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##rasion ) effect, similar to sandpapering. = = = solution = = = solution is the process in which acids contained in sea water will dissolve some types of rock such as chalk or limestone. = = = abrasion = = = abrasion, also known as corrasion, occurs when waves break on cliff faces and slowly erode it. as the sea pounds cliff faces it also uses the scree from other wave actions to batter and break off pieces of rock from higher up the cliff face which can be used for this same wave action and attrition. = = = corrosion = = = corrosion or solution / chemical weathering occurs when the sea's ph ( anything below ph 7. 0 ) corrodes rocks on a cliff face. limestone cliff faces, which have a moderately high ph, are particularly affected in this way. wave action also increases the rate of reaction by removing the reacted material. = = factors that influence erosion rates = = = = = primary factors = = = the ability of waves to cause erosion of the cliff face depends on many factors. the hardness ( or inversely, the erodibility ) of sea - facing rocks is controlled by the rock strength and the presence of fissures, fractures, and beds of non - cohesive materials such as silt and fine sand. the rate at which cliff fall debris is removed from the foreshore depends on the power of the waves crossing the beach. this energy must reach a critical level to remove material from the debris lobe. debris lobes can be very persistent and can take many years to completely disappear. beaches dissipate wave energy on the foreshore and provide a measure of protection to the adjoining land. the stability of the foreshore, or its resistance to lowering. once stable, the foreshore should widen and become more effective at dissipating the wave energy, so that fewer and less powerful waves reach beyond it. the provision of updrift material coming onto the foreshore beneath the cliff helps to ensure a stable beach. the adjacent bathymetry, or configuration of the seafloor, controls the wave energy arriving at the coast, and can have an important influence on the rate of cliff erosion. shoals and bars offer protection from wave erosion by causing storm waves to break and dissipate their energy before reaching the shore. given the dynamic nature of the seafloor, changes in the location of shoals and bars may cause the locus of beach or cliff erosion to change position along the shore. coastal erosion
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to break and dissipate their energy before reaching the shore. given the dynamic nature of the seafloor, changes in the location of shoals and bars may cause the locus of beach or cliff erosion to change position along the shore. coastal erosion has been greatly affected by the rising sea levels globally. there has been great measures of increased coastal erosion on the eastern seaboard of the united states and in areas of coastal guyana. locations such as florida have noticed increased coastal erosion. in reaction to these increases florida and its individual counties have increased budgets to replenish the eroded sands that attract visitors to florida and help support its multibillion - dollar tourism industries. coastal erosion = = = secondary factors = = = weathering and transport slope processes slope hydrology vegetation cliff foot erosion cliff foot sediment accumulation resistance of cliff foot sediment to attrition and transport human activities = = = tertiary factors = = = resource extraction coastal management = = control methods = = there are three common forms of coastal erosion control methods. these three include : soft - erosion controls, hard - erosion controls, and relocation. = = = hard - erosion controls = = = hard - erosion control methods provide a more permanent solution than soft - erosion control methods. seawalls and groynes serve as semi - permanent infrastructure. these structures are not immune from normal wear - and - tear and will have to be refurbished or rebuilt. it is estimated the average life span of a seawall is 50 – 100 years and the average for a groyne is 30 – 40 years. because of their relative permanence, it is assumed that these structures can be a final solution to erosion. seawalls can also deprive public access to the beach and drastically alter the natural state of the beach. groynes also drastically alter the natural state of the beach. some claim that groynes could reduce the interval between beach nourishment projects though they are not seen as a solution to beach nourishment. other criticisms of seawalls are that they can be expensive, difficult to maintain, and can sometimes cause further damage to the beach if built improperly. as we learn more about hard erosion controls it can be said for certain that these structural solutions cause more problems than they solve. they interfere with the natural water currents and prevent sand from shifting along coasts, along with the high costs to install and maintain them, their tendency to cause erosion in adjacent beaches and dunes, and the unintended diversion of stormwater and into other properties. natural forms of hard
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water currents and prevent sand from shifting along coasts, along with the high costs to install and maintain them, their tendency to cause erosion in adjacent beaches and dunes, and the unintended diversion of stormwater and into other properties. natural forms of hard - erosion control include planting or maintaining native vegetation, such as mangrove forests and coral reefs. = = = soft - erosion controls = = = soft erosion strategies refer to temporary options of slowing the effects of erosion. these options, including sandbag and beach nourishment, are not intended to be long - term solutions or permanent solutions. another method, beach scraping or beach bulldozing allows for the creation of an artificial dune in front of a building or as means of preserving a building foundation. however, there is a u. s. federal moratorium on beach bulldozing during turtle nesting season, 1 may – 15 november. one of the most common methods of soft erosion control is beach nourishment projects. these projects involve dredging sand and moving it to the beaches as a means of reestablishing the sand lost due to erosion. in some situations, beach nourishment is not a suitable measure to take for erosion control, such as in areas with sand sinks or frequent and large storms. dynamic revetment, which uses loose cobble to mimic the function of a natural storm beach, may be a soft - erosion control alternative in high energy environments such as open coastlines. over the years beach nourishment has become a very controversial shore protection measure : it has the potential to negatively impact several of the natural resources. some large issues with these beach nourishment projects are that they must follow a wide range of complex laws and regulations, as well as the high expenses it takes to complete these projects. just because sand is added to a beach does not mean it will stay there. some communities will bring in large volumes of sand repeatedly only for it to be washed away with the next big storm. despite these factors, beach nourishment is still used often in many communities. lately, the u. s. army corps of engineers emphasized the need to consider a whole new range of solutions to coastal erosion, not just structural solutions. solutions that have potential include native vegetation, wetland protection and restoration, and relocation or removal of structures and debris. = = = living shorelines = = = the solutions to coastal erosion that include vegetation are called " living shorelines ". living shorelines use plants and other natural elements. living shorelines are found to
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and relocation or removal of structures and debris. = = = living shorelines = = = the solutions to coastal erosion that include vegetation are called " living shorelines ". living shorelines use plants and other natural elements. living shorelines are found to be more resilient against storms, improve water quality, increase biodiversity, and provide fishery habitats. marshes and oyster reefs are examples of vegetation that can be used for living shorelines ; they act as natural barriers to waves. fifteen feet of marsh can absorb fifty percent of the energy of incoming waves. = = = relocation = = = relocation of infrastructure any housing farther away from the coast is also an option. the natural processes of both absolute and relative sea level rise and erosion are considered in rebuilding. depending on factors such as the severity of the erosion, as well as the natural landscape of the property, relocation could simply mean moving inland by a short distance or relocation can be to completely remove improvements from an area. a coproduction approach combined with managed retreat has been proposed as a solution that keeps in mind environmental justice. typically, there has been low public support for " retreating ". however, if a community does decide to relocate their buildings along the coast it is common that they will then turn the land into public open space or transfer it into land trusts in order to protect it. these relocation practices are very cost - efficient, can buffer storm surges, safeguard coastal homes and businesses, lower carbon and other pollutants, create nursery habitats for important fish species, restore open space and wildlife, and bring back the culture of these coastal communities. = = tracking = = storms can cause erosion hundreds of times faster than normal weather. before - and - after comparisons can be made using data gathered by manual surveying, laser altimeter, or a gps unit mounted on an atv. remote sensing data such as landsat scenes can be used for large scale and multi year assessments of coastal erosion. moreover, geostatistical models can be applied to quantify erosion effects and the natural temporal and spatial evolution of tracked coastal coastal profiles. the results can be used to determine the required temporal and spatial distances between the measured profiles for ecomic tracking. = = examples = = a place where erosion of a cliffed coast has occurred is at wamberal in the central coast region of new south wales where houses built on top of the cliffs began to collapse into the sea. this is due to waves causing erosion of the primarily sedimentary material on which the buildings foundations sit. dunwich, the capital of the english
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the central coast region of new south wales where houses built on top of the cliffs began to collapse into the sea. this is due to waves causing erosion of the primarily sedimentary material on which the buildings foundations sit. dunwich, the capital of the english medieval wool trade, disappeared over the period of a few centuries due to redistribution of sediment by waves. human interference can also increase coastal erosion : hallsands in devon, england, was a coastal village washed away over the course of a year, 1917, directly due to earlier dredging of shingle in the bay in front of it. the california coast, which has soft cliffs of sedimentary rock and is heavily populated, regularly has incidents of house damage as cliffs erodes. devil's slide, santa barbara, the coast just north of ensenada, and malibu are regularly affected. the holderness coastline on the east coast of england, just north of the humber estuary, is one of the fastest eroding coastlines in europe due to its soft clay cliffs and powerful waves. groynes and other artificial measures to keep it under control has only accelerated the process further down the coast, because longshore drift starves the beaches of sand, leaving them more exposed. the white cliffs of dover have also been affected. the coastline of north cove, washington has been eroding at a rate of over 100 feet per year, earning the area the nickname " washaway beach ". much of the original town has collapsed into the ocean. the area is said to be the fastest - eroding shore of the united states'west coast. measures were finally taken to slow the erosion, with substantial slowing of the process noted in 2018. fort ricasoli, a historic 17th century fortress in malta is being threatened by coastal erosion, as it was built on a fault in the headland which is prone to erosion. a small part of one of the bastion walls has already collapsed since the land under it has eroded, and there are cracks in other walls as well. in el campello, spain, the erosion and failure of a roman fish farm excavated from rock during the first century b. c. was exacerbated by the construction of a close sport harbour. hampton - on - sea is suffering from this problem as well. hampton - on - sea is located in kent, england. it was at one time very popular for its oyster fishing and was very reliant on the sea. hampton - on - sea has undergone the effects of coastal erosion since before the 1800s. hampton -
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on - sea is located in kent, england. it was at one time very popular for its oyster fishing and was very reliant on the sea. hampton - on - sea has undergone the effects of coastal erosion since before the 1800s. hampton - on - sea's coastal erosion worsened with the increase in global warming and climate change. global warming is causing a rise in sea level, more intense and frequent storms, and an increase in ocean temperature and precipitation levels. another reason hampton - on - sea had such a horrific case of coastal erosion is due to an increase in the frequency and the intensity of storms it experienced. these natural events had destroyed the hampton pier, hernecliffe gardens, a set of villas, several roads, and many other structures that once lay on hampton - on - sea. after this destruction, in 1899 they started building a sea wall to protect the rest of the remaining land and buildings. however, the sea wall did not offer much help : buildings continued to be affected by the erosion. then a storm came and broke the sea wall, it then flooded the land behind it. these events cause many land investors to back out. eventually, hampton - on - sea had to be abandoned because the erosion overtook so much of the land. by 1916 hampton - on - sea had been completely abandoned. by the 1920s only a couple of structures still stood. it was at that point that hampton - on - sea was said to have been finally drowned. today only three landmarks have survived the tragedy that hampton - on - sea had faced. these landmarks include the hampton inn, the hampton pier, and a few roads. although the hampton pier is not the same size as the original it is still available for people to fish from. a study published in earth's future, a journal by the american geophysical union in 2025 shows that coastal areas in arid regions, for example, in the mediterranean, are severely affected by erosion. in 2025, for example, more than 7, 000 buildings in the harbor city of alexandria are at risk of collapsing due to erosion processes and groundwater changes. in south america, the chilean coast has experienced erosion on certain beaches due to an increased frequency in severe storms during warm phases of the el nino - southern oscillation phenomenon. = = see also = = = = references = = = = = works cited = = = ipcc ( 2014 ). field, c. b. ; barros, v. r. ; dokken, d. j. ; mach, k. j.
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= = = = references = = = = = works cited = = = ipcc ( 2014 ). field, c. b. ; barros, v. r. ; dokken, d. j. ; mach, k. j. ; et al. ( eds. ). climate change 2014 : impacts, adaptation, and vulnerability. part a : global and sectoral aspects. contribution of working group ii to the fifth assessment report of the intergovernmental panel on climate change. cambridge university press. isbn 978 - 1 - 107 - 05807 - 1. = = external links = = sustainable coastal erosion management in europe " coastal erosion information from the coastal ocean institute ". woods hole oceanographic institution. archived from the original on 23 june 2011. retrieved 13 december 2019. environment agency guide to coastal erosion wave erosion time - lapse movie of beach erosion in australia on youtube examine an example of wave erosion archived 6 may 2020 at the wayback machine erosion & flooding in the parish of easington archived 29 april 2016 at the wayback machine some interesting teaching resources examples of coastal landforms us economic costs of coastal erosion & inundation noaa economics british geological survey coastal erosion and landslides case studies " coastal erosion ". u. s. climate resilience toolkit. new england federal partners. retrieved 29 november 2021. shoreline retreat and beach nourishment are projected to increase in southern california = = = images = = = images of coastal features
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a flow limiter or flow restrictor is a device to restrict the flow of a fluid, in general a gas or a liquid. some designs use single stage or multi - stage orifice plates to handle high and low flow rates. flow limiters are often used in manufacturing plants as well as households. safety is usually the main purpose of using a flow limiter. an example is manufacturing facilities and laboratories using flow limiters to prevent injury or death from noxious gases that are in use. the flow limiter prevents gases from causing injury or death by reducing its cross - sectional area where gas flows. = = uses = = reduce flow of fluid ( velocity ) through a system, e. g. to reduce water usage in a shower reduce the amount of gas passing through a system reduce pressure in a system applications in medical instrumentation as a safety valve to provide limited flow after closing in the event of a broken hose. ( see hydraulic fuse ). = = specifications = = orifice diameter flow tolerance media temperature maximum flow rate for liquid or gas maximum pressure = = design = = flow limiters are designed with the intent of reducing the cross - section area with a plate and a laser drill is used to create a small hole. the diameter of the hole will vary based on the flow rate, inlet pressure, and outlet pressure. the design can also be created with drilled orifices with threaded ends. another flow limiter design option is the use of porous media. this design is created with hundreds of pores within a central plug. the porous media design has the purpose of lowering the velocity of flow, and the lifespan is extended with lower rates of erosion. the disadvantage to the porous media design is the poor removal of particles and a drop in pressure. debris buildup will not be a concern with the porous media flow limiter with multiple holes allowing liquid or gas to flow with ease. = = features = = flow limiters have features that may be added to expand on their applications. the device can have bidirectional flow and have increased flow control with multiple openings. flow limiters can also be made of various materials to better improve quality and applications. the materials involve the use of metals, metal alloys, and thermoplastics. metals like copper and aluminium are materials that have good conductivity with heat and electricity. stainless steel has the material strength to withstand high pressures and resists chemical corrosion. flow limiters are also capable of being designed out of nylon and fluoropolymers. for the connections
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are materials that have good conductivity with heat and electricity. stainless steel has the material strength to withstand high pressures and resists chemical corrosion. flow limiters are also capable of being designed out of nylon and fluoropolymers. for the connections to the flow limiter, there are a variety of ends featuring plain ends, pipe clamp ends, flanges, and compression fittings. = = see also = = flow control valve mass flow controller needle valve = = references = =
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an anabranch is a section of a river or stream that diverts from the main channel or stem of the watercourse and rejoins the main stem downstream. local anabranches can be the result of small islands in the watercourse. in larger anabranches, the flow can diverge for a distance of several or even hundreds of kilometers before rejoining the main channel. = = word usage and related terms = = the term anabranch, in its hydrological meaning, is used more frequently in australia than in the rest of the english - speaking world. the term anabranching river describes a river with many anabranches, whilst an anastomosing river is an organic - rich subset of this river type. the term braided river describes watercourses which are divided by small islands into multiple channel threads within a single main channel, but the term does not describe the multiple channels of an anabranching river. a distributary is a branch of a river that does not rejoin the main channel ; these are common on and near river deltas. a bayou is often an anabranch. an anabranch that gets cut off from the main channel becomes an oxbow lake, known in australia as a billabong. = = examples = = the magdalena river, in colombia, bifurcates in el banco in two branches : brazo de loba ( shewolf branch in spanish ) and brazo de mompox. the first one, brazo de loba is the main navigable channel and is 177 km long. brazo de mompox is thus the anabranch. there are several other branches that join those two main branches, interconnected by swamps ( " cienagas " ), the main ones being quitasol, chicagua and la victoria. between brazo de loba and brazo de mompox is the island of mompox or margarita island, a sunken geological block of 2. 200 square km between the faults of chicagua and el romeral. in the fraser river delta of british columbia, canada, north arm fraser river, middle arm fraser river, and south arm fraser river each fall into georgia strait separately. on the other hand, annacis island splits ( south arm ) fraser river into the ( main ) annieville channel and the ( smaller ) annacis channel, which rejoin below the island. in western new south wales the great darling anabranch is the ancestral path
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hand, annacis island splits ( south arm ) fraser river into the ( main ) annieville channel and the ( smaller ) annacis channel, which rejoin below the island. in western new south wales the great darling anabranch is the ancestral path of the darling river, dividing south of menindee and extending for 460 km before joining the murray river. the anabranch contains flowing water only in wetter years. in the lower simpson desert, in south australia, kallakoopah creek is an anabranch of the warburton river that flows during major warburton floods of over 5 m in depth. the kallakoopah is approximately 400 km long and members of the lake eyre yacht club and others have used it to sail a circular route to lake eyre by traveling down the kallakoopah and returning via the warburton. the bahr el zeraf in southern sudan splits from the bahr al jabal section of the white nile and flows for 240 km ( 150 mi ), before rejoining the white nile proper upriver from malakal. approximately 15 km out of charters towers ( queensland / australia ) is a section of the burdekin river known as'the anabranch '. this strip of water is separate from the main flood way, and is typically dry during the sunnier months. once there is consistent rain, it will meet up with the river again and flood with fresh water. it is well known for barramundi fishing. probably because waterways played an important role in infrastructure, anabranches and the resulting river islands are often found in old cities as with the ile de la cite in paris. = = see also = = city barrage, wrocław = = references = =
