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57,048,333 | https://en.wikipedia.org/wiki/Nifurtimox/eflornithine | Nifurtimox/eflornithine is a combination of two antiparasitic drugs, nifurtimox and eflornithine, used in the treatment of African trypanosomiasis (sleeping sickness). It is included in the World Health Organization's Model List of Essential Medicines.
A treatment regimen known as nifurtimox-eflornithine combination treatment (NECT) is used in second stage gambiense African trypanosomiasis throughout Africa where the disease is endemic. The regimen involves slow infusion of 400 mg of eflornithine every 12 hours for 7 days combined with 15 mg/kg of nifurtimox orally three times a day for 10 days.
References
Antiparasitic agents | Nifurtimox/eflornithine | Biology | 160 |
26,732,377 | https://en.wikipedia.org/wiki/Geodat | Geodat was a commercial project, begun in 1980 and completed by 1991, that provided digital geographic mapping data for commercial users at scales equal to or greater than 1:1,000,000. The term "Geodat" was derived from "GEOgraphic DATa". Geodat data was primarily "medium scale", a nominal 1:100,000, but ranged from 1:50,000 to 1:250,000. The cartographic data was vector-based digitisation of coastline, hydrography, internal and international political boundaries, primary transportation routes and city locations. The data was intended to be used on its own to produce quick, cheap, consistent maps, initially for oil exploration firms. Harry Wassall, the founder of Petroconsultants SA, a Geneva-based energy information services firm, began the project in 1979 by hiring a researcher from the Harvard Laboratory for Computer Graphics and Spatial Analysis, Michael Mainelli, to explore how to automate Petroconsultants' extensive paper map series. Mainelli became Project Director in 1981. Petroconsultants concluded that a cooperative project among the oil firms acknowledged the high degree of overlap in their computer mapping interests.
Petroconsultants SA assessed client interest at a meeting in Geneva on 20–21 August 1981 with attendees from Amoco, BP, Cities Service, Deminex, Elf Acquitaine, Exxon, Gulf and Shell. The need for computerised mapping data was high and the response positive enough to form an advisory committee with paid sponsorship. The sponsors commissioned Petroconsultants to produce four sample digitised maps of the Ivory Coast. The Ivorian pilot project resulted in four 1:200,000 maps with 800 features and 40,000 data points. The pilot established Common Geographic Format (CGF) records, for a time the industry standard for computer cartographic information exchange. These digitised map files, and their attendant file structures, feature codes, segment records, map records, annotation records and set records were reviewed at a meeting in Dublin on 10–11 November 1981 with participation from Amoco, BP, Chevron, Cities Service, Elf Acquitaine, Exxon, Gulf, Phillips Petroleum and Shell. Geodat was formally launched in Houston on 9–10 February 1982 with attendees from Amoco, BP, Chevron, Elf Acquitaine, Exxon, Getty, Gulf, Texas Easter and Union Texas. Four primary sponsors were Shell, BP, Elf Acquitaine and Chevron, while ten other firms were partial sponsors. Full sponsors received a guarantee of six million digitised points (approximately 360 maps) digitised to a specified quality level.
First data delivery was in June 1983, consisting of 57 maps and 1.24 million points. By the end of 1985, Geodat had delivered twenty million data points and 750 map sheets in the 1:50,000 to 1:250,000 scale range. Alongside mainstream production for the project sponsors, the Geodat project produced a complete digital map of the world at a scale of 1:1,000,000, MundoCart, in 1985. MundoCart was based on digitisation of paper prints of the United States Defense Mapping Agency's (DMA) Operational Navigation Chart (ONC) 1:1,000,000 scale paper map series, produced by the US, Australia, Canada, and the United Kingdom. ONC charts were designed to meet the needs of pilots and air crews in medium-and low-altitude navigation and to support military operational planning, intelligence briefings, and other needs. Some 270 1:1million maps, plus six 1:2million maps for Antarctica, resulted in 30 million data points. MundoCart provided numerous commercial and academic Geographic information system (GIS) users with their first complete vector map of the world. The data was sold, along with a complete set of FORTRAN mapping software, by Petroconsultants (CES), a UK subsidiary of Petroconsultants SA, subsequently sold to IHS in 1996, that sponsored the project.
Prior to Geodat, the only complete digital map of the world was World Data Bank 2 (WDB-II), a dataset digitized between 1972 and 1977 by the US Department of State's (DoS) Central Intelligence Agency (CIA). WDBII was of variable scale, nominally 1:3,000,000 but digitised from sources ranging from 1:1,000,000 to 1:4,000,000, and of variable quality. WDB-II was released at nominal cost from 1977, but users desired higher resolution and more consistent quality. Until the release of the US Department of Defense's Digital Chart of the World in 1992, and subsequent free issue from 2006, MundoCart was the primary global GIS database for commercial users.
Geodat was unusual in the 1980s in that the software was often given away free, while data downloads or tapes were charged. Geodat set out a quality management process for digitisation covering acquisition, cataloguing, map stability, transformation algorithms, merging and node coalescing. Geodat also set out a quality standard for comparing digitised maps with source maps, based on using generalisation and interpolation against a maximum orthogonal offset distance. Originally delivered as five large tapes, MundoCart was burned on CD-ROM in 1987. MundoCart was one of the first CD-ROM applications not brought out by the creators, Philips and Sony. In the early releases of MundoCart, a CD-ROM reader accompanied each purchase.
Production was based from late 1982 to 1991 in Burleigh House, Newmarket Road in Cambridge, England. Coincidentally, Burleigh House had been the former Star Brewery headquarters and the cellars provided good storage facilities for paper maps. At its height, the project employed 30 people, principally programmers and digitisers. Processing was based on hand digitisation using DEC PDP-11 minicomputers alongside digitisation tables. Further processing was done on DEC VAX computers. The computer programs were almost entirely written in FORTRAN, though some PL/1 and assembler programming was used. At the time, scanning systems were not suitable for large-scale production, but the project did help design, build and use a laser line-following digitiser, combining a laser photovoltaic feedback system with stepper motors, mounted on a cowboy boot sewing machine chassis from the USA. The effect of the laser line-following digitiser was that the operator felt as if he or she was directing the laser along a "groove" that followed the line being acquired.
The Geodat project drew heavily on the experience of the Harvard Laboratory for Computer Graphics and Spatial Analysis, founded in 1963 and disbanded in 1991. Unable to purchase the Laboratory's software while Harvard University was exploring licensing options, Geodat developed its own software. The Laboratory and Geodat both employed "flat" computer files and streamed processing, instead of hierarchical and direct access processing. Wherever possible, the software operated in FORTRAN processing sequential files to enhance portability among operating systems. Geodat also emulated other Laboratory ideas, most notably the idea of "cycling", using software to resolve disconnected vectors.
References
Geodesy
Geographical technology
Surveying | Geodat | Mathematics,Engineering | 1,502 |
14,411,733 | https://en.wikipedia.org/wiki/Madelung%20equations | In theoretical physics, the Madelung equations, or the equations of quantum hydrodynamics, are Erwin Madelung's equivalent alternative formulation of the Schrödinger equation for a spinless non relativistic particle, written in terms of hydrodynamical variables, similar to the Navier–Stokes equations of fluid dynamics. The derivation of the Madelung equations is similar to the de Broglie–Bohm formulation, which represents the Schrödinger equation as a quantum Hamilton–Jacobi equation.
History
In the fall of 1926, Erwin Madelung reformulated Schrödinger's quantum equation in a more classical and visualizable form resembling hydrodynamics. His paper was one of numerous early attempts at different approaches to quantum mechanics, including those of Louis de Broglie and Earle Hesse Kennard. The most influential of these theories was ultimately de Broglie's through the 1952 work of David Bohm now called Bohmian mechanics
Equations
The Madelung equations are quantum Euler equations:
where
is the flow velocity,
is the mass density,
is the Bohm quantum potential,
is the potential from the Schrödinger equation.
The Madelung equations answer the question whether obeys the continuity equations of hydrodynamics and, subsequently, what plays the role of the stress tensor.
The circulation of the flow velocity field along any closed path obeys the auxiliary quantization condition for all integers .
Derivation
The Madelung equations are derived by first writing the wavefunction in polar form
with and both real and
the associated probability density. Substituting this form into the probability current gives:
where the flow velocity is expressed as
However, the interpretation of as a "velocity" should not be taken too literal, because a simultaneous exact measurement of position and velocity would necessarily violate
the uncertainty principle.
Next, substituting the polar form into the Schrödinger equation
and performing the appropriate differentiations, dividing the equation by and separating the real and imaginary parts, one obtains a system of two coupled partial differential equations:
The first equation corresponds to the imaginary part of Schrödinger equation and can be interpreted as the continuity equation. The second equation corresponds to the real part and is also referred to as the quantum Hamilton-Jacobi equation.
Multiplying the first equation by and calculating the gradient of the second equation results in the Madelung equations:
with quantum potential
Alternatively, the quantum Hamilton-Jacobi equation can be written in a form similar to the Cauchy momentum equation:
with an external force defined as
and a quantum pressure tensor
The integral energy stored in the quantum pressure tensor is proportional to the Fisher information, which accounts for the quality of measurements. Thus, according to the Cramér–Rao bound, the Heisenberg uncertainty principle is equivalent to a standard inequality for the efficiency of measurements.
Quantum energies
The thermodynamic definition of the quantum chemical potential
follows from the hydrostatic force balance above:
According to thermodynamics, at equilibrium the chemical potential is constant everywhere, which corresponds straightforwardly to the stationary Schrödinger equation. Therefore, the eigenvalues of the Schrödinger equation are free energies, which differ from the internal energies of the system. The particle internal energy is calculated as
and is related to the local Carl Friedrich von Weizsäcker correction.
See also
Quantum potential
Quantum hydrodynamics
Bohmian quantum mechanics
Pilot wave theory
Notes
References
Partial differential equations
Quantum mechanics | Madelung equations | Physics | 707 |
2,081,987 | https://en.wikipedia.org/wiki/Chapman%20function | A Chapman function describes the integration of atmospheric absorption along a slant path on a spherical Earth, relative to the vertical case. It applies to any quantity with a concentration decreasing exponentially with increasing altitude. To a first approximation, valid at small zenith angles, the Chapman function for optical absorption is equal to
where z is the zenith angle and sec denotes the secant function.
The Chapman function is named after Sydney Chapman, who introduced the function in 1931.
Definition
In an isothermal model of the atmosphere, the density varies exponentially with altitude according to the Barometric formula:
,
where denotes the density at sea level () and the so-called scale height.
The total amount of matter traversed by a vertical ray starting at altitude towards infinity is given by the integrated density ("column depth")
.
For inclined rays having a zenith angle , the integration is not straight-forward due to the non-linear relationship between altitude and path length when considering the
curvature of Earth. Here, the integral reads
,
where we defined ( denotes the Earth radius).
The Chapman function is defined as the ratio between slant depth and vertical column depth . Defining , it can be written as
.
Representations
A number of different integral representations have been developed in the literature. Chapman's original representation reads
.
Huestis developed the representation
,
which does not suffer from numerical singularities present in Chapman's representation.
Special cases
For (horizontal incidence), the Chapman function reduces to
.
Here, refers to the modified Bessel function of the second kind of the first order. For large values of , this can further be approximated by
.
For and , the Chapman function converges to the secant function:
.
In practical applications related to the terrestrial atmosphere, where , is a good approximation for zenith angles up to 60° to 70°, depending on the accuracy required.
See also
Air mass
Atmospheric physics
Ionosphere
References
External links
Chapman function at Science World
Radio frequency propagation
Special functions | Chapman function | Physics,Mathematics | 390 |
76,439,689 | https://en.wikipedia.org/wiki/Dorsal%20pancreatic%20agenesis | Dorsal pancreatic agenesis is a congenital anomaly characterised by the absence of the duct of Santorini, tail and body of the pancreas. It is regarded as asymptomatic and the most common clinical manifestation is non-specific abdominal pain. While the cause is unclear, its mechanism is thought to be impaired dorsal buds or mutation of genes that regulate organogenesis during embryogenesis.
Early diagnostic methods are laparotomy and autopsy. Endoscopic retrograde cholangiopancreatography (ERCP) and computed tomography scan (CT scan) are combined for diagnosis of this agenesis in recent years. No specific medications are needed for relieving symptoms, but pancreatic enzymes capsule and insulin are prescribed.
Scholars have studied several transcription factors and proteins that can manipulate pancreatic growth and related to dorsal pancreatic agenesis. This malformation is associated with other pancreatic disorders including pancreatitis and pancreatic tumors. Also, patients with this dysgenesis are usually accompanied with pancreatic exocrine dysfunction such as diabetes mellitus.
The prevalence and geographical pattern are unknown. First reported in 1911 by Heiberg in an autopsy.
Signs and symptoms
The agenesis of the dorsal pancreas is asymptomatic in most cases due to the functional reserves of exocrine and endocrine pancreas. Thereby it is often diagnosed incidentally by autopsy, surgery, endoscopy, or imaging technologies during evaluation of other diseases. Some common indicators reported by patients include abdominal pain, weight loss, and jaundice. Abdominal pain could be associated with acute or chronic pancreatitis, pancreatic tumor, diabetic autonomic neuropathy; and weight loss can also be due to diabetes mellitus in some patients.
The localisation of abdominal pain is at epigastrium and aggregates after meals. The two possible reasons for abdominal pain include the underdevelopment of the papillary muscle of the sphincter of Oddi or the autonomic neuropathy due to diabetes mellitus. Dorsal pancreatic agenesis is associated with diabetes mellitus because the β cells in the islets of Langerhans are present in the pancreatic body and tail, which are both absent in agenesis of the dorsal pancreas. Patients with dorsal pancreatic agenesis may result in a defect in the metabolism of hepatic glycogen, which may be related to the reduced β cell mass.
Associated conditions
Pancreatitis
Pancreatitis is a common disorder associated with dorsal pancreatic agenesis. However, it is unclear whether the high occurrence of pancreatitis is due to repetitive imaging procedures or whether it is a comorbidity of agenesis.
Diabetes mellitus
Diabetes mellitus is an endocrine disease that is due to insufficient amount of insulin produced by the pancreas, and it is another common disease linked with dorsal pancreatic agenesis. Insulin is produced by the β cells of the islet of Langerhans in the dorsal pancreas. In patients with agenesis of the dorsal pancreas, the amount of β cells are reduced thus leading to a high possibility of causing diabetes mellitus.
Pancreatic tumors
Tumors can also be associated with dorsal pancreatic agenesis. Reported pancreatic tumors include solid papillary, solid pseudopapillary tumors, adenocarcinomas, and intraductal papillary mucinous neoplasms (IPMN).
Organ malfunction
Organ malfunction is also associated with dorsal pancreatic agenesis. Disorders such as polycystic kidney disease, Kartagener syndrome, multiple splenic deformities, congenital choledochal cysts, and biliary atresia have been reported.
Cause
There is no suggested cause for the dorsal pancreatic agenesis, however there are several hypotheses for the underlying mechanism. As the dorsal pancreatic bud is the ancestor for the majority of pancreas, one possible explanation to this rare anomaly is the dorsal mesentery ischemia which induces the dysgenesis of pancreas. In spite of the unknown molecular mechanism, some scholars have speculated the mode of inheritance of this agenesis, which is autosomal-dominant or X-linked disease.
Genetics
Scientists have demonstrated a wide spectrum of genes that can manipulate and regulate the embryonic pancreatic development by in vivo animal study. The formation of dorsal and ventral buds is reliant on the interaction of transcription factors, for instance the Pax4, Pax6 and Ptf1a. By expressing sonic hedgehog (Shh) or Indian hedgehog (Ihh), the growth of both dorsal and ventral buds from the foregut endoderm is repressed to a large extent, inhibition of Shh or Ihh signaling pathway favor the pancreatic development. The Homeodomain protein HB9 (Hlxb9) is critical for the formation of the dorsal bud, however it is not significant to the ventral bud. Another homeodomain protein, PDX1 (also known as Ipf-1 insulin promoter factor 1) is the initiator of buds expression, genetic mutation on gene Ipf-1 can lead to pancreatic agenesis. Also, both heterozygous and homozygous variant of PDX1 can cause dysgenesis of pancreas and neonatal diabetes.
CDH2 (CD352) gene encoded Neural-cadherin (N-cadherin) is identified to have an active role in recruiting dorsal pancreatic mesenchyme for pancreatic morphogenesis, depletion of N-cadherin in mice can lead to the apoptosis of dorsal pancreatic mesenchyme cells. Moreover, research suggests that retinoid acid is significant for the development of pancreas as the deficiency of retinoid acid can induce dorsal pancreatic agenesis in mice.
Embryonic development of pancreas
The pancreas is responsible for secreting various enzymes for most digestion. It is a retroperitoneal organ posterior to the great curvature of the stomach. Its anterior surface is covered by the parietal peritoneum while the posterior surface contacts the aorta as well as other viscera on the left posterior body wall. Its 15 cm entity is divided into three parts, a globular head attached to the right side of duodenum, a long body, and a blunt head.
In embryonic development, the pancreas is formed by the convergence of the two pancreatic buds (dorsal and ventral) during the sixth and seventh week of gestation, but the development of these two buds is initiated at about week 4. During the gestation phase which takes place at week 4, the dorsal bud develops from the dorsal mesentery, and form the body and tail of the pancreas. Meanwhile, the ventral bud arises inferior to form the head of the pancreas. Two weeks later, the ventral bud will rotate dorsally and fuse with the dorsal bud to form the pancreas. The fusion of the duct happened at the same time, to form the duct of Wirsung and the duct of Santorini. Any deviation from the normal pancreatic embryogenesis process can potentially leads to congenital malformation of the pancreas. Among all anomalies, Pancreatic Divisum is the most prevalent one, followed by Pancreatic Heterotopia. In comparison, a complete agenesis of dorsal pancreas is rare and often associated with infant mortality.
The agenesis of dorsal pancreas can be classified into two classes based on the morphological features: complete and partial agenesis. For the former one, the accessory pancreatic duct (also known as duct of Santorini) as well as the body and tail of the pancreas are missing. For partial agenesis, the tail of the pancreas is still present.
Diagnosis
Dorsal pancreatic agenesis with advancement in modern day technology, is currently diagnosed with the following imaging technologies, and sometimes a combination of these methods.
Endoscopic retrograde cholangiopancreatography (ERCP). An invasive, operator-dependent gold standard for diagnosis. It presents the pancreatic duct; the absence or presence of the dorsal ductal system and the minor papilla can be used to indicate dorsal pancreatic agenesis.
Magnetic resonance cholangiopancreatography (MRCP). A non-invasive, accurate type of MRI to depict the major and accessory pancreatic ducts.
Magnetic resonance imaging (MRI). A non-invasive, non-radiation exposed method that can be used to identify the morphological structure of the pancreas.
Computed Tomography (CT). A non-invasive method to diagnose dorsal pancreatic agenesis by an absence of pancreatic tissue ventral to the splenic vein.
Stomach/intestine sign. Can be used to distinguish dorsal pancreatic agenesis from distal pancreatic lipomatosis.
Transabdominal Ultrasound (US). The diagnostic ability depends on pancreatic bowel gas or the patient's body habitus.
Agenesis of dorsal pancreas has to be differentiated with pancreatic fat infiltration, chronic pancreatitis and atrophy of pancreatic body and tail. The absence of pancreatic body and tail is the usual manifestation of dorsal pancreatic agenesis, the density and morphological features of the pancreatic head should be either normal or slightly enlarged due to compensation of the absent body and tail.
Stomach/intestine sign can combine with CT for better diagnosis. Since dorsal pancreatic agenesis can be at times complicated with pancreatic tumors, CT is a visualisation tool that can be used to exclude both pancreatic tumors and abdominal tumors, which allows for improved observation.
Management
Vast majority of dorsal pancreatic agenesis cases are diagnosed incidentally and asymptomatic, hence there is no special medication for dorsal pancreatic agenesis.
Medication
1. Pancreatic enteric-coated capsules. A proposed study suggested dorsal pancreatic agenesis patients show Exocrine Pancreatic Insufficiency (EPI) related symptoms. Oral administration of pancreatic enzymes, including lipase, protease and amylase is useful for relieving EPI related symptoms. In addition, pay attention to drugs that may interact with pancreatic enzymes such as Acarbose and Miglitol.
2. Exogenous insulin. Patients with dorsal pancreatic agenesis have lost the tail of pancreas which contain the Islet of Langerhan for insulin production. Therefore, exogenous insulin can be used to treat the accompanied Diabetes Mellitus.
History
Dorsal pancreatic agenesis is an extremely rare disease, there are only about 100 cases reported so far and no association discovered between a specific geographical location and disease prevalence. First reported in 1911 by Heiberg in an autopsy. The patient was diagnosed with diabetes mellitus and associated with pulmonary tuberculosis, the observed morphology of pancreatic head was described as "large and thick". Two years later, the second case was reported by Ghon and Roman (1913).
References
Medicine | Dorsal pancreatic agenesis | Biology | 2,386 |
34,829,638 | https://en.wikipedia.org/wiki/Hammerkit | Hammerkit is a company which has developed a platform as a service (PaaS) which allows web formats and repeatable solutions to be created and distributed globally using its CloudStore.
History
Hammerkit was a piece of software first developed by Jani Vähäsöyrinki, Heikki Luhtala, and Ari Tenhunen between 2002 and 2006. This team was joined by Robin Lindroos and these four became the core team of driving the development of Hammerkit as a web application development platform. A detailed history of the founding and early years of the Hammerkit platform and the players involved has been published by Ari Tenhunen. The initial ideas started as a spin-off of Njet Commununications' Anvil project to develop a Java development language to make development of Java applications faster and easier. The team of Vähäsöyrinki, Luhtala and Tenhunen could see that the Composer application in Anvil was still too complex for web designers to use and set about creating a new toolset that became Hammerkit. It was the first truly component-based web application builder available on the web. From 2002 to 2006, the new versions were release up to v3.5. A final release of Hammerkit v3.x was published in 2007.
The team chose the name Hammerkit simply because they liked the simplicity of a hammer (everyone knows how to use one) and because of its association with the project Anvil name.
In 2006, Hammerkit Oy was established to commercialise the software. Mark Sorsa-Leslie joined the team in October 2007 as Managing Director and in December 2008, the company was named as a Red Herring Global 100 award winner. In July 2010, Hammerkit debuted version 4.0 of their platform. The major enhancement in v4.0 was the move to a fully hosted architecture and the renewal of the user interface to utilise drag and drop design rather than the previous point and click approach.
In December 2011, Hammerkit announced a new funding round to internationalize the business. A new office was opened in Liverpool, England and a new product, the CloudStore was launched to support the creation, reuse and distribution of web formats as repeatable web solutions. The concept is based on the approach utilised in the TV industry to create global formats that are localized for particular markets. Hammerkit now specialises in the creation of web formats for the global public relations industry, serving clients such as Edelman and Hill+Knowlton Strategies. The company was noted by Nick Jones, head of Digital at the UK prime minister's office and the cabinet office as an example of a technology that will deskill the task of creating web services in his view from Downing Street 2011 published in The Drum.
In late 2011, the company was announced as one of five winners of a World Summit Award in the e-business and commerce category together with Star, Monaqasat, Hootsuite and Aeroscan.
In March 2012, Hammerkit launched Hammerkit.org as a community-based platform to promote the creation and sharing of repeatable digital solutions.
In 2013, Hammerkit is populating its CloudStore with off-the-shelf applications for the PR industry to choose from. Hammerkit will carry on designing and developing websites for companies using its Hammerkit Studio.
Awards
2009 – Mindtrek Startup Launchpad Winner
2010 – Mindtrek World Summit Award 2010 Finnish Winner – e-business/e-commerce
2011 – World Summit Award Global Winner – best e-business/e-commerce application
See also
Web application framework
Web interoperability
References
External links
Taking a full Hammerkit to websites
Cloud platforms
Collaborative real-time editors
Web applications
Web development software
PHP frameworks
Web frameworks
Content management systems
Cross-platform software | Hammerkit | Technology | 765 |
5,751,674 | https://en.wikipedia.org/wiki/Linnda%20R.%20Caporael | Linnda Caporael is a professor at the Science and Technology Studies Department at Rensselaer Polytechnic Institute.
Educational background
Linnda R. Caporael is a professor at Rensselaer Polytechnic Institute in the department of Technical Studies and Science. She received her PhD in Psychology at the University of California, Santa Barbara, and she also studied human ethology at the Institute of Child Development at the University of London. She is a Fulbright-Hayes Scholar and a visiting scientist in the Dept. of Invertebrate Paleontology and in the Dept. of Anthropology at the American Museum of Natural History. She researches culture from a biological perspective and biology from a cultural perspective.
Hypothesis of ergotism and the Salem witch trials
In the April 2, 1976, weekly issue of Science magazine, Caporael debuted a hypothesis that the accusations of witchcraft in Salem, Massachusetts, in 1692 could have been caused by ergotism. A fungus that grows on grains of rye, ergot contains a toxin which resembles LSD, and which can remain toxic in bread baked with flour tainted by it. Her evidence to support this theory includes historic weather reports and other growing conditions that foster the growth of this fungus, and the reported symptoms of several accusers, including hallucinations and crawling sensations in skin, which appear to match symptoms of ergot poisoning. Within days of the article's publication, historian Stephen Nissenbaum, co-author of Salem Possessed, publicly disputed the notion, saying that it "appears unlikely to me that this would not happen in any other year, in any other household and in any other village." In the December 24, 1976, issue of Science, psychologists Nicholas P. Spanos and Jack Gottlieb published a complete review of all the evidence, historical and medical, and concluded that the data did not support Caporael's hypothesis. In 1982, historian Mary Matossian defended Caporael by restating that the weather conditions were prime for growing ergot and that the symptoms of ergot matched the symptoms of the victims. A year later, Nicholas Spanos challenged Matossian's defense of Caporael, defending his original rebuttal, stating that her argument was "irrelevant to the ergot hypothesis, incorrect, and presented in a highly misleading manner."
Published works
Caporael, L. R. (1976). Ergotism: The Satan loosed in Salem? Science, 192, 21-26.
Caporael, L. R. & Atherton, P. R. (1985). A Subjective Judgment Study of Polygon Based Curved Surface Imagery. In L. Borman and & B. Curtis (Eds.), Proceedings of the ACM CHI 85 Human Factors in Computing Systems Conference. April 14–18, 1985, San Francisco, California. p. 27-34.
Caporael, L. R. (1986). Anthropomorphism and mechanomorphism: Two faces of the human machine. Computers in Human Behavior, 2, 215-234.
Caporael, L. R. (1987). Homo sapiens, Homo faber, Homo socians: Technology and the social animal. In W. Callebaut & R. Pinxten (Eds.), Evolutionary epistemology: A multiparadigm program (pp. 233–244). Dordrecht: Reidel.
Caporael, L. R. (1987). A window on war: Women and militarism in Ancient Greece. Paper presented at the American Anthropological Association, Chicago.
Caporael, L. R., Dawes, R. M., Orbell, J. M., & van de Kragt, A. J. C. (1989). Selfishness examined: Cooperation in the absence of egoistic incentives. Behavioral and Brain Sciences, 12, 683-739.
Caporael, L. R. (1997). Vehicles of knowledge: Artifacts and social groups. Evolution and Cognition, 3, 39-43.
Caporael, L. R. (2001). Evolutionary psychology: Toward a unifying theory and a hybrid science. Annual Review of Psychology, 52, 607-628.
Caporael, L. R. (2003). Repeated assembly. In S. Schur & F. Rauscher (Eds.), Alternative approaches to evolutionary psychology (pp. 71–90): Kluwer.
Caporael, L. R. (2007). Evolutionary theory for social and cultural psychology. In E. T. Higgins & A. Kruglanski (Eds.), Social psychology: Handbook of basic principles (pp. 3–18). New York: Guildford Press.
References
Living people
Rensselaer Polytechnic Institute faculty
Year of birth missing (living people)
Science and technology studies scholars
American women academics | Linnda R. Caporael | Technology | 1,007 |
8,546,244 | https://en.wikipedia.org/wiki/Wet%20scrubber | The term wet scrubber describes a variety of devices that remove pollutants from a furnace flue gas or from other gas streams. In a wet scrubber, the polluted gas stream is brought into contact with the scrubbing liquid, by spraying it with the liquid, by forcing it through a pool of liquid, or by some other contact method, so as to remove the pollutants.
Wet scrubbers capture relatively small dust particles with the wet scrubber's large liquid droplets. In most wet scrubbing systems, droplets produced are generally larger than 50 micrometres (in the 150 to 500 micrometres range). As a point of reference, human hair ranges in diameter from 50 to 100 micrometres. The size distribution of particles to be collected is source specific.
For example, particles produced by mechanical means (crushing or grinding) tend to be large (above 10 micrometres); whereas, particles produced from combustion or a chemical reaction will have a substantial portion of small (less than 5 micrometres) and submicrometre particles.
The most critical sized particles are those in the 0.1 to 0.5 micrometres range because they are the most difficult for wet scrubbers to collect.
Design
The design of wet scrubbers or any air pollution control device depends on the industrial process conditions and the nature of the air pollutants involved. Inlet gas characteristics and dust properties (if particles are present) are of primary importance. Scrubbers can be designed to collect particulate matter and/or gaseous pollutants. The versatility of wet scrubbers allow them to be built in numerous configurations, all designed to provide good contact between the liquid and polluted gas stream.
Wet scrubbers remove dust particles by capturing them in liquid droplets. The droplets are then collected, the liquid dissolving or absorbing the pollutant gases. Any droplets that are in the scrubber inlet gas must be separated from the outlet gas stream by means of another device referred to as a mist eliminator or entrainment separator (these terms are interchangeable). Also, the resultant scrubbing liquid must be treated prior to any ultimate discharge or being reused in the plant.
A wet scrubber's ability to collect small particles is often directly proportional to the power input into the scrubber. Low energy devices such as spray towers are used to collect particles larger than 5 micrometers. To obtain high efficiency removal of 1 micrometer (or less) particles generally requires high-energy devices such as venturi scrubbers or augmented devices such as condensation scrubbers. Additionally, a properly designed and operated entrainment separator or mist eliminator is important to achieve high removal efficiencies. The greater the number of liquid droplets that are not captured by the mist eliminator, the higher the potential emission levels.
Wet scrubbers that remove gaseous pollutants are referred to as absorbers. Good gas-to-liquid contact is essential to obtain high removal efficiencies in absorbers. Various wet-scrubber designs are used to remove gaseous pollutants, with the packed tower and the plate tower being the most common.
If the gas stream contains both particulate matter and gases, wet scrubbers are generally the only single air pollution control device that can remove both pollutants. Wet scrubbers can achieve high removal efficiencies for either particles or gases and, in some instances, can achieve a high removal efficiency for both pollutants in the same system. However, in many cases, the best operating conditions for particles collection are the poorest for gas removal.
In general, obtaining high simultaneous gas and particulate removal efficiencies requires that one of them be easily collected (i.e., that the gases are very soluble in the liquid or that the particles are large and readily captured), or by the use of a scrubbing reagent such as lime or sodium hydroxide.
The "cleaned" gases are normally passed through a mist eliminator (demister pads) to remove water droplets from the gas stream. The dirty water from the scrubber system is either cleaned and discharged or recycled to the scrubber. Dust is removed from the scrubber in a clarification unit or a drag chain tank. In both systems solid material settles on the bottom of the tank. A drag chain conveyor system removes the sludge and deposits in into a dumpster or stockpile.
Droplet production
Droplets are produced by several methods:
Injecting liquid at high pressure through specially designed nozzles
Aspirating the particle-laden gas stream through a liquid pool
Submerging a whirling rotor in a liquid pool.
These droplets collect particles by using one or more of several collection mechanisms such as impaction, direct interception, diffusion, electrostatic attraction, condensation, centrifugal force and gravity. However, impaction and diffusion are the main ones.
Impaction
In a wet scrubbing system, dust particles will tend to follow the streamlines of the exhaust stream. However, when liquid droplets are introduced into the exhaust stream, particles cannot always follow these streamlines as they diverge around the droplet (Figure 1). The particle's mass causes it to break away from the streamlines and impact or hit the droplet.
Impaction increases as the diameter of the particle increases and as the relative velocity between the particle and droplets increases. As particles get larger they are less likely to follow the gas streamlines around droplets. Also, as particles move faster relative to the liquid droplet, there is a greater chance that the particle will hit a droplet. Impaction is the predominant collection mechanism for scrubbers having gas stream velocities greater than 0.3 m/s (1 ft/s) (Perry 1973).
Most scrubbers operate with gas stream velocities well above 0.3 m/s. Therefore, at these velocities, particles having diameters greater than 1.0 μm are collected by this mechanism. Impaction also increases as the size of the liquid droplet decreases because the presence of more droplets within the vessel increases the probability that particles will impact on the droplets.
Diffusion
Very small particles (less than 0.1 μm in diameter) experience random movement in an exhaust stream. These particles are so tiny that they are bumped by gas molecules as they move in the exhaust stream. This bumping, or bombardment, causes them to first move one way and then another in a random manner, or to diffuse, through the gas. This irregular motion can cause the particles to collide with a droplet and be collected (Figure 2). Because of this, diffusion is the primary collection mechanism in wet scrubbers for particles smaller than 0.1 μm.
The rate of diffusion depends on the following:
The relative velocity between the particle and droplet
The particle diameter
The liquid-droplet diameter.
For both impaction and diffusion, collection efficiency increases with an increase in relative velocity (liquid- or gas-pressure input) and a decrease in liquid-droplet size.
However, collection by diffusion increases as particle size decreases. This mechanism enables certain scrubbers to effectively remove the very tiny particles (less than 0.1 μm).
In the particle size range of approximately 0.1 to 1.0 μm, neither of these two collection mechanisms (impaction or diffusion) dominates. This relationship is illustrated in Figure 3.
Other collection mechanisms
In recent years, some scrubber manufacturers have utilized other collection mechanisms such as electrostatic attraction and condensation to enhance particle collection without increasing power consumption.
In electrostatic attraction, particles are captured by first inducing a charge on them. Then, the charged particles are either attracted to each other, forming larger, easier-to-collect particles, or they are collected on a surface.
Condensation of water vapor on particles promotes collection by adding mass to the particles. Other mechanisms such as gravity, centrifugal force, and direct interception slightly affect particle collection.
Advantages and disadvantages
For particulate control, wet scrubbers (also referred to as wet collectors) are evaluated against fabric filters and electrostatic precipitators (ESPs). Some advantages of wet scrubbers over these devices are as follows:
Wet scrubbers have the ability to handle high temperatures and moisture.
In wet scrubbers, flue gases are cooled, resulting in smaller overall size of equipment.
Wet scrubbers can remove both gases and particulate matter.
Wet scrubbers can neutralize corrosive gases
Some disadvantages of wet scrubbers include corrosion, the need for entrainment separation or mist removal to obtain high efficiencies and the need for treatment or reuse of spent liquid.
Wet scrubbers have been used in a variety of industries such as acid plants, fertilizer plants, steel mills, asphalt plants, and large power plants.
Components
Some components that are specific to the wet scrubbing process include:
venturi scrubber
spray chamber/tower
cyclonic spray scrubber
packed bed
ejector venturi scrubber
A system may include one or multiple of these components in addition to various supporting components such as:
Ductwork and fan system
A saturation chamber (optional)
Entrainment separator or mist eliminator
Pumping (and possible recycle system)
Spent scrubbing liquid treatment and/or reuse system
An exhaust stack
A typical wet scrubbing process can be described as follows:
Hot flue gas from a furnace enters a saturator (if present) where gases are cooled and humidified prior to entering the scrubbing area. The saturator removes a small percentage of the particulate matter present in the flue gas.
Next, the gas enters a venturi scrubber where approximately half of the gases are removed. Venturi scrubbers have a minimum particle removal efficiency of 95%.
The gas flows through a second scrubber, a packed bed absorber, where the rest of the gases (and particulate matter) are collected.
An entrainment separator or mist eliminator removes any liquid droplets that may have become entrained in the flue gas.
A recirculation pump moves some of the spent scrubbing liquid back to the venturi scrubber where it is recycled and the remainder is sent to a treatment system.
Treated scrubbing liquid is recycled back to the saturator and the packed bed absorber.
Fans and ductwork move the flue gas stream through the system and eventually out the stack.
Categorization
By configuration
Wet scrubbers can be categorized by the manner in which the gas and liquid phases are brought into contact. Scrubbers are designed to use power, or energy, from the gas stream or the liquid stream, or some other method to bring the pollutant gas stream into contact with the liquid. These categories are given in the table below.
There is a large variety of wet scrubbers; however, all have one of three basic configurations:
1. Gas-humidification - The gas-humidification process agglomerates fine particles, increasing the bulk, making collection easier.
2. Gas-liquid contact - This is one of the most important factors affecting collection efficiency. The particle and droplet come into contact by four primary mechanisms:
a) Inertial impaction - When water droplets placed in the path of a dust-laden gas stream, the stream separates and flows around them. Due to inertia, the larger dust particles will continue on in a straight path, hit the droplets, and become encapsulated.
b) Interception - Finer particles moving within a gas stream do not hit droplets directly but brush against and adhere to them.
c) Diffusion - When liquid droplets are scattered among dust particles, the particles are deposited on the droplet surfaces by Brownian movement, or diffusion. This is the principal mechanism in the collection of submicrometre dust particles.
d) Condensation nucleation - If a gas passing through a scrubber is cooled below the dewpoint, condensation of moisture occurs on the dust particles. This increase in particle size makes collection easier.
3. Gas-liquid separation - Regardless of the contact mechanism used, as much liquid and dust as possible must be removed. Once contact is made, dust particulates and water droplets combine to form agglomerates. As the agglomerates grow larger, they settle into a collector.
By energy
Since wet scrubbers vary greatly in complexity and method of operation, devising categories into which all of them neatly fit is extremely difficult. Scrubbers for particle collection are usually categorized by the gas-side pressure drop of the system. Gas-side pressure drop refers to the pressure difference, or pressure drop, that occurs as the exhaust gas is pushed or pulled through the scrubber, disregarding the pressure that would be used for pumping or spraying the liquid into the scrubber.
Spray-tower scrubber wet scrubbers may be categorized by pressure drop as follows:
Low-energy scrubbers (0.5 to 2.5 inches water gauge - 124.4 to 621.9 Pa)
Low- to medium-energy scrubbers (2.5 to 6 inches water gauge - 0.622 to 1.493 kPa)
Medium- to high-energy scrubbers (6 to 15 inches water gauge - 1.493 to 3.731 kPa)
High-energy scrubbers (greater than 15 inches water gauge - greater than 3.731 kPa)
However, most scrubbers operate over a wide range of pressure drops, depending on their specific application, thereby making this type of categorization difficult.
Due to the large number of commercial scrubbers available, it is not possible to describe each individual type here. However, the following sections provide examples of typical scrubbers in each category.
Low-energy scrubbers
In the simple, gravity-spray-tower scrubber, liquid droplets formed by liquid atomized in spray nozzles fall through rising exhaust gases. Dirty water is drained at the bottom.
These scrubbers operated at pressure drops of 1 to 2 in. water gauge (¼ to ½ kPa) and are approximately 70% efficient on 10 μm particles. Their efficiency is poor below 10 μm. However, they are capable of treating relatively high dust concentrations without becoming plugged.
Low- to medium-energy scrubbers
Wet cyclones use centrifugal force to spin the dust particles (similar to a cyclone), and throw the particulates upon the collector's wetted walls. Water introduced from the top to wet the cyclone walls carries these particles away. The wetted walls also prevent dust reentrainment.
Pressure drops for these collectors range from 2 to 8 in. water (½ to 2 kPa), and the collection efficiency is good for 5 μm particles and above.
High-energy scrubbers co-current-flow scrubber
Packed-bed scrubbers consist of beds of packing elements, such as coke, broken rock, rings, saddles, or other manufactured elements. The packing breaks down the liquid flow into a high-surface-area film so that the dusty gas streams passing through the bed achieve maximum contact with the liquid film and become deposited on the surfaces of the packing elements. These scrubbers have a good collection efficiency for respirable dust.
Three types of packed-bed scrubbers are:
Cross-flow scrubbers
Co-current flow scrubbers
Counter-current flow scrubbers
Efficiency can be greatly increased by minimizing target size, i.e., using 0.003 in. (0.076 mm) diameter stainless steel wire and increasing gas velocity to more than 1,800 ft/min (9.14 m/s).
High-energy scrubbers
Venturi scrubbers consist of a venturi-shaped inlet and separator. The dust-laden gases venturi scrubber enter through the venturi and are accelerated to speeds between 12,000 and 36,000 ft/min (60.97-182.83 m/s). These high-gas velocities immediately atomize the coarse water spray, which is injected radially into the venturi throat, into fine droplets. High energy and extreme turbulence promote collision between water droplets and dust particulates in the throat. The agglomeration process between particle and droplet continues in the diverging section of the venturi. The large agglomerates formed in the venturi are then removed by an inertial separator.
Venturi scrubbers achieve very high collection efficiencies for respirable dust. Since efficiency of a venturi scrubber depends on pressure drop, some manufacturers supply a variable-throat venturi to maintain pressure drop with varying gas flows.
By use
Another way to classify wet scrubbers is by their use - to primarily collect either particulates or gaseous pollutants. Again, this distinction is not always clear since scrubbers can often be used to remove both types of pollutants.
Material of construction and design
Corrosion can be a prime problem associated with chemical industry scrubbing systems. Fibre-reinforced plastic and dual keys are often used as most dependable materials of construction.
References
Bibliography
*Bethea, R. M. 1978. Air Pollution Control Technology. New York: Van Nostrand Reinhold.
National Asphalt Pavement Association. 1978. The Maintenance and Operation of Exhaust Systems in the Hot Mix Batch Plant. 2nd ed. Information Series 52.
Perry, J. H. (Ed.). 1973. Chemical Engineers’ Handbook. 5th ed. New York: McGraw-Hill.
Richards, J. R. 1995. Control of Particulate Emissions (APTI Course 413). U.S. Environmental Protection Agency.
Richards, J. R. 1995. Control of Gaseous Emissions. (APTI Course 415). U.S. Environmental Protection Agency.
Schifftner, K. C. 1979, April. Venturi scrubber operation and maintenance. Paper presented at the U.S. EPA Environmental Research Information Center. Atlanta, GA.
Semrau, K. T. 1977. Practical process design of particulate scrubbers. Chemical Engineering. 84:87-91.
U.S. Environmental Protection Agency. 1982, September. Control Techniques for Particulate Emissions from Stationary Sources. Vol. 1. EPA 450/3-81-005a.
Wechselblatt, P. M. 1975. Wet scrubbers (particulates). In F. L. Cross and H. E. Hesketh (Eds.), Handbook for the Operation and Maintenance of Air Pollution Control Equipment. Westport: Technomic Publishing.
Pollution control technologies
Air pollution control systems
Particulate control
NOx control
Volatile organic compound abatement
Acid gas control
Scrubbers
Gas technologies | Wet scrubber | Chemistry,Engineering | 3,837 |
70,687,909 | https://en.wikipedia.org/wiki/Neodymium%20arsenate | Neodymium arsenate, also known as neodymium(III) arsenate, is the arsenate of neodymium with the chemical formula of NdAsO4. In this compound, neodymium exhibits the +3 oxidation state. It has good thermal stability, and its pKsp,c is 21.86±0.11.
Preparation
Neodymium arsenate can be obtained from the reaction between sodium arsenate (Na3AsO4) and neodymium chloride (NdCl3) in solution:
Na3AsO4 + NdCl3 → 3 NaCl + NdAsO4↓
When crystallizing from a lead pyroarsenate flux, neodymium arsenate crystals produced explode when cooled.
Neodymium arsenate also occurs in nature as a mineral.
See also
Arsenic
References
Neodymium(III) compounds
Arsenates | Neodymium arsenate | Chemistry | 190 |
65,783,425 | https://en.wikipedia.org/wiki/Pakistani%20women%20in%20STEM | While STEM (Science, technology, engineering and mathematics) fields all over the world are dominated by men, the number of Pakistani women in 'STEM' is low due to one of the highest gender gaps in STEM fields. However, over the time, some Pakistani women have emerged as scientists in fields like Physics, Biology and computer sciences.
Gender gap in Pakistan
Pakistan has one of the highest gender gaps in the world, and it is the third least performer in gender parity according to a report published by World Economic Forum in 2020. The low literacy rate of women in Pakistan, despite women making almost half the population, is one of the factors in a high gender gap in STEM fields. This literacy rate is even lower in science and technology.
Facts
According to UNESCO, among students enrolled in bachelor's degrees, 47% are women while 53% are men. The number of women pursuing doctoral studies is only 36%, while the percentage of men is 64%. There is also a significant gender gap in research sector, with women making only 34% of researchers.
Among students in universities, the field of natural sciences is reported to have only 40% women students, while medical sciences have 45%, engineering has 21% and agricultural sciences have only 12%.
Engineering gender gap
According to the World Economic Forum, only 4.9% of engineering jobs are held by women in Pakistan. The numbers are particularly low in the energy sector with only 3% female engineers in the power transmission sector. The field of artificial intelligence has also seen few numbers of women engineers, with only 22% part of the workforce.
Bridging the gap
Efforts have been done by the government of Pakistan as well as women who are part of STEM fields, to reduce the wide gender gap in STEM. Since 2018, the government of Pakistan has worked to improve wage equality and its position on educational attainment index. Workplace sexual harassment laws have also been made to encourage women to become part of the workforce in both STEM fields as well as non STEM fields. Many private organizations like Women in tech, Women Engineers Pakistan have been founded to encourage STEM education in women.
Notable women
Some notable Pakistani women contributing to STEM are:
Nergis Mavalvala : is Pakistani-American physicist known for her breakthrough research in gravitational waves detection in 2015. She has also received the prestigious MacArthur Foundation Award in 2010. Nergis became the first female Dean of school of sciences at MIT in 2020.
Tasneem Zehra Husain : is theoretical physicist and among the few Pakistani women to obtain a doctorate in physics. She is also the first Pakistani woman working on string theory. Husain has represented Pakistan at the Meeting of Nobel Laureates in Lindau, Germany and led the Pakistan team to the World Year of Physics (WYP) Launch Conference in Paris.
Asma Zaheer : is computer scientist and the first Pakistani to receive "the best of IBM award, 2019".
Azra Quraishi : She was a botanist who is credited for increasing potato yield by 5% in Pakistan. This improved Pakistan's position in trade and brought Azra, national recognition. She was awarded the Norman Borlaug Award in 1997.
Arfa Karim : was a computer prodigy who became the youngest person to become a Microsoft certified Professional in 2004. She was personally invited by Bill Gates to the Microsoft headquarters in USA. Arfa was also named in the Guinness book of world records.
Mariam Sultana : is an astrophysicist. She became the first female astrophysicist in Pakistan after she obtained her PhD in 2012.
Talat Shahnaz Rahman is a condensed matter physicist. Her research topics include surface phenomena and excited media, including catalysis, vibrational dynamics, and magnetic excitations.
Aban Markar Kabraji: is a biologist and scientist of Parsi origin. She is a regional director of the Asia Regional Office of IUCN, the International Union for Conservation of Nature. She was awarded the Tamgha-e-Imtiaz for her outstanding contribution and dedication to the cause of environmental protection, sustainable development and nature conservation.
Asifa Akhtar: is a biologist who has worked in the area of chromosomes. She became the first international female vice president of the biology and medicine section at Germany's prestigious Max Planck Society. Asifa has also been awarded the European Life Science Organization (ELSO) award.
Farzana Aslam: is a physicist and astronomer. She has worked in the area of polymer composite sensitized with semiconductor nanoparticles, photon and laser sciences. For her contributions, Farzana was awarded a commendation award at the Photon 04 conference held by Institute of Physics at Glasgow.
References
External links
Women in Tech
Women in science and technology
Employment by country
Statistics of education
Women's education in Pakistan | Pakistani women in STEM | Technology | 978 |
18,813,336 | https://en.wikipedia.org/wiki/Szpiro%27s%20conjecture | In number theory, Szpiro's conjecture relates to the conductor and the discriminant of an elliptic curve. In a slightly modified form, it is equivalent to the well-known abc conjecture. It is named for Lucien Szpiro, who formulated it in the 1980s. Szpiro's conjecture and its equivalent forms have been described as "the most important unsolved problem in Diophantine analysis" by Dorian Goldfeld, in part to its large number of consequences in number theory including Roth's theorem, the Mordell conjecture, the Fermat–Catalan conjecture, and Brocard's problem.
Original statement
The conjecture states that: given ε > 0, there exists a constant C(ε) such that for any elliptic curve E defined over Q with minimal discriminant Δ and conductor f,
Modified Szpiro conjecture
The modified Szpiro conjecture states that: given ε > 0, there exists a constant C(ε) such that for any elliptic curve E defined over Q with invariants c4, c6 and conductor f (using notation from Tate's algorithm),
abc conjecture
The abc conjecture originated as the outcome of attempts by Joseph Oesterlé and David Masser to understand Szpiro's conjecture, and was then shown to be equivalent to the modified Szpiro's conjecture.
Consequences
Szpiro's conjecture and its modified form are known to imply several important mathematical results and conjectures, including Roth's theorem, Faltings's theorem, Fermat–Catalan conjecture, and a negative solution to the Erdős–Ulam problem.
Claimed proofs
In August 2012, Shinichi Mochizuki claimed a proof of Szpiro's conjecture by developing a new theory called inter-universal Teichmüller theory (IUTT). However, the papers have not been accepted by the mathematical community as providing a proof of the conjecture, with Peter Scholze and Jakob Stix concluding in March 2018 that the gap was "so severe that … small modifications will not rescue the proof strategy".
See also
Arakelov theory
References
Bibliography
Conjectures
Unsolved problems in number theory
Abc conjecture | Szpiro's conjecture | Mathematics | 454 |
51,998,538 | https://en.wikipedia.org/wiki/Hygrocybe%20umbilicata | Hygrocybe umbilicata is a species of the fungal family Hygrophoraceae. This species is the first of its genus reported for Bangladesh. It was found in Singra Forest, Birganj, Dinajpur district of Bangladesh.
References
Fungi of Bangladesh
umbilicata
Fungi described in 2016
Fungus species | Hygrocybe umbilicata | Biology | 71 |
2,108,626 | https://en.wikipedia.org/wiki/Lambda%20Velorum | )
Lambda Velorum (λ Velorum, abbreviated Lambda Vel, λ Vel), officially named Suhail , is a star in the southern constellation of Vela. With a mean apparent visual magnitude of 2.21, this is the third-brightest star in the constellation and one of the brighter stars in the sky. The distance to this star can be measured directly using the parallax technique, yielding an estimated from the Sun.
Nomenclature
λ Velorum (Latinised to Lambda Velorum) is the star's Bayer designation.
It bore the traditional Arabic name سهيل الوزن Suhail al Wazn, but as a modern navigation star this was shortened to Suhail. 'Suhail' (a common Arabic male first name) was traditionally used for at least three other stars: Canopus; Gamma Velorum (Suhail al Muhlif); and Zeta Puppis (Suhail Hadar). In 2016, the International Astronomical Union organized a Working Group on Star Names (WGSN) to catalogue and standardize proper names for stars. The WGSN approved the name Suhail for this star on 21 August 2016 and it is now so entered in the IAU Catalog of Star Names (Canopus had its name approved as is, and Zeta Puppis was given the name Naos).
In Chinese astronomy, Suhail is called 天記 (Pinyin: Tiānjì), meaning Judge for Estimating the Age of Animals, because this star is marking itself and stands alone in the Judge for Estimating the Age of Animals asterism. Ghost mansion (see: Chinese constellation), 天記 (Tiānjì), was westernized into Tseen Ke, but the name Tseen Ke was designated for Psi Velorum by R. H. Allen works and the meaning is "Heaven's Record".
Properties
It has an spectral classification of K4 Ib, with the luminosity class Ib meaning that it is a lower luminosity red supergiant star. The outer envelope of λ Velorum has an effective temperature of about , giving it the cool orange hue of a K-type star. It is an Lc-type, slow irregular variable star with its brightness varying between apparent magnitudes +2.14 to +2.30.
λ Velorum is an evolved star that has exhausted the hydrogen in its core region. It has about seven times the mass of the Sun. Despite having the luminosity class of a red supergiant star, it is likely to be on or approaching the asymptotic giant branch (AGB), although its properties do not exclude it being a slightly more massive star on the red giant branch (RGB). As an AGB star it has an inert core of carbon and oxygen and is alternately fusing helium and hydrogen in two shells outside the core. The star's outer envelope has expanded to form a deep, convective, hydrogen-burning layer that is generating a magnetic field. The surface strength of this field has been measured at . Massive stars use their hydrogen "fuel" much faster than do smaller stars and Lambda Velorum is estimated to be only some 32 million years old.
λ Velorum is near the upper end of the mass range for intermediate stars, which end their lives by producing a planetary nebula and a white dwarf remnant. It may be massive enough to produce an electron-capture supernova (like the supernova that formed the Crab Nebula), and hence a neutron star.
References
K-type supergiants
Vela (constellation)
Velorum, Lambda
Durchmusterung objects
078647
044816
3634
Suhail
TIC objects
Slow irregular variables | Lambda Velorum | Astronomy | 772 |
37,067,559 | https://en.wikipedia.org/wiki/Delta1%20Gruis | {{DISPLAYTITLE:Delta1 Gruis}}
Delta1 Gruis, Latinized from δ1 Gruis, is a candidate binary star system in the constellation Grus. With a peak apparent visual magnitude of 4.0 it is bright enough to be seen with the naked eye at night. The distance to this system, as determined using an annual parallax shift of 10.54 mas as seen from the Earth, is around 309 light years. It is gradually moving away from the Sun with a radial velocity of +4.9 km/s.
The brighter component of this system is an evolved, yellow-hued, G-type giant star with a stellar classification of G6/8 III. It is a semiregular variable that ranges between apparent magnitudes 3.99 and 4.2, located 325 light-years from Earth. Delta1 Gruis has around 3 times the mass and 24 times the diameter of the Sun. The fainter companion is a magnitude 12.8 star at an angular separation of 5.6 arc seconds, as of 2008.
See also
List of stars in Grus
References
G-type giants
Grus (constellation)
Gruis, Delta1
Durchmusterung objects
213009
110997
8556 | Delta1 Gruis | Astronomy | 260 |
1,567,335 | https://en.wikipedia.org/wiki/Derived%20set%20%28mathematics%29 | In mathematics, more specifically in point-set topology, the derived set of a subset of a topological space is the set of all limit points of It is usually denoted by
The concept was first introduced by Georg Cantor in 1872 and he developed set theory in large part to study derived sets on the real line.
Definition
The derived set of a subset of a topological space denoted by is the set of all points that are limit points of that is, points such that every neighbourhood of contains a point of other than itself.
Examples
If is endowed with its usual Euclidean topology then the derived set of the half-open interval is the closed interval
Consider with the topology (open sets) consisting of the empty set and any subset of that contains 1. The derived set of is
Properties
If and are subsets of the topological space then the derived set has the following properties:
implies
implies
A subset of a topological space is closed precisely when that is, when contains all its limit points. For any subset the set is closed and is the closure of (that is, the set ).
The derived set of a subset of a space need not be closed in general. For example, if with the trivial topology, the set has derived set which is not closed in But the derived set of a closed set is always closed.
In addition, if is a T1 space, the derived set of every subset of is closed in
Two subsets and are separated precisely when they are disjoint and each is disjoint from the other's derived set
A bijection between two topological spaces is a homeomorphism if and only if the derived set of the image (in the second space) of any subset of the first space is the image of the derived set of that subset.
A space is a T1 space if every subset consisting of a single point is closed. In a T1 space, the derived set of a set consisting of a single element is empty (Example 2 above is not a T1 space). It follows that in T1 spaces, the derived set of any finite set is empty and furthermore,
for any subset and any point of the space. In other words, the derived set is not changed by adding to or removing from the given set a finite number of points. It can also be shown that in a T1 space, for any subset
A set with (that is, contains no isolated points) is called dense-in-itself. A set with is called a perfect set. Equivalently, a perfect set is a closed dense-in-itself set, or, put another way, a closed set with no isolated points. Perfect sets are particularly important in applications of the Baire category theorem.
The Cantor–Bendixson theorem states that any Polish space can be written as the union of a countable set and a perfect set. Because any Gδ subset of a Polish space is again a Polish space, the theorem also shows that any Gδ subset of a Polish space is the union of a countable set and a set that is perfect with respect to the induced topology.
Topology in terms of derived sets
Because homeomorphisms can be described entirely in terms of derived sets, derived sets have been used as the primitive notion in topology. A set of points can be equipped with an operator mapping subsets of to subsets of such that for any set and any point :
implies
implies
Calling a set if will define a topology on the space in which is the derived set operator, that is,
Cantor–Bendixson rank
For ordinal numbers the -th Cantor–Bendixson derivative of a topological space is defined by repeatedly applying the derived set operation using transfinite recursion as follows:
for limit ordinals
The transfinite sequence of Cantor–Bendixson derivatives of is decreasing and must eventually be constant. The smallest ordinal such that is called the of
This investigation into the derivation process was one of the motivations for introducing ordinal numbers by Georg Cantor.
See also
Notes
Proofs
References
Further reading
Sierpiński, Wacław F.; translated by Krieger, C. Cecilia (1952). General Topology. University of Toronto Press.
External links
PlanetMath's article on the Cantor–Bendixson derivative
General topology | Derived set (mathematics) | Mathematics | 871 |
7,706 | https://en.wikipedia.org/wiki/Cartesian%20coordinate%20system | In geometry, a Cartesian coordinate system (, ) in a plane is a coordinate system that specifies each point uniquely by a pair of real numbers called coordinates, which are the signed distances to the point from two fixed perpendicular oriented lines, called coordinate lines, coordinate axes or just axes (plural of axis) of the system. The point where the axes meet is called the origin and has as coordinates. The axes directions represent an orthogonal basis. The combination of origin and basis forms a coordinate frame called the Cartesian frame.
Similarly, the position of any point in three-dimensional space can be specified by three Cartesian coordinates, which are the signed distances from the point to three mutually perpendicular planes. More generally, Cartesian coordinates specify the point in an -dimensional Euclidean space for any dimension . These coordinates are the signed distances from the point to mutually perpendicular fixed hyperplanes.
Cartesian coordinates are named for René Descartes, whose invention of them in the 17th century revolutionized mathematics by allowing the expression of problems of geometry in terms of algebra and calculus. Using the Cartesian coordinate system, geometric shapes (such as curves) can be described by equations involving the coordinates of points of the shape. For example, a circle of radius 2, centered at the origin of the plane, may be described as the set of all points whose coordinates and satisfy the equation ; the area, the perimeter and the tangent line at any point can be computed from this equation by using integrals and derivatives, in a way that can be applied to any curve.
Cartesian coordinates are the foundation of analytic geometry, and provide enlightening geometric interpretations for many other branches of mathematics, such as linear algebra, complex analysis, differential geometry, multivariate calculus, group theory and more. A familiar example is the concept of the graph of a function. Cartesian coordinates are also essential tools for most applied disciplines that deal with geometry, including astronomy, physics, engineering and many more. They are the most common coordinate system used in computer graphics, computer-aided geometric design and other geometry-related data processing.
History
The adjective Cartesian refers to the French mathematician and philosopher René Descartes, who published this idea in 1637 while he was resident in the Netherlands. It was independently discovered by Pierre de Fermat, who also worked in three dimensions, although Fermat did not publish the discovery. The French cleric Nicole Oresme used constructions similar to Cartesian coordinates well before the time of Descartes and Fermat.
Both Descartes and Fermat used a single axis in their treatments and have a variable length measured in reference to this axis. The concept of using a pair of axes was introduced later, after Descartes' La Géométrie was translated into Latin in 1649 by Frans van Schooten and his students. These commentators introduced several concepts while trying to clarify the ideas contained in Descartes's work.
The development of the Cartesian coordinate system would play a fundamental role in the development of the calculus by Isaac Newton and Gottfried Wilhelm Leibniz. The two-coordinate description of the plane was later generalized into the concept of vector spaces.
Many other coordinate systems have been developed since Descartes, such as the polar coordinates for the plane, and the spherical and cylindrical coordinates for three-dimensional space.
Description
One dimension
An affine line with a chosen Cartesian coordinate system is called a number line. Every point on the line has a real-number coordinate, and every real number represents some point on the line.
