate, iodate , and halide minerals . Ammonium nitrate was mined there until the Haber–Bosch process made it possible to synthesize nitrates from atmospheric nitrogen, rendering nitrate mining obsolete.
The industrial production of ammonium nitrate entails the acid-base reaction of ammonia with nitric acid : [ 12 ]
The ammonia required for this process is obtained by the Haber process from nitrogen and hydrogen. Ammonia produced by the Haber process can be oxidized to nitric acid by the Ostwald process . Ammonia is used in its anhydrous form (a gas) and the nitric acid is concentrated. The reaction is violent owing to its highly exothermic nature. After the solution is formed, typically at about 83% concentration, the excess water is evaporated off to leave an ammonium nitrate (AN) content of 95% to 99.9% concentration (AN melt), depending on grade. The AN melt is then made into "prills" or small beads in a spray tower , or into granules by spraying and tumbling in a rotating drum. The prills or granules may be further dried, cooled, and then coated to prevent caking. These prills or granules are the typical AN products in commerce.
Another production method is a variant of the nitrophosphate process :
The products, calcium carbonate and ammonium nitrate, may be separately purified or sold combined as calcium ammonium nitrate .
Ammonium nitrate can also be made via metathesis reactions :
As ammonium nitrate is a salt , both the cation, NH + 4 , and the anion, NO − 3 , may take part in chemical reactions.
Solid ammonium nitrate decomposes on heating. At temperatures below around 300 °C, the decomposition mainly produces nitrous oxide and water:
At higher temperatures, the following reaction predominates. [ 13 ]
Both decomposition reactions are exothermic and their products are gases. Under certain conditions, this can lead to a runaway reaction , with the decomposition process becoming explosive. [ 14 ] See § Disasters for details. Many ammonium nitrate disasters , with loss of lives, have occurred.
The red–orange colour in an explosion cloud is due to nitrogen dioxide , a secondary reaction product. [ 14 ]
Several crystalline phases of ammonium nitrate have been observed. The following occur under atmospheric pressure.
The transition between β-rhombic to α-rhombic forms (at 32.3 °C) occurs at ambient temperature in many parts of the world. These forms have a 3.6% difference in density and hence transition between them causes a change in volume. One practical consequence of this is that ammonium nitrate cannot be used as a solid rocket motor propellant, as it develops cracks. Stabilized ammonium nitrate (PSAN) was developed as a solution to this and incorporates metal halides stabilisers, which prevent density fluctuations. [ 16 ]
Ammonium nitrate is an important fertilizer with NPK rating 34-0-0 (34% nitrogen). [ 17 ] It is less concentrated than urea (46-0-0), giving ammonium nitrate a slight transportation disadvantage. Ammonium nitrate's advantage over urea is that it is more stable and does not rapidly lose nitrogen to the atmosphere.
Ammonium nitrate readily forms explosive mixtures with varying properties when combined with explosives such as TNT or with fuels like aluminium powder or fuel oil.
Examples of explosives containing ammonium nitrate include:
ANFO is a mixture of 94% ammonium nitrate ("AN") and 6% fuel oil ("FO") widely used as a bulk industrial explosive . [ 18 ] : 1 It is used in coal mining , quarrying , metal mining , and civil construction in undemanding applications where the advantages of ANFO's low cost, relative safety, and ease of use matter more than the benefits offered by conventional industrial explosives, such as water resistance, oxygen balance , high detonation velocity, and performance in small diameters. [ 18 ] : 2
Ammonium nitrate-based explosives were used in the Sterling Hall bombing in Madison, Wisconsin, 1970, the Oklahoma City bombing in 1995, the 2011 Delhi bombings , the 2011 bombing in Oslo , the Myyrmanni bombing and the 2013 Hyderabad blasts .
In November 2009, the government of the KPK (previously termed as NWFP) of Pakistan imposed a ban on ammonium sulfate , ammonium nitrate, and calcium ammonium nitrate fertilizers in the former Malakand Division – comprising the Upper Dir , Lower Dir , Swat , Chitral , and Malakand districts of the NWFP – following reports that those chemicals were used by militants to make explosives. Due to these bans, " Potassium chlorate – the material which allows safety matches to catch fire – has surpassed fertilizer as the explosive of choice for insurgents." [ 19 ]
Ammonium nitrate is used in some instant cold packs , as its dissolution in water is highly endothermic . In 2021, King Abdullah University of Science and Technology in Saudi Arabia conducted experiments to study the potential for dissolving ammonium nitrate in water for off-grid cooling systems and as a refrigerant. They suggested that the water could be distilled and reused using solar energy to avoid water wastage in severe environments. [ 20 ]
It was once used, in combination with independently explosive "fuels" such as guanidine nitrate , [ 21 ] [ 22 ] as a cheaper (but less stable) alternative to 5-aminotetrazole in the inflators of airbags manufactured by Takata Corporation , which were recalled as unsafe after killing 14 people. [ 23 ] The current USA death total is 27. [ 24 ]
Numerous safety guidelines are available for storing and handling ammonium nitrate. Health and safety data are shown on the safety data sheets available from suppliers and from various governments. [ 25 ] [ 26 ] [ 27 ]
Pure ammonium nitrate does not burn, but as a strong oxidizer, it supports and accelerates the combustion of organic (and some inorganic) material. [ 25 ] [ 28 ] [ 29 ] It should not be stored near combustible substances.
While ammonium nitrate is stable at ambient temperature and pressure under many conditions, it may detonate from a strong initiation charge. It should not be stored near high explosives or blasting agents.
Molten ammonium nitrate is very sensitive to shock and detonation, particularly if it becomes contaminated with incompatible materials such as combustibles, flammable liquids, acids, chlorates, chlorides, sulfur, metals, charcoal and sawdust. [ 30 ] [ 25 ]
Contact with certain substances such as chlorates , mineral acids and metal sulfides , can lead to vigorous or even violent decomposition capable of igniting nearby combustible material or detonating. [ 31 ] [ 32 ]
Ammonium nitrate begins decomposition after melting, releasing NO x , HNO 3 , NH 3 and H 2 O . It should not be heated in a confined space. [ 25 ] The resulting heat and pressure from decomposition increases the sensitivity to detonation and increases the speed of decomposition. Detonation may occur at 80 atmospheres . Contamination can reduce this to 20 atmospheres. [ 30 ]
Ammonium nitrate has a critical relative humidity of 59.4% at 30 °C. At higher humidity it will absorb moisture from the atmosphere. Therefore, it is important to store ammonium nitrate in a tightly sealed container. Otherwise, it can coalesce into a large, solid mass. Ammonium nitrate can absorb enough moisture to liquefy. Blending ammonium nitrate with certain other fertilizers can lower the critical relative humidity. [ 33 ]
The potential for use of the material as an explosive has prompted regulatory measures. For example, in Australia, the Dangerous Goods Regulations came into effect in August 2005 to enforce licensing in dealing with such substances. [ 34 ] Licenses are granted only to applicants (industry) with appropriate security measures in place to prevent any misuse. [ 35 ] Additional uses such as education and research purposes may also be considered, but individual use will not. Employees of those with licenses to deal with the substance are still required to be supervised by authorized personnel and are required to pass a security and national police check before a license may be granted.
Ammonium nitrate is not hazardous to health and is usually used in fertilizer products. [ 36 ] [ 37 ] [ 38 ]
Ammonium nitrate has an LD 50 of 2217 mg/kg, [ 39 ] which for comparison is about two-thirds that of table salt .
Ammonium nitrate decomposes, non-explosively, into the gases nitrous oxide and water vapor when heated. However, it can be induced to decompose explosively by detonation . [ 40 ] Large stockpiles of the material can also be a major fire risk due to their supporting oxidation , a situation which can easily escalate to detonation. Explosions are not uncommon: relatively minor incidents occur most years, and several large and devastating explosions have also occurred. Examples include the Oppau explosion of 1921 (one of the largest artificial non-nuclear explosions ), the Texas City disaster of 1947, the 2015 Tianjin explosions in China, and the 2020 Beirut explosion . [ 41 ]
Ammonium nitrate can explode through two mechanisms: | https://en.wikipedia.org/wiki/NH4NO3 |
Ammonium perrhenate (APR) is the ammonium salt of perrhenic acid , NH 4 ReO 4 . It is the most common form in which rhenium is traded. It is a white salt; soluble in ethanol and water, and mildly soluble in NH 4 Cl. [ 2 ] It was first described soon after the discovery of rhenium. [ 3 ]
The crystal structure of APR resembles that of scheelite , with atomic cation is replaced by ammonium. The pertechnetate (NH 4 TcO 4 ), periodate (NH 4 IO 4 ), tetrachlorothallate (NH 4 TlCl 4 ), and tetrachloroindate (NH 4 InCl 4 ) follow this motif. [ 4 ] It undergoes a molecular orientational ordering transition on cooling without change of space group, but with a highly anisotropic change in the shape of the unit cell , resulting in the unusual property of having a positive temperature and pressure Re NQR coefficient. [ 5 ] APR does not give hydrates. [ 2 ]
Ammonium perrhenate may be prepared from virtually all common sources of rhenium. The metal, oxides, and sulfides can be oxidized with nitric acid and the resulting solution treated with aqueous ammonia. Alternatively an aqueous solution of Re 2 O 7 can be treated with ammonia followed by crystallisation. [ 6 ] [ 7 ]
Ammonium perrhenate is weak oxidizer. It slowly reacts with hydrochloric acid: [ 2 ]
It is reduced to metallic Re upon heating under hydrogen : [ 1 ]
Ammonium perrhenate decomposes to volatile Re 2 O 7 starting at 250 °C. When heated in a sealed tube at 500 °C, It decomposes to rhenium dioxide : [ 1 ]
The ammonium ion can be displaced with some concentrated nitrates e.g. potassium nitrate,, silver nitrate, etc.: [ 2 ]
It can be reduced to nonahydridorhenate with sodium in ethanol: [ 2 ] | https://en.wikipedia.org/wiki/NH4ReO4 |
Ammonium hydrosulfide is the chemical compound with the formula [NH 4 ]SH .
It is the salt derived from the ammonium cation and the hydrosulfide anion . The salt exists as colourless, water-soluble, micaceous crystals. On Earth the compound is encountered mainly as a solution, not as the solid, but [NH 4 ]SH ice is believed to be a substantial component of the cloud decks of the gas-giant planets Jupiter and Saturn , with sulfur produced by its photolysis responsible for the color of some of those planets' clouds. It can be generated by mixing hydrogen sulfide and ammonia .
Solutions of ammonium hydrosulfide can be prepared by passing hydrogen sulfide gas through concentrated ammonia solution. [ 4 ] According to a detailed 1895 report, hydrogen sulfide reacts with concentrated aqueous ammonia solution at room temperature to give [NH 4 ] 2 S·2[NH 4 ]SH . When this species is cooled to 0 °C and treated with additional hydrogen sulfide, one obtains [NH 4 ] 2 S·12[NH 4 ]SH . [ 5 ] An ice-cold solution of this substance kept at 0 °C and having hydrogen sulfide continually passed through it gives the hydrosulfide.
The common " stink bomb " consists of an aqueous solution of ammonium sulfide. The mixture easily converts to ammonia and hydrogen sulfide gases. This conversion illustrates the ease of the following equilibrium:
Ammonia and hydrogen sulfide each possesses a powerful stench.
Solid ammonium hydrosulfide can be produced by reacting an equimolar mixture of ammonia and hydrogen sulfide under -18 °C: [ 6 ]
Aqueous solutions of ammonium sulfide (CAS registry number 12135-76-1 ), also known as diammonium sulfide are commercially available, although the composition of these solutions is uncertain as they could consist of a mixture of ammonia and [NH 4 ]SH . Ammonium sulfide solutions are used occasionally in photographic developing , to apply patina to bronze , and in textile manufacturing. It can be used as a selective reducing agent (cf. 2,4-dinitrochlorobenzene ); where there are two nitro groups, only one of them is selectively reduced.
The 1990–91 CRC Handbook of Chemistry and Physics gives information for anhydrous ammonium monosulfide ( [NH 4 ] 2 S ) and ammonium pentasulfide ( [NH 4 ] 2 S 5 ) as separate from anhydrous ammonium hydrosulfide ( [NH 4 ]SH ), describing the former two both as yellow crystalline substances that are soluble in cold water and alcohol, and which both decompose in hot water or at high temperature in general (115 °C for the pentasulfide), but the latter as a white crystalline solid (which also decomposes in hot water). [ 1 ] Thus, it seems that solid ammonium sulfide can be distinct from solid ammonium hydrosulfide, even if this is not true in aqueous solution. | https://en.wikipedia.org/wiki/NH4SH |
Ammonium sulfate (American English and international scientific usage; ammonium sulphate in British English ); (NH 4 ) 2 SO 4 , is an inorganic salt with a number of commercial uses. The most common use is as a soil fertilizer. It contains 21% nitrogen and 24% sulfur .
The primary use of ammonium sulfate is as a fertilizer for alkaline soils . In the soil, the ammonium ion is released and forms a small amount of acid, lowering the pH balance of the soil , while contributing essential nitrogen for plant growth. One disadvantage to the use of ammonium sulfate is its low nitrogen content relative to ammonium nitrate , which elevates transportation costs. [ 2 ]
It is also used as an agricultural spray adjuvant for water-soluble insecticides , herbicides , and fungicides . There, it functions to bind iron and calcium cations that are present in both well water and plant cells. It is particularly effective as an adjuvant for 2,4-D (amine), glyphosate , and glufosinate herbicides.
Ammonium sulfate precipitation is a common method for protein purification by precipitation. As the ionic strength of a solution increases, the solubility of proteins in that solution decreases. Being extremely soluble in water, ammonium sulfate can "salt out" (precipitate) proteins from aqueous solutions. [ 3 ] [ 4 ] Precipitation by ammonium sulfate is a result of a reduction in solubility rather than protein denaturation , thus the precipitated protein can be resolubilized through the use of standard buffers . [ 5 ] Ammonium sulfate precipitation provides a convenient and simple means to fractionate complex protein mixtures. [ 6 ]
In the analysis of rubber lattices, volatile fatty acids are analyzed by precipitating rubber with a 35% ammonium sulfate solution, which leaves a clear liquid from which volatile fatty acids are regenerated with sulfuric acid and then distilled with steam. Selective precipitation with ammonium sulfate, opposite to the usual precipitation technique which uses acetic acid, does not interfere with the determination of volatile fatty acids. [ 7 ]
As a food additive, ammonium sulfate is considered generally recognized as safe (GRAS) by the U.S. Food and Drug Administration , [ 8 ] and in the European Union it is designated by the E number E517. It is used as an acidity regulator in flours and breads. [ 9 ] [ 10 ] [ 11 ]
Ammonium sulfate is a precursor to other ammonium salts, especially ammonium persulfate .
Ammonium sulfate is listed as an ingredient for many United States vaccines per the Centers for Disease Control . [ 12 ]
Ammonium sulfate has also been used in flame retardant compositions acting much like diammonium phosphate . As a flame retardant, it increases the combustion temperature of the material, decreases maximum weight loss rates, and causes an increase in the production of residue or char. [ 13 ]
Ammonium sulfate is made by treating ammonia with sulfuric acid :
A mixture of ammonia gas and water vapor is introduced into a reactor that contains a saturated solution of ammonium sulfate and about 2% to 4% of free sulfuric acid at 60 °C. Concentrated sulfuric acid is added to keep the solution acidic, and to retain its level of free acid. The heat of reaction keeps reactor temperature at 60 °C. Dry, powdered ammonium sulfate may be formed by spraying sulfuric acid into a reaction chamber filled with ammonia gas. The heat of reaction evaporates all water present in the system, forming a powdery salt. Approximately 6,000 million tons were produced in 1981. [ 2 ]
Ammonium sulfate also is manufactured from gypsum (CaSO 4 ·2H 2 O). Finely divided gypsum is added to an ammonium carbonate solution. Calcium carbonate precipitates as a solid, leaving ammonium sulfate in the solution.
Ammonium sulfate occurs naturally as the rare mineral mascagnite in volcanic fumaroles and due to coal fires on some dumps. [ 14 ]
Ammonium sulfate is a byproduct in the production of methyl methacrylate . [ 15 ]
Ammonium sulfate becomes ferroelectric at temperatures below −49.5 °C. At room temperature it crystallises in the orthorhombic system, with cell sizes of a = 7.729 Å, b = 10.560 Å, c = 5.951 Å. When chilled into the ferrorelectric state, the symmetry of the crystal changes to space group Pna2 1 . [ 16 ]
Ammonium sulfate decomposes upon heating above 250 °C (482 °F), first forming ammonium bisulfate . Heating at higher temperatures results in decomposition into ammonia , nitrogen , sulfur dioxide , and water. [ 17 ]
As a salt of a strong acid (H 2 SO 4 ) and weak base (NH 3 ), its solution is acidic; the pH of 0.1 M solution is 5.5. In aqueous solution the reactions are those of NH + 4 and SO 2− 4 ions. For example, addition of barium chloride , precipitates out barium sulfate . The filtrate on evaporation yields ammonium chloride .
Ammonium sulfate forms many double salts (ammonium metal sulfates) when its solution is mixed with equimolar solutions of metal sulfates and the solution is slowly evaporated. With trivalent metal ions, alums such as ferric ammonium sulfate are formed. Double metal sulfates include ammonium cobaltous sulfate, ferrous diammonium sulfate , ammonium nickel sulfate which are known as Tutton's salts and ammonium ceric sulfate . [ 2 ] Anhydrous double sulfates of ammonium also occur in the Langbeinites family. The ammonia produced has a pungent smell and is toxic.
Airborne particles of evaporated ammonium sulfate comprise approximately 30% of fine particulate pollution worldwide. [ 18 ]
It reacts with additional sulfuric acid to give triammonium hydrogen disulphate,, (NH 4 ) 3 H(SO 4 ) 2 . [ 19 ]
In November 2009, a ban on ammonium sulfate, ammonium nitrate and calcium ammonium nitrate fertilizers was imposed in the former Malakand Division —comprising the Upper Dir , Lower Dir , Swat , Chitral and Malakand districts of the North West Frontier Province (NWFP) of Pakistan , by the NWFP government, following reports that they were used by militants to make explosives. In January 2010, these substances were also banned in Afghanistan for the same reason. [ 20 ] | https://en.wikipedia.org/wiki/NH4SO4 |
Ammonium metavanadate is the inorganic compound with the formula NH 4 VO 3 . It is a white salt, although samples are often yellow owing to impurities of V 2 O 5 . It is an important intermediate in the purification of vanadium. [ 2 ]
The compound is prepared by the addition of ammonium salts to solutions of vanadate ions, generated by dissolution of V 2 O 5 in basic aqueous solutions, such as hot sodium carbonate. The compound precipitates as a colourless solid. [ 3 ] [ 4 ] This precipitation step can be slow.
The compound adopts a polymeric structure consisting of chains of [VO 3 ] − , formed as corner-sharing VO 4 tetrahedra. These chains are interconnected via hydrogen bonds with ammonium ions. [ 5 ]
Vanadium is often purified from aqueous extracts of slags and ore by selective precipitation of ammonium metavanadate. The material is then roasted to give vanadium pentoxide : [ 2 ]
Vanadates can behave as structural mimics of phosphates, and in this way they exhibit biological activity. [ 6 ] [ 7 ]
Ammonium metavanadate is used to prepare Mandelin reagent , a qualitative test for alkaloids . [ citation needed ] | https://en.wikipedia.org/wiki/NH4VO3 |
NHS Research Scotland ( NRS , formerly Health Science Scotland and Scottish Academic Health Science Collaboration ), is a government agency that supports clinical and translational research in Scotland. [ 1 ] NRS is a partnership between 4 of Scotland's medical schools ( Edinburgh , Glasgow , Dundee and Aberdeen ), the Scottish NHS Boards and the Chief Scientist Office . [ 1 ] [ 2 ] NRS brings together the most senior figures from across Government, academia and the NHS.
This article related to government in Scotland is a stub . You can help Wikipedia by expanding it .
This article about a scientific organization is a stub . You can help Wikipedia by expanding it . | https://en.wikipedia.org/wiki/NHS_Research_Scotland |
Ammonia is an inorganic chemical compound of nitrogen and hydrogen with the formula N H 3 . A stable binary hydride and the simplest pnictogen hydride , ammonia is a colourless gas with a distinctive pungent smell. Biologically, it is a common nitrogenous waste , and it contributes significantly to the nutritional needs of terrestrial organisms by serving as a precursor to fertilisers . [ 13 ] Around 70% of ammonia produced industrially is used to make fertilisers [ 14 ] in various forms and composition, such as urea and diammonium phosphate . Ammonia in pure form is also applied directly into the soil.
Ammonia, either directly or indirectly, is also a building block for the synthesis of many chemicals.
Ammonia occurs in nature and has been detected in the interstellar medium. In many countries, it is classified as an extremely hazardous substance . [ 15 ]
Ammonia is toxic, causing damage to cells and tissues. For this reason it is excreted by most animals in the urine, in the form of dissolved urea.