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polydioxanone ( pdo, pds ) or poly - p - dioxanone is a colorless, crystalline, biodegradable synthetic polymer. = = chemistry = = chemically, polydioxanone is a polymer of multiple repeating ether - ester units. it is obtained by ring - opening polymerization of the monomer p - dioxanone. the process requires heat and an organometallic catalyst like zirconium acetylacetone or zinc l - lactate. it is characterized by a glass transition temperature in the range of −10 and 0 °c and a crystallinity of about 55 %. for the production of sutures, polydioxanone is generally extruded into fibers, however care should be taken to process the polymer to the lowest possible temperature, in order to avoid its spontaneous depolymerization back to the monomer. the ether oxygen group in the backbone of the polymer chain is responsible for its flexibility. = = medical use = = polydioxanone is used for biomedical applications, particularly in the preparation of surgical sutures. other biomedical applications include orthopedics, maxillofacial surgery, plastic surgery, drug delivery, cardiovascular applications, and tissue engineering. for example, with the use of electrospinning, the flexible nature of pds allows the control of its structure and can be used in applications such as tissue scaffolding. it is degraded by hydrolysis, and the end products are mainly excreted in urine, the remainder being eliminated by the digestive system or exhaled as co2. the biomaterial is completely reabsorbed in 6 months and can be seen only a minimal foreign body reaction tissue in the vicinity of the implant. materials made of pds can be sterilized with ethylene oxide. = = see also = = other biodegradable polymers : polycaprolactone polyglycolide polylactic acid poly ( lactic - co - glycolic acid ) poly - 3 - hydroxybutyrate = = references = =
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breed method is a laboratory technique used for counting microorganisms in milk. it was introduced in 1910 by american biologists samuel cate prescott and robert stanley breed. = = purpose = = it is a method for somatic cell count, to know the number of living and dead microorganisms. when the method only recounts living organisms is called " viable count ". there are many methods for the quantification of microorganisms, including microscopy methods, coulter counter, mass spectrometry ( for estimating cell mass ), and cell culture methods which form and grow colonies of bacteria. the existing security in dairy products is given by the microbiological quality of the same, which ensures consumption from the point of view of health. the analysis of the quality of raw milk is a common practice in the dairy industry and aims to control the quality of the samples and the material introduced into the processing plant, culminating in a mass - consumption to ensure quality standards. = = sample preparation = = it is important first, to homogenize milk, heating it in a water bath at 40 °c for somatic cells that float to the surface along with the fat. the laboratory apparatus must be clean but not necessarily sterile, since the method is based on cell count and asepsis is not accurate. if later it is going to make detailed microbiological analyzes on the same sample, then it is necessary to be obtained and manipulated with sterile material. after this process, the sample is transported to the laboratory in a 4 °c conservative container. it can be preserved in these conditions for 24 hours. for sampling there are two basic conditions to consider : the first one is to represent the total volume of milk from which it was removed, and the second condition involves to be stored and transported at the correct temperature so that they see their unmodified source properties, prior to analysis in the laboratory. in case of delay in completion of the analysis a preservative that not alter the subsequent analytical result should be added to the milk. = = application of the technique = = be made extended and 0. 01 ml of 1 cm2 on fat - free slides ( which are cleaned with xylene ). after allowing to dry, it is colored and performs counting. for this, the average of existing cells is performed in the field of the microscope, dividing total somatic cells from microscopic factor ( mf ) which corresponds to the number of fields in one inch, i. e. 100 mm, obtaining in this way the
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, the average of existing cells is performed in the field of the microscope, dividing total somatic cells from microscopic factor ( mf ) which corresponds to the number of fields in one inch, i. e. 100 mm, obtaining in this way the number of somatic cells per milliliter of milk. microscopic factor calculation m f = 100 m m f ´ i e l d a r e a i n m m { \ displaystyle mf = { { 100 \ mm } \ over { \ acute { f } } ield \ \ area \ in \ mm } } getting the average n u m b e r o f s o m a t i c s c e l l s = t o t a l s o m a t i c c e l l s n u m b e r o f c o u n t e d f i e l d s { \ displaystyle number \ of \ somatics \ cells = { total \ somatic \ cells \ \ over number \ of \ counted \ fields } } = = see also = = somatic cell count = = references = =
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rule - based modeling is a modeling approach that uses a set of rules that indirectly specifies a mathematical model. the rule - set can either be translated into a model such as markov chains or differential equations, or be treated using tools that directly work on the rule - set in place of a translated model, as the latter is typically much bigger. rule - based modeling is especially effective in cases where the rule - set is significantly simpler than the model it implies, meaning that the model is a repeated manifestation of a limited number of patterns. an important domain where this is often the case is biochemical models of living organisms. groups of mutually corresponding substances are subject to mutually corresponding interactions. bionetgen is a suite of software tools used to generate mathematical models consisting of ordinary differential equations without generating the equations directly. for example below is an example rule in the bionetgen format : a ( a, a ) + b ( b ) − > a ( a! 1 ). b ( b! 1 ) { \ displaystyle a ( a, a ) + b ( b ) - > a ( a! 1 ). b ( b! 1 ) } where : a ( a, a ) : represents a model species a with two free binding sites a b ( b ) : represents a model species b with one free binding site a ( a! 1 ). b ( b! 1 ) : represents model species where at least one binding site of a is bound to the binding site of b with the above line of code, bionetgen will automatically create an ode for each model species with the correct mass balance. additionally, an additional species will be created because the rule above implies that two b molecules can bind to a single a molecule since there are two binding sites. therefore, the following species will be generated : 4. a ( a! 1, a! 2 ). b ( b! 1 ). b ( b! 2 ) : molecule a with both binding sites occupied by two different b molecules. = = for biochemical systems = = early efforts to use rule - based modeling in simulation of biochemical systems include the stochastic simulation systems stochsim a widely used tool for rule - based modeling of biochemical networks is bionetgen it is released under the gnu gpl, version 3. bionetgen includes a language to describe chemical substances, including the states they can assume and the bindings they can undergo. these rules can be used to create a reaction network model or to perform computer simulations directly on the
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gpl, version 3. bionetgen includes a language to describe chemical substances, including the states they can assume and the bindings they can undergo. these rules can be used to create a reaction network model or to perform computer simulations directly on the rule set. the biochemical modeling framework virtual cell includes a bionetgen interpreter. a close alternative is the kappa language. another alternative is biochemical space language. = = references = =
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lorenzo's oil is a 1992 drama film directed and co - written by george miller. it is based on the true story of augusto and michaela odone, parents who search for a cure for their son lorenzo's adrenoleukodystrophy ( ald ), leading to the development of lorenzo's oil. the film was shot in pittsburgh, pennsylvania, primarily from september 1991 to february 1992. it had a limited release in north america on december 30, 1992, with a nationwide release two weeks later, on january 15, 1993. though it was a box office disappointment, grossing $ 7. 2 million against its $ 30 million budget, the film was generally well received by critics and garnered two nominations at the 65th academy awards. = = plot = = lorenzo is a bright and vibrant young boy living in the comoro islands, as his father augusto odone works for the world bank and is stationed there. however, after relocating with his parents to the united states, he begins to show signs of neurological problems ( such as falling, loss of hearing, tantrums, etc. ). the boy is diagnosed as having adrenoleukodystrophy ( ald ), which is fatal within two years. failing to find a doctor capable of treating their son's rare disease, augusto and his wife, michaela, set out on a mission to find a treatment to save their son. in their quest, the odones clash with doctors, scientists and a support group that is skeptical that anything could be done about ald, much less by laypeople. but they persist, setting up camp in medical libraries, reviewing animal experiments, enlisting the aid of professor gus nikolais, badgering researchers, questioning top doctors all over the world and even organizing an international symposium about the disease. despite research dead - ends, the horror of watching their son's health decline and being surrounded by skeptics ( including the coordinators of the support group they attend ), they persist until they finally hit upon a possible therapy. the odones sponsor an international meeting of scientists doing research on ald, requiring two conditions ahead of time. first they insist that the meeting focus on potential treatments and second, they require that they be allowed to participate, despite being non - scientist laypeople. the pivotal scene in the movie portrays this meeting, in which the scientists are presenting their research. when dr. william b. rizzo mentions his studies in which the addition of oleic
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allowed to participate, despite being non - scientist laypeople. the pivotal scene in the movie portrays this meeting, in which the scientists are presenting their research. when dr. william b. rizzo mentions his studies in which the addition of oleic acid to cultured cells blocked accumulation of the factors which cause ald, the odones jump into the conversation, asking if this oil might help their son. although the scientists play down their hope, pointing out that it would take years of work to produce the oil and test in clinical trials, the odones seize the promise of this possible curative treatment. as the scene ends, michaela odone is shown beginning the effort to find someone able and willing to produce the same oil dr. rizzo gave to his cells. they obtain oleic acid from an industrial manufacturer of lubricants, but this only lowers lorenzo's levels by 50 % before leveling off, and they realize they are only countering some of the shorter chains produced by one enzyme. to remove the other, they will have to add a distillation of erucic acid. they contact over 100 firms around the world until they find an elderly british chemist, don suddaby, who is working for croda international and is willing to take on the challenge of distilling the proper formula. the odones obtain a precious vial of the oil ( actually containing two specific long chain fatty acids, isolated from rapeseed oil and olive oil ) and add it to their son's diet. this treatment proves successful in normalizing the accumulation of the very long chain fatty acids ( which had been causing their son's steady decline ), as measured in blood levels. this treatment halts the progression of his disease and is dubbed " lorenzo's oil ". this oil is soon found to be successful in preventing the progression of harm in other patients with ald. meanwhile, lorenzo has a great deal of neurological damage, and the odones are dismayed to see that the oil can reverse their son's symptoms only very, very slowly. the odones realize that more rapid improvement of their son's severe condition will require treatments to repair the myelin sheath ( a lipid insulator ) around the nerves, and augusto is shown taking on the new challenge of organizing biomedical efforts to heal myelin damage in patients. finally, lorenzo, at the age of 14, shows definite improvement ( swallowing for himself and answering " yes " or " no " questions by blinking )
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augusto is shown taking on the new challenge of organizing biomedical efforts to heal myelin damage in patients. finally, lorenzo, at the age of 14, shows definite improvement ( swallowing for himself and answering " yes " or " no " questions by blinking ) and it is revealed that he has regained his sight, can move his head from side to side, vocalize simple sounds and is learning to use a computer. the movie ends with scenes of ald patients who were treated with lorenzo's oil earlier in the course of their disease. in these patients the devastating neurological degeneration from which lorenzo suffered was able to be prevented. = = cast = = = = production = = principal photography for lorenzo's oil began on september 9, 1991 in the pittsburgh suburb of ben avon, pennsylvania and continued throughout the city and area. possibly to emphasize the " everyman " aspect of the plot ( the notion that a cure could affect families and individuals anywhere ), many smaller roles were played by inexperienced actors or non - actors with unusual physical features and mannerisms. for example, the poet james merrill was noticed by a casting director at a new york public reading of his poetry. his rarefied speaking cadences were utilized in a symposium scene in which he played a questioning doctor. = = = music = = = the film uses allegri's miserere, edward elgar's cello concerto, as well as barber's adagio for strings and mozart's ave verum corpus k. 618. the opening song is " kijana mwana mwali " ( swahili, " song about a young lady " ), sung by the gonda traditional entertainers. a 1960 recording of maria callas with the la scala orchestra and chorus is heard singing selections from bellini's norma at several points. the music for the easter midnight mass scene is a russian orthodox church hymn, " bogoroditse devo " ( rejoice, o virgin ) from " three choruses from'tsar feodor ioannovich'", taken from the album sacred songs of russia by gloriae dei cantores. other music include barber's agnus dei and mahler's symphony no. 5. the original music from the motion picture soundtrack was scored and composed by stewart copeland. = = reception = = = = = critical response = = = roger ebert of the chicago sun - times gave the film four out of four stars and called it an " immensely moving and challenging movie ", adding that " it was
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by stewart copeland. = = reception = = = = = critical response = = = roger ebert of the chicago sun - times gave the film four out of four stars and called it an " immensely moving and challenging movie ", adding that " it was impossible not to get swept up in it. " james berardinelli of reelviews gave it three out of four stars and claimed, " it was about the war for knowledge and the victory of hope through perseverance. " review aggregation website rotten tomatoes retrospectively collected reviews from 40 critics to give the film a score of 93 %, with an average rating of 7. 10 / 10, as of may 2023. the website's consensus reads, " a harrowing tribute to the heroism of parental love, lorenzo's oil is kept from abject misery by george miller's sensitive direction and outstanding performances from nick nolte and susan sarandon. " on metacritic, the film has a weighted average score of 80 out of 100, based on 21 critics, indicating " generally favorable " reviews. audiences polled by cinemascore gave the film a grade of " a " on an a + to f scale. = = = medical response = = = though the film seemed to accurately portray the events related to the boy's condition and his parents'efforts during the time period covered by the film, it was criticized for falsely painting a picture of a miracle cure. subsequent research with lorenzo's oil has not clearly proven its long - term effectiveness in treating ald after its onset. however, it prevented the onset of ald in two - thirds of the susceptible boys. the actual subject of the film, lorenzo odone, died of pneumonia in may 2008 at the age of 30, having lived two decades longer than originally predicted by doctors. hugo moser, on whom the character of professor nikolais was based, called the film's portrayal of him " an abomination ". = = = box office = = = the film grossed $ 7, 286, 388 domestically with a budget of around $ 30 million. = = = accolades = = = = = see also = = voglia di vivere ( film ), a 1990 italian television film depicting the same story. " lorenzo ", a song by phil collins, released on the 1996 album dance into the light, is based on a poem michaela odone wrote about lorenzo. extraordinary measures, a 2010 film depicting the true story of another set of parents'struggle to find a cure for their
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phil collins, released on the 1996 album dance into the light, is based on a poem michaela odone wrote about lorenzo. extraordinary measures, a 2010 film depicting the true story of another set of parents'struggle to find a cure for their children's rare disease. = = references = = = = external links = = lorenzo's oil at imdb lorenzo's oil at the tcm movie database lorenzo's oil at oz movies
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the european cloud partnership ( ecp ) is an advisory group set up by the european commission as part of the european cloud computing strategy to provide guidance on the development of cloud computing in the european union. the ecp is led by a steering board composed of representatives of the it and telecom industry as well as european government policymakers. = = history = = after publishing a document, " unleashing the potential of cloud computing in europe ", the european commission set up the european cloud partnership in 2012, with a steering board including both government and industry representatives. the ecp's first meeting was held on 19 november 2012 ; it was chaired by the president of estonia toomas hendrik ilves. in 2013 the ecp began drafting its charter. that year, as information about the prism scandal came to light, the ecp emphasized the need for europe to develop its own cloud infrastructure, rather than depend on that of the united states. it completed a report titled " trusted cloud europe " in february 2014 defining its policy, and outlining a process for effective public and private sector participation in cloud computing development in europe. the report recommended that the commission identify technical, legal and operational best practices, and promote these through certifications and guidelines, and facilitate recognition across national boundaries. the report also recommended that the commission identify cloud computing stakeholders and help them work together through consultations and workshops. in march 2014, the european commission invited external parties to submit opinions, take part in a discussion forum and complete an online survey in response to the report. = = references = = = = external links = = trusted cloud europe - a policy vision document by the steering board of the european cloud partnership - page 15
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de dicto and de re are two phrases used to mark a distinction in intensional statements, associated with the intensional operators in many such statements. the distinction is used regularly in analytical metaphysics and in philosophy of language. the literal translation of the phrase de dicto is " about what is said ", whereas de re translates as " about the thing ". the original meaning of the latin locutions may help to elucidate the living meaning of the phrases, in the distinctions they mark. the distinction can be understood by examples of intensional contexts of which three are considered here : a context of thought, a context of desire, and a context of modality. = = context of thought = = there are two possible interpretations of the sentence " peter believes someone is out to get him " : on the de dicto interpretation,'someone'is unspecific and peter suffers a general paranoia ; he believes that it is true that a person is out to get him, but does not necessarily have any beliefs about who this person may be. what peter believes is that the predication'someone is out to get peter'is satisfied. on the de re interpretation,'someone'is specific, picking out some particular individual. there is some person peter has in mind, and peter believes that person is out to get him. in the context of thought, the distinction helps us explain how people can hold seemingly self - contradictory beliefs. say lois lane believes clark kent is weaker than superman. since clark kent is superman, taken de re, lois's belief is untenable ; the names'clark kent'and'superman'pick out an individual in the world, and a person ( or super - person ) cannot be stronger than himself. understood de dicto, however, this may be a perfectly reasonable belief, since lois is not aware that clark and superman are one and the same. = = context of desire = = consider the sentence " jana wants to marry the tallest man in fulsom county ". it could be read either de dicto or de re ; the meanings would be different. one interpretation is that jana wants to marry the tallest man in fulsom county, whoever he might be. on this interpretation, what the statement tells us is that jana has a certain unspecific desire ; what she desires is for jana is marrying the tallest man in fulsom county to be true. the desire is directed at that situation, regardless of how it
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, what the statement tells us is that jana has a certain unspecific desire ; what she desires is for jana is marrying the tallest man in fulsom county to be true. the desire is directed at that situation, regardless of how it is to be achieved. the other interpretation is that jana wants to marry a certain man, who in fact happens to be the tallest man in fulsom county. her desire is for that man, and she desires herself to marry him. the first interpretation is the de dicto interpretation, because jana's desire relates to the words " the tallest man in fulsom county ", and the second interpretation is the de re interpretation, because jana's desire relates to the man those words refer to. another way to understand the distinction is to ask what jana would want if a nine - foot - tall immigrant moved to fulsom county. if she continued to want to marry the same man – and perceived this as representing no change in her desires – then she could be taken to have meant the original statement in a de re sense. if she no longer wanted to marry that man but instead wanted to marry the new tallest man in fulsom county, and saw this as a continuation of her earlier desire, then she meant the original statement in a de dicto sense. = = context of modality = = the number of discovered chemical elements is 118. take the sentence " the number of chemical elements is necessarily greater than 100 ". again, there are two interpretations as per the de dicto / de re distinction. the de dicto interpretation n c h e m ( n c h e m > 100 ) { \ displaystyle \ box \ exists { n _ { chem } } ( n _ { chem } > 100 ) } says that, in other accessible possible worlds, even if the inner workings of the atom could differ ( so that n c h e m { \ displaystyle n _ { chem } } have different values ), the number of elements still could not be 100 or fewer. the de re interpretation n c h e m ( n c h e m > 100 ) { \ displaystyle \ exists { n _ { chem } } \ box ( n _ { chem } > 100 ) } says that, the inner workings of the atom are what they are ( n c h e m = 118 { \ displaystyle n _ { chem } = 118 } in all accessible possible worlds ),