There are two degrees of freedom in the choice of Cartesian coordinate system for a line, which can be specified by choosing two distinct points along the line and assigning them to two distinct real numbers (most commonly zero and one). Other points can then be uniquely assigned to numbers by linear interpolation. Equivalently, one point can be assigned to a specific real number, for instance an origin point corresponding to zero, and an oriented length along the line can be chosen as a unit, with the orientation indicating the correspondence between directions along the line and positive or negative numbers. Each point corresponds to its signed distance from the origin (a number with an absolute value equal to the distance and a or sign chosen based on direction).
A geometric transformation of the line can be represented by a function of a real variable, for example translation of the line corresponds to addition, and scaling the line corresponds to multiplication. Any two Cartesian coordinate systems on the line can be related to each-other by a linear function (function of the form taking a specific point's coordinate in one system to its coordinate in the other system. Choosing a coordinate system for each of two different lines establishes an affine map from one line to the other taking each point on one line to the point on the other line with the same coordinate.
Two dimensions
A Cartesian coordinate system in two dimensions (also called a rectangular coordinate system or an orthogonal coordinate system) is defined by an ordered pair of perpendicular lines (axes), a single unit of length for both axes, and an orientation for each axis. The point where the axes meet is taken as the origin for both, thus turning each axis into a number line. For any point P, a line is drawn through P perpendicular to each axis, and the position where it meets the axis is interpreted as a number. The two numbers, in that chosen order, are the Cartesian coordinates of P. The reverse construction allows one to determine the point P given its coordinates.
The first and second coordinates are called the abscissa and the ordinate of P, respectively; and the point where the axes meet is called the origin of the coordinate system. The coordinates are usually written as two numbers in parentheses, in that order, separated by a comma, as in . Thus the origin has coordinates , and the points on the positive half-axes, one unit away from the origin, have coordinates and .
In mathematics, physics, and engineering, the first axis is usually defined or depicted as horizontal and oriented to the right, and the second axis is vertical and oriented upwards. (However, in some computer graphics contexts, the ordinate axis may be oriented downwards.) The origin is often labeled O, and the two coordinates are often denoted by the letters X and Y, or x and y. The axes may then be referred to as the X-axis and Y-axis. The choices of letters come from the original convention, which is to use the latter part of the alphabet to indicate unknown values. The first part of the alphabet was used to designate known values.
A Euclidean plane with a chosen Cartesian coordinate system is called a . In a Cartesian plane, one can define canonical representatives of certain geometric figures, such as the unit circle (with radius equal to the length unit, and center at the origin), the unit square (whose diagonal has endpoints at and ), the unit hyperbola, and so on.
The two axes divide the plane into four right angles, called quadrants. The quadrants may be named or numbered in various ways, but the quadrant where all coordinates are positive is usually called the first quadrant.
If the coordinates of a point are , then its distances from the X-axis and from the Y-axis are and , respectively; where denotes the absolute value of a number.
Three dimensions
A Cartesian coordinate system for a three-dimensional space consists of an ordered triplet of lines (the axes) that go through a common point (the origin), and are pair-wise perpendicular; an orientation for each axis; and a single unit of length for all three axes. As in the two-dimensional case, each axis becomes a number line. For any point P of space, one considers a plane through P perpendicular to each coordinate axis, and interprets the point where that plane cuts the axis as a number. The Cartesian coordinates of P are those three numbers, in the chosen order. The reverse construction determines the point P given its three coordinates.
Alternatively, each coordinate of a point P can be taken as the distance from P to the plane defined by the other two axes, with the sign determined by the orientation of the corresponding axis.
Each pair of axes defines a coordinate plane. These planes divide space into eight octants. The octants are:
The coordinates are usually written as three numbers (or algebraic formulas) surrounded by parentheses and separated by commas, as in or . Thus, the origin has coordinates , and the unit points on the three axes are , , and .
Standard names for the coordinates in the three axes are abscissa, ordinate and applicate. The coordinates are often denoted by the letters x, y, and z. The axes may then be referred to as the x-axis, y-axis, and z-axis, respectively. Then the coordinate planes can be referred to as the xy-plane, yz-plane, and xz-plane.
In mathematics, physics, and engineering contexts, the first two axes are often defined or depicted as horizontal, with the third axis pointing up. In that case the third coordinate may be called height or altitude. The orientation is usually chosen so that the 90-degree angle from the first axis to the second axis looks counter-clockwise when seen from the point ; a convention that is commonly called the right-hand rule.
Higher dimensions
Since Cartesian coordinates are unique and non-ambiguous, the points of a Cartesian plane can be identified with pairs of real numbers; that is, with the Cartesian product , where is the set of all real numbers. In the same way, the points in any Euclidean space of dimension n be identified with the tuples (lists) of n real numbers; that is, with the Cartesian product .
Generalizations
The concept of Cartesian coordinates generalizes to allow axes that are not perpendicular to each other, and/or different units along each axis. In that case, each coordinate is obtained by projecting the point onto one axis along a direction that is parallel to the other axis (or, in general, to the hyperplane defined by all the other axes). In such an oblique coordinate system the computations of distances and angles must be modified from that in standard Cartesian systems, and many standard formulas (such as the Pythagorean formula for the distance) do not hold (see affine plane).
Notations and conventions
The Cartesian coordinates of a point are usually written in parentheses and separated by commas, as in or . The origin is often labelled with the capital letter O. In analytic geometry, unknown or generic coordinates are often denoted by the letters (x, y) in the plane, and (x, y, z) in three-dimensional space. This custom comes from a convention of algebra, which uses letters near the end of the alphabet for unknown values (such as the coordinates of points in many geometric problems), and letters near the beginning for given quantities.
These conventional names are often used in other domains, such as physics and engineering, although other letters may be used. For example, in a graph showing how a pressure varies with time, the graph coordinates may be denoted p and t. Each axis is usually named after the coordinate which is measured along it; so one says the x-axis, the y-axis, the t-axis, etc.
Another common convention for coordinate naming is to use subscripts, as (x1, x2, ..., xn) for the n coordinates in an n-dimensional space, especially when n is greater than 3 or unspecified. Some authors prefer the numbering (x0, x1, ..., xn−1). These notations are especially advantageous in computer programming: by storing the coordinates of a point as an array, instead of a record, the subscript can serve to index the coordinates.
In mathematical illustrations of two-dimensional Cartesian systems, the first coordinate (traditionally called the abscissa) is measured along a horizontal axis, oriented from left to right. The second coordinate (the ordinate) is then measured along a vertical axis, usually oriented from bottom to top. Young children learning the Cartesian system, commonly learn the order to read the values before cementing the x-, y-, and z-axis concepts, by starting with 2D mnemonics (for example, 'Walk along the hall then up the stairs' akin to straight across the x-axis then up vertically along the y-axis).
Computer graphics and image processing, however, often use a coordinate system with the y-axis oriented downwards on the computer display. This convention developed in the 1960s (or earlier) from the way that images were originally stored in display buffers.
For three-dimensional systems, a convention is to portray the xy-plane horizontally, with the z-axis added to represent height (positive up). Furthermore, there is a convention to orient the x-axis toward the viewer, biased either to the right or left. If a diagram (3D projection or 2D perspective drawing) shows the x- and y-axis horizontally and vertically, respectively, then the z-axis should be shown pointing "out of the page" towards the viewer or camera. In such a 2D diagram of a 3D coordinate system, the z-axis would appear as a line or ray pointing down and to the left or down and to the right, depending on the presumed viewer or camera perspective. In any diagram or display, the orientation of the three axes, as a whole, is arbitrary. However, the orientation of the axes relative to each other should always comply with the right-hand rule, unless specifically stated otherwise. All laws of physics and math assume this right-handedness, which ensures consistency.
For 3D diagrams, the names "abscissa" and "ordinate" are rarely used for x and y, respectively. When they are, the z-coordinate is sometimes called the applicate. The words abscissa, ordinate and applicate are sometimes used to refer to coordinate axes rather than the coordinate values.
Quadrants and octants
The axes of a two-dimensional Cartesian system divide the plane into four infinite regions, called quadrants, each bounded by two half-axes. These are often numbered from 1st to 4th and denoted by Roman numerals: I (where the coordinates both have positive signs), II (where the abscissa is negative − and the ordinate is positive +), III (where both the abscissa and the ordinate are −), and IV (abscissa +, ordinate −). When the axes are drawn according to the mathematical custom, the numbering goes counter-clockwise starting from the upper right ("north-east") quadrant.
Similarly, a three-dimensional Cartesian system defines a division of space into eight regions or octants, according to the signs of the coordinates of the points. The convention used for naming a specific octant is to list its signs; for example, or . The generalization of the quadrant and octant to an arbitrary number of dimensions is the orthant, and a similar naming system applies.
Cartesian formulae for the plane
Distance between two points
The Euclidean distance between two points of the plane with Cartesian coordinates and is
This is the Cartesian version of Pythagoras's theorem. In three-dimensional space, the distance between points and is
which can be obtained by two consecutive applications of Pythagoras' theorem.
Euclidean transformations
The Euclidean transformations or Euclidean motions are the (bijective) mappings of points of the Euclidean plane to themselves which preserve distances between points. There are four types of these mappings (also called isometries): translations, rotations, reflections and glide reflections.
Translation
Translating a set of points of the plane, preserving the distances and directions between them, is equivalent to adding a fixed pair of numbers to the Cartesian coordinates of every point in the set. That is, if the original coordinates of a point are , after the translation they will be
Rotation
To rotate a figure counterclockwise around the origin by some angle is equivalent to replacing every point with coordinates (x,y) by the point with coordinates (x',y'), where
Thus:
Reflection
If are the Cartesian coordinates of a point, then are the coordinates of its reflection across the second coordinate axis (the y-axis), as if that line were a mirror. Likewise, are the coordinates of its reflection across the first coordinate axis (the x-axis). In more generality, reflection across a line through the origin making an angle with the x-axis, is equivalent to replacing every point with coordinates by the point with coordinates , where
Thus:
Glide reflection
A glide reflection is the composition of a reflection across a line followed by a translation in the direction of that line. It can be seen that the order of these operations does not matter (the translation can come first, followed by the reflection).
General matrix form of the transformations
All affine transformations of the plane can be described in a uniform way by using matrices. For this purpose, the coordinates of a point are commonly represented as the column matrix The result of applying an affine transformation to a point is given by the formula
where
is a 2×2 matrix and is a column matrix. That is,
Among the affine transformations, the Euclidean transformations are characterized by the fact that the matrix is orthogonal; that is, its columns are orthogonal vectors of Euclidean norm one, or, explicitly,
and
This is equivalent to saying that times its transpose is the identity matrix. If these conditions do not hold, the formula describes a more general affine transformation.
The transformation is a translation if and only if is the identity matrix. The transformation is a rotation around some point if and only if is a rotation matrix, meaning that it is orthogonal and
A reflection or glide reflection is obtained when,
Assuming that translations are not used (that is, ) transformations can be composed by simply multiplying the associated transformation matrices. In the general case, it is useful to use the augmented matrix of the transformation; that is, to rewrite the transformation formula
where
With this trick, the composition of affine transformations is obtained by multiplying the augmented matrices.
Affine transformation
Affine transformations of the Euclidean plane are transformations that map lines to lines, but may change distances and angles. As said in the preceding section, they can be represented with augmented matrices:
The Euclidean transformations are the affine transformations such that the 2×2 matrix of the is orthogonal.
The augmented matrix that represents the composition of two affine transformations is obtained by multiplying their augmented matrices.
Some affine transformations that are not Euclidean transformations have received specific names.
Scaling
An example of an affine transformation which is not Euclidean is given by scaling. To make a figure larger or smaller is equivalent to multiplying the Cartesian coordinates of every point by the same positive number m. If are the coordinates of a point on the original figure, the corresponding point on the scaled figure has coordinates
If m is greater than 1, the figure becomes larger; if m is between 0 and 1, it becomes smaller.
Shearing
A shearing transformation will push the top of a square sideways to form a parallelogram. Horizontal shearing is defined by:
Shearing can also be applied vertically:
Orientation and handedness
In two dimensions
Fixing or choosing the x-axis determines the y-axis up to direction. Namely, the y-axis is necessarily the perpendicular to the x-axis through the point marked 0 on the x-axis. But there is a choice of which of the two half lines on the perpendicular to designate as positive and which as negative. Each of these two choices determines a different orientation (also called handedness) of the Cartesian plane.
The usual way of orienting the plane, with the positive x-axis pointing right and the positive y-axis pointing up (and the x-axis being the "first" and the y-axis the "second" axis), is considered the positive or standard orientation, also called the right-handed orientation.
A commonly used mnemonic for defining the positive orientation is the right-hand rule. Placing a somewhat closed right hand on the plane with the thumb pointing up, the fingers point from the x-axis to the y-axis, in a positively oriented coordinate system.
The other way of orienting the plane is following the left-hand rule, placing the left hand on the plane with the thumb pointing up.
When pointing the thumb away from the origin along an axis towards positive, the curvature of the fingers indicates a positive rotation along that axis.
Regardless of the rule used to orient the plane, rotating the coordinate system will preserve the orientation. Switching any one axis will reverse the orientation, but switching both will leave the orientation unchanged.
In three dimensions
Once the x- and y-axes are specified, they determine the line along which the z-axis should lie, but there are two possible orientations for this line. The two possible coordinate systems, which result are called 'right-handed' and 'left-handed'. The standard orientation, where the xy-plane is horizontal and the z-axis points up (and the x- and the y-axis form a positively oriented two-dimensional coordinate system in the xy-plane if observed from above the xy-plane) is called right-handed or positive.
The name derives from the right-hand rule. If the index finger of the right hand is pointed forward, the middle finger bent inward at a right angle to it, and the thumb placed at a right angle to both, the three fingers indicate the relative orientation of the x-, y-, and z-axes in a right-handed system. The thumb indicates the x-axis, the index finger the y-axis and the middle finger the z-axis. Conversely, if the same is done with the left hand, a left-handed system results.
Figure 7 depicts a left and a right-handed coordinate system. Because a three-dimensional object is represented on the two-dimensional screen, distortion and ambiguity result. The axis pointing downward (and to the right) is also meant to point towards the observer, whereas the "middle"-axis is meant to point away from the observer. The red circle is parallel to the horizontal xy-plane and indicates rotation from the x-axis to the y-axis (in both cases). Hence the red arrow passes in front of the z-axis.
Figure 8 is another attempt at depicting a right-handed coordinate system. Again, there is an ambiguity caused by projecting the three-dimensional coordinate system into the plane. Many observers see Figure 8 as "flipping in and out" between a convex cube and a concave "corner". This corresponds to the two possible orientations of the space. Seeing the figure as convex gives a left-handed coordinate system. Thus the "correct" way to view Figure 8 is to imagine the x-axis as pointing towards the observer and thus seeing a concave corner.
Representing a vector in the standard basis
A point in space in a Cartesian coordinate system may also be represented by a position vector, which can be thought of as an arrow pointing from the origin of the coordinate system to the point. If the coordinates represent spatial positions (displacements), it is common to represent the vector from the origin to the point of interest as . In two dimensions, the vector from the origin to the point with Cartesian coordinates (x, y) can be written as:
where and are unit vectors in the direction of the x-axis and y-axis respectively, generally referred to as the standard basis (in some application areas these may also be referred to as versors). Similarly, in three dimensions, the vector from the origin to the point with Cartesian coordinates can be written as:
where and
There is no natural interpretation of multiplying vectors to obtain another vector that works in all dimensions, however there is a way to use complex numbers to provide such a multiplication. In a two-dimensional cartesian plane, identify the point with coordinates with the complex number . Here, i is the imaginary unit and is identified with the point with coordinates , so it is not the unit vector in the direction of the x-axis. Since the complex numbers can be multiplied giving another complex number, this identification provides a means to "multiply" vectors. In a three-dimensional cartesian space a similar identification can be made with a subset of the quaternions.
See also
Cartesian coordinate robot
Horizontal and vertical
Jones diagram, which plots four variables rather than two
Orthogonal coordinates
Polar coordinate system
Regular grid
Spherical coordinate system
Citations
General and cited references
Further reading
External links
Cartesian Coordinate System
Coordinate Converter – converts between polar, Cartesian and spherical coordinates
Coordinates of a point – interactive tool to explore coordinates of a point
open source JavaScript class for 2D/3D Cartesian coordinate system manipulation
Analytic geometry
Elementary mathematics
René Descartes
Orthogonal coordinate systems
Three-dimensional coordinate systems | Cartesian coordinate system | Mathematics | 5,119 |
24,535,618 | https://en.wikipedia.org/wiki/Majumdar%E2%80%93Ghosh%20model | 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 - model, with . The model is named after Indian physicists Chanchal Kumar Majumdar and Dipan Ghosh.
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.
Definition
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 , which in turn can be decomposed into a direct sum of spin 1/2 and 3/2 representations. It has the eigenvalues for the spin 1/2 subspace and for the spin 3/2 subspace.
Ground states
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.
Generalizations
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, also has the same aforementioned exactly dimerised ground state for all real .
See also
Heisenberg model (quantum)
Heisenberg model (classical)
J1 J2 model
Bethe ansatz
Ising model
t-J model
References
C K Majumdar and D Ghosh, On Next‐Nearest‐Neighbor Interaction in Linear Chain. J. Math. Phys. 10, 1388 (1969);
C K Majumdar, Antiferromagnetic model with known ground state. J. Phys. C: Solid State Phys. 3 911–915 (1970)
Assa Auerbach, Interacting Electrons and Quantum Magnetism, Springer-Verlag New York (1992) p. 83
Spin models
Statistical mechanics
Quantum magnetism
Lattice models | Majumdar–Ghosh model | Physics,Materials_science | 774 |
38,992,861 | https://en.wikipedia.org/wiki/Food%20and%20Chemical%20Toxicology | Food and Chemical Toxicology is a peer-reviewed scientific journal covering aspects of food safety, chemical safety, and other aspects of consumer product safety. It is published by Elsevier and was established in 1963. The editor-in-chief is Bryan Delaney.
Abstracting and indexing
The journal is abstracted and indexed in Analytical Abstracts, BIOSIS Previews, CAB International, Chemical Abstracts Service, Current Contents/Agriculture, Biology & Environmental Sciences, Current Contents/Life Sciences, Elsevier BIOBASE, EMBASE, MEDLINE/PubMed, Science Citation Index, and Scopus. According to the Journal Citation Reports, it has a 2014 impact factor of 2.895, ranking it 30th out of 87 journals in the category "Toxicology" and 14th out of 123 journals in the category "Food Science & Technology".
Controversies
In September 2012 F&CT was the original journal which published the paper in question in the Séralini affair. In November 2013 the publisher (Elsevier) then retracted it, however, only for it to be republished by Environmental Sciences Europe in June 2014.
In 2022, after a call from the editor for articles on alleged adverse effects of the COVID-19 vaccine, Seneff et al. published a paper alleging various mechanisms for various diseases that the authors intend to link to COVID-19 vaccination. Several scientists have warned of the biases and shortcomings that this article contains.
References
External links
Academic journals established in 1963
Toxicology journals
Chemistry journals
English-language journals
Monthly journals
Elsevier academic journals | Food and Chemical Toxicology | Environmental_science | 314 |
35,575,382 | https://en.wikipedia.org/wiki/Schmidt%E2%80%93Kalman%20filter | The Schmidt–Kalman Filter is a modification of the Kalman filter for reducing the dimensionality of the state estimate, while still considering the effects of the additional state in the calculation of the covariance matrix and the Kalman gains. A common application is to account for the effects of nuisance parameters such as sensor biases without increasing the dimensionality of the state estimate. This ensures that the covariance matrix will accurately represent the distribution of the errors.
The primary advantage of utilizing the Schmidt–Kalman filter instead of increasing the dimensionality of the state space is the reduction in computational complexity. This can enable the use of filtering in real-time systems. Another usage of Schmidt–Kalman is when residual biases are unobservable; that is, the effect of the bias cannot be separated out from the measurement. In this case, Schmidt–Kalman is a robust way to not try and estimate the value of the bias, but only keep track of the effect of the bias on the true error distribution.
For use in non-linear systems, the observation and state transition models may be linearized around the current mean and covariance estimate in a method analogous to the extended Kalman filter.
Naming and historical development
Stanley F. Schmidt developed the Schmidt–Kalman filter as a method to account for unobservable biases while maintaining the low dimensionality required for implementation in real time systems.
See also
Kalman filter
Extended Kalman filter
References
Control theory | Schmidt–Kalman filter | Mathematics | 300 |
995,994 | https://en.wikipedia.org/wiki/Electro-galvanic%20oxygen%20sensor | An electro-galvanic fuel cell is an electrochemical device which consumes a fuel to produce an electrical output by a chemical reaction. One form of electro-galvanic fuel cell based on the oxidation of lead is commonly used to measure the concentration of oxygen gas in underwater diving and medical breathing gases.
Electronically monitored or controlled diving rebreather systems, saturation diving systems, and many medical life-support systems use galvanic oxygen sensors in their control circuits to directly monitor oxygen partial pressure during operation. They are also used in oxygen analysers in recreational, technical diving and surface supplied mixed gas diving to analyse the proportion of oxygen in a nitrox, heliox or trimix breathing gas before a dive.
These cells are lead/oxygen galvanic cells where oxygen molecules are dissociated and reduced to hydroxyl ions at the cathode. The ions diffuse through the electrolyte and oxidize the lead anode. A current proportional to the rate of oxygen consumption is generated when the cathode and anode are electrically connected through a resistor
Function
The cell reaction for a lead/oxygen cell is: 2Pb + O2 → 2PbO, made up of the cathode reaction: O2 + 2H2O + 4e− → 4OH−, and anode reaction: 2Pb + 4OH− → 2PbO + 2H2O + 4e−.
The cell current is proportional to the rate of oxygen reduction at the cathode, but this is not linearly dependent on the partial pressure of oxygen in the gas to which the cell is exposed: Linearity is achieved by placing a diffusion barrier between the gas and the cathode, which limits the amount of gas reaching the cathode to an amount that can be fully reduced without significant delay, making the partial pressure in the immediate vicinity of the electrode close to zero. As a result of this the amount of oxygen reaching the electrode follows Fick's laws of diffusion and is proportional to the partial pressure in the gas beyond the membrane. This makes the current proportional to PO2.
The load resistor over the cell allows the electronics to measure a voltage rather than a current. This voltage depends on the construction and age of the sensor, and typically varies between 7 and 28 mV for a PO2 of 0.21 bar
Diffusion is linearly dependent on the partial pressure gradient, but is also temperature dependent, and the current rises about two to three percent per kelvin rise in temperature. A negative temperature coefficient resistor is used to compensate, and for this to be effective it must be at the same temperature as the cell. Oxygen cells which may be exposed to relatively large or rapid temperature changes, like rebreathers, generally use thermally conductive paste between the temperature compensating circuit and the cell to speed up the balancing of temperature.
Temperature also affects the signal response time, which is generally between 6 and 15 seconds at room temperature for a 90% response to a step change in partial pressure. Cold cells react much slower and hot cells much faster. As the anode material is oxidised the output current drops and eventually will cease altogether. The oxidation rate depends on the oxygen reaching the anode from the sensor membrane. Lifetime is measured in oxygen-hours, and also depends on temperature and humidity
Applications
Gas mixture analysis
The oxygen content of a stored gas mixture can be analysed by passing a small flow of the gas over a recently calibrated cell for long enough that the output stabilises. The stable output represents the fraction of oxygen in the mixture. Care must be taken to ensure that the gas flow is not diluted by ambient air, as this would affect the reading.
Breathing gas composition monitoring
The partial pressure of oxygen in anaesthetic gases is monitored by siting the cell in the gas flow, which is at local atmospheric pressure, and can be calibrated to directly indicate the fraction of oxygen in the mix.
The partial pressure of oxygen in diving chambers and surface supplied breathing gas mixtures can also be monitored using these cells. This can either be done by placing the cell directly in the hyperbaric environment, wired through the hull to the monitor, or indirectly, by bleeding off gas from the hyperbaric environment or diver gas supply and analysing at atmospheric pressure, then calculating the partial pressure in the hyperbaric environment. This is frequently required in saturation diving and surface oriented surface supplied mixed gas commercial diving.
Diving rebreather control systems
The breathing gas mixture in a diving rebreather loop is usually measured using oxygen cells, and the output of the cells is used by either the diver or an electronic control system to control addition of oxygen to increase partial pressure when it is below the chosen lower set-point, or to flush with diluent gas when it is above the upper set-point. When the partial pressure is between the upper and lower set-points, it is suitable for breathing at that depth and is left until it changes as a result of consumption by the diver, or a change in ambient pressure as a result of a depth change.
Accuracy and reliability of measurement is important in this application for two basic reasons. Firstly, if the oxygen content is too low, the diver will lose consciousness due to hypoxia and probably die, or if the oxygen content is too high, the risk of central nervous system oxygen toxicity causing convulsions and loss of consciousness, with a high risk of drowning becomes unacceptable. Secondly, decompression obligations cannot be accurately or reliably calculated if the breathing gas composition is not known. Pre-dive calibration of the cells can only check response to partial pressures up to 100% at atmospheric pressure, or 1 bar. As the set points are commonly in the range of 1.2 to 1.6 bar, special hyperbaric calibration equipment would be required to reliably test the response at the set-points. This equipment is available, but is expensive and not in common use, and requires the cells to be removed from the rebreather and installed in the test unit. To compensate for the possibility of a cell failure during a dive, three cells are generally fitted, on the principle that failure of one cell at a time is most likely, and that if two cells indicate the same PO2, they are more likely to be correct than the single cell with a different reading. Voting logic allows the control system to control the circuit for the rest of the dive according to the two cells assumed to be correct. This is not entirely reliable, as it is possible for two cells to fail on the same dive.
The sensors should be placed in the rebreather where a temperature gradient between the gas and the electronics in the back of the cells will not occur.
Lifespan
Oxygen cells behave in a similar way to electrical batteries in that they have a finite lifespan which is dependent upon use. The chemical reaction described above causes the cell to create an electrical output that has a predicted voltage which is dependent on the materials used. In theory they should give that voltage from the day they are made until they are exhausted, except that one component of the planned chemical reaction has been left out of the assembly: oxygen.
Oxygen is one of the fuels of the cell so the more oxygen there is at the reaction surface, the more electrical current is generated. The chemistry sets the voltage and the oxygen concentration controls the electric current output. If an electrical load is connected across the cell it can draw up to this current but if the cell is overloaded the voltage will drop. When the lead electrode has been substantially oxidised, the maximum current that the cell can produce will drop, and eventually linearity of output current to partial pressure of oxygen at the reactive surface will fail within the required range of measurement, and the cell will no longer be accurate.
There are two commonly used ways to specify expected sensor life span: The time in months at room temperature in air, or volume percentage oxygen hours (Vol%O2h). Storage at low oxygen partial pressure when not in use would seem an effective way to extend cell life, but when stored in anoxic conditions the sensor current will cease and the surface of the electrode may be passivated, which can lead to sensor failure. High ambient temperatures will increase sensor current, and reduce cell life. In diving service a cell typically lasts for 12 to 18 months, with perhaps 150 hours service in the diving loop at an oxygen partial pressure of about 1.2 bar and the rest of the time in storage in air at room temperature.
Failures in cells can be life-threatening for technical divers and in particular, rebreather divers. The failure modes common to these cells are: failing with a higher than expected output due to electrolyte leaks, which is usually attributable to physical damage, contamination, or other defects in manufacture, or current limitation due to exhausted cell life and non linear output across its range.
Shelf life can be maximised by keeping the cell in the sealed bag as supplied by the manufacturer until being put into service, storing the cell before and between use at or below room temperature, - a range of from 10 to 22 °C is recommended by a manufacturer - and avoid storing the cell in warm or dry environments for prolonged periods, particularly areas exposed to direct sunlight.
Failure modes
When new, a sensor can produce a linear output for over 4 bar partial pressure of oxygen, and as the anode is consumed the linear output range drops, eventually to below the range of partial pressures which may be expected in service, at which stage it is no longer fit to control the system. The maximum output current eventually drops below the amount needed to indicate the full range of partial pressures expected in operation. This state is called current-limited. Current limited cells do not give a high enough output in high concentrations of oxygen. The rebreather control circuit responds as if there is insufficient oxygen in the loop and injects more oxygen in an attempt to reach a setpoint the cell can never indicate, resulting in hyperoxia. When a current limited sensor can no longer reliably activate the control system at the upper set-point in a life support system, there is a severe risk of an excessive oxygen partial pressure occurring which will not be noticed, which can be life-threatening.
Other failure modes include mechanical damage, such as broken conductors, corroded contacts and loss of electrolyte due to damaged membranes.
Failing high – producing an output indicating partial pressure higher than reality – is invariably a result of a manufacturing fault or mechanical damage. In rebreathers, failing high will result in the rebreather assuming that there is more oxygen in the loop than there actually is which can result in hypoxia.
Non-linear cells do not perform in the expected manner across the required range of oxygen partial pressures. Two-point calibration against diluent and oxygen at atmospheric pressure will not pick up this fault which results in inaccurate loop contents of a rebreather. This gives the potential for decompression illness if the loop is maintained at a lower partial pressure than indicated by the cell output, or hyperoxia if the loop is maintained at a higher partial pressure than indicated by cell output.
Testing cells in the field
Preventing accidents in rebreathers from cell failures is possible in most cases by accurately testing the cells before use. Some divers carry out in-water checks by pushing the oxygen content in the loop to a pressure that is above that of pure oxygen at sea level to indicate if the cell is capable of high outputs. This test is only a spot check and does not accurately assess the quality of that cell or predict its failure. The only way to accurately test a cell is with a test chamber which can hold a calibrated static pressure above the upper set-point without deviation and the ability to record the output voltage over the full range of working partial pressures and graph them.
Managing cell failure in a life-support system
If more than one statistically independent cell is used, it is unlikely that more than one will fail at a time. If one assumes that only one cell will fail, then comparing three or more outputs which have been calibrated at two points is likely to pick up the cell which has failed by assuming that any two cells that produce the same output are correct and the one which produces a different output is defective. This assumption is usually correct in practice, particularly if there is some difference in the history of the cells involved. The concept of comparing the output from three cells at the same place in the loop and controlling the gas mixture based on the average output of the two with the most similar output at any given time is known as voting logic, and is more reliable than control based on a single cell. If the third cell output deviates sufficiently from the other two, an alarm indicates probable cell failure. If this occurs before the dive, the rebreather is deemed unsafe and should not be used. If it occurs during a dive, it indicates an unreliable control system, and the dive should be aborted. Continuing a dive using a rebreather with a failed cell alarm significantly increases the risk of a fatal loop control failure. This system is not totally reliable. There has been at least one case reported where two cells failed similarly and the control system voted out the remaining good cell.
If the probability of failure of each cell was statistically independent of the others, and each cell alone was sufficient to allow safe function of the rebreather, the use of three fully redundant cells in parallel would reduce risk of failure by five or six orders of magnitude.
The voting logic changes this considerably. A majority of cells must not fail for safe function of the unit. In order to decide whether a cell is functioning correctly, it must be compared with an expected output. This is done by comparing it against the outputs of other cells. In the case of two cells, if the outputs differ, then one at least must be wrong, but it is not known which one. In such a case the diver should assume the unit is unsafe and bail out to open circuit. With three cells, if they all differ within an accepted tolerance, they may all be deemed functional. If two differ within tolerance, and the third does not, the two within tolerance may be deemed functional, and the third faulty. If none are within tolerance of each other, they may all be faulty, and if one is not, there is no way of identifying it.
Using this logic, the improvement in reliability gained by use of voting logic where at least two sensors must function for the system to function is greatly reduced compared to the fully redundant version. Improvements are only in the order of one to two orders of magnitude. This would be great improvement over the single sensor, but the analysis above has assumed statistical independence of the failure of the sensors, which is generally not realistic.
Factors which make the cell outputs in a rebreather statistically dependent include:
Common calibration gas - They are all calibrated together in the pre-dive check using the same diluent and oxygen supply.
Sensors are often from the same manufacturing batch - Components, materials and processes are likely to be very similar.
Sensors are often installed together and have since been exposed to the same PO2, temperature profile over the subsequent time.
Common working environment, particularly with regards to temperature and relative humidity, as they are usually mounted in very close proximity in the loop, to ensure that they measure similar gas.
Common measurement systems
Common firmware for processing the signals
This statistical dependency can be minimised and mitigated by:
Using sensors from different manufacturers or batches, so that no two are from the same batch
Changing sensors at different times, so they each have a different history
Ensuring that the calibration gases are correct
Adding an statistically independent PO2 measuring system to the loop at a different place, using a different model sensor, and using different electronics and software to process the signal.
Calibrating this sensor using a different gas source to the others
An alternative method of providing redundancy in the control system is to recalibrate the sensors periodically during the dive by exposing them to a flow of either diluent or oxygen or both at different times, and using the output to check whether the cell is reacting appropriately to the known gas as the known depth. This method has the added advantage of allowing calibration at higher oxygen partial pressure than 1 bar. This procedure may be done automatically, where the system has been designed to do it, or the diver can manually perform a diluent flush at any depth at which the diluent is breathable to compare the cell PO2 readings against a known FO2 and absolute pressure to verify the displayed values. This test does not only validate the cell. If the sensor does not display the expected value, it is possible that the oxygen sensor, the pressure sensor (depth), or the gas mixture FO2, or any combination of these may be faulty. As all three of these possible faults could be life-threatening, the test is quite powerful.
Testing
The first commercially available certified oxygen cell checking device was launched in 2005 by Narked at 90, but did not achieve commercial success. A much revised model was released in 2007 and won the "Gordon Smith Award" for Innovation at the Diving Equipment Manufacturers Exhibition in Florida. Narked at 90 Ltd also won the Innovation Award for "an technical diving product that has made diving safer" at EUROTEK.2010 for their Oxygen Cell Checker. . The Cell Checker has been used by organisations such as Teledyne, Vandagraph, National Oceanic and Atmospheric Administration, NURC (NATO Undersea Research Centre), and Diving Diseases Research Centre.
A small pressure vessel for hyperbaric testing of cells is also available in which a pressurised oxygen atmosphere of up to 2 bar can be used to check linearity at higher pressures using the electronics of the rebreather.
See also
References
Fuel cells
Underwater diving safety equipment
Sensors
Oxygen | Electro-galvanic oxygen sensor | Technology,Engineering | 3,679 |
54,045,177 | https://en.wikipedia.org/wiki/Biopolymers%20%28journal%29 | Biopolymers is a biweekly peer-reviewed scientific journal covering the study of biopolymers from a biochemical and biophysical perspective. It was established in 1963 and is published by John Wiley & Sons. The editor-in-chief is Hilary J. Crichton. The journal has three sections: Peptide Science (established in 1995, published bimonthly), Nucleic Acid Sciences (established in 1997, published four times per year), and Biospectroscopy (merged with Biopolymers in 2004). Peptide Science is the affiliate journal of the American Peptide Society. According to the Journal Citation Reports, the journal has a 2015 impact factor of 2.248, ranking it 39th out of 72 journals in the category "Biophysics" and 186th out of 289 in the category "Biochemistry & Molecular Biology".
References
External links
Biweekly journals
Wiley (publisher) academic journals
Academic journals established in 1963
Biochemistry journals
Biophysics journals
English-language journals | Biopolymers (journal) | Chemistry | 202 |
10,836,468 | https://en.wikipedia.org/wiki/Erd%C5%91s%E2%80%93Stone%20theorem | In extremal graph theory, the Erdős–Stone theorem is an asymptotic result generalising Turán's theorem to bound the number of edges in an H-free graph for a non-complete graph H. It is named after Paul Erdős and Arthur Stone, who proved it in 1946, and it has been described as the “fundamental theorem of extremal graph theory”.
Statement for Turán graphs
The extremal number ex(n; H) is defined to be the maximum number of edges in a graph with n vertices not containing a subgraph isomorphic to H; see the Forbidden subgraph problem for more examples of problems involving the extremal number. Turán's theorem says that ex(n; Kr) = tr − 1(n), the number of edges of the Turán graph T(n, r − 1), and that the Turán graph is the unique such extremal graph. The Erdős–Stone theorem extends this result to H = Kr(t), the complete r-partite graph with t vertices in each class, which is the graph obtained by taking Kr and replacing each vertex with t independent vertices:
Statement for arbitrary non-bipartite graphs
If H is an arbitrary graph whose chromatic number is r > 2, then H is contained in Kr(t) whenever t is at least as large as the largest color class in an r-coloring of H, but it is not contained in the Turán graph T(n,r − 1), as this graph and therefore each of its subgraphs can be colored with r − 1 colors.
It follows that the extremal number for H is at least as large as the number of edges in T(n,r − 1), and at most equal to the extremal function for Kr(t); that is,
For bipartite graphs H, however, the theorem does not give a tight bound on the extremal function. It is known that, when H is bipartite, ex(n; H) = o(n2), and for general bipartite graphs little more is known. See Zarankiewicz problem for more on the extremal functions of bipartite graphs.
Turán density
Another way of describing the Erdős–Stone theorem is using the Turán density of a graph , which is defined by . This determines the extremal number up to an additive error term. It can also be thought of as follows: given a sequence of graphs , each not containing , such that the number of vertices goes to infinity, the Turán density is the maximum possible limit of their edge densities. The Erdős–Stone theorem determines the Turán density for all graphs, showing that any graph with chromatic number has a Turán density of
Proof
One proof of the Erdős–Stone theorem uses an extension of the Kővári–Sós–Turán theorem to hypergraphs, as well as the supersaturation theorem, by creating a corresponding hypergraph for every graph that is -free and showing that the hypergraph has some bounded number of edges. The Kővári–Sós–Turán says, among other things, that the extremal number of , the complete bipartite graph with vertices in each part, is at most for a constant . This can be extended to hypergraphs: defining to be the -partite -graph with vertices in each part, then for some constant .
Now, for a given graph with , and some graph with vertices that does not contain a subgraph isomorphic to , we define the -graph with the same vertices as and a hyperedge between vertices in if they form a clique in . Note that if contains a copy of , then the original graph contains a copy of , as every pair of vertices in distinct parts must have an edge. Thus, contains no copies of , and so it has hyperedges, indicating that there are copies of in . By supersaturation, this means that the edge density of is within of the Turán density of , which is by Turán's theorem; thus, the edge density is bounded above by .
On the other hand, we can achieve this bound by taking the Turán graph , which contains no copies of but has edges, showing that this value is the maximum and concluding the proof.
Quantitative results
Several versions of the theorem have been proved that more precisely characterise the relation of n, r, t and the o(1) term. Define the notation sr,ε(n) (for 0 < ε < 1/(2(r − 1))) to be the greatest t such that every graph of order n and size
contains a Kr(t).
Erdős and Stone proved that
for n sufficiently large. The correct order of sr,ε(n) in terms of n was found by Bollobás and Erdős: for any given r and ε there are constants c1(r, ε) and c2(r, ε) such that c1(r, ε) log n < sr,ε(n) < c2(r, ε) log n. Chvátal and Szemerédi then determined the nature of the dependence on r and ε, up to a constant:
for sufficiently large n.
Notes
Extremal graph theory
Theorems in graph theory
Stone theorem | Erdős–Stone theorem | Mathematics | 1,108 |
11,437,936 | https://en.wikipedia.org/wiki/Mycosphaerella%20angulata | Mycosphaerella angulata is a fungal plant pathogen infecting muscadine grapes. This pathogen causes the common disease angular leaf spot. Mycosphaerella angulate is an ascomycete in the fungi kingdom.
Host and symptoms
Mycosphaerella angulata is a major pathogen affecting the muscadine grape. Infection occurs mainly after midseason. The primary symptoms of this disease are faint chlorotic spots on the leaves. The chlorotic spots continue to grow in size during the growing season, forming angular brown lesions in the center. The irregular lesions on the leaves inhibit normal photosynthesis, which results in leaf loss and exposure of the grapes to sun scald. This weakens the vines and makes them more susceptible to cold damage. The pre-harvest infection of this pathogen can slow or stop berry development before maturity. The symptoms of the angular leaf spot disease are relatively easy to recognize late in the season.
Environment
Mycosphaerella angulate is commonly found in Southeastern United States and around the coastal regions where their host, muscadine grapes, are commonly grown. A case study was done by researchers from Florida A&M University looking at the effects of angular leaf spot on muscadine grapes. It was observed that in years that are wet early in the year and mild over the rest of the growing season caused worse disease symptoms than years that were dry in the spring and wet and stormy in the growing season. Showing that the pathogen thrives in conditions that are warm, wet, and humid - especially earlier in the growing season of the grape, when initial infection occurs. Although important, this disease and pathogen has not had much research done on it, making it difficult to determine what environmental factors are key for the pathogen's spread and development.
Disease cycle
Mycosphaerella angulate is part of the ascomycete division, so it is a fungus with a sexual and an asexual stage. The asexual stage of this pathogen was first found in 1902, while the sexual stage was later discovered in 1942. The asexual stage produces conidiophores with conidia, and the sexual stage is an ascus with ascospores - produced by meiosis. Starting with the primary inoculum, the spores get disseminated by the wind. These spores go and infect the leaves by penetration through wounds or stomata penetration. Inter- and intracellular hyphae then infect into the leaf and a conidiophore tuft gets formed on the lower leaf surface. These conidiophore tufts produce conidia which are the second inoculum that go out and infect other leaves. The infected grape leaf produces pseudothecium's, which is a certain type of ascocarp that shoots out the ascospores when conditions are right. They infected grape leaves also produce conidiophores with conidia. These ascospores and conidia start the life cycle over again with the primary inoculum.
Importance
Muscadine grapes are an important source of dietary fiber and ellagic acid, which is an anticancer compound. An increase in the use of muscadine grapes in the wine industry and production is expected, making this pathogen very economically important. The pre-harvest infection of this pathogen can slow or stop berry development before maturity. Muscadine wines have a fruity flavor and the quality of these wines/grapes is dependent upon the growth and maturation of the grapes - which angular leaf spot has a direct effect on. Yield loss due to angular leaf spot disease has not been studied much, but it is thought to be one of the most severe of all of the diseases affecting muscadine grapes.
Management
There are a few management practices commonly used to control angular leaf spot. These include: destroying crop residue, removing nearby wild muscadine vines, applying fungicides (especially mid to late season), keep vines healthy, and trimming the canopy cover. Some muscadine plants have also been observed to have some degree of resistance to Mycosphaerella angulate.
See also
List of Mycosphaerella species
References
External links
USDA ARS Fungal Database
angulata
Fungal grape diseases
Fungi described in 1942
Fungus species | Mycosphaerella angulata | Biology | 867 |
2,728,068 | https://en.wikipedia.org/wiki/Anomalous%20magnetic%20dipole%20moment | In quantum electrodynamics, the anomalous magnetic moment of a particle is a contribution of effects of quantum mechanics, expressed by Feynman diagrams with loops, to the magnetic moment of that particle. The magnetic moment, also called magnetic dipole moment, is a measure of the strength of a magnetic source.
The "Dirac" magnetic moment, corresponding to tree-level Feynman diagrams (which can be thought of as the classical result), can be calculated from the Dirac equation. It is usually expressed in terms of the g-factor; the Dirac equation predicts . For particles such as the electron, this classical result differs from the observed value by a small fraction of a percent. The difference is the anomalous magnetic moment, denoted and defined as
Electron
The one-loop contribution to the anomalous magnetic moment—corresponding to the first and largest quantum mechanical correction—of the electron is found by calculating the vertex function shown in the adjacent diagram. The calculation is relatively straightforward and the one-loop result is:
where is the fine-structure constant. This result was first found by Julian Schwinger in 1948 and is engraved on his tombstone. As of 2016, the coefficients of the QED formula for the anomalous magnetic moment of the electron are known analytically up to and have been calculated up to order :
The QED prediction agrees with the experimentally measured value to more than 10 significant figures, making the magnetic moment of the electron one of the most accurately verified predictions in the history of physics. (See Precision tests of QED for details.)
The current experimental value and uncertainty is:
According to this value, is known to an accuracy of around 1 part in 10 billion (1010). This required measuring to an accuracy of around 1 part in 10 trillion (1013).
Muon
The anomalous magnetic moment of the muon is calculated in a similar way to the electron. The prediction for the value of the muon anomalous magnetic moment includes three parts:
Of the first two components, represents the photon and lepton loops, and the W boson, Higgs boson and Z boson loops; both can be calculated precisely from first principles. The third term, , represents hadron loops; it cannot be calculated accurately from theory alone. It is estimated from experimental measurements of the ratio of hadronic to muonic cross sections (R) in electron–antielectron (–) collisions. As of July 2017, the measurement disagrees with the Standard Model by 3.5 standard deviations, suggesting physics beyond the Standard Model may be having an effect (or that the theoretical/experimental errors are not completely under control). This is one of the long-standing discrepancies between the Standard Model and experiment.
The E821 Experiment at Brookhaven National Laboratory (BNL) studied the precession of muon and antimuon in a constant external magnetic field as they circulated in a confining storage ring. The E821 Experiment reported the following average value
In 2024, the Fermilab collaboration "Muon g−2" doubled the accuracy of this value over the group’s previous measurements from the 2018 data set. The data for the experiment were collected during the 2019–2020 runs. The independent value came in at (0.21 ppm), which, combined with measurements from Brookhaven National Laboratory, yields a world average of (0.19 ppm).
In April 2021, an international group of fourteen physicists reported that by using ab-initio quantum chromodynamics and quantum electrodynamics simulations they were able to obtain a theory-based approximation agreeing more with the experimental value than with the previous theory-based value that relied on the electron–positron annihilation experiments.
Tau
The Standard Model prediction for the tau's anomalous magnetic dipole moment is
while the best measured bound for is
reported by the CMS experiment at the CERN LHC.
Composite particles
Composite particles often have a huge anomalous magnetic moment. The nucleons, protons and neutrons, both composed of quarks, are examples. The nucleon magnetic moments are both large and were unexpected; the proton's magnetic moment is much too large for an elementary particle, while the neutron's magnetic moment was expected to be zero due to its charge being zero.
See also
Anomalous electric dipole moment
Electron magnetic moment
g-factor (physics)
Gordon decomposition
References
Bibliography
External links
Overview of the g−2 experiment
Magnetic moment
Quantum electrodynamics
Quantum field theory
Standard Model | Anomalous magnetic dipole moment | Physics,Mathematics | 944 |
5,039,858 | https://en.wikipedia.org/wiki/Shear%20flow | In fluid dynamics, shear flow is the flow induced by a force in a fluid. In solid mechanics, shear flow is the shear stress over a distance in a thin-walled structure.
In solid mechanics
For thin-walled profiles, such as that through a beam or semi-monocoque structure, the shear stress distribution through the thickness can be neglected. Furthermore, there is no shear stress in the direction normal to the wall, only parallel. In these instances, it can be useful to express internal shear stress as shear flow, which is found as the shear stress multiplied by the thickness of the section. An equivalent definition for shear flow is the shear force V per unit length of the perimeter around a thin-walled section. Shear flow has the dimensions of force per unit of length. This corresponds to units of newtons per meter in the SI system and pound-force per foot in the US.
Origin
When a transverse force is applied to a beam, the result is variation in bending normal stresses along the length of the beam. This variation causes a horizontal shear stress within the beam that varies with distance from the neutral axis in the beam. The concept of complementary shear then dictates that a shear stress also exists across the cross section of the beam, in the direction of the original transverse force. As described above, in thin-walled structures, the variation along the thickness of the member can be neglected, so the shear stress across the cross section of a beam that is composed of thin-walled elements can be examined as shear flow, or the shear stress multiplied by the thickness of the element.
Applications
The concept of shear flow is particularly useful when analyzing semi-monocoque structures, which can be idealized using the skin-stringer model. In this model, the longitudinal members, or stringers, carry only axial stress, while the skin or web resists the externally applied torsion and shear force. In this case, since the skin is a thin-walled structure, the internal shear stresses in the skin can be represented as shear flow. In design, the shear flow is sometimes known before the skin thickness is determined, in which case the skin thickness can simply be sized according to allowable shear stress.
Shear center
For a given structure, the shear center is the point in space at which shear force could be applied without causing torsional deformation (e.g. twisting) of the cross-section of the structure. The shear center is an imaginary point, but does not vary with the magnitude of the shear force - only the cross-section of the structure. The shear center always lies along the axis of symmetry, and can be found using the following method:
Apply an arbitrary resultant shear force
Calculate the shear flows from this shear force
Choose a reference point o an arbitrary distance e from the point of application of the load
Calculate the moment about o using both shear flows and the resultant shear force, and equate the two expressions. Solve for e
The distance e and the axis of symmetry give the coordinate for the shear center, independent of the shear force magnitude.
Calculating shear flow
By definition, shear flow through a cross section of thickness t is calculated using , where . Thus the equation for shear flow at a particular depth in a particular cross-section of a thin-walled structure that is symmetric across its width is
where
q, the shear flow
Vy, the shear force perpendicular to the neutral axis x at the cross-section of interest
Qx, the first moment of area (aka statical moment) about the neutral axis x for the cross section of the structure above the depth in question
Ix, the second moment of area (aka moment of inertia) about the neutral axis x for the structure (a function only of the shape of the structure)
In fluid mechanics
Unlike in solid mechanics where shear flow is the shear stress force per unit length, in fluid mechanics, shear flow (or shearing flow) refers to adjacent layers of fluid moving parallel to each other with different speeds. Viscous fluids resist this shearing motion. For a Newtonian fluid, the stress exerted by the fluid in resistance to the shear is proportional to the strain rate or shear rate.
A simple example of a shear flow is Couette flow, in which a fluid is trapped between two large parallel plates, and one plate is moved with some relative velocity to the other. Here, the strain rate is simply the relative velocity divided by the distance between the plates.
Shear flows in fluids tend to be unstable at high Reynolds numbers, when fluid viscosity is not strong enough to dampen out perturbations to the flow. For example, when two layers of fluid shear against each other with relative velocity, the Kelvin–Helmholtz instability may occur.
Notes
References
Riley, W. F. F., Sturges, L. D. and Morris, D. H. Mechanics of Materials. J. Wiley & Sons, New York, 1998 (5th Ed.), 720 pp.
Weisshaar, T. A. Aerospace Structures: An Introduction to Fundamental Problems. T.A. Weisshaar, West Lafayette, 2009, 140pp.
Aerospace Mechanics and Materials. TU Delft OpenCourseWare. 11/22/16. <https://ocw.tudelft.nl/courses/aerospace-mechanics-of-materials/>
External links
Horizontal shearing stress
Shear flow
Solid mechanics
Fluid dynamics | Shear flow | Physics,Chemistry,Engineering | 1,098 |
27,470,400 | https://en.wikipedia.org/wiki/SEMI%20font | SEMI Font, also known as SEMI OCR font, is used for marking silicon wafers in the semi-conductor industry.
The SEMI font character set include 26 uppercase letters, 10 numbers, dash and period.
Their shapes and dimensions are specified by SEMI M12/M13 standard, which was approved by Global Traceability Committee and North American Traceability Committee.
When used in “single-density” mode, laser scribers use a dot matrix of 5 dots horizontal and 9 dots vertical, in “double-density” mode, the matrix is 10 dots horizontal and 18 dots vertical.
References
semi.org
barcodesoft.com
Semiconductor technology
Typefaces
OCR typefaces | SEMI font | Materials_science | 139 |
47,162,990 | https://en.wikipedia.org/wiki/Technology%20Education%20and%20Literacy%20in%20Schools | Technology Education and Literacy in Schools (TEALS) is a program that pairs high schools with software engineers who serve as part-time computer science teachers.
The program was started in 2009 by Microsoft software engineer Kevin Wang, but after Wang's divisional president learned about the program, Microsoft incubated the program. TEALS' goal is to create self-perpetuating computer science programs within two or three years by having the software engineers teach the teachers. Volunteers undergo a three-month summer class that teach them about making lesson plans and leading classes. Afterwards, software engineers visit classrooms four or five mornings a week for the entire school year to teach computer science concepts to both students and teachers.
TEALS volunteers are not required to be Microsoft employees and can have formal degrees or be self-taught in computer science. TEALS offers support for three classes: Introduction to Computer Science, Web Design, and AP Computer Science A.
History
Kevin Wang graduated from the University of California, Berkeley in 2002 with a degree in electrical engineering and computer science. To pursue his teaching passion, he declined several industry job offers. Wang taught in the Bay Area for several years, and attended the Harvard Graduate School of Education, where he received a Master of Education. He became a computer science teacher at Woodside Priory School in Portola Valley, California, teaching grades seven–twelve for three years. He convinced fellow Microsoft employees and other acquaintances to teach computer science at other schools. After joining Microsoft, Wang started volunteering to teach the morning computer science class at Issaquah High School, a nearby high school, in 2009.
In 2009, Wang founded Technology Education and Literacy in Schools (TEALS), a program that aims to bring software engineers to high school classrooms to teach computer science part-time. He thought that he would have to resign from Microsoft to oversee the program's significant expansion. Wang sold his Porsche 911 to bankroll the program. After the vice president of Wang's Microsoft division discovered TEALS, the vice president took him to the divisional president who recommended he work full-time at Microsoft on managing TEALS. According to CNN, Microsoft chose to "incubate" TEALS for three primary reasons. First, the program fit with Microsoft's philanthropic goals. Second, Microsoft founder Bill Gates had an enduring desire to advocate for learning. Third, the software industry had a shortage of engineers. In a 2012 interview with GeekWire, Wang said TEALS has two long-term goals. The first is to give every American high school student the opportunity to take an introductory computer science course and an AP Computer Science course. The second is to have the same proportion of students taking AP Computer Science as those taking AP Biology, AP Chemistry, and AP Physics.
TEALS is part of YouthSpark, a Microsoft initiative that plans to give more educational and employment to 300 million young people between 2012 and 2015. A 2015 article in the Altavista Journal quoted the TEALS website, noting that the United States has 80,000 unfilled jobs that need a computer science degree. The Altavista Journal further reported that this would cause the United States to lose $500 billion over the following 10 years and that only 10% of American high schools have computer science courses. TEALS is managed by Microsoft's Akhtar Badshah, the senior director of citizenship and public affairs.
Program format
Wang designed a three-month summer class for Microsoft employees who wanted to volunteer with TEALS. The class taught the employees about devising lesson plans and leading classes. TEALS aims to create self-perpetuating computer science programs within two or three years. The software engineers commit to being physically present at the school for around four or five days weekly. The classes are scheduled for first period since many volunteers do not start work until later in the morning. For rural schools that lack the capital to run a computer science class, TEALS enables software engineers to instruct students distantly through videoconferencing.
The first two semesters, the software engineers to educate the teachers side by side with the students. The third semester, the software engineers and teachers coteach the students. By the fourth semester, the teachers lead the class, and the software engineers become "teaching assistants". The aim is to enable the teachers who have math and science backgrounds in the future to lead the classes by themselves.
TEALS provides support for three classes. Two of the classes are one-semester long: Introduction to Computer Science and Web Design. The third class, Advanced Placement Computer Science A, is two-semesters long. In a 2015 interview with the Altavista Journal, Microsoft spokesperson Kate Frischmann said, "TEALS is open to everyone, inside and outside of Microsoft, who have a background or formal degree in the field of computer science."
School participation
In the 2010–2011 school year, the program's trial year, ten TEALS volunteers instructed 250 Puget Sound region high school students from four schools. In 2011–2012 school year, TEALS expanded to 30 volunteers and six assistants educating 800 high school students in 13 schools. In the 2012–2013 school year, 22 schools around Seattle participated in TEALS. Microsoft invited the students in Seattle to visit the company's campus, hoping to spark excitement in technology. That school year, TEALS expanded to 120 volunteers in seven states teaching 2,000 students at 37 high schools. The schools were in Washington, Kentucky, California, Virginia, Utah, Washington, D.C., Minnesota, and North Dakota. In the 2013–2014 school year, TEALS grew to 280 volunteers in 12 states educating 3,000 students at 70 schools. In the 2014–2015 school year, 490 TEALS volunteers worked in 131 schools educating 6,600 students.
References
External links
Official website
TEALS at Microsoft
Computer science education
Microsoft divisions
Microsoft initiatives
Educational charities based in the United States
Organizations established in 2009 | Technology Education and Literacy in Schools | Technology | 1,195 |
40,851,738 | https://en.wikipedia.org/wiki/Sequence-controlled%20polymer | A sequence-controlled polymer is a macromolecule, in which the sequence of monomers is controlled to some degree. This control can be absolute but not necessarily. In other words, a sequence-controlled polymer can be uniform (its dispersity Ð is equal to 1) or non-uniform (Ð>1). For example, an alternating copolymer synthesized by radical polymerization is a sequence-controlled polymer, even if it is also a non-uniform polymer, in which chains have different chain-lengths and slightly different compositions. A biopolymer (for example a protein) with a perfectly-defined primary structure is also a sequence-controlled polymer. However, in the case of uniform macromolecules, the term sequence-defined polymer can also be used.
With comparison to traditional polymers, the composition of sequence-controlled polymers can be precisely defined via chemical synthetic methods, such as multicomponent reactions, click reactions etc. Such tunable polymerizing manner endows sequence-controlled polymers with particular properties and thereby, sequence-controlled polymers-based applications (e.g. information storage, biomaterials, nanomaterials etc.) are developed.
In nature, DNA, RNA, proteins and other macromolecules can also be recognized as sequence-controlled polymers for their well-ordered structural skeletons. DNA, based on A-T, C-G base pairs, are formed in well-aligned sequences. Through precise sequences of DNA, 20 amino acids are able to generate sequential peptide chains with three-dimensional structures by virtue of transcription and translation process. These ordered sequences of different constituents endow organisms with complicated and diverse functions.
Synthetic methods
Traditional polymers are usually consist of one repeating unit or several repeating units, arranged in random sequences. Sequence-controlled polymers are composed of different repeating units, which are arranged in an ordered manner. In order to control the sequence, various kinds of synthetic methodologies are developed.
Sequence-controlled biological polymerization
DNA, RNA and proteins are most common sequence-controlled polymers in living creatures. Inspired by them, polymerization methods, utilizing DNA or RNA as templates to control sequences of polymer, are developed. At first, taking DNA or RNA as templates, scientists developed a series of peptide nucleic acid (PNA)-based polymers, without using DNA polymerases. But this method is limited to polymerization scale and yield. After that, polymerase chain reaction (PCR) is developed, which currently is still the most extensively used sequence-regulated method. By employing enzymes, the yields and scales are greatly increased, but the specificity of enzymes towards natural peptides limits this technique to a certain degree. Nowadays, more attention is paid to utilization of ribosomes to directly mimic the transcription and translation process. This technology called protein engineering is considered as the most promising biological polymerization method for synthesis of sequence-controlled polymers.
Sequence-controlled chemical polymerizations
Other than biological polymerization methods, scientists have also developed numerous chemical synthetic methods for sequence-controlled polymers. Compared with biological polymerization, chemical polymerization can provide better diversity but most of the chemical methods cannot offer the efficiency and specificity of biological methods.
Solid-phase synthesis
One of the chemical polymerization methods is solid-phase synthesis, which can be used to synthesize peptides consisted of natural and non-natural amino acids. In this method, the monomers are attached to the polymer chain via amidation between carbonyl group and amino group. For purpose of sequence control, the amino groups are usually protected by 9-fluorenylmethyloxycarbonyl group (Fmoc) and t-butyloxycarbonyl (Boc), which can be removed under base and acid environment respectively to participate into next-round chain elongation.
Sequence-controlled radical polymerization
Radical polymerization is one of the most commonly used polymerization methods. About 50% of commercially available polymers are synthesized via radical polymerization. However, the disadvantages of this method are apparent that sequences and polymeric features cannot be well modulated. To overcome these constraints, scientists optimized the employed protocols. The first reported example was the time-controlled sequential addition of highly-reactive N-substituted maleimides in the atom transfer radical polymerization of styrene, which led to programmed sequences of functional monomers. The development of single-molecule addition into atom-transfer radical polymerization (ATRP), which enhances the sequence control of radical polymerization was also reported. Other solutions include the use of intermediate purification steps to isolate the desired oligomer sequence in between subsequent reversible addition−fragmentation chain-transfer polymerization (RAFT-polymerizations). Both flash column chromatography and recycling size exclusion chromatography have been proven successful in this regard. RAFT single unit monomer insertion (SUMI) is recently developed as an emerging technology for precise control of monomer sequence.
Sequence controlled non-radical polymerization
For the intrinsic shortages of radical polymerization for sequence-controlled polymers, other non-radical polymerizations are also developed. Within those non-radical methods, azide-alkyne cycloaddition (also known as click reaction), olefin metathesis among others are utilized to construct sequence-controlled polymers. Depending on these specific chemical reactions, monomers are accurately added to the polymer chain and a well-ordered chain is accomplished stepwise. Meanwhile, by applying multiple chemical reactions, chemists have also developed multi-component reactions to accelerate the construction of polymer skeletons and also enhance variety. Beyond the aforementioned, there was a research group developing a molecule machine, which successfully achieve a sequence-controlled polymerization of oligopeptides.
