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Maia Garcia Vergniory is a Spanish computational physicist who is a Professor at the University of Sherbrooke . [ 1 ] Her work in topological quantum chemistry investigates the phases of topological materials. [ 2 ] She was elected Fellow of the American Physical Society in 2022. [ 3 ]
Vergniory was born in Getxo . [ 4 ] She was a doctoral researcher at the University of the Basque Country . Her research considered many-body effects on the interactions between excited electronic states and the mobile ions on surfaces. [ 5 ] She started working on topological materials in 2012. [ 6 ]
Vergniory worked as a research fellow at the Ikerbasque and the Donostia International Physics Center. [ 7 ] She studied novel materials and computational strategies to realise new condensed matter systems. [ 8 ]
Verginory became interested in the design of new topological materials with optimised functional properties. [ 9 ] [ 10 ] Topological materials are insulators in the bulk but conductive on their surfaces. [ 11 ] The conducting channels that facilitate current flow are robust and independent of size.
Vergniory studied the Inorganic Crystal Structure Database to identify topologically nontrivial materials. [ 12 ] She designed a computational effort to simulate real materials and determine whether or not they showed topological properties. [ 13 ] This included complex theoretical analysis that could classify topological phases, and information from materials scientists on whether materials were suitable or not. [ 14 ] Vergniory uses her supercomputers to perform her calculations ab initio . [ 6 ] In an interview with Physics World , Verginory said that she had been surprised by how many materials she identified with topological properties. [ 14 ] As an output of this work, the high-order topological insulator Bi 4 Br 4 was synthesised and studied experimentally. She showed that if it was possible to identify the symmetry of the crystalline symmetry of a material, she could easily anticipate the behaviour of the charge. [ 14 ] She has since started investigating organic materials. [ 14 ] She believes that topological crystals with a chiral structure will display several exotic physical phenomena. [ 15 ] | https://en.wikipedia.org/wiki/Maia_Vergniory |
The maiden flight , also known as first flight , of an aircraft is the first occasion on which it leaves the ground under its own power. The same term is also used for the first launch of rockets .
In the early days of aviation it could be dangerous, because the exact handling characteristics of the aircraft were generally unknown. The maiden flight of a new type is almost invariably flown by a highly experienced test pilot . Maiden flights are usually accompanied by a chase plane , to verify items like altitude , airspeed , and general airworthiness .
A maiden flight is only one stage in the development of an aircraft type. Unless the type is a pure research aircraft (such as the X-15 ), the aircraft must be tested extensively to ensure that it delivers the desired performance with an acceptable margin of safety. In the case of civilian aircraft, a new type must be certified by a governing agency (such as the Federal Aviation Administration in the United States) before it can enter operation.
An incomplete list of maiden flights of notable aircraft types, organized by date, follows. | https://en.wikipedia.org/wiki/Maiden_flight |
Mail-in-a-Box is a free and open-source program for mail server hosting developed by Joshua Tauberer . [ 1 ] [ 2 ] The software's goal is to enable any user to turn a cloud system into a mail server in a few hours. [ 3 ] The tool enables developers to host mail for multiple users and multiple domain names . [ 4 ] [ 5 ]
The default configuration provides a spam detection system, monitoring, reporting and backup mechanisms. [ 6 ] It can also set up and automatically renew a Let's Encrypt certificate , as well as configuring the detailed DNS configurations needed to ensure that a mail server's IP address is trusted by other servers, and less likely to be blacklisted. [ 6 ] [ 7 ] Its support for IMAP / SMTP facilitates synchronizing across devices. [ 7 ]
First developed in 2013 by Tauberer, the tool is written in Python . The project supports Ubuntu LTS. [ 8 ] [ 9 ]
It has been recommended by the notable Hackaday and MakeTechEasier. [ 10 ] [ 11 ]
This software article is a stub . You can help Wikipedia by expanding it . | https://en.wikipedia.org/wiki/Mail-in-a-Box |
A mail chute is a device by which mail is collected for pick-up by a post office from within high-rise buildings, such as offices, hospitals, and hotels. Deposit boxes on upper floors are connected via a chute to a central depository at ground level, from which the mail is picked up.
The mail chute was patented by James Goold Cutler , an architect from Rochester, New York , in 1883. A company founded by Cutler would become the principal manufacturer of such systems for new hotels, apartment buildings, and offices, defending the original patent and modifications. Use of the mail chute declined with the advent of modern mailrooms designed to more efficiently handle increased volumes of mail and issues that could be caused by clogs or letters falling through. In 1997, the National Fire Protection Association updated its voluntary codes to ban new chute installations, as the vertical shafts could spread smoke in the event of fire. However, thousands of existing mail chutes continue in use, including hundreds in New York City alone.
On September 11, 1883, James Goold Cutler received U.S. patent 284,951, for a system connecting deposit boxes on multiple floors to a single ground-floor receptacle; the chute had to have a front of at least three-fourths glass to allow for the identification of mail clogs, and, if installed at a height of greater than two stories, an elastic cushion was to be fitted in the receptacle to "prevent injury to the mail". [ 1 ]
The design of chute letter boxes also evolved over time to fit architectural styles and become less utilitarian. [ 2 ] : 20 [ 3 ]
In 1884, a year after Cutler obtained his patent, the first such system was installed in the Cutler-designed Elwood Building in Rochester, with the goal of saving tenants the hassle of depositing mail in a box on the street. It was well received, winning awards at 1884's World Cotton Centennial in New Orleans and an exhibition the same year in Cincinnati, [ 4 ] : 20 but federal law of the time only permitted the placement of mailboxes in public buildings, such as government offices, hotels, theatres, and rail stations; thus, postmen refused to mail the collected letters. [ 5 ] In 1893, under revised postal laws, chutes came under the regulatory authority of the United States Post Office Department . [ 1 ] As a result, all repairs to malfunctioning chute systems had to be undertaken by post office-approved engineers, a problem in smaller cities (such as Rochester) where the post office did not employ mechanics. [ 6 ]
In 1884, the same year as the Elwood installation, the Cutler Manufacturing Company was incorporated by James Goold Cutler and his brother, J. Warren Cutler. [ 7 ] Cutler contracted some of the work of producing systems to the Yawman & Erbe Manufacturing Company, which continued to work for Cutler until the company built its own factory on Anderson Avenue in 1908. [ 7 ] By 1905, some 1,600 chutes had been installed as a boom in skyscraper construction dovetailed with the new invention. [ 3 ] Cutler's firm remained the sole manufacturer of chute systems until 1904, when the Post Office Department permitted competitors. [ 8 ] In 1905, the Automatic Mail Delivery Company of New York City started making chutes; Cutler sued for patent infringement and won the case. The two firms then merged in 1909 as the Cutler Mail Chute Company, headquartered out of offices in Rochester and the New York Times Building in New York City. [ 9 ] The next year, the Cutler Mail Chute Company won a patent infringement lawsuit against the United States Mail Chute Equipment Company. [ 10 ] The firm's grip on the technology was so firm that in 1911, a competitor testified at a congressional hearing that "every architect and builder in the country has rebelled for years against the prices they have been forced to pay for mail chutes to the Cutler Co."; [ 8 ] even in 1961, after the original patent and those for later improvements expired, Cutler was said to hold 70 percent of the market. [ 11 ] James Goold Cutler stepped aside in 1915, when a Maine-domiciled holding company acquired the New York firm, and J. Warren Cutler was named president. [ 7 ]
London's Savoy Hotel featured the first installation of a Cutler chute in England when it was expanded in 1904. [ 12 ] The Canadian Cutler Mail Chute Company Limited was incorporated in Montreal in 1910. [ 13 ] By 1920, Cutler mail chutes had been installed in buildings in countries including Mexico, Cuba, Japan, South Africa, India, and Australia. [ 14 ]
In 1958, the Federal Equipment Company of Carlisle, Pennsylvania , purchased the Cutler Mail Chute Company, which maintained a Rochester-area presence in Honeoye Falls until 1974. [ 15 ] [ 16 ] Federal Equipment produced equipment for post offices. [ 15 ] The firm was known as Cutler-Federal, Inc., after 1959, and engaged in the creation of automated sorting equipment and pneumatic tube systems. [ 17 ] Cutler was acquired by the Florence Corporation, a manufacturer of mailboxes, in 2000, and this firm was purchased by Gibraltar Industries of Buffalo, New York , in 2007. [ 8 ]
The introduction of modern building mailrooms to handle larger volumes of mail led to chutes falling out of favor, particularly after 1980. [ 3 ] In 1997, the National Fire Protection Association banned the construction of new mail chutes because smoke could spread among floors through their vertical shafts, much as with chimneys. [ 3 ] By 2001, 900 chutes were in active use in New York City and another 360 in Chicago, though some buildings had discontinued their use; buildings such as the Chrysler Building and McGraw-Hill Building had experienced jams, including in the case of the latter a 1986 clog blocking the passage of 40,000 pieces of mail, while the John Hancock Center shuttered its chutes because of increased volume. [ 3 ] In 1999, the New York City district of the United States Postal Service responded to at least two calls a week to clear mail chutes that were hung up with stuck mail. [ 18 ] In rare cases, items could remain stuck for decades; in 1995, a widow received a love letter and other correspondence that had been caught in a Cutler mail chute 50 years prior, [ 19 ] and several items intended to be mailed at the Wilkes-Barre City Hall in Pennsylvania in 1923 were discovered in 1980. [ 20 ] | https://en.wikipedia.org/wiki/Mail_chute |
The Maillard reaction ( / m aɪ ˈ j ɑːr / my- YAR ; French: [majaʁ] ) is a chemical reaction between amino acids and reducing sugars to create melanoidins , the compounds that give browned food its distinctive flavor. Seared steaks, fried dumplings, cookies and other kinds of biscuits, breads, toasted marshmallows, falafel and many other foods undergo this reaction. It is named after French chemist Louis Camille Maillard , who first described it in 1912 while attempting to reproduce biological protein synthesis . [ 1 ] [ 2 ] The reaction is a form of non-enzymatic browning which typically proceeds rapidly from around 140 to 165 °C (280 to 330 °F). Many recipes call for an oven temperature high enough to ensure that a Maillard reaction occurs. [ 3 ] At higher temperatures, caramelization (the browning of sugars, a distinct process) and subsequently pyrolysis (final breakdown leading to burning and the development of acrid flavors) become more pronounced. [ 4 ]
The reactive carbonyl group of the sugar reacts with the nucleophilic amino group of the amino acid and forms a complex mixture of poorly characterized molecules responsible for a range of aromas and flavors. This process is accelerated in an alkaline environment (e.g., lye applied to darken pretzels; see lye roll ), as the amino groups ( RNH + 3 → RNH 2 ) are deprotonated , and hence have an increased nucleophilicity . This reaction is the basis for many of the flavoring industry's recipes. At high temperatures, a probable [ 5 ] carcinogen called acrylamide can form. [ 6 ] This can be discouraged by heating at a lower temperature, adding asparaginase , or injecting carbon dioxide. [ 5 ]
In the cooking process, Maillard reactions can produce hundreds of different flavor compounds depending on the chemical constituents in the food, the temperature, the cooking time, and the presence of air. These compounds, in turn, often break down to form yet more flavor compounds. Flavor scientists have used the Maillard reaction over the years to make artificial flavors, the majority of patents being related to the production of meat-like flavors. [ 7 ]
In 1912, Louis Camille Maillard published a paper describing the reaction between amino acids and sugars at elevated temperatures. [ 1 ] In 1953, chemist John E. Hodge with the U.S. Department of Agriculture established a mechanism for the Maillard reaction. [ 8 ] [ 9 ]
The Maillard reaction is responsible for many colors and flavors in foods, such as the browning of various meats when seared or grilled, the browning and umami taste in fried onions and coffee roasting . It contributes to the darkened crust of baked goods , the golden-brown color of French fries and other crisps, browning of malted barley as found in malt whiskey and beer, and the color and taste of dried and condensed milk , dulce de leche , toffee , black garlic , chocolate , toasted marshmallows , and roasted peanuts . [ citation needed ]
6-Acetyl-2,3,4,5-tetrahydropyridine is responsible for the biscuit or cracker-like flavor present in baked goods such as bread, popcorn, and tortilla products. The structurally related compound 2-acetyl-1-pyrroline has a similar smell and also occurs naturally without heating. The compound gives varieties of cooked rice and the herb pandan ( Pandanus amaryllifolius ) their typical smells. Both compounds have odor thresholds below 0.06 nanograms per liter. [ 10 ]
The browning reactions that occur when meat is roasted or seared are complex and occur mostly by Maillard browning [ 11 ] with contributions from other chemical reactions, including the breakdown of the tetrapyrrole rings of the muscle protein myoglobin . Maillard reactions also occur in dried fruit [ 12 ] and when champagne ages in the bottle. [ 13 ]
Caramelization is an entirely different process from Maillard browning, though the results of the two processes are sometimes similar to the naked eye (and taste buds). Caramelization may sometimes cause browning in the same foods in which the Maillard reaction occurs, but the two processes are distinct. They are both promoted by heating, but the Maillard reaction involves amino acids, whereas caramelization is the pyrolysis of certain sugars. [ 14 ]
In making silage , excess heat causes the Maillard reaction to occur, which reduces the amount of energy and protein available to the animals that feed on it. [ 15 ]
In archaeology, the Maillard process occurs when bodies are preserved in peat bogs . The acidic peat environment causes a tanning or browning of skin tones and can turn hair to a red or ginger tone. The chemical mechanism is the same as in the browning of food, but it develops slowly over time due to the acidic action on the bog body . It is typically seen on Iron Age bodies and is the result of the interaction of anaerobic, acidic, and cold (typically 4 °C (39 °F)) sphagnum acid on the polysaccharides .
The Maillard reaction also contributes to the preservation of paleofeces . [ 16 ]
The open-chain Amadori products undergo further dehydration and deamination to produce dicarbonyls. [ 17 ] This is a crucial intermediate.
Dicarbonyls react with amines to produce Strecker aldehydes through Strecker degradation . [ 18 ]
Acrylamide , a possible human carcinogen , [ 19 ] can be generated as a byproduct of Maillard reaction between reducing sugars and amino acids, especially asparagine , both of which are present in most food products. [ 20 ] [ 21 ] | https://en.wikipedia.org/wiki/Maillard_reaction |
Main-group element-mediated activation of dinitrogen is the N 2 activation facilitated by reactive main group element centered molecules (e.g., low valent main group metal calcium, [ 1 ] dicoordinate borylene, [ 2 ] [ 3 ] [ 4 ] boron radical, [ 5 ] carbene, [ 6 ] [ 7 ] etc.).
Dinitrogen fixation is essential for human life. Currently [ when? ] , the industry uses the Haber–Bosch process to convert N 2 and H 2 to NH 3 based on the metal catalysis under very high pressure and temperature conditions. Alternative strategies that realize the transformation from N 2 to NH 3 under mild conditions are a long-lasting goal in chemistry. In the past decades [ when? ] , a number of transition-metal species have been found to bind (and even functionalize) N 2 . The prevalence of transition metals in dinitrogen activation is attributed to the fact that the unoccupied and occupied d orbitals could be both energetically and symmetrically accessible to accept electron density from and back donate to N 2 . Nevertheless, the development of low-valent, low-coordinate main-group elements which mimic the electronic properties of transition metal provides more opportunities to unearth the N 2 activation by main group elements. [ 8 ]
Lithium can also react with N 2 at room temperature to give an isolable product Li 3 N. [ 9 ] [ 10 ] However, it was until recently [ when? ] that the controllable, stepwise N 2 activation by main group element began to thrive [ editorializing ] , especially for those whose key intermediates were well structurally characterized and even isolated. [ citation needed ]
In 2021, Harder et al. achieved dinitrogen activation by a low-valent calcium complex, which was generated by the reduction of a calcium (II) complex [CaI(BDI)] 2 . [ 1 ] With the presence of THF, the reduction of [CaI(BDI)] 2 with K/KI could afford red-brown crystals. The single crystal X-ray analysis revealed a centrosymmetric dimer with terminal BDI ligands and side-on bridging N 2 units. The N-N distance in complex (1.258(3) and 1.268(3) Å) is remarkably [ editorializing ] longer than that of dinitrogen triple-bond (1.098 Å) and comparable with N=N double bond character in N 2 2- . The N 2 2ˉ anion could also be protonated to diazene (N 2 H 2 ) with the intramolecular deprotonation of THF under the heating condition. [ citation needed ]
Dicoordinate borylene has a filled p orbital and an empty sp-hybridized orbital in appropriate symmetry that can interact with inert small molecules like dinitrogen. In 2018, Braunschweig et al. reported the nitrogen fixation and reduction by active borylene species. [ 2 ] [(CAAC)BDurBr 2 ] could smoothly undergo one-electron reduction with the limited amount of KC 8 (1.5 equiv.) and afford a radical complex [(CAAC)BDurBr]·. The radical complex could be further reduced, forming the transient dicoordinate borylene species and thus had the ability to activate dinitrogen. The filled p orbital of borylene, which acted as a Lewis base, donated to the π* antibonding orbital of N 2 . The empty sp 2 orbital, which acted as a Lewis acid, accepted the electrons from N 2 through σ donation. Following the further reduction by KC 8 and stabilization by another borylene molecule, the dipotassium complex {[(CAAC)DurB] 2 (μ 2 -N 2 K 2 )} was formed in crystalline solid. Exposure of the dipotassium complex with ambient air and distilled water leads to the formation of dinitrogen bis(borylene) compound {[(CAAC)DurB] 2 (μ 2 -N 2 )} and a paramagnetic diradical complex {[(CAAC)DurB] 2 (μ 2 -N 2 H 2 )}. Further protonation and reduction of {[(CAAC)DurB] 2 (μ 2 -N 2 H 2 )} could lead to the cleavage of central N-N bond, which could finally lead to the formation of ammonium chloride in one-pot reaction. [ 4 ]
Repeating the same reaction but replacing Dur (2,3,5,6-tetramethyl-phenyl) group by a bulkier Tip (2,4,6-triisopropylphenyl) group resulted in a very different result: after the dinitrogen was coordinated by the first borylene molecule, the second coordination by another borylene molecule was considerably hindered by steric repulsion in the case of the bulkier 4-Tip. Instead, the reductive dimerization of transient borylene [(CAAC)BTip] could occur in the presence of extra KC 8 , affording the complex {[(CAAC)-TipB] 2 (μ 2 -N 4 K 2 )}, a product with catenation of two N 2 molecules, forming a N4 chain. It should be mentioned [ editorializing ] that this kind of coupling reaction was never found in the transition-metal-mediated N 2 activation processes. [ 3 ]
For borylene molecules, two-electron-filled p orbital and vacant sp2 orbital provide two push–pull channels to activate dinitrogen. Similarly, for boron radicals, one-electron-filled p orbital and vacant sp2 orbital provide two channels to activate N 2 . In 2022, Mézailles et al. reported the N 2 activation by in situ generated boron-centered radicals. [ 5 ] Though key intermediate which activated N 2 is unclear, DFT calculation suggested that the coordination of N 2 occurs prior to the second chloride elimination. Following the further reduction and coordination of boron, N 2 was finally reduced to its lowest oxidation state and a mixture of two borylamine compounds, N(BCy 2 ) 3 and NH(BCy 2 ) 2 , were generated. [ citation needed ]
Carbene species have also been considered a good choice to activate N 2 . The decomposition of diazoalkanes with the release of N 2 is one of the most widely used strategies to produce carbenes. Its reverse reaction could be considered as the activation of N 2 with carbenes. [ 6 ] For example, in 1992, Dailey et al. reported that the photolysis of 3-bromo-3-(trifluoromethyl)diazirines in an argon matrix could afford bromo(trifluoromethyl)carbene. Bromo(trifluoromethyl)carbene could rebound N 2 photochemically in matrix to form the corresponding diazo compound. [ 7 ] | https://en.wikipedia.org/wiki/Main-group_element-mediated_activation_of_dinitrogen |
Main group organometallic chemistry concerns the preparation and properties of main-group elements directly bonded to carbon. The inventory is large. The compounds exhibit a wide range of properties, including ones that are water-stable and others that are pyrophoric . [ 1 ] Many are very useful themselves, as chemical reagents, or as catalysts. [ 2 ]
Main group organometallic chemistry are typically categorized according to their position in the periodic table. Another possible classification scheme organizes these compounds according to the nature of the organic substituent: alkyls , aryls , vinyls, etc.
Most homoleptic organo-main group compounds adopt a characteristic oxidation state: RLi, R 2 Be, R 3 B/R 3 Al, R 4 Si, R 3 P, R 2 S. Members where the simplest stoichiometry violates the octet rule often aggregate by formation of bridging alkyl groups. When the alkyl group bridges two main group elements, the bonding is called three-center two-electron bonds . This pattern is seen for dimethyl beryllium and trimethylaluminium . In the case of methyl lithium , the methyl group can be shared (bonded to) three Li centers. These bonding aspects influence the structures: Trimethylaluminium, dimethyl beryllium, and methyl lithium are dimers, polymers, and clusters, respectively.
Academic research often seeks exceptions to conventional stoichiometries and oxidation states, often by use of bulky ligands . Examples include (pentamethylcyclopentadienyl)aluminium(I) (Al(I)), stannylenes (Sn(II)), and diphosphenes (P(I)).
Thus organic derivatives of the electropositive alkali metals and alkaline earth metals tend to be highly reactive toward electrophiles , e.g. oxygen and water. Organic derivatives of the less electropositive main group elements are often robust.
Like their derivatives lacking organic substituents, halides and alkoxide ligands for the later organomain group compounds tend to hydrolyze. Organophosphorus and silanes exhibit this pattern:
Consisting of the terrestrially most abundant elements , main group organometallic compounds have many and often large-scale uses. Commercially important examples include:
Main group organometallic chemistry is sometimes thought to start with publications on the organoarsenic compound called " Cadet's fuming liquid ". This derivative of dimethylarsine is easily prepared and hence the subject of an early discovery. [ 3 ] A major development was the popularization of Salvarsan , another organoarsenic compound at the beginning of the 1910s. Although ultimately a failed therapeutic, its use ushered in the field of chemotherapy . [ 4 ]
An early step in main group organometallic chemistry (if one considers Zn to be a main group element) involved the synthesis of organozinc compounds diethyl zinc by Frankland. [ 5 ]
Tetraethyllead is the focus of an infamous episode involving main group organometallic compounds. It was widely used as a fuel additive for much of the 20th century, until it was found to be chronic toxin. [ 6 ] | https://en.wikipedia.org/wiki/Main_group_organometallic_chemistry |
The technical meaning of maintenance involves functional checks, servicing, repairing or replacing of necessary devices, equipment, machinery , building infrastructure and supporting utilities in industrial, business, and residential installations. [ 1 ] [ 2 ] Terms such as "predictive" or "planned" maintenance describe various cost-effective practices aimed at keeping equipment operational; these activities occur either before [ 3 ] or after a potential failure.
Maintenance functions can be defined as maintenance, repair and overhaul ( MRO ), and MRO is also used for maintenance, repair and operations . [ 4 ] Over time, the terminology of maintenance and MRO has begun to become standardized. The United States Department of Defense uses the following definitions: [ 5 ]
Maintenance is strictly connected to the utilization stage of the product or technical system, in which the concept of maintainability must be included. In this scenario, maintainability is considered as the ability of an item, under stated conditions of use, to be retained in or restored to a state in which it can perform its required functions, using prescribed procedures and resources. [ 6 ]
In some domains like aircraft maintenance , terms maintenance, repair and overhaul [ 7 ] also include inspection, rebuilding, alteration and the supply of spare parts, accessories, raw materials, adhesives, sealants, coatings and consumables for aircraft maintenance at the utilization stage. In international civil aviation maintenance means:
This definition covers all activities for which aviation regulations require issuance of a maintenance release document (aircraft certificate of return to service – CRS).
The marine and air transportation, [ 9 ] offshore structures, [ 10 ] industrial plant and facility management industries depend on maintenance, repair and overhaul (MRO) including scheduled or preventive paint maintenance programmes to maintain and restore coatings applied to steel in environments subject to attack from erosion, corrosion and environmental pollution. [ 10 ]
The basic types of maintenance falling under MRO include:
Architectural conservation employs MRO to preserve, rehabilitate, restore, or reconstruct historical structures with stone, brick, glass, metal, and wood which match the original constituent materials where possible, or with suitable polymer technologies when not. [ 12 ]
Preventive maintenance ( PM ) is "a routine for periodically inspecting" with the goal of "noticing small problems and fixing them before major ones develop." [ 13 ] Ideally, "nothing breaks down." [ 14 ]
The main goal behind PM is for the equipment to make it from one planned service to the next planned service without any failures caused by fatigue, extreme fluctuation in temperature(such as heat waves [ 15 ] ) during seasonal changes, neglect, or normal wear (preventable items), which Planned Maintenance and Condition Based Maintenance help to achieve by replacing worn components before they actually fail. Maintenance activities include partial or complete overhauls at specified periods, oil changes, lubrication, minor adjustments, and so on. In addition, workers can record equipment deterioration so they know to replace or repair worn parts before they cause system failure.
The New York Times gave an example of "machinery that is not lubricated on schedule" that functions "until a bearing burns out." Preventive maintenance contracts are generally a fixed cost, whereas improper maintenance introduces a variable cost: replacement of major equipment. [ 13 ]
Main objective of PM are:
Preventive maintenance or preventative [ 16 ] maintenance ( PM ) has the following meanings:
Other terms and abbreviations related to PM are:
Planned preventive maintenance (PPM), more commonly referred to as simply planned maintenance ( PM ) or scheduled maintenance , is any variety of scheduled maintenance to an object or item of equipment. Specifically, planned maintenance is a scheduled service visit carried out by a competent and suitable agent, to ensure that an item of equipment is operating correctly and to therefore avoid any unscheduled breakdown and downtime. [ 23 ]
The key factor as to when and why this work is being done is timing, and involves a service, resource or facility being unavailable. [ 18 ] [ 19 ] By contrast, condition-based maintenance is not directly based on equipment age.
Planned maintenance is preplanned, and can be date-based, based on equipment running hours, or on distance travelled.
Parts that have scheduled maintenance at fixed intervals, usually due to wearout or a fixed shelf life , are sometimes known as time-change interval, or TCI items.
Predictive maintenance techniques are designed to help determine the condition of in-service equipment in order to estimate when maintenance should be performed. This approach promises cost savings over routine or time-based preventive maintenance , because tasks are performed only when warranted. Thus, it is regarded as condition-based maintenance carried out as suggested by estimations of the degradation state of an item. The main promise of predictive maintenance is to allow convenient scheduling of corrective maintenance , and to prevent unexpected equipment failures. [ 3 ] This maintenance strategy uses sensors to monitor key parameters within a machine or system, and uses this data in conjunction with analysed historical trends to continuously evaluate the system health and predict a breakdown before it happens. [ 24 ] This strategy allows maintenance to be performed more efficiently, since more up-to-date data is obtained about how close the product is to failure. [ 25 ]
Predictive replacement is the replacement of an item that is still functioning properly. [ 26 ] Usually it is a tax-benefit based [ citation needed ] replacement policy whereby expensive equipment or batches of individually inexpensive supply items are removed and donated on a predicted/fixed shelf life schedule. These items are given to tax-exempt institutions. [ 27 ] [ citation needed ]
Condition-based maintenance ( CBM ), shortly described, is maintenance when need arises . Albeit chronologically much older, It is considered one section or practice inside the broader and newer predictive maintenance field, where new AI technologies and connectivity abilities are put to action and where the acronym CBM is more often used to describe 'condition Based Monitoring' rather than the maintenance itself. CBM maintenance is performed after one or more indicators show that equipment is going to fail or that equipment performance is deteriorating.
This concept is applicable to mission-critical systems that incorporate active redundancy and fault reporting . It is also applicable to non-mission critical systems that lack redundancy and fault reporting.
Condition-based maintenance was introduced to try to maintain the correct equipment at the right time. CBM is based on using real-time data to prioritize and optimize maintenance resources. Observing the state of the system is known as condition monitoring . Such a system will determine the equipment's health, and act only when maintenance is actually necessary. Developments in recent years have allowed extensive instrumentation of equipment, and together with better tools for analyzing condition data, the maintenance personnel of today is more than ever able to decide what is the right time to perform maintenance on some piece of equipment. Ideally, condition-based maintenance will allow the maintenance personnel to do only the right things, minimizing spare parts cost, system downtime and time spent on maintenance.
Despite its usefulness of equipment, there are several challenges to the use of CBM. First and most important of all, the initial cost of CBM can be high. It requires improved instrumentation of the equipment. Often the cost of sufficient instruments can be quite large, especially on equipment that is already installed. Wireless systems have reduced the initial cost. Therefore, it is important for the installer to decide the importance of the investment before adding CBM to all equipment. A result of this cost is that the first generation of CBM in the oil and gas industry has only focused on vibration in heavy rotating equipment.
Secondly, introducing CBM will invoke a major change in how maintenance is performed, and potentially to the whole maintenance organization in a company. Organizational changes are in general difficult.
Also, the technical side of it is not always as simple. Even if some types of equipment can easily be observed by measuring simple values such as vibration (displacement, velocity or acceleration), temperature or pressure, it is not trivial to turn this measured data into actionable knowledge about the health of the equipment.
As systems get more costly, and instrumentation and information systems tend to become cheaper and more reliable, CBM becomes an important tool for running a plant or factory in an optimal manner. Better operations will lead to lower production cost and lower use of resources. And lower use of resources may be one of the most important differentiators in a future where environmental issues become more important by the day.
Another scenario where value can be created is by monitoring the health of a car motor. Rather than changing parts at predefined intervals, the car itself can tell you when something needs to be changed based on cheap and simple instrumentation.
It is Department of Defense policy that condition-based maintenance (CBM) be "implemented to improve maintenance agility and responsiveness, increase operational availability, and reduce life cycle total ownership costs". [ 28 ]
CBM has some advantages over planned maintenance:
Its disadvantages are:
Today, due to its costs, CBM is not used for less important parts of machinery despite obvious advantages. However it can be found everywhere where increased safety is required, and in future will be applied even more widely. [ 29 ] [ 30 ]
Corrective maintenance is a type of maintenance used for equipment after equipment break down or malfunction is often most expensive – not only can worn equipment damage other parts and cause multiple damage, but consequential repair and replacement costs and loss of revenues due to down time during overhaul can be significant. Rebuilding and resurfacing of equipment and infrastructure damaged by erosion and corrosion as part of corrective or preventive maintenance programmes involves conventional processes such as welding and metal flame spraying, as well as engineered solutions with thermoset polymeric materials. [ 31 ] | https://en.wikipedia.org/wiki/Maintenance |
Maintenance-free operating period ( MFOP ) is an alternative measure of performance to the mean time between failures (MTBF), defined as the time period during which a device will be able to perform each of its intended functions, requiring only a minimal degree of maintenance. [ 1 ] It was originally proposed in 1996 by the United Kingdom 's Ministry of Defence , with intended application to military aircraft. [ 2 ]
This engineering-related article is a stub . You can help Wikipedia by expanding it . | https://en.wikipedia.org/wiki/Maintenance-free_operating_period |
Maintenance Engineering is the discipline and profession of applying engineering concepts for the optimization of equipment, procedures, and departmental budgets to achieve better maintainability , reliability , and availability of equipment.
Maintenance, and hence maintenance engineering, is increasing in importance due to rising amounts of equipment, systems, machineries and infrastructure. Since the Industrial Revolution , devices, equipment, machinery and structures have grown increasingly complex, requiring a host of personnel, vocations and related systems needed to maintain them. [ 1 ] Prior to 2006, the United States spent approximately US$300 billion annually on plant maintenance and operations alone. [ 1 ] Maintenance is to ensure a unit is fit for purpose, with maximum availability at minimum costs. A person practicing maintenance engineering is known as a maintenance engineer.
A maintenance engineer should possess significant knowledge of statistics , probability , and logistics , and in the fundamentals of the operation of the equipment and machinery he or she is responsible for. A maintenance engineer should also possess high interpersonal, communication, and management skills, as well as the ability to make decisions quickly.
Typical responsibilities include: [ 2 ] [ 3 ]
Institutions across the world have recognised the need for maintenance engineering. Maintenance engineers usually hold a degree in mechanical engineering , industrial engineering , or other engineering disciplines. In recent years specialised bachelor and master courses have developed. The bachelor degree program in maintenance engineering at the German-Jordanian University in Amman is addressing the need, as well as the master's program in maintenance engineering at Luleå University of Technology . With an increased demand for Chartered Engineers, The University of Central Lancashire in United Kingdom has developed a MSc in maintenance engineering currently under accreditation with the Institution of Engineering and Technology and a top-up Bachelor of Engineering with honour degree for technicians holding a Higher National Diploma and seeking a progression in their professional career.
School of Applied Technical Sciences - Maintenance Engineering | https://en.wikipedia.org/wiki/Maintenance_engineering |
Maintenance of an organism is the collection of processes to stay alive, excluding production processes. The Dynamic Energy Budget theory delineates two classes
The theory assumes that maturity maintenance costs can be reduced more easily during starvation than somatic maintenance costs. Under extreme starvation conditions, somatic maintenance costs are paid from structural mass, which causes shrinking. Some organism manage to switch to the torpor state under starvation conditions, and reduce their maintenance costs.
This developmental biology article is a stub . You can help Wikipedia by expanding it . | https://en.wikipedia.org/wiki/Maintenance_of_an_organism |
Maintenance respiration (or maintenance energy ) refers to metabolism occurring in an organism that is needed to maintain that organism in a healthy, living state. Maintenance respiration contrasts with growth respiration , which is responsible for the synthesis of new structures in growth, nutrient uptake, nitrogen (N) reduction and phloem loading, whereas maintenance respiration is associated with protein and membrane turnover and maintenance of ion concentrations and gradients. [ 1 ]
Maintenance respiration in plants refers to the amount of cellular respiration , measured by the carbon dioxide (CO 2 ) released or oxygen (O 2 ) consumed, during the generation of usable energy (mainly ATP , NADPH , and NADH ) and metabolic intermediates used for (i) resynthesis of compounds that undergo renewal (turnover) in the normal process of metabolism (examples are enzymatic proteins , ribonucleic acids, and membrane lipids); (ii) maintenance of chemical gradients of ions and metabolites across cellular membranes that are necessary for cellular integrity and plant health; and (iii) operation of metabolic processes involved in physiological adjustment (i.e., acclimation ) to a change in the plant's environment. [ 2 ] [ 3 ] [ 4 ] The metabolic costs of the repair of injury from biotic or abiotic stress may also be considered a part of maintenance respiration. [ 2 ]
Maintenance respiration is essential for biological health and growth of plants. It is estimated that about half of the respiration carried out by terrestrial plants during their lifetime is for the support of maintenance processes. [ 5 ] Because typically more than half of global terrestrial plant photosynthesis (or gross primary production ) is used for plant respiration, [ 4 ] more than one quarter of global terrestrial plant photosynthesis is presumably consumed in maintenance respiration.
Maintenance respiration is a key component of most physiologically based mathematical models of plant growth, including models of crop growth and yield and models of ecosystem primary production and carbon balance. [ 6 ] [ 7 ] [ 8 ] | https://en.wikipedia.org/wiki/Maintenance_respiration |
Majda's model is a qualitative model (in mathematical physics ) introduced by Andrew Majda in 1981 for the study of interactions in the combustion theory of shock waves and explosive chemical reactions. [ 1 ]
The following definitions are with respect to a Cartesian coordinate system with 2 variables. For functions u ( x , t ) {\displaystyle u(x,t)} , z ( x , t ) {\displaystyle z(x,t)} of one spatial variable x {\displaystyle x} representing the Lagrangian specification of the fluid flow field and the time variable t {\displaystyle t} , functions f ( w ) {\displaystyle f(w)} , ϕ ( w ) {\displaystyle \phi (w)} of one variable w {\displaystyle w} , and positive constants k , q , B {\displaystyle k,q,B} , the Majda model is a pair of coupled partial differential equations : [ 2 ]
Since its introduction in the early 1980s, Majda's simplified "qualitative" model for detonation ... has played an important role in the mathematical literature as test-bed for both the development of mathematical theory and computational techniques. Roughly, the model is a 2 × 2 {\displaystyle 2\times 2} system consisting of a Burgers equation coupled to a chemical kinetics equation. For example, Majda (with Colella & Roytburd) used the model as a key diagnostic tool in the development of fractional-step computational schemes for the Navier-Stokes equations of compressible reacting fluids ... [ 3 ]
This explosives -related article is a stub . You can help Wikipedia by expanding it . | https://en.wikipedia.org/wiki/Majda's_model |
The Major immunogene complex (MIC) is a gene sequence containing loci coding for antigens on lymphocyte surface (Ia) histocompatibility (H) antigens, products of immune responses , and components system proteins . [ 1 ]
The genes that code for immunoglobulins are assorted independently of the MIC, but the plasma cells which produce immunoglobulins are under the control of products of the MIC. [ 2 ] [ 3 ] | https://en.wikipedia.org/wiki/Major_immunogene_complex |
Major irrigation project is a classification of irrigation projects used in India. A project with a cultivable command area of more than 10,000 hectares is classified as a major irrigation project. [ 1 ] Before the Fifth Five-Year Plan , irrigation schemes were classified on the basis of investments needed to implement the scheme. [ 2 ] Since the Fifth Five-Year Plan, India has adopted the command area-based system of classification. [ 2 ] | https://en.wikipedia.org/wiki/Major_irrigation_project |
Majorana 1 is a hardware device developed by Microsoft , with potential applications to quantum computing . [ 1 ] It is the first device produced by Microsoft intended for use in quantum computing. It is an indium arsenide - aluminium hybrid device that admits superconductivity at low temperatures. Microsoft claims that it shows some signals of hosting boundary Majorana zero modes . [ 2 ] [ non-primary source needed ] The device can fit eight qubits. Majorana zero modes, if confirmed, could have potential application to making topological qubits , and eventually a large-scale topological quantum computers . [ 3 ] [ unreliable source? ]
In its February 2025 announcement, Microsoft claimed that the Majorana 1 represents progress in its long-running project to create a quantum computer based on topological qubits . [ 4 ] [ 5 ] [ unreliable source ] The announcement has generated both excitement and skepticism within the scientific community, in the absence of definitive public evidence that the Majorana 1 device exhibits Majorana zero modes. [ 6 ] [ 7 ] [ 8 ]
Quantum computing research has historically faced challenges in achieving qubit stability and scalability. Traditional qubits, such as those based on superconducting circuits or trapped ions, are highly susceptible to noise and decoherence, which can introduce errors in computations. To overcome these limitations, researchers have been exploring various approaches to building more robust and fault-tolerant quantum computers. Topological qubits, first theorized in 1997 by Alexei Kitaev and Michael Freedman , [ 9 ] [ 10 ] offer a promising solution by encoding quantum information in a way that is inherently protected from environmental disturbances. This protection stems from the topological properties of the system, which are resistant to local perturbations. Microsoft's approach, based on Majorana fermions in semiconductor-superconductor heterostructures, is one of several efforts to realize topological quantum computing.
Microsoft's quantum hardware has been the subject of controversy since its high-profile retracted article from Nature in 2018, [ 11 ] and the announcement of Majorana 1 has generated both excitement and skepticism within the scientific community. [ 6 ] [ 7 ]
In the announcement of Majorana 1, the hardware device was described as "the world’s first Quantum Processing Unit (QPU) powered by a Topological Core". [ 12 ] The hardware demonstrations currently available only demonstrate a method for readout, [ 2 ] and do not demonstrate any quantum processing on the zero-mode. Moreover, the publicly available demonstration does not test coherence of their two-level quantum system. This is in contrast to other QPUs, which typically demonstrate both coherent quantum information and coherent logical operations on that quantum information. [ 13 ] [ 14 ] [ 15 ]
In their February 2025 press release, [ 5 ] Microsoft claimed that "The Nature paper marks peer-reviewed confirmation that Microsoft has... been able to create Majorana particles". This is in contrast to the content of the Nature paper, [ 2 ] in which the authors state that the measurements "do not, by themselves, determine whether the low-energy states detected by interferometry are topological". [ 16 ] [ 8 ]
The reason for the uncertainty is the difficulty in distinguishing Majorana modes and Andreev modes . [ 17 ] Both types of modes can exist in the sorts of devices that Microsoft is constructing. The Majorana modes are topological and could potentially be used for making a topological quantum computer, but the Andreev modes are topologically trivial and are not directly useful for making a quantum computer. The current results of Majorana 1 are completely consistent with the possibility that the device consists of Andreev modes, and does not contain any Majorana modes. [ 2 ]
The difficulty in distinguishing between Majorana modes and other topologically trivial possibilities like Andreev modes was also the source of the high-profile Nature retraction in 2018. [ 11 ] In this article the authors, which were affiliated with Microsoft, claimed to have conclusive evidence of Majorana zero modes, but the data was shown to be entirely consistent with Andreev modes. [ 18 ] [ 19 ]
In their February 2025 press releases, Microsoft claimed that the Majorana 1 hardware device created "a new state of matter that previously existed only in theory." [ 12 ] This is in contrast to the long history of experiments based on semiconducting nanowires in similar regimes to the one exhibited by the Majorana 1 chip, [ 20 ] which should putatively be in the same state of matter. This is highlighted in the peer review file for Microsoft's Majorana 1 paper, [ 2 ] where one reviewer describes the paper by saying that "the novelty of this manuscript does not lie in providing stronger evidence for [Majorana Zero modes], but in its methodological approach: it demonstrates that rf-parity readout 'can be done' within [a] complicated loop geometry". Despite a split among the four reviewers, with two expressing reservations and two offering conditional support, Nature published the paper, basing its decision on the innovative device architecture rather than on definitive evidence for Majorana modes. [ 21 ]
Microsoft introduced the term topoconductor to describe the material on which Majorana 1 is based. In their February 2025 press release, Microsoft defined topoconductors as a "class of materials [which] enables... topological superconductivity ". [ 2 ] According to Microsoft, these materials are widely theorized to allow for the creation and manipulation of Majorana zero modes, which could then serve as the basis for topological qubits. [ 22 ] [ 23 ] Topological superconductors are characterized by their unique electronic band structure, which gives rise to topologically protected surface states. [ 24 ] These surface states are robust against disorder and imperfections, making them ideal for hosting Majorana zero modes. Microsoft's topoconductor is made of indium arsenide and aluminum. [ 25 ]
Internal whitepapers from Microsoft outline a topoconductor-based architecture which facilitates braiding processes —key operations for error-resistant qubit logic. [ 26 ] Braiding involves exchanging the positions of Majorana zero modes in a controlled manner, which can be used to perform quantum computations. This process is inherently fault-tolerant because the topological protection of the Majorana modes makes them resistant to local disturbances. | https://en.wikipedia.org/wiki/Majorana_1 |
In error detection and correction , majority logic decoding is a method to decode repetition codes , based on the assumption that the largest number of occurrences of a symbol was the transmitted symbol.
In a binary alphabet made of 0 , 1 {\displaystyle 0,1} , if a ( n , 1 ) {\displaystyle (n,1)} repetition code is used, then each input bit is mapped to the code word as a string of n {\displaystyle n} -replicated input bits. Generally n = 2 t + 1 {\displaystyle n=2t+1} , an odd number.
The repetition codes can detect up to [ n / 2 ] {\displaystyle [n/2]} transmission errors. Decoding errors occur when more than these transmission errors occur. Thus, assuming bit-transmission errors are independent, the probability of error for a repetition code is given by P e = ∑ k = n + 1 2 n ( n k ) ϵ k ( 1 − ϵ ) ( n − k ) {\displaystyle P_{e}=\sum _{k={\frac {n+1}{2}}}^{n}{n \choose k}\epsilon ^{k}(1-\epsilon )^{(n-k)}} , where ϵ {\displaystyle \epsilon } is the error over the transmission channel.
Assumption: the code word is ( n , 1 ) {\displaystyle (n,1)} , where n = 2 t + 1 {\displaystyle n=2t+1} , an odd number.
This algorithm is a boolean function in its own right, the majority function .
In a ( n , 1 ) {\displaystyle (n,1)} code, if R=[1 0 1 1 0], then
it would be decoded as, | https://en.wikipedia.org/wiki/Majority_logic_decoding |
In mathematics , majorization is a preorder on vectors of real numbers . For two such vectors, x , y ∈ R n {\displaystyle \mathbf {x} ,\ \mathbf {y} \in \mathbb {R} ^{n}} , we say that x {\displaystyle \mathbf {x} } weakly majorizes (or dominates) y {\displaystyle \mathbf {y} } from below , commonly denoted x ≻ w y , {\displaystyle \mathbf {x} \succ _{w}\mathbf {y} ,} when
where x i ↓ {\displaystyle x_{i}^{\downarrow }} denotes i {\displaystyle i} th largest entry of x {\displaystyle x} . If x , y {\displaystyle \mathbf {x} ,\mathbf {y} } further satisfy ∑ i = 1 n x i = ∑ i = 1 n y i {\displaystyle \sum _{i=1}^{n}x_{i}=\sum _{i=1}^{n}y_{i}} , we say that x {\displaystyle \mathbf {x} } majorizes (or dominates) y {\displaystyle \mathbf {y} } , commonly denoted x ≻ y {\displaystyle \mathbf {x} \succ \mathbf {y} } .
Both weak majorization and majorization are partial orders for vectors whose entries are non-decreasing, but only a preorder for general vectors, since majorization is agnostic to the ordering of the entries in vectors, e.g., the statement ( 1 , 2 ) ≺ ( 0 , 3 ) {\displaystyle (1,2)\prec (0,3)} is simply equivalent to ( 2 , 1 ) ≺ ( 3 , 0 ) {\displaystyle (2,1)\prec (3,0)} .
Specifically, x ≻ y ∧ y ≻ x {\displaystyle \mathbf {x} \succ \mathbf {y} \wedge \mathbf {y} \succ \mathbf {x} } if and only if x , y {\displaystyle \mathbf {x} ,\mathbf {y} } are permutations of each other. Similarly for ≻ w {\displaystyle \succ _{w}} .
Majorizing also sometimes refers to entrywise ordering, e.g. the real-valued function f majorizes the real-valued function g when f ( x ) ≥ g ( x ) {\displaystyle f(x)\geq g(x)} for all x {\displaystyle x} in the domain, or other technical definitions, such as majorizing measures in probability theory . [ 1 ]
For x , y ∈ R n , {\displaystyle \mathbf {x} ,\ \mathbf {y} \in \mathbb {R} ^{n},} we have x ≺ y {\displaystyle \mathbf {x} \prec \mathbf {y} } if and only if x {\displaystyle \mathbf {x} } is in the convex hull of all vectors obtained by permuting the coordinates of y {\displaystyle \mathbf {y} } . This is equivalent to saying that x = D y {\displaystyle \mathbf {x} =\mathbf {D} \mathbf {y} } for some doubly stochastic matrix D {\displaystyle \mathbf {D} } . [ 2 ] : Thm. 2.1 In particular, x {\displaystyle \mathbf {x} } can be written as a convex combination of n {\displaystyle n} permutations of y {\displaystyle \mathbf {y} } . [ 3 ] In other words, x {\displaystyle \mathbf {x} } is in the permutahedron of y {\displaystyle \mathbf {y} } .
Figure 1 displays the convex hull in 2D for the vector y = ( 3 , 1 ) {\displaystyle \mathbf {y} =(3,\,1)} . Notice that the center of the convex hull, which is an interval in this case, is the vector x = ( 2 , 2 ) {\displaystyle \mathbf {x} =(2,\,2)} . This is the "smallest" vector satisfying x ≺ y {\displaystyle \mathbf {x} \prec \mathbf {y} } for this given vector y {\displaystyle \mathbf {y} } .
Figure 2 shows the convex hull in 3D. The center of the convex hull, which is a 2D polygon in this case, is the "smallest" vector x {\displaystyle \mathbf {x} } satisfying x ≺ y {\displaystyle \mathbf {x} \prec \mathbf {y} } for this given vector y {\displaystyle \mathbf {y} } .
Each of the following statements is true if and only if x ≻ y {\displaystyle \mathbf {x} \succ \mathbf {y} } .
Among non-negative vectors with three components, ( 1 , 0 , 0 ) {\displaystyle (1,0,0)} and permutations of it majorize all other vectors ( p 1 , p 2 , p 3 ) {\displaystyle (p_{1},p_{2},p_{3})} such that p 1 + p 2 + p 3 = 1 {\displaystyle p_{1}+p_{2}+p_{3}=1} . For example, ( 1 , 0 , 0 ) ≻ ( 1 / 2 , 0 , 1 / 2 ) {\displaystyle (1,0,0)\succ (1/2,0,1/2)} . Similarly, ( 1 / 3 , 1 / 3 , 1 / 3 ) {\displaystyle (1/3,1/3,1/3)} is majorized by all other such vectors, so ( 1 / 2 , 0 , 1 / 2 ) ≻ ( 1 / 3 , 1 / 3 , 1 / 3 ) {\displaystyle (1/2,0,1/2)\succ (1/3,1/3,1/3)} .
This behavior extends to general-length probability vectors : the singleton vector majorizes all other probability vectors, and the uniform distribution is majorized by all probability vectors.