Ammonia is produced biologically in a process called nitrogen fixation , but even more is generated industrially by the Haber process . The process helped revolutionize agriculture by providing cheap fertilizers. The global industrial production of ammonia in 2021 was 235 million tonnes. [ 16 ] [ 17 ] Industrial ammonia is transported by road in tankers , by rail in tank wagons , by sea in gas carriers , or in cylinders . [ 18 ]
Ammonia boils at −33.34 °C (−28.012 °F) at a pressure of one atmosphere , but the liquid can often be handled in the laboratory without external cooling. Household ammonia or ammonium hydroxide is a solution of ammonia in water.
Pliny , in Book XXXI of his Natural History , refers to a salt named hammoniacum , so called because of the proximity of its source to the Temple of Jupiter Amun ( Greek Ἄμμων Ammon ) in the Roman province of Cyrenaica . [ 19 ] However, the description Pliny gives of the salt does not conform to the properties of ammonium chloride . According to Herbert Hoover 's commentary in his English translation of Georgius Agricola 's De re metallica , it is likely to have been common sea salt. [ 20 ] In any case, that salt ultimately gave ammonia and ammonium compounds their name.
Traces of ammonia/ammonium are found in rainwater. Ammonium chloride ( sal ammoniac ), and ammonium sulfate are found in volcanic districts. Crystals of ammonium bicarbonate have been found in Patagonia guano . [ 21 ]
Ammonia is found throughout the Solar System on Mars , Jupiter , Saturn , Uranus , Neptune , and Pluto , among other places: on smaller, icy bodies such as Pluto, ammonia can act as a geologically important antifreeze, as a mixture of water and ammonia can have a melting point as low as −100 °C (−148 °F; 173 K) if the ammonia concentration is high enough and thus allow such bodies to retain internal oceans and active geology at a far lower temperature than would be possible with water alone. [ 22 ] [ 23 ] Substances containing ammonia, or those that are similar to it, are called ammoniacal . [ 24 ]
Ammonia is a colourless gas with a characteristically pungent smell . It is lighter than air , its density being 0.589 times that of air . It is easily liquefied due to the strong hydrogen bonding between molecules. Gaseous ammonia turns to a colourless liquid , which boils at −33.1 °C (−27.58 °F), and freezes to colourless crystals [ 21 ] at −77.7 °C (−107.86 °F). Little data is available at very high temperatures and pressures, but the liquid-vapor critical point occurs at 405 K and 11.35 MPa. [ 25 ]
The crystal symmetry is cubic, Pearson symbol cP16, space group P2 1 3 No.198, lattice constant 0.5125 nm . [ 26 ]
Liquid ammonia possesses strong ionising powers reflecting its high ε of 22 at −35 °C (−31 °F). [ 27 ] Liquid ammonia has a very high standard enthalpy change of vapourization (23.5 kJ/mol ; [ 28 ] for comparison, water 's is 40.65 kJ/mol, methane 8.19 kJ/mol and phosphine 14.6 kJ/mol) and can be transported in pressurized or refrigerated vessels; however, at standard temperature and pressure liquid anhydrous ammonia will vaporize. [ 29 ]
Ammonia readily dissolves in water. In an aqueous solution, it can be expelled by boiling. The aqueous solution of ammonia is basic , and may be described as aqueous ammonia or ammonium hydroxide . [ 30 ] The maximum concentration of ammonia in water (a saturated solution ) has a specific gravity of 0.880 and is often known as '.880 ammonia'. [ 31 ]
Liquid ammonia is a widely studied nonaqueous ionising solvent. Its most conspicuous property is its ability to dissolve alkali metals to form highly coloured, electrically conductive solutions containing solvated electrons . Apart from these remarkable solutions, much of the chemistry in liquid ammonia can be classified by analogy with related reactions in aqueous solutions . Comparison of the physical properties of NH 3 with those of water shows NH 3 has the lower melting point, boiling point, density, viscosity , dielectric constant and electrical conductivity . These differences are attributed at least in part to the weaker hydrogen bonding in NH 3 . The ionic self- dissociation constant of liquid NH 3 at −50 °C is about 10 −33 .
Liquid ammonia is an ionising solvent, although less so than water, and dissolves a range of ionic compounds, including many nitrates , nitrites , cyanides , thiocyanates , metal cyclopentadienyl complexes and metal bis(trimethylsilyl)amides . [ 32 ] Most ammonium salts are soluble and act as acids in liquid ammonia solutions. The solubility of halide salts increases from fluoride to iodide . A saturated solution of ammonium nitrate ( Divers' solution , named after Edward Divers ) contains 0.83 mol solute per mole of ammonia and has a vapour pressure of less than 1 bar even at 25 °C (77 °F). However, few oxyanion salts with other cations dissolve. [ 34 ]
Liquid ammonia will dissolve all of the alkali metals and other electropositive metals such as Ca , [ 35 ] Sr , Ba , Eu and Yb (also Mg using an electrolytic process [ 33 ] ). At low concentrations (<0.06 mol/L), deep blue solutions are formed: these contain metal cations and solvated electrons , free electrons that are surrounded by a cage of ammonia molecules.
These solutions are strong reducing agents. At higher concentrations, the solutions are metallic in appearance and in electrical conductivity. At low temperatures, the two types of solution can coexist as immiscible phases.
The range of thermodynamic stability of liquid ammonia solutions is very narrow, as the potential for oxidation to dinitrogen, E ° ( N 2 + 6 [NH 4 ] + + 6 e − ⇌ 8 NH 3 ), is only +0.04 V. In practice, both oxidation to dinitrogen and reduction to dihydrogen are slow. This is particularly true of reducing solutions: the solutions of the alkali metals mentioned above are stable for several days, slowly decomposing to the metal amide and dihydrogen. Most studies involving liquid ammonia solutions are done in reducing conditions; although oxidation of liquid ammonia is usually slow, there is still a risk of explosion, particularly if transition metal ions are present as possible catalysts.
The ammonia molecule has a trigonal pyramidal shape, as predicted by the valence shell electron pair repulsion theory (VSEPR theory) with an experimentally determined bond angle of 106.7°. [ 36 ] The central nitrogen atom has five outer electrons with an additional electron from each hydrogen atom. This gives a total of eight electrons, or four electron pairs that are arranged tetrahedrally . Three of these electron pairs are used as bond pairs, which leaves one lone pair of electrons. The lone pair repels more strongly than bond pairs; therefore, the bond angle is not 109.5°, as expected for a regular tetrahedral arrangement, but 106.7°. [ 36 ] This shape gives the molecule a dipole moment and makes it polar . The molecule's polarity, and especially its ability to form hydrogen bonds , makes ammonia highly miscible with water. The lone pair makes ammonia a base , a proton acceptor. Ammonia is moderately basic; a 1.0 M aqueous solution has a pH of 11.6, and if a strong acid is added to such a solution until the solution is neutral ( pH = 7 ), 99.4% of the ammonia molecules are protonated . Temperature and salinity also affect the proportion of ammonium [NH 4 ] + . The latter has the shape of a regular tetrahedron and is isoelectronic with methane .
The ammonia molecule readily undergoes nitrogen inversion at room temperature; a useful analogy is an umbrella turning itself inside out in a strong wind. The energy barrier to this inversion is 24.7 kJ/mol, and the resonance frequency is 23.79 GHz , corresponding to microwave radiation of a wavelength of 1.260 cm. The absorption at this frequency was the first microwave spectrum to be observed [ 37 ] and was used in the first maser .
One of the most characteristic properties of ammonia is its basicity . Ammonia is considered to be a weak base. It combines with acids to form ammonium salts ; thus, with hydrochloric acid it forms ammonium chloride (sal ammoniac); with nitric acid , ammonium nitrate , etc. Perfectly dry ammonia gas will not combine with perfectly dry hydrogen chloride gas; moisture is necessary to bring about the reaction. [ 38 ] [ 39 ]
As a demonstration experiment under air with ambient moisture, opened bottles of concentrated ammonia and hydrochloric acid solutions produce a cloud of ammonium chloride , which seems to appear 'out of nothing' as the salt aerosol forms where the two diffusing clouds of reagents meet between the two bottles.
The salts produced by the action of ammonia on acids are known as the ammonium salts and all contain the ammonium ion ( [NH 4 ] + ). [ 38 ]
Although ammonia is well known as a weak base, it can also act as an extremely weak acid. It is a protic substance and is capable of formation of amides (which contain the NH − 2 ion). For example, lithium dissolves in liquid ammonia to give a blue solution ( solvated electron ) of lithium amide :
Like water, liquid ammonia undergoes molecular autoionisation to form its acid and base conjugates :
Ammonia often functions as a weak base , so it has some buffering ability. Shifts in pH will cause more or fewer ammonium cations ( NH + 4 ) and amide anions ( NH − 2 ) to be present in solution . At standard pressure and temperature,
Ammonia does not burn readily or sustain combustion , except under narrow fuel-to-air mixtures of 15–28% ammonia by volume in air. [ 40 ] When mixed with oxygen , it burns with a pale yellowish-green flame. Ignition occurs when chlorine is passed into ammonia, forming nitrogen and hydrogen chloride ; if chlorine is present in excess, then the highly explosive nitrogen trichloride ( NCl 3 ) is also formed.
The combustion of ammonia to form nitrogen and water is exothermic :
The standard enthalpy change of combustion , Δ H ° c , expressed per mole of ammonia and with condensation of the water formed, is −382.81 kJ/mol. Dinitrogen is the thermodynamic product of combustion : all nitrogen oxides are unstable with respect to N 2 and O 2 , which is the principle behind the catalytic converter . Nitrogen oxides can be formed as kinetic products in the presence of appropriate catalysts , a reaction of great industrial importance in the production of nitric acid :
A subsequent reaction leads to NO 2 :
The combustion of ammonia in air is very difficult in the absence of a catalyst (such as platinum gauze or warm chromium(III) oxide ), due to the relatively low heat of combustion , a lower laminar burning velocity, high auto-ignition temperature , high heat of vapourization , and a narrow flammability range . However, recent studies have shown that efficient and stable combustion of ammonia can be achieved using swirl combustors, thereby rekindling research interest in ammonia as a fuel for thermal power production. [ 41 ] The flammable range of ammonia in dry air is 15.15–27.35% and in 100% relative humidity air is 15.95–26.55%. [ 42 ] [ clarification needed ] For studying the kinetics of ammonia combustion, knowledge of a detailed reliable reaction mechanism is required, but this has been challenging to obtain. [ 43 ]
Ammonia is a direct or indirect precursor to most manufactured nitrogen-containing compounds . It is the precursor to nitric acid, which is the source for most N-substituted aromatic compounds.
Amines can be formed by the reaction of ammonia with alkyl halides or, more commonly, with alcohols :
Its ring-opening reaction with ethylene oxide give ethanolamine , diethanolamine , and triethanolamine .
Amides can be prepared by the reaction of ammonia with carboxylic acid and their derivatives. For example, ammonia reacts with formic acid (HCOOH) to yield formamide ( HCONH 2 ) when heated. Acyl chlorides are the most reactive, but the ammonia must be present in at least a twofold excess to neutralise the hydrogen chloride formed. Esters and anhydrides also react with ammonia to form amides. Ammonium salts of carboxylic acids can be dehydrated to amides by heating to 150–200 °C as long as no thermally sensitive groups are present.
Other organonitrogen compounds include alprazolam , ethanolamine , ethyl carbamate and hexamethylenetetramine .
Nitric acid is generated via the Ostwald process by oxidation of ammonia with air over a platinum catalyst at 700–850 °C (1,292–1,562 °F), ≈9 atm. Nitric oxide and nitrogen dioxide are intermediate in this conversion: [ 44 ]
Nitric acid is used for the production of fertilisers , explosives , and many organonitrogen compounds.
The hydrogen in ammonia is susceptible to replacement by a myriad substituents.
Ammonia gas reacts with metallic sodium to give sodamide , NaNH 2 . [ 38 ]
With chlorine, monochloramine is formed.
Pentavalent ammonia is known as λ 5 -amine, nitrogen pentahydride decomposes spontaneously into trivalent ammonia (λ 3 -amine) and hydrogen gas at normal conditions. This substance was once investigated as a possible solid rocket fuel in 1966. [ 45 ]
Ammonia is also used to make the following compounds:
Ammonia is a ligand forming metal ammine complexes . For historical reasons, ammonia is named ammine in the nomenclature of coordination compounds . One notable ammine complex is cisplatin ( Pt(NH 3 ) 2 Cl 2 , a widely used anticancer drug. Ammine complexes of chromium (III) formed the basis of Alfred Werner 's revolutionary theory on the structure of coordination compounds. Werner noted only two isomers ( fac - and mer -) of the complex [CrCl 3 (NH 3 ) 3 ] could be formed, and concluded the ligands must be arranged around the metal ion at the vertices of an octahedron .
Ammonia forms 1:1 adducts with a variety of Lewis acids such as I 2 , phenol , and Al(CH 3 ) 3 . Ammonia is a hard base (HSAB theory) and its E & C parameters are E B = 2.31 and C B = 2.04. Its relative donor strength toward a series of acids, versus other Lewis bases, can be illustrated by C-B plots .
Ammonia and ammonium salts can be readily detected, in very minute traces, by the addition of Nessler's solution , which gives a distinct yellow colouration in the presence of the slightest trace of ammonia or ammonium salts. The amount of ammonia in ammonium salts can be estimated quantitatively by distillation of the salts with sodium (NaOH) or potassium hydroxide (KOH), the ammonia evolved being absorbed in a known volume of standard sulfuric acid and the excess of acid then determined volumetrically ; or the ammonia may be absorbed in hydrochloric acid and the ammonium chloride so formed precipitated as ammonium hexachloroplatinate , [NH 4 ] 2 [PtCl 6 ] . [ 46 ]
Sulfur sticks are burnt to detect small leaks in industrial ammonia refrigeration systems. Larger quantities can be detected by warming the salts with a caustic alkali or with quicklime , when the characteristic smell of ammonia will be at once apparent. [ 46 ] Ammonia is an irritant and irritation increases with concentration; the permissible exposure limit is 25 ppm , and lethal above 500 ppm by volume. [ 47 ] Higher concentrations are hardly detected by conventional detectors, the type of detector is chosen according to the sensitivity required (e.g. semiconductor, catalytic, electrochemical). Holographic sensors have been proposed for detecting concentrations up to 12.5% in volume. [ 48 ]
In a laboratorial setting, gaseous ammonia can be detected by using concentrated hydrochloric acid or gaseous hydrogen chloride. A dense white fume (which is ammonium chloride vapor) arises from the reaction between ammonia and HCl(g). [ 49 ]
Ammoniacal nitrogen (NH 3 –N) is a measure commonly used for testing the quantity of ammonium ions, derived naturally from ammonia, and returned to ammonia via organic processes, in water or waste liquids. It is a measure used mainly for quantifying values in waste treatment and water purification systems, as well as a measure of the health of natural and man-made water reserves. It is measured in units of mg/L ( milligram per litre ).
The ancient Greek historian Herodotus mentioned that there were outcrops of salt in an area of Libya that was inhabited by a people called the 'Ammonians' (now the Siwa oasis in northwestern Egypt, where salt lakes still exist). [ 50 ] [ 51 ] The Greek geographer Strabo also mentioned the salt from this region. However, the ancient authors Dioscorides , Apicius , Arrian , Synesius , and Aëtius of Amida described this salt as forming clear crystals that could be used for cooking and that were essentially rock salt . [ 52 ] Hammoniacus sal appears in the writings of Pliny , [ 53 ] although it is not known whether the term is equivalent to the more modern sal ammoniac (ammonium chloride). [ 21 ] [ 54 ] [ 55 ]
The fermentation of urine by bacteria produces a solution of ammonia ; hence fermented urine was used in Classical Antiquity to wash cloth and clothing, to remove hair from hides in preparation for tanning, to serve as a mordant in dyeing cloth, and to remove rust from iron. [ 56 ] It was also used by ancient dentists to wash teeth. [ 57 ] [ 58 ] [ 59 ]
In the form of sal ammoniac (نشادر, nushadir ), ammonia was important to the Muslim alchemists . It was mentioned in the Book of Stones , likely written in the 9th century and attributed to Jābir ibn Hayyān . [ 60 ] It was also important to the European alchemists of the 13th century, being mentioned by Albertus Magnus . [ 21 ] It was also used by dyers in the Middle Ages in the form of fermented urine to alter the colour of vegetable dyes. In the 15th century, Basilius Valentinus showed that ammonia could be obtained by the action of alkalis on sal ammoniac. [ 61 ] At a later period, when sal ammoniac was obtained by distilling the hooves and horns of oxen and neutralizing the resulting carbonate with hydrochloric acid , the name 'spirit of hartshorn' was applied to ammonia. [ 21 ] [ 62 ]
Gaseous ammonia was first isolated by Joseph Black in 1756 by reacting sal ammoniac ( ammonium chloride ) with calcined magnesia ( magnesium oxide ). [ 63 ] [ 64 ] It was isolated again by Peter Woulfe in 1767, [ 65 ] [ 66 ] by Carl Wilhelm Scheele in 1770 [ 67 ] and by Joseph Priestley in 1773 and was termed by him 'alkaline air'. [ 21 ] [ 68 ] Eleven years later in 1785, Claude Louis Berthollet ascertained its composition. [ 69 ] [ 21 ]
The production of ammonia from nitrogen in the air (and hydrogen) was invented by Fritz Haber and Robert LeRossignol. The patent was sent in 1909 (USPTO Nr 1,202,995) and awarded in 1916. Later, Carl Bosch developed the industrial method for ammonia production ( Haber–Bosch process ). It was first used on an industrial scale in Germany during World War I , [ 70 ] following the allied blockade that cut off the supply of nitrates from Chile . The ammonia was used to produce explosives to sustain war efforts. [ 71 ] The Nobel Prize in Chemistry 1918 was awarded to Fritz Haber "for the synthesis of ammonia from its elements".
Before the availability of natural gas, hydrogen as a precursor to ammonia production was produced via the electrolysis of water or using the chloralkali process .
With the advent of the steel industry in the 20th century, ammonia became a byproduct of the production of coking coal.
In the US as of 2019 [update] , approximately 88% of ammonia was used as fertilisers either as its salts, solutions or anhydrously . [ 72 ] When applied to soil, it helps provide increased yields of crops such as maize and wheat . [ 73 ] 30% of agricultural nitrogen applied in the US is in the form of anhydrous ammonia, and worldwide, 110 million tonnes are applied each year. [ 74 ] Solutions of ammonia ranging from 16% to 25% are used in the fermentation industry as a source of nitrogen for microorganisms and to adjust pH during fermentation. [ 75 ]
Because of ammonia's vapourization properties, it is a useful refrigerant . [ 70 ] It was commonly used before the popularisation of chlorofluorocarbons (Freons). Anhydrous ammonia is widely used in industrial refrigeration applications and hockey rinks because of its high energy efficiency and low cost. It suffers from the disadvantage of toxicity, and requiring corrosion resistant components, which restricts its domestic and small-scale use. Along with its use in modern vapour-compression refrigeration it is used in a mixture along with hydrogen and water in absorption refrigerators . The Kalina cycle , which is of growing importance to geothermal power plants, depends on the wide boiling range of the ammonia–water mixture.
Ammonia coolant is also used in the radiators aboard the International Space Station in loops that are used to regulate the internal temperature and enable temperature-dependent experiments. [ 76 ] [ 77 ] The ammonia is under sufficient pressure to remain liquid throughout the process. Single-phase ammonia cooling systems also serve the power electronics in each pair of solar arrays.
The potential importance of ammonia as a refrigerant has increased with the discovery that vented CFCs and HFCs are potent and stable greenhouse gases. [ 78 ]
As early as in 1895, it was known that ammonia was 'strongly antiseptic ; it requires 1.4 grams per litre to preserve beef tea (broth).' [ 79 ] In one study, anhydrous ammonia destroyed 99.999% of zoonotic bacteria in three types of animal feed , but not silage . [ 80 ] [ 81 ] Anhydrous ammonia is currently used commercially to reduce or eliminate microbial contamination of beef . [ 82 ] [ 83 ] Lean finely textured beef (popularly known as ' pink slime ') in the beef industry is made from fatty beef trimmings (c. 50–70% fat) by removing the fat using heat and centrifugation , then treating it with ammonia to kill E. coli . The process was deemed effective and safe by the US Department of Agriculture based on a study that found that the treatment reduces E. coli to undetectable levels. [ 84 ] There have been safety concerns about the process as well as consumer complaints about the taste and smell of ammonia-treated beef. [ 85 ]
Ammonia has been used as fuel, and is a proposed alternative to fossil fuels and hydrogen. Being liquid at ambient temperature under its own vapour pressure and having high volumetric and gravimetric energy density, ammonia is considered a suitable carrier for hydrogen, [ 86 ] and may be cheaper than direct transport of liquid hydrogen. [ 87 ]
Compared to hydrogen, ammonia is easier to store. Compared to hydrogen as a fuel , ammonia is much more energy efficient, and could be produced, stored and delivered at a much lower cost than hydrogen, which must be kept compressed or as a cryogenic liquid. [ 88 ] [ 89 ] The raw energy density of liquid ammonia is 11.5 MJ/L, [ 88 ] which is about a third that of diesel .