Methodology towards improving sequence control
The most important character of sequence-controlled polymers is its controllable sequence of polymer backbone. Nonetheless, to realize a precise sequence control and to regulate sequences in greater polymer backbones are also the most urgent issue, which needs to be addressed in the field of sequence-controlled polymers. Great efforts have been made in development and optimization of methods to improve the sequence-control properties of currently existed synthetic methods and also to further brand-new methods with better synthetic efficiency and sequence control.
Utilization of templates
One of the most significant character of sequence-controlled biosynthesis against other chemical synthetic methods is that the biomolecules (including DNA and RNA) can initiate their polymerization using highly programmed templates. Hence, biosynthetic methods, like PCR, are still considered one of the most cogent manner to develop sequence-controlled polymers.
Regulation of reactivity of monomer
To modulate the reactivity between monomer and growing polymeric chain is another approach to enhance sequence control. The rationale for this method is that monomer has to be activated with first catalyst at beginning as a dormant species, which could then participate into polymerization as the second catalyst is introduced. A real example is utilization of HI as first catalyst and ZnI2 as second catalyst to achieve sequence-controlled polymerization of vinyl ethers and styrene derivatives.
Recognition-oriented insertion
In this approach, a recognition site at polymer is offered to non-covalently anchor the monomer at polymer chain, which can subsequently go through a chemical insertion into polymeric backbone. One successful example demonstrates that methacrylic acid (monomer) can be radically incorporated into a backbone featuring a recognizable cationic site (protonated primary amine pendant). Driven by this site-specific reaction, the sequence-controlled polymerization can be achieve by using a template adorned with differenrt recognizable pendants.
Properties and applications
The most distinguishable feature of sequence-controlled polymers is the well-ordered chains composed of different repeating units. By encoding the repeating units, the correspondingly synthesized sequence-controlled polymer can be used for data storage. To modify the monomer with some bioactive moieties, the obtained sequence-controlled polymer is able to treat diseases. The property of sequence control make sequence-controlled polymers an ideal platform to install various kinds of pendants (like drugs, catalyst), whereby diverse functions and applications can be realized.
References
Polymers | Sequence-controlled polymer | Physics,Chemistry,Materials_science | 1,666 |
42,057,256 | https://en.wikipedia.org/wiki/Hemispherical%20resonator%20gyroscope | The hemispherical resonator gyroscope (HRG), also called wine-glass gyroscope or mushroom gyro, is a compact, low-noise, high-performance angular rate or rotation sensor. An HRG is made using a thin solid-state hemispherical shell, anchored by a thick stem. This shell is driven to a flexural resonance by electrostatic forces generated by electrodes which are deposited directly onto separate fused-quartz structures that surround the shell. The gyroscopic effect is obtained from the inertial property of the flexural standing waves. Although the HRG is a mechanical system, it has no moving parts, and can be very compact.
Operation
The HRG makes use of a small thin solid-state hemispherical shell, anchored by a thick stem. This shell is driven to a flexural resonance by dedicated electrostatic forces generated by electrodes which are deposited directly onto separate fused quartz structures that surround the shell.
For a single-piece design (i.e., the hemispherical shell and stem form a monolithic part) made from high-purity fused quartz, it is possible to reach a Q factor of over 30-50 million in vacuum, thus the corresponding random walks are extremely low. The Q factor is limited by the coating (extremely thin film of gold or platinum) and by fixture losses. Such resonators have to be fine-tuned by ion-beam micro-erosion of the glass or by laser ablation in order to be perfectly dynamically balanced. When coated, tuned, and assembled within the housing, the Q factor remains over 10 million.
In application to the HRG shell, Coriolis forces cause a precession of vibration patterns around the axis of rotation. It causes a slow precession of a standing wave around this axis, with an angular rate that differs from input one. This is the wave inertia effect, discovered in 1890 by British scientist George Hartley Bryan (1864–1928). Therefore, when subject to rotation around the shell symmetry axis, the standing wave does not rotate exactly with the shell, but the difference between both rotations is nevertheless perfectly proportional to the input rotation. The device is then able to sense rotation.
The electronics which sense the standing waves are also able to drive them. Therefore, the gyros can operate in either a "whole angle mode" that sense the standing waves' position or a "force rebalance mode" that holds the standing wave in a fixed orientation with respect to the gyro.
Originally used in space applications (attitude and orbit control systems for spacecraft), HRG is now used in advanced inertial navigation systems, in attitude and heading reference systems, and HRG gyrocompasses.
Advantages
The HRG is extremely reliable because of its very simple hardware (two or three pieces of machined fused quartz). It has no moving parts; its core is made of a monolithic part which includes the hemispherical shell and its stem. They have demonstrated outstanding reliability since their initial use in 1996 on the NEAR Shoemaker spacecraft.
The HRG is highly accurate and is not sensitive to external environmental perturbations. The resonating shell weighs only a few grams and it is perfectly balanced, which makes it insensitive to vibrations, accelerations, and shocks.
The HRG exhibits superior SWAP (size, weight, and power) characteristics compared to other gyroscope technologies.
The HRG generates neither acoustic nor radiated noise because the resonating shell is perfectly balanced and operates under vacuum.
The material of the resonator, the fused quartz, is naturally radiation hard in any space environment. This confers intrinsic immunity to deleterious space radiation effects to the HRG resonator. Thanks to the extremely high Q factor of the resonating shell, the HRG has an ultra-low angular random walk and extremely low power dissipation.
The HRG, unlike optical gyros (fibre-optic gyroscope and ring laser gyroscope), has inertial memory: if the power is lost for a short period of time (typically a few seconds), the sensitive element continues to integrate the input motion (angular rate) so that when the power returns, the HRG signals the angle turned while power was off.
Disadvantages
The HRG is a very high-tech device which requires sophisticated manufacturing tools and processes. The control electronics required to sense and drive the standing waves are sophisticated. This high level of sophistication limits the availability of this technology; few companies were able to produce it. Currently three companies are manufacturing HRG: Northrop Grumman, Safran Electronics & Defense and Raytheon Anschütz.
Classical HRG is relatively expensive due to the cost of the precision ground and polished hollow quartz hemispheres. This manufacturing cost restricts its use to high-added-value applications such as satellites and spacecraft. Nevertheless manufacturing costs can be dramatically reduced by design changes and engineering controls. Rather than depositing electrodes on an internal hemisphere that must perfectly match the shape of the outer resonating hemisphere, electrodes are deposited on a flat plate that matches the equatorial plane of the resonating hemisphere. In such configuration, HRG becomes very cost effective and is well suitable for high grade but cost sensitive applications.
Applications
Space – Inside the Spacecraft Bus in the James Webb Space Telescope and other satellites and spacecraft
Sea – Marine maintenance-free gyrocompasses as well as attitude and heading reference systems. Naval navigation systems for both surface vessels and submarines.
Land – Target locators, land navigation systems, and artillery pointing
Air – HRG are poised to be used in commercial air transport navigation systems
See also
Fibre-optic gyroscope
Gyroscope
HRG gyrocompass
Inertial measurement unit
Quantum gyroscope
Ring laser gyroscope
Vibrating structure gyroscope a.k.a. Coriolis vibratory gyroscope
References
Bibliography
Lynch D.D. HRG Development at Delco, Litton, and Northrop Grumman. Proceedings of Anniversary Workshop on Solid-State Gyroscopy (19–21 May 2008. Yalta, Ukraine). - Kyiv-Kharkiv. ATS of Ukraine. 2009.
L.Rosellini, JM Caron - REGYS 20: A promising HRG-based IMU for space application - 7th International ESA Conference on Guidance, Navigation & Control Systems. 2–5 June 2008, Tralee, County Kerry, Ireland
D. Roberfroid, Y. Folope, G. Remillieux (Sagem Défense Sécurité, Paris, FRANCE) - HRG and Inertial Navigation - Inertial Sensors and Systems – Symposium Gyro Technology 2012
A Carre, L Rosellini, O Prat (Sagem Défense Sécurité, Paris, France) HRG and North Finding -17th Saint Petersburg International Conference on Integrated Navigation Systems 31 May – 2 June 2010, Russia
Alain Jeanroy; Gilles Grosset; Jean-Claude Goudon; Fabrice Delhaye - HRG by Sagem from laboratory to mass production - 2016 IEEE International Symposium on Inertial Sensors and Systems
Alexandre Lenoble, Thomas Rouilleault - SWAP-oriented IMUs for multiple applications- Inertial Sensors and Systems (ISS), 2016 DGON - Karlsruhe, Germany
Fabrice Delhaye - HRG by Safran - The game-changing technology - 2018 IEEE International Symposium on Inertial Sensors and Systems - Lake Como, Italy
Fabrice Delhaye; Jean-Philippe Girault - SpaceNaute®, HRG technological breakthrough for advanced space launcher inertial reference system - 25th Saint Petersburg International Conference on Integrated Navigation Systems 31–29 May 2018, Russia
B.Deleaux, Y.Lenoir - The world smallest, most accurate and reliable pure inertial navigator: ONYX™ - Inertial Sensors and Systems 2018, Braunschweig - 12 September 2018, Germany
Y. Foloppe, Y.Lenoir - HRG CrystalTM DUAL CORE: Rebooting the INS revolution - Inertial Sensors and Systems 2019, Braunschweig - 10 September 2019, Germany
F. Delhaye, Ch. De Leprevier - SkyNaute by Safran – How the HRG technological breakthrough benefits to a disruptive IRS (Inertial Reference System) for commercial aircraft - Inertial Sensors and Systems 2019, Braunschweig - 11 September 2019, Germany
Aerospace engineering
Aircraft instruments
Avionics
Missile guidance
Navigational aids
Navigational equipment
Spacecraft components
Technology systems | Hemispherical resonator gyroscope | Technology,Engineering | 1,782 |
8,000,513 | https://en.wikipedia.org/wiki/Home%20Gateway%20Initiative | The Home Gateway Initiative (HGI) was a nonprofit trade organization to discuss the key specifications and standards of residential gateways, also known as home gateways.
It was founded by telephone companies (Belgacom, BT, Deutsche Telekom, France Telecom, KPN, Nippon Telegraph and Telephone (NTT), Swiss Telecom, Telenor, Telecom Italia and Teliasonera) in December 2004.
Several manufacturers such as ADB, Devolo, Huawei, Ikanos Communications, Intel, Lantiq, SoftAtHome or ZTE also joined the alliance.
HGI's aims included:
Release specifications of the home gateway.
Boost the market of home communication services to the millions of customers served by its founding members.
Improve the interoperability of gateways with home devices.
HGI also built on work of other standards bodies such as the Broadband Forum, Digital Living Network Alliance (DLNA) and Open Services Gateway initiative (OSGi) Alliance.
The initiative made an agreement with the Telecommunication Standardization Sector of the International Telecommunication Union (ITU-T) in 2006. HGI established relations with oneM2M and initiated a transfer of HGI work into oneM2M, especially regarding a Smart Device Template (SDT) specification which was transferred as ETSI TR 118 522 V2.0.0 (2016-09)
HGI closed operations in June 2016, wrapping up according to its statutes, and archiving all specifications for five years. The HGI website and documents were permanently archived on www.archive.org on 21 February 2021. The organisation webpage www.homegatewayinitiative.org is no longer owned and might potentially be taken over by some other organisation in future.
References
External links
The archived home page of the forum
Publications
Home Gateway Technical Requirements: Residential Profile Version 1.01 - 28 April 2008
Home Gateway Technical Requirements: Release 1 Version 1.0 - 1 July 2006 (obsolete)
Networking standards
BT Group
Deutsche Telekom
Orange S.A.
KPN
Nippon Telegraph and Telephone
Telenor
TIM Group | Home Gateway Initiative | Technology,Engineering | 424 |
597,727 | https://en.wikipedia.org/wiki/List%20of%20Internet%20phenomena | Internet phenomena are social and cultural phenomena specific to the Internet, such as Internet memes, which include popular catchphrases, images, viral videos, and jokes. When such fads and sensations occur online, they tend to grow rapidly and become more widespread because the instant communication facilitates word of mouth transmission.
This list focuses on the internet phenomena that is accessible regardless of local internet regulations.
Advertising and products
Amazon Coat – an unnamed coat sold on the online store Amazon.com by the Chinese clothing brand Orolay, previously known for its home furnishings. It became a viral phenomenon from the period between December 2018 and the COVID-19 pandemic.
Beanie Babies – Cited as being the world's first Internet sensation in 1995.
Cerveza Cristal – A Chilean beer company that produced a series of advertisements during a Star Wars original trilogy broadcast in 2003. The commercials, titled The Force is with Cristal Beer, would air seamlessly with the scenes in the trilogy, such as a pair of hands like Obi Wan's opening a chest, revealing the beer. The advertisements were critically acclaimed in the country and became internationally viral on Twitter in March 2024.
Cooks Source infringement controversy – This publication drew backlash after it committed copyright infringement by using an online article without permission for commercial purposes. This backlash further increased due to Cooks Source's response which showed a misunderstanding of copyright and an increasing agitation to the original writer of the article.
Elf Yourself (2006) and Scrooge Yourself (2007) – Interactive websites created by Jason Zada and Evolution Bureau for OfficeMax's holiday season advertising campaign. Elf Yourself allows visitors to upload images of themselves or their friends, see them as dancing elves, and includes options to save or share the video. According to ClickZ, visiting the Elf Yourself site "has become an annual tradition that people look forward to". While not selling any one specific product, the two were created to raise consumer awareness of the sponsoring firm.
Flex Tape – An infomercial of the product Flex Tape. It became a meme after YouTuber JonTron made a video reviewing the infomercial.
FreeCreditReport.com – A series of TV commercials that were posted on the Internet; many spoofs of the commercials were made and posted on YouTube.
HeadOn – A June 2006 advertisement for a homeopathic product claimed to relieve headaches. Ads featured the tagline, "HeadOn. Apply directly to the forehead", stated three times in succession, accompanied by a video of a model using the product without ever directly stating the product's purpose. The ads were successively parodied on sites such as YouTube and rapper Lil Jon even made fun of it.
Kerfuś – A robot with cat face use as a mascot for Carrefour. The robot became viral in Poland in 2022, where Kerfuś became the main character of many memes and erotic pictures
Little Darth Vader – An advertisement by Volkswagen featuring young Max Page dressed in a Darth Vader costume running around his house trying to use "the Force". It was released on the Internet a few days prior to Super Bowl XLV in 2011, and quickly became popular. As of 2013 it was the most shared ad of all time.
LowerMyBills.com – Banner ads from this mortgage company feature endless loops of cowboys, women, aliens, and office workers dancing.
The Man Your Man Could Smell Like – A television commercial starring Isaiah Mustafa reciting a quick, deadpan monologue while shirtless about how "anything is possible" if men use Old Spice. It eventually led to a popular viral marketing campaign which had Mustafa responding to various Internet comments in short YouTube videos on Old Spice's YouTube channel.
"Mac Tonight/Moon Man" – A McDonald's commercial made to promote dinner sales. Starting in 2007, the character in the commercial, "Mac Tonight" was used in videos where he is depicted promoting violence against minorities and promoting the KKK with racist parodies of rap songs. The best-known parody, "Notorious KKK" (a parody of Hypnotize by The Notorious B.I.G.), has accumulated over 119,000 views on YTMND.
Nicole Kidman AMC Theatres commercial – In September 2021, AMC Theatres began airing a commercial starring actress Nicole Kidman in its theaters and on television. The ad, written by screenwriter Billy Ray, was intended to spur theater attendance following the COVID-19 pandemic by highlighting the "magic" of the movie theater experience. The commercial's grand style and the earnest melodrama of Kidman's monologue has led the commercial to be appreciated as an artifact of camp. The commercial has been the subject of internet memes, parodies, merchandise, and audience participation rituals.
"Nope, Chuck Testa" – A local commercial made for Ojai Valley Taxidermy, owned by Chuck Testa, suggesting that the stuffed creatures were alive until Testa appeared, saying "Nope, Chuck Testa!"; the ad soon went viral.
Potato Parcel – a web site that allows the user to send anonymous personalized messages on potatoes via the mail.
Pepsi MAX & Jeff Gordon Present: Test Drive – A short film where NASCAR driver Jeff Gordon poses as an average car buyer to prank a cars salesman. A sequel, Test Drive 2, was released the following year, with Gordon pranking a writer who had branded the original video as fake.
"Rivals" – A commercial for video game retailer EB Games that promoted Call of Duty: Advanced Warfare. The commercial drew criticism for its concept and the performances of its actors.
Shake Weight – Infomercial clips of the modified dumbbell went viral as a result of the product's sexually suggestive nature.
Vans (2016) – Featured in the "Damn Daniel" viral internet meme.
What Would You Do for a Klondike Bar? – A slogan at the end of commercials advertising the ice cream sandwich Klondike bar. People on YouTube and Facebook began posting videos depicting people in dangerous and absurdist situations attempting to reach a Klondike Bar in response to the slogan.
Whopper Whopper – A song by American restaurant fast-food chain Burger King which serves as a jingle for the restaurant's signature burger, the Whopper
Will It Blend? – The blender product Blendtec, claimed by its creator Tom Dickson to be the most powerful blender, is featured in a series of YouTube videos, "Will It Blend?" where numerous food and non-food items are used within the blender.
Xtranormal – A website allowing users to create videos by scripting the dialog and choosing from a menu of camera angles and predesigned CGI characters and scenes. Though originally designed to be used to ease storyboard development for filmmakers, the site quickly became popular after videos made with the tool, including "iPhone 4 vs HTC Evo", became viral.
Animation and comics
Animutations – Early Adobe Flash-based animations, pioneered by Neil Cicierega in 2001, typically featuring foreign language songs (primarily Japanese, such as "Yatta"), set to random pop-culture images. The form is said to have launched the use of Flash for inexpensive animations that are now more common on the Internet.
Arthur – A 1996 PBS educational series that became popular on the Internet in July 2016 through humorous stills, including a still of the title character's clenched fist.
Ate my balls – One of the earliest examples of an internet meme, which involved web pages depicting a particular celebrity, fictional character, or other subject's relish for eating testicles.
Axe Cop – Initially a web comic series with stories created by five-year-old Malachai Nicolle and drawn into comic form by his 29-year-old brother Ethan, the series gained viral popularity on the Internet due to the vividness and non-sequitur nature of Malachai's imagination, and has led to physical publication and a series of animated shorts in the 2012–2013 season for the Fox Television Network.
Badger Badger Badger – A hypnotic loop of animal calisthenics set to the chant of "badger, badger, badger", created by Jonti "Weebl" Picking.
Big Chungus – A still frame of the 1941 Merrie Melodies short Wabbit Twouble when Bugs Bunny mocks a fat Elmer Fudd. The meme originated from fictitious cover art for a video game titled Big Chungus (with "chungus" being a neologism associated with video game commentator James Stephanie Sterling), which featured a still from the scene, and was popularized by a Facebook post by a GameStop manager who alleged that a colleague's mother had inquired about purchasing the "game" as a gift. Warner Bros. later incorporated Big Chungus into its own video game Looney Tunes World of Mayhem.
Bongo Cat – Originated on Twitter on 7 May 2018, when a simple animated cat GIF, was edited for it to play the song "Athletic" from the Super Mario World soundtrack. This cat has since been edited to play various songs on bongos, and later other instruments.
"Caramelldansen" – A spoof from the Japanese visual novel opening Popotan that shows the two main characters doing a hip swing dance with their hands over their heads, imitating rabbit ears, while the background song plays the sped-up version of the song "Caramelldansen", sung by the Swedish music group Caramell. Also known as Caramelldansen Speedycake Remix or Uma uma dance in Japan, the song was parodied by artists and fans who then copy the animation and include characters from other anime performing the dance.
Charlie the Unicorn – A five-part series of videos involving the titular unicorn who is repeatedly hoodwinked by two other blue and pink unicorns, Lolz and Roffle, who take him on elaborate adventures to steal his belongings or cause him physical harm.
Dancing baby – A 3D-rendered dancing baby that first appeared in 1996 by the creators of Character Studio for 3D Studio MAX, and became something of a late 1990s cultural icon, in part due to its exposure on worldwide commercials, editorials about Character Studio, and the popular television series Ally McBeal.
The End of the World – A Flash-animated video by Jason Windsor in 2003 that depicts a situation when the entire world is nuked by rivalling countries.
Happy Tree Friends – A series of Flash cartoons featuring cartoon animals experiencing violent and gruesome accidents.
Homestar Runner – A Flash animated Internet cartoon by Mike Chapman, Craig Zobel, and Matt Chapman, created in 1996 and popularized in 2000. The cartoon contains many references to popular culture from the 1980s and 1990s, including video games, television, and popular music.
Joe Cartoon – Creator of interactive Flash animations Frog in a Blender and Gerbil in a Microwave, which were two of the first Flash cartoons to receive fame on the Internet.
Kung Fu Bear – an Internet meme involving an Asian black bear who skillfully twirls, throws and catches a long staff.
Loituma Girl (also known as Leekspin) – A looped Flash animation of an anime girl Orihime Inoue from the Bleach series twirling a leek, set to a scat singing section of the traditional Finnish folk song "Ievan Polkka", sung by the Finnish quartet Loituma on their 1995 debut album Things of Beauty. The band's popularity rose tremendously after the animation was posted in Russian LiveJournal in 2006. The song clip soon enjoyed overwhelming popularity as a ringtone.
"Loss" – A webcomic strip published on 2 June 2008, by Tim Buckley for his gaming-related webcomic Ctrl+Alt+Del. Set during a storyline in which the main character Ethan and his fiancée Lilah are expecting their first child, the strip – presented as a four-panel comic with no dialogue – shows Ethan entering a hospital, where he sees Lilah weeping in a hospital bed; she has suffered a miscarriage. It has received negative reception from critics and webcomic creators and been adapted and parodied many times.
Motu Patlu – An Indian cartoon aired on Nickelodeon (India), made widely popular by a Nick India ad celebrating Teacher's Day in India, which has been reposted under the title "D se Dab".
Nyan Cat – A YouTube video of an animated flying cat, set to an Utau song.
Polandball (more commonly known as Countryballs) – A user-generated Internet meme which originated on the /int/ board of German imageboard Krautchan.net in the latter half of 2009. The meme is manifested in a large number of online comics, where countries are presented as spherical personas that interact in often broken English, poking fun at national stereotypes and international relations, as well as historical conflicts.
Pusheen – An animated grey tabby cat, originally drawn as a character in the webcomic "Everyday Cute" by artists Clare Belton and Andrew Duff. Belton has since released a Pusheen book.
Rage comics – A large set of pre-drawn images including crudely drawn stick figures, clip art, and other artwork, typically assembled through website generators, to allow anyone to assemble a comic and post to various websites and boards. The New York Times reports that thousands of these are created daily. Typically these are drawn in response to a real-life event that has angered the comic's creator, hence the term "rage comics", but comics assembled for any other purpose are also made. Certain images from rage comics are known by specific titles, such as "trollface" (a widely grinning man), "forever alone" (a man crying to himself), or "rage guy" (a man shouting "FUUUUU...").
Salad Fingers – A Flash animation series surrounding a green man with severely elongated fingers in a desolate world populated mostly by deformed, functionally mute people.
Shut the fuck up, TERF – A crudely photoshopped image featuring Zombie Land Saga character Lily Hoshikawa, a trans girl, holding a gun with the caption "Shut the fuck up, TERF". The image was criticized as constituting a threat of violence, and presented in UK Parliament in May 2019 during a convening of the Human Rights Committee while questioning a Twitter employee on the subject of abuse. In a tweet in January 2023, J. K. Rowling likened the meme to early twentieth century anti-suffragist artwork.
Simpsonwave – A genre of videos where clips of the American animated sitcom The Simpsons are filtered with tinted, VHS-like effects and played over psychedelic vaporwave or chillwave tracks.
Skibidi Toilet – A series of viral YouTube animations made by animator Alexey Gerasimov using Source Filmmaker which depicts a war between skibidi toilets (disembodied heads inside moving toilets which can be killed by being flushed down) and a faction of people with cameras, TVs and loudspeakers for heads.
The Spirit of Christmas – Consists of two different animated short films made by Trey Parker and Matt Stone, which are precursors to the animated series South Park. To differentiate between the two homonymous shorts, the first short is often referred to as Jesus vs. Frosty (1992), and the second short as Jesus vs. Santa (1995). Fox executive Brian Graden sent copies of Jesus vs. Santa to several of his friends, and from there it was copied and distributed, including on the internet, where it became one of the first viral videos. They were created by animating construction paper cut-outs with stop motion, and features prototypes of the main characters of South Park.
Steamed Hams – Remixes of a segment of The Simpsons episode "22 Short Films About Springfield" involving Principal Skinner and Superintendent Chalmers, in which Skinner has invited Chalmers over to dinner, inadvertently sets his ham on fire, and covers it up by serving fast food hamburgers as "steamed hams".
"This is fine" – A two-panel comic drawn in 2013 by KC Green as part of the Gunshow webcomic, showing an anthropomorphic dog sitting in a room on fire, and saying "This is fine". The comic emerged as a meme in 2016, used in situations, as described by The New York Times, "halfway between a shrug and complete denial of reality". Numerous derivatives of the "This is fine" comic have been made.
"Tuxedo Winnie the Pooh" – A photoshopped image of Winnie the Pooh sitting in an armchair from the featurette Winnie the Pooh and the Honey Tree, which became popular on Reddit in 2019. The meme, which is also known as "A fellow man of culture", features Winnie the Pooh wearing a tuxedo and smiling.
The Ultimate Showdown of Ultimate Destiny – A lethal battle royale between many notable real and fictitious characters from popular culture. Set to a song of the same name, written and performed by Neil Cicierega under his musician alias, "Lemon Demon."
Ultra Instinct Shaggy – A character interpretation that the Scooby-Doo character Shaggy is immensely more powerful than he presents himself. The meme is usually presented as still frames of a behind-the-scenes interview of the 2002 live-action movie with subtitles implying that Shaggy is restraining his power to prevent catastrophe. Subsequently, Warner Bros. canonized the meme as part of a credits gag in the animated film Mortal Kombat Legends: Battle of the Realms, as well as including Shaggy as a fighter in the MultiVersus crossover fighting game.
Weebl and Bob – A series of Flash cartoons created by Jonti Picking featuring two egg-shaped characters that like pie and speak in a stylistic manner.
xkcd – A webcomic created by Randall Munroe, popularized on the Internet due to a high level of math-, science- and geek-related humor, with certain jokes being reflected in real-life, such as using Wikipedia's "" tag on real world signs or the addition of an audio preview for YouTube comments.
Challenges
Challenges generally feature Internet users recording themselves performing certain actions, and then distributing the resulting video through social media sites, often inspiring or daring other users to repeat the challenge.
Dance
Coffin Dance/Dancing Pallbearers – A group of Ghanaian pallbearers that respectfully dance during funeral processions were covered by the BBC in 2017 and gained some initial Internet popularity. In the wake of the COVID-19 pandemic, a popular TikTok video mashed the BBC footage with the EDM song "Astronomia" from Russian artist Tony Igy, creating a meme that appeared to spread as a morbidly humorous reminder about the dangers of COVID-19.
Dab – A dance move where a person drops their head into a bent, slanted arm, with the other arm out straight and parallel.
"Dancing Banana" – A banana dancing to the song "Peanut Butter Jelly Time" by the Buckwheat Boyz.
Hampster Dance – A page filled with hamsters dancing, linking to other animated pages. It spawned a fictional band complete with its own CD album release.
Harlem Shake – A video based on Harlem shake dance, originally created by YouTube personality Filthy Frank, and using an electronica version of the song by Baauer. In such videos, one person is dancing or acting strange among a room full of others going about routine business. After the drop in the song and a video cut, everyone starts dancing or acting strangely. The attempts to recreate the dance led to a viral spread on YouTube.
"Hit the Quan" – A viral dance challenge to the song "Hit the Quan" by American rapper iLoveMemphis. Rich Homie Quan originally performed this dance in his music video for his song "Flex (Ooh, Ooh, Ooh)". iLoveMemphis produced the "Hit The Quan" based around Rich Homie Quan's dance. iLoveMemphis' song launched the "Hit the Quan" viral dance challenge because of its convenient lyrics to dance to. "Hit the Quan" reached 20 on the Billboard Hot 100 chart because of the popularity of the dance. The dance challenge was very popular on social media platforms, especially Vine. Many celebrities participated in the popular dance challenge.
"Indian Thriller" – A viral scene from the Indian film Donga with added subtitles phonetically approximating the original lyrics as English sentences.
JK Wedding Entrance Dance – The wedding procession for Jill Peterson and Kevin Heinz of St. Paul, Minnesota, choreographed to the song "Forever" by Chris Brown. Popularized on YouTube with 1.75 million views in less than five days in 2009. The video was later imitated in an episode of The Office on NBC.
"Kiki Challenge" or "#DoThe Shiggy" – A viral dance challenge to the song "In My Feelings" by Drake. This challenge was started by a comedian named Shiggy on the night that Drake released the album Scorpion. Shiggy posted a video of himself on his Instagram account dancing along to part of the lyrics in what looks like in the middle of a neighborhood street. Shiggy commented #DoTheShiggy. Drake claims the success of the song was due to Shiggy's popular dance to his song. The dance challenge is often filmed with a twist of the original. The most popular twist of the dance is filmed from the passenger side of a moving vehicle through the open driver door where the would be driver is dancing moves along with the slowly moving car. This challenge received a lot of controversy due to the fact nobody was in control of the car. Performers have received fines and sometimes suffered injury. This viral dance challenge was performed by a number of professional athletes and celebrities. The dance challenge was performed by people in the U.S. and spread to the rest of the world.
Little Superstar – A video of Thavakalai, a short Indian actor, break-dancing to MC Miker G & DJ Sven's remix of the Madonna song "Holiday". The clip comes from a 1990 Tamil film Adhisaya Piravi, featuring actor Rajnikanth.
Running Man Challenge – A dance move where participants in a way resembling running to the 1996 R&B song "My Boo" by Ghost Town DJ's. First posted to Vine by two teenagers from New Jersey, the dance went viral in 2016 after two University of Maryland basketball players posted their rendition. The dance gets its name because it is an adaptation of the original running man dance move.
T-pose – A surrealist "dance move" that became popular in April 2018 modelled after the default pose (also known as a bind pose) that many 3D models in games, animations, and more take in their raw file form.
Techno Viking – A muscular Nordic raver dancing in a technoparade in Berlin.
"Thriller" by the CPDRC Dancing Inmates – A recreation of Michael Jackson's hit performed by prisoners at the Cebu Provincial Detention and Rehabilitation Center (CPDRC) in the Philippines. In January 2010, it was among the ten most popular videos on YouTube with over 20 million hits.
Triangle Dance Challenge – Three individuals place hands on each other's shoulders and jump to a different point on an invisible triangle. This gained popularity in 2019.
Email
Bill Gates Email Beta Test – An email chain-letter that first appeared in 1997 and still circulates. The message claims that America Online and Microsoft are conducting a beta test and for each person one forward the email to, they will receive a payment from Bill Gates of more than $200. Realistic contact information for a lawyer appears in the message.
Craig Shergold – A British former cancer patient who is most famous for receiving an estimated 350 million greeting cards, earning him a place in the Guinness Book of World Records in 1991 and 1992. Variations of the plea for greeting cards sent out on his behalf in 1989 are still being distributed through the Internet, although Shergold himself died in 2020, making the plea one of the most persistent urban legends.
Goodtimes virus – An infamous, fraudulent virus warning that first appeared in 1994. The email claimed that an email virus with the subject line "Good Times" was spreading, which would "send your CPU into a nth-complexity infinite binary loop", among other dire predictions.
Lighthouse and naval vessel urban legend – Purportedly an actual transcript of an increasingly heated radio conversation between a U.S. Navy ship and a Canadian who insists the naval vessel change a collision course, ending in the punchline. This urban legend first appeared on the Internet in its commonly quoted format in 1995, although versions of the story predate it by several decades. It continues to circulate; the Military Officers Association of America reported in 2011 that it is forwarded to them an average of three times a day. The Navy has a page specifically devoted to pointing out that many of the ships named weren't even in service at the time.
MAKE.MONEY.FAST – One of the first spam messages that was spread primarily through Usenet, or even earlier BBS systems, in the late 1980s or early 1990s. The original email is attributed to an individual who used the name "Dave Rhodes", who may or may not have existed. The message is a classic pyramid scheme – one receives an email with a list of names and is asked to send $5 by postal mail to the person whose name is at the top of the list, add their own name to the bottom, and forward the updated list to a number of other people.
Neiman Marcus Cookie recipe – An email chain-letter dating back to the early 1990s, but originating as Xeroxlore, in which a person tells a story about being ripped off for over $200 for a cookie recipe from Neiman Marcus. The email claims the person is attempting to exact revenge by passing the recipe out for free.
Nigerian Scam/419 scam – A mail scam attempt popularized by the ability to send millions of emails. The scam claims the sender is a high-ranking official of Nigeria with knowledge of a large sum of money or equivalent goods that they cannot claim but must divest themselves of; to do so, they claim to require a smaller sum of money up front to access the sum to send to the receiver. The nature of the scam has mutated to be from any number of countries, high-ranking persons, barristers, or relationships to said people.
Film and television
The Babadook (2014) – An Australian psychological horror film that started trending on Twitter in June 2017 when the title character became an unofficial mascot for the LGBT community. Prior to that, rumors of the Babadook's sexuality began in October 2016, when some Netflix users reported seeing the film categorized as an LGBT movie on Netflix.
Barbenheimer (2023) – A portmanteau of Barbie and Oppenheimer. Barbenheimer began circulating ahead of the theatrical release of both films on 21 July 2023, with social media users creating and sharing memes noting the juxtaposition between the films.
Bee Movie (2007) – Sped-up or slowed-down clips of the film have become popular on YouTube. One upload by "Avoid at All Costs" exceeded 12 million views as of December 2016. Many of the edited videos in this trend were taken down for spam due to the volume of videos posted by some channels. From September 2013 onwards, a few Internet users posted the entirety of the Bee Movie script on sites like Tumblr and Facebook.
The Blair Witch Project (1999) – The film's producers used Internet marketing to create the impression that the documentary-style horror film featured real, as opposed to fictional events.
Bye, Felicia – A line from the 1995 film Friday originally uttered by Ice Cube's character to dismiss Angela Means' character, Felisha. The line became viral beginning in the 2010s.
Cloverfield (2008) – Paramount Pictures used a viral marketing campaign to promote this monster movie.
Dahmer – Monster: The Jeffrey Dahmer Story (2022) – An anthology thriller true crime series by Ryan Murphy and Ian Brennan for Netflix. after its release, it became viral over Twitter and TikTok.
Dear Evan Hansen (2021) – A film adaptation of the stage musical of the same name that featured then 27-year-old Ben Platt reprising his role as 17-year-old high schooler Evan Hansen, a casting decision that sparked widespread backlash from critics and the public, all of whom attributed it to nepotism. Two scenes from the film instantly became internet memes the moment it was made available digitally as a result of the controversy: a close-up of Evan crying during the climax of "Words Fail," his expression wrenched and tortured, and the moment Evan runs off from Zoe Murphy (Kaitlyn Dever) in the hallways during their first meeting at school. Jameson Rich of The New York Times observed "The image of a crying Platt is already a much-iterated joke, and its thrust is, overwhelmingly, derisive. But being the target of the internet's scorn is not de facto a bad thing. When a meme circulates far enough, the underlying movie can gain what feels like cultural currency. The very fact that the images are not part of any intentional advertising actually lends them a note of authenticity. They are, in a perverse way, resonating on their own merit. Is there a better form of contemporary publicity?"
Downfall (2004) – A film depicting Adolf Hitler (portrayed in this film by Swiss actor Bruno Ganz) during his final days of his life. Multiple scenes in which Hitler rants in German have been parodied innumerable times on the Internet, including when Hitler finds out that Felix Steiner has failed to carry out his orders and when Hitler finds out SS-Gruppenführer Hermann Fegelein has gone AWOL. This scene often has its English subtitles replaced by mock subtitles to give the appearance that Hitler is ranting about modern, often trivial topics, and sometimes even breaks the fourth wall by referencing the Internet meme itself. While the clips are frequently removed for copyright violations, the film's director, Oliver Hirschbiegel, has stated that he enjoys them, and claimed to have seen about 145 of them.
Figwit (abbreviated from "Frodo is great...who is that?") – A background elf character with only seconds of screen time and one line of dialog from The Lord of the Rings film trilogy played by Flight of the Conchords member Bret McKenzie, which became a fascination with a large number of fans. This ultimately led to McKenzie being brought back to play an elf in The Hobbit.
Goncharov – A nonexistent film invented by users on Tumblr. It is purported to be "the greatest mafia movie ever made," released in 1973. In 2020, a user posted a picture of a tag found on a pair of boots which featured details on the nonexistent film Goncharov in place of a brand label, which suggested it was "A film by Matteo JWHJ0715" and "presented" by Martin Scorsese. Users have inconsistently described the film as being directed by either Matteo JWHJ0715 or Scorsese. This label was speculated by several users to be a misprint of Gomorrah. Goncharov picked up traction again in late November 2022 when a user created a poster for the film that featured a lineup of actors and character names, ultimately sparking an elaborate fiction of the film's existence. Discussion of the film involved detailed critical analysis of the plot, themes, symbolism, and characters, as well as creation of gifs, fan art, and theme music, all presented as if the film were real. The meme's popularity caused it to become a trending topic on the Tumblr platform. A similar meme that emerged on TikTok nine months later—about a fictional 1980s horror film, Zepotha—drew comparisons to Goncharov.
LazyTown (2004) – A children's television program originating from Iceland, which became very popular after one of the primary actors, Stefán Karl Stefánsson, was diagnosed with cancer and set up a GoFundMe page for support. The song "We Are Number One" became a meme in October 2016, and many videos were created. It became one of the fastest growing memes in history, with 250 videos uploaded in 5 days.
Les Misérables (2012) – Tom Hooper's film adaptation of the globally popular stage musical of the same name based on Victor Hugo's 1862 novel of the same name. In April 2022, a clip of the film's version of the "Do You Hear the People Sing?" musical sequence circulated on Twitter in protest of the lockdown during the 2022 Shanghai COVID-19 outbreak. The clip was ultimately blocked by the Chinese government to stop further protest.
The Lord of the Rings trilogy – Released between 2001 and 2003, just as meme culture was taking off, several moments from the films became part of the online culture, with, most notably, Sean Bean's character of Boromir stating "One does not simply walk into Mordor" as one of the most commonly referenced.
Marble Hornets – A documentary-style horror, suspense short film series based on alternate reality experiences of the Slenderman tale. Marble Hornets was instrumental in codifying parts of the Slender Man mythos, but is not part of the inter-continuity crossover that includes many of the blogs and vlogs that followed it, although MH does feature in other canons as either a chronicle of real events or a fictional series.
Marriage Story (2019) – Noah Baumbach's critically acclaimed drama about a warring couple going through a coast-to-coast divorce spawned multiple memes despite its serious tone. According to Wired, a meme of Adam Driver punching a wall during Charlie and Nicole's argument scene has contributed to "re-contextualizing Charlie and Nicole's fight into something light and silly". Driver punching a wall has been repurposed to represent general arguments over trivial matters in which a participant becomes angry and overreacts.
Mega Shark Versus Giant Octopus (2009) – The theatrical trailer released in mid-May 2009 became a viral hit, scoring over one million hits on MTV.com and another 300,000 hits on YouTube upon launch, prompting brisk pre-orders of the DVD.
Minions - The mischievous yellow creatures from the Despicable Me franchise have, since their introduction in 2010, become ubiquitous in certain layers of meme culture. The memes created with images of Minions have frequently been derided as bland or unintentionally absurd. In 2022, a phenomenon known as "Gentleminions" arose, in which young men and teen boys would arrive to Minions: The Rise of Gru in formal attire.
My Little Pony: Friendship Is Magic – Hasbro's 2010 animated series to revive its toy line was discovered by members of 4chan and subsequently spawned a large adult, mostly male fanbase calling themselves "bronies" and creating numerous Internet memes and mashups based on elements from the show.
Re-cut trailer – User-made trailers for established films, using scenes, voice-overs, and music, to alter the appearance of the film's true genre or meaning or to create a new, apparently seamless, film. Examples include casting the thriller-drama The Shining into a romantic comedy, or using footage from the respective films to create Robocop vs. Terminator.
The Nutshack (2007) – a Filipino-American adult animated television series that has been widely mocked for its obnoxious characters, bad writing and animation, and especially for the theme song.
Pingu – An animated Swiss children's television series. The show's animation style has spawned many memes. In particular, a meme in which Mozart's Requiem accompanies a viral video of Pingu the penguin saying "Noot Noot" gained popularity, using the choir symphony to depict feelings of terror and dread.
The Room (2003) – Written, produced, directed, and starring Tommy Wiseau, the low- budget independent film is considered one of the worst films ever made. However, through social media and interest from comedians, gained a large number of ironic fans and turned into a cult classic. It is a popular source for memes based on some of the poorly delivered lines in the movie, such as "You're tearing me apart, Lisa!" (a shoehorned reference to an iconic James Dean line in Rebel Without a Cause) and "Oh hi, Mark."
Saltburn (2023) – A black comedy psychological thriller film written, directed, and co-produced by Emerald Fennell. After its theatrical release, it became a streaming hit on Amazon Prime Video and went viral on TikTok.
Sharknado (2013) – A made-for-television film produced by The Asylum and aired on the SyFy network as a mockbuster of other disaster films, centered on the appearance of a tornado filled with sharks in downtown Los Angeles. Though similar to other films from the Asylum, elements of the film, such as low-budget effects and choice of actors, led to the film becoming a social media hit and leading to at least four additional sequels.
Shrek – A DreamWorks franchise that has an internet fandom likes the series. The viral video "Shrek is Love, Shrek is Life" was based on a homoerotic story on 4chan depicting the titular ogre engaging in anal sex with a young boy.
Snakes on a Plane (2006) – Attracted attention a year before its planned release, and before any promotional material was released, due to the film's working title, its seemingly absurd premise, and the piquing of actor Samuel L. Jackson's interest to work on the film. Producers of the film responded to the Internet buzz by adding several scenes and dialogue imagined by the fans.
SpongeBob SquarePants – A Nickelodeon animated television series that has spawned various Internet memes. These memes include "Surprised Patrick", "Mr. Krabs Blur", "Caveman SpongeBob", "Handsome Squidward", and "Mocking SpongeBob". In 2019, Nickelodeon officially released merchandise based on the memes.
Star War: The Third Gathers: The Backstroke of the West – Around the time of release, a bootleg recording circulated on the internet via peer-to-peer sharing websites. It quickly became notorious for its notable use of Engrish, like the translation of Darth Vader's line "No!" rendered as "Do not want". About a decade after the release of the bootleg, a fandub matching its subtitles was posted on YouTube.
Steamed Hams – A clip from the season seven episode of The Simpsons, 22 Short Films About Springfield, gained popularity with many remixes and edits to the Skinner and The Superintendent segment.
Take This Lollipop (2011) – An interactive horror short film and Facebook app, written and directed by Jason Zada to personalize and underscore the dangers inherent in posting too much personal information about oneself on the Internet. Information gathered from a viewer's Facebook profile by the film's app, used once and then deleted, makes the film different for each viewer.
The Three Bears (1939) – An animated short film made by Terrytoons based on the story Goldilocks and the Three Bears. One of the scenes from the short depicting Papa Bear saying "Somebody toucha my spaghet!" in a stereotypically thick Italian accent became an internet meme in December 2017.
Treasure Island (1988) – A Russian animated film developed and distributed by Kievnauchfilm based on the novel of the same name by Robert Louis Stevenson. A loop of a scene from the film showing three characters in a walk cycle with Dr. Livesey showing a highly pronounced swagger, often overlaid with the phonk song, "Why Not" by Ghostface Playa, became an internet meme in August 2022.
A Very Brady Sequel (1996) – A moment where Marcia Brady says "Sure, Jan" became a popular internet meme during the mid-2010s, usually as a response gif. The original writers and actors responded to the meme during a 2021 interview with Vice.
West Side Story (2021) – A clip of the opening long take shot of "The Dance at the Gym" sequence from Steven Spielberg's 2021 film version of the musical was uploaded to Twitter on 25 February 2022, and went viral over the weekend, reaching 3 million views and over 32,000 likes. It led to many users sharing images and clips of their favorite scenes and shots from the film during that time, while praising Spielberg's direction and Janusz Kamiński's cinematography. This was further amplified by a Twitter thread by filmmaker Guillermo del Toro analyzing the camerawork and blocking on this particular shot.
Gaming
"All your base are belong to us" – Badly translated English from the opening cutscene of the European Mega Drive version of the 1989 arcade game Zero Wing. It has become a catchphrase, inspiring videos and other derivative works.
Angry Birds – A mobile game series made by Rovio Entertainment in December 2009 for the iOS and Nokia app stores, with a Google Play version releasing in October 2010. Since its release, the game has amassed a large following on both the internet and in media for its visuals and simple-to-understand game mechanics of launching a bird from a slingshot. The game has also seen many forms of merchandising, with 30% of Rovio Entertainment's revenue coming from merchandise sales in 2011. One of the largest earlier endeavors was the brand's first licensed theme park in Tampere, Finland that was set to open on 1 May 2012.
Among Us – A game made by game studio Innersloth released on Steam in 2018. The game reached internet fame in 2020 due to Twitch streamers and YouTubers playing the game frequently. Still images from the game, phrases from the game like "Emergency Meeting" and "Dead body reported" as well as typical gameplay events have influenced internet memes. Other terms like "Sus", "Sussy", "Sussy Baka", "Amogus", and "When the imposter is sus" also became notable memes on social media platforms, later taking on a more ironic usage.
Arrow in the knee – City guards in The Elder Scrolls V: Skyrim would utter the line: "I used to be an adventurer like you, then I took an arrow in the knee". The latter part of this phrase quickly took off as a catchphrase and a snowclone in the form of "I used to X, but then I took an arrow in the knee" with numerous image macros and video parodies created.
Bowsette – A fan-made depiction of the Super Mario character Bowser using Toadette's Super Crown power-up from the Nintendo Switch title New Super Mario Bros. U Deluxe to transform into a lookalike of Princess Peach. The character became popular following a four-panel webcomic posted by a user on Twitter and DeviantArt in September 2018.
But can it run Crysis? – A question often asked by PC gaming and hardware enthusiasts. When released in 2007, Crysis was extremely taxing on computer hardware, with even the most advanced consumer graphics cards of the time unable to provide satisfactory frame rates when the game was played on its maximum graphical settings. As a result, this question is asked as a way of judging a certain computer's capability at gaming.
Can it run Doom? – A common joke question with any hardware that has a CPU, due to the vast amount of ports the game has received. Examples of unconventional hardware that Doom has been ported to include a Canon Proxima printer, the VIC-20, the Touch Bar on the 2016 MacBook Pro, a smart fridge, an ATM, a billboard truck, and within the game itself.
Doomguy and Isabelle – The pairing of Isabelle from the Animal Crossing video game series and Doomguy from the Doom franchise due to the shared release date of Animal Crossing: New Horizons and Doom Eternal.
Elden Ring – A 2022 video game that spawned multiple memes, such as:
– The colloquial name for an Elden Ring player who specializes in fighting Malenia, one of the game's most difficult bosses, and whose character wears no armor but a jar as a helmet. "Let me solo her" became widely acclaimed within the game's online community after volunteering to deal with Malenia on behalf of other players through the game's player summoning feature, and successfully defeating her at least four thousand times without assistance. Videos of the player's performances became popular and widely shared on multiple social news websites. The player's exploits was acknowledged by the game's publisher, and became the subject of fan labor. Let me solo her was awarded PC Gamer's Player of the Year award for 2022.
"Maidenless" – a term used by multiple non-player characters to describe the player character. In its original context, it implies that the player character lacks a type of important ally, a "maiden", but it has been appropriated by the player community as a joke or insult, who uses it to imply that its recipient lacks a romantic partner.
Flappy Bird – A free-to-play casual mobile game released on the iOS App Store on 24 May 2013, and on Google Play on 30 January 2014, by indie mobile app developer Dong Nguyen. The game began rapidly rising in popularity in late-December 2013 to January 2014 with up to 50 million downloads by 5 February. On 9 February, Nguyen removed the game from the mobile app stores citing negative effects of the game's success on his health and its addictiveness to players. Following the game's removal from the app stores, numerous clones and derivatives of the game were released with varying similarities to the original game.
I Love Bees – An alternate reality game that was spread virally after a one-second mention inside a Halo 2 advertisement. Purported to be a website about honey bees that was infected and damaged by a strange artificial intelligence, done in a disjointed, chaotic style resembling a crashing computer. At its height, over 500,000 people were checking the website every time it updated.
Lamar Roasts Franklin – A cutscene in the 2013 action-adventure video game Grand Theft Auto V where Lamar Davis, portrayed by comedian Slink Johnson, berates Franklin Clinton, portrayed by actor and former rapper Shawn Fonteno, for Franklin's haircut and his relationship with his girlfriend, ending in Lamar uttering the word "nigga" in a condescending, sing-song voice and giving Franklin the middle finger, much to the latter's chagrin. The cutscene experienced a resurgence in popularity in late 2020 when parodies of the scene were uploaded on YouTube and other video hosting sites. It usually involves Lamar's character model being replaced with various popular culture icons such as Darth Vader, Vegeta, and Snow White among others, with Lamar's dialogue dubbed to account for the characters used. In 2021, Fonteno and Johnson reprised their roles as Franklin and Lamar respectively in a live-action re-enactment of the cutscene. Later that year, Fonteno and Johnson once again reprised their roles in The Contract DLC for Grand Theft Auto Online, complete with a homage to the original roast cutscene.
Leeroy Jenkins – A World of Warcraft player charges into a high-level dungeon with a distinctive cry of "Leeeeeeeerooooy... Jeeenkins!", ruining the meticulous attack plans of his group and getting them all killed.
Let's Play – Videos created by video game players that add their commentary and typically humorous reactions atop them playing through a video game. These videos have created a number of Internet celebrities who have made significant money through ad revenue sharing, such as PewDiePie who earned over $12 million from his videos in 2015.
Line Rider – A Flash game where the player draws lines that act as ramps and hills for a small rider on a sled.
Mafia City – A mobile game that has become infamous for its odd advertising involving a person drastically increasing their stats for doing various mob-related activities, and for the phrase "That's how mafia works".
Portal – The games in the Portal series introduced several Internet memes, including the phrase "the cake is a lie", and the space-obsessed "Space Core" character.
Press to pay respects – A prompt for the player to press a button on the PC version of Call of Duty: Advanced Warfare, where the player character would approach the coffin of a fallen comrade in response. The mechanic is repeatedly criticized and ridiculed for both being arbitrary and unnecessary, uninteresting gameplay, as well as being inappropriate to the tone of the funeral the game otherwise intends to convey. The phrase has since become an Internet meme in its own right, sometimes used unironically: during the tribute stream for the Jacksonville Landing shooting, viewers posted a single letter "F" in the chat.
Roblox – a sandbox game that has spawned several memes, such as its "oof" sound.
QWOP – A browser-based game requiring the player to control a sprint runner by using the Q, W, O, and P keys to control the runner's legs. The game is notoriously difficult to control, typically leaving the runner character flailing about. The concept developed into memes based on the game, as well as describing real-life mishaps as attributable to QWOP.
Six Degrees of Kevin Bacon – A trivia/parlor game based around linking an actor to Kevin Bacon through a chain of co-starring actors in films, television, and other productions, with the hypothesis that no actor was more than six connections away from Bacon. It is similar to the theory of six degrees of separation or the Erdős number in mathematics. The game was created in 1994, just at the start of the wider spread of Internet use, populated further with the creation of movie database sites like IMDb, and since has become a board game and contributed towards the field of network science.
Sonic the Hedgehog – A video game series created by Sega that has spawned multiple memes, such as:
Sonic Real-Time Fandubs – The YouTube channel SnapCube has produced a series of improvisational comedy gag dubs of several Sonic titles, including Sonic Adventure 2, Sonic the Hedgehog (2006) and Shadow the Hedgehog, in which their cutscenes are dubbed with new, inaccurate dialogue on purpose. They have themselves earned their own fandom and derivative works based on jokes from the series. The dub over the scene in Sonic Adventure 2 where Doctor Eggman destroys half of the moon featuring an expletive-filled rant from the actor has spawned several memes.
Sanic – A purposely misdrawn Sonic that has been referenced by Sega themselves, and used in merchandise;
and "Ugandan Knuckles" – A meme that gained high popularity thanks to the social game VRChat, where players with a crude Knuckles model asked other players if they "knew da wae" ("know the way"), who their "queen" was, clicking their tongue, and spitting repeatedly.
Surprised Pikachu – An image of the Pokémon Pikachu with a blank look and an open mouth. It is used as a reaction image to show either shock or lack thereof.
Twitch Plays Pokémon – An "experiment" and channel created by an anonymous user on Twitch in February 2014. Logged-in viewers to the channel can enter commands in chat corresponding to the physical inputs used in the JRPG video game Pokémon Red. These are collected and parsed by a chat software robot that uses the commands to control the main character in the game, which is then live-streamed from the channel. The stream attracted more than 80,000 simultaneous players with over 10 million views with a week of going live, creating a chaotic series of movements and actions within the game, a number of original memes, and derivative fan art. The combination has been called an entertainment hybrid of "a video game, live video and a participatory experience," which has inspired similar versions for other games.
U R MR GAY – A message allegedly hidden in the Super Mario Galaxy box art, which appears when each letter not decorated with a star is removed from the art. It was first noticed by a NeoGAF poster in September 2007. Video game journalists have debated as to whether the message was placed on purpose or was simply a humorous coincidence. In Super Mario Galaxy 2, an alleged response to the former's message can be inferred in the title by reading the letters that sparkle in the box art from bottom to top, spelling out "YA I M R U?"
Untitled Goose Game – A 2019 video game developed by Australian game studio House House, in which the player controls a goose causing mischief in an English village. An early teaser for the game in 2017 led to strong interest in the title, and on release, the game quickly became an Internet meme.
Wordle – A word-guessing game similar to Jotto and Mastermind, where the player has only six tries to guess a five-letter word each day, the game indicating whether letters are in the word and/or in the correct position. The game grew popular over a few weeks after the ability to share results with others via social media was added near the end of 2021. The game's popularity led to The New York Times Company acquiring the game from its creator Josh Wardle at the end of January 2022 for an undisclosed seven-figure sum.
Images
Baby mugging and Baby suiting – MommyShorts blogger Ilana Wiles began posting pictures of babies in mugs, and later adult business suits, both of which led to numerous others doing the same.
Babylonokia – A clay tablet, shaped like a mobile phone designed by Karl Weingärtner. Fringe scientists and alternative archaeology proponents subsequently misrepresented a photograph of the artwork as showing an 800-year-old archaeological find; that story was popularised in a video on the YouTube channel Paranormal Crucible and led to the object being reported by some press sources as a mystery.
Bert is Evil – A satirical website stated that Bert of Sesame Street is the root of many evils. A juxtaposition of Bert and Osama bin Laden subsequently appeared in a real poster in a Bangladesh protest.
Blinking white guy – An animated GIF of former Giant Bomb video producer Drew Scanlon blinking in surprise, originating from a 2013 video on the website, became an internet meme in 2017. Multiple outlets have noted the versatility of the GIF's use as a reaction.
Blue waffle – A hoax originating in 2010 claiming to show the effects of an unknown sexually transmitted disease affecting only women, causing severe vaginal infection with a blue discoloration. The disease has been confirmed as false. In Trenton, New Jersey, councilwoman Kathy McBride cited the image in a 2013 city council meeting, not realizing that it was a hoax.
#BreakTheInternet – The November 2014 issue of Paper included a cover image of Kim Kardashian in a partially nude pose, exposing her buttocks, taken by photographer Jean-Paul Goude. It was captioned "#breaktheinternet", as the magazine desired to set a record in social media response from it. Several other photos from the shoot were also released, including one that mimicked one that Goude took for his book Jungle Fever involving a "campaign incident". Papers campaign set a record for hits for their site, and the photographs became part of Internet memes.
Brian Peppers – In 2005, a photo surfaced of a man named Brian Peppers, noted for his appearance, which suggests Apert syndrome or Crouzon syndrome. Found on the Ohio sex offender registry website, the photo gained traction after being shared on website YTMND. Peppers died in 2012 at the age of 43.
Crasher Squirrel – A photograph by Melissa Brandts of a squirrel which popped up into a timer-delayed shot of Brandts and her husband while vacationing in Banff National Park, Canada, just as the camera went off. The image of the squirrel has since been added into numerous images on the Internet.
CSI: Miami Puts on Sunglasses – The cold opening for nearly all CSI: Miami episodes ended with star David Caruso as Horatio Caine, in the initial stages of an investigation, putting on his sunglasses and making a quip or pun related to the crime, before the show hard cut to the opening credits, played against the scream of "Yeah!" in The Who's "Won't Get Fooled Again". Image macros of Caruso putting on sunglasses, or similar images for other fictional characters, and the introductory scenes of the CSI: Miami opening became frequent, typically used as response to other puns made on user forums or with the puns and the following "YEAH!" incorporated into the image macro.
Cursed images – Images (usually photographs) that are perceived as odd or disturbing due to their content, poor quality or both.
Dat Boi – An animated GIF of a unicycling frog associated with the text "here come dat boi!" that began on Tumblr in 2015 before gaining popularity on Twitter in 2016.
DashCon Ball Pit – A convention held in July 2014 by users of Tumblr that "imploded" due to a number of financial difficulties and low turnout. During the convention, a portable ball pit was brought into a large empty room. When some premium panels were cancelled, the attendees were offered an extra hour in the ball pit as compensation. The implosion and absurdity of aspects like the ball pit quickly spread through social media.
DALL-E – A web-based program introduced in 2022 that uses artificial intelligence to construct an array of images from a text prompt. The resulting images, often shared across social media, can range from humorous, to uncanny, to near-perfect results.
Distracted boyfriend – A stock photograph taken in 2015 which went viral as an Internet meme in August 2017.
Dog shaming – Originating on Tumblr, these images feature images of dogs photographed with signs explaining what antics they recently got up to.
Doge – Images of dogs, typically of the Shiba Inus, overlaid with simple but poor grammatical expressions, typically in the Comic Sans MS font, gaining popularity in late 2013. The meme saw an ironic resurgence towards the end of the decade, and was recognised by multiple media outlets as one of the most influential memes of the 2010s. The meme has also spawned Dogecoin, a form of cryptocurrency.
Don't talk to me or my son ever again – Images of a subject, be they product or individual, pictured with a smaller version of themself, captioned with the text "don't talk to me or my son ever again". Popular in 2016.
The Dress – An image of a dress posted to Tumblr that, due to how the photograph was taken, created an optical illusion where the dress would either appear white and gold, or blue and black. Within 48 hours, the post gained over 400,000 notes and was later featured on many different websites.
Ecce Homo / Ecce Mono / Potato Jesus – An attempt in August 2012 by a local woman to restore Elías García Martínez's aging fresco of Jesus in Borja, Spain led to a botched, amateurish, monkey-looking image, leading to several memes.
Every time you masturbate... God kills a kitten – An image featuring a kitten being chased by two Domos, and has the tagline "Please, think of the kittens".
First World problems – A stock image of a woman crying with superimposed text mocking people with trivial complaints compared to that of issues in the Third World.
Floppa – a collection of images either portraying caracals or a specific caracal by the name of Goshe, Shlepa or more commonly Big Floppa. The collection of images do not portray to a specific theme per se, but always hold Floppa as a centerpoint or personification of something.
Goatse.cx – A shock image of a distended anus.
Grogu – The popularity of the TV series The Mandalorian led to many memes of the "Baby Yoda" character.
Grumpy Cat – A cat named Tardar Sauce that appears to have a permanent scowl on her face due to feline dwarfism, according to its owner. Pictures of the cat circulated the Internet, leading it to win the 2013 Webby for Meme of the Year, and her popularity has led her to star in a feature film. Tardar Sauce died on 14 May 2019.
Hide the Pain Harold – A Hungarian electrical engineer named András Arató became a meme after posing for stock photos on the websites iWiW and Dreamstime. He initially wasn't very happy with his popularity, but has grown to accept it. He realized he did similar things when he was younger such as drawing on Hungarian poet John Arany's portraits, making him look like a pirate. The meme depicts photos of Arató smiling, while viewers believe the smile masks serious sorrow and pain, hence the name "Hide the Pain Harold".