A function f : R n → R {\displaystyle f:\mathbb {R} ^{n}\to \mathbb {R} } is said to be Schur convex when x ≻ y {\displaystyle \mathbf {x} \succ \mathbf {y} } implies f ( x ) ≥ f ( y ) {\displaystyle f(\mathbf {x} )\geq f(\mathbf {y} )} . Hence, Schur-convex functions translate the ordering of vectors to a standard ordering in R {\displaystyle \mathbb {R} } . Similarly, f ( x ) {\displaystyle f(\mathbf {x} )} is Schur concave when x ≻ y {\displaystyle \mathbf {x} \succ \mathbf {y} } implies f ( x ) ≤ f ( y ) . {\displaystyle f(\mathbf {x} )\leq f(\mathbf {y} ).}
An example of a Schur-convex function is the max function, max ( x ) = x 1 ↓ {\displaystyle \max(\mathbf {x} )=x_{1}^{\downarrow }} . Schur convex functions are necessarily symmetric that the entries of it argument can be switched without modifying the value of the function. Therefore, linear functions, which are convex, are not Schur-convex unless they are symmetric. If a function is symmetric and convex, then it is Schur-convex.
Majorization can be generalized to the Lorenz ordering , a partial order on distribution functions . For example, a wealth distribution is Lorenz-greater than another if its Lorenz curve lies below the other. As such, a Lorenz-greater wealth distribution has a higher Gini coefficient , and has more income disparity . [ 6 ]
The majorization preorder can be naturally extended to density matrices in the context of quantum information . [ 5 ] [ 7 ] In particular, ρ ≻ ρ ′ {\displaystyle \rho \succ \rho '} exactly when s p e c [ ρ ] ≻ s p e c [ ρ ′ ] {\displaystyle \mathrm {spec} [\rho ]\succ \mathrm {spec} [\rho ']} (where s p e c {\displaystyle \mathrm {spec} } denotes the state's spectrum ).
Similarly, one can say a Hermitian operator , H {\displaystyle \mathbf {H} } , majorizes another, M {\displaystyle \mathbf {M} } , if the set of eigenvalues of H {\displaystyle \mathbf {H} } majorizes that of M {\displaystyle \mathbf {M} } . | https://en.wikipedia.org/wiki/Majorization |
The Majumdar–Ghosh model is a one-dimensional quantum Heisenberg spin model in which the nearest-neighbour antiferromagnetic exchange interaction is twice as strong as the next-nearest-neighbour interaction. It is a special case of the more general J 1 {\displaystyle J_{1}} - J 2 {\displaystyle J_{2}} model, with J 1 = 2 J 2 {\displaystyle J_{1}=2J_{2}} . The model is named after Indian physicists Chanchal Kumar Majumdar and Dipan Ghosh . [ 1 ]
The Majumdar–Ghosh model is notable because its ground states (lowest energy quantum states) can be found exactly and written in a simple form, making it a useful starting point for understanding more complex spin models and phases.
The Majumdar–Ghosh model is defined by the following Hamiltonian :
where the S vector is a quantum spin operator with quantum number S = 1/2.
Other conventions for the coefficients may be taken in the literature, but the most important fact is that the ratio of first-neighbor to second-neighbor couplings is 2 to 1. As a result of this ratio, it is possible to express the Hamiltonian (shifted by an overall constant) equivalently in the form
The summed quantity is none other than the quadratic Casimir operator for representation of the spin algebra on the three consecutive sites j − 1 , j , j + 1 {\displaystyle j-1,j,j+1} , which in turn can be decomposed into a direct sum of spin 1/2 and 3/2 representations. It has the eigenvalues 1 2 ( 1 2 + 1 ) = 3 4 {\displaystyle {\tfrac {1}{2}}({\tfrac {1}{2}}+1)={\tfrac {3}{4}}} for the spin 1/2 subspace and 3 2 ( 3 2 + 1 ) = 15 / 4 {\displaystyle {\tfrac {3}{2}}({\tfrac {3}{2}}+1)=15/4} for the spin 3/2 subspace.
It has been shown that the Majumdar–Ghosh model has two minimum energy states, or ground states, namely the states in which neighboring pairs of spins form singlet configurations.
The wavefunction for each ground state is a product of these singlet pairs. This explains why there must be at least two ground states with the same energy, since one may be
obtained from the other by merely shifting, or translating, the system by one lattice spacing. Furthermore, it has been shown that these (and linear combinations of them) are the unique ground states.
The Majumdar–Ghosh model is one of a small handful of realistic quantum spin models that may be solved exactly. Moreover, its ground states are simple examples
of what are known as valence-bond solids (VBS). Thus the Majumdar–Ghosh model is related to another famous spin model, the AKLT model , whose ground state is the unique one dimensional spin one (S=1) valence-bond solid.
The Majumdar–Ghosh model is also a useful example of the Lieb–Schultz–Mattis theorem which roughly states that an infinite, one dimensional, half-odd-integer spin system must either have no energy spacing (or gap)
between its ground and excited states or else have more than one ground state. The Majumdar–Ghosh model has a gap and falls under the second case.
The isotropy of the model is actually not important to the fact that it has an exactly dimerised ground state. For example, H ^ = J ∑ j = 1 N ( X j X j + 1 + Y j Y j + 1 + δ Z j Z j + 1 ) + J 2 ∑ j = 1 N ( X j X j + 2 + Y j Y j + 2 + δ Z j Z j + 2 ) {\displaystyle {\hat {H}}=J\sum _{j=1}^{N}({X}_{j}{X}_{j+1}+{Y}_{j}{Y}_{j+1}+\delta {Z}_{j}{Z}_{j+1})+{\frac {J}{2}}\sum _{j=1}^{N}({X}_{j}{X}_{j+2}+{Y}_{j}{Y}_{j+2}+\delta {Z}_{j}{Z}_{j+2})} also has the same aforementioned exactly dimerised ground state for all real δ > − 1 / 2 {\displaystyle \delta >-1/2} . | https://en.wikipedia.org/wiki/Majumdar–Ghosh_model |
In computing , MakeModes is an application which is used to generate data which allows RISC OS computers to produce display output compatible with various computer monitors . It can generate and modify data which is used by the operating system to produce different graphics display resolutions .
MakeModes was released in 1994, [ 1 ] [ 2 ] [ 3 ] for use with the RiscPC (initially running RISC OS 3.5 ). [ 4 ] The documentation was revised for clarity by Frank Watkinson in 2003. [ 5 ] [ 6 ] [ 7 ] The issuing of this revised documentation was supported by RISCOS Ltd . [ 7 ]
MakeModes assists in mode setting , via the editing and creation of monitor definition files (MDFs). It can be used to define screen modes suited to particular monitors. [ 8 ]
This software article is a stub . You can help Wikipedia by expanding it . | https://en.wikipedia.org/wiki/MakeModes |
In operations research , the makespan of a project is the length of time that elapses from the start of work to the end. This type of multi-mode resource constrained project scheduling problem (MRCPSP) seeks to create the shortest logical project schedule, by efficiently using project resources, adding the lowest number of additional resources as possible to achieve the minimum makespan. [ 1 ] The term commonly appears in the context of scheduling .
There is a complex project that is composed of several sub-tasks. We would like to assign tasks to workers, such that the project finishes in the shortest possible time. As an example, suppose the "project" is to feed the goats. There are three goats to feed, one child can only feed one goat at a time, and there are two children that can feed them: Shmuel feeds each goat in 10 minutes and Shifra feeds each goat in 12 minutes. Several schedules are possible:
So in this case, the second schedule attains the shortest makespan, which is 20.
This computing article is a stub . You can help Wikipedia by expanding it .
This computer science article is a stub . You can help Wikipedia by expanding it .
This mathematics -related article is a stub . You can help Wikipedia by expanding it . | https://en.wikipedia.org/wiki/Makespan |
Maki Kawai ( 川合眞紀 , Kawai Maki ) is a Japanese chemist who developed spatially selective single-molecule spectroscopy. In 2018, she became the first woman to become president of the Chemical Society of Japan .
Kawai earned her bachelor's degree at the University of Tokyo in 1975. [ 1 ] She completed her doctoral studies at the University of Tokyo in 1980. [ 1 ] Her PhD was supervised by Kenji Tamaru.
Kawai was a postdoctoral researcher at Riken between 1980 and 1982. [ 2 ] She joined the University of Tokyo as a Japan Society for the Promotion of Science fellow in 1982. [ 2 ] Her research considers the vibrational dynamics of single-molecules at surfaces. [ 3 ] [ 4 ] [ 5 ] Her group use STM to monitor molecules and atoms on top of surfaces. [ 6 ] She uses this to understand the chemical and physical phenomena of nanowires, nanodots and biomolecules. [ 1 ] She was awarded fellowships from the Surface Science Society of Japan and American Physical Society to develop single molecule spectroscopy. [ 7 ] Her group monitor the vibrational and relaxation energies of single molecules using scanning tunneling microscopy and inelastically tunnelled electrons. [ 8 ] She has contributed to several books and hundreds of peer-reviewed publications. [ 9 ] [ 10 ] [ 11 ] [ 12 ] Kawai continued to be supported by the Japan Society for the Promotion of Science , investigating nanoscale electron transport through molecular layers. [ 13 ] By combining single molecule spectroscopy (using scanning tunneling spectroscopy ) with inelastic electron tunneling spectroscopy to identify electron transfer channels. [ 14 ] [ 5 ] She discovered a new reaction pathway on the surface of titanium dioxide . [ 15 ] [ 16 ] [ 17 ]
Kawai became Chief Scientist and Director of Surface Chemistry Laboratory at Riken in 1991 and an executive director in 2010. [ 18 ] She was made a professor at the University of Tokyo in 2004. [ 2 ] Kawai joined the Institute of Molecular Science as Director General in 2016. [ 2 ] She was appointed President of the Chemical Society of Japan in 2018. [ 2 ] [ 19 ] | https://en.wikipedia.org/wiki/Maki_Kawai |
Makoto Fujita ( 藤田 誠 , Fujita Makoto ) is a Japanese chemist who specializes in supramolecular coordination chemistry .
He is a professor in the Department of Applied Chemistry at the University of Tokyo . He has published extensively on the multicomponent assembly of large coordination cages. Compounds designed and prepared in his research group are variously described as three-dimensional synthetic receptors, coordination assemblies, molecular paneling, molecular flasks, crystalline sponges , and coordination capsules. [ 1 ] [ 2 ] [ 3 ]
He shared the 2018 Wolf Prize in Chemistry with Omar Yaghi "for conceiving metal-directed assembly principles leading to large highly porous complexes".
Hideki Shirakawa predicted in 2014 that Fujita would win the Nobel Prize in Chemistry . [ 4 ] | https://en.wikipedia.org/wiki/Makoto_Fujita_(chemist) |
Malachite green is an organic compound that is used as a dyestuff and controversially as an antimicrobial in aquaculture . Malachite green is traditionally used as a dye for materials such as silk , leather , and paper . Despite its name the dye is not prepared from the mineral malachite ; the name just comes from the similarity of color.
Malachite green is classified in the dyestuff industry as a triarylmethane dye and also using in pigment industry. Formally, malachite green refers to the chloride salt [C 6 H 5 C(C 6 H 4 N(CH 3 ) 2 ) 2 ]Cl , although the term malachite green is used loosely and often just refers to the colored cation . The oxalate salt is also marketed. The anions have no effect on the color. The intense green color of the cation results from a strong absorption band at 621 nm ( extinction coefficient of 10 5 M −1 cm −1 ).
Malachite green is prepared by the condensation of benzaldehyde and dimethylaniline to give leuco malachite green (LMG):
Second, this colorless leuco compound, a relative of triphenylmethane , is oxidized to the cation that is MG:
A typical oxidizing agent is manganese dioxide .
Hydrolysis of MG gives an alcohol : [ 2 ]
This alcohol is important because it, not MG, traverses cell membranes. Once inside the cell, it is metabolized into LMG. Only the cation MG is deeply colored, whereas the leuco and alcohol derivatives are not. This difference arises because only the cationic form has extended pi-delocalization, which allows the molecule to absorb visible light.
The leuco form of malachite green was first prepared by Hermann Fischer in 1877 by condensing benzaldehyde and dimethylaniline in the molecular ratio 1:2 in the presence of sulfuric acid . [ 3 ]
Malachite green is traditionally used as a dye. Kilotonnes of MG and related triarylmethane dyes are produced annually for this purpose. [ 4 ]
MG is active against the oomycete Saprolegnia , which infects fish eggs in commercial aquaculture , MG has been used to treat Saprolegnia and is used as an antibacterial . [ 5 ] It is a very popular treatment against Ichthyophthirius multifiliis in freshwater aquaria . The principal metabolite , leuco-malachite green (LMG), is found in fish treated with malachite green, and this finding is the basis of controversy and government regulation. See also Antimicrobials in aquaculture .
MG has frequently been used to catch thieves and pilferers. The bait, usually money, is sprinkled with the anhydrous powder. Anyone handling the contaminated money will find that on upon washing the hands, a green stain on the skin that lasts for several days will result. [ citation needed ]
Numerous niche applications exploit the intense color of MG. It is used as a biological stain for microscopic analysis of cell biology and tissue samples . In the Gimenez staining method , basic fuchsin stains bacteria red or magenta, and malachite green is used as a blue-green counterstain . Malachite green is also used in endospore staining , since it can directly stain endospores within bacterial cells; here a safranin counterstain is often used. Malachite green is a part of Alexander's pollen stain . Malachite green can also be used as a saturable absorber in dye lasers , or as a pH indicator between pH 0.2–1.8. However, this use is relatively rare. Leuco-malachite green (LMG) is used as a detection method for latent blood in forensic science . Hemoglobin catalyzes the reaction between LMG and hydrogen peroxide , converting the colorless LMG into malachite green. Therefore, the appearance of a green color indicates the presence of blood . [ 6 ]
A set of malachite green derivatives is also a key component in a fluorescence microscopy tool called the fluorogen activating protein/fluorogen system. Malachite green is in a class of molecules called fluorophores. When malachite green's rotational freedom is restricted, it transforms from a non fluorescent molecule to a highly fluorescent molecule. [ 7 ] In the fluorogen activating protein tool, established by a group at Carnegie Mellon University, Malachite green binds a specific fluorogen activating protein to become highly fluorescent. Expression of the fluorogen activating protein as fusions of targeting domains can impart subcellular localization. Its use is similar to that of GFP but has the added benefit of having a 'dark state' before the malachite green fluorophore is added. This is especially useful for FRET studies.
In 1992, Canadian authorities determined that eating fish contaminated with malachite green posed a significant health risk. [ 8 ] Malachite green was classified a Class II Health Hazard. Due to its low manufacturing cost, malachite green is still used in certain countries with less restrictive laws for non aquaculture purposes. In 2005, analysts in Hong Kong found traces of malachite green in eels and fish imported from China . In 2006, the United States Food and Drug Administration (FDA) detected malachite green in seafood from China, among others , where the substance is also banned for use in aquaculture. [ 9 ] In June 2007, the FDA blocked the importation of several varieties of seafood due to continued malachite green contamination. [ 10 ]
Malachite green has been banned in the United States since 1983 in food-related applications. The substance is also banned in the United Kingdom. [ 11 ] It is prohibited from the use in food in Macao. [ 12 ]
Animals metabolize malachite green to its leuco form. Being lipophillic (the leuco form has a log P of 5.70), the metabolite is retained in catfish muscle longer ( HL = 10 days) than is the parent molecule (HL = 2.8 days).
The LD 50 (oral, mouse) is 80 mg/kg. [ citation needed ] Rats fed malachite green experience "a dose-related increase in liver DNA adducts " along with lung adenomas . Leucomalachite green causes an "increase in the number and severity of changes". As leucomalachite green is the primary metabolite of malachite green and is retained in fish muscle much longer, most human dietary intake of malachite green from eating fish would be in the leuco form. During the experiment, rats were fed up to 543 ppm of leucomalachite green, an extreme amount compared to the average 5 ppb discovered in fish. After a period of two years, an increase in lung adenomas in male rats was discovered but no incidences of liver tumors. Therefore, it could be concluded that malachite green caused carcinogenic symptoms, but a direct link between malachite green and liver tumor was not established. [ 13 ]
Although malachite green has almost no fluorescence in aqueous solution ( quantum yield 7.9x10 −5 ), [ 14 ] several research groups have developed technologies to detect malachite green. For example, Zhao et al., demonstrated the use of malachite green aptamer in microcantilever based sensors to detect low concentration of malachite green. [ 15 ] | https://en.wikipedia.org/wiki/Malachite_green |
Malacidins are a class of chemicals made by bacteria found in soil that can kill Gram-positive bacteria . Their activity appears to be dependent on calcium . The discovery of malacidins was published in 2018. [ 2 ]
The malacidin family were discovered using a new method of soil microbiome screening that does not require cell culturing. [ 3 ] This allowed researchers to identify genetic components necessary to produce the chemical. Malacidin A was shown to kill Staphylococcus aureus and other Gram-positive bacteria.
At the time of publication it was not certain if the discovery would lead to any new antibiotic drugs, because large investments of time and money are required to determine whether any drug is safe and effective. [ 4 ]
Malacidins are macrocycle lipopeptides . The 2018 paper described two chemicals in the malacidin family, differing only by a methylene at their lipid tails. [ 2 ] Their peptide cores include four non-proteinogenic amino acids . [ 2 ] The name "malacidin" is derived from the abbreviation of metagenomic acidic lipopeptide antibiotic and the suffix -cidin . [ 5 ]
Malacidins appear to take on their active conformation after they bind to calcium; the calcium-bound molecule then appears to bind to lipid II , a bacterial cell wall precursor molecule, leading to destruction of the cell wall and death of the bacteria. [ 2 ] [ 6 ] Therefore, they would be a new member of the class of calcium-dependent antibiotics. [ 2 ] [ 4 ] The discovery of malacidins supported the view that the calcium-dependent antibiotics are a larger class than previously thought. [ 2 ]
Malacidins were discovered by researchers at Rockefeller University , led by Brad Hover and Sean Brady. The group had been looking into antibiotics related to daptomycin and their calcium-dependent nature, but determined that it would be impractical to culture variations in lab conditions. [ 5 ] Instead, the team used a genetics approach that was more scalable. They focused on searching for novel biosynthetic gene clusters (BGCs) – genes that are usually expressed together, that bacteria use to make secondary metabolites. To do this, they extracted DNA from around 2,000 soil samples to build metagenomic libraries that captured the genetic diversity of the environmental microbiome. They then designed degenerate primers to amplify genes likely to be similar to the BGC that make daptomycin by using a polymerase chain reaction (PCR) procedure, sequenced the amplified genes, and then used metagenomics to confirm that these genes were indeed likely to be the kind of BGCs they sought. One of the novel BGCs they found was present in around 19% of the screened soil samples but not readily found in cultured microbial collections, so they took that BGC, put it into other host bacteria, and then isolated and analyzed the secondary metabolites. [ 2 ] [ 5 ] The work was published in Nature Microbiology in February 2018. [ 2 ] [ 7 ]
The approach of screening the soil for useful compounds using genomics has been done by others, and is likely to continue to be pursued as a method to further explore primary metabolites and secondary metabolites made by microorganisms. [ 4 ] [ 8 ]
As of February 2018 [update] , the malacidins had not been tested on humans. At the time of their discovery it was unknown whether the discovery would lead to any new antibiotic drugs; showing that a potential drug is safe and effective takes years of work and millions of dollars, and the scientists said at the time that they had no plans to try to develop a drug based on the work. [ 4 ] [ 8 ] In the 2018 paper, malacidins were shown to kill only Gram-positive bacteria and not Gram-negative bacteria . [ 2 ] [ 7 ] They were, however, able to kill multidrug-resistant pathogens, including bacteria resistant to vancomycin in the laboratory, and methicillin-resistant Staphylococcus aureus (MRSA) skin infections in an animal wound model. [ 2 ] [ 7 ]
Brady, Hover, and two other authors disclosed in the 2018 paper that they had "competing financial interests, as they are employees or consultants of Lodo Therapeutics." [ 2 ] Lodo was founded in 2016 out of Brady's laboratory, to discover new chemicals in nature as starting points for drug discovery . [ 9 ] | https://en.wikipedia.org/wiki/Malacidin |
Malacology [ a ] , from Ancient Greek μαλακός ( malakós ), meaning "soft", and λόγος ( lógos ), meaning "study", is the branch of invertebrate zoology that deals with the study of the Mollusca (molluscs or mollusks), the second-largest phylum of animals in terms of described species [ 1 ] after the arthropods . Mollusks include snails and slugs , clams , and cephalopods , along with numerous other kinds, many of which have shells .
Fields within malacological research include taxonomy , ecology and evolution . Several subdivisions of malacology exist, including conchology , devoted to the study of mollusk shells, and teuthology , the study of cephalopods such as octopus , squid , and cuttlefish . Applied malacology studies medical, veterinary, and agricultural applications, for example the study of mollusks as vectors of schistosomiasis and other diseases.
Archaeology employs malacology to understand the evolution of the climate , the biota of the area, and the usage of the site. [ citation needed ]
Zoological methods are used in malacological research. Malacological field methods and laboratory methods (such as collecting, documenting and archiving, and molecular techniques) were summarized by Sturm et al. (2006). [ 2 ]
Malacology evolved from the earlier discipline of conchology , which focused solely on the collection and classification of shells. The transformation into a comprehensive field of biological study occurred over several key historical milestones.
Before the late 18th century , the study of mollusks was limited to conchology, emphasizing the aesthetic and taxonomic value of shells . During this time, the term "mollusks" referred only to shell-less species such as cephalopods and slugs . Organisms with shells were classified under " Testacea ", reflecting a limited understanding of their broader biological characteristics. [ 3 ]
In 1795, French naturalist Georges Cuvier introduced a new classification system for invertebrates based on anatomical observations. He proposed that mollusks represented a distinct group of organisms unified by common morphological traits. This approach laid the groundwork for the transition from conchology to malacology, as it highlighted the importance of internal anatomy over external shell features. [ 3 ]
Following Cuvier’s work, the early 19th century saw an expansion of the field’s focus. Scientists began studying not only the external shells of mollusks but also their internal anatomy, physiological functions, and ecological roles. This marked a shift toward viewing mollusks as complete organisms, rather than merely as shell producers. The term "malacology" was officially introduced in 1825 by French zoologist and anatomist Henri-Marie Ducrotay de Blainville . Derived from the Greek word "malakos" (meaning "soft"), it reflected a broader interest in the biological and ecological characteristics of mollusks, including their soft body structures. This moment is considered the formal establishment of malacology as a distinct scientific discipline. [ 3 ]
By the late 19th century, malacology had expanded further to encompass evolutionary biology , taxonomy , and ecology . Researchers investigated the relationships between mollusks and other invertebrates, as well as their roles in various ecosystems. The discipline continued to integrate new methodologies and technologies, solidifying its place within zoology . [ 3 ]
Those who study malacology are known as malacologists. Those who study primarily or exclusively the shells of mollusks are known as conchologists , while those who study mollusks of the class Cephalopoda are teuthologists .
More than 150 journals within the field of malacology are being published from more than 30 countries, producing an overwhelming amount of scientific articles. [ 7 ] They include:
Museums that have either exceptional malacological research collections (behind the scenes) and/or exceptional public exhibits of mollusks:
Media related to Malacology at Wikimedia Commons | https://en.wikipedia.org/wiki/Malacology |
In evolution , a maladaptation ( /ˌmælædæpˈteɪʃən/ ) is a trait that is (or has become) more harmful than helpful, in contrast with an adaptation , which is more helpful than harmful. All organisms, from bacteria to humans , display maladaptive and adaptive traits. In animals (including humans), adaptive behaviors contrast with maladaptive ones. Like adaptation, maladaptation may be viewed as occurring over geological time, or within the lifetime of one individual or a group.
Maladaptation can arise when adaptations to environmental challenges have unintended harmful effects by either decreasing the current fitness of the organism or creating new risks which may decrease survivability. This could be caused by changes in trait distribution from genetic loading, exogenous environmental changes in the fitness landscape, or feedback in eco-plasticity, altering the fitness landscape. [ 1 ]
It can also signify an adaptation that, whilst reasonable at the time, has become less and less suitable and more of a problem or hindrance in its own right, as time goes on. This is because it is possible for an adaptation to be poorly selected or become more of a dysfunction than a positive adaptation, over time.
Neuroplasticity is defined as "the brain's ability to reorganize itself by forming new neural connections throughout life". [ 2 ] Neuroplasticity is seen as an adaptation that helps humans to adapt to new stimuli, especially through motor functions in musically inclined people, as well as several other hand-eye coordination activities. An example of maladaptation in neuroplasticity within the evolution of the brain is phantom pain in individuals who have lost limbs. While the brain is exceptionally good at responding to stimuli and reorganizing itself in a new way to then later respond even better and faster in the future, it is sometimes unable to cope with the loss of a limb, even though the neurological connections are lost. According to the findings of one journal "Adaptation and Maladaptation" in some cases, the changes that had previously aided the human brain to best suit an environment could also become maladaptive. [ 3 ] In this case, with the loss of a limb, the brain is perceiving pain, though there are no nerves or signals from the now missing limb to give the brain that perception. | https://en.wikipedia.org/wiki/Maladaptation |
A Malaise trap is a large, tent-like structure used for trapping , killing, and preserving flying insects , particularly Hymenoptera and Diptera . The trap is made of a material such as PET (polyester) netting and can be various colours. Insects fly into the tent wall and are funneled into a collecting vessel attached to its highest point. It was invented by René Malaise in 1934. [ 1 ]
Many versions of the Malaise trap are used, but the basic structure consists of a tent with a large opening at the bottom for insects to fly into and a tall central wall that directs the flying insects upward to a cylinder containing a killing agent. [ 2 ] The chemical varies according to purpose and access. Conventionally, cyanide was used inside the jar with an absorbent material. [ 3 ]
However, due to restrictions, many people use ethanol . Ethanol damages some flying insects such as lepidopterans , but most people use the malaise trap primarily for hymenopterans and dipterans . In addition, the ethanol keeps the specimens preserved for a longer period of time. Other dry killing agents including no-pest strips ( dichlorvos ) and ethyl acetate need to be checked more regularly. [ 2 ]
When choosing a Malaise trap design, the types of insects to catch must be considered. The opening to the cylinder is of key importance. Typically, the opening is around 12–15 mm (0.47–0.59 in), and can vary according to the size of insect desired. If using a dry agent, a smaller hole results in a faster death, limiting the amount of damage a newly caught insect can inflict on older, fragile specimens. In ethanol , this is less of a concern. Larger holes potentially allow in more butterflies , moths , and dragonflies . [ 3 ]
Placement of the trap is very important. It should be positioned to maximize the number of flying insects that pass through the opening. This is determined by the natural features of the site. One should evaluate topography, vegetation, wind, and water. For example, if a wide corridor in a forest such as a trail is used, the trap should be oriented with its opening toward the corridor. Also, places where vegetation is growing high around the opening limits the number of flying insects that enter the trap. Other ideal places may be above small streams or on edges of forests. [ 3 ]
A well-placed trap in ideal seasonal conditions can catch over 1,000 insects a day. Even in less-ideal conditions, such as rain, the trap is still effective. [ 3 ]
The Malaise trap can also function as a light trap . If a lamp is placed at the end opposite of the opening, the light will attract insects into the trap. Specimens should be collected and removed at dawn and dusk to determine insects caught in daytime versus the night. Specimens should be removed from the trap at least once a week if using ethanol, or more often if using a dry killing agent. [ 3 ]
The design of the trap catches insects that naturally fly upward when they hit a barrier. However, some insects drop when meeting with a barrier. Addition of a pan with ethanol at the bottom of the main wall will catch specimens such as beetles that fall before reaching the top. [ 2 ] A trap without the netting on top, but with just a preservative-filled basin under the barrier is commonly named a flight interception trap . | https://en.wikipedia.org/wiki/Malaise_trap |
In organic chemistry , the Malaprade reaction or Malaprade oxidation is a reaction that converts vicinal diols by periodic acid or a periodate salt to give a pair of carbonyl derivatives. [ 1 ] [ 2 ] The reaction was first reported by Léon Malaprade in 1928. [ 3 ] [ 4 ] Amino alcohols are also cleaved. [ 5 ]
In terms of mechanism, the reaction is assumed to proceed by formtion cyclic diester of iodine(VII). [ 6 ]
This organic chemistry article is a stub . You can help Wikipedia by expanding it . | https://en.wikipedia.org/wiki/Malaprade_reaction |
The malaria therapy (or malaria inoculation , [ 1 ] and sometimes malariotherapy [ 2 ] ) is an archaic medical procedure of treating diseases using artificial injection of malaria parasites . [ 3 ] It is a type of pyrotherapy (or pyretotherapy) by which high fever is induced to stop or eliminate symptoms of certain diseases. In malaria therapy, malarial parasites ( Plasmodium ) are specifically used to cause fever, and an elevated body temperature reduces the symptoms of or cures the diseases. As the primary disease is treated, the malaria is then cured using antimalarial drugs . [ 4 ] The method was developed by Austrian physician Julius Wagner-Jauregg in 1917 for the treatment of neurosyphilis for which he received the 1927 Nobel Prize in Physiology or Medicine . [ 5 ]
The beneficial effects of infections in mental problems were known in the Ancient world. Hippocrates in the 4th century BCE recorded bacterial infections such as dysentery and dropsy reducing the symptoms of madness; and that malaria (quartan fever) could stop epileptic convulsions . Galen in the 2nd century CE described a case of mental illness that ended after malarial infection. There are medical records from the 19th century which indicate that insanity stopped temporarily or permanently when the individuals had severe infections. [ 6 ]
Russian psychiatrist Alexander Samoilovich Rosenblum [ ru ] was the first to experimentally use infections for the treatment of psychosis. In 1876, he induced fever in psychotic individuals using malaria, typhoid , and relapsing fever . He claimed that he cured 50% of all those he treated. However, his work was not widely known as his publication in 1877 was in a small journal in Odesa , Ukraine, and written in Russian. [ 7 ] He also preferred not to spread his findings. He understood that it was a dangerous experiment and potentially controversial. [ 8 ] It was, however, reported by J. Motschukoffsky in a German medical journal Centralblatt für die Medicinischen Wissenschaften , [ 9 ] but the underlying cause of how malaria cured psychosis was not understood, and Rosenblum's experiment remained unknown for several decades. [ 10 ] Rosenblum never repeated the study or tried to develop specific methods for the medical treatment. [ 11 ] The importance of the study was realised only in 1938 when Austrian physician Julius Wagner-Jauregg discussed the research at the International Neurological Congress in London. [ 12 ]
In 1943, Samuel J. Zakon at the Northwestern University Medical School in Chicago, US, acquired the original paper of Rosenblum and published an English translation with commentary in the Journal of the American Medical Association . [ 7 ] The commentary concluded:
Rosenblium [alternative spelling [ 11 ] [ 13 ] ] was certainly the first to appreciate the curative effect of fever itself on the psychoses. He understood and reported on the value of malaria and typhoid in the treatment of mental disease. He was the first to inoculate psychotic patients with a febrile disease. Rosenblium, though practically forgotten for over half a century, must be acknowledged as the true pioneer in this field. [ 8 ] [ 7 ]
Although the priority of using malaria therapy in brain disorders is generally attributed to Rosenblum, the credit of developing malaria therapy as a standard medical practice and explaining the underlying scientific principle is to Austrian physician Julius Wagner-Jauregg. [ 11 ] [ 14 ] Wagner-Jauregg, working at the First Psychiatry Clinic at the Asylum of Lower Austria, investigated cases of brain disorders since 1883, publishing his first paper on psychosis in 1887 titled " Über die Einwirkung fieberhafter Erkrankungen auf Psychosen " ("The Effect of Feverish Disease on Psychoses"). [ 6 ] He soon realised that a severe type of psychosis was related to neurosyphilis, an infection of the central nervous system with syphilis (caused by a bacterium identified in 1905 as Spirochaeta pallida , later renamed Treponema pallidum [ 15 ] ). Syphilis was at the time a deadly disease characterised by delusions, paralysis, and dementia; and known as "The Great Pox" and the "disease of the century." [ 6 ] Neurosyphilis was prevalent in Europe during the 19th century, leading to an increased asylum population during this period. [ 16 ]
Wagner-Jauregg came to the conclusion that fever could cure psychosis after reviewing his own experiments and the historical accounts based on three phenomena: (a) the appearance of fever coincided with the disappearance of the symptoms of psychosis in medical history; (b) his findings that fever was the only possible cause for the cure of psychosis; and (c) although all psychotic individuals were not cured, the number of cures increased whenever malaria spread. [ 6 ] He made three postulates: | https://en.wikipedia.org/wiki/Malaria_therapy |
Malate dehydrogenase ( EC 1.1.1.37 ) ( MDH ) is an enzyme that reversibly catalyzes the oxidation of malate to oxaloacetate using the reduction of NAD + to NADH. This reaction is part of many metabolic pathways , including the citric acid cycle . Other malate dehydrogenases , which have other EC numbers and catalyze other reactions oxidizing malate, have qualified names like malate dehydrogenase (NADP + ) .
Several isozymes of malate dehydrogenase exist. There are two main isoforms in eukaryotic cells. [ 1 ] One is found in the mitochondrial matrix, participating as a key enzyme in the citric acid cycle that catalyzes the oxidation of malate. The other is found in the cytoplasm , assisting the malate-aspartate shuttle with exchanging reducing equivalents so that malate can pass through the mitochondrial membrane to be transformed into oxaloacetate for further cellular processes. [ 2 ]
Humans and most other mammals express the following two malate dehydrogenases:
The malate dehydrogenase family contains L-lactate dehydrogenase and L-2-hydroxyisocaproate dehydrogenases . L-lactate dehydrogenases catalyzes the conversion of L-lactate to pyruvate , the last step in anaerobic glycolysis. The N-terminus is a Rossmann NAD-binding fold and the C-terminus is an unusual alpha+beta fold. [ 3 ] [ 4 ]
In most organisms, malate dehydrogenase (MDH) exists as a homodimeric molecule and is closely related to lactate dehydrogenase (LDH) in structure. It is a large protein molecule with subunits weighing between 30 and 35 kDa. [ 5 ] Based on the amino acid sequences, it seems that MDH has diverged into two main phylogenetic groups that closely resemble either mitochondrial isozymes or cytoplasmic/chloroplast isozymes. [ 6 ] Because the sequence identity of malate dehydrogenase in the mitochondria is more closely related to its prokaryotic ancestors in comparison to the cytoplasmic isozyme, the theory that mitochondria and chloroplasts were developed through endosymbiosis is plausible. [ 7 ] The amino acid sequences of archaeal MDH are more similar to that of LDH than that of MDH of other organisms. This indicates that there is a possible evolutionary linkage between lactate dehydrogenase and malate dehydrogenase. [ 8 ]
Each subunit of the malate dehydrogenase dimer has two distinct domains that vary in structure and functionality. A parallel β-sheet structure makes up the NAD+ binding domain, while four β-sheets and one α-helix comprise the central NAD + binding site. The subunits are held together through extensive hydrogen-bonding and hydrophobic interactions. [ 9 ]
Malate dehydrogenase has also been shown to have a mobile loop region that plays a crucial role in the enzyme's catalytic activity. Studies have shown that conformational change of this loop region from the open conformation to the closed conformation after binding of substrate enhances MDH catalysis through shielding of substrate and catalytic amino acids from solvent. Studies have also indicated that this loop region is highly conserved in malate dehydrogenase. [ 6 ]
The active site of malate dehydrogenase is a hydrophobic cavity within the protein complex that has specific binding sites for the substrate and its coenzyme , NAD + . In its active state, MDH undergoes a conformational change that encloses the substrate to minimize solvent exposure and to position key residues in closer proximity to the substrate. [ 6 ] The three residues in particular that comprise a catalytic triad are histidine (His-195), aspartate (Asp-168), both of which work together as a proton transfer system, and arginines (Arg-102, Arg-109, Arg-171), which secure the substrate. [ 10 ]
Mechanistically, malate dehydrogenase catalyzes the oxidation of the hydroxyl group of malate by utilizing NAD + as an electron acceptor. This oxidation step results in the elimination of a proton and a hydride ion from the substrate. NAD + receives the hydride ion (specifically, the hydride ion is transferred to the nicotinamide ring of the NAD + ) and becomes reduced to NADH while concomitantly, the His-195 residue on the enzyme accepts the proton. [ 11 ] The positively charged His-195 residue, which is involved in base catalysis of the substrate, is stabilized by the adjacent, negatively charged Asp-168 residue. This electrostatic stabilization helps facilitate the transfer of the proton. [ 1 ] Arg-102, Arg-109, and Arg-171 (which are protonated, and thus positively charged) participate in electrostatic catalysis and help to bind the negatively charged carboxylates on the substrate. Additionally, the Arginine residues on the enzyme provide additional substrate specificity and binding through hydrogen bonding between the guanidinium side chain of the Arginine amino acid residues and the carboxylates of the substrate. [ 12 ]
Studies have also identified a mobile loop in malate dehydrogenase that participates in the catalytic activity of the enzyme. The loop undergoes a conformational change to shield the substrate and catalytic amino acids from the solvent in response to the binding of the malate dehydrogenase:coenzyme complex to substrate. This flipping of the loop to the up position to cover the active site also promotes enhanced interaction of the catalytically important amino residues on the enzyme with the substrate. Additionally, the movement of the loop has been shown to correlate with the rate determining step of the enzyme. [ 13 ]
Malate dehydrogenases catalyzes the interconversion of malate to oxaloacetate. In the citric acid cycle, malate dehydrogenase is responsible for catalyzing the regeneration of oxaloacetate This reaction occurs through the oxidation of hydroxyl group on malate and reduction of NAD + . The mechanism of the transfer of the hydride ion to NAD + is carried out in a similar mechanism seen in lactate dehydrogenase and alcohol dehydrogenase. The ΔG'° of malate dehydrogenase is +29.7 kJ/mol and the ΔG (in the cell) is 0 kJ/mol. [ 11 ]
Malate dehydrogenase is also involved in gluconeogenesis , the synthesis of glucose from smaller molecules. Pyruvate in the mitochondria is acted upon by pyruvate carboxylase to form oxaloacetate, a citric acid cycle intermediate. In order to get the oxaloacetate out of the mitochondria, malate dehydrogenase reduces it to malate, and it then traverses the inner mitochondrial membrane. Once in the cytosol, the malate is oxidized back to oxaloacetate by cytosolic malate dehydrogenase. Finally, phosphoenolpyruvate carboxykinase (PEPCK) converts oxaloacetate to phosphoenolpyruvate (PEP). [ 14 ]
Kinetic studies show that malate dehydrogenase enzymatic activity is ordered. The cofactor NAD + /NADH is bound to the enzyme before the substrate. [ 15 ] The Km value for malate, i.e., the concentration at which the enzyme activity is half-maximal, is 2 mM. The Kcat value is 259.2 s −1 . [ 16 ]
Additionally, pH levels control specificity of substrate binding by malate dehydrogenase due to proton transfer in the catalytic mechanism. [ 17 ] A histidine moiety with a pK value of 7.5 has been suggested to play a role in the pH-dependency of the enzyme. Studies have indicated that the binding of the enol form oxaloacetate with the malate dehydrogenase:NADH complex forms much more rapidly at higher pH values. [ 12 ] Additionally, L-malate binding to malate dehydrogenase is promoted at alkaline conditions. Consequently, the non-protonated form malate dehydrogenase binds preferentially to L-malate and the enol form of oxaloacetate. In contrast, D-malate, hydroxymalonate, and the keto form of oxaloacetate have been found to bind exclusively to the protonated form of the enzyme. Specifically, when the histidine is protonated, the His residue can form a hydrogen bond with the substrate's carbonyl oxygen, which shifts electron density away from the oxygen and makes it more susceptible to nucleophilic attack by hydride. This promotes the binding of malate dehydrogenase to these substrates. As a result, at lower pH values malate dehydrogenase binds preferentially to D-malate, hydroxymalonate, and keto-oxaloacetate. [ 18 ]
Because malate dehydrogenase is closely tied to the citric acid cycle, studies have proposed and experimentally demonstrated that citrate is an allosteric regulator of malate dehydrogenase depending on the concentrations of L-malate and NAD + . This may be due to deviations observed in the kinetic behavior of malate dehydrogenase at high oxaloacetate and L-malate concentrations. Experiments have shown that Citrate can both allosterically activate and inhibit the enzymatic activity of malate dehydrogenase. Citrate has been shown to inhibit the oxidation of L-malate when there are low levels of L-malate and NAD + . However, in the presence of high levels of malate and NAD + , citrate can stimulate the production of oxaloacetate. Although malate dehydrogenase is typically considered a reversible enzyme, it is believed that there is an allosteric regulatory site on the enzyme where citrate can bind to and drive the reaction equilibrium in either direction. [ 19 ]
Glutamate has also been shown to inhibit malate dehydrogenase activity. Furthermore, it has been shown that alpha ketoglutarate dehydrogenase can interact with mitochondrial aspartate aminotransferase to form a complex, which can then bind to malate dehydrogenase, forming a ternary complex that reverses inhibitory action on malate dehydrogenase enzymatic activity by glutamate. Additionally, the formation of this complex enables glutamate to react with aminotransferase without interfering activity of malate dehydrogenase. The formation of this ternary complex also facilitates the release of oxaloacetate from malate dehydrogenase to aminotransferase. Kinetically, the binding of malate dehydrogenase to the binary complex of alpha ketoglutarate dehydrogenase and aminotrannferase has been shown to increase reaction rate of malate dehydrogenase because the Km of malate dehydrogenase is decreased when it is bound as part of this complex. [ 20 ]
Click on genes, proteins and metabolites below to link to respective articles. [ § 1 ] | https://en.wikipedia.org/wiki/Malate_dehydrogenase |
The malate–aspartate shuttle (sometimes simply the malate shuttle ) is a biochemical system for translocating electrons produced during glycolysis across the semipermeable inner membrane of the mitochondrion for oxidative phosphorylation in eukaryotes . These electrons enter the electron transport chain of the mitochondria via reduction equivalents to generate ATP . The shuttle system is required because the mitochondrial inner membrane is impermeable to NADH , the primary reducing equivalent of the electron transport chain. To circumvent this, malate carries the reducing equivalents across the membrane.
The shuttle consists of four protein parts:
The primary enzyme in the malate–aspartate shuttle is malate dehydrogenase. Malate dehydrogenase is present in two forms in the shuttle system: mitochondrial malate dehydrogenase and cytosolic malate dehydrogenase. The two malate dehydrogenases are differentiated by their location and structure, and catalyze their reactions in opposite directions in this process.
First, in the cytosol, malate dehydrogenase catalyses the reaction of oxaloacetate and NADH to produce malate and NAD + . In this process, two electrons generated from NADH, and an accompanying H + , are attached to oxaloacetate to form malate.
Once malate is formed, the first antiporter (malate- alpha-ketoglutarate ) imports the malate from the cytosol into the mitochondrial matrix and also exports alpha-ketoglutarate from the matrix into the cytosol simultaneously. After malate reaches the mitochondrial matrix, it is converted by mitochondrial malate dehydrogenase into oxaloacetate, during which NAD + is reduced with two electrons to form NADH. Oxaloacetate is then transformed into aspartate (since oxaloacetate cannot be transported into the cytosol) by mitochondrial aspartate aminotransferase. Since aspartate is an amino acid, an amino radical needs to be added to the oxaloacetate. This is supplied by glutamate, which in the process is transformed into alpha-ketoglutarate by the same enzyme.
The second antiporter (AGC1 or AGC2) imports glutamate from the cytosol into the matrix and exports aspartate from the matrix to the cytosol. Once in the cytosol, aspartate is converted by cytosolic aspartate aminotransferase to oxaloacetate.
The net effect of the malate–aspartate shuttle is purely redox : NADH in the cytosol is oxidized to NAD + , and NAD + in the matrix is reduced to NADH. The NAD + in the cytosol can then be reduced again by another round of glycolysis, and the NADH in the matrix can be used to pass electrons to the electron transport chain so ATP can be synthesized.
Since the malate–aspartate shuttle regenerates NADH inside the mitochondrial matrix, it is capable of maximizing the number of ATPs produced in glycolysis (3/NADH), ultimately resulting in a net gain of 38 ATP molecules per molecule of glucose metabolized. Compare this to the glycerol 3-phosphate shuttle , which reduces FAD + to produce FADH 2 , donates electrons to the quinone pool in the electron transport chain , and is capable of generating only 2 ATPs per NADH generated in glycolysis (ultimately resulting in a net gain of 36 ATPs per glucose metabolized). (These ATP numbers are prechemiosmotic, and should be reduced in light of the work of Mitchell and many others [ citation needed ] . Each NADH produces only 2.5 ATPs, and each FADH 2 produces only 1.5 ATPs. Hence, the ATPs per glucose should be reduced to 32 from 38 and 30 from 36. The extra H + required to bring in the inorganic phosphate during oxidative-phosphorylation contributes to the 30 and 32 numbers as well).
The activity of malate–aspartate shuttle is modulated by arginine methylation of malate dehydrogenase 1 (MDH1). Protein arginine N-methyltransferase CARM1 methylates and inhibits MDH1 by disrupting its dimerization, which represses malate–aspartate shuttle and inhibits mitochondria respiration of pancreatic cancer cells. [ 2 ]
Click on genes, proteins and metabolites below to link to respective articles. [ § 1 ] | https://en.wikipedia.org/wiki/Malate–aspartate_shuttle |
Malathion is an organophosphate insecticide which acts as an acetylcholinesterase inhibitor . In the USSR , it was known as carbophos , in New Zealand and Australia as maldison and in South Africa as mercaptothion . The compound's name is presumably related to malic acid (2-hydroxybutanedioic acid) owning to the 2-substituted diethyl malate substructure.
Malathion is a pesticide that is widely used in agriculture, residential landscaping, public recreation areas, and in public health pest control programs such as mosquito eradication. [ 5 ] In the US, it is the most commonly used organophosphate insecticide. [ 6 ]
A malathion mixture with corn syrup was used in the 1980s in Australia and California to combat the Mediterranean fruit fly . [ 7 ] In Canada and the US starting in the early 2000s, malathion was sprayed in many cities to combat west Nile virus . [ 8 ] Malathion was used over the last couple of decades on a regular basis during summer months to kill mosquitoes, but homeowners were allowed an exemption for their properties if they chose. [ citation needed ]
In the United Kingdom, malathion was withdrawn from sale in 2002. [ 9 ]
Malathion is an acetylcholinesterase inhibitor , a diverse family of chemicals. Upon uptake into the target organism, it binds irreversibly to the serine residue in the active catalytic site of the cholinesterase enzyme. The resultant phosphoester group is strongly bound to the cholinesterase, and irreversibly deactivates the enzyme which leads to rapid build-up of acetylcholine at the synapse. [ 10 ]
Malathion is produced by the addition of dimethyl dithiophosphoric acid to diethyl maleate or diethyl fumarate . The compound is chiral but is used as a racemate . [ citation needed ]
Malathion in low doses (0.5% preparations) is used as a treatment for:
Preparations include Derbac-M, Prioderm, Quellada-M [ 15 ] and Ovide. [ 16 ]
Malathion is of low toxicity. In arthropods it is metabolized into malaoxon [ 17 ] which is 61x more toxic, [ 18 ] being a more potent inhibitor of acetylcholinesterase. [ 19 ] According to the United States Environmental Protection Agency , no reliable information is available on adverse health effects of chronic exposure. [ 20 ]
In 1989, Malathion was sprayed over a 1,400 sq mi (3,600 km 2 ) area to control an outbreak of Mediterranean fruit flies in California . In order to demonstrate the chemical's safety, B. T. Collins , director of the California Conservation Corps, publicly swallowed a mouthful of dilute malathion solution. [ 21 ]
Malathion is classified by the IARC as probable carcinogen (group 2A) . Malathion is classified by US EPA as having "suggestive evidence of carcinogenicity". [ 18 ] This classification was based on the occurrence of liver tumors at excessive doses in mice and female rats and the presence of rare oral and nasal tumors in rats that occurred following exposure to very large doses. Exposure to organophosphates is associated with non-Hodgkin's lymphoma . Malathion used as a fumigant was not associated with increased cancer risk. Between 1993 and 1997, as part of the Agricultural Health Study, no clear association between malathion exposure and cancer was reported. [ 22 ]
Malathion is toxic to leopard frog tadpoles. [ 23 ]
Malathion is of low toxicity; however, absorption or ingestion into the human body readily results in its metabolism to malaoxon , which is substantially more toxic. [ 24 ] In studies of the effects of long-term exposure to oral ingestion of malaoxon in rats, malaoxon has been shown to be 61 times more toxic than malathion, [ 24 ] and malaoxon is 1,000 times more potent than malathion in terms of its acetylcholinesterase inhibition. [ 19 ] Indoor spillage of malathion can thus be more poisonous than expected, as malathion breaks down in a confined space into the more toxic malaoxon. It is cleared from the body quickly, in three to five days. [ 25 ]
Because it is an acetylcholinesterase inhibitor, this resistance is a type of AChEI resistance . [ 17 ] Malathion resistance is thought to always be due to either increased carboxylesterase concentrations or altered acetylcholinesterases . [ 17 ] COE because it metabolizes malathion but into non -malaoxon products, altered AChEs because we mean specifically those altered to be less sensitive to malathion and malaoxon. [ 17 ] | https://en.wikipedia.org/wiki/Malathion |
Malayalee Engineers Association in North America (MEANA) is a non-profit , non-political fellowship of Malayali (Malayalee) engineers in the United States. The primary objective is to provide a platform for sharing common interests of the engineers with Malayalee origin, find resolution for issues and contribute to the betterment of the society as a whole as well as address specific needs of home state Kerala , India. Current activities include Project-1000, [ 1 ] a scholarship program to support Engineering Education in Kerala,
Project Homeland, a program that has been initiated in 2007 to try and assist various initiatives in Kerala from an engineering standpoint. [ 2 ] MEANA also honors outstanding contributions of Malayalee Engineers via its Engineer of the year award every year. [ 3 ]
MEANA has its headquarters in Chicago , IL , United States and has started establishing chapters in various states in the USA starting in 2007. [ 4 ] The Florida chapter was the first outside Chicago. [ 5 ] | https://en.wikipedia.org/wiki/Malayalee_Engineers_Association_in_North_America |
Malcolm Cuthbert Nokes MC MA BSc (20 May 1897 – 22 November 1986) was a British schoolteacher, soldier, research scientist and Olympic athlete, who competed in the hammer throw and discus throw . [ 3 ]
He won the bronze medal in the hammer throw at the 1924 Summer Olympics . Four years later he finished eleventh in the 1928 Olympic hammer throw competition . In 1923 he beat the British hammer throw record, but did so in a demonstration rather than a competition, so his throw did not count for record purposes. [ 4 ]
He won the gold medal for England in the 1930 British Empire Games in the hammer throw contest and finished fifth in the discus throw event. At the 1934 British Empire Games he won again the gold medal in the hammer throw competition. [ 1 ]
Nokes was the Amateur Athletic Association (AAA) Champion from 1923 [ 5 ] to 1926 and placed second at the 1921 AAA Championships [ 6 ] [ 7 ] and 1922 AAA Championships and 1927–28. [ 1 ] He was chairman of the AAA's Coaching Committee, and also a member of the Achilles Club .