Ammonia can be converted back to hydrogen to be used to power hydrogen fuel cells, or it may be used directly within high-temperature solid oxide direct ammonia fuel cells to provide efficient power sources that do not emit greenhouse gases . [ 90 ] [ 91 ] Ammonia to hydrogen conversion can be achieved through the sodium amide process [ 92 ] or the catalytic decomposition of ammonia using solid catalysts. [ 93 ]
Ammonia engines or ammonia motors, using ammonia as a working fluid , have been proposed and occasionally used. [ 94 ] The principle is similar to that used in a fireless locomotive , but with ammonia as the working fluid, instead of steam or compressed air. Ammonia engines were used experimentally in the 19th century by Goldsworthy Gurney in the UK and the St. Charles Streetcar Line in New Orleans in the 1870s and 1880s, [ 95 ] and during World War II ammonia was used to power buses in Belgium . [ 96 ]
Ammonia is sometimes proposed as a practical alternative to fossil fuel for internal combustion engines . [ 96 ] [ 97 ] [ 98 ] [ 99 ] However, ammonia cannot be easily used in existing Otto cycle engines because of its very narrow flammability range . Despite this, several tests have been run. [ 100 ] [ 101 ] [ 102 ] Its high octane rating of 120 [ 103 ] and low flame temperature [ 104 ] allows the use of high compression ratios without a penalty of high NO x production. Since ammonia contains no carbon, its combustion cannot produce carbon dioxide , carbon monoxide , hydrocarbons , or soot .
Ammonia production currently creates 1.8% of global CO 2 emissions. 'Green ammonia' is ammonia produced by using green hydrogen (hydrogen produced by electrolysis with electricity from renewable energy), whereas 'blue ammonia' is ammonia produced using blue hydrogen (hydrogen produced by steam methane reforming) where the carbon dioxide has been captured and stored. [ 105 ]
Rocket engines have also been fueled by ammonia. The Reaction Motors XLR99 rocket engine that powered the X-15 hypersonic research aircraft used liquid ammonia. Although not as powerful as other fuels, it left no soot in the reusable rocket engine, and its density approximately matches the density of the oxidiser, liquid oxygen , which simplified the aircraft's design.
In 2020, Saudi Arabia shipped 40 metric tons of liquid 'blue ammonia' to Japan for use as a fuel. [ 106 ] It was produced as a by-product by petrochemical industries, and can be burned without giving off greenhouse gases . Its energy density by volume is nearly double that of liquid hydrogen. If the process of creating it can be scaled up via purely renewable resources, producing green ammonia, it could make a major difference in avoiding climate change . [ 107 ] The company ACWA Power and the city of Neom have announced the construction of a green hydrogen and ammonia plant in 2020. [ 108 ]
Green ammonia is considered as a potential fuel for future container ships. In 2020, the companies DSME and MAN Energy Solutions announced the construction of an ammonia-based ship, DSME plans to commercialize it by 2025. [ 109 ] The use of ammonia as a potential alternative fuel for aircraft jet engines is also being explored. [ 110 ]
Japan intends to implement a plan to develop ammonia co-firing technology that can increase the use of ammonia in power generation, as part of efforts to assist domestic and other Asian utilities to accelerate their transition to carbon neutrality . [ 111 ] In October 2021, the first International Conference on Fuel Ammonia (ICFA2021) was held. [ 112 ] [ 113 ]
In June 2022, IHI Corporation succeeded in reducing greenhouse gases by over 99% during combustion of liquid ammonia in a 2,000-kilowatt-class gas turbine achieving truly CO 2 -free power generation. [ 114 ] In July 2022, Quad nations of Japan, the U.S., Australia and India agreed to promote technological development for clean-burning hydrogen and ammonia as fuels at the security grouping's first energy meeting. [ 115 ] As of 2022 [update] , however, significant amounts of NO x are produced. [ 116 ] Nitrous oxide may also be a problem as it is a " greenhouse gas that is known to possess up to 300 times the Global Warming Potential (GWP) of carbon dioxide ". [ 117 ]
The IEA forecasts that ammonia will meet approximately 45% of shipping fuel demands by 2050. [ 118 ]
At high temperature and in the presence of a suitable catalyst ammonia decomposes into its constituent elements. [ 119 ] Decomposition of ammonia is a slightly endothermic process requiring 23 kJ/mol (5.5 kcal/mol ) of ammonia, and yields hydrogen and nitrogen gas.
Ammonia is used to scrub SO 2 from the burning of fossil fuels, and the resulting product is converted to ammonium sulfate for use as fertiliser. Ammonia neutralises the nitrogen oxide ( NO x ) pollutants emitted by diesel engines. This technology, called SCR ( selective catalytic reduction ), relies on a vanadia -based catalyst. [ 120 ]
Ammonia may be used to mitigate gaseous spills of phosgene . [ 121 ]
Ammonia, as the vapour released by smelling salts , has found significant use as a respiratory stimulant. Ammonia is commonly used in the illegal manufacture of methamphetamine through a Birch reduction . [ 123 ] The Birch method of making methamphetamine is dangerous because the alkali metal and liquid ammonia are both extremely reactive, and the temperature of liquid ammonia makes it susceptible to explosive boiling when reactants are added. [ 124 ]
Liquid ammonia is used for treatment of cotton materials, giving properties like mercerisation , using alkalis. In particular, it is used for prewashing of wool. [ 125 ]
At standard temperature and pressure, ammonia is less dense than atmosphere and has approximately 45–48% of the lifting power of hydrogen or helium . Ammonia has sometimes been used to fill balloons as a lifting gas . Because of its relatively high boiling point (compared to helium and hydrogen), ammonia could potentially be refrigerated and liquefied aboard an airship to reduce lift and add ballast (and returned to a gas to add lift and reduce ballast). [ 126 ]
Ammonia has been used to darken quartersawn white oak in Arts & Crafts and Mission-style furniture. Ammonia fumes react with the natural tannins in the wood and cause it to change colour. [ 127 ]
The US Occupational Safety and Health Administration (OSHA) has set a 15-minute exposure limit for gaseous ammonia of 35 ppm by volume in the environmental air and an 8-hour exposure limit of 25 ppm by volume. [ 129 ] The National Institute for Occupational Safety and Health (NIOSH) recently reduced the IDLH (Immediately Dangerous to Life or Health, the level to which a healthy worker can be exposed for 30 minutes without suffering irreversible health effects) from 500 to 300 ppm based on recent more conservative interpretations of original research in 1943. Other organisations have varying exposure levels. US Navy Standards [U.S. Bureau of Ships 1962] maximum allowable concentrations (MACs): for continuous exposure (60 days) is 25 ppm; for exposure of 1 hour is 400 ppm. [ 130 ]
Ammonia vapour has a sharp, irritating, pungent odor that acts as a warning of potentially dangerous exposure. The average odor threshold is 5 ppm, well below any danger or damage. Exposure to very high concentrations of gaseous ammonia can result in lung damage and death. [ 129 ] Ammonia is regulated in the US as a non-flammable gas, but it meets the definition of a material that is toxic by inhalation and requires a hazardous safety permit when transported in quantities greater than 3,500 US gallons (13,000 L; 2,900 imp gal). [ 131 ]
Liquid ammonia is dangerous because it is hygroscopic and because it can cause caustic burns . See Gas carrier § Health effects of specific cargoes carried on gas carriers for more information.
The toxicity of ammonia solutions does not usually cause problems for humans and other mammals, as a specific mechanism exists to prevent its build-up in the bloodstream. Ammonia is converted to carbamoyl phosphate by the enzyme carbamoyl phosphate synthetase , and then enters the urea cycle to be either incorporated into amino acids or excreted in the urine. [ 132 ] Fish and amphibians lack this mechanism, as they can usually eliminate ammonia from their bodies by direct excretion. Ammonia even at dilute concentrations is highly toxic to aquatic animals, and for this reason it is classified as "dangerous for the environment" . Atmospheric ammonia plays a key role in the formation of fine particulate matter . [ 133 ]
Ammonia is a constituent of tobacco smoke . [ 134 ]
Ammonia is present in coking wastewater streams, as a liquid by-product of the production of coke from coal . [ 135 ] In some cases, the ammonia is discharged to the marine environment where it acts as a pollutant. The Whyalla Steelworks in South Australia is one example of a coke-producing facility that discharges ammonia into marine waters. [ 136 ]
Ammonia toxicity is believed to be a cause of otherwise unexplained losses in fish hatcheries . Excess ammonia may accumulate and cause alteration of metabolism or increases in the body pH of the exposed organism. Tolerance varies among fish species. [ 137 ] At lower concentrations, around 0.05 mg/L, un-ionised ammonia is harmful to fish species and can result in poor growth and feed conversion rates, reduced fecundity and fertility and increase stress and susceptibility to bacterial infections and diseases. [ 138 ] Exposed to excess ammonia, fish may suffer loss of equilibrium, hyper-excitability, increased respiratory activity and oxygen uptake and increased heart rate. [ 137 ] At concentrations exceeding 2.0 mg/L, ammonia causes gill and tissue damage, extreme lethargy, convulsions, coma, and death. [ 137 ] [ 139 ] Experiments have shown that the lethal concentration for a variety of fish species ranges from 0.2 to 2.0 mg/L. [ 139 ]
During winter, when reduced feeds are administered to aquaculture stock, ammonia levels can be higher. Lower ambient temperatures reduce the rate of algal photosynthesis so less ammonia is removed by any algae present. Within an aquaculture environment, especially at large scale, there is no fast-acting remedy to elevated ammonia levels. Prevention rather than correction is recommended to reduce harm to farmed fish [ 139 ] and in open water systems, the surrounding environment.
Similar to propane , anhydrous ammonia boils below room temperature when at atmospheric pressure. A storage vessel capable of 250 psi (1.7 MPa ) is suitable to contain the liquid. [ 140 ] Ammonia is used in numerous different industrial applications requiring carbon or stainless steel storage vessels. Ammonia with at least 0.2% by weight water content is not corrosive to carbon steel. NH 3 carbon steel construction storage tanks with 0.2% by weight or more of water could last more than 50 years in service. [ 141 ] Experts warn that ammonium compounds not be allowed to come in contact with bases (unless in an intended and contained reaction), as dangerous quantities of ammonia gas could be released.
The hazards of ammonia solutions depend on the concentration: 'dilute' ammonia solutions are usually 5–10% by weight (< 5.62 mol/L); 'concentrated' solutions are usually prepared at >25% by weight. A 25% (by weight) solution has a density of 0.907 g/cm 3 , and a solution that has a lower density will be more concentrated. The European Union classification of ammonia solutions is given in the table.
The ammonia vapour from concentrated ammonia solutions is severely irritating to the eyes and the respiratory tract , and experts warn that these solutions only be handled in a fume hood . Saturated ('0.880'–see § Properties ) solutions can develop a significant pressure inside a closed bottle in warm weather, and experts also warn that the bottle be opened with care. This is not usually a problem for 25% ('0.900') solutions.
Experts warn that ammonia solutions not be mixed with halogens , as toxic and/or explosive products are formed. Experts also warn that prolonged contact of ammonia solutions with silver , mercury or iodide salts can also lead to explosive products: such mixtures are often formed in qualitative inorganic analysis , and that it needs to be lightly acidified but not concentrated (<6% w/v) before disposal once the test is completed.
Anhydrous ammonia is classified as toxic ( T ) and dangerous for the environment ( N ). The gas is flammable ( autoignition temperature : 651 °C) and can form explosive mixtures with air (16–25%). The permissible exposure limit (PEL) in the United States is 50 ppm (35 mg/m 3 ), while the IDLH concentration is estimated at 300 ppm. Repeated exposure to ammonia lowers the sensitivity to the smell of the gas: normally the odour is detectable at concentrations of less than 50 ppm, but desensitised individuals may not detect it even at concentrations of 100 ppm. Anhydrous ammonia corrodes copper - and zinc -containing alloys , which makes brass fittings not appropriate for handling the gas. Liquid ammonia can also attack rubber and certain plastics.
Ammonia reacts violently with the halogens . Nitrogen triiodide , a primary high explosive , is formed when ammonia comes in contact with iodine . Ammonia causes the explosive polymerisation of ethylene oxide . It also forms explosive fulminating compounds with compounds of gold , silver , mercury , germanium or tellurium , and with stibine . Violent reactions have also been reported with acetaldehyde , hypochlorite solutions, potassium ferricyanide and peroxides .
Ammonia has one of the highest rates of production of any inorganic chemical. Production is sometimes expressed in terms of 'fixed nitrogen'. Global production was estimated as being 160 million tonnes in 2020 (147 tons of fixed nitrogen). [ 143 ] China accounted for 26.5% of that, followed by Russia at 11.0%, the United States at 9.5%, and India at 8.3%. [ 143 ]
Before the start of World War I , most ammonia was obtained by the dry distillation [ 144 ] of nitrogenous vegetable and animal waste products, including camel dung , where it was distilled by the reduction of nitrous acid and nitrites with hydrogen; in addition, it was produced by the distillation of coal , and also by the decomposition of ammonium salts by alkaline hydroxides [ 145 ] such as quicklime : [ 21 ]
For small scale laboratory synthesis, one can heat urea and calcium hydroxide or sodium hydroxide :
The Haber process , [ 146 ] also called the Haber–Bosch process, is the main industrial procedure for the production of ammonia . [ 147 ] [ 148 ] It converts atmospheric nitrogen (N 2 ) to ammonia (NH 3 ) by a reaction with hydrogen (H 2 ) using finely divided iron metal as a catalyst:
N 2 + 3 H 2 ↽ − − ⇀ 2 NH 3 Δ H 298 K ∘ = − 92.28 kJ per mole of N 2 {\displaystyle {\ce {N2 + 3H2 <=> 2NH3}}\qquad {\Delta H_{\mathrm {298~K} }^{\circ }=-92.28~{\text{kJ per mole of }}{\ce {N2}}}}
This reaction is exothermic but disfavored in terms of entropy because four equivalents of reactant gases are converted into two equivalents of product gas. As a result, high pressures and temperatures that are not too high are needed to drive the reaction forward .
The German chemists Fritz Haber and Carl Bosch developed the process in the first decade of the 20th century, and its improved efficiency over existing methods such as the Birkeland-Eyde and Frank-Caro processes was a major advancement in the industrial production of ammonia. [ 149 ] [ 150 ] [ 151 ]
The electrochemical synthesis of ammonia involves the reductive formation of lithium nitride , which can be protonated to ammonia, given a proton source. The first use of this chemistry was reported in 1930, where lithium solutions in ethanol were used to produce ammonia at pressures of up to 1000 bar, with ethanol acting as the proton source. [ 152 ] Beyond simply mediating proton transfer to the nitrogen reduction reaction, ethanol has been found to play a multifaceted role, influencing electrolyte transformations and contributing to the formation of the solid electrolyte interphase, which enhances overall reaction efficiency. [ 153 ] [ 154 ]
In 1994, Tsuneto et al. used lithium electrodeposition in tetrahydrofuran to synthesize ammonia at more moderate pressures with reasonable Faradaic efficiency . [ 155 ] Subsequent studies have further explored the ethanol–tetrahydrofuran system for electrochemical ammonia synthesis. [ 154 ] [ 156 ]
In 2020, a solvent-agnostic gas diffusion electrode was shown to improve nitrogen transport to the reactive lithium. NH 3 production rates of up to 30 ± 5 nmol/(s⋅cm 2 ) and Faradaic efficiencies of up to 47.5 ± 4% at ambient temperature and 1 bar pressure were achieved. [ 157 ]
In 2021, it was demonstrated that ethanol could be replaced with a tetraalkyl phosphonium salt . [ 158 ] The study observed NH 3 production rates of 53 ± 1 nmol/(s⋅cm 2 ) at 69 ± 1% Faradaic efficiency experiments under 0.5 bar hydrogen and 19.5 bar nitrogen partial pressure at ambient temperature. [ 158 ] Technology based on this electrochemistry is being developed for commercial fertiliser and fuel production. [ 159 ] [ 160 ]
In 2022, ammonia was produced via the lithium mediated process in a continuous-flow electrolyzer also demonstrating the hydrogen gas as proton source. The study synthesized ammonia at 61 ± 1% Faradaic efficiency at a current density of −6 mA/cm 2 at 1 bar and room temperature. [ 161 ]
Ammonia is essential for life. [ 163 ] For example, it is required for the formation of amino acids and nucleic acids , fundamental building blocks of life. Ammonia is however quite toxic. Nature thus uses carriers for ammonia. Within a cell, glutamate serves this role. In the bloodstream, glutamine is a source of ammonia. [ 164 ]
Ethanolamine, required for cell membranes, is the substrate for ethanolamine ammonia-lyase , which produces ammonia: [ 165 ]
Ammonia is both a metabolic waste and a metabolic input throughout the biosphere . It is an important source of nitrogen for living systems. Although atmospheric nitrogen abounds (more than 75%), few living creatures are capable of using atmospheric nitrogen in its diatomic form, N 2 gas. Therefore, nitrogen fixation is required for the synthesis of amino acids, which are the building blocks of protein . Some plants rely on ammonia and other nitrogenous wastes incorporated into the soil by decaying matter. Others, such as nitrogen-fixing legumes , benefit from symbiotic relationships with rhizobia bacteria that create ammonia from atmospheric nitrogen. [ 166 ]
In humans, inhaling ammonia in high concentrations can be fatal. Exposure to ammonia can cause headaches , edema , impaired memory, seizures and coma as it is neurotoxic in nature. [ 167 ]
In certain organisms, ammonia is produced from atmospheric nitrogen by enzymes called nitrogenases . The overall process is called nitrogen fixation . Intense effort has been directed toward understanding the mechanism of biological nitrogen fixation. The scientific interest in this problem is motivated by the unusual structure of the active site of the enzyme, which consists of an Fe 7 MoS 9 ensemble. [ 168 ]
Ammonia is also a metabolic product of amino acid deamination catalyzed by enzymes such as glutamate dehydrogenase 1 . Ammonia excretion is common in aquatic animals. In humans, it is quickly converted to urea (by liver ), which is much less toxic, particularly less basic . This urea is a major component of the dry weight of urine . Most reptiles, birds, insects, and snails excrete uric acid solely as nitrogenous waste.
Ammonia plays a role in both normal and abnormal animal physiology . It is biosynthesised through normal amino acid metabolism and is toxic in high concentrations. The liver converts ammonia to urea through a series of reactions known as the urea cycle . Liver dysfunction, such as that seen in cirrhosis , may lead to elevated amounts of ammonia in the blood ( hyperammonemia ). Likewise, defects in the enzymes responsible for the urea cycle, such as ornithine transcarbamylase , lead to hyperammonemia . Hyperammonemia contributes to the confusion and coma of hepatic encephalopathy , as well as the neurological disease common in people with urea cycle defects and organic acidurias . [ 169 ]
Ammonia is important for normal animal acid/base balance. After formation of ammonium from glutamine , α-ketoglutarate may be degraded to produce two bicarbonate ions, which are then available as buffers for dietary acids. Ammonium is excreted in the urine, resulting in net acid loss. Ammonia may itself diffuse across the renal tubules , combine with a hydrogen ion, and thus allow for further acid excretion . [ 170 ]
Ammonium ions are a toxic waste product of metabolism in animals . In fish and aquatic invertebrates, it is excreted directly into the water. In mammals, sharks, and amphibians, it is converted in the urea cycle to urea , which is less toxic and can be stored more efficiently. In birds, reptiles, and terrestrial snails, metabolic ammonium is converted into uric acid , which is solid and can therefore be excreted with minimal water loss. [ 171 ]
Ammonia has been detected in the atmospheres of the giant planets Jupiter , Saturn , Uranus and Neptune , along with other gases such as methane , hydrogen , and helium . The interior of Saturn may include frozen ammonia crystals. [ 172 ] It is found on Deimos and Phobos –the two moons of Mars . [ citation needed ]
Ammonia was first detected in interstellar space in 1968, based on microwave emissions from the direction of the galactic core . [ 173 ] This was the first polyatomic molecule to be so detected. The sensitivity of the molecule to a broad range of excitations and the ease with which it can be observed in a number of regions has made ammonia one of the most important molecules for studies of molecular clouds . [ 174 ] The relative intensity of the ammonia lines can be used to measure the temperature of the emitting medium.
The following isotopic species of ammonia have been detected: NH 3 , 15 NH 3 , NH 2 D , NHD 2 , and ND 3 . The detection of triply deuterated ammonia was considered a surprise as deuterium is relatively scarce. It is thought that the low-temperature conditions allow this molecule to survive and accumulate. [ 175 ]
Since its interstellar discovery, NH 3 has proved to be an invaluable spectroscopic tool in the study of the interstellar medium. With a large number of transitions sensitive to a wide range of excitation conditions, NH 3 has been widely astronomically detected–its detection has been reported in hundreds of journal articles. Listed below is a sample of journal articles that highlights the range of detectors that have been used to identify ammonia.
The study of interstellar ammonia has been important to a number of areas of research in the last few decades. Some of these are delineated below and primarily involve using ammonia as an interstellar thermometer.