Homophobic dog – A series of images of a white dachshund accompanied by homophobic captions, such as "not too fond of gay people" and "let's hope it's just a phase". According to the dog's owners, a gay couple, most of those memes were made and shared by members of the LGBTQ community to mock homophobic people. A fake Washington Post headline describing the dog as "the new face of online homophobia" was criticized by Christina Pushaw, press secretary of Florida Governor Ron DeSantis, unaware that it was not a real article.
Hurricane Shark or Street Shark, a recurring hoax circulated after a variety of natural disasters, appearing to show a shark swimming in a flooded urban area, usually after a hurricane. Several images have been used, most often one of a freeway that first appeared during Hurricane Irene in 2011. However, a 2022 video of a shark or other large fish swimming in Hurricane Ian's floodwaters in Fort Myers, Florida, proved to be real, itself becoming part of the phenomenon and leading to phrases like "Hurricane Shark is real".
Instagram egg – A photograph of an egg on Instagram, which formerly received the most number of likes on both the platform and the highest in any social media.
Islamic Rage Boy – A series of photos of Shakeel Bhat, a Muslim activist whose face became a personification of angry Islamism in the western media. The first photo dates back to his appearance in 2007 at a rally in Srinigar, the capital of Indian-administered Kashmir. Several other photos in other media outlets followed, and by November 2007, there were over one million hits for "Islamic Rage Boy" on Google and his face appeared on boxer shorts and bumper stickers.
Keep Calm and Carry On – A phrasal template or snowclone that was originally a motivational poster produced by the UK government in 1939 intended to raise public morale. It was rediscovered in 2000, became increasingly used during the 2009 global recession, and has spawned various parodies and imitations.
Listenbourg – An image of a photoshopped map of Europe with a red arrow pointing to the outline of a fictional country adjacent to Portugal and Spain.
Little Fatty – Starting in 2003, the face of Qian Zhijun, a student from Shanghai, was superimposed onto various other images.
Lolcat – A collection of humorous image macros featuring cats with misspelled phrases, such as "I Can Has Cheezburger?". The earliest versions of LOLcats appeared on 4chan, usually on Saturdays, which were designated "Caturday", as a day to post photos of cats.
Manul – A Russian meme that was introduced in 2008. It is typically an image macro with a picture of an unfriendly and stern-looking Pallas's cat (also known as a manul) accompanied by a caption in which the cat invites you to pet it.
McKayla is not impressed – A Tumblr blog that went viral after taking an image of McKayla Maroney, the American gymnast who won the silver medal in the vault at the 2012 Summer Olympics, on the medal podium with a disappointed look on her face, and photoshopping it into various "impressive" places and situations, e.g. on top of the Great Wall of China and standing next to Usain Bolt.
Nimoy Sunset Pie – A Tumblr blog that posted mashups combining American actor Leonard Nimoy, sunsets, and pie.
O RLY? – Originally a text phrase on Something Awful, and then an image macro done for 4chan. Based around a picture of a snowy owl.
Oolong – Photos featured on a popular Japanese website of a rabbit that is famous for its ability to balance a variety of objects on its head.
Pepe the Frog – A cartoon frog character from a 2005 web cartoon became widely used on 4chan in 2008, often with the phrase "feels good man". In 2015, the New Zealand government accepted proposals for a new national flag and a flag with Pepe, known as "Te Pepe", was submitted.
Seriously McDonalds – A photograph apparently showing racist policies introduced by McDonald's. The photograph, which is a hoax, went viral, especially on Twitter, in June 2011.
Spider-Man Pointing at Spider-Man – An image of the episode "Double Identity" of the 1967 TV series Spider-Man where the character Spider-Man and a criminal with the same costume point at each other. It is often used online when a person coincidentally acts or looks like another person. The meme was referenced in the post-credit scene of Spider-Man: Into the Spider-Verse and a real-life version with three Spider-Man actors – Tom Holland, Andrew Garfield and Tobey Maguire – was tweeted by Marvel to announce the release of Spider-Man: No Way Home on 4K UHD and Blu-ray.
Stonks – An image featuring Meme Man in a suit against an image of the stock market, used to highlight or satirize absurd topics related to finance or the economy.
Success Kid – An image of a baby who is clenching his fist while featuring a determined look on his face.
Trash Doves – A sticker set of a purple bird for iOS, Facebook messenger, Facebook comments, and other messaging apps created by Syd Weiler. The animated headbanging pigeon from the sticker set started to go viral in Thailand and it became globally viral on social media.
Tron Guy – Jay Maynard, a computer consultant, designed a Tron costume, complete with skin-tight spandex and light-up plastic armor, in 2003 for Penguicon 1.0 in Detroit, Michigan. The Internet phenomenon began when an article was posted to Slashdot, followed by Fark, including images of this costume.
Vancouver Riot Kiss – An image supposedly of a young couple lying on the ground kissing each other behind a group of rioters during the riots following the Vancouver Canucks' Stanley Cup loss to the Boston Bruins on 15 June 2011. The couple, later identified as Australian, Scott Jones, and local resident, Alexandra Thomas, were not actually kissing but Jones was consoling Thomas after being knocked down by a police charge.
Wojak – also known "Feels Guy", a bald male character with a sad expression on his face, often used as a reaction image to represent feelings such as melancholy, regret or loneliness. It has been used to convey different feelings by means of memetic transformation and modification into many various unique forms, all with different meanings. Some represent specific ideas or roles in certain situations, such as the NPC meme, which mocks supposed groupthink and a lack of individuality among a group of people. It has also spawned many derived characters, all based on the original but used to represent different emotions.
Woman yelling at a cat – A screenshot of the members of the television show The Real Housewives of Beverly Hills Taylor Armstrong and Kyle Richards showing Armstrong shouting and pointing with the finger, followed by a photo of a confused cat (identified as Smudge) sitting behind a table with food. The meme emerged in mid-2019, when Twitter users joined the photos and included texts that looked like a mockery of the cat to the angry woman.
Worst person you know – a satirical article by ClickHole with a picture of Josep Maria García.
Wood Sitting on a Bed – An image of a nude man sitting on a bed that gained notoriety at the beginning of the COVID-19 pandemic.
"You are not immune to propaganda." – A glitch art representation of Garfield, with the caption "You are not immune to propaganda" surrounding it.
What the fuck did I just read? – two side-by-side portraits of English lexicographer Samuel Johnson which indicate bewilderment.
Music
The Most Mysterious Song on the Internet – A song recorded on an audio cassette off German radio in the early 1980s, the artist and song title of which remained unknown for many years, despite efforts by devoted internet sleuths who have attempted to identify the band. In November 2024, the song was finally identified as "Subways of Your Mind" by the German band FEX.
"Sigma Boy" – A song by Russian bloggers 11-year-old Betsy and 12-year-old Maria Yankovskaya. German TikToker Streichbruder (@simonbth1) started a trend in which he put the song on at full volume in public transport. It was part of a larger trend where bloggers go to a public place and blast silly songs that you would normally be ashamed of listening to in front of other people.
People
Krzysztof Kononowicz – Polish man who became a phenomenon of the Polish Internet in 2006 after appearing in the debate of candidates for the president of Białystok.
Meme Man – Fictional character often featured in surreal memes, depicted as a 3D render of a smooth, bald, and often disembodied and blue-eyed male head.
Salt Bae – Turkish chef and restaurateur Nusret Gökçe earned fame in 2017 for his camera-friendly approach to preparing and seasoning meat, including a video in 2017 which he sprinkles salt, sparkling in the sunlight, onto a steak. Gökçe's approach has been compared to dinner theater, in that his actual finished product is secondary to the performance.
Hide the Pain Harold – Hungarian model András István Arató became the subject of a meme in 2011, due to his seemingly fake smile as the model in stock images.
Politics
Arrest of Vladimir Putin – A viral video showing the mock arrest of Vladimir Putin and his trial.
Barack Obama vs. Mitt Romney – A fictitious rap battle between 2012 election candidates Barack Obama and Mitt Romney. As of October 2020, the video has over 150 million views.
Bernie or Hillary? – A political poster that compares the positions of Hillary Clinton and Bernie Sanders on certain issues. It was typically used by Sanders supporters to make fun of Clinton's attempts to seem relatable to the voter base while they perceived Sanders to be more knowledgeable and in-depth on the issues. However, some critiqued the meme by saying that it played into sexist stereotypes.
Joe Biden – There are numerous iterations of President Joe Biden as a meme. The portrayal of Biden in The Onion was popular on the Internet and influenced other memes about him, as well as his broader public image. After Donald Trump won the 2016 U.S. presidential election, images of Biden as the "Biden Bro" or "Prankster Joe Biden" began circulating online. In these memes, Biden was paired with Barack Obama and captioned with various fictional conversations planning pranks and jokes on the president-elect. Biden is portrayed as the immature prankster of the duo, with Obama as his exasperated straight man.
Bush shoeing incident – During a press conference in 2008, Muntadhar al-Zaidi threw both of his shoes at then-president George W. Bush. Afterwards, various Flash-based browser games and gifs were created to poke fun of the incident.
Crush on Obama – A music video by Amber Lee Ettinger that circulated during the 2008 United States presidential election. As well as its sequels, the video caught the attention of bloggers, mainstream media, and other candidates, and achieved 12.5 million views on YouTube by 1 January 2009.
Dean scream – Former Governor of Vermont Howard Dean's concession speech following the 2004 New Hampshire Democratic primaries included Dean rattling off a list of states in escalating volume as crowd noise rose, resulting in increasingly distorted audio and culminating in an unusual "yeehaw" scream. It was one of the first political Internet memes.
Delete your account – A phrase used on Twitter to criticize the opinions of opponents. On 9 June 2016, Hillary Clinton tweeted this phrase towards Donald Trump. Afterwards, the tweet has become her most retweeted tweet of all time.
Don't Tase Me, Bro! – An incident at a campus talk by Senator John Kerry where a student yelled his now-infamous phrase while being restrained by police.
Eastwooding – After Clint Eastwood's speech at the 2012 Republican National Convention, in which he spoke to an empty chair representing President Barack Obama, photos were posted by users on the Internet of people talking to empty chairs, with various captions referring to the chair as either Obama or Eastwood.
"Epstein didn't kill himself" – A bait-and-switch joke originating on the app iFunny in October 2019, two months after his death in August. Many memes alleged involvement of Donald Trump, Hillary Clinton, or other notable figures. The meme saw mainstream popularity in late 2019, being unexpectedly snuck into cable news interviews by guests such as on FOX News and MSNBC. It was also referenced by Ricky Gervais at the 77th Golden Globe Awards due to the alleged connections between Epstein and people in the Hollywood film industry.
Forest raking – After U.S. President's Donald Trump's comments that Finland spent "a lot of time on raking and cleaning its forest floor", Finnish people began circulating satirical images of themselves raking the forests to stop wildfires.
Jesusland map – A map created shortly after the 2004 U.S. presidential election that satirizes the red/blue states scheme by dividing the United States and Canada into "The United States of Canada" and "Jesusland".
Kekistan – A fictional country created by 4chan members that has become a political meme and online movement used notably by the alt-right.
Ladies and Gentlemen, We Got Him – A quote said by American diplomat Paul Bremer during a 2003 press conference announcing the capture of Saddam Hussein. The scene, coupled with audio from the Breakbot song "Baby I'm Yours", began to be widely used with clips of people being apprehended or caught off-guard in some fashion, often in the context of FBI operations.
Miss Me Yet? – Billboards that appeared on American highways in early 2010 that featured George Bush asking "Miss me yet?". Inspired a series of themed merchandise from online agencies such as CafePress.
Mug shot of Donald Trump – the first ever mugshot of the U.S. president, Donald Trump, in August 2023.
Series of tubes – A phrase originally coined as an analogy by Senator Ted Stevens to describe the Internet in the context of opposing network neutrality. His statement was later remixed on YouTube and YTMND.
Strong – A political advertisement issued by Texas Governor Rick Perry presidential campaign in December 2011 for the 2012 Republican Party presidential primaries. The video was parodied and became one of the most disliked videos on YouTube.
Ted Cruz–Zodiac meme – A mock conspiracy theory suggesting that American Senator and Presidential candidate Ted Cruz was the Zodiac Killer, an unidentified Californian serial killer of the late 1960s and early 1970s.
Thanks Obama – A sarcastic expression used by critics of President Barack Obama to blame personal troubles and inconveniences on public policies supported or enacted by the administration.
This Land – Flash animation produced by JibJab featuring cartoon faces of George W. Bush and John Kerry singing a parody of "This Land Is Your Land" that spoofs the 2004 United States presidential election. The video became a viral hit and viewed by over 100 million, leading to the production of other JibJab hits, including Good to Be in D.C. and Big Box Mart.
"Running through fields of wheat" – In 2017, then UK Prime Minister Theresa May was asked by interviewer Julie Etchingham what the "naughtiest thing" she had done as a child was. May responded that she and her friend "used to run through the fields of wheat", something "the farmers weren't too pleased about". The statement became the subject of mockery and a meme.
Winnie the Pooh comparison to Xi Jinping – In 2013, a still image of China Chinese leader Xi Jinping meeting with US President Barack Obama was compared to Winnie the Pooh and Tigger. As comparisons of Pooh to Xi persists, the government tightened its censorship to suppress the trend. The comparisons are not limited from internet users in China. The phenomenon has been reported to occur in the Philippines.
Videos
Other phenomena
"And I oop" – A video of drag queen Jasmine Masters stopping a story to say the phrase "and I oop" after accidentally hitting himself in the testes.
April the Giraffe – A reticulated giraffe who had two of her live births streamed on the Internet to much fanfare.
"Banana for scale" – An internet meme that became popular for humorously measuring lengths of various objects. In this internet phenomenon, other objects juxtaposed with a banana are accompanied with the text "banana for scale".
Ben Drowned – A self-published three-part multimedia ARG web serial and web series inspired by creepypasta and The Legend of Zelda: Majora's Mask, created by Alexander D. Hall.
Binod – An internet fad which became popular in India in 2020. It originated from a comment by a user with the screen name 'Binod', who had added only the word 'Binod' as a comment. This was followed by a video by Slayy Point, mocking "Binod" and YouTube comment sections in general. People started spamming the word 'Binod' across social media, primarily in YouTube comments and stream chats. A number of organisations also posted memes, including Netflix India, Twitter and Tinder. Paytm temporarily changed its Twitter name to 'Binod'.
Brad's Wife – On 27 February 2017, Brad Byrd of Harrison County, Indiana posted on Cracker Barrel's Facebook page, asking them why they fired his wife, Nanette, after 11 years of service. The intense and serious nature of the post drew viral attention, and internet users began semi-sarcastically demanding answers, using hashtags such as #BradsWife and #JusticeForBradsWife. This meme was notable for being popular with baby boomers as well as younger internet users. After the post was about a week old, several corporations jumped on the viral bandwagon and began to publicly send job offers to Nanette Byrd.
Cats on the Internet – Images of cats are very popular on the Internet, and have seen extensive use in internet memes, as well as some cats becoming Internet celebrities.
Chuck Norris facts – Satirical factoids about martial artist and actor Chuck Norris that became popular culture after spreading through the Internet.
Creepypasta – Urban legends or scary stories circulating on the Internet, many times revolving around specific videos, pictures, or video games. The term "creepypasta" is a mutation of the term "copypasta": a short, readily available piece of text that is easily copied and pasted into a text field. "Copypasta" is derived from "copy/paste", and in its original sense commonly referred to presumably initially sincere text (e.g. a blog or forum post) perceived by the copy/paster as undesirable or otherwise preposterous, which was then copied and pasted to other sites as a form of trolling. In the pre-Internet era, such material regularly circulated as faxlore.
Dicks out for Harambe – A slogan that was popularized months after the death of Harambe, a gorilla in a Cincinnati zoo, which could be interpreted as telling individuals to expose their penises in public in honor of the gorilla (although the word "dicks" here is slang for guns). The line was notably uttered by actor Danny Trejo.
DignifAI – A 4chan-linked campaign to use AI tools to make women in photos look more modestly dressed. The trend is the opposite of deepfake pornography in that it is used to add clothes rather than remove them, and it has been used as a form of slut-shaming.
Dumb Ways to Die – A 2012 Metro Trains Melbourne safety campaign that became popular on the Internet in November 2012.
Elsagate – controversy surrounding children's YouTube videos in the late 2010s and 2020s.
Florida Man – Crimes involving bizarre behavior, perpetrated by men from the state of Florida.
Freecycling – The exchange of unwanted goods via the Internet.
Gabe the Dog – Gabe was a miniature American Eskimo dog owned by YouTube user gravycp. In January 2013, gravycp uploaded a short video of Gabe barking. The footage itself never went viral though it was used in dozens of song remixes, some of which accrued up to half a million views.
Get stick bugged lol a video clip of a stick insect swaying as bait-and-switch meme similar to Rickrolling, in which an irrelevant video would unexpectedly transition to the clip when the stickbug revealed with the caption "Get stick bugged LOL".
Get Out of My Car – an animated video created by Psychicpebbles, which uses the real audio of a man yelling at a woman to get out of his car.
Have You Seen This Man? – A viral website that emerged on the Internet in the late 2000s, claiming to gather data about a mysterious figure only known as This Man that appears in dreams of people who never saw him before.
Horse ebooks / Pronunciation Book – A five-year-long viral marketing alternate reality game for a larger art project developed by Synydyne. "Horse_ebooks" was a Twitter account that seemed to promote e-books, while "Pronunciation Book" was a YouTube channel that provided ways to pronounce English words. Both accounts engaged in non-sequiturs, making some believe that the accounts were run by automated services. Pronunciation Book shifted to pronouncing numerals in a countdown fashion in mid-2013, concluding in late September 2013 revealing the connection to Horse_ebook and identity of Synydyne behind the accounts, and the introduction of their next art project.
Hou De Kharcha, a meme in Marathi
Unregistered HyperCam 2 – The watermark which displayed in the upper-left corner of footage recorded with free versions of the HyperCam 2 screen capture software developed by Hyperionics, Inc. The software was widely used to screen record for YouTube videos during late 2000s to early 2010s, and was frequently used in the production of tutorial videos and Club Penguin gameplay. Videos with the watermark were often accompanied by "Trance" or "Dreamscape" by 009 Sound System.
I am lonely will anyone speak to me – A thread created on MovieCodec.com's forums, which has been described as the "Web's Top Hangout for Lonely Folk" by Wired magazine.
Johnny Johnny Yes Papa – a children's nursery rhyme series.
Ligma joke – a meme to set up a crude joke.
Most Awesomest Thing Ever – a defunct website that randomly paired two objects, celebrities and activities, and asked viewers to decide their favourite. The ultimate goal of the project was to see what viewers considered the most "awesomest". At the website's closure in 2022, teleportation was ranked number 1.
Netflix and chill – An English language slang term using an invitation to watch Netflix together as a euphemism for sex, either between partners or casually as a booty call. The phrase has been popularized through the Internet.
Omission of New Zealand from maps – New Zealand is often excluded from world maps, which has caught the attention of New Zealander users on the Internet.
One red paperclip – The story of a Canadian blogger who bartered his way from a red paperclip to a house in a year's time.
Planking – Also known as the Lying Down Game. An activity consisting of lying in a face down position, with palms touching the body's sides and toes touching the ground, sometimes in bizarre locations. Some compete to find the most unusual and original location in which to play.
Reality shifting – A mental phenomenon similar to lucid dreaming or maladaptive daydreaming that appeared on TikTok, in which practitioners believe they travel to alternate realities, usually fictional (for example the Wizarding World of the Harry Potter franchise).
Rickrolling – an internet prank in which a video unexpectedly plays the music video for "Never Gonna Give You Up" by Rick Astley instead of what was advertised.
Savage Babies – also known as the Most Savage Babies in Human History, a meme popular in 2016 that uses clips from the Indian children's YouTube channel VideoGyan 3D Rhymes, namely their series of nursery rhymes "Zool Babies". The videos are heavily distorted and given edgy, ironic titles that exaggerate the meaning of the video, such as "Five Little Babies Dressed as Pilots" becoming "Savage Babies Cause 9/11".
SCP Foundation – A creative writing website that contains thousands of fictitious containment procedures for paranormal objects captured by the in-universe SCP Foundation, a secret organization tasked with securing and documenting objects that violate natural law and/or pose a threat to humanity's perception of normalcy and further existence. The website has inspired numerous spin-off works, including a stage play and video games such as SCP – Containment Breach.
Siren Head – A fictional cryptid which has an air raid siren as a head, created by horror artist Trevor Henderson. It has accumulated a fan following which has spawned numerous pieces of fan works and fan-made video games. Many video edits have depicted Siren Head playing various songs over a populated area. Siren Head has been erroneously recognized as an SCP, most notably when the character was briefly submitted to the SCP Foundation Wiki as SCP-6789; the entry was removed after Henderson and site users expressed intention to keep Siren Head independent of the SCP Foundation Wiki. Another entry, SCP-5987, was inspired by the character name and the controversy from the deleted entry.
Smash or Pass – A game in which players decide whether they would hypothetically "smash" (have sex with) someone or "pass" (choose not to).
Spiders Georg – A meme which imagines that the (untrue) statistic that the "average person eats 3 spiders a year" is the result of a statistical error caused by the incorporation of "Spiders Georg", a fictional character who resides in a cave and eats over ten thousand spiders every day, into the study from which this conclusion was drawn. The meme originated with a Tumblr post by user Max Lavergne, and has inspired many derivative works about the character. Variations of the meme have imagined other characters named "Georg" to explain other real or imagined statistics and beliefs.
Steak and Blowjob Day – A meme suggesting that a complementary holiday to Valentine's Day, primarily for men, takes place on 14 March each year.
Storm Area 51 – A joke event created on Facebook to "storm" the highly classified Area 51 military base, with over 1,700,000 people claiming to be attending and another 1,300,000 claiming they were "interested" in going. 1,500 people arrived in the vicinity of Area 51 the day of the event, 20 September 2019, only one of whom actually breached the boundary and was quickly escorted off the premises.
Slender Man or Slenderman – A creepypasta meme and urban-legend fakelore tale created on 8 June 2009, by user Victor Surge on Something Awful as part of a contest to edit photographs to contain "supernatural" entities and then pass them off as legitimate on paranormal forums. The Slender Man gained prominence as a frightening malevolent entity: a tall thin man wearing a suit and lacking a face with "his" head only being blank, white, and featureless. After the initial creation, numerous stories and videos were created by fans of the character. Slender Man was later adapted into a video game in 2012 and became more widely known. There is also a film released in 2018 to negative reviews.
Surreal memes – A type of meme that are artistically bizarre in appearance and whose humor derives from their absurd style. Certain qualities and characters, such as Meme Man, Mr. Orange, and a minimalist style, are frequent markers of the meme.
The Million Dollar Homepage – A website conceived in 2005 by Alex Tew, a student from Wiltshire, England, to raise money for his university education. The home page consists of a million pixels arranged in a 1000 × 1000 pixel grid. The image-based links on it were sold for $1 per pixel in 10 × 10 blocks.
Three Wolf Moon – A t-shirt with many ironic reviews on Amazon.
Throwback Thursday – The trend of posting older, nostalgic photos on Thursdays under the hashtag #ThrowbackThursday or #TBT.
The Undertaker vs. Mankind – A copypasta where at the end of a comment of an irrelevant topic, the event is referenced.
Vibe Check – Generally ascribed as a spiritual evaluation of a person's mental and emotional state.
Vuvuzelas – The near-constant playing of the buzz-sounding vuvuzela instrument during games of the 2010 World Cup in South Africa led to numerous vuvuzela-based memes, including YouTube temporarily adding a vuvuzela effect that could be added to any video during the World Cup.
Willy's Chocolate Experience – An unlicenced event based on the Charlie and the Chocolate Factory franchise held in Glasgow, Scotland. Due to the misleading AI-generated advertisements and its sparsely decorated warehouse location, images of the event went viral. Notable viral images include a dispirited woman dressed as an Oompa-Loompa and an original character called "The Unknown".
Yanny or Laurel – An audio illusion where individuals hear either the word "Yanny" or "Laurel".
YouTube poop – Video mashups in which users deconstruct and piece together video for psychedelic or absurdist effect.
See also
List of Internet phenomena in China
List of Internet phenomena in Pakistan
Cats and the Internet
Index of Internet-related articles
Internet culture
Internet meme
Know Your Meme
List of YouTubers
Outline of the Internet
Urban legends and myths
Usenet personality
Viral phenomenon
Notes
References
Phenomena
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Phenomena
Urban legends
Lists of phenomena | List of Internet phenomena | Technology | 18,956 |
201,718 | https://en.wikipedia.org/wiki/Principle%20of%20maximum%20entropy | The principle of maximum entropy states that the probability distribution which best represents the current state of knowledge about a system is the one with largest entropy, in the context of precisely stated prior data (such as a proposition that expresses testable information).
Another way of stating this: Take precisely stated prior data or testable information about a probability distribution function. Consider the set of all trial probability distributions that would encode the prior data. According to this principle, the distribution with maximal information entropy is the best choice.
History
The principle was first expounded by E. T. Jaynes in two papers in 1957, where he emphasized a natural correspondence between statistical mechanics and information theory. In particular, Jaynes argued that the Gibbsian method of statistical mechanics is sound by also arguing that the entropy of statistical mechanics and the information entropy of information theory are the same concept. Consequently, statistical mechanics should be considered a particular application of a general tool of logical inference and information theory.
Overview
In most practical cases, the stated prior data or testable information is given by a set of conserved quantities (average values of some moment functions), associated with the probability distribution in question. This is the way the maximum entropy principle is most often used in statistical thermodynamics. Another possibility is to prescribe some symmetries of the probability distribution. The equivalence between conserved quantities and corresponding symmetry groups implies a similar equivalence for these two ways of specifying the testable information in the maximum entropy method.
The maximum entropy principle is also needed to guarantee the uniqueness and consistency of probability assignments obtained by different methods, statistical mechanics and logical inference in particular.
The maximum entropy principle makes explicit our freedom in using different forms of prior data. As a special case, a uniform prior probability density (Laplace's principle of indifference, sometimes called the principle of insufficient reason), may be adopted. Thus, the maximum entropy principle is not merely an alternative way to view the usual methods of inference of classical statistics, but represents a significant conceptual generalization of those methods.
However these statements do not imply that thermodynamical systems need not be shown to be ergodic to justify treatment as a statistical ensemble.
In ordinary language, the principle of maximum entropy can be said to express a claim of epistemic modesty, or of maximum ignorance. The selected distribution is the one that makes the least claim to being informed beyond the stated prior data, that is to say the one that admits the most ignorance beyond the stated prior data.
Testable information
The principle of maximum entropy is useful explicitly only when applied to testable information. Testable information is a statement about a probability distribution whose truth or falsity is well-defined. For example, the statements
the expectation of the variable is 2.87
and
(where and are probabilities of events) are statements of testable information.
Given testable information, the maximum entropy procedure consists of seeking the probability distribution which maximizes information entropy, subject to the constraints of the information. This constrained optimization problem is typically solved using the method of Lagrange multipliers.
Entropy maximization with no testable information respects the universal "constraint" that the sum of the probabilities is one. Under this constraint, the maximum entropy discrete probability distribution is the uniform distribution,
Applications
The principle of maximum entropy is commonly applied in two ways to inferential problems:
Prior probabilities
The principle of maximum entropy is often used to obtain prior probability distributions for Bayesian inference. Jaynes was a strong advocate of this approach, claiming the maximum entropy distribution represented the least informative distribution.
A large amount of literature is now dedicated to the elicitation of maximum entropy priors and links with channel coding.
Posterior probabilities
Maximum entropy is a sufficient updating rule for radical probabilism. Richard Jeffrey's probability kinematics is a special case of maximum entropy inference. However, maximum entropy is not a generalisation of all such sufficient updating rules.
Maximum entropy models
Alternatively, the principle is often invoked for model specification: in this case the observed data itself is assumed to be the testable information. Such models are widely used in natural language processing. An example of such a model is logistic regression, which corresponds to the maximum entropy classifier for independent observations.
Probability density estimation
One of the main applications of the maximum entropy principle is in discrete and continuous density estimation.
Similar to support vector machine estimators,
the maximum entropy principle may require the solution to a quadratic programming problem, and thus provide
a sparse mixture model as the optimal density estimator. One important advantage of the method is its ability to incorporate prior information in the density estimation.
General solution for the maximum entropy distribution with linear constraints
Discrete case
We have some testable information I about a quantity x taking values in {x1, x2,..., xn}. We assume this information has the form of m constraints on the expectations of the functions fk; that is, we require our probability distribution to satisfy the moment inequality/equality constraints:
where the are observables. We also require the probability density to sum to one, which may be viewed as a primitive constraint on the identity function and an observable equal to 1 giving the constraint
The probability distribution with maximum information entropy subject to these inequality/equality constraints is of the form:
for some . It is sometimes called the Gibbs distribution. The normalization constant is determined by:
and is conventionally called the partition function. (The Pitman–Koopman theorem states that the necessary and sufficient condition for a sampling distribution to admit sufficient statistics of bounded dimension is that it have the general form of a maximum entropy distribution.)
The λk parameters are Lagrange multipliers. In the case of equality constraints their values are determined from the solution of the nonlinear equations
In the case of inequality constraints, the Lagrange multipliers are determined from the solution of a convex optimization program with linear constraints.
In both cases, there is no closed form solution, and the computation of the Lagrange multipliers usually requires numerical methods.
Continuous case
For continuous distributions, the Shannon entropy cannot be used, as it is only defined for discrete probability spaces. Instead Edwin Jaynes (1963, 1968, 2003) gave the following formula, which is closely related to the relative entropy (see also differential entropy).
where q(x), which Jaynes called the "invariant measure", is proportional to the limiting density of discrete points. For now, we shall assume that q is known; we will discuss it further after the solution equations are given.
A closely related quantity, the relative entropy, is usually defined as the Kullback–Leibler divergence of p from q (although it is sometimes, confusingly, defined as the negative of this). The inference principle of minimizing this, due to Kullback, is known as the Principle of Minimum Discrimination Information.
We have some testable information I about a quantity x which takes values in some interval of the real numbers (all integrals below are over this interval). We assume this information has the form of m constraints on the expectations of the functions fk, i.e. we require our probability density function to satisfy the inequality (or purely equality) moment constraints:
where the are observables. We also require the probability density to integrate to one, which may be viewed as a primitive constraint on the identity function and an observable equal to 1 giving the constraint
The probability density function with maximum Hc subject to these constraints is:
with the partition function determined by
As in the discrete case, in the case where all moment constraints are equalities, the values of the parameters are determined by the system of nonlinear equations:
In the case with inequality moment constraints the Lagrange multipliers are determined from the solution of a convex optimization program.
The invariant measure function q(x) can be best understood by supposing that x is known to take values only in the bounded interval (a, b), and that no other information is given. Then the maximum entropy probability density function is
where A is a normalization constant. The invariant measure function is actually the prior density function encoding 'lack of relevant information'. It cannot be determined by the principle of maximum entropy, and must be determined by some other logical method, such as the principle of transformation groups or marginalization theory.
Examples
For several examples of maximum entropy distributions, see the article on maximum entropy probability distributions.
Justifications for the principle of maximum entropy
Proponents of the principle of maximum entropy justify its use in assigning probabilities in several ways, including the following two arguments. These arguments take the use of Bayesian probability as given, and are thus subject to the same postulates.
Information entropy as a measure of 'uninformativeness'
Consider a discrete probability distribution among mutually exclusive propositions. The most informative distribution would occur when one of the propositions was known to be true. In that case, the information entropy would be equal to zero. The least informative distribution would occur when there is no reason to favor any one of the propositions over the others. In that case, the only reasonable probability distribution would be uniform, and then the information entropy would be equal to its maximum possible value, . The information entropy can therefore be seen as a numerical measure which describes how uninformative a particular probability distribution is, ranging from zero (completely informative) to (completely uninformative).
By choosing to use the distribution with the maximum entropy allowed by our information, the argument goes, we are choosing the most uninformative distribution possible. To choose a distribution with lower entropy would be to assume information we do not possess. Thus the maximum entropy distribution is the only reasonable distribution. The dependence of the solution on the dominating measure represented by is however a source of criticisms of the approach since this dominating measure is in fact arbitrary.
The Wallis derivation
The following argument is the result of a suggestion made by Graham Wallis to E. T. Jaynes in 1962. It is essentially the same mathematical argument used for the Maxwell–Boltzmann statistics in statistical mechanics, although the conceptual emphasis is quite different. It has the advantage of being strictly combinatorial in nature, making no reference to information entropy as a measure of 'uncertainty', 'uninformativeness', or any other imprecisely defined concept. The information entropy function is not assumed a priori, but rather is found in the course of the argument; and the argument leads naturally to the procedure of maximizing the information entropy, rather than treating it in some other way.
Suppose an individual wishes to make a probability assignment among mutually exclusive propositions. He has some testable information, but is not sure how to go about including this information in his probability assessment. He therefore conceives of the following random experiment. He will distribute quanta of probability (each worth ) at random among the possibilities. (One might imagine that he will throw balls into buckets while blindfolded. In order to be as fair as possible, each throw is to be independent of any other, and every bucket is to be the same size.) Once the experiment is done, he will check if the probability assignment thus obtained is consistent with his information. (For this step to be successful, the information must be a constraint given by an open set in the space of probability measures). If it is inconsistent, he will reject it and try again. If it is consistent, his assessment will be
where is the probability of the th proposition, while ni is the number of quanta that were assigned to the th proposition (i.e. the number of balls that ended up in bucket ).
Now, in order to reduce the 'graininess' of the probability assignment, it will be necessary to use quite a large number of quanta of probability. Rather than actually carry out, and possibly have to repeat, the rather long random experiment, the protagonist decides to simply calculate and use the most probable result. The probability of any particular result is the multinomial distribution,
where
is sometimes known as the multiplicity of the outcome.
The most probable result is the one which maximizes the multiplicity . Rather than maximizing directly, the protagonist could equivalently maximize any monotonic increasing function of . He decides to maximize
At this point, in order to simplify the expression, the protagonist takes the limit as , i.e. as the probability levels go from grainy discrete values to smooth continuous values. Using Stirling's approximation, he finds
All that remains for the protagonist to do is to maximize entropy under the constraints of his testable information. He has found that the maximum entropy distribution is the most probable of all "fair" random distributions, in the limit as the probability levels go from discrete to continuous.
Compatibility with Bayes' theorem
Giffin and Caticha (2007) state that Bayes' theorem and the principle of maximum entropy are completely compatible and can be seen as special cases of the "method of maximum relative entropy". They state that this method reproduces every aspect of orthodox Bayesian inference methods. In addition this new method opens the door to tackling problems that could not be addressed by either the maximal entropy principle or orthodox Bayesian methods individually. Moreover, recent contributions (Lazar 2003, and Schennach 2005) show that frequentist relative-entropy-based inference approaches (such as empirical likelihood and exponentially tilted empirical likelihood – see e.g. Owen 2001 and Kitamura 2006) can be combined with prior information to perform Bayesian posterior analysis.
Jaynes stated Bayes' theorem was a way to calculate a probability, while maximum entropy was a way to assign a prior probability distribution.
It is however, possible in concept to solve for a posterior distribution directly from a stated prior distribution using the principle of minimum cross-entropy (or the Principle of Maximum Entropy being a special case of using a uniform distribution as the given prior), independently of any Bayesian considerations by treating the problem formally as a constrained optimisation problem, the Entropy functional being the objective function. For the case of given average values as testable information (averaged over the sought after probability distribution), the sought after distribution is formally the Gibbs (or Boltzmann) distribution the parameters of which must be solved for in order to achieve minimum cross entropy and satisfy the given testable information.
Relevance to physics
The principle of maximum entropy bears a relation to a key assumption of kinetic theory of gases known as molecular chaos or Stosszahlansatz. This asserts that the distribution function characterizing particles entering a collision can be factorized. Though this statement can be understood as a strictly physical hypothesis, it can also be interpreted as a heuristic hypothesis regarding the most probable configuration of particles before colliding.
See also
Akaike information criterion
Dissipation
Info-metrics
Maximum entropy classifier
Maximum entropy probability distribution
Maximum entropy spectral estimation
Maximum entropy thermodynamics
Principle of maximum caliber
Thermodynamic equilibrium
Molecular chaos
Notes
References
Giffin, A. and Caticha, A., 2007, Updating Probabilities with Data and Moments
Jaynes, E. T., 1986 (new version online 1996), "Monkeys, kangaroos and ", in Maximum-Entropy and Bayesian Methods in Applied Statistics, J. H. Justice (ed.), Cambridge University Press, Cambridge, p. 26.
Kapur, J. N.; and Kesavan, H. K., 1992, Entropy Optimization Principles with Applications, Boston: Academic Press.
Kitamura, Y., 2006, Empirical Likelihood Methods in Econometrics: Theory and Practice, Cowles Foundation Discussion Papers 1569, Cowles Foundation, Yale University.
Owen, A. B., 2001, Empirical Likelihood, Chapman and Hall/CRC. .
Further reading
Ratnaparkhi A. (1997) "A simple introduction to maximum entropy models for natural language processing" Technical Report 97-08, Institute for Research in Cognitive Science, University of Pennsylvania. An easy-to-read introduction to maximum entropy methods in the context of natural language processing.
Open access article containing pointers to various papers and software implementations of Maximum Entropy Model on the net.
Entropy and information
Bayesian statistics
maximum entropy
Probability assessment
maximum entropy | Principle of maximum entropy | Physics,Mathematics | 3,322 |
57,185,370 | https://en.wikipedia.org/wiki/Passiflora%20%C3%97%20exoniensis | Passiflora × exoniensis, the Exeter passion flower, is a hybrid of garden origin between two species of flowering plants, Passiflora antioquiensis × Passiflora tripartita var. mollissima in the family Passifloraceae. It was hybridised in the Veitch Nurseries in Exeter, Devon, England, in the 1870s. The name Passiflora × exoniensis has yet to be resolved as a correct scientific name; nevertheless it is widely found in the horticultural literature.
It is a robust evergreen climber growing to at least with three-lobed leaves and pendent deep pink tubular flowers followed by egg-shaped yellow fruits. It is hardy down to about so may be grown outdoors with shelter in mild temperate areas; alternatively under glass, for instance in an unheated greenhouse.
Passiflora × exoniensis has won the Royal Horticultural Society's Award of Garden Merit.
References
exoniensis
Hybrid plants | Passiflora × exoniensis | Biology | 201 |
18,729,970 | https://en.wikipedia.org/wiki/Correlation%20swap | A correlation swap is an over-the-counter financial derivative that allows one to speculate on or hedge risks associated with the observed average correlation, of a collection of underlying products, where each product has periodically observable prices, as with a commodity, exchange rate, interest rate, or stock index.
Payoff Definition
The fixed leg of a correlation swap pays the notional times the agreed strike , while the floating leg pays the realized correlation . The contract value at expiration from the pay-fixed perspective is therefore
Given a set of nonnegative weights on securities, the realized correlation is defined as the weighted average of all pairwise correlation coefficients :
Typically would be calculated as the Pearson correlation coefficient between the daily log-returns of assets i and j, possibly under zero-mean assumption.
Most correlation swaps trade using equal weights, in which case the realized correlation formula simplifies to:
The specificity of correlation swaps is somewhat counterintuitive, as the protection buyer pays the fixed, unlike in usual swaps.
Pricing and valuation
No industry-standard models yet exist that have stochastic correlation and are arbitrage-free.
See also
Variance swap
Rainbow option
Sources
Derivatives (finance)
Mathematical finance
Banking
Swaps (finance) | Correlation swap | Mathematics | 252 |
14,507,786 | https://en.wikipedia.org/wiki/Petrochemical%20industry%20in%20Romania | The emergence of oil production in the territory now known as Romania dates back to 1857, with oil facilities gaining strategic military significance in 1916 during World War I. Throughout World War II, the Kingdom of Romania held the position as the largest oil producer in Europe, second only to the USSR, whose primary oil source was located in Azerbaijan. The oil extracted from Romania played a pivotal role in Axis military operations, a fact underscored in Adolf Hitler's 1942 speech.
The Romanian petrochemical industry, particularly centered around Ploiești, became a focal point for Allied bombing raids, notably during Operation Tidal Wave. The Soviet Red Army later occupied the Romanian oilfields in August 1944. Post-World War II, extensive reconstruction and expansion initiatives were undertaken under the communist regime. Following the events of 1989, a significant portion of the industry underwent privatization.
Present-day Romania boasts significant oil-refining capabilities, demonstrating a notable interest in the Central Asia-Europe pipelines while actively cultivating relations with select Arab States of the Persian Gulf. With a total of 10 refineries and an overall refining capacity of approximately 504,000 barrels per day (80,100 cubic meters per day), Romania stands as the leading nation in the eastern European region in terms of refining industry scale.
Romania's extensive refining capacity surpasses its domestic demand for refined petroleum products, enabling the country to engage in substantial exports of various oil products and petrochemicals. This includes, but is not limited to, lubricants, bitumen, and fertilizers, distributed across the eastern European region.
By 2017, the number of refineries possessing the capability to produce had dwindled to just five, with the overall capacity experiencing a decline to 13.7 million metric tons per year.
Refineries
This is an incomplete list of oil refineries in Romania:
Petrobrazi Refinery, (Petrom/OMV),
Petrotel Lukoil Refinery, (LUKOIL),
Petromidia Constanța Refinery, (Rompetrol),
Vega Refinery, (Rompetrol),
Petrolsub Suplacu de Barcău Refinery, (Petrom/OMV),
Dormant refineries:
Astra Refinery, (Interagro),
Steaua Română Câmpina Refinery, (Omnimpex Chemicals),
Closed refineries:
Arpechim Refinery, (Petrom/OMV), which used to process
RAFO Onești Refinery, (Calder A), which used to process
Petrochemical processing platforms
Romania has closed down the majority of the petrochemical processing platforms. Those remaining are:
KazMunayGas: Petromidia
Chimcomplex
Oltchim
See also
Oil campaign of World War II
Economy of Romania
Industry of Romania
Operation Tidal Wave
References
Economy of Romania
Romania
Energy in Romania
Petrochemical industry
Petroleum in Romania | Petrochemical industry in Romania | Chemistry | 592 |
34,738,934 | https://en.wikipedia.org/wiki/OmpA%20domain | In molecular biology, the OmpA domain is a conserved protein domain with a beta/alpha/beta/alpha-beta(2) structure found in the C-terminal region of many Gram-negative bacterial outer membrane proteins, such as porin-like integral membrane proteins (such as ompA), small lipid-anchored proteins (such as pal), and MotB proton channels. The N-terminal half of these proteins is variable although some of the proteins in this group have the OmpA-like transmembrane domain at the N terminus. OmpA from Escherichia coli is required for pathogenesis, and can interact with host receptor molecules. MotB (and MotA) serve two functions in E. coli, the MotA(4)-MotB(2) complex attaches to the cell wall via MotB to form the stator of the flagellar motor, and the MotA-MotB complex couples the flow of ions across the cell membrane to movement of the rotor.
See also
OmpA-like transmembrane domain
References
Protein families
Outer membrane proteins | OmpA domain | Biology | 231 |
53,234,343 | https://en.wikipedia.org/wiki/NGC%20419 | NGC 419 is a globular cluster located approximately from Earth in the constellation Tucana. It was discovered on September 2, 1826, by James Dunlop. It was described by Dreyer as "pretty large, pretty bright, round, gradually brighter middle". At a distance of about 186,000 light years (57,000 parsecs), it is located within the Small Magellanic Cloud. At an aperture of 50 arcseconds, its apparent V-band magnitude is 10.30, but at this wavelength, it has 0.15 magnitudes of interstellar extinction.
NGC 419 is about 1.45 billion years old. Its estimated mass is , and its total luminosity is , leading to a mass-to-luminosity ratio of 0.18 /. All else equal, older star clusters have higher mass-to-luminosity ratios; that is, they have lower luminosities for the same mass.
See also
List of NGC objects (1–1000)
References
External links
0419
18260902
Tucana
Open clusters
Small Magellanic Cloud
Discoveries by James Dunlop | NGC 419 | Astronomy | 231 |
18,857,436 | https://en.wikipedia.org/wiki/6-phosphogluconate%20dehydrogenase%20deficiency | 6-Phosphogluconate dehydrogenase deficiency (6PGD deficiency), or partial deficiency, is an autosomal hereditary disease characterized by abnormally low levels of 6-phosphogluconate dehydrogenase (6PGD), a metabolic enzyme involved in the Pentose phosphate pathway. It is very important in the metabolism of red blood cells (erythrocytes). 6PDG deficiency affects less than 1% of the population, and studies suggest that there may be race variant involved in many of the reported cases. Although it is similar, 6PDG deficiency is not linked to glucose-6-phosphate dehydrogenase (G6PD) deficiency, as they are located on different chromosomes. However, a few people have had both of these metabolic diseases.
Signs and symptoms
Many patients with 6-phosphogluconate dehydrogenase deficiency are carriers and have no symptoms. It has been discovered that symptoms manifest more frequently in female carriers. Depending on how severe the deficiency is, it has been demonstrated that enzyme activity is reduced by 35–65%.
Abnormal red blood cell breakdown (hemolysis) in 6PGD deficiency can be symptomatic in a number of ways, including the following:
Neonatal jaundice,
Possibility of leading to kernicterus due to a hyperbilirubinemia
Hemolytic crises in response to:
Illness and infections
Certain drugs
Certain foods
Certain chemicals
In extreme cases, kidney failure
Genetics
6PGD deficiency is a recessive hereditary disorder located on the P arm of chromosome 1. It is an autosomal disease, not associated with the sex chromosomes and can affect both sexes. The lack of synthesis of a specific protein on chromosome 1 has reduced a subject suffering from 6PGD deficiency from producing adequate amounts of the 6-phosphogluconate dehydrogenase enzyme. Transfer of the disease can be passed from a parent, even when the parent is asymptomatic.
Pathophysiology
Reaction mechanism
6-Phosphogluconate dehydrogenase (6PGD) is an enzyme in the pentose phosphate pathway (see image). 6PGD catalyzes the reaction of 6-phosphogluconate to an unstable form of 3-keto-6-phosphogluconate, and yields a co-enzyme nicotinamide adenine dinucleotide phosphate (NADPH) as a byproduct. NADPH supplies reducing power to cells. The reaction is the second NADPH releasing reaction in the pentose phosphate pathway, the first being catalyzed by glucose-6-phosphate dehydrogenase. 3-keto-6-phosphogluconate then rapidly (in an irreversible reaction) decarboxylates to CO2 and ribulose-5-phosphate, which is the precursor to many vital metabolic processes.
Importance of NADPH
The NADPH pathway (both 6PGD and G6PD reactions) is the only source of reductant to reduce glutathione in red blood cells. The role of erythrocytes as oxygen carriers puts them at risk of being damaged by oxidizing free radicals. The reduction of glutathione acts as an antioxidant and prevents damage from reactive oxygen species.
Oxidative stress
People suffering from 6PGD or G6PD deficiency (or both) are at risk of hemolytic anemia in states of oxidative stress. Oxidative stress can result from infection and from chemical exposure to medication and certain foods. Broad beans, e.g., fava beans, contain high levels of vicine, divicine, convicine and isouramil, all of which are oxidants.
When all remaining reduced glutathione is consumed, enzymes and other proteins, such as hemoglobin are subsequently damaged by the free radicals, leading to electrolyte imbalance, cross-bonding and protein deposition in the red cell membranes. Damaged red cells are phagocytosed and sequestered (taken out of circulation) in the spleen. The hemoglobin is metabolized to bilirubin (causing jaundice). The red blood cells rarely disintegrate in the circulation, so hemoglobin is rarely excreted directly by the kidney, but this can occur in severe cases, causing acute kidney injury.
Diagnosis
Treatment
Prevention
The most important measure taken for treatment of 6-phosphoglucanate dehydrogenase is prevention. Avoidance of chemical exposures to drugs and foods that have the potential to cause hemolysis. Although some foods and supplements have antioxidant properties, their use does not decrease the severity of G6PD deficiency.
Diagnosis is difficult during haemolytic episodes since reticulocytes have increased levels of enzymes and may produce erroneously normal results. Testing can be useful after a steady state is reached (about six weeks after the most recent episode of haemolysis), including a G6PD assay to confirm a diagnosis and G6PD spectrophotometry to detect the level of activity.
Vaccinations against some common pathogens (e.g. hepatitis A and hepatitis B) may prevent infection-induced attacks.
Blood transfusion
In the acute phase of hemolysis, blood transfusions might be necessary, or even dialysis in acute kidney injury. Blood transfusion is an important symptomatic measure, as the transfused red cells are generally not 6PGD deficient and will live a normal lifespan in the recipient's circulation.
References
External links
Inborn errors of carbohydrate metabolism | 6-phosphogluconate dehydrogenase deficiency | Chemistry | 1,186 |
30,006,925 | https://en.wikipedia.org/wiki/G1%20and%20G1/S%20cyclins-%20budding%20yeast | Cln1, Cln2, and Cln3 are cyclin proteins expressed in the G1-phase of the cell cycle of budding yeast. Like other cyclins, they function by binding and activating cyclin-dependent kinase. They are responsible for initiating entry into a new mitotic cell cycle at Start. As described below, Cln3 is the primary regulator of this process during normal yeast growth, with the other two G1 cyclins performing their function upon induction by Cln3. However, Cln1 and Cln2 are also directly regulated by pathways sensing extracellular conditions, including the mating pheremone pathway.
Cln3
Cln3 is thought to be the main regulator linking cell growth to the cell cycle. This is because it is the most upstream regulator of Start and because, unlike other cyclins, concentration of Cln3 does not oscillate much with the cell cycle (see Cln3). Rather, Cln3 activity is thought to increase gradually throughout the cycle in response to cell growth. Furthermore, Cln3 levels differ between mother and daughter cells, a difference that explains the asymmetry in cell cycle behavior between these two cell types. Cln3 regulation also responds to external signals, including stress signals that stop division.
Cln1,2
The G1 cyclins CLN1 and CLN2, upon transcriptional activation by Cln3 in mid-G1, bind Cdk1 (Cdc28) to complete progression through Start. These cyclins oscillate during the cell cycle - rise in late G1 and fall in early S phase. The primary function of G1/S cyclin-Cdk complexes is to trigger progression through Start and initiate the processes leading to DNA replication, principally by shutting down the various braking systems that suppress S-phase Cdk activity in G1. G1/S cyclins also initiate other early cell-cycles events such as duplication of the spindle pole body in yeast. The rise of G1/S cyclins is accompanied by the appearance of the S cyclins (Clb5 and Clb6 in budding yeast), which form S cyclin-Cdk complexes that are directly responsible for stimulating DNA replication.
Cln1 and Cln2 are involved in regulation of the cell cycle. Cln1 is closely related to Cln2 and has overlapping functions with Cln2. For instance, Cln1 and Cln2 repress the mating factor response pathway at Start. Additionally, both Cln1 and Cln2 are expressed in late G1 phase when they associate with Cdc28p to activate its kinase activity. Lastly, late G1-specific expression for both of them depends on transcription factor complexes, MBF and SBF.
References
Cell cycle | G1 and G1/S cyclins- budding yeast | Biology | 586 |
19,217,621 | https://en.wikipedia.org/wiki/Nonintrusive%20load%20monitoring | Nonintrusive load monitoring (NILM), nonintrusive appliance load monitoring (NIALM), or energy disaggregation is a process for analyzing changes in the voltage and current going into a house and deducing what appliances are used in the house as well as their individual energy consumption. Electric meters with NILM technology are used by utility companies to survey the specific uses of electric power in different homes. NILM is considered a low-cost alternative to attaching individual monitors on each appliance. It does, however, present privacy concerns.
Background and theory
Nonintrusive load monitoring was invented by George W. Hart, Ed Kern and Fred Schweppe of MIT in the early 1980s with funding from the Electric Power Research Institute.
The basic process is described in . As shown in figure 1 from the patent, a digital AC monitor is attached to the single-phase power going into a residence. Changes in the voltage and current are measured (i.e. admittance measurement unit), normalized (scaler) and recorded (net change detector unit). A cluster analysis is then performed to identify when different appliances are turned on and off. If a 60-watt bulb is turned on, for example, followed by a 100-watt bulb being turned on, followed by the 60-watt bulb being turned off followed by the 100-watt bulb being turned off, the NIALM unit will match the on and off signals from the 60-watt bulb and the on and off signals from the 100-watt bulb to determine how much power was used by each bulb and when. The system is sufficiently sensitive that individual 60-watt bulbs can be discriminated due to the normal variations in actual power draw of bulbs with the same nominal rating (e.g. one bulb might draw 61 watts, another 62 watts).
The system can measure both reactive power and real power. Hence two appliances with the same total power draw can be distinguished by differences in their complex impedance. As shown in figure 8 from the patent, for example, a refrigerator electric motor and a pure resistive heater can be distinguished in part because the electric motor has significant changes in reactive power when it turns on and off, whereas the heater has almost none.
NILM systems can also identify appliances with a series of individual changes in power draw. These appliances are modeled as finite-state machines. A dishwasher, for example, has heaters and motors that turn on and off during a typical dishwashing cycle. These will be identified as clusters, and power draw for the entire cluster will be recorded. Hence “dishwasher” power draw can be identified as opposed to “resistor heating unit” and “electric motor”.
Applications
"Extremely cost-effective" load identification
Cheap detection of startup transients, line or equipment faults, etc.
Perform surveys of both residential and commercial energy consumption.
Demand response system for use on the smart grid.
Monitor systems on-board ships for safe systems operation with fewer sensors.
Privacy concerns
NILM can detect what types of appliances people have and their behavioral patterns. Patterns of energy use may indicate behavior patterns, such as routine times that nobody is at home, or embarrassing or illegal behavior of residents. It could, for example, reveal when the occupants of a house are using the shower, or when individual lights are turned on and off.
If the NILM is running remotely at a utility or by a third party, the homeowner may not know that their behavior is being monitored and recorded.
A stand-alone in-home system, under the control of the user, can provide feedback about energy use, without revealing information to others. Drawing links between their behavior and energy consumption may help reduce energy consumption, improve efficiency, flatten peak loads, save money, or balance appliance use with green energy availability. However the use of a stand-alone system does not protect one from remote monitoring.
The accuracy and capability of this technology is still developing and is not 100% reliable in near-real-time, such that complete information is accumulated and analyzed over periods ranging from minutes to hours.
Software
A framework for non-intrusive load monitoring and diagnostics (M. Eng. thesis) contains code listings for an implementation
Non-Intrusive Load Monitoring Toolkit (NILMTK) - An open source project written in Python
See also
Energy monitoring and targeting
Google PowerMeter
Home energy monitor
Smart meter
References
Electricity meters
Electrical engineering
Surveillance | Nonintrusive load monitoring | Engineering | 915 |
16,499,897 | https://en.wikipedia.org/wiki/Pseudo%20amino%20acid%20composition | In molecular biology, pseudo amino acid composition (PseACC) is a method introduced by Kuo-Chen Chou to convert the protein sequence into a numerical vector for enhancing pattern recognition techniques, such as during discrimination between classes of proteins based on their sequences (e.g. between membrane proteins, transmembrane proteins, cytosolic proteins, and other types). This method represented an advance beyond using the immediate amino acid composition (AAC). Instead, the protein is characterized into a matrix of amino-acid frequencies. This matrix incorporates not only amino acid composition, but can also incorporate information from local features of the protein sequence.
Due to the success and widespread application of the PseACC method, it was extended to address sequence-order effects in nucleotide compositions, giving rise to a comparative method called PseKNC.
Sequential and discrete models
Two kinds of models are usually used to represent protein samples: the sequential and the discrete (or non-sequential) models. The most elementary sequential model is to use the entire amino acid sequence, as expressed by:
where, P represents the amino acid sequence, is the number of amino acid residues, R1 is the first residue of the protein P, R2 is the second residue, and so forth.
The problem with this approach was that in some sequence-similarity-search-based tools, the query protein often lacked significant homology (or sequence similarity) with any other known protein in the database. To resolve this problem, discrete models for representing protein samples were proposed. The simplest discrete model is using the amino acid composition (AAC) to represent protein samples. Under the AAC model, the protein P of Eq.1 can also be expressed by
where are the normalized occurrence frequencies of the 20 native amino acids in P, and T is the transposing operator.
Pseudo-Amino Acid Composition (PseAAC) model
The primary weakness of the discrete model that relies on the amino acid composition (AAC) is that the information on the frequencies of each amino acid from the sample alone involves a loss of sequence-order information, or information obtained by the order of the amino acid residues. To avoid this information loss, the concept of PseAAC (pseudo amino acid composition) was proposed.
Under this new model, the first 20 discrete factors represent amino acid frequencies are retained, but additional discrete factors are included that also ascertain information about sequence order. The sequence order information is represented by what are called "pseudo components". The number of additional components, beyond the first 20 frequencies, is called λ (or upper-case Λ), and so 20+λ components are included in the model. The upper limit for λ is one less than the length of the shortest protein sample in the dataset. The total number of components (20+λ) may be denoted Ω. Any additional factors can be incorporated so long as they, in some way, obtain or represent information about the sequence-order. Typically, these are a series of rank-different correlation factors along the protein chain.
The additional factors are a series of rank-different correlation factors along a protein chain, but they can also be any combinations of other factors so long as they can reflect some sorts of sequence-order effects one way or the other. Therefore, the essence of PseAAC is that on one hand it covers the AA composition, but on the other hand it contains the information beyond the AA composition and hence can better reflect the feature of a protein sequence through a discrete model.
Meanwhile, various modes to formulate the PseAAC vector have also been developed, as summarized in a 2009 review article.
Algorithm
According to the PseAAC model, the protein P of Eq.1 can be formulated as
where the () components are given by
where is the weight factor, and the -th tier correlation factor that reflects the sequence order correlation between all the -th most contiguous residues as formulated by
with
where is the -th function of the amino acid , and the total number of the functions considered. For example, in the original paper by Chou, , and are respectively the hydrophobicity value, hydrophilicity value, and side chain mass of amino acid ; while , and the corresponding values for the amino acid . Therefore, the total number of functions considered there is . It can be seen from Eq.3 that the first 20 components, i.e. are associated with the conventional AA composition of protein, while the remaining components are the correlation factors that reflect the 1st tier, 2nd tier, ..., and the -th tier sequence order correlation patterns (Figure 1).
It is through these additional factors that some important sequence-order effects are incorporated.
in Eq.3 is a parameter of integer and that choosing a different integer for will lead to a dimension-different PseAA composition.
Using Eq.6 is just one of the many modes for deriving the correlation factors in PseAAC or its components. The others, such as the physicochemical distance mode and amphiphilic pattern mode, can also be used to derive different types of PseAAC, as summarized in a 2009 review article. In 2011, the formulation of PseAAC (Eq.3) was extended to a form of the general PseAAC as given by:
where the subscript is an integer, and its value and the components will depend on how to extract the desired information from the amino acid sequence of P in Eq.1.
The general PseAAC can be used to reflect any desired features according to the targets of research, including those core features such as functional domain, sequential evolution, and gene ontology to improve the prediction quality for the subcellular localization of proteins. as well as their many other important attributes.
References
External links
PseAAC web server
Pse-in-One web server
Amino acids
Bioinformatics algorithms | Pseudo amino acid composition | Chemistry,Biology | 1,202 |
1,654,769 | https://en.wikipedia.org/wiki/Artificial%20intelligence%20in%20video%20games | In video games, artificial intelligence (AI) is used to generate responsive, adaptive or intelligent behaviors primarily in non-playable characters (NPCs) similar to human-like intelligence. Artificial intelligence has been an integral part of video games since their inception in 1948, first seen in the game Nim. AI in video games is a distinct subfield and differs from academic AI. It serves to improve the game-player experience rather than machine learning or decision making. During the golden age of arcade video games the idea of AI opponents was largely popularized in the form of graduated difficulty levels, distinct movement patterns, and in-game events dependent on the player's input. Modern games often implement existing techniques such as pathfinding and decision trees to guide the actions of NPCs. AI is often used in mechanisms which are not immediately visible to the user, such as data mining and procedural-content generation. One of the most infamous examples of this NPC technology and gradual difficulty levels can be found in the game Mike Tyson's Punch-Out!! (1987).
In general, game AI does not, as might be thought and sometimes is depicted to be the case, mean a realization of an artificial person corresponding to an NPC in the manner of the Turing test or an artificial general intelligence.