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_ { chem } > 100 ) } says that, the inner workings of the atom are what they are ( n c h e m = 118 { \ displaystyle n _ { chem } = 118 } in all accessible possible worlds ), and the number 118 is greater than 100. another example : " the president of the us in 2001 could not have been al gore ". the de dicto reading p r e s 2001 ( p r e s 2001 = a l ) { \ displaystyle \ box \ exists { pres _ { 2001 } } ( pres _ { 2001 } \ neq al ) } says that, in other accessible possible worlds, even if the result of the 2000 election could differ, the president of the us in 2001 still could not have been al gore. this claim seems false ; presumably, in some other accessible possible worlds where the supreme court did not rule that bush had won the election, al gore could have been the president of the us in 2001 in that possible world. the de re reading p r e s 2001 ( p r e s 2001 = a l ) { \ displaystyle \ exists { pres _ { 2001 } } \ box ( pres _ { 2001 } \ neq al ) } says that, the president of the us in 2001 is who he is, and that is george bush in all accessible possible worlds, and george bush could not have been al gore. = = representing de dicto and de re in modal logic = = in modal logic the distinction between de dicto and de re is one of scope. in de dicto claims, any existential quantifiers are within the scope of the modal operator, whereas in de re claims the modal operator falls within the scope of the existential quantifier. for example : generally speaking, x a x { \ displaystyle \ box \ forall { x } ax } is logically equivalent to x a x { \ displaystyle \ forall { x } \ box ax }, both meaning that all x in all the possible worlds are a ( assuming that the range of quantification / domain of discourse is the same in all the accessible possible worlds ) ; however, x a x { \ displaystyle \ box \ exists { x } ax } means that each accessible possible world has its own x that is a, but they are not necessarily the same, whereas x a x { \
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however, x a x { \ displaystyle \ box \ exists { x } ax } means that each accessible possible world has its own x that is a, but they are not necessarily the same, whereas x a x { \ displaystyle \ exists { x } \ box ax } means that there is a special x that is a in all accessible possible worlds. similarly, x a x { \ displaystyle \ diamond \ exists { x } ax } is logically equivalent to x a x { \ displaystyle \ exists { x } \ diamond ax }, both meaning that in some accessible possible world, there is some x that is a ; however, x a x { \ displaystyle \ diamond \ forall { x } ax } means that in some accessible possible world, all x are a, whereas x a x { \ displaystyle \ forall { x } \ diamond ax } means that for each x in the range of quantification / domain of discourse, there is some accessible possible world where x is a, but it can be true that no world has two x that are both a. = = see also = = barcan formula evaluation strategy de se latitudinarianism ( philosophy ) quantifier raising temperature paradox modal scope fallacy = = references = = = = bibliography = = burge, tyler. 1977. belief de re. journal of philosophy 74, 338 - 362. donnellan, keith s. 1966. reference and definite descriptions. philosophical review 75, 281 - 304. frege, gottlob. 1892. uber sinn und bedeutung. zeitschrift fur philosophie und philosophische kritik 100, 25 - 50. translated as on sense and reference by peter geach & max black, 1970, in translations from the philosophical writings of gottlob frege. oxford, blackwell, 56 - 78. kaplan, david. 1978. dthat. in peter cole, ed., syntax and semantics, vol. 9 : pragmatics. new york : academic press, 221 - 243 kripke, saul. 1977. speaker's reference and semantic reference. in peter a. french, theodore e. uehling, jr., and howard k. wettstein, eds., midwest studies in philosophy vol. ii : studies in the philosophy of language. morris, mn : university of minnesota, 255 - 276. larson, richard & gabriel sega
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##ehling, jr., and howard k. wettstein, eds., midwest studies in philosophy vol. ii : studies in the philosophy of language. morris, mn : university of minnesota, 255 - 276. larson, richard & gabriel segal. 1995. definite descriptions. in knowledge of meaning : an introduction to semantic theory. cambridge, ma : mit press, 319 - 359. ludlow, peter & stephen neale. 1991. indefinite descriptions : in defense of russell. linguistics and philosophy 14, 171 - 202. ostertag, gary. 1998. introduction. in gary ostertag, ed., definite descriptions : a reader. cambridge, ma : mit press, 1 - 34. russell, bertrand. 1905. on denoting. mind 14, 479 - 493. wettstein, howard. 1981. demonstrative reference and definite descriptions. philosophical studies 40, 241 - 257. wilson, george m. 1991. reference and pronominal descriptions. journal of philosophy 88, 359 - 387. = = external links = = the de re / de dicto distinction, stanford encyclopedia of philosophy
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in topology and related fields of mathematics, a topological space x is called a regular space if every closed subset c of x and a point p not contained in c have non - overlapping open neighborhoods. thus p and c can be separated by neighborhoods. this condition is known as axiom t3. the term " t3 space " usually means " a regular hausdorff space ". these conditions are examples of separation axioms. = = definitions = = a topological space x is a regular space if, given any closed set f and any point x that does not belong to f, there exists a neighbourhood u of x and a neighbourhood v of f that are disjoint. concisely put, it must be possible to separate x and f with disjoint neighborhoods. a t3 space or regular hausdorff space is a topological space that is both regular and a hausdorff space. ( a hausdorff space or t2 space is a topological space in which any two distinct points are separated by neighbourhoods. ) it turns out that a space is t3 if and only if it is both regular and t0. ( a t0 or kolmogorov space is a topological space in which any two distinct points are topologically distinguishable, i. e., for every pair of distinct points, at least one of them has an open neighborhood not containing the other. ) indeed, if a space is hausdorff then it is t0, and each t0 regular space is hausdorff : given two distinct points, at least one of them misses the closure of the other one, so ( by regularity ) there exist disjoint neighborhoods separating one point from ( the closure of ) the other. although the definitions presented here for " regular " and " t3 " are not uncommon, there is significant variation in the literature : some authors switch the definitions of " regular " and " t3 " as they are used here, or use both terms interchangeably. this article uses the term " regular " freely, but will usually say " regular hausdorff ", which is unambiguous, instead of the less precise " t3 ". for more on this issue, see history of the separation axioms. a locally regular space is a topological space where every point has an open neighbourhood that is regular. every regular space is locally regular, but the converse is not true. a classical example of a locally regular space that is not regular is the bug - eyed line. = =
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is a topological space where every point has an open neighbourhood that is regular. every regular space is locally regular, but the converse is not true. a classical example of a locally regular space that is not regular is the bug - eyed line. = = relationships to other separation axioms = = a regular space is necessarily also preregular, i. e., any two topologically distinguishable points can be separated by neighbourhoods. since a hausdorff space is the same as a preregular t0 space, a regular space which is also t0 must be hausdorff ( and thus t3 ). in fact, a regular hausdorff space satisfies the slightly stronger condition t2½. ( however, such a space need not be completely hausdorff. ) thus, the definition of t3 may cite t0, t1, or t2½ instead of t2 ( hausdorffness ) ; all are equivalent in the context of regular spaces. speaking more theoretically, the conditions of regularity and t3 - ness are related by kolmogorov quotients. a space is regular if and only if its kolmogorov quotient is t3 ; and, as mentioned, a space is t3 if and only if it's both regular and t0. thus a regular space encountered in practice can usually be assumed to be t3, by replacing the space with its kolmogorov quotient. there are many results for topological spaces that hold for both regular and hausdorff spaces. most of the time, these results hold for all preregular spaces ; they were listed for regular and hausdorff spaces separately because the idea of preregular spaces came later. on the other hand, those results that are truly about regularity generally don't also apply to nonregular hausdorff spaces. there are many situations where another condition of topological spaces ( such as normality, pseudonormality, paracompactness, or local compactness ) will imply regularity if some weaker separation axiom, such as preregularity, is satisfied. such conditions often come in two versions : a regular version and a hausdorff version. although hausdorff spaces aren't generally regular, a hausdorff space that is also ( say ) locally compact will be regular, because any hausdorff space is preregular. thus from a certain point of view, regularity is not really the issue here
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' t generally regular, a hausdorff space that is also ( say ) locally compact will be regular, because any hausdorff space is preregular. thus from a certain point of view, regularity is not really the issue here, and we could impose a weaker condition instead to get the same result. however, definitions are usually still phrased in terms of regularity, since this condition is more well known than any weaker one. most topological spaces studied in mathematical analysis are regular ; in fact, they are usually completely regular, which is a stronger condition. regular spaces should also be contrasted with normal spaces. = = examples and nonexamples = = a zero - dimensional space with respect to the small inductive dimension has a base consisting of clopen sets. every such space is regular. as described above, any completely regular space is regular, and any t0 space that is not hausdorff ( and hence not preregular ) cannot be regular. most examples of regular and nonregular spaces studied in mathematics may be found in those two articles. on the other hand, spaces that are regular but not completely regular, or preregular but not regular, are usually constructed only to provide counterexamples to conjectures, showing the boundaries of possible theorems. of course, one can easily find regular spaces that are not t0, and thus not hausdorff, such as an indiscrete space, but these examples provide more insight on the t0 axiom than on regularity. an example of a regular space that is not completely regular is the tychonoff corkscrew. most interesting spaces in mathematics that are regular also satisfy some stronger condition. thus, regular spaces are usually studied to find properties and theorems, such as the ones below, that are actually applied to completely regular spaces, typically in analysis. there exist hausdorff spaces that are not regular. an example is the k - topology on the set r { \ displaystyle \ mathbb { r } } of real numbers. more generally, if c { \ displaystyle c } is a fixed nonclosed subset of r { \ displaystyle \ mathbb { r } } with empty interior with respect to the usual euclidean topology, one can construct a finer topology on r { \ displaystyle \ mathbb { r } } by taking as a base the collection of all sets u { \ displaystyle u } and u c { \ displaystyle u \ setminus c } for
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construct a finer topology on r { \ displaystyle \ mathbb { r } } by taking as a base the collection of all sets u { \ displaystyle u } and u c { \ displaystyle u \ setminus c } for u { \ displaystyle u } open in the usual topology. that topology will be hausdorff, but not regular. = = elementary properties = = suppose that x is a regular space. then, given any point x and neighbourhood g of x, there is a closed neighbourhood e of x that is a subset of g. in fancier terms, the closed neighbourhoods of x form a local base at x. in fact, this property characterises regular spaces ; if the closed neighbourhoods of each point in a topological space form a local base at that point, then the space must be regular. taking the interiors of these closed neighbourhoods, we see that the regular open sets form a base for the open sets of the regular space x. this property is actually weaker than regularity ; a topological space whose regular open sets form a base is semiregular. = = references = =
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lindley's paradox is a counterintuitive situation in statistics in which the bayesian and frequentist approaches to a hypothesis testing problem give different results for certain choices of the prior distribution. the problem of the disagreement between the two approaches was discussed in harold jeffreys'1939 textbook ; it became known as lindley's paradox after dennis lindley called the disagreement a paradox in a 1957 paper. although referred to as a paradox, the differing results from the bayesian and frequentist approaches can be explained as using them to answer fundamentally different questions, rather than actual disagreement between the two methods. nevertheless, for a large class of priors the differences between the frequentist and bayesian approach are caused by keeping the significance level fixed : as even lindley recognized, " the theory does not justify the practice of keeping the significance level fixed " and even " some computations by prof. pearson in the discussion to that paper emphasized how the significance level would have to change with the sample size, if the losses and prior probabilities were kept fixed ". in fact, if the critical value increases with the sample size suitably fast, then the disagreement between the frequentist and bayesian approaches becomes negligible as the sample size increases. the paradox continues to be a source of active discussion. = = description of the paradox = = the result x { \ displaystyle x } of some experiment has two possible explanations – hypotheses h 0 { \ displaystyle h _ { 0 } } and h 1 { \ displaystyle h _ { 1 } } – and some prior distribution π { \ displaystyle \ pi } representing uncertainty as to which hypothesis is more accurate before taking into account x { \ displaystyle x }. lindley's paradox occurs when the result x { \ displaystyle x } is " significant " by a frequentist test of h 0, { \ displaystyle h _ { 0 }, } indicating sufficient evidence to reject h 0, { \ displaystyle h _ { 0 }, } say, at the 5 % level, and the posterior probability of h 0 { \ displaystyle h _ { 0 } } given x { \ displaystyle x } is high, indicating strong evidence that h 0 { \ displaystyle h _ { 0 } } is in better agreement with x { \ displaystyle x } than h 1. { \ displaystyle h _ { 1 }. } these results can occur at the same time when h 0 { \ displaystyle h _ { 0 } } is very specific,
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better agreement with x { \ displaystyle x } than h 1. { \ displaystyle h _ { 1 }. } these results can occur at the same time when h 0 { \ displaystyle h _ { 0 } } is very specific, h 1 { \ displaystyle h _ { 1 } } more diffuse, and the prior distribution does not strongly favor one or the other, as seen below. = = numerical example = = the following numerical example illustrates lindley's paradox. in a certain city 49, 581 boys and 48, 870 girls have been born over a certain time period. the observed proportion x { \ displaystyle x } of male births is thus 49581 / 98451 ≈ 0. 5036. we assume the fraction of male births is a binomial variable with parameter θ. { \ displaystyle \ theta. } we are interested in testing whether θ { \ displaystyle \ theta } is 0. 5 or some other value. that is, our null hypothesis is h 0 : θ = 0. 5, { \ displaystyle h _ { 0 } : \ theta = 0. 5, } and the alternative is h 1 : θ = 0. 5. { \ displaystyle h _ { 1 } : \ theta \ neq 0. 5. } = = = frequentist approach = = = the frequentist approach to testing h 0 { \ displaystyle h _ { 0 } } is to compute a p - value, the probability of observing a fraction of boys at least as large as x { \ displaystyle x } assuming h 0 { \ displaystyle h _ { 0 } } is true. because the number of births is very large, we can use a normal approximation for the fraction of male births x n ( μ, σ 2 ), { \ displaystyle x \ sim n ( \ mu, \ sigma ^ { 2 } ), } with μ = n p = n θ = 98 451 × 0. 5 = 49 225. 5 { \ displaystyle \ mu = np = n \ theta = 98 \, 451 \ times 0. 5 = 49 \, 225. 5 } and σ 2 = n θ ( 1 − θ ) = 98 451 × 0. 5 × 0. 5 = 24 612. 75, { \ displaystyle \ sigma ^ { 2 } = n \ theta ( 1 - \ theta ) = 98 \, 451 \ times 0. 5 \ times 0. 5 = 24 \, 612. 75, }
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612. 75, { \ displaystyle \ sigma ^ { 2 } = n \ theta ( 1 - \ theta ) = 98 \, 451 \ times 0. 5 \ times 0. 5 = 24 \, 612. 75, } to compute p ( x ≥ x μ = 49 225. 5 ) = x = 49 581 98 451 1 2 π σ 2 e − 1 2 ( u − μ σ ) 2 d u = x = 49 581 98 451 1 2 π ( 24 612. 75 ) e − ( u − 49 225. 5 ) 2 2 × 24 612. 75 d u ≈ 0. 0117. { \ displaystyle { \ begin { aligned } p ( x \ geq x \ mid \ mu = 49 \, 225. 5 ) = \ int _ { x = 49 \, 581 } ^ { 98 \, 451 } { \ frac { 1 } { \ sqrt { 2 \ pi \ sigma ^ { 2 } } } } e ^ { - { \ frac { 1 } { 2 } } \ left ( { \ frac { u - \ mu } { \ sigma } } \ right ) ^ { 2 } } \, du \ \ = \ int _ { x = 49 \, 581 } ^ { 98 \, 451 } { \ frac { 1 } { \ sqrt { 2 \ pi ( 24 \, 612. 75 ) } } } e ^ { - { \ frac { ( u - 49 \, 225. 5 ) ^ { 2 } } { 2 \ times 24 \, 612. 75 } } } \, du \ approx 0. 0117. \ end { aligned } } } we would have been equally surprised if we had seen 49581 female births, i. e. x ≈ 0. 4964, { \ displaystyle x \ approx 0. 4964, } so a frequentist would usually perform a two - sided test, for which the p - value would be p ≈ 2 × 0. 0117 = 0. 0235. { \ displaystyle p \ approx 2 \ times 0. 0117 = 0. 0235. } in both cases, the p - value is lower than the significance level α = 5 %, so the frequentist approach rejects h 0, { \ displaystyle h _ { 0 }, } as it disagrees with the observed data. = = = bayesian approach = = = assuming
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is lower than the significance level α = 5 %, so the frequentist approach rejects h 0, { \ displaystyle h _ { 0 }, } as it disagrees with the observed data. = = = bayesian approach = = = assuming no reason to favor one hypothesis over the other, the bayesian approach would be to assign prior probabilities π ( h 0 ) = π ( h 1 ) = 0. 5 { \ displaystyle \ pi ( h _ { 0 } ) = \ pi ( h _ { 1 } ) = 0. 5 } and a uniform distribution to θ { \ displaystyle \ theta } under h 1, { \ displaystyle h _ { 1 }, } and then to compute the posterior probability of h 0 { \ displaystyle h _ { 0 } } using bayes'theorem : p ( h 0 k ) = p ( k h 0 ) π ( h 0 ) p ( k h 0 ) π ( h 0 ) + p ( k h 1 ) π ( h 1 ). { \ displaystyle p ( h _ { 0 } \ mid k ) = { \ frac { p ( k \ mid h _ { 0 } ) \ pi ( h _ { 0 } ) } { p ( k \ mid h _ { 0 } ) \ pi ( h _ { 0 } ) + p ( k \ mid h _ { 1 } ) \ pi ( h _ { 1 } ) } }. } after observing k = 49 581 { \ displaystyle k = 49 \, 581 } boys out of n = 98 451 { \ displaystyle n = 98 \, 451 } births, we can compute the posterior probability of each hypothesis using the probability mass function for a binomial variable : p ( k h 0 ) = ( n k ) ( 0. 5 ) k ( 1 − 0. 5 ) n − k ≈ 1. 95 × 10 − 4, p ( k h 1 ) = 0 1 ( n k ) θ k ( 1 − θ ) n − k d θ = ( n k ) b ( k + 1, n − k + 1 ) = 1 / ( n + 1 ) ≈ 1. 02 × 10 − 5, { \ displaystyle { \ begin { aligned } p ( k \ mid h _ { 0 } ) & = { n \ choose k } ( 0. 5 ) ^ { k } ( 1 - 0. 5 ) ^ { n - k }
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\ displaystyle { \ begin { aligned } p ( k \ mid h _ { 0 } ) & = { n \ choose k } ( 0. 5 ) ^ { k } ( 1 - 0. 5 ) ^ { n - k } \ approx 1. 95 \ times 10 ^ { - 4 }, \ \ p ( k \ mid h _ { 1 } ) & = \ int _ { 0 } ^ { 1 } { n \ choose k } \ theta ^ { k } ( 1 - \ theta ) ^ { n - k } \, d \ theta = { n \ choose k } \ operatorname { \ mathrm { b } } ( k + 1, n - k + 1 ) = 1 / ( n + 1 ) \ approx 1. 02 \ times 10 ^ { - 5 }, \ end { aligned } } } where b ( a, b ) { \ displaystyle \ operatorname { \ mathrm { b } } ( a, b ) } is the beta function. from these values, we find the posterior probability of p ( h 0 k ) ≈ 0. 95, { \ displaystyle p ( h _ { 0 } \ mid k ) \ approx 0. 95, } which strongly favors h 0 { \ displaystyle h _ { 0 } } over h 1 { \ displaystyle h _ { 1 } }. the two approaches — the bayesian and the frequentist — appear to be in conflict, and this is the " paradox ". = = = reconciling the bayesian and frequentist approaches = = = = = = = almost sure hypothesis testing = = = = naaman proposed an adaption of the significance level to the sample size in order to control false positives : αn, such that αn = n − r with r > 1 / 2. at least in the numerical example, taking r = 1 / 2, results in a significance level of 0. 00318, so the frequentist would not reject the null hypothesis, which is in agreement with the bayesian approach. = = = = uninformative priors = = = = if we use an uninformative prior and test a hypothesis more similar to that in the frequentist approach, the paradox disappears. for example, if we calculate the posterior distribution p ( θ x, n ) { \ displaystyle p ( \ theta \ mid x, n ) }, using a uniform prior distribution on θ { \ displaystyle \ theta }
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paradox disappears. for example, if we calculate the posterior distribution p ( θ x, n ) { \ displaystyle p ( \ theta \ mid x, n ) }, using a uniform prior distribution on θ { \ displaystyle \ theta } ( i. e. π ( θ ∈ [ 0, 1 ] ) = 1 { \ displaystyle \ pi ( \ theta \ in [ 0, 1 ] ) = 1 } ), we find p ( θ k, n ) = b ( k + 1, n − k + 1 ). { \ displaystyle p ( \ theta \ mid k, n ) = \ operatorname { \ mathrm { b } } ( k + 1, n - k + 1 ). } if we use this to check the probability that a newborn is more likely to be a boy than a girl, i. e. p ( θ > 0. 5 k, n ), { \ displaystyle p ( \ theta > 0. 5 \ mid k, n ), } we find 0. 5 1 b ( 49 582, 48 871 ) ≈ 0. 983. { \ displaystyle \ int _ { 0. 5 } ^ { 1 } \ operatorname { \ mathrm { b } } ( 49 \, 582, 48 \, 871 ) \ approx 0. 983. } in other words, it is very likely that the proportion of male births is above 0. 5. neither analysis gives an estimate of the effect size, directly, but both could be used to determine, for instance, if the fraction of boy births is likely to be above some particular threshold. = = = the lack of an actual paradox = = = the apparent disagreement between the two approaches is caused by a combination of factors. first, the frequentist approach above tests h 0 { \ displaystyle h _ { 0 } } without reference to h 1 { \ displaystyle h _ { 1 } }. the bayesian approach evaluates h 0 { \ displaystyle h _ { 0 } } as an alternative to h 1 { \ displaystyle h _ { 1 } } and finds the first to be in better agreement with the observations. this is because the latter hypothesis is much more diffuse, as θ { \ displaystyle \ theta } can be anywhere in [ 0, 1 ] { \ displaystyle [ 0, 1 ] }, which results in it having a very low posterior probability. to understand why, it is helpful to consider the two
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θ { \ displaystyle \ theta } can be anywhere in [ 0, 1 ] { \ displaystyle [ 0, 1 ] }, which results in it having a very low posterior probability. to understand why, it is helpful to consider the two hypotheses as generators of the observations : under h 0 { \ displaystyle h _ { 0 } }, we choose θ ≈ 0. 500 { \ displaystyle \ theta \ approx 0. 500 } and ask how likely it is to see 49581 boys in 98451 births. under h 1 { \ displaystyle h _ { 1 } }, we choose θ { \ displaystyle \ theta } randomly from anywhere within 0 to 1 and ask the same question. most of the possible values for θ { \ displaystyle \ theta } under h 1 { \ displaystyle h _ { 1 } } are very poorly supported by the observations. in essence, the apparent disagreement between the methods is not a disagreement at all, but rather two different statements about how the hypotheses relate to the data : the frequentist finds that h 0 { \ displaystyle h _ { 0 } } is a poor explanation for the observation. the bayesian finds that h 0 { \ displaystyle h _ { 0 } } is a far better explanation for the observation than h 1. { \ displaystyle h _ { 1 }. } the ratio of the sex of newborns is improbably 50 / 50 male / female, according to the frequentist test. yet 50 / 50 is a better approximation than most, but not all, other ratios. the hypothesis θ ≈ 0. 504 { \ displaystyle \ theta \ approx 0. 504 } would have fit the observation much better than almost all other ratios, including θ ≈ 0. 500. { \ displaystyle \ theta \ approx 0. 500. } for example, this choice of hypotheses and prior probabilities implies the statement " if θ { \ displaystyle \ theta } > 0. 49 and θ { \ displaystyle \ theta } < 0. 51, then the prior probability of θ { \ displaystyle \ theta } being exactly 0. 5 is 0. 50 / 0. 51 ≈ 98 % ". given such a strong preference for θ = 0. 5, { \ displaystyle \ theta = 0. 5, } it is easy to see why the bayesian approach favors h 0 { \ displaystyle h _ { 0 } } in the face of x ≈ 0.