The interstellar abundance for ammonia has been measured for a variety of environments. The [ NH 3 ]/[ H 2 ] ratio has been estimated to range from 10 −7 in small dark clouds [ 176 ] up to 10 −5 in the dense core of the Orion molecular cloud complex . [ 177 ] Although a total of 18 total production routes have been proposed, [ 178 ] the principal formation mechanism for interstellar NH 3 is the reaction:
The rate constant, k , of this reaction depends on the temperature of the environment, with a value of 5.2 × 10 − 6 {\displaystyle 5.2\times 10^{-6}} at 10 K. [ 179 ] The rate constant was calculated from the formula k = a ( T / 300 ) B {\displaystyle k=a(T/300)^{B}} . For the primary formation reaction, a = 1.05 × 10 −6 and B = −0.47 . Assuming an NH + 4 abundance of 3 × 10 − 7 {\displaystyle 3\times 10^{-7}} and an electron abundance of 10 −7 typical of molecular clouds, the formation will proceed at a rate of 1.6 × 10 −9 cm −3 s −1 in a molecular cloud of total density 10 5 cm −3 . [ 180 ]
All other proposed formation reactions have rate constants of between two and 13 orders of magnitude smaller, making their contribution to the abundance of ammonia relatively insignificant. [ 181 ] As an example of the minor contribution other formation reactions play, the reaction:
has a rate constant of 2.2 × 10 −15 . Assuming H 2 densities of 10 5 and [ NH 2 ]/[ H 2 ] ratio of 10 −7 , this reaction proceeds at a rate of 2.2 × 10 −12 , more than three orders of magnitude slower than the primary reaction above.
Some of the other possible formation reactions are:
There are 113 total proposed reactions leading to the destruction of NH 3 . Of these, 39 were tabulated in extensive tables of the chemistry among C, N and O compounds. [ 182 ] A review of interstellar ammonia cites the following reactions as the principal dissociation mechanisms: [ 174 ]
with rate constants of 4.39×10 −9 [ 183 ] and 2.2×10 −9 , [ 184 ] respectively. The above equations ( 1 , 2 ) run at a rate of 8.8×10 −9 and 4.4×10 −13 , respectively. These calculations assumed the given rate constants and abundances of [ NH 3 ]/[ H 2 ] = 10 −5 , [ [H 3 ] + ]/[ H 2 ] = 2×10 −5 , [ HCO + ]/[ H 2 ] = 2×10 −9 , and total densities of n = 10 5 , typical of cold, dense, molecular clouds. [ 185 ] Clearly, between these two primary reactions, equation ( 1 ) is the dominant destruction reaction, with a rate ≈10,000 times faster than equation ( 2 ). This is due to the relatively high abundance of [H 3 ] + .
Radio observations of NH 3 from the Effelsberg 100-m Radio Telescope reveal that the ammonia line is separated into two components–a background ridge and an unresolved core. The background corresponds well with the locations previously detected CO. [ 186 ] The 25 m Chilbolton telescope in England detected radio signatures of ammonia in H II regions , HNH 2 O masers , H–H objects, and other objects associated with star formation. A comparison of emission line widths indicates that turbulent or systematic velocities do not increase in the central cores of molecular clouds. [ 187 ]
Microwave radiation from ammonia was observed in several galactic objects including W3(OH), Orion A , W43 , W51 , and five sources in the galactic centre. The high detection rate indicates that this is a common molecule in the interstellar medium and that high-density regions are common in the galaxy. [ 188 ]
VLA observations of NH 3 in seven regions with high-velocity gaseous outflows revealed condensations of less than 0.1 pc in L1551, S140, and Cepheus A . Three individual condensations were detected in Cepheus A, one of them with a highly elongated shape. They may play an important role in creating the bipolar outflow in the region. [ 189 ]
Extragalactic ammonia was imaged using the VLA in IC 342 . The hot gas has temperatures above 70 K, which was inferred from ammonia line ratios and appears to be closely associated with the innermost portions of the nuclear bar seen in CO. [ 190 ] NH 3 was also monitored by VLA toward a sample of four galactic ultracompact HII regions: G9.62+0.19, G10.47+0.03, G29.96−0.02, and G31.41+0.31. Based upon temperature and density diagnostics, it is concluded that in general such clumps are probably the sites of massive star formation in an early evolutionary phase prior to the development of an ultracompact HII region. [ 191 ]
Absorption at 2.97 micrometres due to solid ammonia was recorded from interstellar grains in the Becklin–Neugebauer Object and probably in NGC 2264-IR as well. This detection helped explain the physical shape of previously poorly understood and related ice absorption lines. [ 192 ]
A spectrum of the disk of Jupiter was obtained from the Kuiper Airborne Observatory , covering the 100 to 300 cm −1 spectral range. Analysis of the spectrum provides information on global mean properties of ammonia gas and an ammonia ice haze. [ 193 ]
A total of 149 dark cloud positions were surveyed for evidence of 'dense cores' by using the (J,K) = (1,1) rotating inversion line of NH 3 . In general, the cores are not spherically shaped, with aspect ratios ranging from 1.1 to 4.4. It is also found that cores with stars have broader lines than cores without stars. [ 194 ]
Ammonia has been detected in the Draco Nebula and in one or possibly two molecular clouds, which are associated with the high-latitude galactic infrared cirrus . The finding is significant because they may represent the birthplaces for the Population I metallicity B-type stars in the galactic halo that could have been borne in the galactic disk. [ 195 ]
By balancing and stimulated emission with spontaneous emission, it is possible to construct a relation between excitation temperature and density. Moreover, since the transitional levels of ammonia can be approximated by a 2-level system at low temperatures, this calculation is fairly simple. This premise can be applied to dark clouds, regions suspected of having extremely low temperatures and possible sites for future star formation. Detections of ammonia in dark clouds show very narrow lines – indicative not only of low temperatures, but also of a low level of inner-cloud turbulence. Line ratio calculations provide a measurement of cloud temperature that is independent of previous CO observations. The ammonia observations were consistent with CO measurements of rotation temperatures of ≈10 K. With this, densities can be determined, and have been calculated to range between 10 4 and 10 5 cm −3 in dark clouds. Mapping of NH 3 gives typical clouds sizes of 0.1 pc and masses near 1 solar mass. These cold, dense cores are the sites of future star formation.
Ultra-compact HII regions are among the best tracers of high-mass star formation. The dense material surrounding UCHII regions is likely primarily molecular. Since a complete study of massive star formation necessarily involves the cloud from which the star formed, ammonia is an invaluable tool in understanding this surrounding molecular material. Since this molecular material can be spatially resolved, it is possible to constrain the heating/ionising sources, temperatures, masses, and sizes of the regions. Doppler-shifted velocity components allow for the separation of distinct regions of molecular gas that can trace outflows and hot cores originating from forming stars.
Ammonia has been detected in external galaxies, [ 196 ] [ 197 ] and by simultaneously measuring several lines, it is possible to directly measure the gas temperature in these galaxies. Line ratios imply that gas temperatures are warm (≈50 K), originating from dense clouds with sizes of tens of parsecs. This picture is consistent with the picture within our Milky Way galaxy – hot dense molecular cores form around newly forming stars embedded in larger clouds of molecular material on the scale of several hundred parsecs (giant molecular clouds; GMCs). | https://en.wikipedia.org/wiki/NH₃ |
Nitrogen triiodide is an inorganic compound with the formula N I 3 . It is an extremely sensitive contact explosive : small quantities explode with a loud, sharp snap when touched even lightly, releasing a purple cloud of iodine vapor; it can even be detonated by alpha radiation . NI 3 has a complex structural chemistry that is difficult to study because of the instability of the derivatives.
Nitrogen triiodide was first characterized by Raman spectroscopy in 1990, when it was prepared by an ammonia-free route. Boron nitride reacts with iodine monofluoride in trichlorofluoromethane at −30 °C to produce pure NI 3 in low yield: [ 3 ]
NI 3 is pyramidal (C 3v molecular symmetry ), as are the other nitrogen trihalides and ammonia . [ 4 ]
The material that is usually called "nitrogen triiodide" is prepared by the reaction of iodine with ammonia . When this reaction is conducted at low temperatures in anhydrous ammonia, the initial product is NI 3 · (NH 3 ) 5 , but this material loses some ammonia upon warming to give the 1:1 adduct NI 3 · NH 3 . This adduct was first reported by Bernard Courtois in 1812, and its formula was finally determined in 1905 by Oswald Silberrad . [ 5 ] Its solid state structure consists of chains of -NI 2 -I-NI 2 -I-NI 2 -I-. [ 6 ] Ammonia molecules are situated between the chains. When kept cold in the dark and damp with ammonia, NI 3 · NH 3 is stable.
The instability of NI 3 and NI 3 · NH 3 can be attributed to the large steric strain caused by the three large iodine atoms being held in proximity to each other around the relatively tiny nitrogen atom. This results in a very low activation energy for its decomposition, a reaction made even more favorable due to the great stability of N 2 . Nitrogen triiodide has no practical commercial value due to its extreme shock sensitivity, making it impossible to store, transport, and utilize for controlled explosions. Whereas pure nitroglycerin is powerful and also greatly shock-sensitive (although not nearly as much so as nitrogen triiodide, which can be set off with the touch of a feather), it was only due to phlegmatizers that nitroglycerin's shock sensitivity was reduced and it became safer to handle and transport in the form of dynamite .
The decomposition of NI 3 proceeds as follows to give nitrogen gas and iodine:
However, the dry material is a contact explosive, decomposing approximately as follows: [ 4 ]
Consistent with this equation, these explosions leave orange-to-purple stains of iodine, which can be removed with sodium thiosulfate solution. An alternate method of stain removal is to simply allow the iodine time to sublime.
Small amounts of nitrogen triiodide are sometimes synthesized as a demonstration to high school chemistry students or as an act of "chemical magic." [ 7 ] To highlight the sensitivity of the compound, it is usually detonated by touching it with a feather, but even the slightest air current, laser light, or other movement can cause detonation . Nitrogen triiodide is also notable for being the only known chemical explosive that detonates when exposed to alpha particles and nuclear fission products. [ 8 ] | https://en.wikipedia.org/wiki/NI3 |
The ChemDB HIV, Opportunistic Infection and Tuberculosis Therapeutics Database is a publicly available tool developed by the National Institute of Allergy and Infectious Diseases to compile preclinical data on small molecules with potential therapeutic action against HIV/AIDS and related opportunistic infections. [ 1 ]
Since 1989, the ChemDB has been updated with information extracted from peer-reviewed published literature, conference proceedings and patents. [ 2 ] Data are compiled on compound structure, chemical properties, biological activity (e.g. targeted protein, IC50 , EC50 , Cytotoxicity , TI , Ki , and or MIC ), and reference details (e.g. Author, Journal). [ 3 ]
The ChemDB web interface supports searching of biological, textual and chemical data using Oracle Text , the Accelrys Direct chemical search engine, and ChemAxon’s Marvin tools. [ 1 ] These tools allow web users to search the database by comparing the degree of similarity or flexibility match to chemical structures that have either been uploaded or drawn. Additional Boolean searches can be combined with structure search to include other fields on interest, including target organism or Lipinski score . In addition to the publicly available web interface, whole database downloads can be obtained by the scientific research community. [ 2 ] The database is used frequently in peer-reviewed scientific research. [ 4 ] [ 5 ] [ 6 ] [ 7 ] [ 8 ] [ 9 ] [ 10 ] [ 11 ] [ 12 ] [ 13 ]
Opportunistic pathogens included in this database are: [ 1 ] | https://en.wikipedia.org/wiki/NIAID_ChemDB |
An NIH shift is a chemical rearrangement where a hydrogen atom on an aromatic ring undergoes an intramolecular migration primarily during a hydroxylation reaction. This process is also known as a 1,2-hydride shift. These shifts are often studied and observed by isotopic labeling . An example of an NIH shift is shown below:
In this example, a hydrogen atom has been isotopically labeled using deuterium (shown in red). As the hydroxylase adds a hydroxyl (the −OH group), the labeled site shifts one position around the aromatic ring relative to the stationary methyl group (−CH 3 ).
Several hydroxylase enzymes are believed to incorporate an NIH shift in their mechanism, including 4-hydroxyphenylpyruvate dioxygenase and the tetrahydrobiopterin dependent hydroxylases . The name NIH shift arises from the US National Institutes of Health from where studies first reported observing this transformation. | https://en.wikipedia.org/wiki/NIH_shift |
NIMBY ( / ˈ n ɪ m b i / , or nimby ), [ 1 ] an acronym for the phrase " not in my back yard ", [ 2 ] [ 3 ] is a characterization of opposition by residents to proposed real estate development and infrastructure developments in their local area, as well as support for strict land use regulations. It carries the connotation that such residents are only opposing the development because it is close to them and that they would tolerate or support it if it were built farther away. The residents are often called nimbys , and their viewpoint is called nimbyism . The opposite movement is known as YIMBY for "yes in my back yard". [ 4 ]
Some examples of projects that have been opposed by nimbys include housing development [ 5 ] (especially for affordable housing [ 6 ] or trailer parks [ 7 ] ), high-speed rail lines, [ 8 ] homeless shelters , [ 9 ] day cares , [ 10 ] schools , universities and colleges , [ 11 ] [ 12 ] bike lanes and transportation planning that promotes pedestrian safety infrastructure, [ 13 ] solar farms , [ 14 ] wind farms , [ 15 ] incinerators , sewage treatment systems, [ 16 ] fracking , [ 17 ] and nuclear waste repositories . [ 18 ]
Developments likely to attract local objections include:
The claimed reasons against these developments vary, and some are given below.
The cause of NIMBYism is seen by some due to spatially concentrated costs and diffuse benefits together with regulatory transaction costs which result in a failure of conflict resolution . [ 26 ]
As hinted by the list, protests can occur for opposite reasons. A new road or shopping center can cause increased traffic and work opportunities for some, and decreased traffic for others, harming local businesses.
People in an area affected by plans sometimes form an organization which can collect money and organize the objection activities. NIMBYists can hire a lawyer to file formal appeals , and contact media to gain public support for their case.
The acronym first appeared in a February 1979 newspaper article in Virginia 's Daily Press .
agencies need to be better coordinated and the "nimby" (not in my backyard) syndrome must be eliminated.
The article may have been quoting Joseph A. Lieberman, a member of the United States Atomic Energy Commission . [ 27 ] The phrase '"not in my back yard" syndrome,' without the acronym, also appeared in an environmental journal in February 1980. [ 28 ] The Oxford English Dictionary ' s earliest citation is a Christian Science Monitor article from November 1980, although even there the author indicates the term is already used in the hazardous waste industry. [ 29 ] [ 30 ] The concept behind the term, that of locally organized resistance to unwanted land uses, is likely to have originated earlier. One suggestion is it emerged in the 1950s. [ 31 ]
In the 1980s, the term was popularized by British politician Nicholas Ridley , who was the Conservative Secretary of State for the Environment . [ 32 ] Comedian George Carlin used the term in 1992 for his Jammin' in New York special, implying that people had already heard of it. [ 33 ]
The NIMBY acronym has also been used by social scientists since the early 1980s to describe the resistance of communities to the siting of controversial facilities and land use. [ 34 ]
The term's connotation has harshened since its introduction in the 1980s. [ 35 ] Beyond their impact on any single development or neighborhood, NIMBY organizations and policies are now painted as worsening racial segregation , deepening economic inequality , and limiting the overall supply of affordable housing . [ 35 ] There have been a variety of books and articles on how to address NIMBY perspectives. One such article discussing NIMBY opposition to affordable housing by the National Low Income Housing Coalition . [ 36 ]
NIMBY and its derivative terms nimbyism , nimbys , and nimbyists , refer implicitly to debates of development generally or to a specific case. As such, their use is inherently contentious. The term is usually applied to opponents of a development, implying that they have narrow, selfish, or myopic views. Its use is often pejorative . [ 37 ]
The term Not in my neighborhood , or NIMN , is also frequently used. [ 38 ] "NIMN" additionally refers to legislative actions or private agreements made with the sole purpose of maintaining racial identity within a particular neighborhood or residential area by forcefully keeping members of other races from moving into the area. [ 39 ] In that regard, "Not in My Neighborhood," by author and journalist Antero Pietila, describes the toll NIMN politics had on housing conditions in Baltimore throughout the 20th century and the systemic, racially based citywide separation it caused. [ 40 ]
BANANA is an acronym for "build absolutely nothing anywhere near anything" (or "anyone"). [ 41 ] [ 42 ] The term is most often used to criticize the ongoing opposition of certain advocacy groups to land development . [ 43 ] The term is commonly used within the context of planning in the United Kingdom. Sunderland City Council lists the term in their online dictionary of jargon. [ 44 ]
In the United States, the related phenomenon CAVE people or "CAVE dwellers" serves as an acronym for "citizens against virtually everything." [ 45 ] [ 46 ] It is a pejorative term for citizens who regularly oppose any changes in their community, organization or workplace. [ 45 ] [ 46 ] : 65 [ 47 ] [ 48 ] A reference to the term "CAVE dwellers" can be found in the September 30, 1990, edition of the Orlando Sentinel . [ 49 ] The term apparently existed before the publication of the article.
CAVE/BANANA people are characterized by implacable opposition to change in any form, regardless of what other local residents and stakeholders feel. This attitude is manifested in opposition to changes in public policy as varied as tax levies , sewer rates , public transportation routes, parking regulations and municipal mergers or annexations . CAVE/BANANA people often express their views publicly by attending community meetings , [ 50 ] writing letters to the local newspaper, or calling in to talk radio shows, similar to NIMBYs.
The terms "CAVE people" and "BANANAs" were used in a 2022 op-ed to describe the populace of Stamford , Connecticut. [ 51 ] The op-ed was written by a former municipal employee and described CAVE people as seeing "no issue simultaneously arguing conflicting points so long as nothing changes."
Similar is "NIABY" or "not in anyone's backyard".