Overview
The term game AI is used to refer to a broad set of algorithms that also include techniques from control theory, robotics, computer graphics and computer science in general, and so video game AI may often not constitute "true AI" in that such techniques do not necessarily facilitate computer learning or other standard criteria, only constituting "automated computation" or a predetermined and limited set of responses to a predetermined and limited set of inputs.
Many industries and corporate voices argue that game AI has come a long way in the sense that it has revolutionized the way humans interact with all forms of technology, although many expert researchers are skeptical of such claims, and particularly of the notion that such technologies fit the definition of "intelligence" standardly used in the cognitive sciences. Industry voices make the argument that AI has become more versatile in the way we use all technological devices for more than their intended purpose because the AI allows the technology to operate in multiple ways, allegedly developing their own personalities and carrying out complex instructions of the user.
People in the field of AI have argued that video game AI is not true intelligence, but an advertising buzzword used to describe computer programs that use simple sorting and matching algorithms to create the illusion of intelligent behavior while bestowing software with a misleading aura of scientific or technological complexity and advancement. Since game AI for NPCs is centered on appearance of intelligence and good gameplay within environment restrictions, its approach is very different from that of traditional AI.
History
Game playing was an area of research in AI from its inception. One of the first examples of AI is the computerized game of Nim made in 1951 and published in 1952. Despite being advanced technology in the year it was made, 20 years before Pong, the game took the form of a relatively small box and was able to regularly win games even against highly skilled players of the game. In 1951, using the Ferranti Mark 1 machine of the University of Manchester, Christopher Strachey wrote a checkers program and Dietrich Prinz wrote one for chess. These were among the first computer programs ever written. Arthur Samuel's checkers program, developed in the middle 1950s and early 1960s, eventually achieved sufficient skill to challenge a respectable amateur. Work on checkers and chess would culminate in the defeat of Garry Kasparov by IBM's Deep Blue computer in 1997. The first video games developed in the 1960s and early 1970s, like Spacewar!, Pong, and Gotcha (1973), were games implemented on discrete logic and strictly based on the competition of two players, without AI.
Games that featured a single player mode with enemies started appearing in the 1970s. The first notable ones for the arcade appeared in 1974: the Taito game Speed Race (racing video game) and the Atari games Qwak (duck hunting light gun shooter) and Pursuit (fighter aircraft dogfighting simulator). Two text-based computer games, Star Trek (1971) and Hunt the Wumpus (1973), also had enemies. Enemy movement was based on stored patterns. The incorporation of microprocessors would allow more computation and random elements overlaid into movement patterns.
It was during the golden age of video arcade games that the idea of AI opponents was largely popularized, due to the success of Space Invaders (1978), which sported an increasing difficulty level, distinct movement patterns, and in-game events dependent on hash functions based on the player's input. Galaxian (1979) added more complex and varied enemy movements, including maneuvers by individual enemies who break out of formation. Pac-Man (1980) introduced AI patterns to maze games, with the added quirk of different personalities for each enemy. Karate Champ (1984) later introduced AI patterns to fighting games. First Queen (1988) was a tactical action RPG which featured characters that can be controlled by the computer's AI in following the leader. The role-playing video game Dragon Quest IV (1990) introduced a "Tactics" system, where the user can adjust the AI routines of non-player characters during battle, a concept later introduced to the action role-playing game genre by Secret of Mana (1993).
Games like Madden Football, Earl Weaver Baseball and Tony La Russa Baseball all based their AI in an attempt to duplicate on the computer the coaching or managerial style of the selected celebrity. Madden, Weaver and La Russa all did extensive work with these game development teams to maximize the accuracy of the games. Later sports titles allowed users to "tune" variables in the AI to produce a player-defined managerial or coaching strategy.
The emergence of new game genres in the 1990s prompted the use of formal AI tools like finite-state machines. Real-time strategy games taxed the AI with many objects, incomplete information, pathfinding problems, real-time decisions and economic planning, among other things. The first games of the genre had notorious problems. Herzog Zwei (1989), for example, had almost broken pathfinding and very basic three-state state machines for unit control, and Dune II (1992) attacked the players' base in a beeline and used numerous cheats. Later games in the genre exhibited more sophisticated AI.
Later games have used bottom-up AI methods, such as the emergent behaviour and evaluation of player actions in games like Creatures or Black & White. Façade (interactive story) was released in 2005 and used interactive multiple way dialogs and AI as the main aspect of game.
Games have provided an environment for developing artificial intelligence with potential applications beyond gameplay. Examples include Watson, a Jeopardy!-playing computer; and the RoboCup tournament, where robots are trained to compete in soccer.
Views
Many experts complain that the "AI" in the term game AI overstates its worth, as game AI is not about intelligence, and shares few of the objectives of the academic field of AI. Whereas "real AI" addresses fields of machine learning, decision making based on arbitrary data input, and even the ultimate goal of strong AI that can reason, "game AI" often consists of a half-dozen rules of thumb, or heuristics, that are just enough to give a good gameplay experience. Historically, academic game-AI projects have been relatively separate from commercial products because the academic approaches tended to be simple and non-scalable. Commercial game AI has developed its own set of tools, which have been sufficient to give good performance in many cases.
Game developers' increasing awareness of academic AI and a growing interest in computer games by the academic community is causing the definition of what counts as AI in a game to become less idiosyncratic. Nevertheless, significant differences between different application domains of AI mean that game AI can still be viewed as a distinct subfield of AI. In particular, the ability to legitimately solve some AI problems in games by cheating creates an important distinction. For example, inferring the position of an unseen object from past observations can be a difficult problem when AI is applied to robotics, but in a computer game a NPC can simply look up the position in the game's scene graph. Such cheating can lead to unrealistic behavior and so is not always desirable. But its possibility serves to distinguish game AI and leads to new problems to solve, such as when and how to cheat.
The major limitation to strong AI is the inherent depth of thinking and the extreme complexity of the decision-making process. This means that although it would be then theoretically possible to make "smart" AI the problem would take considerable processing power.
Usage
In computer simulations of board games
Computer chess
Computer shogi
Computer Go
Computer checkers
Computer Othello
Computer poker players
Akinator
Computer Arimaa
Logistello, which plays Reversi
Rog-O-Matic, which plays Rogue
Computer players of Scrabble
A variety of board games in the Computer Olympiad
General game playing
Solved games have a computer strategy which is guaranteed to be optimal, and in some cases force a win or draw.
In modern video games
Game AI/heuristic algorithms are used in a wide variety of quite disparate fields inside a game. The most obvious is in the control of any NPCs in the game, although "scripting" (decision tree) is currently the most common means of control. These handwritten decision trees often result in "artificial stupidity" such as repetitive behavior, loss of immersion, or abnormal behavior in situations the developers did not plan for.
Pathfinding, another common use for AI, is widely seen in real-time strategy games. Pathfinding is the method for determining how to get a NPC from one point on a map to another, taking into consideration the terrain, obstacles and possibly "fog of war". Commercial videogames often use fast and simple "grid-based pathfinding", wherein the terrain is mapped onto a rigid grid of uniform squares and a pathfinding algorithm such as A* or IDA* is applied to the grid. Instead of just a rigid grid, some games use irregular polygons and assemble a navigation mesh out of the areas of the map that NPCs can walk to. As a third method, it is sometimes convenient for developers to manually select "waypoints" that NPCs should use to navigate; the cost is that such waypoints can create unnatural-looking movement. In addition, waypoints tend to perform worse than navigation meshes in complex environments. Beyond static pathfinding, navigation is a sub-field of Game AI focusing on giving NPCs the capability to navigate in a dynamic environment, finding a path to a target while avoiding collisions with other entities (other NPC, players...) or collaborating with them (group navigation). Navigation in dynamic strategy games with large numbers of units, such as Age of Empires (1997) or Civilization V (2010), often performs poorly; units often get in the way of other units.
Rather than improve the Game AI to properly solve a difficult problem in the virtual environment, it is often more cost-effective to just modify the scenario to be more tractable. If pathfinding gets bogged down over a specific obstacle, a developer may just end up moving or deleting the obstacle. In Half-Life (1998), the pathfinding algorithm sometimes failed to find a reasonable way for all the NPCs to evade a thrown grenade; rather than allow the NPCs to attempt to bumble out of the way and risk appearing stupid, the developers instead scripted the NPCs to crouch down and cover in place in that situation.
Video game combat AI
Many contemporary video games fall under the category of action, first-person shooter, or adventure. In most of these types of games, there is some level of combat that takes place. The AI's ability to be efficient in combat is important in these genres. A common goal today is to make the AI more human or at least appear so.
One of the more positive and efficient features found in modern-day video game AI is the ability to hunt. AI originally reacted in a very black and white manner. If the player were in a specific area then the AI would react in either a complete offensive manner or be entirely defensive. In recent years, the idea of "hunting" has been introduced; in this 'hunting' state the AI will look for realistic markers, such as sounds made by the character or footprints they may have left behind. These developments ultimately allow for a more complex form of play. With this feature, the player can actually consider how to approach or avoid an enemy. This is a feature that is particularly prevalent in the stealth genre.
Another development in recent game AI has been the development of "survival instinct". In-game computers can recognize different objects in an environment and determine whether it is beneficial or detrimental to its survival. Like a user, the AI can look for cover in a firefight before taking actions that would leave it otherwise vulnerable, such as reloading a weapon or throwing a grenade. There can be set markers that tell it when to react in a certain way. For example, if the AI is given a command to check its health throughout a game then further commands can be set so that it reacts a specific way at a certain percentage of health. If the health is below a certain threshold then the AI can be set to run away from the player and avoid it until another function is triggered. Another example could be if the AI notices it is out of bullets, it will find a cover object and hide behind it until it has reloaded. Actions like these make the AI seem more human. However, there is still a need for improvement in this area.
Another side-effect of combat AI occurs when two AI-controlled characters encounter each other; first popularized in the id Software game Doom, so-called 'monster infighting' can break out in certain situations. Specifically, AI agents that are programmed to respond to hostile attacks will sometimes attack each other if their cohort's attacks land too close to them. In the case of Doom, published gameplay manuals even suggest taking advantage of monster infighting in order to survive certain levels and difficulty settings.
Procedural content generation
Procedural content generation (PCG) is an AI technique to autonomously create ingame content through algorithms with minimal input from designers. PCG is typically used to dynamically generate game features such as levels, NPC dialogue, and sounds. Developers input specific parameters to guide the algorithms into making content for them. PCG offers numerous advantages from both a developmental and player experience standpoint. Game studios are able to spend less money on artists and save time on production. Players are given a fresh, highly replayable experience as the game generates new content each time they play. PCG allows game content to adapt in real time to the player's actions.
Procedurally generated levels
Generative algorithms (a rudimentary form of AI) have been used for level creation for decades. The iconic 1980 dungeon crawler computer game Rogue is a foundational example. Players are tasked with descending through the increasingly difficult levels of a dungeon to retrieve the Amulet of Yendor. The dungeon levels are algorithmically generated at the start of each game. The save file is deleted every time the player dies. The algorithmic dungeon generation creates unique gameplay that would not otherwise be there as the goal of retrieving the amulet is the same each time.
Opinions on total level generation as seen in games like Rogue can vary. Some developers can be skeptical of the quality of generated content and desire to create a world with a more "human" feel so they will use PCG more sparingly. Consequently, they will only use PCG to generate specific components of an otherwise handcrafted level. A notable example of this is Ubisoft's 2017 tactical shooter Tom Clancy's Ghost Recon Wildlands. Developers used a pathfinding algorithm trained with a data set of real maps to create road networks that would weave through handcrafted villages within the game world. This is an intelligent use of PCG as the AI would have a large amount of real world data to work with and roads are straightforward to create. However, the AI would likely miss nuances and subtleties if it was tasked with creating a village where people live.
As AI has become more advanced, developer goals are shifting to create massive repositories of levels from data sets. In 2023, researchers from New York University and the University of the Witwatersrand trained a large language model to generate levels in the style of the 1981 puzzle game Sokoban. They found that the model excelled at generating levels with specifically requested characteristics such as difficulty level or layout. However, current models such as the one used in the study require large datasets of levels to be effective. They concluded that, while promising, the high data cost of large language models currently outweighs the benefits for this application. Continued advancements in the field will likely lead to more mainstream use in the future.
Procedurally generated music and sound
The musical score of a video game is an important expression of the emotional tone of a scene to the player. Sound effects such as the noise of a weapon hitting an enemy help indicate the effect of the player's actions. Generating these in real time creates an engaging experience for the player because the game is more responsive to their input. An example is the 2013 adventure game Proteus where an algorithm dynamically adapts the music based on the angle the player is viewing the ingame landscape from.
Recent breakthroughs in AI have resulted in the creation of advanced tools that are capable of creating music and sound based on evolving factors with minimal developer input. One such example is the MetaComposure music generator. MetaComposure is an evolutionary algorithm designed to generate original music compositions during real time gameplay to match the current mood of the environment. The algorithm is able to assess the current mood of the game state through "mood tagging". Research indicates that there is a significant positive statistical correlation regarding player rated game engagement and the dynamically generated musical compositions when they accurately match their current emotions.
Monte Carlo tree search method
Game AI often amounts to pathfinding and finite-state machines. Pathfinding gets the AI from point A to point B, usually in the most direct way possible. State machines permit transitioning between different behaviors. The Monte Carlo tree search method provides a more engaging game experience by creating additional obstacles for the player to overcome. The MCTS consists of a tree diagram in which the AI essentially plays tic-tac-toe. Depending on the outcome, it selects a pathway yielding the next obstacle for the player. In complex video games, these trees may have more branches, provided that the player can come up with several strategies to surpass the obstacle.
Uses in games beyond NPCs
Academic AI may play a role within game AI, outside the traditional concern of controlling NPC behavior. Georgios N. Yannakakis highlighted four potential application areas:
Player-experience modeling: Discerning the ability and emotional state of the player, so as to tailor the game appropriately. This can include dynamic game difficulty balancing, which consists in adjusting the difficulty in a video game in real-time based on the player's ability. Game AI may also help deduce player intent (such as gesture recognition).
Procedural-content generation: Creating elements of the game environment like environmental conditions, levels, and even music in an automated way. AI methods can generate new content or interactive stories.
Data mining on user behavior: This allows game designers to explore how people use the game, what parts they play most, and what causes them to stop playing, allowing developers to tune gameplay or improve monetization.
Alternate approaches to NPCs: These include changing the game set-up to enhance NPC believability and exploring social rather than individual NPC behavior.
Rather than procedural generation, some researchers have used generative adversarial networks (GANs) to create new content. In 2018 researchers at Cornwall University trained a GAN on a thousand human-created levels for Doom; following training, the neural net prototype was able to design new playable levels on its own. Similarly, researchers at the University of California prototyped a GAN to generate levels for Super Mario. In 2020 Nvidia displayed a GAN-created clone of Pac-Man; the GAN learned how to recreate the game by watching 50,000 (mostly bot-generated) playthroughs.
Non-player characters (NPCs)
Non-player characters are entities within video games that are not controlled by players, but instead are managed by AI systems. NPCs contribute to the immersion, storytelling, and the mechanics of a game. They often serve as companions, quest-givers, merchants and much more. Their realism has advanced significantly in the past few years, thanks to improvements in AI technologies.
Narratives and gameplay roles
NPCs are essential in both narrative-driven as well as open-world games. They help convey the lore and context of the game, making them pivotal to world-building and narrative progression. For instance, an NPC can provide critical information, offer quests, or simply populate the world to add a sense of realism to the game. Additionally, their role as quest-givers or merchants makes them integral to the gameplay loop, giving players access to resources, missions, or services that enable further progression.
Additionally, NPCs can be designed to serve functional roles in games, such as a merchant or to provide a service to the player. These characters are central to facilitating game mechanics by acting as intermediaries between the player and in-game systems. Academics say the interactions between players and NPCs are often designed to be straightforward but contextually relevant, ensuring that the player receives necessary feedback or resources for gameplay continuity.
Advancements in NPC artificial intelligence
Recent advancements in artificial intelligence have significantly enhanced the complexity and realism of NPCs. Before these advancements, AI operated on pre-programmed behaviors, making them predictable and repeatable. With AI developing NPCs have become more adaptive and able to dynamically respond to players. Experts think the integration of deep learning and reinforcement learning techniques has enabled NPCs to adjust their behavior in response to player actions, creating a more interactive and personalized gameplay experience.
One such development is the use of adaptive behavior models. These allow NPCs to analyze and learn from players decisions in real time. This behavior allows for a much more engaging experience. For example as said by experts in the field, NPCs in modern video games can now react to player actions with increased sophistication, such as adjusting their tactics in combat or changing their dialogue based on past interactions. By using deep learning algorithms these systems emulate human-like decisions-making, thus making NPCs feel more like real people rather than static game elements.
Another advancements in NPC AI is the use of natural language processing, which allows NPCs to engage in more realistic conversations with players. Before this NPC dialogue was limited to a fixed set of responses. It is said that NLP has improved the fluidity of NPC conversations, allowing them to respond more contextually to player inputs. This development has increased the depth and immersion of player-NPC interactions, as players can now engage in more complex dialogues that affect the storyline and gameplay outcomes.
Additionally, deep learning models have allowed NPCs to become more capable of predicting players behaviors. Deep learning allows NPCs to process large amounts of data and adapt to player strategies, making interactions with them less predictable and more varied. This creates a more immersive experience, as NPCs are now able to "learn" from player behavior, which provides a greater sense of realism within the game.
Challenges in NPC development
Despite all of these advancements in NPC AI, there are still significant challenges that developers face in designing NPCs. They need to balance realism, functionally, and players expectations. The key challenge is to make sure that NPCs enhance the players experience, rather than disturb the gameplay. Overly realistic NPCs that behave unpredictably can frustrate players by hindering progression or breaking immersion. Conversely, NPCs that are too predictable or simplistic may fail to engage players, reducing the overall effectiveness of the game's narrative and mechanics.
Another factor that needs to be accounted for is the computation cost of implementing advanced AI for NPCs. The use of these Advanced AI techniques requires large amount of processing power, which can limit its usage. Balancing the performance of AI-driven NPCs with the game's overall technical limitations is crucial for ensuring smooth gameplay. Experts mentioned how developers must allocate resources efficiently to avoid overburdening the game’s systems, particularly in large, open-world games where numerous NPCs must interact with the player simultaneously.
Finally, creating NPCs that can respond dynamically to a wide range of player behaviors remains a difficult task. NPCs must be able to handle both scripted interactions and unscripted scenarios where players may behave in unexpected ways. Designing NPCs capable of adapting to such variability requires complex AI models that can account for numerous possible interactions, which can be resource-intensive and time-consuming for developers.
Cheating AI
In the context of artificial intelligence in video games, cheating refers to the programmer giving agents actions and access to information that would be unavailable to the player in the same situation. Believing that the Atari 8-bit could not compete against a human player, Chris Crawford did not fix a bug in Eastern Front (1941) that benefited the computer-controlled Russian side. Computer Gaming World in 1994 reported that "It is a well-known fact that many AIs 'cheat' (or, at least, 'fudge') in order to be able to keep up with human players".
For example, if the agents want to know if the player is nearby they can either be given complex, human-like sensors (seeing, hearing, etc.), or they can cheat by simply asking the game engine for the player's position. Common variations include giving AIs higher speeds in racing games to catch up to the player or spawning them in advantageous positions in first-person shooters. The use of cheating in AI shows the limitations of the "intelligence" achievable artificially; generally speaking, in games where strategic creativity is important, humans could easily beat the AI after a minimum of trial and error if it were not for this advantage. Cheating is often implemented for performance reasons where in many cases it may be considered acceptable as long as the effect is not obvious to the player. While cheating refers only to privileges given specifically to the AI—it does not include the inhuman swiftness and precision natural to a computer—a player might call the computer's inherent advantages "cheating" if they result in the agent acting unlike a human player. Sid Meier stated that he omitted multiplayer alliances in Civilization because he found that the computer was almost as good as humans in using them, which caused players to think that the computer was cheating. Developers say that most game AIs are honest but they dislike players erroneously complaining about "cheating" AI. In addition, humans use tactics against computers that they would not against other people.
Examples
In the 1996 game Creatures, the user "hatches" small furry animals and teaches them how to behave. These "Norns" can talk, feed themselves, and protect themselves against vicious creatures. It was the first popular application of machine learning in an interactive simulation. Neural networks are used by the creatures to learn what to do. The game is regarded as a breakthrough in artificial life research, which aims to model the behavior of creatures interacting with their environment.
In the 2001 first-person shooter Halo: Combat Evolved the player assumes the role of the Master Chief, battling various aliens on foot or in vehicles. Enemies use cover very wisely, and employ suppressing fire and grenades. The squad situation affects the individuals, so certain enemies flee when their leader dies. Attention is paid to the little details, with enemies notably throwing back grenades or team-members responding to being bothered. The underlying "behavior tree" technology has become very popular in the games industry since Halo 2.
The 2005 psychological horror first-person shooter F.E.A.R. has player characters engage a battalion of cloned super-soldiers, robots and paranormal creatures. The AI uses a planner to generate context-sensitive behaviors, the first time in a mainstream game. This technology is still used as a reference for many studios. The Replicas are capable of utilizing the game environment to their advantage, such as overturning tables and shelves to create cover, opening doors, crashing through windows, or even noticing (and alerting the rest of their comrades to) the player's flashlight. In addition, the AI is also capable of performing flanking maneuvers, using suppressing fire, throwing grenades to flush the player out of cover, and even playing dead. Most of these actions, in particular the flanking, is the result of emergent behavior.
The survival horror series S.T.A.L.K.E.R. (2007–) confronts the player with man-made experiments, military soldiers, and mercenaries known as Stalkers. The various encountered enemies (if the difficulty level is set to its highest) use combat tactics and behaviors such as healing wounded allies, giving orders, out-flanking the player and using weapons with pinpoint accuracy.
The 2010 real-time strategy game StarCraft II: Wings of Liberty gives the player control of one of three factions in a 1v1, 2v2, or 3v3 battle arena. The player must defeat their opponents by destroying all their units and bases. This is accomplished by creating units that are effective at countering opponents' units. Players can play against multiple different levels of AI difficulty ranging from very easy to Cheater 3 (insane). The AI is able to cheat at the difficulty Cheater 1 (vision), where it can see units and bases when a player in the same situation could not. Cheater 2 gives the AI extra resources, while Cheater 3 gives an extensive advantage over its opponent.
Red Dead Redemption 2, released by Rockstar Games in 2018, exemplifies the advanced use of AI in modern video games. The game incorporates a highly detailed AI system that governs the behavior of NPCs and the dynamic game world. NPCs in the game display complex and varied behaviors based on a wide range of factors including their environment, player interactions, and time of day. This level of AI integration creates a rich, immersive experience where characters react to players in a realistic manner, contributing to the game's reputation as one of the most advanced open-world games ever created.
The 2024 browser-based sandbox game Infinite Craft uses generative AI software, including LLaMA. When two elements are being combined, a new element is generated by the AI.
The 2024 browser-based game Oasis uses generative AI to simulate the video game Minecraft. Oasis is trained on millions of hours of footage from Minecraft, and predicts how the next frame of gameplay looks using this dataset. Oasis does not have object permanence because it does not store any data.
Generative artificial intelligence in video games
Generative artificial intelligence, AI system that can response to prompts and produce text, images, and audio and video clips, arose in 2023 with systems like ChatGPT and Stable Diffusion. In video games, these systems could create the potential for game assets to be created indefinitely, bypassing typical limitations on human creations. However, there are similar concerns in other fields particularly the potential for loss of jobs normally dedicated to the creation of these assets.
In January 2024, SAG-AFTRA, a United States union representing actors, signed a contract with Replica Studios that would allow Replica to capture the voicework of union actors for creating AI voice systems based on their voices for use in video games, with the contract assuring pay and rights protections. While the contract was agreed upon by a SAG-AFTRA committee, many members expressed criticism of the move, having not been told of it until it was completed and that the deal did not do enough to protect the actors.
Advancements in AI
Recent advancements in AI for video games have led to more complex and adaptive behaviors in non-playable characters (NPCs). For instance, AI systems now utilize sophisticated techniques such as decision trees and state machines to enhance NPC interactions and realism, as discussed in "Artificial Intelligence in Games". Recent advancements in AI for video games have also focused on improving dynamic and adaptive behaviors in NPCs. For example, recent research has explored the use of complex neural networks to enable NPCs to learn and adapt their behavior based on player actions, enhancing the overall gaming experience. This approach is detailed in the IEEE paper on "AI Techniques for Interactive Game Systems".
See also
Utility system – robust technique for decision making in video games
Kynapse – game AI middleware, specializing in path finding and spatial reasoning
AiLive – suite of game AI middleware
Artificial intelligence in architecture
xaitment – graphical game AI software
Lists
List of emerging technologies
List of game AI middleware
Outline of artificial intelligence
References
Bibliography
Bogost, Ian (2017). "'Artificial Intelligence' Has Become Meaningless."
Bourg; Seemann (2004). AI for Game Developers. O'Reilly & Associates. .
Buckland (2002). AI Techniques for Game Programming. Muska & Lipman. .
Buckland (2004). Programming Game AI By Example. Wordware Publishing. .
Champandard (2003). AI Game Development. New Riders. .
Eaton, Eric et al. (2015). "Who speaks for AI?"
Funge (1999). AI for Animation and Games: A Cognitive Modeling Approach. A K Peters. .
Funge (2004). Artificial Intelligence for Computer Games: An Introduction. A K Peters. .
Kaplan, Jerry (2017). "AI's PR Problem."
Millington (2005). Artificial Intelligence for Games . Morgan Kaufmann. .
Schwab (2004). AI Game Engine Programming. Charles River Media. .
Smed and Hakonen (2006). Algorithms and Networking for Computer Games. John Wiley & Sons. .
External links
Special Interest Group on Artificial Intelligence @IGDA
AI Game Programming Wisdom on aiwisdom.com
Georgios N. Yannakakis and Julian Togelius
Video game development | Artificial intelligence in video games | Mathematics | 7,063 |
71,739,917 | https://en.wikipedia.org/wiki/Monocyte%20monolayer%20assay | The monocyte monolayer assay (MMA) is used to determine the clinical significance of alloantibodies produced by blood transfusion recipients. The assay is used to assess the potential for intravascular hemolysis when incompatible cellular blood products are transfused to the anemic patient. When donor cells possess substances that are not produced by the recipient, the recipient's immune system produces antibodies against the substance; these are called alloantibodies. Specific white blood cells, called monocytes, are tasked with ingesting foreign material and become activated during certain inflammatory events. These activated monocytes come in contact with antibody-sensitized red blood cells (RBC) and may or may not exhibit phagocytosis (ingestion) and destroy the donor red blood cells. If monocytes destroy the RBC, the antibody attached to those RBC is considered clinically significant.
Background
Blood banking
Blood banking is a concentration within a clinical laboratory that analyzes specimens from potential transfusion recipients and provides compatible blood products to the healthcare team in charge of that patient's care. Several routine tests are performed including blood typing (determination of ABO/Rh status), antibody screening, serologic cross-matching, direct antiglobulin testing, and antibody identification. Beyond the presence of naturally occurring antibodies (isohemagglutinins) to the ABO and Rh(D) blood group antigens, additional immune-stimulated antibodies are considered unexpected alloantibodies.
The identification of unexpected antibodies is a labor-intensive process, and sometimes requires the addition of special laboratory techniques to aid in the proper identification of the antibody. Among these techniques are elutions, adsorptions, and enzyme treatment. Some patients produce antibodies to high frequency antigens. That is, the red cell antigens are present in a significant portion of the human population. It may be questionable and very difficult to assess if the antibody is considered clinically significant or not. A clinically significant antibody is an antibody that is capable of causing in vitro hemolysis or a decreased survival of transfused donor red blood cells. Antibodies to high frequency antigens can be assessed for clinical significance using the monocyte monolayer assay.
Hemolytic transfusion reaction
There are many different varieties of abnormal reactions to blood transfusion. Among these, a potentially life-threatening reaction is known as a hemolytic transfusion reaction. This is an immune mediated reaction where recipient antibodies attack donor red blood cell antigen(s), causing hemolysis of donor cells. The reaction may occur during, immediately after, or up to 28 days later. An acute reaction is observed within the first 24 hours, whereas a delayed reaction will be observed between 24 hours and 28 days after transfusion.
Alloantibody formation and clinical significance
When talking about the ABO blood group system, Landsteiner's Law states that if an individual possesses the A and/or B antigen, they will not form antibodies to these antigens. However, if an individual does not have either A or B antigens, they will naturally produce anti-A and anti-B antibodies. According to the International Society of Blood Transfusion (ISBT), 43 blood group systems containing hundreds of different red blood cell antigens have been described. With some exceptions, many non-ABO blood group system antigens require a sensitizing event to stimulate antibody production. In other words, the immune system must be exposed to the antigen in order to illicit antibody production. Exposure to antigens can occur through blood transfusion, stem cell/bone marrow transplant, and pregnancy.
The clinical significance of an alloantibody depends on its ability to cause a decrease in donor red blood cell survival. Characteristics of clinically significant alloantibodies include: immunoglobulin G antibody subclass, reactivity at body temperature, and ability to cause red blood cell agglutination in the presence of anti-human globulin (AHG) in an indirect antiglobulin test. Sometimes, clinical significance of an antibody can be difficult to determine. Antibodies to high prevalence red cell antigens can sometimes mask the detection of clinically significant alloantibodies because the corresponding antigen is present on most, if not all, of the screening red blood cells used to detect these antibodies possess the antigen. This is where the monocyte monolayer assay may be useful.
Principle
The MMA is a very labor-intensive, manual laboratory testing method. The following steps are performed in this assay:
Anticoagulated blood is collected from normal, healthy individuals. Acid citrate dextrose is preferred.
Peripheral blood mononuclear cells (PBMC) are harvested from the blood sample using a Ficoll-Paque® density gradient.
The PBMC's are washed using a phosphate-buffered saline (PBS) and then suspended in tissue culture media in order to keep the monocytes viable.
The PBMC-media mixture is then added to a tissue culture chamber slide. Monocytes will adhere to the glass slide forming a monocyte monolayer.
Serum is mixed and incubated at body temperature (37°C) with a 5% group O RBC suspension. (This step sensitizes or coats RBC with antibody)
The sensitized RBC's are washed with PBS to remove any unbound antibody or interfering substances.
The washed, sensitized RBC are then added to the monocyte monolayer tissue culture chamber slide.
After a 60-minute, 37°C incubation, the supernatant is removed from the chamber slides and rinsed with PBS.
Once the slide is completely dry, it is stained with a Wrights-Giemsa stain.
At least 600 (200 if positivity is greater than 20%) monocytes are observed under the microscope for evidence of RBC phagocytosis.
A positive and negative control is also performed in tandem with the patient specimen for quality assurance.
Interpretation
If the positive or negative controls fail, than the entire testing procedure is invalid and must be repeated. Criteria for a positive MMA will vary by laboratory, though the originally established threshold set by Sandra Nance et al., is >20% phagocytic activity observed.
Clinically, a positive MMA would indicate that the patient's serum used in the assay contains clinically significant antibodies that are capable of causing antibody-mediated phagocytosis.
See also
Acute hemolytic transfusion reaction
Antibody opsonization
Alloantibodies
References
Transfusion medicine
Blood tests | Monocyte monolayer assay | Chemistry | 1,353 |
5,688,857 | https://en.wikipedia.org/wiki/Mothers%20against%20decapentaplegic%20homolog%209 | Mothers against decapentaplegic homolog 9 also known as SMAD9, SMAD8, and MADH6 is a protein that in humans is encoded by the SMAD9 gene.
SMAD9, as its name describes, is a homolog of the Drosophila gene: "Mothers against decapentaplegic". It belongs to the SMAD family of proteins, which belong to the TGFβ superfamily of modulators. Like many other TGFβ family members, SMAD9 is involved in cell signalling. When a bone morphogenetic protein binds to a receptor (BMP type 1 receptor kinase) it causes SMAD9 to interact with SMAD anchor for receptor activation (SARA).The binding of ligands causes the phosphorylation of the SMAD9 protein and the dissociation from SARA and the association with SMAD4. It is subsequently transferred to the nucleus where it forms complexes with other proteins and acts as a transcription factor. SMAD9 is a receptor regulated SMAD (R-SMAD) and is activated by bone morphogenetic protein type 1 receptor kinase. There are two isoforms of the protein. Confusingly, it is also sometimes referred to as SMAD8 in the literature.
Nomenclature
The SMAD proteins are homologs of both the drosophila protein, mothers against decapentaplegic (MAD) and the C. elegans protein SMA. The name is a combination of the two. During Drosophila research, it was found that a mutation in the gene, MAD, in the mother, repressed the gene, decapentaplegic, in the embryo. The phrase "Mothers against" was added since mothers often form organizations opposing various issues e.g. Mothers Against Drunk Driving or (MADD); and based on a tradition of such unusual naming within the gene research community.
References
Developmental genes and proteins
MH1 domain
MH2 domain
R-SMAD
Transcription factors
Human proteins | Mothers against decapentaplegic homolog 9 | Chemistry,Biology | 411 |
38,908,542 | https://en.wikipedia.org/wiki/.223%20Wylde%20chamber | A .223 Wylde chamber is a wildcat rifle chamber designed to accurize the 5.56×45mm NATO chamber for NRA High Power competition.
Background
In 1957, during research into the development of a military .22 caliber rifle, the .222 Remington Special was created by a joint effort of Fairchild Industries, Remington Arms, and U.S. Continental Army Command. Based on the .222 Remington, and with several other .222 caliber cartridges under development for civilian rifles at the same time, the .222 Remington Special was renamed .223 Remington. In 1963 it was adopted as the standard intermediate cartridge for the United States Army, as the M193 Cartridge.
In 1972, Fabrique Nationale (FN) created a new type of service ammunition for NATO. 5.56×45mm NATO was based on the .223 Remington cartridge being used by the U.S. Army but had greater range and effectiveness. The first iteration of this ammunition was designated SS109 in NATO countries, and later adopted in the U.S. as the M855.
Chamber dimensions
Bill Wylde of Greenup, Illinois, compared the two cartridges and changed the chamber of the rifle's barrel to a specification he called the .223 Wylde chamber. The chamber is made with the external dimensions and leade angle found in the military 5.56×45mm NATO cartridge and the freebore diameter found in the civilian SAAMI.
The .223 Wylde chamber is used by rifle manufacturers who sell "National Match" configuration AR-15 rifles, barrels and upper receivers.
Comparison
The major dimensional difference between the chambers that fire the .223 Remington and the 5.56×45mm NATO is the longer and larger-diameter "freebore" in the 5.56 chamber ( vs length, vs diameter). Freebore is a short and smooth section of the barrel that is located after the case mouth, located before the start of the rifling "grooves and lands", also often referred to as leade.
See also
5 mm caliber
Southern Cross Small Arms Taipan
References
External links
Brownells Tech Tip: AR-15 5.56/.223/.223 Wylde
Chamber Choices ('Guns Magazine')
5.56×45mm NATO
Bullets
Firearm components | .223 Wylde chamber | Technology | 470 |
28,094,935 | https://en.wikipedia.org/wiki/First-pass%20yield | First-pass yield (FPY), also known as throughput yield (TPY), is defined as the number of units coming out of a process divided by the number of units going into that process over a specified period of time.
Example
Consider the following:
You have a process that is divided into four sub-processes: A, B, C and D. Assume that you have 100 units entering process A. To calculate first time yield (FTY) you would:
Calculate the yield (number out of step/number into step) of each step.
Multiply these together.
For example:
(# units leaving the process as good parts) / (# units put into the process) = FTY
100 units enter A and 90 leave as good parts. The FTY for process A is 90/100 = 0.9000
90 units go into B and 80 leave as good parts. The FTY for process B is 80/90 = 0.8889
80 units go into C and 75 leave as good parts. The FTY for C is 75/80 = 0.9375
75 units go into D and 70 leave as good parts. The FTY for D is 70/75 = 0.9333
The total first time yield is equal to FTYofA * FTYofB * FTYofC * FTYofD or 0.9000 * 0.8889 * 0.9375 * 0.9333 = 0.7000.
You can also get the total process yield for the entire process by simply dividing the number of good units produced by the number going into the start of the process. In this case, 70/100 = 0.70 or 70% yield.
The same example using first pass yield (FPY) would take into account rework:
(# units leaving process A as good parts with no rework) / (# units put into the process)
100 units enter process A, 5 were reworked, and 90 leave as good parts. The FPY for process A is (90-5)/100 = 85/100 = 0.8500
90 units go into process B, 0 are reworked, and 80 leave as good parts. The FPY for process B is (80-0)/90 = 80/90 = 0.8889
80 units go into process C, 10 are reworked, and 75 leave as good parts. The FPY for process C is (75-10)/80 = 65/80 = 0.8125
75 units go into process D, 8 are reworked, and 70 leave as good parts. The FPY for process D is (70-8)/75 = 62/75 = 0.8267
First pass yield is only used for an individual sub-process. Multiplying the set of processes would give you Rolling throughput yield (RTY). RTY is equal to FPYofA * FPYofB * FPYofC * FPYofD = 0.8500 * 0.8889 * 0.8125 * 0.8267 = 0.5075
Notice that the number of units going into each next process does not change from the original example, as that number of good units did, indeed, enter the next process. Yet the number of FPY units of each process counts only those that made it through the process as good parts that needed no rework to be good parts. The calculation of RTY, rolling throughput yield, shows how good the overall set of processes is at producing good overall output without having to rework units.
See also
Rolled throughput yield
Six Sigma
Statistical quality control
Quality management
References
Business terms
Statistical process control
Production planning
Six Sigma | First-pass yield | Engineering | 761 |
36,942,597 | https://en.wikipedia.org/wiki/9%20Cephei | 9 Cephei (9 Cep), also known as V337 Cephei, is a variable star in the constellation Cepheus. It is visible to the naked eye.
In 1967, Graham Hill announced his discovery that 9 Cephei is a variable star. 9 Cephei was given the name V337 Cephei and classified as an α Cygni variable in 1979. It varies irregularly between magnitude 4.69 and 4.78. A study of the Hipparcos satellite photometry showed an amplitude of 0.56 magnitudes, but could find no periodicity.
9 Cephei is considered to be a member of the Cepheus OB2 stellar association, a scattering of massive bright stars around a thousand parsecs away in the southern part of the constellation Cepheus.
Calculations of the physical properties of 9 Cephei vary considerably even from broadly similar observational data. Modelling using the non-LTE line-blanketed CMFGEN atmospheric code gives a temperature of 18,000 K, radius of , luminosity of , and mass of . Calculations using the FASTWIND model give gives a temperature of 19,200 K, radius of , luminosity of , and mass of .
References
Cepheus (constellation)
B-type supergiants
Cephei, 09
Alpha Cygni variables
106801
Cephei, V337
8279
206165
BD+61 2169
J21375521+6204548
IRAS catalogue objects | 9 Cephei | Astronomy | 307 |
74,578,936 | https://en.wikipedia.org/wiki/Sodium%20ammonium%20tartrate | Sodium ammonium tartrate (NAT) is an organic compound with the formula . The salt is derived from tartaric acid by neutralizing with ammonia and with sodium hydroxide. Louis Pasteur obtained enantiopure crystals of the tetrahydrate of NAT, via the process of spontaneous resolution. His discovery led to increased study of optical activity, which eventually was shown to have broad implications. Many modifications of this salt have been investigated by X-ray crystallography, including the racemate, which crystallizes as the monohydrate.
Related compounds
, known as Rochelle salt, was the first ferroelectric material discovered.
References
Organic sodium salts
Ferroelectric materials
Tartrates
Double salts
Ammonium compounds | Sodium ammonium tartrate | Physics,Chemistry,Materials_science | 152 |
36,778,368 | https://en.wikipedia.org/wiki/HD%20202951 | HD 202951 is a probable binary star system located in the northern constellation of Equuleus. It is near the lower limit of visibility to the naked eye, having an apparent visual magnitude of 5.97. The distance to this system can be estimated from the annual parallax shift of , yielding a value of roughly 1,190 light years. It is moving closer with a heliocentric radial velocity of −37 km/s.
Griffin (2012) found this to be a single-lined spectroscopic binary system with an orbital period of and an eccentricity of 0.23. The a sin i value for the primary component is , where a is the semimajor axis and i is the (unknown) orbital inclination. This value provides a lower bound for the actual semimajor axis.
The visible component is an evolved K-type giant star with a stellar classification of K5 III. It is a candidate variable star of unknown type, showing an amplitude variation of 0.0115 magnitude with a frequency of 0.47645 times per day, or one cycle per 2.1 days. X-ray emission has been detected from this system.
References
K-type giants
Durchmusterung objects
Equuleus
202951
0105224
8149
Spectroscopic binaries | HD 202951 | Astronomy | 270 |
432,459 | https://en.wikipedia.org/wiki/Bullying | Bullying is the use of force, coercion, hurtful teasing, comments, or threats, in order to abuse, aggressively dominate, or intimidate one or more others. The behavior is often repeated and habitual. One essential prerequisite is the perception (by the bully or by others) that an imbalance of physical or social power exists or is currently present. This perceived presence of physical or social imbalance is what distinguishes the behavior from being interpreted or perceived as bullying from instead being interpreted or perceived as conflict. Bullying is a subcategory of aggressive behavior characterized by hostile intent, the goal (whether consciously or subconsciously) of addressing or attempting to "fix" the imbalance of power, as well as repetition over a period of time.
Bullying can be performed individually or by a group, typically referred to as mobbing, in which the bully may have one or more followers who are willing to assist the primary bully or who reinforce the bully's behavior by providing positive feedback such as laughing. Bullying in school and in the workplace is also referred to as "peer abuse". Robert W. Fuller has analyzed bullying in the context of rankism. The Swedish-Norwegian researcher Dan Olweus stated that bullying occurs when a person is "exposed, repeatedly and over time, to negative actions on the part of one or more other persons", and that negative actions occur "when a person intentionally inflicts injury or discomfort upon another person, through physical contact, through words or in other ways". Individual bullying is usually characterized by a person using coercive, intimidating, or hurtful words or comments, exerting threatening or intimidating behavior, or using harmful physical force in order to gain power over another person.
A bullying culture can develop in any context in which humans regularly interact with one another. This may include settings such as within a school, family, or the workplace, the home, and within neighborhoods. When bullying occurs in college and university settings, the practice is known as ragging in certain countries, especially those of the Indian subcontinent. The main platform for bullying in contemporary culture involves the use of social media websites. In a 2012 study of male adolescent American football players, "the strongest predictor [of bullying] was the perception of whether the most influential male in a player's life would approve of the bullying behavior." A study by The Lancet Child & Adolescent Health medical journal in 2019 showed a relationship between social media use by girls and an increase in their exposure to bullying.
Bullying may be defined in many different ways. In the United Kingdom, there is no legal definition of the term "bullying", while some states in the United States currently have laws specifically against it. Bullying is divided into four basic types of abuse: psychological (sometimes referred to as "emotional" or "relational"), verbal, physical, and cyber (or "electronic"), though an encounter can fall into more than one of these categories.
Behaviors used to assert such domination may include physical assault or coercion, verbal harassment, or the use of threats, and such acts may be directed repeatedly toward particular targets. Rationalizations of such behavior sometimes include differences of social class, race, religion, gender, sexual orientation, appearance, behavior, body language, personality, reputation, lineage, strength, size, or ability.
Etymology
The word "bully" was first used in the 1530s, meaning "sweetheart", applied to either sex, from the , "lover, brother", probably diminutive of , "brother", of uncertain origin (compare with the German word buhle "lover"). The meaning deteriorated through the 17th century through "fine fellow", "blusterer", to "harasser of the weak". This may have been as a connecting sense between "lover" and "ruffian" as in "protector of a prostitute", which was one sense of "bully" (though not specifically attested until 1706). The verb "to bully" was first attested in 1710.
In the past, in the American culture, the term has been used as an exclamation and exhortation. The term has been especially known famously in association with Theodore Roosevelt. In 1907, Roosevelt coined the phrase as a deprecating term, "bully for him". Currently, in the present day, the bully pulpit refers to the use of a high position to influence the general public's thoughts and to initiate changes. The term "bully" has been significantly modified through the years, and through language translations, it has shifted from terms of endearment to a form of sarcastic jesting, and then to one or more actions made against others, as well as behavior or activity to be fearful of.
Types
Bullying has been classified by the body of literature into different types. These can be in the form of nonverbal, verbal, or physical behavior. Another classification is based on the perpetrators or the participants involved, so that the types include individual and collective bullying. Other interpretation also cite emotional and relational bullying in addition to physical harm inflicted towards another person or even property.
This is present in extreme forms of bullying, such as hate crimes. A hate crime is when a perpetrator harms a victim because they perceive them to be a member of an outgroup that they are biased against. Perpetrators often harm victims that are perceived as belonging to a group based on their race, ethnicity, skin color, religion, nationality, gender, gender identity, sexual orientation, and or disability. Both bullying and hate crimes involve the devaluing and disrespecting of another person for what is deemed or determined by the perpetrator to be justified reasons. Yet, not all bullying is considered to be a hate crime. Bullies often select their victims because of specific characteristics that the bully views as nonconforming to their specific requirements or sense of belonging. This means that individuals in minority groups are more likely to be targeted. However, bullies usually choose victims that are more available and or vulnerable. This is a more broad approach or motivation than with the engagement of hate crimes.
There are also cases being researched now and in the more recent years regarding the phenomenon called "cyberbullying", which takes place in the virtual or electronic world, typically over the internet. Physical, verbal, and relational bullying are most prevalent in primary school and could also begin much earlier while continuing into later stages of individual's lives. The cases of cyberbullying usually start in early adolescence, when the possession, ownership, or occurrence of cellular or mobile devices are more common.
Individual
Individual bullying tactics are perpetrated by a single person against one or more victims. Individual bullying can be classified into four types.
Physical
Physical bullying is any bullying that physically harms someone's body or damages their possessions. Stealing, shoving, hitting, fighting, pantsing, and intentionally destroying someone's property are examples of physical bullying. Physical bullying is rarely the first form of bullying that a victim will experience. Often, bullying will begin in a different form and later progress to physical violence. In physical bullying, the main weapon the bully uses is their body, or some part thereof; or an object as a weapon when attacking their victim. Sometimes groups of young adults will target and alienate a peer because of some adolescent prejudice. This can quickly lead to a situation where they are being taunted, tortured, and "beaten up" by their classmates. Physical bullying will often escalate over time, and can lead to a detrimental or fatal ending, and therefore many try to stop it quickly when such cases are reported or observed in order to prevent any further escalation.
Verbal
Verbal bullying is one of the most common types of bullying. This is any bullying that is conducted by speaking, other use of the voice, or some form of body language, and does not involve any form of physical contact. Bullying usually begins at this stage and includes any of the following:
Derogatory name-calling and nicknaming
Spreading rumors or lying about someone
Making threats or engaging in threatening behavior toward someone
Yelling at or talking to someone in a rude or unkind tone of voice, especially without justifiable cause
Mocking someone's voice or style of speaking
Laughing at someone
Use of body language (i.e., the middle finger) to torment someone
Making insults or otherwise making fun of someone
In verbal bullying, the main weapon the bully uses is their voice. In many cases, verbal bullying is common in both genders. However, girls are more likely to perform this type of bullying compared to boys. Girls, in general, are also more subtle with insults than boys. Girls use verbal bullying, as well as social exclusion techniques, to dominate and control other individuals and show their superiority and power, often to try to impress someone they idolize. Many boys are subtle enough to use verbal techniques for dominance, and often exhibit this type of bullying when they want to avoid the trouble or possible consequences that can come with physically bullying someone else.
Relational
Relational bullying (sometimes referred to as social aggression) is the type of bullying that uses relationships to hurt others. The term also denotes any bullying that is done with the intent to hurt somebody's reputation or social standing which can also link in with the techniques included in physical and verbal bullying. Relational bullying is a form of bullying common among youth, but more particularly upon girls. Social exclusion (slighting or making someone feel "left out") is one of the most common types of relational bullying. Relational bullying can be used as a tool by bullies to both improve their social standing and in order to control others. Unlike physical bullying, which is obvious, relational bullying is not overt and can continue for a long time without being noticed.
Cyber
Cyberbullying involves the use of technology (typically the internet) in order to harass, threaten, embarrass, or target another person. When an adult is involved, it may meet the definition of cyber-harassment or cyberstalking, a crime that can have legal consequences and possibly involve penalties such as jail time when cases are reported and the perpetrators are legally prosecuted. This includes bullying by use of email, instant messaging, social media websites (such as Facebook), text messages, and phone calls from cell phones or mobile devices. It is stated that Cyberbullying is more common in secondary school than in primary school.
The internet provides people with limited accountability and often with no filter. Bullying can feel easier and less restrictive through the use of the internet. This phenomenon is described and detailed in a principle (or effect), called "the online disinhibition effect". The use of technology for purposes of bullying can be detrimental to someone's online reputation. The information published online will often remain there indefinitely, unless it is taken down or removed by the person who published it, or by moderators of the website or platform, or (if allowed) by other users. Future employers and other people with access to the internet will be able to see others' digital footprint and how individuals behaved or treated other people - especially if concerted efforts are allocated in order to search for and find any posts, webpages, or content that may negatively impact the target person's evaluation or eligibility for a position. Another problem with cyberbullying is the possibility that other people are able to get involved. Technology, especially the use of social media, allows others to repost or share published content, whether it is positive or negative.
Collective
Collective bullying tactics are employed by more than one individual against one or more victims. Collective bullying is known as "mobbing", and can include any of the individual types of bullying. Trolling behavior on social media, although generally assumed to be individual in nature by casual readers, is sometimes a result of organized efforts made by sponsored astroturfers.
Mobbing
Mobbing refers to the bullying of an individual by a group, in any context, such as a family, peer group, school, workplace, neighborhood, community, or online. When it occurs as emotional abuse in the workplace, such as "ganging up" by co-workers, subordinates or superiors, to force someone out of the workplace through rumor, innuendo, intimidation, humiliation, discrediting, and isolation, it is also referred to as malicious, nonsexual, nonracial/racial, general harassment.
Characteristics
Bullies and accomplices
Studies have shown that envy and resentment may be motives for bullying. Research on the self-esteem of bullies has produced equivocal results. While some bullies are arrogant and narcissistic, they can also use bullying as a tool to conceal shame or anxiety or to boost self-esteem: by demeaning others, the abuser feels empowered. Bullies may bully out of jealousy or because they themselves are bullied. Psychologist Roy Baumeister asserts that people who are prone to abusive behavior tend to have inflated but fragile egos. Because they think too highly of themselves, they are frequently offended by the criticisms and lack of deference of other people, and react to this disrespect with violence and insults.
Researchers have identified other risk factors such as depression and personality disorders, as well as quickness to anger and use of force, addiction to aggressive behaviors, mistaking others' actions as hostile, concern with preserving self-image, and engaging in obsessive or rigid actions. A combination of these factors may also be causes of this behavior. In one study of youth, a combination of antisocial traits and depression was found to be the best predictor of youth violence, whereas video game violence and television violence exposure were not predictive of these behaviors.
Bullying may also result from a genetic predisposition or a brain abnormality in the bully. While parents can help a toddler develop emotional regulation and control to restrict aggressive behavior, some children fail to develop these skills due to insecure attachment with their families, ineffective discipline, and environmental factors such as a stressful home life and hostile siblings. Moreover, according to some researchers, bullies may be inclined toward negativity and perform poorly academically. Dr. Cook says, "A typical bully has trouble resolving problems with others and also has trouble academically. He or she usually has negative attitudes and beliefs about others, feels negatively toward himself/herself, comes from a family environment characterized by conflict and poor parenting, perceives school as negative and is negatively influenced by peers."
Contrarily, some researchers have suggested that some bullies are psychologically strongest and have high social standing among their peers, while their targets are emotionally distressed and socially marginalized. Peer groups often promote the bully's actions, and members of these peer groups also engage in behaviors, such as mocking, excluding, punching, and insulting one another as a source of entertainment. Other researchers also argued that a minority of the bullies, those who are not in-turn bullied, enjoy going to school, and are least likely to take days off sick.
Research indicates that adults who bully have authoritarian personalities, combined with a strong need to control or dominate. It has also been suggested that a prejudicial view of subordinates can be a particularly strong risk factor.
In a recent study, bullies showed lower school performance-related self-esteem than non-involved students. They also showed higher social self-esteem than victims of traditional bullying.
Brain studies have shown that the section of the brain associated with reward becomes active when bullies are shown a video of someone inflicting pain on another.
Bystanders
Often, bullying takes place in the presence of a large group of relatively uninvolved bystanders. In many cases, it is the bully's ability to create the illusion they have the support of the majority present that instills the fear of "speaking out" in protestation of the bullying activities being observed by the group. Unless the "bully mentality" is effectively challenged in any given group in its early stages, it often becomes an accepted, or supported, norm within the group.
Unless action is taken, a "culture of bullying" is often perpetuated within a group for months, years, or longer.
Bystanders who have been able to establish their own "friendship group" or "support group" have been found to be far more likely to opt to speak out against bullying behavior than those who have not.
In addition to communication of clear expectations that bystanders should intervene and increasing individual self-efficacy, there is growing research to suggest interventions should build on the foundation that bullying is morally wrong.
Among adults, being a bystander to workplace bullying was linked to depression.
The Bystander effect can be detrimental to the person being bullied. People are less likely to stand up for someone or something when others are around. In the case of cyberbullying, people that see bullying happen on social media are less likely to say something back, whether online or in person. People can have good intentions and want to help, but with no action, nothing will be accomplished. "The act of others stepping in is what will stop bullying". To stop the Bystander effect, people should be confident and stand up for what they believe in. Do not worry what people think of you, rather think of what the benefits can be for the person being bullied.
Victims
Dr. Cook says, "A typical victim is likely to be aggressive, lack social skills, think negative thoughts, experience difficulties in solving social problems, come from a negative family, school and community environments and be noticeably rejected and isolated by peers." Victims often have characteristics such as being physically and mentally weak, as well as being easily distraught emotionally. They may also have physical characteristics that make them easier targets for bullies such as being overweight or having some type of physical deformity. Boys are more likely to be victims of physical bullying while girls are more likely to be bullied indirectly.
Low levels of self-esteem has been identified as a frequent antecedent of bullying victimization. Victims of traditional bullying tend to have lower global, social, body-related, and emotional self-esteem compared to uninvolved students.
Victims of cyberbullying, on the other hand, may not have lower self-esteem scores than uninvolved students but might have higher body-related self-esteem than both victims of traditional bullying and bullies.
It has also been shown that victims are more likely to employ self-defeating or self-deprecating humor intended to entertain others at the expense of themselves and their own feelings.
The results of a meta-analysis conducted by Cook and published by the American Psychological Association in 2010 concluded the main risk factors for children and adolescents being bullied, and also for becoming bullies, are the lack of social problem-solving skills.
Children who are bullied often show physical or emotional signs, such as: being afraid to attend school, complaining of headaches or a loss of appetite, a lack of interest in school activities, or in spending time with friends or family, reluctance to go out in public for fear they may encounter their bullies in public places other than school, and having an overall sense of sadness.
Effects
Mona O'Moore of the Anti-Bullying Centre at Trinity College in Dublin, has written, "There is a growing body of research which indicates that individuals, whether child or adult, who are persistently subjected to abusive behavior are at risk of stress related illness which can sometimes lead to suicide."
Those who have been the targets of bullying can develop long-term emotional and behavioral problems. Bullying can cause loneliness, depression, anxiety, lead to low self-esteem and increased susceptibility to illness. Bullying has also been shown to cause maladjustment in young children, and targets of bullying who were also bullies themselves exhibit even greater social difficulties. A mental health report also found that bullying was linked to eating disorders, anxiety, body dysmorphia and other negative psychological effects. Both victims and perpetrators have been shown to exhibit higher levels of loneliness.
Suicide
Even though there is evidence that bullying increases the risk of suicide, bullying alone does not cause suicide. Depression is one of the main reasons why kids who are bullied die by suicide. It is estimated that between 15 and 25 children die by suicide every year in the UK alone because they are being bullied. Certain groups seem to incur a higher risk for suicide, such as Native Americans, Alaskan Natives, Asian Americans, and LGBT people. When someone feels unsupported by family or friends, it can make the situation much worse for the victim.
In a self-report study completed in New York by 9th through 12th graders, victims of bullying reported more depressive symptoms and psychological distress than those who did not experience bullying. All types of involvement in bullying among both boys and girls is associated with depression even a couple years later. Another study that followed up with Finnish teens two years after the initial survey showed that depression and suicidal ideation is higher with teens who are bullied than those who did not report experiencing bullying. A Dutch longitudinal study on elementary students reported that boys who are bully-victims, who play both roles of a victim and a bully, were more likely to experience depression or serious suicidal ideation than the other roles, victims or bullies only, while girls who have any involvement in bullying have a higher level of risk for depression. In a study of high school students completed in Boston, students who self reported being victims of bullying were more likely to consider suicide when compared to youth who did not report being bullied. The same study also showed a higher risk of suicidal consideration in youth who report being a perpetrator, victim, or victim-perpetrator. Victims and victim-bullies are associated with a higher risk of suicide attempts. The place where youth live also appears to differentiate their bullying experiences such that those living in more urban areas who reported both being bullied and bullying others appear to show higher risk of suicidal ideation and suicide attempts. A national survey given to American 6th through 10th grade students found that cyberbullying victims experience a higher level of depression than victims experiencing other forms of bullying. This can be related to the anonymity behind social media. If a teen is being bullied and is displaying symptoms of depression it should be questioned and interventions should be implemented. The Danish study showed that kids who are bullied talked to their parents and teachers about it and some reported a decrease in bullying or a stop in the bullying after a teacher or parent intervened. The study emphasizes the importance of implementing program-collaborations in schools to have programs and anti-bullying interventions in place to prevent and properly intervene when it occurs. The study also shows the importance of having parents and teachers talk to the bullies about their bullying behavior in order to provide the necessary support for those experiencing bullying.
While some people find it very easy to ignore a bully, others may find it very difficult and reach a breaking point. There have been cases of apparent bullying suicides that have been reported closely by the media. These include the deaths of Ryan Halligan, Phoebe Prince, Dawn-Marie Wesley, Nicola Ann Raphael, Megan Meier, Audrie Pott, Tyler Clementi, Jamey Rodemeyer, Kenneth Weishuhn, Jadin Bell, Kelly Yeomans, Rehtaeh Parsons, Amanda Todd, Brodie Panlock, Jessica Haffer, Hamed Nastoh, Sladjana Vidovic, April Himes, Cherice Moralez and Rebecca Ann Sedwick. According to the suicide awareness voices for education, suicide is one of the leading causes of death for youth from 15 to 24 years old. Over 16 percent of students seriously consider suicide, 13 percent create a plan, and 8 percent have made a serious attempt.
Strength and wisdom
Some have argued that bullying can teach life lessons and instill strength. Helene Guldberg, a child development academic, sparked controversy when she argued that being a target of bullying can teach a child "how to manage disputes and boost their ability to interact with others", and that teachers should not intervene but leave children to respond to the bullying themselves. Others, however, have pointed out that this is only true for normal peer conflicts but not for bullying cases.
The teaching of anti-bullying coping skills to children, carers and teachers has been found to be an effective long-term means of reducing bullying incidence rates and a valuable skill-set for individuals.
Testosterone production
Statistically controlling for age and pubertal status, results indicated that on average verbally bullied girls produced less testosterone, and verbally bullied boys produced more testosterone than their nonbullied counterparts.
Dark triad
Research on the dark triad (narcissism, Machiavellianism, and psychopathy) indicate a correlation with bullying as part of evidence of the aversive nature of those traits.
Studies have shown that bullying behavior is positively correlated with Dark Triad traits. Out of the three traits of the Dark Triad, psychopathy is most strongly correlated to bullying. It is posited that this is because aggression related to psychopathy is more likely to be unprovoked than Machiavellianism and narcissism. This holds true in traditional bullying as well as with cyberbullying. Psychopathy has the strongest correlations, followed by Machiavellianism, and narcissism. Although the lower of the three, narcissism is still correlated, being more prevalent in types of indirect bullying than physical bullying.
Projection
A bully may project their own feelings of vulnerability onto the target(s) of the bullying activity. Despite the fact that a bully's typically denigrating activities are aimed at the bully's targets, the true source of such negativity is ultimately almost always found in the bully's own sense of personal insecurity and/or vulnerability. Such aggressive projections of displaced negative emotions can occur anywhere from the micro-level of interpersonal relationships, all the way up through to the macro-level of international politics, or even international armed conflict.