He was a graduate of Magdalen College, Oxford , where he studied chemistry and wrote a thesis on metaphenetidine . Nokes served in the Great War in the Royal Artillery in the trenches and then as an observer in the Royal Flying Corps . He was awarded a Military Cross for his service, [ 1 ] becoming MC Nokes MC. In the Second World War he served as an officer in the Royal Air Force Volunteer Reserve (Training Branch) while a schoolmaster. [ 8 ]
He taught chemistry at Malvern College and later at Harrow School , where he was appointed Head of Science; he had come to the attention of Harrow when two schools colocated during the Second World War, although they did not merge. His practical demonstrations of the reaction of sodium with water were popular and famous among his pupils. These often entailed an explosion as MC Nokes put more than the recommended quantity of sodium into the water, and as the smoke cleared and noise subsided, MC Nokes would say "Note the small report." He was a member of the Science Masters' Association . [ 9 ] Later he worked at Harwell and then was Head of Laboratories [ 10 ] at CENTO Institute of Nuclear & Applied Science in Tehran . In retirement he lived in Honiton, Devon, and then in Alton, Hampshire. His nicknames included "Nokey", "Glaxo" and "Stally."
The chronology of his career was:
During his time at Harrow, he served as a councillor in what is now Harrow London Borough Council , being elected as a Conservative for the ward of Harrow-on-the-Hill & Greenhill. [ 13 ] During his service as a borough councillor, he proposed and was instrumental in bringing into service one of the first electric dust carts to be used in England, as part of the modernization of public health services in Harrow.
MC Nokes was one of eight children of Walter Nokes. His brothers included Gerald Dacre Nokes, [ 14 ] [ 15 ] a barrister and Indian judge, and George Augustus Nokes . | https://en.wikipedia.org/wiki/Malcolm_Nokes |
Male contraceptives , also known as male birth control , are methods of preventing pregnancy by interrupting the function of sperm. [ 1 ] The main forms of male contraception available today are condoms , vasectomy , and withdrawal , which together represented 20% of global contraceptive use in 2019. [ 2 ] [ 3 ] [ 4 ] [ 5 ] New forms of male contraception are in clinical and preclinical stages of research and development , but as of 2025, none have reached regulatory approval for widespread use. [ 6 ] [ 7 ] [ 8 ] [ 9 ] They could be available before 2030 , assuming smooth development and clinical trials . [ 10 ]
These new methods include topical creams, daily pills, injections, long-acting implants, and external devices, and these products have both hormonal and non-hormonal mechanisms of action. [ 6 ] [ 11 ] [ 12 ] [ 13 ] [ 14 ] [ 15 ] [ 16 ] Some of these new contraceptives could even be unisex , or usable by any person, because they could theoretically incapacitate mature sperm in the man's body before ejaculation , or incapacitate sperm in the body of a woman after insemination . [ 17 ] [ 18 ]
In the 21st century, surveys indicated that around half of men in countries across the world have been interested in using a variety of novel contraceptive methods, [ 19 ] [ 20 ] [ 21 ] [ 22 ] and men in clinical trials for male contraceptives have reported high levels of satisfaction with the products. [ 13 ] [ 23 ] Women worldwide have also shown a high level of interest in new male contraceptives, and though both male and female partners could use their own contraceptives simultaneously, women in long-term relationships have indicated a high degree of trust in their male partner's ability to successfully manage contraceptive use. [ 19 ] [ 24 ] [ 25 ]
A modelling study from 2018 suggested that even partial adoption of new male contraceptives would significantly reduce unintended pregnancy rates around the globe, [ 26 ] which remain at nearly 50%, even in developed countries where women have access to modern contraceptives. [ 27 ] [ 28 ] [ 29 ] Unintended pregnancies are associated with negative socioeconomic, educational, and health outcomes for women, men, and the resulting children (especially in historically marginalized communities), [ 28 ] [ 30 ] [ 31 ] [ 32 ] [ 33 ] [ 34 ] [ 35 ] and 60% of unintended pregnancies end in abortions , [ 36 ] [ 37 ] many of which are unsafe and can lead to women's harm or death. [ 38 ] [ 39 ] [ 40 ] [ 41 ] Therefore, the development of new male contraceptives has the potential to improve racial, economic, and gender equality across the world, advance reproductive justice and reproductive autonomy for all people, and save lives.
Vasectomy is surgical procedure for permanent male sterilization usually performed in a physician's office in an outpatient procedure. [ 42 ] During the procedure, the vasa deferentia of a patient are severed, and then tied or sealed to prevent sperm from being released during ejaculation. [ 43 ] Vasectomy is an effective procedure, with less than 0.15% of partners becoming pregnant within the first 12 months after the procedure. [ 44 ] Vasectomy is also a widely reliable and safe method of contraception, and complications are both rare and minor. [ 45 ] [ 46 ] Vasectomies can be reversed, though rates of successful reversal decline as the time since vasectomy increases, and the procedure is technically difficult and often costly. [ 43 ] [ 47 ] [ 42 ]
A condom is a barrier device made of latex or thin plastic film that is rolled onto an erect penis before intercourse and retains ejaculated semen , thereby preventing pregnancy. [ 48 ] Condoms are less effective at preventing pregnancy than vasectomy or modern methods of female contraception, with a real-world failure rate of 13%. [ 44 ] However, condoms have the advantage of providing protection against some sexually transmitted infections such as HIV/AIDS . [ 49 ] [ 50 ] Condoms may be combined with other forms of contraception (such as spermicide ) for greater protection. [ 51 ]
The withdrawal method, also known as coitus interruptus or pulling out, is a behavior that involves halting penile-vaginal intercourse to remove the penis out and away from the vagina prior to ejaculation. [ 52 ] [ 53 ] Withdrawal is considered a less-effective contraceptive method, with typical-use failure rates around 20%. [ 42 ] [ 44 ] However, it requires no equipment or medical procedures. [ 52 ]
Researchers have been working to generate novel male contraceptives with diverse mechanisms of action and possible delivery methods, including long-acting reversible contraceptives (LARCs), daily transdermal gels , daily and on-demand oral pills, monthly injectables , and implants. [ 54 ] [ 55 ] [ 56 ] Efforts to develop male contraceptives have been ongoing for many decades, but progress has been slowed by a lack of funding and industry involvement. As of 2024, most funding for male contraceptive research is derived from government or philanthropic sources. [ 57 ] [ 58 ] [ 59 ] [ 60 ]
Novel male contraceptives could work by blocking various steps of the sperm development process , blocking sperm release, or interfering with any of the sperm functions necessary to reach and fertilize an egg in the female reproductive tract. [ 61 ] Advantages and disadvantages of each of these approaches will be discussed below, along with relevant examples of products in development.
These methods work by preventing the testes from producing sperm, or interfering with sperm production in a way that leads to the production of nonfunctional sperm. [ 62 ] This approach can be accomplished by either hormonal or nonhormonal small-molecule drugs, or potentially by thermal methods. The effectiveness of contraceptives in this group can be easily assessed microscopically, by measuring sperm count or abnormalities in sperm shape, but because spermatogenesis takes approximately 70 days to complete, [ 63 ] these methods are likely to require approximately three months of use before they become effective, and approaches that halt sperm production at an early stage of the process may result in reduced testicular size. [ 64 ] Methods have been suggested in the 1980s. [ 65 ]
Hormonal contraceptives for men work similarly to hormonal female methods , using steroids to interrupt the hypothalamic-pituitary-gonadal axis and thereby block sperm production. Administering external androgens and progestogens suppresses secretion of the gonadotropins LH and FSH , which impairs testosterone production and sperm generation in the testes, leading to reduced sperm counts in ejaculates within 4–12 weeks of use. [ 66 ] However, since the contraceptives contain testosterone or related androgens, the levels of androgens in the blood remain relatively constant, thereby limiting side effects and maintaining masculine secondary sex characteristics like muscle mass and hair growth. [ 66 ]
Multiple methods of male hormonal contraception have been tested in clinical trials since the 1990s, and although one trial was halted early, leading to a large amount of press attention, [ 67 ] [ 68 ] [ 69 ] [ 70 ] [ 71 ] most hormonal male contraceptives have been found to be effective, reversible, and well-tolerated. [ 72 ] [ 73 ] [ 74 ] [ 75 ] [ 76 ] [ 77 ]
As of 2024 [update] , the following hormonal male contraceptive products are in clinical trials:
Some anabolic steroids may exhibit suppressive effects on spermatogenesis, but none are being investigated for use as a male contraceptive. [ 85 ]
Non-hormonal contraceptives for men are a diverse group of molecules that act by inhibiting any of the many proteins involved in sperm production, release, or function. Because sperm cells are highly specialized, they express many proteins that are rare in the rest of the human body. [ 86 ] [ 87 ] [ 88 ] This suggests the possibility that non-hormonal contraceptives that specifically block these sperm proteins could have fewer side effects than hormonal contraceptives, since sex steroid receptors are found in tissues throughout the body. [ 89 ] Non-hormonal contraceptives can work by blocking spermatogenesis, sperm release, or mature sperm function, resulting in products with a wide variety of usage patterns, from slow onset to on-demand usage. [ 90 ] Contraceptives targeting mature sperm functions could even be taken by both sperm-producing and egg producing people. [ 18 ] [ 17 ] Challenges of non-hormonal contraceptive development include bioavailability and delivery past the blood-testis barrier . [ 91 ]
As of 2024 [update] , the following non-hormonal male contraceptive product is in clinical trials:
As of 2024 [update] , the following non-hormonal male contraceptive products are in preclinical development :
New male contraceptive methods could be available before 2030 , assuming smooth development and clinical trials . [ 116 ]
Prolonged testicular heating had been shown to reduce sperm counts in 1941, [ 117 ] considered as a method of birth control after 1968 and in the 1980s [ 118 ] [ 119 ] No modern clinical trials have demonstrated the safety, contraceptive effectiveness, or reversibility of this approach. Various devices are in early preclinical stages of development, and as of 2017 some approaches have been used by men through self-experimentation . [ 15 ] [ 120 ] As of 2015, the mechanism by which heating disrupts spermatogenesis was still not fully understood. [ 121 ] There have been theoretical concerns that prolonged heating could increase the risk of testicular cancer since the inborn birth defect of cryptorchidism carries a risk of testicular cancer [ 122 ] or that heating could damage sperm DNA, resulting in harm to potential offspring. [ 123 ]
These approaches work by either physically or chemically preventing the emission of sperm during ejaculation, and are likely to be effective on-demand.
α1-adrenoceptor antagonists and P2X1 antagonists have been shown to inhibit smooth muscle contractions in the vas deferens during ejaculation, and therefore prevent the release of semen and sperm while maintaining the sensation of orgasm . [ 124 ] [ 125 ] [ 126 ] Various molecules in these categories are under consideration as possible on-demand male contraceptives.
Vas-occlusive contraception is a form of male contraception that blocks sperm transport in the vas deferens , the tubes that carry sperm from the epididymis to the ejaculatory ducts .
Vas-occlusive contraception provides a contraceptive effect through physical blockage of the vas deferens , the duct connecting the epididymis to the urethra . While a vasectomy excises, or removes, a piece of each vas deferens and occludes the remaining open ends of the duct, vas-occlusive methods aim to block the duct while leaving it intact. Vas-occlusive methods generally aim to create long-acting reversible options, through a second procedure that removes the blockage. [ 140 ] However, full reversibility remains questionable, since animal and human studies have shown sperm abnormalities, incomplete recovery of sperm parameters, and the development of fertility-impairing antibodies against one's own sperm after blockage removal. [ 112 ] [ 141 ] [ 142 ] [ 143 ] [ 144 ] [ 145 ]
As of 2024 [update] , the following vas-occlusive male contraceptive products are in clinical trials:
As of 2024 [update] , the following vas-occlusive male contraceptive products are in preclinical development:
Research into new, more acceptable designs of condoms is ongoing. [ 166 ] [ 167 ]
These approaches work by blocking functions that mature sperm need in order to reach and fertilize an egg in the female reproductive tract, such as motility , capacitation , semen liquification, or fertilization . Drugs or devices that target mature sperm are likely to be effective on-demand (taken just before intercourse), and could even be delivered either in sperm-producing or egg-producing bodies, leading to unisex contraceptives. [ 18 ] [ 17 ]
As of 2024 [update] , the following non-hormonal male contraceptive approaches are in preclinical or early development:
Although some people question whether men would be interested in managing their own contraceptives [ 190 ] or whether women would trust their male partners to do so successfully, [ 191 ] studies consistently show that men around the world have significant levels of interest in novel forms of male contraception [ 19 ] [ 24 ] [ 192 ] [ 20 ] [ 193 ] [ 194 ] and that women in committed relationships would generally trust their male partners to manage the contraceptive burden in the relationship. [ 24 ] Additionally, males participating in various contraceptive clinical trials have reported high satisfaction with the products they were using. [ 82 ] [ 13 ] [ 23 ]
Studies on potential uptake indicate that in most countries, more than half of men surveyed would be willing to use a new method of male contraception. [ 19 ] [ 21 ] [ 192 ] [ 195 ] [ 196 ] [ 197 ] Interestingly, some of the highest rates were reported in low-income countries like Nigeria and Bangladesh where 76% of men surveyed indicated that they would be willing to use a new method within the first 12 months that it is available. [ 19 ] This is particularly compelling, since it has been estimated that a mere 10% uptake of new male contraceptive methods could avert nearly 40% of unintended pregnancies in Nigeria. [ 26 ] Across the world, many young and middle-aged men especially want the ability to control their own fertility, and are not well-served by existing family planning programs. [ 198 ]
Although a phase II trial for an injectable male contraceptive was halted in 2011 by an independent data safety monitoring board due likely to rare adverse effects experienced by some participants, [ 199 ] [ 68 ] leading many popular articles to suggest men could not tolerate side effects similar to those that many women endure on hormonal birth control, [ 71 ] [ 200 ] in reality more than 80% of the study's male participants stated at the end of the trial that they were satisfied with the contraceptive injection, and would be willing to use the method if it were available. [ 201 ] Subsequent hormonal male contraceptive clinical trials have progressed successfully, showing high levels of efficacy and acceptability among the participants. [ 13 ] [ 23 ] [ 82 ] [ 202 ]
It is sometimes assumed that women won't trust men to take contraceptives, since women would bear the consequences of a male partner's missed dose or misuse. [ 191 ] Of course, male contraceptive options would not have to replace female contraceptives, and in casual sexual encounters both partners may prefer to independently control their own contraceptive methods. On the other hand, some long-term couples might want only one partner to bear the contraceptive burden. Indeed, there is evidence that a large proportion of women in relationships in many countries around the world would trust their partners to take a potential male method, [ 25 ] [ 19 ] and many women want more male partner involvement in their own reproductive health services. [ 203 ] Further, current contraceptive use data show that more than a quarter of women worldwide already rely on male-controlled methods for contraception (such as condoms and vasectomy), [ 204 ] and this figure could grow as more male contraceptive methods become available.
Despite the fact that modern female pharmaceutical contraception has been on the market since the 1960s, [ 205 ] 40-50% of pregnancies are still unintended worldwide, leading to an approximate total of 121 million unintended pregnancies annually. [ 206 ] [ 207 ] [ 208 ] Importantly, most studies on unintended pregnancies only measure women's intentions about the pregnancy, and so pregnancies that were unintended by men are understudied and may be under-reported. [ 209 ] Unintended pregnancies have been shown to be linked with a wide variety of negative outcomes on mental and physical health, as well as educational and socioeconomic attainment in both parents and the children born of unintended pregnancies. [ 28 ] [ 30 ] [ 31 ] [ 33 ] [ 34 ] [ 35 ]
Surprisingly, although the rate of unintended pregnancies (per 1000 women of childbearing age) is higher in developing countries , [ 207 ] [ 210 ] [ 211 ] the percentage of pregnancies that are unintended is actually higher in developed countries , since a lower proportion of women in developed countries are intending to conceive at any given time. [ 207 ] Research indicates that unmet need for modern contraception is the cause of 84% of unintended pregnancies in developing countries. [ 212 ] In the United States, which has a higher unintended pregnancy rate than many other developed nations, [ 213 ] one important reason that women cite for nonuse of contraceptives is concerns about the side effects of existing products. [ 214 ] Taken together, these statistics suggests that the current suite of contraceptives is insufficient to meet the fertility planning needs of people across the world, and therefore the introduction of new male contraceptives is likely to decrease the stubbornly high global rates of unintended pregnancy. [ 26 ]
International market research indicates that 49% of men in the United states and 76% of men in Nigeria would try a novel male contraceptive within the first year of its existence. [ 19 ] Independent modelling predicts that even if real-world usage is only 10% as high as the market research suggests, the introduction of a male contraceptive would avert roughly 200,000 unintended pregnancies per year in the USA and Nigeria each. [ 26 ]
Fathers with unintended births report lower proportions of happiness than in fathers with intentional births [ 215 ] and unintended fatherhood for men in their early 30s is associated with a significant increase in depressive symptoms. [ 216 ] In addition, men in insecure financial situations are more likely to report a recent unintended pregnancy, [ 209 ] and supporting and raising a child brings significant costs that can exacerbate financial insecurity. [ 217 ] [ 218 ] More broadly, access to effective and reliable contraception would advance men's ability to "maintain personal bodily autonomy, have children, not have children, and parent the children we have in safe and sustainable communities" in accordance with the principles of Reproductive Justice . [ 219 ]
Family planning has been found to be associated with overall well-being and is one of the most efficient tools for women's empowerment. [ 220 ] [ 221 ] [ 222 ] Positive outcomes of effective birth control include improvements in women's health, self-agency, education, labor force participation, financial stability, as well as decreases in pregnancy-related deaths, [ 223 ] [ 224 ] [ 225 ] and these positive social and health impacts may be further realized by the addition of novel male and unisex methods. [ 26 ] [ 19 ] New male contraceptive options would not come at the expense of women’s reproductive autonomy, since women would still be able to take advantage of all of the contraceptive methods available to them, choose to have both partners use their own contraceptive methods at the same time, or rely solely on their male partners’ form of contraception.
Interventions encouraging male engagement in couples' reproductive health and decisionmaking have shown positive outcomes related to promoting more equitable gender norms in the context of family planning, [ 226 ] and increased joint decision making in couples. It is reasonable to assume from these data that increasing male involvement as contraceptive users will further improve gender equity. [ 227 ]
While this article has used the term "male" contraception for clarity, these contraceptives are most accurately described as "sperm-targeting" contraceptives, since they would work effectively in any body that produces sperm, regardless of that person's gender identity or external genitalia. [ 18 ] Importantly, contraceptives that block functions of mature sperm could be delivered in a unisex manner, incapacitating sperm before ejaculation in sperm-producing people, or after sperm arrives in the body of egg-producing people. [ 17 ] [ 18 ]
Transgender , nonbinary , and intersex people are underserved by current contraceptive options. For example, many trans men can become pregnant (both intentionally and unintentionally), [ 228 ] but may prefer not to use estrogen - or progestin -containing hormonal birth control (both because of the social classification of these hormones as "female sex hormones" and because of a fear they will interfere with masculinizing hormone therapy , although the American College of Obstetricians and Gynecologists states that these hormonal contraceptives have little effect on masculinization.) [ 229 ] [ 230 ] [ 231 ] Trans women who have not had gender-affirming genital surgery may have similar unmet contraceptive needs as those of cisgender men, since gender-affirming hormonal therapy is not effective contraception. [ 231 ] Nonbinary and intersex people may be less likely to use current methods of birth control, since they are popularly categorized by the labels "male" and "female", which may not match an individual's gender identity or may invoke feelings of gender dysphoria . [ 230 ] This dynamic may contribute to the higher rates of unintended pregnancies seen in the LGBTQ+ community as compared to heterosexual peers, [ 232 ] [ 233 ] [ 234 ] which could in theory be ameliorated by the introduction of unisex contraceptives.
Novel male contraceptive options are predicted to reduce the incidence unintended pregnancies, [ 26 ] [ 19 ] and being the product of an intended rather than unintended pregnancy has been shown to correlate with improved health and wellbeing outcomes in children. [ 32 ] [ 224 ] [ 235 ] [ 236 ] Additionally, reduced family size correlates with improved educational outcomes, [ 237 ] and children born after the introduction of family planning programs in the USA experienced a reduction in poverty rates, both in childhood and adulthood. [ 238 ]
Unintended pregnancies rates increase as income decreases, both between countries [ 37 ] and between socioeconomic and racial groups within a given country. [ 213 ] [ 239 ] Women of color, especially Black women, in the United States and other developed countries have dramatically higher rates of death during and after birth and worse maternal health outcomes, due in part to systemic discrimination . [ 240 ] [ 224 ] Since unintended pregnancies can have negative effects on an individual's physical and mental health, educational attainment, and economic prospects, these higher unintended pregnancy rates likely contribute to the persistent socioeconomic gaps within and between societies. [ 28 ] [ 30 ] [ 31 ] [ 32 ] [ 33 ] [ 34 ] [ 35 ] It's therefore possible that the introduction of new male contraceptives would not only mitigate gender inequities, as discussed above, but racial and income inequities as well, by providing more ways for individuals to avoid unintended pregnancies. [ 26 ]
In addition to the personal financial savings of avoiding unintended pregnancy mentioned above, on a societal level, contraceptives are a public health intervention with a high return on investment: for every dollar the United States government spends on family planning programs, it saves $7.09, for a total of over $13 billion per year. [ 241 ] Unintended pregnancies in the United States are estimated to cause $4.5 billion in direct medical costs. [ 35 ] [ 33 ] New male contraceptives are likely to prevent some unintended pregnancies [ 26 ] and therefore reduce these costs.
61% of unintended pregnancies end in abortion , [ 36 ] whereas only 20% of all pregnancies end in abortion. [ 242 ] Interestingly, unintended pregnancy rates are higher in countries where abortion is illegal than those where abortion is legal, yet the incidence of abortion is similar between these groups of countries. [ 36 ] [ 243 ] Illegal abortions are more likely to be unsafe , and there are an estimated 25 million unsafe abortions globally each year, leading to 50,000 - 70,000 yearly deaths and 5 million people with long-term health consequences. [ 38 ] [ 39 ] [ 40 ] [ 41 ] Importantly, increases in the prevalence and uptake of modern contraceptives have been shown to decrease unintended pregnancy and abortion rates when fertility rates are constant. [ 244 ] [ 245 ] [ 246 ] This suggests that the introduction of new forms of male contraception could prevent a significant number of abortions, save lives, and avoid unnecessary suffering.
A variety of plant extracts have been used throughout history in attempts to prevent pregnancy, though most were used by women, and the efficacy and safety of these methods is questionable. [ 247 ] [ 248 ] [ 249 ]
Condoms made of animal organs or fabric have been in documented use since at least the 16th century, [ 250 ] and various types of penile coverings have been depicted and referenced in materials from cultures around the world as early as 3000 BCE , though it is not always clear that these coverings were used for birth control or protection from sexually transmitted infections. [ 251 ] The 1800s saw the development of thick reusable rubber condoms, [ 250 ] [ 251 ] and thinner disposable latex rubber condoms entered production in the 1920s. [ 252 ] [ 253 ] [ 254 ]
Vasectomy was first performed in humans in the late 1800s, but not initially as a method of voluntary birth control. Instead, it was first used as an attempted treatment (later proved to be ineffective) for enlarged prostates , and within a few years, one-sided vasectomy became popular as a supposed method of sexual rejuvenation in older men. [ 255 ] [ 256 ] Although this rejuvenation treatment was ineffective pseudoscience and any perceived effects were likely due only to the placebo effect , many prominent men, such as Sigmund Freud and W.B. Yeats, sought out the procedure. [ 257 ] In the early 1900s, the use of vasectomy took a darker turn, and it became widely promoted and practiced as a means of eugenic involuntary sterilization. [ 256 ] [ 255 ] It was not until the 1950s that vasectomy became widely used as a method for voluntary sterilization and family planning. [ 256 ] [ 255 ] Since then, vasectomy has undergone extensive technical improvements and innovations, such that it is no longer a single procedure, but a family of related procedures . [ 255 ] [ 258 ]
In the 1990s, and into the early 2000s, major pharmaceutical companies Organon , Wyeth , and Schering were pursuing preclinical and clinical development of various male contraceptive products, but in 2006, all three companies ceased development of these products within a short time of each other, for reasons that have not been publicly released. [ 259 ] [ 111 ]
In 2013, the Male Contraceptive Initiative was founded with the goal of funding and supporting the development of new male contraceptives. [ 260 ] [ 261 ]
In 2020, Dr. Polina Lishko was awarded the MacArthur "Genius" Fellowship for her contributions to the understanding of sperm physiology, with the award specifically noting her work on "opening up new avenues in ... the development of male-specific or unisex contraceptives." [ 262 ]
Many researchers have attempted to develop male contraceptive products over the last hundred years. A selection of these efforts (that are no longer in development as of 2024) are listed below. | https://en.wikipedia.org/wiki/Male_contraceptive |
Male egg can refer to either:
This article focuses on the first definition.
Male eggs are the result of a process in which the eggs of a female would be emptied of their genetic contents (a technique similar to that used in the cloning process), and those contents would be replaced with male DNA. Such eggs could then be fertilized by sperm. The procedure was conceived by Calum MacKellar , a Scottish bioethicist. With this technique, two males could be the biological parents of a child. However, such a procedure would additionally require an artificial womb or a female gestational carrier . [ 4 ] [ 5 ] [ 1 ]
In 2023, male eggs from male mice cells were developed and used to create bi-paternal mice that grew into adulthood; [ 6 ] [ 7 ] bi-paternal mice had been obtained in 2008, but they only survived for a few days. [ 8 ] [ 9 ] [ 10 ]
This genetics article is a stub . You can help Wikipedia by expanding it . | https://en.wikipedia.org/wiki/Male_egg |
In ethology , male-male intrasexual competition occurs when two males of the same species compete for the opportunity to mate with a female . Sexually dimorphic traits, size, sex ratio , [ 1 ] and the social situation [ 2 ] may all play a role in the effects male-male competition has on the reproductive success of a male and the mate choice of a female. Larger males tend to win male-male conflicts due to their sheer strength and ability to ward off other males from taking over their females. For instance, in the fly Dryomyza anilis , size shows the strongest correlation to the outcome of male-male conflicts over resources like territory and females. [ 3 ]
There are multiple types of male-male competition that may occur in a population at different times depending on the conditions. Competition variation occurs based on the frequency of various mating behaviours present in the population. [ 1 ] One factor that can influence the type of competition observed is the population density of males. [ 1 ] When there is a high density of males present in the population, competition tends to be less aggressive and therefore sneak tactics and disruptions techniques are more often employed. [ 1 ] These techniques often indicate a type of competition referred to as scramble competition. [ 1 ] In Japanese medaka, Oryzias latipes , sneaking behaviours refer to when a male interrupts a mating pair during copulation by grasping on to either the male or the female and releasing their own sperm in the hopes of being the one to fertilize the female. [ 1 ] Disruption is a technique which involves one male bumping the male that is copulating with the female away just before his sperm is released and the eggs are fertilized. [ 1 ]
However, all techniques are not equally successful when in competition for reproductive success. Disruption results in a shorter copulation period and can therefore disrupt the fertilization of the eggs by the sperm, which frequently results in lower rates of fertilization and smaller clutch size. [ 1 ]
Another factor that can influence male-male competition is the value of the resource to competitors. Male-male competition can pose many risks to a male's fitness, such as high energy expenditure, physical injury, lower sperm quality and lost paternity. [ 4 ] The risk of competition must therefore be worth the value of the resource. A male is more likely to engage in competition for a resource that improves their reproductive success if the resource value is higher. While male-male competition can occur in the presence or absence of a female, competition occurs more frequently in the presence of a female. [ 2 ] The presence of a female directly increases the resource value of a territory or shelter and so the males are more likely to accept the risk of competition when a female is present. [ 2 ] The smaller males of a species are also more likely to engage in competition with larger males in the presence of a female. [ 2 ] Due to the higher level of risk for subordinate males, they tend to engage in competition less frequently than larger, more dominant males and therefore breed less frequently than dominant males. [ 4 ] This is seen in many species, such as the Omei treefrog, Rhacophorus omeimontis , where larger males obtain more mating opportunities and mate with larger females. [ 5 ]
A third factor that can impact the success of a male in competition is winner-loser effects . [ 6 ] Burrowing crickets, Velarifictorus aspersus , compete for burrows to attract females using their large mandibles for fighting. [ 6 ] Female burrowing crickets are more likely to choose winner of a competition in the 2 hours after the fight. [ 6 ] The presence of a winning male suppresses mating behaviours of the losing males because the winning male tends to produce more frequent and enhanced mating calls in this period of time. [ 6 ]
Male-male competition can both positively and negatively affect female fitness. When there is a high density of males in a population and a large number of males attempting to mate with the female, she is more likely to resist mating attempts, resulting in lower fertilization rates. [ 1 ] High levels of male-male competition can also result in a reduction in female investment in mating. [ 4 ] Many forms of competition can also cause significant distress for the female negatively impacting her ability to reproduce. [ 1 ] An increase in male-male competition can affect a female's ability to select the best mates, and therefore decrease the likelihood of successful reproduction. [ 7 ]
However, group mating in Japanese medaka increases the fitness of females due to an increase in genetic variation, a higher likelihood of paternal care, and a higher likelihood of successful fertilization. [ 1 ] Exposure to environmental estrogens, such as some herbicides, can confuse female choice of males. [ 8 ] | https://en.wikipedia.org/wiki/Male_intrasexual_competition |
Maleic hydrazide , often known by the brand name Fazor , is a plant growth regulator that reduces growth through preventing cell division but not cell enlargement. [ 1 ] [ 2 ] It is applied to the foliage of potato, onion, garlic and carrot crops to prevent sprouting during storage. [ 3 ] It can also be used to control volunteer potatoes that are left in the field during harvesting. [ 4 ] It was first identified in the 1940s but was not used commercially in the United Kingdom until 1984. The banning of chlorpropham as a sprout suppressant in 2019 has led renewed interest in how maleic hydrazide can be used in potatoes. [ 5 ]
This organic chemistry article is a stub . You can help Wikipedia by expanding it . | https://en.wikipedia.org/wiki/Maleic_hydrazide |
The Malewicki equations (or Fehskens–Malewicki equations) for sub-sonic endo-atmospheric rocket flight describe the maximum altitude and coast time of a vehicle such as a model rocket. Aerospace engineer and inventor Douglas Malewicki first published them as a technical report by the model rocket company Estes Industries in 1967. [ 1 ] [ 2 ] | https://en.wikipedia.org/wiki/Malewicki_equations |
In mathematics, the Malgrange preparation theorem is an analogue of the Weierstrass preparation theorem for smooth functions . It was conjectured by René Thom and proved by B. Malgrange ( 1962–1963 , 1964 , 1967 ).
Suppose that f ( t , x ) is a smooth complex function of t ∈ R and x ∈ R n near the origin, and let k be the smallest integer such that
Then one form of the preparation theorem states that near the origin f can be written as the product of a smooth function c that is nonzero at the origin and a smooth function that as a function of t is a polynomial of degree k . In other words,
where the functions c and a are smooth and c is nonzero at the origin.
A second form of the theorem, occasionally called the Mather division theorem , is a sort of "division with remainder" theorem: it says that if f and k satisfy the conditions above and g is a smooth function near the origin, then we can write
where q and r are smooth, and as a function of t , r is a polynomial of degree less than k . This means that
for some smooth functions r j ( x ).
The two forms of the theorem easily imply each other: the first form is the special case of the "division with remainder" form where g is t k , and the division with remainder form follows from the first form of the theorem as we may assume that f as a function of t is a polynomial of degree k .
If the functions f and g are real, then the functions c , a , q , and r can also be taken to be real. In the case of the Weierstrass preparation theorem these functions are uniquely determined by f and g , but uniqueness no longer holds for the Malgrange preparation theorem.
The Malgrange preparation theorem can be deduced from the Weierstrass preparation theorem. The obvious way of doing this does not work: although smooth functions have a formal power series expansion at the origin, and the Weierstrass preparation theorem applies to formal power series , the formal power series will not usually converge to smooth functions near the origin. Instead one can use the idea of decomposing a smooth function as a sum of analytic functions by applying a partition of unity to its Fourier transform.
For a proof along these lines see ( Mather 1968 ) or ( Hörmander 1983a , section 7.5)
The Malgrange preparation theorem can be restated as a theorem about modules over rings of smooth, real-valued germs . If X is a manifold , with p ∈ X , let C ∞ p ( X ) denote the ring of real-valued germs of smooth functions at p on X . Let M p ( X ) denote the unique maximal ideal of C ∞ p ( X ), consisting of germs which vanish at p. Let A be a C ∞ p ( X )-module, and let f : X → Y be a smooth function between manifolds. Let q = f ( p ). f induces a ring homomorphism f * : C ∞ q (Y) → C ∞ p ( X ) by composition on the right with f . Thus we can view A as a C ∞ q ( Y )-module. Then the Malgrange preparation theorem says that if A is a finitely-generated C ∞ p ( X )-module, then A is a finitely-generated C ∞ q ( Y )-module if and only if A / M q ( Y )A is a finite-dimensional real vector space. | https://en.wikipedia.org/wiki/Malgrange_preparation_theorem |
In mathematics, the Malgrange–Ehrenpreis theorem states that every non-zero linear differential operator with constant coefficients has a Green's function . It was first proved independently by Leon Ehrenpreis ( 1954 , 1955 ) and Bernard Malgrange ( 1955–1956 ).
This means that the differential equation
where P {\displaystyle P} is a polynomial in several variables and δ {\displaystyle \delta } is the Dirac delta function , has a distributional solution u {\displaystyle u} . It can be used to show that
has a solution for any compactly supported distribution f {\displaystyle f} . The solution is not unique in general.
The analogue for differential operators whose coefficients are polynomials (rather than constants) is false: see Lewy's example .
The original proofs of Malgrange and Ehrenpreis did not use explicit constructions as they used the Hahn–Banach theorem . Since then several constructive proofs have been found.
There is a very short proof using the Fourier transform and the Bernstein–Sato polynomial , as follows. By taking Fourier transforms the Malgrange–Ehrenpreis theorem is equivalent to the fact that every non-zero polynomial P {\displaystyle P} has a distributional inverse. By replacing P {\displaystyle P} by the product with its complex conjugate , one can also assume that P {\displaystyle P} is non-negative. For non-negative polynomials P {\displaystyle P} the existence of a distributional inverse follows from the existence of the Bernstein–Sato polynomial, which implies that P s {\displaystyle P^{s}} can be analytically continued as a meromorphic distribution-valued function of the complex variable s {\displaystyle s} ; the constant term of the Laurent expansion of P s {\displaystyle P^{s}} at s = − 1 {\displaystyle s=-1} is then a distributional inverse of P {\displaystyle P} .
Other proofs, often giving better bounds on the growth of a solution, are given in ( Hörmander 1983a , Theorem 7.3.10), ( Reed & Simon 1975 , Theorem IX.23, p. 48) and ( Rosay 1991 ).
( Hörmander 1983b , chapter 10) gives a detailed discussion of the regularity properties of the fundamental solutions.
A short constructive proof was presented in ( Wagner 2009 , Proposition 1, p. 458):
is a fundamental solution of P ( ∂ ) {\displaystyle P(\partial )} , i.e., P ( ∂ ) E = δ {\displaystyle P(\partial )E=\delta } , if P m {\displaystyle P_{m}} is the principal part of P {\displaystyle P} , η ∈ R n {\displaystyle \eta \in \mathbb {R} ^{n}} with P m ( η ) ≠ 0 {\displaystyle P_{m}(\eta )\neq 0} , the real numbers λ 0 , … , λ m {\displaystyle \lambda _{0},\ldots ,\lambda _{m}} are pairwise different, and | https://en.wikipedia.org/wiki/Malgrange–Ehrenpreis_theorem |
Malic acid is an organic compound with the molecular formula HO 2 CCH(OH)CH 2 CO 2 H . It is a dicarboxylic acid that is made by all living organisms, contributes to the sour taste of fruits, and is used as a food additive . Malic acid has two stereoisomeric forms ( L - and D -enantiomers), though only the L -isomer exists naturally. The salts and esters of malic acid are known as malates . The malate anion is a metabolic intermediate in the citric acid cycle .
The word 'malic' is derived from Latin mālum , meaning 'apple'. The related Latin word mālus , meaning 'apple tree', is used as the name of the genus Malus , which includes all apples and crabapples; [ 5 ] and is the origin of other taxonomic classifications such as Maloideae , Malinae , and Maleae .
L -Malic acid is the naturally occurring form, whereas a mixture of L - and D -malic acid is produced synthetically.
Malate plays an important role in biochemistry . In the C4 carbon fixation process, malate is a source of CO 2 in the Calvin cycle . In the citric acid cycle , ( S )-malate is an intermediate, formed by the addition of an -OH group on the si face of fumarate. It can also be formed from pyruvate via anaplerotic reactions .
Malate is also synthesized by the carboxylation of phosphoenolpyruvate in the guard cells of plant leaves. Malate, as a double anion, often accompanies potassium cations during the uptake of solutes into the guard cells in order to maintain electrical balance in the cell. The accumulation of these solutes within the guard cell decreases the solute potential , allowing water to enter the cell and promote aperture of the stomata.
Malic acid was first isolated from apple juice by Carl Wilhelm Scheele in 1785. [ 6 ] Antoine Lavoisier in 1787 proposed the name acide malique , which is derived from the Latin word for apple, mālum —as is its genus name Malus . [ 7 ] [ 8 ] In German it is named Äpfelsäure (or Apfelsäure ) after plural or singular of a sour thing from the apple fruit, but the salt(s) are called Malat(e) .
Malic acid is the main acid in many fruits, including apricots , blackberries , blueberries , cherries , grapes , mirabelles , peaches , pears , plums , and quince , [ 9 ] and is present in lower concentrations in other fruits, such as citrus. It contributes to the sourness of unripe apples. Sour apples contain high proportions of the acid. It is present in grapes and in most wines with concentrations sometimes as high as 5 g/L. [ 10 ] It confers a tart taste to wine ; the amount decreases with increasing fruit ripeness . The taste of malic acid is very clear and pure in rhubarb , a plant for which it is the primary flavor. It is also the compound responsible for the tart flavor of sumac spice. It is also a component of some artificial vinegar flavors, such as "salt and vinegar" flavored potato chips. [ 11 ]
The process of malolactic fermentation converts malic acid to much milder lactic acid . Malic acid occurs naturally in all fruits and many vegetables, and is generated in fruit metabolism. [ 12 ]
Malic acid, when added to food products, is denoted by E number E296. It is sometimes used with or in place of the less sour citric acid in sour sweets. These sweets are sometimes labeled with a warning stating that excessive consumption can cause irritation of the mouth. It is approved for use as a food additive in the EU, [ 13 ] US [ 14 ] and Australia and New Zealand [ 15 ] (where it is listed by its INS number 296).
Malic acid contains 10 kJ (2.39 kilocalories) of energy per gram. [ 16 ]
Racemic malic acid is produced industrially by the double hydration of maleic anhydride . In 2000, American production capacity was 5,000 tons per year. The enantiomers may be separated by chiral resolution of the racemic mixture. S -Malic acid is obtained by fermentation of fumaric acid . [ 17 ]
Self-condensation of malic acid in the presence of fuming sulfuric acid gives the pyrone coumalic acid : [ 18 ]
Carbon monoxide and water are liberated during this reaction.
Malic acid was important in the discovery of the Walden inversion and the Walden cycle , in which (−)-malic acid first is converted into (+)-chlorosuccinic acid by action of phosphorus pentachloride . Wet silver oxide then converts the chlorine compound to (+)-malic acid, which then reacts with PCl 5 to the (−)-chlorosuccinic acid. The cycle is completed when silver oxide takes this compound back to (−)-malic acid.
L -malic acid is used to resolve α-phenylethylamine , a versatile resolving agent in its own right. [ 19 ]
Soil supplementation with molasses increases microbial synthesis of malic acid. This is thought to occur naturally as part of soil microbe suppression of disease , so soil amendment with molasses can be used as a crop treatment in horticulture. [ 20 ]
Click on genes, proteins and metabolites below to link to respective articles. [ § 1 ]
Acetyl-CoA
Oxaloacetate
Malate
Fumarate
Succinate
Succinyl-CoA
Citrate
cis- Aconitate
Isocitrate
Oxalosuccinate
2-oxoglutarate | https://en.wikipedia.org/wiki/Malic_acid |
Malignant transformation is the process by which cells acquire the properties of cancer . This may occur as a primary process in normal tissue, or secondarily as malignant degeneration of a previously existing benign tumor .
There are many causes of primary malignant transformation, or tumorigenesis . Most human cancers in the United States are caused by external factors, and these factors are largely avoidable. [ 1 ] [ 2 ] [ 3 ] These factors were summarized by Doll and Peto in 1981, [ 1 ] and were still considered to be valid in 2015. [ 2 ] These factors are listed in the table.
a Reproductive and sexual behaviors include: number of partners; age at first menstruation; zero versus one or more live births
Colon cancer provides one example of the mechanisms by which diet, the top factor listed in the table, is an external factor in cancer. The Western diet of African Americans in the United States is associated with a yearly colon cancer rate of 65 per 100,000 individuals, while the high fiber/low fat diet of rural Native Africans in South Africa is associated with a yearly colon cancer rate of <5 per 100,000. [ 4 ] Feeding the Western diet for two weeks to Native Africans increased their secondary bile acids, including carcinogenic deoxycholic acid , [ 5 ] by 400%, and also changed the colonic microbiota. [ 4 ] Evidence reviewed by Sun and Kato [ 6 ] indicates that differences in human colonic microbiota play an important role in the progression of colon cancer.
A second example, relating a dietary component to a cancer, is illustrated by lung cancer. Two large population-based studies were performed, one in Italy and one in the United States. [ 7 ] In Italy, the study population consisted of two cohorts: the first, 1721 individuals diagnosed with lung cancer and no severe disease, and the second, 1918 control individuals with absence of lung cancer history or any advanced diseases. All individuals filled out a food frequency questionnaire including consumption of walnuts, hazelnuts, almonds, and peanuts, and indicating smoking status. In the United States, 495,785 members of AARP were questioned on consumption of peanuts, walnuts, seeds, or other nuts in addition to other foods and smoking status. In this U.S. study 18,533 incident lung cancer cases were identified during up to 16 years of follow-up. Overall, individuals in the highest quintile of frequency of nut consumption had a 26% lower risk of lung cancer in the Italian study and a 14% lower risk of lung cancer in the U.S. study. Similar results were obtained among individuals who were smokers.
The most important chemical compounds in smoked tobacco that are carcinogenic are those that produce DNA damage since such damage appears to be the primary underlying cause of cancer. [ 8 ] Cunningham et al. [ 9 ] combined the microgram weight of the compound in the smoke of one cigarette with the known genotoxic effect per microgram to identify the most carcinogenic compounds in cigarette smoke. These compounds and their genotoxic effects are listed in the article Cigarette . The top three compounds are acrolein , formaldehyde and acrylonitrile , all known carcinogens .
In 2002 the World Health Organizations International Agency for Research on Cancer [ 10 ] estimated that 11.9% of human cancers are caused by one of seven viruses (see Oncovirus overview table ). These are Epstein-Barr virus (EBV or HHV4); Kaposi's sarcoma-associated herpesvirus (KSHV or HHV8); Hepatitis B and Hepatitis C viruses (HBV and HCV); Human T-lymphotrophic virus 1 (HTLV-1); Merkel cell polyomavirus (MCPyV); and a group of alpha Human papillomaviruses (HPVs). [ 11 ]
In 1995 epidemiologic evidence indicated that Helicobacter pylori infection increases the risk for gastric carcinoma. [ 12 ] More recently, experimental evidence showed that infection with Helicobacter pylori cagA-positive bacterial strains results in severe degrees of inflammation and oxidative DNA damage, leading to progression to gastric cancer. [ 13 ]
Perera et al. [ 14 ] referred to a number of articles pointing to roles of bacteria in other cancers. They pointed to single studies on the role of Chlamydia trachomatis in cervical cancer, Salmonella typhi in gallbladder cancer, and both Bacteroides fragilis and Fusobacterium nucleatum in colon cancer. Meurman has recently summarized evidence connecting oral microbiota with carcinogenesis. [ 15 ] Although suggestive, these studies need further confirmation.
One underlying commonality in cancers is genetic mutation, acquired either by inheritance, or, more commonly, by mutations in one's somatic DNA over time. The mutations considered important in cancers are those that alter protein coding genes (the exome ). As Vogelstein et al. point out, a typical tumor contains two to eight exome "driver gene" mutations, and a larger number of exome mutations that are "passengers" that confer no selective growth advantage. [ 16 ]
Cancers also generally have genome instability , that includes a high frequency of mutations in the noncoding DNA that makes up about 98% of the human genome. The average number of DNA sequence mutations in the entire genome of breast cancer tissue is about 20,000. [ 17 ] In an average melanoma (where melanomas have a higher exome mutation frequency [ 16 ] ) the total number of DNA sequence mutations is about 80,000. [ 18 ]
A second underlying commonality in cancers is altered epigenetic regulation of transcription . In cancers, loss of gene expression occurs about 10 times more frequently by epigenetic transcription silencing (caused, for example, by promoter hypermethylation of CpG islands ) than by mutations. As Vogelstein et al. [ 16 ] point out, in a colorectal cancer there are usually about 3 to 6 driver mutations and 33 to 66 hitchhiker , or passenger, mutations. [ 16 ] In contrast, the frequency of epigenetic alterations is much higher. In colon tumors compared to adjacent normal-appearing colonic mucosa, there are about 600 to 800 heavily methylated CpG islands in promoters of genes in the tumors while the corresponding CpG islands are not methylated in the adjacent mucosa. [ 19 ] [ 20 ] [ 21 ] Such methylation turns off expression of a gene as completely as a mutation would. Around 60–70% of human genes have a CpG island in their promoter region. [ 22 ] [ 23 ] In colon cancers, in addition to hypermethylated genes, several hundred other genes have hypomethylated (under-methylated) promoters, thereby causing these genes to be turned on when they ordinarily would be turned off. [ 21 ]
Epigenetic alterations are also carried out by another major regulatory element, that of microRNAs (miRNAs). In mammals, these small non-coding RNA molecules regulate about 60% of the transcriptional activity of protein-encoding genes. [ 24 ] Epigenetic silencing or epigenetic over-expression of miRNA genes, caused by aberrant DNA methylation of the promoter regions controlling their expression, is a frequent event in cancer cells. Almost one third of miRNA promoters active in normal mammary cells were found to be hypermethylated in breast cancer cells, and that is a several fold greater proportion of promoters with altered methylation than is usually observed for protein coding genes. [ 25 ] Other microRNA promoters are hypomethylated in breast cancers, and, as a result, these microRNAs are over-expressed. Several of these over-expressed microRNAs have a major influence in progression to breast cancer. BRCA1 is normally expressed in the cells of breast and other tissue, where it helps repair damaged DNA , or destroy cells if DNA cannot be repaired. [ 26 ] BRCA1 is involved in the repair of chromosomal damage with an important role in the error-free repair of DNA double-strand breaks. [ 27 ] BRCA1 expression is reduced or undetectable in the majority of high grade, ductal breast cancers. [ 28 ] Only about 3–8% of all women with breast cancer carry a mutation in BRCA1 or BRCA2. [ 29 ] BRCA1 promoter hypermethylation was present in only 13% of unselected primary breast carcinomas. [ 30 ] However, breast cancers were found to have an average of about 100-fold increase in miR-182, compared to normal breast tissue. [ 31 ] In breast cancer cell lines, there is an inverse correlation of BRCA1 protein levels with miR-182 expression. [ 32 ] Thus it appears that much of the reduction or absence of BRCA1 in high grade ductal breast cancers may be due to over-expressed miR-182. In addition to miR-182, a pair of almost identical microRNAs, miR-146a and miR-146b-5p, also repress BRCA1 expression. These two microRNAs are over-expressed in triple-negative tumors and their over-expression results in BRCA1 inactivation. [ 33 ] Thus, miR-146a and/or miR-146b-5p may also contribute to reduced expression of BRCA1 in these triple-negative breast cancers.