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for θ = 0. 5, { \ displaystyle \ theta = 0. 5, } it is easy to see why the bayesian approach favors h 0 { \ displaystyle h _ { 0 } } in the face of x ≈ 0. 5036, { \ displaystyle x \ approx 0. 5036, } even though the observed value of x { \ displaystyle x } lies 2. 28 σ { \ displaystyle 2. 28 \ sigma } away from 0. 5. the deviation of over 2σ from h 0 { \ displaystyle h _ { 0 } } is considered significant in the frequentist approach, but its significance is overruled by the prior in the bayesian approach. looking at it another way, we can see that the prior distribution is essentially flat with a delta function at θ = 0. 5. { \ displaystyle \ theta = 0. 5. } clearly, this is dubious. in fact, picturing real numbers as being continuous, it would be more logical to assume that it would be impossible for any given number to be exactly the parameter value, i. e., we should assume p ( θ = 0. 5 ) = 0. { \ displaystyle p ( \ theta = 0. 5 ) = 0. } a more realistic distribution for θ { \ displaystyle \ theta } in the alternative hypothesis produces a less surprising result for the posterior of h 0. { \ displaystyle h _ { 0 }. } for example, if we replace h 1 { \ displaystyle h _ { 1 } } with h 2 : θ = x, { \ displaystyle h _ { 2 } : \ theta = x, } i. e., the maximum likelihood estimate for θ, { \ displaystyle \ theta, } the posterior probability of h 0 { \ displaystyle h _ { 0 } } would be only 0. 07 compared to 0. 93 for h 2 { \ displaystyle h _ { 2 } } ( of course, one cannot actually use the mle as part of a prior distribution ). = = see also = = bayes factor = = notes = = = = further reading = = shafer, glenn ( 1982 ). " lindley's paradox ". journal of the american statistical association. 77 ( 378 ) : 325 – 334. doi : 10. 2307 / 2287244. jstor 2287244. mr 0664677.
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a febrile seizure, also known as a fever fit or febrile convulsion, is a seizure associated with a high body temperature but without any serious underlying health issue. they most commonly occur in children between the ages of 6 months and 5 years. most seizures are less than five minutes in duration, and the child is completely back to normal within an hour of the event. there are two types : simple febrile seizures and complex febrile seizures. simple febrile seizures involve an otherwise healthy child who has at most one tonic - clonic seizure lasting less than 15 minutes in a 24 - hour period. complex febrile seizures have focal symptoms, last longer than 15 minutes, or occur more than once within 24 hours. about 80 % are classified as simple febrile seizures. febrile seizures are triggered by fever, typically due to a viral infection. they may run in families. the underlying mechanism is not fully known, but it is thought to involve genetics, environmental factors, brain immaturity, and inflammatory mediators. the diagnosis involves verifying that there is not an infection of the brain, there are no metabolic problems, and there have not been prior seizures that have occurred without a fever. blood testing, imaging of the brain, or an electroencephalogram ( eeg ) is typically not needed. examination to determine the source of the fever is recommended. in otherwise healthy - looking children a lumbar puncture is not necessarily required. neither anti - seizure medication nor anti - fever medication are recommended in an effort to prevent further simple febrile seizures. in the few cases that last greater than 5 minutes, a benzodiazepine such as lorazepam or midazolam may be used. efforts to rapidly cool during a seizure is not recommended. febrile seizures affect 2 – 10 % of children. they are more common in boys than girls. after a single febrile seizure there is an approximately 35 % chance of having another one during childhood. outcomes are generally excellent with similar academic achievements to other children and no change in the risk of death for those with simple seizures. there is tentative evidence that affected children have a slightly increased risk of epilepsy at 2 % compared to the general population. = = signs and symptoms = = signs and symptoms depend on if the febrile seizure is simple versus complex. in general, the child's temperature is greater than 38 °c ( 100. 4 °f ), although most have a fever of 39 °c
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= signs and symptoms = = signs and symptoms depend on if the febrile seizure is simple versus complex. in general, the child's temperature is greater than 38 °c ( 100. 4 °f ), although most have a fever of 39 °c ( 102. 2 °f ) or higher. most febrile seizures will occur during the first 24 hours of developing a fever. signs of typical seizure activity include loss of consciousness, opened eyes which may be deviated or appear to be looking towards one direction, irregular breathing, increased secretions or foaming at the mouth, and the child may look pale or blue ( cyanotic ). they may become incontinent ( wet or soil themselves ) and may also vomit. = = = types = = = there are two types of febrile seizures : simple and complex. febrile status epilepticus is a subtype of complex febrile seizures that lasts for longer than 30 minutes. it can occur in up to 5 % of febrile seizure cases. = = causes = = febrile seizures are due to fevers, usually those greater than 38 °c ( 100. 4 °f ). the cause of the fevers is often a viral illness. the likelihood of a febrile seizure is related to how high the temperature reaches. some feel that the rate of increase is not important while others feel the rate of increase is a risk factor. this latter position has not been proven. in children, illnesses that often cause a fever include middle ear infections and viral upper respiratory infections. other infections associated with febrile seizures include shigellosis, salmonellosis, and roseola. although the exact mechanism is unknown, it is speculated that these infections may affect the brain directly or via a neurotoxin leading to seizures. there is a small chance of a febrile seizure after certain vaccines. the risk is only slightly increased for a few days after receiving one of the implicated vaccines during the time when the child is likely to develop a fever as a natural immune response. implicated vaccines include : measles / mumps / rubella / varicella combined diphtheria / tetanus / acellular pertussis / polio / haemophilus influenzae type b diphtheria - tetanus - whole - cell pertussis, which is not used in north america anymore some versions of the pneumococcal vaccine some types of inactivated influenza vaccine it was previously thought that febrile seizures
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diphtheria - tetanus - whole - cell pertussis, which is not used in north america anymore some versions of the pneumococcal vaccine some types of inactivated influenza vaccine it was previously thought that febrile seizures were more likely to occur with the combined mmrv vaccine, but recent studies have found there to be no significant increase. overall, febrile seizures triggered by vaccines are uncommon. children who have a genetic predisposition towards febrile seizures are more likely to have one after vaccination. the seizures occur, by definition, without an intracranial infection or metabolic problems. they run in families with reported family history in approximately 33 % of people. several genetic associations have been identified, including gefs + and dravet syndrome. possible modes of inheritance for genetic predisposition to febrile seizures include autosomal dominance with reduced penetrance and polygenic multifactorial inheritance. an association with iron deficiency has also been reported, particularly in the developing world. = = mechanism = = the exact underlying mechanism of febrile seizures is still unknown, but it is thought to be multi - factorial involving genetic and environmental factors. speculation includes immaturity of the central nervous system at younger ages, making the brain more vulnerable to the effects of fever. the increased activity of neurons during rapid brain development, may help explain why children, particularly younger than age 3, are prone to febrile seizures, with occurrences decreasing after age 5. other proposed mechanisms include the interactions of inflammatory mediators, particularly cytokines, which are released during a fever, causing elevated temperatures in the brain, which may somehow lead to a seizure. specific cytokines implicated include elevated csf il - 1β and serum il - 6. = = diagnosis = = the diagnosis is made by eliminating more serious causes of seizure and fever : in particular, meningitis and encephalitis. however, in children who are immunized against pneumococcal and haemophilus influenzae, the risk of bacterial meningitis is low. if a child has recovered and is acting normally, bacterial meningitis is very unlikely, making further procedures such as a lumbar puncture unnecessary. diagnosis involves gathering a detailed history including the value of highest temperature recorded, timing of seizure and fever, seizure characteristics, time to return to baseline, vaccination history, illness exposures, family history, etc. ; and performing a physical exam that looks for
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gathering a detailed history including the value of highest temperature recorded, timing of seizure and fever, seizure characteristics, time to return to baseline, vaccination history, illness exposures, family history, etc. ; and performing a physical exam that looks for signs of infection including meningitis and neurological status. blood tests, imaging of the brain and an electroencephalogram are generally not needed. however, for complex febrile seizures, eeg and imaging with an mri of the brain may be helpful. lumbar puncture is recommended if there are obvious signs and symptoms of meningitis or if there is high clinical suspicion. however, lumbar puncture is an option that may be considered in children younger than 12 months of age since signs and symptoms of meningitis may be atypical, if the child does not return to baseline, or if the child lacks immunization against haemophilus influenzae and pneumococcal or vaccination status is unknown. differential diagnosis includes other causes of seizures such as cns infections ( i. e. meningitis, encephalitis ), metabolic disturbances ( i. e. electrolyte imbalances ), cns trauma, drug use and / or withdrawal, genetic conditions ( i. e. gefs + ), fires, shivering, febrile delirium, febrile myoclonus, breath holding spells, and convulsive syncope. however, febrile seizures are still the most likely cause of convulsions in children under the age of 5 years old. = = prevention = = there is no benefit from the use of phenytoin, valproate, ibuprofen, diclofenac, acetaminophen, pyridoxine, or zinc sulfate. there is no evidence to support administering fever reducing medications such as acetaminophen at the time of a febrile seizure or to prevent the rate of recurrence. rapid cooling methods such as an ice bath or a cold bath should be avoided as a method to lower the child's temperature, especially during a febrile seizure. there is a decrease of recurrent febrile seizures with intermittent diazepam and phenobarbital but there is a high rate of adverse effects. they are thus not recommended as an effort to prevent further seizures. = = treatment = = if a child is having a febrile seizure, the following recommendations are
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##am and phenobarbital but there is a high rate of adverse effects. they are thus not recommended as an effort to prevent further seizures. = = treatment = = if a child is having a febrile seizure, the following recommendations are made for caregivers : note the start time of the seizure. if the seizure lasts longer than 5 minutes, call an ambulance. medication to stop seizure, such as rectal diazepam or intranasal midazolam may be used. the child should be taken immediately to the nearest medical facility for further diagnosis and treatment. gradually place the child on a protected surface such as the floor or ground to prevent accidental injury. do not restrain or hold a child during a convulsion. position the child on his or her side or stomach to prevent choking. when possible, gently remove any objects from the child's mouth. nothing should ever be placed in the child's mouth during a convulsion. these objects can obstruct the child's airway and make breathing difficult. seek immediate medical attention if this is the child's first febrile seizure and take the child to the doctor once the seizure has ended to check for the cause of the fever. this is especially urgent if the child shows symptoms of stiff neck, extreme lethargy, or abundant vomiting, which may be signs of meningitis, an infection over the brain surface. in those with a single seizure lasting greater than 5 minutes or two consecutive seizures lasting greater than 5 minutes in which the person has not returned to their baseline mental status, defined as status epilepticus, intravenous lorazepam, rectal diazepam, or intranasal midazolam is recommended. anti - seizure medication are used in status epilepticus in an effort to prevent complications such as injury to the hippocampus or temporal lobe epilepsy. secondary causes of a seizure should be addressed if present. questions that may be asked of the caregivers who witnessed the seizure include the length of the seizure, the timing of the day, loss of consciousness, loss of bowel or urinary continence, a period of altered level of consciousness or confusion once the seizure stopped, movement of the eyes to a specific side, recent infections, recent medication usage including antibiotics or fever reducer medications, family history of febrile and afebrile seizures, vaccination and travel history. vital signs should be monitored in the emergency department along with
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to a specific side, recent infections, recent medication usage including antibiotics or fever reducer medications, family history of febrile and afebrile seizures, vaccination and travel history. vital signs should be monitored in the emergency department along with observation for 6 hours. evaluation for the cause of fever should be performed including signs of an infection such as a bulging tympanic membrane ( otitis media ), red pharynx, enlarged tonsils, enlarged cervical lymph nodes ( streptococcal pharyngitis or infectious mononucleosis ), and a widespread rash. cns infections such as meningitis, encephalitis and brain abscesses should be ruled out, along with electrolyte abnormalities. = = prognosis = = long term outcomes are generally good with little risk of neurological problems or epilepsy. those who have one febrile seizure have an approximately 30 - 40 % chance of having another one in the next two years, with the risk being greater in those who are younger. simple febrile seizures do not tend to recur frequently ( children tend to outgrow them ) and do not make the development of adult epilepsy significantly more likely ( about 3 – 5 % ) compared with the general public ( 1 % ). children with febrile convulsions are more likely to have a febrile seizure in the future if they were young at their first seizure ( less than 18 months old ), have a family history of a febrile convulsions in first - degree relatives ( a parent or sibling ), have a short time between the onset of fever and the seizure, had a low degree of fever before their seizure, or have a seizure history of abnormal neurological signs or developmental delay. similarly, the prognosis after a complex febrile seizure is excellent, although an increased risk of death has been shown for complex febrile seizures, partly related to underlying conditions. = = epidemiology = = febrile seizures happen between the ages of 6 months and 5 years. the peak age for a febrile seizure is 18 months, with the most common age range being 12 – 30 months of age. they affect between 2 - 5 % of children. they are more common in boys than girls. febrile seizures can occur in any ethnic group, although there have been higher rates in guamanians ( 14 % ), japanese ( 6 - 9 % ) and indians ( 5 - 10
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children. they are more common in boys than girls. febrile seizures can occur in any ethnic group, although there have been higher rates in guamanians ( 14 % ), japanese ( 6 - 9 % ) and indians ( 5 - 10 % ). = = references = = = = external links = =
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the direct sum is an operation between structures in abstract algebra, a branch of mathematics. it is defined differently but analogously for different kinds of structures. as an example, the direct sum of two abelian groups a { \ displaystyle a } and b { \ displaystyle b } is another abelian group a ⊕ b { \ displaystyle a \ oplus b } consisting of the ordered pairs ( a, b ) { \ displaystyle ( a, b ) } where a ∈ a { \ displaystyle a \ in a } and b ∈ b { \ displaystyle b \ in b }. to add ordered pairs, the sum is defined ( a, b ) + ( c, d ) { \ displaystyle ( a, b ) + ( c, d ) } to be ( a + c, b + d ) { \ displaystyle ( a + c, b + d ) } ; in other words, addition is defined coordinate - wise. for example, the direct sum r ⊕ r { \ displaystyle \ mathbb { r } \ oplus \ mathbb { r } }, where r { \ displaystyle \ mathbb { r } } is real coordinate space, is the cartesian plane, r 2 { \ displaystyle \ mathbb { r } ^ { 2 } }. a similar process can be used to form the direct sum of two vector spaces or two modules. direct sums can also be formed with any finite number of summands ; for example, a ⊕ b ⊕ c { \ displaystyle a \ oplus b \ oplus c }, provided a, b, { \ displaystyle a, b, } and c { \ displaystyle c } are the same kinds of algebraic structures ( e. g., all abelian groups, or all vector spaces ). that relies on the fact that the direct sum is associative up to isomorphism. that is, ( a ⊕ b ) ⊕ c a ⊕ ( b ⊕ c ) { \ displaystyle ( a \ oplus b ) \ oplus c \ cong a \ oplus ( b \ oplus c ) } for any algebraic structures a { \ displaystyle a }, b { \ displaystyle b }, and c { \ displaystyle c } of the same kind. the direct sum is also commutative up to isomorphism, i. e. a ⊕ b b ⊕ a { \ displaystyle a \ oplus b \ cong b \ oplus a } for
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##tyle c } of the same kind. the direct sum is also commutative up to isomorphism, i. e. a ⊕ b b ⊕ a { \ displaystyle a \ oplus b \ cong b \ oplus a } for any algebraic structures a { \ displaystyle a } and b { \ displaystyle b } of the same kind. the direct sum of finitely many abelian groups, vector spaces, or modules is canonically isomorphic to the corresponding direct product. that is false, however, for some algebraic objects like nonabelian groups. in the case where infinitely many objects are combined, the direct sum and direct product are not isomorphic even for abelian groups, vector spaces, or modules. for example, consider the direct sum and the direct product of ( countably ) infinitely many copies of the integers. an element in the direct product is an infinite sequence, such as ( 1, 2, 3,... ) but in the direct sum, there is a requirement that all but finitely many coordinates be zero, so the sequence ( 1, 2, 3,... ) would be an element of the direct product but not of the direct sum, while ( 1, 2, 0, 0, 0,... ) would be an element of both. often, if a + sign is used, all but finitely many coordinates must be zero, while if some form of multiplication is used, all but finitely many coordinates must be 1. in more technical language, if the summands are ( a i ) i ∈ i { \ displaystyle ( a _ { i } ) _ { i \ in i } }, the direct sum i ∈ i a i { \ displaystyle \ bigoplus _ { i \ in i } a _ { i } } is defined to be the set of tuples ( a i ) i ∈ i { \ displaystyle ( a _ { i } ) _ { i \ in i } } with a i ∈ a i { \ displaystyle a _ { i } \ in a _ { i } } such that a i = 0 { \ displaystyle a _ { i } = 0 } for all but finitely many i. the direct sum i ∈ i a i { \ textstyle \ bigoplus _ { i \ in i } a _ { i } } is contained in the direct product i ∈ i a i { \ textstyle \ prod _ { i \ in i
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∈ i a i { \ textstyle \ bigoplus _ { i \ in i } a _ { i } } is contained in the direct product i ∈ i a i { \ textstyle \ prod _ { i \ in i } a _ { i } }, but is strictly smaller when the index set i { \ displaystyle i } is infinite, because an element of the direct product can have infinitely many nonzero coordinates. = = examples = = the xy - plane, a two - dimensional vector space, can be thought of as the direct sum of two one - dimensional vector spaces : the x and y axes. in this direct sum, the x and y axes intersect only at the origin ( the zero vector ). addition is defined coordinate - wise ; that is, ( x 1, y 1 ) + ( x 2, y 2 ) = ( x 1 + x 2, y 1 + y 2 ) { \ displaystyle ( x _ { 1 }, y _ { 1 } ) + ( x _ { 2 }, y _ { 2 } ) = ( x _ { 1 } + x _ { 2 }, y _ { 1 } + y _ { 2 } ) }, which is the same as vector addition. given two structures a { \ displaystyle a } and b { \ displaystyle b }, their direct sum is written as a ⊕ b { \ displaystyle a \ oplus b }. given an indexed family of structures a i { \ displaystyle a _ { i } }, indexed with i ∈ i { \ displaystyle i \ in i }, the direct sum may be written a = i ∈ i a i { \ textstyle a = \ bigoplus _ { i \ in i } a _ { i } }. each ai is called a direct summand of a. if the index set is finite, the direct sum is the same as the direct product. in the case of groups, if the group operation is written as + { \ displaystyle + } the phrase " direct sum " is used, while if the group operation is written ∗ { \ displaystyle * } the phrase " direct product " is used. when the index set is infinite, the direct sum is not the same as the direct product since the direct sum has the extra requirement that all but finitely many coordinates must be zero. = = = internal and external direct sums = = = a distinction is made between internal and external direct sums though both
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is not the same as the direct product since the direct sum has the extra requirement that all but finitely many coordinates must be zero. = = = internal and external direct sums = = = a distinction is made between internal and external direct sums though both are isomorphic. if the summands are defined first, and the direct sum is then defined in terms of the summands, there is an external direct sum. for example, if the real numbers r { \ displaystyle \ mathbb { r } } are defined, followed by r ⊕ r { \ displaystyle \ mathbb { r } \ oplus \ mathbb { r } }, the direct sum is said to be external. if, on the other hand, some algebraic structure s { \ displaystyle s } is defined, and s { \ displaystyle s } is then defined as a direct sum of two substructures v { \ displaystyle v } and w { \ displaystyle w }, the direct sum is said to be internal. in that case, each element of s { \ displaystyle s } is expressible uniquely as an algebraic combination of an element of v { \ displaystyle v } and an element of w { \ displaystyle w }. for an example of an internal direct sum, consider z 6 { \ displaystyle \ mathbb { z } _ { 6 } } ( the integers modulo six ), whose elements are { 0, 1, 2, 3, 4, 5 } { \ displaystyle \ { 0, 1, 2, 3, 4, 5 \ } }. this is expressible as an internal direct sum z 6 = { 0, 2, 4 } ⊕ { 0, 3 } { \ displaystyle \ mathbb { z } _ { 6 } = \ { 0, 2, 4 \ } \ oplus \ { 0, 3 \ } }. = = types of direct sums = = = = = direct sum of abelian groups = = = the direct sum of abelian groups is a prototypical example of a direct sum. given two such groups ( a, ∘ ) { \ displaystyle ( a, \ circ ) } and ( b, ), { \ displaystyle ( b, \ bullet ), } their direct sum a ⊕ b { \ displaystyle a \ oplus b } is the same as their direct product. that is, the underlying set is the cartesian product a × b { \ displaystyle a \ times b } and
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, } their direct sum a ⊕ b { \ displaystyle a \ oplus b } is the same as their direct product. that is, the underlying set is the cartesian product a × b { \ displaystyle a \ times b } and the group operation ⋅ { \ displaystyle \, \ cdot \, } is defined component - wise : ( a 1, b 1 ) ⋅ ( a 2, b 2 ) = ( a 1 ∘ a 2, b 1 b 2 ). { \ displaystyle \ left ( a _ { 1 }, b _ { 1 } \ right ) \ cdot \ left ( a _ { 2 }, b _ { 2 } \ right ) = \ left ( a _ { 1 } \ circ a _ { 2 }, b _ { 1 } \ bullet b _ { 2 } \ right ). } this definition generalizes to direct sums of finitely many abelian groups. for an arbitrary family of groups a i { \ displaystyle a _ { i } } indexed by i ∈ i, { \ displaystyle i \ in i, } their direct sum i ∈ i a i { \ displaystyle \ bigoplus _ { i \ in i } a _ { i } } is the subgroup of the direct product that consists of the elements ( a i ) i ∈ i ∈ i ∈ i a i { \ textstyle \ left ( a _ { i } \ right ) _ { i \ in i } \ in \ prod _ { i \ in i } a _ { i } } that have finite support, where, by definition, ( a i ) i ∈ i { \ displaystyle \ left ( a _ { i } \ right ) _ { i \ in i } } is said to have finite support if a i { \ displaystyle a _ { i } } is the identity element of a i { \ displaystyle a _ { i } } for all but finitely many i. { \ displaystyle i. } the direct sum of an infinite family ( a i ) i ∈ i { \ displaystyle \ left ( a _ { i } \ right ) _ { i \ in i } } of non - trivial groups is a proper subgroup of the product group i ∈ i a i. { \ textstyle \ prod _ { i \ in i } a _ { i }. } = = = direct sum of modules = = = the direct sum of modules is a construction that combines