Emotional intelligence
Bullying is abusive social interaction between peers which can include aggression, harassment, and violence. Bullying is typically repetitive and enacted by those who are in a position of power over the victim. A growing body of research illustrates a significant relationship between bullying and emotional intelligence (EI). Mayer et al., (2008) defines the dimensions of overall EI as "accurately perceiving emotion, using emotions to facilitate thought, understanding emotion, and managing emotion". The concept combines emotional and intellectual processes. Lower emotional intelligence appears to be related to involvement in bullying, as the bully and/or the victim of bullying. EI seems to play an important role in both bullying behavior and victimization in bullying; given that EI is illustrated to be malleable, EI education could greatly improve bullying prevention and intervention initiatives.
Context
Internet
Cyberbullying is any bullying done through the use of technology. This form of bullying can easily go undetected because of lack of authoritative (including parental) supervision. Because bullies can pose as someone else, it is the most anonymous form of bullying. Cyberbullying includes abuse using email, instant messaging, text messaging, websites, and social networking sites. Particular watchdog organizations have been designed to contain the spread of cyberbullying.
Disability
Disabled people are disproportionately affected by bullying and abuse, and such activity has been cited as a hate crime. The bullying is not limited to those who are visibly disabled, such as wheelchair users or physically deformed such as those with a cleft lip, but also those with developmental disabilities such as autism and developmental coordination disorder.
There is an additional problem that those with learning disabilities are often not as able to explain things to other people, so are more likely to be disbelieved or ignored if they do complain.
Homosexuality
Gay bullying and gay bashing designate direct or indirect verbal or physical actions by a person or group against someone who is gay or lesbian, or perceived to be so due to rumors or because they are considered to fit gay stereotypes. Gay and lesbian youth are more likely than straight youth to report bullying, as well as be bullied.
Law
Legal bullying is the bringing of a vexatious legal action to control and punish a person. Legal bullying can often take the form of frivolous, repetitive, or burdensome lawsuits brought to intimidate the defendant into submitting to the litigant's request, not because of the legal merit of the litigant's position, but principally due to the defendant's inability to maintain the legal battle. This can also take the form of Strategic Lawsuit Against Public Participation (SLAPP). It was partially concern about the potential for this kind of abuse that helped to fuel the protests against SOPA and PIPA in the United States in 2011 and 2012.
Military
In 2000, the UK Ministry of Defence (MOD) defined bullying as "the use of physical strength or the abuse of authority to intimidate or victimize others, or to give unlawful punishments".
Some argue that this behaviour should be allowed, due to ways in which "soldiering" is different from other occupations. Soldiers expected to risk their lives should, according to them, develop strength of body and spirit to accept bullying.
Parenting
Parents who may displace their anger, insecurity, or a persistent need to dominate and control upon their children in excessive ways have been proven to increase the likelihood that their own children will in turn become overly aggressive or controlling towards their peers.
The American Psychological Association advises on its website that parents who may suspect their own children may be engaging in bullying activities among their peers should carefully consider the examples which they themselves may be setting for their own children regarding how they typically interact with their own peers, colleagues, and children.
Prison
The prison environment is known for bullying. An additional complication is the staff and their relationships with the inmates. Thus, the following possible bullying scenarios are possible:
Inmate bullies inmate (echoing school bullying)
Staff bullies inmate
Staff bullies staff (a manifestation of workplace bullying)
Inmate bullies staff
School
It is important to distinguish school bullying that per definition has the goal of harming the victim from normal peer conflict that is an inherent part of everyday school life and often promotes social development. Unlike normal conflict, bullying is a systematic and repeated abuse committed intentionally by another student who has more power (physical, social, or otherwise). School bullies may taunt and tease their target before finally physically bullying them. Bystanders typically choose to either participate or watch, sometimes out of fear of becoming the next target.
Bullying can occur in nearly any part in or around the school building, although it may occur more frequently during physical education classes and activities such as recess. Bullying also takes place in school hallways, bathrooms, on school buses and while waiting for buses, and in classes that require group work and/or after school activities. Bullying in school sometimes consists of a group of students taking advantage of or isolating one student in particular and gaining the loyalty of bystanders who want to avoid becoming the next target. The 2011 documentary Bully showcases the lives of five American public school students who face bullying in school and while on the school bus. The bullying is shown to affect the students both at school and in their homes.
Teachers play an important role in bullying prevention and intervention because they are the adults who spend most of their time with the students.
Bullying can, however, also be perpetrated by teachers and the school system itself; there is an inherent power differential in the system that can easily predispose to subtle or covert abuse (relational aggression or passive aggression), humiliation, or exclusioneven while maintaining overt commitments to anti-bullying policies.
In 2016, in Canada, a North American legal precedent was set by a mother and her son, after the son was bullied in his public school. The mother and son won a court case against the Ottawa-Carleton District School Board, making this the first case in North America where a school board has been found negligent in a bullying case for failing to meet the standard of care (the "duty of care" that the school board owes to its students). Thus, it sets a precedent of a school board being found liable in negligence for harm caused to a child, because they failed to protect a child from the bullying actions of other students. There has been only one other similar bullying case and it was won in Australia in 2013 (Oyston v. St. Patricks College, 2013).
Gendered
Sexual bullying is "any bullying behaviour, whether physical or non-physical, that is based on a person's sexuality or gender. It is when sexuality or gender is used as a weapon by boys or girls towards other boys or girls – although it is more commonly directed at girls. It can be carried out to a person's face, behind their back or through the use of technology."
Transsexuality
Trans bashing is the act of victimizing a person physically, sexually, or verbally because they are transgender or transsexual. Unlike gay bashing, it is committed because of the target's actual or perceived gender identity, not sexual orientation.
Work
Workplace bullying occurs when an employee experiences a persistent pattern of mistreatment from others in the workplace that causes harm. Workplace bullying can include such tactics as verbal, nonverbal, psychological, physical abuse and humiliation. This type of workplace aggression is particularly difficult because, unlike the typical forms of school bullying, workplace bullies often operate within the established rules and policies of their organization and their society. Bullying in the workplace is in the majority of cases reported as having been perpetrated by someone in authority over the target. Bullies can also be peers, and occasionally can be subordinates.
The first known documented use of "workplace bullying" is in 1992 in a book by Andrea Adams called Bullying at Work: How to Confront and Overcome It.
Research has also investigated the impact of the larger organizational context on bullying as well as the group-level processes that impact on the incidence, and maintenance of bullying behavior. Bullying can be covert or overt. It may be missed by superiors or known by many throughout the organization. Negative effects are not limited to the targeted individuals, and may lead to a decline in employee morale and a change in organizational culture. A Cochrane Collaboration systematic review has found very low quality evidence to suggest that organizational and individual interventions may prevent bullying behaviors in the workplace.
Academia
Bullying in academia is workplace bullying of scholars and staff in academia, especially places of higher education such as colleges and universities. It is believed to be common, although has not received as much attention from researchers as bullying in some other contexts.
Blue-collar jobs
Bullying has been identified as prominent in blue-collar jobs, including on oil rigs and in mechanic shops and machine shops. It is thought that intimidation and fear of retribution cause decreased incident reports. In industry sectors dominated by males, typically of little education, where disclosure of incidents are seen as effeminate, reporting in the socioeconomic and cultural milieu of such industries would likely lead to a vicious circle. This is often used in combination with manipulation and coercion of facts to gain favour among higher-ranking administrators.
Information technology
A culture of bullying is common in information technology (IT), leading to high sickness rates, low morale, poor productivity, and high staff-turnover. Deadline-driven project work and stressed-out managers take their toll on IT workers.
Courts
Bullying in the legal profession is believed to be more common than in some other professions. It is believed that its adversarial, hierarchical tradition contributes towards this. Women, trainees and solicitors who have been qualified for five years or less are more affected, as are ethnic minority lawyers and lesbian, gay and bisexual lawyers.
Medicine
Bullying in the medical profession is common, particularly of student or trainee doctors and of nurses. It is thought that this is at least in part an outcome of conservative traditional hierarchical structures and teaching methods in the medical profession, which may result in a bullying cycle.
Even though The American Nurses Association believes that all nursing personnel have the right to work in safe, non-abusive environments, bullying has been identified as being particularly prevalent in the nursing profession although the reasons are not clear. It is thought that relational aggression (psychological aspects of bullying such as gossiping and intimidation) are relevant. Relational aggression has been studied among girls but not so much among adult women.
Teaching
School teachers are commonly the subject of bullying but they are also sometimes the originators of bullying within a school environment.
Machines
Children have been observed bullying anthropomorphic robots designed to assist the elderly. Their attacks start with blocking the robots' paths of movement and then escalate to verbal abuse, hitting and destroying the object. Seventy-five percent of the kids interviewed perceived the robot as "human-like" yet decided to abuse it anyway, while 35% of the kids who beat up the robot did so "for enjoyment".
Prevention
Bullying prevention is the collective effort to prevent, reduce and stop bullying. Many campaigns and events are designated to bullying prevention throughout the world. Bullying prevention campaigns and events include Anti-Bullying Day, Anti-Bullying Week, International Day of Pink, International STAND UP to Bullying Day and National Bullying Prevention Month. Anti-bullying laws in the U.S. have also been enacted in 23 of its 50 states, making bullying in schools illegal.
A 2019 study by McCallion & Feder found that school-based anti-bullying programs may lower the incidence of bullying by 25%.
Bullying prevention programs allow schools to help decrease cyberbullying within the realm of school. The prevention methods are targeted mainly for middle schoolers, where we see the most bullying occur. To help decrease cyberbullying, people need to take preventative measures. One preventative method was implemented to determine the effectiveness against cyberbullying. This program called "Media Heroes" showed how educating teachers on bullying behaviors in school can help them educate and stop students from bullying. This educational program decreased bullying in their schools. Having trusted adults become educated on what can go on online, can help prevent further cyberbullying.
Responses
Bullying is typically ongoing and not isolated behaviour. Common responses are to try to ignore it, to confront the bullies, or to turn to an authority figure.
Ignoring it often does nothing to stop the bullying continuing, and it can become worse over time.
It can be important to address bullying behaviour early on, as it can be easier to control the earlier it is detected.
Bystanders play an important role in responding to bullying, as doing nothing can encourage it to continue, while small steps that oppose the behaviour can reduce it.
Authority figures can play an important role, such as parents or teachers in child or adolescent situations, or supervisors, human-resources staff or parent-bodies in workplace and volunteer settings. In the school context, teachers who set clear boundaries, communicate seriously that bullying behavior is unacceptable and will not be tolerated, and involve school administrators have been shown to reduce bullying. Discussing bullying and its consequences with the whole class is also an important intervention that not only reduces bullying, but also encourages other students to step in and stop bullying even before it reaches its full form. In general, authority figures can be influential in recognising and stopping bullying behaviour, and creating an environment that does not encourage or promote bullying.
In many situations, authority figures are untrained and unqualified, do not know how to respond, and can make the situation worse.
In some cases the authority figures even support the people doing the bullying, facilitating it continuing and increasing the isolation and marginalising of the target.
Some of the most effective ways to respond are to recognise that harmful behaviour is taking place, and to create an environment where it will not continue.
See also
References
Further reading
Kohut MR The Complete Guide to Understanding, Controlling, and Stopping Bullies & Bullying: A Complete Guide for Teachers & Parents (2007)
Bullies and Victims in Schools: a guide to understanding and management by Valerie E. Besag (1989)
The Fight That Never Ends by Tim Brown
Odd Girl Out: The Hidden Culture of Aggression in Girls by Rachel Simmons
Bullycide, Death at Playtime by Neil Marr and Tim Field
Bullycide in America: Moms Speak Out about the Bullying/Suicide Connection – by Brenda High, Bullycide.org
A Journey Out of Bullying: From Despair to Hope by Patricia L. Scott
"Peer Abuse Know More! Bullying From A Psychological Perspective" By Elizabeth Bennett
New Perspectives on Bullying by Ken Rigby
Garbarino, J. & de Lara, E. (2003). And Words Can Hurt Forever: How to Protect Adolescents from Bullying, Harassment, and Emotional Violence. The Free Press: New York.
Joanne Scaglione, Arrica Rose Scaglione Bully-proofing children: a practical, hands-on guide to stop bullying 2006
Why Is Everybody Always Picking on Me: A Guide to Handling Bullies for Young People. by Terrence Webster-Doyle. Book and Teaching curriculum.
"Why Nerds are Unpopular", by Paul Graham. This essay is an example of how even medium differences, in a hierarchical, zero-sum, or negative environments, can lead to ostracism or persecution.
Lord of the Flies by William Golding (1954). A famous work describing how a group of schoolboys trapped on an island descends into savagery.
External links
Citizens Advice in the UK
Bullying. No Way! (Australian Education Authorities)
Bullying in schools (UK – schools)
PBSKids.org "Great Books About Bullies"
Be Brave Against Bullying, a UFT project
U.S. Department of Education's Education Resources Information Center (ERIC)
Bully Online
Abuse
Aggression
Injustice
Interpersonal conflict
Persecution
Psychological abuse | Bullying | Biology | 8,544 |
53,907,927 | https://en.wikipedia.org/wiki/Intelsat%20704 | Intelsat 704 (also known as IS-704 and Intelsat 7-F4) is a geostationary communication satellite that was built by Space Systems/Loral (SSL). It is located in the orbital position of 29.5 degrees east longitude and it is currently in an inclined orbit. The same is owned by Intelsat and after sold to SES World Skies on November 30, 1998. The satellite was based on the LS-1300 platform and its estimated useful life was 15 years.
The satellite was successfully launched into space on January 10, 1995, at 06:18, using an Atlas II vehicle from the Cape Canaveral Air Force Station, United States. It had a launch mass of 3,695 kg.
The Intelsat 704 is equipped with 26 transponders in C band and 10 in Ku band to provide broadcasting, business-to-home services, telecommunications, VSATnetworks.
Specifications
Apogee:
Perigee:
Semimajor axis:
Orbital inclination: 6.9°
Orbital period: 24,54 hours
Propulsion: R-4D-11
Power: 5 transponders of 35 W and 5 transponders of 50 W
Bandwidth: 6 transponders of 72 MHz and 4 transponders of 112 MHz
EIRP: Spot 1: 45.4 dBW, Spot 2: 44.5 dBW, and Spot 3: 46 dBW
Polarization: Linear
Beacons: 11.701 GHz, 12.501 GHz (linear)11.198 GHz, 11.452 GHz (RHCP)
Frequency: Downlink 10.95-11.20 GHz, 11.45-11.70 GHz,11.70-11.95 GHz, and 12.50-12.75 GHz
External links
Intelsat 704 TBS satellite
Intelsat 7 Gunter's Space Page
Intelsat 704 SatBeams
Spacecraft launched in 1995
Intelsat satellites
Spacecraft decommissioned in 2009 | Intelsat 704 | Astronomy | 402 |
15,181,461 | https://en.wikipedia.org/wiki/Cartilage-derived%20angiogenesis%20inhibitor | A cartilage-derived angiogenesis inhibitor is an angiogenesis inhibitor produced from cartilage. Examples include the peptide troponin I and chondromodulin I.
The antiangiogenic effect may be an inhibition of basement membrane degradation.
These inhibitory agents prevent 'vascular invasion', which is the proliferation of tumor cells in the blood or lymph vessels. They are usually highly expressed in cartilage and within chondrocytes. Their genetic transcription increases upon the expansion of cartilaginous regions.
Recent studies on Troponin I hypothesize that this protein performs its anti-proliferation effect on endothelial cells via interactions with a bFGF receptor. Neighboring studies on other anti-angiogenic factors are evolving, however, the general mechanism of action is still unknown today.
References
Angiogenesis inhibitors | Cartilage-derived angiogenesis inhibitor | Chemistry,Biology | 177 |
30,853,464 | https://en.wikipedia.org/wiki/Tributyltin%20azide | Tributyltin azide is an organotin compound with the formula (C4H9)3SnN3. It is a colorless solid although samples can appear as yellow oils. The compound is used as a reagent in organic synthesis.
Synthesis and reactions
Tributyltin azide is synthesized by the salt metathesis reaction of tributyltin chloride and sodium azide.
It is a reagent used in the synthesis of tetrazoles, which in turn are used to generate angiotensin II receptor antagonists. In some applications, tributyltin azide has been replaced by the less toxic trioctyltin azide and organoaluminium azides.
Safety
Tributyl tin compounds are highly toxic and have penetrating odors. Tributyltin azide causes skin rashes, itching or blisters.
References
Organotin compounds
Azido compounds
Reagents for organic chemistry
Tin(IV) compounds
Butyl compounds | Tributyltin azide | Chemistry | 207 |
10,533,337 | https://en.wikipedia.org/wiki/Skewb%20Ultimate | The Skewb Ultimate, originally marketed as the Pyraminx Ball, is a twelve-sided puzzle derivation of the Skewb, produced by German toy-maker Uwe Mèffert. Most versions of this puzzle are sold with six different colors of stickers attached, with opposite sides of the puzzle having the same color; however, some early versions of the puzzle have a full set of 12 colors.
Description
The Skewb Ultimate is made in the shape of a dodecahedron, like the Megaminx, but cut differently. Each face is cut into four parts, two equal and two unequal. Each cut is a deep cut: it bisects the puzzle. This results in eight smaller corner pieces and six larger "edge" pieces.
The object of the puzzle is to scramble the colors, and then restore them to the original configuration.
Solutions
At first glance, the Skewb Ultimate appears to be much more difficult to solve than the other Skewb puzzles, because of its uneven cuts which cause the pieces to move in a way that may seem irregular or strange.
Mathematically speaking, however, the Skewb Ultimate has exactly the same structure as the Skewb Diamond. The solution for the Skewb Diamond can be used to solve this puzzle, by identifying the Diamond's face pieces with the Ultimate's corner pieces, and the Diamond's corner pieces with the Ultimate's edge pieces. The only additional trick here is that the Ultimate's corner pieces (equivalent to the Diamond's face pieces) are sensitive to orientation, and so may require an additional algorithm for orienting them after being correctly placed.
Similarly, the Skewb Ultimate is mathematically identical to the Skewb, by identifying corners with corners, and the Skewb's face centers with the Ultimate's edges. The solution of the Skewb can be used directly to solve the Skewb Ultimate. The only addition is that the edge pieces of the Skewb Ultimate are sensitive to orientation, and may require an additional algorithm to orient them after being placed correctly.
Number of combinations
The Skewb Ultimate has six large "edge" pieces and eight smaller corner pieces. Only even permutations of the larger pieces are possible, giving 6!/2 possible arrangements. Each of them has two possible orientations, although the orientation of the last piece is determined by the orientations of the other pieces, hence giving a total of 25 possible orientations.
The positions of four of the smaller corner pieces depend on the positions of the other four corner pieces, and only even permutations of these positions are possible. Hence the number of arrangements of corner pieces is 4!/2. Each corner piece has three possible orientations, although the orientation of the last corner is determined by the orientations of the other corners, so the number of possible corner orientations is 37. However, the orientations of four of the corners plus the position of one of the other corners determines the positions of the remaining three, so the total number of possible combinations of corners is only .
Therefore, the number of possible combinations is:
See also
Skewb Diamond
Combination puzzles
Mechanical puzzles
External links
Jaap's Skewb Ultimate page
Twisty Puzzles Skewb Ultimate
Mechanical puzzles
Combination puzzles | Skewb Ultimate | Mathematics | 671 |
525,101 | https://en.wikipedia.org/wiki/Hypersurface | In geometry, a hypersurface is a generalization of the concepts of hyperplane, plane curve, and surface. A hypersurface is a manifold or an algebraic variety of dimension , which is embedded in an ambient space of dimension , generally a Euclidean space, an affine space or a projective space.
Hypersurfaces share, with surfaces in a three-dimensional space, the property of being defined by a single implicit equation, at least locally (near every point), and sometimes globally.
A hypersurface in a (Euclidean, affine, or projective) space of dimension two is a plane curve. In a space of dimension three, it is a surface.
For example, the equation
defines an algebraic hypersurface of dimension in the Euclidean space of dimension . This hypersurface is also a smooth manifold, and is called a hypersphere or an -sphere.
Smooth hypersurface
A hypersurface that is a smooth manifold is called a smooth hypersurface.
In , a smooth hypersurface is orientable. Every connected compact smooth hypersurface is a level set, and separates Rn into two connected components; this is related to the Jordan–Brouwer separation theorem.
Affine algebraic hypersurface
An algebraic hypersurface is an algebraic variety that may be defined by a single implicit equation of the form
where is a multivariate polynomial. Generally the polynomial is supposed to be irreducible. When this is not the case, the hypersurface is not an algebraic variety, but only an algebraic set. It may depend on the authors or the context whether a reducible polynomial defines a hypersurface. For avoiding ambiguity, the term irreducible hypersurface is often used.
As for algebraic varieties, the coefficients of the defining polynomial may belong to any fixed field , and the points of the hypersurface are the zeros of in the affine space where is an algebraically closed extension of .
A hypersurface may have singularities, which are the common zeros, if any, of the defining polynomial and its partial derivatives. In particular, a real algebraic hypersurface is not necessarily a manifold.
Properties
Hypersurfaces have some specific properties that are not shared with other algebraic varieties.
One of the main such properties is Hilbert's Nullstellensatz, which asserts that a hypersurface contains a given algebraic set if and only if the defining polynomial of the hypersurface has a power that belongs to the ideal generated by the defining polynomials of the algebraic set.
A corollary of this theorem is that, if two irreducible polynomials (or more generally two square-free polynomials) define the same hypersurface, then one is the product of the other by a nonzero constant.
Hypersurfaces are exactly the subvarieties of dimension of an affine space of dimension of . This is the geometric interpretation of the fact that, in a polynomial ring over a field, the height of an ideal is 1 if and only if the ideal is a principal ideal. In the case of possibly reducible hypersurfaces, this result may be restated as follows: hypersurfaces are exactly the algebraic sets whose all irreducible components have dimension .
Real and rational points
A real hypersurface is a hypersurface that is defined by a polynomial with real coefficients. In this case the algebraically closed field over which the points are defined is generally the field of complex numbers. The real points of a real hypersurface are the points that belong to The set of the real points of a real hypersurface is the real part of the hypersurface. Often, it is left to the context whether the term hypersurface refers to all points or only to the real part.
If the coefficients of the defining polynomial belong to a field that is not algebraically closed (typically the field of rational numbers, a finite field or a number field), one says that the hypersurface is defined over , and the points that belong to are rational over (in the case of the field of rational numbers, "over " is generally omitted).
For example, the imaginary -sphere defined by the equation
is a real hypersurface without any real point, which is defined over the rational numbers. It has no rational point, but has many points that are rational over the Gaussian rationals.
Projective algebraic hypersurface
A of dimension in a projective space of dimension over a field is defined by a homogeneous polynomial in indeterminates. As usual, means that all monomials of have the same degree, or, equivalently that for every constant , where is the degree of the polynomial. The of the hypersurface are the points of the projective space whose projective coordinates are zeros of .
If one chooses the hyperplane of equation as hyperplane at infinity, the complement of this hyperplane is an affine space, and the points of the projective hypersurface that belong to this affine space form an affine hypersurface of equation Conversely, given an affine hypersurface of equation it defines a projective hypersurface, called its , whose equation is obtained by homogenizing . That is, the equation of the projective completion is with
where is the degree of .
These two processes projective completion and restriction to an affine subspace are inverse one to the other. Therefore, an affine hypersurface and its projective completion have essentially the same properties, and are often considered as two points-of-view for the same hypersurface.
However, it may occur that an affine hypersurface is nonsingular, while its projective completion has singular points. In this case, one says that the affine surface is . For example, the circular cylinder of equation
in the affine space of dimension three has a unique singular point, which is at infinity, in the direction .
See also
Affine sphere
Coble hypersurface
Dwork family
Null hypersurface
Polar hypersurface
References
Shoshichi Kobayashi and Katsumi Nomizu (1969), Foundations of Differential Geometry Vol II, Wiley Interscience
P.A. Simionescu & D. Beal (2004) Visualization of hypersurfaces and multivariable (objective) functions by partial globalization, The Visual Computer 20(10):665–81.
Algebraic geometry
Multi-dimensional geometry
Surfaces
Dimension theory | Hypersurface | Mathematics | 1,301 |
46,237,919 | https://en.wikipedia.org/wiki/Energy%20for%20Sustainable%20Development | Energy for Sustainable Development is a peer-reviewed academic journal covering research on energy-related aspects of sustainable development. It is published by Elsevier and the editor-in-chief is Daniel B. Jones. According to the Journal Citation Reports, the journal has a 2018 impact factor of 3.307, and a five-year impact factor (from 2018 backwards) of 3.691.
References
External links
Elsevier academic journals
Academic journals established in 1993
English-language journals
Energy and fuel journals
Sustainable development | Energy for Sustainable Development | Environmental_science | 102 |
1,248,903 | https://en.wikipedia.org/wiki/XCBL | xCBL is a collection of XML specifications (both DTD and XML Schema) for use in e-business. It was created by Commerce One Inc. and is maintained by Perfect Commerce.
History
xCBL was originally called Common Business Library (CBL). The xCBL standardization began in 1997.
This led to the creation of xCBL 2.0 which covered 12 different business document specifications, mainly meant for electronic document communication in business-to-business (B2B) procurement over the Internet. xCBL 2.0 was mainly based on existing Electronic Data Interchange (EDI) standards and introduced the Schema for Object-Oriented XML (SOX) schema library for XML validation.
xCBL 3.0 contained several new business specifications and categories. It also introduced the use of several XML Schema standards.
xCBL 3.5 (October 2001) contained nine new business documents. OASIS used this version as the starting point for defining business documents in Universal Business Language (UBL).
xCBL 4.0 (March 2003) is the latest version of xCBL. It consists of 44 business documents in eight categories.
Use
As an XML document standard, xCBL is used primarily in B2B procurement tools for buyers, order and invoice management tools for suppliers and document routing tools for public and private marketplaces.
For xCBL message transport, Commerce One created an envelope messaging standard called MML (Marketsite Messaging Layer) based on the SMTP MIME format to provide both payload (xCBL) and attachment support.
External links
xCBL Home
XML-based standards | XCBL | Technology | 335 |
5,089,577 | https://en.wikipedia.org/wiki/Council%20for%20Registered%20Gas%20Installers | The Council for Registered Gas Installers (CORGI) operates a voluntary registration scheme for gas installers in the United Kingdom. From 1991 to 2009 registration with CORGI was a legal requirement for gas operatives and businesses throughout the UK, and before April 2010 in Northern Ireland and Guernsey
CORGI registration requires (beside payment of fees) that gas operatives hold a certificate of competence under the Accredited Certification Scheme (ACS) demonstrating an appropriate level of competence and experience in particular types of gas work. The ACS replaced a number of different certification schemes in 1998.
CORGI lost its status as official registration body in England, Scotland and Wales on 1 April 2009 and in Northern Ireland and Guernsey in April 2010, with this role being taken on by the Gas Safe Register, run on behalf of the Health and Safety Executive by Capita Group.
Background
CORGI was originally established in 1970 as the Confederation for the Registration of Gas Installers to operate a voluntary register. This followed a gas explosion in 1968 which led to the partial collapse of Ronan Point, a tower block in London.
Notwithstanding gas explosions, the greatest danger to the public in using gas is from carbon monoxide (CO), which is a highly toxic by-product of the combustion process. Most of the concern for gas safety focuses on avoiding excessive production of CO through adequate ventilation and correct combustion, and the safe dispersal of the small amounts produced by correct combustion through effective flue systems. Modern room-sealed gas appliances are much safer in this respect and the number of fatalities from CO poisoning has greatly declined. Each year in the UK around 30 people are killed as a result of CO poisoning.
Previous responsibilities
Registration with CORGI was a legal requirement under the Gas Safety (Installation and Use) Regulations 1998 for any gas installation business and there were around 55,000 CORGI registered businesses in the UK employing nearly 110,000 gas operatives.
CORGI was answerable to the Health and Safety Executive, which is the Government watchdog on all safety issues, including gas. The HSE has the authority to appoint CORGI and/or other agencies to operate the Register of Gas Installers. In 2006 another body (NAPIT) made an application to the HSE to operate a rival registration scheme. This application was turned down by the Health and Safety Executive. It is the CORGI view - a view that is supported by many other organisations too such as the All Party Parliamentary Gas Safety Group - that introducing another gas registration body would cause confusion. However some registered gas installers believe that CORGI's decision to run schemes for plumbing, electrics and ventilation will itself create public confusion, as well as taking away its focus from the prime consideration of gas safety. However, CORGI has been clear that gas safety is at the core of its business and will remain so. CORGI realises that gas installers often do jobs other than just gas and the decision to offer plumbing, electrical and ventilation schemes was made to help installers that are CORGI registered for gas to comply with Building Regulations in areas closely related to gas work.
Controversy
Some gas installers, primarily individual, independent installers through associations such as ARGI (Association of Registered Gas Installers) felt that the organisation was overbearing and an excessive financial burden, and that little was being done to stop unregistered installers operating and that they were not being supported by or listened to by the organisation. There were also concerns that it abused its monopolistic position as the sole awarding body for UK gas installers. The perception was, that CORGI used the customer and installer data to sell products and services (initially by including a sales booklet along with the Installation certificate sent to the customer), which some believed was contrary to their remit for the care of that data. Others considered that use of this data to promote gas safety, including products and services to installers and public safety information to consumers raised safety standards. The funds raised through the commercial operations also supported lower gas registration fees for installers - this was demonstrated by the fees barely increasing over the years that CORGI ran the gas scheme.
CORGI Trust
In 2005, CORGI set up the CORGI Trust, which sees all profits from the commercial side of the business being donated to the Trust. These funds will then be used to help advance gas safety within the UK. Recommendations for the use of these funds has ranged from getting the Government to change the law so that only CORGI registered installers can buy gas appliances, through to doing a national television campaign to increase awareness on the need for customers to only use CORGI registered installers and the dangers of carbon monoxide.
Gas Safe Register
Gas Safe Register is the official gas registration body for the United Kingdom, Isle of Man and Guernsey, appointed by the relevant Health and Safety Authority for each area. By law all gas engineers must be on the Gas Safe Register.
Gas Safe Register replaced CORGI as the gas registration body in Great Britain and Isle of Man on 1 April 2009 and Northern Ireland and Guernsey on 1 April 2010.
Gas Safe Register work to protect the public from unsafe gas work through;
a dedicated national investigations team tracking down individuals working illegally
regular inspections of Gas Safe registered engineers
educating consumers and raising awareness of gas safety
investigating reports of unsafe gas work
Gas Safe Register is run by Capita Gas Registration and Ancillary Services Limited, a division of Capita plc.
See also
Gas Safety (Installation and Use) Regulations 1998
Landlord's gas safety certificate
Health and Safety Executive
Natural gas
British Gas
Notes
External links
Official website
HSE gas
Basingstoke
Natural gas industry in the United Kingdom
Natural gas organizations
Natural gas safety
Organisations based in Hampshire
Organizations established in 1970
Plumbing organizations
Registered Gas Installers
1970 establishments in the United Kingdom | Council for Registered Gas Installers | Chemistry,Engineering | 1,172 |
6,208,069 | https://en.wikipedia.org/wiki/Rop%20protein | Rop (also known as repressor of primer, or as RNA one modulator (ROM)) is a small dimeric protein responsible for keeping the copy number of ColE1 family and related bacterial plasmids low in E. coli by increasing the speed of pairing between the preprimer RNA, RNA II, and its antisense RNA, RNA I. Structurally, Rop is a homodimeric four-helix bundle protein formed by the antiparallel interaction of two helix-turn-helix monomers. The Rop protein's structure has been solved to high resolution. Due to its small size and known structure, Rop has been used in protein design work to rearrange its helical topology and reengineer its loop regions. In general, the four-helix bundle has been extensively used in de novo protein design work as a simple model to understand the relationship between amino acid sequence and structure.
External links
Rop protein from Proteopedia
References
Proteins | Rop protein | Chemistry | 206 |
69,818,125 | https://en.wikipedia.org/wiki/Mycena%20roseoflava | Mycena roseoflava is a species of agaric mushroom in the family Mycenaceae. It was first discovered in 1964 by New Zealand mycologist Greta Stevenson. It is a wood-inhabiting mushroom native to New Zealand.
The small fungus is saprotrophic, meaning it gains nutrients from decaying organic matter and appears on stressed or dying plants, often found on rotting wood and twigs. As matter decomposes within a medium in which a saprotroph is residing, the saprotroph breaks such matter down into its composites.
M. roseoflava has white spores with small white caps, normally standing at a height of 5-10 millimeters and an equal width. It is most active in the autumn season and is not considered edible. The stem relatively short is often attached to the side of wood, usually with a slightly swollen stem base. It is rare to see in Victoria, where it has only found only in wetter forests and rainforests, but is somewhat common in Tasmania.
In the first descriptions of the mushroom, Stevenson noted the caps were "pink fading yellowish, hemispherical with a shallow central umbilicus." The texture of the caps were smooth to minutely floccose. The gills were described as adnate to slightly concurrent. The spores were observed to be globose, amyloid, and thin-walled.
In 2021, the species was discovered to be bioluminescent, this never having been recorded previously. According to New Zealand Fungarium curator Dr. Maj Padamsee, "It could have been found before but it just hadn’t been recorded – people who had been out in the forest might have seen something because it’s not very bright… it’s a very pale light colour." The enzymes produced from the compound luciferin gives the mushrooms their glow, as it also does with fireflies and some marine organisms. The discovery of bioluminescence was made during an event dedicated to studying fungus that took place on Stewart Island.
References
Bioluminescent fungi
roseoflava
Taxa named by Greta Stevenson
Fungi described in 1964
Fungi of New Zealand
Fungus species | Mycena roseoflava | Biology | 444 |
1,745,715 | https://en.wikipedia.org/wiki/Thymidine%20diphosphate | Thymidine diphosphate (TDP) or deoxythymidine diphosphate (dTDP) (also thymidine pyrophosphate, dTPP) is a nucleotide diphosphate. It is an ester of pyrophosphoric acid with the nucleoside thymidine. dTDP consists of the pyrophosphate group, the pentose sugar ribose, and the nucleobase thymine. Unlike the other deoxyribonucleotides, thymidine diphosphate does not always contain the "deoxy" prefix in its name.
See also
Nucleoside
Nucleotide
DNA
RNA
Oligonucleotide
dTDP-glucose
References
Nucleotides
Pyrophosphate esters
Pyrimidinediones | Thymidine diphosphate | Chemistry,Biology | 172 |
4,229,382 | https://en.wikipedia.org/wiki/NGC%205253 | NGC 5253 is an irregular galaxy in the constellation Centaurus. It was discovered by William Herschel on 15 March 1787.
Properties
NGC 5253 is located within the M83 Subgroup of the Centaurus A/M83 Group, a relatively nearby galaxy group that includes the radio galaxy Centaurus A and the spiral galaxy M83 (the Southern Pinwheel Galaxy). NGC 5253 is considered a dwarf starburst galaxy and also a blue compact galaxy.
Supernovae
Two supernovae have been observed in NGC 5253:
SN 1895B (type unknown, mag. 8) was discovered by Williamina Fleming on 7 July 1895.
SN 1972E (type Ia, mag. 8.5), the second-brightest recent supernova visible from Earth, was discovered by Charles Kowal on 6 May 1972. With a peak apparent magnitude of 8.5, the only brighter supernova observed in the 20th century was SN 1987A.
Contents
NGC 5253 contains a giant dust cloud hiding a cluster (believed to be a super star cluster) of more than one million stars, among them up to 7,000 O-type stars. The cluster is 3 million years old and has a total luminosity of more than one billion suns. It is the site of efficient star formation, with a rate at least 10 times higher than comparable regions in the Milky Way.
Image gallery
References
External links
17870315
Discoveries by William Herschel
Irregular galaxies
Peculiar galaxies
Centaurus A/M83 Group
Centaurus
5253
048334
369
-05-32-060
445-004
13370-3123 | NGC 5253 | Astronomy | 336 |
1,512,655 | https://en.wikipedia.org/wiki/Hagen%20number | The Hagen number (Hg) is a dimensionless number used in forced flow calculations. It is the forced flow equivalent of the Grashof number and was named after the German hydraulic engineer G. H. L. Hagen.
Definition
It is defined as:
where:
is the pressure gradient
L is a characteristic length
ρ is the fluid density
ν is the kinematic viscosity
For natural convection
and so the Hagen number then coincides with the Grashof number.
Hagen number vs. Bejan number
Awad: presented Hagen number vs. Bejan number. Although their physical meaning is not the same because the former represents the dimensionless pressure
gradient while the latter represents the dimensionless pressure drop, it will be
shown that Hagen number coincides with Bejan number in cases where the characteristic
length (l) is equal to the flow length (L). Also, a new expression of Bejan
number in the Hagen-Poiseuille flow will be introduced. In addition, extending the Hagen number to a general form will be presented. For the case of Reynolds analogy (Pr = Sc = 1), all these three definitions of Hagen number will be the same. The general form of the Hagen number is
where
is the corresponding diffusivity of the process in consideration
References
Dimensionless numbers of physics | Hagen number | Mathematics | 265 |
71,354,664 | https://en.wikipedia.org/wiki/Lyra%20%28codec%29 | Lyra is a lossy audio codec developed by Google that is designed for compressing speech at very low bitrates. Unlike most other audio formats, it compresses data using a machine learning-based algorithm.
Features
The Lyra codec is designed to transmit speech in real-time when bandwidth is severely restricted, such as over slow or unreliable network connections. It runs at fixed bitrates of 3.2, 6, and 9 kbit/s and it is intended to provide better quality than codecs that use traditional waveform-based algorithms at similar bitrates. Instead, compression is achieved via a machine learning algorithm that encodes the input with feature extraction, and then reconstructs an approximation of the original using a generative model. This model was trained on thousands of hours of speech recorded in over 70 languages to function with various speakers. Because generative models are more computationally complex than traditional codecs, a simple model that processes different frequency ranges in parallel is used to obtain acceptable performance. Lyra imposes 20 ms of latency due to its frame size. Google's reference implementation is available for Android and Linux.
Quality
Lyra's initial version performed significantly better than traditional codecs at similar bitrates. Ian Buckley at MakeUseOf said, "It succeeds in creating almost eerie levels of audio reproduction with bitrates as low as 3 kbps." Google claims that it reproduces natural-sounding speech, and that Lyra at 3 kbit/s beats Opus at 8 kbit/s. Tsahi Levent-Levi writes that Satin, Microsoft's AI-based codec, outperforms it at higher bitrates.
History
In December 2017, Google researchers published a preprint paper on replacing the Codec 2 decoder with a WaveNet neural network. They found that a neural network is able to extrapolate features of the voice not described in the Codec 2 bitstream and give better audio quality, and that the use of conventional features makes the neural network calculation simpler compared to a purely waveform-based network. Lyra version 1 would reuse this overall framework of feature extraction, quantization, and neural synthesis.
Lyra was first announced in February 2021, and in April, Google released the source code of their reference implementation. The initial version had a fixed bitrate of 3 kbit/s and around 90 ms latency. The encoder calculates a log mel spectrogram and performs vector quantization to store the spectrogram in a data stream. The decoder is a WaveNet neural network that takes the spectrogram and reconstructs the input audio.
A second version (v2/1.2.0), released in September 2022, improved sound quality, latency, and performance, and permitted multiple bitrates. V2 uses a "SoundStream" structure where both the encoder and decoder are neural networks, a kind of autoencoder. A residual vector quantizer is used to turn the feature values into transferrable data.
Support
Implementations
Google's implementation is available on GitHub under the Apache License. Written in C++, it is optimized for 64-bit ARM but also runs on x86, on either Android or Linux.
Applications
Google Meet uses Lyra to transmit sound for video chats when bandwidth is limited.
References
External links
Lyra: A New Very Low-Bitrate Codec for Speech Compression Google blog post with a demonstration comparing codecs
See also
Satin (codec), an AI-based codec developed by Microsoft
Comparison of audio coding formats
Speech coding
Videotelephony
Speech codecs
Lossy compression algorithms
Software using the Apache license
Google software
Machine learning
2021 software | Lyra (codec) | Engineering | 764 |
67,358,788 | https://en.wikipedia.org/wiki/Galperin%20configuration | Galperin configuration are a particular configuration of sensing elements found in a class of seismic instruments measuring ground motion and are named after Soviet seisomologist Evsey Iosifovich Galperin, who introduced it in 1955 for petroleum exploration.
Description
Common triaxial seismometers provide signal outputs in three orthogonal axes oriented towards east–west (E), north–south (N) and up-down (Z), i.e. in the Cartesian coordinate system. In contrast, the Galperin configuration consists of three orthogonal axes (U, V, W) that are oriented at precisely the same angle with respect to the horizontal plane (α=35.26°). The projection of all three axes onto the horizontal plane are all separated by 120°, which results in the "symmetric triaxial" design. The recordings acquired with the Galperin configuration are brought to the Cartesian coordinate system by the following coordinate transformation, where β=30°:
A main advantage of the Galperin configuration is that all three receivers have identical orientation with respect to the vertical axis and, thus have identical instrument responses. Another advantage is the ability to build smaller packages (i.e., instruments) compared to the Cartesian orientation, which makes the Galperin configuration especially applicable for borehole installations. Other benefits of the Galperin configuration include easier distinction between external and internal noise sources and the fact that the configuration is not sensitive to rotation around the vertical axis. However, the main drawback of the configuration is that all input vectors are linked by the rotational matrix, which causes failure of the entire system when one of the three sensor is malfunctioning. In the Cartesian configuration, for example, both horizontal components still provide useful data in case the vertical (Z) component fails.
The Galperin configuration found wide application in seismometer design, including models for borehole, ocean bottom, and vault installations. The Galperin configuration can also be applied at the source side to simulate three-component seismic sources
References
Seismology instruments
Seismology measurement
Soviet inventions | Galperin configuration | Technology,Engineering | 427 |
44,516,005 | https://en.wikipedia.org/wiki/Pauling%27s%20principle%20of%20electroneutrality | Pauling's principle of electroneutrality states that each atom in a stable substance has a charge close to zero. It was formulated by Linus Pauling in 1948 and later revised. The principle has been used to predict which of a set of molecular resonance structures would be the most significant, to explain the stability of inorganic complexes and to explain the existence of π-bonding in compounds and polyatomic anions containing silicon, phosphorus or sulfur bonded to oxygen; it is still invoked in the context of coordination complexes. However, modern computational techniques indicate many stable compounds have a greater charge distribution than the principle predicts (they contain bonds with greater ionic character).
History
Pauling first stated his "postulate of the essential electroneutrality of atoms" in his 1948 Liversidge lecture (in a broad-ranging paper that also included his ideas on the calculation of oxidation states in molecules):
“...the electronic structure of substances is such as to cause each atom to have essentially zero resultant electrical charge, the amount of leeway being not greater than about +/- ½, and these resultant charges are possessed mainly by the most electropositive and electronegative atoms and are distributed in such a way as to correspond to electrostatic stability."
A slightly revised version was published in 1970:
“Stable molecules and crystals have electronic structures such that the electric charge of each atom is close to zero. Close to zero means between -1 and +1.”
Pauling said in his Liversidge lecture in 1948 that he had been led to the principle by a consideration of ionic bonding. In the gas phase, molecular caesium fluoride has a polar covalent bond. The large difference in electronegativity gives a calculated covalent character of 9%. In the crystal (CsF has the NaCl structure with both ions being 6-coordinate) if each bond has 9% covalent character the total covalency of Cs and F would be 54%. This would be represented by one bond of around 50% covalent character resonating between the six positions and the overall effect would be to reduce the charge on Cs to about + 0.5 and fluoride to -0.5. It seemed reasonable to him that since CsF is the most ionic of ionic compounds, most, if not all substances will have atoms with even smaller charges.
Applications of the principle
Explanation of the structure adopted by hydrogen cyanide
There are two possible structures for hydrogen cyanide, HCN and CNH, differing only as to the position of the hydrogen atom. The structure with hydrogen attached to nitrogen, CNH, leads to formal charges of -1 on carbon and +1 on nitrogen, which would be partially compensated for by the electronegativity of nitrogen and Pauling calculated the net charges on H, N and C as -0.79, +0.75 and +0.04 respectively. In contrast the structure with hydrogen bonded to carbon, HCN, has formal charges on carbon and nitrogen of 0, and the effect of the electronegativity of the nitrogen would make the charges on H, C and N +0.04, +0.17 and -0.21. The triple bonded structure is therefore favored.
Relative contribution of resonance structures (canonicals)
As an example the cyanate ion (OCN)− can be assigned three resonance structures:-
^-O-C{\equiv}N <-> O=C=N^- <-> {^+O{\equiv}C-N^{2-}}
The rightmost structure in the diagram has a charge of -2 on the nitrogen atom. Applying the principle of electroneutrality this can be identified as only a minor contributor. Additionally as the most electronegative atom should carry the negative charge, then the triple bonded structure on the left is predicted to be the major contributor.
Stability of complexes
The hexammine cobalt(III) complex [Co(NH3)6]3+ would have all of charge on the central Co atom if the bonding to the ammonia molecules were electrostatic. On the other hand, a covalent linkage would lead to a charge of -3 on the metal and +1 on each of the nitrogen atoms in the ammonia molecules. Using the electroneutrality principle the assumption is made that the Co-N bond will have 50% ionic character thus resulting in a zero charge on the cobalt atom. Due to the difference in electronegativity the N-H bond would 17% ionic character and therefore a charge of 0.166 on each of the 18 hydrogen atoms. This essentially spreads the 3+ charge evenly onto the "surface" of the complex ion.
π-bonding in oxo compounds of Si, P, and S
Pauling invoked the principle of electroneutrality in a 1952 paper to suggest that pi bonding is present, for example, in molecules with 4 Si-O bonds. The oxygen atoms in such molecules would form polar covalent bonds with the silicon atom because their electronegativity (electron withdrawing power) was higher than that of silicon. Pauling calculated the charge build up on the silicon atom due to the difference in electronegativity to be +2. The electroneutrality principle led Pauling to the conclusion that charge transfer from O to Si must occur using d orbitals forming a π-bond and he calculated that this π-bonding accounted for the shortening of the Si-O bond.
The adjacent charge rule
The "adjacent charge rule" was another principle of Pauling's for determining whether a resonance structure would make a significant contribution. First published in 1932, it stated that structures that placed charges of the same sign on adjacent atoms would be unfavorable.
References
Chemical bonding
Quantum chemistry | Pauling's principle of electroneutrality | Physics,Chemistry,Materials_science | 1,190 |
21,392,376 | https://en.wikipedia.org/wiki/Opal%20Storage%20Specification | The Opal Storage Specification is a set of specifications for features of data storage devices (such as hard disk drives and solid state drives) that enhance their security. For example, it defines a way of encrypting the stored data so that an unauthorized person who gains possession of the device cannot see the data. That is, it is a specification for self-encrypting drives (SED).
The specification is published by the Trusted Computing Group Storage Workgroup.
Overview
The Opal SSC (Security Subsystem Class) is an implementation profile for Storage Devices built to:
Protect the confidentiality of stored user data against unauthorized access once it leaves the owner's control (involving a power cycle and subsequent deauthentication).
Enable interoperability between multiple SD vendors.
Functions
The Opal SSC encompasses these functions:
Security provider support
Interface communication protocol
Cryptographic features
Authentication
Table management
Access control and personalization
Issuance
SSC discovery
Features
Security Protocol 1 support
Security Protocol 2 support
Communications
Protocol stack reset commands
Security
Radboud University researchers indicated in November 2018 that some hardware-encrypted SSDs, including some Opal implementations, had security vulnerabilities.
Implementers of SSC
Device companies
Hitachi
Intel Corporation
Kingston Technology
Lenovo
Micron Technology
Samsung
SanDisk
Seagate Technology as "Seagate Secure"
Toshiba
Storage controller companies
Marvell
Avago/LSI SandForce flash controllers
Software companies
Absolute Software
Check Point Software Technologies
Dell Data Protection
Cryptomill
McAfee
Secude
Softex Incorporated
Sophos
Symantec (Symantec supports OPAL drives, but does not support hardware-based encryption.)
Trend Micro
WinMagic
OpalLock(OpalLock support Self-Encrypt-Drive capable SSD and HDD. Develop by Fidelity Height LLC)
Computer OEMs
Dell
HP
Lenovo
Fujitsu
Panasonic
Getac
References
External links
Storage Work Group Storage Security Subsystem Class: Opal
Computer storage technologies
Cybersecurity engineering | Opal Storage Specification | Technology,Engineering | 410 |
42,240,565 | https://en.wikipedia.org/wiki/Karl%20Spencer%20Lashley%20Award | The Karl Spencer Lashley Award is awarded by The American Philosophical Society as a recognition of research on the integrative neuroscience of behavior. The award was established in 1957 by a gift from Dr. Karl Spencer Lashley.
Recipients
2024 Margaret Livingstone
2023 Silvia Arber
2022 Nicholas Spitzer
2021 Patricia K. Kuhl «in recognition of her fundamental discoveries concerning how human infants acquire language, and how brain structure and activity changes during language learning in both monolingual and bilingual children»
2020 Winrich Freiwald and Doris Tsao - "In recognition of their ground-breaking discoveries of primate cortical areas that selectively encode visual information about faces, the computational principles underlying face encoding in these areas, and the implications of these discoveries for social cognition."
2019 Wolfram Schultz
2018 Catherine Dulac - "In recognition of her incisive studies of the molecular and circuit basis of instinctive behaviors mediated through olfactory systems in the mammalian brain"
2017 Michael Shadlen - "In recognition of his pioneering experimental and theoretical studies of decision-making, identifying neural mechanisms that accumulate and convert sensory information toward behavioral choices"
2016 Charles G. Gross - "In recognition of his pioneering studies of the neurophysiology of higher visual functions and the neural basis of face recognition and object perception"
2015 David W. Tank - "In recognition of his pioneering application of intracellular recording and two-photon microscopy in awake animals, which has revealed new insights into the neural circuits underlying cognition"
2014 Edvard and May-Britt Moser - "In recognition of their discovery of grid cells in entorhinal cortex, and their pioneering physiological studies of hippocampus, which have transformed understanding of the neural computations underlying spatial memory"
2013 J. Anthony Movshon - "In recognition of his studies of how neurons in the cerebral cortex process visual information and how cortical information processing enables seeing"
2012 Eve Marder - "In recognition of her comprehensive work with a small nervous system, demonstrating general principles by which neuromodulatory substances reconfigure the operation of neuronal networks"
2011 Joseph E. LeDoux - "In recognition of his seminal studies of the neural mechanisms of emotional learning, particularly fear learning and fear memory"
2010 William T. Newsome - "In recognition of his pioneering studies of the primate visual system demonstrating the relation between perception and the activity of individual neurons"
2009 James L. McGaugh - "In recognition of his comprehensive study of the biological processes that modulate the formation and consolidation of memory"
2008 Eric Knudsen - "In recognition of his comprehensive study of visual and auditory perception in the owl and for his elucidation of how the auditory map is calibrated by the visual system during development"
2007 Richard F. Thompson - "In recognition of his distinguished contributions to understanding the brain substrates of learning and memory"
2006 Jon H. Kaas - "In recognition of his comprehensive analyses of the primate cerebral cortex, its evolution, functional organization, and plastic response to injury"
2005 Bruce McEwen - "In recognition of his extensive demonstrations of the role of circulating steroid hormones as regulators of neuroplasticity and behavioral adaption"
2004 Masakazu Konishi and Fernando Nottebohm - "In recognition of their fundamental contributions in identifying the organization and function of the avian brain systems for learning and executing birdsong"
2003 Horace B. Barlow - "In recognition of his fundamental contributions to understanding how the eye and brain accomplish vision"
2002 Jean-Pierre Changeux - "In recognition of his pioneering, comprehensive studies into the fundamental molecular mechanisms underlying interneuronal communication and their role in network formation, learning, and reward"
2001 Edward G. Jones - "In recognition of his comprehensive determination of the organization of the thalamus and the basis for the dynamic regulation of cortical excitability"
2000 Charles Stevens - "In recognition of his penetrating contributions to synaptic transmission and synaptic plasticity"
1999 Michael Merzenich - "In recognition of his original contributions to cortical plasticity"
1998 Michael I. Posner and Marcus E. Raichle - "Jointly, for their pioneering contributions to brain imaging"
1996 Patricia S. Goldman-Rakic - "For seminal contributions to the current understanding of prefrontal cortex and its role in working memory and for effectively applying insights from basic biological sciences to mental health"
1996 Mortimer Mishkin - "For his pioneering analysis of the memory and the perceptual systems of the brain, and his seminal contributions to the understanding of the higher nervous system function"
1995 Larry R. Squire - "For his seminal contribution to the delineation of implicit and explicit memory systems in the brain"
1994 Robert H. Wurtz - "For brilliant technical innovations in recording the activity of single visual neurons of alert, behaviorally-trained monkeys that made possible salient scientific discoveries relating individual nerve cells to visual perception and to the generation of eye movement"
1993 Paul Greengard - "For his pioneering work on the molecular basis of signal transduction and vesicle mobilization in nerve cells"
1992 Seymour Kety - "For major contributions to understanding the genetics of schizophrenia and depression, and for developing reliable methods for studying cerebral blood flow which paved the way for PET imaging of brain activity"
1991 Sanford L. Palay - "For pioneering the study of the nervous system on the ultrastructural level, for revolutionizing understanding, and especially for his seminal contribution - characterization of the chemical synapse in the central nervous system"
1990 Viktor Hamburger - "For pioneering the study of neuroembryology, and especially the landmark contributions to understanding neural cell death, nerve growth factor, and the developmental program for motor behavior"
1989 Bela Julesz - "For his illuminating discoveries concerning the human visual capacity, particularly for stereoscopic vision, depth perception, and pattern recognition"
1989 Gian Franco Poggio - "For discoveries of visual cortical mechanisms in stereopsis and depth perception which have significantly influenced modern studies of the brain mechanisms in vision"
1988 Seymour Benzer - "A pioneer in using genetic techniques to study the genetic code and the transfer of information from DNA to proteins. By a brilliant selection of suitable experimental systems, he has succeeded over the last twenty years in advancing these techniques and applying them to the analysis of development and behavior. These contributions have greatly expanded the power of the genetic approach in neurobiology and fostered a merger between molecular biology and neurobiology that is having profound consequences on every aspect of the field"
1987 Louis Sokoloff - "For his elucidation of the physiological and biochemical processes involved in the metabolism of the brain and the application of these discoveries to the measurement of functional activity within that organ"
1986 Pasko Rakic - "For his seminal contributions to the field of developmental neurobiology through research on the development of the central nervous system"
1985 David Bodian - "In recognition of his fundamental neurobiological studies studies that laid the foundation for the successful development of a vaccine against poliomyelitis. He has continued to make important discoveries in the development and structure of the nervous system"
1984 W. Maxwell Cowan - "For his long record of important contributions to understanding the embryological development of the brain"
1983 Edward V. Evarts
1982 Herbert H. Jasper
1981 Eric R. Kandel
1980 Curt P. Richter
1979 Brenda Milner
1978 Victor Percy Whittaker
1977 Torsten Nils Wiesel and David Hunter Hubel
1976 Roger Wolcott Sperry
1975 Paul Weiss
1974 Vernon Benjamin Mountcastle
1973 Janos Szentagothai
1972 Paul D. MacLean
1971 Sir Wilfrid Le Gros Clark
1970 Horace Winchell Magoun
1969 Elizabeth C. Crosby
1968 Theodore H. Bullock
1967 George H. Bishop
1966 Hans-Lukas Teuber
1965 Giuseppe Moruzzi
1964 Walle H . J. Nauta
1963 Alexander Forbes
1962 Philip Bard
1961 Edgar Douglas Adrian
1960 Heinrich Kluver
1959 Rafael Lorente de Nó
See also
List of neuroscience awards
Kavli Prize
Golden Brain Award
Gruber Prize in Neuroscience
W. Alden Spencer Award
The Brain Prize
Mind & Brain Prize
Ralph W. Gerard Prize in Neuroscience
References
External links
American Philosophical Society, Lashley Award
Awards established in 1957
Neuroscience awards | Karl Spencer Lashley Award | Technology | 1,680 |
40,119,464 | https://en.wikipedia.org/wiki/Rheubarbariboletus%20armeniacus | Rheubarbariboletus armeniacus is a small mushroom in the family Boletaceae native to Europe. It was formerly placed in the genera Boletus, Xerocomus, and Xerocomellus. It acquired its current name when it was transferred to genus Rheubarbariboletus in 2015.
Taxonomy
French naturalist Lucien Quélet described this species as Boletus armeniacus in 1885, before placing it in the genus Xerocomus in his 1888 work Flore mycologique de la France et des pays limitrophes (Mycological flora of France and neighbouring countries).
It was transferred to the new genus Xerocomellus described by Czech mycologist Josef Šutara in 2008, and then to Rheubarbariboletus in 2015.
Description
The cap is initially globular before expanding to become convex and flattening somewhat; it grows to a diameter of . The cap margin initially adheres to the stipe and has a tendency to become lobed or undulated in age. The cap surface is first somewhat pubescent but later becomes smooth and hairless, and may develop cracks in age. Its color is orangish-apricot, aging to ochre. Tubes are initially pale yellow, but become more vivid in age, and eventually develop greenish-yellow to greenish-olive tones. They will become pale blue upon with bruising. The pores are circular or a bit angular, with the same coloring and bruising reaction as the tubes. The robust stipe measures long by thick. It is usually thicker in the middle or lower region, and its base roots into the substrate. The top part of the stipe is yellow; under this the coloration tends to be masked by a dense and fine reticulation that becomes brown to brownish-crimson in age. In some specimens the stipe cuticle cracks and pointed patches lift from the surface. The flesh is pale yellow in the cap, with a narrow strip of pinkish-yellow under the cuticle; in the stipe, the flesh is orange-ochre, with a reddish tint. The flesh sometimes shows a slight and temporary color change to blue when cut or otherwise injured, but this feature is not consistent. It has a pleasant odor and a fruity-acid taste. The base of the stem has a green-blue reaction with iron salts (FeSO4).
Spores are fusiform (spindle shaped), measuring 10–15 by 4.5–6 μm. The basidia (spore-bearing cells) are club-shaped, four-spored, and contain internal oil droplets; they measure 28–35 by 9–12 μm. The cystidia are fusiform, hyaline (translucent), and 40–55 by 9–12 μm.
Ecology
It has been recorded forming ectomycorrhizal association with white poplar (Populus alba) in Hungary. Its ectomycorrhizae contain bright yellow pigments, especially the rhizomorphs, and have warts on the outer surfaces of both the rhizomorphs and the mantle. The ectomycorrhizae of R. armeniacus cannot be reliably distinguished from those of Xerocomus subtomentosus.
References
Boletaceae
Fungi of Europe
Fungi described in 1885
Taxa named by Lucien Quélet
Fungus species | Rheubarbariboletus armeniacus | Biology | 706 |
31,941,424 | https://en.wikipedia.org/wiki/Suicide%20bidding | Suicide bidding is a response to a tendering exercise in which a potential supplier, anxious to win business, submits a proposal to carry out the work for less than it will cost. These procurement processes are typically modelled as reverse sealed-bid auctions with the lowest bid winning.
The motive for such bidding is to keep the company's skilled labour employed, even if the project only breaks even or makes a loss.
This can result in poor quality work, poor service and debates over loopholes in contract wording in attempts to charge clients extra, or even insolvency on the part of the contractor.
The practice has particularly been noted in construction bidding. Around 2010, suicide bidding was widespread due to the economic crisis and strong competition. 2010 survey by the Chartered Institute of Building found that 82% of respondents believed that “suicide bidding” existed within the industry. It was considered to have contributed to the financial collapse of British firms Connaught plc and Rok plc in 2010.
The Civil Engineering Contractors Association acknowledged that the practice had become "rife" in the desperate competition for work during the late-2000s recession, but blamed the public sector procurement process for focussing on the lowest price rather than best value.
Some commissioning bodies, such as Crossrail, openly discourage the practice. In 2011, some housing associations began including specific terms in tenders to protect them from legal challenge in the event of refusing to award the contract according to the lowest tender.
See also
Loss leader
References
Procurement
Insolvency
Construction industry
Bidding strategy | Suicide bidding | Engineering | 309 |
57,596,406 | https://en.wikipedia.org/wiki/Contact-dependent%20growth%20inhibition | Contact-dependent growth inhibition (CDI) is a phenomenon where a bacterial cell may deliver a polymorphic toxin molecule into neighbouring bacterial cells upon direct cell-cell contact, causing growth arrest or cell death.