Post-transcriptional regulation by microRNA occurs either through translational silencing of the target mRNA or through degradation of the target mRNA, via complementary binding, mostly to specific sequences in the three prime untranslated region of the target gene's mRNA. [ 34 ] The mechanism of translational silencing or degradation of target mRNA is implemented through the RNA-induced silencing complex (RISC).
Silencing of a DNA repair gene by hypermethylation or other epigenetic alteration appears to be a frequent step in progression to cancer. As summarized in a review, [ citation needed ] promoter hypermethylation of DNA repair gene MGMT occurs in 93% of bladder cancers, 88% of stomach cancers, 74% of thyroid cancers, 40%-90% of colorectal cancers and 50% of brain cancers. In addition, promoter hypermethylation of DNA repair genes LIG4 , NEIL1 , ATM , MLH1 or FANCB occurs at frequencies of between 33% and 82% in one or more of head and neck cancers , non-small-cell lung cancers or non-small-cell lung cancer squamous cell carcinomas. Further, the article Werner syndrome ATP-dependent helicase indicates the DNA repair gene WRN has a promoter that is often hypermethylated in a variety of cancers, with WRN hypermethylation occurring in 11% to 38% of colorectal , head and neck , stomach , prostate , breast , thyroid , non-Hodgkin lymphoma , chondrosarcoma and osteosarcoma cancers.
Such silencing likely acts similarly to a germ-line mutation in a DNA repair gene, and predisposes the cell and its descendants to progression to cancer. [ 35 ] Another review [ 36 ] points out that when a gene necessary for DNA repair is epigenetically silenced, DNA repair would tend to be deficient and DNA damages can accumulate. Increased DNA damage can cause increased errors during DNA synthesis, leading to mutations that give rise to cancer.
The heavy metals cadmium , arsenic and nickel are all carcinogenic when present above certain levels. [ 37 ] [ 38 ] [ 39 ] [ 40 ]
Cadmium is known to be carcinogenic, possibly due to reduction of DNA repair. Lei et al. [ 41 ] evaluated five DNA repair genes in rats after exposure of the rats to low levels of cadmium. They found that cadmium caused repression of three of the DNA repair genes: XRCC1 needed for base excision repair , OGG1 needed for base excision repair, and ERCC1 needed for nucleotide excision repair . Repression of these genes was not due to methylation of their promoters.
Arsenic carcinogenicity was reviewed by Bhattacharjee et al. [ 39 ] They summarized the role of arsenic and its metabolites in generating oxidative stress, resulting in DNA damage. In addition to causing DNA damage, arsenic also causes repression of several DNA repair enzymes in both the base excision repair pathway and the nucleotide excision repair pathway. Bhattacharjee et al. further reviewed the role of arsenic in causing telomere dysfunction, mitotic arrest, defective apoptosis, as well as altered promoter methylation and miRNA expression. Each of these alterations could contribute to arsenic-induced carcinogenesis.
Nickel compounds are carcinogenic and occupational exposure to nickel is associated with an increased risk of lung and nasal cancers. [ 42 ] Nickel compounds exhibit weak mutagenic activity, but they considerably alter the transcriptional landscape of the DNA of exposed individuals. [ 42 ] Arita et al. [ 42 ] examined the peripheral blood mononuclear cells of eight nickel-refinery workers and ten non-exposed workers. They found 2756 differentially expressed genes with 770 up-regulated genes and 1986 down-regulated genes. DNA repair genes were significantly over-represented among the differentially expressed genes, with 29 DNA repair genes repressed in the nickel-refinery workers and two over-expressed. The alterations in gene expression appear to be due to epigenetic alterations of histones, methylations of gene promoters, and hypermethylation of at least microRNA miR-152. [ 40 ] [ 43 ]
Malignant transformation of cells in a benign tumor may be detected by pathologic examination of tissues. Often the clinical signs and symptoms are suggestive of a malignant tumor. The physician, during the medical history examination, can find that there have been changes in size or patient sensation and, upon direct examination, that there has been a change in the lesion itself.
Risk assessments can be done and are known for certain types of benign tumor which are known to undergo malignant transformation. One of the better-known examples of this phenomenon is the progression of a nevus to melanoma . | https://en.wikipedia.org/wiki/Malignant_transformation |
Malleability of intelligence describes the processes by which intelligence can increase or decrease over time and is not static. These changes may come as a result of genetics , pharmacological factors, psychological factors, behavior , or environmental conditions . Malleable intelligence may refer to changes in cognitive skills , memory , reasoning , or muscle memory related motor skills .
In general, the majority of changes in human intelligence occur at either the onset of development, during the critical period , or during old age (see neuroplasticity ).
Charles Spearman , who coined the general intelligence factor "g", described intelligence as one's ability to adapt to his environment with a set of useful skills including reasoning and understanding patterns and relationships. He believed individuals highly developed in one intellectual ability tended to be highly developed at other intellectual abilities. A more intelligent individual was thought to be able to more easily "accommodate" experiences into existing cognitive structures to develop structures more compatible with environmental stimuli. [ 1 ]
In general, intelligence is thought to be attributed to both genetic and environmental factors, but the extent to which each plays a key role is highly disputed. Studies of identical and non-identical twins raised separately and together show a strong correlation between child IQ and socio-economic level of the parents. Children raised in lower-class families tend to score lower on intelligence tests when compared to children raised in both middle and upper-class families. However, there is no difference in intelligence scores between children raised in middle versus upper-class families. [ 2 ]
The biological basis of intelligence is founded in the degree of connectivity of neurons in the brain and the varying amounts of white and grey matter. Studies show that intelligence is positively correlated with total cerebral volume. [ 1 ] While it is true that the number of neurons in the brain actually decreases throughout development, as neural connections grow and the pathways become more efficient, the supporting structures in the brain increase. This increase in supporting tissues, which include myelination , blood vessels , and glial cells , leads to an increase in overall brain size. [ 1 ] When brain circumference and IQ were compared in 9 year olds, a positive correlation was found between the two. An increase of 2.87 IQ points occurred for each standard deviation increase in brain circumference . [ 5 ]
The brain grows rapidly for the first five years of human development. At age five, the human brain is 90% of its total size. Then the brain finishes growing gradually until mid to late twenties. From start to finish, the brain increases in size by over 300% from birth. [ 2 ] The critical period , defined as the beginning years of brain development, is essential to intellectual development, as the brain optimizes the overproduction of synapses present at birth. [ 2 ] During the critical period , the neuronal pathways are refined based on which synapses are active and receiving transmission. It is a "use it or lose it" phenomenon. [ 2 ]
Neural plasticity refers to any change in the structure of the neural network that forms the central nervous system. Neural plasticity is the neuronal basis for changes in how the mind works, including learning, the formation of memory, and changes in intelligence. One well-studied form of plasticity is Long-Term Potentiation (LTP). [ 6 ] It refers to a change in neural connectivity as a result of high activation on both sides of a synaptic cleft. This change in neural connectivity allows information to be more easily processed, as the neural connection associated with that information becomes stronger through LTP. [ 2 ] Other forms of plasticity involve the growth of new neurons, the growth of new connections between neurons, and the selective elimination of such connection, called "dendritic pruning". [ 7 ]
Humans have varying degrees of neuroplasticity due to their genetic makeups, which affects their ability to adapt to conditions in their environments and effectively learn from experiences. [ 1 ] The degree to which intelligence test scores can be linked to genetic heritability increases with age. There is presently no explanation for this puzzling result, but flaws in the testing methods are suspected. A study of Dutch twins concludes that intelligence of 5 year olds is 26% heritable, while the test scores of 12-year-olds is 64% heritable. Structurally, genetic influences explain 77–88% of the variance in the thickness of the mid-sagittal area of the corpus callosum , the volume of the caudate nucleus , and the volumes of the parietal and temporal lobes. [ 3 ]
Numerous pharmacological developments have been made to help organize neural circuitry for patients with learning disorders. The cholinergic and glutamatergic systems in the brain serve an important role in learning, memory, and the developmental organization of neuronal circuitry. These systems help to capitalize on the critical period and organize synaptic transmission . Autism and other learning disabilities have been targeted with drugs focusing on cholinergic and glutamatergic transmission. These drugs increase the amount of acetylcholine present in the brain by increasing the production of acetylcholine precursors, as well as inhibiting acetylcholine degradation by cholinesterases . By focusing on heightening the activity of this system, the brain's responsiveness to activity-dependent plasticity is improved. Specifically, glutamatergic drugs may reduce the threshold for LTP , promote more normal dendritic spine morphology, and retain a greater number of useful synaptic connections. Cholinergic drugs may reconnect the basal forebrain with the cortex and hippocampus , connections that are often disrupted in patients with learning disorders. [ 8 ]
Psychological factors and preconceived notions about intelligence can be as influential on intelligence as genetic makeup. Children with early chronic stress show impaired corticolimbic connectivity in development. Early chronic stress is defined as inconsistent or inadequate care-giving and disruption to early rearing environment. These children showed decreased cognitive function , especially in fluid cognition , or the ability to effectively utilize working memory . The lack of connectivity between the limbic system and the prefrontal cortex can be blamed for this deficiency. [ 9 ]
In the study of malleable intelligence, behavioral factors are often the most intriguing because these are factors humans can seek to control. There are numerous behavioral factors that affect intellectual development and neural plasticity . The key is plasticity, which is caused by experience-driven electrical activation of neurons . This experience-driven activation causes axons to sprout new branches and develop new presynaptic terminals . [ 2 ] These new branches often lead to greater mental processing in different areas.
As previously discussed, the critical period is a time of neural pruning and great intellectual development. [ 2 ] | https://en.wikipedia.org/wiki/Malleability_of_intelligence |
In mathematics — specifically, in measure theory — Malliavin's absolute continuity lemma is a result due to the French mathematician Paul Malliavin that plays a foundational rôle in the regularity ( smoothness ) theorems of the Malliavin calculus . Malliavin's lemma gives a sufficient condition for a finite Borel measure to be absolutely continuous with respect to Lebesgue measure .
Let μ be a finite Borel measure on n - dimensional Euclidean space R n . Suppose that, for every x ∈ R n , there exists a constant C = C ( x ) such that
for every C ∞ function φ : R n → R with compact support . Then μ is absolutely continuous with respect to n -dimensional Lebesgue measure λ n on R n . In the above, D φ ( y ) denotes the Fréchet derivative of φ at y and || φ || ∞ denotes the supremum norm of φ . | https://en.wikipedia.org/wiki/Malliavin's_absolute_continuity_lemma |
In probability theory and related fields, Malliavin calculus is a set of mathematical techniques and ideas that extend the mathematical field of calculus of variations from deterministic functions to stochastic processes . In particular, it allows the computation of derivatives of random variables . Malliavin calculus is also called the stochastic calculus of variations . P. Malliavin first initiated the calculus on infinite dimensional space. Then, the significant contributors such as S. Kusuoka, D. Stroock, J-M. Bismut , Shinzo Watanabe , I. Shigekawa, and so on finally completed the foundations.
Malliavin calculus is named after Paul Malliavin whose ideas led to a proof that Hörmander's condition implies the existence and smoothness of a density for the solution of a stochastic differential equation ; Hörmander 's original proof was based on the theory of partial differential equations . The calculus has been applied to stochastic partial differential equations as well.
The calculus allows integration by parts with random variables; this operation is used in mathematical finance to compute the sensitivities of financial derivatives . The calculus has applications in, for example, stochastic filtering .
Malliavin introduced Malliavin calculus to provide a stochastic proof that Hörmander's condition implies the existence of a density for the solution of a stochastic differential equation ; Hörmander 's original proof was based on the theory of partial differential equations . His calculus enabled Malliavin to prove regularity bounds for the solution's density. The calculus has been applied to stochastic partial differential equations .
Consider a Wiener functional F {\displaystyle F} (a functional from the classical Wiener space ) and consider the task of finding a derivative for it. The natural idea would be to use the Gateaux derivative
however this does not always exist. Therefore it does make sense to find a new differential calculus for such spaces by limiting the directions.
The toy model of Malliavin calculus is an irreducible Gaussian probability space X = ( Ω , F , P , H ) {\displaystyle X=(\Omega ,{\mathcal {F}},P,{\mathcal {H}})} . This is a (complete) probability space ( Ω , F , P ) {\displaystyle (\Omega ,{\mathcal {F}},P)} together with a closed subspace H ⊂ L 2 ( Ω , F , P ) {\displaystyle {\mathcal {H}}\subset L^{2}(\Omega ,{\mathcal {F}},P)} such that all H ∈ H {\displaystyle H\in {\mathcal {H}}} are mean zero Gaussian variables and F = σ ( H : H ∈ H ) {\displaystyle {\mathcal {F}}=\sigma (H:H\in {\mathcal {H}})} . If one chooses a basis for H {\displaystyle {\mathcal {H}}} then one calls X {\displaystyle X} a numerical model . On the other hand, for any separable Hilbert space G {\displaystyle {\mathcal {G}}} exists a canonical irreducible Gaussian probability space Seg ( G ) {\displaystyle \operatorname {Seg} ({\mathcal {G}})} named the Segal model (named after Irving Segal ) having G {\displaystyle {\mathcal {G}}} as its Gaussian subspace. In this case for a g ∈ G {\displaystyle g\in {\mathcal {G}}} one notates the associated random variable in Seg ( G ) {\displaystyle \operatorname {Seg} ({\mathcal {G}})} as W ( g ) {\displaystyle W(g)} .
Properties of a Gaussian probability space that do not depend on the particular choice of basis are called intrinsic and such that do depend on the choice extrensic . [ 1 ] We denote the countably infinite product of real spaces as R N = ∏ i = 1 ∞ R {\displaystyle \mathbb {R} ^{\mathbb {N} }=\prod \limits _{i=1}^{\infty }\mathbb {R} } .
Recall the modern version of the Cameron-Martin theorem
In fact one can use here the Feldman–Hájek theorem to find that for any other h ∉ R {\displaystyle h\not \in R} such measure would be singular.
Let γ {\displaystyle \gamma } be the canonical Gaussian measure, by transferring the Cameron-Martin theorem from ( R N , B ( R N ) , γ N = ⊗ n ∈ N γ ) {\displaystyle (\mathbb {R} ^{\mathbb {N} },{\mathcal {B}}(\mathbb {R} ^{\mathbb {N} }),\gamma ^{\mathbb {N} }=\otimes _{n\in \mathbb {N} }\gamma )} into a numerical model X {\displaystyle X} , the additive group of H {\displaystyle {\mathcal {H}}} will define a quasi-automorphism group on Ω {\displaystyle \Omega } . A construction can be done as follows: choose an orthonormal basis in H {\displaystyle {\mathcal {H}}} , let τ α ( x ) = x + α {\displaystyle \tau _{\alpha }(x)=x+\alpha } denote the translation on R N {\displaystyle \mathbb {R} ^{\mathbb {N} }} by α {\displaystyle \alpha } , denote the map into the Cameron-Martin space by j : H → ℓ 2 {\displaystyle j:{\mathcal {H}}\to \ell ^{2}} , denote
we get a canonical representation of the additive group ρ : H → End ( L ∞ − 0 ( Ω , F , P ) ) {\displaystyle \rho :{\mathcal {H}}\to \operatorname {End} (L^{\infty -0}(\Omega ,{\mathcal {F}},P))} acting on the endomorphisms by defining
One can show that the action of ρ {\displaystyle \rho } is extrinsic meaning it does not depend on the choice of basis for H {\displaystyle {\mathcal {H}}} , further ρ ( h + h ′ ) = ρ ( h ) ρ ( h ′ ) {\displaystyle \rho (h+h')=\rho (h)\rho (h')} for h , h ′ ∈ H {\displaystyle h,h'\in {\mathcal {H}}} and for the infinitesimal generator of ( ρ ( h ) ) h {\displaystyle (\rho (h))_{h}} that
where I {\displaystyle I} is the identity operator and M h {\displaystyle M_{h}} denotes the multiplication operator by the random variable h ∈ H {\displaystyle h\in {\mathcal {H}}} (acting on the endomorphisms). In the case of an arbitrary Hilbert space G {\displaystyle {\mathcal {G}}} and the Segal model Seg ( G ) {\displaystyle \operatorname {Seg} ({\mathcal {G}})} one has j : G → ℓ 2 {\displaystyle j:{\mathcal {G}}\to \ell ^{2}} (and thus ρ : G → End ( L ∞ − 0 ( Ω , F , P ) ) {\displaystyle \rho :{\mathcal {G}}\to \operatorname {End} (L^{\infty -0}(\Omega ,{\mathcal {F}},P))} . Then the limit above becomes the multiplication operator by the random variable W ( g ) {\displaystyle W(g)} associated to g ∈ G {\displaystyle g\in {\mathcal {G}}} . [ 3 ]
For F ∈ L ∞ − 0 ( Ω , F , P ) {\displaystyle F\in L^{\infty -0}(\Omega ,{\mathcal {F}},P)} and h ∈ H {\displaystyle h\in {\mathcal {H}}} one now defines the directional derivative
Given a Hilbert space H {\displaystyle H} and a Segal model Seg ( H ) {\displaystyle \operatorname {Seg} (H)} with its Gaussian space H = { W ( h ) : h ∈ H } {\displaystyle {\mathcal {H}}=\{W(h):h\in H\}} . One can now deduce for F ∈ L ∞ − 0 ( Ω , F , P ) {\displaystyle F\in L^{\infty -0}(\Omega ,{\mathcal {F}},P)} the integration by parts formula
The usual invariance principle for Lebesgue integration over the whole real line is that, for any real number ε and integrable function f , the
following holds
This can be used to derive the integration by parts formula since, setting f = gh , it implies
A similar idea can be applied in stochastic analysis for the differentiation along a Cameron-Martin-Girsanov direction. Indeed, let h s {\displaystyle h_{s}} be a square-integrable predictable process and set
If W {\displaystyle W} is a Wiener process , the Girsanov theorem then yields the following analogue of the invariance principle:
Differentiating with respect to ε on both sides and evaluating at ε=0, one obtains the following integration by parts formula:
Here, the left-hand side is the Malliavin derivative of the random variable F {\displaystyle F} in the direction φ {\displaystyle \varphi } and the integral appearing on the right hand side should be interpreted as an Itô integral .
One of the most useful results from Malliavin calculus is the Clark–Ocone theorem , which allows the process in the martingale representation theorem to be identified explicitly. A simplified version of this theorem is as follows:
Consider the standard Wiener measure on the canonical space C [ 0 , 1 ] {\displaystyle C[0,1]} , equipped with its canonical filtration. For F : C [ 0 , 1 ] → R {\displaystyle F:C[0,1]\to \mathbb {R} } satisfying E ( F ( X ) 2 ) < ∞ {\displaystyle E(F(X)^{2})<\infty } which is Lipschitz and such that F has a strong derivative kernel, in the sense that
for φ {\displaystyle \varphi } in C [0,1]
then
where H is the previsible projection of F '( x , ( t ,1]) which may be viewed as the derivative of the function F with respect to a suitable parallel shift of the process X over the portion ( t ,1] of its domain.
This may be more concisely expressed by
Much of the work in the formal development of the Malliavin calculus involves extending this result to the largest possible class of functionals F by replacing the derivative kernel used above by the " Malliavin derivative " denoted D t {\displaystyle D_{t}} in the above statement of the result. [ citation needed ]
The Skorokhod integral operator which is conventionally denoted δ is defined as the adjoint of the Malliavin derivative in the white noise case when the Hilbert space is an L 2 {\displaystyle L^{2}} space, thus for u in the domain of the operator which is a subset of L 2 ( [ 0 , ∞ ) × Ω ) {\displaystyle L^{2}([0,\infty )\times \Omega )} ,
for F in the domain of the Malliavin derivative, we require
where the inner product is that on L 2 [ 0 , ∞ ) {\displaystyle L^{2}[0,\infty )} viz
The existence of this adjoint follows from the Riesz representation theorem for linear operators on Hilbert spaces .
It can be shown that if u is adapted then
where the integral is to be understood in the Itô sense. Thus this provides a method of extending the Itô integral to non adapted integrands.
The calculus allows integration by parts with random variables ; this operation is used in mathematical finance to compute the sensitivities of financial derivatives . The calculus has applications for example in stochastic filtering . | https://en.wikipedia.org/wiki/Malliavin_calculus |
In mathematics , the Malliavin derivative [ 1 ] is a notion of derivative in the Malliavin calculus . Intuitively, it is the notion of derivative appropriate to paths in classical Wiener space , which are "usually" not differentiable in the usual sense. [ citation needed ]
Let H {\displaystyle H} be the Cameron–Martin space , and C 0 {\displaystyle C_{0}} denote classical Wiener space :
By the Sobolev embedding theorem , H ⊂ C 0 {\displaystyle H\subset C_{0}} . Let
denote the inclusion map .
Suppose that F : C 0 → R {\displaystyle F:C_{0}\to \mathbb {R} } is Fréchet differentiable . Then the Fréchet derivative is a map
i.e., for paths σ ∈ C 0 {\displaystyle \sigma \in C_{0}} , D F ( σ ) {\displaystyle \mathrm {D} F(\sigma )\;} is an element of C 0 ∗ {\displaystyle C_{0}^{*}} , the dual space to C 0 {\displaystyle C_{0}\;} . Denote by D H F ( σ ) {\displaystyle \mathrm {D} _{H}F(\sigma )\;} the continuous linear map H → R {\displaystyle H\to \mathbb {R} } defined by
sometimes known as the H -derivative . Now define ∇ H F : C 0 → H {\displaystyle \nabla _{H}F:C_{0}\to H} to be the adjoint of D H F {\displaystyle \mathrm {D} _{H}F\;} in the sense that
Then the Malliavin derivative D t {\displaystyle \mathrm {D} _{t}} is defined by
The domain of D t {\displaystyle \mathrm {D} _{t}} is the set F {\displaystyle \mathbf {F} } of all Fréchet differentiable real-valued functions on C 0 {\displaystyle C_{0}\;} ; the codomain is L 2 ( [ 0 , T ] ; R n ) {\displaystyle L^{2}([0,T];\mathbb {R} ^{n})} .
The Skorokhod integral δ {\displaystyle \delta \;} is defined to be the adjoint of the Malliavin derivative: | https://en.wikipedia.org/wiki/Malliavin_derivative |
Malligyong-1 ( Korean : 《만리경-1》호 ; Hanja : 萬里鏡 1号 ; lit. Telescope-1) is a type of North Korean reconnaissance satellite . [ 2 ]
The mission's first two launch attempts failed, with the third one succeeding on 21 November 2023. This was also the first successful flight of North Korea's new launch vehicle, the Chollima-1 . [ 3 ]
Malligyong-1 is North Korea's first spy satellite. [ 4 ] It is in a sun-synchronous orbit at about 500 kilometres (310 mi) altitude, [ 5 ] and will provide a global optical imaging surveillance capability of several countries. [ 6 ] [ 7 ] The resolution of the imaging capability is not generally known, [ 8 ] [ 9 ] [ 10 ] [ 11 ] but according to Daily NK , the Malligyong-1's imagery resolution is lower than the resolution of Google 's satellite imagery. [ 12 ]
Daily NK also stated that the satellite used Japanese camera, but it was alleged to be not capable of providing meaningful military surveillance data. [ 12 ]
The first launch attempt occurred on 31 May 2023. The second stage of the launch vehicle, Chollima-1 , ignited too early into the mission, causing the mission to fail. [ 7 ] Evacuation alerts were issued in Seoul and Okinawa Prefecture . [ 13 ] The North Korean government quickly announced the launch failure. [ 14 ]
The remains crashed into the Yellow Sea [ 2 ] and South Korea attempted to salvage the remainder of the rocket, searching a site 200 kilometres (120 mi) off the coast of Eocheongdo. The South Korean Ministry of Defence released an image of a white cylinder, suspected to be a part of the rocket. [ 14 ]
North Korea's National Aerospace Technology Administration (NATA) said it would investigate before conducting a second satellite launch. The White House, Japan, and the UN Secretary-General condemned the launch, citing violations of Security Council resolutions prohibiting the use of ballistic missile technology . [ 15 ]
A second launch attempt of the satellite took place on 23 August 2023, again onboard a Chollima-1 launch vehicle. The launch resulted again in a failure with the loss of the satellite, this time caused by an error in the emergency flight termination system during the third-stage flight. [ 16 ]
A third launch attempt was initially scheduled to take place in October 2023 but was later moved to November due to some delays in fixing the technical issues that caused the previous failures. The launch took place on 21 November 2023. The South Korean news agency Yonhap quoted its counterpart in the North, the Korean Central News Agency, as saying the satellite had been successfully inserted in the predetermined orbit, resulting in the first successful flight of the Chollima-1 launch vehicle. [ 3 ] However, no immediate independent observations could be made. [ 17 ] The probe has been confirmed to be in orbit, however, its status is not known. [ 18 ]
According to NATA, Kim Jong Un oversaw the launch. [ 17 ]
On 27 February 2024, South Korean Defense Minister , Shin Won-sik stated that there were no signs of Malligyong-1 being operational, as well as the possibility of a satellite launch by North Korea in March 2024. [ 19 ]
According to Dutch astronomer Marco Langbroek, between 18 and 24 February 2024, Malligyong-1 had made orbital raising maneuvers to prolong time in orbit and to circularize its orbit, this has demonstrated that satellite has on-board propulsion and is communicating with ground communication stations in North Korea. [ 20 ] [ 21 ] Commands for orbit raising maneuvers were transmitted from North Korea. [ 22 ] Further orbital raising maneuvers were made from 3-7 June 2024, 6-10 September 2024 and 16-18 January 2025. [ 23 ] [ 24 ] [ 25 ]
A fourth launch attempt of a new satellite, called Malligyong-1-1 ( 《만리경-1-1》호 ; lit. Telescope-1-1), took place on 27 May 2024, onboard an unnamed new launch vehicle using liquid-oxygen and petroleum propellants. The launch resulted again in a failure with the loss of the satellite. [ 26 ] | https://en.wikipedia.org/wiki/Malligyong-1 |
In organic chemistry , the Mallory reaction is a photochemical -cyclization– elimination reaction of di aryl - ethylene structures to form phenanthrenes and other polycyclic form polycyclic aromatic hydrocarbons and heteroaromatics. [ 1 ] [ 2 ] This name reaction is named for Frank Mallory , who discovered it while a graduate student. [ 3 ]
Under UV irradiation, stilbene and its derivatives undergo intramolecular cyclization to form dihydrophenanthrenes . In the presence of an oxidant , the dihydrophenanthrenes aromatize to give polycyclic aromatics. Typically, the dihydrophenanthrenes themselves are relatively unstable, and revert to cis -stilbenes in the absence of a hydrogen-trapping agent. Suitably substituted stilbenes may undergo irreversible, rearomatizing elimination or [1,n]-shift processes in the absence of an oxidant. Aryl enynes, [ 4 ] heteroatomic stilbene derivatives (e.g. amides [ 5 ] ), and substrates containing a single heteroatom in place of the stilbene double bond [ 6 ] also undergo the reaction.
Regardless of the presence or absence of an oxidant, the first step of the reaction is photochemical excitation of a stilbene or similar structure, leading to formation of a dihydrophenanthrene or similar intermediate. For stilbene and other chemicals containing a double-bond linker between the two aromatic rings, the excited structure can undergo reversible cis - trans isomerization. Although only cis structures can undergo the cyclization step themselves, trans structures can isomerize in situ and then cyclize. [ 2 ] In keeping with the Woodward–Hoffmann rules , molecular orbital symmetry analysis of the photochemical reaction of the six-electron system explains the trans relative configuration at the newly bound centers by a conrotatory process. [ 7 ]
This cyclization is reversible, but several other subsequent reactions can occur instead, depending on structural details and whether certain other reagents are present.
In the presence of an oxidizing agent , the cyclized intermediate can be oxidized to aromatize the rings. For example, dihydrophenanthrene becomes phenanthrene. Oxygen and iodine are the most commonly employed oxidants.
For most substrates, in the absence of an oxidant, the dihydrophenanthrene intermediate may reversibly open to the corresponding cis -stilbene. However, suitably substituted stilbenes cyclize irreversibly if an aromatizing elimination or hydrogen shift process can take place. Examples of these transformations are provided below. [ 8 ] [ 9 ] [ 10 ]
Photocyclization can be carried out with ortho -, meta -, and para -substituted stilbene substrates. ortho -Substituted substrates generally give 1-substituted phenanthrenes, unless the substituent
is a good leaving group, in which case elimination to form unsubstituted phenanthrene occurs. [ 11 ] meta -
Substituted substrates give mixtures of 2- and 4-substituted products.
Substitution of the exocyclic double bond is well tolerated. Polycyclic aromatic compounds can be
synthesized using substrates containing multiple aromatic rings. [ 9 ]
Stilbene derivatives containing fused aromatic systems may cyclize using either of two nonequivalent ortho carbons. Which carbon reacts depends on both steric and electronic factors. Electronically, the
dihydrophenanthrene intermediate exhibiting greater aromatic stabilization is preferred. For instance, in
1-naphthyl-2-phenylethylene, electronic factors favor the formation of 1 over 2 in a ratio of 98.5:1.5. [ 12 ]
ortho -Terphenyl substrates cyclize to the corresponding triphenylenes in the presence of an
oxidant, such as iodine. Oxygen is unsatisfactory because ring-opening to highly stabilized terphenyl is
faster than oxidation when oxygen is used. [ 13 ]
Amides may cyclize to form lactams. Esters, which exist primarily in the trans conformation about the
C-O single bond, do not undergo this process efficiently. [ 14 ]
Photocyclization can also form five-membered rings. In the vinyl naphthalene series, both oxidative [ 10 ] and
non-oxidative processes are possible; although the latter requires a proton-transfer catalyst. [ 15 ]
Cyclization of arylvinyl- or diarylamines provides indolines and carbazoles, respectively. In one
interesting example, the use of circularly polarized light provided 3 in slight enantiomeric excess. [ 16 ]
In 2015, Li and Twieg reported a novel derivative of Mallory type photocyclizations and named it as photocyclodehydrofluorination (PCDHF). In the cyclization a stilbene (or ortho-terphenyl) with a pentafluorophenyl group, the fluorine atom can be used as a facile leaving group. [ 17 ]
Photocyclization can be used as the final step of a sequence to generate a fused aromatic ring at a benzylic position. After benzylic bromization with N -bromosuccinimide, transformation to the phosphonium salt, and a Wittig reaction with anaromatic aldehyde, photocyclization fuses the aromatic rings. Iteration of this sequence results in helicenes. [ 18 ]
Several other methods are available to synthesize the phenanthrene ring system; however, most of these are longer or less functional group tolerant than photocyclization. The Haworth reaction and the Wagner-Meerwein -type ring-expansion are two such alternatives. [ 19 ] | https://en.wikipedia.org/wiki/Mallory_reaction |
In mathematics , Malmquist's theorem , is the name of any of the three theorems proved by Axel Johannes Malmquist ( 1913 , 1920 , 1941 ). These theorems restrict the forms of first order algebraic differential equations which have transcendental meromorphic or algebroid solutions.
Theorem (1913). If the differential equation
where R ( z , w ) is a rational function , has a transcendental meromorphic solution, then R is a polynomial of degree at most 2 with respect to w ; in other words the differential equation is a Riccati equation , or linear.
Theorem (1920). If an irreducible differential equation
where F is a polynomial, has a transcendental meromorphic solution, then the equation has no movable singularities . Moreover, it can be algebraically reduced either to a Riccati equation or to
where P is a polynomial of degree 3 with respect to w .
Theorem (1941). If an irreducible differential equation
where F is a polynomial, has a transcendental algebroid solution, then it can be algebraically reduced to an equation that has no movable singularities.
A modern account of theorems 1913, 1920 is given in the paper of A. Eremenko (1982) | https://en.wikipedia.org/wiki/Malmquist's_theorem |
Malnutrition occurs when an organism gets too few or too many nutrients , resulting in health problems. [ 11 ] [ 12 ] Specifically, it is a deficiency , excess, or imbalance of energy, protein and other nutrients which adversely affects the body's tissues and form. [ 13 ]
Malnutrition is a category of diseases that includes undernutrition and overnutrition . [ 14 ] Undernutrition is a lack of nutrients, which can result in stunted growth , wasting , and being underweight . [ 15 ] A surplus of nutrients causes overnutrition, which can result in obesity or toxic levels of micronutrients. In some developing countries , overnutrition in the form of obesity is beginning to appear within the same communities as undernutrition. [ 16 ]
Most clinical studies use the term 'malnutrition' to refer to undernutrition. However, the use of 'malnutrition' instead of 'undernutrition' makes it impossible to distinguish between undernutrition and overnutrition, a less acknowledged form of malnutrition. [ 13 ] [ 17 ] Accordingly, a 2019 report by The Lancet Commission suggested expanding the definition of malnutrition to include "all its forms, including obesity, undernutrition, and other dietary risks." [ 18 ] The World Health Organization [ 19 ] and The Lancet Commission have also identified "[t]he double burden of malnutrition", which occurs from "the coexistence of overnutrition (overweight and obesity) alongside undernutrition (stunted growth and wasting)." [ 20 ] [ 21 ]
It was estimated in 2017 that nearly one in three persons globally had at least one form of malnutrition: wasting , stunting , vitamin or mineral deficiency, overweight, obesity, or diet-related noncommunicable diseases. [ 22 ] Undernutrition is more common in developing countries . [ 23 ] Stunting is more prevalent in urban slums than in rural areas. [ 24 ]
Studies on malnutrition have the population categorised into different groups including infants, under-five children, children, adolescents, pregnant women, adults and the elderly population. The use of different growth references in different studies leads to variances in the undernutrition prevalence reported in different studies. Some of the growth references used in studies include the National Center for Health Statistics (NCHS) growth charts, WHO reference 2007, Centers for Disease Control and Prevention (CDC) growth charts, National Health and Nutrition Examination Survey (NHANES), WHO reference 1995, Obesity Task Force (IOTF) criteria and Indian Academy of Pediatrics (IAP) growth charts. [ 25 ] In 2023, an estimated 28.9 percent of the global population – 2.33 billion people – were moderately or severely food insecure. [ 26 ]
The prevalence of undernutrition is highest among children under five. [ 24 ] In 2021, 148.1 million children under five years old were stunted, 45 million were wasted, and 37 million were overweight or obese. [ 27 ] The same year, an estimated 45% of deaths in children were linked to undernutrition. [ 27 ] [ 5 ] As of 2020 [update] , the prevalence of wasting among children under five in South Asia was reported to be 16% moderately or severely wasted. [ 24 ] As of 2022 [update] , UNICEF reported this prevalence as having slightly improved, but still being at 14.8%. [ 28 ] India has one of the highest burdens of wasting in Asia with over 20% wasted children. [ 29 ] However, the burden of undernutrition among under-five children in African countries is much higher. A pooled analysis of the prevalence of chronic undernutrition among under-five children in East Africa was identified to be 33.3%. This prevalence of undernutrition among under-five children ranged from 21.9% in Kenya to 53% in Burundi. [ 30 ]
In Tanzania, the prevalence of stunting, among children under five varied from 41% in lowland and 64.5% in highland areas. Undernutrition by underweight and wasting was 11.5% and 2.5% in lowland and 22.% and 1.4% in the highland areas of Tanzania respectively. [ 31 ] In South Sudan, the prevalence of undernutrition explained by stunting, underweight and wasting in under-five children were 23.8%, 4.8% and 2.3% respectively. [ 32 ] In 28 countries, at least 30% of children were still affected by stunting in 2022. [ 33 ]
Vitamin A deficiency affects one third of children under age 5 around the world, [ 34 ] leading to 670,000 deaths and 250,000–500,000 cases of blindness . [ 35 ] Vitamin A supplementation has been shown to reduce all-cause mortality by 12 to 24%. [ 36 ]
As of June 2021, 1.9 billion adults were overweight or obese, and 462 million adults were underweight. [ 27 ] Globally, two billion people had iodine deficiency in 2017. [ 37 ] In 2020, 900 million women and children had anemia, which is often caused by iron deficiency. [ 38 ] More than 3.1 billion people in the world – 42% – were unable to afford a healthy diet in 2021. [ 39 ]
Certain groups have higher rates of undernutrition, including elderly people and women (in particular while pregnant or breastfeeding children under five years of age). Undernutrition is an increasing health problem in people aged over 65 years, even in developed countries, especially among nursing home residents and in acute care hospitals. [ 40 ] In the elderly, undernutrition is more commonly due to physical, psychological, and social factors, not a lack of food. [ 41 ] Age-related reduced dietary intake due to chewing and swallowing problems, sensory decline, depression, imbalanced gut microbiome, poverty and loneliness are major contributors to undernutrition in the elderly population. Malnutrition is also attributed due to wrong diet plan adopted by people who aim to reduce their weight without medical practitioners or nutritionist advice. [ 42 ]
There has been a global increase in food insecurity and hunger between 2011 and 2020. In 2015, 795 million people (about one in ten people on earth) had undernutrition. [ 9 ] [ 43 ] It is estimated that between 691 and 783 million people in the world faced hunger in 2022. [ 44 ] According to UNICEF, 2.4 billion people were moderately or severely food insecure in 2022, 391 million more than in 2019. [ 45 ]
These increases are partially related to the COVID-19 pandemic , which continues to highlight the weaknesses of current food and health systems. It has contributed to food insecurity , increasing hunger worldwide; meanwhile, lower physical activity during lockdowns has contributed to increases in overweight and obesity. [ 46 ] In 2020, experts estimated that by the end of the year, the pandemic could have double the number of people at risk of suffering acute hunger, around 130 million more undernourished people. [ 47 ] [ 48 ] Similarly, experts estimated that the prevalence of moderate and severe wasting could increase by 14% due to COVID-19; coupled with reductions in nutrition and health services coverage, this could result in over 128,000 additional deaths among children under 5 in 2020 alone. [ 46 ] Although COVID-19 is less severe in children than in adults, the risk of severe disease increases with undernutrition. [ 49 ]
Other major causes of hunger include manmade conflicts, climate changes , and economic downturns. [ 50 ]
Undernutrition can occur either due to protein-energy wasting or as a result of micronutrient deficiencies. [ 2 ] [ 51 ] [ 27 ] [ 1 ] [ 3 ] [ 52 ] [ 53 ] It adversely affects physical and mental functioning, and causes changes in body composition and body cell mass. [ 54 ] [ 55 ] Undernutrition is a major health problem, causing the highest mortality rate in children, particularly in those under 5 years, and is responsible for long-lasting physiologic effects. [ 56 ] It is a barrier to the complete physical and mental development of children. [ 53 ]
Undernutrition can manifest as stunting, wasting, and underweight. If undernutrition occurs during pregnancy, or before two years of age, it may result in permanent problems with physical and mental development. [ 1 ] [ 52 ] Extreme undernutrition can cause starvation , chronic hunger, Severe Acute Malnutrition (SAM), and/or Moderate Acute Malnutrition (MAM).
The signs and symptoms of micronutrient deficiencies depend on which micronutrient is lacking. [ 2 ] However, undernourished people are often thin and short, with very poor energy levels; and swelling in the legs and abdomen is also common. [ 1 ] [ 2 ] [ 52 ] People who are undernourished often get infections and frequently feel cold. [ 2 ]
Micronutrient undernutrition results from insufficient intake of vitamins and minerals. [ 27 ] Worldwide, deficiencies in iodine , Vitamin A , and iron are the most common. Children and pregnant women in low-income countries are at especially high risk for micronutrient deficiencies. [ 27 ] [ 52 ]
Anemia is most commonly caused by iron deficiency , but can also result from other micronutrient deficiencies and diseases. This condition can have major health consequences. [ 57 ]
It is possible to have overnutrition simultaneously with micronutrient deficiencies; this condition is termed the double burden of malnutrition .
'Undernutrition' sometimes refers specifically to protein–energy malnutrition (PEM). [ 2 ] [ 58 ] This condition involves both micronutrient deficiencies and an imbalance of protein intake and energy expenditure. [ 51 ] It differs from calorie restriction in that calorie restriction may not result in negative health effects. Hypoalimentation (underfeeding) is one cause of undernutrition. [ 59 ]
Two forms of PEM are kwashiorkor and marasmus ; both commonly coexist. [ 11 ]
Kwashiorkor is primarily caused by inadequate protein intake. [ 11 ] Its symptoms include edema , wasting, liver enlargement , hypoalbuminaemia , and steatosis ; the condition may also cause depigmentation of skin and hair. [ 11 ] The disorder is further identified by a characteristic swelling of the belly , and extremities which disguises the patient's undernourished condition. [ 60 ] 'Kwashiorkor' means 'displaced child' and is derived from the Ga language of coastal Ghana in West Africa. It means "the sickness the baby gets when the next baby is born," as it often occurs when the older child is deprived of breastfeeding and weaned to a diet composed largely of carbohydrates. [ 61 ]
Marasmus (meaning 'to waste away') can result from a sustained diet that is deficient in both protein and energy. This causes their metabolism to adapt to prolong survival. [ 11 ] The primary symptoms are severe wasting, leaving little or no edema ; minimal subcutaneous fat ; and abnormal serum albumin levels. [ 11 ] It is traditionally seen in cases of famine , significant food restriction, or severe anorexia . [ 11 ] Conditions are characterized by extreme wasting of the muscles and a gaunt expression. [ 60 ]
Excessive consumption of energy-dense foods and drinks and limited physical activity causes overnutrition. [ 62 ] It causes overweight, defined as a body mass index (BMI) of 25 or more, and can lead to obesity (a BMI of 30 or more). [ 27 ] [ 2 ] Obesity has become a major health issue worldwide. [ 63 ] Overnutrition is linked to chronic non-communicable diseases like diabetes , certain cancers, and cardiovascular diseases . Hence identifying and addressing the immediate risk factors has become a major health priority. [ 64 ] The recent evidence on the impact of diet-induced obesity in fathers and mothers around the time of conception is identified to negatively program the health outcomes of multiple generations. [ 65 ]
According to UNICEF, at least 1 in every 10 children under five is overweight in 33 countries. [ 66 ]
In 1956, Gómez and Galvan studied factors associated with death in a group of undernourished children in a hospital in Mexico City , Mexico. They defined three categories of malnutrition: first, second, and third degree. [ 67 ] The degree of malnutrition is calculated based on a child's body size compared to the median weight for their age. [ 68 ] The risk of death increases with increasing degrees of malnutrition. [ 67 ]
An adaptation of Gomez's original classification is still used today. While it provides a way to compare malnutrition within and between populations, this classification system has been criticized for being " arbitrary " and for not considering overweight as a form of malnutrition. Also, height alone may not be the best indicator of malnutrition; children who are born prematurely may be considered short for their age even if they have good nutrition. [ 69 ]
In the 1970s, John Conrad Waterlow established a new classification system for malnutrition. [ 70 ] Instead of using just weight for age measurements, Waterlow's system combines weight-for-height (indicating acute episodes of malnutrition) with height-for-age to show the stunting that results from chronic malnutrition. [ 71 ] One advantage of the Waterlow classification is that weight for height can be calculated even if a child's age is unknown. [ 70 ]
The World Health Organization frequently uses these classifications of malnutrition, with some modifications. [ 68 ]
Undernutrition weakens every part of the immune system . [ 72 ] Protein and energy undernutrition increases susceptibility to infection; so do deficiencies of specific micronutrients (including iron, zinc , and vitamins). [ 72 ] In communities or areas that lack access to safe drinking water , these additional health risks present a critical problem. [ citation needed ]
Undernutrition plays a major role in the onset of active tuberculosis . [ 73 ] It also raises the risk of HIV transmission from mother to child, and increases replication of the virus . [ 72 ] Undernutrition can cause vitamin-deficiency-related diseases like scurvy and rickets . As undernutrition worsens, those affected have less energy and experience impairment in brain functions. [ citation needed ]
Undernutrition can also cause acute problems, like hypoglycemia (low blood sugar ). This condition can cause lethargy, limpness, seizures , and loss of consciousness . Children are particularly at risk and can become hypoglycemic after 4 to 6 hours without food. Dehydration can also occur in malnourished people, and can be life-threatening, especially in babies and small children. [ citation needed ]
There are many different signs of dehydration in undernourished people. These can include sunken eyes; a very dry mouth; decreased urine output and/or dark urine; increased heart rate with decreasing blood pressure; and altered mental status .
Protein-calorie malnutrition can cause cognitive impairments . This most commonly occurs in people who were malnourished during a "critical period ... from the final third of gestation to the first 2 years of life". [ 74 ] For example, in children under two years of age, iron deficiency anemia is likely to affect brain function acutely, and probably also chronically. Similarly, folate deficiency has been linked to neural tube defects . [ 75 ]
Iodine deficiency is "the most common preventable cause of mental impairment worldwide." [ 76 ] [ 77 ] "Even moderate [iodine] deficiency, especially in pregnant women and infants , lowers intelligence by 10 to 15 I.Q. points , shaving incalculable potential off a nation's development." [ 76 ] Among those affected, very few people experience the most visible and severe effects: disabling goiters , cretinism and dwarfism . These effects occur most commonly in mountain villages. However, 16 percent of the world's people have at least mild goiter (a swollen thyroid gland in the neck)." [ 76 ] [ 78 ]
Social conditions have a significant influence on the health of people. [ 79 ] The social determinants of undernutrition mainly include poor education, poverty, disease burden and lack of women's empowerment. [ 80 ] Identifying and addressing these determinants can eliminate undernutrition in the long term. [ 80 ] Identification of the social conditions that causes malnutrition in children under five has received significant research attention as it is a major public health problem. [ citation needed ]
Undernutrition most commonly results from a lack of access to high-quality, nutritious food. [ 5 ] The household income is a socio-economic variable that influences the access to nutritious food and the probability of under and overnutrition in a community. [ 81 ] In the study by Ghattas et al. (2020), the probability of overnutrition is significantly higher in higher-income families than in disadvantaged families. [ 21 ] High food prices is a major factor preventing low income households from getting nutritious food [ 1 ] [ 5 ] For example, Khan and Kraemer (2009) found that in Bangladesh , low socioeconomic status was associated with chronic malnutrition since it inhibited purchase of nutritious foods (like milk, meat, poultry, and fruits). [ 82 ]
Food shortages may also contribute to malnutritions in countries which lack technology. However, in the developing world, eighty percent of malnourished children live in countries that produce food surpluses, according to estimates from the Food and Agriculture Organization (FAO) . [ 83 ] The economist Amartya Sen observes that, in recent decades, famine has always been a problem of food distribution , purchasing power , and/or poverty, since there has always been enough food for everyone in the world. [ 84 ]
There are also sociopolitical causes of malnutrition. For example, the population of a community might be at increased risk for malnutrition if government is poor and the area lacks health-related services. On a smaller scale, certain households or individuals may be at an even higher risk due to differences in income levels , access to land, or levels of education. [ 85 ] Community plays a crucial role in addressing the social causes of malnutrition. [ 86 ] For example, communities with high social support and knowledge sharing about social protection programs can enable better public service demands. [ 87 ] Better public service demands and social protection programs minimise the risk of malnutrition in these communities.