PIBBY is an acronym for "place in blacks' back yard." This principle indicates that the people with perceived social, racial, and economic privileges object to a development in their own back yards, and if the objectionable item must be built, then it should be built so that its perceived harms disproportionately affect poor, socially disadvantaged people. Economically disadvantaged people might not be willing or able to hire a lawyer to appeal the right way, or might have more immediate troubles than a new nearby construction project. The environmental justice movement has pointed out nimbyism leads to environmental racism . Robert D. Bullard , Director of the Environmental Justice Resource Center at Clark Atlanta University, has argued that official responses to NIMBY phenomena have led to the PIBBY principle. [ 52 ] [ 53 ] [ 54 ] [ 55 ] [ 56 ] [ 57 ] [ 58 ]
Reverse NIMBY is a phenomenon opposite to the widely known concept of NIMBY. Instead of arguing that it is troublesome that a hazardous facility is located in my backyard, proponents and people who exploit the concept of reverse NIMBY would say that "If it happens in my backyard, it matters more because, well, it's my backyard." [ 59 ] It appears within the U.S. Congress where politicians actively use the mentality after major catastrophic events to garner recovery funds from the federal government. [ 59 ] This is a viable strategy for members of Congress to garner benefits for their constituents because it is difficult for the federal government to understand needs at the local level. [ 60 ]
Although often used rather pejoratively, the use of the concept NIMBY and similar terms have been critiqued by those who have been called NIMBYs. For instance, the term is frequently used to dismiss groups as selfish or ill-informed, even though these same groups claim to have virtues that are overlooked. [ 61 ]
YIMBY , an acronym for "yes, in my back yard", is a pro-development movement in contrast and opposition to the NIMBY phenomenon. [ 62 ]
Frequently argued debate points in favor of development include higher employment, tax revenue, marginal cost of remote development, safety, and environmental benefits. Proponents of development may accuse locals of egotism , elitism , parochialism, drawbridge mentality , racism and anti- diversity , the inevitability of criticism, and misguided or unrealistic claims of prevention of urban sprawl . If people who do not want to be disturbed see the general need of an establishment, such as an airport, they generally suggest another location. But seen from society's perspective, the other location might not be better, since people living there get disturbed instead. [ 63 ] Strict land use regulations are an important driver of racial housing segregation in the United States . [ 64 ] White communities are more likely to have strict land use regulations (and white people are more likely to support those regulations). [ 64 ]
Those labeled as NIMBYs may have a variety of motivations and may be unified only because they oppose a particular project. For example, some may oppose any significant change or development, regardless of type, purpose, or origin. Others, if the project is seen as being imposed by outsiders, may hold strong principles of self-governance , local sovereignty , local autonomy, and home rule . These people believe that local people should have the final choice, and that any project affecting the local people should clearly benefit themselves, rather than corporations with distant investors or central governments. Still others may object to a particular project because of its nature, e.g., opposing a nuclear power plant over fear of radiation, or opposing a local apartment complex due to worries about overcrowding or crime, but accepting a local waste management facility as a municipal necessity. [ opinion ]
Studies show that stricter land use regulation, such as the kind that arises from NIMBY advocacy, raises the price of housing, and consequently increases cost of living . [ 65 ] Housing prices are affected by demand and supply of housing. [ 65 ] [ 66 ] The effect of moving chains is shown for change of housing prices. [ 67 ]
Homelessness is connected to lower housing supply and higher rents. [ 68 ] Strict land use regulations contribute to racial housing segregation in the United States . [ 69 ] [ 70 ]
A study by economists Chang-Tai Hsieh and Enrico Moretti estimated that the housing restrictions brought on by NIMBY activists are costing US workers $1 trillion in reduced wages (several thousand dollars per worker) by making it unaffordable to relocate to higher-productivity cities. [ 71 ]
A 1994 paper by Michael Gerrard found that NIMBY movements generally oppose three types of facilities: waste disposal, low-income housing, and social services (such as homeless shelters). [ 72 ] While opposition to waste disposal may have community benefits by encouraging recycling, it has also perpetuated the existence of those facilities in minority communities, while opposition to low-income housing and social services facilities has significant negative effects for society at large. [ 73 ]
An Australian politician, Zali Steggall , representing Sydney Manly Beach , advocates action on climate change , including the installation of wind turbines. [ 74 ] Suspecting the political proposal is to install wind turbines, Not In My Backyard, a tongue-in-cheek , online petition was set up to assess support for the establishment of wind farms on the Manly Beach. [ 75 ] [ 76 ]
In Vancouver , the city hall's licensing department rejected a day care 's expansion from 8 to 16 kids after a small number of neighbors attended public meetings in 2023 to discuss the parking issues, noise, and traffic the additional children would bring to the neighborhood. [ 10 ] According to city projections, Vancouver has a shortfall of 14,911 licensed child-care spaces. [ 10 ]
In July 2012, residents of Kings County rallied against a bylaw, developed over three years of consultation and hearings, allowing wind generators to be constructed nearby. [ 77 ] A similar theme arose in September 2009, where residents there rallied against a wind generator in Digby Neck . [ 78 ] In January 2011, residents of Lawrencetown in Halifax County openly opposed a cellular telephone tower being built. [ 79 ] A proposed development of downtown Dartmouth in August 2012 was also contested by residents. [ 80 ] In February 2013, some residents of Lunenburg County opposed wind farms being built in the area, saying, "It's health and it's property devaluation" and "This is an industrial facility put in the middle of rural Nova Scotia. It does not belong there." [ 81 ]
In March 2013, some residents of the community of Blockhouse opposed the building and development of a recycling plant, referred to by one business owner as a "dump." The plant would offer 75 jobs to the community of roughly 5,900 people. [ 82 ] In the same month, the municipal councilors of Chester approved the building of wind turbines in the area in a 6–1 vote, despite some local opposition. [ 83 ]
There have been successful NIMBY movements in China over the last few decades. In May 2014, in the city of Yuhang in Zhejiang Province, a NIMBY movement prevented the construction of a giant refuse incinerator. [ 84 ] The victory came at enormous costs with many grassroot leaders arrested and many government infrastructures destroyed. [ 84 ] However, in the case of China, many socially harmful projects simply continue their operation or relocate once media attention subsides and government authorities start to suppress the protestors [ zh ] . [ 84 ]
The Chinese government has also been accused of "weaponizing" NIMBY movements abroad through influence operations that drive opposition against perceived economic threats such as the development projects that compete with the rare earth industry in China . [ 85 ]
In 2020, there was significant opposition to the development of 650 apartments in the grounds of St Paul's College school in the Dublin suburb of Raheny . [ 86 ] [ 87 ] [ 88 ] [ 89 ] [ 90 ] 650 individual objections were received against the planning submission as well as several protests held. [ 91 ]
Court challenges were taken by residents groups against the permission which was granted on the basis of not adequately addressing the EU habitats directive. [ 92 ] Following a revised submission with a report on the effects to light-bellied Brent geese and other protected birds, the development was finally granted permission in August 2020.
The No TAV opposition to the Turin–Lyon high-speed railway is often characterized as a NIMBY movement. [ 93 ]
Starting in 1966, the Sanrizuka Struggle movement opposed the construction of Narita International Airport . Originally the plan for the airport also included a high speed railway line that was later scrapped. [ 94 ] NIMBYs also prevented extension of the airport's short second runway (unusable for anything but short-haul narrow-body aircraft ) until the late 2000s, when cross-town Haneda Airport was opened to international traffic, as additional runways on landfill were completed at an extra cost of billions of dollars; the second runway was extended to 2,500 metres (8,200 ft).
Odakyu Electric Railway , now providing transit along a corridor with 5 million people living in walking distance of its rail and feeder bus service area, [ 95 ] was originally built in the pre-war era, and as the city of Tokyo's population ballooned, rail demand in suburbs exploded. By the 1960s, oshiya pushers were required to squash people into packed trains, and Odakyu Railway sought to expand its two-track lines to four, [ 96 ] thus allowing more passing trains and faster run times as well as less crowding and congestive wait and hold of trains. NIMBY residents living near the line in the Setagaya ward fought attempts by the railway to acquire land; Odakyu attempted to buy each piece of land individually, offering high prices. The Setagaya Residents' opposition established a long-term and remarkable [ according to whom? ] NIMBY case in the courts and legislature. [ 97 ] By 1993, after three decades of trying, it was apparent this plan was failing, and the company decided to go for a multi-billion dollar solution: tunneling two lines underground, and then adding back two new lines stacked on top, to make four tracks in each direction for 12 stations and 10.4 km, instead of acquiring the land. [ 95 ] The company's decision began in 1993 and completed in 2004 for one critical section, meanwhile, for the second smaller section, this same decision was made in 2003 with project completion finally approaching fruition in March 2018, nearly six decades later. [ 96 ] [ 95 ] [ clarification needed ]
There is mounting opposition to the exploitation of lithium at the Jadar mine site by Rio Tinto in Western Serbia. [ 98 ] The local residents are concerned about the impact of lithium mining on the local environment including water pollution with no regard to the economic and other environmental benefits including battery production reducing reliance on oil, less air pollution and lower CO 2 emissions. [ citation needed ] . Opposition to lithium mining has been expressed by the Serbian Academy of Sciences and Arts and most Serbian opposition parties and organisations
. [ 99 ] [ 100 ] [ 101 ] [ 102 ] In September 2021, a series of environmental protests began in Belgrade and other locations in Serbia. Protesters demanded the rejection of Rio Tinto's mine investment and the withdrawal of proposed changes to the Expropriation and Referendum Laws.
The Oxford Spanish Civil War memorial , built in 2017, is dedicated to locals who served the International Brigades against Spanish nationalist forces backed by Hitler and Mussolini. The memorial sits outside the city centre because all planning proposals to erect the memorial in the centre were rejected for numerous reasons, with Liberal Democrat councillors opposing all the suggested locations. The creation of the monument was also opposed by the Oxford Preservation Trust and the London Place Residents' Association. [ 103 ] The current placement of the memorial was the third proposed location, with the previous two having their planning applications rejected by Oxford City Council. [ 104 ] The first proposed spot was Bonn Square which was rejected citing that granite was not a stone native to Oxford. [ 105 ] The second proposed location was St Giles' which was also rejected by councillors, claiming that the close proximity of an anti-fascist memorial to current war memorials would insult the memory of people who died during the Second World War. [ 105 ] Some objected to the memorial because it did not honour "both sides ... in a spirit of reconciliation and forgiveness", and called the design "aggressive towards the memory of the victims of conflict". [ 106 ]
Liberal Democrat councillor Elizabeth Wade opposed each proposed location for a monument in Oxford, although she claimed she was never opposed in principle. She described the second proposal on St Giles' near Oxford's First and Second World War memorials as “aggressive and triumphalist”. [ 107 ] Describing herself as a historian and speaking to the Oxford Mail , she then opposed the third and current location because she believed a monument with a red flag would glorify communism, despite no red flag ever being proposed to appear on the monument. [ 103 ] Her rejection of every proposal led to Britain's largest and longest running left-wing newspaper, the Morning Star , labelling her as a NIMBY. [ 105 ]
In 2007, residents of the affluent English village of Ashtead , Surrey, which lies on the outskirts of London , objected to the conversion of a large, £ 1.7 million residential property into a family support centre for relatives of wounded British service personnel. [ 108 ] The house was to be purchased by a registered charity, SSAFA Forces Help . [ 108 ] [ 109 ] Local residents objected to the proposal out of fear of increased traffic and noise, as well as the possibility of an increased threat of terrorism. [ 108 ] They also contended that the SSAFA charity is actually a business, thereby setting an unwelcome precedent. [ 110 ] British newspapers ran articles titled "No heroes in my backyard". [ 108 ]
Ex-servicemen and several members of the British general public organised a petition in support of SSAFA, and even auctioned the "Self Respect of Ashtead" on eBay . [ 111 ]
Particularly in the time period preceding the final decision on the route of the high-speed railway known as High Speed 2 , [ timeframe? ] BBC News Online reported that many residents of conservative constituencies were launching objections to the HS2 route based on the effects it would have on them, whilst also showing concerns that HS2 is unlikely to have a societal benefit at a macro level under the current economic circumstances. [ 112 ] [ 113 ] Likewise, Labour MP Natascha Engel —through whose constituency the line will pass—offered a "passionate defence of nimbyism" in the House of Commons, with regards to the effects the line would have on home- and business-owning constituents. [ 114 ] HS2 has also been opposed by residents of the Chilterns and Camden who argue that there is an insufficient business case for the line. On 17 March 2014, it was announced that Camden residents were successful in their campaign to prevent the construction of the HS1–HS2 link railway. [ 115 ]
In November 2007, a consultation process began for the building of a new third runway and a sixth terminal and it was controversially [ 116 ] approved on 15 January 2009 by UK government ministers. [ 117 ] The project was then cancelled on 12 May 2010 by the Cameron Government . [ 118 ] The project was adopted by the House of Commons in June 2018. NIMBYs and political protestors appealed to the courts, [ 119 ] but lost in the UK Supreme Court in December 2020. [ 120 ]
Coventry Airport is owned by CAFCO (Coventry) Limited, a joint venture between Howard Holdings plc [ 121 ] and Convergence-AFCO Holdings Limited (CAFCOHL). In June 2007, it had its application to build permanent terminal and passenger facilities rejected by the UK government due to public pressure. [ 122 ] [ 123 ] [ 124 ] [ 125 ] [ 126 ] [ 127 ]
The London Borough of Merton did not have enough school places for local children who would be reaching school age in 2012 and 2013. Almost all local schools had expanded, but the group "Save Our Rec" ( recreation ground ) (dedicated in the preservation of green areas in the local community) opposed the expansion of Dundonald School as their interest was focused on protecting one of the few green spaces left in the Borough of Merton. Those that disagreed with the "Save our Rec" group labelled the group NIMBYs. [ 128 ] Despite efforts to protect green spaces, the expansion proceeded onto a portion of the park and the park's pavilion . [ 129 ]
In April 2023, the UK Government announced a plan to use the engineless barge, the Bibby Stockholm , to house around 500 asylum seekers in Portland Harbour , in an attempt to save money housing asylum seekers. [ 130 ] Whilst most of the controversy outside of the town of Portland stemmed from its apparent overcrowding , ethical issues, and economic inefficiency, many protests from the inside of the town were because of impacts on the towns tourism industry, and a possible increase in crime and anti-social behaviour , with some saying it puts the women of the town at risk. [ 131 ] They were dubbed as NIMBYs by some facets of the media.
Research shows that conservatives and liberals are equally likely to oppose new housing developments in their localities. White neighborhoods and cities tend to favor more restrictive housing development policy. [ 132 ] [ 64 ] [ 133 ] A study in Perspectives on Politics found that "individuals who are older, male, longtime residents, voters in local elections, and homeowners are significantly more likely to participate" in local government, and that "these individuals overwhelmingly (and to a much greater degree than the general public) oppose new housing construction." [ 134 ] Nimbys tend to be homeowners, and have been described as acting to keep home prices high in self-interest [ 135 ] and as working against their financial interests. [ 136 ] Some economists believe that this is due to a public misunderstanding of how the new construction of housing affects housing prices. [ 137 ] For example, only 30-40% of Americans believe that new housing construction reduces housing prices, and meanwhile a comparable amount of Americans believe that new construction increases housing prices. [ 137 ]
According to a 2017 report from the National Low Income Housing Coalition , there is a shortage of 7.4 million affordable homes available for rent to extremely low income (ELI) households in the United States. As a result, seventy-one percent of ELI households are forced to spend over half of their income on housing costs, leading to severe financial burdens. [ 138 ] [ 139 ] Despite this apparent need for more affordable housing, opposition from NIMBY activists presents significant challenges to affordable housing developments, resulting in costly design changes, construction delays, and permit denials. [ 140 ] However, research suggests that proactive outreach and communication by affordable housing developers and proponents through the leveraging of social marketing and positive messaging can overcome common NIMBY barriers. [ 141 ] [ 142 ]
Activism from both individuals and organizations opposed to new housing construction has been cited as a major reason for the state's ongoing housing shortage and high cost of living. [ 143 ]
Many local residents (including farmers) in Hanford , California and surrounding areas are opposed to the California High-Speed Rail Authority building high-speed rail near farmland, citing that it will bring environmental and economic problems. [ 144 ]
Wealthy residents of southern Orange County , California defeated a local measure that proposed to convert the decommissioned El Toro Marine Base into a commercial airport, claiming that the airport would be "unsafe" during landings and takeoffs, as well as create air quality issues. The real issue was the FAA planned the flight paths for the airport over expensive neighborhoods of south Orange County and residents feared that their property values would decrease. The airport proposal, however, was strongly supported by northern Orange County residents. The defeat of the local measure resulted in the creation of the Orange County Great Park . [ citation needed ]
For over 60 years, environmentalists, historic preservationists and long-time residents of South Pasadena , California have been opposing the completion of the highly controversial State Route 710 through the cities of Los Angeles (El Sereno), South Pasadena and Pasadena. [ 145 ] In 1973, a federal injunction was granted, halting the construction of the surface freeway pending an environmental impact analysis. [ 146 ] The Federal Highway Administration withdrew support for the surface freeway in 2003. [ 146 ]
On 29 September 2017, 15 housing bills were signed into law by Governor Jerry Brown to combat the state's housing shortage. Many of these bills are considered direct attempts to reduce the ability of private citizens to suppress housing construction, even being referred to by some as "Anti-NIMBY" bills. [ 147 ] [ 148 ]
In 2022, California governor Gavin Newsom declared that "nimbyism is destroying the state" and promised to hold cities and counties accountable for stopping new housing development. [ 149 ]
Nimbyism in San Francisco, including several members of the San Francisco Board of Supervisors , has led to a suppression of new housing construction , transit expansion, bike infrastructure, and new retail stores in the city. Nimbys have cited negative impact on local communities, low affordable housing quotas, restrictions on buildings' shadows, increased car traffic, and concerns with parking as reasons for opposing projects. [ 150 ] [ 151 ] [ 152 ] Those who favor housing developments argue that new housing construction makes housing more affordable, thereby reducing displacement, personal property tax burdens, and homelessness. Examples of nimbyism in San Francisco include 8 Washington housing project, 1846 Grove Street housing, 1060 Folsom housing, 1979 Mission housing, 2675 Folsom housing, 250 Laguna Honda Boulevard housing, 770 Woolsey, UCSF Parnassus Heights hospital expansion, and the Polk Street bike lane. [ 153 ] [ 154 ] [ 155 ] [ 156 ]
San Francisco nimbys have also been described as "housing conservatives". [ 157 ] [ improper synthesis? ]
Many residents of Marin County , an affluent bedroom community in the San Francisco Bay Area, have for many years exemplified the idea of nimbyism through their ardent resistance to housing developments and housing quotas. [ 158 ] [ 159 ] [ 160 ] [ 161 ] [ 35 ] Residents believe housing developments will lead to increased population density which can lead to increased traffic, increased pollution, crowded schools, a lack of open space, and a poor quality of life.
In 2018, some Marin residents started the NIMBY group Livable California . [ 162 ]
A minority of residents in St. Lucie County , Florida have vehemently opposed the construction of wind turbines in the county. The construction of the wind turbines was strongly supported by over 80% of county residents according to a 2008 Florida Power and Light (FPL) poll. [ 163 ] Additionally, the power company proposed building the turbines in a location on a beach near a prior existing nuclear power plant owned by the company. [ 164 ]
In the 1980s, plans were made to develop a series of east/west highways to connect Palm Beach County 's suburbs with downtown West Palm Beach . [ 165 ] Many residents in the area opposed the plan, largely due to the highway expansion requiring the demolition of over 100 homes. [ 165 ] Ultimately, the plan was revised to transform the existing SR-80 (Southern Boulevard) into a full expressway to minimize disruptions to local residents and businesses, [ 166 ] however all of the proposals were later abandoned. [ 167 ]
In 1959, when Deerfield officials learned that a developer building a neighborhood of large new homes planned to make houses available to African Americans , they issued a stop-work order. An intense debate began about racial integration, property values, and the good faith of the residents, community officials and builders. For a brief time, Deerfield was spotlighted in the national news as "the Little Rock of the North." [ 168 ] Supporters of integration were denounced and ostracized by residents. Eventually, the village passed a referendum to build parks on the property, thus putting an end to the housing development. Two model homes already partially completed were sold to village officials. [ 168 ] Otherwise, the land lay dormant for years before it was developed into what is now Mitchell Pool and Park and Jaycee Park. The first black family did not move into Deerfield until much later, and in years since Deerfield has seen a greater influx of minorities, including Jews, Asians, Greeks and others. This episode in Deerfield's history is described in But Not Next Door by Harry and David Rosen, both residents of Deerfield.
In the late 1990s a proposal for commuter rail on the Dan Patch Corridor between Minneapolis and Northfield was studied. In 2002, due to opposition from neighborhoods along the corridor, two state representatives from the suburbs of Bloomington and Edina passed a legislative ban that prohibited further study, discussion, funding, and construction of the project. Several attempts have been made to lift the ban, and in 2023 it was finally lifted. [ 169 ] As of 2023 the communities along the route have no official position on the Dan Patch Corridor except Lakeville , Minnesota, which is opposed. [ 170 ]
In 2018, Minneapolis became the first US city to end single-family zoning , with a guiding framework called the "Minneapolis 2040 Comprehensive Plan". The plan faced years of legal challenges, and eventually required intervention from the state legislature to proceed. [ 171 ]
In 1858, a group of residents in Staten Island burned down the New York Marine Hospital , at the time the largest quarantine facility in the United States, citing its negative effect on local property values. [ 172 ]
On Long Island , various electrification and expansion projects of the Long Island Rail Road (LIRR) were substantially delayed due to the protests of people living near the railroad. For example, the Metropolitan Transportation Authority built a third track on the Main Line from Floral Park station to Hicksville station in order to increase capacity. [ 173 ] [ 174 ] Although most communities along the route supported grade crossing eliminations as part of the project, there was fierce opposition for building a third track from the villages of Floral Park , New Hyde Park , and Garden City , which said the construction and the resulting increased train service will reduce the quality of life in their neighborhoods. [ 175 ] [ 176 ] [ 177 ] The third track project was suspended indefinitely in 2008, [ 178 ] but new funding for the project was included in a 2016 infrastructure improvement plan announced by New York Governor Andrew Cuomo , which included measures intended to mitigate locals' concerns. [ 179 ] Despite the promise of mitigation efforts, several local politicians denounced the governor's plan within a day of its announcement. [ 180 ] [ 181 ] In December 2017, the LIRR awarded a contract to build the third track. [ 182 ] It was completed in October 2022 and a new service pattern was ultimately implemented in February 2023, concurrent with the full opening of Grand Central Madison . [ 183 ] [ 184 ]
In Port Washington, New York , a dispute broke out between the town of North Hempstead and the LIRR over a proposed yard expansion at Port Washington station . To expand the yard, a parking lot belonging to the town would need to be reduced in size, but a local councilperson stated that the addition of the tracks "will completely ruin the character of the town." [ 185 ] The LIRR was able to expand the yard without the agreement of North Hempstead by tearing up 140 parking spaces of its own parking lot, also adjacent to the station. [ 185 ]
Community opposition also led to the cancellation of a proposed extension of the New York City Subway 's Astoria Line (carrying the N and W trains) to LaGuardia Airport . [ 186 ] [ 187 ] Similarly, opposition has stopped any proposal to build a bridge or tunnel across the Long Island Sound with some believing it will harm their communities with an influx of unwanted traffic as well as concerns regarding the environment and the number of homes that would be cleared as a result. [ 188 ]
In early 2020, in Campbell County , Tennessee , complaints occurred after an out-of-state company began controlled blasting at a rock quarry in the county. [ 189 ] Campbell County Schools had dismissed their schools early due to the quarry, located less than 2,000 feet from the high school, performing a scheduled blast. [ 189 ] Residents gathered for pleas to shut down the quarry. [ 189 ] Campbell County officials later passed a resolution banning the development of quarries within 2,000 feet of a public building or power grid structure. [ 190 ]
In 2009, Norfolk Southern Railway released plans of a proposed 1,300 acres (5.3 km 2 ) intermodal freight transport truck-and-train facility in Jefferson County , Tennessee as a part of the US$2.5 billion Crescent Corridor project in a US$133 million private-public partnership with state and Jefferson County officials. [ 191 ] [ 192 ] The proposed facility, if completed, would have generated 77 on-site jobs, 1,700 related-industry jobs in Jefferson and surrounding counties, and the potential of an annual income of US$60 million dollars a year. [ 191 ] The project received extensive backlash from an organized group of affected property owners and farmers, citing the massive loss of land as a negative impact on Jefferson County's agricultural industry. [ 193 ] The project status has remained stagnant since 2015, as Norfolk had no plans of constructing the facility in the short-term future, but plans on having the site property as a "long-term investment" according to a press release by the company's public relations director. [ 194 ]
In 1994, opposition from residents and historians contributed to the cancellation of the Disney's America theme park outside of Haymarket , Virginia. [ 195 ]
In 1988, residents of Seattle's Broadmoor golf course and gated community successfully opposed the construction of a bike path between Washington Park Arboretum and Madison Park . [ 196 ]
According to New York Times opinion writer Farhad Manjoo , "What Republicans want to do with I.C.E. and border walls, wealthy progressive Democrats are doing with zoning and Nimbyism. Preserving “local character,” maintaining “local control,” keeping housing scarce and inaccessible—the goals of both sides are really the same: to keep people out." [ 197 ]
In a 2020 paper exploring the relationship between homeowners' self-interest and pro-NIMBY attitudes among both self-identified liberals and conservatives, William Marble and Clayton Nall note: “Whether they are responding to different housing policies, responding to persuasive political messaging, or evaluating hypothetical proposals for local development, homeowners remain opposed to local development policies that threaten their self-interest.“ [ 198 ]
Historian Nancy Shoemaker cites "Not-in-My-Backyard Colonialism" as one of twelve types of colonialism , in which an area is colonized to dispose of convicts or conduct dangerous experiments. She cites Australia and the Marshall Islands —used as a nuclear test site by the United States—as examples. [ 199 ]
Various means to overcome NIMBY opposition to infrastructure or development have been used, including persuasion, leaving the decision to an appointed board, or broadening the decision-making community (such as by overriding municipal zoning rules with countywide or statewide regulations). Another proposal is to pay neighbors of new housing developments, so that they experience benefits as well as costs, giving them an incentive to express political support. [ 200 ] | https://en.wikipedia.org/wiki/NIMBY |
An approach of an antenna and beamforming system, NIMO (non-interfering multiple output) , is introduced that can be used to overcome bandwidth and capacity limitations on dense wireless networks . The new system combines beamforming technology with MIMO, providing a higher quality of service (QoS), and supports transparent integration with any telecommunication system. NIMO provides multiple narrow beams using a single antenna, and provides improved characteristics compared to conventional beamforming techniques such as reduced interference. Such a multi-beam antenna system increases spectral efficiency , user capacity, and throughput, as well as QoS. [ 1 ]
This article about wireless technology is a stub . You can help Wikipedia by expanding it . | https://en.wikipedia.org/wiki/NIMO_(non-interfering_multiple_output) |
In model theory , a branch of mathematical logic , a complete theory T is said to satisfy NIP ("not the independence property") if none of its formulae satisfy the independence property —that is, if none of its formulae can pick out any given subset of an arbitrarily large finite set.