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product group i ∈ i a i. { \ textstyle \ prod _ { i \ in i } a _ { i }. } = = = direct sum of modules = = = the direct sum of modules is a construction that combines several modules into a new module. the most familiar examples of that construction occur in considering vector spaces, which are modules over a field. the construction may also be extended to banach spaces and hilbert spaces. = = = direct sum in categories = = = an additive category is an abstraction of the properties of the category of modules. in such a category, finite products and coproducts agree, and the direct sum is either of them : cf. biproduct. general case : in category theory the direct sum is often but not always the coproduct in the category of the mathematical objects in question. for example, in the category of abelian groups, the direct sum is a coproduct. that is also true in the category of modules. = = = = direct sums versus coproducts in category of groups = = = = however, the direct sum s 3 ⊕ z 2 { \ displaystyle s _ { 3 } \ oplus \ mathbb { z } _ { 2 } } ( defined identically to the direct sum of abelian groups ) is not a coproduct of the groups s 3 { \ displaystyle s _ { 3 } } and z 2 { \ displaystyle \ mathbb { z } _ { 2 } } in the category of groups. therefore, for that category, a categorical direct sum is often called simply a coproduct to avoid any possible confusion. = = = direct sum of group representations = = = the direct sum of group representations generalizes the direct sum of the underlying modules by adding a group action. specifically, given a group g { \ displaystyle g } and two representations v { \ displaystyle v } and w { \ displaystyle w } of g { \ displaystyle g } ( or, more generally, two g { \ displaystyle g } - modules ), the direct sum of the representations is v ⊕ w { \ displaystyle v \ oplus w } with the action of g ∈ g { \ displaystyle g \ in g } given component - wise, that is, g ⋅ ( v, w ) = ( g ⋅ v, g ⋅ w ). { \ displaystyle g \ cdot ( v, w ) = ( g \ cdot
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g \ in g } given component - wise, that is, g ⋅ ( v, w ) = ( g ⋅ v, g ⋅ w ). { \ displaystyle g \ cdot ( v, w ) = ( g \ cdot v, g \ cdot w ). } another equivalent way of defining the direct sum is as follows : given two representations ( v, ρ v ) { \ displaystyle ( v, \ rho _ { v } ) } and ( w, ρ w ) { \ displaystyle ( w, \ rho _ { w } ) } the vector space of the direct sum is v ⊕ w { \ displaystyle v \ oplus w } and the homomorphism ρ v ⊕ w { \ displaystyle \ rho _ { v \ oplus w } } is given by α ∘ ( ρ v × ρ w ), { \ displaystyle \ alpha \ circ ( \ rho _ { v } \ times \ rho _ { w } ), } where α : g l ( v ) × g l ( w ) → g l ( v ⊕ w ) { \ displaystyle \ alpha : gl ( v ) \ times gl ( w ) \ to gl ( v \ oplus w ) } is the natural map obtained by coordinate - wise action as above. furthermore, if v, w { \ displaystyle v, \, w } are finite dimensional, then, given a basis of v, w { \ displaystyle v, \, w }, ρ v { \ displaystyle \ rho _ { v } } and ρ w { \ displaystyle \ rho _ { w } } are matrix - valued. in this case, ρ v ⊕ w { \ displaystyle \ rho _ { v \ oplus w } } is given as g ↦ ( ρ v ( g ) 0 0 ρ w ( g ) ). { \ displaystyle g \ mapsto { \ begin { pmatrix } \ rho _ { v } ( g ) & 0 \ \ 0 & \ rho _ { w } ( g ) \ end { pmatrix } }. } moreover, if v { \ displaystyle v } and w { \ displaystyle w } are treated as modules over the group ring k g { \ displaystyle kg }, where k { \ displaystyle k } is the field, the direct sum of the representations v { \ displaystyle v } and w { \ displaystyle w } is
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treated as modules over the group ring k g { \ displaystyle kg }, where k { \ displaystyle k } is the field, the direct sum of the representations v { \ displaystyle v } and w { \ displaystyle w } is equal to their direct sum as k g { \ displaystyle kg } modules. = = = direct sum of rings = = = some authors speak of the direct sum r ⊕ s { \ displaystyle r \ oplus s } of two rings when they mean the direct product r × s { \ displaystyle r \ times s }, but that should be avoided since r × s { \ displaystyle r \ times s } does not receive natural ring homomorphisms from r { \ displaystyle r } and s { \ displaystyle s }. in particular, the map r → r × s { \ displaystyle r \ to r \ times s } sending r { \ displaystyle r } to ( r, 0 ) { \ displaystyle ( r, 0 ) } is not a ring homomorphism since it fails to send 1 to ( 1, 1 ) { \ displaystyle ( 1, 1 ) } ( assuming that 0 = 1 { \ displaystyle 0 \ neq 1 } in s { \ displaystyle s } ). thus, r × s { \ displaystyle r \ times s } is not a coproduct in the category of rings, and should not be written as a direct sum. ( the coproduct in the category of commutative rings is the tensor product of rings. in the category of rings, the coproduct is given by a construction similar to the free product of groups. ) the use of direct sum terminology and notation is especially problematic in dealing with infinite families of rings. if ( r i ) i ∈ i { \ displaystyle ( r _ { i } ) _ { i \ in i } } is an infinite collection of nontrivial rings, the direct sum of the underlying additive groups may be equipped with termwise multiplication, but that produces a rng, a ring without a multiplicative identity. = = = direct sum of matrices = = = for any arbitrary matrices a { \ displaystyle \ mathbf { a } } and b { \ displaystyle \ mathbf { b } }, the direct sum a ⊕ b { \ displaystyle \ mathbf { a } \ oplus \ mathbf { b } } is defined as the block diagonal matrix of a { \ displaystyle \
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displaystyle \ mathbf { b } }, the direct sum a ⊕ b { \ displaystyle \ mathbf { a } \ oplus \ mathbf { b } } is defined as the block diagonal matrix of a { \ displaystyle \ mathbf { a } } and b { \ displaystyle \ mathbf { b } } if both are square matrices ( and to an analogous block matrix, if not ). a ⊕ b = [ a 0 0 b ]. { \ displaystyle \ mathbf { a } \ oplus \ mathbf { b } = { \ begin { bmatrix } \ mathbf { a } & 0 \ \ 0 & \ mathbf { b } \ end { bmatrix } }. } alternatively, the forms [ a b ] { \ displaystyle \ left [ { \ begin { matrix } \ mathbf { a } \ \ \ mathbf { b } \ end { matrix } } \ right ] } or [ a b ] { \ displaystyle \ left [ { \ begin { matrix } \ mathbf { a } & \ mathbf { b } \ end { matrix } } \ right ] } may also be encountered in the literature and are isomorphic to the aforementioned block form. = = = direct sum of topological vector spaces = = = a topological vector space ( tvs ) x, { \ displaystyle x, } such as a banach space, is said to be a topological direct sum of two vector subspaces m { \ displaystyle m } and n { \ displaystyle n } if the addition map m × n → x ( m, n ) ↦ m + n { \ displaystyle { \ begin { alignedat } { 4 } \ \ ; & & m \ times n & & \ ; \ to \ ; & x \ \ [ 0. 3ex ] & & ( m, n ) & & \ ; \ mapsto \ ; & m + n \ \ \ end { alignedat } } } is an isomorphism of topological vector spaces ( meaning that this linear map is a bijective homeomorphism ) in which case m { \ displaystyle m } and n { \ displaystyle n } are said to be topological complements in x. { \ displaystyle x. } that is true if and only if when considered as additive topological groups ( so scalar multiplication is ignored ), x { \ displaystyle x } is the topological direct sum of the topological subgroups m { \ displays
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{ \ displaystyle x. } that is true if and only if when considered as additive topological groups ( so scalar multiplication is ignored ), x { \ displaystyle x } is the topological direct sum of the topological subgroups m { \ displaystyle m } and n. { \ displaystyle n. } if this is the case and if x { \ displaystyle x } is hausdorff then m { \ displaystyle m } and n { \ displaystyle n } are necessarily closed subspaces of x. { \ displaystyle x. } if m { \ displaystyle m } is a vector subspace of a real or complex vector space x { \ displaystyle x }, there is always another vector subspace n { \ displaystyle n } of x, { \ displaystyle x, } called an algebraic complement of m { \ displaystyle m } in x, { \ displaystyle x, } such that x { \ displaystyle x } is the algebraic direct sum of m { \ displaystyle m } and n { \ displaystyle n }, which happens if and only if the addition map m × n → x { \ displaystyle m \ times n \ to x } is a vector space isomorphism. in contrast to algebraic direct sums, the existence of such a complement is no longer guaranteed for topological direct sums. a vector subspace m { \ displaystyle m } of x { \ displaystyle x } is said to be a ( topologically ) complemented subspace of x { \ displaystyle x } if there exists some vector subspace n { \ displaystyle n } of x { \ displaystyle x } such that x { \ displaystyle x } is the topological direct sum of m { \ displaystyle m } and n. { \ displaystyle n. } a vector subspace is called uncomplemented if it is not a complemented subspace. for example, every vector subspace of a hausdorff tvs that is not a closed subset is necessarily uncomplemented. every closed vector subspace of a hilbert space is complemented. but every banach space that is not a hilbert space necessarily possess some uncomplemented closed vector subspace. = = homomorphisms = = the direct sum i ∈ i a i { \ textstyle \ bigoplus _ { i \ in i } a _ { i } } comes equipped with a projection homomorphism π j : i ∈ i a i → a j { \ texts
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sum i ∈ i a i { \ textstyle \ bigoplus _ { i \ in i } a _ { i } } comes equipped with a projection homomorphism π j : i ∈ i a i → a j { \ textstyle \ pi _ { j } \ colon \, \ bigoplus _ { i \ in i } a _ { i } \ to a _ { j } } for each j in i and a coprojection α j : a j → i ∈ i a i { \ textstyle \ alpha _ { j } \ colon \, a _ { j } \ to \ bigoplus _ { i \ in i } a _ { i } } for each j in i. given another algebraic structure b { \ displaystyle b } ( with the same additional structure ) and homomorphisms g j : a j → b { \ displaystyle g _ { j } \ colon a _ { j } \ to b } for every j in i, there is a unique homomorphism g : i ∈ i a i → b { \ textstyle g \ colon \, \ bigoplus _ { i \ in i } a _ { i } \ to b }, called the sum of the gj, such that g α j = g j { \ displaystyle g \ alpha _ { j } = g _ { j } } for all j. thus the direct sum is the coproduct in the appropriate category. = = see also = = direct sum of groups direct sum of permutations direct sum of topological groups restricted product whitney sum feferman – vaught theorem = = notes = = = = references = = lang, serge ( 2002 ), algebra, graduate texts in mathematics, vol. 211 ( revised third ed. ), new york : springer - verlag, isbn 978 - 0 - 387 - 95385 - 4, mr 1878556, zbl 0984. 00001
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laser surgery is a type of surgery that cuts tissue using a laser instead of a scalpel. soft - tissue laser surgery is used in a variety of medical specialties, including general surgery, neurosurgery, ent, dentistry, orthodontics, oral and maxillofacial surgery, and veterinary surgery. the primary uses of lasers in soft - tissue surgery are to cut, ablate, vaporize, and coagulate tissue. different types of lasers are used depending on the application, including co2, diode, and erbium lasers. each type offers different benefits in terms of cutting efficiency and hemostasis. laser surgery is commonly used on the eye in procedures such as lasik and photorefractive keratectomy, where an excimer laser reshapes the cornea. = = laser surgery in proctology = = laser techniques have also been adopted in proctology, particularly for minimally invasive treatments of conditions such as hemorrhoids, anal fistulas, and anal fissures. notable procedures include * * laser hemorrhoidoplasty ( lhp ) * * and * * fistula laser closure ( filac ) * *, which offer reduced post - operative pain, shorter recovery time, and minimal bleeding compared to conventional surgeries. in india, * * healing hands clinic * *, founded by colorectal surgeon dr. ashwin porwal in 2009, has been a pioneer in implementing laser techniques for proctologic disorders. with more than 35 centers across india, the clinic has played a significant role in promoting awareness and accessibility of laser - based anorectal procedures. these procedures, such as lhp and filac, are increasingly preferred for their outpatient feasibility and reduced complication rates, contributing to the broader shift toward minimally invasive surgical techniques in colorectal care. = = effects = = photochemical effect : clinically referred to as photodynamic therapy. photosensitizer ( photophrin ii ) is administered which is taken up by the tumor tissue and later irradiated by laser light resulting in highly toxic substances with resultant necrosis of the tumor. photodynamic therapy is used in palliation of oesophageal and bronchial carcinoma and ablation of mucosal cancers of gastrointestinal tract and urinary bladder. photoablative effect : used in eye surgeries like band keratoplasty, and endarte
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##geal and bronchial carcinoma and ablation of mucosal cancers of gastrointestinal tract and urinary bladder. photoablative effect : used in eye surgeries like band keratoplasty, and endartectomy of peripheral blood vessels. photothermal effect : this property is used for endoscopic control of bleeding e. g. bleeding peptic ulcers, oesophageal varices photomechanical effect : used in intraluminal lithotripsy = = equipment = = surgical laser systems, sometimes called " laser scalpels ", are differentiated not only by the wavelength, but also by the light delivery system : flexible fiber or articulated arm, as well as by other factors. types of surgical lasers include carbon dioxide, argon, nd : yag laser, and potassium titanyl phosphate. co2 lasers were the dominant soft - tissue surgical lasers as of 2010. = = applications = = = = = dermatology and plastic surgery = = = a range of lasers such as erbium, dye, q switch lasers, and co2 are used to treat various skin conditions including scars, vascular and pigmented lesions, and for photorejuvenation. the laser surgery for dermatology often bypasses the skin surface. the principle of laser surgery for dermatologic problems is based on sptl ( selective photothermolysis ). the laser beam penetrates the skin until it encounters chromophore which absorbs the laser beam. after absorption of the laser beam, heat is generated to induce coagulation, necrosis of the targeted tissue, this results in the removal of unwanted tissue by laser surgery. laser resurfacing is a technique in which covalent bonds of a material are dissolved by a laser, a technique invented by aesthetic plastic surgeon thomas l. roberts, iii using co2 lasers in the 1990s. lasers are also used for laser - assisted lipectomy. = = = eye surgery = = = various types of laser surgery are used to treat refractive error. in lasik, a flap is created in the cornea — either with a microkeratome or femtosecond laser — and the underlying corneal layers are reshaped using an excimer laser. intralasik is a variant in which the flap is also cut with a laser. in photorefractive keratectomy ( prk, lasek ), the cornea is reshaped without first cutting a flap
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##cimer laser. intralasik is a variant in which the flap is also cut with a laser. in photorefractive keratectomy ( prk, lasek ), the cornea is reshaped without first cutting a flap. in laser thermal keratoplasty, a ring of concentric burns is made in the cornea, which causes its surface to steepen, allowing better near vision. relex smile is the latest advancement in laser vision correction technology. in smile surgery, zeiss visumax femtosecond laser is used to make a small incision and to create a pre - calculated mini lens tissue ( or lenticule ) inside the cornea. lasers are also used to treat non - refractive conditions, such as phototherapeutic keratectomy ( ptk ) in which opacities and surface irregularities are removed from the cornea and laser coagulation in which a laser is used to cauterize blood vessels in the eye, to treat various conditions. lasers can be used to repair tears in the retina. = = = endovascular surgery = = = laser endarterectomy is a technique in which an entire atheromatous plaque in the artery is excised. other applications include laser assisted angioplasties and laser - assisted vascular anastomosis. = = = foot and ankle surgery = = = lasers are used to treat several disorders in foot and ankle surgery. they are used to remove benign and malignant tumors, treat bunions, debride ulcers and burns, excise epidermal nevi, blue rubber bleb nevi, and keloids, and the removal of hypertrophic scars and tattoos. a carbon dioxide laser ( co2 ) is used in surgery to treat onychocryptosis ( ingrown nails ), onychauxis ( club nails ), onychogryposis ( rams horn nail ), and onychomycosis ( fungus nail ). = = = gastro - intestinal tract = = = peptic ulcer disease and oesophageal varices - laser photoablation is done. coagulation of vascular malformations of stomach, duodenum, and colon. lasers can be effectively used to treat early gastric cancers provided they are less than 4 cm and without lymph node involvement. lasers are also used in treating oral submucous fibrosis. pal
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stomach, duodenum, and colon. lasers can be effectively used to treat early gastric cancers provided they are less than 4 cm and without lymph node involvement. lasers are also used in treating oral submucous fibrosis. palliative laser therapy is given in advanced oesophageal cancers with obstruction of lumen. recanalisation of the lumen is done which allows the patient to resume a soft diet and maintain hydration. ablative laser therapy is used in advanced colorectal cancers to relieve obstruction and to control bleeding. laser surgery used in hemorrhoidectomy, and is a relatively popular and non - invasive method of hemorrhoid removal. laser - assisted liver resections have been done using carbon dioxide and nd : yag lasers. the ablation of liver tumors can be achieved by selective photovaporization of the tumor. endoscopic laser lithotripsy is a safer modality compared to electrohydraulic lithotripsy. = = = oral and dental surgery = = = the co2 laser is used in oral and dental surgery for virtually all soft - tissue procedures, such as gingivectomies, vestibuloplasties, frenectomies, and operculectomies. the co2 10, 600 nm wavelength is safe around implants as it is reflected by titanium, and thus has been gaining popularity in the field of periodontology. the laser may also be effective in treating peri - implantitis. = = = spine surgery = = = laser spine surgery first began seeing clinical use in the 1980s and was primarily used within discectomy to treat lumbar disc disease under the notion that heating a bulging disc vaporized enough tissue to relieve pressure on the nerves and help alleviate pain. since that time, laser spine surgery has become one of the most marketed forms of minimally invasive spine surgery, despite the fact that it has never been studied in a controlled clinical trial to determine its effectiveness apart from disc decompression. evidence - based data surrounding the use of lasers in spine surgery is limited and its safety and efficacy were poorly understood as of 2017. = = = thoracic surgery = = = in thoracic surgery, surgical laser applications are most often used to remove pulmonary metastases and tumors of different primary localizations. other areas of application are surgical sectioning of the parenchyma, anatomic segmental resections, removal of tumors from the thor
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laser applications are most often used to remove pulmonary metastases and tumors of different primary localizations. other areas of application are surgical sectioning of the parenchyma, anatomic segmental resections, removal of tumors from the thoracic wall and abrasion of the pleura parietalis. since the introduction of surgical lasers, the amount of potentially surgically resectable pulmonary nodules has significantly increased. compared to laser surgery, other conventional surgical methods such as segmental or wedge resections with surgical stapling will normally lead to a bigger loss of lung tissue, especially in patients with multiple pulmonary nodules methods. other advantages of laser surgery compared to conventional methods are that it leads to an improved postoperative lung function and that it gives the additional possibility to histologically analyze the removed material which would otherwise be destroyed through radiation or heat. = = = hard tissues = = = lasers are used to cut or ablate bones and teeth in dentistry. = = treatment = = various treatment options are available for hemorrhoids, including dietary changes, medications, and surgery. minimally invasive procedures such as rubber band ligation and sclerotherapy are commonly used. laser hemorrhoidoplasty ( lhp ), a minimally invasive laser - based procedure, is increasingly being used as an outpatient treatment for grade ii and iii hemorrhoids. = = = other surgery = = = the co2 laser is also used in gynecology, genitourinary, general surgery, otorhinolaryngology, orthopedic, and neurosurgery. = = see also = = photodynamic therapy minimally invasive surgery lasik laser ablation = = references = =
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ionomics is the measurement of the total elemental composition of an organism to address biological problems. questions within physiology, ecology, evolution, and many other fields can be investigated using ionomics, often coupled with bioinformatics, chemometrics and other genetic tools. observing an organism's ionome is a powerful approach to the functional analysis of its genes and the gene networks. information about the physiological state of an organism can also be revealed indirectly through its ionome, for example iron deficiency in a plant can be identified by looking at a number of other elements, rather than iron itself. a more typical example is in a blood test, where a number of conditions involving nutrition or disease may be inferred from testing this single tissue for sodium, potassium, iron, chlorine, zinc, magnesium, calcium and copper. in practice, the total elemental composition of an organism is rarely determined. the number and type of elements measured are limited by the available instrumentation, the assumed value of the element in question, and the added cost of measuring each additional element. also, a single tissue may be measured instead of the entire organism, as in the example given above of a blood test, or in the case of plants, the sampling of just the leaves or seeds. these are simply issues of practicality. various techniques may be fruitfully used to measure elemental composition. among the best are inductively - coupled plasma optical emission spectroscopy ( icp - oes ), inductively - coupled plasma mass spectrometry ( icp - ms ), x - ray fluorescence ( xrf ), synchrotron - based microxrf, and neutron activation analysis ( naa ). this latter technique has been applied to perform ionomics in the study of breast cancer, colorectal cancer and brain cancer. high - throughput ionomic phenotyping has created the need for data management systems to collect, organize and share the collected data with researchers worldwide. = = references = = = = external links = = the ionomicshub ( ihub ) is a collaborative international network for ionomics [ 10 ]