Discovery
CDI is now a blanket term to describe interbacterial competition that relies on direct cell-cell contact in bacteria. However, the phenomenon was first discovered in 2005 in the isolate EC93 of Escherichia coli found in rat intestine, and, in this case, was mediated by a Type V secretion system. This isolate dominated the rat's gut flora and appeared to be particularly good at outcompeting lab strains of E. coli when grown in co-culture. The novel part of this discovery was the fact that the inhibitory effects of the isolated E. coli appeared to require direct cell-cell contact. Before CDI was discovered in this isolate, the only systems known to mediate direct interbacterial competition by intoxication were toxins secreted into the extracellular space. Thus, these did not require cell-cell contact. A second system that could mediate CDI was discovered in 2006 in the pathogenic bacterium Vibrio cholerae, the cause of the gastro-intestinal disease cholera, and the opportunistic pathogen Pseudomonas aerugenosa. This system was much different that the Type V secretion system identified in E. coli, and thus formed a new class of CDI: the Type VI Secretion System.
Types of CDI
Type IV
The Type IV Secretion System T4SS is found in many species of Gram-negative and Gram-positive bacteria as well as in archea and are typically associated with conjugation or delivery of virulence proteins to eukaryotic cells. Some species of plant pathogen Xanthomonas, however, possess a particular T4SS capable of mediating CDI by delivering a peptidoglycan hydrolase. This effector kills targets that do not have the cognate immunity protein similar to other CDI systems.
Type V
The first CDI system to be discovered was a Type V secretion system, encoded by the cdiBAI gene cluster found widespread throughout pathogenic Gram-negative bacteria. The first protein encoded in the operon, CdiB, is an outer membrane beta-barrel protein that exports CdiA, presenting it on the cell surface of a CDI-expressing (CDI+) bacterium. CdiA is predicted to form a filament several nanometers long that extends outward from the CDI+ cell in order to interact with neighbouring bacteria via outer membrane protein receptors to which it will bind. The C-terminal 200-300 amino acids of CdiA harbours a highly variable toxic domain (CdiA-CT), which is delivered into a neighbouring bacterium upon receptor recognition, enabling the CDI+ cell to arrest the growth of the cell into which it delivers this CdiA-CT toxin. This toxic domain is linked to the rest of CdiA via a VENN peptide motif and vary significantly more between species than does the rest of CdiA. CdiI is an immunity protein to prevent auto-inhibition by the C-terminal toxin. This also prevents the bacteria from killing or inhibiting the growth of their siblings as long as these possess the immunity gene. Many CDI systems contain additional pairs called "orphans" following the first copy and these orphans can be connected to different main CdiA:s in a modular fashion.
Type VI
The Type VI Secretion System T6SS is widely spread amongst Gram-negative bacteria and consists of a protein complex with 13 core components (TssA to TssM), forming a needle-like structure capable of injecting effector molecules into neighbouring target cells similar to the contractile tail of the T4 bacteriophage. The T6SS is capable of delivering effectors to both prokaryote and eukaryotes target cells. Upon contraction of the T6SS, effectors are transported across the cytosol of the bacteria cell into the target cells. Effectors are loaded onto this dynamic secretion system through interactions with Hcp, VgrG and PAAR-domains. The full list of T6SS effectors is not known.
Rhs toxins
The Rearrangement hotspot system (Rhs) exists in both Gram-negative and Gram-positive bacteria. Similar to CdiA, these systems consists of big proteins with a conserved N-terminal domain and a variable C-terminal toxin domain requiring a cognate immunity protein. Many Rhs systems contain PAAR-domains (Proline-Alanine-Alanine-Arginine) which can interact with the VgrG of the T6SS apparatus making it required for Rhs secretion. The name Rearrangement hotspots comes from the discovery when the system was first identified as elements on the E. coli chromosome that were continuously rearranging. The Gram-positive soil bacterium Bacillus subtilis possesses an Rhs homolog called Wall-associated protein A (WapA) capable of mediating CDI whilst requiring a cognate immunity protein, WapI, to prevent auto-inhibition.
Other functions
Cell aggregation and biofilm formation
In E. coli, CdiA molecules may interact with those found on neighboring cells, independent of the receptor to which CdiA binds. In addition with receptor binding, these homotypic interactions cause cell-cell aggregation and promote biofilm formation for CDI+ bacteria. In a similar fashion, the CdiA homolog BcpA in Burkholderia thailandensis causes up-regulation of genes encoding pili and polysaccharides when delivered to sibling cells which are in possession of the immunity protein BcpI. This change in gene expression leads to increased biofilm formation in the bacterial population through a phenomenon now known as Contact-Dependent Signalling. Furthermore, the T6SS in V. cholerae is active in biofilms, enabling a cell expressing T6SS to kill nearby cells which do not have the specific immunity. The release of DNA from target cell death can be beneficial for gene transfer as well as the release of extra cellular DNA into the matrix.
Antibiotic persistence
In E. coli, CdiA-CT toxins have been found to induce persister cell formation in a clonal population when delivered to cells that lack sufficient levels of CdiI immunity to neutralise the incoming toxins. The intoxication of the cells leads to an increase of cellular (p)ppGpp levels, which in turn leads to degradation of the immunity protein and eventually to a higher extend of intoxication, resulting in persister formation.
References
Microbial growth and nutrition
Microbiology terms | Contact-dependent growth inhibition | Biology | 1,371 |
22,662,840 | https://en.wikipedia.org/wiki/Australasian%20Journal%20of%20Bone%20%26%20Joint%20Medicine | The Australasian Journal of Bone & Joint Medicine (originally titled the Australasian Journal of Musculoskeletal Medicine) was a periodical presented in the style of a scientific journal, published by Elsevier but established and funded by pharmaceutical company Merck. Publication began in 2002, and the last issue appeared in 2005. According to The Scientist:
The publication was not included in the MEDLINE literature database and did not have its own website.
In May 2009, Elsevier admitted that a series of similar industry sponsored publications had been produced, and that "high standards for disclosure were not followed in this instance". In a formal statement, the CEO of Elsevier's Health Sciences Division, Michael Hansen, admitted that the practice was "unacceptable", and expressed regret for the publications. Merck has denied claims that articles within it were ghost written by Merck and has stated that the articles were all reprinted from peer-reviewed medical journals.
Several medical experts stated that their names were included in the Honorary Editorial Board of the Australasian Journal of Bone and Joint Medicine without their knowledge and consent.
There were six such "industry-sponsored" publications brought out by Elsevier without proper disclosure of their nature, and which had the superficial appearance of a legitimate independent journal. The six publications involved were:
Australasian Journal of General Practice
Australasian Journal of Neurology
Australasian Journal of Cardiology
Australasian Journal of Clinical Pharmacy
Australasian Journal of Cardiovascular Medicine
Australasian Journal of Bone & Joint Medicine
See also
Academic dishonesty
Vioxx
References
External links
Volume 2 (2003), Issue 1
Volume 2 (2003), Issue 2
Ethics of science and technology
Elsevier academic journals
Academic journals established in 2002
Publications disestablished in 2005
Orthopedics journals
English-language journals
2002 establishments in Australia | Australasian Journal of Bone & Joint Medicine | Technology | 369 |
34,119,149 | https://en.wikipedia.org/wiki/Geotechnical%20centrifuge%20modeling | Geotechnical centrifuge modeling is a technique for testing physical scale models of geotechnical engineering systems such as natural and man-made slopes and earth retaining structures and building or bridge foundations.
The scale model is typically constructed in the laboratory and then loaded onto the end of the centrifuge, which is typically between in radius. The purpose of spinning the models on the centrifuge is to increase the g-forces on the model so that stresses in the model are equal to stresses in the prototype. For example, the stress beneath a layer of model soil spun at a centrifugal acceleration of 50 g produces stresses equivalent to those beneath a prototype layer of soil in earth's gravity.
The idea to use centrifugal acceleration to simulate increased gravitational acceleration was first proposed by Phillips (1869). Pokrovsky and Fedorov (1936) in the Soviet Union and Bucky (1931) in the United States were the first to implement the idea. Andrew N. Schofield (e.g. Schofield 1980) played a key role in modern development of centrifuge modeling.
Principles of centrifuge modeling
Typical applications
A geotechnical centrifuge is used to test models of geotechnical problems such as the strength, stiffness and capacity of foundations for bridges and buildings, settlement of embankments, stability of slopes, earth retaining structures, tunnel stability and seawalls. Other applications include explosive cratering, contaminant migration in ground water, frost heave and sea ice. The centrifuge may be useful for scale modeling of any large-scale nonlinear problem for which gravity is a primary driving force.
Reason for model testing on the centrifuge
Geotechnical materials such as soil and rock have non-linear mechanical properties that depend on the effective confining stress and stress history. The centrifuge applies an increased "gravitational" acceleration to physical models in order to produce identical self-weight stresses in the model and prototype. The one to one scaling of stress enhances the similarity of geotechnical models and makes it possible to obtain accurate data to help solve complex problems such as earthquake-induced liquefaction, soil-structure interaction and underground transport of pollutants such as dense non-aqueous phase liquids. Centrifuge model testing provides data to improve our understanding of basic mechanisms of deformation and failure and provides benchmarks useful for verification of numerical models.
Scaling laws
Note that in this article, the asterisk on any quantity represents the scale factor for that quantity. For example, in , the subscript m represents "model" and the subscript p represents "prototype" and represents the scale factor for the quantity .
The reason for spinning a model on a centrifuge is to enable small scale models to feel the same effective stresses as a full-scale prototype. This goal can be stated mathematically as
where the asterisk represents the scaling factor for the quantity, is the effective stress in the model and is the effective stress in the prototype.
In soil mechanics the vertical effective stress, for example, is typically calculated by
where is the total stress and is the pore pressure. For a uniform layer with no pore pressure, the total vertical stress at a depth may be calculated by:
where represents the density of the layer and represents gravity. In the conventional form of centrifuge modeling, it is typical that the same materials are used in the model and prototype; therefore the densities are the same in model and prototype, i.e.,
Furthermore, in conventional centrifuge modeling all lengths are scaled by the same factor . To produce the same stress in the model as in the prototype, we thus require , which may be rewritten as
The above scaling law states that if lengths in the model are reduced by some factor, n, then gravitational accelerations must be increased by the same factor, n in order to preserve equal stresses in model and prototype.
Dynamic problems
For dynamic problems where gravity and accelerations are important, all accelerations must scale as gravity is scaled, i.e.
Since acceleration has units of , it is required that
Hence it is required that :, or
Frequency has units of inverse of time, velocity has units of length per time, so for dynamic problems we also obtain
Diffusion problems
For model tests involving both dynamics and diffusion, the conflict in time scale factors may be resolved by scaling the permeability of the soil
Scaling of other quantitites
(this section obviously needs work!)
scale factors for energy, force, pressure, acceleration, velocity, etc.
Note that stress has units of pressure, or force per unit area. Thus we can show that
Substituting F = m∙a (Newton's law, force = mass ∙ acceleration) and r = m/L3 (from the definition of mass density).
Scale factors for many other quantities can be derived from the above relationships. The table below summarizes common scale factors for centrifuge testing.
Scale Factors for Centrifuge Model Tests (from Garnier et al., 2007 )
(Table is suggested to be added here)
Value of centrifuge in geotechnical earthquake engineering
Large earthquakes are infrequent and unrepeatable but they can be devastating. All of these factors make it difficult to obtain the required data to study their effects by post earthquake field investigations. Instrumentation of full scale structures is expensive to maintain over the large periods of time that may elapse between major temblors, and the instrumentation may not be placed in the most scientifically useful locations. Even if engineers are lucky enough to obtain timely recordings of data from real failures, there is no guarantee that the instrumentation is providing repeatable data. In addition, scientifically educational failures from real earthquakes come at the expense of the safety of the public. Understandably, after a real earthquake, most of the interesting data is rapidly cleared away before engineers have an opportunity to adequately study the failure modes.
Centrifuge modeling is a valuable tool for studying the effects of ground shaking on critical structures without risking the safety of the public. The efficacy of alternative designs or seismic retrofitting techniques can compared in a repeatable scientific series of tests.
Verification of numerical models
Centrifuge tests can also be used to obtain experimental data to verify a design procedure or a computer model. The rapid development of computational power over recent decades has revolutionized engineering analysis. Many computer models have been developed to predict the behavior of geotechnical structures during earthquakes and other loads. Before a computer model can be used with confidence, it must be proven to be valid based on evidence. The meager and unrepeatable data provided by natural earthquakes, for example, is usually insufficient for this purpose. Verification of the validity of assumptions made by a computational algorithm is especially important in the area of geotechnical engineering due to the complexity of soil behavior. Soils exhibit highly non-linear behavior, their strength and stiffness depend on their stress history and on the water pressure in the pore fluid, all of which may evolve during the loading caused by an earthquake. The computer models which are intended to simulate these phenomena are very complex and require extensive verification. Experimental data from centrifuge tests is useful for verifying assumptions made by a computational algorithm. If the results show the computer model to be inaccurate, the centrifuge test data provides insight into the physical processes which in turn stimulates the development of better computer models.
See also
Andrew N. Schofield
Civil engineer
Geotechnical engineering
Network for Earthquake Engineering Simulation
Physical model
Scale model
Soil mechanics
References
Schofield (1993), From cam clay to centrifuge models, JSSMFE Vol. 41, No. 5 Ser. No. 424 pp 83– 87, No. 6 Ser. No. 425 pp 84–90, No. 7, Ser. No. 426 pp 71–78.
External links
Technical committee on physical modelling in geotechnics
International Society for Soil Mechanics and Geotechnical Engineering
American Society of Civil Engineers
Tests in geotechnical laboratories
Civil engineering
Scale modeling | Geotechnical centrifuge modeling | Physics,Engineering | 1,655 |
7,965,029 | https://en.wikipedia.org/wiki/Excitation%20table | In electronics design, an excitation table shows the minimum inputs that are necessary to generate a particular next state (in other words, to "excite" it to the next state) when the current state is known. They are similar to truth tables and state tables, but rearrange the data so that the current state and next state are next to each other on the left-hand side of the table, and the inputs needed to make that state change happen are shown on the right side of the table.
Flip-flop excitation tables
In order to complete the excitation table of a flip-flop, one needs to draw the Q(t) and Q(t + 1) for all possible cases (e.g., 00, 01, 10, and 11), and then make the value of flip-flop such that on giving this value, one shall receive the input as Q(t + 1) as desired.
T flip-flop
The characteristic equation of a T flip-flop is .
SR flip-flop
("X" is "don't care")
The characteristic equation of a SR flip-flop is .
JK flip-flop
("X" is "don't care")
The characteristic equation of a JK flip-flop is .
D flip-flop
The characteristic equation of a D flip-flop is
References
External links
umd.edu's explanation - an explanation of excitation tables.
Types of Flip-flop Behaviour
Electronic design | Excitation table | Engineering | 308 |
68,887,812 | https://en.wikipedia.org/wiki/Samsung%20Galaxy%20M52%205G | The Samsung Galaxy M52 5G is a mid-range Android smartphone developed by Samsung Electronics as a part of its Galaxy M series. The device was scheduled to be launched on 19 September 2021 in India but the launch event was postponed to 28 September 2021. It was unveiled on 24 September 2021. Its key features are Qualcomm's new upper mid-range SoC Snapdragon 778G 5G, 120 Hz Super AMOLED Plus display, a triple camera setup with a 64 MP main camera and a 5000 mAh battery with 25W fast charging support. It went on sale on 3 October 2021 in India.
Specifications
Design
Samsung Galaxy M52 5G has a plastic frame and a plastic back panel, the front side is covered by glass. It has volume buttons and a recessed power button that doubles as a fingerprint reader at the right, a SIM/microSD card tray at the left and a USB-C port at the bottom. It has a 6.7 inch Infinity-O Display with a circular punch hole for the front-facing camera. It measures 164.2 x 76.4 x 7.4 mm and weighs 173 grams. It is available in Icy Blue, Blazing Black and White.
Hardware
Samsung Galaxy M52 5G is powered by Qualcomm Snapdragon 778G 5G system-on-chip with 6 nm process, an integrated 5G modem, an octa-core CPU consisting of a high performance cluster with 4x 2.4 GHz Kryo 670 Gold cores and a power efficiency cluster with 4x 1.8 GHz Kryo 670 Silver cores, and an Adreno 642L GPU. It has a 6.7-inch (172 mm) Super AMOLED Plus display with 1080×2400 pixels resolution, 20:9 aspect ratio, ~393 ppi pixel density, 120 Hz refresh rate and 16M colors. It features a triple camera setup at the rear with a 64 MP main camera with f/1.8 aperture, a 12 MP wide-angle camera with f/2.2 aperture and 123° field-of-view, and a 5 MP macro camera with f/2.4 aperture. There is a 32 MP front-facing camera with f/2.2 aperture located in the circular punch hole of the display. It supports 4K video recording from the main camera and the front facing camera. It has a 5000 mAh non-removable battery with 25W fast charging support. However, there isn't a 25W charger in the box, and it needs to be bought separately. It comes with 6/8 GB RAM and 128 GB internal storage and supports memory expansion via the hybrid SIM/microSD card slot up to 1 TB. It supports 11 5G bands. Unlike most of the phones in the Galaxy M series, Galaxy M52 5G doesn't have a headphone jack.
Software
Samsung Galaxy M52 5G is shipped with Android 11 and Samsung's proprietary user interface One UI 3.1. It comes with Knox Security Suite and AltZMode. The camera application includes the Single Take mode that enables users to take photo and record video from all the supported camera simultaneously. The software will be updated quarterly.
References
Android (operating system) devices
Galaxy M52
Phablets
Mobile phones introduced in 2021
M52
Mobile phones with multiple rear cameras
Mobile phones with 4K video recording
M52 | Samsung Galaxy M52 5G | Technology | 704 |
5,644,032 | https://en.wikipedia.org/wiki/Earth-centered%2C%20Earth-fixed%20coordinate%20system | The Earth-centered, Earth-fixed coordinate system (acronym ECEF), also known as the geocentric coordinate system, is a cartesian spatial reference system that represents locations in the vicinity of the Earth (including its surface, interior, atmosphere, and surrounding outer space) as X, Y, and Z measurements from its center of mass. Its most common use is in tracking the orbits of satellites and in satellite navigation systems for measuring locations on the surface of the Earth, but it is also used in applications such as tracking crustal motion.
The distance from a given point of interest to the center of Earth is called the geocentric distance, , which is a generalization of the geocentric radius, , not restricted to points on the reference ellipsoid surface.
The geocentric altitude is a type of altitude defined as the difference between the two aforementioned quantities: ; it is not to be confused for the geodetic altitude.
Conversions between ECEF and geodetic coordinates (latitude and longitude) are discussed at geographic coordinate conversion.
Structure
As with any spatial reference system, ECEF consists of an abstract coordinate system (in this case, a conventional three-dimensional right-handed system), and a geodetic datum that binds the coordinate system to actual locations on the Earth. The ECEF that is used for the Global Positioning System (GPS) is the geocentric WGS 84, which currently includes its own ellipsoid definition. Other local datums such as NAD 83 may also be used. Due to differences between datums, the ECEF coordinates for a location will be different for different datums, although the differences between most modern datums is relatively small, within a few meters.
The ECEF coordinate system has the following parameters:
The origin at the center of the chosen ellipsoid. In WGS 84, this is center of mass of the Earth.
The Z axis is the line between the North and South Poles, with positive values increasing northward. In WGS 84, this is the international reference pole (IRP), which does not exactly coincide with the Earth's rotational axis The slight "wobbling" of the rotational axis is known as polar motion, and can actually be measured against an ECEF.
The X axis is in the plane of the equator, passing through the origin and extending from 180° longitude (negative) to the prime meridian (positive); in WGS 84, this is the IERS Reference Meridian.
The Y axis is also in the plane of the equator, passing through extending from 90°W longitude (negative) to 90°E longitude (positive)
An example is the NGS data for a brass disk near Donner Summit, in California. Given the dimensions of the ellipsoid, the conversion from lat/lon/height-above-ellipsoid coordinates to X-Y-Z is straightforward—calculate the X-Y-Z for the given lat-lon on the surface of the ellipsoid and add the X-Y-Z vector that is perpendicular to the ellipsoid there and has length equal to the point's height above the ellipsoid. The reverse conversion is harder: given X-Y-Z can immediately get longitude, but no closed formula for latitude and height exists. See "Geodetic system." Using Bowring's formula in 1976 Survey Review the first iteration gives latitude correct within 10 degree as long as the point is within 10,000 meters above or 5,000 meters below the ellipsoid.
In astronomy
Geocentric coordinates can be used for locating astronomical objects in the Solar System in three dimensions along the Cartesian X, Y, and Z axes. They are differentiated from topocentric coordinates, which use the observer's location as the reference point for bearings in altitude and azimuth.
For nearby stars, astronomers use heliocentric coordinates, with the center of the Sun as the origin. The plane of reference can be aligned with the Earth's celestial equator, the ecliptic, or the Milky Way's galactic equator. These 3D celestial coordinate systems add actual distance as the Z axis to the equatorial, ecliptic, and galactic coordinate systems used in spherical astronomy.
See also
Earth-centered inertial (ECI)
Geodetic system
International Terrestrial Reference System and Frame (ITRS)
Orbital state vectors
Planetary coordinate system
References
External links
ECEF datum transformation Notes on converting ECEF coordinates to WGS-84 datum
Datum Transformations of GPS Positions Application Note Clearer notes on converting ECEF coordinates to WGS-84 datum
geodetic datum overview orientation of the coordinate system and additional information
GeographicLib includes a utility CartConvert which converts between geodetic and geocentric (ECEF) or local Cartesian (ENU) coordinates. This provides accurate results for all inputs including points close to the center of the Earth.
EPSG:4978
Global Positioning System
Astronomical coordinate systems | Earth-centered, Earth-fixed coordinate system | Astronomy,Mathematics,Technology,Engineering | 1,016 |
77,126,298 | https://en.wikipedia.org/wiki/Seamus%20Martin%20%28biochemist%29 | Seamus J. Martin is an Irish molecular biologist and immunologist working at The Smurfit Institute of Genetics in Trinity College Dublin. Since 1999, he has held the Smurfit Chair of Medical Genetics at Trinity College Dublin, and his research focuses on the links between cell death, cell stress, and inflammation. Martin is known for his contributions to understanding the molecular control of the mode of regulated cell death known as apoptosis. Martin received the 'GlaxoSmithKline Award' of the Biochemical Society in 2006, the British Science Association's 'Charles Darwin Award' in 2005, and The 'RDS-Irish Times Boyle Medal' in 2014, for his work on deciphering the role of caspases in apoptosis. In 2006, he was elected to the Royal Irish Academy, in 2009 he awarded EMBO Membership, and in 2023 he was elected to the Academia Europaea. His research work is widely cited and he received a European Research Council Advanced Research award in 2021.
Martin is an author of the 11th, 12th, and 13th editions of the award-winning textbook, Essential Immunology, and since 2014, he has served as Editor-in-Chief of The FEBS Journal (Cambridge, UK), an international life sciences academic journal.
Biography
Martin studied biology and chemistry as an undergraduate at The National University of Ireland, Maynooth (NUIM), followed by a PhD in Cell Biology working with Tom Cotter at Maynooth University. After completion of his PhD, he moved to the Dept. of Immunology at University College London (UK) to carry out a post-doctoral fellowship working on HIV immunopathology with internationally known immunologist Ivan Roitt, FRS. Supported by a Wellcome Trust International Prize Fellowship, he then relocated to the La Jolla Institute for Immunology, University of California, San Diego, USA, to undertake a second post-doc with US Immunologist and National Academy Member Douglas R. Green. In 1999 Martin moved to the Dept. of Genetics, Trinity College Dublin, where he was appointed to the Smurfit Chair of Medical Genetics.
Scientific contributions
Martin's research focuses on the molecular mechanisms governing regulated cell death and inflammation. Initially working on the role of proteases in coordinating programmed cell death (apoptosis), he made contributions to our understanding of how caspases become activated during apoptosis, the order of caspase activation events in the intrinsic and extrinsic caspase activation cascades, and how caspases coordinate apoptosis through proteolysis of hundreds of substrate proteins. More recently, his work has focused on how caspases coordinate inflammatory cascades downstream of death receptor engagement. In parallel to his work on caspases, he has also made contributions to our understanding of how neutrophil proteases promote inflammation through processing and activation of members of the extended IL-1 family and has championed the idea that IL-1 family members represent the canonical ‘damage-associated molecular patterns’ that promote inflammation upon release from necrotic cells
While working with Doug Green at La Jolla, Martin pioneered annexin V labeling as a probe for apoptotic cells which has become the ‘gold standard’ for the measurement of apoptosis. He also established a mammalian ‘cell-free’ system for the study of caspase activation pathways in mammals,[13][14] and continued this work upon establishing his own laboratory.[15][16][17][18] Martin's recent work has focused on exploring the links between cell death signals and inflammatory signaling cascades. His laboratory has published a series of studies demonstrating that essentially all initiators of programmed cell death can also promote inflammation[19][20][21] and his current research is focused upon understanding how chemotherapeutic drugs can frequently trigger inflammation that may be detrimental to killing cancer cells.[222]
Select publications
Martin, S. J., Amarante-Mendes, G. P., Shi, L., Chuang, T.-H., Casiano, C. A., O'Brien, G. A., Fitzgerald, P., Tan, E. M., Bokoch, G. M., Greenberg, A. H., and Green, D. R. (1996) The cytotoxic cell protease granzyme B initiates apoptosis in a cell-free system by proteolytic processing and activation of the ICE/CED-3 family protease, CPP32, via a novel two-step mechanism. EMBO Journal. 15, 2407-2416.
Slee, E.A., Harte, M.T., Kluck, R.M., Wolf, B.B., Casiano, C.A., Newmeyer, D.D., Wang, H.-G., Reed, J.C., Nicholson, D.W., Alnemri, E.S., Green D.R., and Martin S.J. (1999) Ordering the Cytochrome c-Initiated Caspase Cascade: Hierarchical Activation of Caspases -2, -3, -6, -7, -8 and -10 in a Caspase-9-Dependent Manner. The Journal of Cell Biology 144:281-292.
Lüthi, A.U., Cullen, S.P., McNeela, E.A., Duriez, P.J., Afonina, I.S., Sheridan, C., Brumatti, G., Taylor, R.C., Kersse, K., Vandenabeele, P., Lavelle, E.C. and Martin SJ (2009) Suppression of IL-33 Bioactivity through Proteolysis by Apoptotic Caspases. Immunity 31:84-98.
Cullen, SP, Henry CM, Kearney, CJ, Logue SE, Feoktistova M, Tynan GA, Lavelle EC, Leverkus M, and Martin SJ (2013) Fas/CD95-Induced Chemokines can Serve as ‘Find-Me’ Signals for Apoptotic Cells. Molecular Cell, 49, 1034–1048.
Hollville, E., Carroll, R., and Martin SJ. (2014) Bcl-2 Family Proteins Participate in Mitochondrial Quality Control by Regulating Parkin/PINK1-Dependent Mitophagy. Molecular Cell 55:451-66.
Henry CM and Martin SJ (2017) Caspase-8 Acts in a Non-enzymatic Role as a Scaffold for Assembly of a Pro-inflammatory "FADDosome" Complex upon TRAIL Stimulation. Molecular Cell, 65, 715-729.
Sullivan GP, O'Connor H, Henry CM, Davidovich P, Clancy DM, Albert ML, Cullen SP, and Martin SJ. (2020) TRAIL Receptors Serve as Stress-Associated Molecular Patterns to Promote ER-Stress-Induced Inflammation. Developmental Cell 52, 714-730.
Sullivan GP, Davidovich P, Muñoz-Wolf N, Ward RW, Hernandez Santana YE, Clancy DM, Gorman A, Najda Z, Turk B, Walsh PT, Lavelle EC, and Martin SJ. (2022) Myeloid cell-derived proteases produce a pro-inflammatory form of IL-37 that signals via IL-36 receptor engagement. Science Immunology 7, eade5728 1-15.
References
External links
Google Scholar
Official website
Living people
21st-century Irish biologists
Irish immunologists
Molecular biologists
Academics of Trinity College Dublin
Irish biochemists
Year of birth missing (living people) | Seamus Martin (biochemist) | Chemistry | 1,630 |
66,182,787 | https://en.wikipedia.org/wiki/Surface%20magnon%20polariton | Surface magnon-polaritons (SMPs) are a type of quasiparticle in condensed matter physics. They arise from the coupling of incident electromagnetic (EM) radiations to the magnetic dipole polarization in the surface layers of a solid. Magnons are analogous to other forms of polaritons, such as plasmons and phonons, but represent an oscillation of the magnetic component of the solid's EM field rather than its electric component or a mechanical oscillation in the solid's atomic structure.
They are sometimes referred to as magnetic surface polaritons (MSPs).
By employing artificially constructed metamaterials whose properties mainly stem from their engineered internal fine structures rather than their bulk physical make up, it is possible to more easily achieve useful SMPs. However, they can be found in several natural magnetic materials, including at THz frequencies in antiferromagnetic crystals.
Magnons offer a way to control light-matter interactions at Terahertz frequencies.
References
Quasiparticles
Plasmonics | Surface magnon polariton | Physics,Chemistry,Materials_science | 220 |
24,982,361 | https://en.wikipedia.org/wiki/Cache%20timing%20attack | Cache timing attacks also known as Cache attacks are a type of side-channel attack that allows attackers to gain information about a system purely by tracking cache access made by the victim system in a shared environment.
References
Side-channel attacks
Web security exploits | Cache timing attack | Technology | 50 |
11,512,390 | https://en.wikipedia.org/wiki/Exobasidium%20burtii | Exobasidium burtii is a species of fungus in the family Exobasidiaceae. It is a plant pathogen.
References
Fungal plant pathogens and diseases
Ustilaginomycotina
Fungi described in 1934
Fungus species
Taxa named by Sanford Myron Zeller | Exobasidium burtii | Biology | 55 |
62,379,588 | https://en.wikipedia.org/wiki/Rotary%20atomizers | Rotary atomizers use a high speed rotating disk, cup or wheel to discharge liquid at high speed to the perimeter, forming a hollow cone spray. The rotational speed controls the drop size. Spray drying and spray painting are the most important and common uses of this technology.
Many industries need to convert a large mass of liquid into a dispersion of small (micron-size) droplets (generate a spray). Some examples of this need are evaporative cooling, meteorology, printing, medical applications, spray combustion, coating, and drying. Various devices exist to generate sprays, such as atomizers, sprayers, nozzles, and applicators. Sprays are typically generated by producing a high speed difference between the phase of gases and the liquid to be atomized. These devices achieve this atomization by releasing the liquid at very high speed into the unagitated air. The liquid can also be atomized by using a reverse process, instead of accelerating the liquid, gas can be accelerated to achieve a relatively higher speed than the liquid. The devices using this method to achieve atomization are called as airblast, air-assist, or popularly twin-fluid atomizers. In a Rotary Atomizer, the rotating cup or disc forces the liquid to come out at a very high speed through its rim.
The Rotary, Pressure-swirl or Twin-fluid Atomizers are the most common methods for spray generation. For special applications, alternative atomizer types exist such as the electrostatic atomizer in which electrical pressure is used to drive the atomization, and the ultrasonic atomizing device in which the liquid is passed through a transducer vibrating at ultrasonic frequencies to generate shorter wavelengths which convert the fluid into smaller droplets. Since the flow rate of liquid is low in both of these devices, their applications are limited.
Working Principle
Rotary atomizers work on the principle of centrifugal energy; this energy is used to produce a high relative speed between the fluid and air which is essential for atomization. A rotary atomizer comprises a rotating surface. This surface can be in the form of a flat or a vaned disc, a cup, or a slotted wheel. A basic rotary atomizer is displayed in the figure.
The liquid first flows radially outwards in the disc and is then released from the disc's outer limits at a relatively very high speed. The atomization relies on the liquid's flow rate and the disc's rotational speed. The fluid is released from the disc's outer limits as uniform-sized droplets at low flow rates. At a comparatively high flow rate, ligaments are generated along the disc's outer limits which later on break into smaller droplets. When the flow rate is further increased, the ligaments become unable to fit in with the liquid flow, and hence a fine sheet of liquid is produced which expands past the disc's rim. This sheet, later on, disintegrates into ligaments and finally, drops are formed. The transition from ligament to sheet formation can be delayed by ragging the disc's edges. Rotary atomizers belong to the mechanical atomizers; hence, neither a high-pressure liquid nor a pressurized gas is required for atomization. The energy required for atomization is transferred directly from the atomizer body to the liquid. This gives us an advantage that the energy required for atomizing the liquid is directly supplied mechanically and energetically. The complicated and costly production of compressed gas, for example, compressed air, is no longer necessary. It is sufficient to feed the liquid to be atomized to the atomizer under low pressure. Sometimes a low hydrostatic pressure is adequate.
Working Formulae
The spray generated by a device like a rotary atomizer can be viewed as liquid droplets submerged in a continuous phase of gases. The size of droplet formed by atomizer depends on various properties of the fluid (both liquid and gaseous fluid) such as density, viscosity and surface tension between fluids.
Generally, small gas turbines operate under high rotational speed of more than 100,000 rpm. Even small-sized atomizer of 10 cm diameter revolving at 30,000 rpm can impart an acceleration of 490, 000 m/s2 (which is fifty thousand times of gravity) on the liquid fuel. Eventually, such fuel atomizers create very tiny droplets. The rotary atomizer in which liquid is revolving along with it at the rate of ω and has radial channels at nominal radius R=(R1+R2)/2 in the edge from which high-speed liquid interacts with gas to form droplets.
Considering the nominal radius of the channel and thus of mass of liquid inside channel equal to R, the liquid inside channel will experience the centrifugal acceleration of Rω2, which causes the liquid to form a thin layer of thickness t on both walls of the channel. At very high acceleration thickness of the liquid layer (film) is very small in order μm. The shape of the channel also decides the effectiveness of atomization and the size of droplets. That is one aspect of determining the size of the droplet is the velocity of liquid in the channel (v=Rω).
So, we have four dimensionless terms derived from the above properties which determine the performance of atomization.
1. Liquid-gas density ratio
r = [ρL / ρG] where ρL and ρG are densities of liquid and gas respectively
2. Viscosity ratio
m = [μL / μG] where, μL and μG are viscosities of liquid and gas respectively
3. Weber Number
Wet = [ρG Vc2 t/σs] where σs is surface tension between liquid and gas contact surface. It is the ratio of the force applied by the gas on the liquid layer to the surface tension force acting on liquid.
4. Ohnesorge Number
Oht= [μL / (ρL σs t) 1/2]
It is the ratio of viscous force inside the layer to the surface tension force acting on liquid. Altogether, all these terms describe three main phenomena of atomization viz., inertia, viscous diffusion and surface tension. For practical fuel atomizer, Ohnesorge number is limited to Oht<<1 and the size of the droplet are not much affected by Ohnesorge number. So, viscous effects can be neglected. But Weber number can't be neglected since surface tension and inertia are the major phenomena of the atomization process.
For small values of We, surface tension is dominant, and this force pulls the liquid towards the wall of the channel, making a single column that eventually breaks after meeting air resulting in comparatively larger droplets. This is known as the subcritical breakup of liquid. Whereas, for the supercritical breakup of liquid (more significant values of We), force applied by gas is dominant for breaking of liquid which results in fine small size of droplets.
Features of a Rotary Atomizer
Because of the breakup energy which the wheel's high-speed supplies in liquid feed systems, they can run at relatively low pressure. The atomizer drive gives the high speed to the wheel.
Clogging can be a problem for spray nozzle systems, whereas rotary atomizers can work in such situations.
A rotary atomizer can manage large amounts of abrasive and non-abrasive feeds.
A rotary atomizer can take very viscous liquids.
A rotary atomizer is flexible according to particle size. It can be modified from 5 μ to 150 μ by changing the wheel speed.
A rotary atomizer can give different powder characteristics and bulk density by equipping with different wheel designs.
A rotary atomizer can be fitted with a wide variety of wheels with various designs and sizes for abrasive and non-abrasive feeds.
Applications
Industrial Finishing
Rotary atomizer technology is found often on paint lines in the industrial finishing industry. A rotary atomizer is mounted to a paint robot or a reciprocator. Often call a Rotary bell atomizer, this paint applicator is often paired with electrostatic technology in order to maximize transfer efficiency of the paint. Rotary atomizers spin at extremely high speeds to break up the paint into fine, even particle sizes. Leading to a very high quality, consistent finish. This technology is used to paint a variety of industries including automotive, aerospace, aluminum extrusion, agricultural equipment, cosmetics, household cookware, electronics and more.
References
Fluid mechanics
Turbomachinery | Rotary atomizers | Chemistry,Engineering | 1,745 |
27,997,823 | https://en.wikipedia.org/wiki/Refined%20Bitumen%20Association | The Refined Bitumen Association is the trade association for UK bitumen companies.
History
It was formed in 1968.
Asphalt Industry Alliance
In 2000, it formed the Asphalt Industry Alliance with the Mineral Products Association, based in London. Asphalt is a mixture of bitumen and quarried mineral products, represented by both trade organisations.
Structure
Its five main members cover 95% of the UK market
ExxonMobil Bitumen, based in Leatherhead, Surrey
Nynas UK (a Swedish company), based in Eastham, Merseyside, Wirral, north of Ellesmere Port
Petroplus Bitumen (formerly BP Bitumen before Petroplus bought the Coryton Refinery in 2007), based in Llandarcy, Neath Port Talbot
Shell Bitumen, based in Wythenshawe
Total Bitumen UK Ltd, based in Ashton-on-Ribble in Preston, Lancashire
Function
It represents the UK bitumen industry at a national level. The UK produces around 1.5 million tonnes of bitumen a year. 90% of UK bitumen is used on roads.
References
External links
RBA
Eurobitume - based in Brussels
Asphalt Industry Alliance
Asphalt
Trade associations based in the United Kingdom
Organisations based in Harrogate
Organizations established in 1968
Oil and gas companies of the United Kingdom
Road construction | Refined Bitumen Association | Physics,Chemistry,Engineering | 263 |
34,903,260 | https://en.wikipedia.org/wiki/Animal%20navigation | Animal navigation is the ability of many animals to find their way accurately without maps or instruments. Birds such as the Arctic tern, insects such as the monarch butterfly and fish such as the salmon regularly migrate thousands of miles to and from their breeding grounds, and many other species navigate effectively over shorter distances.
Dead reckoning, navigating from a known position using only information about one's own speed and direction, was suggested by Charles Darwin in 1873 as a possible mechanism. In the 20th century, Karl von Frisch showed that honey bees can navigate by the Sun, by the polarization pattern of the blue sky, and by the Earth's magnetic field; of these, they rely on the Sun when possible. William Tinsley Keeton showed that homing pigeons could similarly make use of a range of navigational cues, including the Sun, Earth's magnetic field, olfaction and vision. Ronald Lockley demonstrated that a small seabird, the Manx shearwater, could orient itself and fly home at full speed, when released far from home, provided either the Sun or the stars were visible.
Several species of animal can integrate cues of different types to orient themselves and navigate effectively. Insects and birds are able to combine learned landmarks with sensed direction (from the Earth's magnetic field or from the sky) to identify where they are and so to navigate. Internal 'maps' are often formed using vision, but other senses including olfaction and echolocation may also be used.
The ability of wild animals to navigate may be adversely affected by products of human activity. For example, there is evidence that pesticides may interfere with bee navigation, and that lights may harm turtle navigation.
Early research
In 1873, Charles Darwin wrote a letter to Nature magazine, arguing that animals including man have the ability to navigate by dead reckoning, even if a magnetic 'compass' sense and the ability to navigate by the stars is present:
Later in 1873, Joseph John Murphy replied to Darwin, writing back to Nature with a description of how he, Murphy, believed animals carried out dead reckoning, by what is now called inertial navigation:
Karl von Frisch (1886–1982) studied the European honey bee, demonstrating that bees can recognize a desired compass direction in three different ways: by the Sun, by the polarization pattern of the blue sky, and by the Earth's magnetic field. He showed that the Sun is the preferred or main compass; the other mechanisms are used under cloudy skies or inside a dark beehive.
William Tinsley Keeton (1933–1980) studied homing pigeons, showing that they were able to navigate using the Earth's magnetic field, the Sun, as well as both olfactory and visual cues.
Donald Griffin (1915–2003) studied echolocation in bats, demonstrating that it was possible and that bats used this mechanism to detect and track prey, and to "see" and thus navigate through the world around them.
Ronald Lockley (1903–2000), among many studies of birds in over fifty books, pioneered the science of bird migration. He made a twelve-year study of shearwaters such as the Manx shearwater, living on the remote island of Skokholm. These small seabirds make one of the longest migrations of any bird—10,000 kilometres—but return to the exact nesting burrow on Skokholm year after year. This behaviour led to the question of how they navigated.
Mechanisms
Lockley began his book Animal Navigation with the words:
Many mechanisms of spatial cognition have been proposed for animal navigation: there is evidence for a number of them. Investigators have often been forced to discard the simplest hypotheses - for example, some animals can navigate on a dark and cloudy night, when neither landmarks nor celestial cues like Sun, Moon, or stars are visible. The major mechanisms known or hypothesized are described in turn below.
Remembered landmarks
Animals including mammals, birds and insects such as bees and wasps (Ammophila and Sphex), are capable of learning landmarks in their environment, and of using these in navigation.
Orientation by the Sun
Some animals can navigate using celestial cues such as the position of the Sun. Since the Sun moves in the sky, navigation by this means also requires an internal clock. Many animals depend on such a clock to maintain their circadian rhythm. Animals that use sun compass orientation are fish, birds, sea-turtles, butterflies, bees, sandhoppers, reptiles, and ants.
When sandhoppers (such as Talitrus saltator) are taken up a beach, they easily find their way back down to the sea. It has been shown that this is not simply by moving downhill or towards the sight or sound of the sea. A group of sandhoppers were acclimatised to a day/night cycle under artificial lighting, whose timing was gradually changed until it was 12 hours out of phase with the natural cycle. Then, the sandhoppers were placed on the beach in natural sunlight. They moved away from the sea, up the beach. The experiment implied that the sandhoppers use the sun and their internal clock to determine their heading, and that they had learnt the actual direction down to the sea on their particular beach.
Experiments with Manx shearwaters showed that when released "under a clear sky" far from their nests, the seabirds first oriented themselves and then flew off in the correct direction. But if the sky was overcast at the time of release, the shearwaters flew around in circles.
Monarch butterflies use the Sun as a compass to guide their southwesterly autumn migration from Canada to Mexico.
Orientation by the night sky
In a pioneering experiment, Lockley showed that warblers placed in a planetarium showing the night sky oriented themselves towards the south; when the planetarium sky was then very slowly rotated, the birds maintained their orientation with respect to the displayed stars. Lockley observes that to navigate by the stars, birds would need both a "sextant and chronometer": a built-in ability to read patterns of stars and to navigate by them, which also requires an accurate time-of-day clock.
In 2003, the African dung beetle Scarabaeus zambesianus was shown to navigate using polarization patterns in moonlight, making it the first animal known to use polarized moonlight for orientation. In 2013, it was shown that dung beetles can navigate when only the Milky Way or clusters of bright stars are visible, making dung beetles the only insects known to orient themselves by the galaxy.
Orientation by polarised light
Some animals, notably insects such as the honey bee, are sensitive to the polarisation of light. Honey bees can use polarized light on overcast days to estimate the position of the Sun in the sky, relative to the compass direction they intend to travel. Karl von Frisch's work established that bees can accurately identify the direction and range from the hive to a food source (typically a patch of nectar-bearing flowers). A worker bee returns to the hive and signals to other workers the range and direction relative to the Sun of the food source by means of a waggle dance. The observing bees are then able to locate the food by flying the implied distance in the given direction, though other biologists have questioned whether they necessarily do so, or are simply stimulated to go and search for food. However, bees are certainly able to remember the location of food, and to navigate back to it accurately, whether the weather is sunny (in which case navigation may be by the Sun or remembered visual landmarks) or largely overcast (when polarised light may be used).
Magnetoreception
Some animals, including mammals such as blind mole rats (Spalax) and birds such as pigeons, are sensitive to the Earth's magnetic field.
Homing pigeons use magnetic field information with other navigational cues. Pioneering researcher William Keeton showed that time-shifted homing pigeons could not orient themselves correctly on a clear sunny day, but could do so on an overcast day, suggesting that the birds prefer to rely on the direction of the Sun, but switch to using a magnetic field cue when the Sun is not visible. This was confirmed by experiments with magnets: the pigeons could not orient correctly on an overcast day when the magnetic field was disrupted.
Olfaction
Olfactory navigation has been suggested as a possible mechanism in pigeons. Papi's 'mosaic' model argues that pigeons build and remember a mental map of the odours in their area, recognizing where they are by the local odour. Wallraff's 'gradient' model argues that there is a steady, large-scale gradient of odour which remains stable for long periods. If there were two or more such gradients in different directions, pigeons could locate themselves in two dimensions by the intensities of the odours. However it is not clear that such stable gradients exist. Papi did find evidence that anosmic pigeons (unable to detect odours) were much less able to orient and navigate than normal pigeons, so olfaction does seem to be important in pigeon navigation. However, it is not clear how olfactory cues are used.
Olfactory cues may be important in salmon, which are known to return to the exact river where they hatched. Lockley reports experimental evidence that fish such as minnows can accurately tell the difference between the waters of different rivers. Salmon may use their magnetic sense to navigate to within reach of their river, and then use olfaction to identify the river at close range.
Gravity receptors
GPS tracing studies indicate that gravity anomalies could play a role in homing pigeon navigation.
Other senses
Biologists have considered other senses that may contribute to animal navigation. Many marine animals such as seals are capable of hydrodynamic reception, enabling them to track and catch prey such as fish by sensing the disturbances their passage leaves behind in the water. Marine mammals such as dolphins, and many species of bat, are capable of echolocation, which they use both for detecting prey and for orientation by sensing their environment.
Way-marking
The wood mouse is the first non-human animal to be observed, both in the wild and under laboratory conditions, using movable landmarks to navigate. While foraging, they pick up and distribute visually conspicuous objects, such as leaves and twigs, which they then use as landmarks during exploration, moving the markers when the area has been explored.
Path integration
Dead reckoning, in animals usually known as path integration, means the putting together of cues from different sensory sources within the body, without reference to visual or other external landmarks, to estimate position relative to a known starting point continuously while travelling on a path that is not necessarily straight. Seen as a problem in geometry, the task is to compute the vector to a starting point by adding the vectors for each leg of the journey from that point.
Since Darwin's On the Origins of Certain Instincts (quoted above) in 1873, path integration has been shown to be important to navigation in animals including ants, rodents and birds. When vision (and hence the use of remembered landmarks) is not available, such as when animals are navigating on a cloudy night, in the open ocean, or in relatively featureless areas such as sandy deserts, path integration must rely on idiothetic cues from within the body.
Studies by Wehner in the Sahara desert ant (Cataglyphis bicolor) demonstrate effective path integration to determine directional heading (by polarized light or sun position) and to compute distance (by monitoring leg movement or optical flow).
Path integration in mammals makes use of the vestibular organs, which detect accelerations in the three dimensions, together with motor efference, where the motor system tells the rest of the brain which movements were commanded, and optic flow, where the visual system signals how fast the visual world moves past the eyes. Information from other senses such as echolocation and magnetoreception may also be integrated in certain animals. The hippocampus is the part of the brain that integrates linear and angular motion to encode a mammal's relative position in space.
David Redish states that "The carefully controlled experiments of Mittelstaedt and Mittelstaedt (1980) and Etienne (1987) have demonstrated conclusively that [path integration in mammals] is a consequence of integrating internal cues from vestibular signals and motor efferent copy".
Effects of human activity
Neonicotinoid pesticides may impair the ability of bees to navigate. Bees exposed to low levels of thiamethoxam were less likely to return to their colony, to an extent sufficient to compromise a colony's survival.
Light pollution attracts and disorients photophilic animals, those that follow light. For example, hatchling sea turtles follow bright light, particularly bluish light, altering their navigation. Disrupted navigation in moths can easily be observed around bright lamps on summer nights. Insects gather around these lamps at high densities instead of navigating naturally.
See also
Animal migration
Salmon run
Notes
References
Sources
Further reading
Keeton, William (1972) Effects of magnets on pigeon homing. pages 579–594 in Animal Orientation and Navigation. NASA SP-262.
Keeton, William (1977) Magnetic Reception (biology). In Encyclopedia of Science and Technology, 2nd Ed. McGraw-Hill.
Keeton, William (1979) Pigeon Navigation. pages 5–20 in Neural Mechanisms of Behavior in the Pigeon. (A. M. Granda and J. H. Maxwell, Eds.) Plenum Publishing.
External links
How Stuff Works: Animal Navigation
Oldenburg University: Animal Navigation
National Geographic: Animal Navigation (resources for teachers)
Navigation
Animal migration
Cognitive neuroscience
Ethology
Navigation
Spatial cognition | Animal navigation | Physics,Biology | 2,818 |
38,274,928 | https://en.wikipedia.org/wiki/Lambda1%20Phoenicis | {{DISPLAYTITLE:Lambda1 Phoenicis}}
λ1 Phoenicis, Latinized as Lambda1 Phoenicis, is a double star in the southern constellation of Phoenix. It is visible to the naked eye as a faint, white-hued point of light with a combined apparent visual magnitude of 4.76. The system is located approximately 183 light years away from the Sun based on parallax. It is a member of the Hyades Supercluster.
The brighter component is an A-type main-sequence star with a stellar classification of A0Va. It may form a binary system of two roughly equal stars. An infrared excess suggests there is a debris disk orbiting from the star with a mean temperature of 95 K. It has one visual companion at an angular separation of about and magnitude 13.7.
References
A-type main-sequence stars
Circumstellar disks
Double stars
Hyades Stream
Phoenix (constellation)
Phoenicis, Lambda1
Durchmusterung objects
002834
002472
0125 | Lambda1 Phoenicis | Astronomy | 222 |
40,066,832 | https://en.wikipedia.org/wiki/Arca%20%28musician%29 | Alejandra Ghersi Rodríguez (born October 14, 1989), known professionally as Arca, is a Venezuelan musician and record producer based in Barcelona, Spain. She initially began releasing music under the name of Nuuro. After attending the Clive Davis Institute of Recorded Music, Ghersi first released the EP Baron Libre (2012) under the name Arca and subsequently released the EPs Stretch 1 and Stretch 2; the latter experimented with hip hop and brought her attention from prominent music publications.
She released her first two albums, Xen and Mutant, in 2014 and 2015 respectively. Her eponymous third album, Arca (2017), became the first to prominently feature her vocals. From 2020 to 2021, Ghersi released the Kick quintet, starting with the album Kick I (2020) and ending with Kick IIIII (2021); these recordings drew from styles such as IDM, reggaeton, avant-pop, techno, and ambient. Ghersi has frequently incorporated themes related to gender identity, non-binary identification, and psychosexuality in her work, particularly after coming out in 2018.
Ghersi has also worked frequently with other artists as producer and collaborator. She received production credits on releases such as Kanye West's Yeezus (2013), FKA Twigs' EP2 (2013), LP1 (2014), and Björk's Vulnicura (2015), Utopia (2017). She has additionally contributed to music by artists such as Kelela, The Weeknd, Frank Ocean, Planningtorock, Rosalía, Sia, Shygirl, and Lil Uzi Vert.
Early life
Arca was born in Caracas as Alejandro Ghersi on October 14, 1989. Her father, Henrique Ghersi Rossón, is an investment banker and founder of VIP Capital (Venezuelan Investment Partners), an investment banking firm in Venezuela. Additionally, she has an older brother whose music collection she would frequently listen to during her childhood.
The Ghersi family relocated to Darien, Connecticut when Ghersi was three years old, before returning to Caracas when she was nine years old. Ghersi described Darien as a "white picket fences" town with "deer and tick". After returning to Caracas, Ghersi eventually began playing the friction drum and started producing electronic music on FL Studio. She released music in her adolescence by the name of Nuuro, and received moderate popularity in her home country, with praise from big national artists such as Los Amigos Invisibles. She also did collaborations with fellow Venezuelan artists during this period, such as programming the synthesizers in La Vida Bohème's Grammy nominated album Nuestra. She later attended the Clive Davis Institute of Recorded Music at NYU.
Career
2012–2016: Production work, Stretch EPs, &&&&&, Xen, and Mutant
On 1 February 2012, Ghersi released Arca's debut extended play (EP), Baron Libre, through UNO NYC. Later that year, she released the Stretch 1 and Stretch 2 EPs on 19 April and 6 August respectively.
In 2013, she was credited for additional production, programming and songwriting for five of the songs on Kanye West's Yeezus, which was released on 18 June. Ghersi also served as one of the three production consultants. That same year on 23 July, she released her debut mixtape, &&&&& through SoundCloud and Hippos in Tanks. The project included an audio-visual performance alongside Jesse Kanda, who contributed the visuals, at MoMA PS1 in October 2013. On 17 September, FKA Twigs' EP2 was released, on which Arca produced and co-wrote every song.
On 11 September 2014, it was announced that Arca signed with British label Mute Records and released the lead single, "Thievery", from her then upcoming debut studio album, Xen. One more single was released prior to the album's release, "Now You Know" on 31 October 2014 alongside a music video.Xen was released on 4 November 2014 via Mute Records. Arca made significant contributions to Björk's eighth studio album Vulnicura which was released on 20 January 2015. She was credited as the co-producer of seven of the tracks, and the co-writer of two. According to Ghersi, the two began collaborating after her manager sent &&&&& to Björk's team and the musician contacted her through email.
Ghersi collaborated with American singer Kelela on her Hallucinogen EP, which was released in October 2015. She was credited for producing, recording, mixing and co-writing two of the tracks, including the title track, which is an instrumental from &&&&& with Kelela adding improvised vocals. The following month, Arca's second studio album, Mutant, was released on 20 November 2015. She released the Entrañas mixtape on 4 July 2016, following the single "Sin Rumbo".
2017–present: Arca and Kick series
On 22 February 2017, Arca signed with XL Recordings and released "Piel", the lead single from the eponymous third studio album, Arca. The track was noted for featuring Ghersi singing which many reviewers considered a contrast from her older works. The release of Arca was preceded by three more singles: "Anoche", "Reverie" and "Saunter". Arca was released on 7 April 2017 via XL Recordings to widespread acclaim from music critics and was featured on numerous year-end lists. To promote the album, a music video for "Desafío" was released while "Saunter" and "Reverie" were released as twelve-inch singles.
Later in 2017, Arca collaborated with Björk again on her ninth studio album Utopia, producing the vast majority of the record. Björk explained that the album explored "the Arca-Björk overlap". A music video featuring Arca for "Arisen My Senses" was released on 18 December 2017. Arca also collaborated with Kelela on her debut studio album, Take Me Apart, released in October 2017. Kelela said she "anchored" the album and produced a bulk of it. She is credited for producing on four tracks, and co-writing two.
In September 2019, Arca held a series of performances at New York City cultural venue The Shed during a live shoot for a "yet-to-be released project". The series, titled "Mutant;Faith" was held from 25 September - 28 September and consisted of four acts. It was noted by fashion magazines Vogues Rachel Hahn and Papers Matt Moen for its improvised nature while the latter also noticed the interactive element of the performances. The performances featured guest appearances from Björk and American actor Oscar Isaac.
On 19 February 2020, Arca released a 62-minute single named "@@@@@" along with an audiovisual directed by Frederik Heyman. The track was released on XL Recordings on 21 February. Along with the single, 13 international tour dates were announced for Spring 2020. Her fourth album Kick I, featuring Björk, Rosalía, Shygirl and Sophie, was announced on 8 March 2020 as part of an anthology and released on 26 June 2020; for this album Arca was nominated to the Grammys 2021. On 2 April, Arca had a 6 hour long twitch stream with a DJ mix named “^^^^^ (Circumflex)”, which later premiered on NTS radio on 2 May. In July 2020, it was announced that a reissue of &&&&& would be released and the track "Knot" was released as the lead single. The mixtape was reissued to celebrate the anniversary of Berlin based experimental label PAN. In September 2021, Arca's remix of "Rain on Me" by Lady Gaga and Ariana Grande, which samples the songs "Time" and "Mequetrefe" from Kick I, was released as part of Gaga's remix album Dawn of Chromatica.
On June 24th, 2021, Arca showcased a seven track extended play (EP) named "Issued by Bottega", and was only available on Bottega Veneta 2021 Digital Journal. The follow-up albums to Kick I, titled Kick II, Kick III and Kick IIII, were originally scheduled to be released on December 3, 2021. However, starting with Kick II on November 30, albums were released in sequence within that week. A fifth installment, Kick IIIII, was released "as a surprise" on December 3. Arca co-produced the track "Tears in the Club" by FKA Twigs featuring Canadian singer the Weeknd, which was released later that month as the lead single for FKA Twigs' mixtape Caprisongs. Arca also produced the track "Thank You Song" by FKA Twigs, the closing track from the same mixtape.
Arca appears briefly in a video interlude during Beyoncé's Renaissance World Tour, and made a surprise appearance at the June 8, 2023, show in Barcelona to open for Beyoncé.
Artistry
Musical style and lyrical themes
Ghersi's work published under the Arca name has been labelled as experimental music, hip hop music and IDM, while her music released under Nuuro has been described as "electronic indie pop" and "dreamy synth-pop". She frequently incorporates themes of psychosexuality, science fiction and gender identity into her music.
Ghersi's music as Arca has been compared to the music of British electronic producer Aphex Twin while the eponymous album Arca (2017) was compared to compositions by German composers Robert Schumann and Felix Mendelssohn. The latter is known for being her first album as Arca to prominently incorporate lyricism. Stretch 1 and Stretch 2 which were released in 2012, have been compared to hip hop and club music. Reviewing Mutant (2015), Mark Richardson retrospectively compared Xen (2014) to classical music while the former leaned "toward soundscape". Xen was noted by The Quietus Gary Suarez to contain themes of gender and sexuality which were opined to be mainly implicit through the album's music videos. Kick I (2020) has been considered avant-pop while reggaeton was a prominent genre featured, on Kick II (2021). Kick III (2021) has been noted of its influences of IDM while Kick IIIII (2021) has been dubbed ambient techno music. Kick IIIII (2021) has been dubbed "dark electronica" music by Joe Goggins of DIY.
Influences
During her childhood, Ghersi cites her brother's music, which included Aphex Twin, British musician Squarepusher and Björk as heavily influencing her. The American composer and electronic musician Wendy Carlos has also been a major influence.
According to Ghersi, the latter inspired her to use her voice prominently on her eponymous third studio album, Arca and also helped her "find" her voice, following the development of a creative partnership between the pair. She has also cited her love for pop music which influenced the making of Kick I. Arca also cites Madonna as an influence, saying: "I don't know if I can overstate how major Madonna's music and persona were in my household".
She cited German composer Richard Wagner's Der Ring des Nibelungen as a primary inspiration for the Kick series and called nightclubs the place she found a "home". Remezcla's Alberto De La Roza noted the influence of reggaeton on Ghersi's work.
Visuals
From 2012 to 2018, Ghersi often collaborated with Jesse Kanda on the visual aspect of her albums. He created the album artwork for her albums Xen (2014), Mutant (2015) and Arca (2017). She also collaborated with German photographer and director Daniel Sannwald to create her music videos.
For the Kick series, Frederik Heyman created the album artwork for all of the albums except for Kick I, which was created by her, Catalan artist Carlota Guerrero and Spanish multimedia artist Carlos Sáez.
Ghersi's visuals for covers, music videos and packaging are, at times, sexually explicit or intentionally unsettling. In particular, the imagery featured in the artwork for Ghersi's single "Vanity" and the music video for her single "Thievery" were marked as NSFW, the former of which, resulted in a temporary ban on her Instagram account. Arca's music video for "Reverie" (directed by Jesse Kanda) is age-restricted on YouTube for its graphic, violent imagery and sexual content.
Personal life
Arca came out as non-binary in 2018, later adding that she identifies as a trans woman, and goes by she/her and it/its pronouns. As of 2022 Arca has stated on her Instagram bio that she also uses they/them pronouns. In 2020 she stated in an interview for Vice: "I see my gender identity as non-binary, and I identify as a trans Latina woman, and yet, I don't want to encourage anyone to think that my gayness has been banished. And when I talk about gayness, it's funny because I'm not thinking about who I'm attracted to. It's a form of cultural production that is individual and collective, which I don't ever want to renounce". In May 2023, Arca underwent facial feminization surgery. She commented on the surgery, by stating that she "feel[s] so free after [it], like a load was lifted from [her] chakras".