Let T be a complete L -theory. An L -formula φ( x , y ) is said to have the independence property (with respect to x , y ) if in every model M of T there is, for each n = {0,1,..., n − 1} < ω, a family of tuples b 0 ,..., b n −1 such that for each of the 2 n subsets X of n there is a tuple a in M for which
The theory T is said to have the independence property if some formula has the independence property. If no L -formula has the independence property then T is called dependent, or said to satisfy NIP. An L -structure is said to have the independence property (respectively, NIP) if its theory has the independence property (respectively, NIP). The terminology comes from the notion of independence in the sense of boolean algebras .
In the nomenclature of Vapnik–Chervonenkis theory , we may say that a collection S of subsets of X shatters a set B ⊆ X if every subset of B is of the form B ∩ S for some S ∈ S . Then T has the independence property if in some model M of T there is a definable family ( S a | a ∈ M n ) ⊆ M k that shatters arbitrarily large finite subsets of M k . In other words, ( S a | a ∈ M n ) has infinite Vapnik–Chervonenkis dimension .
Any complete theory T that has the independence property is unstable . [ 1 ]
In arithmetic, i.e. the structure ( N ,+,·), the formula " y divides x " has the independence property. [ 2 ] This formula is just
So, for any finite n we take the n 1-tuples b i to be the first n prime numbers , and then for any subset X of {0,1,..., n − 1} we let a be the product of those b i such that i is in X . Then b i divides a if and only if i ∈ X .
Every o-minimal theory satisfies NIP. [ 3 ] This fact has had unexpected applications to neural network learning. [ 4 ]
Examples of NIP theories include also the theories of all the following structures: [ 5 ] linear orders , trees , abelian linearly ordered groups , algebraically closed valued fields , and the p-adic field for any p. | https://en.wikipedia.org/wiki/NIP_(model_theory) |
The NIROSETI ( Near-InfraRed Optical Search for Extraterrestrial Intelligence ) is an astronomical program to search for artificial signals in the optical ( visible ) and near infrared (NIR) wavebands of the electromagnetic spectrum . It is the first dedicated near-infrared SETI experiment. [ 1 ] [ 2 ] The instrument was created by a collaboration of scientists from the University of California, San Diego , Berkeley SETI Research Center at the University of California, Berkeley , University of Toronto , and the SETI Institute . It uses the Anna Nickel 1-m telescope at the Lick Observatory , situated on the summit of Mount Hamilton, east of San Jose, California, USA. [ 3 ] [ 4 ] The instrument was commissioned (saw its first light ) on 15 March 2015 and has been operated for more than 150 nights, and is still operational today.
The NIROSETI project is designed to detect infrared pulses. Near-infrared offers a possible way for signal transmission since there is a decrease in both interstellar extinction and Galactic background compared to optical wavelengths. [ 4 ] [ 5 ] The near-infrared bands remain largely unexplored because instruments capable of capturing short pulses of infrared light have only recently become available. [ 5 ] [ 6 ]
The NIROSETI instrument makes use of the 1-meter optical Nickel telescope located at the Lick Observatory in California to search for near-infrared ( laser ) transmissions from extraterrestrial communication or technosignatures . This project was funded by the Bill and Susan Bloomfield Foundation and is based upon a predecessor called Lick Optical SETI instrument, conducted between 2001 and 2006. [ 4 ] [ 5 ] Professor Shelley Wright leads the team that built and operates the NIROSETI program. [ 7 ]
The NIROSETI instrument employs a new generation of near-infrared (900 to 1700 nm) detectors, cooled at -25 °C, that have a high speed response (>1 GHz) and gain comparable to photomultiplier tubes, while also producing very low noise, [ 2 ] [ 5 ] and significantly reducing false positives. [ 4 ] Its field-of-view is 2.5"x2.5" each, [ 8 ] and focuses
on detecting short (nanosecond) pulsed laser emissions. The NIROSETI instrument is also being used to study variability of very short natural near-infrared transient stars. [ 2 ] [ 6 ]
The NIROSETI survey has been designed for observing several thousand objects over a few years, and commenced full operations on 28 January 2016. During a clear night of observations, about 20 to 30 objects are observed. [ 4 ] Because infrared light penetrates farther through gas and dust than visible light, this search will extend to stars thousands of light-years away. [ 6 ] The initial target sample is mostly main-sequence and giant stars located within 50 parsecs from Earth, drawn from the Breakthrough Listen program target list. [ 4 ] [ 9 ] [ 10 ]
The sample of targets also includes 82 galaxies for being the nearest representatives of the five major morphological classes of galaxies (20 spirals , 36 ellipticals , 15 dwarf spheroidals , 9 irregulars , and 2 lenticular galaxies), [ 4 ] as well as stars that triggered alarms on other targeted SETI surveys . [ 4 ]
A significant drawback is that the extraterrestrial laser signals would need to be transmitted in the direction of the Solar System in order to be detected. [ 6 ] | https://en.wikipedia.org/wiki/NIROSETI |
NISO Circulation Interchange Protocol (NCIP) is a protocol that is limited to the exchange of messages between and among computer-based applications to enable them to perform functions necessary to lend and borrow items, to provide controlled access to electronic resources, and to facilitate cooperative management of these functions.
Released in May 2001 and approved on October 17, 2002, ANSI / NISO Z39.83-2002 or NCIP is a "NISO Draft Standard for Trial Use." This protocol defines a repertoire of messages and associated rules of syntax and semantics for use by applications: to perform the functions necessary to lend items; to provide controlled access to electronic resources; and to facilitate co-operative management of these functions. It is intended to address conditions in which the application or applications that initiate the lending of items or control of access must acquire or transmit information about the user, items, and/or access that is essential to successful conclusion of the function.
This computing article is a stub . You can help Wikipedia by expanding it . | https://en.wikipedia.org/wiki/NISO_Circulation_Interchange_Protocol |
The Digital Library of Mathematical Functions ( DLMF ) is an online project at the National Institute of Standards and Technology (NIST) to develop a database of mathematical reference data for special functions and their applications. It is intended as an update of Abramowitz's and Stegun's Handbook of Mathematical Functions (A&S). [ 1 ] It was published online [ 2 ] on 7 May 2010, though some chapters appeared earlier. In the same year it appeared at Cambridge University Press under the title NIST Handbook of Mathematical Functions . [ 3 ]
In contrast to A&S, whose initial print run was done by the U.S. Government Printing Office and was in the public domain , NIST asserts that it holds copyright to the DLMF under Title 17 USC 105 of the U.S. Code. [ 4 ] | https://en.wikipedia.org/wiki/NIST_Handbook_of_Mathematical_Functions |
The NITROS ( N etwork for I nnovative T raining on RO torcraft S afety) project [ 1 ] [ 2 ] is an ongoing project which began in November 2016 consisting of 12 Early-Stage Researchers (ESRs). It is funded through the European Union 's Marie Skłodowska-Curie Actions (MSCA) research grant which is an Innovative Training Network (ITN) to support European Joint Doctorates (EJD). [ 3 ] The collective aim of this specific MSCA scheme is for fostering new skills by means of excellent initial training of researchers. [ 4 ]
NITROS aims to train aerospace engineers in Control Engineering , Computational Fluid Dynamics (CFD), Modeling and Simulation , Structural Dynamics and Human perception cognition and action, to address complex solutions for rotorcraft safety. [ 1 ] Rotorcraft accident rates remain disproportionately high in comparison with fixed-wing aircraft. [ 5 ] [ 6 ]
The network is composed of four universities spread over four countries namely: Politecnico di Milano ( Italy ), Delft University of Technology ( Netherlands ), University of Liverpool ( England ) and the University of Glasgow ( Scotland ). Whilst there are also six international industrial partners involved in helping collaborate: Bristow Helicopters , Civil Aviation Authority , Eurocontrol , Leonardo Helicopter , National Aerospace Laboratory and the Max Planck Institute .
The NITROS project will be presented at the 44th European Rotorcraft Forum in Delft [ 7 ] and the subsequent 45th and 46th European Rotorcraft Forums, where the 12 projects will be presented.
Each research project is focused on a problem that affects the safety of the current or innovative rotorcraft configurations. | https://en.wikipedia.org/wiki/NITROS_Project |
The NIXT , or Normal Incidence X-ray Telescope , was a sounding rocket payload flown in the 1990s by Professor Leon Golub of the Smithsonian Astrophysical Observatory , to prototype normal-incidence (conventional) optical designs in extreme ultraviolet (EUV) solar imaging. In the EUV, the surface of the Sun appears dark, and hot structures in the solar corona appear bright; this allows study of the structure and dynamics of the solar corona near the surface of the Sun, which is not possible using visible light .
NIXT and its sister rocket, the MSSTA , were the prototypes for all normal-incidence EUV imaging instruments in use today, including SOHO/EIT , TRACE , and STEREO/SECCHI .
In 1989, a NIXT sounding rocket launch detected soft X-Rays coming from a Solar flare . [ 1 ] It was launched when the solar event was detected to allow high resolution imaging of the Sun's corona . [ 1 ] Results from the observations were presented in 1990 in different papers. [ 1 ] NIXT was launched throughout the early 1990s and a paper summarizing the results from these mission was published in 1996. [ 2 ]
A successor program to NIXT, was the TXI (Tunable XUV Imager) sounding rocket program [ 2 ] [ 3 ]
This astronomy -related article is a stub . You can help Wikipedia by expanding it . | https://en.wikipedia.org/wiki/NIXT |
NJIT Steel Bridge Team is a team within the New Jersey Institute of Technology 's ASCE chapter). It consists of undergraduate students who are attending at NJIT , majoring in civil engineering , and also members of ASCE . Every year, the team competes against other schools in a steel bridge competition .
Every year, the team has a few fund raising events, which are very crucial for the competition because the team needs to have proper finance in order to order parts and fabricate them. Besides fund raising, sponsors from other corporates and companies are very important too.
A lot of time the team members get together and have outside activities such as hiking, paint ball, go cart, or whatever anyone wants to do. The team also does many productive activities such as visiting high schools and talking about civil engineering and the steel bridge competition.
There is at least a meeting every week talking about the process of the team and keeping members informed. Meetings are always held during common hours. Sometimes pizzas and drinks are served.
The objective of the competition is to design a light bridge yet strong and economically and assembly it fast with as few team members as possible.
The competition has 3 processes: Design & testing, which students do that themselves using programs, knowledges they learned from classes, and sometimes help from professors and alumni; Fabrication, which is when students grind, weld, and fit the parts together; and finally Assembly, which is when students put the parts together to achieve the designed bridge.
There are 6 categories in scoring: Display (how the bridge look), construction speed (time management), construction economy (low cost to build), lightness, stiffness (aggregate deflection), and structural efficiency (a formula used to calculate this based on weight and deflection).
The competition occurs every year. It is hosted at different places every time. This year, 2024, the regional competition will be hosted at Stonybrook University, Long Island on Saturday April 13th, 2024; and the national competition will be hosted at Louisiana Tech, Ruston Louisiana.
If there are 1-4 teams competing in the region, the best team will proceed to the national competition
If there are 5-10 teams competing in the region, the 2 best teams will proceed to the national competition
If there are more than 10 teams competing in the region, the 3 best teams will proceed to the national competition
The price for winning the national competition is $2,500
2012 National Competition at Clemson, SC
15th Place Overall - Highest in History
9th Place in Construction Speed
2012 Regional Competition
1st Place Overall
1st Place Economy
1st Place Stiffness
1st Place Build Time
2010 National Competition (at Purdue University ) [ 1 ]
2010 Regional Competition [ 2 ] ( Regional competition score-sheet )
2009 National Competition (at University of Nevada, Las Vegas ) [ 3 ]
2009 Regional Competition [ 4 ] ( Regional competition score-sheet )
2008 National Competition (at University of Florida ) [ 5 ]
2008 Regional Competition
2007 National Competition 2007 Regional Competition
2006 National Competition 2006 Regional Competition 2005 National Competition 2005 Regional Competition · Second Place Overall · First Place Efficiency · First Place Aesthetics · First Place Stiffness 2004 National Competition 2004 Regional Competition 2003 National Competition 2003 Regional Competition · First Place Overall · First Place Lightness · First Place Efficiency · First Place Economy · First Place Stiffness · First Place Construction Speed 2002 National Competition 2002 Regional Competition · First Place Overall · First Place Efficiency · First Place Stiffness 2001 National Competition 2001 Regional Competition · Second Place Overall · First Place Efficiency · First Place Aesthetics | https://en.wikipedia.org/wiki/NJIT_Steel_Bridge_Team |
The NK-92 cell line is an immortalised cell line that has the characteristics of a type of immune cell found in human blood called ’ natural killer ’ (NK) cells. Blood NK cells and NK-92 cells recognize and attack cancer cells as well as cells that have been infected with a virus , bacteria , or fungus . [ 1 ] NK-92 cells were first isolated in 1992 in the laboratory of Hans Klingemann at the British Columbia Cancer Agency in Vancouver, Canada, from a patient who had a rare NK cell non-Hodgkin-lymphoma . [ 2 ] These cells were subsequently developed into a continuously growing cell line. NK-92 cells are distinguished by their suitability for expansion to large numbers, ability to consistently kill cancer cells and testing in clinical trials. When NK-92 cells recognize a cancerous or infected cell, they secrete perforin that opens holes into the diseased cells and releases granzymes that kill the target cells. NK-92 cells are also capable of producing cytokines such as tumor necrosis factor alpha (TNF-a) and interferon gamma (IFN-y), [ 3 ] which stimulates proliferation and activation of other immune cells.
Several phase 1 clinical trials have been performed by experts in the field of adoptive immunotherapy of cancer. Hans Klingemann and Sally Arai completed a US trial at Rush University Medical Center ( Chicago ) in renal cell cancer and melanoma patients in 2008, [ 4 ] and Torsten Tonn, MD and Oliver Ottmann, MD completed the European trial at the University of Frankfurt in patients with various solid and hematological malignancies in 2013. [ 5 ] Armand Keating at Princess Margaret Hospital in Toronto conducted a trial in which NK-92 cells were given to patients who had relapsed after autologous bone marrow transplants for leukemia or lymphoma. In all clinical trials so far, NK-92 cells were administered as a simple intravenous infusion, dosed two or three times per treatment course, and given in the outpatient setting.
Of the 39 patients enrolled across the three studies, 2 serious (grade 3–4) side-effects occurred during or after the infusion of NK-92 cells, the side effects disappeared afterward. The doses given to patients ranged from 1x10 8 cells/m 2 to 1x10 10 cells/m 2 per infusion. Patients received between two and three infusions over a period of less than a week. About one-third of the treated patients had clinically meaningful responses with some of them fully recovering.
In a 2017 study by Congcong Zhang and Winfried S. Wels, NK-92 cells were genetically engineered to recognize and kill specific human cancers by expressing chimeric antigen receptors (CARs). [ 6 ] CAR-engineered T-lymphocytes (CAR-T) have garnered attention in immuno-oncology, as the infusion of CAR-T cells has been shown to induce remissions in some patients with acute and chronic leukemia and lymphoma . However, CAR-T cells can cause cytokine release syndrome (CRS). CAR-engineered NK cells from either peripheral or cord blood have not proved to be as feasible for use to treat diseases as they are difficult to expand to get sufficient numbers, and the yields can be variable and/or too low. Also, genetic transduction to introduce the CAR into blood NK cells requires lentiviral or retroviral vectors, which are only moderately efficient.