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process flowsheeting is the use of computer aids to perform steady - state heat and mass balancing, sizing and costing calculations for a chemical process. it is an essential and core component of process design. the process design effort may be split into three basic steps synthesis analysis and optimization. = = synthesis = = synthesis is the step where the structure of the flowsheet is chosen. it is also in this step that one initializes values for variables which one is free to set. = = analysis = = analysis is usually made up of three steps solving heat and material balances sizing and costing the equipment and evaluating the economic worth, safety, operability etc. of the chosen flow sheet = = optimization = = optimization involves both structural optimization of the flow sheet itself as well as optimization of parameters in a given flowsheet. in the former one may alter the equipment used and / or its connections with other equipment. in the latter one can change the values of parameters such as temperature and pressure. parameter optimization is a more advanced stage of theory than process flowsheet optimization. = = plant design project = = the first step in the sequence leading to the construction of a process plant and its use in the manufacture of a product is the conception of a process. the concept is embodied in the form of a " flow sheet ". process design then proceeds on the basis of the flow sheet chosen. physical property data are the other component needed for process design apart from a flow sheet. the result of process design is a process flow diagram, pfd. detailed engineering for the project and vessel specifications then begin. process flowsheeting ends at the point of generation of a suitable pfd. general purpose flowsheeting programs became usable and reliable around 1965 - 1970. = = see also = = list of chemical process simulators cape - open interface standard process simulation = = references = = westerberg a. w., hutchinson h. p., motard r. l., and winter p., ( 1979 ), " process flowsheeting ", cambridge universities press, isbn 0 - 521 - 22043 - 2 veverka v. v., and madron, f. ( 1997 ), " material and energy balancing in the process industries ", elsevier, isbn 0 - 444 - 82409 - x babu, b. v. ( 2004 ), " process plant simulation ", oxford universities press, isbn = = external links = = process flowsheet development using process simulation software
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protein arginine phosphatase ( paps ), also known as phosphoarginine phosphatase, is an enzyme that catalyzes the dephosphorylation of phosphoarginine residues in proteins. protein phosphatases ( pps ) are " obligatory heteromers " made up of two maximum catalytic subunits attached to a non - catalytic subunit. arginine modification is a post - translational protein modification in gram - positive bacteria. mcsb and ywie were recently identified as phosphorylating enzymes in bacillus subtilis ( b. subtilis ). ywie was thought to be a protein - tyrosine - phosphatase, and mcsb a tyrosine - kinase, however in 2012 elsholz et al. showed that mcsb is a protein - arginine - kinase ( pak ) and ywle is a phosphatase - arginine - phosphatase ( pap ). many proteins rely on protein phosphatase activity for regulating their stability, localization, and interaction with other proteins. arginine modification is a post - translational protein modification in gram - positive bacteria, and protein arginine phosphorylation regulates transcription factors, in addition to tagging rogue proteins for degradation in gram - positive bacteria. like phosphorylation, dephosphorylation is a reversible post - translational event. it is reversible through the action of kinases ( enzymes that adds a phosphate group to a protein via phosphorylation ), and this antagonist activity of phosphorylation and dephosphorylation of proteins controls all aspect of prokaryotic and eukaryotic life. in general, protein phosphatases play a crucial role in cell signaling regulation in both eukaryotes and prokaryotes. they act by removing a phosphate group from proteins, and their activity counteracts that of protein kinases. = = function = = ywie is a member of the low - molecular - weight protein tyrosine phosphatase ( lmw - ptp ). it is the only active pap present in b. subtilis, and paps exhibits almost no activity against protein serine, protein tyrosine, and protein threonine peptides. also, ywie has been shown to play a role
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only active pap present in b. subtilis, and paps exhibits almost no activity against protein serine, protein tyrosine, and protein threonine peptides. also, ywie has been shown to play a role in b. subtilis's resistance to stress. elsholz et al. ( 2012 ), reported in their paper that protein arginine phosphorylation likely plays a critical physiological and regulatory role in bacteria. they showed that protein arginine phosphorylation is involved in the regulation of homeostasis, biofilm formation, motility, competence, stress, and stringent responses by regulating gene expression and protein activity in bacillus subtilis. their results suggested that the combined action of protein arginine phosphatase and kinase allows for rapid and reversible regulation of protein activity. also, that protein - arginine - phosphatases reverse the effect of protein arginine kinases ( paks ) in living organisms. in b. subtilis, ywie, a pap, counteracts the action of mcsb, a protein arginine kinase ( pak ). mcsb phosphorylates arginine residues in the winged helix - turn - helix domain of ctsr4, preventing it from binding to dna, allowing for the expression of the repressed gene. however, ywie is capable of restoring the dna - binding ability of the ctsr repressor, a stress response & heat shock regulator in b. subtilis, by reversing the mcsb - mediated phosphorylation4. it accomplishes this by dephosphorylating the ctsr protein. additionally, mcsb and ywie are capable of differentiating between phosphoarginine and other amino acid residues = = = known paps = = = as of 2020, ywie is the only known active pap in b. subtilis, although fuhrmann et al. ( 2013 ). identified a ywie homolog in drosophila, but its role in the species is still unknown. in contrast, suzuki et al. ( 2013 ) identified the presence of mcsb in over 150 bacteria species = = mechanism = = the specific molecular mechanism of action of the ywie protein is currently unknown. however, ywie is believed to dephosphorylate phosphoarginine residues using a concerted
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150 bacteria species = = mechanism = = the specific molecular mechanism of action of the ywie protein is currently unknown. however, ywie is believed to dephosphorylate phosphoarginine residues using a concerted, 2 - step process via sn2 reactions. step 1 involves a nucleophilic attack of cys7 on the phosphorus atom of the phosphoric group. then a thiophosphate intermediate is formed. in the second step, a phosphorylation - enzyme intermediate is hydrolyzed following the deprotonation of a water molecule by asp118. fuhrmann et al. ( 2016 ) believe that asp118 likely promotes the reaction through the stabilization of the positive charge of the amino group via electrostatic interaction. sample general dephosphorylation reaction equation : h 2 o + c 6 h 15 n 4 o 5 p c 6 h 14 n 4 o 2 + po 4 3 − { \ displaystyle { \ ce { h2o + c6h15n4o5p - > c6h14n4o2 + po4 ^ 3 - } } } = = history = = = = = 2005 : ywie was classified as a tyrosine phosphatase and mcsb was identified as a tyrosine kinase = = = in 2005, suskiewicz et al. classified the enzyme ywie as a tyrosine phosphatase. and kirstein et al. ( 2005 ) found that mcsb is a tyrosine kinase that needs mcsa to become activated. they also found that the interaction of mcsa and mcsb with ctsr results in the formation of a 3 - protein complex that stops the binding of ctsr to its target dna and leads to subsequent phosphorylation of mcsb, mcsa, and ctsr. = = = 2009 : mcsb was unequivocally identified as a protein arginine kinase = = = in their study, fuhrmann et al. ( 2009 ), performed a biochemical and structural analysis of the bacterial transcriptional regulators ctsr / mcsb stress response. they sort to clarify and outline the exact function of ctsr and mcsb in bacterial stress response. so, they screened proteins from various gram - negative bacteria for recombinant production and succeeded in reconstituting the bacillus stearothermophilus ctsr / mcsb system
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##sr and mcsb in bacterial stress response. so, they screened proteins from various gram - negative bacteria for recombinant production and succeeded in reconstituting the bacillus stearothermophilus ctsr / mcsb system in vitro. subsequently, they identified mcsb as a protein kinase that targets arginine. = = = 2012 : ywle was identified as a protein arginine phosphatase ( pap ) in vivo & mcsb was identified as a protein arginine kinase ( pak ) = = = elsholz et al. ( 2012 ), showed that mcsb and ywle are a protein arginine kinase and phosphatase, rather than a tyrosine kinase and phosphatase because they observed only an mcsb / ywle - dependent detection of protein arginine phosphorylation or dephosphorylation in vivo. specifically, they suggested that ywie acts as a pap in vivo. mcsb and ywle were thought to be tyrosine kinases and phosphatases. however, in 2012, elsholz et al. detected 121 arginine phosphorylation sites in 87 proteins in living bacillus subtilis ( b. subtillis ), a gram - positive bacterium present in soil and human gastrointestinal tract. their observations led them to believe that protein arginine phosphorylation exists in vivo as a posttranslational modification in bacteria. the arginine - phosphorylated proteins they detected were distributed among " distinct physiological classes of proteins " such as regulators, metabolic enzymes, stress, and ribosomal proteins. this result suggested that ywle acts as a protein arginine phosphatase that explicitly dephosphorylates arginine residues both in vitro and in vivo secondly, elsholz et al. ( 2012 ) were only able to detect protein arginine phosphorylation in a ywie mutant gene and not the wild - type strain. but protein phosphorylates on either serine, threonine, or tyrosine were detected in both wild - type and a ywie mutant strain in equal amounts. therefore, they thought that ywie might solely act as a protein arginine phosphatase. that is, the detection of protein arginine phosphorylation depended on the presence of ywie
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strain in equal amounts. therefore, they thought that ywie might solely act as a protein arginine phosphatase. that is, the detection of protein arginine phosphorylation depended on the presence of ywie. they confirmed this hypothesis after failing to detect protein arginine phosphorylation after ( 1 ) analyzing a mutant extract treated in vitro with purified ywie protein before conducting mass spectroscopy analysis ; and ( 2 ) overexpressing the ywie in trans in a ywie mutant in - vivo. the close interaction of the arginine phosphorylated proteins with ywie suggested that the stability of the modifications was indeed influenced by the ywie protein. = = references = =
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natrocarbonatite is a rare carbonatite lava which erupts from the ol doinyo lengai volcano in tanzania within the east african rift of eastern africa. natrocarbonatite lavas were first documented in 1962, by j. b. dawson. = = composition = = whereas most lavas are rich in silicate minerals, the natrocarbonatite lavas of ol doinyo lengai are rich in two rare sodium and potassium carbonate minerals, nyerereite and gregoryite. due to this unusual composition, the lava is erupted at relatively low temperatures ( approximately 500 – 600 °c ). this temperature is so low that the molten lava appears black in sunlight, rather than having the red glow common to most lavas. it is also much more fluid than silicate lavas. = = impact = = the sodium and potassium carbonate minerals of the lavas erupted at ol doinyo lengai are unstable at the earth's surface and susceptible to rapid weathering, the minerals are anhydrous and when they come into contact with the moisture of the atmosphere, they begin to react extremely quickly. the black or dark brown lava and ash erupted begins to turn white within a few hours. the resulting volcanic landscape is different from any other in the world. = = in popular culture = = notable appearances etnatao : ol doinyo lengai volcano tanzania eruption ol doinyo lengai volcano hdtv ( from a french tv documentary ) = = references = = world's coolest lava is in africa, 2003, usgs, hawaii volcano observatory ol doinyo lengai – the mountain of god
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the great rivers greenway district is a public agency in the state of missouri that works to develop a regional network of greenways, parks, and trails in the st. louis metropolitan area. the agency engages citizens and community partners to plan, build, and care for the greenways. = = history = = in 1996, a nonprofit organization called st. louis 2004 was created with the aim of bringing about a renaissance in the region by 2004. it developed a list of 11 priorities, including developing a regional network of greenways. in 2000, organization president peter sortino led a successful drive to place a proposition on local ballots to create a one - tenth - of - one - cent sales tax to support greenway development. in november of that year, voters in the city of st. louis, st. louis county, and st. charles county approved proposition c, also dubbed the clean water, safe parks and community trails initiative. the tax enabled the creation of the great rivers greenway district. the agency's distribution of funds is governed by a board of directors whose members are appointed by the chief executives of the city and two counties. a chief executive officer and staff develop the river ring, working with local, county, and state agencies and private and non - profit agencies throughout the st. louis region. in 2003, great rivers greenway published " building the river ring : a citizen - driven regional plan ", developed with advice from citizens, local governments, private companies, non - profit organizations and advocacy groups. the plan proposed to create the river ring, a system of more than 40 greenways, parks, and trails comprising over 600 miles in st. louis city, st. louis county, and st. charles county. the system will connect with trails developed by the metro east park and recreation district of st. clair and madison counties in illinois. the concept was designed to raise awareness of the natural beauty found in the region's many rivers and streams and to reconnect residents to the city's primary natural feature : the confluence of the mississippi and missouri rivers. in 2011 and 2016, great rivers greenway engages citizens, civic leaders and partners to update and republish the citizen - driven regional plan. pursuant to the 2016 update, a great rivers greenway foundation was formed to seek private funding for greenway projects. by 2020, the agency had built more than 128 miles of greenways connecting parks, rivers, schools, neighborhoods, business districts and transit. the agency began surveying citizens about priorities to build and care for the
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to seek private funding for greenway projects. by 2020, the agency had built more than 128 miles of greenways connecting parks, rivers, schools, neighborhoods, business districts and transit. the agency began surveying citizens about priorities to build and care for the greenways to inform the next update to the plan. = = greenways = = greenways within the district : boschert greenway : the boschert greenway stretches from new town in st. charles through fox hill park to the missouri river near historic downtown st. charles and the katy trail. a 30 - foot flower sculpture, “ blomstre ” – the norwegian word for bloom – stands at the intersection of mel wetter parkway and the little hills expressway. the sculpture was created by artist andrew andrasko from old bicycle parts. brickline greenway : the plan for the brickline greenway, formerly known as the chouteau greenway, calls for 20 miles of trails and green space connecting 17 neighborhoods across the city of st. louis. it will connect fairground park in the north to tower grove park in the south and forest park in the west to gateway arch national park in the east. the project planners aim to knit together diverse communities through the greenway to overcome barriers that have fragmented the city over time. the plan incorporates input from citizens on strategies to promote economic growth and equitable outcomes. busch greenway : the busch greenway in st. charles county connects the katy trail to missouri research park and august a. busch memorial conservation area. centennial greenway : the centennial greenway will extend from forest park in the city of st. louis to st. charles county. three sections have been completed. from forest park, the trail runs through the washington university campus to delmar boulevard and vernon avenue in university city. another section extends from shaw park in clayton north to olive boulevard. a third section goes from the katy trail to the st. charles heritage museum and connects east across the missouri river to creve coeur lake memorial park via the creve coeur connector trail. dardenne greenway - the dardenne greenway follows dardenne creek across st. charles county. one section loops through the barathaven community and a restored prairie landscape in dardenne prairie. another links legacy park in cottleville to st. charles community college and dardenne park in st. peters. deer creek greenway - the deer creek greenway extends from deer creek park in maplewood to lorraine davis park in webster groves. fee fee greenway -
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cottleville to st. charles community college and dardenne park in st. peters. deer creek greenway - the deer creek greenway extends from deer creek park in maplewood to lorraine davis park in webster groves. fee fee greenway - the fee fee greenway extends from the maryland heights recreation complex to creve coeur lake memorial park. gravois greenway : grant's trail - grant's trail on the gravois greenway runs along gravois creek on the rail corridor of the former kirkwood - carondelet branch of the missouri pacific railroad. trailnet, a st. louis - based organization that advocates for active communities and safe spaces for walking and bicycling, purchased the corridor in 1991 and built the first six miles of grant's trail which opened in 1994. since 2006, great rivers greenway has extended the trail to reach 10 miles from kirkwood to the river des peres greenway near interstate 55 and added two miles of trail in officer blake c. snyder memorial park, adjacent to grant's trail. points of interest on the greenway include the ulysses s. grant national historic site, grant's farm and the thomas sappington house museum. maline greenway : the maline greenway connects with other paved trails in bella fontaine county park in north st. louis county. it is the first segment of a planned seven mile, east – west link that will connect the mississippi and st. vincent greenways. meramec greenway : the meramec river greenway concept plan calls for a greenway stretching 50 river miles from the city of pacific to the meramec's confluence with the mississippi river. five sections have been completed. the westernmost section connects lions park in eureka to route 66 state park. the next section runs along the river on the al foster trail between glencoe and sherman beach county park with a spur on the rock hollow trail. a third section links arnold's grove park in valley park to simpson county park and greentree park in kirkwood. in fenton the greenway connects unger park to fenton city park and george winter park. the fifth segment meanders through the river bottomland in lower meramec park. mississippi greenway : the mississippi greenway, formerly known as the confluence greenway, is planned as a 32 - mile corridor that will connect with the missouri, maline, river des peres and meramec greenways. three sections have been built. the riverfront trail runs from the
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formerly known as the confluence greenway, is planned as a 32 - mile corridor that will connect with the missouri, maline, river des peres and meramec greenways. three sections have been built. the riverfront trail runs from the downtown mississippi riverfront north to the old chain of rocks bridge. at 5, 353 feet long, the old chain of rocks bridge was part of route 66 in 1936 and is one of the world's longest bicycle and pedestrian bridges. another segment connects jefferson barracks county park with river city casino near the river des peres greenway. a third section runs through cliff cave county park overlooking the mississippi river. missouri greenway : the master plan for the missouri greenway is a 55 river mile corridor from the confluence of the mississippi and missouri rivers to chesterfield that will connect with the mississippi, sunset, centennial, fee fee and western greenways. three sections have been built. one runs from riverwoods park in bridgeton along the earth city levee to the discovery bridge on missouri route 370 where a protected pedestrian and bike path connects with the katy trail. in chesterfield, the greenway runs along the monarch chesterfield levee trail and connects to the katy trail on a protected path on the daniel boone bridge. a third segment in hazelwood runs through truman park. river des peres greenway : the river des peres greenway plan calls for a 11 - mile corridor from forest park to the mississippi river. currently it runs from francis r. slay park in the city of st. louis past the shrewsbury / lansdowne metrolink station to carondelet park and lemay park and connects to the gravois greenway : grant's trail. st. vincent greenway : the st. vincent greenway will extend seven miles from the north hanley metrolink station through the university of missouri – st. louis ( umsl ) campus to forest park. two sections have been completed. the north section runs from the north hanley station through the umsl campus and st. vincent county park. the south section connects trojan park through ruth porter mall park to forest park. sunset greenway : the sunset greenway in north st. louis county runs from the old st. ferdinand shrine in the historic district of florissant through st. ferdinand park to sunset park on the missouri river. western greenway : the western greenway runs from the meramec greenway at glencoe to rockwoods reservation. the master plan is to extend the greenway to connect with babler state
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. ferdinand park to sunset park on the missouri river. western greenway : the western greenway runs from the meramec greenway at glencoe to rockwoods reservation. the master plan is to extend the greenway to connect with babler state park and the missouri greenway in west st. louis county. = = cityarchriver project = = in 2007, four decades after completion of the gateway arch, the site remained an island, severed from the rest of the city by busy highways and disconnected from the mississippi river. walter metcalfe, an attorney and civic leader in st. louis, led the formation of cityarchriver2015 foundation in 2009 to transform the st. louis riverfront and arch grounds. michael van valkenburgh associates of new york won an international competition to redesign the arch grounds in 2010. the project received $ 20 million in capital funding in 2011 from the u. s. department of transportation, a $ 25 million matching grant from the missouri department of transportation and $ 10 million in private donations raised by cityarchriver. with a total project cost of $ 380 million, more funding was needed. great rivers greenway joined the effort in 2012, becoming part of a public - private partnership with the cityarchriver2015 foundation, national park service, missouri department of transportation, bi - state development, and jefferson national parks association. the partners planned a ballot issue known as proposition p to generate sales tax revenue for the cityarchriver project and other park improvements. in april 2013 voters in the city of st. louis and st. louis county approved proposition p : the safe and accessible arch and public parks initiative. the proposition authorized a 3 / 16th - cent sales tax to fund the cityarchriver project and accelerate local park and greenway construction. the tax was projected to generate $ 780 million over the next 20 years, with 60 percent going to great rivers greenway and 40 percent going to support local parks in st. louis city and county. half of the great rivers greenway revenue supported the cityarchriver project and the other half would be used to accelerate greenway construction. great rivers greenway stewarded $ 85 million in proposition p funds to complete several major projects over the next five years : the park over the highway, a land bridge over the i - 44 and i - 70 highways, connected downtown st. louis from luther ely smith square to the arch grounds and the riverfront, making it easy and safe for people to travel through the area on foot or by bike.