It is argued that commodity speculators are increasing the cost of food. As the real-estate bubble in the United States was collapsing, it is said that trillions of dollars moved to invest in food and primary commodities, causing the 2007–2008 food price crisis . [ 88 ]
The use of biofuels as a replacement for traditional fuels raises the price of food. [ 89 ] The United Nations special rapporteur on the right to food , Jean Ziegler proposes that agricultural waste , such as corn cobs and banana leaves , should be used as fuel instead of crops. [ 90 ]
In some developing countries, overnutrition (in the form of obesity) is beginning to appear in the same communities where malnutrition occurs. [ 91 ] Overnutrition increases with urbanisation, food commercialisation and technological developments and increases physical inactivity. [ 92 ] Variations in the health status of individuals in the same society are associated with the societal structure and an individual's socioeconomic status which leads to income inequality, racism, educational differences and lack of opportunities. [ 93 ]
Infectious diseases which increase nutrient requirements, such as gastroenteritis , [ 94 ] pneumonia , malaria , and measles , can cause malnutrition. [ 5 ] So can some chronic illnesses, especially HIV/AIDS . [ 95 ] [ 96 ]
Malnutrition can also result from abnormal nutrient loss due to diarrhea or chronic small bowel illnesses, like Crohn's disease or untreated coeliac disease . [ 4 ] [ 8 ] [ 97 ] "Secondary malnutrition" can result from increased energy expenditure. [ 68 ] [ 98 ]
In infants, a lack of breastfeeding may contribute to undernourishment. [ 68 ] [ 98 ] Anorexia nervosa and bariatric surgery can also cause malnutrition. [ 99 ] [ 100 ]
Undernutrition due to lack of adequate breastfeeding is associated with the deaths of an estimated one million children annually. Illegal advertising of breast-milk substitutes contributed to malnutrition and continued three decades after its 1981 prohibition under the WHO International Code of Marketing Breast Milk Substitutes . [ 101 ]
Maternal malnutrition can also factor into the poor health or death of a baby. Over 800,000 neonatal deaths have occurred because of deficient growth of the fetus in the mother's womb . [ 102 ]
Deriving too much of one's diet from a single source, such as eating almost exclusively potato, maize or rice, can cause malnutrition. This may either be from a lack of education about proper nutrition, only having access to a single food source, or from poor healthcare access and unhealthy environments. [ 103 ] [ 104 ]
It is not just the total amount of calories that matters but specific nutritional deficiencies such as vitamin A deficiency, iron deficiency or zinc deficiency can also increase risk of death. [ 105 ]
Overnutrition caused by overeating is also a form of malnutrition. In the United States, more than half of all adults are now overweight—a condition that, like hunger, increases susceptibility to disease and disability, reduces worker productivity , and lowers life expectancy . [ 83 ] Overeating is much more common in the United States, since most people have adequate access to food. Many parts of the world have access to a surplus of non-nutritious food. Increased sedentary lifestyles also contribute to overnutrition. Yale University psychologist Kelly Brownell calls this a " toxic food environment ", where fat- and sugar-laden foods have taken precedence over healthy nutritious foods. [ 83 ]
In these developed countries, overnutrition can be prevented by choosing the right kind of food. More fast food is consumed per capita in the United States than in any other country. This mass consumption of fast food results from its affordability and accessibility. Fast food, which is low in cost and nutrition, is high in calories. Due to increasing urbanization and automation , people are living more sedentary lifestyles. These factors combine to make weight gain difficult to avoid. [ 106 ]
Overnutrition also occurs in developing countries. It has appeared in parts of developing countries where income is on the rise. [ 83 ] It is also a problem in countries where hunger and poverty persist. Economic development, rapid urbanisation and shifting dietary patterns have increased the burden of overnutrition in the cities of low and middle-income countries. [ 107 ] In China, consumption of high-fat foods has increased, while consumption of rice and other goods has decreased. [ 83 ] Overeating leads to many diseases, such as heart disease and diabetes, that may be fatal.
Local food shortages can be caused by a lack of arable land , adverse weather, and/or poorer farming skills (like inadequate crop rotation ). They can also occur in areas which lack the technology or resources needed for the higher yields found in modern agriculture. These resources include fertilizers , pesticides , irrigation , machinery , and storage facilities. As a result of widespread poverty, farmers and governments cannot provide enough of these resources to improve local yields. [ citation needed ]
Additionally, the World Bank and some wealthy donor countries have pressured developing countries to use free market policies. Even as the United States and Europe extensively subsidized their own farmers, they urged developing countries to cut or eliminate subsidized agricultural inputs, like fertilizer. [ 108 ] [ 109 ] Without subsidies, few (if any) farmers in developing countries can afford fertilizer at market prices . This leads to low agricultural production, low wages, and high, unaffordable food prices. [ 108 ] Fertilizer is also increasingly unavailable because Western environmental groups have fought to end its use due to environmental concerns. The Green Revolution pioneers Norman Borlaug and Keith Rosenberg cited as the obstacle to feeding Africa by . [ 110 ]
In the future, variety of factors could potentially disrupt global food supply and cause widespread malnutrition. According to UNICEF's projections, it is projected that almost 600 million people will be chronically undernourished in 2030. [ 111 ] [ 112 ]
Global warming is of importance to food security. Almost all malnourished people (95%) live in the tropics and subtropics , where the climate is relatively stable. According to the Intergovernmental Panel on Climate Change report in 2007, temperature increases in these regions are "very likely." [ 113 ] Even small changes in temperatures can make extreme weather conditions occur more frequently. [ 113 ] Extreme weather events, like drought, have a major impact on agricultural production, and hence nutrition. For example, the 1998–2001 Central Asian drought killed about 80 percent of livestock in Iran and caused a 50% reduction in wheat and barley crops there. [ 114 ] Other central Asian nations experienced similar losses. An increase in extreme weather such as drought in regions such as Sub-Saharan Africa would have even greater consequences in terms of malnutrition. Even without an increase of extreme weather events, a simple increase in temperature reduces the productivity of many crop species , and decreases food security in these regions. [ 113 ] [ 115 ]
Another threat is colony collapse disorder , a phenomenon where bees die in large numbers. [ 116 ] Since many agricultural crops worldwide are pollinated by bees , colony collapse disorder represents a threat to the global food supply. [ 117 ]
Reducing malnutrition is key part of the United Nations' Sustainable Development Goal 2 ( SDG2 ), "Zero Hunger", which aims to reduce malnutrition, undernutrition, and stunted child growth. [ 118 ] Managing severe acute undernutrition in a community setting has received significant research attention. [ 80 ] [ 53 ]
In the 1950s and 1960s, the Green Revolution aimed to bring modern Western agricultural techniques (like nitrogen fertilizers and pesticides ) to Asia. Investments in agriculture, such as fund fertilizers and seeds, increased food harvests and thus food production . Consequently, food prices and malnutrition decreased (as they had earlier in Western nations). [ 108 ] [ 119 ]
The Green Revolution was possible in Asia because of existing infrastructure and institutions, such as a system of roads and public seed companies that made seeds available. [ 120 ] These resources were in short supply in Africa, decreasing the Green Revolution's impact on the continent.
For example, almost five million of the 13 million people in Malawi used to need emergency food aid . However, in the early 2000s, the Malawian government changed its agricultural policies, and implemented subsidies for fertilizer and seed introduced against World Bank strictures. By 2007, farmers were producing record-breaking corn harvests. Corn production leaped to 3.4 million in 2007 compared to 1.2 million in 2005, making Malawi a major food exporter. [ 108 ] Consequently, food prices lowered and wages for farmworkers rose. [ 108 ] Such investments in agriculture are still needed in other African countries like the Democratic Republic of the Congo (DRC). Despite the country's great agricultural potential, the prevalence of malnutrition in the DRC is among the highest in the world. [ 121 ] Proponents for investing in agriculture include Jeffrey Sachs , who argues that wealthy countries should invest in fertilizer and seed for Africa's farmers. [ 108 ] [ 122 ]
Imported Ready to Use Therapeutic Food (RUTF) has been used to treat malnutrition in northern Nigeria . Some Nigerians also use soy kunu , a locally sourced and prepared blend consisting of peanut, millet and soybeans . [ 123 ]
New technology in agricultural production has great potential to combat undernutrition. It makes farming easier, thus improving agricultural yields. [ 124 ] By increasing farmers' incomes, this could reduce poverty. It would also open up area which farmers could use to diversify crops for household use.
The World Bank claims to be part of the solution to malnutrition, asserting that countries can best break the cycle of poverty and malnutrition by building export-led economies, which give them the financial means to buy foodstuffs on the world market.
Many aid groups have found that giving cash assistance (or cash vouchers) is more effective than donating food. Particularly in areas where food is available but unaffordable, giving cash assistance is a cheaper, faster, and more efficient way to deliver help to the hungry. [ 125 ] In 2008, the UN's World Food Program , the biggest non-governmental distributor of food, announced that it would begin distributing cash and vouchers instead of food in some areas, which Josette Sheeran , the WFP's executive director, described as a "revolution" in food aid. [ 125 ] [ 126 ] The aid agency Concern Worldwide piloted a method of giving cash assistance using a mobile phone operator , Safaricom , which runs a money transfer program that allows cash to be sent from one part of a country to another. [ 125 ]
However, during a drought, delivering food might be the most appropriate way to help people, especially those who live far from markets and thus have limited access to them. [ 125 ] Fred Cuny stated that "the chances of saving lives at the outset of a relief operation are greatly reduced when food is imported. By the time it arrives in the country and gets to people, many will have died." [ 127 ] U.S. law requires food aid to be purchased at home rather than in the countries where the hungry live; this is inefficient because approximately half of the money spent goes for transport. [ 128 ] Cuny further pointed out that "studies of every recent famine have shown that food was available in-country—though not always in the immediate food deficit area" and "even though by local standards the prices are too high for the poor to purchase it, it would usually be cheaper for a donor to buy the hoarded food at the inflated price than to import it from abroad." [ 129 ]
Food banks and soup kitchens address malnutrition in places where people lack money to buy food. A basic income has been proposed as a way to ensure that everyone has enough money to buy food and other basic needs. This is a form of social security in which all citizens or residents of a country regularly receive an unconditional sum of money, either from a government or some other public institution, in addition to any income received from elsewhere. [ 130 ]
Ethiopia pioneered a program that later became part of the World Bank's prescribed method for coping with a food crisis. Through the country's main food assistance program, the Productive Safety Net Program, Ethiopia provided rural residents who were chronically short of food a chance to work for food or cash. Foreign aid organizations like the World Food Program were then able to buy food locally from surplus areas to distribute in areas with a shortage of food. [ 131 ] Aid organizations now view the Ethiopian program as a model of how to best help hungry nations. [ citation needed ]
Successful initiatives also include Brazil 's recycling program for organic waste , which benefits farmers, the urban poor, and the city in general. City residents separate organic waste from their garbage, bag it, and then exchange it for fresh fruit and vegetables from local farmers. This reduces the country's waste while giving the urban poor a steady supply of nutritious food. [ 106 ]
Restricting population size is a proposed solution to malnutrition. Thomas Malthus argues that population growth can be controlled by natural disasters and by voluntary limits through "moral restraint." [ 132 ] Robert Chapman suggests that government policies are a necessary ingredient for curtailing global population growth. [ 133 ] The United Nations recognizes that poverty and malnutrition (as well as the environment) are interdependent and complementary with population growth. [ 134 ] According to the World Health Organization, " Family planning is key to slowing unsustainable population growth and the resulting negative impacts on the economy, environment, and national and regional development efforts". [ 135 ] However, more than 200 million women worldwide lack adequate access to family planning services.
There are different theories about what causes famine. Some theorists, like the Indian economist Amartya Sen, believe that the world has more than enough resources to sustain its population. In this view, malnutrition is caused by unequal distribution of resources and under- or unused arable land. [ 136 ] [ 137 ] For example, Sen argues that "no matter how a famine is caused, methods of breaking it call for a large supply of food in the Public Distribution System . This applies not only to organizing rationing and control, but also to undertaking work programmes and other methods of increasing purchasing power for those hit by shifts in exchange entitlements in a general inflationary situation." [ 84 ]
Food sovereignty is one suggested policy framework to resolve access issues. In this framework, people (rather than international market forces) have the right to define their own food, agricultural, livestock, and fishery systems. Food First is one of the primary think tanks working to build support for food sovereignty. Neoliberals advocate for an increasing role of the free market . [ citation needed ]
Another possible long-term solution to malnutrition is to increase access to health facilities in rural parts of the world. These facilities could monitor undernourished children, act as supplemental food distribution centers, and provide education on dietary needs. Similar facilities have already proven very successful in countries such as Peru and Ghana . [ 138 ] [ 139 ]
In 2016, estimates suggested that more widespread breastfeeding could prevent about 823,000 deaths annually of children under age 5. [ 140 ] In addition to reducing infant deaths , breast milk provides an important source of micronutrients - which are clinically proven to bolster children's immune systems – and provides long-term defenses against non-communicable and allergic diseases. [ 141 ] Breastfeeding may improve cognitive abilities in children, and correlates strongly with individual educational achievements. [ 141 ] [ 142 ] As previously noted, lack of proper breastfeeding is a major factor in child mortality rates, and is a primary determinant of disease development for children. The medical community recommends exclusively breastfeeding infants for 6 months, with nutritional whole food supplementation and continued breastfeeding up to 2 years or older for overall optimal health outcomes. [ 142 ] [ 143 ] [ 144 ] Exclusive breastfeeding is defined as giving an infant only breast milk for six months as a source of food and nutrition. [ 142 ] [ 144 ] This means no other liquids, including water or semi-solid foods. [ 144 ]
Breastfeeding is noted as one of the most cost-effective medical interventions benefiting child health. [ 143 ] While there are considerable differences among developed and developing countries , there are universal determinants of whether a mother breastfeeds or uses formula ; these include income, employment, social norms , and access to healthcare. [ 142 ] [ 143 ] Many newly made mothers face financial barriers; community-based healthcare workers have helped to alleviate these barriers, while also providing a viable alternative to traditional and expensive hospital-based medical care. [ 142 ] Recent studies, based upon surveys conducted from 1995 to 2010, show that exclusive breastfeeding rates have risen globally, from 33% to 39%. [ 144 ] Despite the growth rates, medical professionals acknowledge the need for improvement given the importance of exclusive breastfeeding. [ 144 ]
Starting around 2009, there was renewed international media and political attention focused on malnutrition. This resulted in part from spikes in food prices and the 2008 financial crisis . Additionally, there was an emerging consensus that combating malnutrition is one of the most cost-effective ways to contribute to development. This led to the 2010 launch of the UN's Scaling up Nutrition movement (SUN). [ 145 ]
In April 2012, a number of countries signed the Food Assistance Convention , the world's first legally binding international agreement on food aid. The following month, the Copenhagen Consensus recommended that politicians and private sector philanthropists should prioritize interventions against hunger and malnutrition to maximize the effectiveness of aid spending. The Consensus recommended prioritizing these interventions ahead of any others, including the fights against malaria and AIDS. [ 146 ]
In June 2015, the European Union and the Bill & Melinda Gates Foundation launched a partnership to combat undernutrition, especially in children. The program was first implemented in Bangladesh , Burundi , Ethiopia, Kenya , Laos and Niger . It aimed to help these countries improve information and analysis about nutrition, enabling them to develop effective national nutrition policies. [ 147 ]
Also in 2015, the UN's Food and Agriculture Organization created a partnership aimed at ending hunger in Africa by 2025. The African Union 's Comprehensive Africa Agriculture Development Programme (CAADP) provided the framework for the partnership. It includes a variety of interventions, including support for improved food production, a strengthening of social protection, and integration of the right to food into national legislation. [ 148 ]
The EndingHunger campaign is an online communication campaign whose goal is to raise awareness about hunger. The campaign has created viral videos depicting celebrities voicing their anger about the large number of hungry people in the world. [ citation needed ]
After the Millennium Development Goals expired in 2015, the Sustainable Development Goals became the main global policy focus to reduce hunger and poverty. In particular, Goal 2: Zero Hunger sets globally agreed-upon targets to wipe out hunger, end all forms of malnutrition, and make agriculture sustainable . [ 149 ] The partnership Compact2025 develops and disseminates evidence-based advice to politicians and other decision-makers, with the goal of ending hunger and undernutrition by 2025. [ 150 ] [ 151 ] [ 152 ] The International Food Policy Research Institute (IFPRI) led the partnership, with the involvement of UN organisations, non-governmental organizations (NGOs), and private foundations .
Efforts such as infant and young child feeding practices to improve nutrition are some of the common forms of development aid . [ 6 ] [ 153 ] Interventions often promote breastfeeding to reduce rates of malnutrition and death in children. [ 1 ] Some of these interventions have been successful. [ 7 ] For example, interventions with commodities such as ready to use therapeutic foods, ready to use supplementary foods, micronutrient intervention and vitamin supplementation were identified to significantly improve nutrition, reduce stunting and prevent diseases in communities with severe acute malnutrition. [ 80 ] In young children, outcomes improve when children between six months and two years of age receive complementary food (in addition to breast milk). [ 7 ] There is also good evidence that supports giving supplemental micronutrients to pregnant women and young children in the developing world. [ 7 ]
The United Nations has reported on the importance of nutritional counselling and support, for example in the care of HIV-infected persons, especially in "resource-constrained settings where malnutrition and food insecurity are endemic". [ 154 ] UNICEF provides nutritional counselling services for malnourished children in Afghanistan . [ 155 ]
Sending food and money is a common form of development aid, aimed at feeding hungry people. Some strategies help people buy food within local markets. [ 6 ] [ 156 ] Simply feeding students at school is insufficient. [ 6 ]
Longer-term measures include improving agricultural practices, [ 157 ] reducing poverty, and improving sanitation .
Measuring children is crucial to identifying malnourishment. In 2000, the United States Centers for Disease Control and Prevention (CDC) established the International Micronutrient Malnutrition Prevention and Control (IMMPaCt) program. It tested children for malnutrition by conducting a three-dimensional scan, using an iPad or a tablet . Its objective was to help doctors provide more efficient treatments. [ 158 ] There may be some chance of error when using this method. [ 158 ] The Screening Tool for the Assessment of Malnutrition in Paediatrics (STAMPa) is another method for the identification and evaluation of malnutrition in young children. [ 159 ] The assessment tool has fair to medium reliability in the identification of children at risk of malnutrition. [ 159 ]
A systematic review of 42 studies found that many approaches to mitigating acute malnutrition are equally effective; thus, intervention decisions can be based on cost-related factors. Overall, evidence for the effectiveness of acute malnutrition interventions is not robust. The limited evidence related to cost indicates that community and outpatient management of children with uncomplicated malnutrition may be the most cost-effective strategy. [ 160 ]
Regularly measuring and charting children's growth and including activities to promote health (an intervention called growth monitoring and promotion, also known as GPM) is often considered by policy makers and is recommended by the World Health Organization . [ 161 ] This program is often performed at the same time as a child has their regular immunizations . [ 162 ] Despite widespread use of this type of program, further studies are needed to understand the impact of these programs on overall child health and how to better address faltering growth in a child and improve practices related to feeding children in lower to middle income countries. [ 162 ]
It is often possible to manage severe malnutrition within a person's home, using ready-to-use therapeutic foods . [ 7 ] In people with severe malnutrition complicated by other health problems, treatment in a hospital setting is recommended. [ 7 ] In-hospital treatment often involves managing low blood sugar , maintaining adequate body temperature , addressing dehydration , and gradual feeding. [ 7 ] [ 163 ]
Routine antibiotics are usually recommended because malnutrition weakens the immune system, causing a high risk of infection. [ 163 ] Additionally, broad spectrum antibiotics are recommended in all severely undernourished children with diarrhea requiring admission to hospital. [ 164 ]
A severely malnourished child who appears to have dehydration, but has not had diarrhea, should be treated as if they have an infection. [ 164 ]
Among malnourished people who are hospitalized, nutritional support improves protein intake, calorie intake, and weight. [ 165 ]
In response to child malnutrition, the Bangladeshi government recommends ten steps for treating severe malnutrition: [ 166 ]
Due in part to limited research on supplementary feeding, there is little evidence that this strategy is beneficial. [ 167 ] A 2015 systematic review of 32 studies found that there are limited benefits when children under 5 receive supplementary feeding, especially among younger, poorer, and more undernourished children. [ 168 ]
However, specially formulated foods do appear to be useful in treating moderate acute malnutrition in the developing world. [ 169 ] These foods may have additional benefits in humanitarian emergencies, since they can be stored for years, can be eaten directly from the packet, and do not have to be mixed with clean water or refrigerated. [ 170 ] In young children with severe acute malnutrition, it is unclear if ready-to-use therapeutic food differs from a normal diet. [ 171 ]
Severely malnourished individuals can experience refeeding syndrome if fed too quickly. [ 172 ] Refeeding syndrome can result regardless of whether food is taken orally, enterally or parenterally . [ 172 ] It can present several days after eating with potentially fatal heart failure, dysrhythmias , and confusion. [ 172 ] [ 173 ]
Some manufacturers have fortified everyday foods with micronutrients before selling them to consumers. For example, flour has been fortified with iron, zinc, folic acid, and other B vitamins like thiamine, riboflavin, niacin and vitamin B12 . [ 105 ] Baladi bread (Egyptian flatbread ) is made with fortified wheat flour. Other fortified products include fish sauce in Vietnam and iodized salt . [ 170 ]
According to the World Bank, treating malnutrition – mostly by fortifying foods with micronutrients – improves lives more quickly than other forms of aid, and at a lower cost. [ 174 ] After reviewing a variety of development proposals, The Copenhagen Consensus , a group of economists who reviewed a variety of development proposals, ranked micronutrient supplementation as its number-one treatment strategy. [ 175 ] [ 128 ]
In malnourished people with diarrhea , zinc supplementation is recommended following an initial four-hour rehydration period. Daily zinc supplementation can help reduce the severity and duration of the diarrhea. Additionally, continuing daily zinc supplementation for ten to fourteen days makes diarrhea less likely to recur in the next two to three months. [ 176 ]
Malnourished children also need both potassium and magnesium . [ 166 ] Within two to three hours of starting rehydration, children should be encouraged to take food, particularly foods rich in potassium [ 166 ] [ 176 ] like bananas, green coconut water , and unsweetened fresh fruit juice. [ 176 ] Along with continued eating, many homemade products can also help restore normal electrolyte levels. For example, early during the course of a child's diarrhea, it can be beneficial to provide cereal water (salted or unsalted) or vegetable broth (salted or unsalted). [ 176 ] If available, vitamin A, potassium, magnesium, and zinc supplements should be added, along with other vitamins and minerals. [ 166 ]
Giving base (as in Ringer's lactate ) to treat acidosis without simultaneously supplementing potassium worsens low blood potassium . [ 176 ]
Food and drink can help prevent dehydration in malnourished people with diarrhea. Eating (or breastfeeding, among infants) should resume as soon as possible. [ 164 ] Sugary beverages like soft drinks, fruit juices, and sweetened teas are not recommended as they may worsen diarrhea. [ 177 ]
Malnourished people with diarrhea (especially children) should be encouraged to drink fluids; the best choices are fluids with modest amounts of sugar and salt, like vegetable broth or salted rice water . If clean water is available, they should be encouraged to drink that too. Malnourished people should be allowed to drink as much as they want, unless signs of swelling emerge.
Babies can be given small amounts of fluids via an eyedropper or a syringe without the needle. Children under two should receive a teaspoon of fluid every one to two minutes; older children and adults should take frequent sips of fluids directly from a cup. [ 176 ] After the first two hours, fluids and foods should be alternated, rehydration should be continued at the same rate or more slowly, depending on how much fluid the child wants and whether they are having ongoing diarrhea. [ 166 ]
If vomiting occurs, fluids can be paused for 5–10 minutes and then restarted more slowly. Vomiting rarely prevents rehydration, since fluids are still absorbed and vomiting is usually short-term. [ 177 ]
If prevention has failed and dehydration develops, the preferred treatment is rehydration through oral rehydration therapy (ORT). In severely undernourished children with diarrhea, rehydration should be done slowly, according to the World Health Organization.
Oral rehydration solutions consist of clean water mixed with small amounts of sugars and salts. These solutions help restore normal electrolyte levels, provide a source of carbohydrates , and help with fluid replacement. [ 178 ]
Reduced- osmolarity ORS is the current standard of care for oral rehydration therapy, with reasonably wide availability. [ 179 ] [ 180 ] Introduced in 2003 by WHO and UNICEF, reduced-osmolarity solutions contain lower concentrations of sodium and glucose than original ORS preparations. Reduced-osmolarity ORS has the added benefit of reducing stool volume and vomiting while simultaneously preventing dehydration. Packets of reduced-osmolarity ORS include glucose, table salt, potassium chloride , and trisodium citrate . For general use, each packet should be mixed with a liter of water. However, for malnourished children, experts recommend adding a packet of ORS to two liters of water, along with an extra 50 grams of sucrose and some stock potassium solution. [ 181 ]
People who have no access to commercially available ORS can make a homemade version using water, sugar, and table salt. Experts agree that homemade ORS preparations should include one liter (34 oz. ) of clean water and 6 teaspoons of sugar; however, they disagree about whether they should contain half a teaspoon of table salt or a full teaspoon. Most sources recommend using half a teaspoon of salt per liter of water. [ 176 ] [ 182 ] [ 183 ] [ 184 ] However, people with malnutrition have an excess of body sodium. [ 166 ] To avoid worsening this symptom, ORS for people with severe undernutrition should contain half the usual amount of sodium and more potassium.
Patients who do not drink may require fluids by nasogastric tube . Intravenous fluids are recommended only in those who have significant dehydration due to their potential complications, including congestive heart failure . [ 164 ]
Hypoglycemia , whether known or suspected, can be treated with a mixture of sugar and water. If the patient is conscious, the initial dose of sugar and water can be given by mouth. [ 185 ] Otherwise, they should receive glucose by intravenous or nasogastric tube . If seizures occur (and continue after glucose is given), rectal diazepam may be helpful. Blood sugar levels should be re-checked on two-hour intervals. [ 166 ]
Hypothermia (dangerously low core body temperature ) can occur in malnutrition, particularly in children. Mild hypothermia causes confusion, trembling, and clumsiness; more severe cases can be fatal. Keeping malnourished children warm can prevent or treat hypothermia. Covering the child (including their head) in blankets is one method. Another method is to warm the child through direct skin-to-skin contact with their mother or father, then covering both parent and child.
Warming methods are usually most important at night. [ 166 ] Prolonged bathing or prolonged medical exams can further lower body temperature and are not recommended for malnourished children at high risk of hypothermia.
The figures provided in this section on epidemiology all refer to undernutrition even if the term malnutrition is used which, by definition, could also apply to too much nutrition.
The Global Hunger Index (GHI) is a multidimensional statistical tool used to describe the state of countries' hunger situation. The GHI measures progress and failures in the global fight against hunger. [ 187 ] The GHI is updated once a year. The data from the 2015 report shows that Hunger levels have dropped 27% since 2000. Fifty two countries remain at serious or alarming levels. In addition to the latest statistics on Hunger and Food Security, the GHI also features different special topics each year. The 2015 report include an article on conflict and food security. [ 188 ]
The United Nations estimated that there were 821 million undernourished people in the world in 2017. This is using the UN's definition of 'undernourishment', where it refers to insufficient consumption of raw calories, and so does not necessarily include people who lack micro nutrients. [ 9 ] The undernourishment occurred despite the world's farmers producing enough food to feed around 12 billion people—almost double the current world population. [ 189 ]
Malnutrition, as of 2010, was the cause of 1.4% of all disability adjusted life years . [ 190 ]
In 2010 protein-energy malnutrition resulted in 600,000 deaths down from 883,000 deaths in 1990. [ 195 ] Other nutritional deficiencies, which include iodine deficiency and iron deficiency anemia , result in another 84,000 deaths. [ 195 ] In 2010 malnutrition caused about 1.5 million deaths in women and children. [ 196 ]
According to the World Health Organization, malnutrition is the biggest contributor to child mortality , present in half of all cases. [ 197 ] Six million children die of hunger every year. [ 198 ] Underweight births and intrauterine growth restrictions cause 2.2 million child deaths a year. Poor or non-existent breastfeeding causes another 1.4 million. Other deficiencies, such as lack of vitamin A or zinc , for example, account for 1 million. Malnutrition in the first two years is irreversible. Malnourished children grow up with worse health and lower education achievement. Their own children tend to be smaller. Malnutrition was previously [ when? ] seen as something that exacerbates the problems of diseases such as measles, pneumonia and diarrhea, but malnutrition actually causes diseases, and can be fatal in its own right. [ 197 ]
Hunger has been a perennial human problem. However, until the early 20th century, there was relatively little awareness of the qualitative aspects of malnutrition.
Throughout history, various peoples have known the importance of eating certain foods to prevent symptoms now associated with malnutrition. Yet such knowledge appears to have been repeatedly lost and then re-discovered. For example, the ancient Egyptians reportedly knew the symptoms of scurvy . Much later, in the 14th century, Crusaders sometimes used anti-scurvy measures – for example, ensuring that citrus fruits were planted on Mediterranean islands, for use on sea journeys. However, for several centuries, Europeans appear to have forgotten the importance of these measures. They rediscovered this knowledge in the 18th century, and by the early 19th century, the Royal Navy was issuing frequent rations of lemon juice to every crewman on their ships. This massively reduced scurvy deaths among British sailors, which in turn gave the British a significant advantage in the Napoleonic Wars . Later on in the 19th century, the Royal Navy replaced lemons with limes (unaware at the time that lemons are far more effective at preventing scurvy). [ 199 ] [ 200 ]
According to historian Michael Worboys, malnutrition was essentially discovered, and the science of nutrition established, between World War I and World War II . Advances built on prior works like Casimir Funk 's 1912 formulisation of the concept of vitamins. Scientific study of malnutrition increased in the 1920s and 1930s, and grew even more common after World War II.
Non-governmental organizations and United Nations agencies began to devote considerable energy to alleviating malnutrition around the world. The exact methods and priorities for doing this tended to fluctuate over the years, with varying levels of focus on different types of malnutrition like Kwashiorkor or Marasmus ; varying levels of concern on protein deficiency compared to vitamins, minerals and lack of raw calories; and varying priorities given to the problem of malnutrition in general compared to other health and development concerns. The green Revolution of the 1950s and 1960s saw considerable improvement in capability to prevent malnutrition. [ 200 ] [ 199 ] [ 201 ]
One of the first official global documents addressing Food security and global malnutrition was the 1948 Universal Declaration of Human Rights (UDHR). Within this document it stated that access to food was part of an adequate right to a standard of living. [ 202 ] The Right to food was asserted in the International Covenant on Economic, Social and Cultural Rights , a treaty adopted by the United Nations General Assembly on December 16, 1966. The Right to food is a human right for people to feed themselves in dignity, be free from hunger, food insecurity, and malnutrition. [ 203 ] As of 2018, the treaty has been signed by 166 countries, by signing states agreed to take steps to the maximum of their available resources to achieve the right to adequate food.
However, after the 1966 International Covenant the global concern for the access to sufficient food only became more present, leading to the first ever World Food Conference that was held in 1974 in Rome, Italy. The Universal Declaration on the Eradication of Hunger and Malnutrition was a UN resolution adopted November 16, 1974 by all 135 countries that attended the 1974 World Food Conference. [ 204 ] This non-legally binding document set forth certain aspirations for countries to follow to sufficiently take action on the global food problem. Ultimately this document outline and provided guidance as to how the international community as one could work towards fighting and solving the growing global issue of malnutrition and hunger.
Adoption of the right to food was included in the Additional Protocol to the American Convention on Human Rights in the area of Economic, Social, and Cultural Rights , this 1978 document was adopted by many countries in the Americas, the purpose of the document is, "to consolidate in this hemisphere, within the framework of democratic institutions, a system of personal liberty and social justice based on respect for the essential rights of man." [ 205 ]
A later document in the timeline of global initiatives for malnutrition was the 1996 Rome Declaration on World Food Security , organized by the Food and Agriculture Organization . This document reaffirmed the right to have access to safe and nutritious food by everyone, also considering that everyone gets sufficient food, and set the goals for all nations to improve their commitment to food security by halving their number of undernourished people by 2015. [ 206 ] In 2004 the Food and Agriculture Organization adopted the Right to Food Guidelines , which offered states a framework of how to increase the right to food on a national basis.
Undernutrition is an important determinant of maternal and child health, accounting for more than a third of child deaths and more than 10 percent of the total global disease burden according to 2008 studies. [ 207 ]
Undernutrition adversely affects the cognitive development of children, contributing to poor earning capacity and poverty in adulthood. [ 208 ] The development of childhood undernutrition coincides with the introduction of complementary weaning foods which are usually nutrient deficient. [ 209 ] The World Health Organization estimated in 2008 that malnutrition accounted for 54 percent of child mortality worldwide, [ 58 ] about 1 million children. [ 210 ] There is a strong association between undernutrition and child mortality. [ 211 ]
Another estimate in 2008 also by WHO stated that childhood underweight was the cause for about 35% of all deaths of children under the age of five years worldwide. [ 212 ] Over 90% of the stunted children below five years of age live in sub-Saharan Africa and South Central Asia. [ 80 ] Although access to adequate food and improving nutritional intake is an obvious solution to tackling undernutrition in children, the progress in reducing children undernutrition has been disappointing. [ 213 ]
In 2022, more than 1 billion adolescent girls and women suffered from undernutrition, according to UNICEF's 2023 report "Undernourished and Overlooked: A Global Nutrition Crisis in Adolescent Girls and Women". [ 214 ] The gender gap in food insecurity more than doubled between 2019 (49 million) and 2021 (126 million). The report shows that globally, 30% of women aged 15–49 years are living with anaemia while 10 per cent of women aged 20–49 years suffer from underweight. South Asia, West and Central Africa and Eastern and Southern Africa are home to 60% of women with anaemia and 65% of women being underweight. In contrast, overweight is affecting more than 35% of women aged 20–49 years, of which 13% are living with obesity. [ 214 ]
The Middle East and North Africa has the highest prevalence of overweight with 61% affected. North America closely follows at 60%. [ 214 ] Fewer than 1 in 3 adolescent girls and women have diets meeting the minimum dietary diversity in the Sudan (10%), Burundi (12%), Burkina Faso (17%) and Afghanistan (26%). [ 214 ] In Niger, the percentage of women accessing a minimally diverse diet fell from 53% to 37% between 2020 and 2022. [ 214 ]
Researchers from the Centre for World Food Studies in 2003 found that the gap between levels of undernutrition in men and women is generally small, but that the gap varies from region to region and from country to country. [ 215 ] These small-scale studies showed that female undernutrition prevalence rates exceeded male undernutrition prevalence rates in South/Southeast Asia and Latin America and were lower in Sub-Saharan Africa. [ 215 ] Datasets for Ethiopia and Zimbabwe reported undernutrition rates between 1.5 and 2 times higher in men than in women; however, in India and Pakistan, datasets rates of undernutrition were 1.5–2 times higher in women than in men. Intra-country variation also occurs, with frequent high gaps between regional undernutrition rates. [ 215 ] Gender inequality in nutrition in some countries such as India is present in all stages of life. [ 216 ]
Studies on nutrition concerning gender bias within households look at patterns of food allocation, and one study from 2003 suggested that women often receive a lower share of food requirements than men. [ 215 ] Gender discrimination, gender roles, and social norms affecting women can lead to early marriage and childbearing, close birth spacing, and undernutrition, all of which contribute to malnourished mothers. [ 82 ]
Within the household, there may be differences in levels of malnutrition between men and women, and these differences have been shown to vary significantly from one region to another, with problem areas showing relative deprivation of women. [ 215 ] Samples of 1000 women in India in 2008 demonstrated that malnutrition in women is associated with poverty, lack of development and awareness, and illiteracy. [ 216 ] The same study showed that gender discrimination in households can prevent a woman's access to sufficient food and healthcare. [ 216 ] How socialization affects the health of women in Bangladesh, Najma Rivzi explains in an article about a research program on this topic. [ 217 ] In some cases, such as in parts of Kenya in 2006, rates of malnutrition in pregnant women were even higher than rates in children. [ 218 ]
Women in some societies are traditionally given less food than men since men are perceived to have heavier workloads. [ 219 ] Household chores and agricultural tasks can in fact be very arduous and require additional energy and nutrients; however, physical activity, which largely determines energy requirements, is difficult to estimate. [ 215 ]
Women have unique nutritional requirements, and in some cases need more nutrients than men; for example, women need twice as much calcium as men. [ 219 ]
During pregnancy and breastfeeding, women must ingest enough nutrients for themselves and their child, so they need significantly more protein and calories during these periods, as well as more vitamins and minerals (especially iron, iodine, calcium, folic acid, and vitamins A, C, and K). [ 219 ] In 2001 the FAO of the UN reported that iron deficiency affected 43 percent of women in developing countries and increased the risk of death during childbirth. [ 219 ] A 2008 review of interventions estimated that universal supplementation with calcium, iron, and folic acid during pregnancy could prevent 105,000 maternal deaths (23.6 percent of all maternal deaths). [ 220 ] Malnutrition has been found to affect three-quarters of UK women aged 16–49 indicated by them having less folic acid than the WHO recommended levels. [ 221 ]
Frequent pregnancies with short intervals between them and long periods of breastfeeding add an additional nutritional burden. [ 215 ]
" Action for Healthy Kids " has created several methods to teach children about nutrition. They introduce 2 different topics, self-awareness which teaches children about taking care of their own health and social awareness, which is how culinary arts vary from culture to culture. As well as its importance when it comes to nutrition. They include eBooks, tips, cooking clubs. including facts about vegetables and fruits. [ 222 ]
Team Nutrition has created " MyPlate eBooks " this includes 8 different eBooks to download for free. These eBooks contain drawings to color, audio narration, and a large number of characters to make nutrition lessons entertaining for children. [ 223 ]
According to the FAO, women are often responsible for preparing food and have the chance to educate their children about beneficial food and health habits, giving mothers another chance to improve the nutrition of their children. [ 219 ]
Malnutrition and being underweight are more common in the elderly than in adults of other ages. [ 224 ] If elderly people are healthy and active, the aging process alone does not usually cause malnutrition. [ 225 ] However, changes in body composition, organ functions, adequate energy intake and ability to eat or access food are associated with aging, and may contribute to malnutrition. [ 226 ] Sadness or depression can play a role, causing changes in appetite, digestion, energy level, weight, and well-being. [ 225 ] A study on the relationship between malnutrition and other conditions in the elderly found that malnutrition in the elderly can result from gastrointestinal and endocrine system disorders, loss of taste and smell, decreased appetite and inadequate dietary intake. [ 226 ] Poor dental health, ill-fitting dentures, or chewing and swallowing problems can make eating difficult. [ 225 ] As a result of these factors, malnutrition is seen to develop more easily in the elderly. [ 227 ]
Rates of malnutrition tend to increase with age with less than 10 percent of the "young" elderly (up to age 75) malnourished, while 30 to 65 percent of the elderly in home care, long-term care facilities, or acute hospitals are malnourished. [ 228 ] Many elderly people require assistance in eating, which may contribute to malnutrition. [ 227 ] However, the mortality rate due to undernourishment may be reduced. [ 229 ] Because of this, one of the main requirements of elderly care is to provide an adequate diet and all essential nutrients . [ 230 ] Providing the different nutrients such as protein and energy keeps even small but consistent weight gain. [ 229 ] Hospital admissions for malnutrition in the United Kingdom have been related to insufficient social care, where vulnerable people at home or in care homes are not helped to eat. [ 231 ]
In Australia malnutrition or risk of malnutrition occurs in 80 percent of elderly people presented to hospitals for admission. [ 232 ] Malnutrition and weight loss can contribute to sarcopenia with loss of lean body mass and muscle function. [ 224 ] Abdominal obesity or weight loss coupled with sarcopenia lead to immobility, skeletal disorders, insulin resistance, hypertension, atherosclerosis, and metabolic disorders . [ 226 ] A paper from the Journal of the American Dietetic Association noted that routine nutrition screenings represent one way to detect and therefore decrease the prevalence of malnutrition in the elderly. [ 225 ]
This article incorporates text from a free content work. Licensed under CC BY-SA 4.0 ( license statement/permission ). Text taken from The State of Food Security and Nutrition in the World 2024 , Food and Agriculture Organization. | https://en.wikipedia.org/wiki/Malnutrition |
Malonyl-CoA is a coenzyme A derivative of malonic acid .
Malonyl-CoA cannot cross membranes and there is no known malonyl-CoA import mechanism. [ 1 ] [ 2 ] The biosynthesis therefore takes place locally:
It plays a key role in chain elongation in fatty acid biosynthesis and polyketide biosynthesis.
Malonyl-CoA provides 2-carbon units to fatty acids and commits them to fatty acid chain synthesis.
Malonyl-CoA is utilised in fatty acid biosynthesis by the enzyme malonyl coenzyme A:acyl carrier protein transacylase (MCAT). MCAT serves to transfer malonate from malonyl-CoA to the terminal thiol of holo - acyl carrier protein (ACP).
Malonyl-CoA is a highly regulated molecule in fatty acid synthesis; as such, it inhibits the rate-limiting step in beta-oxidation of fatty acids. [ 6 ] Malonyl-CoA inhibits fatty acids from associating with carnitine by regulating the enzyme carnitine palmitoyltransferase , thereby preventing them from entering the mitochondria , where fatty acid oxidation and degradation occur.
MCAT is also involved in bacterial polyketide biosynthesis. The enzyme MCAT together with an acyl carrier protein (ACP), and a polyketide synthase (PKS) and chain-length factor heterodimer, constitutes the minimal PKS of type II polyketides.
Malonyl-CoA plays a special role in the mitochondrial clearance of toxic malonic acid in the metabolic disorders combined malonic and methylmalonic aciduria (CMAMMA) and malonic aciduria . [ 6 ] In CMAMMA, malonyl-CoA synthetase , ACSF3 is impaired, which generates mitochondrial malonyl-CoA from malonic acid, which can then be converted to acetyl-CoA by malonyl-CoA decarboxylase . [ 5 ] [ 6 ] In contrast, in malonic aciduria , malonyl-CoA decarboxylase is decreased, which converts malonyl-CoA to acetyl-CoA. [ 6 ]
M a l o n i c a c i d + C o A + A T P → A C S F 3 M a l o n y l − C o A S y n t h e t a s e M a l o n y l − C o A → M L Y C D M a l o n y l − C o A D e c a r b o x y l a s e A c e t y l − C o A {\displaystyle \mathrm {Malonic\ acid+CoA+ATP\ {\xrightarrow[{ACSF3}]{Malonyl{-}CoA\ Synthetase}}\ Malonyl{-}CoA\ {\xrightarrow[{MLYCD}]{Malonyl-CoA\ Decarboxylase}}\ Acetyl{-}CoA} } | https://en.wikipedia.org/wiki/Malonyl-CoA |
Maltenes are the n - alkane ( pentane or heptane )-soluble molecular components of asphalt , which is the residue remaining after petroleum refiners remove other useful derivatives such as gasoline and kerosene from crude oil . Asphaltene compounds are the other primary component of asphalt.
As viscous liquids , maltenes consist of heavy, dark-colored asphaltic resins , first acidaffins, second acidaffins, and saturates, [ 1 ] combined with lighter colored oils. [ 2 ] The resins provide the adhesive qualities in asphalts; the oils are the carrier medium for both the maltene resins and the asphaltene compounds. Maltenes are characterized by their lower molecular weight and their solubility, in comparison with asphaltenes.
Using adsorption chromatography in the presence of an acid reagent, maltenes can be separated into four fractions:
It had long been suspected that asphalt pavement deterioration resulted from chemical reactions of specific asphalt components. In 1959, Fritz Rostler observed: “It is generally recognized that failures of asphalt pavements caused by embrittlement and other changes in physical properties during the aging process are due to chemical reactions of all or some of the asphalt components.” [ 3 ]
It was Rostler who undertook the necessary research to identify the asphalt components and chemical processes contributing to the aging process. His methodology was to separate the asphalt components [ 4 ] by first using sulfuric acid to separate the soluble components, then using an n-pentane solvent to separate the insoluble components.
Rostler’s work in the rubber industry led to the development of ASTM Test D-2006-70, which accurately identifies the relationships between the light fraction maltenes, acidaffins and saturates. Although this test has not been updated since 1970, it remains an accurate standard for defining the desirable maltene content distribution in asphalt pavement.
Rostler Analysis aka ASTM Test D-2006-70
Where PC represents Polar Compounds, A1 represents First Acidaffins, A2 represents Second Acidaffins, and S represents Saturated Hydrocarbons:
Min. Max.
Maltene Distribution Ratio D-2006-70 0.3 0.6
(PC + A1) / (S + A2)
Rostler determined that the loss of the low-molecular-weight maltene components in asphalt is largely responsible for the cracking and hardening seen in aging pavement. This discovery led to the development of commercial rejuvenators that combine maltene fractions of asphalt with a carrier capable of penetrating asphalt pavements, in order to restore the proper balance of asphalt components.
The geochemical composition of maltenes varies according to the crude oil source, with any given maltene fraction representing a wide variety of base elements of different concentrations, which may include, for example, cobalt , chromium , copper , iron , molybdenum , manganese , nickel , strontium , vanadium , or zinc . [ 5 ] | https://en.wikipedia.org/wiki/Maltenes |
In polymer physics , Maltese Cross is a set of four symmetrically disposed sectors of high extinction that is displayed when a polymer is observed under polarized lights. This is usually observed when trying to observe spheruliltes in polymers.
This article about polymer science is a stub . You can help Wikipedia by expanding it . | https://en.wikipedia.org/wiki/Maltese_cross_(optics) |
A maltoside is a glycoside with maltose as the glycone (sugar) functional group . Among the most common are alkyl maltosides , which contain hydrophobic alkyl chains as the aglycone . Given their amphiphilic properties, these comprise a class of detergents , where variation in the alkyl chain confers a range of detergent properties including CMC and solubility. Maltosides are most often used for the solubilization and purification of membrane proteins .
In 1980 Ferguson-Miller et al. at Michigan State developed n -dodecyl-β- D -maltopyranoside (DDM) as part of a successful effort to purify an active, stable, monodisperse form of cytochrome c oxidase . [ 1 ] Maltosides have been used extensively to stabilize membrane proteins for biophysical and structural studies. | https://en.wikipedia.org/wiki/Maltoside |
MammaPrint is a prognostic and predictive diagnostic test for early stage breast cancer patients that assess the risk that a tumor will metastasize to other parts of the body. [ 1 ] It gives a binary result, high-risk or low-risk classification , and helps physicians determine whether or not a patient will benefit from chemotherapy . Women with a low risk result can safely forego chemotherapy without decreasing likelihood of disease free survival. [ 2 ] MammaPrint is part of the personalized medicine portfolio marketed by Agendia.
MammaPrint is based on the Amsterdam 70-gene breast cancer gene signature and uses formalin-fixed-paraffin-embedded (FFPE) or fresh tissue for microarray analysis. [ 3 ] It is a laboratory developed test (LDT) which falls into the class of In Vitro Diagnostic Multivariate Index Assays (IVDMIA). MammaPrint was the first (2007) IVDMIA to be cleared by the Food and Drug Administration (FDA) in a De Novo Classification Process (Evaluation of Automatic Class III Designation) and is the only molecular diagnostic test with a randomized prospective clinical trial validating clinical utility. [ 4 ] The test uses RNA isolated from tumor samples and run on custom glass microarray slides in order to determine the expression of a 70-gene signature. The expression profile is then used in a proprietary algorithm to categorically classify the patient as being at either high or low risk of breast cancer recurrence.
MammaPrint has been prospectively, clinically validated for use in early stage (I and II) breast cancer patients regardless of estrogen receptor (ER) or Human Epidermal Growth Factor Receptor 2 (HER2) status, with a tumor size ≤ 5.0 cm, and 0-3 positive lymph nodes (LN0-1), with no special specifications for N1mi pathology. [ 5 ] [ 6 ] This differentiates MammaPrint from other multi-gene assays in use today that have only shown predictive value in ER positive, HER2 negative, lymph node (LN) negative patients. MammaPrint is also indicated for patients with ER negative tumors (15% of tumors [ 7 ] ). There are no exclusion criteria based on histopathologic tumor type (i.e. ductal, lobular, mixed, etc.) or age. MammaPrint is predictive for pre- and post-menopausal women. [ 8 ] [ 9 ]
The Human Genome Project identified approximately 25,000 genes in the human genome and created the possibility for personalized medicine. The Netherlands Cancer Institute (NKI) in Amsterdam utilized this information and applied it specifically to breast cancer, creating the Amsterdam 70-gene signature (70-GS). MammaPrint is the commercialized assay that measures the 70-GS. [ 10 ]
The NKI hypothesized that breast cancer is a genetic, heterogeneous disease, where gene expression would be different in aggressive breast tumors that develop recurrences following surgery than from those that are less aggressive and do not recur or spread throughout the body. To identify a novel and independent predictor of breast cancer recurrence, DNA microarray technology was used to interrogate all 25,000 genes in untreated tumor samples from women where follow-up categorized them as being disease free or having distant metastases within five years. Supervised classification identified significantly different expression patterns in 70 genes that were strongly predictive of a short interval to distant metastases. [ 11 ] [ 12 ]
The paradigm used to development the 70-GS makes it unique in molecular breast cancer diagnostics because it allowed the tumor biology itself to show the genes most predictive of known patient outcomes. Rather than pre-selecting a few genes based on literature and known information at a given time, supervised learning from the entire expressed genome gives it farsighted utility as the knowledge of cancer biology evolves. Furthermore, development using untreated tumors allows physicians to know their patient's risk of recurrence, without any treatment bias or assumptions, before making a patient's treatment plan.
Molecular diagnostics are used in combination with traditional clinicopathologic factors to decide on a treatment plan. MammaPrint provides a binary result, either high risk or low risk. Patients with a low risk result are unlikely to develop distant metastases and are therefore unlikely to benefit from chemotherapy. Since many breast cancers are considered genomically low-risk independent from clinicopathology, a significant number of patients can be saved from overtreatment with chemotherapy. [ 13 ]
MammaPrint is included as standard of care with the highest medical level of evidence in the following guidelines
In February 2007, the U.S. Food and Drug Administration (FDA) cleared the MammaPrint test for use in the U.S. for lymph node negative breast cancer patients of all ages, ER negative or ER positive , with tumors of less than 5 cm. [ 19 ] MammaPrint can be considered as a part of standard of care disease management for early stage breast cancer and has significant insurance coverage in the US, including coverage through Medicare and Medicaid . The American Medical Association has granted a Category 1, MAAA Current Procedural Terminology (CPT) code for MammaPrint. [ 20 ]
Indications for ordering MammaPrint include:
Samples from the United States and North America are processed and run in CLIA certified lab in Irvine , CA.
Samples from outside North America are processed and run in Amsterdam , Netherlands.
Mammaprint is now exclusively available in Pakistan through Precision Diagnostic Laboratory [ 21 ]
Tumor samples may be submitted as core needle biopsies or surgical specimen. MammaPrint is FDA cleared to accept fresh, frozen, and formalin fixed paraffin embedded (FFPE) specimen types. [ 22 ] There are two specimen types that can be submitted:
or
The cost of the assay in the U.S. is $4,200. In Europe, the test costs EUR 2675.