NK-92 cells, in contrast to NK-92 CAR-T cells, have predictable expansion kinetics and can be grown in bioreactors that produce billions of cells within a couple of weeks. [ 7 ] Further, NK-92 cells can easily be transduced by physical methods, and mRNA can be shuttled into NK-92 cells with high efficiency. CAR-expressing NK-92 have been generated to target a number of cancer surface receptors [ 8 ] such as programmed death domain ligand 1 (PD-L1), CD19 (a type of B cell receptor), [ 9 ] [ 10 ] human epidermal growth factor receptor 2 (HER2/ErbB2) and epidermal growth factor receptor (EGFR, aka HER1); and many of these engineered NK-92 cells are currently in clinical trials for the treatment of cancer. [ 11 ]
NK-92 cells, which require interleukin-2 (IL-2) for growth, have also been genetically altered with an IL-2 gene to allow them to grow in culture without the addition of IL-2. [ 12 ] They have also been engineered to express a high-affinity Fc-receptor which is the main receptor for monoclonal antibodies to bind to NK-92 and use their cytotoxic load to kill cancer cells. [ 13 ] [ 14 ] The cells have been further engineered to express Chimeric Antigen Receptors (CARs) such as programmed death domain ligand 1 (PD-L1). [ 15 ] During the course of development, NK-92 cells were renamed activated NK cells (aNK) and the different variants have been designated as follows:
NK-92 = parental cells, later designated aNK
NK-92ci = NK-92 cells transfected with an episomal vector for expression of IL-2
NK-92 mi = NK-92 cells transfected with an MFG vector for expression of IL-2
haNK = NK-92 (aNK) transfected with a plasmid expressing high affinity CD16 FcR and erIL-2
taNK = NK-92 (aNK) transfected with either a plasmid or lentiviral vector expressing a CAR
t-haNK = NK-92 (aNK) transfected with a plasmid expressing a CAR and CD16 FcR erIL-2
qt-haNK = NK-92 (aNK) transfected with a plasmid expressing a 4th gene in addition to a CAR, the CD16 FcR, and erIL-2 : examples: homing receptor of the CXCR family or immune-active cytokines
The high affinity Fc-receptor-expressing NK (haNK) cells were administered to patients with advanced Merkel cell carcinoma (MCC) and there were some notable responses. Currently, a HER2-targeted aNK (taNK) line and various t-haNK (CAR and Fc-receptor expressing) cell lines are in clinical trials in patients with various cancers, as described in the review “The NK-92 cell line 30 years later: its impact on natural killer cell research and treatment of cancer." [ 16 ]
Global rights to the NK-92 cell line were assigned to ImmunityBio Inc. (formerly NantKwest, Inc.). ImmunityBio's only authorized NK-92 distributor is Brink Biologics, Inc. (San Diego), which makes NK-92 cells and certain genetically modified CD16+ variants available to third parties for non-clinical research under a limited use license agreement. | https://en.wikipedia.org/wiki/NK-92 |
1KCG , 4PDC , 1HYR , 1MPU , 4S0U
22914
27007
ENSG00000213809
ENSMUSG00000030149
P26718
O54709
NM_007360
NM_001083322 NM_001286018 NM_033078
NP_001186734
NP_001076791 NP_001272947 NP_149069
NKG2D is an activating receptor (transmembrane protein) belonging to the NKG2 family of C-type lectin-like receptors . [ 5 ] NKG2D is encoded by KLRK1 (killer cell lectin like receptor K1) gene which is located in the NK-gene complex (NKC) situated on chromosome 6 in mice [ 6 ] and chromosome 12 in humans. [ 7 ] In mice, it is expressed by NK cells , NK1.1 + T cells , γδ T cells , activated CD8 + αβ T cells and activated macrophages . [ 8 ] In humans, it is expressed by NK cells , γδ T cells and CD8 + αβ T cells . [ 9 ] NKG2D recognizes induced-self proteins from MIC and RAET1/ULBP families which appear on the surface of stressed, malignant transformed, and infected cells. [ 10 ]
Human NKG2D receptor complex assembles into a hexameric structure. NKG2D itself forms a homodimer whose ectodomains serve for ligand binding. [ 11 ] Each NKG2D monomer is associated with DAP10 dimer. This association is maintained by ionic interaction of a positively charged arginine present in a transmembrane segment of NKG2D and negatively charged aspartic acids within both transmembrane regions of DAP10 dimer. [ 12 ] DAP10 functions as an adaptor protein and transduces the signal after the ligand binding by recruiting the p85 subunit of PI3K and Grb2 - Vav1 complex which are responsible for subsequent downstream events. [ 13 ]
In mice, alternative splicing generates two distinct NKG2D isoforms: the long one (NKG2D-L) and the short one (NKG2D-S). NKG2D-L binds DAP10 similarly to human NKG2D. By contrast, NKG2D-S associates with two adaptor proteins: DAP10 and DAP12 . [ 14 ] DAP10 recruits the p85 subunit of PI3K and a complex of Grb2 and Vav1 . [ 13 ] DAP12 bears ITAM motif and activates protein tyrosine kinases Syk and Zap70 signalling. [ 15 ]
NKG2D ligands are induced-self proteins which are completely absent or present only at low levels on surface of normal cells, but they are overexpressed by infected, transformed, senescent and stressed cells. Their expression is regulated at different stages (transcription, mRNA and protein stabilization, cleavage from the cell surface) by various stress pathways. [ 16 ] Among them, one of the most prominent stress pathways is DNA damage response. Genotoxic stress, stalled DNA replication, poorly regulated cell proliferation in tumorigenesis, viral replication or some viral products activate the ATM and ATR kinases. These kinases initiate the DNA damage response pathway which participates in NKG2D ligand upregulation. DNA damage response thus participate in alerting the immune system to the presence of potentially dangerous cells. [ 17 ]
All NKG2D ligands are homologous to MHC class I molecules and are divided into two families: MIC and RAET1/ULBP.
Human MIC genes are located within the MHC locus and are composed of seven members ( MICA-G ), of which only MICA and MICB produce functional transcripts. In mice, MIC genes are absent. [ 18 ]
Among ten known human RAET1/ULBP genes, six encode functional proteins: RAET1E/ULBP4 , RAET1G/ULBP5 , RAET1H/ULBP2 , RAET1/ULBP1 , RAET1L/ULBP6 , RAET1N/ULBP3 . In mice, proteins from orthologous RAET1/ULBP family fall into three subfamilies: Rae-1 , H60 , and MULT-1 . [ 18 ] ULBP2 is a stress-induced ligand often found on senescent cells . [ 19 ]
NKG2D ligand expression is regulated on multiple levels such as transcriptional, RNA splicing , posttranscriptional and posttranslational. On the transcriptional level, NKG2D ligands can be regulated by transcription factors or regulatory sequences in various molecular pathways. Also, the regulation of NKG2D ligands after cell stress , proliferation signals, infection or oxidative stress is able to activate a DNA damage response (DDR). [ 20 ] Ligation of sensor kinases ATM and ATR leads to activation of different checkpoint kinases, such as Chk1 and Chk2 , [ 21 ] which are important for the induction of MIC , ULBP s or Reat1 genes [ 17 ] ). One of the major signals for cell expression of NKG2D is the triggering of DDR along with the induction of senescence program. [ 17 ] RNA splicing is another mechanism influencing NKG2D ligand expression. For MICA, [ 22 ] ULBP4 [ 23 ] and ULBP5, [ 24 ] alternative splicing isoforms have been shown. However, the molecular mechanisms of this type of regulation are unknown. In posttranscriptional regulation, stabilization of NKG2D ligand mRNA plays a key role. For example AUF1 protein, which mediates RNA degradation, constitutively targets mRNA of NKG2D ligands. [ 25 ] Additionally, surface expression levels of NKG2D can be controlled by soluble forms of various protease-mediated cleavages and exosome expression. [ 26 ]
NKG2D is a major recognition receptor for the detection and elimination of transformed and infected cells as its ligands are induced during cellular stress, either as a result of infection or genomic stress such as in cancer . [ 27 ] In NK cells, NKG2D serves as an activating receptor, which itself is able to trigger cytotoxicity. The function of NKG2D on CD8 + T cells is to send co-stimulatory signals to activate them. [ 8 ]
Viruses, as intracellular pathogens, can induce the expression of stress ligands for NKG2D. NKG2D is thought to be important in viral control as viruses have adapted mechanisms by which to evade NKG2D responses. [ 28 ] For example, cytomegalovirus (CMV) encodes a protein, UL16 , which binds to NKG2D ligands ULBP1 and 2 (thus their name "UL16-binding protein") and MICB, which prevents their surface expression. [ 29 ]
As cancerous cells are "stressed", NKG2D ligands become upregulated, rendering the cell susceptible to NK cell-mediated lysis. However, some tumor cells have acquired the capacity to evade this immune surveillance. They have created the capacity of reducing and eliminating the high volume of NKG2DL present on the cell surface of tumor cells by secreting metalloproteases that cleave these ligands, and therefore they escape from the control of NK cells and their cytotoxic activity. TGF-β allows immune surveillance escape by inhibiting T and NK cell function. [ 30 ] Tumor cells that can evade NKG2D responses are thus more likely to propagate. [ 28 ] [ 31 ]
As part of the DNA damage response during induction of cellular senescence , cells upregulate the expression of NKG2D ligands that enable NK-mediated killing of senescent cells via the granule exocytosis pathway. [ 32 ] [ 33 ] Specifically, MICA and ULBP2 proteins on senescent cells are recognized by the NKG2D receptor on Natural Killer cells, which is necessary for efficient recognition and elimination of senescent cells. [ 32 ]
Interventions to increase senescent cell surface ligands of the Natural Killer cell receptor NKG2D have been proposed as a senolytic therapy to remove senescent cells. [ 34 ]
When NKG2D receptor binds to any of its ligands, an activation cascade starts for activating the respective immune cell. NKG2D does not possess any signaling elements within its intracellular domain. NKG2D forms a homodimer and associates with adaptor proteins in its transmembrane domain to a hexameric complex structure and initiate signaling cascades. [ 35 ] In both mice and humans, this signalling depends on the association between NKG2D and DAP10 protein forming a complex. Upon ligand engagement, Tyr-X-X-Meth (YXXM) motif within the cytoplasmic domain of DAP10 recruits PI3K and Grb2 to activate NK cell cytotoxicity pathways. [ 35 ] In mice, NKG2D associates with DAP 12, instead of DAP 10, and NKG2D-DAP12 complex is involved in IFN-γ production through the Syk and ZAP70 pathway. [ 30 ]
Therefore, NKG2D is implicated in NK and other immune cells activation through the PI3K-AKT pathway . This pathway activation depend on two main basis. The first is the plasticity and structural changes of NKG2D (receptor) when binding to its ligands. The last one is the association of DAP10 in the intracellular domain of the receptor and the recruitment of PI3K and Grb.
NK cells are a key part of innate immunity , mainly involved in the early cytolytic defense against infections and tumors. NK cell activity is mediated by a variety of cell surface receptors with stimulatory and inhibitory activity. Under normal conditions, NK cells exist in an inactive state, with signaling dominated by inhibitory receptor activation.
NKG2G is a key stimulatory cell surface receptor. A low expression of the receptor is observed already in the early NK cells precursor stages, also the concentration of receptors is increased with maturation of NK cells. [ 36 ] In mice, both NKG2D isoforms were detected. During resting state, predominance of long forms of NKG2D is typical, while in activated cells there is a higher number of short forms. [ 37 ]
Interaction with IL-15 receptor (IL-15R) is a crucial factor for development, homeostasis and survival of NK cells and NKG2D signaling seems to be similarly critical. [ 38 ] Connection between these two pathways is the binding of DAP10, adaptor protein and signal transducer, which associates with IL-15R or NKG2D, respectively. [ 39 ] This phenomenon was proven by experiments on mice knocked out in Klrk1 – such mice have higher proliferation rate, faster differentiation and maturation of NK cells, resulting in a misbalance of immature NK cell subpopulations and higher susceptibility to apoptosis of NK cells. [ 15 ]
NKG2D is involved in the generation of peripheral tolerance by the effective downregulation of NKG2D ligands, for the prevention from recognition by NK cells. It is supposed to act as a form of obstacle against NK cells' hyper-responsiveness to ligands, without complete education in bone marrow. [ 40 ] Tolerance of NK cells is likewise observed during pregnancy, when placenta produces soluble and exosome-bound ligands for NKG2D and accumulates large number of NK cells which prevent recognition of fetus as non-self. [ 41 ]
For priming of T cells , binding of ligand on T cell receptors (TCR), co-stimulation by membrane receptors and cytokines are all necessary components. Co-stimulation regulates responsiveness of T cells and NKG2D is one of well-documented co-stimulatory molecules for T cells., [ 42 ] CD28 –mediated co-stimulation is required for promotion of cytokine production and cytotoxicity in CD8 + T cells by NKG2D. [ 43 ] For cytokine production and cytolytic killing by γδ T cells , priming is not required, however NKG2D expression is constitutive while solely triggering NKG2D in γδ T cells does not mediate cytotoxicity. [ 44 ]
In T cells, NKG2D is associated with IL15-receptor signaling and also with the development of memory CD8 T cells. [ 45 ] Key role in the transformation of CD8 + T cells into effector or memory types is played by mammalian target of rapamycin complex 1 (mTORC1) – memory precursor cells are characteristic by the low level of mTORC1 and for terminally differentiated CD8 + T cells, high level of mTORC1 activity is typical. [ 46 ] Upregulation of antiapoptic Mcl-1 protein by NKG2D also induces formation of memory T cells. [ 45 ] In murine memory T cell precursors, downregulation of T-bet transcription factor is likewise affected by NKG2D. [ 47 ]
Also development of B cells is regulated by NKG2D—NKG2D deficient mice have reduced number of B cells in spleen, [ 48 ] which is partially depended on DAP10. [ 49 ] In comparison to NK cells, mature B cells do not express NKG2D. [ 48 ] | https://en.wikipedia.org/wiki/NKG2D |
The NK model is a mathematical model described by its primary inventor Stuart Kauffman as a "tunably rugged" fitness landscape . "Tunable ruggedness" captures the intuition that both the overall size of the landscape and the number of its local "hills and valleys" can be adjusted via changes to its two parameters, N {\displaystyle N} and K {\displaystyle K} , with N {\displaystyle N} being the length of a string of evolution and K {\displaystyle K} determining the level of landscape ruggedness.
The NK model has found application in a wide variety of fields, including the theoretical study of evolutionary biology , immunology , optimisation , technological evolution , team science, [ 1 ] and complex systems . The model was also adopted in organizational theory , where it is used to describe the way an agent may search a landscape by manipulating various characteristics of itself. For example, an agent can be an organization , the hills and valleys represent profit (or changes thereof), and movement on the landscape necessitates organizational decisions (such as adding product lines or altering the organizational structure), which tend to interact with each other and affect profit in a complex fashion. [ 2 ]
An early version of the model, which considered only the smoothest ( K = 0 {\displaystyle K=0} ) and most rugged ( K = N − 1 {\displaystyle K=N-1} ) landscapes, was presented in Kauffman and Levin (1987). [ 3 ] The model as it is currently known first appeared in Kauffman and Weinberger (1989). [ 4 ]
One of the reasons why the model has attracted wide attention in optimisation is that it is a particularly simple instance of a so-called NP-complete problem [ 5 ] which means it is difficult to find global optima. Recently, it was shown that the NK model for K > 1 is also PLS-complete [ 6 ] which means than, in general, it is difficult to find even local fitness optima. This has consequences for the study of open-ended evolution .
A plasmid is a small circle of DNA inside certain cells that can replicate independently of their host cells. Suppose we wish to study the fitness of plasmids.
For simplicity, we model a plasmid as a ring of N possible genes, always in the same order, and each can have two possible states (active or inactive, type X or type Y, etc...). Then the plasmid is modelled by a binary string with length N , and so the fitness function is F : { 0 , 1 } N → R {\displaystyle F:\{0,1\}^{N}\to \mathbb {R} } .
The simplest model would have the genes not interacting with each other, and so we obtain F ( S 1 S 2 ⋯ S N ) = f 1 ( S 1 ) + f 2 ( S 2 ) + ⋯ + f N ( S N ) {\displaystyle F(S_{1}S_{2}\cdots S_{N})=f_{1}(S_{1})+f_{2}(S_{2})+\cdots +f_{N}(S_{N})} where each f i ( S i ) {\displaystyle f_{i}(S_{i})} denotes the contribution to fitness of gene S i {\displaystyle S_{i}} at location i {\displaystyle i} .
To model epistasis , we introduce another factor K , the number of other genes that a gene interacts with. It is reasonable to assume that on a plasmid, two genes interact if they are adjacent, thus giving F ( S 1 S 2 ⋯ S N ) = f 1 ( S 1 , S 2 ) + f 2 ( S 2 , S 3 ) + ⋯ + f N − 1 ( S N − 1 , S N ) + f N ( S N , S 1 ) {\displaystyle F(S_{1}S_{2}\cdots S_{N})=f_{1}(S_{1},S_{2})+f_{2}(S_{2},S_{3})+\cdots +f_{N-1}(S_{N-1},S_{N})+f_{N}(S_{N},S_{1})} For example, when K = 1 , and N = 5 ,
The NK model generalizes this by allowing arbitrary finite K, N, as well as allowing arbitrary definition of adjacency of genes (the genes do not necessarily lie on a circle or a line segment).
The NK model defines a combinatorial phase space , consisting of every string (chosen from a given alphabet) of length N {\displaystyle N} . For each string in this search space, a scalar value (called the fitness ) is defined. If a distance metric is defined between strings, the resulting structure is a landscape .
Fitness values are defined according to the specific incarnation of the model, but the key feature of the NK model is that the fitness of a given string S {\displaystyle S} is the sum of contributions from each locus f i ( S ) {\displaystyle f_{i}(S)} in the string:
and the contribution from each locus in general depends on its state and the state of K {\displaystyle K} other loci,:
where k i j {\displaystyle k_{ij}} is the index of the j {\displaystyle j} th neighbor of locus i {\displaystyle i} .
Hence, the fitness function f i {\displaystyle f_{i}} is a mapping between strings of length K + 1 and scalars, which Weinberger's later work calls "fitness contributions". Such fitness contributions are often chosen randomly from some specified probability distribution.
The 1D Ising model of spin glass is usually written as H = − ∑ i = 1 N J i , i + 1 S i S i + 1 − μ ∑ i = 1 N h i S i {\displaystyle H=-\sum _{i=1}^{N}J_{i,i+1}S_{i}S_{i+1}-\mu \sum _{i=1}^{N}h_{i}S_{i}} where H {\displaystyle H} is the Hamiltonian, which can be thought as energy.
We can reformulate it as a special case of the NK model with K=1 : H = F ( S ) = ∑ i , j f i , j ( S i , S j ) {\displaystyle H=F(S)=\sum _{i,j}f_{i,j}(S_{i},S_{j})} by defining f i ( S i , S i + 1 ) = − J i , i + 1 S i S i + 1 − μ h i S i {\displaystyle f_{i}(S_{i},S_{i+1})=-J_{i,i+1}S_{i}S_{i+1}-\mu h_{i}S_{i}} In general, the m-dimensional Ising model on a square grid { 1 , 2 , . . . , n } m {\displaystyle \{1,2,...,n\}^{m}} is an NK model with N = n m , K = m {\displaystyle N=n^{m},K=m} .
Since K roughly measures "ruggedness" of the fitness landscape (see below), we see that as the dimension of Ising model increases, its ruggedness also increases.
When μ = 0 {\displaystyle \mu =0} , this is the Edwards–Anderson model, which is exactly solvable.
The Sherrington–Kirkpatrick model generalizes the Ising model by allowing all possible pairs of spins to interact (instead of a grid graph , use the complete graph ), thus it is also an NK model with K = N − 1 {\displaystyle K=N-1} .
Allowing all possible subsequences of spins to interact, instead of merely pairs, we obtain the infinite-range model, which is also an NK model with K = N − 1 {\displaystyle K=N-1} .
The value of K controls the degree of epistasis in the NK model, or how much other loci affect the fitness contribution of a given locus. With K = 0, the fitness of a given string is a simple sum of individual contributions of loci: for nontrivial fitness functions, a global optimum is present and easy to locate (the genome of all 0s if f (0) > f (1), or all 1s if f (1) > f (0)). For nonzero K , the fitness of a string is a sum of fitnesses of substrings, which may interact to frustrate the system (consider how to achieve optimal fitness in the example above). Increasing K thus increases the ruggedness of the fitness landscape.
The bare NK model does not support the phenomenon of neutral space -- that is, sets of genomes connected by single mutations that have the same fitness value. Two adaptations have been proposed to include this biologically important structure . The NKP model introduces a parameter P {\displaystyle P} : a proportion P {\displaystyle P} of the 2 K {\displaystyle 2^{K}} fitness contributions is set to zero, so that the contributions of several genetic motifs are degenerate [ citation needed ] . The NKQ model introduces a parameter Q {\displaystyle Q} and enforces a discretisation on the possible fitness contribution values so that each contribution takes one of Q {\displaystyle Q} possible values, again introducing degeneracy in the contributions from some genetic motifs [ citation needed ] . The bare NK model corresponds to the P = 0 {\displaystyle P=0} and Q = ∞ {\displaystyle Q=\infty } cases under these parameterisations.
In 1991, Weinberger published a detailed analysis [ 7 ] of the case in which 1 << k ≤ N {\displaystyle 1<<k\leq N} and the fitness contributions are chosen randomly. His analytical estimate of the number of local optima was later shown to be flawed [ citation needed ] . However, numerical experiments included in Weinberger's analysis support his analytical result that the expected fitness of a string is normally distributed with a mean of approximately
μ + σ 2 ln ( k + 1 ) k + 1 {\displaystyle \mu +\sigma {\sqrt {{2\ln(k+1)} \over {k+1}}}}
and a variance of approximately
( k + 1 ) σ 2 N [ k + 1 + 2 ( k + 2 ) ln ( k + 1 ) ] {\displaystyle {{(k+1)\sigma ^{2}} \over {N[k+1+2(k+2)\ln(k+1)]}}} .
The NK model has found use in many fields, including in the study of spin glasses , collective problem solving, [ 8 ] epistasis and pleiotropy in evolutionary biology , and combinatorial optimisation . | https://en.wikipedia.org/wiki/NK_model |
The NLGI consistency number or NLGI grade expresses a measure of the relative hardness of a grease used for lubrication, as specified by the standard classification of lubricating grease established by the National Lubricating Grease Institute (NLGI). Reproduced in standards ASTM D4950 (“standard classification and specification of automotive service greases”) and SAE J310 (“automotive lubricating greases”) , NLGI's classification is widely used. The NLGI consistency number is also a component of the code specified in standard ISO 6743-9 “lubricants, industrial oils and related products (class L) — classification — part 9: family X (greases)” . [ 1 ]
The NLGI consistency number alone is not sufficient for specifying the grease required by a particular application. However, it complements other classifications (such as ASTM D4950 and ISO 6743-9 ). Besides consistency, other properties (such as structural and mechanical stability, apparent viscosity, resistance to oxidation, etc.) can be tested to determine the suitability of a grease to a specific application.
NLGI's classification defines nine grades, each associated to a range of ASTM worked penetration values, measured using the test defined by standard ASTM D217 “cone penetration of lubricating grease” . This involves two test apparatus. The first apparatus consists of a closed container and a piston-like plunger. The face of the plunger is perforated to allow grease to flow from one side of the plunger to another as the plunger is worked up and down. The test grease is inserted into the container and the plunger is stroked 60 times while the test apparatus and grease are maintained at a temperature of 25 °C .