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land bridge over the i - 44 and i - 70 highways, connected downtown st. louis from luther ely smith square to the arch grounds and the riverfront, making it easy and safe for people to travel through the area on foot or by bike. luther ely smith square, a green space leading to the park over the highway was renovated. the riverfront trail on the mississippi greenway was extended 1. 5 miles from biddle street south to chouteau avenue along leonor k. sullivan boulevard and the boulevard was raised by 2. 5 feet to reduce flooding. the north gateway, a new recreation and event space at the north entrance to the arch grounds, opened with a natural amphitheater, a bike and pedestrian path to laclede's landing, shaded lawns, a children's garden and an elevated walkway offering views of the gateway arch and the historic eads bridge. the arch grounds were transformed with sustainable ponds, landscaping and accessible walkways connecting the gateway arch to the mississippi river. kiener plaza was redesigned to serve as a public gathering place with a playground, fountains, an interactive splash pad, a grassy concert area, shade gardens, landscaping, and bicycle parking. the gateway arch national park museum and visitor center was renovated and expanded. renovation of the old courthouse was planned to enhance the visitor experience and accessibility. work was scheduled to begin in late 2021. cityarchriver foundation changed its name to the gateway arch park foundation in 2017. the foundation raised $ 250 million in private funds for the project. = = external links = = great rivers greenway website = = references = =
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a proteolipid is a protein covalently linked to lipid molecules, which can be fatty acids, isoprenoids or sterols. the process of such a linkage is known as protein lipidation, and falls into the wider category of acylation and post - translational modification. proteolipids are abundant in brain tissue, and are also present in many other animal and plant tissues. they include ghrelin, a peptide hormone associated with feeding. many proteolipids have bound fatty acid chains, which often provide an interface for interacting with biological membranes and act as lipidons that direct proteins to specific zones. proteolipids were discovered serendipitously in 1951 by jordi folch pi and marjorie lees while extracting sulfatides from brain lipids. they are not to be confused with lipoproteins, a kind of spherical assembly made up of many molecules of lipids and some apolipoproteins. = = structure = = depending on the type of fatty acid attached to the protein, a proteolipid can often contain myristoyl, palmitoyl, or prenyl groups. these groups each serve different functions and have different preferences as to which amino acid residue they attach to. the processes are respectively named myristoylation ( usually at n - terminal gly ), palmitoylation ( to cysteine ), and prenylation ( also to cysteine ). despite the seemingly specific names, n - myristoylation and s - palmitoylation can also involve some other fatty acids, most commonly in plants and viral proteolipids. the article on lipid - anchored proteins has more information on these canonical classes. lipidated peptides are a type of peptide amphiphile that incorporate one or more alkyl / lipid chains, attached to a peptide head group. as with peptide amphiphiles, they self - assemble depending on the hydrophilic / hydrophobic balance, as well interactions between the peptide units, which is dependent on the charge of the amino acid residues. lipidated peptides combine the structural features of amphiphilic surfactants with the functions of bioactive peptides, and they are known to assemble into a variety of nanostructures. = = function and application = = due to the desirable properties of peptides such as high receptor affinity and bioactivity, and low toxicity,
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bioactive peptides, and they are known to assemble into a variety of nanostructures. = = function and application = = due to the desirable properties of peptides such as high receptor affinity and bioactivity, and low toxicity, the use of peptides in therapeutics ( i. e. as peptide therapeutics ) has great potential ; shown by a fast growing market with over 100 approved peptide - based drugs. the disadvantages are that peptides have low oral bioavailability and stability. lipidation as a chemical modification tool in the development of therapeutic agents has proven to be useful in overcoming these issues, with four lipidized peptide drugs currently approved for use in humans, and various others in clinical trials. two of the approved drugs are long - acting anti - diabetic glp - 1 analogues liraglutide ( victoza® ), and insulin detemir ( levemir® ). the other two are the antibiotics daptomycin and polymyxin b. lipidated peptides also have applications in other areas, such as use in the cosmetic industry. a commercially available lipidated peptide, matrixyl, is used in anti - wrinkle creams. matrixyl is a pentapeptide and has the sequence kttks, with an attached palmitoyl lipid chain, that is able to stimulate collagen and fibronectin production in fibroblasts. several studies have shown promising results of palmitoyl - kttks, and topical formulations have been found to significantly reduce fine lines and wrinkles, helping to delay the aging process in the skin. the hamley group have also carried out investigations of palmitoyl - kttks, and found it so self - assemble into nano tapes in the ph range 3 - 7, in addition to stimulating human dermal and corneal fibroblasts in a concentration dependant manner, suggesting that stimulation occurs above the critical aggregation concentration. there exist some rarer forms of protein acylation that may not have a membrane - related function. they include serine o - octanoylation in ghrelin, serine o - palmitoleoylation in wnt proteins, and o - palmitoylation in histone h4 with lpcat1. hedgehog proteins are double - modified by ( n - ) palmitate and cholesterol. some skin ceramides are proteolipids. the amino group on lysine can
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##tion in histone h4 with lpcat1. hedgehog proteins are double - modified by ( n - ) palmitate and cholesterol. some skin ceramides are proteolipids. the amino group on lysine can also be myristoylation via a poorly - understood mechanism. = = in bacteria = = all bacteria use proteolipids, sometimes confusingly referred to as bacterial lipoproteins, in their cell membrane. a common modification consists of n - acyl - and s ‑ diacylglycerol attached to an n - terminal cystine residue. braun's lipoprotein, found in gram - negative bacteria, is a representative of this group. in addition, mycobacterium o - mycolate proteins destined for the outer membrane. the plant chloroplast is capable of many of the same modifications that bacteria perform to proteolipids. one database for such n - acyl diacyl glycerylated cell wall proteolipids is dolop. pathogenic spirochetes, including borrelia burgdorferi and treponema pallidum, use their proteolipid adhesins to stick to victim cells. these proteins are also potent antigens, and are in fact the main immunogens of these two species. proteolipids include bacterial antibiotics that aren't synthesised in the ribosome. products of nonribosomal peptide synthase may also involve a peptide structure linked to lipids. these are usually referred to as " lipopeptides ". bacterial " lipoproteins " and " lipopeptides " ( lp ) are potent inducers of sepsis, second only to lipopolysaccharide ( lps ) in its ability to cause an inflammation response. while lps is detected by the toll - like receptor tlr4, lps are detected by tlr2. = = = bacillus = = = many proteolipids are produced by the bacillus subtilis family, and are composed of a cyclic structure made up of 7 - 10 amino acids, and a β - hydroxy fatty acid chain of varying length ranging from 13 - 19 carbon atoms. these can be divided into three families depending on the structure of the cyclic peptide sequence : surfactins, iturins, and fengycins. lipidated peptides produced by baci
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varying length ranging from 13 - 19 carbon atoms. these can be divided into three families depending on the structure of the cyclic peptide sequence : surfactins, iturins, and fengycins. lipidated peptides produced by bacillus strains have many useful bio - activities such as anti - bacterial, anti - viral, anti - fungal, and anti - tumour properties, making them very attractive for use in a wide range of industries. = = = = surfactins = = = = as the name implies, surfactins are potent biosurfactants ( surfactants produced by bacteria, yeast, or fungi ), and they have been shown to reduce the surface tension of water from 72 to 27 mn / m at very low concentrations. furthermore, surfactins are also able to permeabilize lipid membranes, allowing them to have specific antimicrobial and antiviral activities. since surfactins are biosurfactants, they have diverse functional properties. these include low toxicity, biodegradability and a higher tolerance towards variation of temperature and ph, making them very interesting for use in a wide range of applications. = = = = iturins = = = = iturins are pore ‐ forming lipopeptides with antifungal activity, and this is dependent on the interaction with the cytoplasmic membrane of the target cells. mycosubtilin is an iturin isoform that can interact with membranes via its sterol alcohol group, to target ergosterol ( a compound found in fungi ) to give it antifungal properties. = = = = fengycins = = = = fengycins are another class of biosurfactant produced by bacillus subtilis, with antifungal activity against filamentous fungi. there are two classes of fengycins, fengycin a and fengycin b, with the two only differing by one amino acid at position 6 in the peptide sequence, with the former having an alanine residue, and the latter having valine. = = = streptomyces = = = daptomycin is another naturally occurring lipidated peptide, produced by the gram positive bacterium streptomyces roseoporous. the structure of daptomycin consists of a decanoyl lipid chain attached to a partially cyclised peptide head group. it has very potent antimicrobial properties and is used as
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bacterium streptomyces roseoporous. the structure of daptomycin consists of a decanoyl lipid chain attached to a partially cyclised peptide head group. it has very potent antimicrobial properties and is used as an antibiotic to treat life - threatening conditions caused by gram positive bacteria including mrsa ( methicillin - resistant staphylococcus aureus ) and vancomycin resistant enterococci. as with the bacillus subtilis lipidated peptides, the permeation of the cell membrane is what gives it its properties, and the mechanism of action with daptomycin is thought to involve the insertion of the decanoyl chain into the bacterial membrane to cause disruption. this then causes a serious depolarization resulting in the inhibition of various synthesis processes including those of dna, protein and rna, leading to apoptosis. = = see also = = myelin proteolipid protein = = references = = this article incorporates text by jessica hutchinson available under the cc by - sa 3. 0 license. = = external links = = proteolipids at the u. s. national library of medicine medical subject headings ( mesh ) go : 0006497 : gene ontology term for protein lipidation
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the power distribution equipment identification ( pdeid ) ( persian : کد شناسایی یکپارچه توزیع ) is a unique identification label used for exclusively identifying equipment and customers of the power distribution network of iran, which has been in use since 1997. pdeid is used to simplify identifying equipment, their approximate address, updating the electrical network information and to transfer information to computers. = = etymology = = the first unique identification code for equipment was introduced in the iran's power distribution network standard in 1969. only three equipment which were medium and low voltage poles, medium and low voltage branching nodes and distribution substations suggested to have equipment identification label. in 1996, at the 6th conference on electrical power distribution networks, an article entitled " application of the integrated equipment identification label for distribution networks in the iran " by gholamreza saffarpour ( persian : غلامرضا صفارپور ) and ali mamdoohi ( persian : علی ممدوحی ) was presented in which a method for uniquely identifying all equipment and subscribers of distribution networks introduced. this method was selected in 1997 with minor modifications by tavanir to integrate the identification of equipment and subscribers of distribution networks. = = structure of power distribution equipment identification label = = every code in the power distribution equipment identification label consists of 12 numbers and letters. the labels are grouped into two categories : network equipment and customers. = = = distribution equipment identification for network equipment = = = the equipment label contains 12 numbers and characters. the first 5 identifies the zip code of the area where the equipment is located. the 5 - digit postcode contains the location information provided by iran post for the whole country. the next two are letters which identify the equipment type - id. the last five digits are an assigned sequence ( or serial ) number for the equipment in the postcode area. the sequence or serial number used in the integrated pdeid is an arbitrary number that is unique within the area of postcode. for example, the first distribution substation in the 13457 postcode should have the serial number 00001 and the second substation in the same postcode area ( 13457 ) should have serial number 00002, and so on. in this system, determining which equipment ( substation in the above example ) is first and which one is second is absolutely arbitrary. = = = distribution equipment identification for customers ( subscribers ) = =
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have serial number 00002, and so on. in this system, determining which equipment ( substation in the above example ) is first and which one is second is absolutely arbitrary. = = = distribution equipment identification for customers ( subscribers ) = = = for customers the power distribution equipment identification label is composed of 12 digits, and similar to the equipment, the 5 leftmost digits are the 5 - digit postcode of the area where the electricity meter of the customer is located. the right 7 digits of the pdeid are the customer - id which is used in the billing system of power distribution utilities. in some parts of the iran where the customer - id is more than 7 digits, the pdeid has 14 digits, and the 9 rightmost digits contain the customer - id number. = = = equipment type id = = = in the power distribution equipment identification label, identification is not considered for all equipment. however, by identifying and labeling 23 equipment, all equipment which is important in regard to engineering calculations or information statistics can be uniquely identified. equipment type - id does not include the letters i ( i ), o ( o ), and q ( q ) to avoid confusion with numerals 1 and 0. in assigning pdeid to the distribution equipment, a single - line diagram is used, so when the three - phase system is used, insulators, cable terminations, and cable joints of all three phases take just one pdeid each. = = changes to the original design = = there are three differences between the final implemented pdeid and what was proposed in the article entitled " application of the integrated equipment identification label for distribution networks in the iran ” as following : suggested outdoor hv cable termination type id was c1, and indoor hv cable termination type id was c3. in final pdeid type id of both outdoor and indoor hv cable termination is ch. suggested outdoor lv cable termination type id was c2, and indoor lv cable termination type id was c4. in final pdeid type id of both outdoor and indoor hv cable termination is cl. adding the jn type id for virtual node. also to improve the readability of the labels, the type id is placed between the postcode ( zip code ) and sequence number ( or customer id number for customers ). = = references = =
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siege is a hypertext transfer protocol ( http ) and https load testing and web server benchmarking utility developed by jeffrey fulmer. it was designed to let web developers measure the performance of their code under stress, to see how it will stand up to load on the internet. it is licensed under the gnu general public license ( gnu gpl ) open - source software license, which means it is free to use, modify, and distribute. siege can stress a single url or it can read many urls into memory and stress them simultaneously. it supports basic authentication, cookies, http, https and ftp protocols. = = performance measures = = performance measures include elapsed time of the test, the amount of data transferred ( including headers ), the response time of the server, its transaction rate, its throughput, its concurrency and the number of times it returned ok. these measures are quantified and reported at the end of each run. this is a sample of siege output : ben : $ siege - u shemp. whoohoo. com / admin. jsp - d1 - r10 - c25.. siege 2. 65 2006 / 05 / 11 23 : 42 : 16.. preparing 25 concurrent users for battle. the server is now under siege... done transactions : 250 hits elapsed time : 14. 67 secs data transferred : 448, 000 bytes response time : 0. 43 secs transaction rate : 17. 04 trans / sec throughput : 30538. 51 bytes / sec concurrency : 7. 38 status code 200 : 250 successful transactions : 250 failed transactions : 0 siege has essentially three modes of operation : regression, internet simulation and brute force. it can read a large number of urls from a configuration file and run through them incrementally ( regression ) or randomly ( internet simulation ). or the user may simply pound a single url with a runtime configuration at the command line ( brute force ). = = platform support = = siege was written on linux and has been successfully ported to aix, bsd, hp - ux, and solaris. it compiles on most unix system v variants and on most newer bsd systems. = = references = =
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the circe effect is a phenomenon proposed by william jencks seen in chemistry and biochemistry where in order to speed up a reaction, the ground state of the substrate is destabilized by an enzyme. = = mechanism = = highly favourable binding of a substrate at a non - reactive site will force the reactive site of the substrate to be more reactive by putting it in a very unfavourable position. this effect was observed in orotidine 5 ‘ - phosphate decarboxylase. this can occur by positioning a charged amino acid group next to the charged substrate thus destabilizing it, thus making the reaction occur faster. furthermore, the substrate is put into an optimal position by the enzyme for the reaction to occur, thus decreasing the entropy greatly. a corollary of the effect is to explain the existence of one - way enzymes that are much more effective catalysts for one direction of reaction than the other. for example, the limiting rate in the forward direction of the reaction catalyzed by methionine adenosyltransferase is about 2 × 105 times higher than it is for the reverse reaction. this concept is frequently misunderstood : it does not imply any violation of thermodynamic principles. it is a kinetic effect, not a thermodynamic one, and the reaction always proceeds toward equilibrium, regardless of where the process starts. and when it is at equilibrium the rate is always zero. = = etymology = = this process was named after circe in homer's odyssey, who lured men and turned them into pigs. = = references = =
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an obstacle ( also called a barrier, impediment, or stumbling block ) is an object, thing, action or situation that causes an obstruction. a obstacle blocks or hinders our way forward. different types of obstacles include physical, economic, biopsychosocial, cultural, political, technological and military. = = types = = = = = physical = = = as physical obstacles, we can enumerate all those physical barriers that block the action and prevent the progress or the achievement of a concrete goal. examples : architectural barriers that hinder access to people with reduced mobility ; doors, gates, and access control systems, designed to keep intruders or attackers out ; large objects, fallen trees or collapses through passageways, paths, roads, railroads, waterways or airfields, preventing mobility ; sandbanks, rocks or coral reefs, preventing free navigation ; hills, mountains and weather phenomena preventing the free traffic of aircraft ; meteors, meteorites, micrometeorites, cosmic dust, comets, space debris, strong electromagnetic radiation or gravitational field, preventing a spacecraft from navigating freely in space. = = = sports = = = in sports, a variety of physical barriers or obstacles were introduced in the competition rules to make them even more difficult and competitive : in the athletics, there are barriers in obstacle running contests of 110 meters and 3000 meters, as well as in high jump and in pole vault ; in equestrian competitions, there are also jumps over obstacles ; in tennis and volleyball, a net stands as an obstacle that divides the court ; in the cycling, motorcycle and motor racing, circuit designs are interposed with difficult paths to obstruct and render more difficult the competition ; in team sports, like soccer, football, basketball and volleyball, attack players are hampered by defensive players, that make it difficult to move or throw the ball towards the goal ; in other sports, such as parkour, the competitor aims to move from one point to another in the most fluid and fast as possible, jumping obstacles of urban architecture that get in the way. obstacle course racing = = = economic = = = can be defined as those elements of material deprivation that people may have to achieve certain goals, such as : the lack of money as an obstacle to the development of certain projects ; the lack of water as an obstacle to the human capacity to produce certain crops on the field and to their own survival ; the lack of light as an obstacle to mobility at night ; the lack of electricity as an obstacle to the benefits provided by electronic devices and
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lack of water as an obstacle to the human capacity to produce certain crops on the field and to their own survival ; the lack of light as an obstacle to mobility at night ; the lack of electricity as an obstacle to the benefits provided by electronic devices and electrical machines ; the lack of schools and teachers as obstacles to education and the fullness of citizenship ; the lack of hospitals and physicians as obstacles to a system for the improvement of public health ; the lack of transportation infrastructure as an obstacle to trade, industrial and tourism activities, among others, and to economic development. = = = biopsychosocial and cultural = = = people are prevented to achieve certain goals by biological, psychological, social or cultural barriers, such as : diseases, as obstacles to human life in its fullness ; physical disabilities as obstacles to the mobility of handicapped, which can be facilitated by accessibility resources ; shyness as an obstacle to social relations ; fear as an obstacle that prevents facing potential enemies or socio - political opponents, or facing possible economic barriers ; social exclusion or the arrest of individuals as obstacles to socio - cultural integration into a community ; the lack of psychomotor coordination as an obstacle to the development of qualified abilities ; the level of mastery of the spoken idiom, or the differences between the spoken languages, as barriers to national or international social relations ; the different religions as obstacles to the mutual moral understanding or interreligious dialogue, nationally or internationally ; = = = political = = = obstacles or difficulties which groups of citizens, their political representatives, political parties or countries interpose to each other in order to hinder the actions of certain of their opponents, such as : the prevention of a political minority group to achieving their aspirations in the parliament by the politically dominant voting majority, in the parliamentary procedure ; the ideological repression, persecution and imprisonment for political reasons ; the blocking of the international political and economic influence of a country by a multilateral treaty or alliance between countries opposed to such influence. = = = technological = = = the improvement of living conditions of any human community is constantly challenged by the need of technologies still inaccessible or unavailable, which can be internally developed or acquired from other communities that have already developed them, and in both cases must overcome such barriers as : in the technology transfer between different countries, the trade and diplomatic negotiating skills with the countries which are providers of the desired new technologies ; in the internal development approach, the educational level of the community or country, the accessible collection of specialized information, their technological and industrial base, their institutional level of scientific and technological research