Several studies show that the use of the MammaPrint is cost-effective for patients in the United States, Europe, Canada and Japan by providing additional information to help doctors tailor treatment to the individual patient. [ 23 ] [ 24 ]
MammaPrint provides definitive results and does not have an intermediate category, making it more cost-effective than other breast cancer risk assays available. [ 25 ]
MammaPrint is the only commercially available breast cancer molecular diagnostic assay to achieve level 1A evidence. Other extensive clinical trials and research collaborations have produced numerous retrospective and prospective validation studies over the past decade which have enabled the successful commercialization of genomic microarray assays, such as the FDA-cleared 70-gene MammaPrint profile. Large, multi-institutional clinical trials, such as MINDACT and ISPY-2, are assessing MammaPrint.
The MINDACT trial provides the highest medical level of evidence , level 1A, for the use of MammaPrint in early stage breast cancer. The MINDACT (Microarray In Node negative and 1-3 positive lymph node Disease may Avoid Chemotherapy) [ 26 ] [ 27 ] clinical trial is a multi-center, prospective, phase III randomized study comparing the MammaPrint 70-gene expression signature with a common clinical-pathological prognostic tool (Adjuvant! Online) in selecting patients with negative or 1-3 positive nodes for adjuvant chemotherapy in breast cancer.
Publication in the New England Journal of Medicine showed 6,693 breast cancer patients enrolled from 112 participating institutions in 9 European Countries.
In the MINDACT trial, women with breast cancer who are assessed as “High Risk” by both MammaPrint and clinical-pathologic guidelines are advised to have chemotherapy whereas for women with “Low Risk” concordance, hormonal therapy alone is recommended. However, discordant cases are randomized to receive either chemotherapy or hormonal therapy based on clinical-pathological risk assessment or MammaPrint and the patients are followed. The results of MINDACT validate MammaPrint as an important prognostic and predictive tool in cancer treatment.
Primary findings of the MINDACT trial are:
Prospective Registry Of MammaPrint in breast cancer patients with an Intermediate recurrence Score ( PROMIS ). This will be a prospective observational, case-only, study of MammaPrint in patients with an Oncotype DX intermediate score (18-30). The clinical data is to be entered online. There will be two Case Report Forms (CRF). The first CRF must be completed before receiving the MammaPrint result. This CRF will capture baseline patient characteristics, pathology information, Oncotype DX score and the recommended treatment plan without knowing the MammaPrint result. The second CRF will be completed within 4 weeks after receiving the MammaPrint result and will capture the recommended treatment based on MammaPrint. It is expected that approximately 20-30 institutions in the US will participate. Around 300 patients will be enrolled in 2 years.
This study has the following objectives:
(CALGB 150007/150012 & ACRIN 6657)
Agendia's MammaPrint signature and its microarray technology are integral components of biomarker analysis and molecular prediction in the landmark National Cancer Institute supported I-SPY I and II I-SPY II breast cancer clinical trials which focus on the prediction of therapeutic response in the neoadjuvant setting. The utilization of MammaPrint and Agendia's whole-genome, microarray platform are anticipated to assist in rapid, focused development of oncologic therapies paired with biomarkers.
Key Objectives of I-SPY breast cancer trials for which the MammaPrint whole-genome microarray is utilized:
Multi Institutional Neo Adjuvant Therapy Mammaprint Project (MINT) . Patients with locally advanced breast cancer (LABC) are often treated with neoadjuvant chemotherapy to shrink the tumor before definitive surgery is performed. This allows oncologists to measure a patient's response to a given chemotherapy regimen in vivo. Achievement of a complete pathologic response (pCR) to neoadjuvant chemotherapy allows for a better prediction of the prospect for a favorable outcome.
Genomics assays that measure specific gene expression patterns in a patient's primary tumor have become important prognostic tools for breast cancer patients. This study is designed to test the ability of MammaPrint® in combination with TargetPrint®, BluePrint®, and TheraPrint®, as well as traditional pathologic and clinical prognostic factors, to predict responsiveness to neo-adjuvant chemotherapy in patients with LABC.
This study has the following objectives:
Prospective neo-adjuvant REGISTRY trial linking MammaPrint, Subtyping and treatment response: Neoadjuvant Breast Registry - Symphony™ Trial (NBRST) (pronounced “in breast”.) This is a prospective observational, case-only, study linking MammaPrint, BluePrint, TargetPrint, TheraPrint and possible additional profiles of interest to treatment response, Recurrence Free Survival (RFS) and Distant Metastases Free Survival (DMFS). Only patients who receive neo-adjuvant therapy can participate. For this project, approximately 20-30 institutions in the US will be invited to contribute clinical patient data from enrolled patients after a MammaPrint, TargetPrint, BluePrint and TheraPrint test has been successfully performed and the patient has started neo-adjuvant therapy. Treatment is at the discretion of the physician, adhering to NCCN approved regimens or a recognized alternative.
The clinical data is to be entered online at 4 time points; amounting to four Case Report Forms (CRFs). Data will be collected on an ongoing basis, the first CRF must be completed within 6 weeks after the MammaPrint, BluePrint, TargetPrint, and TheraPrint result was provided. The second CRF should be completed by 4 weeks after definitive surgery. CRF 3 and CRF4 will be completed 2-3 and 5 years after surgery. It is expected that we will enroll around 500 patients in 4 years.
This registry study has the following objectives: | https://en.wikipedia.org/wiki/MammaPrint |
Mammalian-wide interspersed repeats (MIRs) are transposable elements in the genomes of some organisms and belong to the group of Short interspersed nuclear elements (SINEs) .
MIRs are found in all mammals (including marsupials ). [ 1 ]
It is estimated that there are around 368,000 MIRs in the human genome . [ 2 ]
The MIR consensus sequence is 260 basepairs long and has an A/T-rich 3' end. [ 1 ]
Like other Short interspersed nuclear elements (SINEs) , MIR elements used the machinery of LINE elements for their propagation in the genome, which took place around 130 million years ago. They cannot retrotranspose anymore since the loss of activity of the required reverse transcriptase . [ 3 ]
MIR elements have been first described in human genome 1989-1991 [ 4 ] [ 5 ] [ 6 ] and were first referred as MB1 family repeats (mirror to sequences of mouse B1 repeat). Then this family repeats were found in other mammalian genomes. [ 7 ] Then this family was renamed as "Mammalian interspersed repeats" in 1992 [ 8 ] Later this family was shown to be common for vertebrate genomes. [ 9 ] | https://en.wikipedia.org/wiki/Mammalian-wide_interspersed_repeat |
The mammalian CPEB3 ribozyme is a self cleaving non-coding RNA located in the second intron of the CPEB3 gene which belongs to a family of genes regulating messenger RNA polyadenylation . [ 1 ] This ribozyme is highly conserved and
found only in mammals. [ 1 ] The CPEB3 ribozyme is structurally and biochemically related to the human hepatitis delta virus ribozyme . [ 2 ] Other HDV-like ribozymes have been identified and confirmed to be active in vitro in a number of eukaryotes. [ 3 ]
This molecular or cell biology article is a stub . You can help Wikipedia by expanding it .
This catalysis article is a stub . You can help Wikipedia by expanding it . | https://en.wikipedia.org/wiki/Mammalian_CPEB3_ribozyme |
The Mammalian Promoter Database ( MPromDb ) is a curated database of gene promoters identified from ChIP-seq . [ 1 ] The proximal promoter region (upstream of the core-promoter region) contains the cis-regulatory elements of most of the transcription factors (TFs). [ 2 ]
Recently, a better approach to annotate active promoters has been demonstrated with a combination of ChIP-seq and computational technique. [ 3 ] This technique has been used to find the target genes of TFs in mammalian systems. [ 4 ] The MPromDb is based on this technology. Curated promoter sequences for eukaryotic organisms are provided by an EPD database; [ 5 ] however, promoter activity information at tissue / cell centric level is not offered.
The MPromDb data base added active RNAP-II promoters identified after analyzing ten different mouse cell/tissue ChIP -seq experiments performed with RNAP-II antibodies and six different human cell types. [ 1 ] The data was acquired by a series of computational methods followed by manual correction to ensure its high level quality. [ 2 ] In the newest version of MPromDb, about 507 million uniquely-aligned RNA Pol-II ChIP-seq reads have already been analyzed from 26 different databases, including six human cell-types and 10 distinct mouse cell/tissues. [ 1 ]
This Biological database -related article is a stub . You can help Wikipedia by expanding it . | https://en.wikipedia.org/wiki/Mammalian_promoter_database |
In zoology , mammalogy is the study of mammals – a class of vertebrates with characteristics such as homeothermic metabolism , fur , four-chambered hearts , and complex nervous systems . [ 1 ] The archive of number of mammals on earth is constantly growing, but is currently set at 6,495 different mammal species including recently extinct. [ 2 ] There are 5,416 living mammals identified on earth and roughly 1,251 have been newly discovered since 2006. [ 2 ] The major branches of mammalogy include natural history, taxonomy and systematics, anatomy and physiology, ethology, ecology, and management and control. [ 3 ] Mammalogists are typically involved in activities such as conducting research, managing personnel, and writing proposals. [ 4 ] [ 5 ]
Mammalogy branches off into other taxonomically oriented disciplines such as primatology (study of primates ), and cetology (study of cetaceans ). Like other studies, mammalogy is also a part of zoology which is also a part of biology , the study of all living things.
Mammalogists have stated that there are multiple reasons for the study and observation of mammals. Knowing how mammals contribute or thrive in their ecosystems gives knowledge on the ecology behind it. [ 6 ] Mammals are often used in business industries, agriculture, and kept for pets. Studying mammals habitats and source of energy has led to aiding in survival. The domestication of some small mammals has also helped discover several different diseases, viruses, and cures. [ 7 ]
A mammalogist studies and observes mammals. In studying mammals, they can observe their habitats, contributions to the ecosystem, their interactions, and the anatomy and physiology. A mammalogist can do a broad variety of things within the realm of mammals. A mammalogist on average can make roughly $58,000 a year. This depends on employer and state. [ 8 ] [ 9 ]
The first people recorded to have researched mammals were the ancient Greeks with records on mammals that were not even native to Greece and others that were. Aristotle was one of the first to recognize whales and dolphins as mammals since up until the 18th century most of the study was done by taxonomy. [ 10 ]
This is a list of scientific journals broadly serving mammalogists. In addition, many other more general zoology, ecology and evolution, or conservation journals also deal with mammals, and several journals are specific to only certain taxonomic groups of mammals. | https://en.wikipedia.org/wiki/Mammalogy |
Mammoth Biosciences is a biotechnology company based in Brisbane, California [ 1 ] developing diagnostic tests using CRISPR - Cas12a and CRISPR-based therapies using its proprietary ultra-small CRISPR systems. Several CRISPR-Cas systems identified through the company's metagenomics -based protein discovery platform, including members of the Casφ and Cas14 families of CRISPR-associated enzymes, have demonstrated potential for therapeutic genome editing in in vivo settings. [ 2 ]
The company was founded in 2017 [ 3 ] by Jennifer Doudna , Janice Chen , and Lucas Harrington of the University of California, Berkeley , and Trevor Martin of Stanford University . [ 4 ] Mammoth signed agreements in December 2019 and January 2020 with Horizon Discovery to combine Mammoth's intellectual property in CRISPR with Horizon's expertise in Chinese hamster ovary cells . [ 5 ] Also in 2020, both Mammoth Biosciences and Sherlock Biosciences from the Broad Institute used their similar CRISPR technologies to develop tests for COVID-19 . [ 6 ] The technology, which is owned under the trademark of DETECTR BOOST, has been contracted to be manufactured by Merck & Co. [ 7 ]
In 2023, the company announced that it will focus on developing CRISPR-based therapies. [ 8 ] The company's platform uses "ultra-small" Cas enzymes, such as CasΦ and Cas14, which measure down to a third or less the size of Cas9 , and which could allow for easier delivery in vivo through commonly used non-viral and viral delivery mechanisms, including adeno-associated virus vectors. [ 9 ] [ 10 ] Compared to Cas9, CasΦ and Cas14 may also offer less restrictive protospacer adjacent motif requirements, advantageous off-target activity , and allele-specific editing capabilities, which could broaden the range of targetable diseases in the genome . [ 10 ] [ 9 ] Mammoth previously announced partnerships with Vertex Pharmaceuticals (2021) and Bayer (2022) to research ultra-small CRISPR systems for in vivo editing. [ 11 ] [ 12 ]
This United States corporation or company article is a stub . You can help Wikipedia by expanding it . | https://en.wikipedia.org/wiki/Mammoth_Biosciences |
Man and the Biosphere Programme ( MAB ) is an intergovernmental scientific program, launched in 1971 by UNESCO , that aims to establish a scientific basis for the 'improvement of relationships' between people and their environments. [ 1 ]
MAB engages with the international development agenda, especially the Sustainable Development Goals and the Post 2015 Development Agenda . The MAB programme provides a platform for cooperation in research and development. As of July 2024 [update] , 759 sites across 136 countries, including 22 transboundary sites, have been included in the World Network of Biosphere Reserves . [ 2 ] The reserves cover more than 5% of the world’s surface and are home to over 260 million people. [ 3 ] [ 4 ]
Biosphere reserves are areas comprising terrestrial, marine and coastal ecosystems. [ 3 ] Its biosphere reserves are nominated by national governments and remain under the sovereign jurisdiction of the states where they are located. Their status is internationally recognized. Biosphere reserves are 'Science for Sustainability support sites'.
Biosphere reserves have three zones: [ 1 ] [ 5 ]
The first biosphere reserves were designated in 1976 in several countries including the US, UK, Uruguay, Thailand, Iran and Poland. [ 1 ] [ 7 ]
In 1996, the IUCN and MAB published a guideline for how to assess UNESCO biosphere reserves in the IUCN classification system . The IUCN distinguishes between the biosphere core area, buffer zones, transition zones, and each individual biosphere reserve. Biosphere core zones were in IUCN category I; either Ia ( strict nature reserve ) or Ib ( wilderness area ). Biosphere buffer zones would fall into categories IV, V or VI, and transition zones would be categorized as either V or VI, if possible. [ 8 ] In the 2020s, the zones are categorized as follows: core (category I-IV), buffer (category V-VI), transition (uncategorized). [ 9 ]
Participating countries establish MAB National Committees that define and implement each country's activities. MAB currently operates through 158 national committees established among the 195 member states and nine associate member states of UNESCO.
The agenda of the MAB programme is defined by its main governing body, the International Coordinating Council. The MAB Council consists of 34 member states elected by UNESCO's General Conference. The council elects a chair and five vice-chairs from each of UNESCO's geopolitical regions, one of which functions as a rapporteur. These constitute the MAB Bureau.
The MAB Secretariat is based at UNESCO's Division of Ecological and Earth Sciences, at UNESCO's headquarters in Paris. [ 10 ] It works with field offices at national and regional levels. MAB is funded by UNESCO and mobilizes funds in trust granted by Member States, bilateral and multilateral sources, and extra-budgetary funds provided by countries, the private sector and private institutions.
The first World Congress of Biosphere Reserves was held in Minsk, Belarus in 1983; [ 11 ] the congress created an 'Action Plan for Biosphere Reserves' which was adopted the following year.
The second World Congress was held in Seville, Spain in March 1995. [ 11 ]
The third World Congress was held in Madrid, Spain from February 4–9, 2008. [ 12 ]
The fourth World Congress of Biosphere Reserves took place in Lima , Peru , from March 14–17, 2016. [ 13 ]
The fifth World Congress is due to be held in Hangzhou, China from September 22–27 2025. [ 14 ]
The World Network of Biosphere Reserves are as follows: | https://en.wikipedia.org/wiki/Man_and_the_Biosphere_Programme |
A man engine is a mechanism of reciprocating ladders and stationary platforms installed in mines to assist the miners' journeys to and from the working levels. It was invented in Germany in the 19th century and was a prominent feature of tin and copper mines in Cornwall until the beginning of the twentieth century.
In the Cornish examples the motive power was provided by waterwheels, or one of the mine's steam engines . [ 1 ] The steam engine or water wheel would be linked to a series of beams – known as "rods" – fastened together and reaching to the bottom of the mineshaft. These were arranged to offer a reciprocating motion of, typically, twelve to fifteen feet (three to five metres). Small foot platforms were attached to the rods at the same distance apart as the engine stroke and fixed platforms ("sollars" [ 2 ] ) were built onto the shaft walls, spaced to coincide with the top and bottom positions of each of the moving platforms. The moving platforms were often small, typically 12 inches (30 centimetres) square, to make the miner stand close to the centre-line of the rod and thus keep a safe distance from the sides of the shaft. For the same reason the grab handles were always fitted directly above the foot platforms. [ 3 ]
To go up or down, the miner would step onto the travelling platform and allow himself to be carried to the next fixed platform, where he would step off and wait. At the end of the next stroke the next moving platform would line up and he could step onto it and repeat the process. Miners could ascend and descend at the same time: the pause at the changeover point was made long enough (typically between two and eight seconds) [ 4 ] for two men to change places. To facilitate this some installations (such as at the Devon Great Consols mine , Tavistock ) had a fixed platform at both sides of the shaft, one side for miners descending and one for those on the ascent. [ 5 ] Counterweights – large boxes filled with stones attached through "see-sawing" horizontal beams – were installed to avoid the full weight of the shaft and men bearing on the top linkage. In the deepest mines, which could sink to more than 350 fathoms (640 metres), extra counterweights were provided at regular intervals, in horizontal side galleries. [ 6 ]
In a common variation a pair of rods was used, with one on its upstroke as the other descended. The miner stepped from one to the other, rather than waiting at a fixed rest, as they changed direction. [ 1 ] [ 6 ]
Rotary steam engines were found to be more suitable than beam engines because the steady speed of the heavy flywheel gave a predictable pause between reversals of direction, whereas pistons acting directly on the rods, even when controlled by a cataract governor , could surprise the passenger by irregular waits, longer or shorter. [ 4 ] In Cornwall only the Wheal Reeth man engine, Godolphin , (where a pumping engine was converted to this new use) was powered by a piston acting directly on the rods. [ 3 ] When not in use for the man engine, it was an advantage that a rotary engine could also be used to power a whim .
The earliest known examples of this device were from the first half of the nineteenth century in the silver mining area of the Harz mountains , Germany, where they were driven by cranks connected to water wheels , although bucket hoists ("Hakenkunst") using the same method of operation had been used in Swedish iron mines since the 17th century. [ 1 ] [ 7 ] They appear to have evolved from an informal modification to the beam pumps , where the miners used spikes stuck into the wooden pump rods to get themselves carried up the shaft. [ 1 ] As beam pumps were universal in deep mines, it was a then simple development to make proper platforms to carry the miners. The first formal engine was installed in 1833 at a mine at Clausthal , Lower Saxony, where inspector Wilhelm Albert and manager Georg Dörell fastened foot platforms and hand-holds to adjacent, reciprocating pump rods, using a waterwheel-driven pump put out of use when a new drainage adit was made at a lower level. [ 6 ] [ 8 ] The 1837 man engine at the Samson Pit in Sankt Andreasberg in the same region is still in use, although converted from water to electric power in 1922. [ 9 ]
The device was introduced to Cornwall in January 1842, following the award of a premium for the best design, by the Royal Cornwall Polytechnic Society . The winner, Michael Loam , built one for the proprietors of the Tresavean Mine , in Lanner near Redruth . [ 10 ] [ 11 ] He used a double-rod design, driven by a waterwheel. [ 1 ] In October of that year Loam proposed that the water wheel be replaced by a steam engine. A 36-inch (91 cm) bore, 6-foot (1.8 m) stroke, double-action steam engine was employed, through reduction spur gearing of 5:1. At the same time the stroke of the man-engine beams was increased from 6 feet to 12. [ 6 ] Coal consumption was 24 hundredweight (1,200 kg) per day; the engine was in use for only six hours a day, but the boiler was kept at operating temperature continuously. [ 12 ] The miners' journey time (in either direction) was reduced from about an hour to twenty-four minutes and output per shift increased by one fifth. [ 13 ]
More than a dozen examples were installed in Cornish mines by the end of the century, but these were usually of the single-rod type, which was perceived as safer in use. [ 1 ] When cable operated winding gear became available the man engines continued in use, particularly in cases where the mineshaft was not truly vertical and winding engines drawing suspended cages could not be used; with the provision of a few well-placed rollers, and “fend offs” mounted on trunnions , the rods could reach the bottom of a shaft even at a substantial deviation from the vertical. Economics also played a part: the rods needed for pumping could be used for this extra function at little increased cost. Even when skips or kibbles were used in such shafts, [ 14 ] (running on "skipways") the tipping motion would make them impractical for carrying men.
The miners took to these devices without hesitation as their pay was not calculated until they had reached their underground workplace. Contemporary safety studies concluded that, although intrinsically dangerous, the use of a man engine was in practice safer than climbing long ladders: it was less risky to be carried up at the end of a hard shift than to climb a ladder and risk falling because of exhaustion. [ 15 ] [ 16 ] In some mines, particularly in Germany, wedges or collars placed just above close-fitting rollers, or chains, were installed to limit any drop should a breakage occur. [ 6 ]
In the afternoon of 20 October 1919 an accident occurred on the man engine at the Levant Mine , St Just , Cornwall. More than 100 miners were on the engine being drawn to the surface when a metal bracket at the top of the rod broke. The heavy timbers crashed down the shaft, carrying the side platforms with them, and 31 men died. The topmost safety cross-piece attached to the rod, which should have caught on a fixed ledge (the "sill") in case of its dropping too far, fell out of alignment because of the breakage and failed to engage. [ 17 ] The man engine was not replaced and the lowest levels of the mine were abandoned. [ 18 ] | https://en.wikipedia.org/wiki/Man_engine |
Managed Mobility Services (MMS) is a term used by analysts and businesses to describe the outsourcing and managing services that many businesses provide.
Mobility Managed Services includes the IT and process management service needed for a company to acquire, provision and support smartphones , tablets and other field force devices. These services are designed to support devices for corporations are liable and provide a level of control to companies that support them by accessing corporate resources and information.
Managed Mobility Services has existed for some time, but organizations have increasingly shifted responsibility [ 1 ] for logistics and management as the environments have become more diverse and updates more frequent. Android fragmentation is sometimes cited as a driver of this growth as is the consumerization of IT, including the adoption of mobile devices by IT departments. This accumulation of influences has been referred to as "The 3 V's": Volume (the number of devices and users involved); Variety (policy changes in order to fit changing standards) and Volatility (high rates of change that could threaten the business). [ 2 ]
Gartner includes the following categories of services:
Gartner first officially produced research on MMS in 2011 with Critical Capabilities for Managed Mobility Services, 22 December 2011, G00225198 Analyst(s): Eric Goodness, Phillip Redman. [ 3 ] [ 4 ]
Since then Gartner, Forrester Research , GigaOM [ 5 ] [ 6 ] and other analyst organizations have published research on these services, each with slight variations on what services are included. | https://en.wikipedia.org/wiki/Managed_Mobility_Services |
Managed access is managing cellular network access from contraband phones within a corrections facility. [ 1 ] Managed access differs from cellular jamming technologies , which are outlawed in the United States. [ 2 ] [ 3 ] A managed access system functions like a femtocell or low-power cell tower which passes calls to cellular carriers; however, only communications from approved devices and emergency calling are allowed. [ 4 ] [ 5 ] The managed access signal appears as an extension of nearby commercial cellular signals; once a phone connects to the network its identifying information is compared with approved devices and communications are accepted or denied. [ 6 ] [ 7 ] Managed access networks work with commercial cellular signals including 2G , 3G , 4G/LTE , and WiMAX . [ 5 ]
In 2010, the Mississippi Department of Corrections tested the first managed access system at Parchman Mississippi State Penitentiary ; during one month the system blocked more than 216,000 texts and 600 phone calls. [ 8 ] In 2013, the FCC recommended that prisons be allowed to manage their own network access without having to seek approval from the agency, saying that the process of inspecting the systems is "time-consuming and complex" and "discourages their use". In a 2016 op-ed, FCC Chairman Ajit Pai requested that the reforms proposed in 2013 aimed at loosening regulations on managed access and other solutions used to prevent the use of contraband cell phones should be enacted. [ 9 ]
As of 2016, only California, Maryland, Mississippi, South Carolina, and Texas had tested managed access systems. [ 1 ]
Managed access systems are unable to stop the use of contraband devices using Wi-Fi to connect to the internet. Deployment of managed access systems requires FCC approval [ 1 ] and may require consent from cellular network carriers. The devices can also cause interference outside of the prison if they are not properly implemented. [ 6 ] | https://en.wikipedia.org/wiki/Managed_access_(corrections) |
A managed facilities-based voice network ( MFVN ) is a communications network managed, operated, and maintained by a voice service provider that delivers traditional telephone service via a loop start analog telephone interface. MFVNs are interconnected with the public switched telephone network (PSTN) or other MFVNs and provide dialtone to end users. Historically, this was provided by equipment at Bell company central offices, however today's MFVNs can include a combination of access network (last mile network of copper, coaxial cable, fiber optics, or cellular), battery-backed customer premises equipment (CPE), network switches and routers, network management systems, voice call servers, and gateways to the broader PSTN.
MFVN service providers can include cable operators and telephone companies , as well as new entrants that partner with these traditional carriers, but don't include providers that use customer-managed, non-battery-backed CPE to provide POTS service.
According to NFPA 72 2010, 3.3.141, [ 1 ] an MFVN is defined simply as:
A physical facilities-based network capable of transmitting real time signals with formats unchanged that is managed, operated, and maintained by the service provider to ensure service quality and reliability from the subscriber location to public switched telephone network (PSTN) interconnection points or other MFVN peer networks.
The term MFVN was introduced in 2007 by various telephony user organizations and stakeholders who rely on telephone service to provide security and life safety services. The concern of these organizations and stakeholders was the reliability of new telephone technology and services. This new technology was based on packet voice technology, or the Voice over Internet Protocol , which was not well understood. These organizations and stakeholders increasingly realized that they could no longer simply assume that phone service would be reliable enough, because it was increasingly being delivered in various ways, even by traditional providers. Clear performance requirements were needed to define when a phone line was suitable for security and life safety services.
This issue was not new, as analog copper based networks had been transitioning to digital telephony technology for 25 years (via fiber buildout by telephone companies), and to IP technology methods for the last 10 years (via broadband buildout by telco, cable, and competitive local exchange carriers). What was new was that copper based analog phone service was not even an option anymore in many areas, as it was being completely replaced by digital and IP based phone service.
Starting in the early part of the 2000s, IP based voice services began being offered by non-traditional providers such as cable television service providers and Internet voice service providers. The demand for these services grew due to competitive pricing and value added services not offered by the traditional telephone providers. The use of these non-traditional telephone methods for security and life safety communications was not well understood, so use was discouraged and in some cases not allowed by local authorities. There was no distinction between voice services provided over the "best-effort" Internet and voice services provided over managed facilities. It became clear that only managed facilities based providers could assure reliability end to end. Only facilities based providers could monitor and maintain the expected quality of service (call quality, operation during power failure, wiring procedures that guaranteed pre-emption of existing calls for emergency calls, and local disaster recovery capabilities).
In 2007, the concept of the Managed Facilities-based Voice Network was introduced by non-traditional telephone providers as a way to think about the PSTN as a collection of managed networks, rather than as a single, monolithic entity.
By 2009, the large incumbent carriers were starting to publicly talk about their desire to move away from traditional analog phone lines. At a September investor conference, Verizon Communications CEO Ivan Seidenberg said that Verizon, "was simply no longer concerned with telephones that are connected with wires." [ 2 ] Three months later, AT&T sent a letter to the FCC in which they announced plain old telephone service as a "relic of a by-gone era." [ 3 ]
Due to this national trend, the NFPA felt the need to act quickly in 2009, publishing Tentative Interim Amendment (TIA) 10-3 [ 4 ] for incorporation into the NFPA 72 (National Fire Alarm and Signaling Code) 2010 edition. The new language introduced by TIA 10-3, and incorporated into the final NFPA 72 2010 edition, became the national standard in the United States for determining whether a given phone line is an acceptable method for fire alarm signaling transmission from a protected premises to a supervising central monitoring station.
With this clarification at the national level, local authorities, such as fire inspectors and other Authorities Having Jurisdiction (AHJs), are provided with clear, uniform guidance from the NFPA that operators attesting themselves as providing phone service as an MFVN service provider are an acceptable replacement for the traditional "common carriers".
Most, if not all, states recognize and accept the use of MFVN. For example, in Florida it was adopted by statute, whereby all qualified MFVNs are allowed for fire alarm monitoring. [ 5 ]
Within NFPA 72, there is a section entitled Annex A, Explanatory Material. Within this appendix, NFPA 72 provides further detail of what an MFVN service should entail: [ 1 ]
Managed facilities-based voice network service is functionally equivalent to traditional PSTN-based services provided by authorized common carriers (public utility telephone companies) with respect to dialing, dial plan, call completion, carriage of signals and protocols, and loop voltage treatment and provides all of the following features:
(1) A loop start telephone circuit service interface.
(2) Pathway reliability that is assured by proactive management, operation, and maintenance by the MFVN provider.
(3) 8 hours of standby power supply capacity for MFVN communications equipment either located at the protected premises or field deployed. Industry standards followed by the authorized common carriers (public utility telephone companies), and the other communications service providers that operate MFVNs, specifically engineer the selection of the size of the batteries, or other permanently located standby power source, in order to provide 8 hours of standby power with a reasonable degree of accuracy. Of course, over time, abnormal ambient conditions and battery aging can always have a potentially adverse effect on battery capacity. The MFVN field-deployed equipment typically monitors the condition of the standby battery and signals potential battery failure to permit the communications service provider to take appropriate action.
(4) 24 hours of standby power supply capacity for MFVN communications equipment located at the communication service provider's central office.
(5) Installation of network equipment at the protected premises with safeguards to prevent unauthorized access to the equipment and its connections. | https://en.wikipedia.org/wiki/Managed_facilities-based_voice_network |
Managed retreat involves the purposeful, coordinated movement of people and buildings away from risks. This may involve the movement of a person, infrastructure (e.g., building or road), or community . It can occur in response to a variety of hazards such as flood, wildfire, or drought. Politicians , insurers , and residents are increasingly paying attention to managed retreat from low-lying coastal areas because of the threat of sea level rise due to climate change . [ 1 ] Trends in climate change predict substantial sea level rises worldwide, causing damage to human infrastructure through coastal erosion [ 2 ] and putting communities at risk of severe coastal flooding . [ 3 ]
The type of managed retreat proposed depends on the location and type of natural hazard, [ 4 ] [ 5 ] [ 6 ] and on local policies and practices for managed retreat. In the United Kingdom, managed realignment through removal of flood defences is often a response to sea-level rise exacerbated by local subsidence. In the United States, managed retreat often occurs through voluntary acquisition and demolition or relocation of at-risk properties by government. [ 7 ] [ 8 ] In the Global South, relocation may occur through government programs. [ 9 ] Some low-lying countries, facing inundation due to sea-level rise, are planning for the relocation of their populations, such as Kiribati planning for "Migration with Dignity". [ 10 ]
In the United Kingdom, the main reason for managed realignment is to improve coastal stability, essentially replacing artificial 'hard' coastal defences with natural 'soft' coastal landforms. [ 11 ] According to University of Southampton researchers Matthew M. Linham and Robert J. Nicholls, "one of the biggest drawbacks of managed realignment is that the option requires land to be yielded to the sea." [ 12 ] [ unreliable source? ] One of its benefits is that it can help protect land further inland by creating natural spaces that act as buffers to absorb water or dampen the force of waves.
Managed realignment has also been used to mitigate for loss of intertidal habitat. Although land reclamation has been an important factor for salt marsh loss in the UK in the past, [ 13 ] the majority of current salt marsh loss in the UK is believed to be due to erosion. [ 14 ] This erosion may involve coastal squeeze, where protective sea walls prevent the landward migration of salt marsh in response to sea level rise when sediment supply is limited. [ 14 ] [ 15 ] Salt marshes are protected under the EU Habitats Directive as well as providing habitat for a number of species protected by the Birds Directive (see Natura 2000 ). Following this guidance, the UK's biodiversity action plan aims to prevent net losses to the area of salt marsh present in 1992. It is, therefore, a legal requirement that all losses in marsh area must be compensated by replacement habitat with equivalent biological characteristics. [ 16 ] This equates to the need to restore approximately 1.4 km 2 of salt marsh habitat per year in the UK. One of the major reasons cited for the slow pace of current salt marsh restoration in the UK [ 14 ] is the uncertainty associated with the practice (Foresight).
There are no agreed protocols on the monitoring of managed realignment sites [ 17 ] and, consequently, very few of the sites are being monitored consistently and effectively. [ 18 ] Due to the low levels of monitoring, there is little evidence on which to base future managed realignment projects. This has led to the results of managed realignment schemes being extremely unpredictable.
Managed retreat in the form of relocation has been used in inland and coastal areas in response to severe flooding and hurricanes. In the United States, this often takes the form of "buyout" programs, in which government acquires and relocates or demolishes at-risk properties. [ 7 ] [ 19 ] In some cases, individual homes are purchased after disasters. [ 20 ] In other cases, such as Odanah [ 21 ] and Soldiers Grove, Wisconsin , [ 22 ] or Valmeyer, Illinois , [ 23 ] or Isle de Jean Charles, Louisiana the entire community has relocated.
Managed retreat can be very controversial. [ 24 ] A lawsuit in Del Mar California brought on by residents was initiated to stop a managed retreat program based on worries that home values, insurance costs and restricted home expansion have been effects of the policy. [ 25 ] Some areas included in managed retreat are above sea level and are recommended based primarily on estimated engineering costs and by studies financed by the California Coastal Commission itself. [ 26 ] [ 27 ] [ 28 ]
Despite the controversy, as the costs of climate change adaptation increase, more communities are beginning to consider managed retreat. [ 29 ] One such community is Marina, California , adjacent to Monterey Bay . Marina's general acceptance of managed retreat became the subject of a Los Angeles Times feature article, published in 2020. [ 30 ]
In the UK, the first managed retreat site was an area of 8,000 square metres (86,000 sq ft) at Northey Island in Essex flooded in 1991, followed by larger sites at Tollesbury and Orplands (1995), Freiston Shore (2001) and Abbott's Hall Farm , at Great Wigborough in the Blackwater Estuary , it is one of the largest managed retreat schemes in Europe. It covers nearly 280 hectares (690 acres) of land on the north side of the estuary (2002) and a number of others. The programme was started by the Essex Wildlife Trust (EWT) who own Abbott's Hall Farm. They made five breaches in the original old sea wall to allow the held-back sea to flood through to create salt marshland. The marshland over time reverted to its original state before cultivation, providing excellent bird habitat and breeding grounds. [ 31 ] [ 32 ]
Since 2010, the New Zealand Coastal Policy Statement, a policy under the Resource Management Act of 1991, has required the government to conduct managed retreats. [ 33 ]
As a result of two climate change related landslides in New Zealand in 2005, the Whakatane District Council began to plan for climate-related migration to the Matata township over the next decade. The vast majority of residents accepted the need to relocate and did so with council assistance and compensation but as of October 2021, [update] one resident has rejected both the process and the need to move and is now the neighbourhood's sole remaining occupant. NIWA coastal hazards expert Rob Bell says the issue of retreat is primarily socio-political rather than technocratic. [ 34 ] | https://en.wikipedia.org/wiki/Managed_retreat |
Windows Vista contains a range of new technologies and features that are intended to help network administrators and power users better manage their systems. Notable changes include a complete replacement of both the Windows Setup and the Windows startup processes, completely rewritten deployment mechanisms, new diagnostic and health monitoring tools such as random access memory diagnostic program , support for per-application Remote Desktop sessions, a completely new Task Scheduler , and a range of new Group Policy settings covering many of the features new to Windows Vista . Subsystem for UNIX Applications , which provides a POSIX -compatible environment is also introduced.
The setup process for Windows Vista has been completely rewritten and is now image-based instead of being sector-based as previous versions of Windows were. The Windows Preinstallation Environment (WinPE) has been updated to host the entire setup process in a graphical environment (as opposed to text-based environments of previous versions of Windows), which allows the use of input devices other than the keyboard throughout the entire setup process. The new interface resembles Windows Vista itself, with features such as ClearType fonts and Windows Aero visual effects. Prior to copying the setup image to disk, users can create, format, and graphically resize disk partitions. The new image-based setup also reduces the duration of the installation procedure when contrasted with Windows XP; Microsoft estimates that Windows Vista can install in as few as 20 minutes despite being more than three times the size of its predecessor. [ 1 ]
Windows XP only supported loading storage drivers from floppy diskettes during initialization of the setup process; Windows Vista supports loading drivers for SATA , SCSI , and RAID controllers from any external source in addition to floppy diskettes prior to its installation. [ 2 ]
At the end of the setup process, Windows Vista can also automatically download and apply security and device-driver updates from Windows Update . Previous versions of Windows could only configure updates to be installed after the operating system installation.
The new Windows Recovery Environment ( WinRE ) detects and repairs various operating system problems; it presents a set of options dedicated to diagnostics including Startup Repair , System Restore , Backup and Restore , Windows Memory Diagnostics Tool, Command Prompt , and options specific to original equipment manufacturers . WinRE is accessible by pressing F8 during operating system boot or by booting from a Windows installation source such as optical media.
Startup Repair (formerly System Recovery Troubleshooter Wizard [ 3 ] ) is a diagnostic feature designed to repair systems that cannot boot due to operating system corruption, incompatible drivers, or damaged hardware; it scans for corruption of operating system components such as Boot Configuration Data and the Windows Registry and also checks boot sectors , file system metadata, Master Boot Records , and partition tables for errors and whether the root cause for failure originated during an installation of Windows. [ 4 ] Microsoft designed Startup Repair to repair over eighty percent of issues that users may experience. [ 3 ] [ 5 ] Windows Vista Service Pack 1 enhances Startup Repair to replace additional system files during the repair process that may be damaged or missing due to corruption. [ 6 ]
Package Manager , part of the Windows Vista servicing stack , replaces the previous Package Installer ( Update.exe ) and Update Installer ( Hotfix.exe ). Microsoft delivers updates for Windows Vista as files and resources only. Package Manager, Windows Update , and the Control Panel item to turn Windows features on and off, all use the Windows Vista servicing stack. Package Manager can also install updates to an offline Windows image, including updates, boot-critical device drivers, and language packs.
Windows Vista introduced Component-Based Servicing (CBS) as an architecture for installation and servicing . [ 7 ] [ 8 ] [ 9 ]
The deployment of Windows Vista uses a hardware-independent image, the Windows Imaging Format (WIM). The image file contains the necessary bits of the operating system, and its contents are copied as is to the target system. Other system specific software, such as device drivers and other applications, are installed and configured afterwards. This reduces the time taken for installation of Windows Vista.
Corporations can author their own image files (using the WIM format) which might include all the applications that the organization wants to deploy. Also multiple images can be kept in a single image file, to target multiple scenarios. This ability is used by Microsoft to include all editions of Windows Vista on the same disc, [ 10 ] and install the proper version based on the provided product key. In addition, initial configuration, such as locale settings, account names, etc. can be supplied in XML Answer Files to automate installation. [ 11 ]
Microsoft provides a tool called ImageX to support creation of custom images, and edit images after they have been created. It can also be used to generate an image from a running installation, including all data and applications, for backup purposes. WIM images can also be controlled using the Windows System Image Manager , which can be used to edit images and to create XML Answer Files for unattended installations. Sysprep is also included as part of Windows Vista, and is HAL -independent.
Also included in Windows Vista is an improved version of the Files and Settings Transfer Wizard now known as Windows Easy Transfer which allows settings to be inherited from previous installations. User State Migration Tool allows migrating user accounts during large automated deployments.
ClickOnce is a deployment technology for " smart client " applications that enables self-updating Windows-based applications that can be installed and run with minimal user interaction, and in a fashion that does not require administrator access.
The ActiveX Installer Service is an optional component included with the Business, Enterprise and Ultimate editions that provides a method for network administrators in a domain to authorize the installation and upgrade of specific ActiveX controls while operating as a standard user. ActiveX components that have been listed in Group Policy can be installed without a User Account Control consent dialog being displayed. [ 12 ]
Windows Vista includes a number of self-diagnostic features which help identify various problems and, if possible, suggest corrective actions. The event logging subsystem in Windows Vista also has been completely overhauled and rewritten around XML to allow applications to more precisely log events. Event Viewer has also been rewritten to take advantage of these new features. There are a large number of different types of event logs that can be monitored including Administrative, Operational, Analytic, and Debug log types. For instance, selecting the Application Logs node in the Scope pane reveals numerous new subcategorized event logs, including many labeled as diagnostic logs. Event logs can now be configured to be automatically forwarded to other systems running Windows Vista or Windows Server 2008. Event logs can also be remotely viewed from other computers or multiple event logs can be centrally logged and managed from a single computer. Event logs can be filtered by one or more criteria, and custom views can be created for one or more events. Such categorizing and advanced filtering allows viewing logs related only to a certain subsystem or an issue with only a certain component. Events can also be directly associated with tasks, via the redesigned Event Viewer .
Windows Error Reporting has been improved significantly in Windows Vista . Most importantly a new set of public APIs have been created for reporting failures other than application crashes and hangs. [ 13 ] Developers can create custom reports and customize the reporting user interface. The new APIs are documented in MSDN. The architecture of Windows Error Reporting has been revamped with a focus on reliability and user experience. WER can now report errors even when the process is in a very bad state for example if the process has encountered stack exhaustions, PEB /TEB corruptions, heap corruptions etc. In Windows XP, the process terminated silently without generating an error report in these conditions.
A new feature called Problem Reports and Solutions has also been added. It is a Control Panel applet that keeps a record of all system and application errors and issues, as well as presents probable solutions to problems.
Windows Vista introduces major diagnostic capabilities, which include new feature additions for monitoring performance and for reporting issues: [ 14 ]
Remote Desktop Protocol 6.0 incorporates support for application-level remoting, improved security ( TLS 1.0), support for connections via an SSL gateway, improved remoting of devices, support for .NET remoting including support for remoting of Windows Presentation Foundation applications, WMI scripting, 32-bit color support, dual-monitor support, Network Level Authentication and more.
Remote Assistance , which helps in troubleshooting remotely, is now a full-fledged standalone application and does not use the Help and Support Center or Windows Messenger. It is now based on the Windows Desktop Sharing API. Two administrators can connect to a remote computer simultaneously. Also, a session automatically reconnects after restarting the computer. It also supports session pausing, built-in diagnostics, and XML-based logging. It has been reworked to use less bandwidth for low-speed connections. NAT traversals are also supported, so a session can be established even if the user is behind a NAT device. Remote Assistance is configurable using Group Policy and supports command-line switches so that custom shortcuts can be deployed.
Windows Vista also includes Windows Remote Management (WinRM), which is Microsoft's implementation of WS-Management standard which allows remote computers to be easily managed through a SOAP -based web service . WinRM allows obtaining data (including WMI and other management information) from local and remote computers running Windows XP and Windows Server 2003 (if WinRM is installed on those computers), Windows Server 2008 and all WS-Management protocol implementations on other operating systems. Using WinRM scripting objects along with compatible command-line tools (WinRM or WinRS), allows administrators to remotely run management scripts. A WinRM session is authenticated to minimize security risks.
Windows Vista includes Microsoft Management Console 3.0 (MMC), which introduced several enhancements, including support for writing .NET snap-ins using Windows Forms and running multiple tasks in parallel. In addition, snap-ins present their UI in a different thread than that in which the operation runs, thus keeping the snap-in responsive, even while doing a computationally intensive task.
The new MMC interface includes support for better graphics and as well as featuring a task pane that shows actions available for a snap-in, when it is selected. Task Scheduler and Windows Firewall are also thoroughly configurable through the management console.
Print Management enables centralized installation and management of all printers in an organization. It allows installation of network-attached printers to a group of clients simultaneously, and provides continually updated status information for the printers and print servers. It also supports finding printers needing operator attention by filtering the display of printers based on error conditions, such as out-of-paper, and can also send e-mail notifications or run scripts when a printer encounters the error condition.
Windows Vista introduces a new XML based file format, ADMX as a replacement for now legacy ADM files to manage Group Policy settings, as well as a new ADML file format for Administrative Templates. Windows Vista additionally introduces a Central Store for ADMX files; Group Policy tools use ADMX files in the Central Store, and these files are replicated to all domain controllers in a domain . [ 29 ]
Windows Vista includes over 2400 options for Group Policy , [ 30 ] many of which relate to its new features, and which allow administrators to specify configuration for connected groups of computers, especially in a . Windows Vista supports Multiple Local Group Policy Objects which allows setting different levels of Local Group Policy for individual users. [ 31 ] A new XML based policy definition file format, known as ADMX has been introduced. ADMX files contain the configuration settings for individual Group Policy Objects (GPO). For domain based GPOs, the ADMX files can be centrally stored, and all computers on the domain will retrieve them to configure themselves, using the File Replication Service , which is used to replicate files on a configured system from a remote location. The Group Policy service is no longer attached with the Winlogon service, rather it runs as a service on its own. Group Policy event messages are now logged in the system event log . Group Policy uses Network Location Awareness to refresh the policy configuration as soon as a network configuration change is detected.
New categories for policy settings include power management, device installations, security settings, Internet Explorer settings, and printer settings, among others. Group Policy settings also need to be used, to enable two way communication filtering in the Windows Firewall , which by default enables only incoming data filtering. Printer settings can be used to install printers based on the network location. Whenever the user connects to a different network, the available printers are updated for the new network. Group Policy settings specify which printer is available on which network. Also, printer settings can be used to allow standard users to install printers. Group Policy can also be used for specifying quality of service (QoS) settings. Device installation settings can be used to prevent users from connecting external storage devices, as a means to prevent data theft. [ 30 ]
Windows Vista improves Folder Redirection by introducing the ability to independently redirect up to 10 user profile sub-folders to a network location. [ 32 ] Up to Windows XP, only the Application Data , Desktop , My Documents , My Pictures , and Start Menu folders can be redirected to a file server. There is also a Management Console snap-in in Windows Vista to allow users to configure Folder Redirection for clients running Windows Vista, Windows XP, and Windows 2000 .
The redesigned Task Scheduler is now based on Management Console and can be used to automate management and configuration tasks. It already has a number of preconfigured system-level tasks scheduled to run at various times. In addition to time-based triggers, Task Scheduler also supports calendar and event-based triggers, such as starting a task when a particular event is logged to the event log , or even only when multiple events have occurred. Also, several tasks that are triggered by the same event can be configured to run either simultaneously or in a pre-determined chained sequence of a series of actions, instead of having to create multiple scheduled tasks. Tasks can also be configured to run based on system status such as being idle for a pre-configured amount of time, on startup, logoff, or only during or for a specified time. Tasks can be triggered by an XPath expression for filtering events from the Windows Event Log . Tasks can also be delayed for a specified time after the triggering event has occurred, or repeat until some other event occurs. Actions that need to be done if a task fails can also be configured. There are several actions defined across various categories of applications and components. Task Scheduler keeps a history log of all execution details of all the tasks. [ 33 ] Other features of Task Scheduler include:
Several new command-line tools are included in Windows Vista. [ 34 ] Several existing tools have also been updated and some of the tools from the Windows Resource Kit are now built-in into the operating system.
Services for UNIX has been renamed Subsystem for UNIX-based Applications , and is included with the Enterprise and Ultimate editions of Windows Vista. Network File System (NFSv3) client support is also included. However, the utilities and SDK are required to be downloaded separately. Also, the server components from the SFU product line (namely Server for NFS, User Name Mapping, Server for NIS, Password Synchronization etc.) are not included. [ 36 ]
Windows Vista supports scripting and automation capabilities using Windows PowerShell , an object-oriented command-line shell, released by Microsoft , but not included with the operating system. Also, WMI classes expose all controllable features of the operating system, and can be accessed from scripting languages. 13 new WMI providers are included. [ 37 ] In addition, DHTML coupled with scripting languages or even PowerShell can be used to create desktop gadgets; gadgets can also be created for configuration of various aspects of the system. | https://en.wikipedia.org/wiki/Management_features_new_to_Windows_Vista |
Management System (Open Source) is a socio-technical system that leverages the cumulative knowledge of management practitioners and evidenced based research from the past 130 years. [ 1 ] [ 2 ] [ 3 ] [ 4 ] The system was developed by DoD components in partnership with industry experts [ 5 ] [ 6 ] and academic researchers and builds off of the US Department of Wars version 1.0 open source management system - Training Within Industry .
The system integrates the four organizational components of Product, Structure, Process and People. In addition, the system is based on the 4 capabilities of rapid problem solving underlying the Toyota Production System : [ 1 ]
Derived from the original research of Steven J. Spear (Harvard Business School, Massachusetts Institute for Technology), [ 7 ] the system balances the two dimensions of high performing organizations: integrate the whole (product, structure, process & people); and increase the rate of problem solving to manage the whole (4 capabilities outlined above). [ 1 ] [ 8 ]
Fundamentally, the system sets the standards of management by outlining a doctrine of rules, tactics, techniques, procedures & terms. The standards are intended to motivate change by creating a tension between the organization's "current condition" and the "ideal condition" (i.e. True North). [ 9 ]
The objective of the system is to deliver more value, in less time, at less cost relative to the competition (better, faster, cheaper). [ 3 ] For the DoD, competition is defined by the threats posed by current and potential adversaries.