Once worked, the grease is placed in a penetration test apparatus. This apparatus consists of a container, a specially-configured cone and a dial indicator . The container is filled with the grease and the top surface of the grease is smoothed over. The cone is placed so that its tip just touches the grease surface and the dial indicator is set to zero at this position. When the test starts, the weight of the cone will cause it to penetrate into the grease. After a specific time interval the depth of penetration is measured.
The following table [ 2 ] shows the NLGI classification and compares each grade with household products of similar consistency.
Common greases are in the range 1 through 3. Those with a NLGI No. of 000 to 1 are used in low viscosity applications. Examples include enclosed gear drives operating at low speeds and open gearing . Grades 0, 1 and 2 are used in highly loaded gearing. Grades 1 through 4 are often used in rolling contact bearings . Greases with a higher number are firmer, tend to stay in place and are a good choice when leakage is a concern. | https://en.wikipedia.org/wiki/NLGI_consistency_number |
The Fortran subroutine NLPQLP , a newer [ when? ] version of NLPQL , solves smooth nonlinear programming problems
by a sequential quadratic programming (SQP) algorithm. The new version is specifically
tuned to run under distributed systems.
In case of computational errors, such as inaccurate function or gradient evaluations,
a non-monotone line search is activated. The code is easily transformed to C by f2c and is widely used in academia and industry.
This computer-library -related article is a stub . You can help Wikipedia by expanding it . | https://en.wikipedia.org/wiki/NLPQLP |
In quantum information theory , the no low-energy trivial state (NLTS) conjecture is a precursor to a quantum PCP theorem (qPCP) and posits the existence of families of Hamiltonians with all low-energy states of non-trivial complexity . [ 1 ] [ 2 ] [ 3 ] [ 4 ] It was formulated by Michael Freedman and Matthew Hastings in 2013. NLTS is a consequence of one aspect of qPCP problems – the inability to certify an approximation of local Hamiltonians via NP completeness . [ 2 ] In other words, it is a consequence of the QMA complexity of qPCP problems. [ 5 ] On a high level, it is one property of the non- Newtonian complexity of quantum computation . [ 5 ] NLTS and qPCP conjectures posit the near-infinite complexity involved in predicting the outcome of quantum systems with many interacting states. [ 6 ] These calculations of complexity would have implications for quantum computing such as the stability of entangled states at higher temperatures , and the occurrence of entanglement in natural systems. [ 7 ] [ 6 ] A proof of the NLTS conjecture was presented and published as part of STOC 2023. [ 8 ]
The NLTS property is the underlying set of constraints that forms the basis for the NLTS conjecture. [ citation needed ]
A k -local Hamiltonian (quantum mechanics) H {\displaystyle H} is a Hermitian matrix acting on n qubits which can be represented as the sum of m {\displaystyle m} Hamiltonian terms acting upon at most k {\displaystyle k} qubits each:
The general k -local Hamiltonian problem is, given a k -local Hamiltonian H {\displaystyle H} , to find the smallest eigenvalue λ {\displaystyle \lambda } of H {\displaystyle H} . [ 9 ] λ {\displaystyle \lambda } is also called the ground-state energy of the Hamiltonian.
The family of local Hamiltonians thus arises out of the k -local problem. Kliesch states the following as a definition for local Hamiltonians in the context of NLTS: [ 2 ]
Let I ⊂ N be an index set. A family of local Hamiltonians is a set of Hamiltonians { H ( n ) }, n ∈ I , where each H ( n ) is defined on n finite-dimensional subsystems (in the following taken to be qubits), that are of the form
where each H m ( n ) acts non-trivially on O (1) qubits. Another constraint is the operator norm of H m ( n ) is bounded by a constant independent of n and each qubit is only involved in a constant number of terms H m ( n ) .
In physics , topological order [ 10 ] is a kind of order in the zero-temperature phase of matter (also known as quantum matter). In the context of NLTS, Kliesch states: "a family of local gapped Hamiltonians is called topologically ordered if any ground states cannot be prepared from a product state by a constant-depth circuit". [ 2 ]
Kliesch defines the NLTS property thus: [ 2 ]
Let I be an infinite set of system sizes. A family of local Hamiltonians { H ( n ) }, n ∈ I has the NLTS property if there exists ε > 0 and a function f : N → N such that
There exists a family of local Hamiltonians with the NLTS property. [ 2 ]
Proving the NLTS conjecture is an obstacle for resolving the qPCP conjecture, an even harder theorem to prove. [ 1 ] The qPCP conjecture is a quantum analogue of the classical PCP theorem. The classical PCP theorem states that satisfiability problems like 3SAT are NP-hard when estimating the maximal number of clauses that can be simultaneously satisfied in a hamiltonian system. [ 7 ] In layman's terms, classical PCP describes the near-infinite complexity involved in predicting the outcome of a system with many resolving states, such as a water bath full of hundreds of magnets . [ 6 ] qPCP increases the complexity by trying to solve PCP for quantum states . [ 6 ] Though it hasn't been proven yet, a positive proof of qPCP would imply that quantum entanglement in Gibbs states could remain stable at higher-energy states above absolute zero . [ 7 ]
NLTS on its own is difficult to prove, though a simpler no low-error trivial states (NLETS) theorem has been proven, and that proof is a precursor for NLTS. [ 11 ]
NLETS is defined as: [ 11 ] | https://en.wikipedia.org/wiki/NLTS_conjecture |
NLnet Labs is a Dutch network research laboratory in Amsterdam , founded in 1999 by the board members of NLnet . NLNet Labs develops DNS-related software, such as NSD , Unbound , OpenDNSSEC and getDNS.
NLnet Labs originated from the NLnet Foundation. NLnet's core business is to support independent organisations and people that contribute to an open information society. For long term research projects, NLnet Labs was founded in 1999 by the board members of NLnet and Ted Lindgreen. One of the first activities was creating an implementation for DNSSEC. In 2001 the RIPE NCC asked NLnet Labs to write a DNS implementation geared especially to rootservers, but not containing any code of existing software. This marked the start of the development of NSD, the authoritative nameserver package. [ 1 ]
Other major projects include a validating caching resolver Unbound, and the OpenDNSSEC project. [ 1 ]
On 19 April 2023, NLnet Labs and the Internet Systems Consortium (ISC) sent a joint letter to the European Parliament committee working on the EU Cyber Resilience Act . The letter is a plea for fairness for non-profit developers of open-source software , because the Act mostly focuses on those who supply products in a business related context, while according to the two organisations the non-profit distribution of open source internet infrastructure software should not be regarded as a "commercial activity". [ 2 ]
This computing article is a stub . You can help Wikipedia by expanding it . | https://en.wikipedia.org/wiki/NLnet_Labs |
NMEA 0183 is a combined electrical and data specification for communication between marine electronics such as echo sounder , sonars , anemometer , gyrocompass , autopilot , GPS receivers and many other types of instruments. It has been defined and is controlled by the National Marine Electronics Association (NMEA). It replaces the earlier NMEA 0180 and NMEA 0182 standards. [ 1 ] In leisure marine applications, it is slowly being phased out in favor of the newer NMEA 2000 standard, [ 2 ] [ 3 ] though NMEA 0183 remains the norm in commercial shipping.
The electrical standard that is used is EIA-422 , also known as RS-422, although most hardware with NMEA-0183 outputs are also able to drive a single EIA-232 port. The standard calls for optically isolated inputs. There is no requirement for isolation for the outputs.
The NMEA 0183 standard uses a simple ASCII , serial communications protocol that defines how data are transmitted in a "sentence" from one "talker" to multiple "listeners" at a time. Through the use of intermediate expanders, a talker can have a unidirectional conversation with a nearly unlimited number of listeners, and using multiplexers , multiple sensors can talk to a single computer port.
At the application layer , the standard also defines the contents of each sentence (message) type, so that all listeners can parse messages accurately.
While NMEA 0183 only defines an RS-422 transport, there also exists a de facto standard in which the sentences from NMEA 0183 are placed in UDP datagrams (one sentence per packet) and sent over an IP network.
The NMEA standard is proprietary and sells for at least US$2000 (except for members of the NMEA) as of September 2020. [ 4 ] [ 5 ] However, much of it has been reverse-engineered from public sources. [ 6 ] [ 7 ]
There is a variation of the standard called NMEA-0183HS that specifies a baud rate of 38,400. This is in general use by AIS devices.
As an example, a waypoint arrival alarm has the form:
Another example for AIS messages is:
The main talker ID includes: [ 8 ] [ 9 ]
NMEA message mainly include the following "sentences" in the NMEA message: [ 10 ]
One example, the sentence for Global Positioning System Fixed Data for GPS should be "$GPGGA".
Most GPS manufacturers include special messages in addition to the standard NMEA set in their products for maintenance and diagnostics purposes. Extended messages begin with "$P". These extended messages are not standardized.
NMEA 0183 is supported by various navigation and mapping software. Notable applications include:
A sample file produced by a Tripmate 850 GPS logger. This file was produced in Leixlip , County Kildare , Ireland . The record lasts two seconds.
Note some blank fields, for example:
NMEA 0183 continued to be maintained separately: V4.10 was published in early May 2012, and an erratum noted on 12 May 2012. [ 15 ] On November 27, 2018, it was issued an update to version 4.11, which supports Global Navigation Satellite Systems other than GPS . [ 16 ] | https://en.wikipedia.org/wiki/NMEA_0183 |
NMEA 2000 , abbreviated to NMEA2k or N2K and standardized as IEC 61162-3 , is a plug-and-play communications standard used for connecting marine sensors and display units within ships and boats.
Communication runs at 250 kilobits -per-second and allows any sensor to talk to any display unit or other device compatible with NMEA 2000 protocols.
Electrically, NMEA 2000 is compatible with the Controller Area Network ("CAN Bus") used on road vehicles and fuel engines. The higher-level protocol format is based on SAE J1939 , with specific messages for the marine environment. Raymarine SeaTalk 2 , Raymarine SeaTalk NG , Simrad Simnet, and Furuno CAN are rebranded implementations of NMEA 2000, though may use physical connectors different from the standardised DeviceNet 5-pin A-coded M12 screw connector , all of which are electrically compatible and can be directly connected.
The protocol is used to create a network of electronic devices—chiefly marine instruments—on a boat. Various instruments that meet the NMEA 2000 standard are connected to one central cable, known as a backbone. The backbone powers each instrument and relays data among all of the instruments on the network. This allows one display unit to show many different types of information. It also allows the instruments to work together, since they share data. NMEA 2000 is meant to be "plug and play" to allow devices made by different manufacturers to communicate with each other.
Examples of marine electronics devices to include in a network are GPS receivers, autopilots , wind instruments, depth sounders, navigation instruments, engine instruments, and nautical chart plotters. The interconnectivity among instruments in the network allows, for example, the GPS receiver to correct the course that the autopilot is steering.
The NMEA 2000 standard was defined by, and is controlled by, the US-based National Marine Electronics Association (NMEA). Although the NMEA divulges some information regarding the standard, it claims copyright over the standard and thus its full contents are not publicly available. For example, the NMEA publicizes which messages exist and which fields they contain, but they do not disclose how to interpret the values contained in those fields. However, enthusiasts are slowly making progress in discovering these PGN definitions. [ 1 ]
NMEA 2000 connects devices using Controller Area Network (CAN) technology originally developed for the auto industry. NMEA 2000 is based on the SAE J1939 high-level protocol, but defines its own messages. [ 2 ] [ 3 ] NMEA 2000 devices and J1939 devices can be made to co-exist on the same physical network. [ 4 ]
NMEA 2000 ( IEC 61162-3) can be considered a successor to the NMEA 0183 (IEC 61162-1) serial data bus standard. [ 5 ] It has a significantly higher data rate (250k bits/second vs. 4800 bits/second for NMEA 0183). It uses a compact binary message format as opposed to the ASCII serial communications protocol used by NMEA 0183. Another improvement is that NMEA 2000 supports a disciplined multiple-talker, multiple-listener data network whereas NMEA 0183 requires a single-talker, multiple-listener ( simplex ) serial communications protocol .
The NMEA 2000 network, like the SAE J1939 network on which it is based, is organized around a bus topology, and requires a single 120Ω termination resistor at each end of the bus. (The resistors are in parallel, so a properly terminated bus should have a total resistance of 60Ω). The maximum distance for any device from the bus is six metres. The maximum backbone cable length is 250 meters (820 feet) with Mini cable backbone or 100 meters (328 feet) with Micro cable backbone [ 3 ]
The only cabling standard approved by the NMEA for use with NMEA 2000 networks is the DeviceNet cabling standard, which is controlled by the Open DeviceNet Vendors Association . Such cabling systems are permitted to be labeled "NMEA 2000 Approved". The DeviceNet standard defines levels of shielding, conductor size, weather resistance, and flexibility which are not necessarily met by other cabling solutions marketed as "NMEA 2000" compatible. [ 2 ] [ 3 ]
There are two sizes of cabling defined by the DeviceNet/NMEA 2000 standard. The larger of the two sizes is denoted as "Mini" (or alternatively, "Thick") cable, and is rated to carry up to 8 amperes of power supply current. The smaller of the two sizes is denoted as "Micro" (or alternatively, "Thin") cable using the M12 5-pin barrel connector specified in IEC 61076-2-101, and is rated to carry up to 3 amperes of power supply current.
Mini cable is primarily used as a "backbone" (or "trunk") for networks on larger vessels (typically with lengths of 20 m and above), with Micro cable used for connections between the network backbone and the individual components. Networks on smaller vessels often are constructed entirely of Micro cable and connectors.
An NMEA 2000 network is not electrically compatible with an NMEA 0183 network, and so an interface device is required to send messages between devices on the different types of network. An adapter is also required if NMEA 2000 messages are to be received by or transmitted from a PC.
In accordance with the SAE J1939 protocol, NMEA 2000 messages are sent as packets that consist of a header followed by (typically) 8 bytes of data. The header for a message specifies the transmitting device, the device to which the message was sent (which may be all devices), the message priority, and the PGN (Parameter Group Number). The PGN indicates which message is being sent, and thus how the data bytes should be interpreted to determine the values of the data fields that the message contains. [ 2 ]
Devices go through a certification process overseen by the NMEA, and are permitted to display the "NMEA 2000 Certified" logo once they have completed the certification process. The certification process does not guarantee data content, that is the responsibility of the manufacturers. However, the certification process does assure that products from different manufacturers exchange data in a compatible way and that they can coexist on a network. [ 6 ]
Several manufacturers, including Simrad , Raymarine , Stowe , and BRP , have their own proprietary networks that are compatible with or akin to NMEA 2000. Simrad's is called SimNet , Raymarine's is called SeaTalk NG , Stowe's is called Dataline 2000 , and BRP's is called CZone . Some of these, such as SimNet and Seatalk NG, are a standard NMEA 2000 network but use non-standard connectors and cabling; adapters are available to convert to standard NMEA 2000 connectors, or the user can simply remove the connector and make a direct connection. [ 7 ]
The term "NMEA 2000" is a registered trademark of the National Marine Electronics Association. Devices which are not "NMEA 2000 Certified" may not legally use the NMEA 2000 trademark in their advertising.
The following are some of the companies that have registered with the NMEA for the purpose of producing NMEA 2000 certified products: [ 8 ]
Related standards
Safety Standards using NMEA 2000 | https://en.wikipedia.org/wiki/NMEA_2000 |
NMP22 is a tumor marker for bladder cancer .
NMP22 is the abbreviated form of Nuclear Matrix Protein Number 22. [ 1 ] [ 2 ] [ 3 ] It reflects the mitotic activity of cells.
This biochemistry article is a stub . You can help Wikipedia by expanding it . | https://en.wikipedia.org/wiki/NMP22 |
NMR-STAR is an extension of the STAR file format to store the results of biological NMR experiments.
This article about chemistry software is a stub . You can help Wikipedia by expanding it . | https://en.wikipedia.org/wiki/NMR-STAR_file_format |
In chemistry, NMR line broadening techniques (or NMR line broadening experiments ) can be used to determine the rate constant and the Gibbs free energy of exchange reactions of two different chemical compounds. If the two species are in equilibrium and exchange to each other, peaks of both species get broadened in the spectrum. This observation of broadened peaks can be used to obtain kinetic and thermodynamic information of the exchange reaction.
A basic NMR line broadening experiment is to determine the rotational energy barrier of a certain chemical bond. If the bond rotates slowly enough compared to the NMR time scale (e.g., amide bond), two different species can be detected by the NMR spectrometer. Considering that the time scale of NMR spectroscopy is about a few seconds, this technique can be used to examine the kinetics and/or thermodynamics of chemical exchange reactions on the order of seconds.
In general, the energy barrier to rotate a bond is low enough at room temperature, which means that the rotation is fast, making the two different species indistinguishable. At low temperatures, however, it is harder for a bond to overcome the energy barrier to rotate, resulting in two separate peaks in the spectrum. With these principles, NMR spectra of a molecule with a high rotational barrier should be obtained at several different temperatures (i.e., variable temperature NMR) to distinguish two different peaks at low temperature in slow exchange and to find the temperature at which the two peaks merge. [ 1 ]
Especially at the coalescence temperature ( T c {\displaystyle T_{c}} ), where the two peaks coalesce, the rate constant of rotation at T c {\displaystyle T_{c}} and the energy barrier of the rotation can be easily calculated. As increasing the temperature, the exchange reaction get faster, and at a certain temperature, which is T c {\displaystyle T_{c}} , the appearance of the peaks changes from two separate peaks in slow exchange to a single peak in fast exchange. The rate constant k {\displaystyle k} at T c {\displaystyle T_{c}} can be calculated with the following equation: [ 2 ]
k = π ∣ ν A − ν B ∣ 2 {\textstyle \ k={\frac {\pi \mid \nu _{A}-\nu _{B}\mid }{\sqrt {2}}}} ,
where ν A {\displaystyle \nu _{A}} and ν B {\displaystyle \nu _{B}} are the chemical shift of each species at lower temperatures where they are in slow exchange.
By using the Eyring equation , the Gibbs free energy of rotation, Δ G ‡ {\displaystyle \Delta G^{\ddagger }} , can be determined:
k = k B T h e − Δ G ‡ R T {\displaystyle k={\frac {k_{\text{B}}T}{h}}\mathrm {e} ^{-{\frac {\Delta G^{\ddagger }}{RT}}}} (Eyring equation)
Δ G ‡ = R T c ln k B T c 2 π h ∣ ν A − ν B ∣ {\displaystyle \Delta G^{\ddagger }=RT_{c}\ln {\frac {k_{\text{B}}T_{c}{\sqrt {2}}}{\pi h\mid \nu _{A}-\nu _{B}\mid }}}
where R {\displaystyle R} is gas constant, k B {\displaystyle k_{\text{B}}} is the Boltzmann constant, and h {\displaystyle h} is the Planck constant.
Electron transfer self-exchange rates can be also determined with the experimental value of line-width and chemical shift . [ 3 ] Sharp peaks of diamagnetic compounds can be broadened during the electron transfer with its partner paramagnetic compound (one-electron oxidized species), since paramagnetic compounds exhibit broader peaks at a different chemical shift. If their self-exchange rate is sufficiently faster than the NMR timescale, the line-broadening of the peaks is observed at shifted chemical shifts in the spectrum. In order to determine the self-exchange rate of sample compounds, one can choose a certain characteristic peak of the sample diamagnetic compound, and examine the peak broadening in the mixture with its partner paramagnetic compound. The broadened line-widths are proportional to mole fraction, and the equation can be used to determine self-exchange rate with the value of mole fraction, chemical shift and line-width:
k = 4 π X d X p ( Δ ν ) 2 ( W − X p W p − X d W d ) C {\displaystyle k={\frac {4\pi X_{d}X_{p}(\Delta \nu )^{2}}{(W-X_{p}W_{p}-X_{d}W_{d})C}}} ,
where k {\displaystyle k} is the rate constant of electron transfer self-exchange, X d {\displaystyle X_{d}} and X p {\displaystyle X_{p}} are the mole fractions of diamagnetic and paramagnetic compounds, Δ ν {\displaystyle \Delta \nu } is the chemical shift difference (in Hz) between pure diamagnetic and paramagnetic compounds, and W {\displaystyle W} is the half-width of the peak (width at half height) of the selected peak. W d {\displaystyle W_{d}} and W p {\displaystyle W_{p}} are the peak widths of the pure diamagnetic and paramagnetic species, and C {\displaystyle {\ce {C}}} is the total concentration of the exchanging species in M (mol/L). [ 4 ] For more accurate calculation of each mole fraction, the following equations can be used;
X p = ∣ ν − ν d ∣ Δ ν {\displaystyle X_{p}={\frac {\mid \nu -\nu _{d}\mid }{\Delta \nu }}}
X d = 1 − X d {\displaystyle X_{d}=1-X_{d}} ,
where ν {\displaystyle \nu } is a shifted chemical shift of the selected peak, and ν d {\displaystyle \nu _{d}} is the original chemical shift of the diamagnetic species based on the assumption that the change in chemical shift is linearly correlated to the mole fraction of the paramagnetic species. | https://en.wikipedia.org/wiki/NMR_line_broadening_techniques |
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