Arca lived in London and resides in Barcelona as of 2018. She dated Daniel Sannwald, and later the Spanish multimedia artist Carlos Sáez, who has often collaborated in the realization of her projects. The song "Failed" is written about her relationship with the former while the song "Calor" chronicles her relationship with the latter.
In 2022, Arca signed onto the Musicians For Palestine pledge, refusing to perform in Israel following the 2021 Israel–Palestine crisis.
Discography
Xen (2014)
Mutant (2015)
Arca (2017)
Kick I (2020)
Kick II (2021)
Kick III (2021)
Kick IIII (2021)
Kick IIIII (2021)
Awards and nominations
Notes
References
External links
Year of birth missing (living people)
Living people
20th-century Venezuelan LGBTQ people
21st-century Venezuelan LGBTQ people
Venezuelan transgender people
Venezuelan non-binary people
Audio engineers
Electronic dance music DJs
Experimental musicians
Hip-hop record producers
Industrial musicians
LGBTQ DJs
LGBTQ people in Latin music
Venezuelan LGBTQ songwriters
Venezuelan LGBTQ singers
Transgender songwriters
Musicians from Caracas
Mute Records artists
Non-binary singers
Non-binary songwriters
Tisch School of the Arts alumni
Transgender non-binary people
Venezuelan DJs
Venezuelan electronic musicians
Venezuelan expatriates in England
Venezuelan expatriates in Spain
Venezuelan expatriates in the United States
Venezuelan performance artists
Venezuelan record producers
Women in electronic music
Women in Latin music
LGBTQ record producers
Transgender women singers | Arca (musician) | Engineering | 3,115 |
206,795 | https://en.wikipedia.org/wiki/The%20Rowland%20Institute%20at%20Harvard | The Rowland Institute at Harvard, formerly the Rowland Institute for Science, was founded by Edwin H. Land (founder of Polaroid Corporation) as a nonprofit, privately endowed basic research organization in 1980. The institute merged with Harvard University on July 1, 2002. The Rowland Institute is dedicated to experimental science across a wide range of disciplines. Research subjects at the institute includes chemistry, physics and biology, and focus on interdisciplinary work and the development of new experimental tools. It is located on the Charles River near Kendall Square in Cambridge, Massachusetts, and is a few miles away from the main campus of Harvard.
Rowland Fellows
The flagship program at the Rowland Institute is the Fellows Program. The program supports early career experimental scientists. Rowland Fellows receive funding for salary and research expenses and are allocated their own laboratory space. The Rowland Institute also provides technical support from permanent expert staff. The Fellowship lasts for five years, with continuation past two years contingent on a favorable internal review.
Notable members and alumni
Howard Berg - biophysicist noted for his work on the motility of the bacterium Escherichia coli (E. coli)
Steven Block - pioneered the use of optical tweezers to study step dynamics of kinesin and RNA polymerase on DNA templates
Colleen Cavanaugh - microbiologist recognized for her studies of hydrothermal vent ecosystems
Donald A. Glaser - physicist, neurobiologist, and winner of the 1960 Nobel Prize in Physics for inventing the bubble chamber
Jene Golovchenko - physicist noted for his work on materials for whole genome sequencing
Lene Hau - physicist noted for her work on Bose–Einstein condensate, and ultracold atomic system optics
Winfield Hill - co-authored the popular text The Art of Electronics with Harvard Physicist Paul Horowitz
Past directors
Edwin H. Land: 1980 - 1992
Phil Dubois: 1992 - 1997
Michael Burns: 1998 - 2002
Frans Spaepen: 2002 - 2013
Cynthia Friend: 2013 - 2019
Andrew Murray: 2020–present
References
Harvard University research institutes
Multidisciplinary research institutes
Science and technology studies associations
Research institutes established in 1980
1980 establishments in Massachusetts | The Rowland Institute at Harvard | Technology | 427 |
58,885,083 | https://en.wikipedia.org/wiki/BX%20Andromedae | BX Andromedae (BX And) is an eclipsing binary star in the constellation Andromeda. Its maximum apparent visual magnitude is 8.87. Within a cycle of approximately 14.6 hours, the brightness drops down to a magnitude of 9.53 during the main eclipse, and to a magnitude of 9.12 during the secondary one. It is classified as a Beta Lyrae variable.
Variability
The variability of BX Andromedae was reported first by A. Soloviev, in 1945. He believed it to be an eclipsing binary, but was unable to deduce its period. The star's period was first measured in 1951, by Joseph Ashbrook.
BX Andromedae, like all Beta Lyrae variables, shows a primary and a secondary minimum when, respectively, the most luminous and the less luminous component of the pair is eclipsed by the other. The brightness however changes smoothly, so there is no onset and an end time for the eclipses. This cycle repeats approximately every 14.6 hours.
System
The two stars in the system are orbiting so close to each other that they retain an ellipsoidal shape. The spectrum of the two stars has not been separated yet; as a whole, the system has a spectral type F2V. The physical parameters of the stars (like mass, radius, and temperature) can be inferred from the light curve.
BX Andromedae, however, may be a quadruple system. This system shows slight orbital period variations that could be induced by a third faint body in the system with an orbital period of 62 years. There is also a visual companion star TYC 2833-53-1 of 10.85 magnitude only 20 arcseconds away with a common proper motion and a distance (measured with parallax) compatible with the one of BX Andromedae, and has an estimated mass of 1.04 .
References
Andromeda (constellation)
Andromedae, BX
J02090342+4047392
Beta Lyrae variables
BD+40 442
010027
013078 | BX Andromedae | Astronomy | 447 |
1,406,474 | https://en.wikipedia.org/wiki/Acetic%20anhydride | Acetic anhydride, or ethanoic anhydride, is the chemical compound with the formula . Commonly abbreviated , it is the simplest isolable anhydride of a carboxylic acid and is widely used as a reagent in organic synthesis. It is a colorless liquid that smells strongly of acetic acid, which is formed by its reaction with moisture in the air.
Structure and properties
Acetic anhydride, like most acid anhydrides, is a flexible molecule with a nonplanar structure. The pi system linkage through the central oxygen offers very weak resonance stabilization compared to the dipole-dipole repulsion between the two carbonyl oxygens. The energy barriers to bond rotation between each of the optimal aplanar conformations are quite low.
Like most acid anhydrides, the carbonyl carbon atom of acetic anhydride has electrophilic character, as the leaving group is carboxylate. The internal asymmetry may contribute to acetic anhydride's potent electrophilicity as the asymmetric geometry makes one side of a carbonyl carbon atom more reactive than the other, and in doing so tends to consolidate the electropositivity of a carbonyl carbon atom to one side (see electron density diagram).
Production
Acetic anhydride was first synthesized in 1852 by the French chemist Charles Frédéric Gerhardt (1816-1856) by heating potassium acetate with benzoyl chloride.
Acetic anhydride is produced by carbonylation of methyl acetate:
The Tennessee Eastman acetic anhydride process involves the conversion of methyl acetate to methyl iodide and an acetate salt. Carbonylation of the methyl iodide in turn produces acetyl iodide, which reacts with acetate salts or acetic acid to give the product. Rhodium chloride in the presence of lithium iodide is employed as catalysts. Because acetic anhydride is not stable in water, the conversion is conducted under anhydrous conditions.
To a decreasing extent, acetic anhydride is also prepared by the reaction of ketene (ethenone) with acetic acid at 45–55 °C and low pressure (0.05–0.2 bar).
(ΔH = −63 kJ/mol)
The route from acetic acid to acetic anhydride via ketene was developed by Wacker Chemie in 1922, when the demand for acetic anhydride increased due to the production of cellulose acetate.
Due to its low cost, acetic anhydride is usually purchased, not prepared, for use in research laboratories.
Reactions
Acetic anhydride is a versatile reagent for acetylations, the introduction of acetyl groups to organic substrates. In these conversions, acetic anhydride is viewed as a source of .
Acetylation of alcohols and amines
Alcohols and amines are readily acetylated. For example, the reaction of acetic anhydride with ethanol yields ethyl acetate:
Often a base such as pyridine is added to function as catalyst. In specialized applications, Lewis acidic scandium salts have also proven effective catalysts.
Acetylation of aromatic rings
Aromatic rings are acetylated by acetic anhydride. Usually acid catalysts are used to accelerate the reaction. Illustrative are the conversions of benzene to acetophenone and ferrocene to acetylferrocene:
Preparation of other acid anhydrides
Dicarboxylic acids are converted to the anhydrides upon treatment with acetic anhydride. It is also used for the preparation of mixed anhydrides such as that with nitric acid, acetyl nitrate.
Precursor to geminal diacetates
Aldehydes react with acetic anhydride in the presence of an acidic catalyst to give geminal diacetates. A former industrial route to vinyl acetate involved the intermediate ethylidene diacetate, the geminal diacetate obtained from acetaldehyde and acetic anhydride:
Hydrolysis
Acetic anhydride dissolves in water to approximately 2.6% by weight. Aqueous solutions have limited stability because, like most acid anhydrides, acetic anhydride hydrolyses to give carboxylic acids. In this case, acetic acid is formed, this reaction product being fully water miscible:
Cinnamic acid synthesis
In the last third of the 19th century the main application for the acetic anhydride was the Perkin reaction.
Applications
As indicated by its organic chemistry, acetic anhydride is mainly used for acetylations leading to commercially significant materials. Its largest application is for the conversion of cellulose to cellulose acetate, which is a component of photographic film and other coated materials, and is used in the manufacture of cigarette filters. Similarly it is used in the production of aspirin (acetylsalicylic acid), which is prepared by the acetylation of salicylic acid. It is also used as an active modification agent via autoclave impregnation and subsequent acetylation to make a durable and long-lasting timber.
In starch industry, acetic anhydride is a common acetylation compound, used for the production of modified starches (E1414, E1420, E1422)
Legal status
Because of its use for the synthesis of heroin by the diacetylation of morphine, acetic anhydride is listed as a U.S. DEA List II precursor, and restricted in many other countries.
Safety
Acetic anhydride is an irritant and combustible liquid; it is highly corrosive to skin and any direct contact will result in severe burns. Because of its reactivity toward water and alcohol, foam or carbon dioxide are preferred for fire suppression. The vapour of acetic anhydride is harmful.
References
External links
ICSC 0209
NIOSH Pocket Guide to Chemical Hazards
Carboxylic anhydrides
Lachrymatory agents
Solvents
Acetylating agents
Acetyl compounds | Acetic anhydride | Chemistry | 1,309 |
2,919,807 | https://en.wikipedia.org/wiki/Spent%20fuel%20pool | Spent fuel pools (SFP) are storage pools (or "ponds" in the United Kingdom) for spent fuel from nuclear reactors. They are typically 40 or more feet (12 m) deep, with the bottom 14 feet (4.3 m) equipped with storage racks designed to hold fuel assemblies removed from reactors. A reactor's local pool is specially designed for the reactor in which the fuel was used and is situated at the reactor site. Such pools are used for short-term cooling of the fuel rods. This allows short-lived isotopes to decay and thus reduces the ionizing radiation and decay heat emanating from the rods. The water cools the fuel and provides radiological protection from its radiation.
Pools also exist on sites remote from reactors, for longer-term storage such as the Independent Spent Fuel Storage Installation (ISFSI), located at the Morris Operation, or as a production buffer for 10 to 20 years before being sent for reprocessing or dry cask storage.
While only about 20 feet (about 6 m) of water is needed to keep radiation levels below acceptable levels, the extra depth provides a safety margin and allows fuel assemblies to be manipulated without special shielding to protect the operators.
Operation
About a quarter to a third of the total fuel load of a reactor is removed from the core every 12 to 24 months and replaced with fresh fuel. Spent fuel rods generate intense heat and dangerous radiation that must be contained. Fuel is moved from the reactor and manipulated in the pool generally by automated handling systems, although some manual systems are still in use. The fuel bundles fresh from the core are normally segregated for several months for initial cooling before being sorted into other parts of the pool to wait for final disposal. Metal racks keep the fuel in controlled positions for physical protection and for ease of tracking and rearrangement. High-density racks also incorporate boron-10, often as boron carbide (Metamic, Boraflex, Boral, Tetrabor and Carborundum) or other neutron-absorbing material to ensure subcriticality. Water quality is tightly controlled to prevent the fuel or its cladding from degrading. This can include monitoring the water for contamination by actinides, which could indicate a leaking fuel rod. Current regulations in the United States permit re-arranging of the spent rods so that maximum efficiency of storage can be achieved.
The maximum temperature of the spent fuel bundles decreases significantly between two and four years, and less from four to six years. The fuel pool water is continuously cooled to remove the heat produced by the spent fuel assemblies. Pumps circulate water from the spent fuel pool to heat exchangers, then back to the spent fuel pool. The water temperature in normal operating conditions is held below 50 °C (120 °F). Radiolysis, the dissociation of molecules by radiation, is of particular concern in wet storage, as water may be split by residual radiation and hydrogen gas may accumulate increasing the risk of explosions. For this reason the air in the room of the pools, as well as the water, must be continually monitored and treated.
Other possible configurations
Rather than manage the pool's inventory to minimize the possibility of continued fission activity, China is building a 200 MWt nuclear reactor to run on used fuel from nuclear power stations to generate process heat for district heating and desalination. Essentially an SFP operated as a deep swimming pool reactor; it will operate at atmospheric pressure, which will reduce the engineering requirements for safety.
Other research envisions a similar low-power reactor using spent fuel where instead of limiting the production of hydrogen by radiolysis, it is encouraged by the addition of catalysts and ion scavengers to the cooling water. This hydrogen would then be removed to use as fuel.
Risks
The neutron absorbing materials in spent fuel pools have been observed to degrade severely over time, reducing the safety margins of maintaining subcriticality; in addition, it has been shown that the in-site measurement technique used to evaluate these neutron absorbers (Boron Areal Density Gauge for Evaluating Racks, or BADGER) has an unknown degree of uncertainty.
If there is a prolonged interruption of cooling due to emergency situations, the water in the spent fuel pools may boil off, possibly resulting in radioactive elements being released into the atmosphere.
In the magnitude 9 earthquake that struck the Fukushima nuclear plants in March 2011, three of the spent fuel pools were in buildings which had been damaged and were seen to be emitting water vapour. The US NRC wrongly stated that the pool at reactor 4 had boiled dry—this was denied at the time by the Government of Japan and found to be incorrect in subsequent inspection and data examination.
According to nuclear plant safety specialists, the chances of criticality in a spent fuel pool are very small, usually avoided by the dispersal of the fuel assemblies, inclusion of a neutron absorber in the storage racks and overall by the fact that the spent fuel has too low an enrichment level to self-sustain a fission reaction. They also state that if the water covering the spent fuel evaporates, there is no element to enable a chain reaction by moderating neutrons.
According to Dr. Kevin Crowley of the Nuclear and Radiation Studies Board, "successful terrorist attacks on spent fuel pools, though difficult, are possible. If an attack leads to a propagating zirconium cladding fire, it could result in the release of large amounts of radioactive material." After the September 11, 2001 attacks the Nuclear Regulatory Commission required American nuclear plants "to protect with high assurance" against specific threats involving certain numbers and capabilities of assailants. Plants were also required to "enhance the number of security officers" and to improve "access controls to the facilities".
On August 31, 2010, a diver servicing the spent fuel pool at the Leibstadt Nuclear Power Plant (KKL) was exposed to radiation in excess of statutory annual dose limits after handling an unidentified object, which was later identified as protective tubing from a radiation monitor in the reactor core, made highly radioactive by neutron flux. The diver received a hand dose of about 1,000 mSv which is twice the statutory limit of 500 mSv. According to KKL authorities the diver has not suffered any longtime consequences from the accident.
See also
Deep geological repository
Dry cask storage
Lists of nuclear disasters and radioactive incidents
Nuclear fuel cycle
Radioactive waste
Spent nuclear fuel shipping cask
Cherenkov radiation
References
External links
Radiological Terrorism: Sabotage of Spent Fuel Pool
Storage of Spent Nuclear Fuel U.S. Nuclear Regulatory Commission (NRC)
An example diagram of a Spent Fuel Pool Indian Point Energy Center
"Geek Answers: Does nuclear waste really glow?" BY GRAHAM TEMPLETON 07.17.2014 at Geek.com
Nuclear power plant components
Radioactive waste
Waste treatment technology | Spent fuel pool | Chemistry,Technology,Engineering | 1,380 |
8,951,529 | https://en.wikipedia.org/wiki/Frontiers%20%281989%20TV%20series%29 | Frontiers is an eight-part BBC television series, and accompanying book, that explored the geographic boundaries between countries. Eight writers and journalists in a variety of countries investigated the economic, political, geographical and historical reasons that account for why people are divided. The series was aired in 1989, just a few months before the fall of the Berlin Wall, which was featured in one episode.
Episodes
"Natural Break": Frederic Raphael explored the Pyrenees, the frontier between France and Spain, which at the time was preparing to join the (then) European Economic Community.
"Gone Tomorrow": John Wells covered the Iron Curtain that split East and West Germans.
"Gold and the Gun": Nadine Gordimer visited the war-torn border area between Mozambique and her native South Africa.
"Night and Day": Richard Rodriguez showed how the rich North and poor South converged at the US/Mexican border.
"Long Division": Ronald Eyre looked at the people living on both sides of the border in Ireland that splits the Republic from Ulster.
"Big Brother's Bargain": Nigel Hamilton hiked up the boundary between Russia and Finland.
"Border Run": Jon Swain visited the Thai/Cambodian border where thousands of Cambodian refugees had been stranded for over ten years.
"Cyprus: Stranded in Time": Christopher Hitchens investigated the divided island of Cyprus.
Further reading
Frontiers, published in 1990 by BBC Books,
External links
1989 British television series debuts
1989 British television series endings
1980s British documentary television series
BBC television documentaries
Borders
British English-language television shows | Frontiers (1989 TV series) | Physics | 312 |
41,684,206 | https://en.wikipedia.org/wiki/Husab%20Mine | The Husab Mine (formerly the Rössing South Mine), operated under the Husab Uranium Project, is a uranium mine near the town of Swakopmund in the Erongo region of western-central Namibia. The mine is located approximately south of the larger Rössing uranium mine and from Walvis Bay. Swakop Uranium believes the Husab Mine has the potential to become the second largest uranium mine in the world after the McArthur River uranium mine in northern Saskatchewan, Canada and the largest open-pit mine on the African continent. Mine construction started in February 2013. The Husab Mine started production towards the end of 2016 after completion of the sulfuric acid leaching plant.
Operations
On 1 December 2011, the Namibian Ministry of Mines and Energy granted license to Swakop Uranium to develop the mine.
The uranium in the Husab deposit is granite hosted, and currently consists of an administration and housing area and three open pits. The mine has the potential to produce 15 million pounds (6800 tonnes) of uranium oxide per annum.
The Husab mine contains approximately 280 million tonnes of uranium ore. Mining is expected to last nearly 20 years.
As of at least 2024, the China-Africa Development Fund and China Guangdong Nuclear Power Uranium Resources Co together own approximately 90% of the mine.
Geology
Uranium mineralisation is hosted primarily within sheeted leucogranites that intruse the rocks at various stages during the Damara Orogeny. Formation of the uranium magmatic ore body is stratigraphically controlled with the Khan-Rossing boundary acting as a redox front. The abundance of iron oxides and sulfides provide reducing conditions for uranium to be oxidised and precipitate in the form of uraninite which is the primary ore mineral that is mined at Husab.
Swakop Uranium
Swakop Uranium is an entity established in 2006 by Extract Resources, an Australian company listed on the Australian, Canadian, and Namibian stock exchanges, to explore, evaluate, develop, and produce uranium oxide. In April 2012, Swakop Uranium was acquired by Taurus Minerals Limited of Hong Kong. Swakop Uranium head office is located in Swakopmund. Taurus is a subsidiary of the China General Nuclear Power Company (CGNPC), Uranium Resources Co. Ltd. and the China-Africa Development Fund. Taurus owns ninety percent of Swakop Uranium. The remaining 10% is owned by Epangelo Mining Company, the Namibian state-owned mining company. CGNPC's investment in Swakop Uranium is one of the biggest investments in Namibia since its independence, and by far the single biggest investment by China in Africa. More than US$100-million (in excess of N$1-billion) was spent to reach the construction phase. A further amount of approximately US$2-billion (more than N$20-billion) was spent to bring the mine online.
Environment
Flora and fauna
Swakop Uranium has an environmental management plan committed to caring for all species of fauna and flora found near, or within, its exploration and mining areas. Welwitschia mirabilis, an ancient plant, grows in areas around the mine. Carbon dating shows that medium-sized plants can be as old as 1,000 years.
Water
The Husab Project is challenged to ensure that limited nearby water resources are not adversely affected by mining operations. The Namib Desert is a hyper-arid desert with an average rainfall of between 0–50 mm at Swakopmund and Gobabeb. Long-term records from the Rössing Uranium Mine, situated 5 km north of the Husab mine, show an annual average rainfall of between 30–35 mm per annum.
A hydrogeology report commissioned by Swakop Uranium concluded that the mining activities will have an effect on water levels. Although there are no farmers or settlements in the area, Swakop Uranium has drilled a number of groundwater monitoring holes around the pit, the waste rock dump, the tailings storage facility, the Welwitschia fields as well as the Khan and Swakop Rivers to measure the effect of mining activities in the area. All the boreholes have their water levels measured monthly and strategic boreholes are sampled every three months for water quality.
Air quality
In order to reduce the dust produced by mining operations to acceptable levels, the Husab mine will employ a number of dust suppression methods such as using water, extraction fans, chemicals, and other suppressants. A dust suppressant will be used on the pit, dump haul roads and other gravel site roads. The use of alternative suppression techniques has the potential to save up to 90% of the water that would otherwise have been required to achieve the same level of control.
Community
Swakop Uranium plans to engage in local procurement and recruitment where possible. The company grants bursaries for promising Namibian university students on an annual basis and has funded the construction of a new school. The company has also established a trust, called the Swakop Uranium Foundation Trust that will focus on training and education, the environment, infrastructure, health, and entrepreneurial development. The trust has donated N$100,000 to the Namibian government's Drought Relief fund.
Safety
Swakop Uranium has instituted a radiation management plan. This plan has been submitted to the National Radiation Protection Authority and is regularly audited to ensure compliance.
Related deposits
There are four related deposits in the granite of the Damara Belt in the Erongo Region of western Namibia, namely at Rössing (SJ and Z20 deposits), the Ida Dome, at Goanikontes, and the Valencia. The Husab Uranium Project includes the Ida Dome 20 km south, with 9600 tU inferred resource at 0.02% (contiguous with Reptile's Ongalo). Ida Dome has estimated reserves of 53 million tonnes of ore grading 0.018% uranium. The Valencia deposit has 2,731 t U proven reserves and 23,577 t U probable reserves, and at Goanikontes there are 3,187 t U proven reserves and 20,055 t U probable reserves. The scope of the SJ and Z20 deposits at Rössing have not been significantly proved.
See also
Uranium mining
Uranium mining in Namibia
Mining in Namibia
Radium
Uranium
Radioactivity
References
External links
Swakopuranium.com
Engineering projects
Uranium mines in Namibia | Husab Mine | Engineering | 1,320 |
23,294,843 | https://en.wikipedia.org/wiki/Dixanthogen%20disulfide | Dixanthogen disulfides are a class of organosulfur compounds with the formula . Usually yellow solids, they are the product of the oxidation of xanthate salts. A common derivative is diethyl dixanthogen disulfide. Diisopropyl dixanthogen disulfide is commercially available. They are structurally related to thiuram disulfides.
Uses and reactions
Diethyl dixanthogen disulfide is a component for froth flotations used, inter alia, for the separation of sulfide minerals like pyrrhotite. Diisopropyl dixanthogen disulfide is a reagent in the synthesis of sulfur heterocycles.
Dialkoxy dixanthogen disulfides undergo desulfurization by cyanide to give bis(alkoxythiocarbonyl)sulfides:
Dixanthogens are also ectoparasiticides.
References
Thiocarbonyl compounds
Organic disulfides
Sulfur
Functional groups
Dermatologic drugs | Dixanthogen disulfide | Chemistry | 227 |
49,088,528 | https://en.wikipedia.org/wiki/Deep%20inspiration%20breath-hold | Deep inspiration breath-hold (DIBH) is a method of delivering radiotherapy while limiting radiation exposure to the heart and lungs. It is used primarily for treating left-sided breast cancer.
The technique involves a patient holding their breath during treatment. In DIBH techniques, treatment is only delivered at certain points in the breathing cycle, where the patient holds their breath. Since the relative positions of organs in the chest naturally changes during breathing, this allows treatment to be delivered to the target (tumour) while other organs are in the optimal position to receive least dose.
Treatment Methods
In the DIBH technique, the patient is initially maintained at quiet tidal breathing (i.e. normal, relaxed breathing), followed by a deep inspiration, a deep expiration, a second deep inspiration, and breath-hold. At this point the patient is at approximately 100% vital capacity, and simulation, verification, and treatment take place during this phase of breath-holding. DIBH is performed with several tangential fields for left-sided breast cancer. A patient is instructed to hold the breath while viewing the breathing pattern and the breath-hold position through a head-mounted mirror, thereby ensuring reproducibility of the breath-hold position in each delivery. A pair of video goggles may also be used for monitoring the breathing cycle. Patients who cannot maintain DIBH can still benefit from lung tracking techniques, for example 4DCT.
There are two basic methods of performing DIBH: free-breathing breath-hold, and spirometry-monitored deep inspiration breath hold.
Free-breathing breath-hold
Free-breathing breath-hold, also known as real-time position management (RPM) DIBH utilises an infra-red camera and markers placed on the patient to track movement of their chest, and their breathing. Another device for DIBH is known as Abches that monitors the breathing pattern. With the Abches, a patient is instructed to hold the breath at a specified breathing position by viewing a breathing level indicator, thereby reproducing an identical breath-hold position.
Spirometry-monitored breath-hold
Spirometry based designs are known as active breathing coordinator (ABC) DIBH systems. ABC utilises a mouth piece for the patient which can be used to control the flow of air to provide more reproducible results.
Effectiveness
The DIBH technique provides an advantage to conventional free-breathing treatment by decreasing lung density, reducing normal safety margins, and enabling more accurate treatment. These improvements contribute to the effective exclusion of normal lung tissue from the high-dose region and permit the use of higher treatment doses without increased risks of toxicity.
Treatment of patients with the DIBH technique is feasible in a clinical setting. With this technique, consistent lung inflation levels are achieved in patients, as judged by both spirometry and verification films. Breathing-induced tumor motion is significantly reduced using DIBH compared to free breathing, enabling better target coverage.
Future research
There is currently no clear selection criteria to predict which patients will benefit most from the DIBH technique, other than left breast laterality. There is evidence to suggest parasagittal cardiac contact distance is a promising metric for selection and should be assessed in all future DIBH planning studies.
References
Radiation therapy
Radiation health effects
Medical physics
Radiobiology | Deep inspiration breath-hold | Physics,Chemistry,Materials_science,Biology | 665 |
1,269,716 | https://en.wikipedia.org/wiki/Meropenem | Meropenem, sold under the brand name Merrem among others, is an intravenous carbapenem antibiotic used to treat a variety of bacterial infections. Some of these include meningitis, intra-abdominal infection, pneumonia, sepsis, and anthrax.
Common side effects include nausea, diarrhea, constipation, headache, rash, and pain at the site of injection. Serious side effects include Clostridioides difficile infection, seizures, and allergic reactions including anaphylaxis. Those who are allergic to other β-lactam antibiotics are more likely to be allergic to meropenem as well. Use in pregnancy appears to be safe. It is in the carbapenem family of medications. Meropenem usually results in bacterial death through blocking their ability to make a cell wall. It is resistant to breakdown by many kinds of β-lactamase enzymes, produced by bacteria to protect themselves from antibiotics.
Meropenem was patented in 1983. It was approved for medical use in the United States in 1996. It is on the World Health Organization's List of Essential Medicines. The World Health Organization classifies meropenem as critically important for human medicine.
Medical uses
The spectrum of action includes many Gram-positive and Gram-negative bacteria (including Pseudomonas) and anaerobic bacteria. The overall spectrum is similar to that of imipenem, although meropenem is more active against Enterobacteriaceae and less active against Gram-positive bacteria. Meropenem is effective against bacteria producing extended-spectrum β-lactamases but may be more susceptible to hydrolysis by metallo-β-lactamases produced by bacteria. β-lactamases are enzymes that bacteria produce to hydrolyze β-lactam antibiotics, breaking the β-lactam ring and rendering these antibiotics ineffective. This mechanism helps bacteria resist the effects of antibiotics like penicillins, cephalosporins, and carbapenems, making treatment more challenging. While β-lactam ring in meropenem is more accessible to water molecules than in the other β-lactam antibiotics, that facilitates the hydrolysis process and faster degradation of meropenem's antibacterial properties in aqueous solutions, it is more resistant to degradation by β-lactamase enzymes produced by bacteria than the other β-lactam antibiotics.
Meropenem is frequently given in the treatment of febrile neutropenia. This condition frequently occurs in patients with hematological malignancies and cancer patients receiving anticancer drugs that suppress bone marrow formation. It is approved for complicated skin and skin structure infections, complicated intra-abdominal infections and bacterial meningitis.
Meropenem is effective in treating bacterial pneumonia, including hospital-acquired pneumonia.
In 2017, the U.S. Food and Drug Administration (FDA) granted approval for the combination of meropenem and vaborbactam to treat adults with complicated urinary tract infections.
Administration
Meropenem is administered intravenously as an aqueous solution. Meropenem is stored in vials as white crystalline powder (containing meropenem as the trihydrate blended with anhydrous sodium carbonate). For intravenous administration, if pure meropenem powder is used (rather than the powder blended with sodium carbonate), meropenem is dissolved in 5% monobasic potassium phosphate solution, since meropenem is soluble in 5% monobasic potassium phosphate solution and only sparingly soluble in water (). For intravenous bolus administration, injection vials (that contain meropenem blended with sodium carbonate) are reconstituted with sterile water for injection.
Reconstituted (dissolved) meropenem degrades over time. The degradation may be associated with color change of the solution, typical for a hydrolysis of the amide bond of the β-lactam ring as seen with most β-lactam antibiotics, while particularly for meropenem the color is changing from colorless or pale yellow to vivid yellowish. Upon reconstitution, the meropenem infusion solution, prepared with 0.9% sodium chloride, exhibits both chemical and physical stability for a duration of 3 hours at a temperature up to °C. If refrigerated (°C), the stability extends to 24 hours. However, when the product is reconstituted in a 5% dextrose solution, it is used immediately to ensure its efficacy. The degradation of meropenem in a water-based solution is affected by factors such as pH, temperature, initial concentration, and the specific type of infusion solution used. Meropenem solutions should not be frozen.
There is a bit of a paradox with meropenem that the amide bond in the β-lactam ring of meropenem makes it resistant to many β-lactamases (penicillinases), which are enzymes produced by bacteria that can break down penicillin and related antibiotics such as meropenem. This resistance is due to the stability of the β-lactam ring in meropenem, which is less susceptible to hydrolysis by these enzymes. However, meropenem is not stable in the presence of water. It can undergo hydrolysis in aqueous solutions, which can reduce its effectiveness. This means that while meropenem is designed to resist bacterial enzymes, it can still be broken down by water, which is a bit ironic. That's why meropenem requires frequent or prolonged slow administration to supply new drug to the bloodstream to replace what was hydrolyzed by the water component of blood.
Meropenem is administered every 8 hours.
Dosing must be adjusted for altered kidney function and for haemofiltration.
Studies describe application of meropenem therapeutic drug monitoring (measurements of drug levels in the bloodstream at specific intervals) for optimal application.
As with other β-lactams antibiotics, the effectiveness of treatment depends on the amount of time during the dosing interval that the meropenem concentration is above the minimum inhibitory concentration for the bacteria causing the infection. For β-lactams, including meropenem, prolonged intravenous administration is associated with lower mortality compared to bolus intravenous infusion, especially in severe infections or those caused by less sensitive bacteria, such as Pseudomonas aeruginosa.
Meropenem exhibits poor permeability across the gut and low oral bioavailability because of its hydrophilic properties, which inhibit its passive diffusion across the intestinal epithelium. The challenges related to research of oral delivery of meropenem are related to high susceptibility of meropenem to degradation through hydrolysis of the amide bond in the β-lactam ring, even at relatively low temperatures and humidity. This instability can result in the loss of meropenem's antibacterial activity. Besides that, meropenem is unstable in the acidic environment of the stomach, leading to extensive degradation and loss of the drug after oral administration. In addition, intestinal efflux (secretory) transport can pump the drug back into the gut: efflux transporters, particularly P-glycoprotein (P-gp), present in the gastrointestinal tract can actively pump meropenem back into the gut lumen, limiting its absorption and reducing oral bioavailability; in the attempts of oral administration bacteria can develop resistance to meropenem by enhancing the active efflux of the antibiotic through efflux transporters, such as the MexAB-OprM tripartite efflux system in Pseudomonas aeruginosa. That's why meropenem is administered intravenously.
There is insufficient data regarding the administration of meropenem during breastfeeding. However, it has been observed that, in general, the concentration of this β-lactam antibiotic in breast milk is relatively low, therefore, β-lactam antibiotics are not anticipated to induce detrimental effects in infants who are breastfed. Nonetheless, there have been sporadic reports of disturbances in the gastrointestinal flora of the infant, manifesting as diarrhea or oral candidiasis (thrush), associated with the use of β-lactam antibiotics, however, these potential side effects have not been thoroughly investigated specifically in the context of meropenem use, therefore, the safety profile of meropenem in breastfeeding mothers and their infants is unknown.
Although meropenem is not approved for intramuscular or subcutaneous routes of administration in humans, there were studies that evaluated the drug bioavailability in cats and reported bioavailability of 99.69% for intramuscular route and 96.52 % for subcutaneous route of administration; these studies also compared elimination half-lives for intravenous, intramuscular or subcutaneous routes of administration in cats and reported duration of 1.35, 2.10 and 2.26 hours, respectively. There was also a small study on local tolerance of meropenem intramuscular administration in humans, and it was reported as generally good.
Side effects
Among antibiotic drugs, meropenem is relatively safe. The most common adverse effects are diarrhea (4.8%), nausea and vomiting (3.6%), injection-site inflammation (2.4%), headache (2.3%), rash (1.9%) and thrombophlebitis (0.9%). Many of these adverse effects were observed in severely ill individuals already taking many medications including vancomycin. Meropenem has a reduced potential for seizures in comparison with imipenem. Several cases of severe hypokalemia have been reported.
Interactions
Meropenem rapidly reduces serum concentrations of valproic acid. As a result, people who use valproic acid for epilepsy are at increased risk of seizures during treatment with meropenem. In situations where the use of meropenem cannot be avoided, prescription of an additional anticonvulsant should be considered.
Pharmacology
Mechanism of action
Meropenem is bactericidal except against Listeria monocytogenes, where it is bacteriostatic. It inhibits bacterial cell wall synthesis like other β-lactam antibiotics. In contrast to other β-lactams, it is highly resistant to degradation by β-lactamases or cephalosporinases. In general, resistance arises due to mutations in penicillin-binding proteins, production of metallo-β-lactamases, or resistance to diffusion across the bacterial outer membrane. Unlike imipenem, it is stable to dehydropeptidase-1, so can be given without cilastatin.
In 2016, a synthetic peptide-conjugated PMO (PPMO) was found to inhibit the expression of New Delhi metallo-beta-lactamase 1, an enzyme that many drug-resistant bacteria use to destroy carbapenems.
Research directions
Nebulized meropenem (inhaled route) is researched, but is not approved, for prevention of bronchiectasis exacerbation.
Society and culture
Trade names
References
Carbapenem antibiotics
Enantiopure drugs
Carboxamides
Drugs developed by AstraZeneca
Pyrrolidines
Secondary alcohols
World Health Organization essential medicines
Wikipedia medicine articles ready to translate | Meropenem | Chemistry | 2,357 |
34,712,011 | https://en.wikipedia.org/wiki/Ballistics%20by%20the%20Inch | Ballistics by the Inch (often called BBTI) was a project to test the performance characteristics of a variety of common handgun calibers/cartridges. The initial testing was done in 2008 and tested the velocity of 13 common handgun cartridges as it related to firearm barrel length. In 2009 an additional three calibers were tested and in 2010 and 2011 more calibers were added. Also in 2011 testing was carried out to study the "cylinder gap effect" on the velocity of ammunition shot from revolvers. All testing has been carried out as carefully as possible with no bias toward any particular manufacturer, caliber, or firearm. In November 2008 the BBTI website went online, describing the tests and making the data freely available so that anyone can dig out any particular bit of information they may be interested in. The website underwent a complete redesign in late 2011 with the addition of the 2011 tests, and even more tests have been done in the years since.
As of 1 September 2020, the project has been declared to be in 'archive status', as mentioned on the official website, which has remained accessible to the public.
Barrel length tests
The initial round of tests, and most later ones tested handgun bullet velocity as it relates to the length of the barrel. The BBTI team wanted to test barrel lengths from 2 to 18 inches in one-inch increments. To have a consistent platform to test the various sizes and shapes of ammunition, a gunsmith was commissioned to create a custom barrel to fit each caliber tested. These barrels fit into a single housing and can be swapped out easily, so the team can remove them for cutting. Each brand of ammunition in each caliber/cartridge was tested at 18". Then, the barrel was removed and 1" was cut off the end of the barrel and the cut end was dressed. Once all the cartridges had been tested at 18" and the barrels were cut and ready, each brand was tested again at 17" and so on, right down to a 2" barrel. Three rounds of each brand of ammunition were fired at each barrel length and the velocity of the bullet was recorded as it passed over two commercial chronographs 15 feet away. The resulting six numbers were averaged and the average plotted on a graph for each brand and caliber of ammunition so that the trend in the velocity could be readily seen. As of 2012, tests have been run on 21 different calibers/cartridges.
Cylinder gap tests
The two most common forms of handgun are the revolver and the semi-automatic. The semi-auto contains a number of cartridges in a magazine, usually in the grip of the gun, which are fed one at a time into the chamber for firing. The revolver is an older type, familiar to most as the movie-cowboy's "six-shooter." Because the cylinder of a revolver (where the cartridges are held) must rotate freely, there is a slight gap between the front of the cylinder and the barrel. When a round is fired, the velocity of the bullet is determined by the amount of push it is given by the gunpowder in the cartridge as the bullet leaves the gun. For a long time people have wondered how much energy is lost because it escapes through the gap rather than pushing the bullet through the barrel. So in 2011 the BBTI team devised a way to test how that gap affects the velocity of the bullet. In this case they tested a wide variety of ammunition available in .38 and .357 magnum using a single revolver modified to have a long barrel (so that they could cut it down an inch at a time, as they did with the barrel length tests) and also modified to allow them to change the gap using a set of shims. In this way they were able to test with a fairly standard cylinder gap of six one-thousandths of an inch (0.006"), with a gap of one one-thousandth of an inch (0.001") and with no gap at all. Each of these gaps was tested over the range of ammunition at barrel lengths from 18" down to 2". Because they thought the difference would be subtle, they shot ten rounds for each data point to get as accurate a result as possible. As with the barrel length tests, the results at each point were averaged and a graph created that compared the trend for each of the three gaps over the different barrel lengths for each ammunition.
Real world comparisons
Because they were using an idealized platform, the BBTI team decided to test a variety of actual weapons using the same ammunition used for the other tests. This would allow a comparison of how a "real world" weapon would perform related to the results of the other tests. A handgun in a given caliber with a 6" barrel could then be compared to the same caliber in the other tests to see how closely it might match. To date (2012), the team has tested 100 different real-world firearms with barrels from 24" to 1" in length.
BBTI team
Ballistics by the Inch started as discussions between two friends about ballistic characteristics and where they could find hard data to answer their questions. When it was clear that the data was not easily available, they decided to do the tests themselves and enlisted another friend for the first round. These three men — James Kasper, James Downey, and Steve Meyer — spent most of a week out at the testing site each day shooting the rounds, noting the data, and cutting and dressing the barrels to build up the data for the tests. Each brought their own area of expertise and experience to the project. For the second set of tests in 2009, an additional team member was added — Keith Kimball — who brought another area of expertise and experience into the group. These four have done all the testing available on the BBTI site.
Popular impact
Almost as soon as the BBTI site was launched, it was being cited in gun forums and publications. The website had more than 300,000 hits in the first month and in the first year, more than 1.5 million hits. As of February 2012 the site has had more than eight million hits. Because the team has made all the data freely available to anyone who wants to look at it, their data has become the standard cited when discussing the merits of a specific ammunition or barrel length. The April 2009 edition of Concealed Carry Magazine, the members' publication of the US Concealed Carry Association, ran a feature article on the project. Concealed Carry Magazine carried a follow-up feature in November 2010, discussing the tests of the .380 ACP done that year. Numerous firearms forums and podcasts have done stories or entire programs about BBTI, and American Handgunner ran a piece on BBTI in January 2011. The December 2011 re-launch of the expanded BBTI website/data was profiled by Guns.com in a feature article.
References
External links
Ballistics | Ballistics by the Inch | Physics | 1,386 |
63,337 | https://en.wikipedia.org/wiki/Supersaturation | In physical chemistry, supersaturation occurs with a solution when the concentration of a solute exceeds the concentration specified by the value of solubility at equilibrium. Most commonly the term is applied to a solution of a solid in a liquid, but it can also be applied to liquids and gases dissolved in a liquid. A supersaturated solution is in a metastable state; it may return to equilibrium by separation of the excess of solute from the solution, by dilution of the solution by adding solvent, or by increasing the solubility of the solute in the solvent.
History
Early studies of the phenomenon were conducted with sodium sulfate, also known as Glauber's Salt because, unusually, the solubility of this salt in water may decrease with increasing temperature. Early studies have been summarised by Tomlinson. It was shown that the crystallization of a supersaturated solution does not simply come from its agitation, (the previous belief) but from solid matter entering and acting as a "starting" site for crystals to form, now called "seeds". Expanding upon this, Gay-Lussac brought attention to the kinematics of salt ions and the characteristics of the container having an impact on the supersaturation state. He was also able to expand upon the number of salts with which a supersaturated solution can be obtained. Later Henri Löwel came to the conclusion that both nuclei of the solution and the walls of the container have a catalyzing effect on the solution that cause crystallization. Explaining and providing a model for this phenomenon has been a task taken on by more recent research. Désiré Gernez contributed to this research by discovering that nuclei must be of the same salt that is being crystallized in order to promote crystallization.
Occurrence and examples
Solid precipitate, liquid solvent
A solution of a chemical compound in a liquid will become supersaturated when the temperature of the saturated solution is changed. In most cases solubility decreases with decreasing temperature; in such cases the excess of solute will rapidly separate from the solution as crystals or an amorphous powder.
In a few cases the opposite effect occurs. The example of sodium sulfate in water is well-known and this was why it was used in early studies of solubility.
Recrystallization is a process used to purify chemical compounds. A mixture of the impure compound and solvent is heated until the compound has dissolved. If there is some solid impurity remaining it is removed by filtration. When the temperature of the solution is subsequently lowered it briefly becomes supersaturated and then the compound crystallizes out until chemical equilibrium at the lower temperature is achieved. Impurities remain in the supernatant liquid. In some cases crystals do not form quickly and the solution remains supersaturated after cooling. This is because there is a thermodynamic barrier to the formation of a crystal in a liquid medium. Commonly this is overcome by adding a tiny crystal of the solute compound to the supersaturated solution, a process known as "seeding". Another process in common use is to rub a rod on the side of a glass vessel containing the solution to release microscopic glass particles which can act as nucleation centres. In industry, centrifugation is used to separate the crystals from the supernatant liquid.
Some compounds and mixtures of compounds can form long-living supersaturated solutions. Carbohydrates are a class of such compounds; The thermodynamic barrier to formation of crystals is rather high because of extensive and irregular hydrogen bonding with the solvent, water. For example, although sucrose can be recrystallised easily, its hydrolysis product, known as "invert sugar" or "golden syrup" is a mixture of glucose and fructose that exists as a viscous, supersaturated, liquid. Clear honey contains carbohydrates which may crystallize over a period of weeks.
Supersaturation may be encountered when attempting to crystallize a protein.
Gaseous solute, liquid solvent
The solubility of a gas in a liquid increases with increasing gas pressure. When the external pressure is reduced, the excess gas comes out of solution.
Fizzy drinks are made by subjecting the liquid to carbon dioxide, under pressure. In champagne the CO2 is produced naturally in the final stage of fermentation. When the bottle or can is opened some gas is released in the form of bubbles.
Release of gas from supersaturated tissues can cause an underwater diver to suffer from decompression sickness (a.k.a. the bends) when returning to the surface. This can be fatal if the released gas obstructs critical blood supplies causing ischaemia in vital tissues.
Dissolved gases can be released during oil exploration when a strike is made. This occurs because the oil in oil-bearing rock is under considerable pressure from the over-lying rock, allowing the oil to be supersaturated with respect to dissolved gases.
Liquid formation from a mixture of gases
A cloudburst is an extreme form of production of liquid water from a supersaturated mixture of air and water vapour in the atmosphere. Supersaturation in the vapour phase is related to the surface tension of liquids through the Kelvin equation, the Gibbs–Thomson effect and the Poynting effect.
The International Association for the Properties of Water and Steam (IAPWS) provides a special equation for the Gibbs free energy in the metastable-vapor region of water in its Revised Release on the IAPWS Industrial Formulation 1997 for the Thermodynamic Properties of Water and Steam. All thermodynamic properties for the metastable-vapor region of water can be derived from this equation by means of the appropriate relations of thermodynamic properties to the Gibbs free energy.
Measurement
When measuring the concentration of a solute in a supersaturated gaseous or liquid mixture it is obvious that the pressure inside the cuvette may be greater than the ambient pressure. When this is so a specialized cuvette must be used. The choice of analytical technique to use will depend on the characteristics of the analyte.
Applications
The characteristics of supersaturation have practical applications in terms of pharmaceuticals. By creating a supersaturated solution of a certain drug, it can be ingested in liquid form. The drug can be made driven into a supersaturated state through any normal mechanism and then prevented from precipitating out by adding precipitation inhibitors. Drugs in this state are referred to as "supersaturating drug delivery services," or "SDDS." Oral consumption of a drug in this form is simple and allows for the measurement of very precise dosages. Primarily, it provides a means for drugs with very low solubility to be made into aqueous solutions. In addition, some drugs can undergo supersaturation inside the body despite being ingested in a crystalline form. This phenomenon is known as in vivo supersaturation.
The identification of supersaturated solutions can be used as a tool for marine ecologists to study the activity of organisms and populations. Photosynthetic organisms release O2 gas into the water. Thus, an area of the ocean supersaturated with O2 gas can likely determined to be rich with photosynthetic activity. Though some O2 will naturally be found in the ocean due to simple physical chemical properties, upwards of 70% of all oxygen gas found in supersaturated regions can be attributed to photosynthetic activity.
Supersaturation in vapor phase is usually present in the expansion process through steam nozzles that operate with superheated steam at the inlet, which transitions to saturated state at the outlet. Supersaturation thus becomes an important factor to be taken into account in the design of steam turbines, as this results in an actual mass flow of steam through the nozzle being about 1 to 3% greater than the theoretically calculated value that would be expected if the expanding steam underwent a reversible adiabatic process through equilibrium states. In these cases supersaturation occurs due to the fact that the expansion process develops so rapidly and in such a short time, that the expanding vapor cannot reach its equilibrium state in the process, behaving as if it were superheated. Hence the determination of the expansion ratio, relevant to the calculation of the mass flow through the nozzle, must be done using an adiabatic index of approximately 1.3, like that of the superheated steam, instead of 1.135, which is the value that should have to be used for a quasi-static adiabatic expansion in the saturated region.
The study of supersaturation is also relevant to atmospheric studies. Since the 1940s, the presence of supersaturation in the atmosphere has been known. When water is supersaturated in the troposphere, the formation of ice lattices is frequently observed. In a state of saturation, the water particles will not form ice under tropospheric conditions. It is not enough for molecules of water to form an ice lattice at saturation pressures; they require a surface to condense on to or conglomerations of liquid water molecules of water to freeze. For these reasons, relative humidities over ice in the atmosphere can be found above 100%, meaning supersaturation has occurred. Supersaturation of water is actually very common in the upper troposphere, occurring between 20% and 40% of the time. This can be determined using satellite data from the Atmospheric Infrared Sounder.
References
Thermodynamics
Atmospheric thermodynamics
Underwater diving physics | Supersaturation | Physics,Chemistry,Mathematics | 1,982 |
5,438,469 | https://en.wikipedia.org/wiki/Desire%20path | A desire path, often referred to as a desire line in transportation planning and also known by various other names, is an unplanned small trail created as a consequence of mechanical erosion caused by human or animal traffic. The path usually represents the shortest or the most easily navigated route between an origin and destination, and the width and severity of its surface erosion are often indicators of the traffic level it receives.
An early documented example is Broadway in New York City, which follows the Wecquaesgeek trail which predates American colonization.
Desire paths typically emerge as convenient shortcuts where more deliberately constructed paths take a longer or more circuitous route, have gaps, or are non-existent. Once a path has been trodden out through the natural vegetation, subsequent traffic tends to follow that visibly existing route (as it is more convenient than carving out a new path by oneself), and the repeated trampling will further erode away both the remaining groundcover and the soil quality that allows easy revegetation. Eventually, a clearly visible and easily passable path emerges that humans and animals alike tend to prefer.
Parks and nature areas
Desire paths sometimes cut through sensitive habitats and exclusion zones, threatening wildlife and park security. However, they also provide park management with an indicator of activity concentration. In Yosemite National Park, the National Park Service uses these indicators to help guide its management plan.
Trampling studies have consistently documented that impacts on soil and vegetation occur rapidly with initial use of desire paths. As few as 15 passages over a site can be enough to create a distinct trail, the existence of which then attracts further use. This finding contributed to the creation of the Leave No Trace education program, which instructs travelers in nature areas to either stay on designated trails or, when off trail, distribute their travel lines so as to not inadvertently create new trails in unsustainable locations.
Land managers have devised a variety of techniques to block the creation of desire paths, including fences, dense vegetation, and signage, though none are foolproof. Modern trail design attempts to avoid the need for barriers and restrictions, by aligning trail layout and user desire through physical design and persuasive outreach.
Accommodation
Landscapers sometimes accommodate desire paths by paving them, thereby integrating them into the official path network rather than blocking them. Sometimes, land planners have deliberately left land fully or partially unpathed, waiting to see what desire paths are created, and then paving those. In Finland, planners are known to visit parks immediately after the first snowfall, when the existing paths are not visible. The naturally chosen desire paths, marked by footprints, can then be used to guide the routing of new purpose-built paths.
Other uses of the concept
Images of desire paths have been employed as a metaphor for anarchism, intuitive design, individual creativity, and the wisdom of crowds.
In urban planning, desire paths have been used to analyze traffic patterns for a given mode of travel. For example, the 1959 Chicago Area Transportation Study used desire paths to illustrate commuter choices regarding railroad and subway trips.
In software design, the term is used to describe users' wide adoption of the same methods to overcome limitations in the software. For example, X (Twitter) "paved" a number of desire paths by integrating them into the service, including @ replies, hashtags, and group discussions.
See also
Sneckdown
Wayfinding
Notes
References
External links
Wordspy: Desire Line
Desire Paths
Desire Path subreddit
Tom Hulme's TED Talk on using desire paths for better design and user experience
Cycling infrastructure
Footpaths
Garden features
Landscape architecture
Parks
Pedestrian infrastructure
Psychogeography
Trails
Transportation planning
Types of thoroughfares
Urban design | Desire path | Engineering | 748 |
23,670,760 | https://en.wikipedia.org/wiki/Lark%20%28person%29 | A lark, early bird, morning person, or (in Scandinavian countries) an A-person, is a person who usually gets up early in the morning and goes to bed early in the evening. The term relates to the birds known as larks, which are known to sing before dawn. Human "larks" tend to feel most energetic just after they get up in the morning. They are thus well-suited for working the day shift.
The opposite of the lark is the owl, often awake at night. A person called a night owl is someone who usually stays up late and may feel most awake in the evening and at night. Researchers have traditionally used the terms morningness and eveningness to describe these two chronotypes.
Charting chronotypes
Till Roenneberg, a chronobiologist in Munich, has mapped the circadian rhythms of more than 200,000 people. Biological processes, including sleep-wake patterns, that display an oscillation of about 24 hours are called circadian rhythms. According to Roenneberg, the distribution of circadian rhythms spans from the very early to the very late chronotypes, similarly to how height varies from short to tall.
As circadian rhythm is independent of the number of hours of sleep a person needs, Roenneberg calculates the rhythm based on the midpoint of the sleep period. A person who goes to bed at midnight and rises at 8 thus has the same chronotype as a person who goes to bed at 1 a.m. and rises at 7; the midpoint of sleep is 4 a.m. for both of these individuals.
People with early chronotypes will usually not be able to "sleep in", even if they have stayed up later than usual. While fit for a "lark-like" societal framework, they find it hard to adapt to a context where "sleeping in" is common: despite feeling refreshed in the morning, they may feel hampered socially when confronted with some kinds of social gatherings (such as soirées) that are often scheduled for the evening, even if most kinds of social events are not.
People with late chronotypes go to bed late and rise late. Forced to arise earlier than their circadian rhythm dictates, they have a low body temperature and may require a few hours to feel really awake. They are unable to fall asleep as early as "larks" can.
Prevalence
A 2007 survey of over 55,000 people found that chronotypes tend to follow a normal distribution, with extreme morning and evening types on the far ends. There are studies that suggest genes determine whether a person is a lark or an evening person in the same way it is implicated in people's attitude toward authority, unconventional behavior, as well as reading and television viewing habits. For instance, there is the case of the Per2 gene on chromosome 2, which was discovered in the early 1990s by Urs Albrecht and colleagues at the University of Fribourg in Switzerland. This gene regulates the circadian clock and a variant of it was found in families that demonstrated advanced sleep-phase syndrome. According to the researchers, its existence in people skews sleep pattern even if the period also cover eight hours.
Age is also implicated in the way one becomes a morning or a night person. It is explained that, developmentally, people are generally night owls in their teens while they become larks later in life. Infants also tend to be early risers.
Career options
Morning larks tend to thrive in careers that start early in the morning. Industries that tend to be favorable to morning larks include farming, construction, and working for public utilities. Many employees in these industries start working at or before 7:00 a.m. Some professions are well-known for their early morning hours, including bakers, school teachers, dairy farmers, and surgeons.
Morning larks tend to be less represented among the employees of restaurants, hotels, entertainment venues, and retail stores, which tend to be open until later in the evening. However, morning larks may be perfectly suited to the opening shift of a coffee shop, handling the morning rush at a hotel, or working on the morning news shows for radio or television. Morning larks may also work the early shift in round-the-clock industries, such as emergency services, transportation, healthcare, and manufacturing.
Many large businesses that operate in the evening or at night need employees at all levels, from entry-level employees to managers to skilled staff, whenever they are open. For example, most hospitals employ many types of workers around the clock:
non-medical staff such as security guards, IT specialists, cleaning and maintenance workers, cooks and food service staff, and admissions clerks;
medical staff such as nurses, paramedics, radiology technicians, pharmacists, and phlebotomists;
managers for each of the main hospital wards or activities, including janitorial supervisors and head nurses.
See also
Advanced sleep phase syndrome
Circadian rhythm sleep disorder
Diurnality
FASPS
Morningness–eveningness questionnaire (MEQ)
Munich ChronoType Questionnaire (MCTQ)
Night owl
Nocturnality
Waking up early
References
External links
The Munich ChronoType Questionnaire (MCTQ)
Sleep
Circadian rhythm
Morning | Lark (person) | Astronomy,Biology | 1,079 |
34,191,584 | https://en.wikipedia.org/wiki/Walter%20Hayman | Walter Kurt Hayman FRS (formerly Haymann; 6 January 1926 – 1 January 2020) was a British mathematician known for contributions to complex analysis. He was a professor at Imperial College London.
Life and work
Hayman was born in Cologne, Germany, the son of Roman law professor Franz Haymann (1874-1947) and Ruth Therese Hensel, daughter of mathematician Kurt Hensel. He was a great-grandson of acclaimed composer Fanny Mendelssohn. Because of his Jewish heritage, he left Germany, then under Nazi rule, alone by train in 1938. He continued his schooling at Gordonstoun School, and later at St John's College, Cambridge under John Edensor Littlewood and his doctoral advisor Mary Cartwright. He taught at King's College, Newcastle, and the University of Exeter.
In 1947, he married Margaret Riley Crann after they met at a Quaker meeting. Together, they founded the British Mathematical Olympiad. The pair had three daughters, including the peace activist Carolyn Hayman and the filmmaker Sheila Hayman.
He is known for his asymptotic results in Bieberbach conjecture in 1955, and for Hayman's alternatives in Nevanlinna Theory. His work with Wolfgang Fuchs gave a solution to an inverse problem of the Nevanlinna theory for entire functions, predating David Drasin's 1976 work.
Honours and awards
Hayman was elected to the Royal Society in 1956 and of the Finnish Academy of Science and Letters in 1978: he was elected "Foreign member" of the Accademia dei Lincei on 16 December 1985. In 1992 he received an honorary doctorate from the Faculty of Mathematics and Science at Uppsala University, Sweden In 1995 he was awarded the De Morgan Medal by the London Mathematical Society. In 2008, an issue of the Journal Computational Methods and Function Theory was dedicated to him on the occasion of his 80th birthday.
Selected publications
Papers
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Books
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Notes
References
Biographical references
. The "Yearbook" of the renowned Italian scientific institution, including an historical sketch of its history, the list of all past and present members as well as a wealth of information about its academic and scientific activities.
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General references
. The review of the autobiographical book of Hayman.
(online ).
External links
Obituary at the London Mathematical Society
1926 births
2020 deaths
20th-century British mathematicians
21st-century British mathematicians
People educated at Gordonstoun
Alumni of St John's College, Cambridge
Fellows of the Royal Society
German expatriates in the United Kingdom
British people of German-Jewish descent
Complex analysts
Mathematical analysts
Mathematics education in the United Kingdom
Deans of the Royal College of Science
De Morgan Medallists
British Quakers | Walter Hayman | Mathematics | 544 |
417,652 | https://en.wikipedia.org/wiki/Post-coital%20tristesse | Post-coital tristesse (; PCT), also known as post-coital dysphoria (PCD), is the feeling of sadness, anxiety, agitation or aggression, after orgasm in sexual intercourse or masturbation. Its name comes from Neo-Latin postcoitalis and French tristesse, literally "sadness". Many people with PCT may exhibit strong feelings of anxiety lasting from five minutes to two hours after coitus.
The phenomenon is attributed to the Greek medical writer Galen, who is supposed to have written that "Every animal is sad after coitus except the human female and the rooster." However, this quotation is not found in Galen's surviving writings, so it may be a later fabrication. Sigmund Freud and Havelock Ellis were familiar with the proverb, which they both attributed to an anonymous author, and it was not until decades later that the maxim became connected with Galen among sexologists.
The philosopher Baruch Spinoza, in his Tractatus de Intellectus Emendatione, wrote: "For as far as sensual pleasure is concerned, the mind is so caught up in it, as if at peace in a [true] good, that it is quite prevented from thinking of anything else. But after the enjoyment of sensual pleasure is passed, the greatest sadness follows. If this does not completely engross, still it thoroughly confuses and dulls the mind." Arthur Schopenhauer, writing later on the phenomenon, observed that "directly after copulation the devil's laughter is heard."
One study reported that among a sample of 1208 male participants, 40% of them had experienced PCT at least once in their lifetime and 20% reported experiencing PCT in the four weeks preceding the study. This study also reports that 3–4% of the sample experienced PCT symptoms on a regular basis. According to the same study, PCT among males is associated with current psychological distress, sexual abuse during childhood, and with several sexual dysfunctions.
With respect to symptoms in women, one study involved an epidemiological survey of post-coital psychological symptoms in a United Kingdom population sample of female twins: it found that 3.7% of these women reported suffering from recent PCT and 7.7% of them reported suffering PCT for a long time. Another study reported that almost half of female university students reported PCT symptoms at least once in their lifetime. The study also reported that there appeared to be no correlation between PCT and intimacy in close relationships.
See also
Refractory period (sex)
Prolactin
Post-nut clarity
La petite mort
Post Coïtum, Animal Triste, 1997 film
References
External links
Sexual health
Orgasm
French medical phrases | Post-coital tristesse | Biology | 562 |
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