Over the last 25 years, the US Department of Defense has leveraged evidence based research in their attempt to improve the management capability of the Department. DoD's need for change comes from an increased threat of adversaries and the requirement to improve their effectiveness and efficiency. [ 10 ] This requirement to improve effectiveness and efficiency comes from established laws for "achieving an integrated management system for business support areas within the Department of Defense" (e.g. Government Performance and Results Act of 1993 and section 904 of Public Law 110-181 of the National Defense Authorization Act 2008 ).
The concept of open source promotes a free exchange of ideas within the DoD community to drive creative, scientific and technological advancement. The Management System (Open Source) is a reference model that captures the underlying doctrine driving many of the DoD's efforts to improve. For example, the Chief of Naval Operations line of effort called High Velocity Learning is based on the 4 capabilities outlined above. In addition, The Distribution Management System is based on those same underlying capabilities. [ 6 ] [ 11 ] Given that many programs come and go, it is important that the Department of Defense captures and shares the underlying doctrine of management that evidenced based research shows to be valid for producing high performance organizations.
"When we take stock of the productivity gains that drive our prosperity, technology gets all the credit. In fact, management is doing a lot of the heavy lifting" (Joan Magretta, Harvard Business School). [ 12 ] A growing body of evidence based research is showing the correlation and causation of management's impact on organizational performance (productivity, growth, patents, profit, ROIC, etc.). [ 13 ] [ 14 ] [ 15 ] [ 16 ]
The Management System (Open Source) is based on this body of research and managerial practice. The research findings is best captured by Clayton Christensen , former Kim B. Clark Professor of Business Administration at the Harvard Business School (HBS): "Management is the most noble of professions if it's practiced well. No other occupation offers as many ways to help others learn and grow, take responsibility and be recognized for achievement, and contribute to the success of a team."
As a result, the system establishes the "practice routines" for the management profession. Evidenced based research in the field of practice shows that "practice makes permanent, so practice perfect". [ 17 ] This is echoed in Vince Lombardi's admonishment - "Practice does not make perfect. Only perfect practice makes perfect". Therefore, the Management System outlines the practice routines that enable the profession to engage in daily and "deliberate practice" [ 18 ] [ 19 ] To be successful in the profession of management (as outlined by the Management System), the daily and deliberate practice routines require a manager to commit to three fundamental values: Respect for People, Continuous Improvement, and Customer First (similar to those stated in the Toyota Production System). [ 20 ]
The Management System is a doctrine that outlines the fundamental rules, with supporting tactics, techniques, procedures and terms used for the conduct of managerial work in support of the DoD component's objectives. [ 21 ] It is authoritative but requires judgment in application. Each organizational element of Product, Structure, Process and People outline the standards of management using the following construct:
Rule Statement: Prioritize and develop products (or services) that solve the customer's “job to be done” with no “cost of delay”.
Ideal Condition: [ 36 ] [ 3 ]
Products designed and delivered that generate:
100% Value Creation
100% Value Capture
Rule Statement: Structure the role relationships (vertical and functional) to solve problems that deliver products of value. [ 41 ]
Ideal Condition: [ 4 ]
Roles aligned and structured for:
Rule Statement: Develop the process to deliver “just in time” (right product, right qty, right time, right cost).
Ideal Condition: [ 1 ]
Process that produce and deliver the product:
Rule Statement: Develop and deliver capable people “just in time” (right role, right qty, right time).
Ideal Condition: [ 43 ]
Process that develops and delivers people capable for the role:
"All models are wrong, but some are useful", George E. P. Box . Business research has the potential of falling victim to what Phil Rosenzweig outlines in his book " The Halo Effect " (a book that criticizes pseudoscientific tendencies in the explanation of business performance). The Management System (Open Source) states that it leverages evidenced based research , but in reality, all research can fall victim to some of the below effects. [ 53 ] | https://en.wikipedia.org/wiki/Management_system_(open_source) |
Mānaiakalani is a constellation in Polynesian culture which translates to "The Chief's Fishline". It refers to the fishhook of demi-god Māui . Polynesian mythology tells of Māui pulling large fish from the ocean, representing the discovery of new islands. It is primarily made of Scorpius and the Navigator's Triangle . [ 1 ]
This constellation -related article is a stub . You can help Wikipedia by expanding it . | https://en.wikipedia.org/wiki/Manaiakalani |
Manava (c. 750 BC – 690 BC) is an author of the Hindu geometric text of Sulba Sutras .
The Manava Sulbasutra is not the oldest (the one by Baudhayana is older), nor is it one of the most important, there being at least three Sulbasutras which are considered more important. Historians place his lifetime at around 750 BC.
Manava would have not have been a mathematician in the sense that we would understand it today. Nor was he a scribe who simply copied manuscripts like Ahmes . He would certainly have been a man of very considerable learning but probably not interested in mathematics for its own sake, merely interested in using it for religious purposes. Undoubtedly he wrote the Sulbasutra to provide rules for religious rites and it would appear almost a certainty that Manava himself would be a Hindu priest.
The mathematics given in the Sulbasutras is there to enable accurate construction of altars needed for sacrifices. It is clear from the writing that Manava, as well as being a priest, must have been a skilled craftsman.
Manava's Sulbasutra, like all the Sulbasutras, contained approximate constructions of circles from rectangles, and squares from circles, which can be thought of as giving approximate values of π. There appear therefore different values of π throughout the Sulbasutra, essentially every construction involving circles leads to a different such approximation. The paper of R.C. Gupta is concerned with an interpretation of verses 11.14 and 11.15 of Manava's work which give π = 25/8 = 3.125. [ 1 ] [ 2 ]
This article about a person notable in Hinduism is a stub . You can help Wikipedia by expanding it .
This article about an Indian scientist is a stub . You can help Wikipedia by expanding it .
This article about an Asian mathematician is a stub . You can help Wikipedia by expanding it . | https://en.wikipedia.org/wiki/Manava |
The manca (plural: mancae ) is the post- larval juvenile in some crustaceans . The manca stage is the defining characteristic of a clade called Mancoida which comprises all the members of the Peracarida except the Amphipoda . [ 1 ] Mancae closely resemble the adult form, but for the absence of the last pair of pereiopods . [ 1 ] In some isopods , specifically the family Gnathiidae , the manca stage is a parasite of fish, and is also known as the praniza . [ 2 ]
This developmental biology article is a stub . You can help Wikipedia by expanding it .
This crustacean -related article is a stub . You can help Wikipedia by expanding it . | https://en.wikipedia.org/wiki/Manca |
The Mandarin paradox is an ethical parable used to illustrate the difficulty of fulfilling moral obligations when moral punishment is unlikely or impossible, leading to moral disengagement . [ 1 ] It has been used to underscore the fragility of ethical standards when moral agents are separated by physical, cultural, or other distance, especially as facilitated by globalization . [ 2 ] It was first posed by French writer Chateaubriand in " The Genius of Christianity " (1802): [ 3 ]
I ask my own heart, I put to myself this question: "If thou couldst by a mere wish kill a fellow-creature in China, and inherit his fortune in Europe, with the supernatural conviction that the fact would never be known, wouldst thou consent to form such a wish?"
The paradox is famously used to foreshadow the character development of the arriviste Eugène de Rastignac in Balzac 's novel Père Goriot . [ 1 ] Rastignac asks Bianchon if he recalls the paradox, to which Bianchon first replies that he is "at [his] thirty-third mandarin," but then states that he would refuse to take an unknown man's life regardless of circumstance. [ 3 ] Rastignac wrongly attributes the quote to Jean-Jacques Rousseau , which propagated to later writings. [ 2 ] [ 4 ]
This article about ethics is a stub . You can help Wikipedia by expanding it . | https://en.wikipedia.org/wiki/Mandarin_paradox |
The Mandelin reagent is used as a simple spot-test to presumptively identify alkaloids as well as other compounds. It is composed of a mixture of ammonium metavanadate and concentrated sulfuric acid . Its primary use is for the detection of ketamine and PMA [ 1 ] Unlike the most common reagent test chemicals, it has a deep red colour that changes to yellow if there is no alkaloid, which occurs within about 48 hours of mixing. [ 2 ]
The United States Department of Justice method for producing the reagent is the addition of 100 mL of concentrated (95–98%) sulfuric acid to 0.5 [ 3 ] -1 g of ammonium metavanadate. [ 4 ]
This reagent was invented by the German pharmacologist, Karl Friedrich Mandelin (1854–1906) at the University of Dorpat .
This article about analytical chemistry is a stub . You can help Wikipedia by expanding it . | https://en.wikipedia.org/wiki/Mandelin_reagent |
In theoretical physics , the Mandelstam variables are numerical quantities that encode the energy , momentum , and angles of particles in a scattering process in a Lorentz-invariant fashion. They are used for scattering processes of two particles to two particles. The Mandelstam variables were first introduced by physicist Stanley Mandelstam in 1958.
If the Minkowski metric is chosen to be d i a g ( 1 , − 1 , − 1 , − 1 ) {\displaystyle \mathrm {diag} (1,-1,-1,-1)} , the Mandelstam variables s , t , u {\displaystyle s,t,u} are then defined by
where p 1 and p 2 are the four-momenta of the incoming particles and p 3 and p 4 are the four-momenta of the outgoing particles.
s {\displaystyle s} is also known as the square of the center-of-mass energy ( invariant mass ) and t {\displaystyle t} as the square of the four-momentum transfer.
The letters s,t,u are also used in the terms s-channel (timelike channel), t-channel , and u-channel (both spacelike channels). These channels represent different Feynman diagrams or different possible scattering events where the interaction involves the exchange of an intermediate particle whose squared four-momentum equals s,t,u , respectively.
For example, the s-channel corresponds to the particles 1,2 joining into an intermediate particle that eventually splits into 3,4: the s-channel is the only way that resonances and new unstable particles may be discovered provided their lifetimes are long enough that they are directly detectable. [ citation needed ] The t-channel represents the process in which the particle 1 emits the intermediate particle and becomes the final particle 3, while the particle 2 absorbs the intermediate particle and becomes 4. The u-channel is the t-channel with the role of the particles 3,4 interchanged.
When evaluating a Feynman amplitude one often finds scalar products of the external four momenta. One can use the Mandelstam variables to simplify these:
p 1 ⋅ p 2 = s / c 2 − m 1 2 − m 2 2 2 {\displaystyle p_{1}\cdot p_{2}={\frac {s/c^{2}-m_{1}^{2}-m_{2}^{2}}{2}}}
p 1 ⋅ p 3 = m 1 2 + m 3 2 − t / c 2 2 {\displaystyle p_{1}\cdot p_{3}={\frac {m_{1}^{2}+m_{3}^{2}-t/c^{2}}{2}}}
p 1 ⋅ p 4 = m 1 2 + m 4 2 − u / c 2 2 {\displaystyle p_{1}\cdot p_{4}={\frac {m_{1}^{2}+m_{4}^{2}-u/c^{2}}{2}}}
Where m i {\displaystyle m_{i}} is the mass of the particle with corresponding momentum p i {\displaystyle p_{i}} .
Note that
where m i is the mass of particle i . [ 1 ]
To prove this, we need to use two facts:
So, to begin,
Then adding the three while inserting squared masses leads to,
Then note that the last four terms add up to zero using conservation of four-momentum,
So finally,
In the relativistic limit, the momentum (speed) is large, so using the relativistic energy-momentum equation , the energy becomes essentially the momentum norm (e.g. E 2 = p ⋅ p + m 0 2 {\displaystyle E^{2}=\mathbf {p} \cdot \mathbf {p} +{m_{0}}^{2}} becomes E 2 ≈ p ⋅ p {\displaystyle E^{2}\approx \mathbf {p} \cdot \mathbf {p} } ). The rest mass can also be neglected.
So for example,
because p 1 2 = m 1 2 {\displaystyle p_{1}^{2}=m_{1}^{2}} and p 2 2 = m 2 2 {\displaystyle p_{2}^{2}=m_{2}^{2}} .
Thus, | https://en.wikipedia.org/wiki/Mandelstam_variables |
Maneb (manganese ethylene-bis-dithiocarbamate) is a fungicide and a polymeric complex of manganese with the ethylene bis (dithiocarbamate) anionic ligand . [ 1 ]
Exposure to maneb can occur when breathed in; it can irritate the eyes , nose , and throat as well as cause headache , fatigue , nervousness, dizziness, seizures and even unconsciousness. Prolonged or long-term exposure may interfere with the function of the thyroid . Exposure to maneb is also shown to induce a Parkinson's disease like neurotoxicity in mice. [ 2 ] It is still challenged whether maneb, along with Paraquat , is an environmental risk factor for Parkinson's disease. [ 3 ] [ 4 ]
Manganese(II) ethylenebis(dithiocarbamate) of low ethylenethiourea (ETU) content is prepared by mixing disodium ethylenebis (dithiocarbamate) with formaldehyde in aqueous medium then mixing a water-soluble manganese(II) salt to precipitate the maneb. The product can be further formulated with a metal salt and also with paraformaldehyde . (See External links for the patent citation)
Maneb, is a broad spectrum fungicide that is extensively applied against a wide range of fungal pathogens affecting ornamental plants, food and feed crops. It can also be used to create a toxin-based animal model of Parkinson's disease , usually in primates. [ 5 ] [ 6 ]
Maneb was included in a pesticide ban proposed by the Swedish Chemicals Agency [ 7 ] and approved by the European Parliament on January 13, 2009. [ 8 ] | https://en.wikipedia.org/wiki/Maneb |
Manel De Aguas Muñoz (born 10 October 1996 in Barcelona ), known artistically as Manel De Aguas , [ 1 ] is a Spanish cyborg artist and transpecies activist based in Barcelona , [ 2 ] best known for developing and installing weather sensory fins in his head. [ 3 ] The fins, formally known as 'Weather Fins', allow him to hear atmospheric pressure , humidity and temperature changes through implants at each side of his head. [ 4 ] Depending on the changes he feels, he can predict weather changes as well as sense his current altitude. [ 5 ]
De Aguas studied contemporary photography in Barcelona and became Cyborg Foundation 's artist in residence in 2016. [ 6 ] In 2017, he co-founded the Transpecies Society, [ 7 ] an association that gives voice to people who do not identify as being 100% human and raises awareness on issues they face. [ 8 ] The association, based in Barcelona, offers workshops specialized in the design and creation of new senses and organs. [ 9 ]
De Aguas has shared his experience as a cyborg artist by performing and speaking in conferences and festivals in Germany, UK, Romania, Spain and The Netherlands among others. [ 10 ] He also talks about it extensively in the Shaping Business Minds Through Art podcast. [ 11 ] | https://en.wikipedia.org/wiki/Manel_Muñoz |
Manfred Schidlowski (13 November 1933 – 3 October 2012) was a German Professor of Geochemistry at the Max-Planck-Institut for Chemistry (Otto-Hahn-Institut) in Mainz . [ 1 ] His research was concerned with the biochemistry of the Early Earth with a focus on isotope-biogeochemistry and the evidence of the earliest life processes in Precambrian . [ 2 ] [ 3 ] [ 4 ] Schidlowski is considered the founder of this research direction in Germany and he also shaped international research in isotope biogeochemistry of Precambrian sediments for more than two decades. [ 5 ]
Manfred Schidlowski was born in Stettin on 13 November 1933. His family left his homeland during the Second World War and moved to Greifswald . From 1952-1955 he studied at the Humboldt University of Berlin , and from 1956 at the Free University of Berlin , where he received his diploma in geology in 1960 and one year later his doctorate with the "Contribution to the Geology of the Eastern Alps between the Small Walser Valley and the Upper Lech ( Vorarlberg , Austria )". His desire for a change in geoscientific content led him to South Africa , first as a postdoctoral researcher at the University of Pretoria and then as a mine geologist for the Anglo-Transvaal Consolidated Investment Co. Ltd. at the Loraine Gold Mine to Allanridge in the Orange Free State . In 1962 he met his future wife Ingrid Piegler, a great-great-granddaughter of Heinrich Gottfried Piegler , he married her in 1964.
Scientifically, he worked on the mineralogy of the gold-bearing Witwatersrand sequence. The discovery of detrital, i.e. sedimentary rearranged pyrites and uraninites as well as the frequently occurring carbonaceous material in these layers founded his scientific interest in the early evolution of the Earth and provided the data for his first Nature publication in 1965 with the title "Probable Life-forms from the Precambrian of the Witwatersrand System (South Africa)".
In 1963 Schidlowski returned to Germany to work on the ores of the Witwatersrand succession in Paul Ramdohr 's group in the Heidelberg . Here the idea of a relationship between the presence of detrital pyrites and the oxygen content of the Earth's atmosphere was born. He spent the years 1965-1967 at the University of Göttingen . Evidence for a biological origin of the carbonaceous material in the Witwatersrand sediments was consolidated during this time by carbon isotope investigations in cooperation with Jochen Hoefs. Afterwards, Schidlowski habilitated at the University of Heidelberg . In 1969 he moved to the newly founded Institute for Air Chemistry at the Max Planck Institute for Chemistry in Mainz in 1969. Its director, Christian Junge, sent him back to South Africa on a large sampling campaign. The focus was on the carbonates of early Earth history as archives of ocean-atmosphere evolution. Among these were carbonates of the Lomagundi succession from Rhodesia (now Zimbabwe ) with their unusually positive carbon isotopy. Initially classified as a local feature, it quickly became clear that this was a global phenomenon, one of the most massive changes in global carbon cycle. There is still intense debate about the reasons for this global phenomenon, the basis of which was researched by him. His 1976 publication on this subject (Schidlowski et al., Geochim.Cosmochim. Acta 40: 449-455) is still cited several times in 2012. The move to the Max Planck Institute set the course for Schidlowski's future scientific career: research into the Earth system during the Precambrian. The time in Mainz was interrupted by stays at Harvard University , the University of California Los Angeles and the Weizman Institute in Rehovot, Israel.
From 1979 to 1989, he was chairman of the UNESCO -sponsored IGCP Project 157 (Early Organic Evolution and Mineral and Energy Resources). He established close contacts with geological and geochemical research centres such as the institutes of the Academy of Sciences of the USSR , the Academia Sinica (Lanzhou, Beijing). Since 1996, he was a member of the exobiology science team of the European Space Agency (ESA) . He spent his scientific life researching the development of the atmosphere, the ocean and life on the early Earth. He wrote more than 100 scientific papers in journals and book chapters as well as edited special volumes and books on the topic of the early development of the Earth system.
Schidlowski retired in 1998. In 2005 he moved with his wife to Altusried . Here he died on October 3, 2012. [ 6 ] [ 7 ] [ 8 ] | https://en.wikipedia.org/wiki/Manfred_Schidlowski |
Manganese(II) sulfate usually refers to the inorganic compound with the formula MnSO 4 ·H 2 O. This pale pink deliquescent solid is a commercially significant manganese(II) salt. Approximately 260,000 tonnes of manganese(II) sulfate were produced worldwide in 2005. It is the precursor to manganese metal and many other chemical compounds . Manganese-deficient soil is remediated with this salt . [ 1 ]
Like many metal sulfates , manganese sulfate forms a variety of hydrates : monohydrate, tetrahydrate, pentahydrate, and heptahydrate. All of these salts dissolve in water to give faintly pink solutions of the aquo complex [Mn(H 2 O) 6 ] 2+ . The structure of MnSO 4 ·H 2 O has been determined by X-ray crystallography (see figure). The tetrahydrate also features Mn(II) in an O 6 coordination sphere provided by bridging two sulfate anions and four aquo ligands . [ 3 ]
Typically, manganese ores are purified by their conversion to manganese(II) sulfate. Treatment of aqueous solutions of the sulfate with sodium carbonate leads to precipitation of manganese carbonate , which can be calcined to give the oxides MnO x . In the laboratory, manganese sulfate can be made by treating manganese dioxide with sulfur dioxide : [ 4 ]
It can also be made by mixing potassium permanganate with sodium hydrogen sulfate and hydrogen peroxide .
Manganese sulfate is a by-product of various industrially significant oxidations that use manganese dioxide, including the manufacture of hydroquinone and anisaldehyde . [ 1 ]
Electrolysis of manganese sulfate reverses the above reaction yielding manganese dioxide , which is called EMD for electrolytic manganese dioxide. Alternatively oxidation of manganese sulfate with potassium permanganate yields the so-called chemical manganese dioxide (CMD). These materials, especially EMD, are used in dry-cell batteries . [ 1 ]
Manganese(II) sulfate minerals are very rare in nature and always occur as hydrates. The monohydrate is called szmikite; the tetrahydrate is called ilesite; the pentahydrate is called jōkokuite; the hexahydrate, the most rare, is called chvaleticeite ; and the heptahydrate is called mallardite. [ 5 ] | https://en.wikipedia.org/wiki/Manganese(II)_sulfate |
Manganese(III) acetate describes a family of materials with the approximate formula Mn(O 2 CCH 3 ) 3 . These materials are brown solids that are soluble in acetic acid and water. They are used in organic synthesis as oxidizing agents . [ 1 ]
Although manganese(III) triacetate has not been reported, salts of basic manganese(III) acetate are well characterized. Basic manganese acetate adopts the structure reminiscent of those of basic chromium acetate and basic iron acetate . The formula is [Mn 3 O(O 2 CCH 3 ) 6 L n ]X where L is a ligand and X is an anion. The salt [Mn 3 O(O 2 CCH 3 ) 6 ]O 2 CCH 3 . HO 2 CCH 3 has been confirmed by X-ray crystallography . [ 2 ]
It is usually used as the dihydrate, although the anhydrous form is also used in some situations. The dihydrate is prepared by combining potassium permanganate and manganese(II) acetate in acetic acid . [ 3 ] Addition of acetic anhydride to the reaction produces the anhydrous form. [ 1 ] [ 2 ] It is also synthesized by electrochemical method starting from Mn(OAc) 2 . [ 4 ]
Manganese triacetate has been used as an oxidant in radical cyclizations . It can oxidize alkenes via addition of acetic acid to form lactones . [ 3 ]
This process is thought to proceed through rate determining enolization followed by intramolecular electron transfer to form [{Mn 3 }–enolate]• radical intermediates (e.g., [{Mn 3 }–enolate]), instead of free •CH 2 CO 2 H radical intermediates, which then react with the alkene, followed by additional oxidation steps and finally ring closure. [ 5 ] [ 6 ] When the alkene is not symmetric, the major product depends on the nature of the alkene, and is consistent with initial formation of the more stable radical (among the two carbons of the alkene) followed by ring closure onto the more stable conformation of the intermediate. [ 7 ]
When reacted with enones , the carbon on the other side of the carbonyl reacts rather than the alkene portion, leading to α'- acetoxy enones. [ 8 ] In this process, the carbon next to the carbonyl is oxidized by the manganese, followed by transfer of acetate from the manganese to it. [ 9 ] It can similarly oxidize β-ketoesters at the α carbon, and this intermediate can react with various other structures, including halides and alkenes (see: manganese-mediated coupling reactions ). One extension of this idea is the cyclization of the ketoester portion of the molecule with an alkene elsewhere in the same structure. [ 10 ] | https://en.wikipedia.org/wiki/Manganese(III)_acetate |
Manganese-mediated coupling reactions are radical coupling reactions between enolizable carbonyl compounds and unsaturated compounds initiated by a manganese(III) salt, typically manganese(III) acetate. Copper(II) acetate is sometimes used as a co-oxidant to assist in the oxidation of intermediate radicals to carbocations. [ 1 ]
Manganese(III) acetate is effective for the oxidation of enolizable carbonyl compounds to α-oxoalkyl or α,α'-dioxoalkyl radicals. [ 2 ] Radicals generated in this manner may then undergo inter- or intramolecular addition to carbon-carbon multiple bonds. Pathways available to the adduct radical include further oxidation to a carbocation (and subsequent β-elimination or trapping with a nucleophile) and hydrogen abstraction to generate a saturated carbonyl compound containing a new carbon-carbon bond. Copper(II) acetate is sometimes needed to facilitate the oxidation of adduct radicals to carbocations. [ 3 ] Yields of these reactions are generally moderate, particularly in the intermolecular case, but tandem intramolecular radical cyclizations initiated by Mn(III) oxidation may generate complex carbocyclic frameworks. Because of the limited functional group compatibility of Mn(OAc) 3 , radical couplings employing this reagent have mainly been applied to the synthesis of hydrocarbon natural products, such as pheromones. [ 4 ]
(1)
Manganese(III)-mediated radical reactions begin with the single-electron oxidation of a carbonyl compound to an α-oxoalkyl radical. Addition to an olefin then occurs, generating adduct radical 2 . The fate of 2 is primarily determined by reaction conditions—in the presence of copper(II) acetate, this intermediate undergoes further oxidation to a carbocation and may eliminate to form β,γ-unsaturated ketone 4 . Manganese acetate itself can effect the second oxidation of resonance-stabilized adduct radicals to carbocations 5 ; [ 5 ] unstabilized radicals undergo further transformations before reacting with Mn(OAc) 3 . Atom transfer from another molecule of substrate may generate saturated compound 3 . Adduct radicals or carbocations may undergo ligand-transfer reactions, yielding γ-functionalized carbonyl compounds. When lithium chloride is used as an additive, chlorination takes place. [ 6 ] Alternatively, carbocations may be trapped intramolecularly by the carbonyl oxygen to form dihydrofurans after β-elimination. [ 7 ]
(2)
The outcomes of manganese-mediated coupling reactions depend on both the structure of the substrate(s) and the reaction conditions. This section describes the scope and limitations of inter- and intramolecular manganese-mediated radical coupling reactions and is organized according to the carbonyl compound employed as the substrate.
Intermolecular reactions between ketones/aldehydes and alkenes tend to result in low yields. In the absence of copper(II) acetate , hydrogen atom abstraction occurs, yielding saturated ketones or aldehydes. [ 8 ]
(3)
When Cu(OAc) 2 is present, further oxidation to carbocations followed by elimination takes place, leading to the formation of β,γ-unsaturated carbonyl compounds in moderate yields. [ 9 ]
(4)
Aromatic compounds are also useful radical acceptors in manganese(III)-mediated coupling reactions. Furan reacts selectively at the α position to afford substituted products in high yield. [ 10 ]
(5)
Lactonization of alkenes in the presence of acetic acid and acetate salts is a synthetically useful method for the synthesis of γ-lactones. Selectivity is high for the radical addition that leads to the more stable adduct radical, and trans lactones are selectively formed from either cis or trans acyclic alkenes. [ 11 ]
(6)
β-Dicarbonyl compounds are useful substrates for the formation of dihydrofurans. Copper(II) acetate is not necessary in this case because of the high resonance stabilization of the intermediate diphenylmethyl radical. [ 12 ]
(7)
When alkenes or carbonyl compounds containing pendant unsaturated moiety are treated with manganese(III) acetate , tandem intramolecular cyclization reactions may occur. Generally, exo cyclization of terminal double bonds is favored, as shown in equation (10). [ 13 ] A variety of substitution patterns may be employed for this transformation, and yields are generally higher than intermolecular coupling reactions. [ 14 ]
(8)
The stereochemical course of tandem reactions can be understood in some cases by invoking a chairlike transition state with as many substituents as possible in pseudoequatorial positions; [ 15 ] however, a number of examples exhibiting unpredictable stereochemistry are known. [ 16 ]
(9)
Nitriles are useful as radical acceptors in tandem cyclizations. Hydrolysis of the resulting imine leads to polycyclic ketones in moderate yields with good stereoselectivity. [ 17 ]
(10)
Manganese-mediated couplings have been used for the synthesis of hydrocarbon natural products, such as pheromones . A synthesis of queen bee pheromone uses the intermolecular coupling of acetone and an ω-alkenyl acetate en route to the target. [ 18 ]
(11)
Lactonization is a key step in the synthesis of tomato pinworm sex pheromone. Subsequent Lindlar hydrogenation, reduction and acetylation provided the target compound. [ 19 ]
(12) | https://en.wikipedia.org/wiki/Manganese-mediated_coupling_reactions |
Manganese(VII) oxide (manganese heptoxide) is an inorganic compound with the formula Mn 2 O 7 . Manganese heptoxide is a volatile liquid with an oily consistency. It is a highly reactive and powerful oxidizer that reacts explosively with nearly any organic compound . It was first described in 1860. [ 1 ] It is the acid anhydride of permanganic acid .
The crystalline form of this chemical compound is dark green. The liquid is green by reflected light and red by transmitted light. [ 2 ] It is soluble in carbon tetrachloride , and decomposes when in contact with water.
Its solubility properties indicate a nonpolar molecular species, which is confirmed by its structure. The molecules consist of a pair of tetrahedra that share a common vertex. The vertices are occupied by oxygen atoms and at the centers of the tetrahedra are the Mn(VII) centers. The connectivity is indicated by the formula O 3 Mn−O−MnO 3 . The terminal Mn−O distances are 1.585 Å and the bridging oxygen is 1.77 Å distant from the two Mn atoms. The Mn−O−Mn angle is 120.7°. [ 3 ]
Pyrosulfate , pyrophosphate , and dichromate adopt structures similar to that of Mn 2 O 7 . Probably the most similar main group species is Cl 2 O 7 . Focusing on comparisons within the transition metal series, Tc 2 O 7 and Mn 2 O 7 are structurally similar but the Tc−O−Tc angle is 180°. Solid Re 2 O 7 is not molecular but consists of crosslinked Re centers with both tetrahedral and octahedral sites; [ 4 ] in the vapour phase it is molecular with a similar structure to Tc 2 O 7 . [ 5 ]
Mn 2 O 7 arises as a dark green oil by the addition of cold concentrated H 2 SO 4 to solid KMnO 4 . [ 2 ] The reaction initially produces permanganic acid , HMnO 4 (structurally, HOMnO 3 ), which is dehydrated by cold sulfuric acid to form its anhydride , Mn 2 O 7 :
Mn 2 O 7 can react further with sulfuric acid to give the remarkable manganyl(VII) cation MnO + 3 , which is isoelectronic with CrO 3 :
Mn 2 O 7 decomposes near room temperature, explosively so above 55 °C (131 °F). The explosion can be initiated by striking the sample or by its exposure to oxidizable organic compounds. The products are MnO 2 and O 2 . [ 6 ] Ozone is also produced, giving a strong smell to the substance. The ozone can spontaneously ignite a piece of paper impregnated with an alcohol solution. [ citation needed ]
Manganese heptoxide reacts with hydrogen peroxide in presence of sulfuric acid , liberating oxygen and ozone :
Demonstration of manganese heptoxide's properties on YouTube | https://en.wikipedia.org/wiki/Manganese_heptoxide |
Manganese is an essential biological element in all organisms. [ 1 ] It is used in many enzymes and proteins. [ 2 ] [ 3 ] It is essential in plants . [ 4 ]
The classes of enzymes that have manganese cofactors include oxidoreductases , transferases , hydrolases , lyases , isomerases and ligases . Other enzymes containing manganese are arginase and Mn-containing superoxide dismutase ( Mn-SOD ). Also the enzyme class of reverse transcriptases of many retroviruses (though not lentiviruses such as HIV ) contains manganese. Manganese-containing polypeptides are the diphtheria toxin , lectins and integrins . [ 2 ]
Manganese is an essential human dietary element. It is present as a coenzyme in several biological processes, which include macronutrient metabolism, bone formation, and free radical defense systems. It is a critical component in dozens of proteins and enzymes. [ 3 ] The human body contains about 12 mg of manganese, mostly in the bones. The soft tissue remainder is concentrated in the liver and kidneys. [ 5 ] In the human brain, the manganese is bound to manganese metalloproteins , most notably glutamine synthetase in astrocytes . [ 6 ]
The U.S. Institute of Medicine (IOM) updated Estimated Average Requirements (EARs) and Recommended Dietary Allowances (RDAs) for minerals in 2001. For manganese, there was not sufficient information to set EARs and RDAs, so needs are described as estimates for Adequate Intakes (AIs). As for safety, the IOM sets Tolerable upper intake levels (ULs) for vitamins and minerals when evidence is sufficient. In the case of manganese, the adult UL is set at 11 mg/day. Collectively the EARs, RDAs, AIs and ULs are referred to as Dietary Reference Intakes (DRIs). [ 7 ] Manganese deficiency is rare. [ 8 ]
The European Food Safety Authority (EFSA) refers to the collective set of information as Dietary Reference Values, with Population Reference Intake (PRI) instead of RDA, and Average Requirement instead of EAR. AI and UL are defined the same as in the United States. For people ages 15 and older, the AI is set at 3.0 mg/day. AIs for pregnancy and lactation is 3.0 mg/day. For children ages 1–14 years, the AIs increase with age from 0.5 to 2.0 mg/day. The adult AIs are higher than the U.S. RDAs. [ 9 ] The EFSA reviewed the same safety question and decided that there was insufficient information to set a UL. [ 10 ]
For U.S. food and dietary supplement labeling purposes, the amount in a serving is expressed as a percent of Daily Value (%DV). For manganese labeling purposes, 100% of the Daily Value was 2.0 mg, but as of 27 May 2016 it was revised to 2.3 mg to bring it into agreement with the RDA. [ 11 ] [ 12 ] A table of the old and new adult daily values is provided at Reference Daily Intake .
Excessive exposure or intake may lead to a condition known as manganism , a neurodegenerative disorder that causes dopaminergic neuronal death and symptoms similar to Parkinson's disease . [ 5 ] [ 13 ]
Manganese deficiency in humans, which is rare, results in a number of medical problems. Many common vitamin and mineral supplement products fail to include manganese in their compositions. Relatively high dietary intake of other minerals such as iron, magnesium, and calcium may inhibit the proper intake of manganese. A deficiency of manganese causes skeletal deformation in animals and inhibits the production of collagen in wound healing.
Many enzymatic systems need Mn to function, but in high levels, Mn can become toxic. One environmental reason Mn levels can increase in seawater is when hypoxic periods occur. [ 14 ] Since 1990 there have been reports of Mn accumulation in marine organisms including fish, crustaceans, mollusks, and echinoderms. Specific tissues are targets in different species, including the gills, brain, blood, kidney, and liver/hepatopancreas. Physiological effects have been reported in these species. Mn can affect the renewal of immunocytes and their functionality, such as phagocytosis and activation of pro-phenoloxidase, suppressing the organisms' immune systems. This causes the organisms to be more susceptible to infections. As climate change occurs, pathogen distributions increase, and in order for organisms to survive and defend themselves against these pathogens, they need a healthy, strong immune system. If their systems are compromised from high Mn levels, they will not be able to fight off these pathogens and die. [ 15 ]
Mn-SOD is the type of SOD present in eukaryotic mitochondria , and also in most bacteria (this fact is in keeping with the bacterial-origin theory of mitochondria). The Mn-SOD enzyme is probably one of the most ancient, for nearly all organisms living in the presence of oxygen use it to deal with the toxic effects of superoxide ( O − 2 ), formed from the 1-electron reduction of dioxygen. The exceptions, which are all bacteria, include Lactobacillus plantarum and related lactobacilli , which use a different nonenzymatic mechanism with manganese (Mn 2+ ) ions complexed with polyphosphate, suggesting a path of evolution for this function in aerobic life.
Manganese is also important in photosynthetic oxygen evolution in chloroplasts in plants. The oxygen-evolving complex (OEC) is a part of photosystem II contained in the thylakoid membranes of chloroplasts; it is responsible for the terminal photooxidation of water during the light reactions of photosynthesis , and has a metalloenzyme core containing four atoms of manganese. [ 16 ] [ 17 ] To fulfill this requirement, most broad-spectrum plant fertilizers contain manganese. | https://en.wikipedia.org/wiki/Manganese_in_biology |
Manganese nitrides are salts of manganese and the nitride ion. Four of these compounds are stable at atmospheric pressure . The most important is Mn 3 N 2 , which catalyzes nitrogen fixation and is a high-temperature antiferromagnet . The others are Mn 6 N 5–6 , Mn 4 N, [ 1 ] [ 2 ] and Mn 2 N. [ 3 ] The compounds generally form as surface layer during combustion of manganese metal in nitrogen or ammonia gas, and homogenous samples can be difficult to obtain.
The compounds generally form from combustion of manganese metal in nitrogen or ammonia gas, but as a passivating surface layer; consequently homogenous samples are difficult to obtain. A sufficiently activated manganese sponge results from distillation of manganese amalgam . [ 4 ] As described in 1894, a sponge is essential to Mn 2 N synthesis: [ 5 ] manganese powder, if used instead, instead absorbs excess nitrogen, although the resulting nitrogen-rich salt anneals with manganese metal to the correct stoichiometry. [ 3 ]
Alternatively, manganese(II) chloride undergoes a non–self-propagating solid state metathesis with magnesium nitride at 550 °C to form Mn 3 N 2 ; higher temperatures or differently-sized cations give Mn 2 N instead. [ 6 ] Excess molten sodamide at 240 °C reduces manganese oxides to nitrides, with the final product dependent on stoichiometry, through the following reaction.
The waste sodium hydroxide selectively dissolves in an aqueous ethanol wash. [ 7 ] Manganocene ammonolyzes at 700 °C to give Mn 3 N 2 . [ 8 ] Manganese azides decompose when heated to give Mn 3 N 2 or Mn 6 N 5–6 and nitrogen gas. [ 2 ] [ 9 ]
Several manganese nitrides are stable at atmospheric pressure . The most important is Mn 3 N 2 , which catalyzes nitrogen fixation and is a high-temperature antiferromagnet . [ 6 ] Other salts include Mn 6 N 5–6 , Mn 4 N, [ 1 ] [ 2 ] and Mn 2 N. [ 3 ] [ 10 ] Splat quenching may also form a metastable Mn 8 N that decomposes without diffusion . [ 1 ] In general, no binary compounds of manganese and nitrogen are known in which manganese exhibits a formal oxidation state higher than Mn 2+ , but manganese does form a wide variety of homoleptic nitrido complexes and ternary salts , with oxidation states ranging from Mn + to Mn +6.5 ; indeed, the stablest homoleptic complex is Li 7 MnN 4 . [ 11 ]
Except for Mn 6 N 5–6 , [ 9 ] manganese nitrides are generally stable against hydrolysis , but act as Brønsted bases in concentrated acid . [ 12 ]
Nitrogen-doped manganese experiences a slight freezing point depression , with a eutectic point estimated near 1213 °C and 4 at% nitrogen. Further addition of nitrogen increases the melting point to roughly 1270 °C. [ 1 ]
Mn 4 N is an antiperovskite [ 11 ] superlattice with Pearson symbol cP5 and space group Fm 3 m , the same structure as an iron nitride homologue. [ 1 ] [ 3 ] The cell period is 0.3864 nm, and each nitrogen atom is very nearly at the center of the cell. [ 1 ] Any defects present are believed to be of Frenkel type . [ 11 ] It is the only truly ferromagnetic phase in the manganese-nitride system, with a Curie temperature around 470 °C. However, dissolved hydrogen in the compound is believed to slightly increase the Curie point. The compound metamorphosizes at 890 °C to the hexagonal close-packed Mn 2 N phase. [ 1 ]
Despite the name, Mn 2 N in fact exhibits substantial variation in its stable composition with temperature, and the formula Mn 2 N is only accurate near room temperature . It becomes nitrogen-deficient when heated, with composition Mn 5–6 N above 890 °C. These shifts in composition also correspond to a gradual change in the unit cell, such that the compound has various hexagonal unit cells at high temperatures. [ 1 ] [ 11 ] At its most nitrogen-rich (and coldest), though, the compound has an 0.5668×0.4909×4.537 nm 3 orthorhombic unit cell with space group D 14 2h . Pbna . It is isostructural with Mo 2 C . [ 3 ] [ 11 ]
Mn 3 N 2 is face-centered tetragonal , with Pearson symbol tI6 and space group I 4/ mmm , analogous to thorium hydride . [ 1 ] The unit cell has periods a = 0.42046 nm and c = 1.2131 nm, corresponding to three nearly-cubic unit cells stacked atop each other, but with substantial disorder corresponding to nitrogen vacancies. [ 13 ] It is a metallic conductor [ 1 ] and a Pauli antiferromagnet , with Néel temperature roughly 645 °C. [ 2 ] Around 710 °C, it reversibly decomposes to Mn 2 N, releasing the excess nitrogen as gas [ 1 ] and consuming 25 kJ/mol enthalpy. [ 2 ] Likewise, it decomposes in a 400 °C hydrogen atmosphere to a body-centered cubic alloy. [ 14 ]
Mn 6 N 5–6 resembles CrN . [ 2 ] It is face-centered tetragonal like Mn 3 N 2 , but lacks the vacancies that cause such a large fineness ratio in the latter. Instead Mn 6 N 5–6 is nearly cubic. [ 1 ] [ 2 ] When nitrogen-poor, it has lattice parameters a = 0.42 nm and c = 0.41 nm, [ 1 ] but the unit cell dimensions vary substantially with nitrogen content and temperature, and the material becomes truly cubic at 400 °C. Consequently it exhibits substantial crystal twinning . [ 2 ] Around 580 °C, it decomposes to Mn 3 N 2 and nitrogen gas, [ 1 ] but requires a very high nitrogen vapor pressure (even at lower temperatures) to stabilize the phase. [ 1 ] [ 2 ] The decomposition is somewhat reversible, recovering Mn 6 N 5.18 upon cooling. Between 150 °C and 325 °C, it undergoes a magnetic phase transition, aligning moments along one symmetry axis; the Néel temperature is then 387 °C. [ 2 ]
In principle, a hexagonal MnN monolayer should exhibit very strong spin polarization, thus behaving as a very strong ferromagnet. [ 15 ] | https://en.wikipedia.org/wiki/Manganese_nitrides |
Mangotoxin is a small peptide produced in Pseudomonas syringae . It was found to cause apical necrosis in mango plants. It also causes chlorosis in plants by disrupting ornithine and arginine biosynthesis . [ 1 ]
The proteins required for mangotoxin biosynthesis are encoded by the genes in mangotoxin biosynthetic operon ( mbo ): mboA, mboB, mboC, mboD, mboE , and mboF . All of them are required for the synthesis. The mbo -operon is regulated by gene mgoA in mangotoxin generating operon ( mgo ). [ 1 ] The MgoA protein increases expression of mbo , but lack of MgoA is not enough to silence the mbo . [ 2 ]
The mangotoxin related genes and their homologues are common in Pseudomonas , and they also appear also in other phyla, like Burkholderia . Their purpose is to produce toxin to kill other competing microbes, like fungi or oomycetes . [ 3 ]
This biochemistry article is a stub . You can help Wikipedia by expanding it . | https://en.wikipedia.org/wiki/Mangotoxin |
Mangrove restoration is the regeneration of mangrove forest ecosystems in areas where they have previously existed. Restoration can be defined as "the process of assisting the recovery of an ecosystem that has been degraded, damaged, or destroyed." [ 1 ] Mangroves can be found throughout coastal wetlands of tropical and subtropical environments. Mangroves provide essential ecosystem services such as water filtration, aquatic nurseries, medicinal materials, food, and lumber. [ 2 ] Additionally, mangroves play a vital role in climate change mitigation through carbon sequestration and protection from coastal erosion, sea level rise, and storm surges. Mangrove habitat is declining due to human activities such as clearing land for industry and climate change. [ 2 ] [ 3 ] Mangrove restoration is critical as mangrove habitat continues to rapidly decline. Different methods have been used to restore mangrove habitat, such as looking at historical topography, or mass seed dispersal. [ 4 ] [ 5 ] Fostering the long-term success of mangrove restoration is attainable by involving local communities through stakeholder engagement. [ 6 ]
Mangroves are typically found in tropical regions of the world on the coasts of America, Australia, Asia, and Africa. [ 7 ] Mangrove ecosystems are found in about 120 countries [ 8 ] in the world and make up 0.7% of the world's tropical forests. [ 7 ] In most of these regions mangroves provide many services including; shelter, climate regulation through carbon sequestration, [ 7 ] decrease coastal erosion, create a link between terrestrial and marine ecosystems, and maintain water quality along the coast. Mangroves have recently become susceptible to deforestation due to human activities and extreme weather. Aquaculture, agriculture, and urbanization [ 7 ] are some of the reasons why mangroves are being damaged or destroyed.
Historically, mangroves have been identified two different ways: the species of trees and shrubs that can tolerate brackish water conditions, or the species that fall under the mangrove family, Rhizophoraceae as well as trees of the genus Rhizophora . [ 9 ] The majority of mangrove genera and families are not closely related, but they do however, share some adaptive commonalities. These unique qualities that allow mangroves to thrive in aversive conditions are pneumatophoric roots, stilt roots, salt-excreting leaves, and viviparous water-dispersed propagules . [ 9 ] Mangrove communities occur between the latitudes of 30° N to 37° S and grow in waters where tidal height is between 1 and 4 meters. [ 10 ] They can be found in various geographic areas from oceanic islands to riverine systems and in warm temperate climates to arid and wet tropics. [ 10 ] Despite having a relatively large range of habitat, mangroves thrive in optimal areas. In warmer, humid climates, mangrove canopies may reach a height of 30–40 m. In colder, arid environments, mangroves form isolated patches with stunted growth, reaching about 1–2 m. [ 9 ]
Mangrove forests, along with the animal species they shelter, represent globally significant sources of biodiversity and provide humanity with valuable ecosystem services . They are used by mammals , reptiles and migratory birds as feeding and breeding grounds, and provide crucial habitats for fish and crustacean species of commercial importance. [ 11 ] The Atlantic goliath grouper for instance, which is currently listed as critically endangered due to overfishing, utilizes mangroves as a nursery for the first 5–6 years of life. [ 12 ] The roots of the mangrove physically buffer shorelines from the erosive impacts of ocean waves and storms. [ 11 ] Additionally, they protect riparian zones by absorbing floodwaters and slowing down the flow of sediment -loaded river water. This allows sediments to drop to the bottom where they are held in place, thus containing potentially toxic waste products and improving the quality of water and sanitation in coastal communities.
To the human communities who rely on them, mangrove forests represent local sources of sustainable income from the harvest of fish and timber , as well as non-timber forest products such as medicinal plants , palm leaves and honey . On a global scale, they have been shown to sequester carbon in quantities comparable to higher- canopy terrestrial rainforests , which means that they may play a role in climate change mitigation . [ 13 ] It has been shown that even though mangrove forests only account for 0.5% of the worlds coastal habitats it has a much higher sequestration rate of carbon compared to other coastal habitats (except for salt marshes). [ 14 ] In addition to physically protecting coastlines from the projected sea-level rise associated with climate change. [ 15 ]
Mangrove forests have a potential to mitigate climate change, such as through the sequestration of carbon from the atmosphere directly, and by providing protection from storms, which are expected to become more intense and frequent into the 21st century. A summary of coastal wetland carbon, including mangroves, is seen in the accompanying image. Wetland plants, like mangroves, take in carbon dioxide when they perform photosynthesis. They then convert this into biomass made of complex carbon compounds. [ 16 ] Being the most carbon-rich tropical forest, mangroves are highly productive and are found to store three to four times more carbon than other tropical forests. [ 17 ] This is known as blue carbon . Mangroves make up only 0.7% of tropical forest area worldwide, yet studies calculate the effect of mangrove deforestation to contribute 10% of global CO 2 emissions from deforestation. [ 18 ] The image to the right shows the global distribution of above ground carbon from mangroves. As can be seen, most of this carbon is located in Indonesia, followed by Brazil, Malaysia and Nigeria. [ 19 ] Indonesia has one of the highest rates of mangrove loss, yet the most carbon stored from mangroves. [ 20 ] Therefore, it is suggested that if the correct policy is implemented, countries like Indonesia can make considerable contributions to global carbon fluxes. [ 19 ]
The UN estimate deforestation and forest degradation to make up 17% of global carbon emissions, which makes it the second most polluting sector, following the energy industry. [ 21 ] The cost of this globally is estimated to total $42 billion. [ 22 ] Therefore, in recent years, there has been more focus on the importance of mangroves, with initiatives being developed to use reforestation as a mitigation tool for climate change.
The issue of restoration is critical today since mangrove forests are being lost very quickly – at an even faster rate than tropical rainforests inland. [ 23 ] During the 1970s, mangroves occupied as much as 200,000 km 2 , encompassing approximately 75% of the world's coastlines. [ 24 ] Now, global mangrove area has experienced significant decline where at least 35% has been lost. Mangroves are continuing to diminish at a rate of 1-2% per year. [ 24 ] Much of this lost mangrove area was destroyed to make room for industry, housing and tourism development; for aquaculture , primarily shrimp farms; and for agriculture , such as rice paddies , livestock pasture and salt production . [ 25 ] Other drivers of mangrove forest destruction include activities that divert their sources of freshwater, such as groundwater withdrawals, the building of dams, and the building of roads and drainage canals across tidal flats .
Another indirect human activity, climate change, also threatens mangrove habitat. Sea levels are on the rise as polar ice caps melt from increasing temperatures and thermal expansion. [ 26 ] Depending on sediment accumulation, mangrove habitats will generally respond to sea level change in three different ways: [ 26 ] (1) If the sediment in the mangrove forest rises faster than the sea level, plants from further inland may move into the area as the mangroves retreat; (2) if the rate of sediment accumulation is equal to the rate of sea level rise, the forest survives and is stable during this period and (3) if the rate of soil accumulation is slower than the rate of sea level rise, the mangrove forest will be submerged by the sea. However, mangroves may then adapt and spread more inland as new territory is made for mangrove habitat. It is important to note that changes may deviate from these three general scenarios depending on local morphological/topographical features. [ 26 ] However, there are limits to the capacity of mangroves to adapt to climate change. It is projected that a 1-meter rise in sea level could inundate and destroy mangrove forests in many regions around the globe.