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negotiating skills with the countries which are providers of the desired new technologies ; in the internal development approach, the educational level of the community or country, the accessible collection of specialized information, their technological and industrial base, their institutional level of scientific and technological research, development and innovation, and the level of practiced international collaboration. = = = military = = = when different communities or countries, which border or not, cannot develop good relations, for economic, cultural or political reasons, they may exceed the limits of diplomatic negotiations, creating military defensive or offensive obstacles to their opponents or enemies, such as : building fortifications, entrenchments, barbed wire beds or mine fields, and other similar tactics intended to prevent or hinder movement of the enemy in a certain direction, and to protect your own forces from attack ; blocking or destroying physical resources or logistic interconnections, such as bridges, highways, ports or airports, creating barriers to migration, trade, tourism, etc. ; the invasion of the opponent's territory, seeking to block, destroy or use physical, logistical or strategic resources, in order to hinder existing threats. = = image gallery = = = = references = =
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a chronospecies is a species derived from a sequential development pattern that involves continual and uniform changes from an extinct ancestral form on an evolutionary scale. the sequence of alterations eventually produces a population that is physically, morphologically, and / or genetically distinct from the original ancestors. throughout the change, there is only one species in the lineage at any point in time, as opposed to cases where divergent evolution produces contemporary species with a common ancestor. the related term paleospecies ( or palaeospecies ) indicates an extinct species only identified with fossil material. that identification relies on distinct similarities between the earlier fossil specimens and some proposed descendant although the exact relationship to the later species is not always defined. in particular, the range of variation within all the early fossil specimens does not exceed the observed range that exists in the later species. a paleosubspecies ( or palaeosubspecies ) identifies an extinct subspecies that evolved into the currently - existing form. the connection with relatively - recent variations, usually from the late pleistocene, often relies on the additional information available in subfossil material. most of the current species have changed in size and so adapted to the climatic changes during the last ice age ( see bergmann's rule ). the further identification of fossil specimens as part of a " chronospecies " relies on additional similarities that more strongly indicate a specific relationship with a known species. for example, relatively recent specimens, hundreds of thousands to a few million years old with consistent variations ( such as always smaller but with the same proportions ) as a living species might represent the final step in a chronospecies. the possible identification of the immediate ancestor of the living taxon may also rely on stratigraphic information to establish the age of the specimens. the concept of chronospecies is related to the phyletic gradualism model of evolution, and it also relies on an extensive fossil record since morphological changes accumulate over time, and two very different organisms could be connected by a series of intermediaries. = = examples = = bison ( several paleospecies and - subspecies ) marine sloths ( paleospecies ) coragyps ( chronospecies ) gymnogyps ( paleospecies ) panthera ( numerous chrono - and paleospecies and - subspecies ) valdiviathyris ( no visible change since the priabonian, 35 million years ago ) = = see also = = orthogenesis
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##cies ) panthera ( numerous chrono - and paleospecies and - subspecies ) valdiviathyris ( no visible change since the priabonian, 35 million years ago ) = = see also = = orthogenesis = = references = = = = further reading = = evolutionary species vs. chronospecies from dr. steven m. carr, memorial university of newfoundland biology department stanley, s. m. ( 1978 ) " chronospecies'longevities, the origin of genera, and the punctuational model of evolution, " paleobiology, 4, 26 – 40. = = external links = =
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artificial neural networks are a class of models used in machine learning, and inspired by biological neural networks. they are the core component of modern deep learning algorithms. computation in artificial neural networks is usually organized into sequential layers of artificial neurons. the number of neurons in a layer is called the layer width. theoretical analysis of artificial neural networks sometimes considers the limiting case that layer width becomes large or infinite. this limit enables simple analytic statements to be made about neural network predictions, training dynamics, generalization, and loss surfaces. this wide layer limit is also of practical interest, since finite width neural networks often perform strictly better as layer width is increased. = = theoretical approaches based on a large width limit = = the neural network gaussian process ( nngp ) corresponds to the infinite width limit of bayesian neural networks, and to the distribution over functions realized by non - bayesian neural networks after random initialization. the same underlying computations that are used to derive the nngp kernel are also used in deep information propagation to characterize the propagation of information about gradients and inputs through a deep network. this characterization is used to predict how model trainability depends on architecture and initializations hyper - parameters. the neural tangent kernel describes the evolution of neural network predictions during gradient descent training. in the infinite width limit the ntk usually becomes constant, often allowing closed form expressions for the function computed by a wide neural network throughout gradient descent training. the training dynamics essentially become linearized. mean - field limit analysis, when applied to neural networks with weight scaling of 1 / h { \ displaystyle \ sim 1 / h } instead of 1 / h { \ displaystyle \ sim 1 / { \ sqrt { h } } } and large enough learning rates, predicts qualitatively distinct nonlinear training dynamics compared to the static linear behavior described by the fixed neural tangent kernel, suggesting alternative pathways for understanding infinite - width networks. catapult dynamics describe neural network training dynamics in the case that logits diverge to infinity as the layer width is taken to infinity, and describe qualitative properties of early training dynamics. = = references = =
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an enhanceosome is a protein complex that assembles at an enhancer region on dna and helps to regulate the expression of a target gene. = = formation = = enhancers are bound by transcription activator proteins and transcriptional regulation is typically controlled by more than one activator. enhanceosomes are formed in special cases when these activators cooperatively bind together along the enhancer sequence to create a distinct three - dimensional structure. each enhanceosome is unique towards its specific enhancer. this assembly is facilitated by energetically favorable protein : protein and protein : dna interactions. therefore, all the necessary activators need to be present for the enhanceosome to be formed and able to function. = = function = = once the enhanceosome has been formed, it recruits coactivators and general transcription factors to the promoter region of the target gene to begin transcription. the effectiveness of this is dependent on dna conformation. as a result, the enhanceosome also recruits non histone architectural transcription factors, called high - mobility group ( hmg ) proteins, which are responsible for regulating chromatin structure. these factors do not bind to the enhancer, but instead are used to restructure the dna to ensure that the genes can be accessed by the transcription factors. = = role = = most enhanceosomes have been discovered pertaining to genes requiring tight regulation, like those associated with the cells defense system. using more than one kind of transcriptional activator protein could help to ensure that a gene is not transcribed prematurely. furthermore, the use of multiple factors enables gene regulation through a combination of cellular stimuli that function through multiple signaling cascades. = = examples = = = = = ifn - β = = = the best known example of the enhanceosome acts on the human interferon - beta gene, which is upregulated in cells that are infected by viruses. three activator proteins — nf - κb, an interferon activator protein such as irf - 3, and the atf - 2 / c - jun complex — cooperatively bind to the upstream enhancer region upon viral infection. the interaction is mediated by a fourth protein hmg - i, which assists in stabilizing the complex by promoting inter - protein interactions. the assembled enhanceosome recruits transcriptional machinery such as rna polymerase to the promoter region to initiate gene expression. = = references = = = = external links = = enhanceosome molecule of the month ( february 2010
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promoting inter - protein interactions. the assembled enhanceosome recruits transcriptional machinery such as rna polymerase to the promoter region to initiate gene expression. = = references = = = = external links = = enhanceosome molecule of the month ( february 2010 ) by david goodsell
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a deductive classifier is a type of artificial intelligence inference engine. it takes as input a set of declarations in a frame language about a domain such as medical research or molecular biology. for example, the names of classes, sub - classes, properties, and restrictions on allowable values. the classifier determines if the various declarations are logically consistent and if not will highlight the specific inconsistent declarations and the inconsistencies among them. if the declarations are consistent the classifier can then assert additional information based on the input. for example, it can add information about existing classes, create additional classes, etc. this differs from traditional inference engines that trigger off of if - then conditions in rules. classifiers are also similar to theorem provers in that they take as input and produce output via first - order logic. classifiers originated with kl - one frame languages. they are increasingly significant now that they form a part in the enabling technology of the semantic web. modern classifiers leverage the web ontology language. the models they analyze and generate are called ontologies. = = history = = a classic problem in knowledge representation for artificial intelligence is the trade off between the expressive power and the computational efficiency of the knowledge representation system. the most powerful form of knowledge representation is first - order logic. however, it is not possible to implement knowledge representation that provides the complete expressive power of first - order logic. such a representation will include the capability to represent concepts such as the set of all integers which are impossible to iterate through. implementing an assertion quantified for an infinite set by definition results in an undecidable non - terminating program. however, the problem is deeper than not being able to implement infinite sets. as levesque demonstrated, the closer a knowledge representation mechanism comes to first - order logic, the more likely it is to result in expressions that require infinite or unacceptably large resources to compute. as a result of this trade - off, a great deal of early work on knowledge representation for artificial intelligence involved experimenting with various compromises that provide a subset of first - order logic with acceptable computation speeds. one of the first and most successful compromises was to develop languages based predominately on modus ponens, i. e. if - then rules. rule - based systems were the predominant knowledge representation mechanism for virtually all early expert systems. rule - based systems provided acceptable computational efficiency while still providing powerful knowledge representation. also, rules were highly intuitive to knowledge workers. indeed, one
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if - then rules. rule - based systems were the predominant knowledge representation mechanism for virtually all early expert systems. rule - based systems provided acceptable computational efficiency while still providing powerful knowledge representation. also, rules were highly intuitive to knowledge workers. indeed, one of the data points that encouraged researchers to develop rule - based knowledge representation was psychological research that humans often represented complex logic via rules. however, after the early success of rule - based systems there arose more pervasive use of frame languages instead of or more often combined with rules. frames provided a more natural way to represent certain types of concepts, especially concepts in subpart or subclass hierarchies. this led to development of a new kind of inference engine known as a classifier. a classifier could analyze a class hierarchy ( also known as an ontology ) and determine if it was valid. if the hierarchy was invalid the classifier would highlight the inconsistent declarations. for a language to utilize a classifier it required a formal foundation. the first language to successfully demonstrate a classifier was the kl - one family of languages. the loom language from isi was heavily influenced by kl - one. loom also was influenced by the rising popularity of object - oriented tools and environments. loom provided a true object - oriented capability ( e. g. message passing ) in addition to frame language capabilities. classifiers play a significant role in the vision for the next generation internet known as the semantic web. the web ontology language provides a formalism that can be validated and reasoned on via classifiers such as hermit and fact + +. = = implementations = = the earliest versions of classifiers were logic theorem provers. the first classifier to work with a frame language was the kl - one classifier. a later system built on common lisp was loom from the information sciences institute. loom provided true object - oriented capabilities leveraging the common lisp object system, along with a frame language. in the semantic web the protege tool from stanford provides classifiers ( also known as reasoners ) as part of the default environment. = = external links = = fact + + reasoner hermit reasoner protege ontology editor = = references = =
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in mathematics, light's associativity test is a procedure invented by f. w. light for testing whether a binary operation defined in a finite set by a cayley multiplication table is associative. the naive procedure for verification of the associativity of a binary operation specified by a cayley table, which compares the two products that can be formed from each triple of elements, is cumbersome. light's associativity test simplifies the task in some instances ( although it does not improve the worst - case runtime of the naive algorithm, namely o ( n 3 ) { \ displaystyle { \ mathcal { o } } \ left ( n ^ { 3 } \ right ) } for sets of size n { \ displaystyle n } ). = = description of the procedure = = let a binary operation'·'be defined in a finite set a by a cayley table. choosing some element a in a, two new binary operations are defined in a as follows : x { \ displaystyle \ star } y = x ⋅ ( a ⋅ y ) x ∘ { \ displaystyle \ circ } y = ( x ⋅ a ) ⋅ y the cayley tables of these operations are constructed and compared. if the tables coincide then x · ( a · y ) = ( x · a ) · y for all x and y. this is repeated for every element of the set a. the example below illustrates a further simplification in the procedure for the construction and comparison of the cayley tables of the operations'{ \ displaystyle \ star }'and'∘ { \ displaystyle \ circ } '. it is not even necessary to construct the cayley tables of'{ \ displaystyle \ star }'and'∘ { \ displaystyle \ circ }'for all elements of a. it is enough to compare cayley tables of'{ \ displaystyle \ star }'and'∘ { \ displaystyle \ circ }'corresponding to the elements in a proper generating subset of a. when the operation '.'is commutative, then x { \ displaystyle \ star } y = y ∘ { \ displaystyle \ circ } x. as a result, only part of each cayley table must be computed, because x { \ displaystyle \ star } x = x ∘ { \ displaystyle \ circ } x always holds
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\ displaystyle \ circ } x. as a result, only part of each cayley table must be computed, because x { \ displaystyle \ star } x = x ∘ { \ displaystyle \ circ } x always holds, and x { \ displaystyle \ star } y = x ∘ { \ displaystyle \ circ } y implies y { \ displaystyle \ star } x = y ∘ { \ displaystyle \ circ } x. when there is an identity element e, it does not need to be included in the cayley tables because x { \ displaystyle \ star } y = x ∘ { \ displaystyle \ circ } y always holds if at least one of x and y are equal to e. = = example = = consider the binary operation'·'in the set a = { a, b, c, d, e } defined by the following cayley table ( table 1 ) : the set { c, e } is a generating set for the set a under the binary operation defined by the above table, for, a = e · e, b = c · c, d = c · e. thus it is enough to verify that the binary operations'{ \ displaystyle \ star }'and'∘ { \ displaystyle \ circ }'corresponding to c coincide and also that the binary operations'{ \ displaystyle \ star }'and'∘ { \ displaystyle \ circ }'corresponding to e coincide. to verify that the binary operations'{ \ displaystyle \ star }'and'∘ { \ displaystyle \ circ }'corresponding to c coincide, choose the row in table 1 corresponding to the element c : this row is copied as the header row of a new table ( table 3 ) : under the header a copy the corresponding column in table 1, under the header b copy the corresponding column in table 1, etc., and construct table 4. the column headers of table 4 are now deleted to get table 5 : the cayley table of the binary operation'{ \ displaystyle \ star }'corresponding to the element c is given by table 6. next choose the c column of table 1 : copy this column to the index column to get table 8 : against the index entry a in table 8 copy the corresponding row in table 1, against the index entry b copy the corresponding row in table 1, etc., and construct table 9. the index entries
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column to the index column to get table 8 : against the index entry a in table 8 copy the corresponding row in table 1, against the index entry b copy the corresponding row in table 1, etc., and construct table 9. the index entries in the first column of table 9 are now deleted to get table 10 : the cayley table of the binary operation'∘ { \ displaystyle \ circ }'corresponding to the element c is given by table 11. one can verify that the entries in the various cells in table 6 agrees with the entries in the corresponding cells of table 11. this shows that x · ( c · y ) = ( x · c ) · y for all x and y in a. if there were some discrepancy then it would not be true that x · ( c · y ) = ( x · c ) · y for all x and y in a. that x · ( e · y ) = ( x · e ) · y for all x and y in a can be verified in a similar way by constructing the following tables ( table 12 and table 13 ) : = = = a further simplification = = = it is not necessary to construct the cayley tables ( table 6 and table 11 ) of the binary operations'{ \ displaystyle \ star }'and'∘ { \ displaystyle \ circ } '. it is enough to copy the column corresponding to the header c in table 1 to the index column in table 5 and form the following table ( table 14 ) and verify that the a - row of table 14 is identical with the a - row of table 1, the b - row of table 14 is identical with the b - row of table 1, etc. this is to be repeated mutatis mutandis for all the elements of the generating set of a. = = program = = computer software can be written to carry out light's associativity test. kehayopulu and argyris have developed such a program for mathematica. = = extension = = light's associativity test can be extended to test associativity in a more general context. let t = { t1, t2, … { \ displaystyle \ ldots }, tm } be a magma in which the operation is denoted by juxtaposition. let x = { x1, x2, … { \ displaystyle \ ldots }, xn } be a
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displaystyle \ ldots }, tm } be a magma in which the operation is denoted by juxtaposition. let x = { x1, x2, … { \ displaystyle \ ldots }, xn } be a set. let there be a mapping from the cartesian product t × x to x denoted by ( t, x ) ↦ tx and let it be required to test whether this map has the property ( st ) x = s ( tx ) for all s, t in t and all x in x. a generalization of light's associativity test can be applied to verify whether the above property holds or not. in mathematical notations, the generalization runs as follows : for each t in t, let l ( t ) be the m × n matrix of elements of x whose i - th row is ( ( tit ) x1, ( tit ) x2, … { \ displaystyle \ ldots }, ( tit ) xn ) for i = 1, … { \ displaystyle \ ldots }, m and let r ( t ) be the m × n matrix of elements of x, the elements of whose j - th column are ( t1 ( txj ), t2 ( txj ), … { \ displaystyle \ ldots }, tm ( txj ) ) for j = 1, … { \ displaystyle \ ldots }, n. according to the generalised test ( due to bednarek ), that the property to be verified holds if and only if l ( t ) = r ( t ) for all t in t. when x = t, bednarek's test reduces to light's test. = = more advanced algorithms = = there is a randomized algorithm by rajagopalan and schulman to test associativity in time proportional to the input size. ( the method also works for testing certain other identities. ) specifically, the runtime is o ( n 2 log 1 δ ) { \ displaystyle o ( n ^ { 2 } \ log { \ frac { 1 } { \ delta } } ) } for an n × n { \ displaystyle n \ times n } table and error probability δ { \ displaystyle \ delta }. the algorithm can be modified to produce a triple ⟨ a, b, c ⟩ { \ displaystyle \ langle a, b, c \ rangle } for which ( a b )
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and error probability δ { \ displaystyle \ delta }. the algorithm can be modified to produce a triple ⟨ a, b, c ⟩ { \ displaystyle \ langle a, b, c \ rangle } for which ( a b ) c = a ( b c ) { \ displaystyle ( ab ) c \ neq a ( bc ) }, if there is one, in time o ( n 2 log n ⋅ log 1 δ ) { \ displaystyle o ( n ^ { 2 } \ log n \ cdot \ log { \ frac { 1 } { \ delta } } ) }. = = notes = = = = references = = clifford, alfred hoblitzelle ; preston, gordon bamford ( 1961 ). the algebraic theory of semigroups. vol. i. mathematical surveys, no. 7. providence, r. i. : american mathematical society. isbn 978 - 0 - 8218 - 0272 - 4. mr 0132791. { { cite book } } : isbn / date incompatibility ( help ) ( pp. 7 – 9 )
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