Mangroves play a vital role in delivering essential ecosystem services for the benefit of both humans and wildlife. The loss of these invaluable services will have a significant negative impact on the world. Mangrove habitat loss leaves coastal communities vulnerable to the risks of flooding , shoreline erosion , saline intrusion , and increased storm activity. [ 27 ] Ecosystem services such as water purification and collection of raw materials are not possible if mangroves are utilized unsustainably. [ 28 ] Furthermore, the decline of mangrove communities heavily impacts the plants and animals that rely on the habitat for survival. Loss of mangroves leads to reduced water quality, reduced biodiversity, increased sedimentation threatening coral reefs, and collapse of intertidal food webs and aquatic nurseries. [ 29 ] [ 28 ] Since mangroves are carbon sinks , their destruction can release large amounts of stored carbon and contribute to the effects of global warming. [ 28 ]
Mangroves are sensitive ecosystems , changing dynamically in response to storms, sediment blockage, and fluctuations in sea level and present a "moving target" for restoration efforts. Mangroves are considered to be one of the easiest coastal systems to restore because of their seedlings ability to survive where adult trees are not present. [ 30 ] The most common method simply consists in planting single-species stands of mangroves in areas thought to be suitable, without consideration of whether or not they supported mangroves in the past. This approach usually fails over the long term because the underlying soil and hydrological requirements of the mangroves are not being met. Mangrove survival is dependent on many factors including soil salinity, sedimentation, groundwater availability, and tidal changes which can vary greatly in small areas. This means, each tree in a mangrove forest will grow slightly different resulting from its unique surrounding conditions.
More informed methods aim to bring a damaged mangrove area back into its preexisting condition, taking into account not only ecosystem factors but also social, cultural and political perspectives. These approaches begin with the understanding that a damaged mangrove area may be able to repair itself through the natural processes of secondary succession , without being physically planted, provided that its tidal and freshwater hydrology is functioning normally and there is an adequate supply of seedlings . If natural renewal does occur, Twilley et al. 1996 predicts species composition will be largely determined by the very earliest saplings to colonize the recovering stand. This prediction is supported by the actual studies of Clarke et al. 2000, Clarke et al. 2001, Ross et al. 2006 and Sousa et al. 2007.
A second approach to mangrove restoration is the ecological mangrove restoration (EMR) approach. [ 31 ] This approach mainly focuses on correcting the hydrology of a mangrove ecosystem for long lasting health of the area while the plantation approach does not truly take into account the dynamics of the ecosystem. While some planting may be required in the EMR approach, the expectation is that mangrove seedlings will be able to naturally recolonize. Steps to the EMR approach are as follows:
This may include introducing structures such as detached breakwaters , to protect the site from wave action and allow for adequate sediment build-up. [ 32 ] The actual planting of seedlings is a last resort, since it fails in many cases; [ 33 ] it should be considered only if natural recruitment of seedlings fails to reach the restoration objective.
Restoring mangroves by traditional methods, manually, is slow and difficult work. An alternative has been proposed to use quadcopters to carry and deposit seed pods. According to Irina Fedorenko and Susan Graham of BioCarbon Engineering, a drone can do an amount of work in days that is equivalent to weeks of planting by humans using traditional methods, at a fraction of the cost. Drones can also carry and plant seeds in difficult-to-reach or dangerous areas where humans cannot work easily. Drones can be used to develop planting patterns for areas and to monitor growth of new forests. [ 34 ]
An important but often overlooked aspect of mangrove restoration efforts is the role that the local communities play as stakeholders in the process and the outcome. If a restoration project is put in place without support of the local community, it may result in backlash, wasted funding, and wasted efforts. [ 35 ] An important aspect to consider is whether society deems if restoration of mangroves is worth the investment effort. This is ultimately determined by human self interest, and whether the decision will maximize their personal utility. [ 35 ] Another obstacle that projects may face is how to quantify the economic value of mangrove restoration. Ecological services of mangroves are difficult to determine, "as most of them are of indirect nature and non-marketed." [ 35 ] Support of local communities are a crucial aspect in the long-term success of mangrove restoration. Not only can locals provide knowledge about the environment, their participation through employment and funding strategies will encourage them to keep maintaining the mangroves after initial success of the project. [ 35 ]
A case study in the Philippines gathered data on local people's participation in a mangrove restoration project. Locals can play a major participatory role in mangrove restoration projects, so encouraging and strengthening their participation is particularly important. However, in order for participation to occur, there must be benefits and incentives provided to engage the community. If benefits are not received, local people are discouraged from participating. [ 36 ] This study found that participation in mangrove restoration improves livelihoods and increases social capital, which directly benefits their access to information and services. Participation in mangrove restoration can provide more than just tangible benefits, it also leads to more sustainable and long-term rewards. [ 36 ]
It is estimated that approximately 15% of total anthropogenic carbon emissions a year can be attributed to carbon emissions from tropical deforestation. [ 37 ] In 2008, the United Nations launched the "Reducing Emissions from Deforestation and forest Degradation ( REDD )" program to combat climate change through the reduction of carbon emissions and enhancement of carbon sinks from forests. [ 38 ] It is the opinion of literary scholars that the REDD program can increase carbon sequestration from mangroves and therefore reduce carbon in the atmosphere. [ 39 ] [ 40 ] The REDD+ mechanism, as part of the REDD program, provides financial support to stakeholders in developing countries to avoid deforestation and forest degradation . [ 41 ] The estimated impacts of REDD+ globally, could reach up to 2.5 billion tons of CO 2 each year. [ 42 ] An examples of REDD+ implementation can be seen in Thailand, where carbon markets give farmers incentive to conserve mangrove forests, by compensating for the opportunity cost of shrimp farming. [ 43 ]
Moreover, the Mangroves for the Future (MFF) initiative, led by IUCN and UNDP , encourages the rehabilitation of mangroves by engaging with local stakeholders and creating a platform for change. [ 44 ] In Indonesia, one project planted 40,000 mangroves, which then encouraged local government to take up similar initiatives on a larger scale. [ 45 ] Mangrove restoration and protection is also seen as a climate change mitigation strategy under COP21 , the international agreement to target climate change, with countries being able to submit the act in their Nationally Appropriate Mitigation Approaches (NAMAs). Ten of the world's least developed countries are now prioritizing mangrove restoration in their NAMAs. [ 46 ] | https://en.wikipedia.org/wiki/Mangrove_restoration |
The Manhattan mobility model is a guide which leads the driver of a vehicle on the correct path. It is an urban type of mobility model for vehicular ad-hoc networks (VANET). The Manhattan mobility model uses a " grid road topology. It works optimally where streets are in an organized manner.
In this mobility model, mobile nodes move in horizontal or vertical direction on an urban map . The Manhattan model employs a probabilistic approach in the selection of nodes movements since, at each intersection , a vehicle chooses to keep moving in the same direction. The probability of going straight is 0.5 and taking a left or right is 0.25 each.
The Manhattan model is not suitable for highway systems. Although this model provides flexibility for the nodes to change the direction, it imposes geographic restrictions on node mobility. | https://en.wikipedia.org/wiki/Manhattan_mobility_model |
A Manhattan plot is a type of plot , usually used to display data with a large number of data-points, many of non-zero amplitude, and with a distribution of higher-magnitude values. The plot is commonly used in genome-wide association studies (GWAS) to display significant SNPs . [ 1 ]
It gains its name from the similarity of such a plot to the Manhattan skyline : a profile of skyscrapers towering above the lower level "buildings" which vary around a lower height.
In GWAS Manhattan plots, genomic coordinates are displayed along the x -axis, with the negative logarithm of the association p -value for each single nucleotide polymorphism (SNP) displayed on the y -axis, meaning that each dot on the Manhattan plot signifies an SNP. Because the strongest associations have the smallest p -values (e.g., 10 −15 ), their negative logarithms will be the greatest (e.g., 15). The different colors of each block usually show the extent of each chromosome.
This statistics -related article is a stub . You can help Wikipedia by expanding it . | https://en.wikipedia.org/wiki/Manhattan_plot |
A manhole cover is a removable plate forming the lid over the opening of a manhole , an opening large enough for a person to pass through that is used as an access point for an underground vault or pipe. It is designed to prevent anyone or anything from falling in, and to keep out unauthorized persons and material.
Manhole covers date back at least to the era of ancient Rome, which had sewer grates made from stone.
Manhole covers are often made out of cast iron , concrete or a combination of the two. This makes them inexpensive, strong, and heavy, usually weighing more than 113 kilograms (249 lb). [ citation needed ] The weight helps to keep them in place when traffic passes over them, and makes it difficult for unauthorized people without suitable tools to remove them.
Manhole covers may also be made from glass-reinforced plastic or other composite material (especially in Europe, or where cover theft is of concern). Because of law restricting acceptable manual handling weights, Europe has seen a move towards lighter weight composite manhole cover materials, which also have the benefits of greater slip resistance and electrical insulating properties.
A manhole cover sits on a metal base, with a smaller inset rim which fits the cover. The base and cover are sometimes called "castings", because they are usually made by a casting process , typically sand-casting techniques. [ 1 ]
The covers usually feature "pick holes", into which a hook handle tool is inserted to lift them. Pick holes can be concealed for a more watertight lid, or can allow light to shine through. A manhole pick or hook is typically used to lift them, though other tools can be used as well, including electromagnets.
Although the covers are too large to be easily collectible , their ubiquity and the many patterns and descriptions printed on them has led some people to collect pictures of covers from around the world. According to Remo Camerota, the author of a book on the subject titled Drainspotting , 95% of Japanese municipalities have their own cover design, often with colorful inlaid paint. [ 2 ]
Despite their weight and cumbersome nature, manhole covers are sometimes stolen, usually for resale as scrap, particularly when metal prices rise. [ 3 ] [ 4 ] [ 5 ] [ 6 ]
Manhole covers may be marked to indicate what sort of services exist under them and what group maintains those services, such as the local water system, telecommunications firm, subway or train services, or natural gas firm.
The name "manhole" is sometimes changed to make it gender neutral. The city of Berkeley, California, for example, changed the official term to "maintenance hole" in 2019. [ 7 ]
The question of why manhole covers are typically round (in some countries) was made famous by Microsoft when they began asking it as a job-interview question . [ 8 ] Originally meant as a psychological assessment of how one approaches a question with more than one correct answer, the problem has produced a number of alternative explanations, from the tautological ("Manhole covers are round because manholes are round") [ 8 ] to the philosophical.
Reasons for the shape might include:
Other manhole shapes can be found, usually squares or rectangles. For example, in the United Kingdom nearly all manhole covers are square or rectangular and very occasionally triangular, but almost never circular. Nashua , New Hampshire , is unusual for having triangular manhole covers that point in the direction of the underlying flow. In 2011, the city began gradually phasing out the triangles, [ 9 ] which were made by a local foundry , because they were not large enough to meet modern safety standards and a manufacturer for larger triangles could not be found. [ 10 ] Some manhole covers in Hamilton , Bermuda , are triangular, and hinged. Some triangular water-main covers also exist in San Francisco . [ 11 ]
A robotics research paper in 2011 suggested that robots could examine the shapes of specific manhole covers and use them to calculate their geographic position, as a double-check on GPS data. [ 12 ]
In urban areas, stray voltage issues have become a significant concern for utilities. On January 16, 2004, Jodie S. Lane was electrocuted after stepping on a metal manhole cover, while walking her dog in New York City. [ 13 ] As result of this and other incidents, increased attention has been focused on these hazards, including technical conferences on stray voltage detection and prevention. [ 14 ] Insulation failures can be caused by road salt , age, rats biting the wires, or vibrations from traffic. [ 15 ]
Electrical arcing can ignite insulation, leaking natural gas , methane from decaying organic matter, fumes from smouldering insulation, [ 15 ] or even gasoline poured down the toilet. [ 16 ] This can cause a fire, power outages, and in some cases, an explosion. [ 15 ] In the United States, they are most common in New York City, with 3,369 "manhole events", including 32 explosions recorded in 2014. [ 17 ] They were most common in summer due to increased electricity use. Chicago reported fewer than 10 events with no explosions, despite also using road salt in the winter. [ 17 ]
The Boston area experienced 62 "events" in 2021 (down from 212 in 2018). As of 2022, local utility company Eversource is replacing 38,000 maintenance hole covers, starting in high-traffic areas, with a safer design. A rail allows the cover to lift up to 4 inches (100 mm) and let gases escape, but prevents it from flying into the air and damaging buildings or cars or injuring pedestrians. In some places where road salt is not a concern, the covers have vents to let gases escape. To prevent and mitigate safety problems, the company is also installing monitoring equipment to detect dangerous gases and fires, and increasing inspection frequency. [ 15 ]
Because of their aerodynamic design, some modern racing cars create enough vacuum to lift a manhole cover off its recess. During races on city streets, manhole covers must therefore be welded or locked down to prevent injury. In 1990 , during the Group C World Sportscar Championship race at Circuit Gilles Villeneuve (located in a public park in Montreal, Quebec), a Brun Motorsport Porsche 962 struck a manhole cover that was lifted by the ground effect of the car he was following, a Courage C24 Porsche. This caused the trailing Porsche to catch fire, and safety issues ended the race shortly afterwards. [ citation needed ]
The theft of manhole covers often increases when scrap metal prices are high. [ 18 ] [ 19 ]
Manhole cover theft can be a serious problem in China , where missing manhole covers caused at least eight deaths in 2004. [ 20 ] According to China's Xinhua News Agency , about "240,000 manhole and street-drain covers were stolen in Beijing in 2004." [ 21 ]
In China Shakes the World , James Kynge describes the phenomenon:
... in the several weeks beginning in mid-February 2004, when, slowly at first but with mounting velocity, manhole covers started to disappear from roads and pavements around the world. As Chinese demand drove up the price of scrap metal to record levels, thieves almost everywhere had the same idea. As darkness fell, they levered up the iron covers and sold them to local merchants, who cut them up and loaded them onto ships to China. The first displacements were felt in Taiwan , the island country just off China's southeast coast. The next were in other neighbors such as Mongolia and Kyrgyzstan ... Wherever the sun set, pilferers worked to satisfy China's hunger. More than 150 covers disappeared during one month in Chicago . Scotland 's "great drain robbery" saw more than a hundred vanish in a few days. From Montreal to Gloucester to Kuala Lumpur , unsuspecting pedestrians stumbled into holes.
In Newham , East London , nearly 200 grates and covers were stolen in 2004. [ 22 ] A manhole cover designed by artist Antony Gormley was stolen in 2013, ten years after its installation. [ 23 ]
In the city of Kolkata , India , more than 10,000 manhole covers were taken in two months in 2004. These were replaced with concrete covers, but these were also stolen, this time for the rebar inside them. [ 24 ]
In March and April 2012, Ajax, Ontario , and Niagara Falls, Ontario , [ 25 ] had dozens of manhole covers stolen.
In December 2021, Chatham County, Georgia , [ 26 ] reported 30 manhole covers stolen in a single day.
A manhole cover was accidentally launched from its shaft during an underground nuclear test in 1957. During the Operation Plumbbob nuclear tests, a 900-kilogram (1,984 lb) steel plate cap was blasted off the test shaft at an unknown speed and appeared as a blur on a single frame of film of the test. It was never recovered, but it likely burned up in the atmosphere due to friction. If by some stroke of luck the manhole cover had made it into orbit, it would have been the first man-made object to do so, as it pre-dated the launch of Sputnik 1 by 38 days. A calculation before the event gave a predicted speed of six times Earth escape velocity . After the event, Dr. Robert R. Brownlee described the best estimate of the cover's speed from the photographic evidence as "going like a bat out of hell!" [ 27 ] [ 28 ] [ 29 ]
The European norm EN 124 of 1994 applies to manhole and storm drain tops with a clear opening up to 1 m for areas subjected to pedestrian or vehicular traffic (covers with a clear opening over 1 m are specified in the British Standard BS9124 for example). [ 30 ] EN 124 specifies several weight classes depending on the application and is also being used in some countries outside the European Union. The lightest class A15 (cast iron) manhole cover can withstand a maximum weight of 1.5 tonnes. It would typically be restricted to light duty applications in pedestrian areas, gardens, patios, driveways and similar. By contrast, the heaviest class F900 manhole cover can withstand a maximum weight of 90 tons, making it suitable for docks, airports, and other extreme heavy-duty applications. [ 31 ]
EN 124 does not apply for gratings of prefabricated drainage channels (according to EN 1433) or floor and roof gullies in buildings (specified in EN 1253-1). [ 30 ]
The Fabricated Access Covers Trade Association (FACTA) provides its own specification which came into effect in 2013. It has a similar scope as the EN 124, focuses on wheel loadings and is based on the European standards for structural steelwork.
The FACTA specification applies to solid top covers, recessed covers designed for structural or non-structural infill and surface drainage products. [ 30 ]
In Japan, a number of manhole covers have been featuring artistic designs since the 1980s. There is enough interest in them to allow merchandise and conventions, with an estimated 12,000 designs spread across Japan by 2019. [ 32 ] These could be found in nearly all cities and towns in the country. [ 33 ] Popular media franchises, such as Gundam and Pokémon , have also been featured in the covers with hundreds of Pokémon-themed manhole covers across Japan. [ 34 ]
The utilization of manhole covers as street art has also been done in Taiwan and Vietnam . [ 35 ] [ 36 ] | https://en.wikipedia.org/wiki/Manhole_cover |
The Manhès–David process is a refining process of the copper mattes , invented in 1880 by the French industrialist Pierre Manhès and his engineer Paul David [ fr ] . Inspired by the Bessemer process , it consists of the use of a converter to oxidise with air the undesirable chemical elements (mainly iron and sulfur ) contained in the matte, to transform it into copper.
The quantity of the elements to be oxidized, as well as the low heat produced by the chemical reactions , lead to drastics modifications of the converter. Manhès and David designed it as a horizontal cylinder, with nozzles aligned from one end to the other. A few years later, the Americans engineers William H. Peirce and Elias Anton Cappelen Smith lined it with basic refractory materials, much more durable than that used by the French inventors. While this improvement does not alter the principles of the process, it eases its widespread use, accelerating the switchover of copper production from Britain to the United States.
At the beginning of the 21st century, the Pierce-Smith converters [ fr ] refine 90% of the copper mattes and is used in 60% of the nickel extracted. This converter, like the addition of pure oxygen, the automation of the running, the treatment of smoke and the increasing size of the tools, ensured the durability of the Manhès–David process, even if modern tools have little relationship with their ancestors.
Just as iron produced by a blast furnace comes out alloyed with other chemical elements as cast iron, copper extracted from ore becomes an alloy with sulfur, iron, etc. called matte. To apply the same purification processes to these two metals is therefore logical. Applying the Bessemer process to copper metallurgy was proposed, and the principle validated in 1866, ten years after Henry Bessemer 's invention, by the Russian engineer Semenikow. [ 2 ]
The refinement of the alloy in the converter is possible because the combustion of undesirable elements is strongly exothermic: the oxidation of silicon and carbon respectively produce 32.8 and 10.3 kilojoules per kilogram. [ 3 ] On the other hand, if a copper matte contains an abundance of iron and sulfur, these elements must first be separated (which consumes 6.8 kilojoules per kilogram of FeS) before their oxidation (which only produces 5.9 and 9.1 kJ/kg respectively) can begin. [ 4 ] [ 5 ]
The first refinements of copper alloys by a converter took place in Ducktown, Tennessee where A. Raht worked on a partial refinement of the matte from 1866 to 1875. In 1867, the Russians Jossa and Latelin tried to experimentally verify the studies of Semenikow. In 1870, they stopped their experiments after only having succeeded to increase the copper content from 31% to 72-80%. [ 4 ]
In England, John Hollway continued these trials until 1878. [ 6 ] [ 7 ] Like his predecessors, he observed that if blowing began in a satisfactory manner, it became more and more intermittent as the refinement progressed. The obstacles he encountered were numerous: [ 2 ]
All of the encountered difficulties could not be easily resolved: the thermal heat balance of the refinement reaction in air of copper was not as favorable as for iron, and the matte solidified in the tuyeres before being refined. [ 5 ] Even when modified, a Bessemer converter was capable at best of removing iron and a portion of sulfur. [ 8 ] Hollway failed, but by publishing all of the details of his experiments, he identified the essential problems. [ 9 ]
In the 1870s, the French industrialist Pierre Manhès began his first attempts with a small, ordinary Bessemer converter of 50 kg in his factory in Vedène , then in factories in Éguilles , near Avignon . [ 5 ] He sought to refine a matte with 25 to 30% copper previously melted in a crucible. But like Hollway, he did not succeed in completely refining the matte. The oxidation of undesirable elements occurred as expected, but the operation was quickly disrupted by the appearance of metallic copper. [ 10 ] The matte, which was an ionic compound, was immiscible with the slag, but also with the molten metal. The latter, which is denser (ρ copper ≈ 9), went to the bottom of the converter [ 11 ] and clogged the tuyeres.
Pierre Manhès then patented the use of additives whose oxidation would release enough heat to avoid getting stuck. In the end, it was the Frenchman Paul David, then an engineer in his factory in 1880, who suggested the solution. He proposed horizontal tuyeres placed at a sufficient distance from the bottom of the converter so that the copper could gather below them and the air blow constantly in the matte. By 1881, their converter was both technically operational and cost-effective.
In the autumn of 1884, the process was adopted in the United States by the Parrot Silver and Copper Company in Butte, Montana . [ 6 ] The two types became larger and larger, increasing from a capacity of one ton to eight tons in 1912, [ 2 ] and even fifteen tons for cylindrical converters in 1920. [ 8 ]
As the slag becomes enriched with iron oxide during the reaction in air, it becomes basic and then combines with the siliceous refractory lining, which is very acidic . [ 2 ] A basic refractory lining would not react and would therefore lower the cost of production. The adoption of a lining inspired by one developed by Sidney Thomas and Percy Gilchrist in 1877 [ 12 ] was suggested by Hollway during his last tests in the early 1800s. [ 2 ] However, the idea was not tested, as fundamental problems related to the air blowing were more of a problem than refractory optimization. [ 6 ]
In 1890, a basic refractory lining was tested on one of Parrot Smelter's Manhès-David converters, in Butte, under the direction of Herman A. Keller. The tests did not result in a lining compatible with industrial operation. [ 2 ] In 1906, Ralph Baggaley , still in Montana, succeeded, after a number of tests, in industrializing a basic coating at Pittsmont Smelter, which was abandoned in 1908 after he left the factory. [ 9 ] After all that, the Norwegian Kudsen succeeded as of 1908 in using a basic coating with the Sulitjelma Mines . He carried out two successive blowings there, initially in a small converter with a basic coating, and then in a second traditional converter with an acidic coating. [ 2 ]
Finally, in 1909, [ 13 ] [ 14 ] at the Baltimore Copper Company's Smelter, the Americans William H. Peirce and Elias A.C. Smith succeeded in addressing the main drawbacks of basic refractories; basic refractories were more fragile, and, above all, they dissipated more heat than acidic refractories. [ 2 ] By developing a masonry suitable for the cylindrical converter and increasing the amount of metal fed into the furnace, they solved the remaining problems. [ 2 ]
Peirce and Smith's converter proved much more advantageous than that of Manhès and David. The basic refractory, which did not react with slag, lasted much longer. This improvement eliminated the need for replacement of the converters, the construction of masonry installations, [ 2 ] and replacement converters (there were two masonry converters for every one in service in 1897 at Anaconda Copper [ 15 ] ). It also reduced the risk of piercings due to poor control of wearing of the refractory. [ 6 ] The refractory layer could then be thinner, increasing the capacity of the converter. The capacity was not dependent on wearing of the refractory, thus simplifying the management of the flows of molten metal in factories. [ 2 ]
If the material used to prepare the acid refractory contains copper, or even silver or gold (frequently associated with copper in gold-bearing quartz [ 16 ] ), these metals join the matte as the lining is removed. Considering the refractory's rapid destruction, the economic advantage of an acidic refractory is therefore only realized if its consumption adds value to the process. [ 2 ] This situation is however rather rare and, even if this is the case, silica rich in precious metals can be made by other economically viable means. Therefore, in 1921, the basic refractory was considered the main factor in the cost reduction in the extraction of copper ores. [ 17 ] In some cases, a reduction in conversion costs from $15–20 to $4–5 was reported. [ 18 ]
A mixture of copper and iron sulfides referred to as matte is treated in converters to oxidize iron in the first stage, and oxidize copper in the second stage. In the first stage oxygen enriched air is blown through the tuyeres to partially convert metal sulfides to oxides:
Since iron has greater affinity to oxygen, the produced copper oxide reacts with the remaining iron sulfide:
The bulk of the copper oxide is turned back into the form of sulfide. In order to separate the obtained iron oxide, flux (mainly silica) is added into the converter. Silica reacts with iron oxide to produce a light slag phase, which is poured off through the hood when the converter is tilted around the rotation axis:
After the first portion of slag is poured off the converter, a new portion of matte is added, and the converting operation is repeated many times until the converter is filled with the purified copper sulfide. The converter slag is usually recycled to the smelting stage due to the high content of copper in this by-product. Converter gas contains more than 10% of sulfur dioxide, which is usually captured for the production of sulfuric acid .
The second stage of converting is aimed at oxidizing the copper sulfide phase (purified in the first stage), and produces blister copper . The following reaction takes place in the converter:
Copper content in the obtained blister copper is typically more than 95%. Blister copper is the final product of converting. | https://en.wikipedia.org/wiki/Manhès–David_process |
In general relativity , a manifestly covariant equation is one in which all expressions are tensors . The operations of addition, tensor multiplication , tensor contraction , raising and lowering indices , and covariant differentiation may appear in the equation. Forbidden terms include but are not restricted to partial derivatives . Tensor densities , especially integrands and variables of integration, may be allowed in manifestly covariant equations if they are clearly weighted by the appropriate power of the determinant of the metric.
Writing an equation in manifestly covariant form is useful because it guarantees general covariance upon quick inspection. If an equation is manifestly covariant, and if it reduces to a correct, corresponding equation in special relativity when evaluated instantaneously in a local inertial frame , then it is usually the correct generalization of the special relativistic equation in general relativity.
An equation may be Lorentz covariant even if it is not manifestly covariant. Consider the electromagnetic field tensor
where A a {\displaystyle A_{a}} is the electromagnetic four-potential in the Lorenz gauge . The equation above contains partial derivatives and is therefore not manifestly covariant. Note that the partial derivatives may be written in terms of covariant derivatives and Christoffel symbols as
For a torsion -free metric assumed in general relativity, we may appeal to the symmetry of the Christoffel symbols
which allows the field tensor to be written in manifestly covariant form | https://en.wikipedia.org/wiki/Manifest_covariance |
In mathematics , the Manin–Drinfeld theorem , proved by Manin ( 1972 ) and Drinfeld ( 1973 ), states that the difference of two cusps of a modular curve has finite order in the Jacobian variety .
This number theory -related article is a stub . You can help Wikipedia by expanding it . | https://en.wikipedia.org/wiki/Manin–Drinfeld_theorem |
In mathematics , the arithmetic of abelian varieties is the study of the number theory of an abelian variety , or a family of abelian varieties. It goes back to the studies of Pierre de Fermat on what are now recognized as elliptic curves ; and has become a very substantial area of arithmetic geometry both in terms of results and conjectures. Most of these can be posed for an abelian variety A over a number field K ; or more generally (for global fields or more general finitely-generated rings or fields).
There is some tension here between concepts: integer point belongs in a sense to affine geometry , while abelian variety is inherently defined in projective geometry . The basic results, such as Siegel's theorem on integral points , come from the theory of diophantine approximation .
The basic result, the Mordell–Weil theorem in Diophantine geometry , says that A ( K ), the group of points on A over K , is a finitely-generated abelian group . A great deal of information about its possible torsion subgroups is known, at least when A is an elliptic curve. The question of the rank is thought to be bound up with L-functions (see below).
The torsor theory here leads to the Selmer group and Tate–Shafarevich group , the latter (conjecturally finite) being difficult to study.
The theory of heights plays a prominent role in the arithmetic of abelian varieties. For instance, the canonical Néron–Tate height is a quadratic form with remarkable properties that appear in the statement of the Birch and Swinnerton-Dyer conjecture .
Reduction of an abelian variety A modulo a prime ideal of (the integers of) K — say, a prime number p — to get an abelian variety A p over a finite field , is possible for almost all p . The 'bad' primes, for which the reduction degenerates by acquiring singular points , are known to reveal very interesting information. As often happens in number theory, the 'bad' primes play a rather active role in the theory.
Here a refined theory of (in effect) a right adjoint to reduction mod p — the Néron model — cannot always be avoided. In the case of an elliptic curve there is an algorithm of John Tate describing it.
For abelian varieties such as A p , there is a definition of local zeta-function available. To get an L-function for A itself, one takes a suitable Euler product of such local functions; to understand the finite number of factors for the 'bad' primes one has to refer to the Tate module of A, which is (dual to) the étale cohomology group H 1 (A), and the Galois group action on it. In this way one gets a respectable definition of Hasse–Weil L-function for A. In general its properties, such as functional equation , are still conjectural – the Taniyama–Shimura conjecture (which was proven in 2001) was just a special case, so that's hardly surprising.
It is in terms of this L-function that the conjecture of Birch and Swinnerton-Dyer is posed. It is just one particularly interesting aspect of the general theory about values of L-functions L( s ) at integer values of s , and there is much empirical evidence supporting it.
Since the time of Carl Friedrich Gauss (who knew of the lemniscate function case) the special role has been known of those abelian varieties A {\displaystyle A} with extra automorphisms, and more generally endomorphisms. In terms of the ring E n d ( A ) {\displaystyle {\rm {End}}(A)} , there is a definition of abelian variety of CM-type that singles out the richest class. These are special in their arithmetic. This is seen in their L-functions in rather favourable terms – the harmonic analysis required is all of the Pontryagin duality type, rather than needing more general automorphic representations . That reflects a good understanding of their Tate modules as Galois modules . It also makes them harder to deal with in terms of the conjectural algebraic geometry ( Hodge conjecture and Tate conjecture ). In those problems the special situation is more demanding than the general.
In the case of elliptic curves, the Kronecker Jugendtraum was the programme Leopold Kronecker proposed, to use elliptic curves of CM-type to do class field theory explicitly for imaginary quadratic fields – in the way that roots of unity allow one to do this for the field of rational numbers. This generalises, but in some sense with loss of explicit information (as is typical of several complex variables ).
The Manin–Mumford conjecture of Yuri Manin and David Mumford , proved by Michel Raynaud , [ 1 ] [ 2 ] states that a curve C in its Jacobian variety J can only contain a finite number of points that are of finite order (a torsion point ) in J , unless C = J . There are other more general versions, such as the Bogomolov conjecture which generalizes the statement to non-torsion points. | https://en.wikipedia.org/wiki/Manin–Mumford_conjecture |
In robot kinematics , the manipulability ellipsoid represents the manipulability of a robotic system in a graphical form. Here, the manipulability of a robot arm refers to its ability to alter the position of the end effector based on the joint configuration. A higher manipulability measure signifies a broader range of potential movements in that specific configuration. When the robot is in a singular configuration the manipulability measure diminishes to zero.
The manipulability ellipsoid is defined as the set [ 1 ]
{ ξ : ξ T ( J ( q ) J T ( q ) ) ξ ≤ 1 } {\displaystyle \{\xi :\xi ^{\operatorname {T} }(J(q)J^{\operatorname {T} }(q))\xi \leq 1\}}
where q is the joint configuration of the robot and J is the robot Jacobian relating the end-effector velocity with the joint rates.
A geometric interpretation of the manipulability ellipsoid is that it includes all possible end-effector velocities normalized for a unit input at a given robot configuration. The axis of the ellipsoid can be computed by using the singular value decomposition of the robot Jacobian . [ 1 ] [ 2 ]
This robotics-related article is a stub . You can help Wikipedia by expanding it . | https://en.wikipedia.org/wiki/Manipulability_ellipsoid |
Manish Chhowalla FREng is a material scientist who has been the Goldsmiths' Professor of Materials Science at the University of Cambridge since 2018. [ 1 ] [ 2 ] In early 2024 he received a £2.5 million grant for his research. [ 3 ] Also that year he was named the editor-in-chief of MRS Energy & Sustainability . [ 4 ] Chhowalla previously worked at Rutgers University , where he was a professor of materials science and director of the Rutgers Institute for Advanced Materials, Devices and Nanotechnology. [ 5 ]
He received a PhD from Churchill College, Cambridge . [ 6 ] In 2020 the Institute of Materials, Minerals and Mining awarded him the A. A. Griffith Medal and Prize . [ 7 ]
This article about a British scientist is a stub . You can help Wikipedia by expanding it .
This article about materials science is a stub . You can help Wikipedia by expanding it . | https://en.wikipedia.org/wiki/Manish_Chhowalla |
The Manley–Rowe relations are mathematical expressions developed originally for electrical engineers to predict the amount of energy in a wave that has multiple frequencies. They have since been found to describe systems in non-linear optics , [ 1 ] fluid mechanics and the theory of non-linear dynamical systems , as they provide a pair of invariants or conserved quantities for the three-wave equation . For example, in a resonant interaction in non-linear optics, the Manley–Rowe relations can be interpreted as saying one photon is created as two more are destroyed (or conversely, two are created when one is destroyed.) For the three-wave equation, the Manley–Rowe invariants can be related to the modular invariants g 2 {\displaystyle g_{2}} and g 3 {\displaystyle g_{3}} of the Weierstrass ℘-function . [ 2 ] This essentially follows because the three-wave interaction has exact solutions that are given by elliptic functions .
The original papers, written by two researchers at Bell Labs , J. M. Manley and H. E. Rowe between 1956 and 1960 [ 3 ] [ 4 ] [ 5 ] [ 6 ] was for an electrical circuit containing nonlinear capacitors and inductors . One or more oscillators , operating at specified frequencies, are connected to the input of this circuit. The Manley–Rowe relations predict the energy present in waves at various frequencies, including new frequencies (such as harmonics and sidebands ) that arise in the circuit due to nonlinearity . The theory is based partly on the principle of conservation of energy . It requires that energy storage in the circuit is a stationary process that varies with time only due to the oscillations and not due to some steady increase or decrease with time. More precisely, the theory describes a resonant interaction between waves at various different frequencies; the resonant interaction describes which frequencies can mix and interact, and the strengths by which they couple.
Because the Manley–Rowe relations are based on general concepts like nonlinear waves and conservation of energy , their use is not limited to the original application in radio-frequency electrical circuits . They have also found use in other scientific fields, for example nonlinear optics . In the electrical circuit for the original derivation of Manley–Rowe relations, capacitors and inductors store energy from a wave and then release it. Other physical systems that involve energy storage for waves, and nonlinear generation of new waves, can make use of the same relations.
John Manley and Harrison Rowe were protégés of Ralph Hartley at Bell Laboratories. The work with nonlinear reactances (inductors and capacitors) was started back in 1917 by John Burton and Eugene Peterson. [ 7 ] When Hartley joined Bell Laboratories after being part of Western Electric, he started a research group on nonlinear oscillations. This group was later joined by Peterson, Manley, and Rowe. | https://en.wikipedia.org/wiki/Manley–Rowe_relations |
In additive number theory , the Schnirelmann density of a sequence of numbers is a way to measure how "dense" the sequence is. It is named after Russian mathematician Lev Schnirelmann , who was the first to study it. [ 1 ] [ 2 ]
The Schnirelmann density of a set of natural numbers A is defined as
where A ( n ) denotes the number of elements of A not exceeding n and inf is infimum . [ 3 ]
The Schnirelmann density is well-defined even if the limit of A ( n )/ n as n → ∞ fails to exist (see upper and lower asymptotic density ).
By definition, 0 ≤ A ( n ) ≤ n and n σ A ≤ A ( n ) for all n , and therefore 0 ≤ σ A ≤ 1 , and σ A = 1 if and only if A = N . Furthermore,
The Schnirelmann density is sensitive to the first values of a set:
In particular,
and
Consequently, the Schnirelmann densities of the even numbers and the odd numbers, which one might expect to agree, are 0 and 1/2 respectively. Schnirelmann and Yuri Linnik exploited this sensitivity.
If we set G 2 = { k 2 } k = 1 ∞ {\displaystyle {\mathfrak {G}}^{2}=\{k^{2}\}_{k=1}^{\infty }} , then Lagrange's four-square theorem can be restated as σ ( G 2 ⊕ G 2 ⊕ G 2 ⊕ G 2 ) = 1 {\displaystyle \sigma ({\mathfrak {G}}^{2}\oplus {\mathfrak {G}}^{2}\oplus {\mathfrak {G}}^{2}\oplus {\mathfrak {G}}^{2})=1} . (Here the symbol A ⊕ B {\displaystyle A\oplus B} denotes the sumset of A ∪ { 0 } {\displaystyle A\cup \{0\}} and B ∪ { 0 } {\displaystyle B\cup \{0\}} .) It is clear that σ G 2 = 0 {\displaystyle \sigma {\mathfrak {G}}^{2}=0} . In fact, we still have σ ( G 2 ⊕ G 2 ) = 0 {\displaystyle \sigma ({\mathfrak {G}}^{2}\oplus {\mathfrak {G}}^{2})=0} , and one might ask at what point the sumset attains Schnirelmann density 1 and how does it increase. It actually is the case that σ ( G 2 ⊕ G 2 ⊕ G 2 ) = 5 / 6 {\displaystyle \sigma ({\mathfrak {G}}^{2}\oplus {\mathfrak {G}}^{2}\oplus {\mathfrak {G}}^{2})=5/6} and one sees that sumsetting G 2 {\displaystyle {\mathfrak {G}}^{2}} once again yields a more populous set, namely all of N {\displaystyle \mathbb {N} } . Schnirelmann further succeeded in developing these ideas into the following theorems, aiming towards Additive Number Theory, and proving them to be a novel resource (if not greatly powerful) to attack important problems, such as Waring's problem and Goldbach's conjecture .
Theorem. Let A {\displaystyle A} and B {\displaystyle B} be subsets of N {\displaystyle \mathbb {N} } . Then
σ ( A ⊕ B ) ≥ σ A + σ B − σ A ⋅ σ B . {\displaystyle \sigma (A\oplus B)\geq \sigma A+\sigma B-\sigma A\cdot \sigma B.}
Note that σ A + σ B − σ A ⋅ σ B = 1 − ( 1 − σ A ) ( 1 − σ B ) {\displaystyle \sigma A+\sigma B-\sigma A\cdot \sigma B=1-(1-\sigma A)(1-\sigma B)} . Inductively, we have the following generalization.
Corollary. Let A i ⊆ N {\displaystyle A_{i}\subseteq \mathbb {N} } be a finite family of subsets of N {\displaystyle \mathbb {N} } . Then
σ ( ⨁ i A i ) ≥ 1 − ∏ i ( 1 − σ A i ) . {\displaystyle \sigma \left(\bigoplus _{i}A_{i}\right)\geq 1-\prod _{i}\left(1-\sigma A_{i}\right).}
The theorem provides the first insights on how sumsets accumulate. It seems unfortunate that its conclusion stops short of showing σ {\displaystyle \sigma } being superadditive . Yet, Schnirelmann provided us with the following results, which sufficed for most of his purpose.
Theorem. Let A {\displaystyle A} and B {\displaystyle B} be subsets of N {\displaystyle \mathbb {N} } . If σ A + σ B ≥ 1 {\displaystyle \sigma A+\sigma B\geq 1} , then
A ⊕ B = N . {\displaystyle A\oplus B=\mathbb {N} .}
Theorem. ( Schnirelmann ) Let A ⊆ N {\displaystyle A\subseteq \mathbb {N} } . If σ A > 0 {\displaystyle \sigma A>0} then there exists k {\displaystyle k} such that
⨁ i = 1 k A = N . {\displaystyle \bigoplus _{i=1}^{k}A=\mathbb {N} .}
A subset A ⊆ N {\displaystyle A\subseteq \mathbb {N} } with the property that A ⊕ A ⊕ ⋯ ⊕ A = N {\displaystyle A\oplus A\oplus \cdots \oplus A=\mathbb {N} } for a finite sum, is called an additive basis , and the least number of summands required is called the degree (sometimes order ) of the basis. Thus, the last theorem states that any set with positive Schnirelmann density is an additive basis. In this terminology, the set of squares G 2 = { k 2 } k = 1 ∞ {\displaystyle {\mathfrak {G}}^{2}=\{k^{2}\}_{k=1}^{\infty }} is an additive basis of degree 4. (About an open problem for additive bases, see Erdős–Turán conjecture on additive bases .)
Historically the theorems above were pointers to the following result, at one time known as the α + β {\displaystyle \alpha +\beta } hypothesis. It was used by Edmund Landau and was finally proved by Henry Mann in 1942.
Theorem. ( Mann 1942 ) Let A {\displaystyle A} and B {\displaystyle B} be subsets of N {\displaystyle \mathbb {N} } . In case that A ⊕ B ≠ N {\displaystyle A\oplus B\neq \mathbb {N} } , we still have
σ ( A ⊕ B ) ≥ σ A + σ B . {\displaystyle \sigma (A\oplus B)\geq \sigma A+\sigma B.}
An analogue of this theorem for lower asymptotic density was obtained by Kneser. [ 4 ] At a later date, E. Artin and P. Scherk simplified the proof of Mann's theorem. [ 5 ]
Let k {\displaystyle k} and N {\displaystyle N} be natural numbers. Let G k = { i k } i = 1 ∞ {\displaystyle {\mathfrak {G}}^{k}=\{i^{k}\}_{i=1}^{\infty }} . Define r N k ( n ) {\displaystyle r_{N}^{k}(n)} to be the number of non-negative integral solutions to the equation
and R N k ( n ) {\displaystyle R_{N}^{k}(n)} to be the number of non-negative integral solutions to the inequality
in the variables x i {\displaystyle x_{i}} , respectively. Thus R N k ( n ) = ∑ i = 0 n r N k ( i ) {\displaystyle R_{N}^{k}(n)=\sum _{i=0}^{n}r_{N}^{k}(i)} . We have
The volume of the N {\displaystyle N} -dimensional body defined by 0 ≤ x 1 k + x 2 k + ⋯ + x N k ≤ n {\displaystyle 0\leq x_{1}^{k}+x_{2}^{k}+\cdots +x_{N}^{k}\leq n} , is bounded by the volume of the hypercube of size n 1 / k {\displaystyle n^{1/k}} , hence R N k ( n ) = ∑ i = 0 n r N k ( i ) ≤ n N / k {\displaystyle R_{N}^{k}(n)=\sum _{i=0}^{n}r_{N}^{k}(i)\leq n^{N/k}} . The hard part is to show that this bound still works on the average, i.e.,
Lemma. ( Linnik ) For all k ∈ N {\displaystyle k\in \mathbb {N} } there exists N ∈ N {\displaystyle N\in \mathbb {N} } and a constant c = c ( k ) {\displaystyle c=c(k)} , depending only on k {\displaystyle k} , such that for all n ∈ N {\displaystyle n\in \mathbb {N} } ,
r N k ( m ) < c n N k − 1 {\displaystyle r_{N}^{k}(m)<cn^{{\frac {N}{k}}-1}}
for all 0 ≤ m ≤ n . {\displaystyle 0\leq m\leq n.}
With this at hand, the following theorem can be elegantly proved.
Theorem. For all k {\displaystyle k} there exists N {\displaystyle N} for which σ ( N G k ) > 0 {\displaystyle \sigma (N{\mathfrak {G}}^{k})>0} .
We have thus established the general solution to Waring's Problem:
Corollary. ( Hilbert 1909 ) For all k {\displaystyle k} there exists N {\displaystyle N} , depending only on k {\displaystyle k} , such that every positive integer n {\displaystyle n} can be expressed as the sum of at most N {\displaystyle N} many k {\displaystyle k} -th powers.
In 1930 Schnirelmann used these ideas in conjunction with the Brun sieve to prove Schnirelmann's theorem , [ 1 ] [ 2 ] that any natural number greater than 1 can be written as the sum of not more than C prime numbers , where C is an effectively computable constant: [ 6 ] Schnirelmann obtained C < 800000. [ 7 ] Schnirelmann's constant is the lowest number C with this property. [ 6 ]
Olivier Ramaré showed in ( Ramaré 1995 ) that Schnirelmann's constant is at most 7, [ 6 ] improving the earlier upper bound of 19 obtained by Hans Riesel and R. C. Vaughan .
Schnirelmann's constant is at least 3; Goldbach's conjecture implies that this is the constant's actual value. [ 6 ]
In 2013, Harald Helfgott proved Goldbach's weak conjecture for all odd numbers. Therefore, Schnirelmann's constant is at most 4. [ 8 ] [ 9 ] [ 10 ] [ 11 ]
Khintchin proved that the sequence of squares, though of zero Schnirelmann density, when added to a sequence of Schnirelmann density between 0 and 1, increases the density:
This was soon simplified and extended by Erdős , who showed, that if A is any sequence with Schnirelmann density α and B is an additive basis of order k then
and this was improved by Plünnecke to
Sequences with this property, of increasing density less than one by addition, were named essential components by Khintchin. Linnik showed that an essential component need not be an additive basis [ 14 ] as he constructed an essential component that has x o(1) elements less than x . More precisely, the sequence has
elements less than x for some c < 1. This was improved by E. Wirsing to
For a while, it remained an open problem how many elements an essential component must have. Finally, Ruzsa determined that for every ε > 0 there is an essential component which has at most c (log x ) 1+ ε elements up to x , but there is no essential component which has c (log x ) 1+ o (1) elements up to x . [ 15 ] [ 16 ] | https://en.wikipedia.org/wiki/Mann's_theorem |
Mannans are polymers containing the sugar mannose as a principal component. [ 1 ] [ 2 ] They are a type of polysaccharide found in hemicellulose , a major source of biomass found in higher plants such as softwoods. These polymers also typically contain two other sugars, galactose and glucose . They are often branched (unlike cellulose).
Plant mannans have β(1-4) linkages, occasionally with α(1-6) galactose branches, forming galactomannans . They are insoluble and a form of storage polysaccharide. Ivory nut is a source of mannans. An additional type is galactoglucomannan found in soft wood with a mixed mannose/glucose β(1-4) backbone. Many mannans are acetylated and some from marine sources, have sulfate esters side chains.
Yeast and some plants such as conjac and salep have a different type of mannans in their cell wall, with a α(1-6) linked backbone and α(1-2) and α(1-3) linked glucose branches, hence " glucomannan ". It is water soluble. It is serologically similar to structures found on mammalian glycoproteins. Detection of mannan leads to lysis in the mannan-binding lectin pathway . [ citation needed ]
GDP-mannose is a substrate for glycosyltransferase for enzymes called mannosyltransferases . [ 4 ]
GDP-mannose is produced from GTP and mannose-6-phosphate by the enzyme mannose-1-phosphate guanylyltransferase .
The degradation of mannans (and many related forms of hemicellulose) has been well studied. The hydrolysis of the main mannan backbone is catalyzed by various enzymes including β- mannosidase , β- glucosidase , and β- mannase . The side chains are degraded by esterases and α-galactosidase. [ 1 ]
When a long chain of mannan is hydrolyzed into shorter chains, these smaller molecules are known as mannan oligosaccharide (MOS). MOS by definition can be produced from either insoluble galactomannan or soluble glucomannan, although the latter type is more widely marketed. [ 5 ]
Glucomannan MOS is used as prebiotics in animal husbandry and nutritional supplements due to its bioactivity. [ citation needed ]
From 'manna', produced by several species of tree and shrub e.g. Fraxinus ornus from whose secretions mannitol was originally isolated. | https://en.wikipedia.org/wiki/Mannans |
The Mannheim process is an industrial process for the production of hydrogen chloride and sodium sulfate from sulfuric acid and sodium chloride . [ 1 ] The Mannheim furnace is also used to produce potassium sulfate from potassium chloride . [ 2 ] The Mannheim process is a stage in the Leblanc process for the production of sodium carbonate .
The process is named after Mannheim furnace, a large cast iron kiln in which it is conducted. The furnace was developed at Verein Chemischer Fabriken in Mannheim [ de ] at the turn of the 20th century [ 3 ] and superseded earlier furnace designs formerly used for the same purpose. [ 4 ]
Sodium chloride and sulfuric acid are first fed onto a stationary reaction plate where an initial reaction takes place. The stationary plate is up to 6 m (20 ft) in diameter. Rotating rabble arms constantly turn over the mixture and move the intermediate product to a lower plate. The kiln portion of the furnace is constructed with bricks that have high resistance to direct flame, temperature, and acid. The other parts of the furnace are heat and acid resistant. Hot flue gas passes up over the plates carrying out liberated hydrogen chloride gas. The intermediate product reacts with more sodium chloride in the lower, hotter section of the kiln producing sodium sulfate. This exits the furnace and passes through cooling drums before being milled, screened and sent to product storage facilities. [ 5 ]
The process involves intermediate formation of sodium bisulfate , an exothermic reaction that occurs at room temperature:
The second step of the process is endothermic, requiring energy input:
Temperatures in the range 600-700 °C are required. [ 5 ] | https://en.wikipedia.org/wiki/Mannheim_process |
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